Title :
SHEWMAC: an end-of-line SPC scheme via exponentially weighted moving statistics
Author :
Fan, Chih Min ; Chang, Shi Chung ; Guo, Ruey Shan ; Kung, Hui Hung ; You, Jyh Cheng ; Chen, Hsin Pai ; Lin, Steven ; Wei, Chih Shih
Author_Institution :
Dept. of Electr. Eng., Nat. Taiwan Univ., Taipei, Taiwan
Abstract :
Due to the multiple-stream and sequence-disorder effects, a process change caused by one machine at an in-line step may result in changes in both the mean and variance of end-of-line wafer acceptance test (WAT) data sequence. To speed up WAT data trend detection without resorting to intensive computing power, an end-of-line SHEWMAC scheme was proposed by Fan et al (Proc. Int. Symp. Semicond. Manuf., pp. 233-236, 1999). The SHEWMAC scheme consists of a Shewhart, an exponentially weighted moving average (EWMA), and exponentially weighted moving Cpk (EWMC) charts for jointly monitoring the mean and variance of WAT lot average sequence. This paper aims at the robust design of a SHEWMAC scheme and the analysis of its effectiveness. Simulation results show that the SHEWMAC scheme with robust parameters reduces the time for detecting WAT trends by about 15% as compared to either the exponentially weighted mean square (EWMS) or combined Shewhart-EWMA schemes generally used for trend detection. Field data validation also shows that the incorporation of SHEWMAC complements the existing end-of-line data monitoring system and in-line SPC schemes for process integration
Keywords :
exponential distribution; integrated circuit manufacture; integrated circuit testing; moving average processes; process monitoring; production testing; statistical process control; SHEWMAC end-of-line SPC scheme; SHEWMAC scheme; Shewhart; WAT data trend detection; WAT lot average sequence mean; WAT lot average sequence variance; WAT trends; combined Shewhart-EWMA schemes; end-of-line SHEWMAC scheme; end-of-line data monitoring system; end-of-line wafer acceptance test; end-of-line wafer acceptance test data sequence mean; end-of-line wafer acceptance test data sequence variance; exponentially weighted mean square scheme; exponentially weighted moving Cpk charts; exponentially weighted moving average; exponentially weighted moving statistics; field data validation; in-line SPC scheme; in-line step; monitoring; multiple-stream effects; process change; process integration; robust SHEWMAC scheme design; sequence-disorder effects; simulation; Control charts; Manufacturing industries; Manufacturing processes; Monitoring; Quality control; Robustness; Semiconductor device manufacture; Size control; Statistical analysis; Statistics;
Conference_Titel :
Semiconductor Manufacturing Technology Workshop, 2000
Conference_Location :
Hsinchu
Print_ISBN :
0-7803-6374-4
DOI :
10.1109/SMTW.2000.883105
