Simultaneous Monitoring of Mean and Variance Through Optimally Designed SPRT Charts

Pachano-Azuaje, Felipe; Das, Tapas K.

doi:10.1007/978-1-4615-1635-4_18

Cited by 4 publications

(2 citation statements)

References 11 publications

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“…The region between and limits is also referred as the zone of indifference. Wald also showed that approximate magnitude of and errors associated with a test can be obtained using just the detection limits and as (14) (15)…”

Section: Acceptmentioning

confidence: 99%

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Online End Point Detection in CMP Using SPRT of Wavelet Decomposed Sensor Data

Das

Ganesan

Sikder³

et al. 2005

IEEE Trans. Semicond. Manufact.

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Efficient end point detection (EPD) in chemical mechanical planarization (CMP) is critical to quality and productivity of the wafer fabrication process. The cost of over and under polishing, and the cost of ownership of many expensive metrology-based EPD methods have motivated the researchers to seek cost effective and efficient alternatives. This paper presents a novel method for EPD, which uses a sequential probability ratio test (SPRT) on the wavelet decomposed coefficient of friction (CoF) data from the CMP process. The method is made suitable for online application by developing a moving block data processing strategy, which matches the rate of data acquisition. Tests on both oxide and copper metal CMP show that the developed methodology is uniquely capable of identifying the start and finish of the end point event.Index Terms-Acoustic emission, chemical mechanical planarization (CMP), coefficient of friction (CoF), end point, sequential probability ratio test (SPRT), wavelet-based multiscale analysis.

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Section: Acceptmentioning

confidence: 99%

“…Using log-likelihood ratio, the SPRT for the variance with known mean, presented above in (11) through (13), can be restated as follows [14]. …”

Section: Acceptmentioning

confidence: 99%