Method to make gas permeable shell for MEMS devices with controlled porosity

• US 6,444,135 B1
• Filed: 10/16/2000
• Issued: 09/03/2002
• Est. Priority Date: 01/14/2000
• Status: Expired due to Fees

• Current Assignee: Ball Semiconductor, Inc.
• Original Assignee: Ball Semiconductor, Inc.
• Inventors: Toda, Risaku, Hanabe, Murali
• Primary Examiner(s): Gulakowski, Randy
• Assistant Examiner(s): Ahmed, Shamim
• Application Number:
  US09/688,722
• Time in Patent Office: 687 Days
• Field of Search: 216/41, 216/56, 210/321.84
• US Class Current: 216/56
• CPC Class Codes: B81B 2201/0235 Accelerometers
• CPC Class Codes: B81B 2201/025 Inertial sensors not provided for in B81B2201/0235 - B81B2201/0242
• CPC Class Codes: B81C 1/00198 comprising elements which are movable in relation to each other, e.g. comprising slidable or rotatable elements

Abstract

A method and system for making a gas permeable shell in a micro electromechanical systems (MEMS) device is disclosed. The MEMS device is created with an internal sacrificial layer. The device is then coated with a slurry composition which, after drying, is later exposed to a solvent. As a result, the sacrificial layer is removed to produce interconnected voids.

Claims

1. A method for making a gas permeable shell around a small electro/mechanical device, the method comprising the steps of:

dissolving a first solid in a solvent to form a solution;

mixing the solution with a second solid to form a slurry;

coating the electro/mechanical device with the slurry to form a coated electro/mechanical device;

drying the coated electro/mechanical device; and

exposing the coated electro/mechanical device to the solvent to re-dissolve the first solid.

2. The method of claim 1 wherein the step of exposing the coated electro/mechanical device to the solvent includes producing a plurality of interconnected voids.

3. The method of claim 2 further comprising controlling the size of the voids by the composition of the slurry.

4. The method of claim 2 wherein the mixing is performed in a predetermined manner to control size of the voids.

5. The method of claim 1 wherein the small electro/mechanical device is built around a spherical shaped substrate.

6. A method for making a gas permeable shell around a micro electro-mechanical systems (MEMS) device, comprising the steps of:

dissolving a first solid in a solvent to form a solution;

mixing the solution with a second solid to form a slurry;

coating the MEMS device with the slurry to form a coated MEMS device;

drying the coated MEMS device;

exposing the coated MEMS device to the solvent to re-dissolve the first solid.

7. The method of claim 6 wherein the step of exposing the coated MEMS device to the solvent, produces a plurality of interconnected voids.

8. The method of claim 7 wherein the size of the voids are controlled by the composition of the slurry.

9. The method of claim 7 wherein the size of the voids are controlled by the step of mixing the solution with the second solid.

10. The method of claim 6 wherein the MEMS device is an accelerometer.