Flare Impact and Correction for Critical Dimension Control with Full-Field Exposure Tool

Abstract

Extreme ultraviolet lithography (EUVL) requires flare variation compensation technology and highly accurate critical dimension (CD) control for the fabrication of devices with feature sizes of 32 nm and beyond. To deal with these issues, a mask pattern suitable for evaluating flare and CD variation was designed based on the power spectral density (PSD) of the projection optics of the EUV1. The CD of the replicated patterns clearly varied with the local density of mask patterns, and the variation was affected by mask CD error and flare level. The impact of flare on CD variation was estimated very precisely (<±2 nm) from aerial simulations that took into account the flare level based on the PSD and resist blur, which was modeled as a simple Gaussian function. Mask resizing was found to be useful in compensating for flare variations and was used in the fabrication of the metal-layer patterns for a 22-nm-node static random access memory.