Ta-Sn Absorber Layer for EUV Mask Cleaning Resistance
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Solution Overview
Problem
In EUV lithography, reflective masks face challenges with pattern transfer accuracy due to absorber layer thickness affecting EUV light shadowing and contrast, and existing reflective mask blanks lack sufficient cleaning resistance, leading to unstable pattern formation.
Innovation Solution
A reflective mask blank with a substrate, a reflective layer, a protective layer, and an absorber layer containing Sn as the main component and Ta in an amount of 25 at % or more, providing excellent cleaning resistance and reduced EUV light reflectance while maintaining pattern fidelity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the absorber layer thickness is increased to improve EUV light absorption and pattern contrast, then the shielding properties improve, but the optical path may be intercepted causing shadowing that degrades pattern accuracy
Solution Approach 1:
The patent changes the compositional parameters of the absorber layer by incorporating specific elements (Ta, W, Mo, Re, Os, Ir, Pt, Au, Ag, Pd, Rh, Ru) in controlled amounts to optimize the balance between absorption and shadowing effects, allowing thinner layers to achieve sufficient contrast without excessive shadowing
Solution Approach 2:
The patent uses composite absorber layer materials combining multiple elements (e.g., Ta-Sn, Ta-W, Ta-Mo) to achieve superior EUV absorption properties that provide high contrast with reduced thickness, thereby minimizing shadowing while maintaining shielding effectiveness
2Reliability
If conventional absorber materials are used to achieve EUV light absorption, then the basic masking function is fulfilled, but the cleaning resistance during mask production is insufficient leading to unstable pattern formation
Solution Approach 1:
The patent modifies the material composition parameters by adding specific elements (Ta ≥25 at%, W ≥10 at%, Mo ≥10 at%, Re ≥10 at%, Os ≥10 at%, Ir ≥10 at%, Pt ≥10 at%, Au ≥10 at%, Ag ≥10 at%, Pd ≥10 at%, Rh ≥10 at%, Ru ≥10 at%) to enhance both cleaning resistance and pattern formation stability simultaneously
Solution Approach 2:
The patent employs composite absorber materials with specific element combinations that provide inherent resistance to cleaning processes while maintaining stable pattern formation, such as Ta-based alloys combined with other refractory metals that exhibit superior chemical stability and adhesion properties
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 ensures stable pattern formation with improved cleaning resistance and reduced EUV light reflectance, enhancing pattern accuracy and contrast in EUV lithography.
Implementation Method 1
a reflective layer formed thereon, and an absorber layer formed on the reflective layer in a pattern, the reflective layer reflecting EUV light
Implementation Method 2
the absorber layer which absorbs EUV light, The EUV light which enters the reflective mask is partly absorbed by the absorber layer
Data Source
AI summary
A reflective mask blank includes, on/above a substrate in the following order from the substrate side, a reflective layer which reflects EUV light, and an absorber layer which absorbs EUV light. The absorber layer contains Sn as a main component and Ta in an amount of 25 at % or more.