"Method of Growing PMN-PT Piezoelectric Material on Silicon”

Inventors: C.B. Eom (UWisconsin) and D. Schlom (PSU)
PSU Invention Disclosure No. 2004-2928
WARF Reference No. P04320US
 Licensing Contact: Matthew D. Smith

FIELD OF INVENTION
Microelectromechanical systems (MEMS) and PiezoMEMS devices, tunable dielectrics, and capacitors for charge and energy storage.

BACKGROUND
 Epitaxial perovskite multilayer heterostructures grown on silicon substrates have a number of important advantages; 1) integration of piezoelectric and high dielectric constant materials with silicon-based electronic circuits (e.g. MOSFETs, bipolar transistors), 2) well-developed device fabrication process for the patterning of silicon, and 3) large area and high density device fabrication.  PbMg1/3Nb2/3O3-PbTiO3 (“PMN-PT”) and Pb(Zn1/3Nb2/3)-PbTiO3 (“PZN-PT”) have very high piezoelectric response and high dielectric constants in single crystal form.  However, a major challenge is to prepare these materials as “single crystal” epitaxial films between electrodes and integrate them with silicon so that their properties can be utilized in piezoelectric devices with all of the advantages of microelectronic technology.

DESCRIPTION OF INVENTION
 The invention involves a novel structure and novel thin film deposition method to fabricate a high quality epitaxial perovskite multilayer heretostructures on Silicon and other types of semiconductors.  The multiple layers consist of piezoelectric material having high strain and high electromechanical coupling coefficients including but not limited to PMN-PT and PZN-PT.               

 INVENTION STATUS
 The invention has been reduced to practice.  The researchers have made prototype wafers of three inches and eight inches.  Characterization results including X-ray patterns, photos and comparative data are available upon execution of a confidentiality agreement.  The inventors have produced PMN-PT structures having d33 coefficients of about 1,200 pM/V.  Additional research is on going and supported by federal funding.

UTILITY
 These materials would have application in biomedical ultrasound transducers, inkjet printers and high-speed switches for mobile telecommunications.  For instance, these materials offer the potential of higher performance ultrasonic transducers having better resolution and penetration.  This may allow for deeper tissue imaging and faster, real-time 3-D imaging of internal body organs, tissues and arteries.