Dielectric varactors with offset two-layer electrodes

• US 6,377,440 B1
• Filed: 09/12/2000
• Issued: 04/23/2002
• Est. Priority Date: 09/12/2000
• Status: Expired due to Term

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: Paratek Microwave Incorporated (Blackberry Limited)
• Inventors: Sengupta, Louise C., Zhang, Xubai, Zhu, Yongfei
• Primary Examiner(s): Reichard, Dean A.
• Assistant Examiner(s): HA, NGUYEN T
• Application Number:
  US09/660,309
• Time in Patent Office: 588 Days
• Field of Search: 361/311, 361/321.5, 361/312, 361/321.2, 361/321.3, 361/278, 361/290, 361/292, 29/250.3, 257/595
• US Class Current: 361/311
• CPC Class Codes: H01L 27/0808 Varactor diodes

Abstract

A varactor comprising a substrate, a first conductor positioned on a surface of the substrate, a second conductor positioned on the surface of the substrate forming a gap between the first and second conductors, a tunable dielectric material positioned on the surface of the substrate and within the gap, the tunable dielectric material having a top surface, with at least a portion of said top surface being positioned above the gap opposite the surface of the substrate, and a first portion of the second conductor extending along at least a portion of the top surface of the tunable dielectric material. The second conductor can overlap or not overlap a portion of the first conductor.

Claims

1. A varactor comprising:

a substrate;

a first conductor positioned on a surface of the substrate;

a second conductor positioned on the surface of the substrate forming a gap between the first and second conductors;

a tunable dielectric material positioned on the surface of the substrate and within the gap, said tunable dielectric material having a top surface, at least a portion of said top surface being positioned above the gap opposite the surface of the substrate; and

a first portion of the second conductor extending along at least a portion of the top surface of the tunable dielectric material.

2. The varactor of claim 1, wherein:

a portion of the tunable dielectric material lies along a surface of the first conductor opposite the surface of the substrate.

3. The varactor of claim 2, wherein the first portion of the second conductor has a shape that is one of:

rectangular, triangular, and trapezoidal.

4. The varactor of claim 3, wherein the tunable dielectric layer comprises one 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 composites thereof.

5. The varactor of claim 4, wherein the substrate comprises one of:

MgO, alumina (AL₂O₃), LaAlO₃, sapphire, quartz, silicon, and gallium arsenide.

6. The varactor of claim 5, wherein:

the first portion of the second conductor overlaps a portion of the first conductor.

7. The varactor of claim 3, 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.

8. The varactor of claim 7, wherein the substrate comprises one of:

MgO, alumina (AL₂O₃), LaAlO₃, sapphire, quartz, silicon, and gallium arsenide.

9. The varactor of claim 8, wherein:

the first portion of the second conductor overlaps a portion of the first conductor.

10. The varactor of claim 1, wherein:

the first portion of the second conductor overlaps a portion of the first conductor.

11. The varactor of claim 1, wherein the tunable dielectric layer comprises one 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 composites thereof.

12. The varactor of 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.

13. The varactor of claim 1, wherein the substrate comprises one of:

MgO, alumina (AL₂O₃), LaAlO₃, sapphire, quartz, silicon, and gallium arsenide.

14. The varactor of claim 1, wherein the first conductor comprises one of:

platinum, platinum-rhodium, and ruthenium oxide.

15. The varactor of claim 14, wherein the second conductor comprises one of:

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

16. The varactor of claim 1, wherein the second conductor comprises one of:

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