Silicon Nitride Mask Blank for ArF Lithography EMF Bias Control
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Solution Overview
Problem
Binary masks face challenges with ArF light fastness and electromagnetic field (EMF) bias due to the low light shielding performance of silicon nitride-based materials, which complicates pattern correction and increases manufacturing load.
Innovation Solution
A mask blank with a single-layer silicon nitride-based light shielding film, optimized to have an optical density of 3.0 or more and refractive index and extinction coefficient relationships defined by specific formulas, reducing EMF bias and enhancing light shielding performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon nitride-based material is used for the light shielding film to achieve high light shielding performance, then the light shielding performance is improved, but the ArF light fastness deteriorates
Solution Approach 1:
The patent applies composite materials by stacking the silicon nitride-based light shielding film with a chromium-based film or other materials having high ArF light fastness. This composite structure allows the silicon nitride layer to provide excellent light shielding performance (optical density of 3.0 or more) while the chromium-based layer or alternative materials compensate for the poor light fastness, achieving both high light shielding performance and durability under ArF exposure.
2Reliability
If the film thickness of the light shielding film is increased to improve light shielding performance, then the optical density is improved, but the EMF bias increases
Solution Approach 1:
The patent changes the material parameters by selecting a silicon nitride-based material with specifically controlled optical properties (refractive index n and extinction coefficient k satisfying defined relationships) to achieve the required optical density with reduced EMF bias. Additionally, the patent applies parameter changes through stacking structures where the total optical density is achieved through multiple layers rather than increasing single-layer thickness, thereby controlling EMF bias while maintaining light shielding performance.
3Reliability
If a chromium-based material is used for the light shielding film to achieve high light shielding performance, then the light shielding performance is improved, but the ArF light fastness deteriorates
Solution Approach 1:
The patent uses composite materials by stacking the silicon nitride-based light shielding film with a chromium-based film or other materials having high ArF light fastness. This composite structure allows the silicon nitride layer to provide excellent light shielding performance (optical density of 3.0 or more) while the chromium-based layer or alternative materials compensate for the poor light fastness, achieving both high light shielding performance and durability under ArF exposure.
4Device complexity
If a single-layer silicon nitride-based light shielding film is used to simplify the structure, then the device complexity is reduced, but the ArF light fastness deteriorates
Solution Approach 1:
The patent applies composite materials by stacking the silicon nitride-based light shielding film with a chromium-based film or other materials having high ArF light fastness. This composite structure allows the silicon nitride layer to provide excellent light shielding performance (optical density of 3.0 or more) while the chromium-based layer or alternative materials compensate for the poor light fastness, achieving both high light shielding performance and durability under ArF exposure.
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 optimized mask blank achieves high light shielding performance against ArF exposure light, reducing EMF bias and simplifying the manufacturing process of transfer masks, thereby improving pattern precision and reducing manufacturing complexity.
Implementation Method 1
the light shielding film has an optical density of 3.0 or more to exposure light of an ArF excimer laser
Implementation Method 2
a refractive index n and an extinction coefficient k of the light shielding film to the exposure light simultaneously satisfy relationships defined by Formulas (1) and (2) below
Data Source
AI summary
Provided is a mask blank in which a light shielding film which is a single layer film formed of a silicon nitride-based material has high light shielding performance against ArF exposure light and is capable of reducing EMF bias of a pattern of the light shielding film. The mask blank includes the light shielding film on a transparent substrate. The light shielding film has an optical density of 3.0 or greater to ArF exposure light. A refractive index n and an extinction coefficient k of the light shielding film to ArF exposure light simultaneously satisfy relationships defined by Formulas (1) and (2) below.n≤0.0733×k2+0.4069×k+1.0083 Formula (1)n≥29.316×k2−92.292×k+72.671 Formula (2)