Controlled stress optical coatings for membranes

• US 6,692,850 B2
• Filed: 03/07/2001
• Issued: 02/17/2004
• Est. Priority Date: 03/07/2001
• Status: Active Grant

• Current Assignee: Excelitas Technologies Corporation (Excelitas Technologies Holdings LLC)
• Original Assignee: Axsun Technologies Incorporated
• Inventors: Cook, Christopher C.
• Primary Examiner(s): Zimmerman, John J.
• Assistant Examiner(s): BLACKWELL, GWENDOLYN
• Application Number:
  US09/801,376
• Publication Number:
  US 20020127438A1
• Time in Patent Office: 1,077 Days
• Field of Search: 428/212, 428/697, 428/699, 428/688, 428/689, 428/701, 428/702
• US Class Current: 428/699
• CPC Class Codes: C23C 14/22 characterised by the process of coating
• CPC Class Codes: C23C 14/546 using crystal oscillators
• CPC Class Codes: Y10T 428/24942 including components having same physical characteristic in differing degree

Abstract

A thin membrane having a thin film optical coating thereon is formed from multiple layers of different materials in which the overall stress of the thin film is not more than 15 MPa. Such films can be formed through thermal evaporation with ion assist, by directing an electron beam on a source and evaporating material from the source onto a thin flexible membrane while directing an ion stream onto the membrane. The current of the source of the ion stream should be sufficient to provide a thin film coating that has substantially no porosity. Successive applications at constant current can be deposited, while varying the voltage of the ion stream. The stress of the thin films deposited under each different voltage can be evaluated and the voltage at which the stress is acceptably low can be determined.

Claims

1. A coated membrane structure, comprising:

a membrane having a thin film coating thereon, said coating having an overall residual stress of less than about 15 MPa;

wherein the coating has over 97% reflectivity.

2. The membrane structure of claim 1, wherein the residual stress is less than 10 MPa.

3. The membrane structure of claim 1, wherein the residual stress is substantially not observable.

26. The membrane structure of claim 1, wherein the membrane is less than 50 micrometers thick.

4. A coated membrane structure, comprising:

a membrane having a thin film coating thereon, said coating having an overall residual stress of less than about 15 MPa;

wherein the coating has over 99% reflectivity.

5. A coated membrane structure, comprising:

a membrane having a thin film coating thereon, said coating having an overall residual stress of less than about 15 MPa;

wherein the coating is a reflective coating and comprises alternating layers of different oxides.

6. The membrane structure of claim 5, wherein the coating has over 97% reflectivity.

7. The membrane structure of claim 5, wherein one of the oxides is SiO₂.

8. The membrane structure of claim 5, wherein one of the oxides is Ta₂O₅.

9. The membrane structure of claim 5, wherein one of the oxides is TiO₂.

10. A coated membrane structure, comprising:

a membrane having a thin film coating thereon, said coating having an overall residual stress of less than about 15 MPa;

wherein the coating comprises alternating layers of TiO₂ and SiO₂.

11. A coated membrane structure, comprising:

a membrane having a thin film coating thereon, said coating having an overall residual stress of less than about 15 MPa;

wherein the coating comprises alternating layers of Ta₂O₅ and SiO₂.

12. A coated micro-optical electromechanical systems (MOEMS) structure, comprising:

a device layer having a thin film coating thereon, said coating having an overall residual stress of less than about 15 MPa;

wherein the coating has over 97% reflectivity.

13. The MEOMS structure of claim 12, wherein the residual stress is less than 10 MPa.

14. The MEOMS structure of claim 12, wherein the residual stress is substantially not observable.

24. The membrane structure of claim 12, wherein the device layer is less than 50 micrometers thick.

15. A coated micro-optical electromechanical systems (MOEMS) structure, comprising:

a device layer having a thin film coating thereon, said coating having an overall residual stress of less than about 15 MPa;

wherein the coating has over 99% reflectivity.

16. A coated micro-optical electromechanical systems (MOEMS) structure, comprising:

a device layer having a thin film coating thereon, said coating having an overall residual stress of less than about 15 MPa;

wherein the coating is a reflective coating and comprises alternating layers of different oxides.

17. The MEOMS structure of claim 16, wherein the coating has over 97% reflectivity.

18. The MEOMS structure of claim 16, wherein one of the oxides is SiO₂.

19. The MEOMS structure of claim 16, wherein one of the oxides is Ta₂O₅.

20. The MEOMS structure of claim 16, wherein one of the oxides is TiO₂.

21. A coated micro-optical electromechanical systems (MOEMS) structure, comprising:

a device layer having a thin film coating thereon, said coating having an overall residual stress of less than about 15 MPa;

wherein the coating comprises alternating layers of TiO₂ and SiO₂.

22. A coated micro-optical electromechanical systems (MOEMS) structure, comprising:

a device layer having a thin film coating thereon, said coating having an overall residual stress of less than about 15 MPa;

wherein the coating comprises alternating layers of Ta₂O₅ and SiO₂.

23. A coated micro-optical electromechanical systems (MOEMS) structure, comprising:

a device layer having a thin film coating thereon, said coating having an overall residual stress of less than about 15 MPa;

wherein the device layer is suspended over handle material.

25. A coated micro-optical electromechanical systems (MOEMS) structure, comprising:

a device layer having a thin film coating thereon, said coating having an overall residual stress of less than about 15 MPa;

wherein the membrane is suspended over handle material.