Sub-Resolution Dummy Features in Alignment Marks
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Solution Overview
Problem
Existing alignment structures in integrated circuit manufacturing face challenges with dishing and loading effects during chemical mechanical polishing (CMP) processes due to the larger open centers in alignment marks, which can damage overlay targets and limit CMP process windows.
Innovation Solution
Incorporating sub-resolution dummy features within the alignment marks, such as rectangular or circular assistant features, that are smaller than the resolution of alignment detection systems, to reduce loading and dishing effects while maintaining pattern contrast and alignment signal detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a larger open center region is used in alignment marks, then alignment signal detection is improved, but dishing and loading effects during CMP process worsen
Solution Approach 1:
The patent applies local quality by creating different regions within the alignment mark structure. The alignment mark contains both a detection region (outer box) that provides strong alignment signals and a filled region (inner box with dummy features) that prevents dishing and loading effects. This local differentiation allows each region to serve its specific function optimally.
Solution Approach 2:
The patent implements nesting by placing an inner box structure containing dummy features inside the outer alignment mark box. The inner box is nested within the detection region, creating a hierarchical structure where the outer box provides alignment detection while the inner box fills the open center to prevent CMP defects.
2Object-affected harmful factors
If the open center region of alignment marks is reduced, then dishing and loading effects are minimized, but alignment signal strength may be compromised
Solution Approach 1:
The alignment mark structure differentiates between regions: the outer box maintains sufficient open space for strong alignment detection, while the inner box fills the problematic open center area to prevent dishing and loading effects during CMP processing.
Solution Approach 2:
The alignment mark is segmented into functional regions: an outer detection box that provides alignment signals and an inner filled box that prevents CMP defects. This segmentation allows independent optimization of each region's properties.
3Manufacturing precision
If dummy features are added within alignment marks, then CMP uniformity is improved, but device complexity increases
Solution Approach 1:
The patent merges the alignment mark function with the CMP process control function by integrating dummy features directly into the alignment mark structure. This combination eliminates the need for separate structures and achieves multiple objectives simultaneously.
Solution Approach 2:
The alignment mark structure serves multiple functions: it provides alignment detection signals through the outer box and simultaneously prevents dishing and loading effects during CMP through the inner filled box. This multi-functionality reduces the need for additional separate structures.
Data Source
AI summary
A method and apparatus for alignment are disclosed. An exemplary apparatus includes a substrate having an alignment region; an alignment feature in the alignment region of the substrate; and a dummy feature disposed within the alignment feature. A dimension of the dummy feature is less than a resolution of an alignment mark detector.