In-Zn Oxide Semiconductor Film for Mobility and Thermal Stability
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Solution Overview
Problem
Existing thin film transistors, particularly those using In-Ga-Zn-O amorphous oxide semiconductors, face challenges with carrier mobility below 10 cm²/Vs and insufficient stability with respect to environmental temperature, especially in harsh conditions.
Innovation Solution
An oxide semiconductor film comprising In, Zn, and either La or Nd, with specific content ranges of 30-90 atm% In, 9-70 atm% Zn, and 0.0001-2 atm% La or Nd, enhances both carrier mobility and stability to environmental temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If In-Ga-Zn-O amorphous oxide semiconductor is used in thin film transistor, then the device can be formed at low temperatures with large optical band gap, but the carrier mobility remains less than or equal to 10 cm2/Vs
Solution Approach 1:
The patent changes the compositional parameters of the oxide semiconductor by replacing Ga with specific rare earth elements (La, Nd, Pr, Ce) at controlled concentrations (0.01-5 at%). This compositional modification enables achieving carrier mobility greater than 30 cm2/Vs while maintaining the amorphous structure and low-temperature film formation capability
Solution Approach 2:
The patent creates a composite oxide semiconductor material system consisting of In-Zn-O base composition doped with rare earth elements. This composite approach combines the advantages of In-Zn-O (low temperature processing, large band gap) with the mobility-enhancing effects of rare earth dopants, achieving both ease of manufacture and high carrier mobility
2Speed
If conventional oxide semiconductors are used to achieve high carrier mobility, then the threshold voltage shifts significantly with environmental temperature changes, but using standard compositions maintains better thermal stability at the cost of lower mobility
Solution Approach 1:
The patent optimizes the concentration parameters of rare earth elements (0.01-5 at%) to simultaneously improve carrier mobility and stabilize threshold voltage. This precise parameter control enables achieving carrier mobility greater than 30 cm2/Vs while limiting threshold voltage shift to less than 3.5V between -40°C and 85°C
Solution Approach 2:
The patent identifies specific rare earth element substitutions that replicate and enhance the beneficial effects observed in high-mobility oxide semiconductors. By copying the successful substitution strategy with different rare earth elements (La, Nd, Pr, Ce), the patent achieves both high mobility and thermal stability
Data Source
AI summary
It is an object of the present invention to provide an oxide semiconductor film which enables improving both the carrier mobility and the stability with respect to environmental temperature of a thin film transistor. The oxide semiconductor film according to the one embodiment of the present invention contains, as metal elements: In and Zn; and an element X, being either of La and Nd, wherein contents of the In, the Zn, and the element X in total metal elements are: In: greater than or equal to 30 atm % and less than or equal to 90 atm %; Zn: greater than or equal to 9 atm % and less than or equal to 70 atm %; and X: greater than or equal to 0.0001 atm % and less than or equal to 2 atm %.