Bond Pad Structure with Intervening Metal Layer for Stress Distribution
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Solution Overview
Problem
Conventional integrated circuits (ICs) with thinned substrate and metal layers are susceptible to stress-related defects during wire bonding, leading to warping, bending, cracking, or peeling of bond pads, which affects their functionality and yield.
Innovation Solution
The implementation of an improved bond pad structure with multiple vias that distribute stress, comprising a first via layer, an intervening metal layer, and a second via layer, providing structural rigidity and electrical coupling to withstand wire bonding forces, thus protecting underlying layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the substrate and metal layers are thinned to optimize light transmission in BSI sensors, then light transmission efficiency is improved, but structural strength and stress resistance deteriorate
Solution Approach 1:
The bond pad structure is segmented into multiple functional layers: a bond pad layer, an intervening metal layer, and multiple via layers (first via layer, second via layer). This segmentation allows each layer to perform its specific function - the bond pad layer provides bonding surface, the intervening metal layer provides structural reinforcement, and the via layers provide electrical connection - while collectively maintaining both electrical functionality and mechanical strength in thinned substrates
Solution Approach 2:
The bond pad structure uses composite construction with multiple materials: conductive materials for the bond pad and via layers, and metal materials for the intervening metal layer. This composite structure combines the electrical conductivity needed for signal transmission with the mechanical strength required to resist stress during wire bonding, solving the contradiction between thinning for light transmission and maintaining structural integrity
2Illumination intensity
If the substrate and metal layers are thinned to optimize light transmission in BSI sensors, then light transmission efficiency is improved, but stress resistance during wire bonding deteriorates
Solution Approach 1:
The intervening metal layer is positioned between the bond pad layer and the substrate beforehand to provide cushioning and stress distribution. This pre-positioned structural reinforcement prevents stress concentration during wire bonding operations, protecting the thinned substrate from cracking or peeling while maintaining the optimized light transmission path
3Ease of manufacture
If a simple bond pad structure is used, then manufacturing complexity is reduced, but bonding reliability deteriorates due to stress concentration
Solution Approach 1:
The bond pad structure is divided into distinct segments (bond pad layer, intervening metal layer, first via layer, second via layer) that can be formed through sequential standard semiconductor fabrication processes. Each segment serves a specific function and can be manufactured using established techniques, making the overall complex structure manufacturable while achieving high bonding reliability through proper stress distribution
Data Source
AI summary
Some embodiments relate to a bond pad structure of an integrated circuit (IC). The bond structure includes a bond pad and an intervening metal layer positioned below the bond pad. The intervening metal layer has a first face and a second face. A first via layer is in contact with the first face of intervening metal layer. The first via layer has a first via pattern including a single via. The bond structure also includes a second via layer in contact with the second face of the intervening metal layer. The second via layer has a second via pattern that is different than first via pattern. The second via pattern includes a first via surrounding a second via. The first and second vias are concentric with one another about a central point of the second via layer.