Sensor

• US 5,259,247 A
• Filed: 01/27/1992
• Issued: 11/09/1993
• Est. Priority Date: 02/28/1991
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Bantien, Frank
• Primary Examiner(s): WOODIEL, DONALD
• Application Number:
  US07/825,945
• Time in Patent Office: 652 Days
• Field of Search: 73/718, 73/724, 361/283, 29/25.35, 29/25.42
• US Class Current: 73/718
• CPC Class Codes: G01L 9/0073 using a semiconductive diaphragm
• CPC Class Codes: G01P 15/0802 Details
• CPC Class Codes: G01P 15/125 by capacitive pick-up

Abstract

A sensor for measuring pressure and acceleration is proposed; it has a monocrystalline silicon substrate (10) with a succession of thin films applied to its first primary surface. A deflectable membrane (12) in a frame (11) is structured out of the silicon substrate (10), and the membrane (12) is formed in the first primary surface. The membrane (12) has a reinforcement zone. In the succession of thin films that is applied to the first primary surface, there is a structure (50) having at least one first substructure, which is disposed parallel to the first primary surface of the silicon substrate (10). There is a gap between the first substructure and the silicon substrate (10). The first substructure is joined to the membrane (12) in the region of the reinforcement zone. It protrudes past the membrane (12) and extends at least partway over the frame (11). This first substructure forms one electrode of a capacitor. At least one first counterelectrode (161, 162) of the capacitor is disposed opposite the first substructure, in the region of the frame (11).

Claims

1. A sensor for measuring pressure or acceleration, which has a monocrystalline silicon substrate with a succession of thin films applied to its first primary surface, wherein a structure having at least a first substructure is formed in these films, so that the first substructure is oriented parallel to the first primary surface of the silicon substrate, and there is a gap between the first substructure and the primary surface, characterized in that

the silicon substrate (10) is structured and has a frame (11) with a deflectable membrane (12) formed in the first primary surface;

that the membrane (12) has a reinforcement zone;

that the first substructure is joined to the membrane (12) in the region of the reinforcement zone;

that the first substructure extends past the membrane (12) at least partway over the frame (11);

that the first substructure forms an electrode of a capacitor; and

that at least one first counterelectrode (161,

     162) of the capacitor is disposed in the region of the frame (11) opposite the first substructure.

2. The sensor of claim 1, characterized in that

at least one second substructure is present, which is joined to the silicon substrate (10) in the region of the frame (11);

and that the at least one second substructure forms at least one second counterelectrode for the electrode, so that the at least one second counterelectrode together with the at least one first counterelectrode (161,

     162) and the electrode, as a middle electrode, form a differential capacitor.

3. The sensor of claim 1, characterized in that

the structure (50) is structured from a layer of polysilicon or a layer of monocrystalline silicon.

4. The sensor of claim 1, characterized in that

the membrane (12) in the region of the reinforcement zone, has an additional mass (13).

5. The sensor of claim 1, characterized in that

the silicon substrate (10) has an upper layer (8), in which portions of the membrane (12) are formed.

6. The sensor of claim 1, characterized in that

the electric leads of the electrodes of the capacitor are diffused into the first primary surface of the silicon substrate (10).

7. The sensor of claim 1, characterized in that

the at least one counterelectrode (161, 162) of the capacitor is diffused into the first primary surface of the frame (11).

8. The sensor of claim 1, characterized in that

the structure (50) is hermetically sealed off by a cap (40), of preferably polysilicon or monocrystalline silicon, applied to the first primary surface of the silicon carrier (10).

9. The sensor of claim 8, characterized in that

a defined pressure, preferably a vacuum, prevails inside the cap (40).

10. The sensor of claim 1, characterized in that

a low-voltage passivation layer, preferably a nitride layer, is applied on all sides to all the substructures of the structure (50) and to the first primary surface of the silicon substrate (10), at least in the region of the structure (50).

11. The sensor of claim 1, characterized in that

the at least one substructure has at least one pedestal (311, 312), from which at least one second counterelectrode (301, 302), embodied in tongue-like fashion, begins, wherein the at least one second substructure is joined to the frame (11) via the at least one pedestal (311, 312);

and that the at least one second counterelectrode is oriented parallel to the first substructure forming the middle electrode and extends at least part way past it.

12. The sensor of claim 1, characterized in that

the at least one first substructure has a pedestal (211, 212), from which at least one movable middle electrode (221, 222), formed in a tongue shape, begins,

that at least one first substructure is joined to the membrane (12) via the at least one pedestal (211, 212);

that the at least one pedestal (211,

     212) is disposed on the outer rim of the reinforcement zone, and the at least one movable middle electrode (221,

     222) is oriented parallel to the first primary surface of the silicon substrate (10) and protrudes past the frame (11);

that at least one electrode (15), which is in conductive contact with the at least one movable middle electrode (221,

     22) is disposed on the membrane (12), in the region of the reinforcement zone;

and that above the at least one electrode (15), next to the at least one pedestal (211,

     212) of the at least one first substructure, a bridge-like second counter electrode (25) firmly joined on two sides to the frame (11) is disposed, serving as at least one second substructure.

13. The sensor of claim 4, characterized in that

the membrane (12) is pierced around the additional mass (13), so that the additional mass (13) is suspended only from webs embodied in the membrane (12).

14. The sensor of claim 4, characterized in that

a lower layer (9), preferably a monocrystalline silicon layer, is applied to the second primary surface of the silicon substrate (10);

and that fastening webs (14), which join the additional mass (13) to the frame (11), are formed in the lower layer (9).

15. The sensor of claim 14, characterized in that

a lower covering (45), which has a cavern (4) in the region of the additional mass (13), is applied against the lower layer (9);

that at least one first excitation electrode (46) is disposed in the lower layer (9) in the region of the additional mass (13);

that at least one second excitation electrode (47) is disposed on the bottom face of the cavern (44), opposite the at least one first excitation electrode (46);

and that means are provided for applying a voltage between the excitation electrodes (46,

     47).

16. The sensor of claim 15, characterized in that

the lower covering (45) is formed by a glass or silicon substrate.

17. The sensor of claim 1, characterized in that

a pressure lead is disposed on the second primary surface of the silicon substrate (10).

18. The sensor of claim 2, characterized in that

a pressure lead is disposed on the second primary surface of the silicon substrate (10).

19. The sensor of claim 3, characterized in that a pressure lead is disposed on the second primary surface of the silicon substrate (10).

20. The sensor of claim 4, characterized in that

a pressure lead is disposed on the second primary surface of the silicon substrate (10).