EUV Reflection Mask with Variable Thickness Absorbers
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Solution Overview
Problem
In EUV exposure for semiconductor manufacturing, achieving uniform focusing on photosensitive films with large steps is challenging due to differences in best focus positions for absorbers extending in different directions, leading to incomplete pattern formation at a common focus level.
Innovation Solution
A reflection type exposure mask with a light absorption layer comprising absorbers of varying thicknesses in different directions, allowing the mask pattern to be exposed at the best focus position by compensating for shadowing effects and ensuring uniform image formation across the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If EUV exposure is used to form highly fine patterns on photosensitive films with large steps, then pattern resolution is improved, but uniform focusing across the step difference becomes difficult to achieve
Solution Approach 1:
The patent applies local quality by making the absorber thickness non-uniform: absorbers in the first region (corresponding to the lower step) have a first thickness, while absorbers in the second region (corresponding to the upper step) have a second thickness that is different from the first thickness. This local variation in absorber thickness compensates for the step difference in the photosensitive film, enabling uniform focusing across different regions.
2Reliability
If absorbers of different thicknesses are used to compensate for step differences, then uniform focusing is improved, but manufacturing complexity increases
Solution Approach 1:
The patent segments the absorber layer into multiple regions with different thicknesses. The absorber is divided into a first region and a second region, where each region has a specific thickness optimized for the corresponding step level of the photosensitive film. This segmentation allows independent optimization of each region while maintaining overall uniform focusing performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables the formation of the entire mask pattern at the best focus position, canceling differences in best focus positions for absorbers extending in different directions, thus ensuring uniformity and preventing pattern collapse or working defects.
Implementation Method 1
a reflective layer (10) provided on the substrate (5), and a light absorption layer (20) provided on a surface of the reflective layer (10)... EUV exposure... reflected light of exposure light with which the reflection type exposure mask is irradiated
Implementation Method 2
a light absorption layer (20) provided on a surface of the reflective layer (10)... absorbs the exposure light
Data Source
AI summary
A reflection type exposure mask includes a substrate, a reflective layer provided on the substrate, and a light absorption layer provided on the surface of the reflective layer. The light absorption layer includes a first absorber and a second absorber. The first absorber extends in a first direction along the surface of the reflective layer. The second absorber extends in a second direction along the surface of the reflective layer, which intersects with the first direction. The thickness of the second absorber in a third direction which is perpendicular to the surface of the reflective layer is thinner than the thickness of the first absorber in the third direction.