Oxide Semiconductor TFT Contacts With Hydrogen Barrier Liners
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Solution Overview
Problem
In integrated circuits, the sensitivity of thin film transistors in the back-end-of-line (BEOL) to hydrogen gas and free hydrogen atoms leads to doping of the channel layer, causing negative threshold voltage shifts and affecting electrical properties, which is a challenge in increasing feature density and reducing static power consumption.
Innovation Solution
The use of barrier liners made of hydrogen barrier materials, such as In-rich oxides, surrounding the source/drain contacts to absorb or store hydrogen, preventing its diffusion to the channel layer, thereby maintaining the electrical properties of the thin film transistors and reducing contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If peripheral devices are moved from FEOL to BEOL to increase feature density, then productivity and feature density are improved, but hydrogen diffusion to channel layer causes threshold voltage shifts and electrical property degradation
Solution Approach 1:
A barrier liner made of hydrogen barrier material (such as tungsten oxide, tungsten sub-oxide, or tungsten oxy-nitride) is introduced as an intermediary layer between the source/drain contacts and the channel layer. This barrier liner acts as a mediator that blocks hydrogen diffusion from the contacts to the channel layer, preventing threshold voltage shifts while allowing the peripheral devices to be relocated to BEOL for increased feature density.
Solution Approach 2:
The contact structure is segmented into multiple layers: the source/drain contact, the barrier liner, and the channel layer. This segmentation isolates the channel layer from hydrogen contamination by inserting the barrier liner layer, enabling reliable BEOL peripheral device operation while maintaining high feature density.
2Reliability
If barrier liners made of hydrogen barrier materials are used to prevent hydrogen diffusion, then electrical properties stability is improved, but device complexity increases
Solution Approach 1:
The barrier liner is formed by depositing metal oxide materials (tungsten oxide, tungsten sub-oxide, or tungsten oxy-nitride) that inherently possess hydrogen barrier properties. By selecting materials with specific chemical compositions and controlling their thickness (typically 1-10 nm), the structure achieves effective hydrogen blocking without requiring complex multi-layer designs, thus maintaining relatively simple device structure while ensuring threshold voltage stability.
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 solution effectively prevents hydrogen-induced doping of the channel layer, stabilizes the threshold voltage, and improves the Schottky barrier and contact resistance, contributing to increased feature density and reduced static power consumption by relocating peripheral devices from the front-end-of-line to the BEOL.
Implementation Method 1
The use of barrier liners made of hydrogen barrier materials, such as In-rich oxides, surrounding the source/drain contacts to absorb or store hydrogen, preventing its diffusion to the channel layer
Implementation Method 2
the first barrier liners including a hydrogen barrier material so as to prevent hydrogen from diffusion through the first barrier liners to the channel layer
Data Source
AI summary
A semiconductor device includes a channel layer, source/drain contacts, and first barrier liners. The channel layer includes an oxide semiconductor material. The source/drain contacts are disposed in electrical contact with the channel layer. The first barrier liners surround the source/drain contacts, respectively, and include a hydrogen barrier material so as to prevent hydrogen from diffusion through the first barrier liners to the channel layer.