Base on bias and process capability index monitoring mechanism to improve tool consistency

摘要

The monitoring mechanism uses in-line data which is conservative stratification and grouping to calculation %Bias. (%Bias=bias/process variation.) It represents tools are significant difference when %Bias>10% referring to MSA 2^nd manual. As each tool is too stable, the influence of variation would be so sensitive, and the mechanism would be too strict. We developed if we combined %Bias criteria of MSA 2^nd manual and Cpk monitor in order to solve the sensitive variation of the stable process. Therefore, this mechanism adds Cpk criterion. Due to the method focuses on tools consistency, the Ca formula is made an amendment to measure the degree between difference tools. In general, the criterion of Cpk is 1.67 that means process capability is capable. In the mechanism, the criterion of Cpk is tightened to 1.83. This paper discusses an inline monitoring mechanism to control tools consistency. We use Analysis of variance (ANOVA) test to prove the bias of tools that needs to improve. Therefore, we combined %Bias and Cpk to monitor in our mechanism. After improving the mechanism, it could solve the lack of the past mechanism. Finally, the mechanism can be immediate, comprehensive and effective to control and meet quality requirements.