Graphene Contact Metallization for Damage-Free Wire Bonding
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Solution Overview
Problem
Existing metallization techniques for graphene solid-state devices, such as sputtering and thermal evaporation, cause damage to the graphene film and are limited in thickness, making them unsuitable for high-density packaging and wire bonding processes.
Innovation Solution
A two-stage metallization process involving a plasma-free deposition method followed by a thick metal deposition, ensuring reliable contact without damaging the graphene and enabling subsequent integration in packaging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional metal deposition techniques (e.g., sputtering, evaporation) are used to deposit metal on graphene, then metal contact is achieved, but the graphene structure is damaged and transferable contacts cannot be achieved
Solution Approach 1:
A metal nanoparticle paste serves as an intermediary material between the metal source and graphene substrate. The paste contains metal particles in a binder that enables gentle deposition without direct high-energy metal-vapor or metal-plasma contact with graphene, thus preventing structural damage while achieving electrical contact.
Solution Approach 2:
The invention changes the physical state and deposition parameters of metal by using pre-formed metal nanoparticles in a paste form rather than depositing metal from vapor or plasma phase. This parameter change allows low-temperature, low-energy deposition that preserves graphene integrity.
2Ease of operation
If metal nanoparticle paste is screen-printed onto graphene, then transferable contacts are achieved, but the contact resistance is high and conductivity is low
Solution Approach 1:
The binder composition parameters are optimized to achieve optimal balance between transferability and conductivity. Specific resin types, plasticizer ratios, and curing conditions are controlled to create a paste that transfers well but maintains low contact resistance after drying and curing.
Solution Approach 2:
The metal nanoparticle paste is formulated as a composite material combining metal particles with a specifically designed binder system. The composite structure allows the organic binder to facilitate transfer while the metal particles provide conductive pathways, achieving both transferability and acceptable conductivity.
3Reliability
If the metal nanoparticle paste is not properly cured, then the graphene structure is preserved, but the paste remains tacky and does not form stable contacts
Solution Approach 1:
Curing parameters including temperature, time, and atmosphere are precisely controlled to achieve complete binder crosslinking without exceeding graphene's thermal tolerance. The curing process transforms the paste from a tacky semi-solid to a stable, non-tacky solid while maintaining graphene structural integrity.
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 method allows for reliable top-contact metallization of graphene devices, preserving the integrity of the graphene channel and supporting high-density packaging and wire bonding processes.
Implementation Method 1
The metal nanoparticle paste is screen-printed onto the graphene in a first printing step
Implementation Method 2
the binder is cured to stabilize the metal particles and form stable contacts
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 3A~3B
AI summary
A method of metallizing a solid-state device comprising a substrate (100) and at least one graphene channel (101) disposed on the substrate (100), the method comprising: applying a first metal deposition stage for depositing at least one first metallic structure (104'), the at least one first metallic structure (104') partially occupying the graphene layer (101) and partially occupying the substrate (100), wherein a metal deposition technique which does not use plasma is used to deposit the at least one first metallic structure (104'); applying a second metal deposition stage for depositing at least one second metallic structure (108') on a region of the at least one first metallic structure (104') which is not deposited on the graphene channel (101). A solid-state device comprising a substrate (100) and at least one graphene channel (101) disposed on the substrate (100), the solid-state device comprising at least one first metallic structure (104') partially occupying the graphene layer (101) and partially occupying the substrate (100) and at least one second metallic structure (108') partially deposited on a region of the at least one first metallic structure (104') which is not deposited on the graphene channel (101). A method of packaging in a socket a die (10) comprising at least one graphene-based solid-state device as the one previously disclosed.