Back Gate for Quantum Device via Conformal Deposition

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Solution Overview

Problem

Existing quantum devices with back control electrodes face challenges in mechanical stress resistance and compatibility due to high doping requirements, which can induce residual dopants and crystalline defects, and complex manufacturing methods.

Innovation Solution

A semiconductor-on-insulator substrate with a conductive back gate formed by a layer lining the lateral walls and bottom of an opening through the support layer, allowing for electrostatic control of quantum islands while maintaining mechanical resistance and reducing stress, using a method involving etching and conformal deposition of a supraconductive conductive layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the back gate is produced by high doping through ion implantation, then the gate becomes conductive and functional, but residual dopants and crystalline defects are induced in the semiconductor layer

Engineering Contradiction:

Improvegate conductivityVSAvoidresidual dopants and crystalline defects

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the chemical doping process (ion implantation) with a physical deposition process. A conductive layer is deposited conformally on the insulating layer and lateral walls to form the back gate electrode, eliminating the need for high-energy ion implantation that causes crystalline damage and residual dopants.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a conductive layer as an intermediary material deposited on the insulating layer. This conductive layer serves as the back gate electrode without requiring doping of the semiconductor substrate, thus avoiding the harmful effects of ion implantation while maintaining gate functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If a plate offset step with pre-doped area is used to produce the back gate, then the gate can be formed, but the manufacturing process becomes complicated and exhibits significant variability

Engineering Contradiction:

Improvegate formationVSAvoidmanufacturing process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the back gate formation into distinct functional layers: the insulating layer (BOX) and the conductive layer deposited on it. This segmentation allows each layer to be optimized independently and simplifies the manufacturing process by eliminating the need for complex plate offset steps and pre-doped areas.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The insulating layer is formed preliminarily before the conductive layer is deposited. This preliminary formation of the insulating layer provides a stable foundation that simplifies subsequent back gate formation, eliminating the need for complex pre-doping steps and reducing manufacturing variability.

Inventive Principle:

Principle #10Preliminary action

3Reliability

If the back gate is produced by structuring the front gate and forming conductive vias, then the gate can be formed, but mechanical stresses are exerted on the structure

Engineering Contradiction:

Improvegate formationVSAvoidmechanical stress resistance

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

Instead of forming the back gate by structuring the front gate and creating conductive vias through the substrate (top-down approach), the patent inverts the approach by forming the back gate electrode directly on the insulating layer from the substrate side. This eliminates the need for mechanical structuring of the front gate and avoids inducing stress on the quantum device structure.

Inventive Principle:

Principle #13The other way round (Inversion)

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 solution enables precise control of quantum islands with improved mechanical resistance and reduced stress, maintaining device functionality while avoiding defects and complexity in manufacturing.

Implementation Method 1

a conductive layer lining lateral walls and a bottom of an opening passing through said semiconductor support layer

Methodology Applied

Scientific EffectConformal deposition: Deposition (physical)

Implementation Method 2

said back control gate being formed of a conductive layer... for the electrostatic control of the quantum islands

Methodology Applied

Scientific EffectElectrostatic control: Electric Field

Data Source

PatentUS20230196167A1Back grid for quantum device

Publication Date: 2023.06.22 COMMISSARIAT A LENERGIE ATOMIQUE ET AUX ENERGIES ALTERNATIVES

AI summary

A spin Qbits quantum device includes a substrate of the semiconductor on insulator type provided with a surface semiconductor layer disposed on an insulating layer, the insulating layer being arranged on an upper face of a semiconductor support layer, and a component formed of one or more quantum islands extending in the surface layer and one or more gate electrodes for electrostatic control of the islands. Front gate electrodes are disposed on the surface layer, and the component includes a back electrostatic control gate formed of a conductive layer lining lateral walls and a bottom of an opening passing through the support layer from a lower face opposite the upper face up to the insulating layer. The conductive layer is disposed at the bottom of the opening in contact with the insulating layer, the conductive layer being disposed in contact with the support layer at the lateral walls.