Phase metrology on 45-nm node phase-shift mask structures

Abstract

As PSM (Phase Shift Mask) process moves toward 45nm and 32nm node, phase control is becoming more important than ever. Both attenuated and alternating PSM need precise control of phase as a function of both pitch and target sizes. However conventional interferometer-based phase shift measurements are limited to large CD targets and requires custom designed target in order to function properly, which limits clear understanding and control of small target PSM features. New type of Phase metrology tool created by Zeiss, in collaboration with Intel has been introduced and Intel's 45nm node PSM targets have been measured. In this paper we present test results from AAPSM/EAPSM targets with space CDs down to 45nm a wafer-level. Smallest pitch was 300nm print pitch, 150nm CD at mask (75nm pitch at wafer). In addition to this, phase and transmission matching between conventional phase metrology tool and new tool has been investigated and shown.