Oxide Semiconductor Sputtering for High Mobility
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Solution Overview
Problem
Current methods for forming transistors using semiconductor materials often result in devices with defects such as crystal grain boundaries, leading to suboptimal field-effect mobility, stability, and increased current in the off-state.
Innovation Solution
A method involving a sputtering apparatus with a target containing indium, aluminum, gallium, yttrium, or tin, and zinc, along with a magnet unit, is used to deposit an oxide semiconductor layer under specific magnetic field and temperature conditions, reducing defects and enhancing crystallinity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an amorphous silicon film is used as semiconductor, then it can be formed using established techniques for large substrates, but the field-effect mobility is limited
Solution Approach 1:
The invention changes the material composition parameters by introducing specific metal elements (In, Ga, Zn) in controlled ratios to form In-Ga-Zn oxide semiconductor films with different crystalline structures, achieving both manufacturability and high field-effect mobility through compositional optimization
Solution Approach 2:
The invention uses composite In-Ga-Zn oxide semiconductor materials combining multiple metal elements with oxygen to create a new semiconductor system that exhibits superior electrical characteristics compared to traditional amorphous silicon, while maintaining compatibility with existing manufacturing processes
2Reliability
If high-temperature heat treatment or laser light treatment is applied to amorphous silicon film to form polycrystalline silicon, then field-effect mobility improves, but the manufacturing process becomes more complex
Solution Approach 1:
The invention changes the deposition parameters by controlling sputtering power, gas flow ratios, and substrate temperature to directly form crystalline or CAAC-OS structure In-Ga-Zn oxide films without requiring subsequent high-temperature treatment, thereby reducing process complexity while achieving high field-effect mobility
Solution Approach 2:
The invention replaces the thermal-mechanical treatment process (high-temperature heat treatment or laser treatment) with a controlled sputtering deposition process that directly forms the desired crystalline structure, eliminating the need for complex post-deposition processing steps
3Reliability
If a transistor includes an oxide semiconductor, then field-effect mobility increases and capital investment can be reduced, but defects such as crystal grain boundaries remain
Solution Approach 1:
The invention changes the deposition parameters including sputtering power density, oxygen gas flow ratio, and substrate temperature to promote the formation of CAAC-OS (c-axis aligned crystalline oxide semiconductor) structure, which eliminates crystal grain boundaries and reduces defects while maintaining high field-effect mobility
Solution Approach 2:
The invention utilizes phase transition control during sputtering deposition to transform the oxide semiconductor film from amorphous or polycrystalline phases to the CAAC-OS phase, which has superior electrical characteristics due to the absence of crystal grain boundaries and reduced defects
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 crystalline oxide semiconductor with improved field-effect mobility, stable electric characteristics, and reduced off-state current, leading to a more durable and reliable semiconductor device.
Implementation Method 1
a sputtering apparatus with a target containing indium, aluminum, gallium, yttrium, or tin, and zinc, along with a magnet unit, is used to deposit an oxide semiconductor layer
Implementation Method 2
deposition is performed under specific magnetic field and temperature conditions
Data Source
AI summary
A method of forming an oxide semiconductor includes a step of depositing an oxide semiconductor layer over a substrate by using a sputtering apparatus in which in a target containing indium, an element M (aluminum, gallium, yttrium, or tin), zinc, and oxygen, the substrate which faces a surface of the target, and a magnet unit comprising a first magnet and a second magnet on a rear surface side of the target are provided. In the method, deposition is performed under a condition that a maximum intensity of a horizontal magnetic field is greater than or equal to 350 G and less than or equal to 2000 G in a plane where a vertical distance toward the substrate from a surface of the magnet unit is 10 mm.