SiC Epitaxy Gas Supply Layout for Uniform Impurity Distribution
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Solution Overview
Problem
Existing vapor phase growth methods for forming silicon carbide (SiC) films face challenges in achieving uniform impurity concentration distribution, leading to non-uniform resistance distribution due to variations in carbon-to-silicon (C/Si) ratios and impurity incorporation during epitaxial growth.
Innovation Solution
A vapor phase growth apparatus and method involving a process gas supply system with distinct regions for different C/Si ratios and rotational speed control to direct process gases towards the substrate, ensuring uniform impurity distribution by adjusting flow rates and rotational speed to pull gases towards the substrate center.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If process gases with different C/Si ratios are supplied to central and outer peripheral portions, then uniform impurity concentration distribution is achieved, but device complexity increases due to multiple gas supply regions and flow control mechanisms
Solution Approach 1:
The gas supply part is divided into a first region for supplying first process gas and a second region for supplying second process gas with different C/Si ratios. This segmentation allows independent control of gas composition in different radial zones, enabling uniform impurity concentration distribution across the substrate by compensating for edge effects in the outer peripheral portion.
Solution Approach 2:
Different C/Si ratios are supplied to different radial regions of the substrate. The first process gas is supplied to the central portion while the second process gas with higher C/Si ratio is supplied to the outer peripheral portion, creating local quality variations that compensate for non-uniform temperature and flow distribution across the substrate surface.
2Manufacturing precision
If multiple process gases with different C/Si ratios are supplied, then film quality improves, but process control difficulty increases due to multiple flow rate parameters
Solution Approach 1:
The C/Si ratio parameter is varied spatially by supplying different process gases with different compositions to different regions. The first process gas has a lower C/Si ratio while the second process gas has a higher C/Si ratio, allowing optimization of film quality and impurity distribution by controlling the spatial distribution of this critical parameter.
3Manufacturing precision
If substrate rotation speed is increased to 300 rpm or more, then gas flow uniformity improves, but mechanical stress on substrate holder increases
Solution Approach 1:
The substrate holder is designed to rotate at 300 rpm or more during epitaxial growth, transforming the static gas distribution problem into a dynamic one. The rotation creates centrifugal forces that enhance radial gas flow and improve uniformity of gas distribution across the substrate surface, while the substrate holder structure is designed to withstand the resulting mechanical stresses.
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 solution achieves improved uniformity of n-type impurity concentration in SiC films by controlling gas flow and C/Si ratios, enhancing the in-plane resistance distribution and film quality.
Implementation Method 1
heating the substrate
Implementation Method 2
Thermal reaction of the source gases occurs in the wafer surface
Implementation Method 3
rotating the substrate holder at a rotational speed of 300 rpm or more... forming a flow of the second process gas to be pulled in a direction toward a center of the substrate
Implementation Method 4
process gases such as source gases which are raw materials for film formation are supplied... an epitaxial single crystal film is formed on the wafer surface
Implementation Method 5
epitaxial growth technique for growing a single crystal film by vapor phase growth on a substrate
Data Source
AI summary
A vapor phase growth apparatus according to an embodiment includes a reaction chamber; a substrate holder having a holding wall capable holding an outer periphery of the substrate; a process gas supply part provided above the reaction chamber, the process gas supply part having a first region supplying a first process gas and a second region around the first region supplying a second process gas having a carbon/silicon atomic ratio higher than that of the first process gas, an inner peripheral diameter of the second region being 75% or more and 130% or less of a diameter of the holding wall; a sidewall provided between the process gas supply part and the substrate holder, an inner peripheral diameter of the sidewall being 110% or more and 200% or less of an outer peripheral diameter of the second region; a first heater; a second heater; and a rotation driver.