Ga-Based Semiconductor ICP Etching Profile Control
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Solution Overview
Problem
Current etching methods for Ga-based compound semiconductors, such as wet etching, are inadequate for defining small features and result in isotropic material removal, while dry etching methods like plasma etching face challenges with surface smoothness and verticality, especially at high etch rates.
Innovation Solution
The use of an inductively coupled plasma (ICP) etching process with specific gas flows and power control, including SiCl4, Ar, and H2, in conjunction with a Ni/Cr mask, to achieve high and low etch rates while maintaining surface smoothness and verticality of etched profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ICP etching is used to achieve high etch rates, then productivity is improved, but surface smoothness and verticality deteriorate
Solution Approach 1:
The patent applies parameter changes by optimizing multiple process parameters simultaneously: using specific gas composition (SiCl4/Ar/H2), controlling chamber pressure (1-10 mTorr), adjusting RF power levels, and selecting appropriate gas flow rates. These parameter adjustments enable achieving high etch rates while maintaining surface smoothness and vertical profile quality in Ga-based compound semiconductor etching
Solution Approach 2:
The patent uses a composite gas mixture consisting of SiCl4, Ar, and H2 in specific proportions. This composite gas system provides synergistic effects where SiCl4 contributes to chemical etching, Ar provides physical sputtering and ion bombardment, and H2 helps passivate surface and control etch chemistry, collectively achieving both high rate and high quality etching
2Ease of manufacture
If wet etching is used for material removal, then ease of manufacture is improved, but manufacturing precision and anisotropy deteriorate
Solution Approach 1:
The patent replaces wet chemical etching with plasma-based physical-chemical etching. The plasma process uses ion bombardment and reactive species to achieve anisotropic etching with vertical profiles, substituting the isotropic chemical dissolution mechanism of wet etching with a directed physical-chemical process that provides both precision and control
3Device complexity
If RIE is used for plasma etching, then device complexity is reduced, but etch rate and productivity deteriorate
Solution Approach 1:
The patent employs a dual-power-source ICP system that segments the control functions: one RF power source controls plasma density (affecting etch rate) while another controls ion energy (affecting profile quality). This segmentation of control functions enables independent optimization of etch rate and selectivity, achieving high productivity without excessive system complexity
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 allows for high etch rates with smooth, vertical surfaces and minimizes etch damage, improving the quality of Ga-based compound semiconductor features and reducing surface roughness.
Implementation Method 1
A plasma is generated based on the gases in the process chamber, and regions of a surface of the sample adjacent to one or more masked portions of the surface are etched
Implementation Method 2
The use of an inductively coupled plasma (ICP) etching process with specific gas flows and power control
Data Source
AI summary
A method of plasma etching Ga-based compound semiconductors includes providing a process chamber and a source electrode adjacent thereto. The chamber contains a Ga-based compound semiconductor sample in contact with a platen which is electrically connected to a first power supply, and the source electrode is electrically connected to a second power supply. SiCl4 and Ar gases are flowed into the chamber. RF power is supplied to the platen at a first power level, and RF power is supplied to the source electrode. A plasma is generated. Then, RF power is supplied to the platen at a second power level lower than the first power level and no greater than about 30 W. Regions of a surface of the sample adjacent to one or more masked portions of the surface are etched at a rate of no more than about 25 nm/min to create a substantially smooth etched surface.