Oxide Semiconductor Purification for Low-Leakage Power Transistors
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Solution Overview
Problem
The challenge is to develop a semiconductor device with high reliability and low power consumption that can handle high power applications, as existing semiconductor materials like silicon have reached theoretical limits, and compound semiconductors like silicon carbide and gallium nitride require high process temperatures, limiting their use on glass substrates and reducing mass productivity.
Innovation Solution
A method involving the use of oxide semiconductors, specifically an In--Ga--Zn--O-based oxide semiconductor film, which undergoes heat treatments in a reduced-pressure atmosphere with inert gases to reduce impurities like hydrogen and water, followed by oxygen addition via ion implantation to achieve high purification, resulting in a transistor with low off-state current and high withstand voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compound semiconductors like silicon carbide or gallium nitride are used to improve withstand voltage and reduce power loss, then high power application performance is improved, but process temperature becomes too high for glass substrates
Solution Approach 1:
The invention changes the material parameter from compound semiconductors (silicon carbide, gallium nitride) to oxide semiconductors (In-Ga-Zn-O-based), which have lower processing temperatures while maintaining high withstand voltage characteristics. This material substitution resolves the contradiction between high power performance and glass substrate compatibility.
Solution Approach 2:
The invention uses a composite structure combining oxide semiconductor films with specific metal elements (In, Ga, Zn) to achieve both low processing temperature and high withstand voltage. The composite material approach allows optimization of both thermal and electrical properties simultaneously.
2Ease of manufacture
If oxide semiconductor films are formed by sputtering, then film deposition is achieved, but hydrogen and water impurities are incorporated causing time degradation
Solution Approach 1:
The invention applies preliminary heat treatment to the oxide semiconductor film to remove hydrogen and water impurities before the transistor is fully assembled and before time degradation can occur. This preventive action eliminates the source of threshold voltage drift.
Solution Approach 2:
The invention uses oxygen plasma treatment to accelerate oxidation and remove hydrogen impurities from the oxide semiconductor film. The oxygen plasma acts as a strong oxidizing environment that effectively eliminates harmful impurities while maintaining film integrity.
3Reliability
If heat treatment is applied to remove impurities from oxide semiconductor films, then reliability is improved, but process temperature increases
Solution Approach 1:
The invention replaces thermal heat treatment with oxygen plasma treatment to remove impurities. This substitution uses chemical/physical plasma processes instead of thermal processes, achieving impurity removal without significant temperature increase that would conflict with glass substrate limitations.
4Temperature
If amorphous silicon is used as active layer, then low temperature processing is achieved, but mobility is limited compared to polysilicon
Solution Approach 1:
The invention uses oxide semiconductors with specific metal compositions (In-Ga-Zn-O) that provide both low processing temperature capability and high carrier mobility. The composite material structure achieves performance characteristics of both amorphous silicon (low temperature) and polysilicon (high mobility).
Solution Approach 2:
The invention changes the material composition parameters by incorporating specific metal elements (In, Ga, Zn) in optimized ratios within the oxide semiconductor structure. This compositional optimization enables simultaneous achievement of low processing temperature and high mobility characteristics.
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 approach results in a semiconductor device with significantly reduced off-state current, improved reliability, and high withstand voltage, enabling efficient high-power applications while maintaining low power consumption and allowing for mass production on glass substrates.
Implementation Method 1
heat treatments in a reduced-pressure atmosphere with inert gases to reduce impurities like hydrogen and water
Implementation Method 2
oxygen addition via ion implantation to achieve high purification
Data Source
AI summary
A semiconductor device for high power application in which a novel semiconductor material having high mass productivity is provided. An oxide semiconductor film is formed, and then, first heat treatment is performed on the exposed oxide semiconductor film in order to reduce impurities such as moisture or hydrogen in the oxide semiconductor film. Next, in order to further reduce impurities such as moisture or hydrogen in the oxide semiconductor film, oxygen is added to the oxide semiconductor film by an ion implantation method, an ion doping method, or the like, and after that, second heat treatment is performed on the exposed oxide semiconductor film.