Silicon condenser microphone having an additional back chamber and a fabrication method therefor

A fabrication method of a silicon condenser microphone having an additional back chamber. The method includes applying an adhesive on a substrate and mounting a chamber container thereon by using a mounter; curing the adhesive holding the chamber container; applying an adhesive on the chamber container and mounting a micro electro mechanical system (MEMS) chip thereon by using a mounter; curing the adhesive holding the MEMS chip; and attaching the substrate on which devices are mounted to a case, wherein a back chamber formed by the chamber container is added to a back chamber of the MEMS chip. Therefore, a silicon condenser microphone fabricated by using the method may have improved sensitivity by increasing the small back chamber space of the a micro electro mechanical system (MEMS) chip itself and reduced noise including total harmonic distortion (THD).

TECHNICAL FIELD

The present invention relates to a silicon condenser microphone and a method of fabricating the same, and more particularly, to a silicon condenser microphone having an additional back chamber and a method of fabricating the same.

BACKGROUND ART

Generally, a condenser microphone widely used in mobile communication terminals or mobile audio devices includes a voltage bias component, a pair of diaphragm/back plate for forming a capacitance C that changes in correspondence with sound pressures, and a field effect transistor (JFET) for buffering output signals. Such is a traditional type condenser microphone is completely formed as a single assembly by inserting a diaphragm, a spacer ring, an insulation ring, a back plate, and an electric current application ring into a single case in the stated order, inserting a PCB, on which circuit devices are mounted, into the case, and bending an end of the case toward the PCB.

Recently, a semiconductor fabrication technique using micromachining methods has been used for improving the integration of fine devices. By using this technique, a so-called micro electro mechanical system (MEMS), μm-sized ultra-small sensors, actuators, and electro-mechanical structures may be fabricated by using micromachining methods, and more particularly, integrated circuit methods, in a semiconductor fabrication process. In a MEMS chip microphone fabricated by using such micromachining methods, traditional microphone components, such as a diaphragm, a spacer ring, an insulation ring, a back plate, and an electric current application ring may be miniaturized, multi-functionalized, and densely integrated via ultra-high precision fabrication methods for improved stability and reliability.

FIG. 9shows a structure of a general MEMS chip10used in a silicon condenser microphone. Referring toFIG. 9, the MEMS chip10has a structure in which a back plate13is formed on a silicon wafer14by using a MEMS technique and a diaphragm11is formed on the back plate13by interposing a spacer12therebetween. A sound hole13ais formed in the back plate13, and a rear space of the back plate forms a back chamber. The MEMS chip10is fabricated by using a general micromachining method and a semiconductor chip fabrication method.

FIG. 10is a lateral sectional view of a conventional silicon condenser microphone1embodied by using a MEMS chip10. Referring toFIG. 10, the conventional silicon condenser microphone1is assembled by mounting the MEMS chip10and an ASIC chip20on a PCB40and inserting the PCB40into a case30in which a sound hole30ais formed.

As shown inFIG. 10, a back chamber15of the conventional silicon condenser microphone1is formed by the MEMS chip10. However, the MEMS chip10is a very small-sized semiconductor chip, and thus, the back chamber15formed by the MEMS chip10is very narrow. As a result, air resistance occurs due to a significant back stream and a vibrating force of a diaphragm deteriorates, and thus, the sound quality is (sensitivity) of the conventional silicon condenser microphone1deteriorates.

DISCLOSURE OF THE INVENTION

Technical Problem

The present invention provides a silicon condenser microphone having an additional back chamber and a method of fabricating the same.

Technical Solution

According to an aspect of the present invention, there is provided a method of fabricating a silicon condenser microphone having an additional back chamber, the method including applying an adhesive on a substrate and mounting a chamber container thereon by using a mounter; curing the adhesive holding the chamber container; applying an adhesive on the chamber container and mounting a micro electro mechanical system (MEMS) chip thereon by using a mounter; curing the adhesive holding the MEMS chip; and attaching the substrate on which devices are mounted to a case, wherein a back chamber formed by the chamber container is added to a back chamber of the MEMS chip.

The substrate is a printed circuit board (PCB), a glass substrate, a ceramic substrate, a plastic-based substrate, or a resin substrate. The adhesive is any one of a non-conductive adhesive and a conductive adhesive. The adhesive is any one of a silicon-based adhesive, an epoxy-based adhesive, and a metal solder.

The chamber container has a cuboidal shape or a cylindrical shape with one opne surface, and wherein a penetration hole is formed in a surface opposite to the open surface. A wing may be formed at the open surface of the chamber container.

According to another aspect of the present invention, there is provided a silicon condenser microphone having an additional back chamber, the silicon condenser microphone including a substrate; a chamber container, which has a cuboidal shape or a cylindrical shape with one open surface, forms an additional back chamber space as the open surface is adhered to the substrate via an adhesive, and has a penetration hole formed in a surface opposite to the open surface; a MEMS chip, which is attached to the surface of the chamber container opposite to the open surface and converts externally introduced sound pressures to electric signals; an application specific integrated circuit (ASIC) chip, which is mounted on the substrate, supplies power to the MEMS chip, amplifies electric signals from the MEMS chip, and outputs the amplified signals via a connection terminal of the substrate; and a case, which has a cylindrical shape with one open surface, forms a space for accommodating the chamber container, the MEMS chip, and the ASIC chip as the open surface is attached to the substrate, and shields external noise.

Sound holes are formed in one of or both of the substrate and the case. The chamber container has a cuboidal shape or a cylindrical shape, and wherein a wing is formed outwardly on the open surface.

Advantageous Effects

A silicon condenser microphone fabricated according to the present invention can have improved sensitivity by increasing the small back chamber space of the MEMS chip itself and reduced noise including THD (Total Harmonic Distortion).

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1is a flowchart showing a method of fabricating a silicon condenser microphone according to an embodiment of the present invention.

As shown inFIG. 1, the method of forming a silicon condenser microphone having an additional back chamber includes preparing a substrate (operation S1), preparing a chamber container (operation S2), applying an adhesive on the substrate and mounting the chamber container thereon by using a mounter (operation S3), curing the adhesive holding the chamber container at a predetermined temperature (operation S4), preparing a micro electro mechanical system (MEMS) chip (operation S5), applying an adhesive on the chamber container and mounting the MEMS chip thereon by using a mounter (operation S6), curing the adhesive holding the MEMS chip at a predetermined temperature (operation S7), mounting an application specific integrated circuit (ASIC) (operation S8), and attaching the substrate on which devices are mounted to a case (operation S9).

FIG. 2is an exploded perspective view of a silicon condenser microphone having an additional back chamber that is fabricated according to an embodiment of the present invention.FIG. 3is a combined perspective view of the same.

As shown inFIGS. 2 and 3, a silicon condenser microphone100having an additional back chamber that is fabricated according to the present invention has a structure in which a chamber container104for forming an additional back chamber104cis adhered onto a PCB102, on which a connection terminal112and a conductive pattern are formed, by using an adhesive108, a MEMS chip10is adhered onto the chamber container104by using an adhesive10, and a case106is adhered onto the PCB102by using an adhesive110. Here, an ASIC chip20for driving electric signals of the MEMS chip10is also mounted on the PCB102.

The chamber container104is provided to improve the sensitivity of the silicon condenser microphone100by increasing the small back chamber15space of the MEMS chip itself and reduce noise including total harmonic distortion (THD) and has a cuboidal or cylindrical shape with one open surface. A penetration hole104afor connecting the back chamber15to the additional back chamber104cis formed in a surface opposite to the open surface. Furthermore, although not shown, an electric wiring is formed in the chamber container104for transmitting electric signals from the MEMS chip10to the ASIC chip20. Therefore, the increased back chamber space, which is formed by adding the additional back chamber104cto the back chamber15of the MEMS chip10, may improve the low sensitivity due to a deteriorated vibrating force of a diaphragm caused by air resistance that is formed by a significant back stream due to insufficient back chamber space of the MEMS chip10.

The MEMS chip10is adhered onto the chamber container104by using the adhesive108, the ASIC chip20is mounted on the PCB102, and the case106is adhered to the PCB102by using the adhesive110. Accordingly, the assembly of the silicon condenser microphone is completed.

The case106has a cylindrical shape, which has an inner space for accommodating components and one open surface. A sound hole106afor introducing external sounds is formed in a surface opposite to the open surface, and the case106is attached to the PCB102by aligning the case106formed of a metal material to a conductive pattern formed on the PCB102and welding the case106to the PCB102or adhering the case106to the PCB102by using the adhesive110, such as an epoxy.

FIG. 4is a diagram showing an additional back chamber structure having a cuboidal shape according to an embodiment of the present invention.FIG. 5is a diagram showing an additional back chamber structure having a cylindrical shape according to an embodiment of the present invention.

As shown inFIGS. 4 and 5, the chamber container104for forming the additional back chamber104caccording to the present invention may have a cuboidal shape or a cylindrical shape, and the penetration hole104afor forming a path to the back chamber15that is formed by attaching the MEMS chip10is formed in the top of the cuboid or the cylinder.

A silicon condenser microphone of any of various shapes may be fabricated by attaching the case106of any of various shapes onto the PCB102, on which the MEMS chip10having the additional back chamber104cformed by the chamber container104and the ASIC chip20are mounted.

FIG. 6is a diagram showing an additional back chamber structure having a cuboidal shape and a wing.FIG. 7is a diagram showing an additional back chamber structure having a cylindrical shape and a wing.FIG. 8is a combined perspective view of a silicon condenser microphone having aback chamber structure with a wing.

Referring toFIGS. 6 through 8, the chamber container104for forming the additional back chamber104cmay have a cuboidal shape or a cylindrical shape with a wing as shown inFIGS. 6 and 7, the penetration hole104afor forming a path to the back chamber15that is formed by attaching the MEMS chip10is formed in the top of the cuboid or the cylinder with the wing.

A silicon condenser microphone of any of various shapes may be fabricated by attaching the case106of any of various shapes onto the PCB102, on which the MEMS chip10having the additional back chamber104cformed by the chamber container104with the wing and the ASIC chip20are mounted.

Industrial Applicability

A silicon condenser microphone fabricated according to the present invention can have improved sensitivity by increasing the small back chamber space of the MEMS chip itself and reduced noise including THD (Total Harmonic Distortion). Thus, the silicon condenser microphone may be highly industrially applicable.