Conductivity-Selective Wet-Etching for III-Nitride Surface Quality
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Solution Overview
Problem
Conventional etching techniques for semiconductor devices, particularly in group-III nitride materials, face challenges in achieving smooth surface morphology due to high defect densities and inevitable surface and sub-surface damage, limiting the feasibility of wet-chemical etching for GaN and related materials.
Innovation Solution
A method involving conductivity-selective wet-etching techniques using liquid-phase solutions with specific concentrations of hydroxides and persulfates, combined with UV light and electrochemical processes, allows for differential etching rates between doped regions, enabling the formation of high-quality etched features and air gap regions in semiconductor devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional inductively coupled plasma (ICP) reactive-ion etching (RIE) is used to etch group-III nitride layers, then etching can be performed on the semiconductor sample, but surface and sub-surface damage is inevitable
Solution Approach 1:
The patent replaces the mechanical/physical ICP-RIE etching system with a chemical wet-etching system using liquid-phase solutions. This substitution eliminates the mechanical damage inherent in plasma-based methods while achieving the desired etching through chemical reactions between the liquid etchant and the semiconductor material.
Solution Approach 2:
The patent changes the etching parameters by using liquid-phase chemical solutions with specific compositions (containing hydroxides and persulfates) and controlling their temperature and concentration. This allows for damage-free etching by adjusting chemical parameters rather than relying on physical plasma parameters that cause surface damage.
2Ease of manufacture
If wet-chemical etching is used in GaN device processing, then etching can be performed on the semiconductor sample, but smooth etched surface morphology cannot be achieved due to high defect densities
Solution Approach 1:
The patent modifies the chemical composition parameters of the etching solution by incorporating specific concentrations of hydroxides and persulfates. This parameter optimization enables the wet-chemical etching process to achieve smooth surface morphology even in the presence of high defect densities in GaN materials, resolving the contradiction between ease of manufacture and manufacturing precision.
Solution Approach 2:
The patent uses persulfates as strong oxidizing agents in the etching solution. These oxidants accelerate the chemical etching process and improve the quality of the etched surface by facilitating cleaner removal of material and reducing the impact of defect densities on surface morphology.
3Manufacturing precision
If conductivity-selective wet-etching is used to selectively etch doped regions, then selective etching with high etch rate differential can be achieved, but specific liquid-phase solution composition is required
Solution Approach 1:
The patent achieves conductivity-selective etching by optimizing the chemical parameters of the liquid-phase solution, specifically the concentrations of hydroxides and persulfates. This allows the solution to differentially etch lightly doped and heavily doped regions with high selectivity (10 to 300 times etch rate differential) while maintaining a manageable solution composition that does not overly complicate the manufacturing process.
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 minimizes damage and achieves selective etching, resulting in high-quality etched features and enhanced reflectivity in optoelectronic devices, such as distributed Bragg reflectors, with fewer layer pairs and reduced thickness, while preserving the integrity of lightly doped regions.
Implementation Method 1
selecting a liquid-phase solution such that when the semiconductor sample is etched with the liquid-phase solution, at least a portion of one of the first doped region or the second doped region can be etched at a greater rate than at least a portion of the other of the first doped region or the second doped region
Implementation Method 2
the first etch rate can be from about 10 times to about 300 times greater than the second etch rate
Implementation Method 3
combined with UV light and electrochemical processes
Implementation Method 4
combined with UV light and electrochemical processes
Implementation Method 5
liquid-phase solution with specific concentrations of hydroxides and persulfates
Data Source
AI summary
Methods for wet-etching semiconductor samples and devices fabricated from the same are disclosed. The methods can be for selectively wet-etching a semiconductor sample comprising selecting a liquid-phase solution such that when the semiconductor sample is etched with the liquid-phase solution, at least a portion of one of a first doped region or a second doped region is etched at a greater rate than at least a portion of the other of the first doped region or the second doped region; and wet-etching, with the liquid-phase solution, the at least a portion of one of the first doped region or the second doped region at a first etch rate and the at least a portion of the other of the first doped region or the second doped region at a second etch rate; wherein the first etch rate can be greater than the second etch rate.