13 September 1996 Defect reduction through characterization and equipment modification in tungsten residue caused by deposition process
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Defect reduction is one of the most challenging problems in the fabrication of advanced MOS devices. In-line inspection scheme of product wafers is essential for timely detection of process anomalies and providing real time feedback to the manufacturing process. A particle contamination of a specific module was observed from the inspection results on product wafers. Through partitioning studies, the tungsten (W) deposition process was identified as the particle source. This paper describes the methodology used to identify and diagnose the particle source in the W deposition. After the etch-back process, particles of abut 1 to 2 micrometers were randomly scattered on the entire wafer. The number of residue ranges from several hundred to a few thousand, forming a haze-like defect. A focused ion beam (FIB) cross section showed a hollow section of the W film, indicating improper reaction during grain growth. It was discovered that a variation in the reactant ratio during the nucleation step was causative. The change in the ratio of the reactants was in turn caused by the severe overshoot of the reactant gas at the beginning of the reaction. The pump-down step of the reactant gas prior to the flowing in of the reactant gases, which greatly enhanced the overshoot, was omitted. A two-step gas flow rate in nucleation step was developed to alleviate the effect of gas flow dynamics and thus reduced the overshoot of the gas. With these modifications and other proper corrective actions implemented, the residue was completely eliminated.
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Huitzu Lin, Huitzu Lin, Sheng-Cha Lee, Sheng-Cha Lee, Hsien-Wien Chang, Hsien-Wien Chang, } "Defect reduction through characterization and equipment modification in tungsten residue caused by deposition process", Proc. SPIE 2876, Process, Equipment, and Materials Control in Integrated Circuit Manufacturing II, (13 September 1996); doi: 10.1117/12.250894; https://doi.org/10.1117/12.250894

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