Sealed micromachined vacuum and gas filled devices

• US 5,493,177 A
• Filed: 10/26/1993
• Issued: 02/20/1996
• Est. Priority Date: 12/03/1990
• Status: Expired due to Fees

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Williams, Kirt R., Muller, Richard S., Mastrangelo, Carlos H.
• Primary Examiner(s): Coles, Sr., Edward L.
• Assistant Examiner(s): Grant, II, Jerome
• Application Number:
  US08/143,220
• Time in Patent Office: 847 Days
• Field of Search: 313/582, 313/587, 313/588, 313/309, 313/522, 313/578, 445/24, 445/50, 445/51
• US Class Current: 313/578
• CPC Class Codes: G01J 3/108 for measurement in the infrared range
• CPC Class Codes: G01P 15/0894 by non-contact electron transfer, i.e. electron tunneling
• CPC Class Codes: G03F 7/00 Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor using photoresist structures for special production processes, see the relevant places, e.g. B44C, H01L, e.g. H01L21/00, H05K
• CPC Class Codes: H01J 21/105 with microengineered cathode and control electrodes, e.g. Spindt-type
• CPC Class Codes: H01J 3/00 Details of electron-optical or ion-optical arrangements or of ion traps common to two or more basic types of discharge tubes or lamps
• CPC Class Codes: H01J 5/00 Details relating to vessels or to leading-in conductors common to two or more basic types of discharge tubes or lamps
• CPC Class Codes: H01J 61/30 Vessels; Containers
• CPC Class Codes: H01J 9/02 Manufacture of electrodes or electrode systems
• CPC Class Codes: H01K 1/04 characterised by the material thereof
• CPC Class Codes: H01K 1/12 Bodies which are non-conductive when cold, e.g. for Nernst lamp
• CPC Class Codes: H01K 1/28 Envelopes; Vessels
• CPC Class Codes: H01K 13/00 Lamps having an incandescent body which is substantially non-conductive until heated, e.g. Nernst lamp
• CPC Class Codes: H01K 3/00 Apparatus or processes adapted to the manufacture, installing, removal, or maintenance of incandescent lamps or parts thereof manufacture of vessels from glass C03B
• CPC Class Codes: H01K 7/04 for indicating

Abstract

A surface and/or bulk micromachined hermetically sealed cavity containing at least one suspended structure in a low pressure ambient, and the associated fabrication method. The cavity is bounded by a thin-film membrane and a substrate which may have a recess. The method can be used for the production, for example, of thermionic-emission vacuum tubes, gas filled tubes and electromechanical devices. In vacuum tubes the cathode is a suspended refractory filament. Other electrodes may also be suspended. In electromechanical devices the suspended members may be cantilever beams capable of low friction motion.

Claims

1. A method for forming a microstructure, said method comprising the steps of:

providing a substrate including a first etchable structure, wherein said first etchable structure is at least partly exposed;

forming a patterned planar unetchable structure having at least one layer on said substrate, at least a portion of which is above an exposed portion of said first etchable structure;

forming a patterned second etchable structure on top of said unetchable structure, wherein a portion of said unetchable structure, but not the entire said unetchable structure, is between parts of the first and second etchable structures;

depositing an unetchable membrane layer on top of said patterned second etchable structure;

opening etching holes in said membrane layer in an area thereof where it overlaps one of said first and second etchable structures;

etching said first and second etchable structures to a predetermined extent to form a cavity with a suspended member, the cavity including at least one etching channel bound by said membrane layer;

creating a predetermined ambient in said cavity; and

depositing additional material to fill said etching channel and seal the cavity.

5. The method of claim 3, 1 or 2, further comprising:

after sealing the cavity, changing the ambient within the cavity.

6. The method of claim 5 wherein the ambient is changed by heating the suspended member.

2. A method for forming a microstructure, said method comprising the steps of:

providing a substrate including a first etchable structure, wherein said first etchable structure is at least partly exposed;

forming a patterned planar unetchable structure having at least one layer on said substrate, at least a portion of which is above an exposed portion of said first etchable structure;

forming a patterned second etchable structure on top of said unetchable structure, wherein a portion of said unetchable structure, but not the entire said unetchable structure, is between parts of the first and second etchable structures;

depositing an unetchable membrane layer on top of said patterned second etchable structure;

opening etching holes in said membrane layer in an area thereof where it overlaps one of said first and second etchable structures;

etching said first and second etchable structures to a predetermined extent to form a cavity with a suspended member, the cavity including at least one etching channel not bound by said unetchable structure;

creating a predetermined ambient in said cavity; and

depositing additional material to fill said etching channel and seal the cavity.

3. A method for forming a microstructure, said method comprising the steps of:

providing a substrate including a first etchable structure, wherein said first etchable structure is at least partly exposed;

forming a patterned planar unetchable structure having at least one layer on said substrate, at least a portion of which is above an exposed portion of said first etchable structure;

forming a patterned second etchable structure on top of said unetchable structure, wherein a portion of said unetchable structure, but not the entire said unetchable structure, is between parts of the first and second etchable structures;

depositing an unetchable membrane layer on top of said patterned second etchable structure;

opening etching holes in said membrane layer in an area thereof where it overlaps one of said first and second etchable structures;

etching said first and second etchable structures to a predetermined extent to form a cavity with a suspended member;

creating a predetermined ambient in said cavity; and

depositing additional material to seal the cavity.

4. The method of claim 3 wherein the etching step is self limited.