Papers by Author: Thanh Dau Van

Abstract: Piezoelectric energy harvester with high output and low resonant frequency is required in wireless sensors and portable devices. It can be fabricated by bonding of the bulk PZT ceramics with excellent piezoelectric properties to the Si wafer. Firstly, the basic design principles of piezoelectric energy harvester were analyzed. Then, the novel process flow to manufacture piezoelectric energy harvester using bulk PZT was explored. Using 2µm Au layer as the bonding layer, the bulk PZT was bonded to Si wafer at the temperature of 5500C for 2 hours. With the lapping technique, the thickness of bulk PZT is reduced from 300µm to 60µm. KOH was used to etch the backside of Si from 500µm to 20µm as the supporting layer of the piezoelectric beam. The last procedure was to dice the wafer into many cantilevers with different length or width. One of PZT piezoelectric cantilevers was tested using a mechanical shaker, by applying a sinusoidal oscillation at different frequencies. The resonant frequency is 815 Hz, and the voltage output is around 632 mV at 0.5g. The result shows that the sample has excellent ability to harvest energy of vibration and the novel bonding technology is quite feasible.

Abstract: As an energy conversion material, piezoelectric ceramic lead zirconate titanate (PZT) has been used in a wide range of areas. And a PZT wafer bonding with a silicon wafer technology is a promising method to fabricate micro-sensors and micro-actuators using well-established silicon machining techniques. In order to obtain the excellent piezoelectricity and suitable thickness from the bulk PZT, a method is presented. It is to bond a bulk PZT onto a silicon wafer via an intermediate layer. In this paper, two bonding methods are presented. One is to bond a bulk PZT with a silicon wafer by anodic bonding technique using a thin glass film as the intermediate layer. The other is to bond a bulk PZT with a silicon wafer by eutectic bonding using a thin gold film as the intermediate layer. The glass film is 2µm in thickness, deposited by sputtered method. Anodic bonding conditions are: 0.8MPa in pressure, 500 oC in temperature, 250V in voltage and different bonding time. The bonding strength test shows that the maximum bond strength is 13.93 MPa when the bonding time was 60 min. It is void-free structure in the interface of the PZT-Glass-Si structure. The gold film is 1.6µm in thickness, deposited by evaporation method. The eutectic bonding conditions are: 0.8MPa in pressure, 500 oC in temperature, and different bonding time. The bond strength of the PZT-Au-Si structure was tested and the maximum value was 13.19 MPa when the bonding time was 60 min.