Au-Cu Alloy Electrodes for Biosensor CMOS Compatibility
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Solution Overview
Problem
Conventional biosensor devices with copper electrodes suffer from oxidation and corrosion, which limits their compatibility with CMOS processing and biosensing applications, as they require additional processing steps for protection and alignment.
Innovation Solution
The method involves forming Au-Cu alloy electrodes by depositing a gold layer over copper electrodes and thermally treating them to alloy the metals, eliminating the need for barrier layers and photolithography, and using chemical-mechanical polishing to expose the alloyed electrodes, which are more corrosion-resistant and compatible with CMOS processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If copper electrodes are used in biosensor devices, then compatibility with CMOS processing is improved, but oxidation and corrosion resistance deteriorates
Solution Approach 1:
The patent applies composite materials by creating Au-Cu alloy electrodes that combine copper's CMOS compatibility with gold's corrosion resistance. The alloy structure integrates both metals at the atomic level, allowing the electrode to exhibit properties of both constituent materials - electrical compatibility with CMOS processes from copper and oxidative stability from gold.
Solution Approach 2:
The patent changes the compositional parameter of the electrode material from pure copper to an Au-Cu alloy with specific composition ratios. By adjusting the gold content parameter, the electrode achieves optimal balance between CMOS processing compatibility (requiring copper) and corrosion resistance (requiring gold), transforming the material properties to satisfy both contradictory requirements.
2Reliability
If a gold capping layer is deposited over copper electrodes to prevent oxidation, then corrosion resistance is improved, but manufacturing complexity increases due to photolithography alignment requirements
Solution Approach 1:
The patent merges the copper electrode and gold protective layer into a single Au-Cu alloy electrode structure. Instead of maintaining them as separate layers requiring precise alignment, the合金ing process combines them at the atomic level, eliminating the need for photolithography alignment steps while maintaining the protective function of gold against copper oxidation.
Solution Approach 2:
The patent creates a simplified version of the protective structure by forming the Au-Cu alloy directly in the electrode fabrication process itself, rather than adding a separate gold capping layer through complex photolithography alignment procedures. This copies the protective function in a more integrated and manufacturable way.
3Stability of the object's composition
If barrier layers are used to prevent copper diffusion, then electrode stability is improved, but device complexity and processing steps increase
Solution Approach 1:
The patent extracts and eliminates the need for separate barrier layers by incorporating the diffusion prevention function directly into the Au-Cu alloy structure itself. The alloy's inherent atomic structure prevents further copper diffusion without requiring additional titanium or other barrier material layers, simplifying the overall device architecture.
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 Au-Cu alloy electrodes provide enhanced corrosion resistance and compatibility with CMOS processing, allowing for improved adsorption of self-assembled monolayers and bioreceptors, reducing the need for additional protection layers and alignment steps, and maintaining compatibility with advanced semiconductor processing.
Implementation Method 1
thermally treating the semiconductor device to alloy deposited Au and the Cu electrodes, thereby forming the Au-Cu alloy electrodes
Implementation Method 2
polishing the semiconductor device to expose the Au-Cu alloy electrodes
Data Source
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AI summary
A method of manufacturing a biosensor semiconductor device is disclosed, in which copper electrodes at the major surface of the semiconductor devices are modified to form Au-Cu alloy electrodes. The modification is effected by depositing, typically by sputtering, a gold layer over the device, and then thermally treating the device to promote interdiffusion between the gold and the electrode copper and to alloy them. The alloyed gold-copper is removed from the surface of the device typically by CMP, leaving the exposed electrodes. Since the gold-copper alloy is harder than gold, the CMP process window is wider than would be the case of pure gold; moreover, since the electrode copper has been converted to a gold-copper alloy, it is more corrosion resistant than a conventional copper electrode. The electrodes are thus better compatible with further processing into a biosensor device than is the case with conventional copper electrodes, and the process windows are wider than for gold capped copper electrodes. A biosensor semiconductor device having Au-Cu alloy electrodes is also disclosed.