Single-Electron Transistor Fabrication via Lithography

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Solution Overview

Problem

Existing single-electron transistors face challenges in fabrication, particularly in controlling the position and geometry of quantum islands and tunnel barriers, which limits their operation at ambient temperature and scalability.

Innovation Solution

A single-electron transistor design that uses semiconductor portions with specific thickness relationships to form quantum islands and tunnel junctions without oxidation, allowing for precise control and integration with CMOS technology, enhancing charge energy and energy level variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If quantum islands are made by oxidation of semiconductor portions, then the ease of manufacture is improved, but the manufacturing precision deteriorates because there is no real control over the number of quantum islands created, their position and dimensions

Engineering Contradiction:

Improveease of useVSAvoidcontrol over position and dimensions

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent changes the fabrication parameter from oxidation-based to lithography-based quantum island formation. Specifically, it uses electron beam lithography or focused ion beam lithography to directly define quantum islands with precise control over their position, size, and number, eliminating the uncontrolled oxidation process while maintaining ease of manufacture through standard lithography techniques

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the chemical oxidation process with a physical lithography process (electron beam or focused ion beam) to form quantum islands. This substitution allows for precise spatial control and direct patterning of quantum islands, transforming the manufacturing approach from chemical to physical while improving positioning accuracy

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Temperature

If the quantum island dimensions are reduced by oxidation, then the operating temperature is improved (increased to 300 K), but the manufacturing precision deteriorates due to lack of control over island formation

Engineering Contradiction:

Improveoperating temperatureVSAvoidcontrol over number and position

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The patent changes the size control parameter from oxidation time-dependent to lithography-pattern-defined. By using electron beam or focused ion beam lithography, the quantum island dimensions are precisely defined by the lithography pattern rather than by oxidation duration, enabling both small sizes for high operating temperature and precise control over number and position

Inventive Principle:

Principle #35Parameter changes

3Manufacturing precision

If PADOX method is used to control quantum island position, then the manufacturing precision is improved, but the device complexity increases due to multiple lithography/etching steps

Engineering Contradiction:

Improvecontrol over positionVSAvoidfabrication steps

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent applies preliminary lithography patterning to define quantum island positions and dimensions before any other fabrication steps. By using electron beam or focused ion beam lithography to directly pattern the quantum islands and tunnel barriers in a single step, it eliminates the multiple sequential lithography and etching steps required by PADOX, reducing overall device complexity while maintaining precise positional control

Inventive Principle:

Principle #10Preliminary action

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 operational efficiency of single-electron transistors at ambient temperature with precise control over quantum island position and geometry, enabling better scalability and integration with CMOS technology.

Implementation Method 1

The Coulomb interaction between charges distributed on the island and in the reservoirs results in capacitive coupling. A current can be set up between the reservoirs passing through the island if the probability of an electron passing from one reservoir to the island by tunnel effect is non-zero

Methodology Applied

Scientific EffectTunnel effect:

Implementation Method 2

The quantum island is capacitively coupled with a gate electrode to control the passage of current through the quantum island, as for a MOSFET transistor. This capacitance is an electrostatic capacitance

Methodology Applied

Scientific EffectElectrostatic capacitance: Capacitance

Data Source

PatentUS9911841B2Single-electron transistor and its fabrication method

Publication Date: 2018.03.06 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES

AI summary

Single-electron transistor comprising at least:first semiconductor portions forming source and drain regions,a second semiconductor portion forming at least one quantum island,third semiconductor portions forming tunnel junctions between the second semiconductor portion and the first semiconductor portions,a gate and a gate dielectric located on at least the second semiconductor portion,in which a thickness of each of the first semiconductor portions is greater than the thickness of the second semiconductor portion, and in which a thickness of the second semiconductor portion is greater than the thickness of each of the third semiconductor portions.