Photomask Shading Layer for Edge CD Uniformity
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Solution Overview
Problem
Current lithography techniques face challenges in achieving uniform critical dimensions (CDs) of fine patterns on wafers, particularly in edge regions where CD variations are outside allowable ranges, making it difficult to correct pattern sizes without altering the mask patterns.
Innovation Solution
Incorporating a shading layer in the peripheral region of the photomask that attenuates illumination light, creating spill-over-shading regions to overlap with critical dimension correction areas, allowing for controlled width adjustments of the overlap region to correct CD variations without altering the mask patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a shading layer is added to correct CD variations in edge regions, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The photomask is divided into distinct functional regions: a pattern region containing mask patterns and a peripheral region containing the shading layer. This segmentation allows the shading layer to be added only where needed (in the peripheral region) to correct CD variations in edge regions, rather than modifying the entire photomask structure.
Solution Approach 2:
The shading layer is positioned specifically in the peripheral region of the photomask, creating local optical properties that differ from the pattern region. This local modification allows CD correction in edge regions without affecting the pattern formation in the central region, achieving targeted improvement with minimal added complexity.
2Manufacturing precision
If the position of the shading layer is adjusted to control overlap region width, then manufacturing precision is improved, but ease of operation deteriorates
Solution Approach 1:
The shading layer is pre-positioned in the peripheral region during photomask fabrication, establishing the overlap region width before the lithography process begins. This preliminary positioning ensures consistent CD correction across production runs, eliminating the need for complex real-time adjustments during operation.
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
The shading layer effectively corrects CD variations in resist patterns by controlling illumination light intensity, ensuring uniformity and reducing CD errors in edge regions, thereby improving pattern uniformity without modifying the mask patterns.
Implementation Method 1
a shading layer disposed in the peripheral region, and wherein the shading layer provides a spill-over-shading region extending to overlap with a critical dimension (CD) correction region of the first pattern region
Data Source
AI summary
A photomask and a method of forming patterns using the photomask are provided. The photomask includes a mask body including a pattern region and a peripheral region and having a first surface and a second surface. Mask patterns are disposed on a portion overlapping with the pattern region of the first surface of the mask body. A shading layer is disposed in the peripheral region. The shading layer provides a spill-over-shading region extending to overlap with a critical dimension (CD) correction region in which CD correction in the pattern region is required.