Mask Blank Oxygen-Rich Protective Layer Dry Etching
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Solution Overview
Problem
Conventional methods for producing fine patterns in semiconductor and optical components face challenges such as etching bias, resist recession, and nonuniformity in etching depth and width, limiting the accuracy and dimension of chromium patterns in photomasks and imprint templates.
Innovation Solution
A mask blank with a substrate and thin film, where the thin film has a protective layer with 60% or more oxygen, is subjected to dry etching using an etching gas substantially free from oxygen, such as a chlorine-based gas, to form high-accuracy patterns by reducing etching bias and maintaining resist thickness, thereby achieving vertical profiles and precise dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet etching using di-ammonium cerium (IV) nitrate is used to etch chromium, then resist recession is minimized, but etching bias occurs and the chromium pattern does not have vertical profiles
Solution Approach 1:
The patent changes the etching parameters by switching from wet etching to dry etching using a mixed gas of chlorine-based gas and oxygen. This parameter change enables the chromium pattern to achieve vertical profiles while controlling etching bias through optimized gas composition and process conditions
Solution Approach 2:
The patent uses a composite approach by combining multiple materials in sequence: a protective film (oxide layer) is formed on the chromium film, and then a multi-layer film structure is created. This composite structure allows the chromium pattern to maintain vertical profiles while the protective film prevents excessive etching
2Shape
If dry etching using chlorine-based gas and oxygen is used to etch chromium, then vertical profiles are achieved, but resist recession and disappearance occur
Solution Approach 1:
The patent applies preliminary action by forming a protective film (oxide layer) on the chromium film before performing the dry etching process. This protective film is deposited in advance to prevent resist recession and maintain pattern dimensional accuracy during the etching process
Solution Approach 2:
The protective film acts as a cushioning layer that protects the chromium pattern and resist from excessive etching damage. This beforehand cushioning prevents resist recession and disappearance while allowing the chromium to achieve vertical profiles through the dry etching process
3Manufacturing precision
If multi-stage etching is used to avoid nonuniformity in etching width or depth, then process complexity increases
Solution Approach 1:
The patent achieves etching uniformity by optimizing the parameters of a single-stage dry etching process, specifically using a mixed gas of chlorine-based gas and oxygen with controlled ratios. This parameter optimization eliminates the need for multi-stage etching while maintaining consistent etching width and depth across the pattern
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
This approach enables the formation of high-accuracy fine patterns with reduced etching bias and resist recession, allowing for more precise control over pattern dimensions and improved light-shielding functions in photomasks and imprint templates.
Implementation Method 1
the mask blank is adapted to be subjected to dry etching corresponding to a method of producing an exposure mask by patterning the thin film by dry etching using an etching gas substantially free from oxygen
Implementation Method 2
the thin film having a protective layer formed at least at an upper layer and containing 60 atomic % or more oxygen
Data Source
AI summary
A mask blank includes a substrate and a thin film formed thereon and used to form a pattern. The mask blank is adapted to be subjected to dry etching corresponding to a method of producing an exposure mask by patterning the thin film by dry etching using an etching gas substantially free from oxygen with a resist pattern formed on the thin film used as a mask. The thin film has a protective layer formed at least at its upper layer and containing 60 atomic % or more oxygen. For example, the dry etching is performed by the use of a chlorine-based gas substantially free from oxygen.