Process for making micromechanical structures

• US 6,008,138 A
• Filed: 03/07/1997
• Issued: 12/28/1999
• Est. Priority Date: 03/19/1996
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Laermer, Franz, Schilp, Andrea
• Primary Examiner(s): Powell, William
• Assistant Examiner(s): OKORO, BERNADINE O
• Application Number:
  US08/814,760
• Time in Patent Office: 1,026 Days
• Field of Search: 438/725, 438/735, 438/736, 438/780
• US Class Current: 438/725
• CPC Class Codes: B81B 2203/053 Translation according to an axis perpendicular to the substrate
• CPC Class Codes: B81B 3/0051 For defining the movement, i.e. structures that guide or limit the movement of an element mechanical arrangements for preventing or damping vibration or shock H01H3/60
• CPC Class Codes: B81C 2201/0108 Sacrificial polymer, ashing of organics

Abstract

A process for structuring a movable element out of a membrane region. A sacrificial layer and a sealing layer are applied to the underside of the membrane region. Following removal of the sacrificial layer, sealing layer forms a limit stop and a seal for the movement of the movable element.

Claims

1. A process for making a micromechanical structure, comprising the steps of:

forming a cavity in a silicon wafer such that a membrane region is created;

forming a movable element from the membrane region by etching;

creating a limit stop for limiting a deflection of the movable element;

creating a sacrificial layer on an underside of the membrane region;

covering the sacrificial layer with a sealing layer for the limit stop;

introducing trenches in the membrane region starting from a top side of the membrane region, the trenches reaching as far as the sacrificial layer; and

removing the sacrificial layer by exposing the sacrificial layer to an etching medium.

2. The process according to claim 1, wherein the sacrificial layer is created by evaporating a polymer solution introduced into the cavity.

3. The process according to claim 2, wherein the evaporation of the polymer solution creates a polymer layer on walls of the cavity, and further comprising the step of removing the polymer layer by etching after the polymer solution has evaporated.

4. The process according to claim 1, wherein the sealing layer includes at least one of a silicone polymer and an epoxy resin.

5. The process according to claim 1, wherein the trenches are introduced by etching, and further comprising the step of providing a metal layer acting as an etch stop on the underside of the membrane region.

6. The process according to claim 5, farther comprising the step of removing the metal layer after the sacrificial layer has been removed.

7. The process according to claim 5, wherein the etch stop includes one of aluminum, chromium, and nickel.

8. The process according to claim 5, wherein the metal layer is provided after the step of forming the cavity is completed.

9. The process according to claim 1, wherein the trenches are introduced by etching with a fluorine-containing plasma.

10. The process according to claim 1, wherein the cavity is formed by anisotropic etching of a single-crystal silicon constituting the silicon wafer.

11. The process according to claim 1, further comprising the step of introducing an amount of polymer solution into the cavity.

12. The process according to claim 1, wherein the step of forming the cavity includes the step of removing an amount of silicon from the silicon wafer.