Reflective Mask Phase Shifter EUV Lithography Shadowing
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Solution Overview
Problem
EUV lithographic processes using reflective masks face issues with pattern critical dimension differences and shifts due to mask shadowing effects caused by light absorption patterns, leading to suboptimal resolution and image quality.
Innovation Solution
The use of reflective masks with a first reflection layer, a capping layer, and a phase shifter to create phase differences between light reflecting from different regions, replacing light absorption patterns with reflection patterns to minimize shadowing effects and enhance image transfer accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If light absorption patterns are used in reflective masks, then pattern transfer is achieved, but mask shadowing effects occur causing pattern critical dimension differences and shifts
Solution Approach 1:
The patent changes the optical parameters of the mask by introducing phase shifters that create phase differences (e.g., 180 degrees) between light waves. This transforms the mask from using amplitude modulation (absorption patterns) to phase modulation, eliminating shadowing effects while maintaining pattern transfer capability
Solution Approach 2:
Phase shifters are introduced as intermediary elements between the reflection layer and the pattern transfer medium. These phase shifters modify the phase of reflected light without absorbing it, thereby eliminating shadowing effects while enabling accurate pattern transfer
2Manufacturing precision
If traditional reflective mask structure is used, then basic pattern transfer is achieved, but resolution and image quality are suboptimal
Solution Approach 1:
The patent optimizes optical parameters by introducing phase shifters that create controlled phase differences, improving both resolution and image quality simultaneously through phase modulation rather than amplitude modulation
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 improves the resolution and image quality by eliminating mask shadowing effects, reducing the mask shadowing effect, and enhancing the throughput and contrast characteristics of EUV lithographic processes.
Implementation Method 1
a first reflection layer disposed on a mask substrate, a first capping layer disposed on the first reflection layer, a second reflection pattern disposed over a portion of the first capping layer to cause a first phase difference portion between first light reflecting from the first reflection layer and second light reflecting from the second reflection pattern
Implementation Method 2
a phase shifter disposed between the second reflection pattern and the first capping layer to cause an additional second phase difference portion between the first light and the second light
Data Source
AI summary
A reflective mask includes a first reflection layer disposed on a mask substrate, a first capping layer disposed on the first reflection layer, a second reflection pattern disposed on a portion of the first capping layer, and a phase shifter disposed between the second reflection pattern and the first capping layer to cause a phase difference between a first light reflecting from the first reflection layer and a second light reflecting from the second reflection pattern. Related methods are also provided.