Methods and systems for analysis of wafer scan data

Abstract

Disclosed is a computerized method for detecting defects on a sample. The method includes: (i) receiving scan data corresponding to a pixel on the sample; (ii) computing a difference vector d based on the scan data and corresponding reference data; (iii) computing a parameter D dependent on t=Γd−(G/∥Γs∥)Γs, wherein ΓΓ=Kwith K being a covariance matrix corresponding to the pixel, s is a predetermined kernel characterizing a defect signal, and G=s·(Kd) is a gaussian approximation of a likelihood ratio test expression for distinguishing the defect signal from noise, and wherein D substantially monotonically increases with ∥t∥; and (iv) computing a score q(g, D) indicative of whether the pixel is defective, wherein g is a parameter indicative of a value of Gand q(g, D) substantially monotonically increases with g and substantially monotonically decreases with D.