GaN Crystal Purification via Oxidizing Etching Baking
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Solution Overview
Problem
Conventional methods for growing group-III nitride crystals, such as gallium nitride (GaN), struggle to achieve high purity with extremely low concentrations of impurities like silicon (Si), boron (B), iron (Fe), oxygen (O), and carbon (C), which are essential for improving the quality and performance of semiconductor devices.
Innovation Solution
A novel approach involving a high temperature baking step with an alternately conducted oxidizing and etching sequence using gases like oxygen (O2) and hydrogen chloride (HCl) in the treatment atmosphere, followed by hydride vapor phase epitaxy (HVPE) method, to reduce impurity concentrations below detectable limits, resulting in a GaN crystal with enhanced hardness and insulation properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional crystal growth methods are used, then manufacturing process is simple, but impurity concentration remains high
Solution Approach 1:
The patent applies preliminary action by conducting a high-temperature baking step (1000-1500°C) in the crystal growth furnace before actual crystal growth. This pre-treatment removes adsorbed substances and impurities from the furnace walls and components, ensuring that subsequent crystal growth occurs in a cleaner environment, thereby achieving extremely low impurity concentrations (Si, B, Fe < 1×10^15 at/cm³, O, C < 5×10^15 at/cm³) without overly complicating the overall manufacturing process.
Solution Approach 2:
The patent employs strong oxidants by introducing oxygen (O2) gas at a flow rate of 0.01-5 slm during the high-temperature baking step. This oxygen atmosphere accelerates the oxidation and removal of organic contaminants and reducing impurities from the furnace interior, effectively lowering impurity levels in the grown crystal while maintaining a relatively simple manufacturing process.
2Manufacturing precision
If high temperature baking step with oxidizing and etching sequence is used, then impurity concentration is reduced below detectable limits, but manufacturing process complexity increases
Solution Approach 1:
The patent implements periodic action by alternating between oxidizing atmosphere (oxygen gas) and etching atmosphere (hydrogen chloride gas) during the high-temperature baking step. This periodic switching of gas atmospheres creates a synergistic effect where oxidation removes organic contaminants and etching removes inorganic impurities, achieving extremely low impurity concentrations (below detectable limits of SIMS measurement) while completing the treatment in a reasonable time frame, thus balancing manufacturing precision and productivity.
3Strength
If impurity concentration is reduced to below 1×10^15 at/cm^3, then crystal hardness exceeds 22 GPa, but manufacturing process becomes more complex
Solution Approach 1:
The patent applies parameter changes by precisely controlling the high-temperature baking conditions: temperature (1000-1500°C), oxygen flow rate (0.01-5 slm), hydrogen chloride flow rate (0.1-5 slm), and treatment time (1-24 hours). By optimizing these parameters, the process achieves extremely low impurity concentrations that result in crystal hardness exceeding 22 GPa, while keeping the process complexity manageable through a single integrated baking step rather than multiple separate treatment processes.
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 method achieves a GaN crystal with impurity concentrations below 1×10^15 at/cm^3, significantly improving its hardness to above 22 GPa and maintaining high insulation properties across varying temperatures, thereby enhancing the quality and yield of semiconductor devices.
Implementation Method 1
conducting at least a high temperature baking step disclosed in JP 2018-070405 in a furnace before crystal growth
Implementation Method 2
an alternately conducted oxidizing and etching sequence using gases like oxygen (O2) and hydrogen chloride (HCl) in the treatment atmosphere
Implementation Method 3
followed by hydride vapor phase epitaxy (HVPE) method
Implementation Method 4
hydride vapor phase epitaxy (HVPE) method
Data Source
AI summary
An object of the present invention is to improve quality of a group-III nitride crystal, and also improve performance and manufacturing yield of a semiconductor device manufactured using the crystal.Provided is a nitride crystal represented by the composition formula of InxAlyGa1-x-yN (satisfying 0≤x≤1, 0≤y≤1, 0≤x+y≤1),with a hardness exceeding 22.0 GPa as measured by a nanoindentation method using an indenter with a maximum load applied thereto being within a range of 1 mN or more and 50 mN or less.