Improvement of CD accuracy for next-generation reticles using HL-800M and CA resists

Abstract

The 50 kV electron-beam (EB) writing system HL-800M (Hitachi Co. Ltd.) was developed for 0.25 - 0.18 micrometer design-rule mask fabrication and widely applied. Chemically Amplified Resist (CAR) has merits of high sensitivity, high resolution and dry-etching durability. The combination of 50 kV EB and CAR is one of the best solutions to improve accuracy and throughput of next generation reticles such as 0.18 micrometer design-rule mask and beyond. The purpose of this study is to optimize the exposure and process conditions of the combination of 50 kV EB and CAR for improving Critical Dimension (CD) accuracy. At first, new positive-type CAR; RE515OP (Hitachi Chemical Co. Ltd.) has been evaluated. This resist shows the high resolution of 0.25 micrometer. Because of the vector-scanning EB such as HL-800M, the use of negative-type resist improves throughput of exposure. Negative-type CAR; NEB-22A (Sumitomo Chemical Co. Ltd.) has been also evaluated. This resist shows also the high resolution of 0.14 micrometer. It is clarified that both resists have the characteristic to meet the 0.18 - 0.15 micrometer design-rule mask fabrication. Besides, in order to improve CD accuracy with HL-800M, Proximity Effect Correction (PEC) condition has been optimized. Especially, as parameters of mesh-size and times of smoothing area-density, CD errors are investigated. As a result, CD linearity of 18 nm is obtained in the pattern-widths from 0.7 micrometer to 3 micrometer.