SiC Passivation Interface Layers to Prevent Delamination
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Solution Overview
Problem
The development of silicon carbide (SiC)-based electronic devices is limited by adhesion problems between passivation layers and the SiC substrate due to high thermal expansion mismatch, leading to delamination and potential electric discharges during thermal cycling and high voltage operations.
Innovation Solution
Incorporating adhesion improving layers, such as aluminum oxide (Al2O3) and hafnium oxide (Hf2O3), between the passivation layer and the SiC substrate using Atomic Layer Deposition (ALD) to enhance bonding and prevent delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polymeric materials are used for passivation layers to withstand high operating temperatures and high dielectric strength, then electrical performance is improved, but adhesion to SiC substrate deteriorates due to high coefficient of thermal expansion mismatch
Solution Approach 1:
An adhesion improving layer comprising aluminum oxide (Al2O3) and hafnium oxide (Hf2O3) is introduced between the polymeric passivation layer and the SiC substrate. This intermediary layer has a coefficient of thermal expansion intermediate between the polymeric material and SiC, reducing thermal stress during temperature cycles and preventing delamination while maintaining electrical performance.
2Reliability
If thermal cycling is performed to test device reliability, then device robustness is improved, but delamination occurs at the passivation layer-SiC interface due to accumulated thermal stresses
Solution Approach 1:
The coefficient of thermal expansion parameter of the passivation system is modified by introducing the adhesion improving layer with intermediate CTE properties. This gradient in thermal expansion parameters across the layers reduces thermal stress accumulation during cycling, maintaining interface stability while enabling robustness testing.
3Reliability
If high voltage reverse bias conditions are applied to test device performance, then electrical characteristics are improved, but electric discharges occur at delaminated interfaces causing device damage
Solution Approach 1:
The adhesion improving layer is deposited beforehand to prevent delamination before high voltage stress is applied. This preventive measure ensures continuous passivation coverage, eliminating the harmful effect of electric discharges at delaminated interfaces during reverse bias operation.
4Strength
If multiple dielectric layers are used to reduce mechanical stresses at the interface, then adhesion is improved, but device complexity increases
Solution Approach 1:
Instead of using multiple thick dielectric layers, a thin adhesion improving layer (sufficient but not excessive thickness) is applied. This partial action approach achieves the necessary adhesion improvement without unnecessarily increasing device complexity, as the thin layer provides adequate stress management while maintaining structural simplicity.
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 adhesion improving layers effectively prevent delamination and electric discharges, ensuring high reliability and structural integrity of SiC-based electronic devices under thermal and reverse bias conditions.
Implementation Method 1
a first adhesion improving layer (82; 102; 112) coupled to the passivation layer (69) and to the solid body (53), of a second material having predefined or selected characteristics of adhesion to the first material, and configured to bond together the passivation layer (69) and the solid body (53)
Implementation Method 2
Incorporating adhesion improving layers, such as aluminum oxide (Al2O3) and hafnium oxide (Hf2O3), between the passivation layer and the SiC substrate using Atomic Layer Deposition (ALD)
Implementation Method 3
the high dielectric strength of polymeric materials ensures that the passivation layers withstand high electric fields, and therefore high potential differences thereacross, without breaking or perforating ('electrical breakdown')
Implementation Method 4
polymeric materials have high coefficients of thermal expansion (CTE) (e.g., CTE=43e−6 1/K for Polybenzobisoxazole material, or 'PIX'), and it causes adhesion problems of the passivation layer to SiC, which has a lower coefficient of thermal expansion (CTE=3.8e−6 1/K)
Data Source
AI summary
Electronic device, comprising: a solid body including a Silicon Carbide substrate, and further including an electrical terminal of the electronic device on the substrate; a passivation layer on the electrical terminal, of a first material; and a first adhesion improving layer coupled to the passivation layer and to the solid body, of a second material having predefined characteristics of adhesion to the first material, and configured to bond together the passivation layer and the solid body.