International Technology Roadmap for Semiconductors 2003の要求清浄度について － シリコンウエハ表面と雰囲気環境に要求される清浄度, 分析方法の現状について －

The ability to manufacture a nanogap in between two electrodes has proven a powerful catalyst for scientific discoveries in nanoscience and molecular electronics A wide range of bottom-up and top-down methodologies are now available to fabricate nanogaps that are less than 10 nm wide However, most available techniques involve time-consuming serial processes that are not compatible with large-scale manufacturing of nanogap devices The scalable manufacturing of sub-10 nm gaps remains a great technological challenge that currently hinders both experimental nanoscience and the prospects for commercial exploitation of nanogap devices Here, available nanogap fabrication methodologies are reviewed and a detailed comparison of their merits is provided, with special focus on large-scale and reproducible manufacturing of nanogaps The most promising approaches that could achieve a breakthrough in research and commercial applications are identified Emerging scalable nanogap manufacturing methodologies will ultimately enable applications with high scientific and societal impact, including high-speed whole genome sequencing, electromechanical computing, and molecular electronics using nanogap electrodes

Scalable Manufacturing of Nanogaps

An electron beam (EB) lithography method using inedible cellulose-based resist material derived from woody biomass has been successfully developed. This method allows the use of pure water in the development process instead of the conventionally used tetramethylammonium hydroxide and anisole. The inedible cellulose-based biomass resist material, as an alternative to alpha-linked disaccharides in sugar derivatives that compete with food supplies, was developed by replacing the hydroxyl groups in the beta-linked disaccharides with EB-sensitive 2-methacryloyloxyethyl groups. A 75 nm line and space pattern at an exposure dose of 19 μC/cm2, a resist thickness uniformity of less than 0.4 nm on a 200 mm wafer, and low film thickness shrinkage under EB irradiation were achieved with this inedible cellulose-based biomass resist material using a water-based development process.

Inedible cellulose-based biomass resist material amenable to water-based processing for use in electron beam lithography

ArF immersion lithography combined with double patterning has been used for fabricating below half pitch 40nm devices However, when pattern size shrinks below 20nm, we must use new technology like quadruple patterning process or next generation lithography (NGL) solutions Moreover, with change in lithography tool, next generation mask production will be needed According to ITRS 2013, fabrication of finer patterns less than 15nm will be required on mask plate in NGL mask production 5 years later [1] In order to fabricate finer patterns on mask, higher resolution EB mask writer and high performance fabrication process will be required In a previous study, we investigated a potential of mask fabrication process for finer patterning and achieved 17nm dense line pattern on mask plate by using VSB (Variable Shaped Beam) type EB mask writer and chemically amplified resist [2][3] After a further investigation, we constructed higher performance mask process by using new EB mask writer EBM9000 EBM9000 is the equipment supporting hp16nm generation's photomask production and has high accuracy and high throughput As a result, we achieved 155nm pattern on mask with high productivity Moreover, from evaluation of isolated pattern, we proved that current mask process has the capability for sub-10nm pattern These results show that the performance of current mask fabrication process have the potential to fabricate the next-generation mask

/pdf/high-performance-mask-fabrication-process-for-the-next-27jufd978y.pdf

High performance mask fabrication process for the next-generation mask production

Electron beam (EB) lithography used for mask and mold fabrication is an indispensable technology in the lithography used for high-volume production of semiconductor devices. With the reduction in the critical dimensions of semiconductor devices, the requirement for EB lithography also becomes severe. In this study, the feasibility of single nano patterning using EB lithography with a chemically amplified resist process was investigated. The latent images of line-and-space patterns with a 7 nm quarter-pitch (7 nm space width and 21 nm line width) were calculated on the basis of sensitization and reaction mechanisms of chemically amplified EB resists. Simulations indicated that the line-and-space patterns with 7 nm quarter-pitch can be resolved with line edge roughness of 0.9–1.9 nm with a sensitivity of 270 µC cm−2 using a 3 nm electron beam.

https://iopscience.iop.org/article/10.7567/JJAP.54.056501/pdf

Theoretical study of fabrication of line-and-space patterns with 7 nm quarter-pitch (7 nm space width and 21 nm line width) using electron beam lithography with chemically amplified resist processes: I. Relationship between sensitivity and chemical gradient

To investigate the possibility to catch up the NGL mask pattern size scaling strategy which indicated in ITRS2012, the performance of conventional mask fabricating process was examined. Current EB resist used for mask fabrication doesn’t have enough performance to resolve below hp20nm pattern. With newly developed CAR resist, the resolution limit reached to hp18nm pattern. Furthermore by using higher performance EB writer, the possibility to resolve up to hp16nm pattern was showed. The impact of proximity effect to the resist performance was examined. The resist damage induced by proximity effect degrades the resolution limit about 2nm. This is a serious problem for NGL mask manufacturing. Reducing the impact of proximity effect is one of the major challenges for developing higher resolution EB resist.

https://www.jstage.jst.go.jp/article/photopolymer/27/4/27_511/_pdf

The Performances and Challenges of Today’s EB Lithography and EB-resist Materials

Nano imprint lithography (NIL) is one to one lithography and contact transfer technique using template. Therefore, the lithography performance depends greatly on the quality of the template pattern. In this study, we investigated the resolution and the defect level for hole patterning using chemical amplified resists (CAR) and VSB type EB writer, EBM9000. To form smaller pattern with high quality, high resolution resist process and high sensitivity etching process are needed. After these elements were optimized, we succeeded to form 24 nm dense hole pattern on template. In general, it is difficult to suppress the defect density in a large area because of fogging effect and process loading and so forth. However, from the view point of defect quality, 26 nm hole pattern is achieved to form with practical level in a large area. Therefore, we indicate the capability of forming 26 nm hole master template which will be required in 2019 from ITRS2013. These results show that this process is possible to obtain less than 30 nm hole pattern without enormous writing time. As future work, we will imprint master to replica template and check the printability.

High resolution hole patterning with EB lithography for NIL template production

UV nano imprint lithography (UV-NIL) has high-throughput and cost-effective for complex nano-scale patterns and is
considered as a candidate for next generation lithography tool. In addition, NIL is the unmagnified lithography and
contact transfer technique using template. Therefore, the lithography performance depends greatly on the quality of the
template pattern.
According to ITRS 2013, the minimum half pitch size of Line and Space (LS) pattern will reach 1x nm level within
next five years. On the other hand, in hole pattern, half pith of 2x nm level will be required in five years. Pattern shrink
rate of hole pattern size is slower than LS pattern, but shot counts increase explosively compared to LS pattern due to its
data volume. Therefore, high throughput and high resolution EB lithography process is required.
In previous study, we reported the result of hole patterning on master template which has high resolution resist
material and etching process. This study indicated the potential for fabricating 2xnm hole master template [1].
After above study, we aim at fabricating the good quality of 2xnm master template which is assured about defect, CD
uniformity(CDU), and Image placement(IP). To product high quality master template, we develop not only high
resolution patterning process but also high accuracy quality assurance technology. We report the development progress
about hole master template production.

High-performance fabrication process for 2xnm hole-NIL template production

Photomask used for optical lithography has been developed for purpose of fabrication a pattern along with finer
designed rules and increase the productivity. With regard to pattern fabrication on mask, EB (Electron beam) mask
writer has been used because it has high resolution beam. But in producing photomask, minimum pattern size on mask is
hits a peak around 40nm by the resolution limit of ArF immersion systems. This value is easy to achieve by current EB
writer. So, photomask process with EB writer has gotten attached to increase turnaround time.
In next generation lithography such as EUV (Extreme ultraviolet) lithography and Nano-imprint lithography, it is
enable to fabricate finer pattern beyond the resolution limit of ArF immersion systems. Thereby the pattern on a mask
becomes finer rapidly. According to ITRS 2012, fabrication of finer patterns less than 20nm will be required on EUV
mask and on NIL template. Especially in NIL template, less than 15nm pattern will be required half a decade later. But
today’s development of EB writer is aiming to increase photomask’s productivity, so we will face a difficulty to fabricate
finer pattern in near future.
In this paper, we examined a potential of mask production process with EB writer from the view of finer pattern
fabrication performances. We succeeded to fabricate hp (half-pitch) 17nm pattern on mask plate by using VSB (Variable
Shaped Beam) type EB mask writer with CAR (Chemically Amplified Resist). This result suggests that the photomask
fabrication process has the potential for sub-20nm generation mask production.

Keisuke Yagawa

Papers

High performance mask fabrication process for the next-generation mask production

The Performances and Challenges of Today’s EB Lithography and EB-resist Materials

High resolution hole patterning with EB lithography for NIL template production

High-performance fabrication process for 2xnm hole-NIL template production

Potential of mask production process for finer pattern fabrication