X. Wang et al., "Monolithic Integration of ScAlN MEMS Filter on RFSOI Using ALD Al2O3 as VHF Barrier," 2023 22nd International Conference on Solid-State Sensors, Actuators and Microsystems (Transducers), Kyoto, Japan, 2023, pp. 1240-1243
Abstract:
We present a novel low-temperature process approach that enables the monolithic integration of scandium-doped aluminum nitride (ScAlN)-based radio frequency (RF) micro electromechanical system (MEMS) filters with RF switches. A planarized SiO2-based ankle and cavities for the MEMS device were established through a three-step process: 1) swimming pool pattern and etch, 2) passivation of the side wall and bottom of the swimming pool with atomic layer deposited Al2O3, and 3) swimming pool refill with SiO2 and planarization. ScAlN film based bulk acoustic resonators (FBAR) filters were then fabricated on the planarized surface, and eventually undercut was formed using vapor hydrofluoric acid (VHF) etch. The highest process temperature is 350 °C in the whole integration flow. The approach enabled successful integration of a ScAlN-based MEMS filter on top of the radio-frequency integrated circuit switch wafer. The integrated FBAR shows a center operation frequency of 2.58 GHz, bandwidth of 117 MHz, and an insertion loss of 3.7 dB. The integrated filter with switch has a footprint of 1mm2.
License type:
Publisher Copyright
Funding Info:
This research / project is supported by the Agency for Science, Technology and Research - Ferroelectric Aluminum Scandium Nitride (Al1-xScxN) Thin Films and Devices for mm-Wave and Edge Computing (WP5)
Grant Reference no. : A20G9b01