GaN Power Diode Edge Termination via Hydrogen Plasma
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Solution Overview
Problem
Existing edge termination techniques for GaN power devices, such as mesa etching and ion-implantation, induce damage and increase fabrication costs, while requiring high temperatures that can decompose GaN and compromise device reliability.
Innovation Solution
Hydrogen-plasma-based edge termination techniques that use inductively coupled plasma tools for low-temperature, low-damage processing, eliminating the need for etching and implantation, and thermally annealing to form highly resistant GaN for effective termination and isolation of GaN power diodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ion-implantation is used to form high-resistivity layer at device edge, then breakdown voltage is improved, but fabrication complexity and cost increase due to requirement of high temperature post-implantation thermal annealing
Solution Approach 1:
The patent replaces the mechanical ion-implantation process with a plasma-based chemical process. Instead of physically implanting ions into the GaN lattice and requiring high-temperature annealing to activate them, the invention uses plasma to directly introduce hydrogen atoms that form hydrogen complexes with magnesium dopants at lower temperatures, achieving the same high-resistivity effect without the complex thermal annealing step.
Solution Approach 2:
The patent changes the temperature parameter from high temperature (required for ion-implantation annealing) to low temperature (plasma processing temperature). By using plasma to deliver hydrogen atoms directly to the device edge region, the process achieves high-resistivity formation at temperatures compatible with GaN stability, eliminating the need for high-temperature thermal annealing.
2Reliability
If high temperature thermal annealing is used to activate implanted atoms, then high-resistivity layer is formed, but GaN decomposition occurs leading to reduced device reliability
Solution Approach 1:
The patent substitutes the thermal activation mechanism with a plasma-based chemical reaction mechanism. Instead of using heat to activate implanted ions, the invention uses plasma to deliver reactive hydrogen atoms that chemically bond with magnesium dopants at lower temperatures, forming hydrogen-magnesium complexes that provide the desired high-resistivity effect without thermal decomposition of GaN.
Solution Approach 2:
The patent fundamentally changes the temperature parameter from high temperature (thermal annealing) to low temperature (plasma processing). This parameter change allows the formation of hydrogen complexes with magnesium dopants at temperatures that do not cause GaN decomposition, thereby maintaining device reliability while achieving the high-resistivity layer formation.
3Strength
If mesa etching is used for edge termination, then breakdown at junction edge is mitigated, but etching damages are induced and fabrication process is complicated
Solution Approach 1:
The patent replaces the mechanical etching process with a plasma-based chemical modification process. Instead of physically removing material through etching to create beveled sidewalls or mesa steps, the invention uses plasma to chemically modify the surface region by introducing hydrogen atoms that form hydrogen complexes with magnesium dopants, creating a high-resistivity layer that mitigates edge breakdown without physical damage to the GaN structure.
Solution Approach 2:
The patent extracts the harmful etching step from the edge termination process. By using plasma to directly form the high-resistivity layer through chemical reaction rather than physical removal of material, the invention eliminates etching damages while achieving the same edge termination effect, thereby simplifying the fabrication process.
4Strength
If sophisticated field plates are designed for edge termination, then breakdown voltage is improved, but device capacitance increases and fabrication is complicated
Solution Approach 1:
The patent extracts and eliminates the need for sophisticated field plate structures by using plasma-based edge termination. Instead of adding complex metal field plate structures to redistribute electric fields, the invention directly modifies the semiconductor material properties at the device edge through plasma hydrogenation, creating a high-resistivity layer that naturally terminates the electric field without requiring additional structural elements.
Solution Approach 2:
The patent replaces the structural field plate approach with a material property modification approach. Instead of using metal field plates to control electric field distribution, the invention uses plasma to chemically modify the GaN material at the edge region, creating a high-resistivity layer that provides field termination through its electrical properties rather than through geometric field shaping.
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 approach results in improved breakdown voltage, reduced on-resistance, and enhanced device performance with lower fabrication complexity and costs, achieving specific on-resistance of 0.4 mΩ cm2 and breakdown voltage of ~1.4 kV, and improved rectifying behaviors.
Implementation Method 1
exposing the p-GaN layer to a hydrogen plasma
Implementation Method 2
hydrogenate p-GaN to form the termination
Implementation Method 3
a subsequent thermal annealing can thermally drive down hydrogen to hydrogenate p-GaN
Implementation Method 4
thermally annealing the p-GaN layer
Data Source
AI summary
A p-n diode includes a first electrode, a n-GaN layer on the first electrode, a p-GaN layer on the n-GaN layer, and a second electrode on a first portion of the p-GaN layer. A region of the p-GaN layer surrounding the electrode is a passivated region. Treating a GaN power device having a p-GaN layer includes covering a portion of the p-GaN layer with a metal layer, exposing the p-GaN layer to a hydrogen plasma, and thermally annealing the p-GaN layer, thereby passivating a region of the p-GaN layer proximate the metal layer.