This paper studies the static deformation behavior of a piezoelectric micromachined ultrasonic transducer （PMUT） actuated by a strong external electric field. The transducer membrane consists of a piezoelectric laye...This paper studies the static deformation behavior of a piezoelectric micromachined ultrasonic transducer （PMUT） actuated by a strong external electric field. The transducer membrane consists of a piezoelectric layer, a passive layer and two electrode layers. The nonlinearities of the piezoelectric layer caused by electrostriction under a strong electric field are analyzed. Because the thickness of the transducer membrane is on the microscale, the size dependence of the deformation behavior is evaluated using the couple stress theory. The results show that the optimal ratio of the top electrode diameter and the membrane diameter is around 0.674. It is also found that this optimal value does not depend on any other parameters if the thicknesses of the two electrodes are negligible compared with those of the piezo- electric and passive layers. In addition, the nonlinearities of the piezoelectric layer will become stronger along with the increase of the electric field, which means that softening of the membrane stiffness occurs when a strong external electric field is applied. Meanwhile, the optimal thickness ratio for the passive layer and the piezoelectric layer is not equal to 1.0 which is usually adopted by previous researchers. Because there exists size dependence of membrane deforma-tion, the optimal value of this thickness ratio needs to be greater than 1.0 on the microscale.展开更多
The mechanical characterization of a 4×4 air-coupled array of Piezoelectric Micromachined Ultrasonic Transducers(PMUTs)is pre-sented.The experimental campaign consists of three set of experi-mental tests,namely:t...The mechanical characterization of a 4×4 air-coupled array of Piezoelectric Micromachined Ultrasonic Transducers(PMUTs)is pre-sented.The experimental campaign consists of three set of experi-mental tests,namely:topography measurements,small signal dynamic measurements,and vibrometry in the non-linear dynamic regime.The behavior of three different kinds of PMUT are reported.They differ according to the thermo-electrical treatment that has been applied to the piezoelectric material.The presence of the fabrication induced residual stresses is investigated and the treat-ment effect is evaluated in terms of the initial deflected configura-tion.The results reported in this paper represent an experimental mechanical investigation useful for the design of PMUT structures with advanced functionalities in the linear and non-linear regime.展开更多
This paper presents a 591×438-DPI ultrasonic fingerprint sensor.The sensor is based on a piezoelectric micromachined ultrasonic transducer(PMUT)array that is bonded at wafer-level to complementary metal oxide sem...This paper presents a 591×438-DPI ultrasonic fingerprint sensor.The sensor is based on a piezoelectric micromachined ultrasonic transducer(PMUT)array that is bonded at wafer-level to complementary metal oxide semiconductor(CMOS)signal processing electronics to produce a pulse-echo ultrasonic imager on a chip.To meet the 500-DPI standard for consumer fingerprint sensors,the PMUT pitch was reduced by approximately a factor of two relative to an earlier design.We conducted a systematic design study of the individual PMUT and array to achieve this scaling while maintaining a high fill-factor.The resulting 110×56-PMUT array,composed of 30×43-μm^(2) rectangular PMUTs,achieved a 51.7% fill-factor,three times greater than that of the previous design.Together with the custom CMOS ASIC,the sensor achieves 2 mV kPa^(−1) sensitivity,15 kPa pressure output,75μm lateral resolution,and 150μm axial resolution in a 4.6 mm×3.2 mm image.To the best of our knowledge,we have demonstrated the first MEMS ultrasonic fingerprint sensor capable of imaging epidermis and sub-surface layer fingerprints.展开更多
基金supported by the National Natural Science Foundation of China (11172138, 10727201)
文摘This paper studies the static deformation behavior of a piezoelectric micromachined ultrasonic transducer （PMUT） actuated by a strong external electric field. The transducer membrane consists of a piezoelectric layer, a passive layer and two electrode layers. The nonlinearities of the piezoelectric layer caused by electrostriction under a strong electric field are analyzed. Because the thickness of the transducer membrane is on the microscale, the size dependence of the deformation behavior is evaluated using the couple stress theory. The results show that the optimal ratio of the top electrode diameter and the membrane diameter is around 0.674. It is also found that this optimal value does not depend on any other parameters if the thicknesses of the two electrodes are negligible compared with those of the piezo- electric and passive layers. In addition, the nonlinearities of the piezoelectric layer will become stronger along with the increase of the electric field, which means that softening of the membrane stiffness occurs when a strong external electric field is applied. Meanwhile, the optimal thickness ratio for the passive layer and the piezoelectric layer is not equal to 1.0 which is usually adopted by previous researchers. Because there exists size dependence of membrane deforma-tion, the optimal value of this thickness ratio needs to be greater than 1.0 on the microscale.
基金This work was supported by the ECSEL JOINT UNDERTAKING[826452].
文摘The mechanical characterization of a 4×4 air-coupled array of Piezoelectric Micromachined Ultrasonic Transducers(PMUTs)is pre-sented.The experimental campaign consists of three set of experi-mental tests,namely:topography measurements,small signal dynamic measurements,and vibrometry in the non-linear dynamic regime.The behavior of three different kinds of PMUT are reported.They differ according to the thermo-electrical treatment that has been applied to the piezoelectric material.The presence of the fabrication induced residual stresses is investigated and the treat-ment effect is evaluated in terms of the initial deflected configura-tion.The results reported in this paper represent an experimental mechanical investigation useful for the design of PMUT structures with advanced functionalities in the linear and non-linear regime.
文摘This paper presents a 591×438-DPI ultrasonic fingerprint sensor.The sensor is based on a piezoelectric micromachined ultrasonic transducer(PMUT)array that is bonded at wafer-level to complementary metal oxide semiconductor(CMOS)signal processing electronics to produce a pulse-echo ultrasonic imager on a chip.To meet the 500-DPI standard for consumer fingerprint sensors,the PMUT pitch was reduced by approximately a factor of two relative to an earlier design.We conducted a systematic design study of the individual PMUT and array to achieve this scaling while maintaining a high fill-factor.The resulting 110×56-PMUT array,composed of 30×43-μm^(2) rectangular PMUTs,achieved a 51.7% fill-factor,three times greater than that of the previous design.Together with the custom CMOS ASIC,the sensor achieves 2 mV kPa^(−1) sensitivity,15 kPa pressure output,75μm lateral resolution,and 150μm axial resolution in a 4.6 mm×3.2 mm image.To the best of our knowledge,we have demonstrated the first MEMS ultrasonic fingerprint sensor capable of imaging epidermis and sub-surface layer fingerprints.
