Microelectromechanical switch with fixed metal electrode/dielectric interface with a protective cap layer

• US 6,376,787 B1
• Filed: 08/24/2000
• Issued: 04/23/2002
• Est. Priority Date: 08/24/2000
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Martin, Wallace W., Williams, Byron, Melendez, Jose, Crenshaw, Darius L., Chen, Yu-Pei
• Primary Examiner(s): SCOTT, JAMES R
• Application Number:
  US09/648,288
• Time in Patent Office: 607 Days
• Field of Search: 200/181, 200/600, 333/101, 333/108, 333/262, 361/288, 296/22
• US Class Current: 200/181
• CPC Class Codes: G11C 23/00 Digital stores characterised by movement of mechanical parts to effect storage, e.g. using balls; Storage elements therefor
• CPC Class Codes: H01G 5/16 using variation of distance between electrodes
• CPC Class Codes: H01G 5/40 Structural combinations of variable capacitors with other electric elements not covered by this subclass, the structure mainly consisting of a capacitor, e.g. RC combinations
• CPC Class Codes: H01H 2001/0084 with perpendicular movement of the movable contact relative to the substrate
• CPC Class Codes: H01H 59/0009 making use of micromechanics
• CPC Class Codes: H01P 1/127 Strip line switches
• CPC Class Codes: Y10T 29/49105 Switch making

Abstract

A Micro Electro-Mechanical System (MEMS) switch (100) having a bottom electrode (116) formed over a substrate (112) and a thin protective cap layer (130) disposed over the bottom electrode (116). A dielectric material (118) is disposed over the protective cap layer (130) and a pull-down electrode (122) is formed over the spacer (120) and the dielectric material (118). The protective cap layer (130) prevents the oxidation of the bottom electrode (116). The thin protective cap layer (130) comprises a metal having an associated oxide with a high dielectric constant. A portion (132) of the thin protective cap layer (130) may oxidize during the formation of the dielectric material (118), increasing the capacitance of the dielectric stack (128).

Claims

1. A Micro Electro-Mechanical System (MEMS) switch, comprising:

a bottom electrode formed over a substrate;

a thin protective cap layer disposed over said bottom electrode;

a dielectric material disposed over said protective cap layer;

a spacer proximate said bottom electrode; and

a pull-down electrode over said spacer and said dielectric material, wherein said protective cap layer prevents the oxidation of said bottom electrode.

2. The MEMS switch according to claim 1 wherein said thin protective cap layer comprises a metal.

3. The MEMS switch according to claim 2 wherein said metal comprises a metal M₁ having an associated oxide M_1xO_y having a high dielectric constant.

4. The MEMS switch according to claim 3 wherein said high dielectric constant is at least 20.

5. The MEMS switch according to claim 4 wherein said metal comprises titanium or tantalum.

6. The MEMS switch according to claim 3 wherein said bottom electrode comprises a metal M₂ having an associated oxide M_2xO_y, wherein the dielectric constant of said oxide M_1xO_y is higher than the dielectric constant of said oxide M_2xO_y.

7. The MEMS switch according to claim 6 wherein said thin protective cap layer comprises an oxidized portion comprising said oxide M_1xO_y proximate said dielectric material.

8. The MEMS switch according to claim 7 wherein said thin protective cap layer oxidized portion and said dielectric material comprise a dielectric stack, said dielectric stack having a capacitance value, wherein said thin protective cap layer maintains said dielectric stack capacitance value.

9. The MEMS switch according to claim 8 wherein said thin protective cap layer increases said dielectric stack capacitance value.

10. A Micro Electro-Mechanical System (MEMS) switch, comprising:

a substrate;

an insulator layer disposed over said substrate;

a bottom electrode formed over said insulator layer;

a thin protective cap layer disposed over said bottom electrode,

a dielectric material disposed over said thin protective cap layer;

a spacer proximate said bottom electrode; and

a pull-down electrode over said spacer and said dielectric material, wherein said thin protective cap layer inhibits the oxidation of said bottom electrode.

11. The MEMS switch according to claim 10 wherein said thin protective cap layer comprises a metal M₁ having an associated oxide M_1xO_y having a high dielectric constant.

12. The MEMS switch according to claim 11 wherein said high dielectric constant is at least 20.

13. The MEMS switch according to claim 12 wherein said metal comprises titanium or tantalum.

14. The MEMS switch according to claim 11 wherein said bottom electrode comprises a metal M₂ having an associated oxide M_2xO_y, wherein the dielectric constant of said oxide M_1xO_y is higher than the dielectric constant of said oxide M_2xO_y.

15. The MEMS switch according to claim 14 wherein said thin protective cap layer oxidized portion and said dielectric material comprise a dielectric stack, said dielectric stack having a capacitance value, wherein said thin protective cap layer maintains said dielectric stack capacitance value.

16. The MEMS switch according to claim 15 wherein said thin protective cap layer increases said dielectric stack capacitance value.

17. A method of manufacturing a Micro Electro-Mechanical System (MEMS) switch, comprising the steps of:

providing a substrate;

depositing an insulator layer on said substrate;

forming a bottom electrode on said insulator layer;

depositing a thin protective cap layer over said bottom electrode;

depositing a dielectric material over said bottom electrode and thin protective cap layer; and

forming a pull-down electrode over said dielectric material, wherein said thin protective cap layer prevents the oxidation of said bottom electrode.

18. The method according to claim 17 further comprising the step of oxidizing said thin protective cap layer.

19. The method according to claim 18 wherein said oxidizing step comprises forming a high dielectric material.

20. The method according to claim 19 wherein said depositing a thin protective cap layer step comprises depositing a metal M₁ having an associated oxide M_1xO_y, wherein said step of depositing a bottom electrode comprises depositing a metal M₂ having an associated oxide M_2xO_y, wherein the dielectric constant of said oxide M_1xO_y is higher than the dielectric constant of said oxide M_2xO_y.