Low Impedance ALD HfO2 Partially-Filled-Gap Flexural and Bulk MEMS Resonators Piezoresistively Detected for Distributed Mass Sensing

Abstract

This paper reports the design and characterization of partially-filled-gap capacitive MEMS resonators for distributed mass sensing applications. By filling the gap with HfO2, the coupling coefficient between electrode-resonator increases by ×6.67 times and the motional resistance decreases by ×12 times in comparison with its counterpart in air. An improvement by a factor of ×5.6 in the Signal-To-Noise Ratio (SNR) for DC bias up to ×2.8 lower is accomplished by performing a piezoresistive detection instead of capacitive detection. Quality factor (Q) of 11,350 and motional resistances (Rm) of 926 Ω have been achieved for Parallel Beam Resonators (PBR) vibrating at 22.231 MHz. For the first time, ALD HfO2 partially-filled-gap MEMS resonators are proven to achieve inertial distributed mass sensitivities of the order of 4.28 kHz/pg for beam-type and 1.8k Hz/pg for disk resonators.

Keywords

• micromechanical resonator
• MEMS resonator
• MEMS
• microsystems
• microfabrication
• silicon on insulator
• quality factor
• resonance frequency
• mass sensing
• mass sensor
• Atomic Layer Deposition (ALD)
• high-k dielectric
• hafnium oxide