GaN HFET Composite Passivation for Charge Buildup Control
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Solution Overview
Problem
GaN-based high-voltage field effect transistors (HFETs) face challenges due to charge buildup and electric field redistribution, leading to performance changes and potential failure from dielectric breakdown or cracking of device layers.
Innovation Solution
The implementation of a composite passivation layer with a gate dielectric and insulation layers, which reduces charging in the passivation layers by utilizing materials with wider bandgaps, thereby minimizing the risk of device failure and performance drift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional passivation layers are used in GaN-based HFETs, then device structure is simple, but charge buildup occurs leading to dielectric breakdown and device failure
Solution Approach 1:
The patent applies composite materials by implementing a multi-layer passivation structure consisting of a first passivation layer (e.g., silicon nitride with wide bandgap) and a second passivation layer (e.g., silicon oxide with narrower bandgap). This composite structure combines materials with different electrical properties to prevent charge buildup while maintaining device reliability, directly resolving the contradiction between simple structure and high reliability.
2Reliability
If single-layer passivation is used, then manufacturing process is simple, but charging in passivation layers causes performance drift and device failure
Solution Approach 1:
The patent applies segmentation by dividing the single passivation layer into multiple distinct layers, each with specific functions. The first passivation layer handles charge blocking, while the second layer provides additional protection and stress management. This segmentation improves device stability by preventing charge buildup, while the systematic fabrication process maintains manufacturing feasibility.
3Strength
If thick insulation layers are used to prevent breakdown, then dielectric strength is improved, but device layers may crack due to thermal stress
Solution Approach 1:
The patent applies parameter changes by carefully controlling the thickness parameters of each passivation layer. The first passivation layer is designed with optimal thickness to provide charge blocking without excessive stress, while the second layer compensates for thermal stress. This parameter optimization achieves both high dielectric strength and maintained layer integrity under thermal conditions.
Solution Approach 2:
The composite passivation structure uses materials with different thermal and mechanical properties to balance dielectric strength and stress management. The combination of silicon nitride and silicon oxide layers provides both the required breakdown voltage resistance and stress distribution to prevent cracking, resolving the contradiction between strength and composition stability.
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 use of composite passivation layers effectively mitigates charging issues, leading to improved reliability and stability of GaN-based HFETs by reducing the probability of device failure and maintaining performance over extended operational periods.
Implementation Method 1
reduces charging in the passivation layers by utilizing materials with wider bandgaps
Data Source
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AI summary
A high-voltage field effect transistor (HFET) includes a first semiconductor material, a second semiconductor material, and a heterojunction. The heterojunction is disposed between the first semiconductor material and the second semiconductor material. The HFET also includes a plurality of composite passivation layers, where a first composite passivation layer includes a first insulation layer and a first passivation layer, and a second composite passivation layer includes a second insulation layer and a second passivation layer. A gate dielectric is disposed between the first passivation layer and the second semiconductor material. A gate electrode is disposed between the gate dielectric and the first passivation layer. A first gate field plate is disposed between the first passivation layer and the second passivation layer. A source electrode and a drain electrode are coupled to the second semiconductor material, and a source field plate is coupled to the source electrode.