Oxygen-Excess Silicon Oxide Insulating Layer for Oxide Semiconductor Stability
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Solution Overview
Problem
Transistors using oxide semiconductors face reliability issues due to changes in electric characteristics caused by light irradiation and bias-temperature stress, primarily attributed to hydrogen ions and oxygen deficiencies, leading to unstable threshold voltages.
Innovation Solution
Employing oxygen-excess silicon oxide (SiOX with X>2) as a base or protective insulating layer in contact with the oxide semiconductor layer, which reduces interface state density and supplies oxygen to mitigate hydrogen-related issues, thereby stabilizing the transistor's electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If oxide semiconductor is used as transistor material, then manufacturing ease and operating speed are improved, but reliability deteriorates due to threshold voltage instability
Solution Approach 1:
The patent changes the chemical composition parameter of the insulating layer by using oxygen-excess silicon oxide (SiOx where x>2) instead of conventional stoichiometric silicon oxide. This parameter change supplies excess oxygen to the oxide semiconductor layer, reducing oxygen vacancies and stabilizing the threshold voltage, thereby improving reliability while maintaining manufacturing ease
Solution Approach 2:
The oxygen-excess silicon oxide layer acts as an intermediary between the oxide semiconductor and external environment. It serves as an oxygen reservoir that continuously supplies oxygen to the oxide semiconductor layer, preventing oxygen deficiency and hydrogen-related defects, thus stabilizing electrical characteristics without complicating the manufacturing process
2Device complexity
If conventional insulating layers are used with oxide semiconductor, then device structure is simplified, but threshold voltage shifts due to charge trapping and hydrogen ions
Solution Approach 1:
The patent modifies the compositional parameter of the insulating layer by using SiOx with x>2 (oxygen-excess silicon oxide). This compositional change enables the insulating layer to function as an oxygen source, reducing oxygen vacancies in the oxide semiconductor and minimizing charge trapping, thereby stabilizing threshold voltage without increasing device complexity
Solution Approach 2:
The patent converts the typically harmful effect of oxygen deficiency in oxide semiconductors into a benefit by using oxygen-excess silicon oxide. The excess oxygen in SiOx diffuses into the oxide semiconductor layer, filling oxygen vacancies and reducing carrier trapping, thus transforming what is normally a destabilizing factor into a stabilizing mechanism for threshold voltage
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 use of oxygen-excess silicon oxide significantly reduces the shift in threshold voltage and enhances the reliability of oxide semiconductor transistors by minimizing charge trapping and hydrogen-related instabilities, resulting in stable electrical performance before and after light irradiation or bias-temperature stress tests.
Implementation Method 1
oxygen-excess silicon oxide (SiOX (X>2)) is used for a base insulating layer or a protective insulating layer in contact with an oxide semiconductor layer... the number of oxygen atoms per unit volume is more than twice the number of silicon atoms per unit volume
Data Source
AI summary
An object of an embodiment of the present invention is to manufacture a highly-reliable semiconductor device comprising a transistor including an oxide semiconductor, in which change of electrical characteristics is small. In the transistor including an oxide semiconductor, oxygen-excess silicon oxide (SiOX (X>2)) is used for a base insulating layer of a top-gate structure or for a protective insulating layer of a bottom-gate structure. By using the oxygen-excess silicon oxide, oxygen is discharged from the insulating layer, and oxygen deficiency of an oxide semiconductor layer and the interface state density between the oxide semiconductor layer and the base insulating layer or the protective insulating layer can be reduced, so that the highly-reliable semiconductor device in which change of electrical characteristics is small can be manufactured.