Composite Oxide Semiconductor Structure for Mobility and Threshold Stability
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Solution Overview
Problem
Transistors using oxide semiconductor films face challenges with high field-effect mobility leading to normally-on characteristics and electrical instability due to oxygen vacancies, which affect reliability and power consumption.
Innovation Solution
A composite oxide semiconductor with distinct regions of varying indium, zinc, and oxygen compositions is used, where the first region has higher conductivity and the second region has higher semiconductor properties, connected in a cloud-like manner to enhance carrier mobility and reduce oxygen vacancies, thereby improving transistor reliability and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the field-effect mobility is increased to improve transistor performance, then the transistor tends to be normally on, which deteriorates the electrical characteristics and reliability
Solution Approach 1:
The oxide semiconductor film is divided into two regions with different compositions: a first region with higher indium content for high mobility and a second region with lower indium content for stability. This local differentiation allows each region to perform its specific function optimally while working together as a unified structure.
Solution Approach 2:
The invention uses a composite oxide semiconductor structure combining two different oxide semiconductor regions with distinct compositional characteristics. The first region contains In-M-Zn-O with higher indium proportion for conductivity, while the second region contains In-M-Zn-O with lower indium proportion for stability, creating a composite material that achieves both high mobility and reliability.
2Quantity of substance
If oxygen vacancies are present in the oxide semiconductor film to enable carrier supply, then the threshold voltage shifts negatively causing normally-on characteristics, but reducing oxygen vacancies decreases carrier supply capability
Solution Approach 1:
The first region with higher indium content provides oxygen vacancies for carrier supply, while the second region with lower indium content maintains fewer oxygen vacancies for threshold voltage stability. This spatial separation of functions resolves the contradiction between needing carriers and maintaining stable electrical characteristics.
Solution Approach 2:
The second region acts as an intermediary that suppresses the harmful effects of oxygen vacancies from the first region. By positioning the stable second region adjacent to the high-carrier first region, it mediates the overall electrical characteristics to prevent normally-on behavior while preserving the carrier supply capability of the first region.
Data Source
AI summary
The field-effect mobility and reliability of a transistor including an oxide semiconductor film are improved. A semiconductor layer of a transistor is formed using a composite oxide semiconductor in which a first region and a second region are mixed. The first region includes a plurality of first clusters containing one or more of indium, zinc, and oxygen as a main component. The second region includes a plurality of second clusters containing one or more of indium, an element M (M represents Al, Ga, Y, or Sn), zinc, and oxygen. The first region includes a portion in which the plurality of first clusters are connected to each other. The second region includes a portion in which the plurality of second clusters are connected to each other.