The effects of residual stresses in the composite diaphragm on the performance of piezoelectric microspeakers

• Published in: Electronic materials letters Vol. 9; no. 1; pp. 119 - 123
• Main Authors: Ur, Soon-Chul, Kim, Eun-Sok, Yi, SeungHwan
• Format: Journal Article
• Language: English
• Published: Springer The Korean Institute of Metals and Materials 2013; 대한금속·재료학회
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Chip formation; Condensed Matter Physics; Diaphragms; Electrodes; Materials Science; Nanotechnology; Nanotechnology and Microengineering; Noise levels; Optical and Electronic Materials; Packaging; Piezoelectricity; Residual stress; Resonant frequencies; 전자/정보통신공학; residual stress; AlN film; output pressure; piezoelectric microspeaker; sound pressure level
• ISSN: 1738-8090; 2093-6788
• DOI: 10.1007/s13391-012-2141-8

Piezoelectric microspeakers are fabricated with AlN film on circular and square Mo/Ti electrodes, and the acoustic pressures are measured with and without packaging structure as a function of frequency. As residual stresses of the composite diaphragm are decreased from +20 MPa to −20 MPa, the output pressure of the fabricated chip (square electrodes) is increased from 1.16 mPa to 96.2 mPa. The packaged microspeaker shows enhanced uniform sound pressure level (SPL) from 1 kHz to 15 kHz with more than 100 dB SPL at 2.50 kHz, with square electrodes in particular. For the circular electrodes, the resonant frequency is revealed to be 3.06 kHz, and the SPL at resonant frequency is measured at 107 dB, which is somewhat higher than for the square electrode. However, the output pressures of the microspeaker show lower values than that of the square electrodes at 1 kHz sinusoidal frequency.