Abstract
This manuscript describes the findings of a study to investigate the performance of SiC MEMS resonators with respect to resonant frequency and quality factor under a variety of testing conditions, including various ambient pressures, AC drive voltages, bias potentials and temperatures. The sample set included both single-crystal and polycrystalline 3C-SiC lateral resonators. The experimental results show that operation at reduced pressures increases the resonant frequency as damping due to the gas-rarefaction effect becomes significant. Both DC bias and AC drive voltages result in nonlinearities, but the AC drive voltage is more sensitive to noise. The AC voltage has a voltage coefficient of 1∼4ppm/V at a DC bias of 40V. The coefficient of DC bias is about -11ppm/V to - 21ppm/V for poly-SiC, which is more than a factor of two better than a similarly designed polysilicon resonator (-54 ppm/V). The effective stiffness of the resonator decreases (softens) as the bias potential is increased, but increases (hardens) as drive voltage increase when scan is from low to high frequency. The resonant frequency decreases slightly with increasing temperature, exhibiting a temperature coefficient of -22 ppm/°C, between 22°C and 60°C. The thermal expansion mismatch between the SiC device and the Si substrate could be a reason that thermal coefficient for these SiC resonators is about twofold higher than similar polysilicon resonators. However, the Qs appear to exhibit no temperature dependence in this range.
Highlights
MEMS-based resonators have attracted the attention of the integrated circuits (IC) industry because of their high quality factors (Qs) and their capacity for integration with silicon-based integrated circuits [1, 2]
Extreme biasing can cause nonlinearities at large amplitudes, and cause the nominal Q and resonant frequency to shift. In view of these effects in Si-based devices, this work aims to characterize the performance of 3C-Silicon carbide (SiC) MEMS lateral resonators in terms of resonant frequency and Q as they relate to pressure, temperature and applied voltages
The results of this study show that SiC lateral resonators exhibit a resonant frequency shift along with ambient pressure due to a compact damping of gas-rarefaction effect much like similar devices made from polysilicon
Summary
MEMS-based resonators have attracted the attention of the integrated circuits (IC) industry because of their high quality factors (Qs) and their capacity for integration with silicon-based integrated circuits [1, 2]. Silicon-based MEMS resonators are used as timing references in applications that require a device technology that can range from very low to ultra-high frequencies. Silicon carbide (SiC) is a promising material for RF MEMS because it has a high Young’s modulus-to-density ratio, resulting in an acoustic velocity that is significantly above that of Si [3, 4]. SiC is more resistant to mechanical wear, more electrically stable at higher temperatures, and significantly more inert to environmental conditions than Si, making it a potential substitute for Si in harsh environment applications [5]. Many of the essential characteristics of Si-based MEMS resonators, such as operating frequency and Among more than 100 known polytypes, cubic 3C-SiC is the only polytype that can be grown on single crystal Si substrates, enhancing the possibility of integrating micromachined SiC resonators with silicon microelectronics.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
