Schottky Power Device Isolation Structure Against Passivation Cracking
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Solution Overview
Problem
Conventional semiconductor power devices experience degradation and failure due to cracking of the passivation layer caused by thermal expansion mismatches during reliability tests like TCT, allowing water vapor and ions to enter the device.
Innovation Solution
A power device design featuring a substrate, drift layer, terminal region, active region, electrode layer, Schottky contact layer, isolation layer, and passivation layer, where the isolation layer separates the passivation layer from the electrode layer, and the thermal expansion coefficients are arranged such that a>b>c, preventing cracking during thermal cycling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the passivation layer extends to the surface of the frontal electrode to prevent external water vapor and ions from affecting the internal structure, then the protection against external contaminants is improved, but the passivation layer cracks during thermal cycling due to thermal expansion mismatch, allowing water vapor and ions to enter the device
Solution Approach 1:
The device structure is segmented into distinct functional regions: a terminal region where the passivation layer extends to the electrode surface for protection, and an active region where the passivation layer is separated from the electrode by an isolation layer. This segmentation allows the device to simultaneously achieve protection where needed and stress relief where critical, resolving the contradiction between maintaining passivation layer integrity and providing contaminant protection.
Solution Approach 2:
The passivation layer configuration is made non-uniform across different regions of the device. In the terminal region, the passivation layer directly contacts the electrode surface to provide protection. In the active region, the isolation layer is introduced to separate the passivation layer from the electrode, creating local quality differences that prevent cracking while maintaining protection where required.
2Object-affected harmful factors
If the passivation layer is made continuous to the electrode surface for protection, then the sealing effect is improved, but the thermal stress during reliability tests causes cracking and device failure
Solution Approach 1:
The continuous passivation layer is segmented by introducing an isolation layer in the active region, creating a discontinuous structure that prevents stress accumulation. The isolation layer acts as a stress break point, allowing the device to withstand thermal cycling while maintaining effective sealing in the terminal region where the passivation layer remains continuous with the electrode.
Solution Approach 2:
The isolation layer serves as an intermediary element between the passivation layer and the electrode in the active region. This intermediary structure prevents direct mechanical coupling that causes stress transfer during thermal expansion, thereby preventing cracking while allowing the passivation layer to maintain its protective function in other regions.
3Area of stationary object
If the passivation layer covers the entire electrode surface, then the protection coverage is improved, but the thermal expansion mismatch causes cracking at the interface
Solution Approach 1:
The interface between the passivation layer and electrode is segmented into two types: direct contact in the terminal region for protection, and isolated contact via the isolation layer in the active region. This segmentation maintains large coverage area for protection while preventing stress concentration at the interface, thereby preserving interface strength through strategic discontinuity.
Solution Approach 2:
The interface quality is made non-uniform: in the terminal region, the interface is direct and continuous for maximum protection coverage; in the active region, the interface is mediated by the isolation layer to prevent cracking. This local differentiation of interface quality allows the system to achieve both wide coverage and high interface strength where critical.
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
The design effectively prevents cracking of the passivation layer and electrode layer, enhancing the reliability and longevity of the semiconductor power device by mitigating the effects of thermal stress.
Implementation Method 1
The isolation layer has a thermal expansion coefficient a, the electrode layer has a thermal expansion coefficient b, the passivation layer has a thermal expansion coefficient c, and a>b>c
Data Source
AI summary
A power device includes a substrate, a drift layer disposed on the substrate, a terminal region and an active region disposed in the drift layer, an electrode layer disposed on the active region, a Schottky contact layer disposed between the electrode layer and the active region, a passivation layer disposed on the drift layer, and an isolation layer disposed between the passivation layer and the electrode layer so that the passivation layer and the electrode layer are at least partially separated from each other. The isolation layer, the electrode layer, and the passivation layer each respectively has a thermal expansion coefficient a, b, c, and a>b>c.