JP2003078981A - Microphone mount circuit board, and sound processing apparatus mounted with the board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a microphone mount circuit board small in size, low in cost and improved in reliability. SOLUTION: A vibration membrane 12 vibrated by a sound pressure is formed in the middle of a base 11 and a support 13 surrounding the vibration membrane 12 supports a rear plate 14 to oppose to the vibration membrane 12 so as to interpose the support 13 between the vibration membrane 12 and the rear plate 14 thereby ensuring a vibration space S as a layered structure. Thus, a chip microphone 10 produced by the semiconductor manufacture technology and acting like a condenser microphone is realized and the chip microphone 10 is designed to be a module, which is mounted on the circuit board.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microphone-mounted circuit board and a voice processing device having the board mounted thereon.
More specifically, the present invention relates to a circuit board on which a microphone is mounted and a device that can be downsized.

[0002]

2. Description of the Related Art Conventionally, voice processing devices such as mobile phones have been reduced in size and weight like other electronic devices. A microphone used in such a small-sized audio processing device is mainly of a condenser type and is formed of two polar plates, a vibrating membrane and a back plate.

This type of microphone is excellent in sensitivity and noise and is suitable for miniaturization. For example, a spacer (support portion) is interposed between the vibrating membrane and the back plate, and the microphone is attached to the case. It is mounted on the circuit board by mounting it on the circuit board, making it modular, etc.

[0004]

However, such a conventional microphone has the following problems because it is manufactured by assembling a plurality of types of parts.

Since there is a limit to the miniaturization due to the restriction of the accuracy of the assembly process of parts, the thickness is smaller than that of other modules such as semiconductor parts mounted in small electronic devices such as mobile phones. The occupying area also becomes large, which is an obstacle to increasing the packaging density of the circuit board.

Further, since the material of each component is different and the coefficient of thermal expansion is different, deformation due to thermal strain is caused by thermal shock caused by a plurality of heat treatments (200 ° C. or more) such as soldering in the mounting process. Will occur. In the mounting process using lead-free solder, it is necessary to have resistance to a heat treatment at a higher temperature of 240 to 260 ° C.

Further, when parts made of a resin material are used for the vibrating film and the spacer insulating portion, it is not possible to collectively process them by a mounting process involving high temperature processing such as bump / reflow, which improves efficiency. I can't plan.

Therefore, it is an object of the present invention to reduce the size and cost of a mounted circuit board and mounting device and improve reliability by manufacturing a microphone by utilizing a micromachining technique.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention relates to a microphone mounting circuit board, a vibrating film vibrating by sound pressure, a back plate facing the vibrating film, and a vibrating film. And a back plate, which is provided between the diaphragm and the back plate to secure a vibration space for the vibrating film, and the chip microphone in which the vibrating film, the supporting part, and the back plate are formed in a laminated structure is used as it is, or the chip. It is characterized by being mounted on a circuit board as a module in which a microphone is packaged.

In this invention, the microphone is a vibrating membrane,
Since the supporting portion and the back plate are formed into a laminated structure and formed into chips, a small microphone can be manufactured with high accuracy by using a micromachining technique. Therefore, this chip microphone can be mounted on the circuit board with high density as it is or as a module. Therefore, it can also be applied to high-density mounting such as CSP (chip size packaging).

Here, in the chip microphone, the vibrating film, the supporting portion and the back plate may be formed by joining the same or different substrate materials and removing an unnecessary portion of the substrate material. Further, an etching stop layer for diffusing boron may be formed on one surface side of the substrate material, and the vibrating film may be formed by etching a portion to be the vibrating film. You may form by the oxide of the silicon containing.

The chip microphone according to the present invention may be manufactured by a semiconductor manufacturing technique using silicon and a compound of silicon.

According to the present invention, since the chip microphone can be manufactured by utilizing the micromachining technology of the semiconductor manufacturing technology, it is possible to manufacture the chip microphone in a smaller size and with higher accuracy. Also, when a chip microphone is manufactured using a silicon-based material,
This chip microphone can be subjected to high-temperature heat treatment by utilizing the high heat resistance of the silicon-based material, and can improve resistance to multiple thermal shocks such as reflow during microphone module fabrication and circuit board mounting. . Therefore, it is possible to fabricate a chip microphone having a thickness as small as 1 mm or less and a small mounting area without using a process of assembling a plurality of parts, and a bump / reflow method or the like is used for a circuit board. The efficiency can be improved by adopting a mounting process involving high-temperature processing such as bulk mounting. It should be noted that the heat resistance of the chip microphone is 300 ° C. or higher even when commonly used aluminum is used for the electrodes, and since it has such heat resistance, it can be applied to a high-temperature mounting process using lead-free solder. be able to. Needless to say, this electrode material may be any material that has a good ohmic contact with silicon.

The vibrating membrane, the supporting portion and the back plate of the chip microphone are formed by joining the same or different substrate materials and removing unnecessary portions of the substrate material, or the substrate. An etching stop layer for diffusing boron is formed on one surface of the material to form the vibrating film by etching the portion to be the vibrating film, and further, the supporting portion is made of silicon oxide for diffusing boron. When forming, these processes can be performed easily and inexpensively by the etching process of semiconductor manufacturing technology.

Further, since at least the vibrating membrane and the base are made of the same material, their thermal expansion coefficients are substantially equal to each other, and the influence of thermal strain of the vibrating membrane can be made very small.

Further, in the chip microphone according to the present invention, the vibrating membrane and the supporting portion may be made of the same material.

According to the present invention, the thermal expansion coefficient of the vibrating film and the supporting portion can be made equal to each other to prevent the occurrence of thermal strain, and damage to the vibrating film can be reduced. Therefore, the vibrating film can be manufactured with high accuracy. Here, it goes without saying that not only the vibrating film and the supporting portion but also the back plate may be made of the same material.
The vibrating membrane and the supporting portion may be integrated.

For the purpose of solving the above-mentioned problems, the present invention is characterized in that a microphone-mounted circuit board according to the above-mentioned invention is mounted in a voice processing device.

According to the present invention, it is possible to obtain the function and effect of the invention of the above-mentioned microphone-mounted circuit board, to achieve miniaturization and cost reduction, and to improve heat resistance and reliability.

[0020]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the drawings. 1 to 3 are views showing an embodiment of a microphone-mounted circuit board mounted on a voice processing device according to the present invention. It should be noted that although the present embodiment is described by using the upper and lower sides in the drawings, it does not mean the upper and lower sides in a chip microphone described later.

In FIG. 1, reference numeral 10 denotes a chip microphone. The chip microphone 10 has a vibrating film 12 which vibrates by sound pressure at the center of a base 11 and
The supporting portion 13 supports the back plate 14 around the vibrating membrane 12 to face the vibrating membrane 12 so that the vibrating space S of the vibrating membrane 12 is secured to function as a condenser microphone. The chip microphone 10 is manufactured by the semiconductor manufacturing technology (micromachine processing technology) described later, and thus the vibrating membrane 12 and the back plate 14 are manufactured.
It has a laminated structure in which the support portion 13 is interposed between the and.

The chip microphone 10 has a cap 15 attached to cover the back plate 14.
The electrode 16 formed on the upper surface of the back plate 14 is electrically connected to the outside by electrically connecting the electrode 16 formed on the upper surface of the terminal block 17 formed adjacent to the back plate 14 by wire bonding of the wire 19. Has been pulled out. The cap 15 is fixedly attached to the upper surfaces of the base 11 and the terminal block 17 with a ceramic adhesive 20 or the like.

The cap 15 has a role of adjusting the acoustic characteristics of the microphone according to its volume, and at the same time,
It can also be used to shield electromagnetic waves. Further, the gas flow hole 15a at the center of the cap is for controlling the directivity of the microphone. The back plate 14 has a vibrating membrane 1
A plurality of through holes 14a are formed so as to communicate the front and back so as not to interfere with the vibration of 2.

The chip microphone 10 is
By forming solder bumps 21 on the upper surfaces of the base 11 and the terminal block 17 which are outside the cap 15, a module is manufactured by adhering it to a module substrate (not shown). The module substrate is mounted on a microphone. It is electrically attached to the substrate and mounted on the voice processing device.

Next, a procedure (method) for manufacturing the chip microphone 10 by the semiconductor manufacturing technique will be described with reference to FIGS. 2 and 3.

First, as shown in FIG. 2A, a silicon substrate which is a general semiconductor substrate is prepared as a back plate substrate 114, and the lower surface thereof is coated with powdered silicon oxide containing impurities. Alternatively, the bonding film 11 containing the impurities is formed by a method of depositing an oxide film by a CVD method or the like.
3 is formed, and similarly, as shown in FIG. 2B, a silicon substrate is prepared as the vibration film substrate 111,
An etch stop layer 112 doped with a high concentration of impurities is formed on the upper surface of the silicon substrate by a solid diffusion method in which the impurities are thermally diffused in a high concentration.

At this time, the bonding film 113 and the etch stop layer 112 are made to contain the same impurities so as to have similar physical properties, and the impurities do not diffuse from the etch stop layer 112 to the bonding film 113 side in the bonding film 113. Thus, the etch stop layer 112 is set to contain impurities at a higher impurity concentration than the impurity concentration doped.

Further, the etch stop layer 112 is made to be a thin vibrating film 12 having a thickness of several microns so that boron is diffused as an impurity so as not to be etched in a process described later in order to improve sensitivity as a condenser type microphone. Suitable (for this reason, the bonding film 11
Boron is also included in 3 as an impurity. ),
It is formed by using a solid diffusion method and thermally diffusing boron as an impurity to a high concentration. The thermal diffusion of the impurities results in heat treatment at a high temperature in order to obtain a high-concentration impurity layer, and at this time, the heat treatment is performed at a temperature of 1200 ° C. or lower so as to prevent thermal deformation of the silicon wafer. Although the case where the etch stop layer 112 is formed by using the solid diffusion method is described here, it may be formed by another forming method such as an ion implantation method and a coating method, and the impurity is not limited to boron. Not to mention.

Next, as shown in FIG. 2C, the bonding film 113 and the etch stop layer 112 are bonded by using a bonding technique such as heat welding, anodic bonding, or direct bonding to form the back plate substrate 114. After the bonded substrate 100 is manufactured by bonding the vibrating film substrate 111 to the rear plate substrate 114
The upper surface of the is polished to adjust the entire thickness to a desired thickness. After that, the bonded substrate 100 is heat-treated in an oxygen atmosphere to form oxide films 131 and 132 for etching masks on the upper and lower surfaces of the bonded substrate 100.
The thickness is about 4000 Å from the silicon etching depth of 1. At this time, the oxide films 131 and 13
The heat treatment for forming 2 is performed on the etch stop layer 112.
Etch stop layer 1 to prevent re-diffusion of impurities in
It is preferable to perform the treatment at a temperature lower than the treatment temperature for forming 12 and in the present embodiment, the heat treatment temperature for forming the oxide films 131 and 132 is 900 ° C. or higher below the treatment temperature for forming the etch stop layer 112. . The heat treatment temperature is set to ensure an appropriate rate for growth of the oxide films 131 and 132, and increase the interface charge between the vibration film substrate 111 and the bonding film 113 in the low temperature process. Is known.

Next, as shown in FIG. 3D, the oxide films 131 and 132 of the bonding substrate 100 are processed by photolithography to remove excess portions thereof, thereby removing the oxide films 131 and 132. The vibrating film etching mask 141, the back plate etching mask 142, and the terminal block etching mask 143 are used, and thereafter, excess portions are removed from the vibrating film substrate 111 and the back plate substrate 114 of the bonding substrate 100 by using these etching masks 141 to 143. The vibrating film substrate 1
At the same time as forming the base 11 from 11, the etch stop layer 112 is exposed to form the vibration film 12, and
The back plate 14 and the terminal block 17 are formed from the back plate 114. At this time, TMAH (Tetramethyl ammonium h
Etching can be performed using a predetermined alkaline etching solution such as ydroxide).

Next, as shown in FIG. 3E, after etching for removing the etching masks 141 to 143 and etching for removing the portion other than the supporting portion 13 from the bonding film 113, the back plate 14 and the terminals are removed. By forming thin metal electrodes 16 and 18 on the upper surface side of the stand 17 by sputtering or the like, the chip microphone 10 having an integrated structure is constructed. The electrodes 16 and 18 in the figure are shown as thick films for illustration,
Since a thin film is sufficient, it is not necessary to use a vapor deposition mask other than the back plate 14 and the terminal block 17, and, for example, the base 11
There is no problem even if the thin film 151 is formed on the upper surface of the etch stop layer 112. Further, the electrode on the side of the vibrating film 12 is not particularly described in detail, but the electrode may be similarly formed by sputtering or the like. Note that both electrodes can be formed at the same time by omitting the evaporation mask.

In the chip microphone 10, the electrode 16 of the back plate 14 and the electrode 18 of the terminal block 17 are connected by wire bonding, and the cap 15 is attached with the ceramic adhesive 20 or the like, and then the base 11 is attached. The solder bump 2 is formed on the thin film 151 and the electrode 18 of the terminal block 17.
1 can be formed and bonded to a module board to form a module, and further, can be mounted on a microphone circuit board mounted in a voice processing device.

As described above, in this embodiment, the chip microphone 10 has the vibrating membrane 12, the support portion 13 and the back plate 14 formed in a highly accurate laminated structure by a semiconductor manufacturing technique which can be manufactured inexpensively and easily. It can be made into a chip, and can be mounted on a circuit board with high density as CSP (chip size packaging) together with other components. The vibrating membrane 12, the support portion 13, the back plate 1
Since No. 4 and the like are manufactured using a silicon-based material, the difference in coefficient of thermal expansion is small and it is difficult for thermal strain to occur.
It is possible to reduce damage to the vibrating membrane 12 and the like, and since it has high heat resistance, it is possible to perform high-temperature heat treatment in each process, and when manufacturing a module or mounting on a circuit board. It can be efficiently manufactured by utilizing reflow or the like that has thermal shock.

Therefore, the chip microphone 10 is
Rather than assembling the vibrating membrane, support, back plate, etc. as multiple components, make them into highly reliable and inexpensive components such as LSI chips that are as thin as 1 mm or less and have a small mounting area. In addition, it is possible to realize an efficient circuit board assembling process such as collective mounting using bump / reflow.

As a result, it is possible to contribute to downsizing, cost reduction, and high reliability of a voice processing device such as a circuit board or a mobile phone on which the chip microphone 10 is mounted.

In this embodiment, the vibrating membrane 12, the support portion 13, the back plate 14 and the like are made of the same silicon material, but needless to say, the material is not limited to the silicon material. As long as the vibrating membrane 12 and the supporting portion 13 are made of materials having substantially the same physical properties such as a thermal expansion coefficient, they may be produced by joining different substrate materials.

[0037]

According to the present invention, since the vibrating membrane, the supporting portion, and the back plate are formed into a laminated structure to make the microphone into a chip, the size of the small microphone can be increased by utilizing the micromachining technology such as semiconductor manufacturing technology. It can be manufactured with high accuracy and can be mounted as it is or as a module and mounted on a circuit board or the like.

Further, by manufacturing a chip microphone using a silicon-based material, it is possible to perform high-temperature heat treatment by utilizing the high heat resistance of the silicon-based material. It is possible to improve efficiency by adopting a mounting process involving processing.

Here, since at least the vibrating membrane and the base are made of the same material, their thermal expansion coefficients are substantially the same, and the influence of thermal strain of the vibrating membrane can be made very small. further,
By using at least the vibrating film, the base and the support part of the same material, it is possible to prevent the occurrence of thermal strain. This makes it possible to prevent deformation of the vibrating membrane and the like even when the present microphone is further thinned and distortion resistance is reduced.

Therefore, a small and highly reliable chip microphone can be manufactured with high accuracy and at low cost, and this chip microphone as it is or as a module can be mounted on a circuit board or an audio processing device with high mounting density. Can be implemented in.

[Brief description of drawings]

FIG. 1 is a diagram showing an overall configuration of an embodiment of a microphone-mounted circuit board mounted on a voice processing device according to the present invention, and is a vertical cross-sectional view thereof.

2A to 2C are process drawings for explaining the manufacturing process.

FIG. 3 is a process diagram that explains the manufacturing process, following FIG. 2;

[Explanation of symbols]

10 chip microphone 11 bases 12 vibrating membrane 13 Support 14 Back plate 14a through hole 15 caps 15a Distribution hole 16, 18 electrodes 17 terminal block 100 bonded substrate 111 Vibration film substrate 112 Etch stop layer 113 Bonding film 114 Back plate substrate

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Nobuo Saito             1-10-11 Kinuta, Setagaya-ku, Tokyo, Japan             Broadcasting Association Broadcast Technology Institute (72) Inventor Akira Morita             1-10-11 Kinuta, Setagaya-ku, Tokyo, Japan             Broadcasting Association Broadcast Technology Institute F-term (reference) 5D017 BD04 BD05                 5D020 BB12                 5D021 CC19

Claims (7)

[Claims] 1. A vibrating film vibrating by sound pressure, a back plate facing the vibrating film, and a support portion arranged between the vibrating film and the back plate to secure a vibration space of the vibrating film. A microphone-mounted circuit board comprising the chip microphone, which is provided with the vibrating membrane, the supporting portion, and the back plate in a laminated structure, or is mounted on a circuit board as a module in which the chip microphone is packaged. 2. The chip microphone is characterized in that the vibrating membrane, the support portion and the back plate are formed by joining the same or different substrate materials and removing an unnecessary portion of the substrate material. The microphone mounted circuit board according to claim 1. 3. The chip microphone is characterized in that an etching stop layer for diffusing boron is formed on one surface side of the substrate material, and the vibrating film is formed by etching a portion to be the vibrating film. The microphone-mounted circuit board according to Item 2. 4. The microphone mounted circuit board according to claim 1, wherein the chip microphone has the support portion formed of silicon oxide in which boron is diffused. 5. The microphone-mounted circuit board according to claim 1, wherein the chip microphone is manufactured by a semiconductor manufacturing technique using silicon and a compound of silicon. 6. The microphone-mounted circuit board according to claim 1, wherein at least the vibrating film and the support portion of the chip microphone are made of the same material. 7. A voice processing apparatus comprising the microphone-mounted circuit board according to any one of claims 1 to 6.