Nested Alignment Accuracy Mark for Semiconductor Scribe Line
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Solution Overview
Problem
Current semiconductor processes require multiple alignment accuracy (AA) marks to check alignment between pattern groups, leading to increased time and lateral area usage in the scribe line region due to insufficient lithographic pitch resolution.
Innovation Solution
An alignment accuracy mark that includes multiple pattern sets defined by exposure steps, with x- and y-directional linear patterns forming contiguous rings or separate blocks, allowing for a single AA mark to check alignment between multiple groups of patterns, reducing the lateral area and measurement time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple separate AA marks are used to check alignment between multiple pattern groups, then alignment measurement completeness is improved, but the lateral area occupied in the scribe line region increases
Solution Approach 1:
The patent combines multiple alignment accuracy marks into a single integrated AA mark structure. The mark includes multiple pattern sets (first, second, third pattern sets) that correspond to different exposure steps, all contained within one unified structure. This merging approach allows simultaneous measurement of alignment between multiple pattern groups without requiring separate marks, thereby reducing the lateral area occupied in the scribe line region while maintaining complete alignment measurement capability.
Solution Approach 2:
The single AA mark structure serves multiple functions by incorporating different pattern sets that can measure alignment between various pattern groups formed by different exposure steps. The first pattern set measures alignment with the first exposure step, the second pattern set with the second exposure step, and the third pattern set with the third exposure step, making the structure universal for multi-step alignment verification.
2Measurement precision
If multiple separate AA marks are used to check alignment between multiple pattern groups, then alignment measurement completeness is improved, but measurement time increases
Solution Approach 1:
By merging multiple alignment measurement functions into a single AA mark structure, the patent enables simultaneous measurement of alignment between multiple pattern groups. The aligned mark formation unit can form one aligned mark that contains all necessary pattern sets, and the measurement unit can measure all alignments in one operation, significantly reducing the time required compared to measuring multiple separate marks sequentially.
3Manufacturing precision
If lithographic pitch resolution is increased to meet smaller device dimensions, then pattern resolution is improved, but the number of exposure steps increases requiring more alignment checks
Solution Approach 1:
The AA mark structure is designed to be universal for multi-step exposure processes. It includes multiple pattern sets that can accommodate any number of exposure steps (first, second, third pattern sets for first, second, third exposure steps respectively). This universal design allows the same mark structure to verify alignment across multiple exposure steps without requiring additional marks, thereby managing the complexity introduced by increased exposure steps.
Data Source
AI summary
An alignment accuracy (AA) mark is described, including N (N≧3) pattern sets defined by N exposure steps respectively. The N exposure steps are performed also to a device area disposed on a wafer together with the AA mark. The i-th (i=1, 2 . . . N−1) pattern set surrounds the (i+1)-th pattern set. Each pattern set includes a 1st set of x-directional linear patterns, a 2nd set of x-directional linear patterns arranged opposite to the 1st set of x-directional linear patterns in the y-direction, a 1st set of y-directional linear patterns, and a 2nd set of y-directional linear patterns arranged opposite to the 1st set of y-directional linear patterns in the x-direction, wherein each set of x- or y-directional linear patterns include at least three separate parallel linear patterns.