| 초록 |
Recently, there have been many efforts to use piezoelectric thin film as sensors or actuators to be applied in the field of high-speed AFM (Atomic Force Microscopy) and nano data storage. In this paper, Lead Zirconate Titanate (PZT) degradation during wafer level bonding of thermo-piezoelectric cantilevers with CMOS-wafer was investigated for the application of nano data storage system. It was found that polyimide film which serves as a height adjustment during wafer level bonding between cantilevers and CMOS-wafer caused significant damage in PZT sensor when polyimide was coated entirely on the PZT capacitor followed by heating to 300 oC for bonding process. FTIR (Fourier Transform Infrared Spectroscopy) was used to analyze the reaction product that caused PZT capacitor damage. It was found that NH2 or NH3+ peaks from the sample with Polyimide exposed PZT capacitor were found and these peaks were not detected on a sample with PZT capacitor or on a polyimide coated sample only. These hydrogen ions contained in NH2 or NH3 stretch during heating can lead to hydrogen atmosphere annealing which can attack PZT significantly. With polyimide being hydrogen-rich, Pt served as an active catalyst to decompose H2 molecule to atomic hydrogen during bonding process. However, for the sample with Polyimide coating only on top electrode, degradation was minimized. Therefore, PZT damage was minimized successfully by optimizing polyimide coated area during integration. |
