Semiconductor Alignment Mark Layout for Precise Overlay After CMP
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Solution Overview
Problem
Current pattern alignment techniques in semiconductor integrated circuit fabrication provide less than desirable alignment as technology nodes decrease, leading to inaccuracies in feature formation on successive layers.
Innovation Solution
A method is introduced where a computing device adjusts the density of alignment marks in the scribe line region of an integrated circuit design layout by adding or removing dummy lines, ensuring the alignment mark density matches the pattern density, thereby improving alignment precision and reducing errors during fabrication processes like chemical mechanical polishing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If traditional pattern alignment techniques are used, then the fabrication process is simple, but alignment precision deteriorates as technology nodes decrease
Solution Approach 1:
The alignment mark is divided into multiple segments including a first alignment mark portion and a second alignment mark portion at different heights. This segmentation allows each portion to serve specific alignment functions independently, improving overall alignment precision without requiring a completely complex new structure
Solution Approach 2:
The alignment mark structure is extended into the vertical dimension by creating portions at different heights (first height and second height). This three-dimensional configuration provides multiple alignment references that improve precision while maintaining reasonable structural complexity
2Manufacturing precision
If alignment mark density is increased to improve alignment precision, then alignment precision improves, but dishing effects during chemical mechanical polishing worsen
Solution Approach 1:
Different regions of the alignment mark structure are given different properties - the first alignment mark portion is at a first height while the second alignment mark portion is at a second height. This local variation in vertical position allows the structure to provide adequate alignment references without creating excessive density in a single plane, thereby reducing dishing effects during CMP
Solution Approach 2:
By distributing alignment mark portions across different vertical heights, the structure reduces the concentration of material in any single horizontal plane. This three-dimensional distribution mitigates the dishing effect that occurs during chemical mechanical polishing while maintaining sufficient alignment precision
3Length of moving object
If feature size is reduced to achieve smaller technology nodes, then device capability improves, but alignment precision within the field deteriorates
Solution Approach 1:
The alignment mark is segmented into multiple portions that can serve as independent alignment references. This segmentation provides multiple reference points across the exposure field, maintaining alignment precision even as individual feature sizes are reduced for smaller technology nodes
Solution Approach 2:
The vertical dimension is utilized to create alignment mark portions at different heights, providing multiple alignment references that span the exposure field. This approach maintains alignment precision within the field as technology nodes decrease and feature sizes are reduced
Data Source
AI summary
A method for fabricating a semiconductor device is provided. The method includes forming an alignment mark in a material layer, wherein the alignment mark has a step sidewall in the material layer, and the step sidewall of the alignment mark has a floor surface portion; forming a feature material over the material layer; and performing a planarization process at least on the feature material, wherein the planarization process stops at a level higher than the floor surface portion of the step sidewall of the alignment mark.