Wisconsin Alumni Research Foundation

Semiconductors & Integrated Circuits
Semiconductors Integrated Circuits
Strain-Engineered Ferroelectric Thin Films
WARF: P05036US

Inventors: Chang-Beom Eom, Kyoung-Jin Choi, Darrell Schlom, Long-Qing Chen

The Wisconsin Alumni Research Foundation (WARF) is seeking commercial partners interested in developing thin films that have been strain-engineered to greatly enhance their ferroelectric properties for FeRAM and related applications.
Significant efforts are currently underway to create ferroelectric memory (FeRAM) devices from the materials Pb(Zr,Ti)O3 and SrBi2Ta2O9. The main disadvantages of these materials are the volatility of lead and bismuth, which makes their incorporation into semiconductor fabs difficult, and the serious environmental and health concerns posed by lead.
The Invention
As an alternative to these materials, UW-Madison researchers have developed thin films that have been strain-engineered to greatly enhance their ferroelectric properties for FeRAM and related applications. The invention exploits the fact that enormous strain can develop in a thin film when one material is deposited on another due to factors such as mismatch between the materials’ crystal lattice parameters or thermal expansion between the film and the underlying substrate. The end result is that a thin film under strain will exhibit dramatically different properties than the corresponding unstrained, bulk material.

The researchers showed that by inducing a biaxial compressive strain in a thin film of barium titanate (BaTiO3), they could raise the film’s ferroelectric transition temperature (Tc ) by nearly 500 K and its remnant polarization (Pr) by at least 250 percent over single crystals of BaTiO3. Both a high Tc and a high Pr are needed for FeRAM and electro-optic devices.
  • FeRAM
  • Electro-optic modulators
  • Other ferroelectric devices
Key Benefits
  • Dramatically increases the ferroelectric transition temperature (Tc) and remnant polarization (Pr) of barium titanate (BaTiO3), making it suitable for use in FeRAM, electro-optic modulators and related ferroelectric devices
  • These ferroelectric films are lead-free and environmentally benign.
  • Unlike lead- and bismuth-containing materials, BaTiO3 is compatible with semiconductor fabs and easy to integrate on silicon.
Additional Information
For More Information About the Inventors
  • Choi K.J., Biegalski M., Li Y.L., Sharan A., Schubert J., Uecker R., Reiche P., Chen Y.B., Pan X.Q., Gopalan V., Chen L.Q., Schlom D.G. and Eom C.B. 2004. Enhancement of Ferroelectricity in Strained BaTiO3 Thin Films. Science 306, 1005-1009.
For current licensing status, please contact Michael Carey at [javascript protected email address] or 608-960-9867