GaN HEMT Gate Recess Dry Etching via Plasma Emission Monitoring
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Solution Overview
Problem
Existing methods for manufacturing semiconductor devices with nitride semiconductors, such as GaN and AlGaN, face challenges in achieving a normally-off state while maintaining high efficiency and output, as they often result in increased on-resistance and degraded characteristics due to difficulties in precisely removing p-type layers without damaging the electron supplying layer during etching processes.
Innovation Solution
A method involving the sequential lamination of an electron transit layer, an electron supplying layer, an etching stop layer, and a p-type film on a substrate, where the p-type film is selectively removed using dry etching monitored by plasma emission spectroscopy to stop at the etching stop layer, ensuring the electron supplying layer remains intact and allowing for the formation of a gate electrode on the p-type layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a recess is formed by etching to eliminate 2DEG below the gate electrode, then a normally-off state is achieved, but damage is caused to the electron transit layer and on-resistance increases
Solution Approach 1:
The patent segments the etching process into two distinct stages: first etching the p-GaN layer to form a recess, then performing a controlled second etching step that stops before damaging the electron transit layer. This segmentation allows the process to achieve the normally-off state while preventing damage to critical layers through careful process control and timing.
Solution Approach 2:
The patent performs preliminary actions by forming the recess structure before final device operation, and by using a protective layer or controlled etching parameters in advance to prevent damage. The etching process is designed with predetermined stopping points and protective measures already in place before the actual device function begins, ensuring the electron transit layer remains intact.
2Reliability
If a p-GaN layer is formed and removed by dry etching, then a normally-off state is achieved, but irregular etching causes increased on-resistance and degraded HEMT characteristics
Solution Approach 1:
The patent implements feedback control in the dry etching process by monitoring etching parameters, layer thickness, and process conditions in real-time. This feedback mechanism allows dynamic adjustment of etching parameters to maintain uniform removal of the p-GaN layer while preventing over-etching or irregularities that could damage underlying layers or create variability in device characteristics.
Solution Approach 2:
The patent utilizes parameter changes by systematically varying etching conditions such as gas flow rates, power levels, pressure, and temperature during the dry etching process. These controlled parameter changes enable precise management of the etching rate and uniformity, ensuring consistent removal of the p-GaN layer across different device regions while maintaining high manufacturing precision and avoiding damage to the electron supplying layer.
3Ease of manufacture
If dry etching is used to remove p-GaN layer, then selective removal is attempted, but GaN material resists etching and electron supplying layer may be damaged
Solution Approach 1:
The patent introduces an intermediary protective layer or uses the electron supplying layer itself as a protective barrier during the dry etching process. This intermediary structure allows selective removal of the p-GaN layer while preventing the etchant from reaching and damaging the electron supplying layer. The intermediary acts as a buffer that enables the etching process to proceed without compromising the integrity of critical underlying layers.
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 approach enables the production of semiconductor devices with lower on-resistance and higher yield by accurately removing the p-type layer without damaging the electron supplying layer, thereby achieving a normally-off type HEMT with improved performance.
Implementation Method 1
the dry etching being conducted while plasma emission in the dry etching is observed
Implementation Method 2
removing the p-type film in an area except an area where a gate electrode is to be formed, by dry etching
Data Source
AI summary
A method of manufacturing a semiconductor device includes laminating and forming an electron transit layer, an electron supplying layer, an etching stop layer, and a p-type film on a substrate sequentially, the p-type film being formed of a nitride semiconductor material that includes Al doped with an impurity element that attains p-type, the etching stop layer being formed of a material that includes GaN, removing the p-type film in an area except an area where a gate electrode is to be formed, by dry etching to form a p-type layer in the area where the gate electrode is to be formed, the dry etching being conducted while plasma emission in the dry etching is observed, the dry etching being stopped after the dry etching is started and plasma emission originating from Al is not observed, and forming the gate electrode on the p-type layer.