Reliable Pb(Zr,Ti)O3-based thin film piezoelectric micromirrors for space-applications

Abstract

Although Pb(Zr,Ti)O3 (PZT) piezoelectric thin films are finding widespread applications on Earth, it is yet unclear if they are suitable for space-related applications. In space, their long-term reliability is a significant concern due to the difficulties of repairing and replacing malfunctioning devices. In this work, PZT thin film micromirrors for compact interferometric 3D imaging systems have been exposed to operating conditions encountered on a space mission and tested according to criteria set by the European Space Agency. Thermal cycling in vacuum, sinusoidal and random mechanical vibrations, and [Formula: see text]-radiation with and without bias did not degrade key functional device properties of the micromirror such as angular deflection, resonance frequency, polarization, and permittivity. Apart from [Formula: see text]-radiation, stressing the devices enhanced their large-signal angular deflection and improved their electrical lifetime compared to pristine devices. Their dielectric and ferroelectric characteristics remained comparable to that of a lab-scale environment. Simultaneously applying a 10 V field-down bias while [Formula: see text]-radiating the micromirrors changed the capacitance-field and polarization-field characteristics and enhanced the electrical imprint. After stress-testing, the median time-to-failure in moderate acceleration conditions of 150 kV/cm and 175 °C ranged from 1.95 to 2.64 h, close to 2.11 h as measured for a reference group. All actuator membranes had shorter electrical lifetimes, smaller voltage acceleration factors, and smaller activation energies, ranging from 2.56 to 2.88 V−1 and 1.03 to 1.09 eV, than simple bonding pads. This work is a device-level report covering a full set of space-relevant tests demonstrating that PZT-based thin film piezomicroelectromechanical systems technology is space-ready.

Dynamic piezoelectric MEMS-based acoustic attenuators

“…For PZT, the mechanisms driving electrical degradation in a static electric field are the same at room and elevated temperatures, so that the electrical lifetime can be extrapolated to the relevant conditions 18 . Inserting values for activation-energy and voltage-acceleration obtained in previous work 7 ; 𝐸𝐸 𝐴𝐴 = 1.03 [eV], n = 2.56, in the empirical Prokopowicz-Vaskas relation 19 , the extrapolated electrical lifetime at 30 [V]/30 [ o C] is close to 5000 years. This indicates that the piezoMEMS, even when driven at maximum operating voltage, will not fail electrically within a potential product lifetime.…”

“…electromagnetic 15 , or thermal 16 actuation and lower than or comparable to electrostatic 17 . Highly accelerated lifetime testing (HALT) 7,18,19 from a sample set of 12 devices at V P = 30 [V] and 175 [ o C], showed a median time to failure of 126 [h] within a 95 [%] confidence interval of 111-140 [h] and Weibull modulus of 5.4 20 . For PZT, the mechanisms driving electrical degradation in a static electric field are the same at room and elevated temperatures, so that the electrical lifetime can be extrapolated to the relevant conditions 18 .…”

“…The slits would act as filter elements enabling adjustable acoustic responses. In recent years, thin film piezoelectric MEMS (piezoMEMS) has emerged as a promising technology for addressing challenges with scalability, power consumption, and operational reliability 7 . This technology utilizes the piezoelectric in-plane deformation of a µm thick piezoelectric layer-stack clamped on a substrate to induce mechanical bending in response to an applied electric field.…”

On the Evolution of Stress and Microstructure in Radio Frequency-Sputtered Lead-Free (Ba,Ca)(Zr,Ti)O3 Thin Films

“…BCZT-based compositions have reported values of 11 < α BCZT < 17 µm/K, and required crystallization temperatures of up to 800 • C [25,26]. In comparison, PZT has a CTE of α PZT ~4.5 µm/K, and is typically deposited around 650 • C [2,20,27]. Thus, better CTE-matched substrates, such as (001)-oriented SrTiO 3 (STO) with α STO ~9.4 µm/K [15], or MgO with α MgO ~13.5 µm/K [28], are often used experimentally.…”

“…Lead-containing ferroelectric perovskite oxides, such as Pb(Zr, Ti)O 3 (PZT) and (PbMg 1/3 Nb 2/3 O 3 ) 1−x -(PbTiO 3 ) x (PMN-PT), possess some of the largest piezoelectric responses, which are required for sensors and actuators based on thin-film piezoelectric microelectromechanical systems (piezoMEMSs) [1,2]. However, their content of toxic lead raises environmental concerns [3] and renders them inapplicable for a range of biomedical applications, such as bone regenerative therapy [4] and in-body energy harvesters for powering implanted medical devices [5,6].…”