Environmentally stable lithography with acidity-optimized TARC material

Kenichi Asahi; Yoshiyuki Tani; Ryuichi Yoshida; Koji Shimomura; Yusuke Takano; Yoshino Nishiwaki; Hatsuyuki Tanaka

doi:10.1117/12.388359

23 June 2000 Environmentally stable lithography with acidity-optimized TARC material

Kenichi Asahi, Yoshiyuki Tani, Ryuichi Yoshida, Koji Shimomura, Yusuke Takano, Yoshino Nishiwaki, Hatsuyuki Tanaka

Proceedings Volume 3999, Advances in Resist Technology and Processing XVII; (2000) https://doi.org/10.1117/12.388359
Event: Microlithography 2000, 2000, Santa Clara, CA, United States

Abstract

We have found the Post Coat Delay (PCD) problem in an environment, where ammonia contamination is not controlled, with Top Anti Reflective Coating (TARC) process. The Chemically Amplified (CA) resist coated wafer using the conventional TARC with pH equals 3.2 was kept in the ammonia contaminated environment between the TARC coating and the exposure, the 'T-top' shape resist pattern was formed. To solve the PCD problem, we are considering the advantage to optimize the acidity in TARC material. In the case of using a higher pH TARC (e.g. pH >= 2.5), the 'T-top' shape resist pattern was formed. The TARC was neutralized, after contact with ammonia contamination during the PCD duration, the generated acid by the exposure in the CA resist diffused into the TARC without attacking the protective groups of resist polymer during the Post Exposure Bake (PEB) step. The lack of acid in the resist surface resulted in the formation of the 'T-top' shape resist pattern. On the other hand, in the case of using a lower pH TARC (e.g. pH >= 1.9), the remarkable film thickness loss occurred. Once a lower pH TARC was coated, the acid in the TARC diffused to the CA resist surface. Excess acid existence near the resist surface enhanced CA reaction and resulted in the film thickness loss. Thus, optimizing the acidity of TARC material is very important. A higher pH TARC results in the 'T-top' shape resist pattern, and a lower pH TARC results in the film thickness loss. We have found that a TARC with pH equals 2.2 shows the optimum result in achieving the environmentally stable lithography.

Citation Download Citation

Kenichi Asahi, Yoshiyuki Tani, Ryuichi Yoshida, Koji Shimomura, Yusuke Takano, Yoshino Nishiwaki, and Hatsuyuki Tanaka "Environmentally stable lithography with acidity-optimized TARC material", Proc. SPIE 3999, Advances in Resist Technology and Processing XVII, (23 June 2000); https://doi.org/10.1117/12.388359

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