Amorphous Oxide Semiconductor Thin Film Transistor for High Mobility
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Solution Overview
Problem
Conventional thin film transistors using oxide semiconductors have low field effect mobility and high off current, resulting in an insufficient on-off ratio, which limits their practical application.
Innovation Solution
An oxide semiconductor with a composition of In, Ga, and Zn, where the concentration of Zn is lower than In and Ga, is used to form a channel formation region, accompanied by an amorphous structure and a nitride insulating layer, to reduce off current and enhance the on-off ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional oxide semiconductor materials are used in thin film transistors, then the material can be deposited as a thin film at low temperature, but the field effect mobility remains low and off current is high
Solution Approach 1:
The patent changes the compositional parameters of the oxide semiconductor by controlling the ratio of In, Ga, and Zn atoms, and specifically controlling the concentration of Zn to be lower than In and Ga, thereby achieving both high field effect mobility and low off current simultaneously
Solution Approach 2:
The patent uses a composite oxide semiconductor material containing multiple elements (In, Ga, Zn, and potentially Fe, Ni, Mn, Co, or Al) with specific compositional ratios to achieve superior electrical characteristics that cannot be obtained with single-element oxides
2Ease of manufacture
If the concentration of Zn is increased in the oxide semiconductor, then the material can be formed more easily, but the carrier concentration increases leading to higher off current
Solution Approach 1:
The patent optimizes the concentration parameter of Zn to be lower than that of In and Ga, which simultaneously achieves easy film formation and low off current by controlling the carrier concentration through compositional control
3Speed
If the oxide semiconductor is made crystalline, then the field effect mobility can be increased, but the manufacturing complexity and temperature requirements increase
Solution Approach 1:
The patent changes the structural parameter from crystalline to amorphous while compensating for mobility through compositional optimization (In, Ga, Zn ratios), thereby achieving high performance with simpler manufacturing processes and lower temperature requirements
Data Source
AI summary
An object is to control composition and a defect of an oxide semiconductor, another object is to increase a field effect mobility of a thin film transistor and to obtain a sufficient on-off ratio with a reduced off current. A solution is to employ an oxide semiconductor whose composition is represented by InMO3(ZnO)m, where M is one or a plurality of elements selected from Ga, Fe, Ni, Mn, Co, and Al, and m is preferably a non-integer number of greater than 0 and less than 1. The concentration of Zn is lower than the concentrations of In and M. The oxide semiconductor has an amorphous structure. Oxide and nitride layers can be provided to prevent pollution and degradation of the oxide semiconductor.