Nitride HEMT Recess Etching Without Plasma Damage
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Solution Overview
Problem
Conventional dry etching techniques for manufacturing nitride-based high electron mobility transistors (HEMTs) introduce plasma damage and fail to reduce contact resistance due to the presence of a cap layer, which cannot be effectively removed using existing etching methods.
Innovation Solution
A photoelectrochemical (PEC) etching technique is employed to form recesses for source and drain electrodes without introducing plasma damage, using a conductive member and an oxidizing agent in an etching solution to selectively remove the cap layer and reduce contact resistance by directly etching the cap layer under the electrodes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional dry etching techniques are used to form source and drain recesses, then the etching process can be performed, but plasma damage is introduced into the group III nitride layer
Solution Approach 1:
The patent replaces the mechanical/physical sputtering process of conventional dry etching with a photoelectrochemical etching process. The PEC etching uses light irradiation to generate electron-hole pairs in the semiconductor, where holes migrate to the surface and react with the etching solution to remove material chemically, avoiding plasma-induced damage while maintaining effective material removal capability
Solution Approach 2:
The patent changes the etching mechanism from plasma-based physical sputtering to light-driven electrochemical reaction. By controlling light intensity, wavelength, and etching solution composition, the process achieves selective etching without introducing plasma damage, thus resolving the contradiction between manufacturability and harm reduction
2Stability of the object's composition
If the cap layer is not removed, then the structure remains intact, but contact resistance between electrodes and barrier layer cannot be reduced
Solution Approach 1:
The patent applies local quality by selectively removing the cap layer only in the source and drain recess regions while preserving it in other areas. This is achieved through precise mask patterning and localized light irradiation during PEC etching, creating regions with different cap layer presence - intact in most areas for structural stability, and removed locally for low-resistance contacts
Solution Approach 2:
The cap layer removal is performed as a preliminary step before electrode formation. By removing the cap layer in advance in the recess regions, the electrodes can be directly formed on the barrier layer, establishing low-resistance contacts before subsequent processing steps
3Ease of manufacture
If PEC etching is performed without proper electron consumption mechanism, then etching can proceed, but the process cannot be sustained due to accumulated electrons
Solution Approach 1:
The patent introduces an oxidizing agent as an intermediary substance in the etching solution that mediates electron consumption. The oxidizing agent accepts electrons generated during light irradiation, enabling continuous PEC etching by preventing electron accumulation and maintaining the photoelectrochemical reaction sustainability
Solution Approach 2:
The patent employs strong oxidizing agents in the etching solution to efficiently consume electrons and drive the etching reaction forward. These oxidants accelerate the overall etching process by providing a reliable electron sink, ensuring process sustainability while maintaining high etching rates
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 PEC etching method effectively reduces contact resistance by removing the cap layer without plasma damage, improving the performance of nitride-based HEMTs by allowing direct contact between electrodes and the barrier layer, thereby enhancing the transistor's electrical characteristics.
Implementation Method 1
performing photoelectrochemical etching by irradiating the nitride semiconductor crystal substrate with light
Implementation Method 2
performing photoelectrochemical etching by irradiating the nitride semiconductor crystal substrate with light to form at least one of a source recess and a drain recess, in a state where the nitride semiconductor crystal substrate on which the conductive member is provided and the mask is formed is in contact with an etching solution containing an oxidizing agent that receives electrons
Data Source
AI summary
There is provided a method for manufacturing a nitride-based high electron mobility transistor, including: providing a conductive member on a nitride semiconductor crystal substrate, outside an element region in a plan view; forming a mask on the substrate, the mask having an opening in at least one of a source recess etching region and a drain recess etching region; performing photoelectrochemical etching by irradiating the substrate with light to form at least one of a source recess and a drain recess, in a state where the substrate on which the conductive member is provided and the mask is formed is in contact with an etching solution containing an oxidizing agent that receives electrons; and forming an element separation structure of the high electron mobility transistor.