Oxide TFT Contact Liners for Hydrogen Diffusion Blocking
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Solution Overview
Problem
The challenge in increasing feature density in integrated circuits is exacerbated by hydrogen sensitivity of thin film transistors (TFTs) in the back-end-of-line (BEOL), which can lead to doping of channel layers and negative threshold voltage shifts due to hydrogen gas and free hydrogen atoms generated in processing steps like CVD.
Innovation Solution
The implementation of barrier liners around source/drain contacts made of hydrogen barrier materials, such as In-rich oxides, to absorb or store hydrogen, preventing diffusion to the channel layer and reducing contact resistance, while also improving the Schottky barrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If periphery devices are moved from FEOL to BEOL to increase feature density, then area utilization is improved, but hydrogen sensitivity and threshold voltage instability worsen
Solution Approach 1:
A barrier liner made of hydrogen barrier material (such as tantalum, tungsten, or titanium nitride) is introduced as an intermediary layer between the source/drain contacts and the channel layer. This barrier liner prevents hydrogen diffusion from the contacts to the channel, thereby stabilizing the threshold voltage while allowing the BEOL configuration to be implemented
Solution Approach 2:
The barrier liner is formed in advance during the contact formation process, before any hydrogen-containing processing steps are performed. This preliminary protective layer is deposited conformally on the contact surfaces and then planarized, ensuring that hydrogen barrier protection is already in place before the channel layer is exposed to potential hydrogen sources
2Ease of manufacture
If CVD processing is used to form dielectric layers, then manufacturing capability is improved, but hydrogen generation and channel layer doping worsen
Solution Approach 1:
The barrier liner serves as a protective intermediary that blocks hydrogen atoms generated during CVD processing from reaching and doping the channel layer. By placing this hydrogen barrier material between the CVD processing zone and the channel layer, the harmful hydrogen effects are prevented while maintaining the benefits of CVD manufacturing
Solution Approach 2:
The hydrogen that would normally be harmful to the channel layer is instead directed to be absorbed or stored by the barrier liner material. The barrier liner effectively converts the harmful hydrogen byproduct of CVD processing into a contained element within the barrier structure, preventing it from damaging the channel layer
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 effectively prevents hydrogen-induced doping of the channel layer, stabilizes the threshold voltage, and reduces contact resistance, thereby enhancing the performance and reliability of TFTs in the BEOL.
Implementation Method 1
The conformal liner layer includes a hydrogen barrier material so as to absorb or store hydrogen
Implementation Method 2
the first barrier liners include 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.