Aluminum Nitride Diffusion Barrier for Normally-Off GaN Transistors
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Solution Overview
Problem
The manufacturing steps of semiconductor devices with nitride semiconductors, such as gallium nitride, face challenges in preventing p-type impurity diffusion between the p-type semiconductor layer and the barrier layer, leading to decreased barrier layer thickness and increased access resistance, which hinders the operation of normally-off type field effect transistors.
Innovation Solution
Incorporating an aluminum-containing n-type diffusion preventing layer with a higher aluminum composition ratio than the barrier layer, positioned between the barrier layer and the source and drain electrodes, and a p-type cap layer on top, helps to suppress impurity diffusion and maintain barrier layer thickness during heat treatment and etching processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a p type semiconductor layer is used to create normally-off type operation, then the transistor achieves normally-off characteristics, but p type impurity diffuses into the barrier layer during heat treatment causing performance deterioration
Solution Approach 1:
An aluminum nitride diffusion preventing layer is inserted between the p type cap layer and the barrier layer to act as a mediator that blocks p type impurity diffusion while allowing the normally-off operation to function. This intermediary layer prevents direct contact between the p type layer and barrier layer, stopping impurity migration during heat treatment.
Solution Approach 2:
The structure is segmented by dividing the interface between the p type cap layer and barrier layer into two separate interfaces through the diffusion preventing layer. This segmentation isolates the p type impurities from the barrier layer, allowing each layer to maintain its intended function without interference.
2Ease of manufacture
If etching is performed to form the p type cap layer, then the cap layer is successfully formed, but the barrier layer thickness decreases and access resistance increases
Solution Approach 1:
The aluminum nitride diffusion preventing layer serves as a protective intermediary during the etching process. Since aluminum nitride has different etching characteristics compared to the barrier layer materials, it enables selective etching of the cap layer while the diffusion preventing layer protects the barrier layer from being etched, maintaining precise thickness control.
Solution Approach 2:
The diffusion preventing layer is formed in advance before the cap layer etching process. This preliminary action creates a protective barrier that prevents the etching process from affecting the barrier layer thickness, ensuring manufacturing precision is maintained during subsequent processing steps.
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 enhances the performance of the semiconductor device by maintaining the barrier layer thickness and preventing impurity diffusion, ensuring the device operates as a normally-off type field effect transistor with improved performance and reduced access resistance.
Implementation Method 1
diffusion of a p type impurity may occur between a p type semiconductor layer and a barrier layer
Implementation Method 2
during etching of the p type semiconductor layer, the barrier layer may be etched, resulting in a decrease in the thickness of the barrier layer
Data Source
AI summary
The semiconductor device has a barrier layer formed on a channel layer, an n type diffusion preventing layer formed on the barrier layer and containing aluminum, and a source electrode and a drain electrode formed on the diffusion preventing layer. The semiconductor device further has a p type cap layer formed on the diffusion preventing layer sandwiched between the source electrode and the drain electrode and a gate electrode formed on the cap layer. The diffusion preventing layer has an aluminum composition ratio greater than the aluminum composition ratio of the barrier layer.