Oxide Semiconductor Analog Circuit With Low Off-State Current
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Solution Overview
Problem
Thin film transistors using oxide semiconductors exhibit low on/off ratios and high off-state currents, leading to unstable operation, limited dynamic range, and increased power consumption, which affects signal detection sensitivity and efficiency in analog circuits.
Innovation Solution
The use of a purified oxide semiconductor with reduced hydrogen concentration, forming a channel region with a larger energy gap, to create a thin film transistor with improved carrier concentration and reduced impurities, resulting in a stable and efficient analog circuit with enhanced signal detection sensitivity and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If oxide semiconductor is used as semiconductor thin film for thin film transistor, then the thin film transistor can be formed with simplified process, but the on/off ratio is low and off-state current is high
Solution Approach 1:
The patent applies parameter changes by controlling the oxygen carrier concentration in the oxide semiconductor to be 1×10^18/cm³ or less, and adjusting the ratio of metal atoms to oxygen atoms to be 0.95 or more. These parameter adjustments transform the oxide semiconductor from a high-conductivity state to a low-conductivity state, achieving high on/off ratio exceeding 10^8 while maintaining ease of manufacture through sputtering or evaporation processes.
Solution Approach 2:
The patent applies local quality by creating different regions within the oxide semiconductor layer with distinct oxygen carrier concentrations. The channel-forming region is maintained with low oxygen carrier concentration (≤1×10^18/cm³) for high resistance, while other regions may have different properties. This local differentiation enables the transistor to achieve high on/off ratio while maintaining manufacturability.
2Reliability
If oxide semiconductor with electron carrier concentration less than 10^18/cm³ is used, then the on/off ratio improves, but the circuit operation becomes unstable due to high off-state current
Solution Approach 1:
The patent applies parameter changes by precisely controlling multiple parameters simultaneously: oxygen carrier concentration (≤1×10^18/cm³), metal-to-oxygen atom ratio (≥0.95), and impurity content. These coordinated parameter adjustments reduce off-state current to 1×10^−21 A or less, achieving both high on/off ratio and stable circuit operation with voltage thresholds clearly defined at 0.05V for n-channel and -0.05V for p-channel devices.
3Ease of manufacture
If conventional oxide semiconductor thin film is used, then the manufacturing process is simple, but the dynamic range is limited and power consumption is high
Solution Approach 1:
The patent applies parameter changes by controlling oxygen carrier concentration and metal-to-oxygen ratio to achieve ultra-low off-state current (≤1×10^−21 A). This dramatically reduces power consumption in the off-state while maintaining simple sputtering or evaporation manufacturing processes, enabling analog circuits to achieve wide dynamic range and low power consumption simultaneously.
4Ease of manufacture
If oxide semiconductor with impurities is used, then the thin film transistor can be easily manufactured, but the detection sensitivity to weak signals cannot be increased
Solution Approach 1:
The patent applies parameter changes by严格控制 oxygen carrier concentration (≤1×10^18/cm³) and metal-to-oxygen atom ratio (≥0.95), reducing impurity levels to enable detection of extremely weak signals with currents as low as 1×10^−21 A. This maintains ease of manufacture through standard sputtering or evaporation while achieving high detection sensitivity.
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 purified oxide semiconductor thin film transistor achieves a low off-state current, enabling a wide dynamic range and high sensitivity in signal detection while minimizing power consumption, thereby stabilizing circuit operation and improving detection reliability.
Implementation Method 1
forming a channel region with a larger energy gap, to create a thin film transistor with improved carrier concentration
Data Source
AI summary
An object is to obtain a semiconductor device having a high sensitivity in detecting signals and a wide dynamic range, using a thin film transistor in which an oxide semiconductor layer is used. An analog circuit is formed with the use of a thin film transistor including an oxide semiconductor which has a function as a channel formation layer, has a hydrogen concentration of 5×1019 atoms/cm3 or lower, and substantially functions as an insulator in the state where no electric field is generated. Thus, a semiconductor device having a high sensitivity in detecting signals and a wide dynamic range can be obtained.