Obtuse Angle IC Metal Pads for Stress Relief
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Solution Overview
Problem
Integrated circuit structures with metal pads and lines experience reliability issues due to stress concentration at the interface between the metal lines and pads, leading to cracks, and adjacent dielectric layers also crack under the stress caused by thermal expansion and contraction.
Innovation Solution
Modifying the pattern of the integrated circuit structure by adding patches to form obtuse angles between the metal pads and lines, eliminating acute and right angles through Boolean operations and patching processes, which are then used to create lithography masks for manufacturing, ensuring that the modified pattern is formed on the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal pads with large size are connected to metal lines with small widths using conventional right-angle interfaces, then electrical connection is achieved, but stress concentration occurs at the interface leading to cracks
Solution Approach 1:
The patent applies curvature by replacing the conventional right-angle interface between metal pads and lines with an obtuse-angle interface. This geometric modification creates a smoother transition zone that distributes stress more evenly, eliminating the sharp stress concentration points that occur at 90-degree corners. The obtuse angle design effectively rounds the stress distribution profile, preventing crack initiation at the interface.
Solution Approach 2:
The patent changes the geometric parameter of the interface angle from 90 degrees to an obtuse angle (greater than 90 degrees). This parameter modification fundamentally alters the stress distribution characteristics at the pad-line interface, transforming the stress concentration problem into a stress distribution problem, thereby improving interface reliability and preventing cracks.
2Ease of manufacture
If conventional right-angle patterns are used at the interface between metal lines and pads, then manufacturing is simple, but dielectric layers adjacent to metal pads crack due to stress
Solution Approach 1:
By introducing obtuse angles instead of right angles at the pad-line interface, the patent creates a geometric configuration that reduces stress transfer to adjacent dielectric layers. The curved-like transition of the obtuse angle prevents stress concentration from propagating into the dielectric, thereby preventing cracks while remaining compatible with standard manufacturing processes.
3Productivity
If standard lithography masks with right-angle patterns are used, then manufacturing process is straightforward, but cracks occur at the interface between metal lines and pads
Solution Approach 1:
The patent incorporates the obtuse-angle design directly into the lithography mask pattern before manufacturing. This preliminary design modification ensures that the stress-distributing geometric feature is built-in from the start, preventing interface cracks before they can occur during operation, while maintaining compatibility with existing lithography manufacturing processes.
Data Source
AI summary
A method includes forming a seed layer on a semiconductor wafer, coating a photo resist on the seed layer, performing a photo lithography process to expose the photo resist, and developing the photo resist to form an opening in the photo resist. The seed layer is exposed, and the opening includes a first opening of a metal pad and a second opening of a metal line connected to the first opening. At a joining point of the first opening and the second opening, a third opening of a metal patch is formed, so that all angles of the opening and adjacent to the first opening are greater than 90 degrees. The method further includes plating the metal pad, the metal line, and the metal patch in the opening in the photo resist, removing the photo resist, and etching the seed layer to leave the metal pad, the metal line and the metal patch.