Lateral MEMS microcontact considerations

Kruglick, E.; Pister, Kristofer S. J.

doi:10.1109/84.788630

Cited by 101 publications

(79 citation statements)

References 17 publications

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“…[7][8][9] Low hardness, high conductivity, and inertness to contamination make Au very suitable for low force applications. However, soft gold contacts have been observed to be susceptible to contact wear 10 and adhesive failure.…”

Section: Introductionmentioning

confidence: 99%

Contact resistance study of noble metals and alloy films using a scanning probe microscope test station

Chen

Lee

Guo

et al. 2007

Journal of Applied Physics

108

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The proper selection of electrical contact materials is one of the critical steps in designing a metal contact microelectromechanical system ͑MEMS͒ switch. Ideally, the contact should have both very low contact resistance and high wear resistance. Unfortunately this combination cannot be easily achieved with the contact materials currently used in macroswitches because the available contact force in microswitches is generally insufficient ͑less than 1 mN͒ to break through nonconductive surface layers. As a step in the materials selection process, three noble metals, platinum ͑Pt͒, rhodium ͑Rh͒, ruthenium ͑Ru͒, and their alloys with gold ͑Au͒ were deposited as thin films on silicon ͑Si͒ substrates. The contact resistances of these materials and their evolution with cycling were measured using a specially developed scanning probe microscope test station. These results were then compared to measurements of material hardness and resistivity. The initial contact resistances of the noble metals alloyed with Au are roughly proportional to their resistivities. Measurements of contact resistance during cycling of different metal films were made under a contact force of 200-250 N in a room air environment. It was found that the contact resistance increases with cycling for alloy films with a low concentration of gold due to the buildup of contamination on the contact. However, for alloy films with a high gold content, the contact resistance increase due to contamination is insignificant up to 10 8 cycles. These observations suggest that Rh, Ru, and Pt and their gold alloys of low gold content are prone to contamination failure as contact materials in MEMS switches.

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Section: Introductionmentioning

confidence: 99%

Contact resistance study of noble metals and alloy films using a scanning probe microscope test station

Chen

Lee

Guo

et al. 2007

Journal of Applied Physics

108

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“…13 and 14. A relationship between the increased contact force and the decreased contact resistance has already been demonstrated in [10] and [26]. Fig.…”

Section: B S-parameter Measurementmentioning

confidence: 82%

“…In low-RF power conditions, no difference between cold and hot switching is observed, on the contrary to medium-to high-power conditions, where their impact on the switch performance and reliability is different [28]. There are a number of studies in literature devoted to the exploration of microscale contact physics, which also provide models for the different phenomena associated with resistive contacts [10], [26]- [29]. In this paper, issues related to contact failure mechanisms were not investigated, although, as described in the following paragraph, care was taken in designing a contact that would be as robust as possible (given the manufacturing process restrictions) and with good RF and power-handling performance.…”

Section: Resistive Contactsmentioning

confidence: 99%

“…The performance of this contact is itself influenced by the combination of a number of factors such as material properties (electrical resistivity, roughness, hardness, plasticity, and melting point) [10], real contact area [26] (since the contact occurs only at a number of points scattered across the rough surfaces), contact force [10], adherence force (the force that must be overcome in order to separate the surfaces once contact has occurred), temperature due to current flow through the contact, and manufacturing process [27]. Resistive-contact failure strongly depends on the material selected; it is independent of the actuation principle and is caused by a number of mechanisms such as pitting, hardening, and necking, mainly derived from thermal issues.…”

Section: Resistive Contactsmentioning

confidence: 99%

“…The second contribution of this paper is the use of metal electrothermal actuators in RF applications. Electrothermal actuators develop high forces [9] with a direct impact on optimum resistive contacts [10]. It is shown that the use of nickel as actuator building material permits large displacements with low temperatures (important in terms of packaging), in contrast to the traditional polysilicon electrothermal actuators used in other works [6], [11].…”

Section: Introductionmentioning

confidence: 99%

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Electrothermally Actuated RF MEMS Switches Suspended on a Low-Resistivity Substrate

Girbau

Pradell

Lázaro

et al. 2007

J. Microelectromech. Syst.

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Abstract-This paper presents an electrothermally actuated lateral resistive-contact switch for application to low-gigahertz-band communication systems. It was manufactured on a standard low-resistivity substrate, and its RF performance was improved by suspending the structures 25 µm from the substrate, which is a strategy for future integration with active devices in the system-on-chip concept. Measured insertion losses are −0.26 dB at 1 GHz and −0.65 dB at 6 GHz, return losses are −29 dB at 1 GHz and −25 dB at 6 GHz, and isolations are −52 dB at 1 GHz and −26 dB at 6 GHz. The device is driven by a metal electrothermal actuator, which achieves large displacements and contact forces at much lower temperatures than traditional polysilicon electrothermal actuators. The RF power handling characteristics are also addressed and measured.[ 2007-0051]Index Terms-Electrothermal actuator, low-resistivity substrate, microelectromechanical systems (MEMS) switch, system on chip.

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