Dose modification proximity effect correction scheme with inherent forward scattering corrections

Abstract

A new approach to dose modification proximity effect correction (PEC) has been proposed that accounts for both short range and long range scatter in advanced direct-write electron beam lithography systems. This scheme can be applied to device writing and to optical mask making where critical dimension (CD) control is of increasing importance. This technique is unique because detailed knowledge of the short range scatter dose distribution is unnecessary; by correcting only for long range scatter, both short and long range compensation is obtained. The new approach is based on the fact that if the characteristic distance of short range scatter is about one third or less of the smallest feature, and if each feature is at least five addressable pixels in the beam writer, then the feature can be printed at its coded dimension if the resist clearing or threshold dose is at the midpoint of the dose profile. Si wafers coated with a positive tone e-beam resist were exposed to a test pattern using no PEC, conventional dose modification PEC and the new scheme. Results show that CD control is maintained over a larger pattern density variation and over a larger exposure dose range by the new technique when compared to the older method and to the uncorrected patterns.