AltPSM Inspection Capability and Printability of Quartz Defects

Abstract

Alternating phase shift masks (altPSMs) are a promising resolution enhancement technique to realize smaller design rules at the same lithography wavelength. Quartz defect inspection of altPSMs is challenging, as the optical contrast for defects within the quartz substrate is very small. AltPSM inspection capability was studied with different types of programmed test masks. The programmed quartz defects were characterized with a scanning electron microscope, an atomic force microscope and an aerial imaging microscope system. Finally a defect printability study was done. With the programmed test masks the performance of two altPSM inspection techniques was evaluated. Quartz defect detection was studied with respect to different pattern types and sizes. Quartz defect sensitivity was measured with respect to defect size as well as defect printability. It was found that quartz defect sensitivity with respect to defect size is constant for different pattern types, but decreases for decreasing line widths on 1:1 pitch line and space patterns. Whereas defect detection for the altPSM algorithms studied is governed by the defect’s extension perpendicular to the pattern line, defect printability is determined by the defect’s lateral area.