Silicon Oxynitride Gate Insulation for Stable Nitride Threshold Voltage
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Solution Overview
Problem
In nitride semiconductor devices, the accumulation of holes in the gate insulation film due to the formation of a well potential can lead to variations in the gate threshold voltage, affecting device performance.
Innovation Solution
The formation of a silicon oxynitride film in contact with the nitride semiconductor layer suppresses the accumulation of holes by preventing the formation of a well potential, thereby stabilizing the gate threshold voltage. This is achieved through the oxidation of a film source material containing both silicon and nitrogen, using a mist chemical vapor deposition method that avoids the use of ammonia, thus preventing surface damage to the nitride semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a silicon nitride film is used in the gate insulation film, then the gate insulation film can be formed, but holes are accumulated in the well potential causing variation in gate threshold voltage
Solution Approach 1:
The patent changes the material composition parameter of the gate insulation film from pure silicon nitride to silicon oxynitride by controlling the oxidation process. This parameter change eliminates the well potential that causes hole accumulation, thereby stabilizing the gate threshold voltage without compromising the insulating function.
Solution Approach 2:
The patent uses a composite material approach by forming silicon oxynitride through the oxidation of silicon nitride. The resulting material combines properties of both silicon nitride (insulating capability) and silicon oxide (reduced hole accumulation), resolving the contradiction between forming a functional gate insulation film and preventing harmful hole accumulation.
2Ease of manufacture
If ammonia is used as a nitrogen source in chemical vapor deposition, then the silicon nitride film can be formed, but the nitride semiconductor layer surface is damaged
Solution Approach 1:
The patent extracts ammonia from the deposition process and replaces it with alternative nitrogen sources such as nitrogen gas or nitrous oxide. This removal of the harmful substance (ammonia) eliminates surface damage while maintaining the ability to form nitrogen-containing films through oxidation of silicon-containing precursors.
Solution Approach 2:
The patent introduces an intermediary oxidation step where silicon-containing films are first deposited and then oxidized in a nitrogen-containing atmosphere. This intermediary process allows nitrogen incorporation without direct exposure to damaging ammonia, achieving film formation while protecting the semiconductor surface.
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 use of a silicon oxynitride film in the gate insulation layer effectively suppresses hole accumulation and variation in the gate threshold voltage, enhancing the reliability and performance of nitride semiconductor devices.
Implementation Method 1
The silicon nitride film has a negative band offset with respect to a nitride semiconductor layer. Therefore, in the gate insulation film, a well potential is formed in a valence band of the silicon nitride film, and holes are accumulated in the well potential.
Implementation Method 2
The formation of the silicon oxynitride film includes oxidation of a film source material having both of silicon and nitride in a molecule to form the silicon oxynitride film.
Data Source
AI summary
A method for manufacturing a nitride semiconductor device includes formation of a gate insulation film above a nitride semiconductor layer. The formation of the gate insulation film includes formation of silicon oxynitride film in contact with a surface of the nitride semiconductor layer. The formation of the silicon oxynitride film includes oxidation of a film source material having both of silicon and nitride in a molecule to form the silicon oxynitride film.