Two-Step Microwave Plasma Oxidation for SiC Grooved MOSFETs
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Solution Overview
Problem
The existing thermal oxidation methods for silicon carbide (SiC) MOSFET devices result in defects such as residual carbon clusters, Si—O—C bonds, and oxygen vacancies at the interface, leading to degraded interface quality and reduced mobility, especially when forming a uniform gate oxide layer, which is crucial for the proper functioning of grooved gate MOSFET devices.
Innovation Solution
A two-step microwave plasma oxidation method is employed, involving low-temperature and high-temperature plasma oxidation stages with specific temperature, pressure, and gas composition controls to form a uniform silicon dioxide layer, reducing interface damage and enhancing oxidation efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If thermal oxidation method is used to form gate oxide layer, then oxidation efficiency is improved, but interface quality deteriorates due to defects such as residual carbon clusters, Si-O-C bonds, and oxygen vacancies
Solution Approach 1:
The oxidation process is divided into two distinct stages: a first oxidation stage forming an initial oxide layer, and a second oxidation stage forming the final gate oxide layer. This segmentation allows each stage to be optimized independently - the first stage prepares the interface while the second stage achieves high-quality thick oxide formation, resolving the contradiction between oxidation efficiency and interface quality.
Solution Approach 2:
The first oxidation stage serves as a preliminary action that prepares the SiC surface and forms an initial oxide layer before the main oxidation process. This preliminary oxidation modifies the surface chemistry and reduces interface defects, creating favorable conditions for the subsequent high-quality oxide growth in the second stage.
2Productivity
If high temperature thermal oxidation is used, then oxidation rate is improved, but interface damage increases and oxidation efficiency decreases
Solution Approach 1:
The oxidation process is divided into two distinct stages: a first oxidation stage forming an initial oxide layer, and a second oxidation stage forming the final gate oxide layer. This segmentation allows each stage to be optimized independently - the first stage prepares the interface while the second stage achieves high-quality thick oxide formation, resolving the contradiction between oxidation efficiency and interface quality.
Solution Approach 2:
The patent employs different oxidation parameters for the two stages: the first stage uses lower temperature and different atmospheric conditions, while the second stage uses optimized temperature and pressure parameters. This parameter change approach allows achieving high oxidation rates without causing interface damage, as each stage operates in its optimal parameter range.
3Manufacturing precision
If low temperature plasma oxidation is used, then interface quality is improved, but oxidation efficiency becomes too low
Solution Approach 1:
The oxidation process is divided into two distinct stages: a first oxidation stage forming an initial oxide layer, and a second oxidation stage forming the final gate oxide layer. This segmentation allows each stage to be optimized independently - the first stage prepares the interface while the second stage achieves high-quality thick oxide formation, resolving the contradiction between oxidation efficiency and interface quality.
Solution Approach 2:
The two-stage oxidation process continues the useful action of oxide formation without interruption. The first stage initiates oxide growth and prepares the interface, then the second stage continuously builds upon this foundation to achieve the desired thick oxide layer. This continuous process maintains high oxidation efficiency throughout while ensuring interface quality is preserved from the beginning.
4Productivity
If thermal oxidation is used to form gate oxide on grooved gate, then oxide layer thickness varies significantly on sidewall vs bottom, but uniform thickness is required for proper device operation
Solution Approach 1:
The oxidation process is divided into two distinct stages: a first oxidation stage forming an initial oxide layer, and a second oxidation stage forming the final gate oxide layer. This segmentation allows each stage to be optimized independently - the first stage prepares the interface while the second stage achieves high-quality thick oxide formation, resolving the contradiction between oxidation efficiency and interface quality.
Solution Approach 2:
The patent employs different oxidation parameters for the two stages: the first stage uses lower temperature and different atmospheric conditions, while the second stage uses optimized temperature and pressure parameters. This parameter change approach allows achieving high oxidation rates without causing interface damage, as each stage operates in its optimal parameter range.
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 significantly improves the interface quality, reduces carbon residue and dangling bonds, and achieves a uniform gate oxide layer thickness, enabling normal device operation and preventing premature breakdown of the bottom gate oxide layer.
Implementation Method 1
oxidizing silicon carbide on a surface of the grooved gate to silicon dioxide by microwave plasma
Implementation Method 2
heating generated oxygen plasma to a first temperature at a first heating rate
Implementation Method 3
oxidizing silicon carbide on a surface of the grooved gate to silicon dioxide
Data Source
AI summary
A method of manufacturing a grooved-gate MOSFET device based on a two-step microwave plasma oxidation, including: etching a grooved gate, and oxidizing silicon carbide on a surface of the grooved gate to silicon dioxide by microwave plasma to form a grooved-gate oxide layer, the step of forming the grooved-gate oxide layer including: placing a silicon carbide substrate subjected to the grooved gate etching in a microwave plasma generating device; introducing a first oxygen-containing gas, heating generated oxygen plasma to a first temperature at a first heating rate, and performing low-temperature plasma oxidation at the first temperature and a first pressure; heating the oxygen plasma to a second temperature at a second heating rate, introducing a second oxygen-containing gas, and performing high-temperature plasma oxidation at the second temperature and a second pressure until a predetermined thickness of silicon dioxide is formed; stopping introduction of the oxygen-containing gas, and completing the reaction.