Global and Local Virtual Metrology Models for a Plasma Etch Process
Lynn, Shane and Ringwood, John and MacGearailt, Niall (2012) Global and Local Virtual Metrology Models for a Plasma Etch Process. IEEE Transactions on Semiconductor Manufacturing, 25 (1). pp. 94-103. ISSN 0894-6507
Virtual metrology (VM) is the estimation of metrology variables that may be expensive or difficult to measure using readily available process information. This paper investigates the application of global and local VM schemes to a data set recorded from an industrial plasma etch chamber. Windowed VM models are shown to be the most accurate local VM scheme, capable of producing useful estimates of plasma etch rates over multiple chamber maintenance events and many thousands of wafers. Partial least-squares regression, artificial neural networks, and Gaussian process regression are investigated as candidate modeling techniques, with windowed Gaussian process regression models providing the most accurate results for the data set investigated.
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