SiC Epitaxial Film Stress Control via Periodic Gas Suspension
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Solution Overview
Problem
Conventional epitaxial growth methods for silicon carbide (SiC) films on 4H-SiC substrates result in increased stress and warpage issues when forming thick films necessary for high-voltage devices, leading to substrate susceptibility to defects and inaccuracies in device production.
Innovation Solution
A method involving alternating suspension of silicon and carbon gas supply in a hydrogen or hydrogen chloride atmosphere during chemical vapor deposition (CVD) to control stress, maintaining a peak shift value within ±0.03 cm−1 and stress within ±7.8 MPa, allowing for controlled growth of SiC epitaxial films with reduced tensile and compressive stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional CVD epitaxial growth is used to form thick SiC films, then the film thickness is sufficient for high-voltage devices, but stress and warpage increase leading to substrate defects
Solution Approach 1:
The patent applies periodic action by alternately suspending and resuming the supply of silicon and carbon source gases during CVD epitaxial growth. This periodic interruption of gas supply allows stress accumulation to be controlled and released in cycles, preventing the continuous stress buildup that occurs in conventional continuous growth methods. The periodic action enables thick films to be grown while maintaining substrate integrity and reducing warpage.
Solution Approach 2:
The patent changes the growth parameters by controlling the suspension duration of source gas supply (30 seconds or longer) and limiting the film thickness grown per session to 4 μm or less. These parameter changes optimize the stress distribution during growth, allowing the accumulation of thick films without exceeding the stress threshold that causes substrate defects and warpage.
2Productivity
If continuous source gas supply is used during epitaxial growth, then growth efficiency is high, but stress accumulation causes warpage and reduces manufacturing precision
Solution Approach 1:
The periodic suspension and resumption of source gas supply creates growth cycles that balance efficiency and precision. During each cycle, growth occurs when gases are supplied, and stress relief occurs during suspension periods. This periodic action maintains acceptable growth efficiency while preventing the continuous stress accumulation that leads to warpage and manufacturing precision issues.
Solution Approach 2:
The patent segments the continuous growth process into discrete sessions, with each session producing a film thickness of 4 μm or less. This segmentation allows stress to be managed in manageable increments rather than accumulating continuously, thereby maintaining manufacturing precision while achieving the required total film thickness through multiple segmented growth sessions.
3Productivity
If thick SiC epitaxial films are grown in a single session, then productivity is improved, but stress control becomes difficult leading to substrate warpage
Solution Approach 1:
The periodic suspension of source gas supply during growth creates intervals for stress relief. By implementing regular suspension periods (30 seconds or longer) during the growth process, the patent enables faster overall growth while continuously managing stress accumulation, thus improving productivity without sacrificing stress control.
Solution Approach 2:
The patent divides the growth of thick films into multiple sessions, with each session limited to 4 μm or less. This segmentation strategy allows the total thick film to be produced through accumulated thin layers, each grown with controlled stress, thereby achieving high productivity for thick films while maintaining stress control throughout the process.
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 effectively reduces warpage and stress in SiC epitaxial films, enabling the production of substrates with minimal distortion, thus improving the reliability and accuracy of high-voltage device manufacturing.
Implementation Method 1
epitaxial growth by CVD grows a SiC epitaxial film on a 4H-SiC substrate by thermally decomposing in a carrier gas, a source gas flowing in a reaction vessel (chamber) and continuously depositing silicon (Si) atoms following a crystal lattice of the 4H-SiC substrate
Implementation Method 2
thermally decomposing in a carrier gas, a source gas flowing in a reaction vessel (chamber)
Data Source
AI summary
A method of growing a single-crystal, silicon carbide epitaxial film on a silicon carbide substrate by chemical vapor deposition is disclosed that results in a stress value of the epitaxial film within ±7.8 MPa. For example, from the start of the growth of the epitaxial film until completion, introduction of a source gas including a gas containing silicon, a gas containing carbon, and a gas containing chlorine into a reaction chamber and performing epitaxial growth is alternately performed with suspension of the supply of the gas containing silicon and the gas containing carbon into the reaction chamber while furnace temperature is maintained as is during performing processing in a gas atmosphere containing only hydrogen, or hydrogen and hydrogen chloride, whereby the epitaxial film is grown. Employing such a method enables manufacture of a substrate having a silicon carbide epitaxial film with minimal warpage.