Inspectability and printability of lines and spaces halftone masks for the advanced DRAM node

Abstract

With decreasing pattern sizes the absolute size of acceptable pattern deviations decreases. For mask-makers a new technology requires a review, which mask design variations print on the wafer under production illumination conditions and whether these variations can be found reliably (100%) with the current inspection tools. As defect dispositioning is performed with an AIMS-tool, the critical AIMS values, above which a defect prints lithographically significant on the wafer, needs to be determined. In this paper we present a detailed sensitivity analysis for programmed defects on 2 different KLA 5xx tools employing the pixel P90 at various sensitivity settings in die-to-die transmitted mode. Comparing the inspection results with the wafer prints of the mask under disar illumination it could be shown that all critical design variations are reliably detected using a stateof-the-art tool setup. Furthermore, AIMS measurements on defects with increasing defect area of various defect categories were taken under the same illumination conditions as for the wafer prints. The measurements were evaluated in terms of AIMS intensity variation (AIV ). It could be shown that the AIMS results exhibit a linear behavior if plotted against the square-root area (SRA) of the defects on the mask as obtained from mask SEM images. A consistent lower AIV value was derived for all defect categories.