Takao Higuchi

CAR blanks feasibility study results

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.

CAR blanks performance for advanced reticle fabrication

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.

Photomask blanks enhancement by optimizing resist baking and coating for advanced e-beam reticle fabrication

Advanced e-beam reticle fabrication, including phase-shifting mask (PSM) and optical proximity correction (OPC) reticle, has created a growing need for a resist system with wider process latitude, superior resolution and linearity, better CD uniformity. Some of aqueous-based DNQ-novolak resist systems, including chemical amplified one, have been proposed, however, their feasibility has not reached practical level yet. Accordingly, high-molecular polymer resist systems, conventional PBS for instance, are still the majors. We studied resist behavior to soft-baking conditions for the majors of high-molecular polymer resists in order to bring out their potential at its maximum. We also attempted to optimize coating thickness with an intention of superior linearity in conjunction with a risk of clear defects increase. We then examined very basic patterning features of each resist system in soft-baking latitude, coating thickness latitude, exposure dose latitude, develop latitude, adhesion and so on to make clear advantages and disadvantages of each the above resist system. This paper describes details of our findings on photomask blanks enhancement by optimizing soft-baking condition and coating thickness for the conventional high-molecular polymer resist systems for advanced e-beam reticle fabrication.

Laser resist screening for iP3500/3600 replacement for advanced reticle fabrication

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, γp(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.

Performance study on thin resist for advanced reticle fabrication

In this paper we discuss advantages and disadvantages of super-thin resist coatings for both e-beam and laser applications. First, we verify advantages of super-thin ZEP7000, particularly evaluating the hole-pattern linearity. Second, we discuss disadvantages of super-thin ZEP7000, including pinhole defect risks. Finally, we examine advantages and disadvantages of super-thin laser resist coatings.

Comparative evaluation results of CMS replacement resist for e-beam reticle fabrication

Looking for a CMS replacement resist is an urgent assignment for e-beam reticle fabrication, which enables us to maintain flexibility of reticle fabrications. CMS-EX series was discontinued in 1995, and its stored resin will be used up completely sooner in this year 1999. We then tried to find a replacement resist, and examined commercially available resist SEL-N1000, SEL-N1100 and ZEN4400. We studied their behavior to post-spin baking temperature respectively, in order to bring out their potential, by investigating isolated clear pattern fidelity in details as it was the most tough one to make by a negative-working resist. This paper describes our comparative evaluation results of commercially available negative-working resists to determine a CMS-EX-S replacement for e-beam reticle fabrication.