Micro motors and method for their fabrication

• US 5,252,881 A
• Filed: 12/14/1988
• Issued: 10/12/1993
• Est. Priority Date: 12/14/1988
• 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: Tai, Yu C., Fan, Longsheng, Muller, Richard S.
• Primary Examiner(s): Skudy, R.
• Application Number:
  US07/284,084
• Time in Patent Office: 1,763 Days
• Field of Search: 310/40 MM, 310/49 R, 310/90, 310/162-164, 310/269, 310/261, 310/254, 310/42, 310/309, 310/268, 310/DIG. 6
• US Class Current: 310/309
• CPC Class Codes: H02N 1/004 in which a body is moved along a path due to interaction with an electric field travelling along the path

Abstract

A method for making and the product resulting from the method for making a microminiature electrical motor having a rotor rotatable about a fixed hub member within a surrounding stator, the diameter of the stator being typically in the range of 60-140 microns. Both synchronous and stepper motor configurations are described, each with structural features that provide increased performance and minimal rotor friction. The processes disclosed for making the micro-motors include the steps of: providing a substrate material with a first layer of silicon dioxide covered by an overlayer of silicon nitride; providing a first layer of sacrificial material on said substrate; providing a first structural layer over said sacrificial material; providing patterning and then etching said first structural layer to form said rotor and stator components; providing a second layer of sacrificial material over said first structural layer and patterning it to form an anchor opening in said substrate at the center of the rotor; providing a second structural layer to form a hub member in said anchor opening and patterning said second structural layer to form a flange for said hub member; and etching said sacrificial layers to separate said rotor and stator components and said rotor from said hub member so that it rotates about it. The invention also includes an ancillary method for protecting metallized elements in the motor circuit during the required etching steps for removal of sacrificial layers.

Claims

1. A microminiature electric motor comprising:

a substrate base covered with a first layer of silicon dioxide and a second layer of silicon nitride;

a hub member fixed to and extending above said base;

a rotor having a plurality of poles and rotatable in a circular path on said hub member;

a fixed stator including a series of poles surrounding the circular path of said rotor poles, said hub member, said rotor and said stator all being comprised of sequentially deposited and etched film materials on said substrate base; and

a plurality of conductive lead members on said base connected to said stator poles and adapted for connection with a power source.

2. The electric motor as described in claim 1 including a first layer of polysilicon on said silicon nitride layer located under said rotor and forming a ground plane for said motor.

3. The electric motor as described in claim 2 wherein said stator poles extend upwardly from ends of said lead members and are spaced above said ground plane.

4. The electric motor as described in claim 3 wherein said stator poles are spaced outwardly from and are substantially co-planar with said rotor poles.

5. The electric motor as described in claim 4 in which silicon nitride material forms spacer means on an outer surface of said stator poles and said rotor poles.

6. The electric motor as described in claim 2 wherein a second layer of polysilicon forms a substrate of said rotor, said stator and said lead members, and a third layer of polysilicon providing an upper flange on said hub member.

7. A microminiature electric motor comprising:

a substrate base;

a hub member fixed to said base;

a rotor having a plurality of poles and rotatable in a circular path on said hub member; and

a fixed stator means including a series of poles surrounding the circular path of said rotor poles, the diameter of said stator means between opposite stator poles being from 60 to 140 microns.

8. A microminiature electric motor comprising:

a substrate base;

a hub member fixed to and extending above said base;

a rotor having a plurality of poles and rotatable in a circular path on said hub member, said rotor being a generally circular planar member with an upper surface and a lower surface spaced above said base; and

a plurality of circumferentially spaced apart projections on said lower rotor surface for supporting said rotor on said substrate base as it rotates;

a fixed stator including a series of poles surrounding the circular path of and spaced from said rotor poles, said hub member, said rotor and said stator all being comprised of sequentially deposited and etched film materials on said substrate base; and

a plurality of conductive lead members on said base connected to said stator poles and adapted for connection with a power source.

9. A microminiature electric motor comprising:

a substrate base;

a hub member fixed to and extending above said base;

a rotor having a plurality of poles and rotatable in a circular path on said hub member, said rotor being a generally circular member with peripherally spaced apart poles;

a fixed stator including a series of poles surrounding the circular path of and spaced from said rotor poles, said hub member, said rotor and said stator all being comprised of sequentially deposited and etched film materials on said substrate base;

said rotor poles located in a plane lower than said stator poles and thus closer to said substrate base thereby creating a force component which tends to lift said rotor away from said substrate base to reduce friction on said rotor; and

a plurality of conductive lead members on said base connected to said stator poles and adapted for connection with a power source.

10. A microminiature electric motor comprising:

a substrate base;

a hub member fixed to and extending above said base, said hub member being made entirely of silicon nitride material;

a rotor having a plurality of poles and rotatable in a circular path on said hub member;

a fixed stator including a series of poles surrounding the circular path of said rotor poles, said hub member, said rotor and said stator all being comprised of sequentially deposited and etched film materials on said substrate base; and

a plurality of conductive lead members on said base connected to said stator poles and adapted for connection with a power source.