Reflective Mask Blank with Dual-Layer Thin Film for EUV Lithography
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Solution Overview
Problem
In EUV lithography, phase shift reflective masks face challenges in achieving both high phase shift effect and large exposure margin, requiring multiple masks to manage high and low reflectance regions, which complicates the design and manufacturing process.
Innovation Solution
A reflective mask blank with a multilayer structure comprising a substrate, a multilayer reflective film, and a thin film with specific reflectance and phase difference properties, including a first layer with greater than 2.5% reflectance and a second layer with higher reflectance, allowing for a high phase shift effect and large exposure margin with a single mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high reflectance is used in a phase shift reflective mask, then a high phase shift effect is obtained, but the exposure margin is reduced causing resist to react in regions where it should not
Solution Approach 1:
The patent applies local quality by creating different reflectance regions within the same mask. The mask includes a first region with high reflectance (greater than 6.0%) for pattern regions requiring high phase shift effect, and a second region with low reflectance (2.5% or less) for pattern regions requiring large exposure margin. This allows each region to be optimized independently for its specific function.
Solution Approach 2:
The mask is segmented into multiple regions with different reflectance characteristics. By dividing the mask into high reflectance regions and low reflectance regions, the patent enables simultaneous achievement of high phase shift effect and large exposure margin in different areas of the same mask, eliminating the need for multiple masks.
2Reliability
If a low reflectance is used in a phase shift reflective mask, then the exposure margin is increased, but the phase shift effect is reduced
Solution Approach 1:
The patent applies local quality by creating different reflectance regions within the same mask. The mask includes a first region with high reflectance (greater than 6.0%) for pattern regions requiring high phase shift effect, and a second region with low reflectance (2.5% or less) for pattern regions requiring large exposure margin. This allows each region to be optimized independently for its specific function.
3Manufacturing precision
If two or more phase shift masks are used to form pattern regions with different reflectances, then both high phase shift effect and large exposure margin are achieved, but the device complexity and manufacturing process are complicated
Solution Approach 1:
The patent merges multiple mask functions into a single mask by integrating both high reflectance regions and low reflectance regions in one mask structure. This eliminates the need for multiple masks and simplifies the manufacturing process while maintaining the ability to achieve both high phase shift effect and large exposure margin in different pattern regions.
Solution Approach 2:
The single mask is designed to perform multiple functions simultaneously - it provides both high phase shift effect for certain patterns and large exposure margin for other patterns. This multi-functional design eliminates the need for multiple specialized masks and simplifies the overall system.
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 accurate transfer of fine patterns with high phase shift effect and large exposure margin, simplifying the manufacturing process and improving semiconductor device performance and integration.
Implementation Method 1
a multilayer reflective film formed on the substrate... the first layer has a reflectance greater than 2.5% with respect to EUV light... the second layer has a reflectance greater than the reflectance of the first layer
Implementation Method 2
phase shift reflective mask having a phase shift effect... a phase difference between first reflected light reflected from the first layer irradiated with the EUV light and second reflected light reflected from the second layer
Data Source
AI summary
A reflective mask blank comprises a substrate, a multilayer reflective film formed on the substrate, and a thin film formed on the multilayer reflective film. The thin film includes a first layer and a second layer. The first layer has a reflectance greater than 2.5% with respect to EUV light. The second layer has a reflectance greater than the reflectance of the first layer with respect to the EUV light.