IGZO FET Channel and Contact Layer Segmentation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The challenge in processing field effect transistors (FETs) lies in controlling the electrical properties of the channel layer, particularly with indium gallium zinc oxide (IGZO), as it is difficult to manage oxygen vacancies and hydrogen-based defects, which can lead to damage during fabrication, and modifying the channel layer to optimize contact resistivity without affecting the channel itself.
Innovation Solution
The method involves forming a first and second oxide semiconductor layer, where the second layer acts as a contact layer independent of the channel layer, allowing for optimized contact resistivity without damaging the channel, and performing oxygen annealing to modify the doping of the channel layer after other structures are deposited, thereby reducing defects and restoring desired oxygen concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hydrogen-based chemistries are used in deposition and patterning steps, then the fabrication process is simplified and cost-effective, but oxygen vacancies are generated in the IGZO channel layer causing damage and electrical property degradation
Solution Approach 1:
The patent divides the originally single oxide semiconductor layer into two separate layers: a first oxide semiconductor layer forming the channel and a second oxide semiconductor layer forming the contact. This segmentation allows the channel layer to be protected from hydrogen-based damage while the contact layer can still be processed with hydrogen-based chemistries, thus resolving the contradiction between ease of manufacture and reliability.
Solution Approach 2:
The first oxide semiconductor layer acts as an intermediary protective barrier between the substrate and the second oxide semiconductor layer. It protects the channel from oxygen vacancy generation during hydrogen-based processing of the contact layer, while still allowing the fabrication process to proceed with simplified hydrogen-based chemistries.
2Manufacturing precision
If the channel layer is modified to reduce contact resistivity, then the contact performance is improved, but the channel electrical properties are degraded due to oxygen vacancy generation
Solution Approach 1:
By segmenting the oxide semiconductor into separate channel and contact layers, the patent enables independent optimization of each layer's properties. The contact layer can be modified to achieve low contact resistivity without affecting the channel layer's electrical properties, as the channel layer is physically separated and protected.
Solution Approach 2:
The patent applies different properties to different parts of the device: the first oxide semiconductor layer (channel) maintains high electrical properties with controlled oxygen vacancies, while the second oxide semiconductor layer (contact) is optimized for low contact resistivity. This local differentiation resolves the contradiction between contact performance and channel integrity.
3Reliability
If oxygen annealing is performed after gate structure deposition, then the channel layer electrical properties are restored and defects are reduced, but the process complexity and thermal budget increase
Solution Approach 1:
The patent performs oxygen annealing of the first oxide semiconductor layer at an early stage before gate structure deposition, rather than after. This preliminary action prevents oxygen vacancies from forming in the first place during subsequent hydrogen-based processing, eliminating the need for complex post-deposition repair steps while maintaining channel layer electrical properties.
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 efficiently controls the electrical properties of the FET channel layer, reduces defects, and optimizes contact resistivity between the channel and source/drain structures, enhancing the overall performance of the FET device without negatively impacting the channel layer.
Implementation Method 1
performing oxygen annealing to modify the doping of the channel layer after other structures are deposited, thereby reducing defects and restoring desired oxygen concentrations
Data Source
AI summary
The disclosed technology generally relates to a method of processing a field effect transistor (FET) device, such as a metal-oxide-semiconductor field-effect transistor (MOSFET) or a thin-film-transistor (TFT). In one aspect, the method includes providing a substrate; forming a first oxide semiconductor layer and a second oxide semiconductor layer above the substrate; forming a source structure and a drain structure on the second oxide semiconductor layer; and forming a gate structure on the first oxide semiconductor layer. The first oxide semiconductor layer forms a channel between the source structure and the drain structure. The second oxide semiconductor layer forms a contact layer to the source structure and the drain structure.