Effect of Sparse or Asymmetric Sampling on the Estimation of Photolithography Overlay Regression Parameters

An important consideration for APC feedback control of photolithography overlay is the uncertainty in estimating the correctable overlay parameters. This uncertainty is affected by the metrology sampling plan, particularly the spatial layout of the sampling points along with the number of sampling points. This current study looks at the combined effect of the spatial coverage and sample size factors, under two levels of random noise and a systematic non-correctable factor.