Graphene Passivation Layer Patterning for Clean Biosensor Surfaces
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Solution Overview
Problem
Preparing and incorporating graphene into biosensors or diagnostic devices is challenging due to contamination and damage during the manufacturing process, especially when using photoresist or PMMC layers, which degrade the performance of graphene.
Innovation Solution
A method involving the deposition of a passivation layer, such as silicon dioxide, on graphene sheets using techniques like PECVD, followed by patterning with a photoresist layer to protect and pattern the graphene, using inert metals like gold for additional protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If graphene sheets are transferred to a substrate using a polymer support film, then the graphene can be handled and processed, but the polymer residues contaminate the graphene surface and degrade device performance
Solution Approach 1:
The patent introduces a sacrificial layer as an intermediary substance between the graphene and the substrate during the transfer process. This sacrificial layer serves as a temporary mediator that enables graphene handling and transfer, then is completely removed afterward, leaving no harmful residues on the graphene surface. The sacrificial layer is specifically designed to be removable without damaging the graphene, thus resolving the contradiction between ease of manufacture and surface cleanliness.
2Productivity
If conventional transfer methods are used to move graphene onto substrates, then device fabrication can proceed, but mechanical damage and contamination occur during handling
Solution Approach 1:
The patent applies preliminary action by first depositing the sacrificial layer onto the substrate before transferring the graphene. This pre-prepared sacrificial layer creates a controlled interface that prevents direct contact between the graphene and the substrate during transfer, thereby preventing mechanical damage and contamination. The sacrificial layer is designed to be removed after device fabrication, allowing productivity while maintaining graphene integrity during the critical transfer phase.
3Manufacturing precision
If graphene is grown directly on the final substrate, then device performance is maximized, but selective area growth and pattern transfer become difficult
Solution Approach 1:
The patent applies segmentation by dividing the substrate into distinct regions: areas with the sacrificial layer where graphene should grow, and areas without the sacrificial layer where graphene should not grow. This segmented approach enables selective area growth of graphene on the final substrate. After selective growth, the sacrificial layer is removed from specific regions, allowing precise pattern transfer while maintaining high device performance through direct graphene-substrate contact in the desired areas.
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 effectively prevents contamination and damage to graphene, maintaining its performance by reducing electrical leakage and allowing for accurate chemical and biological sensing.
Implementation Method 1
a first layer of graphene is formed on a copper foil by a chemical vapour deposition process
Implementation Method 2
a polymer solution is deposited onto the copper foil, the solvent is evaporated, and a polymer film is formed
Implementation Method 3
the copper foil is etched in a iron chloride solution, the graphene is transferred to the polymer film
Implementation Method 4
the polymer film is heated to release the graphene, and the graphene is transferred onto a substrate
Data Source
Figure 1A~1F
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AI summary
Embodiments of the disclosed technology include depositing a passivation layer onto a surface of a wafer that may include a graphene layer. The passivation layer may protect and isolate the graphene layer from electrical and chemical conditions that may damage the graphene layer. As such, the passivation layer may further protect the graphene sensor from being damaged and impaired for its intended use. Additionally, the passivation layer may be patterned to expose select areas of the graphene layer below the passivation layer, thus creating graphene wells and exposing the graphene layer to the appropriate chemicals and solutions.