JP2009089100A - Vibrating transducer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent stiction in a diaphragm while increasing sensitivity in a vibrating transducer. <P>SOLUTION: The vibrating transducer has: a substrate; the conductive diaphragm that comprises a deposited film on the substrate and has a center section and a plurality of arm sections radially extended from the center section to the outside; a conductive plate comprising the deposited film on the substrate; and a diaphragm support section that comprises the deposited film on the substrate, is joined to each of the plurality of arm sections, and supports the diaphragm with a gap to the plate. In the vibrating transducer, a plurality of projections, which prevent the diaphragm from adhering to the substrate or the plate, are formed at the arm sections of the diaphragm, and electrostatic capacity, which is formed by the diaphragm and the plate, is changed by vibrating the diaphragm to the plate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a vibration transducer, and more particularly to a wave transducer such as a minute condenser microphone as a MEMS sensor.

  Conventionally, a minute condenser microphone manufactured by applying a semiconductor device manufacturing process is known. Such a condenser microphone is called a MEMS microphone, and the diaphragm and the plate constituting the counter electrode are formed of a thin film deposited on the substrate and are supported on the substrate in a state of being separated from each other. When the diaphragm vibrates with respect to the plate by the sound wave, the capacitance of the capacitor changes due to the displacement, and the capacitance change is converted into an electric signal.

The Institute of Electrical Engineers of Japan MSS-01-34 JP 9-508777 A US Patent No. 4776019 Special table 2004-506394

  The distance between the diaphragm and the plate or substrate is as small as several μm. Therefore, stiction may occur when an impact is applied to the diaphragm or when the diaphragm comes into contact with the plate or the substrate during manufacture. However, although it is necessary to reduce the rigidity of the diaphragm in order to increase the sensitivity, there is a problem that stiction tends to occur as the rigidity of the diaphragm decreases.

  The present invention was created to solve this problem, and aims to prevent diaphragm stiction while increasing the sensitivity of the vibration transducer.

(1) A vibration transducer for achieving the above object is a diaphragm comprising a substrate, a deposited film on the substrate, having conductivity, and a plurality of arms extending radially outward from the center. A diaphragm having a conductive film and a deposited film on the substrate, bonded to each of the plurality of arms, and supporting the diaphragm with a gap between the plates. A plurality of protrusions formed on the arm of the diaphragm to prevent the diaphragm from adhering to the substrate or the plate, and the diaphragm is vibrated with respect to the plate. The capacity changes.
The diaphragm of the vibration transducer according to the present invention is configured such that each of a plurality of arms extending radially from the central portion is joined to the diaphragm support portion, rather than the outer edge portion being joined annularly. Such a diaphragm has lower rigidity than a diaphragm whose outer edge is fixed in an annular shape, and therefore the vibration transducer of the present invention has higher sensitivity. Normally, the amplitude of the diaphragm becomes smaller as it approaches the fixed end from the center, so that stiction near the fixed end of the diaphragm hardly occurs. However, in the configuration of the present invention, the rigidity of the diaphragm arm itself is low, so that it is necessary to take measures against stiction. Therefore, in the present invention, a plurality of protrusions that prevent the diaphragm from adhering to the substrate or the plate are formed on the arm portion of the diaphragm. Therefore, according to the present invention, the stiction of the diaphragm can be prevented while increasing the sensitivity of the vibration transducer.

(2) A region near the circumferential end of the diaphragm of the arm portion is easily warped by stress. That is, at the diaphragm arm, the circumferential end of the diaphragm

Structurally, stiction between an element and a substrate or plate tends to occur as a plurality of pillars rather than a closed wall. Therefore, it is desirable that the protrusion is formed in a region near the circumferential end of the diaphragm of the arm portion.

  (3) The rigidity of the film is locally increased in the region where the protrusion is formed. Therefore, when a plurality of protrusion rows aligned in the circumferential direction of the diaphragm are formed on the arm portion and the distance between the protrusion rows arranged in the radial direction of the diaphragm is wide, the rigidity distribution of the arm portion of the diaphragm is not uniform. Occurs. That is, in this case, a belt-like region having high rigidity and a belt-like region having low rigidity appear alternately in the radial direction of the diaphragm. Then, the arm portion of the diaphragm is easily bent in a band-like region having low rigidity. Stiction occurs when the arm is bent. Therefore, it is desirable that the plurality of protrusions be arranged such that the direction connecting the closest protrusions in the radial direction of the diaphragm is inclined with respect to the circumferential direction of the diaphragm. By arranging the protrusions in this way, stripe-like unevenness is less likely to occur in the rigidity distribution of the arm portion.

  (4) The protrusions may be arranged in a staggered manner. By arranging the protrusions in a staggered arrangement, stripe-like unevenness is less likely to occur in the rigidity distribution. The staggered arrangement here does not have to be a grid array in which all of the plurality of protrusions are aligned in the radial direction and the circumferential direction of the diaphragm. For example, each protrusion is positioned at a lattice point and the periphery of the diaphragm It is sufficient that one or more other protrusions that are not lined up in the radial direction of the diaphragm are present between the two lines of protrusions linearly arranged in the direction.

(5) A vibration transducer for achieving the above object comprises a substrate and a diaphragm comprising a deposited film on the substrate, having conductivity, and a plurality of arms that extend radially outward from the center. A diaphragm having a conductive film and a conductive film and a deposited film on the substrate, joined to each of the plurality of arms, and supporting the diaphragm with a gap between the plates. And a plurality of protrusions for preventing the diaphragm from adhering to the substrate or the plate are formed in the vicinity of the outer periphery of the central portion, and the diaphragm is formed by the diaphragm and the plate by vibrating with respect to the plate. The electrostatic capacity changes.
The diaphragm of the vibration transducer according to the present invention is configured such that each of a plurality of arms extending radially from the central portion is joined to the diaphragm support portion, rather than the outer edge portion being joined annularly. Such a diaphragm is less rigid than a diaphragm in which the outer edge portion is joined in an annular shape, so that the vibration transducer of the present invention has high sensitivity. Normally, the amplitude of the diaphragm decreases as it approaches the fixed end from the center, so that stiction is less likely to occur as it approaches the fixed end of the diaphragm. However, according to the configuration of the present invention, irregular vibration is likely to occur in the vicinity of the outer periphery of the central portion of the diaphragm located between adjacent arm portions because the tension is weakened. Moreover, according to the structure of this invention, the area | region near the outer periphery of the center part of the diaphragm located between adjacent arm parts tends to warp with the stress at the time of manufacture. Therefore, in the present invention, a protrusion for preventing the diaphragm from adhering to the substrate or plate is formed in the vicinity of the outer periphery of the central portion. Therefore, according to the present invention, diaphragm stiction can be prevented while increasing the sensitivity of the vibration transducer.

  (6) In any of the above-described configurations, it is desirable that the protrusion has a tip that is not sharp. This is because if the protrusion tip is sharp, the protrusion or the plate may be damaged by the protrusion. This is because, in particular, when the plate is made of a material with low toughness, the plate may be cracked by collision with a sharp protrusion.

  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.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the corresponding component in each figure, and the overlapping description is abbreviate | omitted.

1. Configuration FIG. 1 shows a sensor chip which is a MEMS structure part of a condenser microphone 1 according to an embodiment of the present invention, FIG. 2 shows a schematic cross section thereof, and FIG. 3 shows a laminated structure of the film. 21 and 22 show a detailed cross section of a part thereof. The condenser microphone 1 includes a sensor chip, a circuit chip (not shown) provided with a power supply circuit and an amplifier circuit, and a package (not shown) that accommodates these.

  The sensor chip of the capacitor microphone 1 is a chip composed of a substrate 100 and a deposited film such as a lower insulating film 110, a lower conductive film 120, an upper insulating film 130, an upper conductive film 160, and a surface insulating film 170 stacked thereon. It is. First, the laminated structure of the film of the MEMS structure portion of the condenser microphone 1 will be described.

  The substrate 100 is made of P-type single crystal silicon. The material of the substrate is not limited to this, and it is only necessary to have rigidity, thickness, and toughness as a base substrate for depositing a thin film and a support substrate for supporting a structure made of the thin film. A through hole is formed in the substrate 100, and the opening 100a of the through hole forms an opening of the back cavity C1.

The lower insulating film 110 bonded to the substrate 100, the lower conductive film 120, and the upper insulating film 130 is a deposited film made of silicon oxide (SiO _x ). The lower insulating film 110 includes a plurality of diaphragm support portions 102 arranged at equal intervals on the circumference, a plurality of guard spacers 103 arranged at equal intervals on the circumference inside the diaphragm support portions 102, and a guard ring. 125c and the guard lead 125d are formed with an annular portion 101 that insulates the substrate 100 from the substrate 100.

  The lower conductive film 120 joined to the lower insulating film 110 and the upper insulating film 130 is a deposited film made of polycrystalline silicon doped with impurities such as P as a whole. The lower conductive film 120 forms a guard part 127 including a guard electrode 125a, a guard connector 125b, a guard ring 125c, and a guard lead 125d, and a diaphragm 123.

  The upper insulating film 130 bonded to the lower conductive film 120, the upper conductive film 160, and the lower insulating film 110 is a deposited film made of silicon oxide. The upper insulating film 130 is arranged on the outer periphery of a plurality of plate spacers 131, an annular annular portion 132 that is positioned outside the plate spacer 131, supports the etch stopper ring 161, and insulates the plate lead 162d and the guard lead 125d. Is configured.

  The upper conductive film 160 bonded to the upper insulating film 130 is a deposited film made of polycrystalline silicon doped with impurities such as P as a whole. The upper conductive film 160 constitutes a plate 162, a plate lead 162d, and an etch stopper ring 161.

  A surface insulating film 170 bonded to the upper conductive film 160 and the upper insulating film 130 is an insulating deposited film made of a silicon oxide film.

  The MEMS structure portion of the condenser microphone 1 is provided with four terminals 125e, 162e, 123e, and 100b. These terminals 125e, 162e, 123e, and 100b are a conductive conductive film such as AlSi, a pad conductive film 180, a bump film 210 that is a conductive deposited film such as Ni, and a conductive material having excellent corrosion resistance such as Au. A bump protective film 220 which is a conductive deposited film. The side walls of the terminals 125e, 162e, 123e, and 100b are protected by a pad protective film 190 that is an insulating deposited film such as SiN and a surface protective film 200 that is an insulating deposited film such as silicon oxide.

  The laminated structure of the MEMS structure film of the condenser microphone 1 has been described above. Next, the mechanical structure of the MEMS structure part of the condenser microphone 1 will be described.

  The diaphragm 123 is formed of a single-layer thin deposited film having conductivity as a whole, and includes a central portion 123a and a plurality of arm portions 123c extending radially outward from the central portion 123a. The diaphragm 123 is supported by being insulated from the plate 162 with a gap between the plate 162 and the substrate 100 by a plurality of columnar diaphragm support portions 102 joined to a plurality of locations near the outer edge thereof. Are stretched parallel to the substrate 100. The diaphragm support portion 102 is joined to the vicinity of the distal end portion of each arm portion 123 c of the diaphragm 123. Since the diaphragm 123 is notched between the arm part 123c and the arm part 123c, the rigidity is lower than that of the form without the notch. Furthermore, since a plurality of diaphragm holes 123b, which are through holes, are formed in each arm portion 123c, the rigidity of the arm portion 123c itself is low.

  In the vicinity of the central portion 123a, the arm portion 123c of the diaphragm 123 becomes longer in the circumferential direction of the diaphragm 123 as it approaches the central portion 123a. Thereby, the stress concentration at the boundary between the arm portion 123c and the central portion 123a can be relaxed. Moreover, stress concentration can be prevented from occurring in the bent portion by not forming the bent portion in the outline of the arm portion 123c in the vicinity of the boundary between the arm portion 123c and the central portion 123a.

  The arm portion 123c of the diaphragm 123 has a wide width in the joining region with the diaphragm support portion 102, that is, the circumferential length of the diaphragm is long. Specifically, the width of the arm portion 123c of the diaphragm 123 decreases in the vicinity of the central portion 123a as it moves away from the central portion 123a, and increases in the vicinity of the diaphragm support portion 102 as it approaches the diaphragm support portion 102. Therefore, the length of the arm portion 123c in the circumferential direction of the diaphragm 123 is the shortest between the diaphragm support portion 102 and the central portion 123a, and in the region joined to the diaphragm support portion 102, the diaphragm support portion 102 and the central portion 123a. It is longer than the shortest length between. For this reason, it is possible to increase the bonding area between the diaphragm 123 and the diaphragm support portion 102 without increasing the radius of the diaphragm 123, and to improve the durability. Furthermore, since the width of the arm portion 123c (the length in the circumferential direction of the diaphragm 123) of the present embodiment is the longest in the region where the diaphragm support portion 102 is joined, the diaphragm 123 can be joined while the rigidity of the diaphragm 123 is kept low. Enough strength can be secured.

  The plurality of diaphragm support portions 102 are arranged at equal intervals in the circumferential direction of the opening 100a around the opening 100a of the back cavity C1. Each diaphragm support portion 102 is formed of an insulating deposited film and has a column shape. The diaphragm 123 is supported on the substrate 100 by these diaphragm support portions 102 so that the central portion 123a covers the opening 100a of the back cavity C1. Each of the diaphragm support portions 102 is located between the plurality of joint portions 162 a of the plate 162 in the radial direction of the plate 162, and is located outside the plate support portion 129 in the radial direction of the plate 162. For this reason, the rigidity of the diaphragm 123 is lower than the rigidity of the plate 162. The width of each diaphragm support 102 (the length in the circumferential direction of the diaphragm) is larger than the width of the arm portion 123c (the length in the circumferential direction of the diaphragm) between the diaphragm support 102 and the central portion 123a of the diaphragm 123. long. Therefore, sufficient bonding strength between the diaphragm 123 and the diaphragm support portion 102 is ensured. A gap C <b> 2 corresponding to the thickness of the diaphragm support 102 is formed between the substrate 100 and the diaphragm 123. The air gap C2 is necessary to balance the atmospheric pressure of the back cavity C1 with the atmospheric pressure. The gap C2 is low and the radial length of the diaphragm 123 is long so that the acoustic wave that vibrates the diaphragm 123 forms the maximum acoustic resistance in the path to the back cavity opening 100a.

  A plurality of diaphragm bumps 123 f are formed on the surface of the diaphragm 123 that faces the substrate 100. The position of the diaphragm bump 123f is indicated by a black circle in FIG. The diaphragm bump 123f is a protrusion for preventing the diaphragm 123 from adhering (sticking) to the substrate 100, and is formed by the undulation of the lower conductive film 120 constituting the diaphragm 123. That is, dimples (dents) are formed on the back side of the diaphragm bump 123f.

FIG. 18 is a partially enlarged view of the diaphragm 123. The position of the diaphragm bump 123f is also indicated by a black circle in FIG.
Between the adjacent arm portions 123c, a region in the vicinity of the outer periphery of the central portion 123a of the diaphragm 123 has a small tension, and therefore irregular vibrations are likely to occur, and warpage is easily caused by stress generated during film formation. Therefore, the diaphragm bumps 123f are arranged in the vicinity of the outer periphery of the central portion 123a of the diaphragm 123 between the adjacent arm portions 123c. The shorter the distance from the diaphragm bump 123f of the central portion 123a to the outer periphery of the central portion 123a, the better. Specifically, for example, the shortest distance from the diaphragm bump 123f of the central portion 123a to the outer periphery of the central portion 123a is desirably smaller than the maximum value of the distance between the diaphragm 123 and the plate 162, and the diaphragm bump 123f protrudes. Desirably shorter than the height. Stiction between the central portion 123a and the substrate 100 is prevented by the diaphragm bumps 123f arranged in this manner on the central portion 123a of the diaphragm 123. If the diaphragm bumps 123f arranged in this way are formed so as to protrude toward the plate 162, stiction between the central portion 123a of the diaphragm 123 and the plate 162 can be prevented.

  Since the arm portion 123c of the diaphragm 123 is less rigid than the central portion 123a, the arm portion 123c is likely to vibrate greatly even though the distance from the diaphragm support portion 102 that forms the fixed end of the diaphragm 123 is short. Therefore, the diaphragm bump 123f is also arranged on the arm portion 123c of the diaphragm 123. In addition, the arm portion 123c tends to warp in the vicinity of the end in the width direction due to stress generated during film formation. Therefore, in each arm portion 123c, diaphragm bumps 123f are arranged in the radial direction of the diaphragm 123 in a row in the vicinity of both ends in the width direction (diaphragm circumferential direction) of the arm portion 123c. The shorter the distance from the diaphragm bump 123f arranged in the vicinity of both ends in the width direction of the arm portion 123c to the end in the circumferential direction of the arm portion 123c, the better. Specifically, for example, the distance from the diaphragm bump 123f arranged in the vicinity of both ends in the width direction of the arm portion 123c to the end in the width direction of the arm portion 123c is larger than the maximum value of the distance between the diaphragm 123 and the plate 162. It is desirable that it is small, and it is desirable that the height is shorter than the height at which the diaphragm bump 123f protrudes. Further, it is desirable that the diaphragm bumps 123f arranged in the vicinity of both ends in the width direction of the arm portion 123c are closer to the end in the width direction of the arm portion 123c than the diaphragm hole 123b. Stiction between the arm portion 123c and the substrate 100 is prevented by the diaphragm bumps 123f arranged in this manner on the arm portion 123c of the diaphragm 123.

  In order to make the arm portion 123c difficult to bend, the diaphragm bumps 123f are arranged in two rows in the central region in the width direction of the arm portion 123c and arranged in the radial direction of the diaphragm 123, and with respect to the two middle rows of diaphragm bumps 123f. Four rows of diaphragms 123f are arranged so that two rows of diaphragm bumps 123f at both ends are staggered. That is, at least a part of the diaphragm bumps 123f has a direction in which the diaphragm bumps 123f closest in the radial direction of the diaphragm 123 are connected to each other (the direction of the AA line shown in FIG. 18) is the circumferential direction of the diaphragm 123 (the line BB shown in FIG. 18). Staggered so as to be inclined with respect to (direction). That is, with respect to a tangent line (BB line) with the diaphragm bump 123f on the circumference passing through the diaphragm bump 123f of the arm portion 123c centering on the center of the diaphragm 123, the contact point and the diaphragm bump 123f at the contact point to the diaphragm 123 The straight line (AA line) connecting the diaphragm bump 123f closest in the radial direction is inclined. As shown in FIG. 1 and FIG. 18, by arranging the diaphragm bumps 123 f in a staggered manner, the arm portion 123 c is not easily bent, so that stiction between the arm portion 123 c and the substrate 100 is further less likely to occur.

  In order to prevent the substrate 100 and the plate 162 from being damaged due to contact with the diaphragm bumps 123f, it is desirable that the protruding ends of the diaphragm bumps 123f have a non-sharp shape. Specifically, for example, the protruding end surface of the diaphragm bump 123f is preferably a flat surface or a spherical surface.

  The diaphragm 123 is connected to the diaphragm terminal 123e by a diaphragm lead 123d extending from one end of the plurality of arm portions 123c. Diaphragm lead 123d is narrower than arm portion 123c and is formed of lower conductive film 120 that is the same as diaphragm 123. The diaphragm lead 123d extends to the diaphragm terminal 123e through a region where the annular guard ring 125c is divided. Since the diaphragm terminal 123e and the substrate terminal 100b are short-circuited in a circuit chip (not shown) (see FIG. 4), the diaphragm 123 and the substrate 100 are at the same potential.

  When the potentials of the diaphragm 123 and the substrate 100 are different, the diaphragm 123 and the substrate 100 form a parasitic capacitance. Even in this case, the diaphragm 123 is supported by the plurality of diaphragm support portions 102. Since an air layer exists between adjacent diaphragm support portions 102, the parasitic capacitance is reduced as compared with a structure in which the diaphragm 123 is supported by a spacer having an annular wall structure.

  The plate 162 is formed of a single layer thin deposited film having conductivity as a whole, and includes a facing portion 162b and a joint portion 162a extending radially outward from the facing portion 162b. The plate 162 is supported by a plurality of columnar plate spacers 131 joined to a plurality of locations near the outer edge thereof. Further, the plate 162 is stretched in parallel with the diaphragm 123 so that the center thereof overlaps the center of the diaphragm 123. The distance from the center of the plate 162 (center of the opposing portion 162b) to the outer edge of the opposing portion 162b, that is, the shortest distance from the center of the plate 162 to the outer edge is the outer edge of the central portion 123a from the center of the diaphragm 123 (center of the central portion 123a). Is shorter than the shortest distance from the center of the diaphragm 123 to the outer edge. Therefore, the plate 162 does not face the diaphragm 123 in the region near the outer edge of the diaphragm 123 having a small amplitude. Further, since a notch is formed between the joint 162a and the joint 162a of the plate 162, the plate 162 and the diaphragm 123 face each other even in the notch region of the plate 162 corresponding to the vicinity of the outer edge of the diaphragm 123. do not do. The arm portion 123 c of the diaphragm 123 extends in the notch region of the plate 162. For this reason, the distance between both ends of the vibration of the diaphragm 123, that is, the distance over which the diaphragm 123 is stretched can be increased without increasing the parasitic capacitance.

  A plurality of plate holes 162 c that are through holes are formed in the plate 162. The plate hole 162c functions as a passage for propagating sound waves to the diaphragm 123, and also functions as a hole through which an etchant for isotropically etching the upper insulating film 130 is passed. The portion remaining after the upper insulating film 130 is etched becomes the plate spacer 131 and the annular portion 132, and the portion removed by the etching becomes the gap C <b> 3 between the diaphragm 123 and the plate 162. That is, the plate hole 162c is a through hole for allowing the etchant to reach the upper insulating film 130 so that the gap C3 and the plate spacer 131 can be formed simultaneously. Therefore, the plate hole 162c is arranged according to the height of the gap C3, the shape of the plate spacer 131, and the etching rate. Specifically, the plate holes 162c are arranged at almost equal intervals over almost the entire region of the facing portion 162b and the joining portion 162a except for the joining region with the plate spacer 131 and its periphery. As the interval between the adjacent plate holes 162c is narrowed, the width of the annular portion 132 of the upper insulating film 130 can be narrowed to reduce the chip area. On the other hand, the rigidity of the plate 162 becomes lower as the interval between the adjacent plate holes 162c is reduced.

  The plate spacer 131 is joined to a guard electrode 125a located in the same layer as the diaphragm 123 (the guard electrode 125a is made of the same lower conductive film 120 as the diaphragm 123). The plate spacer 131 includes an upper insulating film 130 that is an insulating deposited film bonded to the plate 162. The plurality of plate spacers 131 are arranged at equal intervals around the opening 100a of the back cavity C1. Since each plate spacer 131 is located in a notch area between the arm portion 123c and the arm portion 123c of the diaphragm 123, the maximum diameter of the plate 162 can be made smaller than the maximum diameter of the diaphragm 123. This increases the rigidity of the plate 162 and reduces the parasitic capacitance between the plate 162 and the substrate 100.

  The plate 162 is supported on the substrate 100 by a plurality of columnar plate support portions 129 each formed by the guard spacer 103, the guard electrode 125 a, and the plate spacer 131. That is, in this embodiment, the plate support part 129 has a structure composed of a multilayer deposited film. A gap C3 is formed between the plate 162 and the diaphragm 123 by the plate support portion 129, and a gap C3 and a gap C2 are formed between the plate 162 and the substrate 100. Since the guard spacer 103 and the plate spacer 131 are insulative, the plate 162 is insulated from the substrate 100.

  When the guard electrode 125a is not provided and the potential of the plate 162 and the potential of the substrate 100 are different, a parasitic capacitance is generated in the region where the plate 162 and the substrate 100 are opposed to each other, and particularly when there is an insulator between them. Increases the parasitic capacitance (see FIG. 4A). In this embodiment, the structure is such that the plate 162 is supported on the substrate 100 by a plurality of structural bodies 129 that are formed of the guard spacer 103, the guard electrode 125a, and the plate spacer 131 and are separated from each other. Compared to a structure in which the plate 162 is supported on the substrate 100 by an insulator having an annular wall structure, the parasitic capacitance is small.

  A plurality of protrusions (plate bumps) 162 f are provided on the surface of the plate 162 that faces the diaphragm 123. The plate bump 162f includes a silicon nitride (SiN) film bonded to the upper conductive film 160 constituting the plate 162 and a polycrystalline silicon film bonded to the silicon nitride film. The plate bump 162f prevents the diaphragm 123 from sticking (sticking) to the plate 162.

A plate lead 162d that is thinner than the joint 162a extends from the tip of the joint 162a of the plate 162 to the plate terminal 162e. The plate lead 162 d is made of the same upper conductive film 160 as the plate 162. The wiring path of the plate lead 162d overlaps the wiring path of the guard lead 125d. For this reason, the parasitic capacitance between the plate lead 162d and the substrate 100 is reduced.
The mechanical structure of the MEMS structure part of the condenser microphone 1 has been described above.

2. FIG. 4 shows a circuit configured by connecting a circuit chip and a sensor chip. A stable bias voltage is applied to the diaphragm 123 by a charge pump CP provided in the circuit chip. The higher the bias voltage, the higher the sensitivity, but the stiffness of the plate 162 is important because stiction between the diaphragm 123 and the plate 162 tends to occur.

  A sound wave transmitted from a through hole of the package (not shown) is transmitted to the diaphragm 123 through the plate hole 162c and a notch region between the arms of the plate 162. Since the sound wave having the same phase is transmitted from both surfaces to the plate 162, the plate 162 does not substantially vibrate. The sound waves transmitted to the diaphragm 123 cause the diaphragm 123 to vibrate with respect to the plate 162. When the diaphragm 123 vibrates, the capacitance of the parallel plate capacitor having the plate 162 and the diaphragm 123 as the counter electrodes varies. This variation in capacitance is input to the amplifier A of the circuit chip as a voltage signal and amplified. Since the output of the sensor chip is high impedance, an amplifier A is required in the package.

  Since the substrate 100 and the diaphragm 123 are short-circuited, as shown in FIG. 3A, parasitic capacitance is formed by the plate 162 and the substrate 100 that do not vibrate relatively unless the guard electrode 125a of the guard portion 127 is present. As shown in FIG. 3B, the output terminal of the amplifier A is connected to the guard unit 127, and a voltage follower circuit is configured by the amplifier A, so that no parasitic capacitance is formed by the plate 162 and the substrate 100. That is, by providing the guard electrode 125a between the junction 162a and the substrate 100 in the region where the junction 162a of the plate 162 and the substrate 100 face each other, the parasitic in the region where the junction 162a of the plate 162 and the substrate 100 oppose each other. Capacity can be reduced. Furthermore, since a guard lead 125d extending from the guard ring 125c connecting the guard electrodes to the guard terminal 125e is wired in a region facing the plate lead 162d extending from the plate 162, the plate lead 162d and the substrate 100 No parasitic capacitance is formed. The annular guard ring 125 c connects the plurality of guard electrodes 125 a with a substantially shortest path around the diaphragm 123. Further, by forming the guard electrode 125a longer than the joint 162a of the plate 162 in the circumferential direction of the plate 162, the parasitic capacitance is further reduced.

  Note that it is also possible to configure the one-chip capacitor microphone 1 by providing elements provided in the circuit chip such as the charge pump CP and the amplifier A in the sensor chip.

3. Manufacturing Method Next, a manufacturing method of the condenser microphone 1 will be described with reference to FIGS.

  In the process shown in FIG. 5, first, a lower insulating film 110 made of silicon oxide is formed on the entire surface of the substrate 100. Next, dimples 110a for forming the diaphragm bumps 123f are formed on the lower insulating film 110 by etching using a photoresist mask. At this time, a method is selected in which the bottom of the dimple 110a does not become sharp. For example, the dimple 110a is formed by isotropic etching, or the anisotropic etching is terminated within a range where a flat surface remains at the bottom. Next, a lower conductive film 120 made of polycrystalline silicon is formed on the surface of the lower insulating film 110 using a CVD method or the like. Then, the diaphragm bump 123f is formed on the dimple 110a. Finally, the lower layer conductive film 120 is etched using a photoresist mask to form the diaphragm 123 and the guard portion 127 made of the lower layer conductive film 120.

  Subsequently, in the process shown in FIG. 6, an upper insulating film 130 made of silicon oxide is formed on the entire surface of the lower insulating film 110 and the lower conductive film 120. Next, a dimple 130a for forming the plate bump 162f is formed on the upper insulating film 130 by etching using a photoresist mask.

  In the subsequent step shown in FIG. 7, a plate bump 162 f made of a polycrystalline silicon film 135 and a silicon nitride film 136 is formed on the surface of the upper insulating film 130. Since the silicon nitride film 136 is formed after the polycrystalline silicon film 135 is patterned by a known method, the entire exposed surface of the polycrystalline silicon film 135 protruding from the dimple 130a is covered with the silicon nitride film 136. The silicon nitride film 136 is an insulating film that prevents the diaphragm 123 and the plate 162 from being short-circuited during sticking.

  8, an upper conductive film 160 made of polycrystalline silicon is formed on the exposed surface of the upper insulating film 130 and the surface of the silicon nitride film 136 using an ECVD method or the like. Next, the plate 162, the plate lead 162d, and the etch stopper ring 161 are formed by etching the upper conductive film 160 using a photoresist mask. In this step, the plate hole 162c is not formed.

  Subsequently, in the step shown in FIG. 9, contact holes CH1, CH3, and CH4 are formed in the upper insulating film 130, and then a surface insulating film 170 made of silicon oxide is formed on the entire surface. Further, the contact hole CH2 is formed in the surface insulating film 170 by etching using a photoresist mask, and at the same time, the portion formed at the bottom of the contact holes CH1, CH3, and CH4 of the surface insulating film 170 is removed. Next, a pad conductive film 180 made of AlSi that fills each of the contact holes CH1, CH2, CH3, and CH4 is formed, and is patterned by a well-known method leaving a portion that covers the contact holes CH1, CH2, CH3, and CH4. Further, a pad protective film 190 made of silicon nitride is formed on the surface insulating film 170 and the pad conductive film 180 by the CVD method, and the pad conductive film 190 is patterned by a well-known method so as to remain only around the pad conductive film 180. The

  Subsequently, in the step shown in FIG. 10, through holes 170a corresponding to the plate holes 162c are formed in the surface insulating film 170 by anisotropic etching using a photoresist mask, and the plate holes 162c are formed in the upper conductive film 160. Is done. This process is performed continuously, and the surface insulating film 170 in which the through holes 170a are formed functions as a resist mask for the upper conductive film 160.

  Subsequently, in the step shown in FIG. 11, a surface protective film 200 made of silicon oxide is formed on the surface of the surface insulating film 170 and the pad protective film 190. At this time, the through holes 170 a and the plate holes 162 c of the surface insulating film 170 are filled with the surface protective film 200.

  Subsequently, in the step shown in FIG. 12, a bump film 210 made of Ni is formed on the surface of the pad conductive film 180 formed in each of the contact holes CH1, CH2, CH3, and CH4, and the surface of the bump film 210 is made of Au. A bump protective film 220 is formed. Further, at this stage, the back surface of the substrate 100 is ground, and the thickness of the substrate 100 is adjusted to a completed dimension.

  Subsequently, in a step shown in FIG. 13, through holes H5 in which the etch stopper ring 161 is exposed are formed in the surface protective film 200 and the surface insulating film 170 by etching using a photoresist mask.

  The film formation process on the surface side of the substrate 100 is completed through the above steps. In the state where all the film formation processes on the surface side of the substrate 100 have been completed, in the step shown in FIG. 14, a photoresist mask R1 having a through hole H6 for forming a through hole corresponding to the back cavity C1 in the substrate 100 is formed on the substrate 100. Formed on the back surface.

  Subsequently, in a step shown in FIG. 15, through holes are formed in the substrate 100 by deep substrate etching (Deep-RIE). At this time, the lower insulating film 110 serves as an etching stopper.

  Subsequently, in the step shown in FIG. 16, the photoresist mask R1 is removed, and the wall surface 100c of the through hole roughly formed in the substrate 100 is smoothed by the substrate deep etching.

  Subsequently, in the step shown in FIG. 17, an unnecessary surface protective film 200 and surface insulating film 170 on the plate 162 and the plate lead 162d are formed by isotropic etching using the photoresist mask R2 and BHF (dilute hydrofluoric acid). Further, a part of the upper insulating film 130 is removed to form the annular part 132, the plate spacer 131 and the gap C3, and a part of the lower insulating film 110 is removed to remove the guard spacer 103, the diaphragm support part 102, The annular portion 101 and the gap C2 are formed. At this time, the etchant BHF enters from each of the through hole H6 of the photoresist mask R2 and the opening 100a of the substrate 100. The contour of the upper insulating film 130 is defined by the plate 162 and the plate lead 162d. That is, the annular portion 132 and the plate spacer 131 are formed by self-alignment with the plate 162 and the plate lead 162d. As shown in FIG. 21, an undercut is formed on the end surfaces of the annular portion 132 and the plate spacer 131 by isotropic etching. The contour of the lower insulating film 110 is defined by the opening 100a of the substrate 100, the diaphragm 123, the diaphragm lead 123d, the guard electrode 125a, the guard connector 125b, and the guard ring 125c. That is, the guard spacer 103 and the diaphragm support portion 102 are formed by self-alignment with the diaphragm 123. Undercuts are formed on the end surfaces of the guard spacer 103 and the plate spacer 131 by isotropic etching (see FIGS. 21 and 22). Since the guard spacer 103 and the plate spacer 131 are formed in this step, a portion excluding the guard electrode 125a of the plate support portion 129 that supports the plate 162 on the substrate 100 is formed in this step.

  Finally, the photoresist mask R2 is removed and the substrate 100 is diced to complete the sensor chip of the condenser microphone 1 shown in FIG. When the sensor chip and the circuit chip are bonded to a package substrate (not shown), the terminals are connected by wire bonding, and a package cover (not shown) is placed on the package substrate, the capacitor microphone 1 is completed. By bonding the sensor chip to the package substrate, the back cavity C1 is hermetically closed on the back side of the substrate 100.

4). Other Embodiments FIG. 19 and FIG. 20 are diagrams showing modifications of the arrangement of the diaphragm bumps 123f. 19 and 20, the position of the diaphragm bump 123f is indicated by a black circle. As shown in FIG. 19, the direction in which all the diaphragm bumps 123f of the arm portion 123c connect the diaphragm bumps 123f that are closest in the radial direction of the diaphragm 123 (the direction of the AA line in FIG. 19) is the circumferential direction of the diaphragm 123 ( It may be arranged in a staggered manner so as to be inclined with respect to (the direction of the BB line shown in FIG. 19). Further, as shown in FIG. 20, all the diaphragm bumps 123f of the arm portion 123c may be arranged so that a line connecting the diaphragm bumps 123f closest in the radial direction of the diaphragm 123 becomes a zigzag line.

  It should be noted that the technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention. For example, the materials and dimensions shown in the above embodiment are merely examples, and descriptions of addition and deletion of processes and replacement of the process order that are obvious to those skilled in the art are omitted. 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.

The top view concerning embodiment of this invention. The typical sectional view concerning the embodiment of the present invention. The disassembled perspective view concerning embodiment of this invention. The circuit diagram concerning the embodiment of the present invention. Sectional drawing concerning embodiment of this invention. Sectional drawing concerning embodiment of this invention. Sectional drawing concerning embodiment of this invention. Sectional drawing concerning embodiment of this invention. Sectional drawing concerning embodiment of this invention. Sectional drawing concerning embodiment of this invention. Sectional drawing concerning embodiment of this invention. Sectional drawing concerning embodiment of this invention. Sectional drawing concerning embodiment of this invention. Sectional drawing concerning embodiment of this invention. Sectional drawing concerning embodiment of this invention. Sectional drawing concerning embodiment of this invention. Sectional drawing concerning embodiment of this invention. The top view concerning embodiment of this invention. The top view concerning embodiment of this invention. The top view concerning embodiment of this invention. Sectional drawing concerning embodiment of this invention. Sectional drawing concerning embodiment of this invention.

Explanation of symbols

1: condenser microphone, 100: substrate, 100a: opening, 100b: substrate terminal, 101: annular portion, 102: diaphragm support, 103: guard spacer, 110: lower insulating film, 110a: dimple, 120: lower conductive film, 123: Diaphragm, 123a: Center part, 123b: Diaphragm hole, 123c: Arm part, 123d: Diaphragm lead, 123e: Diaphragm terminal, 123f: Diaphragm bump (protrusion), 125a: Guard electrode, 125b: Guard connector, 125c: Guard Ring, 125d: guard lead, 125e: guard terminal, 127: guard part, 129: plate support part, 130: upper layer insulating film, 130a: dimple, 131: plate spacer, 132: annular part, 160: upper layer conductive film, 161 : Etches Pappering, 162: plate, 162a: bonding portion, 162b: facing portion, 162c: plate hole, 162d: plate lead, 162e: plate terminal, 162f: plate bump, 170: surface insulating film, 180: pad conductive film, 190: Pad protective film, 200: surface protective film, 210: bump film, 220: bump protective film, A: amplifier, C1: back cavity, C2: air gap, C3: air gap, CP: charge pump

Claims (6)

A substrate,
A diaphragm comprising a deposited film on the substrate, having conductivity, and having a central portion and a plurality of arms extending radially outward from the central portion;
A plate comprising a deposited film on the substrate and having conductivity;
A diaphragm support portion that is formed of a deposited film on the substrate, is bonded to each of the plurality of arm portions, and supports the diaphragm with a gap between the plates,
With
A plurality of protrusions for preventing the diaphragm from adhering to the substrate or the plate are formed on the arm of the diaphragm,
The capacitance formed by the diaphragm and the plate changes as the diaphragm vibrates with respect to the plate.
Vibration transducer. The protrusion is formed in a region in the vicinity of the circumferential end of the diaphragm of the arm portion,
The vibration transducer according to claim 1. The array of the plurality of protrusions is an array in which the direction connecting the protrusions closest in the radial direction of the diaphragm is inclined with respect to the circumferential direction of the diaphragm.
The vibration transducer according to claim 1. The protrusions are staggered,
The vibration transducer according to claim 1. A substrate,
A diaphragm comprising a deposited film on the substrate, having conductivity, and having a central portion and a plurality of arms extending radially outward from the central portion;
A plate comprising a deposited film on the substrate and having conductivity;
A diaphragm support portion that is formed of a deposited film on the substrate, is bonded to each of the plurality of arm portions, and supports the diaphragm with a gap between the plates,
With
A plurality of protrusions for preventing the diaphragm from adhering to the substrate or the plate are formed in a region near the outer periphery of the central portion,
The capacitance formed by the diaphragm and the plate changes as the diaphragm vibrates with respect to the plate.
Vibration transducer. The projection has a non-sharp tip;
The vibration transducer according to any one of claims 1 to 5.

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