Pressure sensor having a chamber and a method for fabricating the same

• US 7,704,774 B2
• Filed: 05/03/2007
• Issued: 04/27/2010
• Est. Priority Date: 05/23/2006
• Status: Active Grant

• Current Assignee: InvenSense International, LLC
• Original Assignee: Sensirion Holding AG
• Inventors: Buhler, Johannes, Mayer, Felix, Streiff, Matthias, Sunier, Robert
• Primary Examiner(s): Mulpuri; Savitri
• Application Number:
  US11/799,822
• Publication Number:
  US 20070275494A1
• Time in Patent Office: 1,090 Days
• Field of Search: 438 48- 53
• US Class Current: 438/53
• CPC Class Codes: B81B 2201/0264 Pressure sensors
• CPC Class Codes: B81C 1/0023 Packaging together an electronic processing unit die and a micromechanical structure die MEMS packages B81B7/0032; MEMS packaging processes B81C1/00261
• CPC Class Codes: B81C 1/00238 Joining a substrate with an electronic processing unit and a substrate with a micromechanical structure
• CPC Class Codes: B81C 2201/019 Bonding or gluing multiple substrate layers
• CPC Class Codes: G01L 9/0042 Constructional details associated with semiconductive diaphragm sensors, e.g. etching, or constructional details of non-semiconductive diaphragms details about the integration or bonding of piezoresistor in or on the diaphragm G01L9/0052 and G01L9/0057 respectively
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm
• CPC Class Codes: H01L 23/10 characterised by the material or arrangement of seals between parts, e.g. between cap and base of the container or between leads and walls of the container
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

A pressure sensor is manufactured by joining two wafers, the first wafer comprising CMOS circuitry and the second being an SOI wafer. A recess is formed in the top material layer of the first wafer, which is covered by the silicon layer of the second wafer to form a cavity. Part or all of the substrate of the second wafer is removed to forming a membrane from the silicon layer. Alternatively, the cavity can be formed in the second wafer. The second wafer is electrically connected to the circuitry on the first wafer. This design allows to use standard CMOS processes for integrating circuitry on the first wafer.

Claims

1. A method for fabricating a pressure sensor comprising:

providing a first wafer comprising a base substrate of silicon with integrated circuitry integrated thereon and at least one material layer deposited on said base substrate;

providing a second wafer;

manufacturing a recess in said first wafer by locally removing or omitting said material layer; and

mounting said second wafer, or a chip prepared from said second wafer, on said first wafer, and electrically connecting said second wafer to said circuitry on said first wafer,

wherein said recess does not reach into said base substrate, and wherein said second wafer comprises a handle substrate, a silicon layer and an insulating layer between said handle substrate and said silicon layer, said silicon layer being positioned to form at least part of a deformable membrane over said recess for sensing a pressure, said second wafer comprising a cavity closed by said deformable membrane.

2. The method of claim 1 comprising the steps of forming a first electrical contact between said circuitry and said handle substrate and a second electrical contact between said circuitry and said membrane.

3. The method of claim 1 comprising the step of forming said cavity at least partially by forming a recess in said handle substrate.

4. The method of claim 1 wherein said cavity comprises a first chamber and a second chamber, the first chamber having smaller volume and smaller height than the second chamber, wherein said deformable membrane covers said first chamber.

5. The method of claim 1 wherein said material layer is a silicon oxide, silicon nitride, metal or polisilicon layer.

6. The method of claim 5 wherein said recess is formed over a conducting layer, in particular a metal layer on said first wafer.

8. The method of claim 1 wherein said integrated circuitry is manufactured using a CMOS process or a bipolar process.

9. The method of claim 1 further comprising the steps of

forming a cavity between said first and said second wafer,

removing material from said first wafer from a side opposite to said second wafer with a membrane formed by said first wafer remaining for closing said cavity.

10. The method of claim 9 wherein a passivation layer is applied from said second side to said first wafer.

7. A method for fabricating a pressure sensor comprising:

providing a first wafer comprising a base substrate of silicon with integrated circuitry integrated thereon and at least one material layer deposited on said base substrate;

providing a second wafer;

manufacturing a recess in said first wafer by locally removing or omitting said material layer;

mounting said second wafer, or a chip prepared from said second wafer, on said first wafer, and electrically connecting said second wafer to said circuitry on said first wafer;

preparing a contact window on said first wafer;

forming or placing an edge of said second wafer at said contact window; and

applying a metal layer contacting said contact window to said edge, wherein said recess does not reach into said base substrate, said second wafer comprising a silicon layer positioned to form at least part of a deformable membrane over said recess for sensing a pressure, said second wafer comprising a cavity closed by said deformable membrane.

11. A method for fabricating a pressure sensor comprising:

providing a first wafer comprising a base substrate of silicon with integrated circuitry integrated thereon and at least one material layer deposited on said base substrate;

providing a second wafer;

manufacturing a recess in said first wafer by locally removing or omitting said material layer;

mounting said second wafer, or a chip prepared from said second wafer, on said first wafer, and electrically connecting said second wafer to said circuitry on said first wafer;

forming a cavity between said first and said second wafer;

removing material from said first wafer from a side opposite to said second wafer with a membrane formed by said first wafer remaining for closing said cavity, wherein said recess does not reach into said base substrate; and

locally etching off part of said second wafer, wherein said second wafer comprises a silicon top layer, an insulating layer and a handle substrate with the insulating layer being arranged between said top layer and said handle substrate, and, wherein said second wafer is locally etched off thus that top layer extends laterally beyond handle substrate, thereby forming projections, which projections are then enclosed by a wafer interconnect layer.

12. A method for fabricating a pressure sensor comprising:

providing a first wafer comprising a base substrate of silicon with integrated circuitry integrated thereon and at least one material layer deposited on said base substrate;

providing a second wafer;

manufacturing a recess in said first wafer by locally removing or omitting said material layer;

mounting said second wafer, or a chip prepared from said second wafer, on said first wafer, and electrically connecting said second wafer to said circuitry on said first wafer;

forming a cavity between said first and said second wafer;

removing material from said first wafer from a side opposite to said second wafer with a membrane formed by said first wafer remaining for closing said cavity, wherein said recess does not reach into said base substrate; and

forming a recess in said first wafer from a side opposite to said second wafer into said first wafer, with said membrane remaining between said cavity and said recess.