JP4419563B2 - Electret condenser - Google Patents

Electret condenser Download PDF

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JP4419563B2
JP4419563B2 JP2003429469A JP2003429469A JP4419563B2 JP 4419563 B2 JP4419563 B2 JP 4419563B2 JP 2003429469 A JP2003429469 A JP 2003429469A JP 2003429469 A JP2003429469 A JP 2003429469A JP 4419563 B2 JP4419563 B2 JP 4419563B2
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film
silicon oxide
electrode
oxide film
electret
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JP2005191208A (en
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洋 小倉
徹 山岡
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パナソニック株式会社
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  The present invention relates to an electret capacitor having a vibrating electrode, and more particularly to an electret capacitor formed by using a MEMS (Micro Electro Mechanical Systems) technique.

  Conventionally, organic polymer polymers such as FEP materials have been used as electret elements, which are dielectrics having permanent electrical polarization applied to elements such as condenser microphones. There has been a problem that it is difficult to use as a reflow element for mounting.

  In recent years, electrets using a silicon oxide film using a microfabrication technique as shown in Patent Document 1 have been proposed in place of organic polymer polymers in order to achieve thinning and miniaturization of electrets. .

Specifically, a silicon oxide film is formed on the surface of the base material, heat-treated at 200 ° C. to 400 ° C. in a gas atmosphere containing oxygen without moisture from the film formation atmosphere, and then charged The processing is performed.
JP 2002-33241 A

  However, there is a phenomenon in which electrets lose their charge when they come into contact with a liquid. For example, when electretized FEP is immersed in ethanol, the charge does not become zero, but the charge is greatly reduced. According to the experiment by the present inventor, when FEP charged to 300 V (formation of 12.5 μm of FEP on a stainless steel substrate) was immersed in ethanol, the charge became several volts. This phenomenon occurs not only in ethanol but also in other organic solvents and water. In addition, the material is not unique to FEP and is a phenomenon that occurs in general electret materials including a silicon oxide film.

  An object of this invention is to provide ECM which has a structure excellent in moisture resistance. Another object of the present invention is to provide an ECM that is small and does not require a charge supply circuit by manufacturing an ECM constituted by electrets having a permanent charge by MEMS technology.

In order to solve the above-described conventional problems, an electret capacitor according to a first embodiment of the present invention includes a conductive film serving as a first electrode in which an acoustic hole is formed, an air gap connected to the acoustic hole , a silicon oxide A conductive film to be a second electrode on which an electret film made of a film is formed. The air gap and the electret film are formed between the conductive film to be the first electrode and the conductive film to be the second electrode. An insulating film made of a silicon nitride film is formed on the upper and lower surfaces of the silicon oxide film, and the conductive film serving as the second electrode is a vibration film.

An electret capacitor according to a second embodiment of the present invention includes a conductive film serving as a first electrode in which an acoustic hole is formed, an air gap connected to the acoustic hole , and a conductive film serving as a second electrode. electret film made of a silicon oxide film is formed on the conductive film to be the first electrode, the air gap and the electret film is formed between the conductive film to be the conductive film and the second electrode serving as the first electrode, the electret film, a silicon An insulating film made of a silicon nitride film is formed on the upper and lower surfaces of the oxide film, and the conductive film serving as the second electrode is a vibration film.

  As described above, according to the present invention, a highly reliable small and high-performance microphone can be realized. Furthermore, various application devices equipped with them can be widely supplied to society.

  First, an electret condenser microphone (hereinafter referred to as ECM) will be described.

  FIG. 1 shows a configuration diagram of the ECM. 1A shows a top view of the ECM, and FIG. 1B shows a cross-sectional view of the ECM. In FIG. 1A, a microphone portion 17, a surface mount component (hereinafter referred to as SMD) 18 such as a capacitor, and a field effect transistor (hereinafter referred to as FET) 19 are mounted on a printed circuit board 20. FIG. 1B shows an ECM case 21.

  FIG. 2 is a circuit block diagram of the ECM. The internal circuit 22 of the ECM includes a microphone unit 17, an SMD 18, and an FET 19, and is configured to output signals from the output terminal 23 and the output terminal 24 to the external terminal 25 and the external terminal 26. As an actual operation, an input signal of about 2V is made from the terminal 27, and an AC signal output of several tens of mV is made to the terminal 28. The terminals 26 and 29 are connected to an output terminal 24 that is a GND terminal in the internal circuit 22 of the ECM.

  Hereinafter, embodiments of the electret condenser of the present invention will be described in detail.

(First embodiment)
The electret condenser and ECM of the 1st Embodiment of this invention are demonstrated using FIGS. 1-3.

For the frame film 9 having the leak hole 6 in FIG. 3, a polysilicon film or a silicon nitride film having an etching resistance against the HF solution is used. A conductive structure can be obtained by using a low-resistance polysilicon film or by providing a conductive film 11 serving as a second electrode on the frame film 9 and connected to the GND terminal 24 in FIG. . On the other hand, a silicon oxide film 2 is formed between the semiconductor substrate 1 and the silicon nitride film 3, and a conductive film 16 serving as a first electrode is provided on these exposed surfaces to form a first electrode. The conductive film 16 and the gate of the FET 19 are electrically connected. A silicon oxide film (electret film) 4 that stores charges and is covered with the silicon nitride film 3 and the silicon nitride film 5 is disposed below the frame film 9. An air gap layer 15 is formed between the frame film 9 and the silicon nitride film 5, and a silicon oxide film 7 is formed between the frame film 9 and the silicon nitride film 5 on the silicon substrate 1. A silicon oxide film 2 is formed between the silicon substrate 1 and the silicon nitride film 3.

In FIG. 3, when the ECM receives sound pressure through the acoustic hole 10, the frame film 9 and the conductive film 11 and the protective film 12 serving as the second electrode disposed thereon act as the vibration film 13. The acoustic hole 10 is formed in the silicon nitride film 3, the silicon nitride film 5, the silicon oxide film 4, and the conductive film 16 serving as the first electrode . When the vibration film 13 receives sound pressure, it vibrates mechanically according to the sound pressure. In FIG. 3, constitute a capacitor structure of a parallel plate type conductive film 11 serving as the second electrode and the first electrode and composed of a conductive film 16 electrodes, but the change in the distance between the vibrating electrode vibrating film 13 This changes the capacitance (C) of the capacitor. Since stored in the capacitor charge (Q) is constant, the change occurs in the voltage between the conductive film 16 and conductive film 11 serving as the second electrode as a first electrode (V). This is because it is necessary to physically satisfy the condition of the following formula (1).

Q = CV (1)
Since the conductive film 16 serving as the first electrode is electrically connected to the gate of the FET 19, the gate potential of the FET 19 changes due to vibration of the vibration film. A change in the potential of the gate of the FET 19 is output as a change in voltage to the external output terminal 28.

  The capacitance of the capacitor structure in the ECM is determined by a capacitance component that changes due to vibration of the diaphragm and a capacitance component that does not change. If the capacitance component that does not change changes due to the external environment, it greatly affects the performance degradation of the ECM.

  In particular, since the silicon oxide film employed in the present invention is a material that exhibits remarkable moisture adsorption in the atmosphere, the exposure of the electretized silicon oxide film reduces the reliability of the ECM over time. According to the present embodiment, since the silicon nitride film 3 and the silicon nitride film 5 having moisture resistance are provided above and below the silicon oxide film 4, the deterioration of the electretized silicon oxide film 4 is prevented, and the time of ECM is increased. Reliability can be improved. In addition, since the silicon nitride film 3 and the silicon nitride film 5 that are resistant to etching with respect to the HF-based solution are provided above and below the silicon oxide film 4, an ECM composed of electrets having a permanent charge is manufactured by MEMS technology. By doing so, it is possible to realize a small and high-performance ECM that does not require a charge supply circuit.

Further, according to the first embodiment, the vibrating membrane 13 is disposed on the frame membrane 9 and the upper portion thereof.
Since it is composed of the conductive film 11 and the protective film 12 serving as the second electrode, it is possible to easily control the film thickness, that is, control the resonance frequency of the vibration film.

(Second Embodiment)
An electret condenser and an ECM according to a second embodiment of the present invention will be described with reference to FIGS.

For the frame film 9 having the acoustic hole 10 shown in FIG. 4, a polysilicon film or a silicon nitride film having etching resistance to the HF solution is used. A silicon oxide film 2 is formed between the semiconductor substrate 1 and the frame film 9, and a conductive film 16 serving as a first electrode is provided on these exposed surfaces. The conductive film 16 serving as the first electrode is electrically connected to the gate of the FET 19. A silicon oxide film (electret film) 4 that stores charges and is covered with the silicon nitride film 3 and the silicon nitride film 5 is disposed on the frame film 9. An air gap layer 15 is formed between the frame film 9 and the silicon nitride film 3, and a silicon oxide film 7 is formed between the frame film 9 and the silicon nitride film 3 on the silicon substrate 1. A conductive film 11 serving as a second electrode is provided on the silicon nitride film 5 so that conduction can be obtained, and the bonding pad 14 is connected to the GND terminal 24 in FIG. In FIG. 4, when the ECM receives sound pressure, the silicon nitride film 3, the silicon oxide film 4, the silicon nitride film 5, and the conductive film 11 and the protective film 12 serving as the second electrode disposed on the silicon nitride film 3, the silicon oxide film 4 Acts as The leak hole 6 is formed in the vibration film 13. When the vibration film 13 receives sound pressure, it vibrates mechanically according to the sound pressure. Figure in 4 constitute a capacitor structure of a parallel plate type conductive film 11 serving as the second electrode and the first electrode and composed of a conductive film 16 electrodes, but the change in the distance between electrodes when the vibrating membrane 13 vibrates This changes the capacitance (C) of the capacitor. Since stored in the capacitor charge (Q) is constant, the change occurs in the voltage between the conductive film 16 and conductive film 11 serving as the second electrode as a first electrode (V). This is because it is necessary to physically satisfy the condition of the following formula (1).

Q = CV (1)
Since the conductive film 16 serving as the first electrode is electrically connected to the gate of the FET 19, the gate potential of the FET 19 changes due to vibration of the vibration film. A change in the potential of the gate of the FET 19 is output as a change in voltage to the external output terminal 28.

  The capacitance of the capacitor structure in the ECM is determined by a capacitance component that changes due to vibration of the diaphragm and a capacitance component that does not change. If the capacitance component that does not change changes due to the external environment, it greatly affects the performance degradation of the ECM.

  In particular, since the silicon oxide film employed in the present invention is a material that exhibits remarkable moisture adsorption in the atmosphere, the exposure of the electretized silicon oxide film reduces the reliability of the ECM over time. According to the present embodiment, since the silicon nitride film 3 and the silicon nitride film 5 having moisture resistance are provided above and below the silicon oxide film 4, the deterioration of the electretized silicon oxide film 4 is prevented, and the time of ECM is increased. Reliability can be improved. In addition, since the silicon nitride film 3 and the silicon nitride film 5 that are resistant to etching with respect to the HF-based solution are provided above and below the silicon oxide film 4, an ECM composed of electrets having a permanent charge is manufactured by MEMS technology. By doing so, it is possible to realize a small and high-performance ECM that does not require a charge supply circuit.

  Further, according to the second embodiment, the silicon oxide film (electret film) 4 can be formed in the latter half of the manufacturing process as a configuration in which the silicon oxide film (electret film) 4 is disposed on the frame film 9 and the air gap layer 15, and the damage received during the process. Can be reduced.

(Third embodiment)
An electret condenser and an ECM according to a third embodiment of the present invention will be described with reference to FIGS.

For the frame film 9 having the leak hole 6 shown in FIG. 5, a polysilicon film or a silicon nitride film having etching resistance against the HF solution is used. A silicon oxide film 2 is formed between the semiconductor substrate 1 and the frame film 9. A conductive film 16 serving as a second electrode is provided on these exposed surfaces. The conductive film 16 serving as the second electrode is electrically connected to the gate of the FET 19. Further, a silicon oxide film (electret film) 4 that stores charges and is covered with the silicon nitride film 3 and the silicon nitride film 5 is disposed on the frame film 9. Further, an air gap layer 15 is formed between the frame film 9 and the silicon nitride film 3, and a silicon oxide film 7 is formed between the frame film 9 and the silicon nitride film 3 on the silicon substrate 1. Yes. Then, the conductive film 11 serving as the first electrode is provided on the silicon nitride film 5 so as to be conductive, and the bonding pad 14 is connected to the GND terminal 24 in FIG. The surface of the conductive film 11 serving as the first electrode is covered with a protective film 12 except for the bonding pad 14.

In FIG. 5, when the ECM receives sound pressure through the acoustic hole 10, the frame film 9 and the conductive film 16 serving as the second electrode disposed below the frame film 9 act as the vibration film 13. When the vibration film 13 receives sound pressure, it vibrates mechanically according to the sound pressure. Figure in 5 constitute a capacitor structure of parallel plate to the conductive film 11 to be the first electrode and the second electrode to become the conductive film 16 electrodes, but the change in the distance between electrodes when the vibrating membrane 13 vibrates This changes the capacitance (C) of the capacitor. Since stored in the capacitor charge (Q) is constant, the change occurs in the voltage between the conductive film 16 and conductive film 11 serving as the first electrode becomes the second electrode (V). This is because it is necessary to physically satisfy the condition of the following formula (1).

Q = CV (1)
Since the conductive film 16 serving as the second electrode is electrically connected to the gate of the FET 19, the gate potential of the FET 19 changes due to vibration of the vibration film. A change in the potential of the gate of the FET 19 is output as a change in voltage to the external output terminal 28.

  The capacitance of the capacitor structure in the ECM is determined by a capacitance component that changes due to vibration of the diaphragm and a capacitance component that does not change. If the capacitance component that does not change changes due to the external environment, it greatly affects the performance degradation of the ECM.

  In particular, since the silicon oxide film employed in the present invention is a material that exhibits remarkable moisture adsorption in the atmosphere, the exposure of the electretized silicon oxide film reduces the reliability of the ECM over time. According to the present embodiment, since the silicon nitride film 3 and the silicon nitride film 5 having moisture resistance are provided above and below the silicon oxide film 4, the deterioration of the electretized silicon oxide film 4 is prevented, and the time of ECM is increased. Reliability can be improved. In addition, since the silicon nitride film 3 and the silicon nitride film 5 that are resistant to etching with respect to the HF-based solution are provided above and below the silicon oxide film 4, an ECM composed of electrets having a permanent charge is manufactured by MEMS technology. By doing so, it is possible to realize a small and high-performance ECM that does not require a charge supply circuit.

Further, according to the third embodiment, the vibration film 13 is composed of the frame film 9 and the conductive film 11 and the protective film 12 serving as the first electrode disposed on the frame film 9, so that the film thickness control, That is, the resonance frequency of the vibrating membrane can be easily controlled.

  Further, the silicon oxide film (electret film) 4 can be formed in the latter half of the manufacturing process by arranging the silicon oxide film (electret film) 4 on the frame film 9 and the air gap layer 15. Thereby, the damage which the silicon oxide film (electret film) 4 receives in a process can be reduced.

(Fourth embodiment)
A fourth embodiment of the present invention will be described with reference to the drawings.

  Here, the manufacturing method of the electret capacitor demonstrated in 1st Embodiment is demonstrated.

  6 to 11 show process sectional views of the ECM of the present invention.

  First, as shown in FIG. 6, a silicon oxide film 2 a, a silicon nitride film 3, a silicon oxide film 4, and a silicon nitride film 5 are sequentially formed on the semiconductor substrate 1. At this time, the silicon oxide film 2a is formed on the back surface of the semiconductor substrate 1 by forming the silicon oxide film 2a by a thermal oxidation method using a furnace or a low pressure CVD method. The silicon oxide film 2b on the back surface serves as a mask for silicon etching. Further, the silicon oxide film 4 becomes an electret film. Then, an acoustic hole 10 for transmitting sound pressure is opened by photolithography and dry etching.

  Next, as shown in FIG. 7, after the silicon oxide film 7 is formed by the CVD method, the region 8 is formed by photolithography and dry etching. Since the silicon oxide film 7 functions as a sacrificial layer for forming the air gap region 15, a material having a high etching rate with respect to the HF-based solution such as a BPSG film is preferable.

Next, as shown in FIG. 8, a frame film 9 is formed on the BPSG film 7 so as to fill the region 8. As the material of the frame film 9, a film having resistance to etching against an HF solution such as a polysilicon film or a silicon nitride film is selected. At this time, if a low-resistance polysilicon film doped with impurities is selected as the frame film 9, a capacitor electrode can be obtained. Then, a leak hole 6 for adjusting the pressure in the air gap of the ECM is formed in the frame film 9 by photolithography and dry etching. Then, after forming a conductive film such as an Al alloy film, a conductive film 11 serving as a second electrode is formed on the frame film 9 excluding the leak holes 6 by photolithography and dry etching.

  Next, as shown in FIG. 9, a protective film 12 made of a silicon nitride film is formed. Then, the silicon oxide film 2b on the back surface is patterned to form a mask for silicon etching.

Next, as shown in FIG. 10, silicon is etched from the back surface of the semiconductor substrate 1 by dipping in an etching solution such as KOH, and then immersed in BHF solution to be used as a mask for the back surface of the semiconductor substrate 1. The film 2b and the exposed silicon oxide film 2a are removed by etching. Then, the protective film 12 on the region to be the bonding pad 14 is selectively removed by photolithography and dry etching, and at the same time, the protective film 12 on the leak hole 6 is selectively removed. At this time, etching is performed so that at least the protective film 12 on the conductive film 11 to be the second electrode remains.

Next, as shown in FIG. 11, the air gap region 15 is formed by selectively removing the silicon oxide film 7 by dipping in an HF-based liquid. At this time, if the conductive film in the bonding pad 14 region is made of a material that does not have etching resistance to the HF-based liquid, the bonding pad region 14 is prevented from being etched by selectively covering the bonding pad region 14 with a resist. Thereafter, the silicon oxide film 4 is exposed to corona discharge or plasma discharge to inject charges into an electret, and then a conductive film 16 serving as a first electrode such as an Au film is formed on the back surface of the semiconductor substrate 1.

  By forming in this way, a highly reliable ECM can be formed.

(Fifth embodiment)
A fifth embodiment of the present invention will be described with reference to the drawings.

  Here, the manufacturing method of the electret capacitor demonstrated in 1st Embodiment is demonstrated.

  12 to 17 show process sectional views of the ECM of the present invention.

  First, as shown in FIG. 12, a silicon oxide film 2 a, a silicon nitride film 3 a, a silicon oxide film 4, and a silicon nitride film 5 are sequentially formed on the semiconductor substrate 1. At this time, the silicon oxide film 2a is formed on the back surface of the semiconductor substrate 1 by forming the silicon oxide film 2a by a thermal oxidation method using a furnace or a low pressure CVD method, and the silicon nitride film 3a by a low pressure CVD method. The film 3b is formed sequentially. The silicon oxide film 2b on the back surface acts as a mask when performing silicon etching, and the silicon nitride film 3b on the back surface acts as a protective film that prevents damage to the silicon oxide film 2b and film slippage due to an intermediate process. The silicon oxide film 4 and the silicon nitride film 5 are formed by a plasma CVD method. This silicon oxide film 4 becomes an electret film. Then, an acoustic hole 10 for transmitting sound pressure is opened by photolithography and dry etching.

  Next, as shown in FIG. 13, after the silicon oxide film 7 is formed by the CVD method, the region 8 is formed by photolithography and wet etching. Since the silicon oxide film 7 functions as a sacrificial layer for forming the air gap region 15, a material having a high etching rate with respect to the HF-based solution such as a BPSG film is preferable.

Next, as shown in FIG. 14, a frame film 9 is formed so as to fill the region 8. As the material of the frame film 9, a film having resistance to etching against an HF solution such as a polysilicon film or a silicon nitride film is selected. At this time, if a low-resistance polysilicon film doped with impurities is selected as the frame film 9, a capacitor electrode can be obtained. Then, a leak hole region 6 for adjusting the pressure in the air gap of the ECM is formed by photolithography and dry etching. Thereafter, after forming a conductive film such as an Al alloy film, a conductive film 11 serving as a second electrode is selectively formed on the frame film 9 excluding the leak hole 6 by photolithography and dry etching.

  Next, as shown in FIG. 15, a protective film 12 made of a silicon nitride film is formed. Further, after the silicon nitride film 3b on the back surface is removed by dry etching, the silicon oxide film 2b on the back surface is patterned to selectively form a region serving as a mask for silicon etching.

Next, as shown in FIG. 16, silicon is etched from the back surface of the semiconductor substrate 1 by being immersed in an etching solution such as KOH, and then exposed to the silicon oxide film 2b and the silicon exposed to the semiconductor substrate 1 by being immersed in a BHF solution. The oxide film 2a is removed. Then, the protective film 12 on the region to be the bonding pad 14 is selectively removed by photolithography and dry etching, and at the same time, the protective film 12 on the leak hole 6 is selectively removed. At this time, the protective film 12 is formed so as to remain on at least the conductive film 11 serving as the second electrode .

  Next, as shown in FIG. 17, the air gap region 15 is formed by selectively removing the silicon oxide film 7 by dipping in an HF-based liquid.

At this time, in the case where the conductive film of the bonding pad 14 is made of a material that does not have etching resistance to the HF-based liquid, etching is prevented by selectively covering the bonding pad region 14 with a resist. Then, after being exposed to corona discharge or plasma discharge to inject charges into the silicon oxide film 4 to be electreted, a conductive film 16 serving as a first electrode such as an Au film is formed on the back surface of the semiconductor substrate 1.

  By forming in this way, a highly reliable ECM can be formed.

(Sixth embodiment)
A sixth embodiment of the present invention will be described with reference to the drawings.

  Here, the manufacturing method of the electret capacitor demonstrated in 1st Embodiment is demonstrated.

  18 to 23 show process sectional views of the ECM of the present invention.

  First, as shown in FIG. 18, a silicon oxide film 2a, a silicon nitride film 3a, a silicon oxide film 4a, and a silicon nitride film 5a are formed on the semiconductor substrate 1. At this time, the silicon oxide film 2a is formed by a thermal oxidation method using a furnace or a low pressure CVD method, and the silicon nitride film 3a, the silicon oxide film 4a and the silicon nitride film 5a are formed by a low pressure CVD method. A silicon oxide film 2b, a silicon nitride film 3b, a silicon oxide film 4b, and a silicon nitride film 5b are also formed on the back surface of the silicon nitride film. The silicon oxide film 2b on the back surface acts as a mask for the silicon etching of the semiconductor substrate 1. The silicon nitride film 3b, the silicon oxide film 4b and the silicon nitride film 5b on the back surface are damaged or filmed by the intermediate process. Acts as a protective film to prevent slipping. This silicon oxide film 4a functions as an electret film. Then, an acoustic hole 10 for transmitting sound pressure is opened by photolithography and dry etching.

  Next, as shown in FIG. 19, after the silicon oxide film 7 is formed by the CVD method, the region 8 is formed by photolithography and wet etching. Since the silicon oxide film 7 functions as a sacrificial layer for forming the air gap region 15, a material having a high etching rate with respect to the HF-based solution such as a BPSG film is preferable.

Next, as shown in FIG. 20, a frame film 9 is formed so as to be embedded in the region 8. As the material of the frame film 9, a film having resistance to etching against an HF solution such as a polysilicon film or a silicon nitride film is selected. At this time, if a low-resistance polysilicon film doped with impurities is selected as the frame film 9, a capacitor electrode can be obtained. Then, the leak hole 6 for adjusting the pressure in the air gap of the ECM is selectively formed by photolithography and dry etching. Thereafter, after forming a conductive film such as an Al alloy film, a conductive film 11 serving as a second electrode is selectively formed on the frame film 9 by photolithography and dry etching, excluding the leak hole 6.

  Next, as shown in FIG. 21, a protective film 12 made of a silicon nitride film is formed. Further, after removing the silicon nitride film 5b, the silicon oxide film 4b, and the silicon nitride film 3b on the back surface by dry etching, the silicon oxide film 2b on the back surface is patterned to form a mask for silicon etching.

Next, as shown in FIG. 22, silicon is etched from the back surface of the semiconductor substrate 1 by dipping in an etching solution such as KOH, and then dipped in BHF solution to expose the silicon oxide film 2b used as a mask and the exposed silicon. The oxide film 2a is removed. Thereafter, the protective film 12 on the region to be the bonding pad 14 is selectively removed by photolithography and dry etching, and at the same time, the protective film 12 on the leak hole 6 is selectively removed. At this time, it is formed so that at least the protective film 12 on the conductive film 11 to be the second electrode remains.

Next, as shown in FIG. 23, the air gap region 15 is formed by selectively removing the silicon oxide film 7 by dipping in an HF-based liquid. At this time, if the conductive film in the bonding pad 14 region is made of a material that does not have etching resistance to the HF-based liquid, etching is prevented by selectively covering the bonding pad region 14 with a resist. Then, by exposing the silicon oxide film 4 to electret by exposure to corona discharge or plasma discharge, a conductive film 16 serving as a first electrode such as an Au film is formed on the back surface of the silicon substrate 1.

  By forming in this way, a highly reliable ECM can be formed.

(Seventh embodiment)
A seventh embodiment of the present invention will be described with reference to the drawings.

  Here, the manufacturing method of the electret capacitor demonstrated in 2nd Embodiment is demonstrated.

  24 to 29 show process cross-sectional views of the ECM of the present invention.

  First, as shown in FIG. 24, a silicon oxide film 2a and a frame film 9a are formed on a semiconductor substrate 1. At this time, the silicon oxide film 2a is formed by a thermal oxidation method using a furnace or a low pressure CVD method. The silicon oxide film 2b on the back surface acts as a mask when performing silicon etching. As a material of the frame film 9a, a film having resistance to etching with respect to an HF-based solution such as a polysilicon film or a silicon nitride film is selected and formed by a low pressure CVD method using a furnace. The frame film 9b on the back surface functions as a protective film that prevents film damage and damage of the silicon oxide film 2b due to an intermediate process. Then, an acoustic hole 10 for transmitting sound pressure is formed in the frame film 9 by photolithography and dry etching.

  Next, as shown in FIG. 25, after the silicon oxide film 7 is formed by the CVD method, a region 8 connecting the frame film 9a and the vibration film is formed by photolithography and wet etching. Thereafter, the frame film 9b on the back surface is removed. Since the silicon oxide film 7 functions as a sacrificial layer for forming the air gap region 15, a material having a high etching rate with respect to the HF-based solution such as a BPSG film is preferable.

Next, as shown in FIG. 26, the silicon nitride film 3, the silicon oxide film 4, and the silicon nitride film 5 are sequentially formed by the CVD method. This silicon oxide film 4 acts as an electret film. Further, the silicon nitride film 3 and the silicon nitride film 5 function as a protective film that prevents damage to the silicon oxide film 4 and film slippage due to an intermediate process. Then, the leak hole 6 for adjusting the pressure in the air gap of the ECM is selectively formed by photolithography and dry etching. Thereafter , after forming a conductive film such as an Al alloy film, a conductive film 11 serving as a second electrode is selectively formed on the silicon nitride film 5 excluding the leak holes 6 by photolithography and dry etching.

  Next, as shown in FIG. 27, a protective film 12 made of a silicon nitride film is formed. Further, the back side silicon oxide film 2b is patterned to form a mask for silicon etching.

Next, as shown in FIG. 28, after the silicon is etched from the back surface of the semiconductor substrate 1 by dipping in an etching solution such as KOH, the silicon oxide film 2b used as a mask and the exposed silicon are dipped in the BHF solution. The oxide film 2a is removed. Then, the protective film 12 on the region to be the bonding pad 14 is selectively removed by photolithography and dry etching, and at the same time, the protective film 12 on the leak hole 6 is selectively removed. At this time, it is formed so that at least the protective film 12 on the conductive film 11 to be the second electrode remains.

Next, as shown in FIG. 29, the air gap region 15 is formed by selectively removing the silicon oxide film 7 by dipping in an HF-based liquid. At this time, if the conductive film in the bonding pad 14 region is made of a material that does not have etching resistance to the HF-based liquid, etching is prevented by selectively covering the bonding pad region 14 with a resist. Then, by exposing the silicon oxide film 4 to electret by exposure to corona discharge or plasma discharge, a conductive film 16 serving as a first electrode such as an Au film is formed on the back surface of the silicon substrate 1.

  By forming in this way, a highly reliable ECM can be formed.

(Eighth embodiment)
An eighth embodiment of the present invention will be described with reference to the drawings.

  Here, the manufacturing method of the electret capacitor demonstrated in 3rd Embodiment is demonstrated.

  30 to 35 show process sectional views of the ECM of the present invention.

  First, as shown in FIG. 30, a silicon oxide film 2 a and a frame film 9 a are formed on the semiconductor substrate 1. At this time, the silicon oxide film 2a is formed by a thermal oxidation method using a furnace or a low pressure CVD method. The silicon oxide film 2b on the back surface is used as a mask for silicon etching. As a material of the frame film 9a, a film having resistance to etching with respect to an HF-based solution such as a polysilicon film or a silicon nitride film is selected and formed by a low pressure CVD method using a furnace. The frame film 9b on the back surface acts as a protective film that prevents damage to the silicon oxide film 2b and film slippage due to an intermediate process. Then, the leak hole 6 is opened by photolithography and dry etching.

  Next, as shown in FIG. 31, after the silicon oxide film 7 is formed by the CVD method, the region 8 connecting the frame film 9a and the vibration film is selectively formed by photolithography and wet etching, and then the frame film 9b on the back surface is formed. Remove. Since the silicon oxide film 7 functions as a sacrificial layer for forming the air gap region 15, a material having a high etching rate with respect to the HF-based solution such as a BPSG film is preferable.

Next, as shown in FIG. 32, a silicon nitride film 3, a silicon oxide film 4, and a silicon nitride film 5 are formed by the CVD method. The silicon oxide film 4 functions as an electret film. In addition, the silicon nitride film 3 and the silicon nitride film 5 function as a protective film that prevents the silicon oxide film 4 from being damaged or damaged by an intermediate process. An acoustic hole 10 for transmitting sound pressure is opened by photolithography and dry etching. Then, after forming a conductive film such as an Al alloy film, a conductive film 11 serving as a first electrode is selectively formed on the silicon nitride film 5 excluding the acoustic hole 10 by photolithography and dry etching.

  Next, as shown in FIG. 33, a protective film 12 made of a silicon nitride film is formed. Further, the silicon oxide film 2b on the back surface is patterned to selectively form a region serving as a mask for silicon etching.

Next, as shown in FIG. 34, after silicon is etched from the back surface of the semiconductor substrate 1 by immersing in an etching solution such as KOH, the silicon oxide film 2b and the exposed silicon oxide film 2a are immersed in a BHF solution. Remove. Then, the protective film 12 on the region to be the bonding pad 14 is selectively removed by photolithography and dry etching, and at the same time, the protective film 12 on the leak hole 6 is selectively removed. At this time, it is formed so that at least the protective film 12 on the conductive film 11 to be the first electrode remains.

Next, as shown in FIG. 35, the air gap region 15 is formed by selectively removing the silicon oxide film 7 by dipping in an HF-based liquid. At this time, if the conductive film in the bonding pad 14 region is made of a material that does not have etching resistance to the HF-based liquid, etching is prevented by selectively covering the bonding pad region 14 with a resist. Then, by exposing the silicon oxide film 4 to electret by exposure to corona discharge or plasma discharge, a conductive film 16 serving as a second electrode such as an Au film is formed on the back surface of the silicon substrate 1.

  By forming in this way, a highly reliable ECM can be formed.

  Here, the capacitance of the capacitor structure in the ECM is determined by a capacitance component that changes due to vibration of the diaphragm and a capacitance component that does not change. If the capacitance component that does not change changes due to the external environment, it greatly affects the performance degradation of the ECM. In particular, since the silicon oxide film employed in the present invention is a material that exhibits remarkable moisture adsorption in the atmosphere, the exposure of the electretized silicon oxide film reduces the reliability of the ECM over time. According to the first to eighth embodiments of the present invention, since the silicon nitride film 3 and the silicon nitride film 5 having moisture resistance are provided above and below the silicon oxide film 4, they are electretized. It is possible to prevent the deterioration of the silicon oxide film 4 and improve the reliability of the ECM over time. In addition, since the silicon nitride film 3 and the silicon nitride film 5 that are resistant to etching with respect to the HF-based solution are provided above and below the silicon oxide film 4, an ECM composed of electrets having a permanent charge is manufactured by MEMS technology. By doing so, it is possible to realize a small and high-performance ECM that does not require a charge supply circuit.

  As described above, the electret condenser of the present invention has heat resistance and moisture resistance, and is useful for realizing a high-performance and small-sized ECM excellent in reliability.

Configuration diagram of electret condenser microphone of the present invention Circuit block diagram of electret condenser microphone of the present invention Sectional drawing of the electret capacitor | condenser of the 1st Embodiment of this invention Sectional drawing of the electret capacitor | condenser of the 2nd Embodiment of this invention Sectional drawing of the electret capacitor | condenser of the 3rd Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 4th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 4th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 4th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 4th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 4th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 4th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 5th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 5th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 5th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 5th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 5th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 5th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 6th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 6th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 6th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 6th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 6th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 6th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 7th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 7th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 7th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 7th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 7th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 7th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 8th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 8th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 8th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 8th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 8th Embodiment of this invention Process sectional drawing of the electret capacitor | condenser of the 8th Embodiment of this invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Silicon oxide film 2a Silicon oxide film 2b Silicon oxide film 3 Silicon nitride film 3a Silicon nitride film 3b Silicon nitride film 4 Silicon oxide film 4a Silicon oxide film 4b Silicon oxide film 5 Silicon nitride film 5a Silicon nitride film 5b Silicon nitride film Film 6 Leakage hole 7 Silicon oxide film 8 Area 9 Frame film 9a Frame film 9b Frame film 10 Acoustic hole 11 Conductive film 12 Protective film 13 Vibration film 14 Bonding pad 15 Air gap layer 16 Conductive film 17 Microphone part 18 Surface mount component 19 Electric field Effect transistor 20 Printed circuit board 21 Case of ECM 22 Internal circuit of ECM 23 Output terminal 24 Output terminal 25 External terminal 26 External terminal 27 External signal input terminal 28 External signal output terminal 29 External terminal

Claims (5)

  1. A conductive film to be a first electrode in which an acoustic hole is formed;
    An air gap connected to the acoustic hole ;
    A conductive film to be a second electrode on which an electret film made of a silicon oxide film is formed;
    The air gap and the electret film are formed between a conductive film to be the first electrode and a conductive film to be the second electrode,
    The electret film is formed with an insulating film made of a silicon nitride film on the upper and lower surfaces of the silicon oxide film ,
    The electret capacitor, wherein the conductive film to be the second electrode is a vibration film.
  2. A conductive film to be a first electrode in which an acoustic hole is formed;
    An air gap connected to the acoustic hole ;
    A conductive film to be a second electrode,
    An electret film made of a silicon oxide film is formed on the conductive film to be the first electrode,
    The air gap and the electret film are formed between a conductive film to be the first electrode and a conductive film to be the second electrode,
    The electret film is formed with an insulating film made of a silicon nitride film on the upper and lower surfaces of the silicon oxide film ,
    The electret capacitor, wherein the conductive film to be the second electrode is a vibration film.
  3. The insulating layer, the electret condenser according to claim 1 or 2, characterized in that it has a moisture resistance.
  4. Electret condenser according to claim 1 or 2, wherein the first electrode and formed of a conductive film is characterized in that aluminum or an aluminum alloy.
  5. Electret condenser according to claim 1 or 2, wherein the second electrode become conductive film is gold or a refractory metal.
JP2003429469A 2003-12-25 2003-12-25 Electret condenser Expired - Fee Related JP4419563B2 (en)

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JP4424331B2 (en) 2005-08-01 2010-03-03 セイコーエプソン株式会社 Electrostatic actuator, droplet discharge head, method for driving droplet discharge head, and method for manufacturing electrostatic actuator
JP4642634B2 (en) * 2005-10-31 2011-03-02 パナソニック株式会社 Manufacturing method of acoustic sensor
DE102006001493B4 (en) * 2006-01-11 2007-10-18 Austriamicrosystems Ag MEMS sensor and method of manufacture
CN101379373A (en) * 2006-02-28 2009-03-04 松下电器产业株式会社 Electret capacitor type composite sensor
DE102006022378A1 (en) 2006-05-12 2007-11-22 Robert Bosch Gmbh Method for producing a micromechanical component and micromechanical component
JP4480728B2 (en) 2006-06-09 2010-06-16 パナソニック株式会社 Method for manufacturing MEMS microphone
EP1931173B1 (en) 2006-12-06 2011-07-20 Electronics and Telecommunications Research Institute Condenser microphone having flexure hinge diaphragm and method of manufacturing the same
JP4961260B2 (en) * 2007-05-16 2012-06-27 株式会社日立製作所 Semiconductor device
JP2009141591A (en) * 2007-12-05 2009-06-25 Rohm Co Ltd Mems sensor
WO2009101757A1 (en) * 2008-02-14 2009-08-20 Panasonic Corporation Capacitor microphone and mems device
WO2009157122A1 (en) * 2008-06-24 2009-12-30 パナソニック株式会社 Mems device, mems device module and acoustic transducer

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