22 September 1995 Particle contamination within the tungsten etch back chamber
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Low yield of dies near the wafer flat edge were observed for the production wafers with tungsten plug structures. All these low yield lots were processed in the specific tungsten etch back etcher (LAM RAINBOW 4720 etcher) and the total yield drop is approximately 30%. The precision cut cross section SEM picture and KLA scanning result indicate the low yield is caused by the particles fallen on the wafer surfaces during and after the tungsten etch back process. The FTIR techniques were utilized to analyze the particle contents. The particle source had been identified to be originated from the thermal degradation and recombination of the grease applied around the gap housing quad seal region in the RAINBOW 4720 etcher. The temperature near the gap housing is 15 degree(s)C higher than the set point. The high temperature environment increase the degradation and recombination reaction rate for the grease and thus generate enormous amount of particles in the etching chamber.
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Po-Tao Chu, Po-Tao Chu, Kuang-Hui Chang, Kuang-Hui Chang, Tzu-Min Peng, Tzu-Min Peng, Chao-Hsin Chang, Chao-Hsin Chang, Shih-Why Yen, Shih-Why Yen, Ting-hwang Lin, Ting-hwang Lin, Chaur-Rong Chang, Chaur-Rong Chang, } "Particle contamination within the tungsten etch back chamber", Proc. SPIE 2635, Microelectronic Manufacturing Yield, Reliability, and Failure Analysis, (22 September 1995); doi: 10.1117/12.221462; https://doi.org/10.1117/12.221462

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