Modeling of in-plane thin film piezoelectric on silicon MEMS Resonator for RF

  • 16



Name of the Speaker: Bhadri Narayanan K N (EE15D055)
Guide: Dr. Amitava DasGupta
Co-guide : Dr. Deleep R Nair
Date/Time: 16th March 2023, 3pm

In wireless communication systems, high frequency acoustic resonators are used as filters and frequency reference oscillators. Commonly used resonators are surface acoustic wave resonator, FBAR and quartz crystal resonator. Crystal resonators are used as clock generator due to high quality factor and excellent temperature frequency stability. The drawback of these resonators is their bulky size and incompatible fabrication process, which hamper the integration of the high performance oscillators with CMOS circuits. One possible candidate to replace the bulky oscillators is high Q-factor micromachined MEMS resonator, which provides an avenue to bring low power multi modal filters, oscillators and sensors on-chip. Thin film piezoelectric on Silicon (TPoS) technology enables high frequency resonators with low motional impedance, relatively high Q-factor and high linearity. The TPoS resonator comprises of a piezoelectric layer sandwiched between two metal electrodes on Silicon, which is low acoustic loss material. In this work, we had studied the effect of physical dimensions such as length, width and thickness of the TPoS MEMS resonator operating at 1 GHz on its performance. The effects of geometrical dimensions, the order of excitation, and number of anchors on Q-factor were modeled considering different loss mechanisms and excellent agreement with experimental data is achieved. For a resonator of 225 μm width excited in its 23rd mode of resonance at 990 MHz, the measured motional resistance, unloaded quality factor in vaccum and linear thermal coefficient of frequency were 107 Ω, 9556 and -28 ppm respectively. The measured unloaded quality factor is the highest reported in literature for TPoS resonators in this frequency range.