Method of determining a best initial focal position estimate

摘要

The invention provides a method for a method for determining a best initial focal position estimate for a current sample location on a substrate comprising multiple sample locations, comprising determining the best initial focal position estimate by using a result from one or more techniques selected from the group consisting of linear regression analysis of focal positions determined for at least two other sample locations on the substrate and quadratic regression analysis of focal positions determined for at least three other sample locations on the substrate.