Multi-Layer Source Electrode for Nitride Semiconductor Contact Resistance
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Solution Overview
Problem
Existing semiconductor devices with nitride semiconductors face challenges in achieving low ON-resistance for high-frequency operation, particularly due to high contact resistance between metal electrodes and nitride semiconductor layers, which complicates manufacturing and may damage the device during high-temperature processes.
Innovation Solution
A semiconductor device configuration with a source electrode comprising multiple conductor layers, where the first conductor layer has a smaller work function for ohmic contact with a p-type layer and the second conductor layer has a larger work function for a Schottky junction with an n-type layer, reducing ON-resistance and enabling high-frequency operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-layer metal electrode is used for contact with nitride semiconductor layers, then the manufacturing process is simple, but the contact resistance is high and ON-resistance cannot be reduced sufficiently
Solution Approach 1:
The source electrode is divided into multiple conductor layers (first conductor layer and second conductor layer) with different work functions. The first conductor layer contacts the p-type layer while the second conductor layer contacts the n-type layer, allowing each layer to be optimized for its specific interface to reduce contact resistance.
Solution Approach 2:
Different portions of the source electrode have different work function characteristics. The first conductor layer has a smaller work function for optimal contact with the p-type layer, while the second conductor layer has a larger work function for optimal contact with the n-type layer, creating locally optimized contact properties.
2Reliability
If high-temperature annealing is applied to reduce contact resistance, then ON-resistance decreases, but the nitride semiconductor layers may be damaged
Solution Approach 1:
The work function parameter of the conductor layers is carefully selected and controlled to achieve low contact resistance without requiring high-temperature annealing. By choosing materials with appropriate work functions, the contact resistance is reduced through material selection rather than thermal processing.
Solution Approach 2:
The patent uses conductor layer materials that can be deposited at lower temperatures and do not require subsequent high-temperature annealing to achieve the desired electrical properties, avoiding the risk of damaging the nitride semiconductor layers while still achieving low contact resistance.
3Speed
If a short gate length is used for high-frequency operation, then the device can operate in high-frequency region, but the ON-resistance increases
Solution Approach 1:
The source electrode is segmented into multiple conductor layers that can be independently optimized. This allows the gate length to be shortened for high-frequency operation while the multi-layer source electrode structure compensates for the increased ON-resistance through optimized contact properties at each interface.
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 semiconductor device achieves lower ON-resistance and improved high-frequency performance by forming a Schottky junction and ohmic contact, allowing for efficient operation and reduced leakage current, while simplifying the manufacturing process and avoiding damage from high-temperature annealing.
Implementation Method 1
the first conductor layer has a smaller work function for ohmic contact with a p-type layer
Implementation Method 2
the second conductor layer has a larger work function for a Schottky junction with an n-type layer
Data Source
AI summary
A semiconductor device includes first, a second, and third semiconductor layers respectively made of a nitride semiconductor and stacked on a substrate, a drain electrode formed on the third semiconductor layer, a gate electrode formed on the third semiconductor layer, and a source electrode formed within an opening penetrating the third and second semiconductor layers and exposing the first semiconductor layer. The source electrode includes a first conductor layer in contact with the first semiconductor layer, and a second conductor layer stacked on the first conductor layer and in contact with the second semiconductor layer. A work function of a material forming the first conductor layer is smaller than that of a material forming the second conductor layer.