Bonding Pad Overlap Reduces Chip Area
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Solution Overview
Problem
The existing semiconductor devices for compound semiconductor processes face challenges in reducing chip area due to the need for dedicated regions for bonding pads, leading to increased costs and difficulties in integrating protection circuits effectively.
Innovation Solution
A semiconductor device with a bonding pad structure that partially overlaps the circuit element, utilizing a second metal film with higher Young's modulus as a stress dispersion sheet, and including additional metal films for reduced contact resistance and galvanic corrosion prevention, allowing for reduced chip area and enhanced reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a dedicated region is secured for arranging bonding pads, then bonding pad arrangement is enabled, but chip area increases
Solution Approach 1:
The bonding pad is merged with the circuit element by disposing the bonding pad so as to at least partially overlap the circuit element. This integration eliminates the need for separate dedicated regions for bonding pads, thereby reducing chip area while maintaining bonding functionality.
Solution Approach 2:
The bonding pad is extended in the vertical dimension by forming multiple metal films (first metal film, second metal film, and third metal film) stacked in the thickness direction. This multi-layer structure enables the bonding pad to fulfill both electrical connection and stress dispersion functions without requiring additional horizontal space.
2Area of stationary object
If bonding pad overlaps circuit element, then chip area is reduced, but stress-induced breakdown risk increases
Solution Approach 1:
A second metal film with higher Young's modulus than the first metal film is inserted between the bonding pad structure and the circuit element. This intermediary layer serves as a stress dispersion sheet that absorbs and distributes bonding-induced stresses, preventing stress concentration at the circuit element and reducing breakdown risk.
Solution Approach 2:
The bonding pad structure employs a composite multi-layer metal configuration where the first metal film (softer, lower Young's modulus) and second metal film (harder, higher Young's modulus) are stacked together. This composite structure combines the electrical conductivity and bonding affinity of the softer metal with the stress resistance and dispersion capability of the harder metal.
3Reliability
If second metal film with higher Young's modulus is added, then stress dispersion is improved, but manufacturing complexity increases
Solution Approach 1:
The second metal film is designed with specific parameter thresholds: its Young's modulus must be higher than that of the first metal film, and its thickness is controlled to be between 1 nm and 100 nm. These parameter specifications enable the second metal film to provide sufficient stress dispersion capability while maintaining compatibility with existing thin-film deposition processes.
Solution Approach 2:
The second metal film is selectively formed only in the region where the bonding pad overlaps the circuit element. This localized application concentrates the stress dispersion function precisely where it is needed most, avoiding unnecessary addition of structural complexity to other parts of the device.
4Reliability
If multiple metal films are used in bonding pad, then contact resistance and corrosion are reduced, but manufacturing process complexity increases
Solution Approach 1:
The bonding pad is segmented into three distinct metal film layers, each performing a specific function: the first metal film provides electrical conductivity and bonding affinity, the second metal film provides stress dispersion, and the third metal film provides additional corrosion protection and low contact resistance. This functional segmentation allows optimization of each layer independently.
Solution Approach 2:
The multi-metal-film bonding pad employs composite material science by stacking metals with different properties (electrical conductivity, mechanical strength, corrosion resistance) to create a structure that exhibits superior overall performance compared to single-metal configurations, while utilizing standard sequential deposition manufacturing processes.
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 configuration effectively suppresses chip area expansion, reduces stress-induced damage, and maintains low contact resistance, thereby enhancing the reliability and cost-effectiveness of compound semiconductor devices.
Implementation Method 1
the second metal film functions as a stress dispersion sheet to thereby disperse a stress generated in the circuit element during bonding
Implementation Method 2
coating the surface of the electrode pad with NiP by electroless plating
Data Source
AI summary
A circuit element is formed on a substrate made of a compound semiconductor. A bonding pad is disposed on the circuit element so as to at least partially overlap the circuit element. The bonding pad includes a first metal film and a second metal film formed on the first metal film. A metal material of the second metal film has a higher Young's modulus than a metal material of the first metal film.