EQUIPMENT AND METHODS FOR ETCHING OF MEMS

• US 20100219155A1
• Filed: 02/18/2008
• Published: 09/02/2010
• Est. Priority Date: 02/20/2007
• Status: Active Grant

• Current Assignee: Snaptrack Incorporated (Qualcomm, Inc.)
• Original Assignee: Qualcomm MEMS Technologies Incorporated (Qualcomm, Inc.)
• Inventors: Alam, Khurshid Syed, Gousev, Evgeni, Heald, David, Mignard, Marc Maurice, Londergan, Ana R., Floyd, Philip Don
• Granted Patent: US 8,536,059 B2
• Time in Patent Office: Days
• US Class Current: 216/13
• CPC Class Codes: B81B 2201/047 Optical MEMS not provided for in B81B2201/042 - B81B2201/045
• CPC Class Codes: B81C 1/00531 Dry etching
• CPC Class Codes: H01L 21/67069 for drying etching

Abstract

Etching equipment and methods are disclosed herein for more efficient etching of sacrificial material from between permanent MEMS structures. An etching head includes an elongate etchant inlet structure, which may be slot-shaped or an elongate distribution of inlet holes. A substrate is supported in proximity to the etching head in a manner that defines a flow path substantially parallel to the substrate face, and permits relative motion for the etching head to scan across the substrate.

Claims

1. A method for etching a microelectromechanical systems (MEMS) device comprising:

providing a substrate comprising a MEMS device formed on a surface thereof, wherein the MEMS device comprises a sacrificial material disposed between two electrodes;

relatively moving an etching gas inlet and the substrate;

directing a gas stream comprising a gas phase etchant at a surface of the MEMS device through the etching gas inlet; and

selectively etching to remove the sacrificial material from between the two electrodes of the MEMS.

2. The method of claim 1, wherein selectively etching further comprises selectively removing a second sacrificial layer formed over a reflective layer, wherein the reflective layer is part of one of the two electrodes.

3. The method of claim 1, wherein directing the gas stream comprises directing a gas stream comprising an inert gas.

4. The method of claim 1, wherein directing the gas stream comprises directing a gas stream with a substantially laminar flow.

5. The method of claim 1, wherein directing the gas stream comprises directing a gas stream comprising xenon difluoride.

6. The method of claim 1, wherein directing the gas stream comprises flowing the gas stream normal to a surface of the MEMS device.

7. The method of claim 1, wherein directing the gas stream comprises directing at least a portion of the gas stream substantially parallel to a surface of the MEMS device.

8. The method of claim 1, wherein directing the gas stream through the etching gas inlet comprises directing a gas stream through an elongate etching gas inlet.

9. The method of claim 8, wherein directing the gas stream through the elongate etching gas inlet comprises directing the gas stream through a slot-shaped nozzle.

10. The method of claim 9, wherein directing the gas stream through the slot-shaped nozzle comprises positioning substantially an entire longitudinal axis of the elongate etching gas inlet proximal to a surface of the MEMS device.

11. The method of claim 9, wherein directing the gas stream through the slot-shaped nozzle comprises directing the gas stream through a gas curtain nozzle.

12. The method of claim 8, wherein directing the gas stream through the elongate inlet comprises directing the gas stream through an elongate gas inlet at least as long as a dimension of the substrate.

13. The method of claim 1, wherein selectively etching comprises forming one or more cavities in the MEMS device.

14. The method of claim 1, wherein relatively moving the etching gas inlet and the substrate comprises relatively moving the etching gas inlet and the substrate in a direction orthogonal to a long dimension of the etching gas inlet.

15. The method of claim 1, wherein relatively moving the etching gas inlet and the substrate comprises scanning the substrate under the etching gas inlet.

16. The method of claim 1, wherein directing the gas stream, and relatively moving the etching gas inlet and the substrate occur contemporaneously.

17. The method of claim 1, further comprising withdrawing at least a portion of the gas stream through at least one exhaust opening.

18. The method of claim 17, wherein withdrawing at least the portion of the gas stream further comprises withdrawing an etching by-product.

30. The method of claim 1, wherein the MEMS device comprises an interferometric modulator.

19. An etching system comprising:

an etching head comprising longitudinal axis, an etching gas inlet, and a first flow guide surface, wherein the first flow guide surface is disposed on a first side of the etching gas inlet, and wherein the etching head is operable to direct an etching gas out of the etching gas inlet; and

a substrate support operable to simultaneously support a substrate proximal to the etching gas inlet at a predetermined height and to translate the substrate mounted thereon relative to the etching head, wherein the first flow guide surface is dimensioned and configured to guide the flow of a gas from the etching gas inlet substantially parallel to the substrate, and wherein the first flow guide surface and the predetermined height define an active etching zone with an aspect ratio of greater than about 10;

1.

20. The etching system of claim 19, wherein the etching head further comprises a first exhaust port, wherein the first flow guide surface is disposed between the first exhaust port and the etching gas inlet.

21. The etching system of claim 20, wherein the etching head further comprises a second exhaust port, wherein a second flow guide surface is disposed on a second side of the etching gas inlet, and between the second exhaust port and the etching gas inlet, and wherein the first and second flow guide surfaces define the active etching zone.

22. The etching system of claim 21, wherein first exhaust port comprises an elongate slot substantially parallel to the longitudinal axis of the etching head.

23. The etching system of claim 19, wherein the etching gas inlet comprises an elongate slot substantially parallel to the longitudinal axis of the etching head.

24. An etching apparatus comprising:

an elongate etching gas inlet extending in a first direction, the first direction defining a first side and a second side;

a first elongate exhaust port parallel to the elongate etching gas inlet and spaced therefrom on the first side to define part of an active etching area;

a second elongate exhaust port parallel to the elongate etching gas inlet and spaced therefrom on the second side to define another part of the active etching area;

a substrate support operable to simultaneously support a substrate proximal to the etching gas inlet at a predetermined height, wherein the active etching area and the predetermined height define an active etching zone with a width to height ratio of greater than about 10;

1;

a source of a gas phase etchant fluidly connected to the elongate etching gas inlet; and

a source of vacuum fluidly connected to the first and second exhaust ports.

25. The etching apparatus of claim 24, wherein the etching gas inlet comprises a gas curtain nozzle defining an etchant flow gap.

26. The etching apparatus of claim 24, wherein the first and second exhaust ports each comprise an elongate slot, defining a first purge gap and a second purge gap, respectively.

27. A method for etching a microelectromechanical systems (MEMS) device comprising:

providing a substrate having a MEMS device formed on a surface of the substrate, wherein the MEMS device comprises a sacrificial material disposed between two electrodes;

directing a gas stream comprising a gas phase etchant towards the MEMS device through an etching gas inlet;

selectively etching to remove the sacrificial material from between the two electrodes with the gas phase etchant; and

withdrawing at least a portion of the gas stream, contemporaneously with directing the gas stream, through at least one exhaust opening.

28. The method of claim 27, wherein the MEMS device comprises an interferometric modulator.

29. The method of claim 27, wherein directing the gas stream comprises directing the gas stream through a gas curtain nozzle.