SiC MOS Transistor Gate Oxide Process to Prevent Silicon Aggregation
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Solution Overview
Problem
Existing manufacturing methods of MOS transistors face issues with silicon aggregation during silicon film growth, leading to leakage currents and increased interface state densities, which affect channel mobility and resistance.
Innovation Solution
A manufacturing method that includes etching an SiC substrate in hydrogen gas, followed by growing a silicon film at a lower temperature than the etching temperature, forming a silicon oxide gate insulating film, and performing a nitrogen termination process to reduce interface state density and suppress silicon aggregation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a silicon film is grown on the SiC substrate surface by heating in a gas containing hydrogen and silicon source gas, then a silicon film is formed, but silicon aggregation occurs leading to leakage currents and increased interface state density
Solution Approach 1:
The patent changes the heating temperature parameter during silicon film growth, specifically controlling it to be lower than the etching temperature. This parameter modification prevents silicon aggregation while still forming a continuous silicon film, thereby reducing interface state density and preventing leakage currents without sacrificing film formation quality
Solution Approach 2:
The patent performs etching of the SiC substrate surface before growing the silicon film. This preliminary etching action creates a clean, activated surface that promotes uniform silicon film deposition and prevents aggregation during subsequent film growth, directly addressing the interface state density and leakage current issues
2Productivity
If the SiC substrate is heated at high temperature for etching, then etching is effective, but subsequent silicon film growth requires temperature control to prevent aggregation
Solution Approach 1:
The patent performs etching at high temperature as a preliminary step before silicon film growth. This separates the high-temperature etching process from the lower-temperature film growth process, allowing each to be optimized independently - high temperature for effective etching, then lower temperature for uniform film formation without aggregation
Solution Approach 2:
The patent explicitly controls the heating temperature during silicon film growth to be lower than the etching temperature. This parameter change enables the system to transition from high-temperature etching mode to lower-temperature film growth mode, maintaining both etching efficiency and film uniformity
3Productivity
If the silicon film is grown at high temperature, then film growth is efficient, but silicon aggregation occurs on the substrate surface
Solution Approach 1:
The patent modifies the temperature parameter for silicon film growth, setting it lower than the etching temperature. This parameter change balances film growth efficiency with prevention of silicon aggregation, achieving both acceptable productivity and high manufacturing precision by finding the optimal temperature window for film deposition
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 a MOS transistor with reduced interface state density, improved channel mobility, and lower on-resistance by preventing silicon aggregation and suppressing oxidation of the SiC substrate.
Implementation Method 1
etching a surface of an SiC substrate by heating the SiC substrate in hydrogen gas
Implementation Method 2
growing a silicon film on the surface of the SiC substrate by heating the SiC substrate in a gas containing hydrogen gas and a silicon source gas
Implementation Method 3
forming a gate insulating film made of silicon oxide on a surface of the silicon film
Implementation Method 4
heating the SiC substrate in hydrogen gas
Data Source
AI summary
In a manufacturing method of a metal oxide semiconductor transistor, a surface of a silicon carbide (SiC) substrate is etched by heating the SiC substrate in hydrogen gas. After the surface of the SiC substrate is etched, a silicon film is formed on the surface of the SiC substrate by heating the SiC substrate in a gas containing hydrogen gas and a silicon source gas to a temperature lower than a heating temperature of the SiC substrate in the etching, and a gate insulating film made of silicon oxide is formed on a surface of the silicon film. After the gate insulating film is formed, a nitrogen termination process is carried out on the SiC substrate.