Oxide Semiconductor Transistor with Composition Gradient
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Solution Overview
Problem
Current semiconductor devices face challenges in achieving high field-effect mobility, stable electrical characteristics, and low off-state current, particularly in transistors using oxide semiconductor films.
Innovation Solution
A semiconductor device structure incorporating an oxide semiconductor film with a concentration gradient and a zinc oxide layer, where the oxide semiconductor film contains indium, aluminum, gallium, yttrium, or tin, and zinc, and is formed using a thermal chemical vapor deposition method with controlled electron affinity, and a conductive film overlapping with the oxide semiconductor film through an insulating film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an oxide semiconductor film is used as a channel formation region, then field-effect mobility is improved, but off-state current remains too high
Solution Approach 1:
The oxide semiconductor film is divided into multiple layers with different compositions and properties. The first layer has high carrier density for high on-state current, while the second layer has low carrier density for low off-state current, creating local quality differences that resolve the contradiction
Solution Approach 2:
The channel formation region is segmented into multiple oxide semiconductor layers with distinct functions. The first oxide semiconductor layer serves as the main conduction path, while the second oxide semiconductor layer acts as a barrier layer to suppress off-state current leakage
2Speed
If high-temperature heat treatment or laser light treatment is applied to form polycrystalline silicon film, then field-effect mobility is improved, but manufacturing complexity and cost increase
Solution Approach 1:
The invention changes the material parameter from silicon-based to oxide semiconductor-based, allowing transistor fabrication at lower temperatures without requiring high-temperature heat treatment or laser light treatment, thus simplifying the manufacturing process while maintaining high field-effect mobility
Solution Approach 2:
The invention uses composite oxide semiconductor structures with multiple layers having different compositions (e.g., In-Ga-Zn-O with varying atomic ratios) to achieve both high mobility and low off-state current, eliminating the need for complex post-deposition treatments
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 transistors with high field-effect mobility, stable electrical characteristics, and low off-state current, enhancing the performance and reliability of semiconductor devices.
Implementation Method 1
formed using a thermal chemical vapor deposition method with controlled electron affinity
Data Source
AI summary
A transistor having high field-effect mobility is provided. A transistor having stable electrical characteristics is provided. A transistor having low off-state current (current in an off state) is provided. Alternatively, a semiconductor device including the transistor is provided. The semiconductor device includes a first insulating film, an oxide semiconductor film over the first insulating film, a second insulating film over the oxide semiconductor film, and a conductive film overlapping with the oxide semiconductor film with the first insulating film or the second insulating film provided between the oxide semiconductor film and the conductive film. The composition of the oxide semiconductor film changes continuously between the first insulating film and the second insulating film.