JMEMS Letters.1pt Characterization of a Temperature-Sensitive Nano Piezoelectric Mechanical Resonator With a 20nm Free-Standing Hf0.5Zr0.5O₂ Membrane

We studied the temperature effects on the resonant frequency of nano piezoelectric mechanical resonators based on Hf <tex-math notation="LaTeX">0.5</tex-math> Zr <tex-math notation="LaTeX">0.5</tex-math> O <tex-math notation="LaTeX">₂</tex-math> thin films. Two square-shaped resonators of 30 <tex-math notation="LaTeX">μ</tex-math> m and 50 <tex-math notation="LaTeX">μ</tex-math> m in length were fabricated and tested, having a resonant frequency of 225.8 kHz and 98.5 kHz, respectively. The temperature coefficient of frequency (TCF) of the devices was characterized in the range from <tex-math notation="LaTeX">$-$</tex-math> 20 <tex-math notation="LaTeX">∘</tex-math> C to 147 <tex-math notation="LaTeX">∘</tex-math> C. Both devices exhibited a positive TCF around 83.6 ppm/ <tex-math notation="LaTeX">∘</tex-math> C to 105 ppm/ <tex-math notation="LaTeX">∘</tex-math> C in the range from 30 <tex-math notation="LaTeX">∘</tex-math> C to 147 <tex-math notation="LaTeX">∘</tex-math> C, which may result from the combined effect of thermal expansion mismatch between the materials and the temperature coefficient of Young's modulus of the HZO material. Moreover, the 50 <tex-math notation="LaTeX">μ</tex-math> m device shows a negative TCF around <tex-math notation="LaTeX">$-$</tex-math> 110 ppm/ <tex-math notation="LaTeX">∘</tex-math> C to <tex-math notation="LaTeX">$-$</tex-math> 99.9 ppm/ <tex-math notation="LaTeX">∘</tex-math> C within the range from <tex-math notation="LaTeX">$-$</tex-math> 20 <tex-math notation="LaTeX">∘</tex-math> C to 30 <tex-math notation="LaTeX">∘</tex-math> C, which may be due to stress relaxation during the heating process. These results underscore the significance of HZO material in nanoscale piezoelectric resonator applications and lay the foundation for our future work aimed at developing nanoscale piezoelectric devices based on HZO.2024-0040