Micromachined membrane particle filter using parylene reinforcement

• US 6,622,872 B1
• Filed: 11/06/1998
• Issued: 09/23/2003
• Est. Priority Date: 11/07/1997
• Status: Expired due to Term

• Current Assignee: California Institute of Technology
• Original Assignee: California Institute of Technology
• Inventors: Tai, Yu-Chong, Yang, Xing
• Primary Examiner(s): Walker, W. L.
• Assistant Examiner(s): SORKIN, DAVID L
• Application Number:
  US09/187,475
• Time in Patent Office: 1,782 Days
• Field of Search: 210/490, 210/500.1, 210/500.33, 210/506, 427/255.393, 427/255.394, 427/579, 427/255.6, 216/2, 216/56
• US Class Current: 210/490
• CPC Class Codes: B01D 2239/0471 Surface coating material
• CPC Class Codes: B01D 2239/0478 on a layer of the filter
• CPC Class Codes: B01D 2239/10 Filtering material manufacturing
• CPC Class Codes: B01D 2325/021 Pore shapes
• CPC Class Codes: B01D 39/2093 Ceramic foam
• CPC Class Codes: B01D 67/0034 by micromachining techniques, e.g. using masking and etching steps, photolithography
• CPC Class Codes: B01D 67/0062 by micromachining techniques, e.g. using masking and etching steps, photolithography
• CPC Class Codes: B01D 67/0072 by deposition from the gaseous phase, e.g. sputtering, CVD, PVD
• CPC Class Codes: B01D 67/0088 Physical treatment with compounds, e.g. swelling, coating or impregnation
• CPC Class Codes: B01D 71/0213 Silicon
• CPC Class Codes: B01D 71/72 Macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds, not provided for in a single one of the groups B01D71/46 - B01D71/70 and B01D71/701 - B01D71/702

Abstract

A micromachined membrane particle filter is formed by making holes in a silicon derivative overlayer and coating over the holes with Parylene.

Claims

1. A method of forming a micromachined particle filter, comprising:

forming a silicon derivative overlayer on a first side and a second side of a silicon substrate;

etching the second side of the silicon substrate opposite the first side to form a thinned portion of the silicon substrate;

subsequent to etching the second side, etching the silicon derivative overlayer on the first side to form holes in the silicon derivative overlayer, said holes of at least 10 μ

m across one portion thereof;

subsequent to etching the silicon derivative overlayer on the first side, further etching the second side to substantially remove silicon from the substrate below the holes; and

depositing at least 2 μ

m of Parylene over remaining portions of the silicon derivative overlayer, including inner surfaces which define said holes, to form a Parylene coated membrane filter that has increased structural strength.

2. A method as in claim 1 wherein said silicon derivative is silicon nitride.

3. The method of claim 1, wherein forming a silicon derivative overlayer on the first and second side of the substrate comprises forming an overlayer between 0.5 and 1 μ

m thick on at least one of the first and second side.

4. The method of claim 1, wherein etching the second side to form a thinned portion of the silicon substrate comprises etching the second side to form a thinned portion between 20 and 100 μ

m thick.

5. A method of forming a micromachined particle filter, comprising:

obtaining a silicon substrate, with a silicon derivative overlayer on a first side and a second side of the silicon substrate;

etching the second side of the silicon substrate opposite the first side to form a thinned portion of the silicon substrate;

subsequent to etching the second side, etching the silicon derivative overlayer on the first side to form holes in the silicon derivative overlayer;

subsequent to etching the first side, further etching the second side to substantially remove silicon from the substrate below the holes to form a membrane with holes which are at least 10 μ

m across an extend thereof; and

increasing a strength of the membrane with holes, by depositing at least 2 μ

m of Parylene over remaining portions of the silicon derivative overlayer, including inner surfaces which define said holes, to form a Parylene coated membrane filter that has increased structural strength.

6. A method as in claim 5 wherein said silicon derivative is silicon nitride.

7. A method as in claim 5 wherein said holes are circular.

8. A method as in claim 5 wherein said holes are rectangular.

9. A method as in claim 5 wherein said holes are hexagonal.

10. The method of claim 5, wherein obtaining a silicon substrate comprises obtaining a silicon derivative overlayer on the first and second side of the substrate having an overlayer between 0.5 and 1 μ

m thick on at least one of the first and second side.

11. The method of claim 5, wherein etching the second side to form a thinned portion of the silicon substrate comprises etching the second side to form a thinned portion between 20 and 100 μ

m thick.