Variable-Width Gate Electrode Structure for HEMT Turn-Off Reliability
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Solution Overview
Problem
Existing semiconductor devices face challenges in maintaining stable electric characteristics and reliability, particularly in high-power applications, due to issues with gate electrode turn-off and reliability degradation under increased driving voltage and temperature.
Innovation Solution
The semiconductor device incorporates a channel layer, a barrier layer with a different energy band gap, and a gate electrode with a narrower width than the gate semiconductor layer, featuring a varying atomic percentage of Ti to N composition, and includes a groove to disperse electric fields, enhancing reliability and threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the gate electrode width is reduced to improve switching performance, then the turn-off characteristics improve, but the electric field concentration increases causing reliability degradation
Solution Approach 1:
The patent applies local quality by creating a non-uniform gate electrode structure where the width varies along the vertical direction. The upper part has a smaller width than the lower part, which allows the gate to effectively control the channel while distributing the electric field stress to different regions. This local variation in geometry resolves the contradiction by maintaining good turn-off characteristics at the upper narrow region while preventing electric field concentration at the lower wider region.
Solution Approach 2:
The patent transitions from a conventional uniform-width gate electrode (one-dimensional control) to a variable-width gate electrode (two-dimensional control with width variation in the vertical dimension). This dimensional change allows the gate to simultaneously achieve effective channel control and electric field distribution, resolving the contradiction between turn-off performance and reliability.
2Power
If the driving voltage is increased to improve power handling capability, then the power output increases, but the threshold voltage stability decreases
Solution Approach 1:
The variable-width gate electrode structure creates different local electric field distributions that stabilize the threshold voltage. The wider lower portion provides better electrical connection and field distribution, while the narrower upper portion provides precise control, together maintaining threshold voltage stability under high power operating conditions.
Solution Approach 2:
The patent changes the geometric parameter of the gate electrode (width along the vertical direction) to optimize both power handling and threshold voltage stability. By varying the width parameter, the electric field distribution is optimized to maintain stable threshold voltage even when operating at higher power levels.
3Power
If the operating temperature is increased to improve power dissipation capacity, then the power handling improves, but the electric characteristics stability deteriorates
Solution Approach 1:
The non-uniform gate electrode structure creates favorable local thermal and electrical conditions. The wider lower portion provides better thermal conduction path to the substrate, while the narrower upper portion maintains electrical control stability, together preserving electric characteristics stability at elevated operating temperatures.
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 design ensures stable operation and increased reliability by preventing gate electrode turn-off issues and improving threshold voltage, thus enhancing the performance of high electron mobility transistors in high-power applications.
Implementation Method 1
The gate electrode is positioned above the barrier layer between the source and drain electrodes. The atomic percentage of Ti to the atomic percentage of N in an upper part of the gate electrode is lower than the atomic percentage of Ti to the atomic percentage of N in a lower part of the gate electrode.
Data Source
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AI summary
A semiconductor device includes a channel layer (132), a barrier layer (136) positioned above the channel layer and having a material with a different energy band gap than the channel layer, source (173) and drain (175) electrodes positioned on the channel layer, a gate electrode (155) positioned above the barrier layer between the source and drain electrodes and a gate semiconductor layer (152) positioned between the barrier layer and the gate electrode. The width of the gate electrode is smaller than the width of the gate semiconductor layer at a junction surface of the gate electrode and the gate semiconductor layer.