Oxide Semiconductor Nanocrystal Layer for TFT Speed
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Solution Overview
Problem
Existing thin film transistors used in display devices face challenges in achieving high on-off ratios and operation speed, particularly in pixel portions and driver circuits, which are crucial for reducing writing time and maintaining image quality in high-resolution displays.
Innovation Solution
A semiconductor device structure is developed, featuring a gate electrode layer, gate insulating layer, oxide semiconductor layer, and oxide insulating layer, where the oxide semiconductor layer has a crystal region on its surface and is formed using InMO3(ZnO)m with specific metal elements, and the oxide insulating layer functions as a channel protective layer to enhance electrical characteristics and operation speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional thin film transistors are used in high-resolution display devices, then the device can be manufactured with standard processes, but the operation speed is insufficient and writing time cannot be reduced adequately
Solution Approach 1:
The patent changes the material parameter of the semiconductor layer from conventional materials to oxide semiconductor (In-Ga-Zn-O), which inherently provides higher carrier mobility and faster operation speed, directly addressing the speed requirement for high-resolution displays
Solution Approach 2:
The patent employs a composite structure with multiple oxide layers including oxide semiconductor layer, oxide insulating layer, and oxide conductive layer, where each layer has specific composition and function, achieving both high speed operation and low writing time through synergistic effects
2Reliability
If thin film transistors are used for pixel portions requiring high on-off ratio, then switching characteristics are improved, but operation speed for driver circuits becomes insufficient
Solution Approach 1:
The patent applies different oxide material compositions and structures to different regions: the oxide semiconductor layer with specific In-Ga-Zn-O ratio for high mobility in driver circuit regions, and optimized oxide insulating layers for switching characteristics in pixel portions, allowing each region to optimize its performance
Solution Approach 2:
The patent creates a dynamic structure where the oxide semiconductor layer can operate in different regimes - achieving high on-off ratio for switching when needed, and high carrier mobility for fast operation when driven by appropriate gate voltages, adapting to different operational requirements
3Ease of manufacture
If oxide semiconductor layer is formed without crystal region, then manufacturing process is simpler, but contact resistance increases and electrical characteristics deteriorate
Solution Approach 1:
The patent performs preliminary crystal region formation in the oxide semiconductor layer through controlled heating treatment before final device assembly, preparing the material structure in advance to ensure low contact resistance and good electrical characteristics without complicating the overall manufacturing process
Solution Approach 2:
The patent changes the physical state parameter of the oxide semiconductor from amorphous to partially crystalline by controlling heating temperature and time, achieving the optimal balance between manufacturing simplicity and electrical performance through parameter optimization
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 results in a highly reliable thin film transistor with improved electrical characteristics and increased operation speed, suitable for high-resolution display devices by reducing contact resistance and preventing parasitic channel formation.
Implementation Method 1
a crystal region is formed in a superficial portion of the oxide semiconductor layer which is in contact with the oxide insulating layer
Implementation Method 2
an oxide insulating layer in contact with part of the oxide semiconductor layer... functions as a channel protective layer
Data Source
AI summary
In a channel protected thin film transistor in which a channel formation region is formed using an oxide semiconductor, an oxide semiconductor layer which is dehydrated or dehydrogenated by a heat treatment is used as an active layer, a crystal region including nanocrystals is included in a superficial portion in the channel formation region, and the rest portion is amorphous or is formed of a mixture of amorphousness/non-crystals and microcrystals, where an amorphous region is dotted with microcrystals. By using an oxide semiconductor layer having such a structure, a change to an n-type caused by entry of moisture or elimination of oxygen to or from the superficial portion and generation of a parasitic channel can be prevented and a contact resistance with a source and drain electrodes can be reduced.