Cationic graft polymerization lithography is a variation of top surface imaging schemes. This technique uses a spin-coated, inert polymer film as a photoacid generator carrier. UV exposure is used to generate acid in the top surface of the film. A vapor-phase reaction between the generated acid and a silicon-containing monomer occurs in the exposed areas. The silicon-containing polymer formed, or grafted, on the surface is used as an oxygen etch mask for subsequent pattern transfer through the underlying film. A modular approach can be employed in material design, allowing optimization of characteristics of each component. A key criterion is introduced by the interaction between the transfer layer and the graft monomer. The solubility of the monomer into the inert polymer layer influences the growth behavior, and should be minimized to prevent background silylation and potential swelling. The solubility of the monomer in the inert polymer is characterized by measuring the equilibrium sorption of the vapor into the polymer. Solubility behavior can also be estimated from group contribution theories. These estimates guide the rational design of materials for this lithography process. Based on this analysis method, a new monomer, bis(vinyloxymethyl)dimethylsilane, has been designed and tested. Its sorption into a typical polymer layer has been characterized experimentally. Kinetic growth rate data have been obtained on a quartz crystal microbalance system, and preliminary imaging results using 248 nm exposure are presented.
Water is known to play a key role in the solubility switching reaction of novolac-diazonaphthoquinone photoresists and certain chemically amplified resists. In order to quantitatively study these effects, an environmental chamber was built in which the % RH could be controlled while the extent of acid catalyzed deprotection was monitored during the post exposure bake by reflectance FTIR spectroscopy. The extent of acid catalyzed deprotection of tBOC, KRS-XE, UV6, and a tBOC-poly(hydroxystyrene) copolymer have been measured as a function of time over a range of 0-60 % RH. For tBOC, the deprotection reaction rate was found to slow considerably as the %RH was increased. Also, the relative film shrinkage varied considerably with varying % RH. Several possible mechanisms for the dependence of the reaction rate and thickness loss on % RH were investigated. For KRS-XE, the deprotection reaction kinetics were found to increase as the % RH was increased, which was an expected trend. For UV6 and the tBOC-PHOST copolymer, no change in deprotection reaction rate was observed with changes in %RH.
New microlithography patterning technologies must be developed in order to meet the demands of advanced semiconductor manufacturing. This paper describes the development of a new top surface imaging technique that is designed to circumvent the difficulties associated with developing next generation single layer resists. Graft polymerization lithography is an extension of top surface imaging in which exposure creates an acidic surface that activates monomer deposition on top of the base layer. Silicon-containing monomers were synthesized in order to meet the graft polymerization process requirements. A QCM-monitored deposition system was developed to study the fundamental behavior of the deposition process as a function of temperature, pressure, and photoacid generator (PAG) loading. Volumetric, bulk polymer sorption measurements were used to provide insight into the critical sorption behavior that drives the deposition process. These fundamental studies led to a proposed process mechanism that explains the experimentally observed behavior. Finally, proof of concept imaging experiments were conducted that demonstrate the graft polymerization process through all lithographic steps.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.