Oxide Semiconductor Contact Resistance Reduction via Interfacial Oxidation
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Solution Overview
Problem
Conventional thin film transistors (TFTs) using crystalline silicon semiconductor layers have high mobility but complicate the fabrication process and are not suitable for flexible substrates, while oxide semiconductor layers offer higher mobility but require complex doping mechanisms to reduce contact resistance.
Innovation Solution
A method of forming a semiconductor device with an oxide or nitride semiconductor layer, where a first conductive layer with a lower Gibbs free energy of oxide formation is oxidized or nitrogenized at the interface with the semiconductor layer, creating a non-stoichiometric interlayer to enhance crystallinity and reduce contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a crystalline silicon semiconductor layer is used to achieve high mobility, then the mobility is improved (10 to 100 times higher than amorphous silicon), but the fabrication process becomes complicated and production yield decreases
Solution Approach 1:
The invention changes the material parameter from crystalline silicon to oxide semiconductor (such as IGZO), achieving high carrier mobility through material composition change rather than through complex crystallization processes. The oxide semiconductor layer can be formed at lower temperatures and does not require the high-temperature crystallization step (550°C or higher) needed for crystalline silicon, thus simplifying the fabrication process while maintaining high mobility.
2Speed
If a crystalline silicon semiconductor layer is used to achieve high mobility, then the mobility is improved, but the heating temperature for crystallization must be 550° C. or higher, making it difficult to use flexible substrates
Solution Approach 1:
The invention changes the material system to oxide semiconductor, which allows formation at lower temperatures compatible with flexible substrates. The oxide semiconductor layer can be deposited and processed at temperatures below 550°C, enabling the use of plastic or low-melting-point flexible substrates while maintaining high carrier mobility comparable to crystalline silicon.
3Speed
If an oxide semiconductor layer is used to achieve high mobility and transparency, then the mobility is improved (10 to 100 times higher than amorphous silicon), but complex doping mechanisms are required to reduce contact resistance
Solution Approach 1:
The invention extracts and eliminates the need for complex doping mechanisms by using a metal oxide semiconductor layer with inherently high carrier mobility. The high mobility of the oxide semiconductor material itself reduces the requirement for heavy doping, thereby simplifying the manufacturing process and reducing contact resistance without requiring complex doping steps.
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 results in a semiconductor device with reduced contact resistance and improved crystallinity, enabling higher conductivity and flexibility, suitable for use in display devices without the need for high-temperature processing.
Implementation Method 1
oxidizing the first element near an interface region between the first conductive layer and the oxide semiconductor layer
Implementation Method 2
nitrogenizing the first element near an interface region between the first conductive layer and the nitride semiconductor layer
Data Source
AI summary
An oxide or nitride semiconductor layer is formed over a substrate. A first conductive layer including a first element and a second element, and a second conductive layer including the second element are formed over the semiconductor layer. The first element is oxidized or nitrogenized near an interface region between the first conductive layer and the oxide or nitride semiconductor layer by heat treatment or laser irradiation. The Gibbs free energy of oxide formation of the first element is lower than those of the second element or any element in the oxide or nitride semiconductor layer.