Advanced DRAM technology relies heavily on 193nm immersion lithography. Negative tone develop (NTD) layers are becoming increasingly important particularly in nodes below 20nm. NTD is particularly useful for patterning holes on the wafer. Cut layers for multi-patterning (MP) applications and bit line contact structures are common uses of NTD in DRAM. Patterning these structures pose lithographic challenges around process window (PW), layer-to-layer overlay, and critical dimension (CD) control. The mask plays a critical role in optimizing all of these attributes. In this paper, we explore multiple mask enhancements to optimize wafer performance for NTD contacts. These include mask process and mask blank conditions, as well as a data enhancement technique generally known as mask process correction (MPC). Specifically, we implement a litho-aware MPC Application (LAMA) to optimize mask pattern fidelity. Finally, we harmonize these mask enhancements with optimizations to wafer exposure conditions and optical proximity correction (OPC) to demonstrate capability improvement in NTD contact lithography.
Next Generation Lithography (NGL) technologies require masks that are significantly different from each other and from conventional photomasks but possess many similarities and processing challenges. The Next Generation Lithography Mask Center of Competency (NGL-MCOC) was formed to identify these process issues and potential areas for commonality and eventually provide a commercialization path for NGL masks. The NGL-MCOC consists of a partnership between Photronics and IBM. The IBM advanced mask facility is applying the technology developed for x-ray masks to other NGL technologies, and Photronics is supplying the organization and eventual commercialization of the technology. To broadly address NGL mask issues, the NGL-MCOC has collaborated with the NGL industry champions. Mask blanks have been written for SCALPEL./eLith, EUV-LLC, and Infineon/IPL. By utilizing common patterns and as much common processing as possible, rapid process development and efficient comparison of the mask issues with the different NGL technologies is quickly achieved. In addition, the NGL-MCOC has fabricated mask blanks for SCALPEL and stencil to evaluate new materials and process options.
Masks for next generation lithographies present difficult technical processing, challenges for meeting the demanding requirements of future lithography. The Next Generation Lithography Mask Center of Competency is applying the proximity x-ray mask technology developed by the IBM advanced mask facility to all major NGL technologies. Mask fabrication has been demonstrated for proximity x-ray, scattering and stencil electron beam projection, and extreme UV lithographies. The imaging layer for these mask technologies differ significantly from one another and yet present similar processing challenges. This paper discuses the process technology developed at the NGL-MCOC associated with patterning the absorber layers. Issues with chemically amplified resist coating and baking and absorber etching are identified and associated with observed image size variations. The difficulty in the aspect ratio of. the absorber drives much of the processing requirements for the different NGL formats. High-aspect ratios on stencil and proximity x-ray masks require more difficult etch processes than those on lower-aspect ratio absorbers.
Mask fabrication is one of the difficult challenges with all Next Generation Lithography (NGL) technologies. X-ray, e-beam projection, and ion-beam projection lithography all use some form of membrane mask, and extreme ultraviolet (EUV) lithography uses a reflective mask. Despite some differences, the various mask technologies share some common features and present similar fabrication difficulties. Over the past several years, the IBM Advanced Mask Facility (AMF) has focused on the fabrication of x-ray masks. Several key accomplishments have been demonstrated including fabricating masks with critical dimensions (CD) as small as 75 nm, producing line monitor masks in a pilot line mode to evaluate mask yields, and fabricating masks to make working microprocessors with the gate level defined by x-ray lithography. The experience on fabricating 1X x-ray masks is now being applied to the other NGL mask technologies. Progress on membrane and absorber materials can be applied to all the technologies, and patterning with advanced e-beam writing with chemically amplified resists utilizes learning from writing and baking on x-ray membrane masks.
Conference Committee Involvement (8)
Photomask Technology
21 September 2020 | Online Only, California, United States
Photomask Technology
16 September 2019 | Monterey, California, United States
Photomask Technology
17 September 2018 | Monterey, California, United States
Photomask Technology
11 September 2017 | Monterey, California, United States
Photomask Technology
12 September 2016 | San Jose, California, United States
Photomask Technology 2015
29 September 2015 | Monterey, California, United States
Photomask Technology 2014
16 September 2014 | Monterey, California, United States
SPIE Photomask Technology
10 September 2013 | Monterey, California, United States
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