×

Micromachined capacitor structure and method for making

  • US 5,181,156 A
  • Filed: 05/14/1992
  • Issued: 01/19/1993
  • Est. Priority Date: 05/14/1992
  • Status: Expired due to Term
First Claim
Patent Images

1. A method for forming travel limit stops in a micromachined capacitor structure comprising the steps of:

  • providing a substrate having a top surface;

    covering the top surface with a first silicon nitride layer;

    forming a first polysilicon layer on the first silicon nitride layer,patterning the first polysilicon layer to form a first anchor and a lower capacitor plate, wherein portions of the first silicon nitride layer are exposed by the patterning step;

    covering the first patterned polysilicon and the exposed portions of the first silicon nitride with a first sacrificial layer comprising silicon oxide;

    covering the first sacrificial layer with a second silicon nitride layer;

    covering the second silicon nitride layer with a second sacrificial layer comprising silicon oxide;

    etching a first hole in the second sacrificial layer, the second silicon nitride, and the first sacrificial layer to expose the first anchor;

    etching a second hole in the second sacrificial layer over the lower capacitor plate;

    forming a second polysilicon layer that fills the first and second holes and covers the second sacrificial layer;

    patterning the second polysilicon layer to form a middle capacitor plate that is mechanically attached to the anchor, has a portion spaced from the lower capacitor plate by the thickness of the first and second sacrificial layers together with the second silicon nitride layer, and a travel stop portion which is spaced from the lower capacitor plate by the thickness of the first sacrificial layer and the second silicon nitride layer; and

    performing a sacrificial etch of the first and second sacrificial layers using an isotropic etchant that etches the silicon oxide faster than silicon nitride, wherein only a portion of the second silicon nitride layer which is covered by the travel stop portion remains after the sacrificial etching.

View all claims
  • 7 Assignments
Timeline View
Assignment View
    ×
    ×