IGZO Thin Film Transistor Active Layer Oxygen Deficit Control
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Solution Overview
Problem
Existing methods for producing crystalline IGZO-based oxide materials for thin film transistors often result in degenerate semiconductors due to high oxygen deficit values, leading to metallic conductivity, and fail to maintain a single phase, which affects carrier mobility and device performance.
Innovation Solution
A thin film transistor with an active layer composed of IGZO-based oxide material represented by In2-xGaxZnO4-δ, where 0.75<x<1.10 and 0<δ≦1.29161×exp(−x/0.11802)+0.00153, formed from a single phase with a YbFe2O4 crystal structure, is produced using a process involving controlled cooling of thin film materials from crystallization temperature to 300°C at a rate of 50°C/hr to 500°C/hr, ensuring optimal oxygen deficit and phase purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If rapid cooling (quenching) is performed from high annealing temperature, then the oxide material maintains its high-temperature state at room temperature with increased oxygen deficit, but the material becomes a degenerate semiconductor with metallic conductivity
Solution Approach 1:
The patent changes the cooling rate parameter from rapid (quenching) to controlled slow cooling (50-500°C/hr), which fundamentally alters the oxygen deficit development. This parameter change transforms the material from a degenerate semiconductor with metallic conductivity to a proper semiconductor with controllable electrical properties suitable for TFT applications
Solution Approach 2:
The patent utilizes the phase transition behavior of IGZO during cooling. By controlling the cooling rate through the critical temperature range, the material undergoes a controlled phase transition that limits oxygen escape and maintains appropriate oxygen deficit, preventing the formation of metallic conductivity while achieving the desired semiconductor phase
2Quantity of substance
If reduction heat treatment is performed to introduce oxygen deficits, then carrier concentration increases, but the material behaves as a degenerate semiconductor with metallic conductivity
Solution Approach 1:
The patent changes the thermal processing parameters by replacing reduction heat treatment with controlled cooling from crystallization temperature. This parameter change achieves carrier generation through a different mechanism (controlled oxygen deficit during cooling) that does not lead to degenerate semiconductor formation, maintaining proper semiconductor behavior
Solution Approach 2:
Instead of using reduction heat treatment to increase carrier concentration (conventional approach), the patent inverts the approach by using controlled cooling to achieve the same goal through limited oxygen escape. This inverted method increases carriers while preventing metallic conductivity by maintaining thermodynamic equilibrium
3Ease of manufacture
If crystalline IGZO-based oxide material is obtained by annealing at certain conditions, then the material can be formed, but it exhibits metallic conductivity due to high oxygen deficit
Solution Approach 1:
The patent changes the cooling rate parameter from rapid to controlled slow cooling, which maintains crystalline formation ease while fundamentally altering the electrical properties. The controlled cooling allows crystalline structure development while limiting oxygen deficit to appropriate levels for semiconductor behavior
Solution Approach 2:
The patent maintains continuous thermodynamic equilibrium during the cooling process, allowing the material to continuously adjust its oxygen content and crystal structure. This continuous process ensures crystalline formation while preventing the discontinuous jump to metallic conductivity that occurs with rapid quenching
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 approach achieves a resistivity range suitable for semiconductor applications, suppressing carrier generation and maintaining high mobility by controlling oxygen deficit and phase stability, enhancing the material's suitability for thin film transistor active layers.
Implementation Method 1
cooling a thin film material that includes In, Ga and Zn, the thin film material having been formed on a substrate and heated to a crystallization temperature of the thin film material, from the crystallization temperature to 300° C. at an average rate of temperature decrease of from 50° C./hr to 500° C./hr
Implementation Method 2
cooling a thin film material that includes In, Ga and Zn, the thin film material having been formed on a substrate and heated to a crystallization temperature of the thin film material, from the crystallization temperature to 300° C. at an average rate of temperature decrease of from 50° C./hr to 500° C./hr
Data Source
AI summary
The invention provides a thin film transistor comprising an active layer, the active layer comprising an IGZO-based oxide material, the IGZO-based oxide material being represented by a composition formula of In2-xGaxZnO4-δ, where 0.75<x<1.10 and 0<δ≦1.29161×exp(−x/0.11802)+0.00153 and being formed from a single phase of IGZO having a crystal structure of YbFe2O4, and a method of producing the thin film transistor.