Oxide Semiconductor Display Circuits for Accurate Signal Retention
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Solution Overview
Problem
Existing thin film transistors using amorphous silicon for channel layers in display devices suffer from low field-effect mobility and high off-state current, leading to noise, reduced withstand voltage, and increased power consumption, which affects the accuracy of display devices.
Innovation Solution
Utilizing transistors with oxide semiconductors, particularly MOS transistors, which have low off-state current and high withstand voltage, to form circuits in display devices, including a pixel portion and inspection circuits, with gates and terminals connected to reduce unnecessary current leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If thin film transistors using amorphous silicon are used for channel layers, then larger glass substrates can be used, but field-effect mobility is low and off-state current is high
Solution Approach 1:
The patent changes the material parameter of the semiconductor layer from amorphous silicon to oxide semiconductor, which fundamentally alters the electrical properties including field-effect mobility and off-state current characteristics, thereby resolving the contradiction between substrate size capability and transistor performance
Solution Approach 2:
The patent employs oxide semiconductor materials (such as IGZO - indium gallium zinc oxide) that combine the advantages of both amorphous and crystalline semiconductors, achieving high field-effect mobility while maintaining the ability to be manufactured on large-area substrates
2Ease of manufacture
If thin film transistors using amorphous silicon are used for channel layers, then manufacturing is easier on large substrates, but off-state current is high causing noise and increased power consumption
Solution Approach 1:
By changing the semiconductor material from amorphous silicon to oxide semiconductor, the off-state current parameter is reduced by several orders of magnitude, eliminating noise and power consumption issues while preserving large-substrate manufacturability through similar deposition processes
3Ease of operation
If conventional transistors are used in pixel circuits, then circuit operation is simpler, but current leakage occurs reducing display accuracy
Solution Approach 1:
The oxide semiconductor material provides extremely low off-state current characteristics that prevent charge leakage in pixel circuits, thereby maintaining display accuracy without complicating circuit operation, as the same simple transistor switching operations can be performed with significantly improved charge retention
Data Source
AI summary
An object is to provide a display device that performs accurate display. A circuit is formed using a transistor that includes an oxide semiconductor and has a low off-state current. A precharge circuit or an inspection circuit is formed in addition to a pixel circuit. The off-state current is low because the oxide semiconductor is used. Thus, it is not likely that a signal or voltage is leaked in the precharge circuit or the inspection circuit to cause defective display. As a result, a display device that performs accurate display can be provided.