4.2.1. Material: Lead zirconate titanate (PZT)
PZT is a short for lead zirconate titanate inorganic compound that has a chemical formula of Pb [ZrxTi1-x] O3 (0 ≤ x ≤ 1). PZT is made and composed of the two chemical elements lead and zirconium combined with the chemical compound titanate while formed under extremely high temperatures. The dielectric constant of PZT can range from 300 to 3850, depending upon orientation and doping. PZT possesses piezoelectric effect meaning that it changes shape as an electric field is applied. PZT material generates a potential difference across its two faces when compressed. In addition, PZT material changes its shape when an external electric field is applied. These piezoelectric characteristics can be very useful in MEMS area for sensor or actuator applications.[2,17–19]
4.2.2. PZT Dicing
PZT dicing was done in a dicing saw machine. Prior to performing the dicing procedure, the startup steps in the machine have to be completed. This includes ensuring the air, wheel coolant, and spindle coolant supply are enabled. Safety first has to be the concern since this machine has a blade running at 30,000 rpm. It will cut the PZT dice at a speed of 0.4 mm/s. Procedure begins with attaching the dicing tape on the back of the PZT wafer, which then placed on the chuck table by hand. Then, the operator performs the alignment manually through a microscope with two objective lenses. Only the cutting sequence is automatic, while washing and drying is performed externally. Once aligned, operator pushes the start button and the dicer cut the line detected during alignment. Shown in figure below is the mark on the PZT that determines where to align the blade. Figure 10. PZT wafer is 72mm by 72mm with thickness of 0.2mm, will be cut into 6 pieces for each device. 4.2.3. Nickel Wet Etching The PZT wafer purchased is 200 μm thick and has been manufacture-coated by nickel layer of 3000 Å. …show more content…
The nickel layer typically has a purpose as a conducting metal used for sending a potential difference to vibrate the PZT by piezoelectric effect. In addition, the nickel layer is also has a role as a mechanical support having PZT is fragile. Piezo electrode patterning incorporates wet etching process using liquid chemicals or etchants to take off materials from its substrate. The etchant used in this lab is Nickel etchant TFB composed of nitric acid, potassium perfluoroalkyl sulfonate and water. In this lab, our focus is to study the use of wet etching to etch Nickel layer on the PZT wafer. Nickel layer is uniformly manufacture-deposited on the PZT substrate will be etched using wet etching process. AZ5214 photoresist will be used to protect the wanted area given a pattern for the photolithography process. The photolithography is intended to pattern nickel layer creating electrodes to vibrate the PZT material. The photoresist patterns for the electrodes appear to be well transferred from the photomask. This shows a good photolithography has been performed prior to the metal etching. After the photoresist is deposited and patterned on the nickel layer on PZT, the nickel layer uncovered by the photoresist is etched to create electrode pattern. Shown in figures below are the images of the nickel pattern after etching process is completed. Figure 11. The photoresist is removed after the nickel etching is completed leaving patterned nickel electrodes (left). Nickel electrode, shown in light grey, is reservoir patterned on the PZT wafer observed under microscope (right). The dark region represents the bare PZT wafer while the bright region represents the nickel electrodes. The good contrast and cleanliness between the regions indicate that the etching has completely taken off the nickel at the desired region. These figures above also shown that there were no sign of under-etch and over-etch during the process. This is important due to the electrode will be used for biasing the PZT material to generate the vibration in the device. 4.2.4. Parylene Coating Procedure to process the parylene coating begins with weighting the dimer for 0.8 grams. Vacuum was initially at 995 (1 atm) and has been brought down to 63 with a mechanical pump, then brought to lower pressure with a cold trap to 4. Based on a literature,[13] the transducer is non-linear and has been calibrated
PZT is a short for lead zirconate titanate inorganic compound that has a chemical formula of Pb [ZrxTi1-x] O3 (0 ≤ x ≤ 1). PZT is made and composed of the two chemical elements lead and zirconium combined with the chemical compound titanate while formed under extremely high temperatures. The dielectric constant of PZT can range from 300 to 3850, depending upon orientation and doping. PZT possesses piezoelectric effect meaning that it changes shape as an electric field is applied. PZT material generates a potential difference across its two faces when compressed. In addition, PZT material changes its shape when an external electric field is applied. These piezoelectric characteristics can be very useful in MEMS area for sensor or actuator applications.[2,17–19]
4.2.2. PZT Dicing
PZT dicing was done in a dicing saw machine. Prior to performing the dicing procedure, the startup steps in the machine have to be completed. This includes ensuring the air, wheel coolant, and spindle coolant supply are enabled. Safety first has to be the concern since this machine has a blade running at 30,000 rpm. It will cut the PZT dice at a speed of 0.4 mm/s. Procedure begins with attaching the dicing tape on the back of the PZT wafer, which then placed on the chuck table by hand. Then, the operator performs the alignment manually through a microscope with two objective lenses. Only the cutting sequence is automatic, while washing and drying is performed externally. Once aligned, operator pushes the start button and the dicer cut the line detected during alignment. Shown in figure below is the mark on the PZT that determines where to align the blade. Figure 10. PZT wafer is 72mm by 72mm with thickness of 0.2mm, will be cut into 6 pieces for each device. 4.2.3. Nickel Wet Etching The PZT wafer purchased is 200 μm thick and has been manufacture-coated by nickel layer of 3000 Å. …show more content…
The nickel layer typically has a purpose as a conducting metal used for sending a potential difference to vibrate the PZT by piezoelectric effect. In addition, the nickel layer is also has a role as a mechanical support having PZT is fragile. Piezo electrode patterning incorporates wet etching process using liquid chemicals or etchants to take off materials from its substrate. The etchant used in this lab is Nickel etchant TFB composed of nitric acid, potassium perfluoroalkyl sulfonate and water. In this lab, our focus is to study the use of wet etching to etch Nickel layer on the PZT wafer. Nickel layer is uniformly manufacture-deposited on the PZT substrate will be etched using wet etching process. AZ5214 photoresist will be used to protect the wanted area given a pattern for the photolithography process. The photolithography is intended to pattern nickel layer creating electrodes to vibrate the PZT material. The photoresist patterns for the electrodes appear to be well transferred from the photomask. This shows a good photolithography has been performed prior to the metal etching. After the photoresist is deposited and patterned on the nickel layer on PZT, the nickel layer uncovered by the photoresist is etched to create electrode pattern. Shown in figures below are the images of the nickel pattern after etching process is completed. Figure 11. The photoresist is removed after the nickel etching is completed leaving patterned nickel electrodes (left). Nickel electrode, shown in light grey, is reservoir patterned on the PZT wafer observed under microscope (right). The dark region represents the bare PZT wafer while the bright region represents the nickel electrodes. The good contrast and cleanliness between the regions indicate that the etching has completely taken off the nickel at the desired region. These figures above also shown that there were no sign of under-etch and over-etch during the process. This is important due to the electrode will be used for biasing the PZT material to generate the vibration in the device. 4.2.4. Parylene Coating Procedure to process the parylene coating begins with weighting the dimer for 0.8 grams. Vacuum was initially at 995 (1 atm) and has been brought down to 63 with a mechanical pump, then brought to lower pressure with a cold trap to 4. Based on a literature,[13] the transducer is non-linear and has been calibrated