Etching characteristics of PZT thin films and via hole patterning for MMIC capacitors

This paper reports on the etching characteristics of lead zirconate titanate (PZT) thin films and their subsequent employment in thin film capacitors for microwave integrated circuits. Via holes to provide ground paths were constructed using electron beam lithography (EBL) and wet chemical etching. Various compositions of wet etchant were investigated and the images of etched areas were examined in order to find the most suitable etchant for PZT thin films. The successful etched via holes were metallized with 800 A Au using sputtering technique. The via holes were then subjected to a continuity test before characterized using 10 times 10 and 20times 20 mum² capacitor structures at microwave frequencies. From the scanning electron microscopy (SEM) images obtained, etching using the composition of 0.5HF:5HCl:10NH₄Cl:50H₂O resulted in the best results. The traces obtained in Smith chart confirmed that via holes were successfully fabricated on PZT thin films and the contact resistance of the via holes were measured to be between 7 - 20 Omega.