Vertical Quantum Transistor With Tapered Gate Conductor
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Solution Overview
Problem
The challenge in the electronics industry is to fabricate quantum transistors with high precision due to increased sensitivity to fabrication errors caused by the smaller size of these components, which is not effectively addressed by existing methods.
Innovation Solution
A vertical transistor design with gate conductor portions that decrease in thickness near the channel region, fabricated using a method involving epitaxy and specific layer deposition and etching processes, including the use of silicon oxide and silicon nitride insulators, and doped polycrystalline silicon gate conductors, to achieve precise control over the channel and charge passage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of transistors is decreased to achieve quantum transistor dimensions, then the transistor size is reduced to a few atoms, but the impact of fabrication errors increases significantly
Solution Approach 1:
The patent transitions from planar transistor geometry to a vertical three-dimensional structure. The gate electrode extends vertically along the channel region, creating a gate-all-around configuration that controls the channel from multiple directions. This dimensional change allows for better electrostatic control and reduces sensitivity to fabrication variations by distributing the control function across multiple spatial dimensions rather than relying on precise two-dimensional patterning
Solution Approach 2:
The gate conductor thickness is designed to vary locally, being thinner in the vicinity of the channel region and thicker in other areas. This local variation optimizes the electric field distribution and control effectiveness where it is most needed (at the channel interface) while maintaining structural integrity and reducing overall gate resistance in regions where thickness is less critical
2Reliability
If the gate conductor thickness is reduced to achieve better control, then the control over channel and charge passage is improved, but the gate conductor becomes more sensitive to fabrication variations
Solution Approach 1:
The gate conductor is segmented into different thickness regions: a thinner portion adjacent to the channel for optimal control, and thicker portions in other areas for structural support and reduced resistance. This segmentation allows each region to be optimized for its specific function while the overall structure remains robust against fabrication variations
Solution Approach 2:
The gate conductor thickness parameter is deliberately varied across different spatial locations rather than being uniform. By changing the thickness parameter locally, the design achieves better electrostatic control where needed while maintaining manufacturing feasibility through thicker regions that are less sensitive to fabrication tolerances
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 allows for the precise formation of quantum transistors with a slim gate profile, enabling excellent control over the channel and charge passage, and a thermal budget similar to typical MOS and bipolar transistors, facilitating their fabrication on the same wafer.
Implementation Method 1
two portions of a gate conductor extending into a layer of insulator between a drain and a source, on either side of a channel region formed by epitaxy
Implementation Method 2
a channel region formed by epitaxy
Data Source
AI summary
A vertical transistor includes two portions of a gate conductor that extend within a layer of insulator. An opening extending through the later of insulator includes source, channel and drain regions form by epitaxy operations. A thickness of the portions of the gate conductor decreases in the vicinity of the channel region.