Investigation of Similar and Dissimilar Metal Contacts for Reliable Radio Frequency Micorelectromechanical Switches

Kwon, Hanjung; Park, Jae‐Hyoung; Lee, Hee Chul; Choi, Dong-Jun; Park, Yong‐Hee; Nam, Hojung; Joo, Young‐Chang

doi:10.1143/jjap.47.6558

Cited by 13 publications

(4 citation statements)

References 22 publications

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“…A large amount of work has been performed to study the mechanical performance of the contact materials themselves. Various alloys have been used to improve upon the hardness of pure Au contacts and reduce the contact resistance of other metals such as Pt and Ir [15,21,22]. While these approaches have been successful in improving switch lifetime and performance, ultimately, these materials still fail due to high resistance through the switch at large cycle numbers.…”

Section: Introductionmentioning

confidence: 99%

Lifetime limitations of ohmic, contacting RF MEMS switches with Au, Pt and Ir contact materials due to accumulation of ‘friction polymer’ on the contacts

Czaplewski¹,

Nordquist²,

Dyck³

et al. 2012

J. Micromech. Microeng.

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We present lifetime limitations and failure analysis of many packaged RF MEMS ohmic contacting switches with Au-Au, Au-Ir, and Au-Pt contact materials operating with 100 μN of contact force per contact in hermetically sealed glass wall packages. All metals were tested using the same switch design in a controlled environment to provide a comparison between the performance of the different materials and their corresponding failure mechanisms. The switch lifetimes of the different contact materials varied from several hundred cycles to 200 million cycles with different mechanisms causing failures for different contact materials. Switches with Au-Au contacts failed due to adhesion when thoroughly cleaned while switches with dissimilar metal contacts (Au-Ir and Au-Pt) operated without adhesion failures but failed due to carbon accumulation on the contacts even in a clean, packaged environment as a result of the catalytic behavior of the contact materials. Switch lifetimes correlated inversely with catalytic behavior of the contact metals. The data suggests the path to increase switch lifetime is to use favorable catalytic materials as contacts, design switches with higher contact forces to break through any residual contamination, and use cleaner, probably smaller, packages.

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Section: Introductionmentioning

confidence: 99%

Lifetime limitations of ohmic, contacting RF MEMS switches with Au, Pt and Ir contact materials due to accumulation of ‘friction polymer’ on the contacts

Czaplewski¹,

Nordquist²,

Dyck³

et al. 2012

J. Micromech. Microeng.

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show abstract

“…Thus, one has to increase the force in order to reduce the resistance. In addition, a large Fc helps to break contaminating films and enhances the stability of Rc from cycle to cycle [35]. Experimental data suggest the minimum required value of 100 µN per contact [29][30][31]33,38].…”

Section: Methodsmentioning

confidence: 99%

“…The problem is well understood by the MEMS community. The operation of microscopic contacts is thoroughly investigated using indenters [29][30][31], scanning probe microscopes [32,33], and homemade facilities [34][35][36][37][38]. It is demonstrated that the contact resistance rapidly decreases with increasing the force and then reaches saturation.…”

Section: Introductionmentioning

confidence: 99%

Design Guideline for a Cantilever-Type MEMS Switch with High Contact Force

Uvarov,

Belozerov

2023

Micro

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Micromechanical switches are of significant interest for advanced radio frequency and microwave systems, but their practical implementation is limited by low reliability. Electrodes of a microscopic size develop weak contact force that leads to high and unstable contact resistance. The force is typically increased by using a sophisticated switch design with extended lateral dimensions, although a simple and compact cantilever is more preferable. The paper describes for the first time a comprehensive approach to enhance the force of an electrostatically actuated switch. The strategy is applied to a miniature device based on a 50 µm long cantilever. The contact force is increased from 10 to 112 µN, making the switch strong enough to achieve low and stable contact resistance. The restoring force is also enhanced in order to ensure reliable de-actuation. The growth of forces is accompanied by a reduction in the pull-in voltage. Connecting several cantilevers in parallel and manipulating the number and position of contact bumps additionally improves the force and mechanical stability of the switch. An optimal design contains a triple cantilever with two bumps. It provides 50% higher force per contact compared to the single-cantilever switch at the same pull-in voltage and keeps the advantages of a miniature device. The proposed design strategy may be used for building reliable MEMS switches.

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“…It is known that hot-cycling MEMS switches deteriorates the contact area as a function of time due to a multitude of phenomena including surface pitting, fatigue, asperity generation, charge migration, stiction and micro-welding and other physical damages. Despite numerous reports of 10 8 -10 10 successful switching cycles in literature [1][2][3][4][5][6][7][8] and the large research interest [9][10][11][12][13][14], knowledge on understanding this phenomena affecting repeated cycling still remains unclear. The question remains: "What really governs the "perfectly reliable" MEMS/NEMS switch?…”

Section: Introductionmentioning

confidence: 99%

Investigation of contact resistance evolution of Ir, Pt, W, Ni, Cr, Ti, Cu and Al over repeated hot-contact switching for NEMS switches

Chowdhury

Pourzand

Tabib-Azar

2013

2013 IEEE 26th International Conference on Micro Electro Mechanical Systems (MEMS)

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This article reports on the evolution of contact resistance (R c ) of metal contacts over 100,000 cycles. A contact-mode atomic force microscope connected to a current versus voltage (I-V) measurement system was used and successive I-V measurements between a Crcoated AFM conducting tip and Ir, Pt, W, Ni, Cr, Ti, Cu or Al thin-film metals on silicon nitride coated silicon in a nitrogen ambient were carried out. Adhesion forces between the samples and the conducting AFM tip was also measured. The best cyclic I-V performers were Ir, Pt, W & Ti. The trend in changing R c seen in Ir, Pt and W are similar and can be attributed to factors such as their high Young's modulus, high melting temperatures and high density and low adhesion forces. Ti yeilded the best I-V behavior where contact resistance improved slightly as a function of cycling. A relationship between adhesion forces and defect generation in the contact region is observed and the results of both sets of experiments are detailed here.

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Investigation of Similar and Dissimilar Metal Contacts for Reliable Radio Frequency Micorelectromechanical Switches

Cited by 13 publications

References 22 publications

Lifetime limitations of ohmic, contacting RF MEMS switches with Au, Pt and Ir contact materials due to accumulation of ‘friction polymer’ on the contacts

Lifetime limitations of ohmic, contacting RF MEMS switches with Au, Pt and Ir contact materials due to accumulation of ‘friction polymer’ on the contacts

Design Guideline for a Cantilever-Type MEMS Switch with High Contact Force

Investigation of contact resistance evolution of Ir, Pt, W, Ni, Cr, Ti, Cu and Al over repeated hot-contact switching for NEMS switches

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