C-Axis Aligned Oxide Semiconductor for Stable Gate Interfaces
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Solution Overview
Problem
Transistors using oxide semiconductors face instability in electric characteristics due to high defect density at the interface between the oxide semiconductor film and the gate insulating film, especially when in an amorphous state, and are sensitive to light irradiation, making them unreliable for large-scale semiconductor device manufacturing.
Innovation Solution
A semiconductor device is developed using an oxide material with c-axis aligned crystal structure, which has a triangular or hexagonal atomic arrangement, allowing for stable electron states at the interface and improved electric characteristics, achieved through methods like sputtering, molecular beam epitaxy, or pulsed laser deposition, and can be used for gate electrodes, source/drain electrodes, or active layers in transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an amorphous oxide semiconductor film is used, then the manufacturing process is simpler, but the defect density at the interface increases and electric characteristics become unstable
Solution Approach 1:
The patent applies parameter changes by transitioning the oxide semiconductor film from an amorphous state to a crystalline state with specific crystal orientations (c-axis perpendicular to substrate). This phase transition fundamentally changes the material properties, reducing interface defect density and improving electric characteristic stability while maintaining manufacturing feasibility through controlled heating processes
Solution Approach 2:
The patent employs composite material structures by combining the oxide semiconductor film with specifically designed gate insulating films and interface layers. This multi-layer composite structure addresses interface quality issues by creating optimized boundaries between materials, reducing defect density and enhancing overall device reliability
2Reliability
If a polycrystalline silicon transistor is used, then high field effect mobility is achieved, but it is not suitable for large-sized glass substrates
Solution Approach 1:
The patent changes the material parameter from polycrystalline silicon to crystalline oxide semiconductor, which enables formation on large glass substrates while maintaining high field effect mobility. The crystalline structure of the oxide semiconductor provides the necessary electronic properties without the manufacturing constraints of polycrystalline silicon
Solution Approach 2:
The patent substitutes the mechanical crystallization process required for polycrystalline silicon with a chemical vapor deposition or atomic layer deposition process for oxide semiconductors. This replacement enables uniform film formation across large substrate areas while achieving the desired crystalline structure and electronic properties
3Area of stationary object
If an oxide semiconductor transistor is used, then large substrate manufacturing is enabled, but the transistor is sensitive to light irradiation and shows unstable electric characteristics
Solution Approach 1:
The patent applies parameter changes by controlling the crystal orientation of the oxide semiconductor film, specifically ensuring the c-axis is perpendicular to the substrate. This orientational parameter control reduces light sensitivity and stabilizes electric characteristics while maintaining compatibility with large substrate manufacturing
Solution Approach 2:
The patent implements preliminary action by performing interface treatment and crystalline structure optimization before final device operation. This includes controlled heating to establish the desired crystal orientation and interface quality in advance, preventing light-induced degradation and ensuring stable electric 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 solution provides semiconductor devices with excellent electric characteristics and enables mass production of reliable transistors on large substrates, reducing light-induced degradation and enhancing the stability of transistor performance.
Implementation Method 1
an oxide material including crystal with c-axis alignment, which has a triangular or hexagonal atomic arrangement when seen from the direction of the a-b plane, a surface, or an interface
Implementation Method 2
The oxide material can be formed by a sputtering method
Implementation Method 3
The oxide material can be formed by a sputtering method, a molecular beam epitaxy method
Implementation Method 4
The oxide material can be formed by a sputtering method, a molecular beam epitaxy method, an atomic layer deposition method, a pulsed laser deposition method
Data Source
AI summary
An object is to provide a material suitably used for a semiconductor included in a transistor, a diode, or the like. Another object is to provide a semiconductor device including a transistor in which the condition of an electron state at an interface between an oxide semiconductor film and a gate insulating film in contact with the oxide semiconductor film is favorable. Further, another object is to manufacture a highly reliable semiconductor device by giving stable electric characteristics to a transistor in which an oxide semiconductor film is used for a channel. A semiconductor device is formed using an oxide material which includes crystal with c-axis alignment, which has a triangular or hexagonal atomic arrangement when seen from the direction of a surface or an interface and rotates around the c-axis.