Experimental study of electron beam projection lithography mask defect printability

Abstract

Mask defect printability of electron beam projection lithography (EPL) was investigated. We fabricated EPL chip reticles including programmed defects. The design of these programmed defects was based on semiconductor equipment and materials international (SEMI) standards, but we modified it from the original to a new design for the 100–70 nm node. In our defect printability experiment, Nikon’s electron beam (EB) projection experimental column was used as an exposure tool with those chip reticles. The acceleration voltage of the electron beam was 100 kV. In the case of the “size shift” defects, the correlation between the defect size on the reticle (×1/4) and the critical dimension (CD) change on the wafer is linear and the defect down to 40 nm was printed. Furthermore mask error enhancement factor is nearly equal to 1. This is the advantage of the EPL over the optical lithography. On the other hand, in the case of “dot” defects, defects smaller than 100 nm on the reticle has a small impact on the CD change. The allowable defect size with a criterion of a given ΔCD became larger at the defocus condition.