Thick electrodes for high frequency high Q tunable ferroelectric thin film varactors

Gregory T. Stauf, Craig Ragaglia, Jeffrey F. Roeder, Dan Vestyck, Jon-Paul Maria, Tito Ayguavives, Angus Kingon, Amir Mortazawi, Ali Tombak

Research output: Contribution to journalConference article

11 Citations (Scopus)

Abstract

Thin film barium strontium titanate (BST) shows great promise for voltage tunable dielectric devices for use at RF and microwave frequencies. An MOCVD process has been developed for production of BST, resulting in films with very low losses (as low as 0.002-0.004) and tunabilities over 50% at low operation voltages. With these values of BST loss, overall device quality factors at RF (100 MHz+) frequencies are primarily limited by losses in the thin metal electrodes, such as Pt, normally used for ferroelectric thin films. The bottom electrode in parallel plate capacitor structures is particularly challenging, since it must provide a good growth surface for BST and be stable at high (600 C) growth temperatures in an oxidizing atmosphere yet have high conductivity and compatibility with Si or SiO2/Si substrates. These challenges have previously prevented use of Pt thicknesses over 0.1-0.2 urn. Our solution to this problem, involves combinations of adhesion layers at the Pt/SiO2 interface and embedded stabilization layers to make functioning Pt bottom electrodes as thick as 2 m. Devices with dielectric Q factors over 150 at 100 MHz (tan 0.006 as measured and modeled by S-parameters) and overall device Q factors over 50 at 30 MHz are described. We have also inserted these devices into tunable filters, achieving tunabilities of 50% and low insertion losses (0.3 dB) at RF frequencies.

Original languageEnglish (US)
Pages (from-to)321-330
Number of pages10
JournalIntegrated Ferroelectrics
Volume39
Issue number1-4
DOIs
StatePublished - Dec 1 2001
Event13th International Symposium on Integrated Ferroelectrics - Colorado Springs, CO, United States
Duration: Mar 11 2006Mar 14 2006

Fingerprint

Barium strontium titanate
Ferroelectric thin films
varactor diodes
Varactors
Q factors
strontium
barium
Electrodes
electrodes
thin films
Dielectric devices
Microwave frequencies
Metallorganic chemical vapor deposition
Scattering parameters
Electric potential
Growth temperature
Insertion losses
tunable filters
electric potential
microwave frequencies

All Science Journal Classification (ASJC) codes

  • Control and Systems Engineering
  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Condensed Matter Physics
  • Materials Chemistry
  • Electrical and Electronic Engineering

Cite this

Stauf, G. T., Ragaglia, C., Roeder, J. F., Vestyck, D., Maria, J-P., Ayguavives, T., ... Tombak, A. (2001). Thick electrodes for high frequency high Q tunable ferroelectric thin film varactors. Integrated Ferroelectrics, 39(1-4), 321-330. https://doi.org/10.1080/10584580108011955
Stauf, Gregory T. ; Ragaglia, Craig ; Roeder, Jeffrey F. ; Vestyck, Dan ; Maria, Jon-Paul ; Ayguavives, Tito ; Kingon, Angus ; Mortazawi, Amir ; Tombak, Ali. / Thick electrodes for high frequency high Q tunable ferroelectric thin film varactors. In: Integrated Ferroelectrics. 2001 ; Vol. 39, No. 1-4. pp. 321-330.
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abstract = "Thin film barium strontium titanate (BST) shows great promise for voltage tunable dielectric devices for use at RF and microwave frequencies. An MOCVD process has been developed for production of BST, resulting in films with very low losses (as low as 0.002-0.004) and tunabilities over 50{\%} at low operation voltages. With these values of BST loss, overall device quality factors at RF (100 MHz+) frequencies are primarily limited by losses in the thin metal electrodes, such as Pt, normally used for ferroelectric thin films. The bottom electrode in parallel plate capacitor structures is particularly challenging, since it must provide a good growth surface for BST and be stable at high (600 C) growth temperatures in an oxidizing atmosphere yet have high conductivity and compatibility with Si or SiO2/Si substrates. These challenges have previously prevented use of Pt thicknesses over 0.1-0.2 urn. Our solution to this problem, involves combinations of adhesion layers at the Pt/SiO2 interface and embedded stabilization layers to make functioning Pt bottom electrodes as thick as 2 m. Devices with dielectric Q factors over 150 at 100 MHz (tan 0.006 as measured and modeled by S-parameters) and overall device Q factors over 50 at 30 MHz are described. We have also inserted these devices into tunable filters, achieving tunabilities of 50{\%} and low insertion losses (0.3 dB) at RF frequencies.",
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Stauf, GT, Ragaglia, C, Roeder, JF, Vestyck, D, Maria, J-P, Ayguavives, T, Kingon, A, Mortazawi, A & Tombak, A 2001, 'Thick electrodes for high frequency high Q tunable ferroelectric thin film varactors', Integrated Ferroelectrics, vol. 39, no. 1-4, pp. 321-330. https://doi.org/10.1080/10584580108011955

Thick electrodes for high frequency high Q tunable ferroelectric thin film varactors. / Stauf, Gregory T.; Ragaglia, Craig; Roeder, Jeffrey F.; Vestyck, Dan; Maria, Jon-Paul; Ayguavives, Tito; Kingon, Angus; Mortazawi, Amir; Tombak, Ali.

In: Integrated Ferroelectrics, Vol. 39, No. 1-4, 01.12.2001, p. 321-330.

Research output: Contribution to journalConference article

TY - JOUR

T1 - Thick electrodes for high frequency high Q tunable ferroelectric thin film varactors

AU - Stauf, Gregory T.

AU - Ragaglia, Craig

AU - Roeder, Jeffrey F.

AU - Vestyck, Dan

AU - Maria, Jon-Paul

AU - Ayguavives, Tito

AU - Kingon, Angus

AU - Mortazawi, Amir

AU - Tombak, Ali

PY - 2001/12/1

Y1 - 2001/12/1

N2 - Thin film barium strontium titanate (BST) shows great promise for voltage tunable dielectric devices for use at RF and microwave frequencies. An MOCVD process has been developed for production of BST, resulting in films with very low losses (as low as 0.002-0.004) and tunabilities over 50% at low operation voltages. With these values of BST loss, overall device quality factors at RF (100 MHz+) frequencies are primarily limited by losses in the thin metal electrodes, such as Pt, normally used for ferroelectric thin films. The bottom electrode in parallel plate capacitor structures is particularly challenging, since it must provide a good growth surface for BST and be stable at high (600 C) growth temperatures in an oxidizing atmosphere yet have high conductivity and compatibility with Si or SiO2/Si substrates. These challenges have previously prevented use of Pt thicknesses over 0.1-0.2 urn. Our solution to this problem, involves combinations of adhesion layers at the Pt/SiO2 interface and embedded stabilization layers to make functioning Pt bottom electrodes as thick as 2 m. Devices with dielectric Q factors over 150 at 100 MHz (tan 0.006 as measured and modeled by S-parameters) and overall device Q factors over 50 at 30 MHz are described. We have also inserted these devices into tunable filters, achieving tunabilities of 50% and low insertion losses (0.3 dB) at RF frequencies.

AB - Thin film barium strontium titanate (BST) shows great promise for voltage tunable dielectric devices for use at RF and microwave frequencies. An MOCVD process has been developed for production of BST, resulting in films with very low losses (as low as 0.002-0.004) and tunabilities over 50% at low operation voltages. With these values of BST loss, overall device quality factors at RF (100 MHz+) frequencies are primarily limited by losses in the thin metal electrodes, such as Pt, normally used for ferroelectric thin films. The bottom electrode in parallel plate capacitor structures is particularly challenging, since it must provide a good growth surface for BST and be stable at high (600 C) growth temperatures in an oxidizing atmosphere yet have high conductivity and compatibility with Si or SiO2/Si substrates. These challenges have previously prevented use of Pt thicknesses over 0.1-0.2 urn. Our solution to this problem, involves combinations of adhesion layers at the Pt/SiO2 interface and embedded stabilization layers to make functioning Pt bottom electrodes as thick as 2 m. Devices with dielectric Q factors over 150 at 100 MHz (tan 0.006 as measured and modeled by S-parameters) and overall device Q factors over 50 at 30 MHz are described. We have also inserted these devices into tunable filters, achieving tunabilities of 50% and low insertion losses (0.3 dB) at RF frequencies.

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