Multi-Gate Seal Ring Layout for CMP and Etch Uniformity
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Solution Overview
Problem
Existing seal ring structures in semiconductor wafers are not robust enough to provide adequate protection against moisture and chemical degradation, leading to issues such as dishing during chemical mechanical planarization (CMP) and uneven etching, due to differences in pattern sizes and densities between the circuit and seal ring regions.
Innovation Solution
The seal ring region is designed with specific properties, including sloped corner lines, inner and outer corner regions, and uniform active and gate structures, to ensure a smooth transition from the circuit region, thereby alleviating processing issues like dishing and uneven etching. This is achieved by forming the seal ring structures simultaneously with the circuit features during FEOL, MEOL, and BEOL processes, ensuring proper line widths, pitches, and densities that match or closely resemble those of the circuit region.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the seal ring structure uses different pattern sizes and densities compared to the circuit region, then the seal ring can provide protection to the circuit devices, but this causes dishing during CMP and uneven etching
Solution Approach 1:
The patent applies local quality by creating a transition region between the circuit region and seal ring region where the pattern density gradually changes. This transition region contains intermediate structures with pattern densities that bridge the gap between the high-density circuit region and the low-density seal ring region, allowing the seal ring to maintain its protective function while enabling uniform CMP processing across the entire wafer surface.
Solution Approach 2:
The patent segments the seal ring region into multiple zones including a transition region with intermediate structures. This segmentation allows different portions of the seal ring to have different pattern densities - the transition region has intermediate density while the outer seal ring region has lower density. This segmented approach resolves the contradiction by providing both protection (through the seal ring structures) and CMP uniformity (through the graduated density transition).
2Reliability
If the seal ring structure uses different pattern sizes and densities compared to the circuit region, then the seal ring can provide protection to the circuit devices, but this causes uneven etching
Solution Approach 1:
The transition region employs local quality by introducing intermediate structures with pattern densities that are higher than the seal ring region but lower than the circuit region. This gradual change in local pattern density ensures that the etching process experiences a smooth transition in material removal rates, preventing the uneven etching that would occur with abrupt density changes while maintaining the seal ring's protective function.
Solution Approach 2:
The patent segments the seal ring structure into multiple functional zones including the transition region with intermediate structures. This segmentation creates a graduated density profile that progresses from the high-density circuit region through the intermediate transition zone to the low-density outer seal ring region, thereby achieving both protection capability and etching uniformity.
3Reliability
If the seal ring region has abrupt transition from circuit region, then the seal ring provides clear boundary protection, but this creates dishing during CMP
Solution Approach 1:
The patent introduces a transition region that segments the abrupt boundary between the circuit region and seal ring region into a gradual gradient. This transition region contains intermediate structures with pattern densities that progressively change from the circuit region density to the seal ring region density, eliminating the sharp boundary that causes dishing during CMP while preserving the protective boundary function.
Solution Approach 2:
The patent resolves the boundary sharpness issue by adding a dimensional aspect to the transition - creating a spatial gradient in pattern density across the transition region. This dimensional approach (gradual density change across space) replaces the abrupt two-state boundary, thereby preventing CMP dishing while maintaining clear boundary protection through the graduated transition zone.
Data Source
AI summary
The present disclosure provides a semiconductor structure that includes a substrate having a circuit region and a seal ring region around the circuit region, first active regions of a first width disposed in the circuit region, second active regions of a second width disposed in the seal ring region, first gate structures disposed on the first active regions, and second gate structures disposed on longitudinal edges of the second active regions. The first gate structures are longitudinally oriented to be orthogonal with the first active regions. The second gate structures are longitudinally oriented to be in parallel with the second active regions. The second width is greater than the first width.