Multiple Pattern Alignment for IC Lithography
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Solution Overview
Problem
As integrated circuit geometries scale to smaller dimensions, the alignment tolerance of new pattern levels to underlying patterns becomes increasingly critical, and conventional photolithographic alignment methods struggle to maintain precision, particularly when using 193 nm lithography, which necessitates double pattern technology to achieve pitches below 100 nm.
Innovation Solution
A method of aligning a new pattern reticle to multiple previously defined pattern alignment marks in both the x and y directions, using double pattern technology to split interconnect patterns into two patterns with looser pitches, ensuring accurate alignment and minimizing misalignment-induced shorts and high contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photolithographic alignment methods are used, then the manufacturing process is simple, but alignment precision deteriorates as geometries scale to smaller dimensions
Solution Approach 1:
The patent segments the alignment process into multiple independent alignment operations, where each alignment mark is aligned to a different reference pattern. This allows each alignment operation to be optimized independently and enables the use of multiple alignment marks (e.g., first alignment mark aligned to first pattern, second alignment mark aligned to second pattern) to achieve cumulative precision that exceeds single-reference alignment capabilities.
2Ease of manufacture
If 193 nm lithography is used, then manufacturing cost is reduced, but pitch capability deteriorates below 100 nm
Solution Approach 1:
The patent applies segmentation by dividing a single high-pitch pattern into multiple lower-pitch patterns that can be formed using 193 nm lithography. By segmenting the pattern formation into multiple lithography steps with different pitch requirements, the process achieves fine pitch capability (below 100 nm) while maintaining compatibility with cost-effective 193 nm lithography equipment.
3Manufacturing precision
If alignment tolerance is reduced for smaller geometries, then pattern accuracy is improved, but alignment difficulty increases
Solution Approach 1:
The patent introduces alignment marks as intermediary elements that facilitate the alignment process. These alignment marks serve as mediators between the lithography system and the underlying patterns, providing easily detectable reference points that simplify the alignment measurement process while enabling achievement of tight alignment tolerances required for smaller geometries.
Data Source
AI summary
A method of aligning a new pattern to more than one previously defined pattern during the manufacture of an integrated circuit. A method of aligning a photolighography pattern reticle to a first previously defined pattern in a first direction and also aligning the photolithography pattern reticle to a second previously defined pattern in a second direction. A method of aligning a photolighography pattern reticle to two previously defined patterns in the same direction.