SiC Epitaxial Growth via Hydrocarbon Pre-Decomposition
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Solution Overview
Problem
The in-plane uniformity of doping density in epitaxial SiC wafers grown using the thermal CVD process is impaired due to insufficient breakdown of hydrocarbon gas upstream in the gas flow, leading to variations in C/Si ratio and nitrogen incorporation, despite rotational holder mechanisms.
Innovation Solution
The method involves pre-breaking down hydrocarbon gas using a catalyst at 1000°C to 1200°C, ensuring at least 50% decomposition, with a C/Si ratio of 0.5 to 1.5, and using a hydrocarbon decomposition catalyst like ruthenium, rhodium, or platinum to achieve uniform doping density across the SiC substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If hydrocarbon gas is supplied with C/Si ratio < 1 to enable nitrogen incorporation, then doping is achieved, but C/Si ratio becomes non-uniform downstream causing poor in-plane uniformity
Solution Approach 1:
The hydrocarbon gas is pre-decomposed in a decomposition region before reaching the substrate, ensuring uniform C/Si ratio throughout the growth chamber. This preliminary decomposition prevents the C/Si ratio from changing downstream, thereby achieving both nitrogen incorporation and uniform doping density across the substrate surface.
Solution Approach 2:
A decomposition region acts as an intermediary zone between the gas supply and the substrate. In this intermediate region, hydrocarbon gas is decomposed to produce uniform carbon and hydrogen distribution, which then reaches the substrate with consistent C/Si ratio, enabling uniform doping without the downstream ratio variation problem.
2Reliability
If thermal CVD is used for epitaxial growth, then SiC thin film is formed, but hydrocarbon gas decomposition is insufficient upstream causing C/Si ratio variations
Solution Approach 1:
The growth chamber is segmented into a decomposition region and a growth region. The decomposition region is positioned upstream to pre-process the hydrocarbon gas, separating the decomposition function from the epitaxial growth function. This segmentation ensures that by the time gas reaches the growth region, decomposition is complete and C/Si ratio is uniform.
Solution Approach 2:
Hydrocarbon gas decomposition is performed in advance in the decomposition region before the gas reaches the substrate. This preliminary decomposition action ensures that the gas composition is stabilized upstream, preventing C/Si ratio variations downstream and achieving uniform epitaxial growth across the substrate.
3Manufacturing precision
If holder rotation is used to cancel gas flow effects, then some uniformity is improved, but in-plane doping density uniformity remains insufficient
Solution Approach 1:
The mechanical holder rotation system is replaced by a chemical/thermal solution: pre-decomposing the hydrocarbon gas in the decomposition region. Instead of mechanically rotating the holder to average out gas flow variations, the system chemically preprocesses the gas upstream to eliminate C/Si ratio variations, achieving uniform doping without complex mechanical rotation mechanisms.
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 ensures the effective C/Si ratio matches the stoichiometric ratio even in underheated regions, significantly improving in-plane uniformity of doping density and reducing variations among SiC wafers, resulting in more consistent film thickness and doping density.
Implementation Method 1
making the hydrocarbon gas contact a hydrocarbon decomposition catalyst heated to 1000°C to 1200°C so as to make at least part of the hydrocarbon gas break down into carbon and hydrogen
Implementation Method 2
making carbon contained in the hydrocarbon gas and silicon contained in the silicon feedstock gas react at 1500°C to less than 1800°C in temperature on the silicon carbide single crystal substrate and form a silicon carbide thin film
Data Source
Figure 1
Figure 2
Figure 3~4B
AI summary
The present invention provides a method of epitaxial growth of an SiC thin film by the thermal CVD process wherein it is possible to improve the in-plane uniformity of the doping density and possible to grow an SiC thin film by a uniform thickness. This method is an epitaxial growth method for silicon carbide characterized by comprising adjusting a ratio of the hydrocarbon gas and silicon feedstock gas so as to become, by C/Si ratio, 0.5 to 1.5 in range, making the hydrocarbon gas contact a hydrocarbon decomposition catalyst heated to 1000°C to 1200°C so as to make at least part of the hydrocarbon gas break down into carbon and hydrogen, and supplying carbon contained in the hydrocarbon gas and silicon contained in the silicon feedstock gas to the silicon carbide single crystal substrate.