Silicon micromachine with sacrificial pedestal

• US 5,920,013 A
• Filed: 02/07/1997
• Issued: 07/06/1999
• Est. Priority Date: 02/07/1997
• Status: Expired due to Fees

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Ford Motor Company
• Inventors: Boardman, William John, Carper, Judd Steven, Crumlin, John, Ames, John, Carson, Paul Thomas, Lindsey, John Ralph, Stevenson, Paul Elwin
• Primary Examiner(s): CHAPMAN JR, JOHN E
• Application Number:
  US08/797,376
• Time in Patent Office: 879 Days
• Field of Search: 73/514.32, 361/280, 361/283.1, 361/283.2, 156/272.2, 156/273.1, 29/25.41, 428/428
• US Class Current: 73/514.32
• CPC Class Codes: B81C 1/00801 Avoid alteration of functional structures by etching, e.g. using a passivation layer or an etch stop layer B81C1/00595, B81C1/00468 take precedence
• CPC Class Codes: B81C 2201/0133 Wet etching
• CPC Class Codes: B81C 2201/014 by depositing an etch stop layer, e.g. silicon nitride, silicon oxide, metal
• CPC Class Codes: B81C 2203/031 Anodic bondings

Abstract

A protective coating is utilized to protect the silicon during a wet chemical etch step in the process of making a micromachine, thereby preventing the formation of etched holes or pits in the micromachine. In another embodiment, silicon sacrificial pedestals are used to eliminate or greatly reduces the electrical potential difference between metal on the glass substrate and the silicon, thereby eliminating arcing and the resulting damage to silicon and metal. These pedestals may be removed after the anodic bond.

Claims

1. A silicon micromachine comprising:

a substantially planar substrate;

a silicon element including an integral pedestal support portion;

at least one metal conductive pattern mounted on said substrate; and

at least one silicon sacrificial pedestal extending from and integral with said element for reducing the potential difference between said pattern and said element during anodic bonding of said pedestal support portion to said substrate.

2. The silicon micromachine of claim 1 wherein said at least one silicon sacrificial pedestal is in proximity with said pattern.

3. The micromachine of claim 1 further comprising a protective coating between said substrate and said pedestal support portion of said element and said at least one sacrificial pedestal.

4. The micromachine of claim 1 further comprising an insulating layer separating said at least one silicon sacrificial pedestal from direct contact with said pattern during anodic bonding.

5. A silicon micromachine comprising:

a substantially planar substrate;

a silicon element including an integral pedestal support portion;

at least one metal conductive pattern mounted on said substrate;

said pattern including first and second metal capacitor plates;

first and second silicon sacrificial pedestals integral with said element and extending from said element toward said first and second metal capacitor plates, respectively to reduce the potential difference between said element and said plates during anodic bonding of said pedestal support portion to said substrate;

a silicon etch stop layer contacting one surface of each of said pedestals and said element.

6. The micromachine of claim 5 further comprising a protective coating extending between said substrate and said pedestal support portion of said element and said sacrificial pedestals.

7. The micromachine of claim 5 wherein said silicon sacrificial pedestals are in proximity with said pattern during anodic bonding.

8. The micromachine of claim 5 wherein said silicon sacrificial pedestals are separated from said pattern during anodic bonding by an insulating layer.