Corrugated MEMS Contact Electrode for Low Resistance
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Solution Overview
Problem
Microelectromechanical systems (MEMS) switches face reliability issues due to high and variable contact resistance caused by small contact areas and contamination, which can lead to field failures, especially under increased operating temperatures.
Innovation Solution
The method involves etching the contact surfaces of MEMS devices to create a corrugated topography where the outer edge of one gold grain is recessed from adjacent grains, increasing the contact area and reducing resistance by using a liquid etchant that differentially etches gold grains based on their crystallographic orientation, thereby ensuring a larger, more stable contact area of pure metal grains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the contact area is reduced to minimize device size, then the device dimensions are improved, but the contact resistance increases and reliability deteriorates
Solution Approach 1:
The patent applies local quality by creating a corrugated surface morphology with recessed outer edges on the contact surface. This local structural modification ensures that the contact interface is dominated by essentially pure metal grains in the center, while the recessed edges prevent contamination and oxidation. The local change in surface topology (recessed edges) improves contact resistance stability without requiring a larger overall contact area, thus resolving the contradiction between miniaturization and reliability.
2Area of moving object
If the contact area is small to maintain device miniaturization, then the device scale is improved, but the contact resistance becomes highly variable and unreliable
Solution Approach 1:
The invention modifies the local quality of the contact surface by creating a corrugated morphology where the outer edges are recessed from the outer edges of adjacent grains. This local structural feature ensures that the contact interface is dominated by essentially pure metal grains, making the contact resistance less sensitive to contamination and oxidation. The recessed edges act as a protective feature that maintains reliable electrical contact even when the overall contact area is small.
3Ease of manufacture
If the contact surface is left smooth and unmodified, then the manufacturing process is simpler, but the contact resistance increases due to contamination and oxidation
Solution Approach 1:
The patent applies preliminary action by performing an etching treatment on the contact surface before the final device assembly. This preliminary etching step creates the protective corrugated morphology with recessed outer edges, which prevents future contamination and oxidation. By preparing the surface in advance with this specific morphology, the device achieves low and stable contact resistance without requiring complex protective coatings or assembly procedures later in the manufacturing process.
4Reliability
If the contact surface is etched to create corrugated morphology, then the contact resistance is reduced and stabilized, but the manufacturing process complexity increases
Solution Approach 1:
The invention applies parameter changes by modifying the surface morphology parameters through controlled etching. Specifically, the etching process creates a corrugated structure with recessed outer edges at a specific depth (e.g., 0.05-2.0 micrometers) and with specific geometric characteristics. By controlling these morphological parameters, the patent achieves low and stable contact resistance. The etching parameters (time, temperature, reagent concentration) can be optimized to balance the improvement in contact resistance stability with the added manufacturing complexity.
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
This approach significantly reduces and stabilizes contact resistance, improving the reliability and longevity of MEMS switches by maintaining low contact resistance even after numerous switching cycles, reducing the risk of field failures.
Implementation Method 1
The etch rate of the different grains depends on the crystallographic orientation of the grains, leaving the corrugated surface
Implementation Method 2
the drive loop, which is a conductive circuit that expands on application of a drive current to the loop. Upon heating the drive loop with the current, the expansion of the drive loop displaces the cantilevered beam
Data Source
AI summary
A contact electrode for a device is made using an etching process to etch the surface of the contact electrode to form a corrugated contact surface wherein the outer edges of at least one grain is recessed from the outer edges of adjacent grains and is recessed by at least about 0.05 μm from the contact plane. By having such a corrugated surface, the contact electrode is likely to contact another conductor with at least one pure metal grain. This etching treatment reduces contact resistance and contact resistance variability throughout many cycles of use of the contact electrode.