Direct Printing of Lead Zirconate Titanate Thin Films
S. Bathurst, H.W. Lee, and S. G. Kim
We reported a new method for depositing lead zirconate titanate (PZT) thin films based on thermal ink jet printing of a modified sol-gel. It is well known that the strong piezoelectric and ferroelectric coupling present in perovskite phase PZT make it an attractive material for memory applications as well as for MEMS based sensors, actuators, and energy harvesters [1]-[4]. However, the use of PZT in MEMS has thus far been limited due to a lack of compatibility with existing processing techniques. Significant work has been done towards developing reliable PZT deposition methods and towards integrating those methods with established semiconductor manufacturing processes [5]. Direct printing of PZT has several advantages over current methods. First, by placing the sol-gel based ink only where needed, printing enables PZT deposition without requiring patterning. This eliminates the need for photolithography or any type of masking, which shortens the manufacturing lead time and enables the possibility of rapid prototyping of PZT based devices. Direct printing also leads to a reduction in the amount of sol-gel consumed during deposition which, in combination with the removal of photolithography and etching, significantly reduces manufacturing costs. Finally, this deposition method offers increased flexibility over current methods by allowing for controlled deposition over non-planar topographies. This provides an improvement in step coverage over spin coated films and enables uniform deposition on and around large out of plane features.
This work in thermal ink jetting of PZT sol-gel includes modeling of droplet/surface interactions, printing parameter and PZT ink composition optimization, and the fabrication of a ferroelectric capacitor test device. In dot on demand printing the ratio of Reynolds number to the Webber number characterizes the dynamics associated with droplet formation. The test device was a simple capacitor structure with approximately 400nm of printed PZT between two platinum electrodes.
S. Bathurst, J. Jeon, H.W. Lee and S.G. Kim, ”PZT MEMS by Thermal Ink Jet Printing,” Solid-State Sensor and Actuator Workshop, Hilton Head, SC, 2008
