CMOS-Integrated Aluminum Nitride MEMS: A Review

• Published in: Journal of microelectromechanical systems Vol. 31; no. 4; pp. 500 - 523
• Main Authors: Pinto, Rui M. R., Gund, Ved, Dias, Rosana Alves, Nagaraja, K. K., Vinayakumar, K. B.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.08.2022; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Acoustic properties; AlN; Aluminum; Aluminum nitride; Bulk acoustic wave devices; CMOS; Dielectric strength; Energy harvesting; Flexible components; Gallium nitrides; Gas sensors; III-V semiconductor materials; integration; Lead zirconate titanates; Lithium niobates; Material properties; MEMS; Microelectromechanical systems; Micromechanical devices; Microphones; Modulus of elasticity; monolithic; Piezoelectric effect; Piezoelectricity; Resonators; Sensors; SoC; Strain; Thermal conductivity; Thin films; Transducers; Zinc oxide
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2022.3172766

Aluminum nitride (AlN) has gained wide interest owing to its high values of elastic modulus, band gap, dielectric strength, resistivity, thermal conductivity and acoustic velocities, especially because it retains most of its properties and versatility in the thin-film form. This review focuses on applications where the CMOS integration of AlN MEMS has been effectively demonstrated. First, the fundamental concepts of piezoelectricity on polycrystalline <inline-formula> <tex-math notation="LaTeX">c </tex-math></inline-formula>-axis oriented thin-films are introduced and AlN is compared to other common piezoelectric materials, namely LiNbO 3 , LiTaO 3 , quartz, lead zirconate titanate (PZT), ZnO and GaN by thoroughly discussing the material properties, processing and technological implications. After presenting the possible MEMS-CMOS integration strategies, recent demonstrations of AlN-based devices are reviewed, namely energy harvesters, film bulk acoustic resonators (FBAR), contour mode resonators (CMR), gas sensors, imagers, microphones, transducers for chip-scale communication and calorimetric sensors. Finally, other recent applications/integration opportunities are outlined for AlN-based micro-mirrors, flexible sensors and transducers for liquid media and harsh environments. [2022-0006]