Solid state silicon-based condenser microphone

Abstract

A solid state silicon-based condenser microphone comprising a silicon transducer chip (1). The transducer chip includes a backplate (13) and a diaphragm (12) arranged substantially parallel to each other with a small air gap in between, thereby forming an electrical capacitor. The diaphragm (12) is movable relative to the backplate (13) in response to incident sound. An integrated electronic circuit chip (3) or ASIC is electrically coupled to the transducer chip (1). An intermediate layer (2) fixes the transducer chip (1) to the integrated electronic circuit chip (3) with the transducer chip (1) on a first side of the intermediate layer (2) and the integrated electronic circuit chip (3) on a second side of the intermediate layer (2) opposite the first side. The intermediate layer (2) has a sound inlet (4) on the same side as the ASIC giving access of sound to the diaphragm.

Description

Lo to respective ones of solder bumps 8, which connect the diaphragm 12 and the backplate 13 to electrical feedthrough conductors 14 on the surface of the cavity 10 and the opening 18 and further to the upper surface of the intermediate chip 2 where connections to the electronic circuit chip 3 are established via a conventional flip-chip interconnect method e.g. gold studs 7 with conductive adhesive. This is most clearly seen in FIG. 2.

The opening 4 is covered with a filter 5 or a flexible sheet or diaphragm of acoustically transparent material. The whole structure is encapsulated in a polymer encapsulation 16 leaving the filter 5 free.

The function of the above described structure is as follows. The opening 4 functions as a sound inlet, and ambient sound pressure enters through the filter 5 covering the opening 4 to the cavity 10 functioning as a front chamber for the microphone. Through the perforations 19 in the backplate 13 the sound pressure reaches the diaphragm 12. The cavity 11 functions as a backchamber for the microphone. The diaphragm 12 is movable relative to the backplate 13 in response to incident sound. When the diaphragm is moved in response to the incident sound, the electrical capacity of the electrical capacitor formed by the diaphragm 12 and the backplate 13 will vary in response to the incident sound. The circuit on the integrated circuit chip 3 is electrically connected to the diaphragm 12 And and the backplate 13 via the electrical feedthrough conductors 14, and the circuit is designed to detect variations in the electrical capacity of the capacitor formed by the diaphragm 12 and the backplate 13. The circuit has electrical connections for electrically connecting it to a power supply and other electronic circuitry in eg a hearing instrument.

In the illustrated embodiment the transducer element on the transducer chip is a condenser microphone with a diaphragm and a single backplate. In an alternative embodiment the transducer element has its diaphragm arranged between two backplates. Such a microphone can give balanced output signal which is less sensitive to electrical interference.

Claims

1. A solid state silicon-based condenser microphone comprising a silicon transducer chip (1) including a backplate (13) and a diaphragm (12) arranged substantially parallel to each other, thereby forming an electrical capacitor, the diaphragm (12) being movable relative to the backplate (13) in response to incident sound, an integrated electronic circuit chip (3) electrically coupled to the transducer chip (1), an intermediate layer (2) fixing the transducer chip (1) to the integrated electronic circuit chip (3) in a spaced relationship, with the transducer chip (1) on a first side of the intermediate layer (2) and the integrated electronic circuit chip (3) on a second side of the intermediate layer (2) opposite the first side, the intermediate layer (2) having a first through going opening (4, 10) between its first side and its second side giving access of sound to the diaphragm.

2. A condenser microphone according to claim 1 wherein the intermediate layer (2) on a surface thereof has electrical conductors (14) electrically connecting the transducer chip (1) to the integrated circuit chip (3).

3. A condenser microphone according to claim 2 wherein the intermediate layer (2) has a second through going opening (18) with a surface on which the electrical conductors (14) electrically connecting the transducer chip (1) to the integrated circuit chip (3) are situated.

4. A condenser microphone according to claim 1 wherein the opening (4) in the intermediate layer is covered with a film (5) sealing the opening (4) on the second side of the intermediate layer (2).

5. A condenser microphone according to claim 1 wherein a cavity (11) is provided in the transducer chip (1) on a side of the diaphragm (12) opposite the intermediate layer (2).

6. A condenser microphone according to claim 5 wherein the cavity (11) is a closed cavity.

7. A condenser microphone according to claim 2 wherein the integrated electronic circuit chip (3) has a surface including electronic circuits with said surface facing the intermediate layer (2).

8. A condenser microphone according to claim 1 wherein the intermediate layer (2) is a silicon-based chip.

9. A solid state silicon-based condenser microphone, comprising:

a silicon-based transducer chip including a backplate and a diaphragm, said diaphragm being movable relative to said backplate in response to incident sound;

an integrated electronic circuit chip for receiving an electrical signal from said silicon-based transducer chip corresponding to said incident sound; and

an intermediate element fixing said silicon-based transducer chip to said integrated electronic circuit chip in a spaced relationship, said intermediate element including an electrical conductor coupling said integrated electronic circuit chip and said silicon-based transducer chip, said intermediate element further including a cavity and a first through going opening communicating with said cavity, said integrated electronic circuit chip being secured to said transducer chip by flip-chip mounting said integrated electronic circuit chip such that a circuit of said integrated electronic circuit chip faces said intermediate element.

10. The condenser microphone of claim 9, wherein said intermediate element includes a feed-through, said feed-through including a feed-through conductor leading to said integrated electronic circuit chip.

11. The condenser microphone of claim 10, wherein said electrical conductor coupling said integrated electronic circuit chip and said silicon-based transducer chip is said feed-through conductor.

12. The condenser microphone of claim 10, wherein said feed-through is an opening.

13. The condenser microphone of claim 9, wherein said intermediate element is a silicon-based chip.

14. The condenser microphone of claim 9, wherein said integrated electronic circuit chip is an ASIC.

15. The condenser microphone of claim 9, wherein said integrated electronic circuit chip is flip-chip mounted to said intermediate element.

16. The condenser microphone of claim 9, wherein said integrated electronic circuit chip is located on one side of said intermediate element and said silicon-based transducer chip is located on an opposing side of said intermediate element.