Quantum Dot Gate Spacer Layout for Uniform Oxide Isolation
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Solution Overview
Problem
Current methods for producing closely spaced gate structures for quantum dot devices on semiconductor substrates often damage the substrate during plasma etching, leading to non-uniform dielectric spacing and gate heights, which deteriorate qubit states and hinder device operation.
Innovation Solution
A method involving the formation of parallel mandrel structures, side spacers, and selective removal of mandrel portions, followed by thermal oxidation to create a low-defect density gate oxide layer, allowing for uniform gate structures without multiple patterning steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If plasma etching is used to form gate structures, then gate patterning can be achieved, but substrate damage occurs leading to deterioration of qubit states
Solution Approach 1:
The patent extracts the harmful plasma etching step from the gate formation process. Instead of using plasma etching to define gates, the invention uses a self-aligned spacer approach where gates are formed by depositing materials conformally on mandrels and then removing the mandrels, eliminating the need for plasma etching on the substrate and thus preventing substrate damage and qubit state deterioration.
Solution Approach 2:
The patent introduces mandrels as intermediary structures that facilitate gate formation without directly contacting the substrate. These mandrels serve as temporary placeholders that enable the self-aligned spacer process, allowing gate definition through material deposition and selective removal rather than direct plasma etching of the substrate.
2Productivity
If multiple patterning steps are used to form closely spaced gates, then gate density can be increased, but non-uniform dielectric spacing and gate heights result
Solution Approach 1:
The patent performs preliminary actions by first forming mandrels with the desired spacing, then depositing spacers conformally on these mandrels. This preliminary structure formation ensures that the final gate structures will have uniform spacing and height, as the mandrels and spacers are formed before the actual gate materials are deposited, establishing a self-aligned framework that guarantees uniformity.
Solution Approach 2:
The patent merges multiple formation steps into a single self-aligned process. Instead of performing separate patterning steps that would require multiple lithography and etching cycles, the invention combines mandrel formation, spacer deposition, and gate formation into one integrated process where the mandrels and spacers automatically define the gate positions and dimensions, ensuring uniform spacing and height.
3Ease of manufacture
If atomic layer deposition is used to deposit oxide after each gate step, then gate formation can proceed, but oxide defect density increases progressively
Solution Approach 1:
The patent performs preliminary oxide deposition as part of the conformal spacer formation process before gate definition, rather than depositing oxide after each gate formation step. This preliminary oxide layer is formed in a single high-quality deposition process, avoiding the progressive degradation that would result from multiple sequential ALD steps, each potentially introducing defects.
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 enables the production of quantum dot devices with uniformly spaced, uniformly heighted gate structures and low-defect gate oxides, enhancing qubit coherence and device reliability.
Implementation Method 1
The gate oxide of a quantum dot device can then formed in the areas between the spacers, by a thermal oxidation of the semiconductor material of the substrate.
Data Source
AI summary
A method for producing a plurality of mutually parallel mandrel structures of a quantum dot device is provided. The method includes producing mutually parallel mandrel structures on a substrate including at least a top layer of semiconductor material. Side spacers are formed on the mandrel structures, and the mandrel structures are removed with respect to the spacers. The gate oxide of a quantum dot device can be formed in the areas between the spacers, by a thermal oxidation of the semiconductor material of the substrate. The thermal oxidation enables the formation of a gate oxide having low defect density and a constant thickness. The spacer material can be chosen to withstand the thermal oxidation and acts as an insulator between the gate structures.