JPH1188992A - Integrated capacitive transducer and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a subminiature electret condenser microphone suitable for a portable telephone set or the like. SOLUTION: A microphone element 10 is integrated in a ceramic package 20. The microphone element 10 is structured by laminating a conductive film 12 as a back electrode, an electret film 13, a spacer 14 and a diaphragm 15 in this order on a surface of a semiconductor chip 11 stacked with an impedance conversion FET, an amplifier circuit, a noise cancel circuit or the like. The electret film 13 is a thin film whose thickness is about 2 μm that is formed by the film forming method such as vapor deposition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an integrated capacitive converter used for a back electret type condenser microphone and the like, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Electret condenser microphones, which can be easily miniaturized, are frequently used in portable telephones. One of the condenser microphone systems is a back electret system. FIG. 3 shows a conventional structure of a back electret type condenser microphone.

In a condenser microphone of this type, a printed circuit board 2, a holder 3, a back electrode plate 4, an electret layer 5, a spacer 6, a vibrating membrane 7, and a ring 8 are sequentially arranged in a capsule 1 from the rear side to the front side. Then, the structure is such that the IC element 9 is arranged inside the holder 3.

The electret layer 5 forms a capacitor portion together with the vibrating film 7. In this method, the electret layer 5 is located on the rear side of the vibrating film 7 via a space formed by the spacer 6. . For this reason, this method is called a back electret method. Then, the electret layer 5 is formed on the surface of the back electrode plate 4 by 12.5 to 2
It is formed by welding a 5 μm polymer film (usually FEP).

The IC element 9 is an FET for impedance conversion, and its input terminal 9a is connected to the back plate 4 on the front side.
The output terminal 9b is connected to the printed circuit board 2 on the rear side. The printed circuit board 2 is connected to an external circuit such as an amplifier circuit and a noise cancel circuit (not shown).

A sound hole 1a is provided on the front surface of the capsule 1, and a front cloth 1 'is attached to the surface thereof.

[0007]

In such a conventional back electret condenser microphone, an independent IC element 9 is used for impedance conversion.
(FET) is used, and the IC element 9
Is connected to an external circuit such as an amplifier circuit and a noise canceling circuit, so that the entire scale including the external circuit board is considerably large.

The electret condenser microphone of this type is frequently used in portable telephones as described above. As is well known, this application requires the smallest possible size, but as described above, the current situation is that the overall scale including the external circuit cannot be said to be sufficiently small. .

The present invention has been made in view of such circumstances, and is applied to a back-electret type condenser microphone, whereby the overall scale of the integrated microphone can be greatly reduced as compared with the conventional one. It is an object to provide a converter and a method for manufacturing the same.

[0010]

In order to achieve the above object, an integrated capacitive converter according to the present invention comprises a semiconductor chip on which electronic circuits including IC elements are integrated, and a back electrode on a surface of the semiconductor chip. And an electret film formed by directly forming a film on the surface of the conductive film, a spacer formed by printing on the outer edge surface of the electret film, and an electret film formed by being attached to the surface of the spacer. And a vibrating membrane fixed via a space on the front side.

[0011] An integrated capacitive transducer according to the present invention is characterized in that the transducer element in which the semiconductor chip, the conductive film, the electret film, the spacer, and the vibrating film are integrated is provided in a capsule having a front surface provided with a sound hole. And a back electret-type condenser microphone can be formed by attaching a front cross to the front surface of the capsule.

The electronic circuit here preferably includes a microphone FET, an amplifier circuit and / or a noise canceling circuit, and the like.

Further, according to a method of manufacturing an integrated capacitive converter according to the present invention, a step of forming a large number of chip portions by integrating a large number of electronic circuits including IC elements on a semiconductor wafer; Forming a conductive film as a back electrode, forming an electret film by directly forming a film on the surface of the conductive film, printing a spacer corresponding to each of the chip portions on the surface of the electret film, And a step of cutting the semiconductor wafer to each chip portion after attaching the vibration film.

In the integrated capacitive converter according to the present invention, a conductive film as a back electrode and an electret film are formed by film formation on the surface of a semiconductor chip on which electronic circuits including IC elements are integrated. Semiconductor chips, conductive films,
A one-chip transducer element in which the electret film, the spacer, and the vibration film are integrated is formed. In addition, an amplifier circuit for a microphone and a noise canceling circuit can be configured in an electronic circuit integrated on a semiconductor chip.

Therefore, by applying the present invention to the back electret type condenser microphone, the main components including the external circuit are integrated into one chip, and the overall scale is greatly reduced.

Further, since the microphone including the external circuit is constituted simply by incorporating the chip in the capsule,
Mass production is also very high.

Further, by forming the electret film by film formation, the occurrence of distortion is avoided, and the film thickness is reduced to about 1 μm. Because of these, the performance as a converter is greatly improved.

According to the method of manufacturing an integrated capacitive transducer according to the present invention, a conductive film, an electret film, a spacer, and a vibration film are formed on a semiconductor wafer and then cut into individual chips. Transducer elements are manufactured with high efficiency.

The semiconductor material of the semiconductor chip and the semiconductor wafer is preferably Si.

The conductive film serving as the back electrode has a thickness of, for example, 0.1 mm.
It can be formed by an Al film of about 1 μm.

The material of the electret film is SiO.
₂ or FEP can be used. Examples of the film forming method include spinner coating, resistance heating evaporation, EB evaporation (electron beam evaporation), sputtering (sputtering by high frequency, ion beam, planar magnetron, etc.), and CVD (plasma, reduced pressure, normal Pressure,
A known film forming method such as chemical vapor deposition by light or the like can be used.

The thickness of the electret film is preferably as thin as possible within a range in which the film can be formed, and more preferably in the range of 1 to 5 μm. If it is less than 1 μm, it is difficult to form a film having a uniform thickness. If it exceeds 10 μm, a significant improvement in performance as a converter cannot be expected.

The thickness of the spacer is usually about 5 to 15 μm.

As the vibrating film, for example, a PPS film having a thickness of about 2 μm with Ni deposited on one side can be used.

[0025]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of an integrated capacitive transducer (electret condenser microphone) according to an embodiment of the present invention, and FIG. 2 is a semiconductor wafer showing a method of manufacturing a microphone element used in the integrated capacitive transducer. It is a top view and a partial enlarged view.

An integrated capacitive transducer according to an embodiment of the present invention is one in which the present invention is applied to a back electret type condenser microphone.

As shown in FIG. 1, the condenser microphone includes a microphone element 10 as a converter element formed as one chip, and a ceramic package 20 as a capsule for accommodating the microphone element 10.

The microphone element 10 includes the semiconductor chip 1
1 has a structure in which a conductive film 12 as a back electrode, an electret film 13, a spacer 14, and a vibration film 15 are sequentially laminated.

The semiconductor chip 11 is a Si chip, on which an FET for impedance conversion, an amplifier circuit and / or a noise canceling circuit and the like are stacked.
The conductive film 12 is an Al film having a thickness of about 0.1 μm formed on the surface of the semiconductor chip 11 by vapor deposition or the like.

The electret film 13 is formed by spinner coating, resistance heating evaporation, EB evaporation (electron beam evaporation), sputtering (high frequency, ion beam, sputtering by a planar magnetron, etc.), and CVD (plasma, reduced pressure, normal pressure, This is a thin film having a thickness of about 2 μm formed by directly forming a film of SiO ₂ or FEP on the surface of the conductive film 12 by using a known film forming method such as chemical vapor deposition by light or the like. The spacer 14 is formed on the peripheral surface of the electret film 13 by screen printing to a thickness of about 5 to 30 μm.

The vibrating film 15 is a PPS film having a thickness of about 2 μm on which Ni is vapor-deposited on one side, and is fixed to the front side of the electret film 13 via a predetermined space by being adhered to the surface of the spacer 14. I have.

The ceramic package 20 has a sound hole 21 on the front surface, and a front cloth 30 is attached to the surface of the front surface. Terminal portion 11 of semiconductor chip 11
Reference numerals a and 11a penetrate the rear surface of the ceramic package 20 and solder them.

Next, a method for manufacturing the microphone element 10 will be described with reference to FIG.

As shown in FIG. 2, for example, a 6-inch Si
A large number of chip portions 41, 41... Corresponding to the semiconductor chips 11 are formed on the wafer 40. Next, a conductive film is formed on the entire surface of the Si wafer 40 by plating, vapor deposition, or the like. On top of that, spinner coat resistance heating evaporation, EB
By using a known film forming method such as evaporation, sputtering, or CVD, by directly forming a film such as SiO ₂ or FEP,
A thin film having a thickness of about 1 μm is formed. Further, the spacers 14 are formed thereon by screen printing using a screen printing agent containing an adhesive, corresponding to each chip portion 41. Further, the vibration film 15 is bonded thereon.

When the bonding of the vibrating film 15 is completed, the Si wafer 40 is replaced with the chip portions 41, 41.
(2) Cut off and separate at the cutting line L (the center where screen printing was performed) shown in FIG. Thereby, the microphone element 10 is manufactured, and the manufactured microphone element 10 is manufactured.
Is accommodated in the ceramic package 20,
The back electret condenser microphone is completed.

The integrated capacitive transducer (condenser microphone) according to the embodiment of the present invention has the following features as compared with the conventional condenser microphone.

Since the main components including the external circuit are integrated into one chip in the microphone element 10, it is extremely compact and easy to assemble. Also, the microphone element 10 can be efficiently manufactured by using the Si wafer 40.

Since the electret film 13 is formed by directly forming a film on the surface of the conductive film 12 as the back electrode, no distortion occurs in the electret film 13 and no mechanical stress occurs. For this reason, performance degradation due to mechanical stress of the electret film 13 is avoided, and the performance is improved.

In the case of a conventional condenser microphone in which this electret film is formed by welding a polymer film, distortion of the electret film cannot be avoided.
The mechanical stress resulting from the distortion has caused a decrease in performance.

The performance of the microphone is also improved in that the thickness of the electret film 13 can be reduced to about 2 μm. The reason is explained as follows.

The output e of the capacitor section formed by the vibrating film and the electret film is expressed by the following equation (1). Equation 1
Where k is a constant, C ₁ is the capacity of the space formed between the diaphragm and the electret film, C ₂ is the capacity of the electret film, and ΔC ₁ is the amount of change in the capacity of the space when sound pressure is applied. . e = k · [ΔC ₁ / (C ₁ + C ₂ )] · sin (ωt + φ) (1)

In the case of a conventional condenser microphone using a polymer film as the electret film, the thickness of the space (thickness of the spacer) is about 30 μm, and the thickness of the polymer film is 12.5 to 25 μm. Assuming that the capacity of the space is roughly equal to the capacity of the polymer film, the output e ₁ of the capacitor unit in such a case is expressed by Equation 2. e ₁ ≒ k · (1/2) · (ΔC ₁ / C ₁ ) · sin (ωt + φ) (2)

On the other hand, by forming an electret film directly on the surface of the conductive film to form an electret film, the thickness of the electret film is reduced to 1 μm.
m, it can be considered that C ₂ ≒ 0, and the output e ₂ of the capacitor section in such a case is expressed by the following equation (3).
Is represented by e ₂ ≒ k · (ΔC ₁ / C ₁ ) · sin (ωt + φ) (3)

As can be seen from the comparison between the equations (2) and (3), the output is doubled by forming the film directly on the surface of the conductive film to reduce the thickness of the electret film, and the sensitivity is 6 times.
Improve dB. That is, a quasi-condenser type microphone is obtained, and the sensitivity is greatly improved.

The mass productivity is improved by forming the spacer 14 by screen printing. By the way, in the conventional condenser microphone, a spacer formed by punching a polymer film was used,
Many burrs and mistakes in the number of inserts occurred, resulting in low mass productivity. The use of screen printing for forming the spacers 14 solves these problems.

In the above embodiment, the integrated capacitive converter according to the present invention is applied to an electret condenser microphone. However, pressure, acceleration, and the like are detected by using a Ti foil or a SUS foil as a vibrating film. Application to a semiconductor sensor or the like is also possible.

[0047]

As described above, the integrated capacitive converter according to the present invention has a main component including an electronic circuit such as an IC element integrated into one chip, and is thus applied to, for example, a back electret type condenser microphone. As a result, the overall size can be significantly reduced as compared with the conventional case, and it is possible to provide an ultra-small condenser microphone suitable for a mobile phone or the like.

Since the electret film is formed into a thin film when forming one chip, the performance can be greatly improved.

Since the mass productivity of the chip is high, the manufacturing cost can be reduced.

Further, the method of manufacturing an integrated capacitive converter according to the present invention can efficiently manufacture a chip using a semiconductor wafer, thereby contributing to a reduction in the manufacturing cost.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of an integrated capacitive transducer (electret condenser microphone) according to an embodiment of the present invention.

2A and 2B are a plan view and a partially enlarged view of a semiconductor wafer showing a method for manufacturing a microphone element used in the integrated capacitive transducer (electret condenser microphone).

FIG. 3 is a longitudinal sectional view of a conventional electret condenser microphone.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Microphone element (transducer element) 11 Semiconductor chip 12 Conductive film 13 Electret film 14 Spacer 15 Vibration film 20 Ceramic package (capsule) 21 Sound hole 30 Front cross 40 Si wafer (semiconductor wafer) 41 Chip part

Claims (5)

[Claims] A semiconductor chip on which an electronic circuit including an IC element is integrated, a conductive film formed as a back electrode on the surface of the semiconductor chip, and an electret film formed directly on the surface of the conductive film by: An integrated type comprising: a spacer formed by printing on the outer edge surface of an electret film; and a vibrating film attached to the front surface of the electret film via a space by being attached to the surface of the spacer. Capacitive transducer. 2. A transducer element in which the semiconductor chip, the conductive film, the electret film, the spacer, and the vibration film are integrated into a capsule having a front surface provided with a sound hole,
2. The integrated capacitive converter according to claim 1, wherein a front cross is attached to a front surface of the capsule to form a back electret type condenser microphone. 3. The integrated capacitive transducer according to claim 2, wherein said capsule is a ceramic package. 4. The integrated capacitive element according to claim 2, wherein the electronic circuit integrated on the semiconductor chip includes a microphone FET, an amplifier circuit and / or a noise canceling circuit. converter. 5. A step of forming a large number of chip portions by integrating a large number of electronic circuits including IC elements on a semiconductor wafer;
A step of forming a conductive film as a back electrode on the surface of the semiconductor wafer, a step of forming an electret film by directly forming a film on the surface of the conductive film, and printing spacers on the surface of the electret film corresponding to the respective chip portions. Performing a step of: attaching a vibrating film to the surface of the spacer; and, after attaching the vibrating film, cutting the semiconductor wafer to each chip portion.