JP2004200766A - Capacitor microphone and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thin capacitor microphone and its manufacturing method which is simple in structure, and to provide manufacturing process. <P>SOLUTION: The microphone is composed of a microphone chip 5, a field effect transistor 6 and a casing 4. The casing 4 comprises a bottom wall 41 having a recessed groove 411 the opening of which is covered with the chip 5, and an outer side wall 42 extending upward from the bottom wall 41. The chip 5 is composed of an electrode layer 51, a vibration film 52 formed on the downside of the electrode layer 51, a spacer 53 formed at the peripheral edge of the lower side of the film 52, and a perforated bottom plate 54 forming a vibration space 55 with the vibration film 52 and the spacer 53. The chip 5 is mounted on the upside of the bottom wall 41 to cover the groove 411. The field effect transistor 6 is mounted in the casing 4 and electrically connected to a specified portion of the casing 4 with the electrode layer 51 of the chip 5. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a condenser microphone and a method of manufacturing the same, and more particularly, to a condenser microphone that converts an acoustic signal into an electric signal and outputs the electric signal and a method of manufacturing the same.
[0002]
[Prior art]
Conventional condenser microphones generally include a microphone chip, a field effect transistor (FET), and a casing that houses the microphone chip and the field effect transistor. When a sound wave signal of an external sound enters the microphone chip, the condenser microphone vibrates a vibrating membrane in the microphone chip, thereby changing a space (vibration space) between a pair of electrodes serving as a capacitor, and thereby changing electric power. Produce a change in capacity. Then, the change in the capacitance is converted into an electric signal via the field effect transistor and output.
[0003]
Prior art document information related to the vehicle air conditioner of the present invention includes the following.
[0004]
[Patent Document 1]
US Pat. No. 5,870,482 [Patent Document 2]
US Pat. No. 6,243,474
FIG. 4 is a flowchart showing a part of the method of manufacturing a microphone chip disclosed in Patent Document 1. In this manufacturing method, first, the SiO ₂ layer 12 is formed as a sacrificial layer on the upper surface of the silicon substrate 11. Then, the SiO ₂ layer 12 is dug down by an etching method, and a part of the upper surface of the silicon substrate 11 thereunder is exposed to form an inverted trapezoidal concave groove 13. Thereafter, an Si ₃ O ₄ layer 14 as a vibration film is formed so as to cover the exposed portion of the silicon substrate 11 and the upper surface of the SiO ₂ layer 12 by a vapor deposition method or a sputtering method. Finally, the remaining SiO ₂ layer 12 is completely removed with hydrofluoric acid (HF) to form a vibration space 15. Next, other necessary layers are sequentially formed on the upper surface of the vibration film 14.
[0006]
Each layer of the microphone chip is formed by several steps belonging to a photolithography method (semiconductor process) such as coating, exposure, development, etching, vapor deposition, and sputtering. Therefore, at least four steps are required to form only the vibration film and the vibration space as described above. For this reason, there is an inherent problem that the number of steps in manufacturing is large and labor is considerably required.
[0007]
Therefore, in order to reduce the number of steps in manufacturing, Patent Document 2 discloses a micro-electromechanical systems (hereinafter, referred to as MEMS) including the photolithography method and micro-technology in other fields. Technology). FIG. 5 is a sectional view of the microphone chip 2 formed by this MEMS technology.
[0008]
As shown in FIG. 5, the method of manufacturing the microphone chip 2 of Patent Document 2 mainly forms a pair of chips 21 and 22 having different configurations first by a photolithography method. Then, while the pair of chips 21 and 22 formed by the MEMS technology are overlapped and combined, the vibration space 23 is formed to level the microphone chip 2. In the figure, reference numeral 211 denotes a vibrating membrane.
[0009]
[Problems to be solved by the invention]
However, although the method of manufacturing the microphone chip 2 by the MEMS technology as in Patent Document 2 can certainly reduce the number of steps as compared with the conventional manufacturing method, the microphone chip 2 is stacked on a pair of silicon substrates to form a pair of chips 21 and 22, respectively. Since the microphone chip 2 is formed, there is a disadvantage that the microphone chip 2 is too thick and is not suitable for thinning.
[0010]
Further, since the vibrating film 211 is made of an organic material, it may be deformed at a high temperature of 240 ° C. or more. Therefore, the condenser microphone on which the microphone chip 2 is mounted has a surface mounting temperature of 240 ° C. or more. Cannot be used for technology (SMT). For this reason, there is also a drawback that it cannot be connected to, for example, a substrate of a mobile phone by an automation method.
[0011]
The present invention has been made in view of the above problems, and has as its first object to provide a thin condenser microphone having a simple structure and a simple manufacturing process, and a method for manufacturing the same. It is a second object of the present invention to provide a condenser microphone applicable to surface mount technology (SMT) and a method for manufacturing the same.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, a condenser microphone according to the present invention includes a microphone chip that receives an external acoustic signal and causes a change in electric capacity, and a field effect that converts the change in electric capacity into an electric signal and outputs the signal. A transistor and a casing accommodating the microphone chip and the field-effect transistor, wherein the casing has a bottom wall formed with a concave groove whose opening is completely covered by a bottom surface of the microphone chip; An outer peripheral wall extending upward from a peripheral edge, wherein the microphone chip comprises: an electrode layer; a vibrating film formed below the electrode layer so that at least a portion thereof is in contact with the electrode layer; A spacer formed on an outer peripheral edge of a lower surface of the diaphragm, and the space so as to form a vibration space together with the vibration film and the spacer. The microphone chip is mounted on the upper surface of the bottom wall so as to shield the groove of the casing with the bottom plate with the hole facing downward, and the field-effect transistor includes: Attached in the casing, and electrically connected to a predetermined location of the electrode layer and the casing of the microphone chip, when an acoustic sound signal enters the casing from the open end of the casing, the vibration membrane The microphone chip is caused to vibrate to cause a change in capacitance, and the change in the capacitance is converted into an electric signal via the field effect transistor and output.
[0013]
The microphone chip in the condenser microphone according to this configuration has a simple configuration, and the bottom plate with holes is coupled to the spacer by MEMS technology, so that the number of manufacturing steps is smaller than that of a chip formed only by a conventional photolithography method. Can be reduced. Further, since the microphone chip can be manufactured by stacking the microphone chips on one silicon substrate, the microphone chip is thinner than a conventional one using at least a pair of silicon substrates. That is, the present invention can provide a thin condenser microphone that has a simple configuration and can further simplify the manufacturing process.
[0014]
In the condenser microphone, the vibrating membrane is preferably a layer having a predetermined pattern made of an inorganic material that can withstand a temperature of 450 ° C. or higher. Accordingly, the condenser microphone of the present invention can be applied to a surface mount technology (SMT) and coupled to a substrate by an automated method.
[0015]
Further, it is preferable that the vibrating film is formed by vertically stacking a first inorganic material layer having a predetermined pattern and a second inorganic material layer having a predetermined pattern.
[0016]
Further, the casing is preferably provided above the outer peripheral wall and provided with a hole so as to coincide with a position above the microphone chip, and preferably further includes a perforated lid portion for shielding an open end of the casing. .
[0017]
Furthermore, it is preferable that the bottom plate has a thickness of 20 to 100 μm and that at least the outer surface is a flat body made of a metal material.
[0018]
Further, in the present invention, the method for manufacturing the condenser microphone includes a step of forming a bottom wall having a concave groove whose opening is completely covered by a bottom surface of the microphone chip, and an outer peripheral wall extending upward from a peripheral portion of the bottom wall. A casing provided, a microphone chip attached to the casing and receiving an external sound signal to cause a change in electric capacity, and a microphone chip attached to the casing and converting the change in electric capacity into an electric signal and outputting the signal. A method for manufacturing a condenser microphone comprising: a field effect transistor; a step of forming the casing; a step of forming the microphone chip; a step of preparing the field effect transistor; and a step of preparing the microphone chip and the field effect transistor. Assembling the transistor into the casing. In the microphone chip forming step, after a silicon substrate is prepared, a vibrating film forming step of forming a vibrating film on the lower surface of the silicon substrate by a photolithography method, and an outer peripheral edge of the lower surface of the vibrating film by a photolithographic method. A spacer forming step of forming a spacer, a vibrating film charging step of charging the vibrating film, and a vibrating film exposing step of excavating the silicon substrate by an etching method and exposing a part of an upper surface of the vibrating film thereunder, An electrode layer forming step of forming an electrode layer on the exposed portion of the vibrating film and the upper surface of the silicon substrate; and forming a vibrating space together with the vibrating film and the spacer together with a bottom plate having holes whose outer surface is made of a metal material. Forming a bottom plate with a hole, which is bonded to the spacer by heating to form a bottom plate. The assembling step includes a first assembling step of mounting the field effect transistor in the casing so as to be electrically connected to a predetermined portion of the casing, and the microphone chip with the bottom plate with the hole facing downward and the bottom wall of the casing. And a second assembling step of shielding the concave groove of the casing and electrically connecting to the field effect transistor.
[0019]
In the manufacturing method, since each layer of the microphone chip is formed by using the MEMS technology, the number of steps in manufacturing can be reduced as compared with a method of forming only by a conventional photolithography method. Further, since only one silicon substrate is used, the microphone chip can be easily made thinner than a conventional method using at least a pair of silicon substrates. That is, according to the manufacturing method of the present invention, a thinner condenser microphone can be manufactured by a simpler manufacturing process.
[0020]
In the manufacturing method, the vibrating film forming step includes: a first inorganic material layer forming step of forming a first pattern of a first inorganic material layer on a lower surface of the silicon substrate; and a lower surface of the first inorganic material layer. Preferably, the method includes a second inorganic material layer forming step of forming a second inorganic material layer having a predetermined pattern.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a condenser microphone and a method for manufacturing the same according to the present invention will be described in detail with reference to the drawings.
[0022]
As shown in FIG. 1, a condenser microphone 3 according to an embodiment of the present invention has a casing 4 made of ceramics, and is mounted inside the casing 4 and receives an external acoustic signal to cause a change in capacitance. It comprises a microphone chip 5 and a field effect transistor 6 which is mounted in the casing 4 and converts a change in the electric capacity into an electric signal and outputs the electric signal.
[0023]
Specifically, the casing 4 includes a bottom wall 41 having a concave groove 411 whose opening is completely covered by the bottom surface of the microphone chip 5, and an outer peripheral wall 42 extending upward from a peripheral edge of the bottom wall 41. A hole 431 is provided above the outer peripheral wall 42 so as to coincide with the microphone chip 5, and a perforated lid 43 for shielding an open end of the casing 4; It comprises a plurality of terminals 44 provided on the lower surface and coupled to a substrate such as a mobile phone. In the concave groove 411 of the bottom wall 41, a step portion 412 having a plurality of steps is formed on an inner peripheral wall thereof.
[0024]
The microphone chip 5 is mainly formed of a metal electrode layer 51 having a flat plate shape in which only the center portion is recessed downward, and the lower side of the electrode layer 51 so as to be in contact with the lower surface of the recessed portion of the electrode layer 51. After processing a vibration film 52 formed of an inorganic material that can withstand a temperature of 450 ° C. or more and a silicon substrate 7 described later sandwiched between a non-contact portion between the electrode layer 51 and the vibration film 52 And an annular spacer 53 formed on the outer peripheral edge of the lower surface of the vibration film 52, and are coupled to the lower surface of the spacer 53 so as to form a vibration space 55 together with the vibration film 52 and the spacer 53. And a bottom plate 54 with a metal hole.
[0025]
More specifically, the vibration film 52 is formed by vertically stacking a predetermined pattern of an SiO ₂ layer 521 and a predetermined pattern of an Si ₃ O ₄ layer 522. The spacer 53 is formed by vertically stacking an annular SiO ₂ layer 531 made of an inorganic material and an annular metal layer 532 made of a metal material. Further, the thickness of the bottom plate 54 is 20 to 100 μm.
[0026]
The microphone chip 5 having the above configuration shields the concave groove 411 by attaching the holed bottom plate 54 to the stepped portion 412 of the casing 4 with the hole plate facing downward, and the lower surface of the diaphragm 52 is in contact with the upper surface of the bottom wall 41. Contact.
[0027]
The field effect transistor 6 is mounted on the bottom wall 41 and is electrically connected to the electrode layer 51 of the microphone chip 5 and a predetermined terminal 44 of the casing 4.
[0028]
Thereby, in the condenser microphone 3, when a voltage is applied, when an acoustic sound signal enters the casing 4 from the open end of the casing 4, that is, the hole 431 in the perforated lid 43. Then, the vibrating membrane 52 is vibrated to cause the microphone chip 5 to change in electric capacitance. Then, the change in the capacitance can be converted into an electric signal and output through the field effect transistor 6.
[0029]
The vibration space 55 communicates with the groove 411 via a hole 541 formed in the bottom plate 54. Therefore, the air in the vibration space 55 advances out of the hole 541 according to the vibration, and the pressure applied to the bottom plate 54 can be reduced, so that the temporal deformation due to the use of the bottom plate 54 is substantially prevented. be able to.
[0030]
Next, a method for manufacturing the condenser microphone 3 will be specifically described.
[0031]
As shown in FIG. 2, in the manufacturing method of the present embodiment, a step 70 of forming the casing 4, a step 71 of forming the microphone chip 5, and a step 72 of preparing the field-effect transistor 6 by MEMS technology. And a step 73 of assembling the microphone chip 5 and the field effect transistor 6 in the casing 4 are sequentially performed.
[0032]
Specifically, in the casing forming step 70 in the production of the condenser microphone 3, the casing 4 having the bottom wall 41, the outer peripheral wall 42, the perforated lid 43, and the terminal 44 is produced from a ceramic material. I do.
[0033]
In the microphone chip forming step 71 in the manufacture of the condenser microphone 3, as shown in FIG. 3, after preparing a silicon substrate 7, a vibration film forming step, a spacer forming step, a vibration film charging step, a vibration film exposing step, Step, an electrode layer forming step, and a holed bottom plate bonding step are sequentially performed.
[0034]
In the vibration film forming step, the respective layers are formed on the silicon substrate 7 by several processes belonging to a photolithography method such as coating, exposure, development, etching, vapor deposition, and sputtering. That is, after a SiO ₂ layer 521 having a predetermined pattern is formed as a first inorganic material layer on the lower surface of the silicon substrate 7, a Si ₃ O _{4 having a} predetermined pattern is formed on the lower surface of the SiO ₂ layer 521 as a second inorganic material layer. The layer 522 is formed, and the vibration film 52 is formed by the SiO ₂ layer 521 and the Si ₃ O ₄ layer 522.
[0035]
In the spacer forming step, an annular SiO ₂ layer 531 is formed on the outer peripheral edge of the lower surface of the vibration film 52 by photolithography, and then a metal layer 532 is formed on the lower surface of the annular SiO ₂ layer 531. _The spacer 53 is formed by the _two layers 531 and the metal layer 532.
[0036]
In the vibration film charging step, the vibration film 52 is charged by charging or the like.
[0037]
In the vibration film exposing step, the silicon substrate 7 is dug down by an etching method to expose a part of the upper surface of the vibration film 52 thereunder.
[0038]
In the electrode layer forming step, an electrode layer 51 is formed on the exposed portion of the vibration film 52 and the upper surface of the silicon substrate 7 by a photolithography method.
[0039]
In the bottom plate with hole bonding step, a bottom plate with a hole made of nickel having a thickness of 20 to 100 μm and having a plurality of holes formed by etching forms a vibration space 55 together with the vibration film 52 and the spacer 53. As described above, the lower surface of the spacer 53 is joined by heat welding. Thus, the microphone chip 5 having the above configuration is manufactured.
[0040]
In the field effect transistor preparing step 72 in the manufacture of the condenser microphone 3, the field effect transistor 6 is prepared.
[0041]
In the assembling step 73 in the manufacture of the condenser microphone 3, as shown in FIG. 3, first, the bottom wall of the casing 4 is so connected that the field effect transistor 6 is electrically connected to a predetermined terminal 44 of the casing 4. A first assembly step of attaching to 41 is performed.
Then, the microphone chip 5 is attached to the step portion 412 of the casing 4 with the bottom plate 54 with the hole facing downward, thereby shielding the concave groove 411 and electrically connecting to the field effect transistor 6.
[0042]
Subsequently, the open end of the casing 4 is shielded by the perforated lid 43 of the casing 4, whereby the assembly of the condenser microphone 3 is completed.
[0043]
Note that the condenser microphone and the method of manufacturing the same according to the present invention are not limited to the configuration of the above embodiment. That is, the above-described embodiments have been made only with the intention of clarifying the technical contents of the present invention, and the present invention is not limited to such specific examples and is not interpreted in a narrow sense. Various modifications can be made within the spirit and scope of the claims.
[0044]
For example, in the above-described embodiment, the spacer 53 is configured by the annular SiO ₂ layer 531 made of an inorganic material and the annular metal layer 532 made of a metal material. However, for example, BCB (benzocyclobutene) The spacer 53 may be formed by applying a photoresist material such as, for example, SINR, polyimide, or SU-8. This eliminates the need to form the metal layer 532, and allows the bottom plate 54 to be connected to the spacer 53 by heating and pressing.
[0045]
Further, the spacer 53 is not limited to the annular shape, and may be configured by arranging a plurality of island-shaped blocks along the outer peripheral edge of the vibration film 52.
[0046]
Further, in the above-described embodiment, the bottom plate with holes 54 is formed of a metal material, but a plate whose outer surface is formed of a metal material may be used.
[0047]
【The invention's effect】
As is apparent from the above description, the condenser microphone manufactured by the MEMS technology of the present invention has a simple structure, can further simplify the manufacturing process, and is made of an inorganic material that can withstand 450 ° C. or more. Therefore, the terminal can be connected to the substrate by an automatic method by applying to surface mounting technology (SMT).
[Brief description of the drawings]
FIG. 1 is a sectional view showing a condenser microphone according to an embodiment of the present invention.
FIG. 2 is a flowchart illustrating a method for manufacturing a condenser microphone.
FIG. 3 is a block diagram illustrating a method for manufacturing a condenser microphone.
FIG. 4 is a flowchart showing a part of a method for manufacturing a microphone chip in a conventional condenser microphone. FIG. 5 is a sectional view of a microphone chip in a conventional condenser microphone.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 3 ... Condenser microphone 4 ... Casing 41 ... Bottom wall 411 ... Concave groove 412 ... Step part 42 ... Outer peripheral wall 43 ... Perforated lid part 431 ... Hole 44 ... Terminal 5 ... Microphone chip 51 ... Electrode layer 52 ... Vibration film 521 ... First inorganic material layer 522 Second inorganic material layer 53 Spacer 531 Inorganic material layer 532 Metal layer 54 Bottom plate with hole 541 Hole 55 Vibration space 6 Field effect transistor 7 Silicon substrate

Claims (7)

A microphone chip that receives a sound signal from the outside and causes a change in electric capacity, a field-effect transistor that converts the change in electric capacity into an electric signal and outputs the signal, and houses the microphone chip and the field-effect transistor Consisting of a casing,
The casing is
A bottom wall formed with a concave groove whose opening is completely covered by a bottom surface of the microphone chip, and an outer peripheral wall extending upward from a peripheral edge of the bottom wall;
The microphone chip includes:
An electrode layer, a vibrating film formed below the electrode layer so that at least a portion thereof is in contact with the electrode layer, a spacer formed on an outer peripheral edge of a lower surface of the vibrating film, A bottom plate with a hole coupled to the spacer so as to form a vibration space together with the spacer,
The microphone chip is attached to the upper surface of the bottom wall so as to shield the concave groove of the casing with the bottom plate with holes facing downward,
The field effect transistor is mounted in the casing, and is electrically connected to an electrode layer of the microphone chip and a predetermined portion of the casing, and an acoustic sound signal enters the casing from an open end of the casing. A condenser microphone that vibrates the vibrating membrane to cause a change in capacitance in the microphone chip, converts the change in capacitance into an electric signal via the field effect transistor, and outputs the signal. The condenser microphone according to claim 1, wherein the vibration film is a layer having a predetermined pattern made of an inorganic material. The condenser microphone according to claim 1, wherein the vibrating film is formed by vertically stacking a first inorganic material layer having a predetermined pattern and a second inorganic material layer having a predetermined pattern. . The casing is provided above the outer peripheral wall, and is provided with a hole so as to coincide with a position above the microphone chip, and further includes a perforated lid portion that shields an open end of the casing. The condenser microphone according to any one of claims 1 to 3. 5. The condenser microphone according to claim 1, wherein the bottom plate has a thickness of 20 to 100 μm, and at least an outer surface of the bottom plate is a flat body made of a metal material. 6. . A casing having a bottom wall having a concave groove whose opening is completely covered by the bottom surface of the microphone chip, and an outer peripheral wall extending upward from a peripheral edge of the bottom wall; and an external sound attached to the casing. A method for manufacturing a condenser microphone comprising: a microphone chip that receives a signal to cause a change in electric capacity; and a field-effect transistor that is mounted in the casing and converts the change in electric capacity into an electric signal and outputs the electric signal. ,
Forming the casing;
Forming the microphone chip;
Preparing the field effect transistor;
Assembling the microphone chip and the field-effect transistor in the casing,
The microphone chip forming step includes:
After preparing the silicon substrate,
A vibration film forming step of forming a vibration film on the lower surface of the silicon substrate by photolithography,
A spacer forming step of forming a spacer on the outer peripheral edge of the lower surface of the vibration film by photolithography,
A vibration film charging step of charging the vibration film,
A vibration film exposing step of excavating the silicon substrate by an etching method and exposing a part of an upper surface of the vibration film below the silicon substrate;
An electrode layer forming step of forming an electrode layer on the exposed portion of the vibration film and the upper surface of the silicon substrate;
A bottom plate with holes, wherein at least the outer surface of the bottom plate with holes made of a metal material is combined with the spacers by heating to form a vibration space together with the vibration film and the spacers,
The assembling step includes:
A first assembly step of mounting the field-effect transistor in the casing so as to be electrically connected to a predetermined portion of the casing;
A second assembling step of mounting the microphone chip on the upper surface of the bottom wall of the casing with the bottom plate with the hole facing downward, shielding the concave groove of the casing, and electrically connecting to the field effect transistor. A method for manufacturing a condenser microphone, comprising: The vibration film forming step,
A first inorganic material layer forming step of forming a first pattern of a first inorganic material layer on a lower surface of the silicon substrate;
7. The method according to claim 6, further comprising: forming a second inorganic material layer having a predetermined pattern on a lower surface of the first inorganic material layer.

Images