SiC Passivation Anchorage Structure Against Thermal-Cycle Delamination
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Solution Overview
Problem
The development and manufacture of SiC-based electronic devices are limited by the electrical and mechanical properties of passivation layers, particularly due to high coefficients of thermal expansion differences between polymeric materials and SiC, leading to adhesion issues and potential delamination during thermal cycling tests.
Innovation Solution
A manufacturing method for an anchorage element that includes a semiconductor body with a passivation layer extending over its surface, featuring a first portion with a maximum dimension and a second portion with a smaller dimension, both extending into a cavity in the semiconductor body to securely fix the passivation layer, thereby preventing delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polymeric materials (e.g., polyimide) are used for passivation layers to withstand high operating temperatures and high dielectric strength, then electrical performance is improved, but adhesion to SiC deteriorates due to high coefficients of thermal expansion difference
Solution Approach 1:
A silane coupling agent layer is introduced as an intermediary between the polymeric passivation layer and the SiC semiconductor body. This coupling agent has affinity to both materials, reducing the interfacial tension and improving adhesion. The silane layer acts as a chemical bridge that bonds to the SiC surface through siloxane bonds and also interacts with the polymeric material, thereby resolving the adhesion problem caused by CTE mismatch while maintaining the electrical performance benefits of polymeric passivation layers.
Solution Approach 2:
The surface energy parameters of the SiC substrate are modified through plasma treatment or chemical etching before applying the silane coupling agent. This changes the surface chemistry and morphology, creating more reactive sites for silane attachment and improving the overall adhesion system. By altering surface parameters rather than changing the bulk materials, the adhesion is enhanced while the electrical performance characteristics of the polymeric layer are preserved.
2Adaptability or versatility
If large temperature variations are applied to electronic devices, then operational flexibility is improved, but mechanical stresses at the interface increase leading to delamination
Solution Approach 1:
The silane coupling agent serves as a compliant intermediary layer that can accommodate thermal expansion differences between the polymeric passivation and SiC substrate during temperature cycling. This intermediate layer absorbs the mechanical stresses generated by CTE mismatch, preventing stress concentration at the interface and avoiding delamination while allowing the device to operate across wide temperature ranges.
Solution Approach 2:
The passivation system is structured as a composite consisting of three layers: SiC substrate, silane coupling agent layer, and polymeric passivation layer. This composite structure combines the high temperature stability of SiC, the adhesion benefits of silane, and the flexibility of polymeric materials, creating a multi-layer system that can withstand thermal cycling without delamination while maintaining operational flexibility.
3Reliability
If high voltage differences are withstood in reverse-biasing conditions, then electrical performance is improved, but risk of electrical discharge increases due to potential delamination
Solution Approach 1:
The silane coupling agent layer acts as an electrical insulator and mechanical stabilizer at the interface, preventing electrical discharge by ensuring continuous contact between the passivation layer and substrate. This intermediary layer eliminates air gaps that would otherwise form during thermal cycling, thereby preventing electrical breakdown while allowing the device to withstand high reverse-bias voltages.
Solution Approach 2:
The silane coupling agent provides beforehand cushioning by pre-establishing a strong, stable interface that resists delamination under subsequent thermal and electrical stress. This protective layer is applied in advance to prevent the formation of defects that could lead to electrical discharge, thereby cushioning against future harmful effects while maintaining high voltage withstanding capability.
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 anchorage element effectively prevents delamination of the passivation layer from the SiC semiconductor body during thermal cycles and high voltage reverse-biasing conditions, enhancing the reliability and electrical performance of the electronic device.
Implementation Method 1
polymeric materials have high coefficients of thermal expansion (CTEs) (e.g., CTE=43e−6 1/K for the material polybenzobisoxazole—PIX), and this causes problems of adhesion of the passivation layer to the SiC, which has a lower coefficient of thermal expansion (CTE=3.8e−6 1/K)
Data Source
AI summary
A manufacturing method of an anchorage element of a passivation layer, comprising: forming, in a semiconductor body made of SiC and at a distance from a top surface of the semiconductor body, a first implanted region having, along a first axis, a first maximum dimension; forming, in the semiconductor body, a second implanted region, which is superimposed to the first implanted region and has, along the first axis, a second maximum dimension smaller than the first maximum dimension; carrying out a process of thermal oxidation of the first implanted region and second implanted region to form an oxidized region; removing said oxidized region to form a cavity; and forming, on the top surface, the passivation layer protruding into the cavity to form said anchorage element fixing the passivation layer to the semiconductor body.