@article{(International Science Index):http://iastem.com/publications/418,
  author    = {Sheng-Shu Cheng and  Fong-Jung Yu},
  email	    = {alpha@ ydu.edu.tw, fischer@mail.dyu.edu.tw}  ,
  title     = {A CUSUM Control Chart to Monitor Wafer Quality},
  country   = {},
  abstract     = {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.
    journal   = {International Journal of Mechanical, Aerospace, Industrial, Mechatronic and Manufacturing Engineering},  volume    = {7},
  number    = {6},
  year      = {2013},
  pages     = {216 - 221},
  ee        = {http://iastem.com/publications/418},
  url   	= {http://iastem.com/Publications?p=78},
  bibsource = {http://iastem.com/Publications},
  issn  	= {1307-6892},
  publisher = {International Science Index},
  index 	= {International Science Index 78, Industrial and Manufacturing Engineering, 2013},