Monocrystalline Silicon Carbide Wafer Uniform Doping via Sublimation Control
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Solution Overview
Problem
Conventional methods for producing monocrystalline silicon carbide (SiC) wafers face challenges in achieving uniform dopant concentration, leading to low yield and poor crystal quality, particularly when using vanadium as a dopant, which results in insufficient high-resistivity wafers for high-frequency devices.
Innovation Solution
A method involving sublimation-re-crystallization of a sublimation material with a solid dopant element, such as vanadium carbide, is used to control the specific surface area, ensuring a uniform dopant concentration of less than 5×10^17 atoms/cm^3, thereby preventing precipitation and maintaining a consistent sublimation rate, resulting in high-quality, high-resistivity SiC wafers with improved yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional sublimation method is used to grow monocrystalline SiC, then monocrystal can be obtained, but the dopant concentration is non-uniform and crystal quality is poor
Solution Approach 1:
The invention changes the physical state parameters of the dopant material from solid to liquid by controlling the temperature to be above the melting point but below the sublimation point of SiC. This parameter change enables uniform dopant distribution through liquid-phase transport during the sublimation-growth process, resolving the contradiction between dopant uniformity and crystal quality
Solution Approach 2:
The invention uses a composite starting material consisting of SiC powder mixed with dopant material (such as vanadium). This composite approach allows controlled release and uniform distribution of the dopant throughout the SiC crystal during growth, improving both dopant uniformity and overall crystal quality
2Manufacturing precision
If high dopant concentration is used to achieve desired resistivity, then resistivity requirement is met, but dopant precipitation occurs and crystal quality deteriorates
Solution Approach 1:
By changing the temperature parameter to maintain it above the dopant melting point, the invention keeps the dopant in liquid phase during crystal growth. This prevents dopant precipitation that would otherwise occur at high concentrations, allowing achievement of desired resistivity while maintaining crystal quality
Solution Approach 2:
The dopant is pre-mixed with the SiC starting material in a controlled manner before the sublimation process. This preliminary uniform distribution of dopant throughout the starting material ensures that the desired concentration is achieved without local supersaturation that would lead to precipitation
3Manufacturing precision
If conventional doping methods are used, then some dopant is introduced, but uniform distribution cannot be achieved due to vapor pressure differences
Solution Approach 1:
The invention changes the temperature parameter to a specific range (above dopant melting point, below SiC sublimation point) that enables the dopant to be introduced in liquid form. This parameter change simplifies the doping process by eliminating the need to match vapor pressures, while achieving uniform dopant distribution throughout the crystal
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 enables the production of monocrystalline SiC wafers with uniform dopant distribution and high crystal quality, increasing the yield of high-resistivity wafers suitable for high-frequency applications, while maintaining a stable sublimation rate and preventing dopant precipitation.
Implementation Method 1
a method involving sublimation-re-crystallization of a sublimation material with a solid dopant element
Data Source
AI summary
Provided is a monocrystalline silicon carbide ingot containing a dopant element, wherein a maximum concentration of the dopant element is less than 5×1017 atoms/cm3 and the maximum concentration is 50 times or less than that of a minimum concentration of the dopant element. Also provided is a monocrystalline silicon carbide wafer made by cutting and polishing the monocrystalline silicon carbide ingot, wherein a electric resistivity at room temperature of the wafer is 5×103 Ωcm or more. Further provided is a method for manufacturing the monocrystalline silicon carbide including growing the monocrystalline silicon carbide on a seed crystal from a sublimation material by a sublimation method. The sublimation material includes a solid material containing a dopant element, and the specific surface of the solid material containing the dopant element is 0.5 m2/g or less.