Characteristics of Nanoscale Lithography Using AFM with a Current-Controlled Exposure System

Abstract

We have developed an atomic force microscopy (AFM) lithography system using a current-controlled exposure system. The constant current feedback system significantly reduces variation in the width of the line patterns compared with the common constant bias feedback system. We fabricate line-and-space patterns on a commercial negative-type resist, RD2100N (Hitachi Chemical Co.), and evaluate the lithography's characteristics, including the current-voltage (I-V) characteristics, sensitivity curve, cross-sectional shape, dose-margin, resolution, and proximity effect. We find that the cross-sectional shape of the developed resist pattern depends on the exposure dose. The sensitivity, dose-margin, and resolution depend on the resist thickness and a minimum line width of 27 nm is obtained for a 15-nm-thick resist. The proximity effect is much smaller than that of electron beam (EB) lithography. We also evaluate the electric-field mapping inside the resist and explain the characteristics of the AFM exposure system based on the proposed exposure mechanism.