Mechanical Properties of 3C-SiC Films for MEMS Applications
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1049-AA03-06
Mechanical Properties of 3C-SiC Films for MEMS Applications Jayadeep Deva Reddy1, Alex A. Volinsky1, Christopher L. Frewin2, Chris Locke2, and Stephen E. Saddow2 1 Department of Mechanical Engineering, University of South Florida, 4202 E. Fowler Ave. ENB118, Tampa, FL, 33620 2 Department of Electrical Engineering, University of South Florida, 4202 E. Fowler Ave. ENB118, Tampa, FL, 33620 ABSTRACT There is a technological need for hard thin films with high elastic modulus and fracture toughness. Silicon carbide (SiC) fulfills such requirements for a variety of applications at high temperatures and for high-wear MEMS. A detailed study of the mechanical properties of single crystal and polycrystalline 3C-SiC films grown on Si substrates was performed by means of nanoindentation using a Berkovich diamond tip. The thickness of both the single and polycrystalline SiC films was around 1-2 µm. Under indentation loads below 500 µN both films exhibit Hertzian elastic contact without plastic deformation. The polycrystalline SiC films have an elastic modulus of 457 + 50 GPa and hardness of 33.5 + 3.3 GPa, while the single crystalline SiC films elastic modulus and hardness were measured to be 433 + 50 GPa and 31.2 + 3.7 GPa, respectively. These results indicate that polycrystalline SiC thin films are more attractive for MEMS applications when compared with the single crystal 3C-SiC, which is promising since growing single crystal 3C-SiC films is more challenging. INTRODUCTION The development of SiC as a microelectronic material for over 2 decades has resulted in enormous prospects for its use in MEMS applications [1, 2]. Mechanical properties of thin films play a pivotal role in determining the lifetime of MEMS devices. We studied cubic SiC (3C-SiC) films grown on Si substrates, which are chemically inert, can withstand high temperatures, and have a high resistance to oxidation. Silicon carbide also has excellent electronic and thermal properties, including large reverse breakdown voltage, high electron mobility, high saturated electron drift velocity and excellent thermal conductivity relative to Si [3], making SiC attractive for MEMS applications under hostile conditions. Present trends indicate an increasing interest in the cubic polycrystalline form of SiC, namely poly-3C-SiC, as a MEMS material since it can be deposited on various substrates and micromachined in a similar fashion to Si [4]. Silicon carbide exists in more than 200 polytypes, but only a few are useful in fabricating semiconductor devices, of which 3C-SiC has been widely developed for semiconductors. Since silicon carbide can exist in both polycrystalline and single crystal forms, it is important to compare which film is best suited for MEMS applications by measuring their relative mechanical properties. There are various methods used in determining the mechanical properties of thin films, including the bulge test, micro-beam bending, the micro tensile test [2], nanoindentation, etc. In this paper nanoindentation was used to characterize the mecha
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