Large piezoelectricity on Si from highly (001)-oriented PZT thick films via a CMOS-compatible sputtering/RTP process

Abstract

Integration of lead zirconate titanate (PZT) ferroelectrics into CMOS-Si technology has become a perennial challenge due to the continuously shrinking thermal budget in semiconductor processing. In this work, Pb(Zr0.53Ti0.47)O3 (PZT) thick films (∼1 µm) were prepared on LaNiO3 buffered (111)Pt/Ti/SiO2/(100) Si substrates via a low temperature (350 °C) sputtering deposition followed by a rapid thermal process (RTP). This two-step fabrication process resulted in a highly (001)-oriented perovskite PZT film with a dense, fine-grain morphology and reduced strains, hence an optimal electrical performance intrinsic to the chemical composition was achieved. EDS and XPS analyses verified a desirable evolution of the chemical stoichiometry in the RTP, as well as the expected chemical bonding states of the elements in the annealed films. Moreover, prototypical piezoelectric thin film cantilevers fabricated from the PZT/LaNiO3/Pt/Ti/SiO2/(100)Si heterostructure yielded a large transverse piezoelectric coefficient (e31,f) up to 15.7 C/m2, together with a high coupling coefficient k2∼0.23 for energy conversion efficiency. The PZT films showed high e31,f coefficients (∼10 C/m2) even when the RTP annealing time was reduced down to 2 min. Such a piezoelectric performance is close to the highest ones reported in the literature from epitaxial or highly-oriented PZT films, which require a much higher thermal budget for processing. These high quality PZT films open up many possibilities for the integration of piezoelectricity into Si-based micro-electro-mechanical systems (MEMS).