TY - JFULL AU - Sheng-Shu Cheng and Fong-Jung Yu PY - 2013/7/ TI - A CUSUM Control Chart to Monitor Wafer Quality T2 - International Journal of Industrial and Manufacturing Engineering SP - 1182 EP - 1188 VL - 7 SN - 1307-6892 UR - https://publications.waset.org/pdf/418 PU - World Academy of Science, Engineering and Technology NX - Open Science Index 78, 2013 N2 - C-control chart assumes that process nonconformities follow a Poisson distribution. In actuality, however, this Poisson distribution does not always occur. A process control for semiconductor based on a Poisson distribution always underestimates the true average amount of nonconformities and the process variance. Quality is described more accurately if a compound Poisson process is used for process control at this time. A cumulative sum (CUSUM) control chart is much better than a C control chart when a small shift will be detected. This study calculates one-sided CUSUM ARLs using a Markov chain approach to construct a CUSUM control chart with an underlying Poisson-Gamma compound distribution for the failure mechanism. Moreover, an actual data set from a wafer plant is used to demonstrate the operation of the proposed model. The results show that a CUSUM control chart realizes significantly better performance than EWMA. ER -