Oxide Thin Film Transistor Structure with Recessed Source Drain Contacts
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Solution Overview
Problem
Oxide thin film transistors face issues with stability and electrical property degradation due to plasma damage during etching stopper layer formation, leading to increased oxygen defects and reduced conductivity.
Innovation Solution
A manufacturing method involving the formation of recesses in the oxide semiconducting layer to prevent plasma damage, allowing undamaged contact between the source, drain, and oxide semiconducting layer, using dry or wet etching to remove the skin layer and sputtering for source and drain formation, with a SiOx etching stopper layer formed by TEOS+O2 or SiH4+N2O chemical vapor deposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If plasma is used to form the etching stopper layer, then the film formation is efficient and the layer is uniform, but the plasma damage the oxide semiconducting layer surface causing oxygen defects and threshold voltage shift
Solution Approach 1:
The patent applies preliminary action by forming a protective layer on the oxide semiconducting layer before plasma etching of the etching stopper layer. This protective layer prevents plasma damage to the oxide surface, maintaining oxygen stoichiometry and preventing threshold voltage shift while still allowing efficient plasma formation of the etching stopper layer.
Solution Approach 2:
The protective layer acts as an intermediary between the plasma and the oxide semiconducting layer. It absorbs the harmful plasma effects while allowing the plasma process to proceed efficiently for etching stopper layer formation, thus mediating between productivity and reliability requirements.
2Device complexity
If the oxide semiconducting layer is exposed to plasma during etching stopper layer formation, then the manufacturing process is simplified, but the surface property of the oxide semiconducting layer deteriorates leading to increased oxygen defects
Solution Approach 1:
The protective layer is formed preliminarily before plasma exposure to prevent surface property deterioration. This additional step maintains precise control over the oxide surface while still keeping the overall manufacturing process relatively simple by using standard thin film deposition techniques.
Solution Approach 2:
The protective layer provides local quality enhancement specifically at the oxide semiconducting layer surface that will be exposed to plasma. This localized protection maintains surface properties in the critical area while allowing the rest of the manufacturing process to remain straightforward.
3Ease of manufacture
If hydrogen is present in the plasma (using SiH4+N2O), then the etching stopper layer forms effectively, but hydrogen combines with oxygen in the oxide semiconducting layer causing negative threshold voltage shift
Solution Approach 1:
The protective layer serves as an intermediary barrier that prevents hydrogen from the plasma (used for effective etching stopper layer formation) from combining with oxygen in the oxide semiconducting layer. This maintains threshold voltage stability while still allowing effective etching stopper layer formation with SiH4+N2O plasma.
Solution Approach 2:
The protective layer converts the potentially harmful hydrogen plasma exposure into a beneficial process by allowing the plasma to effectively form the etching stopper layer while the protective layer prevents the harmful hydrogen-oxygen combination that would cause threshold voltage shift.
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 method results in a more stable and excellent electrical property for oxide thin film transistors, with improved threshold voltage and subthreshold swing, maintaining the original property of the oxide semiconducting layer.
Implementation Method 1
the etching stopper layer (500) of step 5 is generally formed of a SiOx film layer, which is manufactured with TEOS+O2 or SiH4+N2O chemical vapor deposition
Implementation Method 2
plasma will affect the surface property of the oxide semiconducting layer (400) when the film of the etching stopper layer (500) is formed
Implementation Method 3
sputtering for source and drain formation
Data Source
AI summary
A structure of an oxide thin film transistor includes: an oxide semiconducting layer, an etching stopper layer on the oxide semiconducting layer, and a source and a drain on the etching stopper layer. Two vias are formed in the etching stopper layer. The oxide semiconducting layer includes two recesses formed therein to extend through a skin layer of the oxide semiconducting layer and respectively corresponding to the two vias. The two recesses are respectively connected with and in communication with the two vias. The source and the drain are respectively filled in the two vias and the two recesses connected with the two vias to directly connect to and physically contact the oxide semiconducting layer.