To improve the measure fail rate On SEM through six sigma DMAIC methodology — Chien-Hui Lu

Abstract

A Critical Dimension SEM (CD-SEM: Critical Dimension Scanning Electron Microscope) is a dedicated system for measuring the dimensions of the fine patterns formed on a semiconductor wafer. CD-SEM is mainly used in the manufacturing lines of electronic devices of semiconductors. The measurement process includes OM Alignment, SEM Alignment, Addressing, Measurement, and Image Saved. From May 2015, we found CD-SEM measure fail rate (measured by S-9380 SEM) is too high (its point reject rate is 46.13%). High measure fail rate will reduce the equipment capacity utilization, and increase manufacturing costs. So, we apply six-sigma DMAIC methodology to improve CD SEM fail rate that is our primary task, this is big Y. According to entitlement rules, we make a target to improve CD SEM fail rate from 46.13% to 15.4%. Drilling down CD SEM fail ERR (Error code reject rate) and analyze the data, the most of measurement errors are in addressing code (9007) =43.731%. We choice addressing code (9007) improvement as our small y. To improve this problem, the Six Sigma approach of DMAIC (Define, Measure, Analyze, Improve, Control) is deployed on this project. There are several tools applied in this process improvement, such as SIPOC, Detailed Map, Cause & Effect Matrix analysis, ANOVA, and DOE. Initial investigation indicates several factors in addressing of Photo process contribute this measurement fail phenomenon. By Cause & Effect Matrix, several factors are clarified as most possible root causes, they are X1:Magnification, X2: Algorithm, X3: Kind, and X4: Method. After the statistical comparisons, X1: Magnification and X4: Method are significant & important factors. DOE is conducted to figure out the optimized process control conditions and the results showed significant difference from original conditions. With such implementation, the CE-SEM measurement fail rate is improved from 46.13% to 1%. The total benefits lead to 39 million cost saving! It is a good practice to proceed continuously the quality improvement with Six Sigma Methodology for other defect improvement in the future.