Oxide Semiconductor Transistor Grain Size Control
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Solution Overview
Problem
Current semiconductor technologies face challenges in forming transistors with high field-effect mobility and low off-state current, particularly due to defects such as grain boundaries in oxide semiconductors, which affect the reliability and stability of electrical characteristics.
Innovation Solution
A semiconductor device is developed using an oxide semiconductor with crystal grains of varying sizes, including regions with equivalent circle diameters of 1 nm or more and less than 1 nm, and low impurity concentrations of hydrogen and carbon, to minimize defects and enhance electrical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If oxide semiconductor is used to form transistor, then field-effect mobility is improved, but grain boundaries and defects occur which reduce reliability
Solution Approach 1:
The patent changes the crystalline state parameter of the oxide semiconductor from amorphous to crystalline. Specifically, it forms a crystalline oxide semiconductor layer with specific crystal structures (such as InGaZnO4 with space group I41/amd) to improve field-effect mobility while maintaining reliability by controlling grain boundaries through crystallization treatment.
Solution Approach 2:
The patent uses composite material structures combining oxide semiconductor layers with specific crystal phases. It forms In-Ga-Zn-O crystalline semiconductor layers with controlled composition ratios (In:Ga:Zn = 1:3:4) and specific crystal orientations to achieve both high mobility and reliability.
2Speed
If high-temperature heat treatment or laser light treatment is applied to amorphous silicon to form polycrystalline silicon, then field-effect mobility is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent changes the material composition parameter from silicon-based to oxide semiconductor (In-Ga-Zn-O). This allows forming high-mobility transistors through sputtering and relatively simple heat treatment processes, avoiding the complex laser treatment needed for polycrystalline silicon while achieving comparable or superior mobility.
3Ease of manufacture
If amorphous In-Ga-Zn oxide is used in transistor, then manufacturing is simplified, but electrical characteristics and reliability are insufficient
Solution Approach 1:
The patent changes the structural parameter of the oxide semiconductor from amorphous to crystalline state. By forming a crystalline In-Ga-Zn-O layer through controlled sputtering and heat treatment, it maintains the manufacturing simplicity of oxide semiconductors while dramatically improving electrical characteristics and reliability.
Solution Approach 2:
The patent utilizes phase transition from amorphous to crystalline state of the oxide semiconductor. By controlling the crystallization process through heat treatment after sputtering, it transforms the material structure to achieve both ease of manufacture and high reliability.
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 transistor with improved field-effect mobility, stable electrical characteristics, and reduced off-state current, leading to a more reliable semiconductor device.
Implementation Method 1
the oxide semiconductor includes a crystal grain with an equivalent circle diameter of 1 nm or more and a crystal grain with an equivalent circle diameter less than 1 nm
Data Source
AI summary
A method for forming an oxide that can be used as a semiconductor of a transistor or the like is provided. In particular, a method for forming an oxide with fewer defects such as grain boundaries is provided. One embodiment of the present invention is a semiconductor device including an oxide semiconductor, an insulator, and a conductor. The oxide semiconductor includes a region overlapping with the conductor with the insulator therebetween. The oxide semiconductor includes a crystal grain with an equivalent circle diameter of 1 nm or more and a crystal grain with an equivalent circle diameter less than 1 nm.