III-Nitride Enhancement Mode Device Trench Oxidation
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Solution Overview
Problem
Reliable fabrication and manufacturing of high-voltage III-Nitride (III-N) enhancement-mode (E-mode) semiconductor devices are challenging due to their tendency to operate in depletion mode, requiring complex gate-drive circuits and increased risk of accidental turn-on in power switching applications.
Innovation Solution
A method involving the formation of III-N devices with a III-N channel layer, barrier layer, and insulator layer, where a trench is created by removing parts of the insulator and barrier layers, followed by annealing in an oxygen gas ambient to oxidize the barrier layer, allowing for the formation of a conductive channel with a positive threshold voltage, enabling enhancement-mode operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional III-N device fabrication methods are used, then devices operate in depletion mode with negative threshold voltage, but this requires complex gate-drive circuits and increases risk of accidental turn-on
Solution Approach 1:
The patent changes the threshold voltage parameter from negative (depletion mode) to positive (enhancement mode) by modifying the device structure. Specifically, it introduces a trench structure that removes or reduces the barrier layer thickness in specific regions, thereby changing the electrical characteristics to achieve enhancement-mode operation with positive threshold voltage
Solution Approach 2:
The patent segments the barrier layer by introducing a trench structure that divides the device into different regions. The barrier layer is removed or reduced in the trench region while maintained in other regions, creating spatially varying electrical properties that enable enhancement-mode operation
2Reliability
If trench structure is formed by removing insulator and barrier layers, then enhancement-mode operation is achieved, but manufacturing precision is required to control barrier layer thickness within predetermined range
Solution Approach 1:
The patent performs preliminary etching of the barrier layer to create a trench structure before final device completion. This preliminary action establishes the foundation for enhancement-mode operation by pre-defining the regions where barrier layer thickness will be controlled within specific ranges
Solution Approach 2:
The patent utilizes annealing in oxygen ambient to oxidize the remaining barrier layer, effectively reducing its thickness and changing its electrical properties. This parameter change approach allows precise control of barrier layer characteristics without requiring extremely precise etching
3Manufacturing precision
If barrier layer is oxidized through annealing in oxygen ambient, then threshold voltage is increased to positive values, but process time and temperature control are required
Solution Approach 1:
The patent employs annealing process parameters (temperature, time, oxygen ambient) to transform the barrier layer properties. By controlling these parameters, the barrier layer is oxidized to achieve the desired positive threshold voltage while managing the trade-off between process duration and voltage precision
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 approach results in III-N devices with a threshold voltage greater than 2V and low threshold voltage hysteresis, suitable for high-voltage applications with improved manufacturing yield and reduced risk of accidental turn-on.
Implementation Method 1
annealing the III-N device in a gas ambient including oxygen at an elevated temperature to oxidize the remaining portion of the barrier layer in the first portion of the device
Data Source
AI summary
A method of fabricating a III-N device includes forming a III-N channel layer on a substrate, a III-N barrier layer on the channel layer, an insulator layer on the barrier layer, and a trench in a first portion of the device. Forming the trench comprises removing the insulator layer and a part of the barrier layer in the first portion of the device, such that a remaining portion of the barrier layer in the first portion of the device has a thickness away from a top surface of the channel layer, the thickness being within a predetermined thickness range, annealing the III-N device in a gas ambient including oxygen at an elevated temperature to oxidize the remaining portion of the barrier layer in the first portion of the device, and removing the oxidized remaining portion of the barrier layer in the first portion of the device.