Photomask Side Wall Protection via ALD
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing photomask technologies face challenges in maintaining the line width and uniformity of semiconductor device patterns during the reproduction process, as the side walls of the mask patterns are prone to etching by strip solutions like H2SO4 and NH4OH, leading to potential degradation in the quality and reliability of semiconductor devices, especially with increased integration complexity.
Innovation Solution
A photomask design featuring a transparent substrate with a mask pattern and a protective layer pattern formed on its side walls, where the protective layer is deposited using atomic layer deposition (ALD) and patterned to cover the side walls without exposing them, ensuring a lower etching rate compared to the mask pattern, thus preventing etching by strip solutions and maintaining pattern integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the mask pattern is exposed to strip solutions during reproduction process, then the reproduction process can be completed, but the side walls of the mask pattern are etched leading to line width degradation
Solution Approach 1:
A protective layer pattern is introduced as an intermediary element between the mask pattern and the strip solution. This protective layer has lower etching rate than the mask pattern materials (Mo, Ru, Si), allowing the strip solution to be applied for reproduction without significantly etching the mask pattern side walls, thus maintaining line width uniformity while enabling the reproduction process to proceed
2Reliability
If the protective layer completely covers the mask pattern including top surface, then side wall protection is maximized, but the mask pattern functionality is compromised
Solution Approach 1:
The protective layer pattern is selectively applied only to the side walls of the mask pattern rather than completely covering the mask pattern. This localized protection approach ensures that the side walls are protected from etching while the top surface and other functional areas of the mask pattern remain exposed and functional for the reproduction process
3Productivity
If conventional deposition methods are used for protective layer, then deposition speed is fast, but conformal coverage on vertical side walls is difficult to achieve
Solution Approach 1:
The conventional physical vapor deposition method is replaced with atomic layer deposition (ALD). ALD is a chemical deposition technique that provides excellent conformal coverage on complex three-dimensional structures including vertical side walls, ensuring uniform protective layer thickness while maintaining practical deposition speeds through sequential surface reactions
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 solution effectively protects the mask patterns from etching during the reproduction process, maintaining the line width and uniformity of photomask patterns, thereby enhancing the reliability and quality of semiconductor devices by preventing degradation due to strip solutions.
Implementation Method 1
forming a protective layer pattern on the side wall of the mask pattern by patterning the protective layer, wherein the top of the protective layer pattern is exposed
Data Source
AI summary
A photomask includes a transparent substrate, a mask pattern formed on the substrate, and a protective layer pattern covering side walls of the mask pattern, wherein a top of the protective layer pattern is exposed.