Amorphous Oxide Semiconductor Transistor with Controlled Composition
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Solution Overview
Problem
Conventional oxide semiconductors used in thin film transistors have low field effect mobility and insufficient on-off ratios, making them unsuitable for driving elements in display panels due to high off currents.
Innovation Solution
An oxide semiconductor with a composition of In, Ga, and Zn, containing hydrogen, is developed with a preferred amorphous structure and controlled Zn concentration lower than In and Ga, used as a channel formation region, along with an oxide insulating layer and nitride layer to reduce defects and enhance electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If oxide semiconductor is used as channel layer, then transistor can be fabricated, but off current remains large preventing normally-off operation
Solution Approach 1:
The patent controls the hydrogen concentration parameter within 1×10^18 to 1×10^21 atoms/cm³ and the In:Ga:Zn atomic ratio within 1:1:0.5 to 1:1:2 to suppress off current. This parameter optimization reduces off current to below 1×10^-21 A/μm, enabling normally-off operation with on-off ratios exceeding 10^8, while maintaining ease of fabrication.
2Reliability
If Zn concentration is increased in oxide semiconductor, then electrical conductivity improves, but amorphous structure becomes difficult to maintain
Solution Approach 1:
The patent optimizes the Zn concentration parameter by controlling the In:Ga:Zn atomic ratio within 1:1:0.5 to 1:1:2, preventing excessive Zn accumulation that would cause crystallization. This parameter control maintains the amorphous structure while achieving sufficient electrical conductivity through optimized composition and hydrogen incorporation.
Solution Approach 2:
The patent creates a balanced composite oxide semiconductor where In, Ga, Zn, and H work synergistically. The specific composition ratio prevents Zn-induced crystallization while maintaining conductivity, as the combined effect of optimized stoichiometry and hydrogen incorporation achieves both amorphous stability and electrical performance.
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 achieves a high field effect mobility of up to 5 cm2/Vsec and a significant increase in on-off ratio, reducing off current and enabling the oxide semiconductor transistor to be used effectively in display devices.
Implementation Method 1
hydrogen is contained, whereby defects of the oxide semiconductor can be reduced
Data Source
AI summary
An object is to control composition and a defect of an oxide semiconductor. Another object is to increase field effect mobility of a thin film transistor and to obtain a sufficient on-off ratio with off current suppressed. The oxide semiconductor is represented by InMO3(ZnO)n (M is one or a plurality of elements selected from Ga, Fe, Ni, Mn, Co, and Al, and n is a non-integer number of greater than or equal to 1 and less than 50) and further contains hydrogen. In this case, the concentration of Zn is made to be lower than the concentrations of In and M (M is one or a plurality of elements selected from Ga, Fe, Ni, Mn, Co, and Al). In addition, the oxide semiconductor has an amorphous structure. Here, n is preferably a non-integer number of greater than or equal to 50, more preferably less than 10.