ALD metal coatings for high Q MEMS structures

• US 10,266,398 B1
• Filed: 11/26/2014
• Issued: 04/23/2019
• Est. Priority Date: 07/25/2007
• Status: Active Grant

• Current Assignee: HRL Laboratories LLC (The Boeing Co.)
• Original Assignee: HRL Laboratories LLC (The Boeing Co.)
• Inventors: Kubena, Randall L., Joyce, Richard J.
• Primary Examiner(s): Eslami, Tabassom Tadayyon
• Application Number:
  US14/555,459
• Time in Patent Office: 1,609 Days
• Field of Search: 735033, 427250, 427395, 4272557, 438 15, 438 55, 438 64, 438106, 438 6
• CPC Class Codes: B81B 2201/0242 Gyroscopes
• CPC Class Codes: B81B 2201/0271 Resonators; ultrasonic resonators
• CPC Class Codes: B81B 3/0078 Constitution or structural means for improving mechanical properties not provided for in B81B3/007 - B81B3/0075
• CPC Class Codes: B81B 3/0086 Electrical characteristics, e.g. reducing driving voltage, improving resistance to peak voltage
• CPC Class Codes: B81C 1/00206 Processes for functionalising a surface, e.g. provide the surface with specific mechanical, chemical or biological properties
• CPC Class Codes: B81C 2201/0181 Physical Vapour Deposition [PVD], i.e. evaporation, sputtering, ion plating or plasma assisted deposition, ion cluster beam technology
• CPC Class Codes: C23C 16/045 Coating cavities or hollow spaces, e.g. interior of tubes; Infiltration of porous substrates
• CPC Class Codes: C23C 16/06 characterised by the deposition of metallic material
• CPC Class Codes: C23C 16/18 from metallo-organic compounds
• CPC Class Codes: C23C 16/403 of aluminium, magnesium or beryllium
• CPC Class Codes: C23C 16/45525 Atomic layer deposition [ALD]
• CPC Class Codes: C23C 16/45555 applied in non-semiconductor technology

Abstract

A method for fabricating a Microelectromechanical System (MEMS) resonator includes providing a dielectric substrate defining a resonator and depositing a conductive coating having a resistivity of approximately 1 to 50 μΩ-cm on that substrate by Atomic Layer Deposition (ALD). A resonator fabricated according to this process includes a dielectric substrate defining a resonator and a conductive coating having a resistivity of approximately 1 to 50 μΩ-cm for electrically coupling the resonator to electronics. Another method for fabricating a MEMS resonator includes providing a dielectric substrate defining a resonator, depositing an aluminum oxide film on that substrate by ALD, and depositing a noble metal film on the aluminum oxide film, also by ALD.

Claims

1. A method for fabricating a microelectromechanical system (MEMS) resonator, comprising:

providing a dielectric substrate having a resonator defined therein; and

depositing a bilayer conductive coating on the dielectric substrate, the depositing of the bilayer conductive coating including

(i) depositing a dielectric film on the dielectric substrate by Atomic Layer Deposition, and

(ii) depositing a metal film on the deposited dielectric film by Atomic Layer Deposition, and

wherein the bilayer conductive coating electrically couples the resonator to electronics.

2. The method of claim 1, wherein the bilayer conductive coating is deposited to a thickness of less than 100 nm.

3. The method of claim 1, wherein the metal film has a resistivity of 10⁻

6 to 10<sup>−

5</sup> Ω

-cm.

4. The method of claim 1, wherein the deposited bilayer conductive coating has a uniform thickness.

5. The method of claim 4, wherein the resonator has an aspect ratio greater than 2:

1.

6. The method of claim 4, wherein the resonator has an aspect ratio greater than 5:

1.

7. The method of claim 1, wherein the metal film is a noble metal.

8. The method of claim 7, wherein the noble metal is one of Ru, Rh, Pd, Re, Ir, or Pt.

9. The method of claim 1, wherein the metal film has a thickness of 1 nm to 20 nm.

10. The method of claim 1, wherein the metal film is a pure metal film.

11. The method of claim 1, wherein the dielectric substrate is one of quartz, fused quartz, or fused silica.

12. The method of claim 1, wherein:

the dielectric film is an Al₂O₃ amorphous film and

the metal film is a noble metal film.

13. The method of claim 12, wherein:

the Al₂O₃ amorphous film is deposited to a thickness of 1 nm to 2 nm; and

the noble metal film is deposited to a thickness of 1 nm to 20 nm.

14. The method of claim 12, wherein the noble metal is one of Ru, Rh, Pd, Re, Ir, or Pt.

15. The method of claim 12, wherein the Al₂O₃ amorphous film reduces surface interfacial slippage and provides surface passivation.

16. A method for fabricating a microelectromechanical system (MEMS) resonator, comprising:

providing a dielectric substrate having a resonator defined therein;

depositing an Al₂O₃ amorphous film on the dielectric substrate by Atomic Layer Deposition; and

depositing a noble metal film on the Al₂O₃ amorphous film by Atomic Layer Deposition, wherein the noble metal film for electrically couples the resonator to electronics.

17. The method of claim 16, wherein the deposited noble metal film has a resistivity of 1 to 50 μ

Ω

-cm.

18. The method of claim 16, wherein the deposited noble metal film has a resistivity of 10⁻

6 to 10<sup>−

5</sup> Ω

-cm.

19. The method of claim 16, wherein the noble metal is one of Ru, Rh, Pd, Re, Ir, or Pt.

20. The method of claim 16, wherein the deposited Al₂O₃ amorphous film and the deposited noble metal film each have a uniform thickness.

21. The method of claim 16, wherein the deposited Al₂O₃ amorphous film reduces surface interfacial slippage and provides surface passivation.

22. The method of claim 16, further comprising:

placing the dielectric substrate in a vacuum chamber prior to depositing the Al₂O₃ amorphous film;

creating a vacuum in the vacuum chamber; and

depositing the Al₂O₃ amorphous film and the noble metal film without breaking the created vacuum.