The Study of Basic Pollution on the Negative-Tone Chemically Ampified Resist
As semiconductor industries get into submicron age, the design concept for resists is directed to high sensitivity, high contrast and high resolution, hence, chemically amplified resists with photoacid generators have been developed and become the main stream of resists at present. Problems for the process of chemically amplified resists can be generally divided into acid loss and acid diffusion. The most serious problem for acid loss comes from basic pollution. Basic pollution can cause positive-tone resists to have profiles with T-top and foot and the negative-tone resists a reverse profile. In recent literature review, we found that most studies in the field of basic pollution were related to the measurement of resist profile or to methods of lowering pollution. Few were found about the relationship between pollution and development rate of the resist. In this thesis, using laser interferometry, we observed the development rate of the negative-tone resist SAL601 under the influence of different processes of NH3 pollution. Results are summarized as follows: 1.We can get the range of acid loss in the resist under the pollution of ammonia by using Fukuda's model and Dill's parameters. 2.After chemically amplified negative-tone resist SAL601 underwent the process of exposure/NH3 pollution, NH3 neutralized proton acid and caused the development rate to become faster by lowering the degree of polymer cross-link. 3.After chemically amplified negative-tone resist SAL601 underwent the process of NH3 pollution/exposure, it exhibited development inhibition and made the development rate slowing down. This was not caused by polymer cross-link, but, may be, caused by the generation of development inhibitors. 4.When chemically amplified negative-tone resist SAL601 underwent the process of NH3 pollution/exposure/NH3 pollution, it could reduce the effect of development inhibition resulted from the process of NH3 pollution/exposure before. 5.The effects of NH3 pollution on chemically amplified negative-tone resist SAL601 between processes exposure/NH3 pollution and NH3 pollution/exposure are different. The mechanism for this difference in effect is still unclear. We summarized our studies and proposed the concept that development rate would be changed dramatically by different processes of pollution. The related study is worthy to go on further.
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