Qubit Substrate Groove Layout for Reliable Interlayer Connection

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Solution Overview

Problem

The challenge in quantum devices is to maintain reliable electrical connections between surfaces while preventing a decrease in mechanical strength of conductive films formed in through holes or grooves, which are crucial for connecting qubits in quantum computers.

Innovation Solution

A method involving the formation of first and second grooves in a qubit substrate, with conductive films on their surfaces, ensuring electrical connection through these grooves while maintaining mechanical integrity by controlling the angles and dimensions of the grooves and films.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a through hole with vertical side surface is formed and conductive films are formed from both surfaces, then electrical connection is achieved, but the film thickness becomes thin near the center causing poor electrical connection

Engineering Contradiction:
Improveelectrical connection reliabilityVSAvoidfilm thickness uniformity
Core Design Contradiction:
ReliabilityVSManufacturing precision

Solution Approach 1:

The through hole is divided into two separate grooves: a first groove formed from the first surface and a second groove formed from the second surface. These grooves meet or overlap in the middle region, creating segmented conductive film formation zones that avoid the thin-film problem at the center while maintaining electrical connection.

Inventive Principle:
Principle #1Segmentation

2Manufacturing precision

If the side surface of the through hole is inclined in a tapered shape, then film thickness is maintained, but the contact area between conductive films is reduced

Engineering Contradiction:
Improvefilm thickness controlVSAvoidelectrical connection reliability
Core Design Contradiction:
Manufacturing precisionVSReliability

Solution Approach 1:

Instead of using a single tapered through hole, the structure is segmented into two separate grooves with their own side surfaces. This allows each groove to have optimized geometry for film formation while the grooves meet in the middle to provide sufficient contact area between conductive films.

Inventive Principle:
Principle #1Segmentation

3Reliability

If grooves are formed to improve electrical connection reliability, then connection quality improves, but the mechanical strength of conductive films decreases

Engineering Contradiction:
Improveelectrical connection reliabilityVSAvoidmechanical strength of conductive film
Core Design Contradiction:
ReliabilityVSStrength

Solution Approach 1:

The groove geometry is optimized locally: the side surfaces are configured with specific angles and the grooves have controlled depths and widths. This local optimization allows the conductive films to maintain adequate thickness and mechanical strength in critical regions while still achieving reliable electrical connection at the interface.

Inventive Principle:
Principle #3Local quality

Data Source

PatentEP4694659A1Method of manufacturing quantum device and quantum device
Publication Date: 2026.02.11 FUJITSU LTD
  • EP4694659A1 patent drawingFigure 1
  • EP4694659A1 patent drawingFigure 2A~2B
  • EP4694659A1 patent drawingFigure 3A~3C

AI summary

Provided is a method of manufacturing a quantum device (100) including a qubit and a qubit substrate (10) having a first surface (11) on which the qubit is formed. The method includes forming a first groove (60) in a second surface (12) of the qubit substrate, forming a first conductive film (22) on a bottom surface (61) and a side surface (62) of the first groove, forming a second groove (50) reaching a part of the bottom surface of the first groove in the first surface after the forming the first conductive film, forming a second conductive film (21) on a bottom surface (51) and a side surface (52) of the second groove; and forming the qubit on the first surface.