Qubit Substrate Through-Hole Bonding to Prevent Member Peeling

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Solution Overview

Problem

In manufacturing qubit devices where a member with a recess portion is bonded to a substrate using multiple bonding materials, variations in material height can lead to insufficient bonding, potentially causing the member to peel off from the substrate.

Innovation Solution

A method involving forming a through-hole in the qubit substrate, applying a resist, and then removing it via the through-hole after forming a conductive film and a member over the resist, ensuring uniform bonding forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple bonding materials are used to bond the member to the substrate, then the bonding coverage is improved, but the height uniformity deteriorates due to manufacturing variation

Engineering Contradiction:
Improvebonding coverageVSAvoidheight uniformity
Core Design Contradiction:
ReliabilityVSManufacturing precision

Solution Approach 1:

A resist material is introduced as an intermediary substance between the bonding materials and the member. The resist fills the gaps and height variations among multiple bonding materials, providing a uniform top surface that enables reliable bonding while compensating for manufacturing variations in bonding material heights

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the physical state and properties of materials through controlled heating. By heating the resist to its melting point and then to a higher temperature for curing, the resist transitions from a solid to a melted state that flows into gaps, then to a cured state that provides structural support and uniform bonding surface

Inventive Principle:
Principle #35Parameter changes

2Ease of operation

If the resist is removed from the front surface, then the qubit access is improved, but the member peeling risk increases

Engineering Contradiction:
Improvequbit accessVSAvoidmember bonding stability
Core Design Contradiction:
Ease of operationVSReliability

Solution Approach 1:

The resist removal process is segmented into two distinct stages: (1) removing resist from the front surface to enable qubit access, and (2) retaining resist on the rear surface through through-holes to maintain bonding stability. This segmentation allows each surface to have different resist configurations optimized for its specific function

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Different regions of the resist are treated differently: the front surface resist is completely removed to provide unobstructed access to qubits, while the rear surface resist is intentionally retained and extended through through-holes to provide continuous bonding support. This local differentiation of resist presence solves the conflicting requirements of the two surfaces

Inventive Principle:
Principle #3Local quality

3Manufacturing precision

If the resist is extended to the rear surface through through-holes, then the bonding uniformity is improved, but the device complexity increases

Engineering Contradiction:
Improvebonding uniformityVSAvoidresist structure complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The resist material serves multiple functions: (1) as a bonding filler between bonding materials and substrate, (2) as a height-leveling layer that creates uniform bonding surfaces, (3) as a protective layer during manufacturing processes, and (4) as a retained bonding agent on the rear surface. This multi-functionality simplifies the overall structure by using a single material system for multiple purposes

Inventive Principle:
Principle #6Universality (Multi-functionality)

Data Source

PatentEP4590108B1Method for manufacturing qubit device
Publication Date: 2026.02.11 FUJITSU LTD
  • EP4590108B1 patent drawingFigure 1
  • EP4590108B1 patent drawingFigure 2A~2B
  • EP4590108B1 patent drawingFigure 3A~3C

AI summary

A method for manufacturing a qubit device including: forming a first conductive film (13) over a first surface (11) of a qubit substrate (10); forming a qubit (20) over the first surface (11); forming at least one through-hole (19) that penetrates the qubit substrate (10) in the qubit substrate; forming a resist (54) over the first surface (11) so as to cover the qubit (20) and the through-hole (19); forming a second conductive film (17) over the first conductive film (11) and the resist (54); forming a first member (18) over the second conductive film (17); and removing the resist (54) from a second surface (12) of the qubit substrate (10) via the through-hole (19) after the forming of the first member (18).