By optimization of SUCCESS ST2 an environmentally stable and robust deep UV positive resist has been derived where the generally encountered problems related to chemical amplification resists, the formation of T-tops and linewidth changes during delay have been solved. The previously reported chemistry, protected poly-p-hydroxystyrene and SUCCESS type sulfonium salts, has been proven to be insensitive to airborne contaminations. In this paper the optimization of processing conditions, based on thermal analysis is reported. With the derived conditions linewidth changes during delays could be minimized and excellent performance obtained. At the IBM lithography test center in Boblingen an integrated photosector, consisting of equipment, materials, process and control philosophy, was balanced and 0.25 micrometers pattern can routinely be resolved using an ASM-L DUV stepper (NA 0.5).

In order to reduce or eliminate post-exposure delay-time effects, it is necessary to remove the extra free volume trapped in the lithographic film during the spin-coating process. Depending on the soft-bake conditions, the Tg of the lithographic film can be lower than that of the resist material. The maximum compaction state can only be reached when the lithographic film is baked at above the Tg temperature of the resist material. This condition cannot be fulfilled when the deprotection mechanism occurs below the Tg of the matrix. This case generally applies to the PHS-tBOC based formulations used in microlithography and explains the delay-time problems encountered with these systems. This approach, based on thermal analysis (DSC), can be generalized to systems with different chemistries and allows the design or selection of delay time-free resists.

This paper describes a resist that uses a polymer bound diazoacetoacetate as a photoacid generator in a two component system. The diazoacetoacetate is not used merely as a photoactive component, but its utility is extended to function as a photoacid generator for deprotection chemistry. The carboxylic acid generated upon exposure deprotects carboxylic acid-labile groups bound to another polymer backbone. This scheme has led to a resist with excellent performance like lithographically useful photospeed, resolution, environmental stability and aqueous base solubility combined with wide process latitudes. The resist does not require a topcoat or additives for stabilization towards airborne contaminants. The photo acid is a weak acid and hence allows fairly high concentrations of the acid generator to be used which helps in reducing contamination effects. Furthermore, being bound to a polymer backbone, diffusion into unexposed regions is limited and therefore exhibits greater stability towards PEB delay effects. Loss from surface due to volatility is also reduced in a polymeric acid generator compared to low molecular weight, monomeric compounds.

Similar to most of the reported positive deep-UV resists, this new resist is also a chemically amplified system. However, unlike other resists, this resist if resilient to airborne base contaminants and it shows stable resist linewidth with more than 24 hours delay between exposure and develop. This resist has high sensitivity (17-18 mJ/cm2), high contrast (7), high resolution (0.35 micrometers with (lambda) equals 248 nm and NA equals 0.37) and large process latitude in deep UV-lithography. This system does not require postexposure bake. When a postexposure bake is introduced, the linewidth variation is in the range of 2-3 nm per degree. This eliminates the concern of linewidth variation in resist images due to slight variation of postexposure baking temperature, which is commonly encountered in chemically amplified resist systems. This resist system is environmentally stable like conventional DQ system; at the same time, it retains most of the merits of chemically amplified system.

New positive tone deep UV resists with enhanced post-exposure delay (PED) latitude and process latitude are presented. Additives and functionalized sulfone terpolymers are tailored to optimize the dissolution properties and process stability. Adjustment of the dissolution rate is used as a design criterion for optimizing the resist performance. RX 165 resist, optimized using the above criteria, exhibits 0.25 micron line/space resolution, 0.8 micrometers focus latitude at 0.275 micrometers resolution, and 1 hour post exposure delay latitude.

AZ DX series are chemically amplified, three component resists based on a poly(4-hydroxystyrene-co-3-methyl-4-hydroxystyrene) matrix resin, a poly(N,O-acetal) dissolution inhibitor, and a bis(arylsulfonyl)diazomethane acid generator. The previously described AZ DX 46 is an environmentally and delay time stable, high performance resist capable of lineating structures down to 0.23 micrometers . The material contains a photoactive base to reduce the delay time effects. In this paper the influence of styrene units in the matrix resin, and some new polyacetals on the performance of the resist in comparison to the above mentioned standard formulation AZ DX 46.

We studied the deprotecting chemistry of poly(4-hydroxystyrene) based positive-working CA resist systems by using model reactions. Detailed analyses of acid-catalyzed deprotecting reactions of TMS-, THP-, and t-BOC-protected p-cresols were carried out, and it was found that alkylated derivatives of p- cresol were formed as major products for THP- and t-BOC-protected p-cresol, while no alkylated products were obtained for TMS derivatives after deprotection treatment (90 degree(s)C, 2 min). In the THP- and t-BOC-protected PHS systems were also observed such alkylations, which decreased the alkaline dissolution rate of the polymer film. The alkylations are considered to lower the alkaline dissolution contrast between an exposed area and an unexposed area in a resist film, and to deteriorate the resist performance. Therefore, we propose to introduce an alkylation inhibitor to the resist components so as to improve the performance.

A chemically amplified positive tone resist system, based on new maleimide polymers and a photoacid generator, has been developed, called MISTRAL (Maleimide-Styrene based Resist for Advanced Lithography). These polymers, which are insoluble in aqueous base, consist of two different types of monomers: blocked p- hydroxystyrenes and N-substituted maleimides. In the irradiated zones of the resist film, the phenols are regenerated by the presence of a photoacid, thereby making the resist soluble in an appropriate developer. The maleimides, on the other hand, are needed to introduce high thermal stability and good film properties. The maleimides can further be used to tailor the dissolution properties of the resist. A variety of different MISTRAL polymers have been prepared, starting from the corresponding monomers. Changes in the molecular weight, the types of monomers used and their ratio in the feed have been analyzed: a correlation study between the physical properties of the MISTRAL polymers and their lithographic behavior was systematically performed, revealing quarter micron resolution capabilities.

A design of a 3-components positive chemical amplification (CA) resist system was investigated. A series of model inhibitors were newly synthesized and examined for the structural influence to their inhibition efficiency on novolac (NVK) dissolution. The hydrophobicity and the molecular size of the inhibitor as well as the dispersivity of the acid decomposable groups in the molecule were found influential. By maximizing those parameters, the inhibitor with improved inhibition by three orders of magnitude compared to the previously known ones was obtainable. This even enabled a use of poly(p-hydroxystyrene) (PHS) as a binder, generally known to suffer from poor inhibition, in place of NVK. A molecular conformational analysis as well as IR spectrum analysis was carried out on the key materials for discussing the inhibition mechanism. A molecular interaction model between the inhibitor and the hydrophilic site of binder, a similar model to DNQ-PAC/NVK system, was proposed for the mechanism. The 3- components resist samples formulated with simple phenolic binders and the improved inhibitor performed well on imaging under KrF excimer laser exposure. A 0.24 micrometers L/S image with vertical profile was obtainable.

Dissolution kinetics of a 3-component chemically amplified positive resist, which consists of t-BOC protected phenolic resin, benzenesulfonic acid derivative as a PAG and an additional dissolution inhibitor, have been investigated under various conditions. Especially, the effects of t-BOC protection ratio and molecular weight of the base resin have been studied. In a previous paper, we reported that the dissolution rate R of a 2- component positive resist was determined by one rate determining step, i.e., developer penetration into hydrophobic t-BOC protected phenolic resin. Rapid formation of surface insoluble layer which induced T-toping profiles deteriorated its original resist performance. In this paper, we evaluated both t-BOC protection ratio and the molecular weight dependencies of the dissolution characteristics. The 3-component resist evaluated did not produce distinct T-topping profile when time duration between exposure and PEB was within 30 minutes.

A new series of (alpha) -substituted-2-nitrobenzyl arylsulfonate photo-acid generators (PAG) was synthesized. A study of the thermal stability of the PAG's upon varying the (alpha) - substituent was done. The thermal stability was evaluated because there is a correlation between the PAG thermal stability and the post-exposure bake (PEB) temperature tolerance of resists formulated with 2-nitrobenzyl arylsulfonate PAG's and t-BOC polymers. The best thermal stabilities were obtained by having a bulky electron withdrawing group situated at both the (omicron) - and (alpha) -positions of the 2-nitrobenzyl chromophore. This substitution pattern enhances the thermal stability by suppressing the nucleophilic displacement of the sulfonate group by the 2-nitro group oxygen. Increasing the electron withdrawing ability of the (alpha) -substituent decreased the quantum yield for the photogeneration of acid from the 2-nitrobenzyl chromophore. However, one of these (alpha) -substituents, (alpha) -alkoxycarbonyl, was found to give PAG's with optimum thermal stability and quantum yield. These chromophores were used to synthesize PAG's based on strong arylsulfonic acids. The PAG's protected with these new chromophores allow for a higher PEB tolerance, in poly(4-(t-butyoxycarbonyloxy)styrene-sulfone) based resists, than was possible with the 2-(trifluoromethyl)-6-nitrobenzyl chromophore. It was possible to resolve small features (0.35 micrometers ) with a PEB at 135 degree(s)C with PAG's based on this new chromophore. In contrast, formulations based on a 2- (trifluoromethyl)-6-nitrobenzyl PAG of the same acid do not have this resolution at 135 degree(s)C because of poor thermal stability.

A wide range of molecular weights (3500 to 240000) of poly(p- vinyl)phenol was studied. Polymer dissolution rate vs. molecular weight followed a simple kinetic equation, with the kinetic order m equals2.0. The photospeed of the resist was not strongly affected by the starting resin molecular weight; however, resolution decreased rapidly with increasing M_w. Also, the higher the starting molecular weight, the greater the tendency for the resist to form microbridges between features. The microbridges could be as long as 1.0micrometers for the highest molecular weight resin, M_w equals240000. The lowest molecular weight resins, M_w <EQ5000, showed no evidence of microbridges even at the resolution limit of the stepper, 0.32micrometers , with 0.14N development. However, higher normality developer, such as 0.26N TMAH, showed microbridges across 0.42micrometers features with M_w equals3500 resin. For comparison, a m,p-cresol novolak, also 3500 molecular weight, showed no evidence of microbridging in the higher normality developer. The reason for this difference is that the novolak does not crosslink as effectively as PVP does. Based on extraction experiments, it has been shown that the molecular weight at a sizing dose is 164000 for PVP and 6500 for the novolak. Thus, the novolak must react with the melamine primarily through an intrachain reaction, whereas the PVP- melamine reaction is an interchain reaction. Finally, a mechanism for microbridge formation is discussed.

The chemically amplified negative resist, composed of polyvinylphenol derivative as a base resin, melamine derivative as a crosslinker and alkyl sulfonic acid derivative which has several number of carbon atoms (n equals 3, 4 and 8) as a photoacid generator PAG, has been investigated. The absorbance of this resist system remains constant even in the introduction of different alkyl sulfonic acid type PAG materials. The resolution, as well as the depth of focus, was not so different from each other within the carbon number from n equals 3 (n- and iso-propyl) to n equals 4 (n-butyl). In the case of n equals 8 (n-octyl), however, the resolution capability was degraded drastically and the depth of focus was also reduced. Furthermore, the carbon number of alkyl sulfonic acid affected the resist profile, that is, rounded profile (n equals 3) became rectangular (n equals 4) or overhang (n equals 8) profile. Especially, very heavy overhang profile was observed in the case of n equals 8, therefore, good resolution could not be achieved. And, the standing wave effect at the side wall increased with increasing carbon number. Relationship between lithographic performance and acid size was investigated by evaluating the dissolution rate characteristics. The fact that the dissolution kinetics were almost the same in the cases of n equals 3 and n equals 4 but degraded in the n equals 8, was consistent with lithographic performance as mentioned above. Based on these results, the most suitable acid size for this chemically amplified negative resist could be determined.

Chemical amplification negative resist system composed of a novolak resin, a carbinol and an acid generator is investigated for i-line phase-shift lithography. The reaction in this resist is based on an acid-catalyzed intramolecular dehydration reaction. The dehydration products act as aqueous-base dissolution inhibitors, and carbinol compounds in unexposed areas work as dissolution promoters. The resist composed of a novolak resin, 1,4-bis((alpha) -hydroxyisopropyl) benzene (DIOL-1) and 2- naphthoylmethyltetramethylenesulfonium triflate (PAG-2) gives the best lithographic performance in terms of sensitivity and resolution. Line-and-space patterns of 0.275 micrometers are obtained using an i-line stepper (NA:0.45) in conjunction with a phase shifting mask.

A new class of photodefinable polymers based on phosphonic acid esters has been developed. Photogenerated acid catalysts convert the esters to phosphonic acids in the exposed regions of films during post-exposure bake. Those phosphonic acids, in addition to providing the base-solubility necessary for positive-tone development, are also uniquely capable of binding metal ions and cations from solution. Preliminary lithographic evaluations indicate that these polymers generally show high contrast (approximately 10), good sensitivity, low volume loss (< 15 percent) and the potential for submicron resolution. More importantly, the patterned deposition of refractory metal ions has also been demonstrated which could be useful for at-the- surface imaging and circuit fabrication applications.

A novel photoacid generator, ALS (alkylsulfonium salt; cyclohexylmethyl(2-oxocyclohexyl)sulfonium trifluoromethane- sulfonate) for ArF excimer laser ((lambda) equals193 nm) lithography and a single-layer resist have been developed. ALS shows high transparency at 193 nm and photoacid generating capability on irradiation by ArF excimer laser. A novel methacrylate terpolymer, poly(tricyclo[5.2.1.0^2,6]decanylmethacrylate-co-2- tetrahydropyranylmethacrylate-co-methacrylic acid), is synthesized as a base resin. The resist, consisting of ALS and the polymer, shows chemical amplification and good resolution. A 0.2-micrometers line and space negative-tone image is observed at 15 mJ/cm² dose using an ArF excimer laser.

Quantum chemical calculation is applied to investigate the reaction mechanism of sulfonyl acid generator and the transparency of the resist material. We have found that electron absorbed dimethylsulfone can be easily decomposed by relatively low energy (2.95 Kcal/mol), reaching to the decomposed status of methyl radical and methyl sulfonyl anion. This was thought to be an initial step in the electron acid generation reaction of the sulfonyl compounds. The total molecular energy of dimethyl sulfone anion was found to be higher than that of the neutral dimethylsulfone. On the other hand, sulfone derivatives with electron-withdrawing groups, such as methyl sulfonyl acetonitrile, usually have higher energy (about 41 kcal/mol) than those for their anion. This suggests that the electron withdrawing groups enhance the electron affinity of the sulfone compounds, which are also considered to increase the efficiency of acid generation. Additionally, another quantum chemical study was carried out in order to improve transparency of the aromatic species in resist for ArF excimer laser. Using configuration interaction (CI) methods of molecular orbital theory, the substituent effects of UV absorption in the aromatic compounds were investigated. As a result, significant red sifts in Amax were observed in the conjugated aromatic rings, which increases the transparency at 193 nm wavelength region.

The effect of onium salt structure in partially blocked poly(p- vinyl)phenol/photoacid generator (PAG) resist matrices on resolution, inhibition, and postexposure delay stability is reported. The PAG structure, M⁺X^-, was varied such that M⁺ was either triphenyl sulfonium (TPS⁺) or diphenyl iodonium (DPI⁺), and X^- represented trifluoromethanesulfonate (TFA^-) toluenesulfonate (TSA^-), camphorsulfonate (CSA^-), and hexadecylsulfonate (HDSA^-). The relative photospeed of these resists corresponded to the relative pK_a of the acid generated from the anoin, TFA>TSA>HDSA>CSA. The resolution of the resists using TPS⁺ were better than that of the DPI⁺-based resists. The best PAG from a resolution standpoint was triphenylsulfonium tosylate. The TPS⁺TSA_- also showed the lowest measured diffusion coefficient, D equals 1.1 X 10$=-4) micrometers ²/s. However, variation in PAG structure did not show any advantage in postexposure delay stability, with all the resists studied showing either 't-top' or scumming as failure modes. The larger acids, CSA and HDSA, showed a greater tendency to scum over a one hour delay period, which may indicate less acid evaporation, and more lateral diffusion to unexposed areas. The smaller acids, TSA and TFA, both showed strong 't-top' formation which is due to their increased acid volatility.

To overcome the limitations of two-component formulations, we have synthesized polymeric dyes which offer no or low bake processing and have suitable I line absorbance in films less than 100 nm thick. The polymeric RCL films are synthesized from absorbing dyes which are grafted onto polymers which are insoluble in the resist casting solvents. We have utilized amine dyes which are imidized onto polymeric backbones by a one step synthesis. The peak absorbance of the grafted dye after imidization undergoes a blue shift of about 30 nm and thus appropriate H line dyes are used to achieve I line peak absorbance.

A practical process window, considering the standing wave effect, was investigated for anti-reflective coating (ARC) and top anti- reflector (TAR) in KrF excimer laser lithograph, using an accurate profile simulator. The practical process window was defined on the exposure/defocus plane as the area where two process windows at the resist thicknesses corresponding to maximum and minimum linewidths on a swing curve are overlapped. ARC and TAR thickness latitude values for optimized ARC and TAR refractive indexes are also discussed. Simulation results show that the practical process window for the TAR system is wider than that for the ARC system, since the sidewall angle decreases by the use of ARC. Although TAR thickness latitude is smaller than that for ARC, the TAR system has an advantage in regard to reliable device fabrication, considering both the practical process window and the thickness latitude.

The present paper describes chemically amplified positive tone Deep-UV resists based on N-hydroxybenzyl methacrylamide (HBMAA) copolymers. HBMAA's were found to be attractive comonomers, due to their facile synthesis and their beneficial impact on the physical properties of the copolymers and the photoresists prepared from them. For example, good adhesion was provided to the silicon substrate and high glass transition temperatures were achieved which confer an appreciable thermal flow stability to the resist. HBMAA/4-tetrahydropyranyl vinyl phenol/methacrylic acid terpolymers were synthesized by radical polymerization which proceeds in a statistical manner. This allows for the monomers to be combined in the appropriate ratios, thus, tailoring the polymer properties, such as the glass transition and the dissolution rate. Two and three component resist formulations based on these terpolymrs exhibit linear resolution to 0.35 micrometers (NA 0.37). Thermal flow stability of the resists exceeded 130 degree(s)C. No auto decomposition was observed. Resists were applied without top coat and have a post exposure delay latitude of more than one hour.

The electron-beam lithographic response of CAMP6 is evaluated and compared to the characteristics of the chemically amplified resist under deep UV exposure. The optimization of the electron- beam lithographic properties of the positive deep UV resist CAMP6 has been performed by evaluating the effects of prebake temperature (ranging from 115 to 140 degree(s)C) and post-exposure bake temperature (ranging from 115 to 150 degree(s)C) on the observed resist thickness loss and percent of t-BOC group deprotection as measured by IR spectroscopy.

Information theory has been used to quantify the amount of information transferred during a lithographic process. By calculating the information, a quantity isomorphous with the entropy, we are able to determine the points in the process space where most of the lithographic information is lost and suggest modifications that will increase the overall information content. In this study we use the threshold image density model to evaluate the information content of the latent and printed images in a given set of resist features. The model includes contributions from exposure, acid diffusion, crosslinking or deblocking chemistry, dissolution selectivity and percolation effects. At each step we compute the information gain or loss relative to a given 'prior' distribution and display the results. Selected experimental examples will be shown to illustrate the point.

Photopatterning is described using chemically amplified resists formulated from the copolymer of di-t-butyl fumarate and styrene with various acid-photogenerators. Exposure of the materials to deep- and mid-UV light followed by postbaking results in significant changes in solubility and polarity due to carboxylic functions produced on the polymer chain through the action of photogenerated acid catalyst (chemical amplification). As resists, they possess good sensitivity (14-40 mJ/cm²), contrast ((gamma) >4) and thermostability (up to 300 degree(s) C). Relief images with good resolution can be readily obtained with either aqueous base (positive-tone) or organic (negative-tone) solvents as developer. Such photoinduced changes of the functional groups in the exposed areas were also used to pattern molecules on the surface at micron-scale, thus generating functional images, as illustrated by the selective binding of fluorescent dyes in either exposed (positive-tone) or unexposed (negative-tone) areas.

In chemically amplified resist polymers containing t-butoxycarbonyloxystyrene (TBS), a photogenerated acid catalytically removes the t-butoxycarbonyl (TBOC) protecting groups, yielding hydroxystyrene (HS) and thereby promoting aqueous base solubility of the exposed resist. Areas of concern in the lithographic use of positive tone resist polymers containing TBS include radiation sensitivity, substrate adhesion, optical density, and the loss of mass that accompanies TBOC deprotection. One approach to optimization of the lithographic performance of TBS-containing resists is to partially deprotect the matrix polymer prior to lithographic exposure. Partial deprotection yields a polymer comprised of a mixture of TBS and HS functionalities within the same chain. An easily controlled and reproducible process has been developed that causes partial conversion of TBS to HS in any TBS-containing polymer, prior to resist solution formulation. Lithographic tests of these materials were carried out using a deep UV exposure tool ((lambda) equals248 nm) and a nitrobenzyl sulfonate photoacid generator. Partial deprotection of these polymers, prior to use in lithography, is shown to substantially increase the resist sensitivity and reduce film shrinkage induced by post-exposure bake. The extent of deprotection has also been found to strongly affect the optical density at 248 nm of the sulfone-containing polymers, but to have minimal effect on the optical density of the sulfone-free polymer.

INR, an I-line negative photoresist, is described. Acid catalyzed cross-linking of phenolic resins using a non-metallic photoacid generator, 2,6-bishydroxymethyl-p-cresol as a cross- linker, and 9-anthracene methanol as an I-line sensitizer results in a very high photospeed aqueous TMAH developable photoresist. Poly(p-hydroxystyrene) was found to have advantages over novolac resins for formulation of high performance negative I-line photoresist. Advantages obtained by using PHS rather than novolac include higher thermal stability, elimination of undercut on nuleophilic surfaces and compatibility with 2.38 percent TMAH puddle develop processes. A high resolution version, INR-X, is described. Resolution to 0.30 micrometers and linearity to 0.35 micrometers was obtained using a 0.54NA ASML I-line stepper. 0.35 micrometers line-spaces arrays had 1.2 micrometers depth of focus and 0.40 micrometers line-space arrays had a depth of focus greater than 1.6 micrometers . An unusual characteristic found in INR-X is a very low sensitivity to variation in PEB temperature. A 3nm/ degree(s)C line-width dependency was found.

Evidence from simulation linewidth measurements is presented which suggests that a type II diffusion front is moving through positive tone t-BOC material during post exposure bake. A steady increase in linespace of 50 nm/min is observed in IBM APEX-E and even faster rates can be found in Apex-M. The converse is observed in negative resist systems, which evidence slower linewidth dependencies. The simultaneous reaction and 3D deprotection dependent diffusion simulation was carried out with a massively parallel approach. In addition, two-dimensional diffusion effects were studied with a test structure obtained with a super resolution phase shift mask.

In previous papers, we described initial evaluations of CGR 248 negative resist using a variety of exposure tools. During subsequent studies, the emphasis has been placed on optimizing material and process for Micrascan and Micrascan II pilot line and manufacturing operations. The formulation is based on polyhydroxystyrene (PHS), tetramethoxymethyl glycoluril, and a sulfonate ester of an N-hydroxy compound. We will discuss image stability as a function of delay time between post apply bake (PA) and expose and as a function of delay time between expose and the post expose bake (PEB). Further, data will show that immersion or puddle development provides a larger process window than spray development for features in the 0.30 to 0.35 micrometers range. The thermal stability of the imaged resist will be discussed as well as the shelf life which is at least 6 months at 23 degree(s) C. Finally, additional data is available concerning image uniformity and how print bias and etch bias contribute to the overall nested-isolated line offset for positive tone (APEX-M) and negative tone (CGR) resists. Data obtained from Micrascan II exposures with test reticles will demonstrate an acceptable process latitude for 0.30 and 0.35 micrometers features and a wafer to wafer image uniformity similar to that observed for APEX.

The chemical amplified resists are a good way of the solution of the X-ray, e-beam and DUV resist sensitivity problem. The difficulties of this way are connected with a high temperature diffusion during the process of the chemical amplification [1] (decrease of the contrast) and with the problem of the stable realization of complex thin resist film compositions. The application of photo chemical reactions produces new opportunities to solve this problem [2-4] combined with the traditional methods of the existing technology.The photo chemical amplification of a latent image improving both the resist sensitivity and the contrast is discussed in this report.

We recently introduced a new class of high performance deep-UV photoresists which are deposited via the gas phase plasma polymerization of methylsilane. These materials, particularly plasma polymerized methylsilane (PPMS), undergo efficient oxidation on exposure to deep-UV light in air to form a glasslike siloxane network polymer, providing patterns which may be developed and transferred into underlying substrates using all dry plasma etch processes. Here we describe a simple new procedure which affords the opposite (positive) tone image in the same resist using a wet buffered oxide etch to remove exposed regions. Lithographic performance studies (dose latitude as well as linearity data) are presented for both the negative tone and the new positive tone versions of the process.

As design rules for ULSI chip sets continue to require sub-O.3j.un resolution for high density patterns the drive toward shorter wavelength (248nm), and higher numerical aperture (<O.5NA) steppers will continue. Process development on these advanced lithography systems is made difficult for a variety of reasons. The first of these is cost, the most modem steppers available today can cost <$5 million per system making it necessary to keep manufacturing cost in check by extending life times to more than one generation chip set. Secondly, working at 248nm and high numerical aperture tends to reduce process latitudes making manufacturing processes inherently more difficult to control. Last but not least, photoresist and antireflective coatings needed for even the simplest processes historically have had major environmental sensitivity problems or material compatibility problems associated with them. These issues have been addressed by such developments as phase shift masks, off axis illumination techniques, and major advances in resist technology. So far these types of cures have proven to be both costly and extremely complicated to implement in a manufacturing environment.

The practical limits of i-line top surface imaging process using a novolak based photoresist were investigated dependent on exposure techniques such as conventional and off-axis illumination. Ultimately, quarter micron small geometry was clearly delineated and depth of focus (DOF) latitude of 1.5micrometers and 2.7micrometers was achieved respectively for 0.25micrometers and 0.30micrometers lines and spaces pattern by annular illumination of 0.50NA. To compensate proximity effect caused by pattern density, sub-resolution auxiliary pattern was firstly optimized for off- axis illumination of quadrapole and annular. As a result, critical dimension (CD) difference between dense and isolated pattern in 0.30micrometers reduced to half-level compared to that of non-auxiliary pattern. It was found that desilylation phenomenon was critically affected by the kind of photopolymer reacted with silicon source and molecular weight of silylation agent. Novolak based polymer maintained superior silylation durability to polyvinyl phenolic (PVP) resin. New silylation process concept which is dual silylation method was developed to utilize PVP's merits in the silylation process against desilylation. Dry development lithography of i-line was feasible to practical application of prototype 256 mega bit DRAM which demands 0.30micrometers patterning with a reproducibility.

When printing at the resolution limit of the steppers, optical proximity effects become increasingly important and might limit the useful resist processing window. In this paper proximity effects have been studied for processes based on surface imaging and dry development. Proximity effect resulted in both linewidth and profile differences between dense and isolated lines at 0.35 micrometers and below. Proximity is partly due to optical effects (NA, (sigma) , wavelength, mask tonality) and partly due to processing conditions (silylation and development). To study the optical effects, aerial image simulations have been performed and a comparison with experimental results was carried out. Reduction in proximity is realized by a reduction in 'process offset', improvements in silylation contrast and a reduction in microloading effects during dry development. Positive tone resist processes show a reduced proximity effect as compared to negative tone resist processes and the feasibility for 0.30 micrometers dimensions has been shown. At 0.25 micrometers level, the process optimization should be accompanied with optical solutions in the form of selective mask biasing.

DUV lithography using wet developable resists can be used for the poly gate definition of 0.35micrometers CMOS processes. Four years ago, we demonstrated a resolution of 0.3micrometers L/S obtained with Shipley XP 89131 resist. Nevertheless, in order to make this and other resist processes suitable for real device applications, several problems had to be overcome. First, reflective notching and linewidth variations over steps turned out to be an important limitation. Some strategy to reduce this sensitivity to reflections has to be applied. Furthermore, in order to obtain a stable and reproducible lithographic process, process latitudes should be wide. Furthermore, a comparison between positive tone and negative tone resists is made with respect to their suitability for poly gate patterning. It was observed that negatively sloped resist profiles, as a result of the use of negative tone resists, create a controllability problem during in-line SEM inspections, and such profiles result in positively sloped poly profiles after etching. Positive tone resists have positively sloped resist profiles, but they require the use of a bright field mask, and hence reflections are much more of a problem. Also, positive tone resist are more sensitive to the delay effects.

The advent of deep-UV(DUV), chemically amplified, acid catalyzed photoresists as successors to positive diazoquinones photoresists has brought about a new set of process environment concerns directed towards all materials in contact or absorbed by the photoresists. In addition to the application of DUV bottom anti-reflective coatings (BARCs) to suppress optical reflection and subsequent linewidth distortion, we must consider the properties and interaction of the BARC layer with the labile photoacid of the latent image. In this regard, we have examined the physico-chemical aspects of the DUV BARC with regards to acting as a barrier layer to substrate poisoning, and as an optical absorbing layer that does not interact and/or distort the deep-UV profile. Various single component polymeric BARCs were synthesized and examined. Considerations will be discussed of the optical absorbance, the coating quality, dry etch rate, and the impermeability of the BARC layer to photoacid diffusion to fulfill the performance requirements of BARCs for DUV lithography.

A survey of optical constants for a variety of materials measured at 193 nm suggests that antireflection measures will be necessary for single-layer resist lithography at 193 nm. The extent to which standing waves occur in 193- nm resists is similar in magnitude to those occurring at 248 nm. To help reduce these effects, a new spin-on antireflective layer has been developed. It is composed of a polymeric dye in a phase-compatible blend with a transparent base polymer, can be thermally cured to render it insoluble, and is compatible with chemically amplified resists. In addition to this spin-on material, extension of existing 248-nm dry-deposited antireflective layers to 193 nm should allow for either spin-on or dry-deposited antireflection coatings for 193-nm lithography.

A study optimizing the actinic absorbance of APEX-E positive deep UV photoresist was performed using a variety of dye additives. The selection of a dye and the optimization of dye content for APEX-E positive photoresist has led to substantial process enhancements in reduction of reflective notching and of thin film interference effects. The usual side effects as found in dyed I- line resists such as significant loss of photospeed, decreased focus latitude and sidewall angle decrease were not apparent with selected conjugated aromatic dyes. The benefit of added absorbance has allowed the direct use of dyed APEX-E to counteract the step interference (notching) problems over the severe topography of CMOS gate level and eliminate the reflective notching of surface strap level in the fabrication of 16 Mb devices. In addition, the depth of focus window was enhanced and process latitude was maintained. Geometries of 250nm were printed, with dyed APEX-E for optical densities ranging from 0.4 to 0.8 per micron with a DUV optical scanner.

A new advanced process scheme is presented using a self aligned sidewall oxide film formation. The process technique was evaluated with simulation methods. During the experiments a new effect, the selective silylation, was found.

In the present work, the bilayer system investigated was comprised of a negative working portable conformable mask (PCM) and an underlying planarizing layer. The lithographic evaluation of the PCM as a stand-alone single-layer resist (SLR) was presented in an earlier paper. The DPEPA acts as a sensitizer to e-beam radiation by enhancing exposure-induced crosslinking. The presence of Zr in the form of an organometallic in the PCM results in the formation of an oxide-based barrier to etch in oxygen and CF₄/0₂ plasmas. The PCM in the bilayer system was found to have improved contrast (approximately 0.7-3.0) relative to the SLR, though it was also less sensitive (sensitivity in the range of 1.5-15 (mu) C/cm²). Features of 0.5 micron were delineable with this resist scheme, using acetic acid as a developer. Increasing the DPEPA improved sensitivity but resulted in a deterioration of contrast. The bilayer resist etch rates during RIE were studied in a parallel plate etcher as a function of power density, chamber pressure, etchant gas flow rate and mole% CF₄ in the plasma. For the system described here and under identical etching conditions, the bilayer etched 1/12 as fast as pure PMMA in oxygen and at 80 nm/min (versus 214 nm/min for PMMA) in a 92:8 CF₄/0₂ plasma. The presence of the PCM afforded the PMMA resist more RIE time, the upper limit of etch duration increasing with increased planarizer thickness. Post-etch scanning electron micrographs indicate that the imaged stencils are dimensionally stable to prolonged etches in these environments.

Classical positive resist process for DUV is not yet available and stabilized. We noticed various limiting points such as the delay time for resist material, the limitation of thickness related to ultimate resolution, and the bulk effect. P.R.I.M.E. (Positive Resist Image by dry Etching) process technology using DUV 248 nm exposure wavelength improve solutions for each process parameters, for example, a well known and stable resist (J.S.R- U.C.B PLASMASK 200G) is used with Hexamethyldisilazane (HMDS) as silylated compound. The combination of DUV exposure and top surface imaging P.R.I.M.E. process can open contact holes down to 0.3 micrometers with a large process window and a good wafer uniformity. This publication will show the improvement of each process parameter. Extended information will be given for process latitude (focus and exposure). We demonstrated and verified the feasibility of the contact holes process by etching 1 micrometers oxide (BPSG + USG) through the PRIME process lithography.

DESIM is an exclusive simulator for the DESIRE process. It can model all the three unit processes i.e. surface imaging (projection/contact, conventional/phase-shifted mask), silylation (positive/negative tone, gas/liquid phase, pre-silylation baking), dry development (single and two step). This paper discusses some of the models and then evaluates the performance of the simulator by comparing the simulated results.

The goal of this investigation was to develop a 0.3 micron silylation process for 248 nm exposure, using a commercial photoresist material. Presented are results from investigation into liquid silylation of 248 nm exposure of Dynachem EL IR^TM, a non-melamine image reversal novalac material designed for i-line application. A GCA BOLD 0.42 NA, 248 nm excimer laser projection system was used for exposure. A process has been developed utilizing a silylation solution of hexamethyl- cyclotrisilazane (HMCTS), propylene-glycol-methyl-ether-acetate (PGMEA), and xylene mixtures. Using a 15 run Box-Behnken statistically designed experiment, dry development in 0₂ RIE has been optimized with chamber pressure, flow rate, and 0₂ flow as process factors. Process responses optimized were selectivity, etch rate, and anisotropy. Results show capabilities and sensitivities of the process. Response surfaces are presented, along with resist image results of 0.3 microns at 5:1 aspect ratio.

The dissolution of novolak films in aqueous alkali is controlled by the diffusion of base through a thin penetration zone that forms at the interface between the developer solution and the solid. Base diffusion is a percolation process in which the ions of the base migrate through the zone by stepping from one hydrophilic site (phenol or phenolate) to the next. Dissolution inhibitors function by blocking some of the hydrophilic sites and thereby interrupting the diffusional pathways. Percolation theory suggests a relation between the strength of inhibition and the percolation characteristics of the resin. The two are linked together by the hydrophobic displacement volume of the inhibitor, which is that volume which the inhibitor occupies in the penetration zone. The hydrophobic displacement volume determines the effectiveness of an inhibitor; it depends not only on the molecular volume of the inhibitor, but also on the mobility of the hydrophilic sites in the zone; it is much smaller above the glass transition temperature of the zone than below it. It is also smaller in systems where some degree of motional freedom persists even below the glass transition of the zone.

Poly (p-vinylphenol) was derivatized by reaction with ortho- methylolated precursors to introduce ortho-ortho linked phenolic diad and triad moieties onto the polyethylene backbone. In particular, the resulting polymers obtained by the reaction with 2,4-dimethyl-6-methylolphenol were characterized by spectroscopic and lithographic methods to understand the structure/property relationship. The reaction took place in a sequential fashion so that the diad formation was followed by the triad formation. The diad was found to have two conformations, corresponding to hydrogen-bonded and -unbonded states, while the triad existed only in the hydrogen-bonded conformation. The dissolution behavior of the modified polymers with and without DNQ ester was greatly affected by the degree of HMX incorporation. Optimized resist performance determined by dissolution rate monitoring was obtained on modification of all phenolic moieties with a diad/triad ratio of approximately 1.

The synthesis and lithographic characterization of the three positional isomers of polyhydroxystyrene is described. Large differences in dissolution rates are found as a function of the position of the hydroxy group, which are explained in terms of intra- versus intermolecular hydrogen bonding and steric shielding of the hydroxy group by the polymer backbone. In plots of log(dissolution rate) versus developer strength, linear plots are observed for the 2- and 4-isomers, whereas for poly(3- hydroxystyrene), a break occurs in the plot, leading to two linear regions. While the 2-hydroxy isomer is too slow and the 4- hydroxy isomer too fast for use in conventional dissolution inhibition systems, the copolymerization of both allows one to choose any dissolution rate between these extremes ('dial a dissolution rate'-copolymers). Determination of the copolymerization parameters of the corresponding 4- and 2- acetoxystyrene precursors by the method of Kelen and Tudos shows the polymerization to be nearly ideal and azeotropic (r₁ equals 0.76, r₂ equals 0.94). Analysis of the dissolution rates as a function of developer strength according to the Huang-Reiser-Kwei equation shows that the critical concentrations c are a linear function of copolymer composition, whereas the penetration exponents n show a minimum near unity in the region of the 1:1 copolymer, down from the values of 3.2-3.3 observed for all three homopolymers. The 1:1 copolymer shows a dissolution rate comparable to novolak resins, and when formulated into a photoresist together with a diazonaphthoquinone sensitizer resolved 0.4 micrometers features at a dose of 340 mJ/cm². The thermal flow resistance of the resist was found to be improved over that of novolak resists although not to the degree expected from the increased T_g of the 1:1 copolymer.

Most positive diazonaphthoquinone/novolak resists use mixtures of various DNQ-esters and positional isomers as the photoactive compounds (PACs). Compared to using a single compound, PAC mixtures often offer formulation advantages in terms of optimizing the lithographic response and improving storage stability. We have investigated a broad class of PACs for which the condensation reaction of diazonaphthoquinone sulphonyl chloride with the polyhydroxylated ballast group is highly regioselective; this produces mixtures which strongly favor either even-numbered isomers (tetraesters, hexaesters and octaesters) or odd-numbered isomers (triesters and pentaesters). In this paper we describe observed PAC DNQ-ester distributions as a function of the ballast molecular structure and the DNQ:ballast mole ratio. A synthetic reaction model is offered to explain the origins of these unusual DNQ-ester distributions. The effects of these distributions on resist performance is explored through dissolution kinetics (R_min, R_max and q_effective) and lithography.

The resist processes used for optical lithography are mainly positive tone, based on the use of DNQ/novolac photoresists. It has been demonstrated that enhancing the resist pattern profiles is possible by optimization of the development step. Development techniques, such as two-step or interrupted development, have been introduced to enhance the contrast of DNQ/novolac resists. This paper demonstrates that the resist surface modifications occurring during development can be followed by surface energy measurements. The surface energy changes of four commercial resists (JSR IX 500, Shipley SPRT 510, OCG HPR 504 and Hoechst AZ 5206) during development are investigated. The results are then correlated to the changes in pattern profiles obtained when using the interrupted development technique.

A heat transfer model for hotplate baking is combined with a mass transfer model for solvent diffusion to predict the major effects of photoresist prebaking for photolithography. Solvent diffusivity as a function of solvent concentration and temperature is determined experimentally. The results of the model are a complete time-temperature history of the wafer, final solvent distribution within the resist film, and final resist thickness.

Residual solvent present in resist films following spin casting can significantly influence dissolution behavior. We have used radiolabeling to measure solvent remaining in spin cast films after they have undergone various annealing protocols. Films of poly(3-methyl-4-hydroxystyrene) were found to contain a significant fraction of propylene glycol methyl ether acetate (as much as 50 percent by weight) depending on the annealing conditions. 1100 angstrom films contained a higher percentage of residual solvent than 1.2 micrometers films. A diffusion plus evaporation model was used to deduce the diffusion coefficients of residual solvent as a function of film thickness and annealing temperature. We found that diffusion coefficients of residual solvent in 1100 angstrom polymer films are more than two orders of magnitude less than in 1.2 micrometers thick films.

Solvent evaporation from Novolak solution was characterized by TGA and occurs in two distinct stages of solvent loss: an evaporation limiting state (solvent determined) and a diffusion limiting stage (polymer determined) and is used to understand solvent retention mechanism during spin coating. Retained solvent content in Novolak films, as determined by gas chromatography and FT-IR Spectrometry, is found to reduce the apparent Tg and increase the bulk dissolution rate of the novolak. Solvent distribution in the film, monitored as a function of depth by a reflectance FT-IR technique, is used to develop a Novolak dissolution model which characterizes both surface induction and bulk dissolution behavior.

Photospeed measures of functional performance are widely employed for the characterization, quality control, and quality assurance of photoresists in both their manufacture and end use. In this paper we investigate from both a theoretical and experimental stand point, the precision and reliability of these measures for positive photoresists, and explore the relationships with dissolution rate behavior as determined by DRM. In particular we quantify their dependence upon photolithographic process and resist compositional variants. It is demonstrated that for a given photoresist a 'single point' measure of photospeed may not be predictive of the observed lithographic 'sizing' behavior. Multiple point measurements, which more reliably predict the lithographic process window, are proposed and evaluated for advanced g- and i-line resists. Included amongst these are measures based on the determination of E₀ at different develop times.

The PEB process causes three effects: (1) the diffusion of the PAC, (2) solvent evaporation and, (3) thermally induced chemical reactions. The influences of these mechanisms on the average dissolution rate of the resist are not easily segregated from one another when reflective substrates are used. The effect of standing waves was eliminated by using nonreflective substrates. The effects of the solvent removal and other thermal reactions on the dissolution rates of the resist were investigated at different PEB temperatures concentrating on two different resist systems. In general, the dissolution rates of both resists decreased as a function of the PEB temperature. The magnitude by which the dissolution rate changes with PEB temperature at different exposure energies depends on the resist composition and its chemistry at elevated temperatures. The steepness of DRM average bulk dissolution rate curves generated on nonreflective substrates suggest improved resist performance without PEB. In practice, however, high contrast resists processed without PEB, on non-reflective substrates have poorer lithographic performance than when using a PEB. Accurate analysis of the dissolution rate data revealed that the surface dissolution inhibition caused by the PEB is responsible for the improvement.

A new chemically amplified I-line negative resist (INR) is in use at IBM's eight-inch wafer manufacturing facility in Essex Junction, Vermont. The resist is applied at the ion implant block photo levels for 4-Mb DRAM chip production and shows very good line performance and stability. Process parameters such as focus, exposure dose, post expose bake (PEB) temperature vs. photospeed, and time window from expose to PEB, demonstrate above average latitude. Due to the long develop times (4 min per wafer) required when using a single-wafer spray or puddle develop in an integrated photocluster, INR runs on a stand-alone toolset. This paper reviews several concerns with INR regarding its optical appearance, resist thinning, and undercut. The first two issues were resolved through increased manufacturing-floor training and by more tightly controlling certain components of the resist. The undercut effect required a more advanced version of the resist to be formulated, which is currently under evaluation.

Novolak-polyhydroxystyrene copolymers with a high glass transition temperature were synthesized. Copolymers with different compositions (Novolak/PHS ratio) show improved resin characteristics, compared to either novolak or novolak/PHS blend. The novolak-PHS copolymer formation is confirmed by carbon-13 NMR spectroscopy. This technique has provided detailed information on the substitution characteristic of various carbon atoms in the polymer. For example, the carbons bearing hydroxy groups are observed in the range 148-156 ppm and the methylene carbons at 25-36 ppm. The methyl groups on the aromatic ring show chemical shifts at 16 and 25 ppm. Chemical shifts of carbons in various isomers of model compounds have been assigned to respective carbons, which confirms the structure (structure 1) for this copolymer. Novolak-PHS copolymer can be formulated into a high performance and high thermal stability positive photoresist whereas physical blend of novolak and polyhydroxystyrene is not useful. The synthesis of the copolymer and the micro lithographic properties is discussed. The paper discusses comparative data on Novolak-PHS copolymer and novolak/PHS polymer blends.

Hydrogen bonding between several novolak oligomers as donors and phenylsulfoxide as acceptor was investigated as a model for the interaction of inhibitors with o,o-connected phenolic blocks in practical novolak resins. It was found that the attraction of the novolak dimer for the acceptor was more than twice as strong as that of the corresponding monomeric phenol. In a non-polar solvent, carbon tetrachloride, the higher oligomers assume cyclic conformations where all hydrogen bonds are internally saturated. There are, however, indications, that in sufficiently polar solvents these cyclic structures open up and that the acyclic oligomers then interact strongly with hydrogen bond acceptors.

An investigation of the molecular characteristics of DNQ-PACs both in isolation and in combination with polymer matrices using the techniques of solid state magic angle sample spinning Fourier transform (FT) nuclear magnetic resonance (NMR) spectroscopy and FT-Raman spectroscopy has been initiated. These investigations necessitated a rather fundamental look at the spectroscopic signatures of DNQ's in various environments. Two dimensional NMR techniques have been used to unambiguously assign carbon-13 and proton NMR spectra of the 2,1,5-DNQ moiety in solution. The nitrogen-15 NMR spectrum of 2,1,5-DNQ has also been assigned. While preliminary solid state NMR and FT-Raman spectra have demonstrated that these techniques can be used to monitor the effect of matrices on DNQ/PACs at the molecular level, isotopic labelling will be required to fully understand the nature of the interactions. The correlation of molecular-based information with macroscopic resist performance should lead to the development of new improved resists.

During the course of investigations into the synthesis of novolak resins for use in the microelectronics industry we have observed the rearrangement of the resin. Deeper investigation of this phenomenon has shown it to be a chain scission which leads to a rearrangement of the novolak structure. A possible mechanism is discussed.

The seven possible 2,1-diazonaphthoquinone-5-sulfonates of 2,3,4- trihydroxybenzophenone have been isolated and characterized by IR, chromatographic and advanced NMR techniques. HPLC procedures for their analysis are given which show counterintuitive effects in the HPLC elution sequence due to the effect of intramolecular H-bonding on the polarity of some esters. A reaction scheme is proposed which qualitatively identifies preferred pathways to the trisester.

The universality of a single percolation field scaling law to the tetramethylammonium hydroxide dissolution of derivatized novolac and poly(4-vinylphenol) polymers was investigated. According to this hypothesis, the dissolution of phenolic polymers occurs through a percolative mechanism resulting from the diffusion of base along nascent channels formed by the spatial proximity of phenolic hydroxyl groups (presumably diffusion of the cation is rate limiting). Dissolution inhibition results from the removal of sites from the percolation field. In this study, the polymers were derivatized with increasing amounts of either 2,1,5- diazonaphthoquinone groups or methylsulphonyl ester groups and the dissolution rates of the films were measured. While our experimental data supported adherence to the percolation law (p equals the scaled amount of free hydroxyl sites remaining on the polymer), Rate equals Rate₀ (p-p_c)^t, we did not find that a single exponent of t equals 2 universally described the dissolution behavior. Rather, our data indicated that t varied with different systems, with values of t greater than 5 being observed. These results are explained in terms of multiple simultaneously operant mechanisms of dissolution creating an environment where multiple percolation can occur. The relative shielding effects of the blocking groups are also compared.

Use of safer photoresist solvents such as propylene glycol monomethyl ether acetate (PGMEA, PMA) has been steadily increasing as a positive photoresist casting solvent. This work compares the aging characteristics and shelf life of photoresist prepared with PGMEA versus cellosolve acetate (CA, 2-ethoxyethyl acetate). By comparing samples stored at elevated temperatures with those at room temperature, aging rates are evaluated on photosensitivity, contrast, thickness and absorbance. Using first order reaction kinetic assumptions, these aging rates are compared to product specification limits to estimate shelf life.

Process simulation and modeling techniques have demonstrated significant success in predicting the behavior of optical lithography for semiconductor processes with photoresist thicknesses below 2 microns. An extension of these same principles and methods has been applied to thick resist process up to 10 microns. This study examines the use of simulation analysis in conjunction with experimental results to study the effects of photoresist film thickness and photoresist properties on lithographic performance. The simulation results examine various photoresist model parameters and their impact on typical lithographic process indicators such as depth of focus and exposure latitude. These results show the importance of the photoresist absorption parameter A (micrometers ^-1) and the developer selectivity n in determining lithographic performance. High values of n provide increased process latitude, while low values of A reduce the required exposure energy.

The development processes in microlithography consist in removing of exposure region with rate V exceeding the dissolution rate of unexposed regions. The technology characteristics of the resists are the contrast, the sensitivity and the resolution. These characteristics depend on the resist response to the irritation and on the development conditions. We want to devote this work to the analysis of correlation between the resolution, the contrast, the sensitivity determined by the indicated method and the exposure dose for homogeneous irradiation.

In this work the photochemistry and photoimaging of derivatized polythiophenes will be described. Poly(3-alkylthiophenes) are inherently photolabile. One of the photochemical products leads to cross-linking, which can be utilized in photolithography. During this process, (pi) -conjugation remains virtually intact, and conductivities remain the same as the pristine polymer. The photosensitivity of this polymer to cross-linking, and thereby, insolubilization, can be enhanced by copolymerization with thienyl moieties possessing the methacryoyl functionality. In addition to photoimaging, the stability of the conducting state will be discussed. Strategies for enhancing stabilization will be addressed with a view to assimilating organic wires into integrated circuitry.

Thermal stability of photoresists has been measured using laser scatterometry. This new laser scatterometry technique is more rapid and more sensitive than scanning electron microscopy (SEM) methods. Patterned resists are slowly heated while various diffraction order intensities are measured. Changes in the diffraction intensities correlate well with thermal stabilities measured by SEM methods.

The patented device and procedure described provide a method of processing the flat, thin-film coated surfaces encountered in the ultraclean manufacture of integrated circuit wafers, photomasks, panel displays or other similar substrates. The device provides a means of delivering liquids and vapors to those surfaces while temperature, evaporation and particulate contamination are controlled as a natural consequent of its physical configuration. The essential mechanism exploits the surface tension of liquids and the differences in the wettability of surfaces. By juxtaposing the target surface with a prepared surface on the processing device and maintaining a separation of a few millimeters, the gap formed provides a reaction space into which liquids are easily distributed exploiting so-called capillary behavior. While placing the liquid reagent on the hydrophobic, horizontal surface of the processor, the hydrophilic substrate surface suspended above it is transported laterally. The substrate surface then engages the liquid edge which, driven by its own surface tension, quickly fills the gap. The ending of the reaction and removal of the liquid is effected by further transporting the substrate with its captive liquid reactants to a trench provided in the processor surface where the liquid flows down and away. Thus, the processor surface is seen as a series of 'mesas' allowing a sequence of wet process, rinse and vapor treatments, all with the simple lateral movement of the substrate. The effects of improved reaction kinetics on process precision as well as the benefits mentioned above are discussed and compared to previous immersion and spin methods. Critical dimension measurement data are presented from large photomask substrates processed by the instrument.

In this work the cationic photoinduced crosslinking of the diglycidylether of 4-hydroxyphenyl-4'-hydroxybenzoate was investigated in the liquid crystalline state as well as in the isotropic state. The photochemical curing technique was applied because only small amounts of the initiating species were necessary to form networks of epoxy compounds. As the photoinitiator system, a mixture of (alpha) , (alpha) '- dimethoxydeoxybenzoin and dicumyliodonium-hexafluorophosphate proved to be the most effective. FTIR-spectra of the networks were compared with those of the starting material. Only small amounts of nonreacted epoxy groups were found in the networks synthesized either in the isotropic state or in the liquid crystalline state. Furthermore, different results were obtained with DSC-measurements. Networks prepared in the liquid crystalline state showed two glass transition temperatures. In contrast, networks synthesized in the isotropic state have only one glass transition temperature. Moreover, polarization microscopy was used to find ordered structures. The networks formed in the liquid crystalline state showed frozen ordered structures. Heating of such networks above the melting point of the starting material did not lead to a change of the frozen ordered structures. Additionally, differences between the frozen ordered structure of the networks and the crystalline structure of the starting compound were observed by this method. Finally, the material properties of networks with ordered structures are different from common networks with disordered structures.

Radical polymerization kinetics of different kinds of diacrylates was investigated in linear polymers (binders) by using an isoperibolic calorimeter. For all experiments benzoin compounds were added as photoinitiator. The ester between acrylic acid and bisphenol-A-diglycidylether (DDGDA) and hexamethylenediacrylate were used as monomers. Both compounds have a high limiting conversion and a large polymerization rate in the binders investigated. Additionally, three kinds of termination reaction were observed: first order, second order, and primary radical termination. The last reaction was mainly found in the case of using the hexamethylenediacrylate monomer. The materials were investigated by DSC to determine the phase behavior. Both monomers form one phase with the binder (polymethylmethacrylate, PMMA). In contrast, a phase separation was observed between the crosslinked hexamethylenediacrylate and PMMA. Formations of semi- interpenetrating networks were found in the case of crosslinked DDGDA and PMMA. The glass transition temperatures were determined at different polymerization degrees also. The obtained results indicate that most of the network formation occurred in the glassy state. Fluorescence probe technique was applied to study changes in the mobility during network formation. The fluorescence probe crystal violet (CV) was used because this compound shows a strong free volume-dependent fluorescence. It was found that in the glassy state, where most of networks were formed, a large variation of the molecular mobility was observed during irradiation of the photopolymers. This result was in agreement with the observations during DSC experiments.

We have demonstrated that highly reliable resist patterning is achieved by effectively removing reaction products by means of ultrasonic development and the addition of surfactant to the developer. It has been found that the reaction products form a stagnant layer, resulting in preventing the resist-developer reaction. Thus, the existence of the stagnant layer leads to the fluctuation of the developing characteristics and the degradation of the resist contrast, resist sensitivity, and process margins. To quickly remove the stagnant layer from the resist-developer reaction interface, two techniques are employed: physical method of developing with ultrasonic agitation and chemical method of the addition of surfactant to developer. In addition, it has been found that the agitation of developer lowers the etch rate of (100) Si and prevents the appearance of pyramid-shaped etch pits on Si surface.

A novel synthetic aqueous photoresist has been developed for CCD micro color filters. The resist consists of four-components methacrylate copolymers as a resin and diazo compound as a photosensitizer. The resist uses water as a solvent and a developer. The performance characteristics of this resist are the sensitivity of less than 100 mJ/cm², the contrast of more than 8 ((gamma) value), the resolution of less than 1.5 micrometers lines and spaces, the thermal stability of 250 degree(s)C (the transmittance of more than 90% at visual wavelength) and the shelf life of more than 10 days at 23 degree(s)C. It is easily dyed and dyefixed. Micro color filters for 1/4 inch CCD successfully fabricated by using this resist.

In this paper the chemical and thermal properties of electron beam cured photoresist were investigated and compared with conventional thermal curing methods. The photoresist used in this investigation was AZ P.4620, a positive novolak based photoresist formulated for thick film applications. The films were exposed with varying dosages using an electron beam photoresist curing system. The photoresist films were then analyzed for residual solvent content, photoactive compound decomposition, percentage of crosslinking, and film shrinkage as a function of exposure dose. These properties were then compared with the properties of resist films cured using conventional thermal curing methods. A model of photoresist curing chemistry as a function of dose is proposed as well as a method for optimizing the cure of the photoresist for different applications.

Ultrathin films in the thickness range of 2-10 nm were deposited by plasma polymerization. An AFM (atomic force microscope) was used to evaluate the film surface uniformity. The measured surface roughness of these films is of the order of 0.1 to 0.3 nm. It suggests that uniformly smooth, pinhole free ultra thin film organic films suitable for electronic applications can be deposited by plasma polymerization. The deposited films were tested for nanometer scale patterning using an atomic force microscope. Process of contact electrification was used to deposit local electric charge on these surface enhanced reactions with some adsorbates thus creating patterns.

Increased interest in fabricating deep submicron gratings for diffractive optics has resulted in stronger emphasis on higher performance processing techniques. Gratings with well formed line space dimensions of less than 0.3 micron are needed to fill most applications for planar waveguide gratings on GaAs. Electron beam tools of even modest beam energy have little difficulty in patterning isolated deep submicron features. However, patterns of closely spaced features with dimensions of less than 0.4 micron line and space on GaAs suffer increasingly greater contrast degradation because of the interproximity effect. Higher beam energies or enhanced contrast processing becomes necessary. Higher contrast development techniques may extract more information from the latent image and perhaps provide better process latitude, given the same electron beam pattern generation equipment that was suitable for larger size features. In this paper, MIBK and Cellosolve acetate based developers are investigated for processing areal features and grating patterns down to 0.1 micron line and space dimensions. A Leica Instruments Electron Beam Microfabrication tool EBMF 10.5 was used at 30 keV beam energy to pattern PMMA resist on host Gallium Arsenide substrates. Samples were prepared by a thorough cleaning, followed by a dehydration bake and spin coating of PMMA (496 K mw). A two part softbake regimen was performed to promote adhesion. Lithography was done with close attention given to beam current, spot size and machine calibration to insure that all samples were patterned identically. No post bake is necessary for PMMA. Latent images were then developed in different developers. MIBK based developers in dilution of 1:1, 1:2 and 1:3 with isopropyl alcohol were examined for determination of dose to clear and dose latitude.

The behavior of the focus-exposure window for a half micron process was analyzed across a range of resist thicknesses. The range examined was selected to encompass a minima through maxima region of the I-line swing curve. This analysis is shown for an I-line resist; the undyed version contrasted to the dyed. The process tube characterization method calculates the common corridor exposure latitude for the two resist data sets. The common corridor for a given resist system defines that area in the focus-exposure plane that meets a single process specification for all the resist thicknesses in the selected swing curve range. In this study the undyed resist demonstrates a superior process window at a given resist thickness but is found to be inferior to the dyed resist as determined by the process tube characterization method.

The microfraction of VLSI requires to realize the precision of submicron or even more delicate. Therefore ,the photoresist used in etching technology is required to be made thenner and more even. Yet ,in the etching technology of VLSI device nowadays , it is very difficult to realize it , by the traditional organic photoresist. As to the coarse substrate made by photoetching more than once , the resist film must be thick enough to cover the previous device pattern on substrate by using organic resist and traditional coating way. For example , the nearly 1pm high steps of oxide or metaffic layer are often met in the research of VLSI devices. In order to over them ,the thickness of organic photoresist should be more than 1im at least ,which is much thicker than the desired film thickness for higher distinction. And owing to the uneven thickness of steps , the distortion of etched graphs are easy to arise , which limit the improvement of photoetching precision.

This contribution emphasizes resist application site by communicating lithographic results for AZ DX 46, obtained using the GCA XLS 7800/31 stepper, NA equals 0.53, equipped with krypton fluoride excimer laser ((lambda) equals 248 nm), model 4500 D, as exposure source, delivered by Cymer Laser Technologies. As far as delay time experiments are concerned ASM-L PAS 5500/70 stepper, NA equals 0.42, was used in combination with Lambda Physik excimer laser, model 248 L.