Copper Layer Spacing from Polyimide in Power Semiconductors
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Solution Overview
Problem
The diffusion of Cu atoms into the polyimide layer in power semiconductor devices, particularly those operating at high temperatures, degrades the reliability and performance of the elements due to the contact between the copper layer and the polyimide layer during operation.
Innovation Solution
A power semiconductor device configuration where the copper layer is positioned away from the polyimide layer by a distance greater than half the thickness of the copper layer, preventing direct contact and diffusion, and a method for manufacturing such devices with a copper wire joined to the copper layer located away from the polyimide layer to maintain reliable bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the copper layer is disposed on the electrode and the polyimide layer covers the electrode edge, then the polyimide layer provides protective film function, but Cu atoms diffuse into the polyimide layer causing reliability degradation
Solution Approach 1:
The patent divides the electrode surface into distinct functional zones: a copper layer region for electrical connection and a polyimide layer region for protection. By spatially segmenting these layers and ensuring they do not overlap, the harmful diffusion of Cu atoms into the polyimide is prevented while maintaining both the electrical and protective functions.
Solution Approach 2:
The patent extracts the copper layer from the area where the polyimide layer is disposed, removing the source of harmful Cu atom diffusion from contact with the protective film. This separation eliminates the diffusion pathway while preserving the individual functions of both layers.
2Reliability
If a large-diameter copper wire is used for high current control, then conductivity and yield strength are improved, but the wire bonding process causes greater impact on the electrode site
Solution Approach 1:
The patent positions the copper layer away from the polyimide layer in advance, creating a buffer zone that absorbs the impact forces during wire bonding. This preemptive spatial arrangement protects the electrode structure from damage caused by the greater impact of large-diameter copper wire bonding.
3Reliability
If the copper layer is positioned away from the polyimide layer, then Cu atom diffusion is prevented, but the joining area for copper wire may be reduced
Solution Approach 1:
The patent applies local quality by concentrating the copper layer in specific areas where electrical connection is needed, while allowing the polyimide layer to cover other areas for protection. This localized positioning ensures sufficient joining area for copper wire while preventing diffusion at the interface between layers.
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 reduces reliability degradation and maintains favorable joining of the copper wire, preventing Cu-atom diffusion into the polyimide layer under high-temperature operation, thus enhancing the protection performance and yield of the power semiconductor device.
Implementation Method 1
The copper wire is joined to the aluminum layer along with ultrasonic vibration
Data Source
AI summary
An electrode is disposed on a semiconductor layer. A polyimide layer has an opening disposed on the electrode, covers the edge of the electrode, and extends onto the electrode. A copper layer is disposed on the electrode within the opening, and located away from the polyimide layer on the electrode. A copper wire has one end joined on the copper layer.