GaN Crystal Growth via High-Temperature Baking for Low Impurity Concentration
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Solution Overview
Problem
Existing semiconductor devices using group-III nitride crystals, such as gallium nitride (GaN), face challenges in achieving high-quality crystals with low impurity concentrations, which affects their electrical resistivity and manufacturing yield.
Innovation Solution
The development of semi-insulating, n-type, and p-type semiconductor crystals with specific impurity concentration levels, represented by the composition formula InxAlyGa1-x-yN, where concentrations of Si, B, Fe, and other impurities are minimized, resulting in enhanced electrical resistivity and improved crystal quality through a hydride vapor phase epitaxy method with a high-temperature baking step and controlled gas supply.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional crystal growth methods are used, then manufacturing process is simpler, but impurity concentration increases and crystal quality deteriorates
Solution Approach 1:
The patent applies preliminary action by performing a high-temperature baking step (1500°C or higher) on the reaction vessel walls and internal components before crystal growth. This pre-treatment removes adsorbed impurities and modifies the surface properties of the reaction vessel, preventing impurity contamination during subsequent crystal growth. The baking step is completed in advance to ensure a clean environment for growing high-quality GaN crystals with low impurity concentrations.
Solution Approach 2:
The patent applies parameter changes by significantly increasing the temperature to 1500°C or higher for the baking step, which is much higher than conventional crystal growth temperatures. This extreme temperature parameter change enables effective removal of impurities from the reaction vessel surfaces and allows precise control of impurity concentrations during crystal growth, thereby improving crystal quality.
2Manufacturing precision
If high-temperature baking step is applied, then impurity concentration decreases and electrical resistivity increases, but energy consumption increases
Solution Approach 1:
The high-temperature baking step is performed as a preliminary action before crystal growth to remove impurities from the reaction vessel. By completing the impurity removal in advance, the actual crystal growth can proceed at lower temperatures with minimal energy input, reducing overall energy consumption while achieving low impurity concentrations in the final product.
Solution Approach 2:
The patent converts the potentially harmful high energy consumption of the baking step into a beneficial one-time预处理 that enables lower energy consumption during the main crystal growth process. The initial energy investment removes impurity sources, preventing continuous energy waste from dealing with contaminated crystals and rework.
3Manufacturing precision
If impurity concentration is reduced, then electrical resistivity increases and crystal quality improves, but manufacturing yield decreases
Solution Approach 1:
The patent applies parameter changes by precisely controlling the baking temperature at 1500°C or higher and maintaining specific gas flow rates during crystal growth. These optimized parameters enable consistent production of high-quality crystals with low impurity concentrations, improving manufacturing yield through repeatable process control rather than relying on trial-and-error approaches.
Solution Approach 2:
The patent implements feedback control by monitoring crystal growth conditions and adjusting gas supply parameters to maintain optimal impurity concentrations. By continuously monitoring and adjusting the growth environment, the process ensures consistent production of high-quality crystals, improving manufacturing yield through real-time quality control.
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 results in GaN crystals with extremely low impurity concentrations, leading to improved crystal quality, reduced defect density, and increased electrical resistivity, thereby enhancing the performance and yield of semiconductor devices without the need for compensating impurities, which can degrade crystal quality.
Implementation Method 1
a crystal growth step of loading a seed crystal substrate and raw materials containing a group-III element into a reaction vessel, supplying a halide of the raw material and a nitriding agent to the seed crystal substrate heated to a predetermined crystal growth temperature, and thereby growing a group-III nitride crystal on the seed crystal substrate
Implementation Method 2
supplying a halide of the raw material and a nitriding agent to the seed crystal substrate heated to a predetermined crystal growth temperature, and thereby growing a group-III nitride crystal
Implementation Method 3
a high temperature baking step of raising a temperature of an area in the reaction vessel to 1500° C. or more, the area being heated to at least around the crystal growth temperature, and possibly in contact with the gas supplied to the seed crystal substrate; not conducting supply of the nitriding agent into the reaction vessel, but conducting supply of hydrogen gas and halogen-based gas into the reaction vessel; and cleaning and modifying a surface of a member constituting the high temperature reaction area
Implementation Method 4
cleaning and modifying a surface of a member constituting the high temperature reaction area
Data Source
AI summary
Provided is a semi-insulating crystal represented by a composition formula InxAlyGa1-x-yN (satisfying 0≤x≤1, 0≤y≤1, 0≤x+y≤1),wherein each concentration of Si, B, and Fe in the crystal is less than 1×1015 at/cm3, electric resistivity under a temperature condition of 20° C. or more and 200° C. or less is 1×106 Ωcm or more.