Deterministic Estimation of Stripe Type Defects and Reconstruction of Mask Pattern in L/S Type Mask Inspection

Abstract

In this paper, we consider a method for estimating a stripe-type defect and the reconstruction of a defect-free L/S type mask used in lithography. Comparing diffraction patterns of defected and defect-free masks, we derive equations for the estimation of the location and size of the defect. We construct an analytical model for this problem and derive closed form equations to determine the location and size using phase retrieval problem solving techniques. Consequently, we develop an algorithm that determines a defect-free mask pattern. An example shows the validity of the equations.

Accurate characterization of mask defects by combination of phase retrieval and deterministic approach

“…10 However, additional information such as a reference diffraction pattern is required. We note xðnÞ the defect-free mask pattern, yðnÞ the profile of the mask with a defect, and hðnÞ the defect represented by a linear combination of impulse signals.…”

“…Moreover, even if the theory was derived, 8 the deterministic approach was only demonstrated with simulations and with defects represented by a single impulse 9 or linear combination of impulse signals. 10 To make the deterministic approach suitable for practical use, it is necessary to extend its conditions of application.…”