Design and Simulation of a Mass Sensor Using Nanoscale Hf_0.5Zr_0.5O₂ Piezoelectric Membranes with Loading Platform

Area of Science:

• Materials Science
• Nanotechnology
• Sensor Technology

Background:

• Micro/nanoelectromechanical systems (MEMS/NEMS) resonant mass sensors are vital for label-free gravimetric detection.
• Existing sensors face challenges in loading repeatability and mass loading position dependence.
• High sensitivity and robustness are crucial for practical gravimetric sensing applications.

Purpose of the Study:

• To propose and characterize a novel suspended resonant mass sensor utilizing an ultrathin Hf_0.5Zr_0.5O₂ (HZO) piezoelectric film.
• To investigate the influence of residual stress and platform geometry on sensor performance.
• To achieve repeatable picogram-level mass sensing with reduced position dependence.

Main Methods:

• Fabrication combining SOI micromachining and wet transfer of ultrathin HZO film.
• Development of a Kirchhoff plate model to analyze residual stress and geometry effects.
• Characterization using Laser Doppler Vibrometry and Finite Element Simulations.

Main Results:

• Achieved a first-order resonant frequency of 1.303 MHz and a quality factor of 342.
• Extracted residual stress of approximately 1.319 GPa.
• Demonstrated uniform displacement distribution and linear frequency response for mass loading from 0 to 1 ng.
• Obtained mass sensitivities of 150.7 Hz/pg (FE) and 166.8 Hz/pg (analytical).

Conclusions:

• The proposed suspended resonant mass sensor with a central silicon platform and ultrathin HZO film offers a robust platform.
• The design addresses key limitations of existing sensors, improving loading repeatability and reducing position dependence.
• This work presents a viable approach for highly sensitive, repeatable picogram-level resonant mass sensing using piezoelectric films.