JP2011049752A - Capacitor microphone - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure uniformity of a microphone sensitivity even if a microphone element is fixed to a base substrate in a capacitor microphone having the microphone element manufactured by using an MEMS technology. <P>SOLUTION: A microphone element 20 in which a capacitor structure portion C is laminated and formed on a silicon substrate 22 is fixed to a base substrate 50 with an IC chip 40. At this time, a sound hole 60a for leading a sound to the capacitor structure portion C is formed at an upper location of the capacitor structure portion C in an upper wall 60A of a cover 60 fixed to the base substrate 50 so as to cover the microphone element 20 and the IC chip 40. A sound path wall 70 separating a front space C1 between the capacitor structure portion C and the sound hole 60a, and a circumference space C3 surrounding the front space C1 is placed between the upper wall 60A of the cover 60 and the microphone element 20. Thus, a volume of the front space C1 is reduced. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a condenser microphone, and more particularly, to a condenser microphone having a microphone element manufactured using a MEMS (Micro Electro Mechanical Systems) technique.

  In general, a capacitor microphone has a structure having a capacitor structure in which a diaphragm and a fixed electrode are arranged to face each other. However, in recent years, in order to reduce the size of the capacitor microphone, the capacitor structure is formed using MEMS technology. A device for stacking as part of the microphone element has also been devised.

  For example, in the condenser microphones described in “Patent Document 1” and “Patent Document 2”, a capacitor structure is stacked on a silicon substrate having a central opening so as to close the central opening. Thus, a microphone element is configured.

  At that time, the condenser microphone described in FIG. 6 of the above-mentioned “Patent Document 1” has a configuration in which the microphone element is housed in the housing in a state where the microphone element is mounted and fixed on the base substrate together with the impedance conversion element. .

  On the other hand, the condenser microphone described in FIG. 5 of the “Patent Document 2” has a configuration in which the microphone element is housed in the housing in a state of being suspended and fixed to the top substrate together with the impedance conversion element.

JP 2007-81614 A International Publication No. 2005-86535

  In general, in a condenser microphone, as described in FIG. 6 of the above-mentioned “Patent Document 1” and FIG. 5 of “Patent Document 2”, the capacitor microphone is positioned above the capacitor structure portion on the upper wall of the casing. A sound hole for guiding sound to the capacitor structure is formed.

  However, in the condenser microphone described in FIG. 6 of “Patent Document 1”, a space between the sound hole and the capacitor structure (hereinafter referred to as “front space”) surrounds the front space (hereinafter referred to as “front space”). Since it is formed with a considerably large volume, it has the following problems.

  In other words, if the front space is formed with a large volume, the resonance frequency becomes low, so that sound wave resonance occurs in the audible range or a frequency range close to this, and thus the microphone sensitivity is uniform in the audible range. There is a problem that the performance is impaired.

  On the other hand, in the condenser microphone described in FIG. 5 of “Patent Document 2”, since the microphone element is suspended and fixed to the top substrate, the front space and the outer peripheral space may be partitioned at the suspension fixing portion. This can reduce the volume of the front space.

  However, in the condenser microphone described in FIG. 5 of “Patent Document 2”, the suspension fixing portion of the microphone element serves not only as a suspension fixing function but also as an electrical connection function between the capacitor structure portion and the top substrate. Therefore, the degree of freedom of the shape is small, and therefore the degree of freedom of the volume and shape of the front space is also small, which is insufficient to ensure the uniformity of the microphone sensitivity in the audible range. There is a problem of becoming. In addition, when such a configuration is adopted, in a microphone having a general configuration in which the microphone element is mounted and fixed on the base substrate, the uniformity of the microphone sensitivity in the audible range cannot be ensured. There's a problem.

  The present invention has been made in view of such circumstances, and in a condenser microphone having a microphone element manufactured using MEMS technology, the microphone element may be mounted and fixed on a base substrate. An object of the present invention is to provide a condenser microphone capable of ensuring uniformity of microphone sensitivity.

  In the present invention, the above object is achieved by devising a configuration for partitioning the front space from the outer peripheral space in the housing.

That is, the condenser microphone according to the present invention is
A microphone element in which a capacitor structure part in which a vibration film and a fixed electrode are arranged to face each other on a silicon substrate in which a central opening is formed is laminated so as to close the central opening;
An impedance conversion element for converting the capacitance of the capacitor structure into an electrical impedance; and
A base substrate on which the microphone element and the impedance conversion element are placed and fixed;
A condenser microphone comprising: a cover fixed to the base substrate so as to cover the microphone element and the impedance conversion element;
A sound hole for guiding sound to the capacitor structure is formed at a position above the capacitor structure on the top wall of the cover,
Between the upper surface wall of the cover and the microphone element, a sound path wall that partitions a front space between the capacitor structure portion and the sound hole and an outer peripheral space surrounding the front space is disposed. It is a feature.

  In the above configuration, the terms indicating the direction such as “upper surface wall” and “upward position” are used for the sake of convenience in order to clarify the positional relationship between the members constituting the condenser microphone. The directionality when actually using the microphone is not limited.

  As long as the “cover” is a member that forms a casing that covers the microphone element and the impedance conversion element with the base substrate by being fixed to the base substrate, its specific configuration, fixing structure to the base substrate, and the like Is not particularly limited. In this case, as a specific configuration of the “cover”, for example, a metal plate is formed as a single member by press molding, or mounted on the base substrate so as to surround the microphone element and the impedance conversion element. It is possible to employ a member constituted by a fixed annular member and a lid member placed and fixed on the upper surface of the annular member.

  As long as the “sound road wall” is a member formed so as to partition the front space and the outer peripheral space, the specific configuration such as the height and the cross-sectional shape thereof is not particularly limited. Further, the “sound path wall” may be configured as a part of the microphone element, or may be configured as a member different from the microphone element.

  As shown in the above configuration, the condenser microphone according to the present invention has a configuration in which a microphone element in which a capacitor structure is laminated on a silicon substrate is placed and fixed on a base substrate together with an impedance conversion element, The cover fixed to the base substrate so as to cover the microphone element and the impedance conversion element is provided with a sound hole for guiding sound to the capacitor structure portion at a position above the capacitor structure portion on the upper surface wall. However, the sound path wall that partitions the front space between the capacitor structure and the sound hole and the outer peripheral space surrounding the front space is arranged between the upper surface wall of the cover and the microphone element. The following effects can be obtained.

  That is, since the front space and the outer peripheral space are partitioned by the sound path wall in the housing constituted by the base substrate and the cover, the volume of the front space can be reduced.

  In addition, this sound path wall does not require an electrical connection function to the capacitor structure, and the function can be specialized for the partition function between the front space and the outer space, so the volume and shape of the front space The degree of freedom can be increased, which makes it easy to ensure the uniformity of microphone sensitivity in the audible range.

  As described above, according to the present invention, in the condenser microphone having the microphone element manufactured using the MEMS technology, the uniformity of the microphone sensitivity is ensured even when the microphone element is mounted and fixed on the base substrate. be able to.

  In the above configuration, if at least a part of the sound path wall is composed of a resist layer stacked on the upper surface of the microphone element, the sound path wall is formed in the step of stacking the microphone element using the MEMS technology. Also, at least a part thereof can be laminated. Therefore, the arrangement of the sound path wall can be performed relatively easily, and the positional accuracy can be increased.

  At that time, the sound path wall is assumed to be composed only of the resist layer, and the resist layer is arranged in a state in which the upper end surface thereof is brought into contact with the upper surface wall of the cover and is compressed and elastically deformed in the vertical direction. With the configuration, the following operational effects can be obtained.

  In other words, since the sound path wall is composed only of the resist layer, the entire sound path wall can be simultaneously laminated in the microphone element stacking process, which facilitates the arrangement of the sound path wall. And it can carry out with sufficient position accuracy. In addition, the resist layer laminated as the sound path wall is disposed in a state where the upper end surface of the resist layer is in contact with the upper surface wall of the cover and is compressed and elastically deformed in the vertical direction. Despite being configured, the front space and the outer peripheral space can be reliably partitioned. At that time, even if there is some variation in the distance between the upper end surface of the microphone element and the upper surface wall of the cover, the partition function can be maintained by the compression elastic deformation action of the resist layer formed as a sound path wall. it can.

  On the other hand, a part of the sound path wall may be formed of a resist layer, and an elastic member may be interposed between the upper end surface of the resist layer and the upper surface wall of the cover. is there. Even when such a configuration is adopted, the front space and the outer peripheral space can be reliably partitioned.

  In the above configuration, if an annular flange portion that protrudes downward along the outer peripheral shape of the sound hole is formed on the upper surface wall of the cover, surface contact with the sound path wall is also performed in this annular flange portion. Thus, the partition function between the front space and the outer peripheral space can be further enhanced. Further, when such a configuration is adopted, it is possible to perform positioning when fixing the cover to the base substrate by engaging the annular flange portion with the sound path wall. Further, when an elastic member is interposed between the upper end surface of the resist layer constituting a part of the sound path wall and the upper surface wall of the cover, the elastic member is engaged with the annular flange portion. Thus, it can be temporarily fixed at a predetermined position, thereby improving the workability when the condenser microphone is assembled.

  In the above configuration, if a communication hole is formed in at least one of the silicon substrate and the base substrate so that the central opening of the silicon substrate communicates with the outer peripheral space, the following effects can be obtained. it can.

  That is, in a capacitor microphone, if the space located below the capacitor structure (hereinafter referred to as “rear space”) is small, the force required to displace the diaphragm increases, so the diaphragm is difficult to displace. Therefore, the required acoustic characteristics cannot be ensured. Therefore, if the communication hole is formed in at least one of the silicon substrate and the base substrate so that the central opening of the silicon substrate communicates with the outer peripheral space, the volume of the rear space can be sufficiently increased. Thereby, a required acoustic characteristic can be ensured. In this case, in the condenser microphone according to the present invention, the front space and the outer space are partitioned by the sound path wall, so that the front space and the rear space communicate with each other through the outer space even if the communication hole is formed. Therefore, there is no risk of disturbing the microphone function.

  In this case, if the communication hole is formed by cutting off a part of the lower end portion of the silicon substrate, the communication hole can be formed at the same time in the step of forming the microphone elements. Further, if the communication hole is formed by cutting the upper surface of the base substrate into a concave groove shape, the microphone element stacking process can be simplified.

The sectional side view which shows the condenser microphone which concerns on one Embodiment of this invention in the state arrange | positioned upwards FIG. 4 is a side sectional view showing in detail a microphone element of the condenser microphone, and a sectional view taken along line II-II in FIG. 3. Sectional view taken along line III-III in FIG. Side sectional view showing the manufacturing process of the microphone element (Part 1) Sectional drawing (the 2) which shows the manufacturing process of the said microphone element Sectional drawing (the 3) which shows the manufacturing process of the said microphone element The same figure as FIG. 1 which shows the 1st modification of the said embodiment. The same figure as FIG. 1 which shows the 2nd modification of the said embodiment. The same figure as FIG. 1 which shows the 3rd modification of the said embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a side sectional view showing a condenser microphone 10 according to an embodiment of the present invention in an upwardly arranged state.

  As shown in the figure, the condenser microphone 10 according to this embodiment includes a microphone element 20, an IC chip 40, a base substrate 50, and a cover 60. The condenser microphone 10 is used in a state where it is surface-mounted on a printed circuit board (not shown) of an external device (for example, a mobile phone) on the lower surface of the base substrate 50.

  In the microphone element 20, the vibration film 24 and the fixed electrode 26 are arranged opposite to each other on the silicon substrate 22 in which the central opening 22 a is formed, and thereby the capacitor structure portion C is configured. The microphone element 20 of the condenser microphone 10 is manufactured using MEMS technology (this will be described later).

  The IC chip 40 takes out the change in capacitance between the vibrating membrane 24 and the fixed electrode 26 caused by the vibration of the vibrating membrane 24 as an electric signal by converting the electric impedance, and amplifies the electric signal. Is configured to do.

  The base substrate 50 has a configuration in which a plurality of conductive layers (not shown) are formed in a predetermined wiring pattern on both upper and lower surfaces of an insulating substrate having a rectangular outer shape having a long side of about 4 mm in plan view. . The base substrate 50 is configured to place and fix the microphone element 20 and the IC chip 40 on the upper surface thereof. At this time, the microphone element 20 is mounted and fixed by adhering the microphone element 20 to the upper surface of the base substrate 50 on the lower surface of the silicon substrate 22. The IC chip 40 is mounted and fixed by adhering the IC chip 40 to the upper surface of the base substrate 50 in a state where the IC chip 40 is disposed adjacent to the microphone element 20. In addition, these adhesion | attachment is performed using an epoxy-type adhesive agent etc., for example.

  The IC chip 40 includes a power terminal, an output terminal, a ground terminal, and a bias terminal (not shown). The IC chip 40 has its power supply terminal, output terminal, and grounding terminal electrically connected to each conductive layer formed on the base substrate 50 via bonding wires 42 and its bias. The terminal for use is electrically connected to the terminal portion 32 </ b> A of the vibrating membrane 24 via the bonding wire 44.

  Further, the terminal portion 32 </ b> B of the fixed electrode 26 in the microphone element 20 is electrically connected to a grounding conductive layer formed on the base substrate 50 via a bonding wire 46.

  The cover 60 is placed and fixed on the base substrate 50 so as to cover the microphone element 20 and the IC chip 40. The cover 60 and the base substrate 50 constitute a housing that houses the microphone element 20 and the IC chip 40.

  The cover 60 is formed by press forming a metal plate. The cover 60 includes an upper surface wall 60A that extends in parallel with the base substrate 50 and a peripheral wall 60B that extends downward from the outer peripheral edge of the upper surface wall 60A. The cover 60 is mounted and fixed on the base substrate 50 by soldering the lower edge of the peripheral wall 60B to the grounding conductive layer formed on the outer peripheral edge of the upper surface of the base substrate 50. It is done by.

  A sound hole 60 a for guiding sound to the capacitor structure C is formed in the upper surface wall 60 </ b> A of the cover 60 above the capacitor structure C. The sound hole 60a has a circular opening shape with a diameter of about φ0.8 mm.

  Between the upper surface wall 60A of the cover 60 and the microphone element 20 in the housing, a front space C1 between the capacitor structure C and the sound hole 60a and an outer peripheral space C3 surrounding the front space C1 are partitioned. A cylindrical sound path wall 70 is disposed.

  The sound path wall 70 is formed to extend in a cylindrical shape in the vertical direction so as to surround the sound hole 60a. At this time, the inner diameter of the sound path wall 70 is set to a value of about φ1 mm, and the wall thickness thereof is set to a value of about 0.05 to 0.1 mm.

  The sound path wall 70 is composed of a resist layer laminated on the upper surface of the microphone element 20 (this will be described later).

  2 is a side sectional view showing the microphone element 20 in detail, and FIG. 3 is a sectional view taken along line III-III in FIG. 2 is a cross-sectional view taken along the line II-II in FIG.

  As shown in these drawings, in the microphone element 20, the vibration film 24 and the fixed electrode 26 are disposed opposite to each other on the silicon substrate 22 in which the central opening 22a is formed. It is configured.

  The silicon substrate 22 is composed of a single-crystal silicon chip cut into a size of about 1.6 mm square from a silicon wafer and has a thickness of about 0.4 mm. The central opening 22a of the silicon substrate 22 is formed in a cylindrical shape by etching. At this time, the inner diameter of the central opening 22a is set to about φ0.9 mm.

  An insulating layer 28 made of a silicon oxide film is laminated around the central opening 22 a on the upper surface of the silicon substrate 22. A thin insulating layer 36 made of a silicon oxide film is formed on the lower surface of the silicon substrate 22 by a thermal oxidation process.

  The fixed electrode 26 is made of polycrystalline silicon, and is laminated on the upper surface of the insulating layer 28 so as to close the central opening 22a. A plurality of through holes 26a are formed in the fixed electrode 26 so as to face the central opening 22a.

  A diameter of each through hole 26a is suitably 5 to 20 μm. The reason is as follows. That is, if the hole diameter becomes too small, the acoustic resistance increases, and the vibration of the vibration film 24 tends to be suppressed. On the other hand, if the hole diameter becomes too large, the area of the fixed electrode 26 becomes small, and the vibration film 24 As a result, the area for forming the capacitor structure C is reduced, and as a result, the microphone sensitivity tends to decrease.

  An insulating layer 30 made of a silicon oxide film is laminated on the upper surface of the fixed electrode 26. At this time, the insulating layer 30 is formed with a circular opening 30a having an inner diameter slightly smaller than that of the central opening 22a, and a through hole 30b is formed around the opening 30a.

  The thickness of the insulating layer 30 is optimally 2 to 6 μm. The reason is as follows. That is, the insulating layer 30 is a layer that determines the gap between the fixed electrode 26 and the vibrating membrane 24. However, if the film thickness is too thin, the viscous resistance between the fixed electrode 26 and the vibrating membrane 24 increases. There is a tendency that a sufficient displacement of the vibration film 24 cannot be obtained. On the other hand, if the insulating layer 30 is made too thick, the capacitance of the capacitor structure C is in inverse proportion to the gap, and the microphone sensitivity tends to decrease.

  A pair of terminal portions 32 </ b> A and 32 </ b> B are stacked and formed as conductive layers made of a metal thin film at two locations on the diagonal line on the upper surface of the insulating layer 30. At that time, one terminal portion 32A is formed so that a part thereof is in contact with the upper surface of the vibration film 24, and the other terminal portion 32B is partly provided through the through hole 30b of the insulating layer 30. It is formed so as to contact the fixed electrode 26. Aluminum, chromium / gold, titanium / platinum, or the like is preferably used as the metal to be the terminal portions 32A and 32B.

  The vibration film 24 is made of polycrystalline silicon and is disposed in the vicinity of the upper portion of the fixed electrode 26 so as to extend in parallel with the fixed electrode 26. At this time, the vibration film 24 has a circular outer shape slightly larger than the circular opening 30 a of the insulating layer 30, and is laminated on the insulating layer 30 at the outer peripheral edge portion thereof. A plurality of minute through holes 24 a are formed in the center of the vibrating membrane 24 for ventilation.

  The film thickness of the vibration film 24 is optimally 0.5-2 μm. The reason is as follows. That is, if the film thickness of the vibration film 24 is too thin, the resonance frequency tends to be too small, and resonance of the vibration film 24 may appear in the audible range. On the other hand, if the film thickness of the vibration film 24 is too thick, the vibration film 24 becomes hard and the microphone sensitivity tends to decrease. As the configuration of the vibration film 24, a structure in which a resin film and a metal film are stacked on the silicon substrate 22 may be employed.

  A surface protective layer 34 made of a photoresist is laminated on the upper surface of the insulating layer 30. At this time, the surface protective layer 34 is formed so as to cover the outer peripheral edge portion of the vibration film 24 and the pair of terminal portions 32A and 32B. A pair of holes 34a and 34b for exposing the pair of terminal portions 32A and 32B are formed at two locations on the outer peripheral edge of the surface protective layer 34.

  A resist layer is formed on the upper surface of the surface protective layer 34 so as to surround the sound hole 60a and extend in a cylindrical shape in the vertical direction, thereby forming the sound path wall 70.

  The resist layer constituting the sound path wall 70 is formed of an organic compound called a permanent photoresist. As the permanent photoresist, for example, TMMR series S2000 manufactured by Tokyo Ohka Kogyo Co., Ltd., SU-8 series 3000 manufactured by Nippon Kayaku Co., Ltd., or the like can be used. These permanent photoresists can be increased in film thickness, can be adjusted to various film thicknesses, and have appropriate elasticity.

  The resist layer constituting the sound path wall 70 is disposed in a state where the upper end surface thereof is brought into contact with the lower surface of the upper surface wall 60A of the cover 60 and is compressed and elastically deformed in the vertical direction.

  That is, the resist layer constituting the sound path wall 70 is in an unloaded state as shown by a two-dot chain line in FIG. 2 and the upper surface wall 60A of the cover 60 and the upper surface of the microphone element 20 (that is, the upper surface of the surface protective layer 34). ) To be slightly higher than the interval. For example, if the interval is about 0.3 mm, the distance is 10% higher than that of about 0.33 mm. The resist layer constituting the sound path wall 70 is pressed downward by contact with the upper surface wall 60A in a state where the cover 60 is placed and fixed on the base substrate 50, and is somewhat compressed elastically in the vertical direction. Deformed state.

  The silicon substrate 22 has its lower end portion cut in the radial direction at four locations, thereby forming four concave groove portions 22b. These four concave groove portions 22b are formed at four locations in a cross arrangement in a plan view. At this time, each of the concave groove portions 22b is formed by cutting a part of the lower end portion of the silicon substrate 22 linearly with a trapezoidal cross-sectional shape from the lower end surface. The four concave grooves 22b and the upper surface of the base substrate 50 are formed with four communication holes 80 for communicating the central opening 22a and the outer peripheral space C3.

  As a result, as shown in FIG. 1, the rear space C2 located below the capacitor structure C is divided into a volume corresponding to the central opening 22a and a volume of the outer peripheral space C3 and a volume of the four communication holes 80. Is expanded to the combined volume.

  Next, the manufacturing process of the microphone element 20 will be described.

  4 to 6 are side sectional views showing the manufacturing process of the microphone element 20.

  First, as shown in FIG. 4A, an SOI (Silicon) in which a silicon oxide film 128 and a thin silicon layer 126 as a device layer are laminated in this order on the upper surface of a thick silicon layer 122 as a handle layer. On Insulator) wafer 100 is prepared. In FIG. 4A, the SOI wafer 100 is shown in a size corresponding to the size of one microphone element 20 (the two-dot chain line in the drawing shows a part of the entire shape).

  Next, as shown in FIG. 2B, the SOI wafer 100 is thermally oxidized to form thin silicon oxide films 136 and 102 on the upper and lower surfaces, respectively.

  Next, as shown in FIG. 2C, the concave grooves 122b are formed in the lower end portion of the silicon layer 122 of the SOI wafer 100 in a lattice arrangement in plan view. At this time, first, the silicon oxide film 136 on the lower surface is etched, and anisotropic wet etching is performed using the etched silicon oxide film 136 as a mask to form a plurality of concave grooves 122 b in the silicon layer 122. These concave groove portions 122b are to be the concave groove portions 22b of the microphone element 20.

  Next, as shown in FIG. 4D, fine holes 126a are formed in the silicon layer 126 of the SOI wafer 100 by etching. These holes 126 a are to be the through holes 26 a of the fixed electrode 26 in the microphone element 20.

  Next, as shown in FIG. 5E, the hole 126 a of the silicon layer 126 is refilled with the silicon oxide film 104 and the polycrystalline silicon thin film 106. The silicon oxide film 104 and the polycrystalline silicon thin film 106 can be formed by a CVD (Chemical Vapor Deposition) method or the like.

  Next, a silicon oxide film 130 is formed on the surface of the silicon layer 126 as shown in FIG. The silicon oxide film 130 includes the silicon oxide film 104 in a part thereof. The silicon oxide film 130 is to be the insulating layer 30 that determines the gap between the fixed electrode 26 and the vibration film 24.

  Further, the silicon oxide film 130 is partially etched to form a small hole 130a, and is patterned so as to be electrically connected to the silicon layer 126 of the SOI wafer 100.

  Next, a polycrystalline silicon thin film 124 is formed on the upper surface of the silicon oxide film 130 as shown in FIG. At that time, patterning is performed by partial etching so that fine holes 124a are formed. This polycrystalline silicon thin film 124 should be the vibration film 24.

Next, as shown in FIG. 5H, the metal thin films 132A and 132B are formed and patterned at two locations on the upper surface of the silicon oxide film 130. These metal thin films 132A and 132B should be the terminal portions 32A and 32B, respectively.
Next, as shown in FIG. 6I, a passivation film 134 is formed on the upper surface of the silicon oxide film 130 by spin coating a photoresist. This passivation film 134 should be the surface protective film 34. The passivation film 134 is preferably made of parylene, silicon oxide or the like in addition to the photoresist. At this time, small holes 134a and 134b are formed at two locations on the passivation film 134 in order to establish electrical connection with the metal thin films 132A and 132B.

  Next, as shown in FIG. 6 (j), a permanent photoresist (for example, TMMR series S2000 manufactured by Tokyo Ohka Kogyo Co., Ltd.) is spin coated, exposed and developed on the upper surface of the passivation film 134 and patterned to form a resist layer 170. To do. This resist layer 170 is to be the sound path wall 70. At this time, the height of the resist layer 170 is adjusted by the spin coating rotation speed and the rotation time.

  Next, as shown in FIG. 6 (k), the silicon layer 122 is etched by DRIE (that is, deep reactive etching) from the lower surface of the SOI wafer 100, and the DRIE is terminated at the silicon oxide film 104 that becomes the BOX layer. . Thereby, a cylindrical central opening 122a is formed. The central opening 122a should be the central opening 22a.

  Then, from below the central opening 122a, the silicon oxide film 128 and the polycrystalline silicon thin film 106 and the silicon oxide film 130 refilled in the silicon layer 126 are dry-etched with hydrogen fluoride gas and xenon fluoride gas. Then, the polycrystalline silicon thin film 124 is released as the vibration film 24 (that is, the vibration film 24 is allowed to vibrate) as shown in FIG.

  Finally, the microphone element 20 is divided into chips from the SOI wafer 100 by dicing.

  Next, the effect of this embodiment is demonstrated.

  The condenser microphone 10 according to the present embodiment has a configuration in which a microphone element 20 in which a capacitor structure C is laminated on a silicon substrate 22 is placed and fixed on a base substrate 50 together with an IC chip 40, and The cover 60 fixed to the base substrate 50 so as to cover the microphone element 20 and the IC chip 40 is for guiding sound to the capacitor structure C at a position above the capacitor structure C on the upper surface wall 60A. The sound hole 60a is formed between the upper wall 60A of the cover 60 and the microphone element 20, and surrounds the front space C1 between the capacitor structure C and the sound hole 60a and the front space C1. Since the sound path wall 70 that separates from the outer peripheral space C3 is arranged, the following effects can be obtained. It can be.

  That is, since the front space C1 and the outer peripheral space C3 are partitioned by the sound path wall 70 in the housing constituted by the base substrate 50 and the cover 60, the volume of the front space C1 can be reduced. Thereby, the resonance frequency of the front space C1 can be set to a value of 50 kHz or higher that is sufficiently higher than the audible range (generally 20 Hz to 20 kHz).

  In addition, the sound connection wall 70 does not need an electrical connection function with respect to the capacitor structure C, and the function can be specialized in a partitioning function between the front space C1 and the outer peripheral space C3. The degree of freedom of the volume and shape of the microphone can be increased, which makes it easy to ensure the uniformity of the microphone sensitivity in the audible range.

  As described above, according to the present embodiment, in the condenser microphone 10 having the microphone element 20 manufactured by using the MEMS technology, even if the microphone element 20 is mounted and fixed on the base substrate 50, the microphone sensitivity can be improved. Uniformity can be ensured.

  In particular, in the present embodiment, since the sound path wall 70 is composed of a resist layer formed on the upper surface of the microphone element 20, the sound path wall is formed in the step of forming the microphone element 20 using the MEMS technology. 70 can be laminated at the same time, whereby the sound path wall 70 can be easily and accurately positioned. Moreover, the resist layer laminated as the sound path wall 70 is disposed in a state where the upper end surface thereof abuts on the upper surface wall 60A of the cover 60 and is compressed and elastically deformed in the vertical direction. Despite being composed only of the resist layer, the front space C1 and the outer peripheral space C3 can be reliably partitioned. At this time, even if there is some variation in the distance between the upper end surface of the microphone element 20 and the upper surface wall 60A of the cover 60, the partition function is achieved by the compression elastic deformation action of the resist layer laminated as the sound path wall 70. Can be maintained.

  Further, in the present embodiment, four concave groove portions 22b are formed at the lower end portion of the silicon substrate 22, and the central opening portion 22a and the outer peripheral space C3 are communicated with each other by the concave groove portions 22b and the upper surface of the base substrate 50. Since the four communication holes 80 to be formed are formed, the rear space C2 located below the capacitor structure C is divided into a volume corresponding to the central opening 22a, a volume of the outer peripheral space C3, and four locations of the rear space C2. The volume of the communication hole 80 and the volume of the communication hole 80 can be expanded to ensure the required acoustic characteristics.

  At this time, in the condenser microphone 10 according to the present embodiment, the front space C1 and the outer peripheral space C3 are partitioned by the sound path wall 70, so that even if the communication hole 80 is formed, the front space C1 and the rear space C2 Will not communicate with each other through the outer peripheral space C3, so that there is no possibility of disturbing the microphone function.

  Further, since the communication hole 80 is formed by cutting off a part of the lower end portion of the silicon substrate 22, the communication hole 80 can be formed at the same time in the step of forming the microphone element 20.

  Next, a modification of the above embodiment will be described.

  First, a first modification of the above embodiment will be described.

  FIG. 7 is a view similar to FIG. 1 showing a condenser microphone 210 according to this modification.

  As shown in the figure, the condenser microphone 210 according to this modification is the same in the basic configuration as in the above embodiment, but the configuration of the sound path wall 270 is different from that in the above embodiment. Yes.

  That is, the sound path wall 70 of the above embodiment is configured only by the resist layer laminated on the upper surface of the microphone element 20, but the sound path wall 270 of the present modification is laminated on the upper surface of the microphone element 20. The resist layer 272 is formed, and an annular elastic member 274 interposed between the upper end surface of the resist layer 272 and the upper wall 60A of the cover 60.

  The height of the resist layer 272 of this modification is set to a value smaller than the distance between the upper surface of the microphone element 20 and the lower surface of the upper surface wall 60 </ b> A of the cover 60.

  The elastic member 274 is composed of a member having a lower elastic modulus than the resist layer 272. At this time, the width of the elastic member 274 is formed to be somewhat wider than the width of the resist layer 272, and the thickness is the distance between the upper end surface of the resist layer 272 and the lower surface of the upper surface wall 60A of the cover 60. A slightly larger value is set. In the sound path wall 270, the elastic member 274 is mainly elastically deformed in the vertical direction.

  Also by adopting the configuration of the present modification, the front space C1 and the outer peripheral space C3 can be reliably partitioned. In addition, by adopting the configuration of this modification, it is possible to coarsely set the accuracy when the resist layer 272 is stacked.

  Next, a second modification of the above embodiment will be described.

  FIG. 8 is a view similar to FIG. 1 showing a condenser microphone 310 according to this modification.

  As shown in the figure, the condenser microphone 310 according to this modification has the same basic configuration as that of the first modification, but the configuration of the sound path wall 370 and the cover 360 is the same as that of the first modification. This is different from the case of the first modification.

  That is, the cover 360 of this modification has a configuration in which an annular flange portion 360b protruding downward along the outer peripheral shape of the sound hole 360a is formed on the upper surface wall 360A.

  In addition, the sound path wall 370 of the present modified example is similar to the sound path wall 270 of the first modified example, in that the resist layer 372 is formed on the upper surface of the microphone element 20, the upper end surface of the resist layer 372, and the cover 360. The elastic member 374 is interposed between the upper surface wall 360A and the lower surface of the upper wall 360A. The resist layer 372 and the elastic member 374 are more than the resist layer 272 and the elastic member 274 of the first modification. It is formed with a slightly larger diameter. As a result, the elastic member 374 comes into surface contact with the outer peripheral surface of the annular flange portion 360b of the cover 360 on the inner peripheral surface thereof.

  By adopting the configuration of the present modification, the partition function between the front space C1 and the outer peripheral space C3 can be further enhanced. Further, by engaging the annular flange portion 360b of the cover 360 with the elastic member 374 of the sound path wall 270, the elastic member 374 can be temporarily fixed at a predetermined position, whereby the work for assembling the condenser microphone 10 can be performed. Can increase the sex.

  Next, a third modification of the above embodiment will be described.

  FIG. 9 is a view similar to FIG. 1 showing a condenser microphone 410 according to this modification.

  As shown in the figure, the condenser microphone 410 according to this modification has the same basic configuration as that of the above embodiment, but the configurations of the silicon substrate 422 and the base substrate 450 of the microphone element 420 are the same. This is different from the above embodiment.

  That is, although the central opening 422a is formed in the silicon substrate 422 of the present modification, the concave groove corresponding to the concave groove 22b in the silicon substrate 22 of the above embodiment is not formed.

  On the other hand, the upper surface of the base substrate 450 of this modification is cut out in the shape of a concave groove at four locations. Then, through the recessed grooves 450a formed at these four locations and the lower end surface of the silicon substrate 422, four communication holes 480 are provided for communicating the central opening 22a and the outer peripheral space C3.

  Even when the configuration of this modification is employed, the volume of the rear space C2 can be made sufficiently large, thereby ensuring the required acoustic characteristics. In addition, since the configuration of the base substrate 450 can be simplified by adopting the configuration of this modified example, the layer forming process of the microphone element 420 can also be simplified.

  The formation of the four recessed groove portions 450a can be performed, for example, by partially cutting a plurality of conductive layers stacked on the insulating substrate of the base substrate 50.

  At this time, instead of the configuration in which the concave groove portions 450a are formed in four places as in the present modification, for example, a configuration in which the concave groove portions 450a are formed only in two places or one place can be adopted. is there. Even in this case, the required acoustic characteristics can be ensured by setting the volume of the rear space C2 to be sufficiently large. Further, by adopting such a configuration, it is possible to more easily form the groove portion 450a.

  In addition, the numerical value shown as a specification in the said embodiment and each modification is only an example, and of course, you may set these to a different value suitably.

10, 210, 310, 410 Condenser microphone 20, 420 Microphone element 22, 422 Silicon substrate 22a, 422a Central opening 22b, 450a Concave groove 24 Vibration film 24a Micro through hole 26 Fixed electrode 26a, 30b Through hole 28, 30, 36 Insulating layer 30a Circular opening 32A, 32B Terminal part 34 Surface protective layer 34a, 34b Hole 40 IC chip (impedance conversion element)
42, 44, 46 Bonding wire 50, 450 Base substrate 60, 360 Cover 60A, 360A Upper surface wall 60B Peripheral wall 60a, 360a Sound hole 70, 270, 370 Sound path wall 80, 480 Communication hole 100 SOI wafer 102, 104, 128 , 130, 136 Silicon oxide film 106, 124 Polycrystalline silicon thin film 122, 126 Silicon layer 122a Central opening 122b Recessed groove 124a, 126a Fine hole 130a, 134a, 134b Small hole 132A, 132B Metal thin film 134 Passivation film 170 Resist layer 272, 372 Resist layer 274, 374 Elastic member 360b Annular flange C Capacitor structure C1 Front space C2 Back space C3 Outer space

Claims (7)

A microphone element in which a capacitor structure part in which a vibration film and a fixed electrode are arranged to face each other on a silicon substrate in which a central opening is formed is laminated so as to close the central opening;
An impedance conversion element for converting the capacitance of the capacitor structure into an electrical impedance; and
A base substrate on which the microphone element and the impedance conversion element are placed and fixed;
A condenser microphone comprising: a cover fixed to the base substrate so as to cover the microphone element and the impedance conversion element;
A sound hole for guiding sound to the capacitor structure is formed at a position above the capacitor structure on the top wall of the cover,
Between the upper surface wall of the cover and the microphone element, a sound path wall that partitions a front space between the capacitor structure portion and the sound hole and an outer peripheral space surrounding the front space is disposed. Features a condenser microphone.   2. The condenser microphone according to claim 1, wherein at least a part of the sound path wall is composed of a resist layer laminated on the upper surface of the microphone element. The sound path wall is composed only of the resist layer,
3. The condenser microphone according to claim 2, wherein the resist layer is disposed in a state in which the upper end surface of the resist layer is brought into contact with the upper wall of the cover and is compressed and elastically deformed in the vertical direction.   The condenser microphone according to any one of claims 1 to 3, wherein an annular flange portion that protrudes downward along the outer peripheral shape of the sound hole is formed on an upper surface wall of the cover.   The communication hole which connects the center opening part of the said silicon substrate and the said outer periphery space is formed in at least one of the said silicon substrate and the said base substrate, The any one of Claims 1-4 characterized by the above-mentioned. Condenser microphone.   6. The condenser microphone according to claim 5, wherein the communication hole is formed by cutting a part of a lower end portion of the silicon substrate.   6. The condenser microphone according to claim 5, wherein the communication hole is formed by cutting an upper surface of the base substrate into a concave groove shape.

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