Oxide Semiconductor Logic Circuit for Ultra-Low Off-State Leakage
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Solution Overview
Problem
Conventional transistors in logic circuits often experience leakage currents when turned off, leading to signal voltage fluctuations and potential malfunctions, particularly in display devices like liquid crystal displays and electroluminescent displays.
Innovation Solution
The use of a transistor with an oxide semiconductor layer as the channel formation layer, which is highly purified to reduce impurities and has a larger energy gap than silicon semiconductors, minimizing leakage currents and maintaining stable voltage states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional transistors are used in logic circuits, then manufacturing is easier and cost is lower, but leakage current occurs when the transistor is off, causing signal voltage fluctuations and potential malfunctions
Solution Approach 1:
The patent changes the material parameter of the transistor channel from conventional semiconductor to oxide semiconductor, which has fundamentally different electrical characteristics. The oxide semiconductor material exhibits ultra-low off-state current due to its wide bandgap and unique electronic structure, directly resolving the leakage current issue while maintaining transistor functionality in logic circuits
2Object-generated harmful factors
If oxide semiconductor transistors are used to reduce leakage current, then off-current is reduced to 1×10^-13 A or less, but the fabrication process becomes more complex requiring high-purity material preparation
Solution Approach 1:
The patent applies preliminary purification actions to the oxide semiconductor material before transistor fabrication. The material undergoes multiple purification steps including melt growth in controlled atmosphere, crystal structure optimization, and impurity removal processes. This preliminary preparation ensures the material achieves the required purity level (carrier concentration ≤1×10^12 cm^-3) before being used in transistor fabrication, thereby reducing off-current while managing fabrication complexity through advance material preparation
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.