Oxide Semiconductor TFT Ohmic Contact via Carrier Concentration Control
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Solution Overview
Problem
The existing methods for manufacturing thin film transistors (TFTs) using oxide semiconductors face challenges in forming ohmic contacts between the oxide semiconductor layer and metal electrodes, which affects electrical characteristics and increases manufacturing costs due to the need for additional masks and processes.
Innovation Solution
A method is developed to form an ohmic contact layer with a higher carrier concentration on the oxide semiconductor layer by increasing oxygen partial pressure or performing plasma treatment, allowing for a low-resistance contact without additional masks or processes, using materials like zinc oxide (ZnO) or indium gallium zinc oxide (InZnO) as the semiconductor material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional LTPS process is used to manufacture TFT, then manufacturing cost is high and process control is difficult, but manufacturing precision and reliability are maintained
Solution Approach 1:
The patent changes the material parameter from conventional semiconductor materials to oxide semiconductor materials, enabling low-temperature processing (300°C or less) that simplifies manufacturing while maintaining device characteristics. This parameter change allows large-sized substrate processing without the high costs and control difficulties of conventional LTPS methods.
2Temperature
If oxide semiconductor containing ZnO is used as active layer, then low temperature processing is enabled, but ohmic contact formation between source/drain region and metal electrode is difficult
Solution Approach 1:
The patent applies local quality by creating a high carrier concentration region specifically in the source and drain regions of the oxide semiconductor layer, while maintaining lower carrier concentration in the channel region. This localized modification enables ohmic contact formation at the source/drain electrodes without affecting the low-temperature processing advantage or the channel characteristics.
Solution Approach 2:
The patent performs preliminary action by forming the high carrier concentration region in the source and drain regions before metal electrode deposition. This preliminary modification of the oxide semiconductor layer ensures that when metal electrodes are subsequently formed, ohmic contact is achieved without requiring additional high-temperature processing or complex contact structures.
3Reliability
If additional mask and process are added to form ohmic contact layer, then contact resistance is reduced, but device complexity and manufacturing steps increase
Solution Approach 1:
The patent merges the ohmic contact formation with the existing oxide semiconductor layer formation process. By controlling the carrier concentration within the oxide semiconductor layer itself during the sputtering process, the need for separate ohmic contact layers, additional masks, and extra processing steps is eliminated. The oxide semiconductor layer simultaneously serves as both the active channel and the ohmic contact region.
Solution Approach 2:
The oxide semiconductor layer performs self-service by inherently forming the ohmic contact region through controlled carrier concentration distribution during its own deposition process. The material and process parameters are adjusted so that the source and drain regions automatically develop high carrier concentration, eliminating the need for external intervention or additional processing steps to create ohmic contacts.
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 improves electrical characteristics by reducing contact resistance and simplifying the manufacturing process, enabling the production of TFTs with enhanced performance and cost-effectiveness for applications in flat panel display devices.
Implementation Method 1
forming an ohmic contact layer with a carrier concentration higher than those of the source and drain regions by increasing oxygen partial pressure or performing plasma treatment
Data Source
AI summary
A thin film transistor is provided having an oxide semiconductor as an active layer, a method of manufacturing the thin film transistor and a flat panel display device having the thin film transistor. The thin film transistor includes: a gate electrode formed on a substrate; an oxide semiconductor layer isolated from the gate electrode by a gate insulating layer and including channel, source and drain regions; source and drain electrodes coupled to the source and drain regions, respectively; and an ohmic contact layer interposed between the source and drain regions and the source and drain electrodes. In the TFT, the ohmic contact layer is formed with the oxide semiconductor layer having a carrier concentration higher than those of the source and drain regions.