Voltage tuned dielectric varactors with bottom electrodes

• US 6,404,614 B1
• Filed: 04/27/2001
• Issued: 06/11/2002
• Est. Priority Date: 05/02/2000
• Status: Expired due to Term

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Paratek Microwave Incorporated (Blackberry Limited)
• Inventors: Sengupta, Louise C., Zhu, Yongfei
• Primary Examiner(s): Dinkins, Anthony
• Application Number:
  US09/844,832
• Publication Number:
  US 20020051334A1
• Time in Patent Office: 410 Days
• Field of Search: 361/277, 361/278, 361/281, 361/282, 361/290, 361/292, 361/298.2, 361/298.3, 257/595, 257/602, 257/295
• US Class Current: 361/277
• CPC Class Codes: H01G 7/06 having a dielectric selected for the variation of its permittivity with applied voltage, i.e. ferroelectric capacitors electrets H01G7/02
• CPC Class Codes: H01P 1/181 using ferroelectric devices

Abstract

A voltage tunable dielectric varactor includes a substrate having a first dielectric constant and having generally a planar surface, first and second electrodes positioned on the generally planar surface of the substrate, the first and second electrodes being separated to form a first gap therebetween; a tunable dielectric layer positioned on the first and second electrodes and in the first gap, the tunable dielectric layer having a second dielectric constant greater than the first dielectric constant; and third and fourth electrodes positioned on a surface of the tunable dielectric layer opposite the first and second electrodes, the third and fourth electrodes being separated to form a second gap therebetween.

Claims

1. A voltage tunable dielectric varactor comprising:

a substrate having a first dielectric constant and having a generally planar surface;

first and second electrodes positioned on the generally planar surface of the substrate said first and second electrodes being separated to form a first gap therebetween;

a tunable dielectric layer positioned on the first and second electrodes and in said first gap, the tunable dielectric layer having a second dielectric constant greater than said first dielectric constant; and

third and fourth electrodes positioned on a surface of the tunable dielectric layer opposite the first and second electrodes, said third and fourth electrodes being separated to form a second gap therebetween.

2. A voltage tunable dielectric varactor as recited in claim 1, wherein:

said first gap is narrower than said second gap.

3. A voltage tunable dielectric varactor as recited in claim 1, wherein the tunable dielectric layer has a dielectric constant ranging from 2 to 1000, tuning of greater than 5%, and a loss tangent of less than 0.02.

4. A voltage tunable dielectric varactor as recited in claim 1, wherein the substrate has a permittivity of less than about 30.

5. A voltage tunable dielectric varactor as recited in claim 1, wherein first, second, third and fourth electrodes each comprise one of the group of:

gold, silver, copper, platinum, platinum-rhodium, and ruthenium oxide.

6. A voltage tunable dielectric varactor as recited in claim 1, wherein the substrate comprises one of the group of:

MgO, Alumina, LaAlO₃, sapphire, quartz, silicon, and gallium arsenide.

7. A voltage tunable dielectric varactor as recited in claim 1, wherein the tunable dielectric layer comprises one of:

a tunable ferroelectric thick film;

a tunable ferroelectric bulk ceramic; and

a tunable ferroelectric thin film.

8. A voltage tunable dielectric varactor as recited in claim 1, further including:

an RF input and an RF output for passing an RF signal through the tunable dielectric layer in a first direction, and wherein the first and second gaps lie parallel to a second direction substantially perpendicular to the first direction.

9. A voltage tunable dielectric varactor as recited in claim 1, wherein the tunable dielectric layer comprises a material selected from the group of:

barium strontium titanate, barium calcium titanate, lead zirconium titanate, lead lanthanum zirconium titanate, lead titanate, barium calcium zirconium titanate, sodium nitrate, KNbO₃, LiNbO₃, LiTaO₃, PbNb₂O₆, PbTa₂O₆, KSr(NbO₃), NaBa₂(NbO₃)₅, KH₂PO₄, and combinations thereof.

10. A voltage tunable dielectric varactor as recited in claim 1, wherein the tunable dielectric layer comprises a barium strontium titanate (BSTO) composite selected from the group of:

BSTO—

MgO, BSTO—

MgAl₂O₄, BSTO—

CaTiO₃, BSTO—

MgTiO₃, BSTO—

MgSrZrTiO₆, and combinations thereof.

11. A voltage tunable dielectric varactor as recited in claim 1, wherein the tunable dielectric layer comprises a material selected from the group of:

Mg₂SiO₄, CaSiO₃, BaSiO₃, SrSiO₃, Na₂SiO₃, NaSiO₃—

5H₂O, LiAlSiO₄, Li₂SiO₃, Li₄SiO₄, Al₂Si₂O₇, ZrSiO₄, KAlSi₃O₈, NaAlSi₃O₈, CaAl₂Si₂O₈, CaMgSi₂O₆, BaTiSi₃O₉ and Zn₂SiO₄.

12. A voltage tunable dielectric varactor as recited in claim 1, wherein the tunable dielectric layer comprises:

an electronically tunable phase and at least two metal oxide phases.