Buried-Channel Oxide Semiconductor Transistor Structure
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Solution Overview
Problem
Semiconductor devices with oxide semiconductor films face issues of varying electrical characteristics due to interface states with insulating films and high oxygen vacancy levels, leading to low long-term reliability and damage from plasma exposure during deposition.
Innovation Solution
A buried-channel transistor structure is implemented with multiple oxide semiconductor films, where a second oxide semiconductor film with a crystalline structure is stacked over a first oxide semiconductor film, and a third oxide semiconductor film is provided above the second, with the third film acting as a barrier to reduce plasma damage and oxygen vacancy influence, using specific materials and deposition methods to achieve a well-shaped conduction band structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single oxide semiconductor film is used, then the device structure is simple, but electrical characteristics vary due to interface states with insulating films
Solution Approach 1:
The oxide semiconductor film is divided into multiple layers (first oxide semiconductor film and second oxide semiconductor film) to separate the interface contact function from the channel formation function. The first film contacts the insulating film and serves as a buffer, while the second film forms the functional channel, thus isolating the interface state effects from the active channel region.
Solution Approach 2:
The first oxide semiconductor film acts as an intermediary layer between the insulating film and the second oxide semiconductor film. It absorbs the harmful interface states and prevents them from affecting the electrical characteristics of the second film, thereby protecting the functional channel from interface-related degradation.
2Ease of manufacture
If oxide semiconductor film is exposed to plasma during deposition, then insulating films can be deposited, but the oxide semiconductor film suffers damage and generates oxygen vacancies
Solution Approach 1:
The first oxide semiconductor film is deposited beforehand to create a protective sacrificial layer. This layer is intentionally designed to be exposed to plasma during subsequent insulating film deposition, so that it absorbs the plasma damage and oxygen vacancy generation, protecting the second oxide semiconductor film from such harmful effects.
Solution Approach 2:
The first oxide semiconductor film serves as a protective intermediary that shields the second oxide semiconductor film from plasma exposure. It absorbs the harmful plasma effects and oxygen vacancies, allowing the functional second film to remain intact and undamaged throughout the manufacturing process.
3Ease of manufacture
If oxygen vacancies are present in oxide semiconductor film, then manufacturing is easier, but long-term reliability decreases
Solution Approach 1:
The device is segmented into two oxide semiconductor films with different functions: the first film is designed to tolerate oxygen vacancies and plasma exposure, while the second film is protected and maintains low oxygen vacancy levels for long-term reliability. This functional segmentation allows each layer to be optimized for its specific role.
Solution Approach 2:
The first oxide semiconductor film acts as a sacrificial intermediary that accumulates oxygen vacancies and manufacturing-induced defects, preventing these harmful effects from reaching the second oxide semiconductor film. This protects the functional channel from degradation and ensures long-term device reliability.
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 configuration enhances the reliability and stability of semiconductor devices by reducing oxygen vacancy-induced defects and plasma damage, resulting in improved electrical characteristics and long-term performance.
Implementation Method 1
a second oxide semiconductor film having a crystalline structure is stacked over a first oxide semiconductor film
Implementation Method 2
the third oxide semiconductor film reduces damage to the second oxide semiconductor film which is caused at the time of exposure to plasma
Data Source
AI summary
A highly reliable semiconductor device exhibiting stable electrical characteristics is provided. Further, a highly reliable semiconductor device is provided. Oxide semiconductor films are stacked so that the conduction band has a well-shaped structure. Specifically, a transistor having a multi-layer structure is manufactured in which a second oxide semiconductor film having a crystalline structure is stacked over a first oxide semiconductor film, and at least a third oxide semiconductor film is provided over the second oxide semiconductor film. When a buried channel is formed in the transistor, few oxygen vacancies are generated and the reliability of the transistor is improved.