IGZO Thin Film Transistor Stacked Semiconductor Structure
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Solution Overview
Problem
Indium gallium zinc oxide (IGZO) semiconductor bodies in thin film transistors (TFTs) face challenges in maintaining high carrier mobility while preventing the semiconductor from becoming a conductor when the indium content is increased, which is critical for meeting the demands of high-resolution display panels.
Innovation Solution
A TFT structure with a first semiconductor layer made of IGZO having an atomic ratio In/(Ga+Zn) between 40 to 50% and a second semiconductor layer made of IGZO with an atomic ratio greater than 55%, where the second layer is covered with an oxygen protection layer, and both layers are transformed into conductors using an ion injection or plasma bombard process to form source and drain connection portions, enhancing carrier mobility and preventing conductor transformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the indium content in IGZO is increased to enhance carrier mobility, then the carrier mobility rate increases, but the semiconductor body becomes a conductor
Solution Approach 1:
The patent applies local quality by creating a stacked structure where the first semiconductor layer has lower indium content (In/(Ga+Zn) < 50%) to maintain semiconductor stability, while the second semiconductor layer has higher indium content (In/(Ga+Zn) > 55%) to provide high carrier mobility. Each layer serves a specific local function, resolving the contradiction between mobility enhancement and stability maintenance.
Solution Approach 2:
The patent uses composite materials by combining two different IGZO semiconductor layers with distinct indium compositions. This composite structure allows the device to simultaneously exhibit both the stability of low-indium material and the high mobility of high-indium material, effectively resolving the technical contradiction.
2Productivity
If the indium content is increased to meet high-resolution display demands, then the charge and discharge rate improves, but the TFT characteristics deteriorate
Solution Approach 1:
The stacked semiconductor layer structure enables different regions to have different indium concentrations optimized for specific functions: the first layer maintains TFT characteristics with lower indium content, while the second layer enhances charge and discharge rate with higher indium content, thereby resolving the contradiction between productivity and reliability.
Solution Approach 2:
The patent segments the semiconductor body into two distinct layers with different compositions. This segmentation allows independent optimization of each layer's properties, enabling the overall device to achieve both fast switching performance and stable TFT characteristics simultaneously.
3Ease of manufacture
If ion injection or plasma bombardment is applied to transform exposed active layer into conductors, then source and drain connection portions are formed, but the oxygen protection layer is required to prevent conductor transformation
Solution Approach 1:
The oxygen protection layer is formed in advance over the second semiconductor layer before the ion injection or plasma bombardment process. This preliminary protective action prevents unwanted conductor transformation during manufacturing, enabling ease of connection formation while controlling device complexity through strategic timing of the protection step.
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 proposed TFT structure effectively enhances carrier mobility and maintains the semiconductor body's stability, ensuring high performance and meeting the requirements for high-resolution display panels by optimizing the indium content and using an oxygen protection layer to mitigate ionomer bombardment.
Implementation Method 1
the exposed first semiconductor layer and the second semiconductor layer of the active layer are transformed into conductors by applying an ion injection process or a plasma bombard process
Implementation Method 2
the exposed first semiconductor layer and the second semiconductor layer of the active layer are transformed into conductors by applying an ion injection process or a plasma bombard process
Data Source
AI summary
The present disclosure relates to a TFT includes an active layer formed on a substrate, wherein the active layer includes a first semiconductor layer and a second semiconductor layer stacked together. The first semiconductor layer is made by Indium gallium zinc oxide (IGZO) having an atomic ratio In/(Ga+Zn) smaller than 50%, and the second semiconductor layer is made by IGZO having the atomic ratio In/(Ga+Zn) greater than 55%. The present disclosure also includes an array substrate having the TFT and the manufacturing method thereof. The array substrate may be adopted in LCD or OLED. The TFT adopts two layers of IGZO semiconductor materials to be the semiconductor of the active layer. Not only the demand toward the TFT characteristics may be satisfied, but also the carrier mobility rate of the IGZO active layer may be enhanced.