JP2007267252A - Condenser microphone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a condenser microphone in which stability in microphone operation is ensured without complicating manufacturing steps, the vibration property of a diaphragm is enhanced, and microphone sensitivity is improved by reducing parasitic capacitance of a condenser. <P>SOLUTION: A diaphragm 10 includes a central portion 12 and a peripheral portion 14, and four circular through-holes 16 are provided in an intermediate area of the central portion 12. A back plate 20 is disposed concentrically with the diaphragm 10 and a radius of the back plate 20 is approximately equal with that of the central portion 12 of the diaphragm 10. Therefore, the back plate 20 is in an approximately corresponding relation with the central portion 12 of the diaphragm 10, and the peripheral portion 14 of the diaphragm 10 is being protruded from the back plate 20. The back plate 20 is supported on a supporting substrate 30 by four pillar-like insulating second supporting parts 52 positioned within the four through-holes 16 of the diaphragm 10. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a condenser microphone, and more particularly to a condenser microphone using a semiconductor film.

  Conventionally, a condenser microphone that can be manufactured by applying a semiconductor device manufacturing process is known. The condenser microphone has a movable electrode and a fixed electrode on each of a diaphragm and a plate that are vibrated by sound waves, and supports the diaphragm and the plate in a state of being separated from each other by an insulating spacer. That is, a capacitor is formed by the diaphragm and the counter electrode of the plate.

  In such a condenser microphone, when the diaphragm vibrates due to sound waves, the capacitance of the capacitor changes due to the displacement, and the change in capacitance is converted into an electrical signal and output. Therefore, the sensitivity of the condenser microphone is defined by the output voltage of the microphone when a predetermined sound pressure is applied to the diaphragm, and is expressed by the following equation. Here, the vibration displacement amount refers to a displacement amount at the center portion of the diaphragm when a predetermined sound pressure is applied to the diaphragm.

Microphone sensitivity ∝ Vibration displacement x Applied voltage between electrodes x {Signal capacity / (Signal capacity + Parasitic capacity)}

  From this formula, in order to improve the microphone sensitivity, the vibration displacement amount of the diaphragm with respect to the distance between the counter electrodes is increased, that is, the vibration characteristics of the diaphragm are improved, and the voltage applied between the counter electrodes of the capacitor is increased. It is conceivable to increase the signal size by increasing the microphone size, and to reduce the parasitic capacitance that does not contribute to the capacitance change of the capacitor.

  Non-Patent Document 1 discloses a condenser microphone in which each of a diaphragm and a plate is formed of a conductive thin film. However, since the entire surfaces of the plate and diaphragm are in a substantially opposing relationship, when the applied voltage between the diaphragm and the plate is increased or the microphone size is increased, the plate is deformed by the electrostatic attractive force between the opposing electrodes. Therefore, there is a problem that the stability of the microphone operation is impaired.

  Further, since the entire periphery of the diaphragm is fixed to the spacer, when the sound wave propagates to the diaphragm, the displacement due to the vibration of the diaphragm is large in the central portion, but is extremely small in the peripheral portion around the central portion. As a result, the vibration of the diaphragm is efficiently detected as the signal capacity mainly at the center part of the diaphragm, and the peripheral part of the diaphragm almost only generates parasitic capacitance. Therefore, there is a problem that the microphone sensitivity is not improved due to the presence of the large parasitic capacitance.

  Further, in order to reduce such parasitic capacitance, for example, a large number of small holes are provided in a region of the plate corresponding to the periphery of the diaphragm to reduce the area corresponding to the periphery of the diaphragm and the plate. If it tries to do so, there is a problem that the mechanical strength of the plate is lowered and the deformation of the plate becomes more remarkable.

  In Patent Document 1, a plate facing a diaphragm forming a movable electrode is formed of an insulating material, and a surface of the plate facing the diaphragm (hereinafter referred to as a “diaphragm facing surface”) corresponds to a central portion of the diaphragm. By providing the back electrode only in the area, the correspondence between the peripheral part of the diaphragm and the plate is eliminated, and the signal capacity at the center part of the diaphragm is efficiently detected, while the parasitic capacity at the peripheral part of the diaphragm is reduced. Thus, a condenser microphone with improved microphone sensitivity is disclosed.

  In addition, a protrusion that functions as a diaphragm vibration stopper is installed so that the diaphragm contacts the back electrode even when excessive sound pressure is applied to the diaphragm or mechanical shock is applied from the outside. There is disclosed a condenser microphone in which there is no problem.

  However, since it is necessary to provide the back electrode only in a certain region of the diaphragm facing surface of the plate made of an insulating material, there is a problem that the manufacturing process is complicated, the manufacturing yield is reduced, and the manufacturing cost is increased. In addition, in the step of etching away the sacrificial layer interposed between the diaphragm and the plate to form a gap, the insulating material that fixes the back electrode of the plate is also etched to some extent. Since it becomes necessary to be incorporated into the manufacturing process, the manufacturing cost is further increased.

The Institute of Electrical Engineers of Japan MSS-01-34 Special table 2004-506394

  The present invention provides a condenser microphone that increases the sensitivity of the microphone by ensuring the stability of the microphone operation without complicating the manufacturing process, improving the vibration characteristics of the diaphragm, reducing the parasitic capacitance of the capacitor, and so on. The purpose is to do.

  (1) A condenser microphone for achieving the above object has a central part, a peripheral part provided around the central part, and a plurality of through holes provided in the central part, A conductive diaphragm that vibrates in response, a conductive plate provided opposite to the diaphragm, and provided on the opposite side of the plate with respect to the diaphragm, and applies pressure applied to the diaphragm from the side opposite to the plate A substrate having a cavity for relaxation, an insulating first support portion that supports the peripheral portion of the diaphragm, and a plate that is positioned in the plurality of through holes of the diaphragm and supports the plate on the substrate An insulating second support portion, and a support means that forms a gap between the central portion of the diaphragm and the plate.

  In such a condenser microphone, since the plate is supported by the second support portion that passes through a plurality of through holes provided in the central portion of the diaphragm, the size of the plate corresponds to only the central portion of the diaphragm. In addition, since the mechanical strength of the plate is enhanced, even if the applied voltage between the diaphragm and the plate is increased to improve the microphone sensitivity, the electrostatic capacitance between the counter electrodes is increased. The deformation of the plate due to the attractive force is suppressed, and the deformation of the plate is also suppressed against an external impact, so that the vibration characteristics of the diaphragm can be improved and the stability of the microphone operation is ensured. It becomes possible.

  In addition, since the plate is directly supported on the substrate by the second support portion, the plate is stably held, and even if the microphone size is increased to improve the microphone sensitivity, the static electricity between the counter electrodes can be increased. The deformation of the plate due to the electric attractive force is suppressed, and the deformation of the plate is also suppressed against an external impact, so that the vibration characteristics of the diaphragm can be improved and the stability of the microphone operation can be ensured.

  In addition, since the plate can only correspond to the central part of the diaphragm and not to have a corresponding relationship with the peripheral part of the diaphragm, parasitic capacitance is not generated between the peripheral part of the diaphragm and the plate. As a result, the parasitic capacitance as a whole can be reduced.

  In addition, since both the diaphragm and the plate are formed of a conductive material, a complicated manufacturing process is not required in which an electrode is provided only in a certain region of the diaphragm facing surface of the plate made of an insulating material. Simplification is achieved.

  Further, the support structure of the diaphragm can take various forms as long as the support structure of the plate is not hindered. For example, a structure that directly supports the diaphragm on the substrate, a structure that suspends the diaphragm from the suspension portion supported on the substrate via the spacer, a structure that suspends the diaphragm from the arm portion that extends outward from the plate, etc. Various structures can be selected in consideration of stress relaxation required for the diaphragm and improvement of vibration characteristics.

  Therefore, according to this condenser microphone, the stability of the microphone operation is ensured without complicating the manufacturing process, the vibration characteristics of the diaphragm are improved, the parasitic capacitance of the condenser is reduced, and the microphone sensitivity is improved. be able to.

  In the specification of the present application, “diaphragm” and “plate” mean that the plane including the diaphragm and the plane including the plate are in a parallel or substantially parallel positional relationship, and the “corresponding” relationship. “Present” means that a portion where the opposing diaphragms are located and a portion where the plates are located are in an overlapping positional relationship.

  (2) In the condenser microphone, it is preferable that the plate has a substantially corresponding relationship with the central portion of the diaphragm.

  In this case, compared with the conventional case where the entire surface of the plate and the diaphragm are substantially in a counter relationship, the plate is downsized to the same size as the central part of the diaphragm, so that the deformation of the plate is suppressed, and the vibration characteristics of the diaphragm And stability of microphone operation can be ensured. At the same time, since there is no correspondence with the peripheral portion of the diaphragm, no parasitic capacitance is generated between the peripheral portion of the diaphragm and the plate, and the parasitic capacitance of the entire capacitor is reduced.

  Therefore, according to this condenser microphone, it is possible to ensure the microphone operation stability, improve the vibration characteristics of the diaphragm, reduce the parasitic capacitance of the condenser, and improve the microphone sensitivity.

  (3) In the condenser microphone, it is preferable that an insulating stopper layer is provided in a gap between the diaphragm and the plate.

  In this case, even when excessive sound pressure is applied to the diaphragm or mechanical shock is applied from the outside, excessive displacement of the diaphragm is limited by the presence of the stopper layer, and the diaphragm contacts the plate. Is prevented. Therefore, according to this condenser microphone, the stability of the microphone operation can be ensured.

  (4) In the condenser microphone, it is preferable that the stopper layer is supported by the second support portion.

  In this case, since the stopper layer is directly supported on the substrate by the second support portion, the stopper layer is stably held, and the function of preventing the contact between the diaphragm and the plate is stably achieved. In addition, since the second support part that supports the plate is also used as a support means for the stopper layer, the complexity of the structure is suppressed, and only the step of forming the stopper layer is added in the condenser microphone manufacturing process. Therefore, complication of the manufacturing process is suppressed. Therefore, according to this condenser microphone, the stability of the microphone operation can be ensured.

  (5) In the condenser microphone, it is preferable that a plurality of small through holes are provided in a region corresponding to the substrate of the diaphragm.

  In this case, the rigidity of the diaphragm is lowered by the amount of the plurality of through holes provided, the deformation at the time of vibration is facilitated, and the displacement at the center is increased, so that the vibration characteristics of the diaphragm are improved. In addition, in the manufacturing process of a condenser microphone, a plurality of through holes also function as etching solution entry holes when the sacrificial layer interposed between the diaphragm and the substrate is removed by etching to form a gap. Contributes to simplification of the process. Therefore, according to this condenser microphone, it is possible to improve the vibration sensitivity of the diaphragm and improve the microphone sensitivity while simplifying the manufacturing process.

  The plurality of through holes are provided only in the region corresponding to the substrate and not provided in the region corresponding to the cavity, so that the sound wave that reaches the diaphragm does not contribute to the vibration of the diaphragm. It does not go through the plurality of through holes.

  (6) In the condenser microphone, it is preferable that a predetermined acoustic resistance is formed by the substrate around the cavity and the diaphragm.

  In this case, due to the presence of the predetermined acoustic resistance formed by the substrate and the diaphragm around the cavity, the sound wave reaching the diaphragm can vibrate efficiently in the central portion of the diaphragm without passing elsewhere. Therefore, according to this condenser microphone, it is possible to further improve the vibration characteristics of the diaphragm and improve the microphone sensitivity.

  Embodiments of the present invention will be described below based on a plurality of examples. In each of the embodiments, the component having the same reference sign corresponds to the component of the other embodiment having the reference sign.

(First Example)
1A is a plan view schematically showing the configuration of the condenser microphone according to the first embodiment, FIG. 1B is a plan view when the back plate is removed from FIG. 1A, and FIG. ) Is a cross-sectional view taken along line AA ′ of FIG. 1A, and FIG. 1D is a cross-sectional view taken along line BB ′ of FIG.

  As shown in FIGS. 1A to 1D, the condenser microphone according to the first embodiment includes a diaphragm 10 constituting a counter electrode of the condenser and a back plate 20 as a plate, and the diaphragm 10 and the back plate 20. It has a support substrate 30 provided with support means for supporting while insulating.

  The diaphragm 10 is made of a conductive thin film made of polysilicon doped with, for example, P (phosphorus) as an impurity, and has a disc-shaped central portion 12 and a peripheral portion 14 provided around the central portion 12. is doing. Further, in the central portion 12 of the diaphragm 10, four circular through holes 16 are provided at equal intervals in a region adjacent to the peripheral portion 14 (hereinafter, this region is referred to as “intermediate region”). A number of small through holes 18 are continuously provided. Further, a large number of small through holes 18 are continuously provided in four regions at equal intervals in the peripheral portion 14 of the diaphragm 10. A region where the four through holes 16 and the many small through holes 18 are provided has a corresponding relationship with the support substrate 30. Here, the thickness of the diaphragm 10 is about 0.5 μm, the radius of the central portion 12 is about 0.35 mm, the total radius including the peripheral portion 14 is about 0.5 mm, and the radius of the four through holes 16 is It is about 25 μm.

  The back plate 20 is disposed in parallel with the diaphragm 10 with a gap 40 having a predetermined interval, for example, an interval of about 4 μm. The back plate 20 is also made of a conductive thin film made of polysilicon doped with P, for example, and has a disk shape with a thickness of about 2 μm. The back plate 20 is arranged concentrically with the diaphragm 10, and the radius of the back plate 20 is substantially the same as the radius of the central portion 12 of the diaphragm 10. For this reason, the back plate 20 has a substantially corresponding relationship with the central portion 12 of the diaphragm 10, and the peripheral portion 14 of the diaphragm 10 is in a state of protruding from the back plate 20. The back plate 20 is continuously provided with a large number of small through holes 22 that function as acoustic holes for allowing sound waves from outside to reach the diaphragm 10. However, the large number of small holes 22 are arranged so as not to correspond to the large number of small holes 18 of the diaphragm 10. Furthermore, from the outer edge of the back plate 20, a lead wiring portion 24 connected to the electrode extends outward.

  The outer edge side of the peripheral portion 14 of the diaphragm 10 is supported circumferentially on the support substrate 30 by an insulating first support portion 50. Further, the back plate 20 is supported on the support substrate 30 by four columnar insulating second support portions 52 positioned in the four through holes 16 of the diaphragm 10. The first support part 50 and the second support part 52 are made of, for example, a silicon oxide film.

  The support substrate 30 is made of, for example, a silicon substrate having a thickness of 500 to 600 μm, and is located at a position corresponding to a region surrounded by an intermediate region (hereinafter, this region is referred to as “central region”) in the central portion 12 of the diaphragm 10. And an opening that penetrates the support substrate 30 and reaches the diaphragm 10. Further, an opening that reaches the diaphragm 10 through the support substrate 30 is also provided at a position corresponding to a region where the small through hole 18 is not provided in the peripheral portion 14 of the diaphragm 10. And the cavity 32 is comprised from these opening parts. Such a cavity 32 functions as a pressure buffering chamber for relieving the pressure applied to the diaphragm 10 from the side opposite to the plate.

  Further, a passage 34 that forms a predetermined acoustic resistance is provided by the support substrate 30 around the cavity 32 and the diaphragm 10. The passage 34 has a height (that is, a distance between the diaphragm 10 and the support substrate 30) and a length (that is, the four through holes 16 and the large number of small holes 18 in the end of the cavity 32). The acoustic resistance is controlled by the shortest distance until the diaphragm reaches the diaphragm by the predetermined acoustic resistance so that the central portion of the diaphragm is vibrated efficiently. Here, the height of the passage 34 is, for example, 2 μm, and the length thereof is, for example, 15 μm.

  It should be noted that a lead wiring portion extending outward from the outer edge of the diaphragm 10, electrodes connected to the lead wiring portion, electrodes connected to the back plate 20 via the lead wiring portion 24, and the diaphragm 10 and the back plate 20 through these electrodes. A bias power supply circuit for applying a predetermined voltage between the first and second detection circuits, a detection circuit for detecting a change in capacitance between the diaphragm 10 and the back plate 20 to which the predetermined voltage is applied as an electric signal, and the like. Description is omitted.

  As described above, according to the condenser microphone according to the first embodiment, the back plate 20 is downsized to the same size as the central portion of the diaphragm 10, so that the plate is approximately the same as the size of the diaphragm. Compared to the case, the mechanical strength of the back plate 20 is enhanced. For this reason, even if the applied voltage between the diaphragm 10 and the back plate 20 is increased for the purpose of improving the microphone sensitivity, the deformation of the back plate 20 due to the electrostatic attractive force between the counter electrodes is suppressed, and the external The deformation of the back plate 20 is also suppressed against an impact. Therefore, the vibration characteristics of the diaphragm 10 can be improved and the stability of the microphone operation can be ensured.

  Further, since the back plate 20 is supported directly on the support substrate 30 by the four second support portions 52, the back plate 20 is stably held. From this point, the deformation of the back plate 20 is also prevented. Therefore, the vibration characteristics of the diaphragm 10 can be improved, and the stability of the microphone operation can be ensured.

  Further, the back plate 20 has a substantially corresponding relationship with the central portion 12 of the diaphragm 10 and has no corresponding relationship with the peripheral portion 14 of the diaphragm 10 in a state of protruding from the back plate 20. There is almost no parasitic capacitance between the back plate 20 and the back plate 20. For this reason, as compared with the conventional case in which the entire surfaces of the plate and the diaphragm are substantially in a counter relationship, the overall parasitic capacitance is reduced, and thus the microphone sensitivity can be improved.

  In addition, since four through holes 16 and a large number of small through holes 18 are provided in the middle region 12 and the peripheral portion 14 of the center portion 12 of the diaphragm 10, the rigidity of the diaphragm 10 is reduced, and deformation during vibration is caused. Since the displacement at the central portion 12 is increased, the vibration characteristics of the diaphragm 10 are improved, and therefore the microphone sensitivity can be improved.

  Further, a passage 34 is provided between the support substrate 30 around the cavity 32 and the diaphragm 10, and the acoustic resistance is controlled by the height H and length L of the passage 34, so that the diaphragm is generated by a predetermined acoustic resistance. Since the sound wave having reached 10 vibrates the central portion 12 efficiently, the vibration characteristics of the diaphragm are improved, and thus the microphone sensitivity can be improved. The diaphragm 10 is provided with four through holes 16 and a large number of small through holes 18. However, the through holes 16 and the small through holes 18 are limited to a region corresponding to the support substrate 30. Therefore, the sound wave reaching the diaphragm 10 does not pass through the through-hole 16 or the small through-hole 18 without contributing to the vibration of the diaphragm 10.

  In addition, since both the diaphragm 10 and the back plate 20 are formed of a conductive material, a complicated manufacturing process is not required in which an electrode is provided only on a certain portion of the diaphragm facing surface of a plate made of an insulating material. The manufacturing process can be simplified.

  In addition, a large number of small holes 18 provided in the diaphragm 10 are used when the sacrificial layer interposed between the diaphragm 10 and the support substrate 30 is removed by etching and a gap is formed between them in the manufacturing process of the condenser microphone. Since it also functions as an entrance hole for the etching solution, it can contribute to simplification of the manufacturing process. In addition, a large number of small holes 22 provided in the back plate 20 are also used for etching solution entry holes when the sacrificial layer interposed between the back plate 20 and the diaphragm 10 is removed by etching and a gap 40 is formed therebetween. Can also contribute to simplification of the manufacturing process.

  In the condenser microphone according to the first embodiment, the back plate 20 is supported on the support substrate 30 by the four second support parts 52, but the number of the second support parts 52 is limited to four. It is not something. For example, even if there are three, the back plate 20 can be stably held. In this case, the number of circular through holes 16 provided in the diaphragm 10 may be three.

  Further, the diaphragm 10 is supported by the first support portion 50 on the support substrate 30 in a circumferential manner on the outer edge side of the peripheral portion 14, but is not limited to such a support structure. It is possible to select a structure. For example, when the outer edge side of the peripheral portion 14 of the diaphragm 10 is supported, the support substrate is supported on the support substrate 30 locally at a plurality of locations on the circumference, not in the circumferential shape as in the first embodiment. 30 is provided with a suspension part supported on 30 and suspended from this suspension part via a spacer, and an arm part extending outward from the outer edge of the back plate 20 is provided and suspended from this arm part via a spacer. Conceivable. As long as the support structure of the back plate 20 supported by the second support portion 52 positioned in the plurality of through holes 16 of the diaphragm 10 is not hindered, the stress relaxation and vibration required for the diaphragm 10 are prevented. Various modifications are possible in consideration of improvement of characteristics and the like.

Next, a method for manufacturing the condenser microphone according to the first embodiment will be described.
The condenser microphone according to the first embodiment is a so-called silicon microphone, which is manufactured using a semiconductor manufacturing process, and is basically the same as a normal silicon microphone manufacturing method.

  First, a first conductive layer made of a polysilicon layer doped with P is formed on a support substrate 30 made of a single crystal silicon substrate via a first insulating film made of a silicon oxide film (first sacrificial film). Then, the first conductive layer is etched into a predetermined shape to form the diaphragm 10 and the lead-out wiring portion. As shown in FIG. 1B, the diaphragm 10 includes a disc-shaped central portion 12 and a peripheral portion 14 provided around the central portion 12. In the middle region of the central portion 12 of the diaphragm 10, four circular through holes 16 are provided at equal intervals, and a large number of small through holes 18 are provided continuously. In addition, a large number of small through holes 18 are continuously provided in four regions at equal intervals in the peripheral portion 14 of the diaphragm 10. Furthermore, from the outer edge of the diaphragm 10, a lead wiring portion connected to the electrode extends outward.

  Next, a second conductive layer made of a polysilicon layer to which P is added is formed on the diaphragm 10 and the first insulating film through a second insulating film made of a silicon oxide film (second sacrificial film). The second conductive layer is etched into a predetermined shape to form the back plate 20 and the lead wiring portion 24. As shown in FIG. 1A, the back plate 20 has a disk shape and is arranged concentrically with the diaphragm 10, and the radius of the back plate 20 is equal to the radius of the central portion 12 of the diaphragm 10. It is almost the same. The back plate 20 is continuously provided with a large number of small through holes 22 that function as acoustic holes for allowing external sound waves to pass through and reach the diaphragm 10. Furthermore, from the outer edge of the back plate 20, a lead wiring portion 24 connected to the electrode extends outward.

  Next, after forming a third insulating film made of a silicon oxide film on the back plate 20 and the second insulating film, the back surface of the support substrate 30 is ground to adjust its thickness. Subsequently, for example, the support substrate 30 is selectively removed by an anisotropic etching technique commonly called deep RIE to form an opening reaching the first insulating film. This opening is located at a position corresponding to the central region of the central portion 12 of the diaphragm 10 and a region corresponding to a region where the small through holes 18 of the peripheral portion 14 are not provided.

  Next, using the predetermined photoresist pattern as a mask, the third insulating film, the second insulating film, and the first insulating film are selectively etched away by a wet etching technique using, for example, buffered HF. . At this time, the numerous small through holes 22 of the back plate 20 function as etching solution entrance holes when the second insulating film interposed between the back plate 20 and the diaphragm 10 is removed by etching. In addition, the four through holes 16 and a large number of small through holes 18 of the diaphragm 10 also function as etching solution entrance holes when the first insulating film interposed between the diaphragm 10 and the support substrate 30 is removed by etching. . Further, the buffered hydrofluoric acid selectively removes the first insulating film and the like from the opening side of the support substrate 30 by etching.

  In this way, the second insulating film between the back plate 20 and the diaphragm 10 is removed, and a gap 40 is formed there. Further, the first insulating film is removed, and the opening of the support substrate 30 is expanded until reaching the diaphragm 10 to form a cavity 32, and a desired acoustic wave is formed between the support substrate 30 and the diaphragm 10 around the cavity 32. A passage 34 for forming a resistance is formed.

  At the same time, the first insulating film is intentionally left between the diaphragm 10 and the support substrate 30 to form the first support portion 50. Furthermore, the laminated insulating film in which the first insulating film and the second insulating film are intentionally left is also left between the back plate 20 and the support substrate 30, and the four circular through holes 16 of the diaphragm 10 are left. The second support portion 52 that passes through is formed.

  Through these steps, the condenser microphone according to the first embodiment shown in FIGS. 1A to 1D is manufactured.

  As described above, according to the method of manufacturing the condenser microphone according to the first embodiment, it is possible to follow the conventional manufacturing process almost as it is, except that the resist mask pattern used in each photolithography process is different. In addition, it is possible to prevent an increase in manufacturing cost because there is no need for a process that causes a decrease in manufacturing yield, such as a process of providing a back electrode only on a certain portion of the diaphragm facing surface of a plate made of an insulating material. .

(Second embodiment)
2A is a plan view schematically showing the configuration of the condenser microphone according to the second embodiment, FIG. 2B is a plan view when the back plate is removed from FIG. 2A, and FIG. ) Is a cross-sectional view taken along line AA ′ in FIG. 2A, and FIG. 2D is a cross-sectional view taken along line BB ′ in FIG.

  As shown in FIGS. 2A to 2D, the condenser microphone according to the second embodiment has substantially the same structure as the condenser microphone according to the first embodiment shown in FIGS. I am doing. Therefore, the difference from the condenser microphone according to the first embodiment will be mainly described, and the description of the common points will be omitted.

  Diaphragm 110 has a central portion 112 having a rectangular planar shape and a peripheral portion 114 provided around the central portion 112, and has a rectangular planar shape as a whole. Further, in the central portion 112 of the diaphragm 110, three circular through holes 116 are provided at equal intervals in two regions adjacent to the peripheral portion 114 on the long side facing each other. The small through holes 118 are continuously provided. In addition, a large number of small through holes 118 are continuously provided in a total of four regions adjacent to the through holes 116 on the short side facing each other in the peripheral portion 114 of the diaphragm 110. The region where the total of six through holes 116 and a large number of small through holes 118 are provided has a corresponding relationship with the support substrate 130.

  The back plate 120 is installed in parallel with the gap 140 between the back plate 120 and the diaphragm 110. The back plate 120 also has a rectangular planar shape and is substantially in a corresponding relationship with the central portion 112 of the diaphragm 110, and the peripheral portion 114 of the diaphragm 110 protrudes from the back plate 120. The back plate 120 is continuously provided with a large number of small through holes 122 that function as acoustic holes. Furthermore, a lead wiring portion 124 connected to the electrode extends outward from the outer edge of the back plate 120.

  The diaphragm 110 is supported on the support substrate 130 by an insulating first support 150 at the outer edge side of the long side facing the peripheral portion 114. The back plate 120 is supported on the support substrate 130 by six columnar insulating second support portions 152 located in the six through holes 116 of the diaphragm 110.

  The support substrate 130 penetrates the support substrate 130 at a position corresponding to a region where the six through holes 116 and the many small through holes 118 are not provided in the central portion 112 and the peripheral portion 114 of the diaphragm 110. An opening reaching the diaphragm 110 is provided, and a cavity 132 is formed from these openings. In addition, a passage 134 that forms a predetermined acoustic resistance is provided by the support substrate 130 and the diaphragm 110 around the cavity 132.

  The method of manufacturing the condenser microphone according to the second embodiment is basically the same as the method of manufacturing the condenser microphone according to the first embodiment, except that the resist mask pattern used in each photolithography process is different. The description is omitted.

  As described above, according to the condenser microphone according to the second embodiment, the back plate 120 is supported on the support substrate 130 by the second support portion 152 located in the through hole 116 of the diaphragm 110, and the diaphragm The basic features of the first embodiment are the same as those of the condenser microphone according to the first embodiment, such as being substantially corresponding to the central portion 112 of 110 and not having the corresponding relationship to the peripheral portion 114 of the diaphragm 110. The same effect as in the case of can be obtained.

  In addition, according to the condenser microphone according to the second embodiment, the back plate 120 is supported on the support substrate 130 by the six second support portions 152, so that the condenser microphone according to the first embodiment can be obtained. Furthermore, since the back plate 20 is stably held and its deformation is suppressed, the stability of the microphone operation can be further improved. Therefore, it is suitable, for example, when the microphone sensitivity is increased by increasing the microphone size.

  Further, the outer peripheral side of the peripheral portion 14 of the diaphragm 110 is supported on the support substrate 130 by the pair of first support portions 150, so that the outer peripheral side of the peripheral portion 14 of the diaphragm 10 is supported by the first support portion 50. Compared with the case of the condenser microphone according to the first embodiment supported on the support substrate 30 in a circumferential shape, the vibration characteristic of the diaphragm 110 is further improved, so that the microphone sensitivity can be further improved.

  In the condenser microphone according to the second embodiment, the back plate 120 is supported on the support substrate 130 by the six second support portions 152, but the number of the second support portions 152 is limited to six. It is not something. For example, it is possible to add one to the opposite short sides of the back plate 120 so that the number of the second support parts 152 is eight. In this case, it is necessary to increase the number of through holes 116 provided in the diaphragm 110 to 8 or to change the position of the opening of the cavity 132 provided in the support substrate 130. In general, by increasing the number of second support parts 152, stable holding of the back plate 120 and suppression of deformation are realized, so that the microphone sensitivity can be increased and the microphone sensitivity can be improved.

(Third embodiment)
FIG. 3A is a plan view schematically showing the configuration of the condenser microphone according to the third embodiment, FIG. 3B is a plan view when the back plate is removed from FIG. 3A, and FIG. ) Is a cross-sectional view taken along line AA ′ in FIG. 3A, and FIG. 3D is a cross-sectional view taken along line BB ′ in FIG.

  As shown in FIGS. 3A to 3D, the condenser microphone according to the third embodiment has substantially the same structure as the condenser microphone according to the second embodiment shown in FIGS. 2A to 2D. I am doing. Therefore, the difference from the condenser microphone according to the second embodiment will be mainly described, and the description of the common points will be omitted.

  An insulating stopper layer 160 is provided in the gap 140 between the diaphragm 110 and the back plate 120 and fixed in the middle of the six second support portions 152 that support the back plate 120 on the support substrate 130. Yes. The stopper layer 160 is made of, for example, a thin film made of polysilicon to which no impurity is added, and has a disk shape with a thickness of about 0.5 μm and a radius of about 30 μm. The distance between the stopper layer 160 and the diaphragm 110 is about 3 μm.

  The method for manufacturing the condenser microphone according to the third embodiment is obtained by adding the following steps to the method for manufacturing the condenser microphone according to the second embodiment.

  That is, after the diaphragm 110 is formed in the same manner as in the second embodiment, an additional insulating film (additional sacrificial film) made of, for example, a silicon oxide film having a thickness of about 3 μm is formed on the diaphragm 110 and the first insulating film. Then, a polysilicon layer to which no impurity is added is formed, and this polysilicon layer is etched into a predetermined shape to form the stopper layer 160.

  Thereafter, a second conductive layer is formed on the stopper layer 160 and the additional insulating film via the second insulating film (second sacrificial film) in the same manner as in the second embodiment. The back plate 120 is formed by etching into a predetermined shape, the third insulating film is formed on the back plate 120 and the second insulating film, the back surface of the support substrate 130 is ground, and the support substrate 130 is selectively etched away. Thus, an opening is formed.

  Thereafter, the third insulating film, the second insulating film, the additional insulating film, and the first insulating film are selectively removed by etching to form a gap 140 between the back plate 120 and the diaphragm 110, thereby forming a support substrate 130. A cavity 132 is formed, a passage 134 for forming a desired acoustic resistance is formed, and a first support portion 152 is formed between the diaphragm 110 and the support substrate 130. At this time, a second insulating film between the back plate 120 and the stopper layer 160 and an additional insulating film between the stopper layer 160 and the support substrate 130 and the first insulating film are stacked. Thus, the second support portion 52 that supports the back plate 20 on the support substrate 130 is formed while fixing the stopper layer 160 in the middle.

  In this way, the condenser microphone according to the first example shown in FIGS. 3A to 3D is manufactured.

  As described above, according to the condenser microphone according to the third embodiment, in addition to the effects in the case of the condenser microphone according to the second embodiment, the insulating stopper layer 160 has a gap between the diaphragm 110 and the back plate 120. By being provided in 140, it is possible to prevent the diaphragm 110 from contacting the back plate 120 even when an excessive sound pressure is applied to the diaphragm 110 or a mechanical shock is applied from the outside. The stability of the microphone operation can be ensured.

1A is a plan view schematically showing the configuration of the condenser microphone according to the first embodiment, FIG. 1B is a plan view when the back plate is removed from FIG. 1A, and FIG. ) Is a cross-sectional view taken along line AA ′ of FIG. 1A, and FIG. 1D is a cross-sectional view taken along line BB ′ of FIG. 2A is a plan view schematically showing the configuration of the condenser microphone according to the second embodiment, FIG. 2B is a plan view when the back plate is removed from FIG. 2A, and FIG. ) Is a cross-sectional view taken along line AA ′ in FIG. 2A, and FIG. 2D is a cross-sectional view taken along line BB ′ in FIG. 3A is a plan view schematically showing the configuration of the condenser microphone according to the third embodiment, FIG. 3B is a plan view when the back plate is removed from FIG. 3A, and FIG. ) Is a cross-sectional view taken along line AA ′ in FIG. 3A, and FIG. 3D is a cross-sectional view taken along line BB ′ in FIG.

Explanation of symbols

  10, 110: Diaphragm, 12, 112: Central part, 14, 114: Peripheral part, 16, 116: Through hole, 18, 118: Small through hole, 20, 120: Back plate, 22, 122: Small through hole, 24, 124: Lead wiring part, 30, 130: Support substrate, 32, 132: Cavity, 34, 134: Passage, 40, 140: Gap, 50, 150: First support part, 52, 152: Second support part 160: Stopper fracture.

Claims (6)

A central portion, a peripheral portion provided around the central portion, and a plurality of through holes provided in the central portion, and a conductive diaphragm that vibrates in response to sound waves;
A conductive plate provided opposite to the diaphragm;
A substrate provided on the opposite side of the plate with respect to the diaphragm, and having a cavity for relieving pressure applied to the diaphragm from the side opposite to the plate;
An insulating first support portion that supports the peripheral portion of the diaphragm; and an insulating second support portion that is positioned in the plurality of through holes of the diaphragm and supports the plate on the substrate; And a support means for forming a gap between the central portion of the diaphragm and the plate,
Condenser microphone with The plate substantially corresponds to the central portion of the diaphragm;
The condenser microphone according to claim 1. An insulating stopper layer is provided in the gap between the diaphragm and the plate.
The condenser microphone according to claim 1 or 2. The stopper layer is supported by the second support part,
The condenser microphone according to claim 3. In the peripheral portion of the diaphragm, a plurality of small through holes are provided in a region corresponding to the substrate.
The condenser microphone according to any one of claims 1 to 4. A predetermined acoustic resistance is formed by the substrate and the diaphragm around the cavity.
The condenser microphone according to claim 1.

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