Staggered Oxide TFT Buffer Layer for Ohmic Contact
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Thin film transistors with oxide semiconductor films face challenges in achieving high-speed operation and reliability due to increased contact resistance and capacitance, particularly in large-area display devices, which can lead to signal delay and display unevenness.
Innovation Solution
A staggered thin film transistor structure with an oxide semiconductor film containing indium, gallium, and zinc, where a buffer layer with higher carrier concentration than the semiconductor layer is used between the source/drain electrodes and the semiconductor layer to reduce contact resistance and parasitic capacitance, and a metal oxide layer is employed to form ohmic contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a low resistance metal material is used for source and drain electrodes to reduce wiring resistance, then signal delay is reduced, but contact resistance increases due to Schottky junction formation
Solution Approach 1:
An n-type buffer layer is introduced as an intermediary between the metal electrode and the oxide semiconductor film. This buffer layer has higher carrier concentration than the semiconductor layer, enabling ohmic contact formation while maintaining low resistance characteristics, thus resolving the contradiction between low wiring resistance and low contact resistance
Solution Approach 2:
The carrier concentration parameter is changed by introducing an n-type buffer layer with higher carrier concentration than the oxide semiconductor layer. This parameter change enables the formation of ohmic contact with low contact resistance while maintaining the low resistance properties of the metal electrode
2Ease of manufacture
If source and drain electrodes are in direct contact with oxide semiconductor film to simplify structure, then manufacturing is easier, but parasitic capacitance increases which hinders high speed operation
Solution Approach 1:
The n-type buffer layer serves as a mediator between the electrode and semiconductor layer, reducing parasitic capacitance at the contact interface. While this adds a layer to the structure, it significantly improves operation speed by minimizing capacitive effects that would otherwise hinder high-speed operation
3Ease of manufacture
If oxide semiconductor film is used to achieve easy manufacturing and sufficient reliability, then manufacturing process is simplified, but contact resistance increases reducing operation characteristics
Solution Approach 1:
The structure uses a composite of oxide semiconductor material and n-type buffer layer material. This composite structure maintains the manufacturing advantages of oxide semiconductors while adding the buffer layer to improve contact characteristics and overall 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
The solution results in a thin film transistor with reduced contact resistance, improved operation characteristics, and reliability, enabling high-speed and stable performance with reduced variation in electric properties, thus minimizing display unevenness and luminance variation in liquid crystal and light-emitting display devices.
Implementation Method 1
a buffer layer with higher carrier concentration than the semiconductor layer is used between the source/drain electrodes and the semiconductor layer to reduce contact resistance and parasitic capacitance, and a metal oxide layer is employed to form ohmic contact
Data Source
AI summary
An embodiment is to include a staggered (top gate structure) thin film transistor in which an oxide semiconductor film containing In, Ga, and Zn is used as a semiconductor layer and a buffer layer is provided between the semiconductor layer and a source and drain electrode layers. A metal oxide layer having higher carrier concentration than the semiconductor layer is provided intentionally as the buffer layer between the source and drain electrode layers and the semiconductor layer, whereby an ohmic contact is formed.