Precisely defined microelectromechanical structures and associated fabrication methods

• US 6,277,666 B1
• Filed: 06/24/1999
• Issued: 08/21/2001
• Est. Priority Date: 06/24/1999
• Status: Expired due to Fees

• Current Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Original Assignee: Honeywell Incorporated (Honeywell International Inc.)
• Inventors: Whitcomb, Eugene Coleman, Hays, Kenneth Maxwell
• Primary Examiner(s): Niebling, John F.
• Assistant Examiner(s): Simkovic, Viktor
• Application Number:
  US09/338,962
• Time in Patent Office: 789 Days
• Field of Search: 438/50, 438/51, 438/52, 438/53, 438/164, 438/456, 438/458, 438/459, 438/464
• US Class Current: 438/50
• CPC Class Codes: B81C 1/00047 Cavities
• CPC Class Codes: B81C 2201/019 Bonding or gluing multiple substrate layers
• CPC Class Codes: B81C 2201/0191 Transfer of a layer from a carrier wafer to a device wafer
• CPC Class Codes: G01C 19/5719 using planar vibrating masses driven in a translation vibration along an axis
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: G01P 15/125 by capacitive pick-up
• CPC Class Codes: G01P 2015/0814 for translational movement of the mass, e.g. shuttle type

Abstract

A method is provided for fabricating a MEMS structure from a silicon-on insulator (SOI) wafer that has been bonded to a support substrate, such as a glass substrate, in order to form silicon components that can be both precisely and repeatedly formed. The SOI wafer includes a handle wafer, an insulating layer disposed on the handle wafer and a silicon layer disposed on the insulating layer. At least one trench is etched through the silicon layer by reactive ion etching. By utilizing the reactive ion etching, the trenches can be precisely defined, such as to within a tolerance of 0.1 to 0.2 microns of a predetermined width. After bonding the support substrate to the silicon layer, the handle wafer is removed, such as by reactive ion etching. Thereafter, the insulating layer is selectively removed, again typically by reactive ion etching, to form the resulting MEMS structure that has a very precise and repeatable size and shape, such as to within a fraction of a micron. As such, a MEMS structure is also provided according to the present invention in which a plurality of silicon components that vary in size by no more than 0.2 microns are bonded to a support substrate, such as to form an array having a plurality of MEMS elements that have the same or substantially similar performance characteristics.

Claims

1. A method for fabricating a microelectromechanical (MEMS) structure comprising:

providing a silicon-on-insulator (SOI) wafer comprising a handle wafer, an insulating layer disposed on the handle wafer and a silicon layer disposed on the insulating layer;

etching at least one trench through the silicon layer by reactive ion etching;

bonding a support substrate to the silicon layer following said etching step, wherein a surface of the support substrate that is bonded to the silicon layer is nonplanar such that at least one cavity is defined between the support substrate and the SOI wafer;

removing the handle wafer following said bonding step; and

thereafter selectively removing the insulating layer such that the resulting MEMS structure comprises a silicon component at least partially suspended over the cavity and at least partially defined by the at least one trench etched through the silicon layer.

2. A method according to claim 1 further comprising providing the support substrate having a plurality of mesas separated by recessed portions that are defined by the nonplanar surface to which the SOI wafer is thereafter bonded, and wherein said bonding step comprises bonding the support substrate to the silicon layer such that the silicon component is suspended from a respective mesa over an adjacent recessed portion.

3. A method according to claim 1 further comprising providing the support substrate having at least one conductive element supported by the nonplanar surface to which the SOI wafer is thereafter bonded such that the silicon component at least partially overlies the at least one conductive element.

4. A method according to claim 1 wherein said etching step comprises terminating the reactive ion etching upon reaching the insulating layer.

5. A method according to claim 1 wherein removing the handle wafer comprises etching the handle wafer.

6. A method according to claim 1 wherein selectively removing the insulating layer comprises etching the insulating layer.

7. A method for fabricating a microelectromechanical (MEMS) structure comprising:

providing a silicon-on-insulator (SOI) wafer comprising a handle wafer, an insulating layer disposed on the handle wafer and a silicon layer disposed on the insulating layer;

etching at least one trench through the silicon layer by reactive ion etching;

bonding a support substrate to the silicon layer following said etching step, wherein a surface of the support substrate that is bonded to the silicon layer supports at least one conductive element;

removing the handle wafer following said bonding step; and

thereafter selectively removing the insulating layer such that the resulting MEMS structure comprises a silicon component that at least partially overlies the at least one conductive element supported by the support substrate and that is at least partially defined by the at least one trench etched through the silicon layer.

8. A method according to claim 7 further comprising providing the support substrate prior to said bonding step, wherein the surface of the support substrate that is bonded to the silicon layer is nonplanar to thereby define at least one cavity between the support substrate and the SOI wafer over which the silicon component is at least partially suspended.

9. A method according to claim 8 wherein said providing step comprises providing the support substrate having a plurality of mesas separated by recessed portions that are defined by the nonplanar surface to which the SOI wafer is thereafter bonded, and wherein said bonding step comprises bonding the support substrate to the silicon layer such that the silicon component is suspended from a respective mesa over an adjacent recessed portion.

10. A method according to claim 7 wherein said etching step comprises terminating the reactive ion etching upon reaching the insulating layer.

11. A method according to claim 7 wherein removing the handle wafer comprises etching the handle wafer.

12. A method according to claim 7 wherein selectively removing the insulating layer comprises etching the insulating layer.