Bonding Pad Structure With Stress Buffer for Ultrasonic Bonding
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Solution Overview
Problem
Conventional bonding pads in integrated circuit elements suffer from stress concentration and cracking during ultrasonic bonding due to the high Young's modulus of tungsten plugs, leading to deteriorated bondability between conductive members and the bonding pad.
Innovation Solution
A bonding pad design featuring a stress buffer layer with a lower Young's modulus than the tungsten plug, extending over the entire pad, and a connecting member with insulators and plugs to disperse stress, ensuring the stress buffer layer's thickness is greater than the surface electrode layer's thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a multilayer structure with tungsten plug and island-type insulator is used in the bonding pad, then the manufacturing process is simplified and integration is achieved, but stress concentration occurs during ultrasonic bonding leading to cracks
Solution Approach 1:
The patent changes the physical parameter of Young's modulus by introducing a stress buffer layer with lower Young's modulus than the tungsten plug. This stress buffer layer absorbs and disperses the stress concentrated during ultrasonic bonding, preventing crack formation while maintaining the multilayer structure's manufacturing advantages
Solution Approach 2:
The patent creates a composite structure by combining materials with different mechanical properties - the hard tungsten plug for electrical connection and the softer stress buffer layer for stress absorption. This composite approach allows the bonding pad to maintain structural integrity while withstanding ultrasonic bonding loads
2Strength
If the bonding pad uses a rigid structure with high Young's modulus materials, then electrical connection is achieved, but stress cannot be buffered leading to bondability deterioration
Solution Approach 1:
The patent applies local quality by creating different mechanical properties in different regions of the bonding pad. The tungsten plug maintains high strength for electrical connection, while the stress buffer layer provides localized stress absorption capability. This spatial differentiation of material properties allows simultaneous achievement of strong electrical connection and good bondability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively disperses stress during ultrasonic bonding, reducing the occurrence of cracks in both the plug and insulator, thereby enhancing bondability between the conductive member and the bonding pad.
Implementation Method 1
a Young's modulus of tungsten constituting the integrated mesh-type tungsten plug is higher than a Young's modulus of an insulator material constituting the island-type insulator, a structure including the integrated mesh-type tungsten plug and the island-type insulator hardly buffers a stress
Implementation Method 2
the bonding pad is subjected to ultrasonic bonding to a conductive member such as a wire
Data Source
AI summary
The bonding pad includes a surface electrode layer that has a first surface; a resistance layer that has a second surface; a stress buffer layer that is disposed between the surface electrode layer and the resistance layer in the first direction; and a connecting member that connects the surface electrode layer and the stress buffer layer in the first direction. The connecting member includes an insulator that is in contact with the each of the surface electrode layer and the stress buffer layer in the first direction, and a plurality of plugs that are in contact with the insulator in the direction orthogonal to the first direction and electrically connect the surface electrode layer and the stress buffer layer. In the first direction, a thickness of the stress buffer layer is larger than a thickness of the surface electrode layer.