Multi-Layer Overlay Mark for IC Alignment Accuracy
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Solution Overview
Problem
Conventional overlay marks in IC processes primarily measure alignment accuracy between adjacent layers, failing to effectively address displacement errors between non-adjacent layers, which can compromise IC performance, especially as linewidths narrow.
Innovation Solution
An overlay mark design that includes multiple groups of x-directional and y-directional linear patterns from different pre-layers and the current layer, arranged alternately, allowing for more comprehensive alignment accuracy measurement across multiple layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional overlay marks measure only adjacent layers, then measurement process is simple, but alignment accuracy between non-adjacent layers cannot be ensured
Solution Approach 1:
The patent combines multiple pre-layer patterns (first through fourth pre-layers) and current layer patterns into a single overlay mark structure. This merging allows simultaneous measurement of alignment accuracy across multiple non-adjacent layers, resolving the contradiction by integrating what would otherwise require separate measurement processes.
Solution Approach 2:
The overlay mark structure serves multiple functions: it measures alignment between adjacent layers (first and second pre-layers with current layer) and non-adjacent layers (first and third pre-layers, second and fourth pre-layers with current layer). This multi-functionality enables comprehensive alignment verification without requiring separate measurement systems.
2Productivity
If multiple pre-layers are measured separately, then measurement accuracy is maintained, but measurement time increases
Solution Approach 1:
Multiple measurement functions are merged into a single overlay mark structure that can be measured in one operation. The alternating arrangement of patterns from different pre-layers and the current layer enables simultaneous extraction of alignment data for multiple layer combinations, dramatically reducing total measurement time while preserving accuracy.
3Adaptability or versatility
If overlay mark area is increased to accommodate more layers, then measurement completeness improves, but area utilization efficiency decreases
Solution Approach 1:
The patent efficiently utilizes the two-dimensional space by arranging patterns in alternating sequences along linear directions. This dimensional optimization allows multiple layer patterns to be packed into a compact area while maintaining the completeness needed for measuring alignment across all pre-layers and the current layer.
Data Source
AI summary
An overlay mark is described, including N (N≧2) groups of first x-directional linear patterns each defined from a different one of N pre-layers, N groups of second x-directional linear patterns of a current layer, N groups of first y-directional linear patterns each defined from a different one of the N pre-layers, and N groups of second y-directional linear patterns of the current layer. Each group of second x-directional linear patterns is disposed together with one group of first x-directional linear patterns, wherein the second linear patterns and the x-directional linear patterns are arranged alternately. Each group of second y-directional linear patterns is disposed together with one group of first y-directional linear patterns, wherein the second linear patterns and the first linear patterns are arranged alternately.