Yasunori Yokoya

CARs blanks feasibility study results for the advanced EB reticle fabrication (IV)

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.

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.

Photomask blanks enhancement for the laser reticle writer

The laser writer (CORE) has come to the front for advanced reticle fabrication so that photomask blanks enhancement is much more to be desired for the application. We have investigated novel techniques to bring out photomask blanks potential to expand process windows for the laser writer application, which included optimization of resist coating thickness by studying standing wave effect, optimization of soft-baking by studying resist behavior to soft-baking temperature, and optimization of pretreatment by studying resist adhesion characteristic to chromium oxide based film and molybdenum silicide based film. We have also explored very basic features of several resists in a comparison between the most popular OCG-895i and new candidates under an optimized coating thickness and soft-baking temperature respectively for each resist. This paper describes details of our findings on novel techniques for photomask blanks enhancement, and a comparison result of several resists in very basic features, in order to expand process windows to meet critical dimension performance requirements of advanced reticle fabrication by the laser writer.

Multi-layer resist system for 45-nm-node and beyond: Part II

The CD requirements for the 45nm-node will become tighter so as it will be difficult to achieve with 65nm node technologies. In this paper, a method to improve resolution by using DRECE (Dry-etching Resistance Enhancement bottom-Coating for Eb) will be described. After all, DRECE has five times as high dry-etch resistance than the EB resist, and this enables to accept higher anisotropic dry etching condition. By optimizing dry etching conditions, the CD iso-dense bias dropped to 1/3 and the CD shift was reduced to 1/2. Also, there was no negative effect to CD uniformity. From these results, we propose the use of DRECE for the 45nm-node technology.

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.