Hydrogen Diffusion Barrier in Compound Semiconductor TFTs
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Solution Overview
Problem
Thin film transistors (TFTs) using amorphous silicon have low mobility, while those using polysilicon have non-uniform threshold voltage and require expensive manufacturing processes, and compound semiconductors like zinc oxide exhibit high resistivities and high contact resistance, which complicates their use in high-speed circuits and large-area substrates.
Innovation Solution
A thin film transistor design that includes a hydrogen diffusion barrier layer on the channel region to prevent hydrogen from diffusing into the channel, allowing higher hydrogen concentrations in the source and drain regions, reducing resistivity and contact resistance, while maintaining low resistivity in the channel region, using a semiconductor layer of oxygen-containing compound semiconductors like zinc oxide doped with gallium, indium, or tin, and a hydrogen diffusion barrier layer of nitrides or carbides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hydrogen is implanted into compound semiconductor to reduce resistivity, then contact resistance decreases, but leakage current increases due to hydrogen in channel region
Solution Approach 1:
The patent segments the semiconductor layer into distinct functional regions: a channel region and source/drain regions. By implanting hydrogen selectively into the source and drain regions while avoiding the channel region, the patent reduces contact resistance at the electrodes without increasing leakage current in the channel, thus resolving the technical contradiction.
Solution Approach 2:
The patent applies local quality by creating different hydrogen concentration profiles in different regions of the semiconductor layer. The source and drain regions have high hydrogen concentration to reduce contact resistance, while the channel region maintains low hydrogen concentration to prevent leakage current, optimizing both electrical characteristics simultaneously.
2Ease of manufacture
If amorphous silicon is used for semiconductor layer, then manufacturing is simpler, but mobility is low making high-speed circuits difficult
Solution Approach 1:
The patent changes the material parameter from amorphous silicon to compound semiconductor (such as zinc oxide or tin oxide). This material substitution enables higher carrier mobility suitable for high-speed circuits while maintaining compatibility with low-temperature manufacturing processes, thus resolving the contradiction between manufacturing simplicity and device speed.
3Speed
If polysilicon is used for semiconductor layer, then mobility is high, but threshold voltage is non-uniform requiring additional compensating circuits
Solution Approach 1:
The patent changes the semiconductor material from polysilicon to compound semiconductor (zinc oxide, tin oxide, or their alloys). This material substitution provides both high carrier mobility for fast switching and uniform threshold voltage characteristics, eliminating the need for additional compensating circuits while maintaining high-speed performance.
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 design improves the electrical characteristics of TFTs by reducing contact resistance and preventing increased leakage current, enabling better performance in high-speed circuits and large-area substrates with reduced manufacturing complexity and cost.
Implementation Method 1
a hydrogen diffusion barrier layer on the semiconductor layer, the hydrogen diffusion barrier layer covering the channel region and exposing the source and drain regions
Implementation Method 2
Implanting hydrogen (H) atoms into the compound semiconductor may reduce the resistivity the semiconductor layer
Data Source
AI summary
A thin film transistor includes a gate electrode, a first insulating layer on the gate electrode, a semiconductor layer on the gate electrode and separated from the gate electrode by the first insulating layer, the semiconductor layer including a channel region corresponding to the gate electrode, a source region, and a drain region, a hydrogen diffusion barrier layer on the semiconductor layer, the hydrogen diffusion barrier layer covering the channel region and exposing the source and drain regions, and a second insulation layer on the source and drain regions and on the hydrogen diffusion barrier layer, such that the hydrogen diffusion barrier layer is between the second insulation layer and the channel region.