EUV Phase Shift Mask Structure for Resolution and Alignment
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Solution Overview
Problem
The challenge in semiconductor manufacturing is achieving fine circuit line widths using extreme ultraviolet (EUV) lithography, particularly in reflective mask structures, where existing phase shift masks struggle to enhance resolution and alignment accuracy.
Innovation Solution
A phase shift mask with a reflective layer, device patterns, frame patterns, and alignment holes, along with specific materials and layers to improve reflectivity and alignment, is designed and manufactured through a sequential etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a reflective mask structure is used for EUV lithography, then the resolution is improved, but the alignment accuracy deteriorates
Solution Approach 1:
The mask structure is segmented into distinct functional layers: a reflective layer for resolution enhancement and separate alignment marks/alignment holes for alignment accuracy. This segmentation allows each component to perform its specific function optimally without interfering with the other.
Solution Approach 2:
Alignment holes are introduced as intermediary structures that expose portions of the reflective layer, serving as mediators between the reflective mask structure and the alignment system. These holes provide reference points for alignment without compromising the reflective properties needed for resolution.
2Measurement precision
If a phase shift structure is applied to the reflective mask, then the resolution is enhanced, but the manufacturing complexity increases
Solution Approach 1:
The phase shift structure is applied locally to specific regions of the mask where resolution enhancement is needed, rather than uniformly across the entire mask. This localized application reduces overall manufacturing complexity while maintaining resolution benefits in critical areas.
Solution Approach 2:
The mask employs a composite structure combining reflective materials (for resolution) with phase shift materials in specific layers. This composite approach allows the mask to achieve enhanced resolution through phase modulation while managing manufacturing complexity through material selection and layer configuration.
3Manufacturing precision
If alignment holes are introduced to improve alignment accuracy, then the alignment precision is improved, but the mask structure complexity increases
Solution Approach 1:
Alignment holes are created by selectively removing (taking out) material in specific locations to expose portions of the reflective layer. This extraction approach provides alignment reference points without adding significant structural complexity, as the holes are simple voids rather than added components.
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
Enhances resolution and alignment accuracy in EUV lithography by utilizing materials with controlled reflectivity and phase differences, facilitating precise pattern transfer onto wafers.
Implementation Method 1
a reflective mask structure is applied
Implementation Method 2
a phase shift mask structure in which a phase shift structure is applied to the reflective mask structure
Data Source
AI summary
There is provided a phase shift mask for extreme-ultraviolet lithography and a method of manufacturing the phase shift mask. The phase shift mask includes a substrate, a reflective layer, device patterns, a frame pattern, or phase shift patterns. The frame pattern is a pattern that includes alignment holes exposing portions of the reflective layer. The phase shift patterns overlap with the device patterns.