Multi-Physical Characterization of Micro-Contact Materials for MEMS Switches

Broué, Adrien; Dhennin, Jérémie; Charvet, Pierre-Louis; Pons, Patrick; Jemaa, N. Ben; Heeb, Peter; Coccetti, Fabio; Plana, R.

doi:10.1109/holm.2010.5619519

Cited by 24 publications

(29 citation statements)

References 21 publications

(20 reference statements)

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“…The experimental measurement in [23] showed that the Au/Ru bimetallic contact had the contact resistance of 1.9 Ω at the contact force of 145 µN and the current of 1 mA. This value leads to the contact radius of 13 nm with the diffusive transport mode.…”

Section: Comparison Againt the Experimental Resultsmentioning

confidence: 89%

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An Asperity-Based Finite Element Model for Electrical Contact of Microswitches

Liu

Leray

Pons

et al. 2013

2013 IEEE 59th Holm Conference on Electrical Contacts (Holm 2013)

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Abstract-Precise prediction of electrical contact resistance is important for microswitches. The contact spot used to be considered as a circle in earlier literature, where there was only one geometrical parameter: the radius of the a-spots. However, a real contact asperity has a height and an angle with the interface. In this paper, a 3-dimensional cone-truncated geometry is used to model an asperity, and three parameters are defined: radius, height and the angle of the side with respect to the surface plane. The ranges of their values are extracted from AFM measurement of samples in Au and Ru, and the values match well with the previous mechanical simulation results.Compared to the theoretical results, the finite element (FE) model showed a good capability to predict contact resistance in the diffusive regime, but underestimated it in the ballistic regime. The effects of angle and height of the asperity were investigated for Au-Ru contact in terms of contact resistance, maximum temperature and its location. Regarding multiple spots in contact, this work investigated the influence of the number of spots and their distributions for contact resistance and local Joule heating.

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Section: Comparison Againt the Experimental Resultsmentioning

confidence: 89%

“…Broué et al [23] showed that the bimetallic contact had the advantage of reliability, seeing that the maximum temperature was not localized on the interface of contact, but on the side with higher resistivity [8]. This will be also discussed in this paper.…”

Section: Introductionmentioning

confidence: 92%

An Asperity-Based Finite Element Model for Electrical Contact of Microswitches

Liu

Leray

Pons

et al. 2013

2013 IEEE 59th Holm Conference on Electrical Contacts (Holm 2013)

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“…Hence, a new set-up was developed for the characterization of contact materials used in micro-switches. In previous works the study of the Au/Au, Ru/Ru, and Au/Ru contact resistance, comparing the stability with respect to an increased level of current has been already presented [2][3][4]. The present paper intends to recall these previous results to extend and focus on critical aspects, such as contact asperity, joule-effect-induced heating, and finally contact adhesion.…”

Section: Introductionmentioning

confidence: 99%

Comparative study of RF MEMS micro-contact materials

Broué¹,

Dhennin²,

Charvet

et al. 2012

Int. J. Microw. Wireless Technol.

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A systematic comparison between several pairs of contact materials based on an innovative methodology early developed at NOVA MEMS is hereby presented. The technique exploits a commercial nanoindenter coupled with electrical measurements, and test vehicles specially designed to investigate the underlying physics driving the surface-related failure modes. The study provides a comprehensive understanding of micro-contact behavior with respect to the impact of low-to-medium levels of electrical current. The decrease of the contact resistance, when the contact force increases, is measured for contact pairs of soft material (Au/Au contact), harder materials (Ru/Ru and Rh/Rh contacts), and mixed configuration (Au/Ru and Au/Ni contacts). The contact temperatures have been calculated and compared with the theoretical values of softening temperature for each couple of contact materials. No softening behavior has been observed for mixed contact at the theoretical softening temperature of both materials. The enhanced resilience of the bimetallic contacts Au/Ru and Au/Ni is demonstrated.Keywords: RF-MEMS, micro-contact materials, reliability, temperature I . I N T R O D U C T I O NSince the beginning of their development in the early 2000s, RF MEMS (Micro Electro Mechanical Systems) have always suffered from a lack of reliability, hampering their mass production, and commercialization. These limitations are due to the complex underlying physics of failure dominated by strong multiphysics and multiple scale phenomena, made fuzzier by the shortcoming in technology stability, which needs yet to meet industrial standards. As far as technical bottle-neck issues are concerned, one of the major failure mechanism identified in the past was the dielectric charging, which induces a drift of pull-in and pull-out voltages, and quickly leads to permanent stiction in open or closed state. However recent publications have clearly showed that this phenomenon is no more the main failure cause for ohmic micro-contact switches, since it can be avoided by means of design tricks or control voltages tuning approaches [1]. Consequently, another failure mechanism becomes the predominant one, i.e. the degradation of the resistive micro-contact properties throughout the switch's lifetime.As for dielectric charging, intense research activity is mandatory to study the root causes of this failure, and to derive solutions to overcome it. This is made difficult by the small sizes at stake in these devices, and by the multiphysical aspect of the microcontacts. Indeed, mechanical, thermal, electrical, and even chemical aspects have to be taken into account to elaborate an accurate behavioral model. In particular, the contact pressure and the corresponding temperature have to be determined precisely, knowing that these two parameters are interdependent. In order to do so, the model needs to be completed by sets of data that include the electrical and the thermo-mechanical properties of the thin-film metallizations used to realize the contact. Hence, a new ...

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“…The top radius of the asperity (a) is defined as 120 nm in the modeling, which is based on the finite element mechanical contact modeling [15], with the applied contact force of 150 μN, accordance to the experimental results [16]. And the height of the asperity is defined as h=6 nm and the angle of side as α=10° from the AFM data [14].…”

Section: A Contact Asperity Modelingmentioning

confidence: 99%

Finite element modeling of nickel oxide film for Au-Ni contact of MEMS switches

Liu

Leray

Colin

et al. 2015

2015 IEEE 61st Holm Conference on Electrical Contacts (Holm)

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Abstract-Contamination and oxidation are inevitable in contact surfaces, especially for micro contact under low load (μN-mN). They are considered as major causes for a high contact resistance, and can lead to the failure of a contact. However, as the film formation is complicated, also it is difficult to accurately observe and measure them, the characterization of the films is not well known. In the paper, a finite element model of nickel oxide film is developed for Au-Ni contact of MEMS switches. Considering the fact that the electrical contact area is only a portion of the mechanical contact area, a model featured 'nanospots' is developed: multiple small conductive spots are scattered in a big mechanical contact asperity, and ultrathin oxide film is around the nano-spots. The size of electrical spots and mechanical asperity is calculated based on the measured electrical resistance and mechanical contact modeling respectively. The simulations results show a good match with the experimental results. This model allows us to determine some possible geometry configuration that leads to the measured contact resistance in real devices.

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Multi-Physical Characterization of Micro-Contact Materials for MEMS Switches

Cited by 24 publications

References 21 publications

An Asperity-Based Finite Element Model for Electrical Contact of Microswitches

An Asperity-Based Finite Element Model for Electrical Contact of Microswitches

Comparative study of RF MEMS micro-contact materials

Finite element modeling of nickel oxide film for Au-Ni contact of MEMS switches

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