IGZO Thin Film Transistor Channel Reduction for Electron Mobility
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Metal oxide semiconductors in thin film transistors have lower electron mobility compared to amorphous silicon and polysilicon semiconductors, limiting their application range, and existing methods to reduce variation in electric characteristics increase surface resistance and decrease semiconductor layer thickness, reducing current flow.
Innovation Solution
A reduced region with a higher content of simple metal, such as indium, is formed in the channel portion of the semiconductor layer, increasing electron mobility and improving ON/OFF characteristics, while maintaining satisfactory electric characteristics through a reduction process that stabilizes the metal oxide semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a protective layer is formed by sputtering method, then variation in characteristics is decreased, but resistance of surface layer is increased and thickness is decreased, reducing current flow
Solution Approach 1:
The patent applies local quality by creating distinct regions within the semiconductor layer with different oxidation states. The surface layer is oxidized to reduce variation in characteristics, while the inner layer maintains lower oxidation to preserve high electron mobility and current flow capability. This spatial differentiation of material properties resolves the contradiction between reliability and productivity.
Solution Approach 2:
The semiconductor layer is segmented into multiple layers with different functions: a surface layer for stability and characteristic consistency, and an inner layer for high electron mobility. This segmentation allows each layer to optimize its specific function without compromising the other, thereby resolving the contradiction between reduced variation and maintained current flow.
2Reliability
If semiconductor layer is oxidized to protect from damage, then electric characteristics are stabilized, but electron mobility is reduced
Solution Approach 1:
Different regions of the semiconductor layer are given different oxidation states: the surface layer is highly oxidized for stability, while the inner layer is less oxidized for high electron mobility. This local differentiation resolves the contradiction between characteristic stability and electron mobility.
Solution Approach 2:
The semiconductor structure is designed as a composite of oxidized and non-oxidized regions, combining the advantages of both states: oxidation provides stability and protection, while non-oxidized regions maintain high electron mobility. This composite approach resolves the contradiction between reliability and speed.
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 increased electron mobility and improved ON/OFF characteristics enhance the application range of metal oxide semiconductors in thin film transistors, allowing for higher current flow and stable electric performance.
Implementation Method 1
a reduced region is formed at least in the channel portion of the semiconductor layer, and the reduced region has a higher content of a simple substance of a metal than a remaining portion of the semiconductor layer
Data Source
AI summary
A TFT 20 includes a gate electrode 21, a gate insulating film 22, a semiconductor layer 23, a source electrode 24, a drain electrode 25, etc. The semiconductor layer 23 is comprised of a metal oxide semiconductor (IGZO), and has a source portion 23a that contacts the source electrode 24, a drain electrode 23b that contacts the drain electrode 25, and a channel portion 23c that is located between the source and drain portions 23a, 23b. A reduced region 30 is formed at least in the channel portion 23c of the semiconductor layer 23, and the reduced region 30 has a higher content of a simple substance of a metal such as In than the remaining portion of the semiconductor layer 23.