Two-Dimensional Alignment Mark for Photolithography Overlay Accuracy
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Solution Overview
Problem
Current photolithography systems face challenges with poor overlay (OVL) accuracy due to the limitations of one-dimensional linear alignment marks, which result in lower alignment signal intensity and increased rework rates and production costs.
Innovation Solution
A mask plate with a two-dimensional linear alignment mask pattern is introduced, featuring alternating sub-patterns in perpendicular directions, forming Moire patterns that enhance first-order diffracted signal intensity and alignment signal strength, thereby improving OVL accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If one-dimensional linear alignment marks are used, then the alignment process is simple, but the alignment signal intensity is low and OVL accuracy is poor
Solution Approach 1:
The patent transitions from one-dimensional linear alignment marks to two-dimensional linear alignment marks. The alignment mark includes first linear patterns extending in a first direction and second linear patterns extending in a second direction perpendicular to the first direction, creating a two-dimensional structure that enhances alignment signal intensity and improves OVL accuracy while maintaining structural simplicity
2Reliability
If conventional alignment marks are used, then the process is straightforward, but the alignment signal intensity is insufficient leading to high rework rates
Solution Approach 1:
The patent combines first linear patterns and second linear patterns in a single alignment mark structure. The first linear patterns extend in a first direction and the second linear patterns extend in a second direction perpendicular to the first direction, merging multiple pattern orientations into one unified alignment mark that generates stronger alignment signals and reduces rework
3Manufacturing precision
If CMP is performed on the wafer surface, then the flatness is improved for better pattern transfer, but the alignment pattern thickness may be reduced
Solution Approach 1:
The patent specifies that the size of the first linear pattern in the second direction should be equal to or greater than the size of the second linear pattern in the first direction. This parameter relationship ensures that the alignment patterns maintain sufficient thickness and signal strength even after CMP processing, balancing surface flatness improvement with pattern integrity preservation
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 two-dimensional alignment mark increases OVL accuracy, reduces rework rates, and lowers production costs by providing a stronger alignment signal and maintaining alignment pattern thickness during chemical mechanical polishing.
Implementation Method 1
forming Moire patterns that enhance first-order diffracted signal intensity
Implementation Method 2
forming Moire patterns that enhance first-order diffracted signal intensity
Data Source
AI summary
A mask plate, an alignment mark and a photolithography system are provided. In one form, an alignment mark includes a plurality of alignment patterns arranged at intervals, where the alignment pattern includes a first pattern extending in a first direction and a second pattern extending in a second direction, the first pattern includes a first end and a second end which are opposite to each other in the first direction, the second pattern includes a third end and a fourth end which are opposite to each other in the second direction, the second end is connected to the third end, the fourth end is connected to the first end, and the alignment pattern is a two-dimensional linear pattern.