Low-Stress CMOS-Compatible Silicon Carbide Surface-Micromachining Technology—Part II: Beam Resonators for MEMS Above IC

Abstract

Microelectromechanical beam resonators and arrays are fabricated using a custom low-temperature complementarymetal-oxide-semiconductor-compatible silicon carbide microfabrication process, detailed in Part I of this paper. Theoretical aspects are presented with modal analysis and numerical methods. Measurements of the resonant frequency, the quality factor, the transmission, and the tuning characteristics are presented for different device types and dimensions. Trends are analyzed, and performance metrics dependences are investigated. A tuning method based on integrated heaters is introduced and tested, yielding a very desirable constant insertion-loss tuning and a wide tuning range. Quality factors of up to 1493 and resonant frequencies of up to 26.2 MHz are demonstrated. Both the Young's modulus and the residual stress of the SiC film are extracted (261 GPa and < ±30 MPa, respectively), and favorably compare to values reported for polysilicon. [2010-0235] Index Terms-Micromechanical resonators, microelectromechanical systems (MEMS), resonator arrays, silicon carbide (SiC), surface micromachining, thermal tuning.

Thermal- and Piezo-Tunable Flexural-Mode Resonator With Piezoelectric Actuation and Sensing

“…The negligible variation of the insertion loss (Fig. 3) is consistent with previous findings with the electrostatically actuated and electrothermally tuned resonators [18].…”

Quantitative wafer mapping of residual stress in electroplated NiFe films using independent strain and Young's modulus measurements

“…The measured Young's modulus ranged between 293 GPa and 333 GPa for the free end deflection, and 281 GPa to 302 GPa for the deflection close to the anchor. Although these numbers fit in the reported range values for micro machined 3C-SiC [16] [17], the force range is so low that the instrument performance is close to its limit, as the jumps in figure 5 show. For this reason stiffer cantilevers fabricated with thicker electroplated films were employed for further experiments.…”

Low-Stress CMOS-Compatible Silicon Carbide Surface-Micromachining Technology—Part I: Process Development and Characterization

“…Measurement results of fabricated resonators are presented in a second part of this paper [19], and recently, systems including these resonators were demonstrated successfully. Notably, MEMS-based oscillators and frequency synthesizers were tested and showed promising results, suggesting that the integration potential enabled by the process could lead to more compact and lower cost systems [52]- [54].…”

“…Subsequent sections provide details on the synthesis, characterization, etching, and release of the SiC thin films, and in conclusion, fabricated devices are presented. Detailed results for the performance of beam resonators fabricated with this technology are presented in Part II of this paper [19].…”