Oxide Semiconductor TFT Channel Layer End-Part Off-Current Reduction
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Solution Overview
Problem
Thin film transistors (TFTs) with oxide semiconductor layers as channel layers face high off-current issues due to damage at the end parts of the channel layer during dry etching, and increasing oxygen concentration at the backchannel side only partially reduces this off-current, making it difficult to further minimize the current flowing through the end parts.
Innovation Solution
A TFT design with an oxide semiconductor channel layer featuring two regions of different resistance values, where the higher resistance region is extended to the end parts in the channel width direction, and the source and drain electrodes are strategically overlapped or not overlapped with the gate electrode to optimize contact and reduce parasitic capacitance, along with an etching stopper layer and interlayer insulating layer to enhance the channel layer's integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the oxide semiconductor layer is patterned by dry etching to form the channel layer, then the channel layer structure is defined, but the end parts of the oxide semiconductor layer are damaged by plasma, causing large off-current
Solution Approach 1:
The patent applies local quality by creating a multi-layer oxide semiconductor structure where the first oxide semiconductor layer has different properties (higher resistance) compared to the second oxide semiconductor layer (lower resistance). This local differentiation allows the high-resistance first layer to block off-current at the etched end parts, while the low-resistance second layer maintains good electrical contact with source and drain electrodes.
2Reliability
If the oxygen concentration is increased at the backchannel side to reduce off-current, then the off-current is partially reduced, but it is difficult to further reduce the off-current flowing through the end parts
Solution Approach 1:
The patent segments the oxide semiconductor layer into two distinct layers: a first oxide semiconductor layer and a second oxide semiconductor layer. This segmentation allows each layer to serve different functions - the first layer primarily blocks off-current at etched portions while the second layer ensures electrical contact, thereby more effectively reducing off-current through end parts compared to uniform oxygen concentration control.
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 effectively reduces off-current through the end parts of the channel layer, improves the operation speed, and enhances the reliability of the TFT by repairing lattice defects and minimizing parasitic capacitance, leading to a more stable and efficient thin film transistor.
Implementation Method 1
a gate insulating film formed to cover the gate electrode
Implementation Method 2
a channel layer made of an oxide semiconductor layer which is formed in a region sandwiched between the source electrode and the drain electrode
Data Source
AI summary
The invention provides a thin film transistor that can reduce an off-current flowing in end-parts in a channel width direction of a channel layer and a manufacturing method therefor.