In the field, each customer uses their owned designed reticle case as for shipping, storage. To modify the case is so expensive that it is very difficult to improve, especially in time respect. At the blank suppliers, they ship their mask blanks packing into their owned designed multiple shipper, however the market needs single shipper with next generation blanks to prevent from particle and outgas of case material damage. At the mask shops, most of them use MP567 (Trade mark of Dainichi Shoji K.K.) single case which was designed about 15years ago to ship their products to their customers. It is not designed for robot handling, so contamination from manual handling makes reticle damaged. Adhesive tape is also required to seal it, so chemical contamination will be occurred on quartz glass, i.e. haze. At the IC fabs, scanner case such as Nikon, Canon and ASML case is the most common in their process. However these cases are not airtight, so they cannot be handled under class 10000 circumstances. RSP (Reticle SMIF Pod) has a capability of automatic transportation, however it is not airtight case. We develop new mask case named Universal Reticle Pod (URP) at affordable price, airtight and chemical tight so as to be used as shipping, storage and process case. We evaluate it as blanks shipping case, so we would like to report its results.
DUV (Deep Ultra-Violet) laser reticle writers were released to the market for advanced reticle fabrication in 2002, AZ-DX1100P resist (for KrF lithography) has historically been employed for these tools. To respond to further high-end requirements, a new resist more friendly to DUV reticle fabrication is needed. FEP171 is a positive-type CAR (Chemically amplified resist) developed for EB reticle fabrication, which is sensitive to DUV as well. In this paper, we have investigated the applicability of FEP171-coated blanks for DUV reticle fabrication. As the results show, FEP171 could achieve 200 nm patterns by DUV exposure. FEP171 blanks showed superior performance in resolution and profile as compared to AZ-DX1100P. FEP171 blanks are promising for DUV reticle fabrication as well as EB reticle fabrication.
A negative-CAR for EB reticle fabrication beyond 100 nm node is needed, which is superior in performance such as resolution, sensitivity, pattern quality, CD movement by process delays (PCD, PED) and process latitudes. We started preliminary screening on negative-CARs, and more than 10 resists out of 3 suppliers were examined including some that were still under development. Then, three CARs (A-2, B-1 and C-3) was selected as candidates, and those candidates were evaluated in 'resolution and sensitivity', 'pattern quality', 'CD movement due to process delays' and 'process latitudes'. B-1 turned out to be the best choice in total performance. In addition, thinning coating thickness was investigated for resolution improvement. A negative-CAR for EB reticle fabrication beyond 100 nm node is needed, which is superior in performance such as resolution, sensitivity, pattern quality, CD movement by process delays (PCD, PED) and process latitudes. We started preliminary screening on negative-CARs, and more than 10 resists out of 3 suppliers were examined including some that were still under development. Then, three CARs (A-2, B-1 and C-3) was selected as candidates, and those candidates were evaluated in 'resolution and sensitivity', 'pattern quality', 'CD movement due to process delays' and 'process latitudes'. B-1 turned out to be the best choice in total performance. In addition, thinning coating thickness was investigated for resolution improvement.
In order to provide a platform for the industry, we have been working on positive-working CAR screening by joint-works with resist-makers. In this paper, firstly, we did validation of a technique 'dark erosion analysis by excess develop' on our latest benchmark CAR C-2, to re-introduce our baking optimization technique to all the blanks users. The baking condition described by the technique (the sweet spot) certainly provided us a superior pattern profile, a longer blanks life, and better sensitivity stability for PEB time. To find a CAR that exceeds C-2 performance, we continued CAR screening. A CAR with 'less-footing' and 'high-sensitivity' was found, however, it had still a difficulty of terrible 'spray-damages' due to insufficient remaining thickness after develop. Desiccant (silica-gel) worked significantly to extend CAR blanks life, however, we found that it was not available for practical use unfortunately due to excess particle contamination during shipment. As a technique to solve 'spray-develop damage' issue, it was certainly effective to form a protection layer, and aqueous TAR over-coating layer could be an option to prevent resists film from the spray-damages. Finally, we reported negative-working CARs screening results. And some negative CARs were superior to the most popular one today for sensitivity or pattern profile, however, they had a difficulty of excess-undercut.
For advanced EB reticle fabrication with CAR blanks, we have been trying blanks life improvement and resolution enhancement. This paper describes several options to extend CAR blanks life by shipping package and storage manners. Dry-N2 purged shipping package and desiccant showed efficiency for PCD improvement. However, desiccant is not available for products since it is not investigated yet if particle contamination could be happened. To extend blanks life after blanks package opened, we blanks maker really recommend the fresh dry-N2 purged box (overflowed) as an ideal storage manner, or regular shipping box storage at least. We tried a BARC as isolator and thinning CAR for resolution enhancement, and found that a neutral-BARC showed an improvement. However, we needs further study about its feasibility, especially for coating uniformity and defect quality control. Thin resist showed almost no improvement for CAR resolution enhancement. To improve CAR performance further, we continuously need the resist-makers cooperation to design and develop a CAR that provides us footing-less pattern profile and long-life after coating.
This paper will describe resist screening results for iP3500/3600 replacement for the advanced laser reticle fabrication, resist coating thickness optimization proposal for the next generation as well. THMR-M100 (TOK) showed the best pattern profile with sharp shoulders and almost with no footing, and a newly developed resist, a joint-work between HOYA and a resist maker, showed the best performance in adhesion to chrome. However, there was not the best selection found unfortunately by this screening, which exceeded iP3500 in linearity and iso-dense bias (IDB) that was indispensable one for the advanced laser reticle fabrication. As regards coating thickness, we selected 307.5 nm thick as a candidate for coating thickness standard for the future with considering resist resolution performance such as linearity, y p(0-80) value and undercut, in conjunction with a risk of clear pinhole defects. For more precise comparison of iso-dense bias (IDB) performance, it would be better that the examination method is standardized because of the design pattern dependence of IDB.
The rise of a high acceleration voltage E-beam exposure tool has created a growing need for a chemically amplified resist system with high sensitivity, high contrast, superior resolution, superior PCD and PED stability. While mask- makers have been procuring resist coated blanks, it is generally considered that CARs must be spun on just prior to exposure due to its very short life after coating. However, it is general intention in the industry to stay in the same manner even with CARs for the next generation, which is the mission of blanks supplier also. In order to study feasibility for CARs coated blanks supply, we started screening CARs that were commercially available at present by patterning evaluation especially for PCD stability. We first tried to establish PSB and PEB optimization technique for CARs by using a benchmark resist of RE-5153P. We also tried to establish a stress tests for PCD stability by using NH3 gas and dry-N2 gas mixture. Then, we did comparative evaluation in patterning performance such as sensitivity, contrast, resolution, process latitude, PED and PCD stability among RE-5153P, EP-009, TLE-011, UVIIHS and others. ZEP7000 was also examined as another benchmark, which was the most popular resist at present for advanced EB reticle fabrication in the industry. This paper describes chemically amplified resist feasibility study result especially for blanks supply for the next generation e-beam reticle fabrication.
Appearance of e-beam exposure tools with a high acceleration voltage has created a growing need for a chemically amplified resist (CAR) system with high sensitivity, high contrast, superior resolution and superior post-coating delay stability. While mask-makers have been procuring resist-coated photomask blanks, it is generally considered that CARs must be spin-coated just prior to exposure due to its short shelf-life after coating. However, the industry would like to continue procuring pre-CAR-coated blanks from a blanks supplier, who also intends to support mask-makers in this way. This paper describes the results of a feasibility study on mask blanks coated with CARs for advanced e-beam reticle fabrication.