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Integrating Ba1-xSrxTiO3 Thin Films with Large Area, Affordable, Industry Standard Substrates for Microwave Applications

Published online by Cambridge University Press:  01 February 2011

W. D. Nothwanga ,
M. W. Cole ,
P. C. Joshi ,
S. Hirsch ,
E. Ngo ,
C. Hubbard  and
J. D. Demaree
W. D. Nothwanga
Affiliation:
U.S. Army Research Laboratory, Weapons and Materials Research Directorate, APG, MD 21005, U.S.A.
M. W. Cole
Affiliation:
U.S. Army Research Laboratory, Weapons and Materials Research Directorate, APG, MD 21005, U.S.A.
P. C. Joshi
Affiliation:
Sharp Laboratories of America, Inc. Camas, WA 98607
S. Hirsch
Affiliation:
Oak Ridge Institute for Science & Education (ORISE), Oak Ridge, TN 37831
E. Ngo
Affiliation:
U.S. Army Research Laboratory, Weapons and Materials Research Directorate, APG, MD 21005, U.S.A.
C. Hubbard
Affiliation:
U.S. Army Research Laboratory, Weapons and Materials Research Directorate, APG, MD 21005, U.S.A.
J. D. Demaree
Affiliation:
U.S. Army Research Laboratory, Weapons and Materials Research Directorate, APG, MD 21005, U.S.A.
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Abstract

The US Army is actively pursuing technologies to enable transformation goals of a lighter, faster, more potent force via affordable, electronically scanned phased array antennas (ESA's) that will provide the means for achieving a high data rate with beyond-line-of-sight, mobile communications. In order to transition this technology to Army applications, it is important that the cost of each device be decreased from current technology. Traditionally, paraelectric, active thin films of magnesium doped barium strontium titanate, have been deposited on expensive ceramic (MgO, LaAlO3, SrTiO3, Al2O3) substrates, and compositionally designed for tunable microwave applications. By integrating an active, thin film material with a large area, low cost, microwave friendly substrate, the cost could be significantly reduced. While Si is not a suitable substrate for microwave applications, a low cost, microwave friendly, buffer layer on silicon would be.

A high performance Ta2O5 thin film, passive, buffer layer on Si substrates has been successfully designed, fabricated, characterized, and optimized via metalorganic solution decomposition technique. The optimized Ta2O5 based thin film exhibited suitable microwave material properties, including an enhanced dielectric constant (εr = 45.6), low dielectric loss (tan δ=0.006), low leakage current, high film resistivity (ρ=1012 Ω-cm at E=1 MV/cm), excellent temperature stability (temperature coefficient of capacitance of 52 ppm/°C), and outstanding bias stability of capacitance (∼1.41% at 1 MV/cm). The permittivity and dissipation factor, also of extreme importance, exhibited minimal dielectric dispersion with frequency. The dielectric passive buffer layer film was typified by a uniform dense microstructure with minimal defects, and a smooth, nano-scale fine grain, crack and pinhole free surface morphology. At elevated processing temperature, there was negligible elemental interdiffusion at the interface between the substrate and buffer layer as verified by Rutherford Backscatter Spectroscopy and Auger Spectroscopy, ensuring long-term reliability of the heterostructure.

By developing a passive, thin film material that is microwave friendly, we have demonstrated the direct integration of paraelectric active thin films with silicon substrates. This should allow phase shifter materials technology to be implemented across a wide spectrum of Army and commercial applications, specifically, affordable, mobile phased array antenna systems for a variety of DoD applications.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 833: Symposium G – Materials, Integration, and Packaging Issues for High-Frequency Devices II , 2004 , G1.6
Copyright
Copyright © Materials Research Society 2005

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References

REFERENCES

1. Cole, M.W., Joshi, P.C., Ervin, M.H., Wood, M.C, and Pfeffer, R.L., “The Influence of Mg Doping on the Materials Properties of Ba1-xSrxTiO3 Thin Films For Tunable Device Applications,” Thin Solid Films, 374, 34–41 (2000).Google Scholar
2. Cole, M.W., Nothwang, W.D., Hubbard, C, Ngo, E., and Ervin, M.H., “Low Dilectric Loss And Enhanced Tunability Of Ba1-XSrxTiO3 Thin Films Via Material Compositional Design and Optimized Film Processing Methods,” J. Appl. Phys., 93, 9218–9225 (2003).Google Scholar
3. Cole, M.W., Nothwang, W.D., Hubbard, C, Ngo, E., Hirsch, S.G., “High Performance Nano-Constituent Buffer Layer Thin Films to Enable Low Cost Integrated On-The-Move Communications Systems,” Proc. Army Science Conference, (2004)Google Scholar
4. Doolittle, L.R., “Algorithms For Rapid Simulation Of RBS Spectra, Nucl. Inst. Meth., B15, 334–351 (1985).Google Scholar
5. Geyer, R.G. and Cole, M.W., “Microwave Properties Of Acceptor-Doped Barium Strontium Titanate Thin Films For Tunable Electronic Devices,” Cer. Trans.: Ceramic Materials and Multilayer Electronic Devices, 150, 229–244 (2004).Google Scholar
6. Horwitz, J.S., Chang, W., Carter, A.C., Pond, J.M., Kirchoefer, S.W., Chrisey, D.B., Levy, J., Hubert, C, “Structure/Property Relationships in Ferroelectric Thin Films For Frequency Agile Microwave Electronics,” Integr. Ferroelectrics, 22, 279–289 (1998).Google Scholar
7. Kim, , Ahn, S., Cho, B., Ahn, S., Lee, J.Y., Chun, J.S., and Lee, W., Jpn J., “Wafer Spin Etch Cleaning,” Appl. Phys., Part I, 33, 6691–6699 (1994).Google Scholar
8. Saha, S. and Krupanidhi, K.B., “Impact of Microstructure on the Electrical Stress Induced Effects of Pulsed Laser Ablated (Ba, Sr)TiO3 Thin Films,” J. Appl. Phys., 87, 3056–3062 (2000).Google Scholar
9. Tien, C-L, Jaing, C-C, Lee, C, and Chuang, K-P, “Simultaneous Determination of The Thermal Expansion Coefficient And The Elastic Modulus Of Ta2O5 Thin Films Using Phase Shifting Interferometry,” Journal of Modern Optics, 47, 1681–1691 (2002).Google Scholar
10. Wolf, S.A. and Treger, D., “Frequency Agile Materials For Electronics (FAME)-Progress In The DARPA Program,” Integr. Ferroelectrics, 42, 39–55 (2002).Google Scholar