Semiconductor Seal Ring Layout for Etch Residue Reduction
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Solution Overview
Problem
The challenge in semiconductor fabrication is the occurrence of post etch residue, particularly 'etch islands,' which can cause shorts between neighboring metal structures due to the reduction in die size, leading to increased stress during the wafer sawing process, and existing seal ring structures with narrow widths fail to adequately protect against lateral stress and residue issues.
Innovation Solution
A seal ring layout with acute-angled corners and strategically placed trenches, such as trapezoidal and square regions, is employed to minimize the intersection area and reduce the likelihood of partially etched materials, thereby preventing residue formation and enhancing protection against stress during the wafer sawing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the width of the seal ring is reduced to prevent etching induced defects, then the occurrence of partially etched residue is reduced, but the seal ring cannot protect integrated circuits from lateral stress induced during wafer sawing process
Solution Approach 1:
The seal ring structure employs asymmetric corner design where alternating corners have different configurations. Some corners feature acute angles while others have obtuse angles, creating an asymmetric pattern around the seal ring. This asymmetric design allows different regions of the seal ring to serve different functions: acute corners minimize etching residue while obtuse corners provide stress protection, thereby resolving the contradiction between etching precision and stress protection capability
Solution Approach 2:
Different regions of the seal ring are given different local properties through the asymmetric corner design. Specific corners are optimized for etching residue prevention with acute angles, while other corners are optimized for stress protection with obtuse angles. This local differentiation allows each part of the seal ring to excel at its specific function, resolving the overall contradiction between the two competing requirements
2Productivity
If the physical size of semiconductor die is reduced to maximize productivity, then more semiconductor dies can be produced by a wafer, but two neighboring metal structures become much closer increasing the risk of shorts due to etch residue
Solution Approach 1:
The acute-angled corner design converts what would normally be a problematic sharp corner (prone to etching residue) into a beneficial feature for stress distribution. By carefully designing the acute angles, the structure achieves both reduced residue formation and improved stress management, turning a potential harm into a benefit that supports both high productivity and reliability
Data Source
AI summary
A structure for reducing partially etched materials is described. The structure includes a layout of an intersection area between two trenches. First, a large intersection area having a trapezoidal corner may be replaced with an orthogonal intersection between two trenches. The layout reduces the intersection area as well as the possibility of having partially etched materials left at the intersection area. The structure also includes an alternative way to fill the intersection area with either an un-etched small trapezoidal area or multiple un-etched square areas, so that the opening area at the intersection point is reduced and the possibility of having partially etched materials is reduced too.