Nitride Semiconductor Device with Segmented Threshold Control
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Solution Overview
Problem
Existing nitride semiconductor devices face challenges in fabricating normally-off type devices with low on-resistance and high yield due to precision requirements in processing and etching damage, which affect channel mobility and threshold voltage control.
Innovation Solution
A nitride semiconductor device structure is developed with a carrier transit layer, a barrier layer, a threshold control layer, and a carrier induction layer, where the gate electrode is formed on the threshold control layer, and source and drain electrodes are on the carrier induction layer, allowing for precise control of film thickness and reduced etching damage, thereby achieving stable threshold voltage and low on-resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a recess structure is formed by removing part of the barrier layer to reduce contact resistance, then contact resistance is reduced, but etching damage is introduced which affects channel mobility and threshold voltage control
Solution Approach 1:
The device is divided into multiple functional layers: barrier layer, threshold control layer, and carrier induction layer. Each layer performs a specific function - the barrier layer provides polarization charges, the threshold control layer controls threshold voltage, and the carrier induction layer induces carriers without requiring etching into the barrier layer, thus resolving the contradiction between reducing contact resistance and avoiding etching damage.
Solution Approach 2:
The threshold control layer and carrier induction layer act as intermediary layers between the barrier layer and the electrodes. These intermediary layers allow for electrode formation and contact resistance reduction without directly etching the barrier layer, thereby preventing etching damage while still achieving low contact resistance.
2Measurement precision
If precise control of barrier layer film thickness is required to control threshold voltage, then threshold voltage control is improved, but manufacturing complexity and precision requirements increase
Solution Approach 1:
The threshold control function is segmented from the barrier layer and assigned to a dedicated threshold control layer. This layer can be independently controlled in thickness and composition, allowing threshold voltage control without requiring ultra-precise control of the barrier layer thickness, thus reducing manufacturing precision requirements while maintaining control precision.
Solution Approach 2:
Different layers are assigned different local qualities - the barrier layer provides polarization charges, the threshold control layer provides threshold voltage control through its specific thickness and composition, and the carrier induction layer provides carrier induction. This local differentiation allows each layer to be optimized independently, reducing overall manufacturing complexity.
3Quantity of substance
If the Al composition ratio of the barrier layer is increased to generate more polarization charges, then carrier density is improved, but lattice mismatch strain increases affecting device reliability
Solution Approach 1:
The functionality of generating polarization charges is segmented from the threshold control function. The barrier layer can be optimized for high Al composition ratio to maximize polarization charges and carrier density, while the threshold control layer separately handles threshold voltage control. This segmentation allows the barrier layer to achieve high carrier density without compromising overall device 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
This configuration enables easy control of threshold voltage and low on-resistance with high yield, while also improving pinch-off characteristics by managing polarization charges and film thickness, reducing etching damage, and enhancing carrier concentration.
Implementation Method 1
polarization charges are generated in the barrier layer by piezo polarization and spontaneous polarization resulting from the strain in the barrier layer
Implementation Method 2
polarization charges are generated in the barrier layer by piezo polarization and spontaneous polarization resulting from the strain in the barrier layer
Data Source
AI summary
A nitride semiconductor device includes: a first nitride semiconductor layer formed of non-doped AlXGa1-XN (0≦X<1); a second nitride semiconductor layer formed on the first nitride semiconductor layer of non-doped or n-type AlYGa1-YN (0<Y≦1, X<Y), and having a smaller lattice constant than that of the first nitride semiconductor layer; a third nitride semiconductor layer formed on the second nitride semiconductor layer of a non-doped or n-type nitride semiconductor, and having a lattice constant equal to that of the first nitride semiconductor layer; a fourth nitride semiconductor layer formed on the third nitride semiconductor layer of InWAlZGa1-W-ZN (0<W≦1, 0<Z<1); a gate electrode formed in a recess structure having a bottom face which arrives at the third nitride semiconductor layer; and a source electrode and a drain electrode.