Oxide Semiconductor TFT Buffer Layer for Stable Ohmic Contact
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Thin film transistors using oxide semiconductor layers face challenges in preventing increased off current and negative shifts in threshold voltage, as well as achieving ohmic contact between the oxide semiconductor layer and electrode layers.
Innovation Solution
An inverted staggered thin film transistor structure is implemented, featuring a buffer layer with a metal oxide layer over the oxide semiconductor layer and conductive layers with higher oxygen concentration, which acts as a protective layer to suppress impurity incorporation and facilitate ohmic contact by diffusing oxygen through thermal treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a thin film transistor uses an oxide semiconductor layer, then it can achieve low power consumption and high speed operation, but off current increases and threshold voltage shifts negatively
Solution Approach 1:
A buffer layer is introduced as an intermediary between the oxide semiconductor layer and the source/drain electrode layers. This buffer layer prevents harmful interactions at the interface, suppressing off current increases and threshold voltage shifts while maintaining the low power consumption and high speed characteristics of the oxide semiconductor transistor.
Solution Approach 2:
The buffer layer undergoes oxygen concentration adjustment through thermal treatment to optimize its properties. By controlling oxygen concentration, the buffer layer achieves optimal performance in preventing off current increase and threshold voltage shift, allowing the transistor to maintain low power consumption and high speed operation with improved reliability.
2Speed
If a thin film transistor uses an oxide semiconductor layer, then it can achieve low power consumption and high speed operation, but negative shift of threshold voltage occurs
Solution Approach 1:
The buffer layer serves as a protective intermediary that stabilizes the interface between the oxide semiconductor layer and electrode layers. This prevents composition changes and chemical reactions that would cause threshold voltage shifts, while preserving the high mobility and fast operation speed of the oxide semiconductor channel.
Solution Approach 2:
The buffer layer is formed and undergoes oxygen concentration adjustment before the final transistor assembly. This preliminary preparation ensures that the buffer layer is in its optimal state to prevent threshold voltage shifts during subsequent processing and operation, maintaining both high speed performance and voltage stability.
3Device complexity
If the oxide semiconductor layer directly contacts the electrode layers, then the structure is simple, but ohmic contact is not achieved
Solution Approach 1:
The buffer layer acts as a mediator between the oxide semiconductor layer and electrode layers, enabling ohmic contact by facilitating proper electrical interface. Although this adds a layer to the structure, it ensures reliable low-resistance contact necessary for high-performance transistor operation.
Solution Approach 2:
The buffer layer's oxygen concentration is adjusted through thermal treatment to optimize its electrical properties. This parameter change enables the buffer layer to achieve the appropriate conductivity and interface characteristics for forming ohmic contacts, balancing structural complexity with contact quality.
4Ease of manufacture
If impurities are incorporated into the oxide semiconductor layer, then manufacturing is easier, but off current increases and threshold voltage shifts
Solution Approach 1:
The buffer layer serves as a protective barrier that prevents impurity incorporation into the oxide semiconductor layer during manufacturing and operation. This intermediary layer maintains the high electrical stability and low off current characteristics of the oxide semiconductor while allowing relatively simple manufacturing processes.
Solution Approach 2:
The buffer layer is formed beforehand to provide protection against impurity contamination. This preventive measure ensures that the oxide semiconductor layer remains free from impurities that would cause off current increases and threshold voltage shifts, maintaining electrical stability without requiring overly complex manufacturing procedures.
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 structure effectively prevents off current and threshold voltage shifts while ensuring high-performance and reliable ohmic contact between the oxide semiconductor and electrode layers, enhancing the overall performance of the thin film transistor.
Implementation Method 1
a metal oxide layer which is provided over a middle portion of the oxide semiconductor layer, has the same metal element as the pair of conductive layers, has higher oxygen concentration than the pair of conductive layers
Implementation Method 2
facilitate ohmic contact by diffusing oxygen through thermal treatment
Data Source
AI summary
In a thin film transistor, an increase in off current or negative shift of the threshold voltage is prevented. In the thin film transistor, a buffer layer is provided between an oxide semiconductor layer and each of a source electrode layer and a drain electrode layer. The buffer layer includes a metal oxide layer which is an insulator or a semiconductor over a middle portion of the oxide semiconductor layer. The metal oxide layer functions as a protective layer for suppressing incorporation of impurities into the oxide semiconductor layer. Therefore, in the thin film transistor, an increase in off current or negative shift of the threshold voltage can be prevented.