Oxide Semiconductor Film Stability Against Light Irradiation
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Solution Overview
Problem
Oxygen vacancies in the channel region of oxide semiconductor films used in transistors lead to adverse effects on electrical characteristics, such as shifts in threshold voltage and variability among transistors, necessitating a reduction in oxygen vacancy levels to improve reliability and power efficiency.
Innovation Solution
Incorporating an oxide semiconductor film with In, Zn, and Ga, and a crystal part with c-axis alignment, and using insulating films with excess oxygen to fill oxygen vacancies, while controlling the thickness of the oxide semiconductor film to suppress light absorption and maintain stable electrical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxygen vacancies are reduced in the oxide semiconductor film, then electrical characteristic stability is improved, but manufacturing complexity increases due to additional purification steps
Solution Approach 1:
The patent applies preliminary action by performing heat treatment in an oxygen atmosphere before transistor fabrication to reduce oxygen vacancies in advance. This pre-treatment step removes oxygen vacancies before the oxide semiconductor film is used in device manufacturing, thereby stabilizing electrical characteristics without adding complex purification steps during the main fabrication process
Solution Approach 2:
The patent changes physical parameters by controlling heat treatment temperature (400-700°C) and oxygen partial pressure during treatment. By optimizing these parameters, the patent achieves effective oxygen vacancy reduction while maintaining a relatively simple manufacturing process, resolving the contradiction between reliability improvement and manufacturing complexity
2Reliability
If the oxide semiconductor film thickness is increased, then light absorption is suppressed and electrical characteristic stability under light irradiation is improved, but transistor performance and switching capability deteriorate
Solution Approach 1:
The patent changes the thickness parameter of the oxide semiconductor film to an optimal range (50-200 nm) that balances light absorption suppression with maintaining good transistor performance. This parameter optimization allows the film to be thick enough to resist light-induced electrical characteristic changes while remaining thin enough to ensure adequate switching capability and carrier transport
Solution Approach 2:
The patent applies preliminary anti-action by performing heat treatment in oxygen atmosphere to reduce oxygen vacancies before device fabrication. This pre-treatment counteracts the potential harmful effects of oxygen vacancies that would otherwise be generated or activated during subsequent manufacturing steps and device operation, thereby preventing electrical characteristic instability without requiring excessive film thickness
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
This approach inhibits changes in electrical characteristics due to light irradiation, enhances the reliability of semiconductor devices, and reduces power consumption by stabilizing the transistor performance and reducing oxygen vacancy-induced issues.
Implementation Method 1
an insulating layer that releases oxygen by heating to reduce oxygen vacancy in the oxide semiconductor layer
Implementation Method 2
light irradiation is performed on the oxide semiconductor film with light having an energy greater than or equal to a band gap of the oxide semiconductor film
Data Source
AI summary
Provided is a transistor which includes an oxide semiconductor film in a channel region. A change from a shift value before light irradiation to a shift value under light irradiation is greater than or equal to −1 V and less than or equal to 0.5 V, where the shift value is a gate voltage at a point of intersection of an axis of 1×10−12 A and a steepest tangent line of the logarithm of a drain current in drain current-gate voltage characteristics of the transistor, and where the light irradiation is performed on the oxide semiconductor film with light having an energy greater than or equal to a band gap of the oxide semiconductor film.