Pattern Transfer Mask Absorber Thickness Variation
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Solution Overview
Problem
As semiconductor integrated circuit designs become more complex, the usable depth of focus (UDoF) range of pattern transfer masks decreases, limiting the process window in photolithography due to deviations in exposure processes and critical dimension variations.
Innovation Solution
A manufacturing method for pattern transfer masks involves selecting constrain patterns with the most restrictive depth of focus range and reducing the thickness of the patterned absorber layer in these patterns or non-dominating patterns, using a second writing layout to generate a revised mask with varying absorber layer thicknesses, thereby enhancing the UDoF range and process window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the pattern transfer mask is used for complex integrated circuit designs with multiple pattern groups, then the pattern density varies across different groups, but the usable depth of focus range becomes smaller and the process window is limited
Solution Approach 1:
The patent applies local quality by assigning different absorber layer thicknesses to different pattern groups based on their specific pattern densities. High-density patterns receive thinner absorber layers while low-density patterns receive thicker absorber layers, allowing each pattern group to operate within its optimal depth of focus range, thereby expanding the overall usable depth of focus range for complex integrated circuit designs
2Manufacturing precision
If the absorber layer thickness is reduced in constrain patterns, then the individual depth of focus range is improved, but the manufacturing complexity increases due to requiring second writing layout and thickness modification
Solution Approach 1:
The patent segments the mask manufacturing process into distinct phases: generating a second writing layout that identifies constrain patterns requiring thickness modification, selectively reducing absorber layer thickness only in those specific patterns, and maintaining original thickness in non-dominating patterns. This segmentation allows precise control over which patterns receive thickness modification, improving individual depth of focus ranges while managing manufacturing complexity through systematic process division
Data Source
AI summary
A manufacturing method of a pattern transfer mask includes the following steps. A basic mask is provided. The basic mask includes a plurality of patterns formed by a patterned absorber layer on a substrate according to a first writing layout. A photolithographic process is then performed by the basic mask to obtain individual depth of focus (iDoF) ranges of each of the patterns and a usable depth of focus (UDoF) range of the patterns. At least one constrain pattern dominating the UDoF range is selected from the patterns in the basic mask. The rest of the patterns except the constrain pattern are non-dominating patterns. A second writing layout is then generated for reducing a thickness of the patterned absorber layer in the constrain pattern or in the non-dominating patterns.