HF dielectric properties of PZT thin films processed by sol-gel method on 3-inches Si wafers

Abstract

PZT thin films were processed by sol gel method on Pt electrodes on Si/SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> wafer. Microstructure and orientation of PZT thin films depend on the quality of bottom Pt electrodes. The Pt electrodes were deposited by evaporation or RF-sputtering. Three multilayers were investigated: (Si/SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> /Ti/Pt/Au/Pt), (Si/SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> /Ti/Pt) and (Si/SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> /Ta/Pt). Even though the Pt bottom electrodes were oriented along the [111] axis, crystallization of PZT thin films by thermal annealing led to an [100] oriented structure in the case of a sputtered Pt electrode. Whereas in the case of an evaporated Pt electrode it led to a random orientation. Strong inter diffusion at Pt/Au or Pt/Ti interfaces was observed at 650°C for 30mn. The influence of concentration solution and crystallization temperature were investigated between 700°C and 500°C. Dielectric and ferroelectric properties were correlated with the film thickness (100 nm&#60;t&#60;1000nm) to determine the “dead interfacial layer”. HF lines were processed on 3 inch substrate to realize “frozen MEMS”. Isolation and insertion loss as a function of frequency from 1GHz to 20GHz are also presented.