Investigation of AuNi 5 Films Deposited by Pulsed Laser Deposition for RF MEMS Switch Contacts
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0980-II05-46
Investigation of AuNi5 Films Deposited by Pulsed Laser Deposition for RF MEMS Switch Contacts Noha Sameh Farghal1, Moustafa Yehia Ghannam2, Amr M. Shaarawi1,3, Hussein El Samman4, Philippe Soussan5, and Kris Baert5 1 Yousef Jameel Science and Technology Research Center, the American University in Cairo, Cairo, Egypt 2 EE Department, Kuwait University, Kuwait City, Kuwait 3 Physics Department, The American University in Cairo, Cairo, Egypt 4 Physics Department, Menoufia University, Shibin, Egypt 5 IMEC v.z.w., Leuven, Belgium
ABSTRACT In this work, Pulsed Laser Deposition (PLD) is used to deposit AuNi5 (Au-5at%Ni) thin films for possible application as RF MEMS switch contacts. The films have been physically and chemically characterized using SEM, TEM, Optical Profilimetry, Nano-identation and XRF. The effect of varying the nickel content (within a small range) and laser fluence on some film properties has also been investigated. In the range of Ni content 1-9%, it has been found that film hardness and morphology are affected by the laser fluence during deposition and are less sensitive to small changes in the Ni content. The surface roughness of the deposited films is rather high due to presence of relatively large particulates on the surface. A particulate filter was used to reduce the size and density of these particulates but resulted in incongruent transfer and the deposition of non-stoichiometric films. Finally, patterning the PLD films by lift-off process has been tested and found to be successful, showing that PLD is a low temperature deposition technique suitable for lift-off patterned films. I. INTRODUCTION Pure Au is the most commonly used contact material for micro-switches mainly due to its low resistivity and low susceptibility to corrosion and development of alien surface films. Due to its low hardness, however, Au-Au contacts require considerable force to break contact (lift-off force), although they provide significantly low stable contact resistance at low contact force [1]. Therefore, AuNi5 (Au-5at%Ni) was proposed as a good alternative to Au since it requires a liftoff force considerably smaller than that required for pure Au contacts, while having properties similar to those of Au. Such thin metal films are commonly deposited by RF sputtering and evaporation [2]. Pulsed Laser Deposition (PLD) is used to deposit thin films of a wide variety of materials, including metal alloys and complex materials such as superconductors and magnetic materials, due to the ease of obtaining congruent transfer and stoichiometric films with PLD [4]. Another advantage of PLD over other thin film deposition techniques is crystallinity enhancement at low substrate temperatures by adjusting deposition parameters. This may be needed when the substrate is coated with photoresist that could be degraded at high temperatures [3-7]. In this study, we investigate the possibility of PLD of thin AuNi5 films and study film properties using several physical and chemical characterization techniques. The main concern i
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