SiC Epitaxial Wafer Uniformity via Segmented Gas Flow Control
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Solution Overview
Problem
The growth temperature difference between silicon and silicon carbide epitaxial layers, along with varying temperature and gas concentration distributions in the chamber, makes it difficult to achieve uniform impurity concentration and film thickness in silicon carbide epitaxial wafers, affecting the manufacturing of semiconductor devices.
Innovation Solution
A manufacturing method for silicon carbide epitaxial wafers involves positioning the substrate parallel to injection holes in a horizontal CVD apparatus, where source gases are divided into separate system lines controlled by mass flow controllers, ensuring a flow rate greater than 1 m/sec on the substrate surface to enhance uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If source gas is fed at low flow rate to control decomposition efficiency, then energy consumption is reduced, but wafer in-plane uniformity of impurity concentration deteriorates
Solution Approach 1:
The gas supply system is segmented into multiple independent injection holes arranged in the width direction of the chamber, with each hole or group of holes controlled by separate mass flow controllers. This segmentation allows independent optimization of gas flow to different regions of the wafer, achieving uniform impurity concentration while maintaining energy efficiency through precise local control rather than high overall flow rates.
Solution Approach 2:
Different gas flow rates are applied to different regions of the wafer based on local requirements. The center part and peripheral part of the wafer receive differently controlled gas flows, with each region optimized for its specific decomposition efficiency needs. This local quality approach ensures uniform impurity concentration across the wafer while avoiding excessive energy consumption that would result from uniformly high gas flow rates.
2Manufacturing precision
If source gas flow rate is increased to improve impurity concentration uniformity, then manufacturing precision improves, but device complexity increases due to multiple mass flow controllers
Solution Approach 1:
The gas supply system is divided into multiple independent control lines, each with its own mass flow controller, allowing precise control of gas flow to different regions. This segmentation enables uniform impurity concentration by independently optimizing gas flow to center and peripheral regions, while the modular structure keeps each controller's complexity manageable.
Solution Approach 2:
The system uses multiple mass flow controllers that can be independently adjusted based on measured impurity concentration distributions. This feedback mechanism allows optimization of gas flow rates to achieve uniform impurity concentration, with each controller responding to process data to maintain manufacturing precision without requiring overly complex centralized control.
3Ease of manufacture
If conventional silicon film epitaxial growth method is used for silicon carbide, then ease of manufacture is maintained, but manufacturing precision of impurity concentration and film thickness deteriorates due to temperature difference
Solution Approach 1:
The gas supply system provides different gas flow rates to different regions of the chamber, with center and peripheral injection holes controlled independently. This local quality approach compensates for temperature distribution differences caused by the higher growth temperature of silicon carbide (1500-1700°C) compared to silicon, achieving uniform impurity concentration and film thickness while maintaining the simplicity of CVD processing.
Solution Approach 2:
The system changes gas flow rate parameters across different spatial locations to compensate for temperature effects. By adjusting gas flow rates independently for center and peripheral regions, the method accounts for the temperature distribution inherent in silicon carbide epitaxial growth at 1500-1700°C, achieving uniform manufacturing results without fundamentally changing the CVD 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 method results in epitaxial wafers with excellent in-plane uniformity of impurity concentration, leading to high-yield silicon carbide semiconductor device production with reduced defects.
Implementation Method 1
epitaxially grow a silicon carbide epitaxial growth layer on the silicon carbide substrate
Implementation Method 2
thermal CVD method (thermal chemical vapor phase deposition method)
Implementation Method 3
a flow rate of the source gas on the principal surface of the silicon carbide substrate is greater than 1 m/sec
Data Source
AI summary
A silicon carbide substrate (2) is positioned such that a principal surface of the silicon carbide substrate (2) is parallel to a plurality of injection holes (8) of a horizontal CVD apparatus arranged in a row. Source gas is fed from the plurality of injection holes (8) to epitaxially grow a silicon carbide epitaxial growth layer (10) on the principal surface of the silicon carbide substrate (2). The source gas fed from the plurality of injection holes (8) is divided into a plurality of system lines and controlled individually by separate mass flow controllers. A flow rate of the source gas on the principal surface of the silicon carbide substrate (2) is greater than 1 m/sec.