JP2008022501A - Condenser microphone and manufacturing method thereof - Google Patents

Abstract

An object of the present invention is to increase the sensitivity of a condenser microphone in a low frequency region to realize a flat sensitivity characteristic and to suppress distortion of an acoustic signal due to an external force.
A plate forming a stationary electrode, an island-shaped fixing portion formed in an island shape and fixed relative to the plate, and the island-shaped fixing when viewed from a direction perpendicular to the plate. A peripheral fixing portion that is annularly or discretely formed around the portion and fixed relative to the plate, and a diaphragm that forms a vibration electrode for the stationary electrode, the plate and the diaphragm A condenser microphone in which the diaphragm vibrates with respect to the plate in a state where the diaphragm is fixed to the island-shaped fixing portion and the peripheral fixing portion.
[Selection] Figure 1

Description

  The present invention relates to a condenser microphone and a manufacturing method thereof, and more particularly to a condenser microphone manufactured by a MEMS manufacturing process.

  Conventionally, a condenser microphone manufactured by a MEMS manufacturing process is known (see, for example, Patent Document 1). In conventional condenser microphones, emphasis has been placed on increasing the amplitude of the diaphragm.

  However, in order to increase the amplitude of the diaphragm, it is necessary to widen the distance between the diaphragm and the plate. In a condenser microphone that receives sound waves entering from a sound hole of a plate with a diaphragm, it is necessary to provide a cavity on the opposite side of the diaphragm plate to ensure a passage for balancing the pressure of the cavity with atmospheric pressure. When the sound wave circulates from the diaphragm plate side through the passage to the cavity side of the diaphragm, the sensitivity of the condenser microphone is lowered. However, since it is difficult to increase the acoustic resistance of the passage even for low-frequency sound waves, the conventional condenser microphone has a frequency characteristic in which the sensitivity decreases as the frequency decreases.

In addition, in the structure of the conventional condenser microphone, when an external force other than sound waves is applied due to walking, vehicle running, etc., the resonance frequency of the plate and the diaphragm is different, so the plate vibrates independently of the diaphragm by the external force, Vibration noise is generated.
JP-T-2004-506394

  The present invention has been made in view of the above problems, and an object of the present invention is to increase the sensitivity of a condenser microphone in a low frequency region so as to realize a flat sensitivity characteristic and reduce vibration noise.

  (1) A condenser microphone for achieving the above object includes a plate that forms a stationary electrode, an island-shaped fixing portion that is formed in an island shape and is relatively fixed to the plate, and the plate. A peripheral fixing portion that is annularly or discretely formed around the island-shaped fixing portion as viewed from the vertical direction and is fixed relative to the plate, and a diaphragm that forms a vibrating electrode for the stationary electrode The diaphragm vibrates with respect to the plate in a state where the plate and the diaphragm are fixed to the island-shaped fixing unit and the peripheral fixing unit.

  According to this condenser microphone, the diaphragm vibrates with respect to the stationary electrode in a state where the diaphragm is fixed not only to the peripheral fixing portion but also to the island-shaped fixing portion formed in an island shape surrounded by the peripheral fixing portion. Therefore, in this condenser microphone, the maximum amplitude of the diaphragm is smaller than that of the condenser microphone that vibrates in the state where the diaphragm having the same mechanical characteristics and the same area is fixed relative to the plate only at the periphery. For this reason, in this condenser microphone, the distance between the diaphragm and the plate can be set narrower than that of such a conventional condenser microphone. Therefore, according to this condenser microphone, the capacity can be increased. If the capacity increases, the sensitivity does not decrease even if the maximum amplitude of the diaphragm decreases. Furthermore, since the height of the space formed between the diaphragm and the plate can be made lower than before, the acoustic resistance of the space can be increased to a low frequency. Therefore, even in a structure in which a cavity is formed on the side opposite to the diaphragm plate, the sensitivity in the low frequency region is unlikely to decrease due to the sound waves that enter the cavity on the opposite side of the diaphragm plate from between the diaphragm and the plate. Thus, a condenser microphone having a flat sensitivity characteristic can be realized.

  Further, in this condenser microphone, the distance between diaphragm vibration boundaries is smaller than that of a conventional condenser microphone that vibrates in a state where a diaphragm having the same mechanical characteristics and the same area is fixed relative to the plate only at the periphery. Due to the shortening, the displacement of the diaphragm with respect to the sound pressure is small. Therefore, in this condenser microphone, the relationship between the sound pressure and the output becomes nearly linear.

  (2) In the condenser microphone for achieving the above object, the island-shaped fixing unit and the peripheral fixing unit may be formed between the diaphragm and the plate.

  When the condenser microphone is configured in this way, when an external force that is not a sound wave is applied to the condenser microphone, the diaphragm, the plate, and at least the island-shaped fixing unit vibrate integrally. Therefore, in this condenser microphone, vibration noise due to external force other than sound waves is reduced.

  (3) When an external force other than a sound wave is applied to the condenser microphone, the island-shaped fixing unit and the peripheral fixing unit are coupled to the plate in order to vibrate the diaphragm, the plate, and the island-shaped fixing unit integrally. It is desirable that

  (4) The condenser microphone for achieving the above object may further include a support part coupled to a part of the outer periphery of the diaphragm, and the diaphragm is a static microphone between the spacer and the diaphragm. The island-shaped fixing unit and the peripheral fixing unit may be fixed by electric attraction.

  When the condenser microphone is configured in this way, the internal stress of the diaphragm is reduced compared to the condenser microphone in which the entire circumference of the diaphragm is coupled to the annular support portion, so that the sensitivity of the condenser microphone is increased.

  (5) In the condenser microphone for achieving the above object, the ends of the island-shaped fixing unit and the peripheral fixing unit where the diaphragm is fixed may be tapered.

  When the condenser microphone is configured in this way, the area of the fixing portion of the diaphragm can be reduced while maintaining the bending rigidity and breaking strength of the island-shaped fixing portion and the peripheral fixing portion. Therefore, the sensitivity of the condenser microphone is increased.

  (6) A method of manufacturing a condenser microphone for achieving the above object includes forming the diaphragm, forming a first insulating film on the diaphragm, and forming the plate on the first insulating film. Forming a hole in the first insulating film, and depositing a second insulating film having a composition different from that of the first insulating film inside the hole, whereby the second insulating film is formed in the hole. Forming the island-shaped fixing portion and selectively removing the first sacrificial film from between the diaphragm and the plate by wet etching.

  According to this manufacturing method, the shape of the isolated insulating island-shaped fixing portion can be formed regardless of the remaining shape of the first sacrificial film.

  (7) In the method for manufacturing a condenser microphone for achieving the above object, the depth of the hole may be a depth that does not reach the diaphragm.

  According to this manufacturing method, an island-shaped fixing portion that is not bonded to the diaphragm can be formed.

  (8) A condenser microphone for achieving the above object forms a plate that forms a stationary electrode, a diaphragm that forms a vibrating electrode for the stationary electrode, and a plurality of independent vibration boundaries on the diaphragm And the diaphragm may vibrate while being fixed to the wall.

  According to this condenser microphone, a plurality of vibration boundaries independent of the diaphragm are formed by the wall portion. Therefore, in this condenser microphone, the maximum amplitude of the diaphragm is smaller than that of a condenser microphone that vibrates in a state where a diaphragm having the same mechanical characteristics and the same area is fixed relative to the plate only at the periphery. For this reason, in this condenser microphone, the distance between the diaphragm and the plate can be set narrower than that of such a conventional condenser microphone. Therefore, according to this condenser microphone, the capacity can be increased. If the capacity increases, the sensitivity does not decrease even if the maximum amplitude of the diaphragm decreases. Moreover, the sound wave that has entered between the diaphragm and the plate can be blocked by the wall. Therefore, even in a structure in which a cavity is formed on the side opposite to the diaphragm plate, the sensitivity in the low frequency region is unlikely to decrease due to the sound waves that enter the cavity on the opposite side of the diaphragm plate from between the diaphragm and the plate. Thus, a condenser microphone having a flat sensitivity characteristic can be realized.

  Further, in this condenser microphone, the distance between diaphragm vibration boundaries is smaller than that of a conventional condenser microphone that vibrates in a state where a diaphragm having the same mechanical characteristics and the same area is fixed relative to the plate only at the periphery. Since it becomes shorter, the displacement of the diaphragm with respect to the external force is small. Therefore, in this condenser microphone, the relationship between the sound pressure and the output becomes nearly linear.

  In the claims, “to the top” means both “without an intermediate on the top” and “with an intermediate on the top” unless there is a technical impediment. To do. Further, the order of the operations described in the claims is not limited to the order of description as long as there is no technical obstruction factor, and may be executed at the same time, may be executed in the reverse order of the description order, or may be continuous. It does not have to be executed in order.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. Constituent elements corresponding to each embodiment are denoted by common reference numerals, and redundant description is omitted.

1. First embodiment:
Configuration FIG. 1A and FIG. 1B are schematic cross-sectional views showing a first embodiment of the condenser microphone of the present invention. The cut surface of FIG. 1A is perpendicular to the surface of the plate 12. The cut surface of FIG. 1B is parallel to the surface of the plate 12 and shows a state in which the diaphragm 16 is viewed from the plate 12 side. The condenser microphone 1 includes a plate 12 that forms a stationary electrode and a diaphragm 16 that forms a vibrating electrode. The plate 12 and the diaphragm 16 are fixed on the substrate 14 by a support portion 13. When a bias voltage is applied to the plate 12 and the diaphragm 16, electrostatic attraction acts between the diaphragm 16 and the plate 12, and the diaphragm 16 is fixed to the fixing unit 10 coupled to the plate 12. FIG. 1A shows a state where the diaphragm 16 is fixed to the plate 12 by a broken line.

  The substrate 14 is fixed to the mounting substrate 17 by adhesion or the like. A through hole is formed in the substrate 14, and the through hole forms a cavity 15. The cavity 15 is a space that increases the volume of the space on the side opposite to the plate 12 of the diaphragm 16, and reduces the amplitude of the pressure vibration caused by the vibration of the diaphragm 16 in the space on the side opposite to the plate 12 of the diaphragm 16.

  The support portion 13 is composed of one or more films formed on the substrate 14, and is connected to the diaphragm 16, the plate 12, and the substrate 14. A through hole 18 in which the diaphragm 16 is accommodated is formed in the support portion 13. That is, the support portion 13 is formed in an annular shape surrounding the fixing portion 10 and can correspond to the peripheral fixing portion described in the claims.

  The diaphragm 16 is stretched over the cavity 15 by the support portion 13. The diaphragm 16 is composed of one or more films including a conductive film that forms a vibrating electrode, and has a shape in which an arm part 19 extends from a circular central part 20 that covers the opening of the cavity 15. The ends of the plurality of arm portions 19 are coupled to the support portion 13. The thickness of the diaphragm 16 is set to 0.5 to 1.5 μm, for example.

  A plurality of arm portions 19 of the diaphragm 16 are formed at positions surrounding the circular central portion 20 and are bent so as to function as springs. Since the diaphragm 16 is coupled to the support portion 13 only at the tip of the arm portion 19 which is more easily deformed than the central portion 20, the internal stress of the diaphragm 16 is relieved by the deformation of the arm portion 19. However, in this embodiment, since the distance between the diaphragm 16 and the plate 12 is narrowed, when the tension of the diaphragm 16 is small and the distance between the fixing portions 10 is wide, the diaphragm 16 adheres to the plate 12 by electrostatic attraction. So-called pull-in is likely to occur. Therefore, in order to set the tension of the diaphragm 16 to an appropriate value, the shape of the arm portion 19 and the internal stress of the diaphragm 16 are adjusted.

  The plate 12 is composed of one or more films including a conductive film that forms a stationary electrode. The plate 12 is stretched over the support portion 13 on the side opposite to the substrate 14 of the diaphragm 16 and covers the through hole 18 formed by the support portion 13. A plurality of through holes are formed in the plate 12, and each through hole forms a sound hole 11. The sound wave travels from the sound hole 11 to the inside of the condenser microphone 1 and vibrates the diaphragm 16.

  Between the plate 12 and the diaphragm 16, a fixing unit 10 formed in an island shape separated from the support unit 13 is provided. The base of the fixing unit 10 is coupled to the plate 12. Since the height of the fixing unit 10 is lower than the distance between the plate 12 and the diaphragm 16, the front end of the fixing unit 10 is separated from the diaphragm 16 when no external force is applied to the diaphragm 16. The front end surface of the fixing unit 10 is spherical. That is, since the tip of the fixing unit 10 has a tapered shape, when electrostatic attraction acts between the plate 12 and the diaphragm 16, the area of the fixing unit 10 is smaller than the maximum area of the cross section parallel to the diaphragm 16. The fixing unit 10 and the diaphragm 16 are in contact with each other.

  The number and arrangement of the fixing units 10 are designed according to the shape, film thickness, internal stress, support structure, characteristics of the condenser microphone 1 and the like of the diaphragm 16. For example, as shown in FIG. 1B, a plurality of fixing units 10 may be arranged on lattice points, or only one fixing unit 10 is brought into contact with only the center of the diaphragm 16 as shown in FIGS. 2A and 2B. It may be provided. Among the plurality of fixing units 10, the fixing units 10 arranged inside correspond to the island-shaped fixing unit described in the claims. The fixing unit 10 arranged on the outermost side among the plurality of fixing units 10 corresponds to a peripheral fixing unit described in the claims. When there is only one fixing unit 10, the support unit 13 corresponds to the peripheral fixing unit described in the claims.

-Operation In the condenser microphone 1, a bias voltage boosted by a charge pump (not shown) is applied to the plate 12 and the diaphragm 16, and the diaphragm 16 is fixed to the fixing unit 10 as shown in FIG. 3A by electrostatic attraction. used. In this state, when the sound wave entering from the sound hole 11 reaches the diaphragm 16, the plate 12 vibrates with respect to the plate 12 because the plate 12 is sufficiently thick and has a high deflection composition. At this time, the diaphragm 16 vibrates while being fixed to the fixing unit 10 and the support unit 13 as indicated by a broken line in FIG. 3A.

  Therefore, the vibration boundary of the diaphragm 16 exists not only in the vicinity of the diaphragm 16 but also in a contact portion with the fixing unit 10 inside the diaphragm 16. The larger the distance (W) from the vibration boundary to the vibration boundary, the larger the amplitude of the membrane. Therefore, the amplitude (A) of the diaphragm 16 is a comparative condenser microphone having a vibration boundary only in the periphery as shown in FIG. 3B. The amplitude is smaller than the amplitude (a) of the diaphragm 901 of 900. Therefore, if the rated sound pressure is constant, the amplitude of the diaphragm 16 is small, so the distance (D) between the diaphragm 16 and the plate 12 can be set narrower than that of the condenser microphone 900 of the comparative example. Since the capacity of the diaphragm 16 and the plate 12 is inversely proportional to the distance (D), if the distance between the diaphragm 16 and the plate 12 is narrowed, the capacity of the diaphragm 16 and the plate 12 is increased. Specifically, for example, when the diameter of the diaphragm 16 is 1 mm and the fixing units 10 are arranged at lattice points with an interval of 100 μm, the distance between the diaphragm 16 and the plate 12 can be set to about 0.5 μm.

  Further, since the distance between the diaphragm 16 and the plate 12 can be narrowed, the sound wave that has entered from the sound hole 11 is unlikely to enter the cavity 15 from the periphery of the diaphragm 16. Specifically, by reducing the distance between the diaphragm 16 and the plate 12, the acoustic resistance in the space between the diaphragm 16 and the plate 12 can be increased even for low-frequency sound waves. Therefore, the sensitivity characteristic of the condenser microphone 1 becomes flat.

  Furthermore, since the amplitude A of the diaphragm 16 is small, the distance H between the diaphragm 16 and the substrate 14 can also be narrowed. By setting the gap H between the diaphragm 16 and the substrate 14 around the opening of the cavity 15 to be small, the acoustic resistance of the gap between the diaphragm 16 and the substrate 14 can be increased to a low frequency.

  Further, the diaphragm 16 vibrates integrally with the plate 12 with respect to external force other than sound waves accompanying walking vibration and running vibration. Therefore, even if vibration caused by walking or running of the vehicle occurs in the condenser microphone 1, the diaphragm 16 hardly vibrates with respect to the plate 12 due to the vibration, and therefore the condenser microphone 1 hardly generates vibration noise.

  FIG. 4 is a graph showing the relationship between the capacitance (C) of the condenser microphone and the distance (D) between the counter electrodes under a constant voltage condition. The variation width (Δd, ΔD) of the distance between the counter electrodes corresponding to the amplitude necessary to obtain the capacitance change ΔQ decreases as the distance between the counter electrodes decreases. The relationship between the distance between the counter electrodes (D) and the capacitance (C) becomes closer to the linear as the variation width of the distance between the counter electrodes becomes smaller. Therefore, when comparing the capacitor microphone 1 of the present embodiment and the capacitor microphone 900 of the comparative example under the condition that the same capacitance change is obtained, the capacitor microphone 1 of the present embodiment is more distant from the counter electrode than the comparative example. The relationship between (D) and capacity (C) is nearly linear. That is, the condenser microphone 1 of the present embodiment can bring the relationship between the sound pressure and the output closer to a linearity compared to the condenser microphone 900 of the comparative example.

Comparison The table in FIG. 14 shows the performance of the condenser microphone 1 as an embodiment of the present invention and the condenser microphone 900 as a comparative example. Both the condenser microphone 1 and the condenser microphone 900 are compared as having a diaphragm with a radius of 0.5 mm. As shown in the table of FIG. 14, when the structure of this embodiment is adopted, the microphone capacity of the condenser microphone 1 becomes much larger than that of the comparative example.

2. Second embodiment:
5A and 5B are schematic cross-sectional views showing a second embodiment of the condenser microphone of the present invention. The cut surface of FIG. 5A is perpendicular to the surface of the plate 12. The cut surface in FIG. 5B is parallel to the surface of the plate 12 and shows a state in which the diaphragm 16 is viewed from the plate 12 side. Since the vibration boundary of the diaphragm 16 can be determined by the fixing unit 10, as shown in FIGS. 5A and 5B, the outer shape of the diaphragm 16 may not be a point-symmetric figure. The external shape of the condenser microphone 2 is rectangular because it is determined by the dicing of the substrate 14. Therefore, for example, in order to increase the ratio of the area of the diaphragm 16 to the surface area of the condenser microphone 2, the diaphragm 16 occupies most of the area except the pad 22 and the pad 23 for connecting the signal processing circuit and the condenser microphone 2. Alternatively, the outer shape of the diaphragm 16 may be set.

  The diaphragm 16 may not be stretched over the support portion 13. When the diaphragm 16 is not stretched over the support portion 13, the tension of the diaphragm 16 is substantially zero. The arrangement of the fixing units 10 and the flexural rigidity of the diaphragm 16 are adjusted so that the diaphragm 16 does not adhere to the plate 12 when a bias voltage is applied.

  When the diaphragm 16 is not stretched over the support portion 13, the outermost vibration boundary of the diaphragm 16 is also determined by the fixing portion 10. Therefore, in this case, the fixing unit 10 indicated by a white circle in FIG. 5B corresponds to the island-shaped fixing unit described in the claims, and the fixing unit 10 and the support unit 13 indicated by the black circle are included in the claims. This corresponds to the peripheral fixing portion described.

3. Third embodiment:
FIG. 6 is a schematic cross-sectional view showing a third embodiment of the condenser microphone of the present invention. The cut surface in FIG. 6 is perpendicular to the surface of the plate 12. The fixing unit 10 may be coupled to both the plate 12 and the diaphragm 16. By coupling the fixing unit 10 to both the plate 12 and the diaphragm 16, the diaphragm 16 is less likely to vibrate relative to the plate 12 due to external forces other than sound waves.

4). Fourth embodiment:
7A and 7B are schematic cross-sectional views showing a fourth embodiment of the condenser microphone of the present invention. The cut surface in FIG. 7A is perpendicular to the surface of the plate 12. The cut surface of FIG. 7B is parallel to the surface of the plate 12 and shows a state in which the diaphragm 16 is viewed from the plate 12 side. As illustrated in FIG. 7B, the fixing unit 10 may be formed in a wall shape that forms a plurality of independent vibration boundaries on the diaphragm 16. When the fixing unit 10 is formed in this way, the diaphragm 16 vibrates independently for each area partitioned by the fixing unit 10. In this case, since the diameter of the diaphragm 16 is sufficiently small with respect to the wavelength of the sound wave, each region partitioned by the fixing unit 10 vibrates substantially in phase.

5. Fifth embodiment:
8A and 8B are cross-sectional views showing a fifth embodiment of the condenser microphone of the present invention. The cut surface of FIG. 8A is perpendicular to the surface of the plate 12. The cut surface of FIG. 8B is parallel to the surface of the plate 12 and shows a state in which the fixing unit 10 is viewed through the diaphragm 16 from the plate 12 side. As shown in FIG. 8A, the fixing unit 10 may be provided between the substrate 14 and the diaphragm 16. In this case, the fixing unit 10 is coupled to the substrate 14 and the diaphragm 16. Further, in order to support the island-shaped fixing unit 10, a plurality of cavities 15 that are independent from each other are formed in the substrate 14.

6). Production method:
Before describing an embodiment of a method for manufacturing a condenser microphone of the present invention, an example of a laminated structure of films for realizing the above-described condenser microphones 1, 2, 3, 4 will be described. FIG. 9 is a cross-sectional view showing an example of a laminated structure of films common to the condenser microphones 1, 2, 3, and 4.

The substrate 14 is formed from a wafer 107 made of single crystal Si or the like.
The support portion 13 includes an etch stopper film 102, a spacer film 103 for forming a gap between the diaphragm 16 and the plate 12, a conductive film 104 forming a stationary electrode on the plate 12, and a fixing portion 10. The insulating film 105, the insulating film 106, and the like are included.

  The plate 12 includes a conductive film 104 and an insulating film 105, and the conductive film 104 forms a stationary electrode. Since the surface layer of the support portion 13 and the surface layer of the plate 12 are composed of the insulating film 105, the plate 12 is coupled to the support portion 13.

  The fixing unit 10 includes an insulating film 105. Since the surface layer of the plate 12 and the portion of the insulating film 105 penetrating the plate 12 that protrudes toward the substrate 14 constitutes the fixing unit 10, the fixing unit 10 is coupled to the plate 12. .

  The diaphragm 16 includes a conductive film 108 that forms a vibrating electrode. Since the conductive film 108 is sandwiched between the etch stopper film 102 and the spacer film 103 constituting the support portion 13, the diaphragm 16 is coupled to the support portion 13.

  The pad 22 for connecting the vibration electrode and the signal processing circuit is composed of a conductive film 109 in close contact with the conductive film 108 constituting the vibration electrode of the diaphragm 16.

  The pad 23 for connecting the stationary electrode and the signal processing circuit is composed of a conductive film 109 in close contact with the conductive film 104 constituting the stationary electrode of the plate 12.

  The laminated structure of the films constituting the condenser microphones 1, 2, 3, 4 has been described above. Note that the structure of the condenser microphone 5 can be realized by a laminated structure of films similar to the condenser microphones 1, 2, 3, and 4, except that the fixing unit 10 is composed of the etch stopper film 102.

  10, FIG. 11, FIG. 12, and FIG. 13 are cross-sectional views showing the manufacturing process of the condenser microphone. In each of FIGS. 10, 11, 12, and 13, the inside of one chip area is shown as a cross-sectional view.

First, as shown in FIG. 10A, an etch stopper film 102 is formed on a wafer 107 such as a single crystal Si wafer. The etch stopper film 102 is an insulating sacrificial film made of, for example, SiO ₂ for controlling the end point of Deep-RIE described later. Next, the pattern of the resist mask 201 is transferred to the etch stopper film 102 by wet etching, and dimples 301 are formed in the etch stopper film 102.

  Next, as shown in FIG. 10B, a conductive film 108 is formed on the etch stopper film 102, and the pattern of the resist mask 202 is transferred to form the outline of the diaphragm 16 made of the conductive film 108. The conductive film 108 is made of, for example, a polycrystalline Si film or a metal film deposited by low pressure CVD, doped with impurities such as P, and annealed.

  Next, as shown in FIG. 10C, a spacer film 103 is formed on the etch stopper film 102 and the conductive film 108, and a dimple 302 is formed on the spacer film 103 by transferring the pattern of the resist mask 203. . The spacer film 103 is formed to have a desired thickness by repeating the process of annealing by depositing SiO thinly by CVD, for example.

  Next, as shown in FIG. 10D, a conductive film 104 is formed on the spacer film 103, and the pattern of the resist mask 204 is transferred to form the outer peripheral contour of the plate 12 formed of the conductive film 104. The conductive film 104 is made of, for example, a polycrystalline Si film or a metal film deposited by low pressure CVD, doped with impurities such as P, and annealed.

  Next, as shown in FIG. 11A, holes 304 for forming the fixing portion 10 are formed in the conductive film 104 and the spacer film 103 by transferring the pattern of the resist mask 205 by etching. Specifically, after the conductive film 104 is etched using isotropic etching, the spacer film 103 is etched by anisotropic dry etching. By stopping the anisotropic dry etching before reaching the film 108, it is possible to form the hole 304 for forming the fixing portion 10 having a tapered tip. On the other hand, even when the depth of the hole 304 is set to a depth at which the conductive film 108 is exposed, the fixing unit 10 and the diaphragm 16 are separated by removing the insulating film 106 to be formed next.

Next, as shown in FIG. 11B, an insulating film 106 is formed, and the pattern of the resist mask 206 is transferred to remove unnecessary portions of the insulating film 106. The insulating film 106 is made of SiO deposited by CVD, for example. The insulating film 106 is a film for insulating the conductive film 108 constituting the diaphragm 16 from the conductive film 104 constituting the plate 12.
The fixing portion 10 and the diaphragm 16 can be coupled by setting the depth of the hole 304 to a depth at which the conductive film 108 is exposed and not forming the insulating film 106 on the conductive film 108.

  Next, as shown in FIG. 11C, unnecessary portions of the spacer film 103 and the etch stopper film 102 are removed by transferring the pattern of the resist mask 208, and the holes 307 for joining the pad 22 and the conductive film 108 are formed. Then, a hole 306 for forming a portion where the insulating film 105 functions as an etch stopper for constituting the wall surface of the through hole 18 of the support portion 13 is formed. Specifically, after the spacer film 103 isotropically etched by wet etching, the spacer film 103 and the etch stopper film 102 are anisotropically etched by dry etching to expose the conductive film 108. A hole 306 for exposing the wafer 107 is formed.

  Next, as shown in FIG. 12A, an insulating film 105 is formed on the spacer film 103 and the conductive film 104, and the pattern of the resist mask 209 is transferred to expose the conductive film 108 on the insulating film 105. A hole 309 to be formed and a hole 308 to expose the conductive film 104 are formed. The insulating film 105 is made of a material having etching selectivity with respect to the spacer film 103, and is made of, for example, a SiN film formed to have a desired thickness by repeating deposition by low pressure CVD and annealing.

  Next, as shown in FIG. 12B, a conductive film 109 is formed, and the contour of the pad 22 and the pad 23 is formed by transferring the pattern of the resist mask 210 by etching. The conductive film 109 is made of Al deposited by sputtering, for example.

  Next, as shown in FIG. 12C, the sound hole 11 is formed in the insulating film 105 and the conductive film 104 by transferring the pattern of the resist mask 211 by etching. Specifically, for example, the sound hole 11 is formed by performing anisotropic dry etching twice with different etching gases.

  Next, after the conductive film 108, the conductive film 104, and the insulating film 105 deposited on the back surface of the wafer 107 are removed by back grinding, a resist mask 212 is formed on the back surface of the wafer 107 as shown in FIG. 13A. The cavity 15 is formed in the wafer 107 by Deep-RIE.

Next, as shown in FIG. 13B, the SiO ₂ film formed on the surface of the conductive film 109 and the surface of the insulating film 105 is removed using a resist mask 214.

  Next, as shown in FIG. 13C, an etchant is supplied from the sound hole 11 and the cavity 15 using the insulating film 105 as an etch stopper with the pad 22 and the pad 23 made of the conductive film 109 protected by a resist mask 215. Then, unnecessary portions of the etch stopper film 102 and the spacer film 103 are wet etched to form the through holes 18 of the support portion 13.

  Finally, when the wafer 107 is divided by dicing, condenser microphones 1, 2, 3, and 4 shown in FIG. 9 are completed.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. is there. For example, in the above-described manufacturing process, the film composition, film forming method, film contour forming method, process sequence, etc. are combinations of film materials having physical properties that can constitute a condenser microphone, film thickness, and required contour. It is appropriately selected according to the shape accuracy and the like and is not particularly limited.

FIG. 1A and FIG. 1B are sectional views according to the first embodiment. FIG. 2A and FIG. 2B are sectional views according to the first embodiment. FIG. 3A is a sectional view according to the first embodiment. FIG. 3B is a sectional view according to a comparative example. The graph which shows the relationship between the space | interval of a diaphragm and a plate, and capacity | capacitance. 5A and 5B are cross-sectional views according to the second embodiment. Sectional drawing concerning 3rd embodiment. 7A and 7B are cross-sectional views according to the fourth embodiment. 8A and 8B are cross-sectional views according to the fifth embodiment. Sectional drawing concerning 4th embodiment from 1st embodiment. Sectional drawing which shows the manufacturing method of a condenser microphone. Sectional drawing which shows the manufacturing method of a condenser microphone. Sectional drawing which shows the manufacturing method of a condenser microphone. Sectional drawing which shows the manufacturing method of a condenser microphone. The table | surface which shows the performance of 1st embodiment of this invention, and the performance of a comparative example.

Explanation of symbols

1, 2, 3, 4, 5: condenser microphone, 10: fixing unit, 11: sound hole, 12: plate, 13: support unit, 14: substrate, 15: cavity, 16: diaphragm, 17: mounting substrate, 18 : Through-hole, 19: Arm part, 20: Center part, 22: Pad, 23: Pad, 102: Etch stopper film, 103: Spacer film, 104: Conductive film, 105: Insulating film, 106: Insulating film, 107: Wafer, 108: conductive film, 109: conductive film

Claims (8)

A plate forming a stationary electrode;
An island-shaped fixing portion formed in an island shape and fixed relative to the plate;
A peripheral fixing unit that is annularly or discretely formed around the island-shaped fixing unit as viewed from a direction perpendicular to the plate and is fixed relative to the plate;
A diaphragm forming a vibrating electrode for the stationary electrode;
With
The diaphragm vibrates with respect to the plate in a state where the plate and the diaphragm are fixed to the island-shaped fixing unit and the peripheral fixing unit.
Condenser microphone. The island-shaped fixing portion and the peripheral fixing portion are formed between the diaphragm and the plate.
2. The condenser microphone according to claim 1. The island-shaped fixing unit and the peripheral fixing unit are coupled to the plate.
The condenser microphone according to claim 2. A support portion coupled to a part of the outer periphery of the diaphragm;
The diaphragm is fixed to the island-shaped fixing unit and the peripheral fixing unit by electrostatic attraction between the spacer and the diaphragm.
The condenser microphone according to claim 2 or 3. The ends of the island-shaped fixing unit and the peripheral fixing unit where the diaphragm is fixed are tapered,
The condenser microphone according to claim 4. Forming the diaphragm,
Forming a first insulating film on the diaphragm;
Forming the plate on the first insulating film;
Forming a hole in the first insulating film;
By depositing a second insulating film having a composition different from that of the first insulating film inside the hole, the island-shaped fixing portion made of the second insulating film is formed in the hole,
Selectively removing the first sacrificial film from between the diaphragm and the plate by wet etching;
The manufacturing method of the capacitor | condenser microphone as described in any one of Claims 1-5 containing this. The depth of the hole is a depth that does not reach the diaphragm,
A method for manufacturing a condenser microphone according to claim 6. A plate forming a stationary electrode;
A diaphragm forming a vibrating electrode for the stationary electrode;
A wall that forms a plurality of independent vibration boundaries in the diaphragm;
With
The diaphragm vibrates with respect to the plate in a state of being fixed to the wall.
Condenser microphone.

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