Oxide Semiconductor Logic Circuit for Stable Low-Leakage Switching
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Solution Overview
Problem
Conventional transistors often experience leakage current issues when in the off state, leading to malfunction in logic circuits, especially in display devices where precise voltage control is crucial.
Innovation Solution
The use of a transistor with an oxide semiconductor layer as the channel formation layer, which is highly purified to be intrinsic or substantially intrinsic, reducing the leakage current and minimizing the impact of threshold voltage variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional transistors are used in logic circuits, then manufacturing is easier and device complexity is lower, but leakage current increases causing malfunction
Solution Approach 1:
The patent changes the material parameter of the transistor channel from conventional semiconductor to oxide semiconductor, which fundamentally alters the electrical characteristics to achieve ultra-low leakage current while maintaining acceptable manufacturing complexity
Solution Approach 2:
The patent employs oxide semiconductor materials (such as In-Ga-Zn-O) as composite material in the channel formation layer, combining multiple elements to achieve desired electrical properties including low leakage current and stable threshold voltage
2Reliability
If oxide semiconductor transistors are used, then leakage current is reduced and reliability is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent performs preliminary purification of the oxide semiconductor material before device fabrication, removing impurities that would act as electron donors and cause leakage current, thereby ensuring high material purity prior to manufacturing steps
Solution Approach 2:
The patent applies different quality requirements to different regions of the oxide semiconductor layer, with the channel formation region requiring highest purity to minimize leakage current, while other regions can have relaxed specifications
Data Source
AI summary
To reduce a leakage current of a transistor so that malfunction of a logic circuit can be suppressed. The logic circuit includes a transistor which includes an oxide semiconductor layer having a function of a channel formation layer and in which an off current is 1×10−13 A or less per micrometer in channel width. A first signal, a second signal, and a third signal that is a clock signal are input as input signals. A fourth signal and a fifth signal whose voltage states are set in accordance with the first to third signals which have been input are output as output signals.