VFET Oxygen-Blocking Layer for Channel Fin Oxidation Control
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Solution Overview
Problem
In the fabrication of vertical field effect transistors (VFETs), the exposure of channel fins to oxygen during top spacer deposition leads to the re-growth of oxygen-containing layers, negatively impacting the inversion layer thickness and device performance.
Innovation Solution
An oxygen-blocking layer, formed from an oxygen-gettering material like aluminum, is integrated within trenches adjacent to the channel fin to prevent oxygen diffusion and re-growth of silicon oxide on the channel fin, thereby maintaining the desired inversion layer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If top spacer deposition is performed without oxygen blocking, then the deposition process can proceed normally, but oxygen diffuses into the channel fin causing re-growth of oxygen-containing layers and degrading device performance
Solution Approach 1:
An oxygen-blocking layer is introduced as an intermediary component between the channel fin and the oxygen-containing environment during top spacer deposition. This layer acts as a mediator that prevents oxygen from reaching the channel fin, thereby blocking the harmful oxidation process while allowing the deposition process to proceed normally.
Solution Approach 2:
The patent converts the harmful effect of oxygen exposure into a beneficial process by using oxygen-gettering materials that actively absorb or react with oxygen. The materials such as silicon-rich silicon oxide or germanium-rich germanium oxide transform free oxygen into stable compounds, turning the harmful oxygen diffusion into a controlled chemical reaction that protects the channel fin.
2Reliability
If oxygen-blocking layer is added to prevent oxygen diffusion, then device performance is improved, but fabrication process complexity increases
Solution Approach 1:
The oxygen-blocking layer is formed in advance before the top spacer deposition process. By preparing the oxygen-blocking layer beforehand and integrating it into the fabrication sequence, the patent prevents oxygen diffusion during subsequent processing steps without requiring additional complex interventions during the deposition process itself.
Solution Approach 2:
The patent utilizes parameter changes in material composition and thickness to achieve oxygen blocking. By adjusting the stoichiometry (creating silicon-rich or germanium-rich compositions) and controlling the layer thickness, the oxygen-blocking properties are optimized while maintaining compatibility with existing fabrication processes and minimizing added complexity.
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 oxygen-blocking layer effectively prevents oxygen from reacting with the channel fin, maintaining optimal inversion layer thickness and enhancing the performance characteristics of VFETs by blocking oxygen diffusion during the fabrication process.
Implementation Method 1
The oxygen-blocking layer includes an oxygen gettering material configured to remove oxygen from an environment to which the oxygen-blocking layer is exposed
Data Source
AI summary
Embodiments of the invention are directed to a semiconductor device that includes a channel fin; a trench adjacent to an upper region of the channel fin; and an oxygen-blocking layer within the trench. The oxygen-blocking layer includes an oxygen gettering material configured to remove oxygen from an environment to which the oxygen-blocking layer is exposed.