Piezoelectric sensor

Abstract

To prevent the occurrence of connection failure between a wiring layer and an electrode film.SOLUTION: A plurality of contact holes 81a are formed to overlap an electrode film 62 when viewed from a normal direction relating to the surface direction of a piezoelectric film 50. The plurality of contact holes 81a have different lengths in one direction of surface directions of the piezoelectric film 50, and as the length of the contact hole in the one direction increases, the depth of the contact hole increases. The electrode film 62 is exposed from a bottom of one contact hole 81a of the plurality of contact holes 81a. A wiring layer 81b is provided in each of the plurality of contact holes 81a so as to be electrically connected to portions of the electrode film 62 exposed from the contact holes 81a.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a piezoelectric sensor.

Background Art

[0002] Conventionally, a piezoelectric sensor using a piezoelectric film made of scandium aluminum nitride (hereinafter also simply referred to as ScAlN) or the like and an electrode film made of molybdenum or the like has been proposed (see, for example, Patent Document 1). Specifically, this piezoelectric sensor is configured by laminating a piezoelectric film and an electrode film on a support. And in this piezoelectric sensor, a contact hole for exposing the electrode film in the piezoelectric film is formed, and a wiring layer connected to the electrode film is formed in the contact hole.

[0003] Such a piezoelectric sensor is manufactured as follows. That is, a wafer-shaped support having a plurality of chip formation regions is prepared, and a piezoelectric film and an electrode film are formed on the support. And such a piezoelectric sensor is manufactured by forming a contact hole and a wiring layer in each chip formation region and then dividing each chip formation region into chips. Note that the contact hole is formed by dry etching.

[0004] More specifically, in this manufacturing method, when forming a contact hole for exposing an electrode film disposed at a deep position, a stopper electrode film for an etching stopper is disposed above this electrode film. Note that the stopper electrode film has the same configuration as other electrode films disposed in the same layer. And in this manufacturing method, a contact hole for exposing an electrode film disposed at a deep position is formed by performing dry etching a plurality of times using the stopper electrode film.

[0005] In this manufacturing method, when forming contact holes, the etching rate may vary in each chip formation region. However, the stopper electrode film is used to absorb the variation in the etching rate in each chip formation region. As a result, even if the etching rate varies in each chip formation region, it is possible to suppress the occurrence of a connection failure between the wiring layer disposed in the contact hole and the electrode film due to the contact hole penetrating the electrode film.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] By the way, such a piezoelectric sensor is applied to, for example, a microphone having a vibration region. In this case, an electrode film is also disposed in the vibration region. However, the electrode film disposed in the vibration region is desirably made thin so as not to easily inhibit the deformation of the vibration region.

[0008] However, when the electrode film in the vibration region is made thinner, the stopper electrode film as an etching stopper also becomes thinner. Therefore, depending on the variation in the etching rate when forming the contact hole, there is a possibility that the contact hole may penetrate the stopper electrode film when performing dry etching up to the stopper electrode film. In particular, when the piezoelectric film is made of ScAlN and the electrode film is made of molybdenum, the difference in the etching rate between the piezoelectric film and the electrode film is small. Therefore, in the chip formation region with a high etching rate, the contact hole may penetrate the stopper electrode film. Further, when the Sc concentration of ScAlN constituting the piezoelectric film is increased to improve the sensitivity, the difference in the etching rate between the piezoelectric film and the electrode film becomes even smaller, so the possibility that the contact hole penetrates the stopper electrode film becomes higher. For this reason, in the above manufacturing method, there is a possibility that the connection failure between the wiring layer and the electrode film cannot be sufficiently suppressed.

[0009] An object of the present disclosure is to provide a piezoelectric sensor capable of suppressing the occurrence of a connection failure between a wiring layer and an electrode film.

Means for Solving the Problems

[0010] According to one aspect of the present disclosure, a piezoelectric sensor includes electrode films (61, 62), a piezoelectric film (50) laminated on the electrode films and having contact holes (81a, 82a) formed therein to expose the electrode films, and wiring layers (81b, 82b) disposed in the contact holes and electrically connected to the electrode films. The contact holes are formed in plurality so as to overlap the same electrode film in the normal direction with respect to the plane direction of the piezoelectric film. The plurality of contact holes have different lengths (d1 to d3) in one direction in the plane direction of the piezoelectric film, and the depth is made deeper as the length in one direction is longer. The electrode film is exposed from the bottom of one of the plurality of contact holes, and the wiring layer is disposed in each of the plurality of contact holes and is electrically connected to the portion of the electrode film exposed from the contact hole.

[0011] According to this, a plurality of contact holes having different lengths in one direction are formed, and the electrode film is exposed from the bottom of one contact hole. Therefore, it is possible to suppress the occurrence of a connection failure between the wiring layer and the electrode film. In other words, when manufacturing the piezoelectric sensor, even if the etching rate varies in each chip formation region, since the electrode film is exposed from the bottom of one contact hole, it is possible to suppress the occurrence of a connection failure between the wiring layer and the electrode film.

[0012] Note that the reference numerals in parentheses attached to each component etc. indicate an example of the correspondence relationship between the component etc. and the specific components etc. described in the embodiments described later.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

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Figure 7A

Figure 7B

Figure 7C

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Figure 9

Figure 10

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Figure 12

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Figure 16

Figure 17

Figure 18

Mode for Carrying Out the Invention

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following embodiments, parts that are the same or equivalent to each other will be described with the same reference numerals.

[0015] (First Embodiment) The first embodiment will be described with reference to the drawings. Note that the piezoelectric sensor of this embodiment is preferably used as a microphone, for example. First, the overall configuration of the piezoelectric sensor will be described.

[0016] As shown in FIGS. 1 and 2, the piezoelectric sensor includes a support 10 and a vibrating portion 20, and has a rectangular planar shape. The support 10 includes a support substrate 11 having a first surface 11a and a second surface 11b, and an insulating film 12 formed on the support substrate 11. The support substrate 11 is made of, for example, a silicon substrate or the like, and the insulating film 12 is made of an oxide film or the like. In FIG. 2, the upper electrode film 63, the first electrode portion 81, the second electrode portion 82, etc., which will be described later, are omitted.

[0017] The vibrating portion 20 constitutes a sensing portion 30 that outputs a pressure detection signal corresponding to a sound pressure or the like as pressure, and is disposed on the support 10. A recess 10a is formed in the support 10 to float the inner edge side of the vibrating portion 20. For this reason, the vibrating portion 20 has a configuration including a support region 21a disposed on the support 10 and a floating region 21b that is connected to the support region 21a and floats on the recess 10a. The recess 10a of the present embodiment has a rectangular planar shape at the opening end on the vibrating portion 20 side (hereinafter, also simply referred to as the opening end of the recess 10a). Therefore, the entire floating region 21b has a substantially rectangular planar shape.

[0018] The floating region 21b of the present embodiment is divided by slits 41 so that four vibrating regions 22 are formed. In the present embodiment, two slits 41 are formed so as to pass through the central portion C of the floating region 21b and extend toward the opposite corner portions of the floating region 21b. In other words, the slits 41 extend from each corner portion of the floating region 21b having a rectangular planar shape toward the central portion C, and the slits 41 intersect at the central portion C. As a result, the floating region 21b is separated into four vibrating regions 22 having a substantially planar triangular shape. Although not particularly limited, in the present embodiment, the interval between the vibrating regions 22 (that is, the average width of the slits 41) is about 1 μm. Hereinafter, as shown in FIG. 1, the surface of the vibrating region 22 opposite to the support 10 is referred to as a first surface 22a, and the surface of the vibrating region 22 on the support 10 side is referred to as a second surface 22b for description. The first surface 22a and the second surface 22b of the vibrating region 22 are parallel to each other.

[0019] Since each vibration region 22 is configured by dividing the floating region 21b as described above, one end is a fixed end supported by the support 10 (that is, the support region 21a), and the other end is a free end and is a cantilever. That is, each vibration region 22 is in a state of being connected to the support region 21a and is in a state of being simply supported.

[0020] The vibrating portion 20 of the present embodiment has a configuration including a piezoelectric film 50 and an electrode film 60 connected to the piezoelectric film 50. Specifically, the piezoelectric film 50 has a lower piezoelectric film 51 and an upper piezoelectric film 52 laminated on the lower piezoelectric film 51. Further, the electrode film 60 has a lower electrode film 61 disposed below the lower piezoelectric film 51, an intermediate electrode film 62 disposed between the lower piezoelectric film 51 and the upper piezoelectric film 52, and an upper electrode film 63 disposed on the upper piezoelectric film 52. That is, the vibrating portion 20 has a bimorph structure in which the lower piezoelectric film 51 is sandwiched between the lower electrode film 61 and the intermediate electrode film 62, and the upper piezoelectric film 52 is sandwiched between the intermediate electrode film 62 and the upper electrode film 63.

[0021] Furthermore, the vibrating portion 20 of the present embodiment has a base film 70 on which the lower piezoelectric film 51 and the lower electrode film 61 are disposed. That is, on the support 10, the piezoelectric film 50 and the electrode film 60 are disposed via the base film 70. The base film 70 is not necessarily required, but is provided to facilitate crystal growth when forming the lower piezoelectric film 51 and the like.

[0022] The lower piezoelectric film 51 and the upper piezoelectric film 52 are made of ScAlN. The lower electrode film 61, the intermediate electrode film 62, the upper electrode film 63, etc. are made of molybdenum, copper, platinum, titanium, aluminum, etc. The base film 70 is made of AlN or the like. Also, the piezoelectric film 50 has a thickness of about several thousand nm, and the electrode film 60 has a thickness of about 20 nm. That is, the electrode film 60 is actually made sufficiently thin with respect to the piezoelectric film 50.

[0023] Further, in each vibration region 22 of the present embodiment, the fixed end side is the first region R1, and the free end side is the second region R2. The lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 are formed in the first region R1 and the second region R2, respectively. However, the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 formed in the first region R1 are separated from and insulated from the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 formed in the second region R2. Further, the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 formed in the first region R1 are appropriately extended to the support region 21a.

[0024] In the support region 21a of the vibration part 20, a first electrode part 81 electrically connected to the intermediate electrode film 62 formed in the first region R1 and a second electrode part 82 electrically connected to the lower electrode film 61 and the upper electrode film 63 formed in the first region R1 are formed. Note that FIG. 1 is a cross-sectional view taken along the line I-I in FIG. 2, showing different cross-sections of the vibration region 22 on the left side of the paper surface and the vibration region 22 on the right side of the paper surface.

[0025] The first electrode part 81 is configured by arranging a first wiring layer 81b electrically connected to the intermediate electrode film 62 in a contact hole 81a for the intermediate electrode film that penetrates the upper piezoelectric film 52 and exposes the intermediate electrode film 62. The second electrode part 82 is configured by arranging a second wiring layer 82b electrically connected to the lower electrode film 61 and the upper electrode film 63 in a contact hole 82a for the lower electrode film that penetrates the upper piezoelectric film 52 and the lower piezoelectric film 51 and exposes the lower electrode film 61.

[0026] Details of the first electrode part 81 and the second electrode part 82 will be described later. Note that the first wiring layer 81b and the second wiring layer 82b are configured using molybdenum, copper, platinum, titanium, aluminum, etc., in the same manner as the upper electrode film 63 and are connected to the upper electrode film 63. Therefore, it can be said that the first wiring layer 81b and the second wiring layer 82b are constituted by a part of the upper electrode film 63.

[0027] Further, the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 formed in the second region R2 are not electrically connected to the respective electrode portions 81 and 82 and are in a floating state. Therefore, although the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 formed in the second region R2 are not necessarily required, in the present embodiment, they are provided to protect the portions of the lower piezoelectric film 51 and the upper piezoelectric film 52 located in the second region R2.

[0028] The lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 formed in the first region R1 are divided by the slit 41 in each vibration region 22. That is, the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 formed in the first region R1 of each vibration region 22 are not formed so as to straddle each vibration region 22. And the lower electrode film 61, the intermediate electrode film 62, and the upper electrode film 63 formed in the first region R1 of each vibration region 22 are appropriately connected via an electrode film (not shown) formed in the support region 21a.

[0029] Specifically, the sensing unit 30 of the present embodiment is configured to output the change in charge in the four vibration regions 22 as one pressure detection signal. That is, the four vibration regions 22 are electrically connected in series. More specifically, each vibration region 22 has a bimorph structure, and each lower electrode film 61, each intermediate electrode film 62, and each upper electrode film 63 formed in each vibration region 22 are connected in parallel, while the vibration regions 22 are connected in series.

[0030] The above is the basic configuration of the piezoelectric sensor in the present embodiment. Next, the configurations of the first electrode portion 81 and the second electrode portion 82 in the piezoelectric sensor of the present embodiment will be specifically described. Note that the first electrode portion 81 and the second electrode portion 82 of the present embodiment have the same configuration except that the depths of the contact hole 81a for the intermediate electrode film and the contact hole 82a for the lower electrode film are different. Therefore, hereinafter, the configuration of the first electrode portion 81 will be described, but the configuration of the second electrode portion 82 is the same.

[0031] As shown in FIGS. 1, 3, and 4, a plurality of contact holes 81a for the intermediate electrode film are formed with respect to the connected intermediate electrode film 62. In other words, the plurality of contact holes 81a for the intermediate electrode film are formed so as to overlap the same intermediate electrode film 62 in the normal direction with respect to the plane direction of the piezoelectric film 50 (hereinafter, also simply referred to as the normal direction). Note that, in other words, the normal direction can also mean when viewed from the normal direction with respect to the plane direction of the piezoelectric film 50. In this embodiment, three contact holes, i.e., first to third contact holes 811a to 813a, are formed as the contact holes 81a for the intermediate electrode film. Note that the first to third contact holes 811a to 813a are formed by performing dry etching as described later.

[0032] In the first to third contact holes 811a to 813a of this embodiment, the openings are each rectangular. Hereinafter, one direction in the plane direction of the piezoelectric film 50 will be referred to as the first direction, and a direction intersecting the first direction in the plane direction of the piezoelectric film 50 will be referred to as the second direction. Note that in this embodiment, the first direction and the second direction are orthogonal to each other. For example, in FIG. 3, the horizontal direction of the paper surface is the first direction, and the vertical direction of the paper surface is the second direction.

[0033] In this embodiment, the openings of the first to third contact holes 811a to 813a are rectangular with the first direction being the short side direction and the second direction being the long side direction. In this embodiment, since the first to third contact holes 811a to 813a are formed in this way, the first direction can also be said to be the width direction of the narrowest portion of the first to third contact holes 811a to 813a in the plane direction of the piezoelectric film 50.

[0034] In addition, the first to third contact holes 811a to 813a are formed such that the lengths d1 to d3 in the first direction are different from each other and the lengths L1 to L3 in the second direction are equal. In the present embodiment, the first to third contact holes 811a to 813a are formed such that the lengths d1 to d3 in the first direction become shorter in the order of the first contact hole 811a, the second contact hole 812a, and the third contact hole 813a. In other words, in the first to third contact holes 811a to 813a, the length d1 in the first direction in the first contact hole 811a is the longest, and the length d3 in the first direction in the third contact hole 813a is the shortest. And in the first to third contact holes 811a to 813a, the length d2 in the first direction in the second contact hole 812a is between the lengths d1 and d3 in the first direction in the first and third contact holes 811a and 813a.

[0035] The first to third contact holes 811a to 813a have different depths respectively. Specifically, the first to third contact holes 811a to 813a are formed by dry etching, and due to the microloading effect, the etching rate becomes higher as the lengths d1 to d3 in the first direction (i.e., the width of the narrowest part) are longer. For this reason, the first to third contact holes 811a to 813a are formed such that the depths become shallower in the order of the first contact hole 811a, the second contact hole 812a, and the third contact hole 813a. In other words, in the first to third contact holes 811a to 813a, the depth of the first contact hole 811a is the deepest, the depth of the third contact hole 813a is the shallowest, and the depth of the second contact hole 812a is between the depths of the first and third contact holes 811a and 813a. That is to say, it can also be said that the first to third contact holes 811a to 813a are contact holes formed in a state where the etching rates are different.

[0036] In FIG. 4, the first to third contact holes 811a to 813a are formed such that the intermediate electrode film 62 is exposed from the bottom of the first contact hole 811a. The second contact hole 812a and the third contact hole 813a are not formed to expose the intermediate electrode film 62.

[0037] The first wiring layer 81b is disposed so as to enter the first to third contact holes 811a to 813a from above the piezoelectric film 50. In the portion shown in FIG. 4, the first wiring layer 81b disposed in the first contact hole 811a that exposes the intermediate electrode film 62 is connected to the intermediate electrode film 62.

[0038] In FIG. 4, although the first contact hole 811a shows a structure in which the intermediate electrode film 62 is exposed, as will be described later, the second contact hole 812a or the third contact hole 813a may be formed to expose the intermediate electrode film 62. The first wiring layer 81b is connected to the intermediate electrode film 62 through any one of the first to third contact holes 811a to 813a.

[0039] As described above, the second electrode portion 82 has the same configuration as the above except that the contact hole 82a for the lower electrode film has a different depth from the contact hole 81a for the intermediate electrode film. Briefly, as shown in FIG. 1, the first to third contact holes 821a to 823a are formed in the piezoelectric film 50 as the contact holes 82a for the lower electrode film. The second wiring layer 82b is connected to the lower electrode film 61 through any one of the first to third contact holes 821a to 823a. In FIG. 1, a diagram showing that the second wiring layer 82b is connected to the lower electrode film 61 through the first contact hole 821a is shown.

[0040] The above is the configuration of the first electrode portion 81 and the second electrode portion 82 in the present embodiment. Next, a method for manufacturing a piezoelectric sensor including a method for manufacturing the first electrode portion 81 and the second electrode portion 82 will be described.

[0041] First, as shown in FIG. 5, a wafer-like support 10 having a plurality of chip formation regions RA partitioned by dicing lines DL is prepared. Then, a base film 70, a lower electrode film 61, a lower piezoelectric film 51, an intermediate electrode film 62, an upper piezoelectric film 52, an upper electrode film 63, a first electrode portion 81, a second electrode portion 82, etc. are sequentially arranged on the support 10. Thereafter, slits 41, recesses 10a, etc. are formed, and the piezoelectric sensor is manufactured by dividing each chip formation region RA into chip units along the dicing line DL.

[0042] Hereinafter, the manufacturing method of the first electrode portion 81 and the second electrode portion 82 will be specifically described. Note that the manufacturing methods of the first electrode portion 81 and the second electrode portion 82 are the same except that the depth is changed by adjusting the time when dry etching described later is performed. For this reason, hereinafter, the manufacturing method of the first electrode portion 81 will be described as an example.

[0043] When manufacturing the first electrode portion 81, a mask (not shown) is appropriately arranged, and first to third contact holes 811a to 813a as contact holes 81a for the intermediate electrode film are formed by dry etching in each chip formation region RA. At this time, the etching rates for the first to third contact holes 811a to 813a depend on the lengths d1 to d3 in the first direction (that is, the width of the narrowest part of the opening), as shown in FIG. 6, and the longer the lengths d1 to d3 in the first direction in the opening, the higher the etching rate. Therefore, when the lengths d1 to d3 in the first direction are different as in the first to third contact holes 811a to 813a, the depths of the first to third contact holes 811a to 813a become shallower in the order of the first contact hole 811a, the second contact hole 812a, and the third contact hole 813a.

[0044] Also, when forming the first to third contact holes 811a to 813a as contact holes 81a for the intermediate electrode film by dry etching in each chip formation region RA, a bias or the like occurs in the ion beam for performing the dry etching. For this reason, when performing dry etching, a difference occurs in the etching rate in each chip formation region RA.

[0045] Therefore, for example, in the chip formation region RA that is dry-etched at a low etching rate, as shown in FIG. 7A, the first contact hole 811a is formed to expose the intermediate electrode film 62, and the second and third contact holes 812a and 813a are formed so as not to reach the intermediate electrode film 62. In the chip formation region RA that is dry-etched at a high etching rate, as shown in FIG. 7B, the first and second contact holes 811a and 812a penetrate the intermediate electrode film 62, and the third contact hole 813a is formed to expose the intermediate electrode film 62. In the chip formation region RA that is dry-etched at an etching rate between the low etching rate and the high etching rate, as shown in FIG. 7C, the first contact hole 811a penetrates the intermediate electrode film 62, the second contact hole 812a is formed to expose the intermediate electrode film 62, and the third contact hole 813a is formed so as not to reach the intermediate electrode film 62. However, in the present embodiment, in the chip formation region RA having any etching rate, any one of the first to third contact holes 811a to 813a is formed to expose the intermediate electrode film 62.

[0046] Therefore, when the first wiring layer 81b is formed thereafter, the first wiring layer 81b is connected to the intermediate electrode film 62 through any one of the contact holes 811a to 813a. For this reason, in the piezoelectric sensors obtained from the respective chip formation regions RA, it is possible to suppress the occurrence of a connection failure between the first wiring layer 81b and the intermediate electrode film 62. That is, in the piezoelectric sensor of the present embodiment, the first to third contact holes 811a to 813a having different lengths d1 to d3 in the first direction are formed. For this reason, even if the first contact hole 811a penetrates the intermediate electrode film 62, if the second contact hole 812a is formed so as to expose the intermediate electrode film 62, the first wiring layer 81b and the intermediate electrode film 62 can be connected through the second contact hole 812a. Similarly, even if the first contact hole 811a and the second contact hole 812a penetrate the intermediate electrode film 62, if the third contact hole 813a is formed so as to expose the intermediate electrode film 62, the first wiring layer 81b and the intermediate electrode film 62 can be connected through the third contact hole 813a.

[0047] Although not particularly shown, the same applies to the relationship between the contact hole 82a for the lower electrode film constituting the second electrode portion 82 and the second wiring layer 82b. Further, for example, when the first contact hole 811a penetrates the intermediate electrode film 62 as shown in FIG. 7B, the intermediate electrode film 62 is exposed from the side surface of the first contact hole 811a. For this reason, when the first wiring layer 81b is formed in the first contact hole 811a, it is also conceivable that the first wiring layer 81b and the intermediate electrode film 62 are electrically connected at the side surface of the first contact hole 811a. However, the intermediate electrode film 62 is very thin, about 20 nm, and sufficient electrical connection cannot be achieved only by the contact at this portion.

[0048] As described above, in this embodiment, as the contact hole 81a for the intermediate electrode film, the first to third contact holes 811a to 813a having different widths (i.e., different lengths d1 to d3 in the first direction) are formed. Therefore, when manufacturing the piezoelectric sensor, even if the etching rate varies in each chip formation region, any one of the first to third contact holes 811a to 813a is formed so as to expose the intermediate electrode film 62. Accordingly, it is possible to suppress the occurrence of a connection failure between the first wiring layer 81b and the intermediate electrode film 62.

[0049] Similarly, as the contact hole 82a for the lower electrode film, the first to third contact holes 821a to 823a having different widths (i.e., different lengths in the first direction) are formed. Therefore, when manufacturing the piezoelectric sensor, even if the etching rate varies in each chip formation region, any one of the first to third contact holes 821a to 823a is formed so as to expose the lower electrode film 61. Accordingly, it is possible to suppress the occurrence of a connection failure between the second wiring layer 82b and the lower electrode film 61.

[0050] (Second Embodiment) The second embodiment will be described. This embodiment is different from the first embodiment in that the shapes of the first to third contact holes 811a to 813b are changed. Since the other aspects are the same as those of the first embodiment, the description thereof is omitted here. Hereinafter, as in the first embodiment, the configuration of the first electrode portion 81 will be described, but the configuration of the second electrode portion 82 is the same.

[0051] Similar to the first embodiment, the piezoelectric sensor of this embodiment has, as shown in FIG. 8, the lengths d1 to d3 in the first direction of the first to third contact holes 811a to 813a shortened in the order of the first contact hole 811a, the second contact hole 812a, and the third contact hole 813a. However, in this embodiment, the lengths L1 to L3 in the second direction of the first to third contact holes 811a to 813a are lengthened in the order of the first contact hole 811a, the second contact hole 812a, and the third contact hole 813a.

[0052] Specifically, for the first to third contact holes 811a to 813a, the lengths d1 to d3 in the first direction and the lengths L1 to L3 in the second direction are adjusted so that the areas of the openings are equal. Here, the equality of the areas of the openings includes some manufacturing errors and includes a deviation in the area difference of about ±30%.

[0053] According to the present embodiment described above, as the contact holes 81a for the intermediate electrode film, the first to third contact holes 811a to 813a having different widths are formed. Also, as the contact holes 82a for the lower electrode film, the first to third contact holes 821a to 823a having different widths are formed. Therefore, the same effects as those of the first embodiment can be obtained.

[0054] (1) In this embodiment, the areas of the openings of the first to third contact holes 811a to 813 are made equal. Therefore, when the intermediate electrode film 62 is exposed from the first contact hole 811a, when the intermediate electrode film 62 is exposed from the second contact hole 812a, or when the intermediate electrode film 62 is exposed from the third contact hole 813a, the areas of the exposed intermediate electrode film 62 are substantially equal. Therefore, even if the first wiring layer 81b is connected to the intermediate electrode film 62 through any of the contact holes 811a to 813a, the contact resistance can be made substantially the same.

[0055] In other words, as shown in FIG. 9, even if the contact hole that changes the etching rate to expose the intermediate electrode film 62 changes, the contact resistance can be made substantially equal. For this reason, it is possible to suppress variations in the contact resistance due to variations in the etching rate. That is, the yield can be improved. In FIG. 9, the first contact hole 811a means a case where the intermediate electrode film 62 is exposed from the first contact hole 811a, the second contact hole 812a means a case where the intermediate electrode film 62 is exposed from the second contact hole 812a, and the third contact hole 813a means a case where the intermediate electrode film 62 is exposed from the third contact hole 811a.

[0056] (Modification of the Second Embodiment) A modification of the second embodiment will be described. In the above second embodiment, a plurality of contact holes having equal widths may be formed, and the area of the opening may be made equal as a whole. For example, as shown in FIG. 10, one first contact hole 811a, two second contact holes 812a, and four third contact holes 813a may be provided. The first to third contact holes 813a have the lengths d1 to d3 in the first direction shortened in the order of the first contact hole 811a, the second contact hole 812a, and the third contact hole 813a. Also, the first to third contact holes 813a have the lengths L1 to L3 in the second direction shortened in the order of the first contact hole 811a, the second contact hole 812a, and the third contact hole 813a. And in this configuration, by adjusting the number, the total area of the first to third contact holes 811a to 813a is made equal.

[0057] (Third Embodiment) A description will be given of the third embodiment. This embodiment is different from the first embodiment in the shapes and arrangement methods of the first to third contact holes 811a to 813a. Since other aspects are the same as those of the first embodiment, the description thereof will be omitted here. Hereinafter, the configuration of the first electrode portion 81 will be described in the same manner as in the first embodiment, and the same applies to the configuration of the second electrode portion 82.

[0058] As shown in FIG. 11, in the piezoelectric sensor of this embodiment, the opening of the first contact hole 811a is circular. The second contact hole 812a and the third contact hole 813a have an annular opening so as to surround the first contact hole 811a, with the first contact hole 811a as a reference contact hole. Specifically, the first to third contact holes 811a to 813a are arranged concentrically in a concentric frame shape.

[0059] Also, in this embodiment, the lengths d1 to d3 in the first direction of the first to third contact holes 811a to 813a are adjusted so that the areas of the openings are equal, in the same manner as in the second embodiment. Note that the length d1 in the first direction in the first contact hole 811a can also be referred to as the diameter, and the lengths d2 and d3 in the first direction in the second contact hole 812a and the third contact hole 813a can also be referred to as the radial lengths.

[0060] According to the present embodiment described above, the first to third contact holes 811a to 813a having different widths are formed as the contact holes 81a for the intermediate electrode film. Also, the first to third contact holes 821a to 823a having different widths are formed as the contact holes 82a for the lower electrode film. Therefore, the same effects as those of the first embodiment can be obtained.

[0061] (1) In this embodiment, the first to third contact holes 811a to 813a are formed concentrically. Therefore, compared with the case where the first to third contact holes 811a to 813a are arranged side by side along the plane direction, the area required to form the first to third contact holes 811a to 813a can be reduced. Thus, the piezoelectric sensor can be miniaturized.

[0062] (Modification of the Third Embodiment) The modification of the above third embodiment will be described. In the above third embodiment, as shown in FIG. 12, the opening of the first contact hole 811a may be rectangular. And the openings of the second and third contact holes 812a and 813a may be square frame-shaped so as to surround the first contact hole 811a. However, the first to third contact holes 811a to 813a are arranged in a concentric frame shape.

[0063] Also, although not particularly shown, the first contact hole 811a may be another polygon, and the second and third contact holes 812a and 813a may be polygon frame-shaped so as to surround the first contact hole 811a and arranged in a concentric frame shape.

[0064] (Fourth Embodiment) The fourth embodiment will be described. This embodiment is different from the third embodiment in that the shapes of the first to third contact holes 811a to 813a are changed. Since the rest is the same as the first embodiment, the description is omitted here. Hereinafter, similar to the above first embodiment, the configuration of the first electrode portion 81 will be described, but the same also applies to the configuration of the second electrode portion 82.

[0065] In this embodiment, as shown in FIG. 13, the opening of the first contact hole 811a is semicircular. And the openings of the second and third contact holes 812a and 813a are in a state where a part of the annular shape is missing. That is, the second and third contact holes 812a and 813a are formed along a part of the outer edge of the first contact hole 811a, and are not formed in a frame shape surrounding the entire first contact hole 811a. In other words, the second and third contact holes 812a and 813a are shaped to have end portions 812b and 813b connecting the inner edge portion on the side of the first contact hole 811a and the outer edge portion on the side opposite to the first contact hole 811a. That is, the openings of the second and third contact holes 812a and 813a are shaped to have end portions 813b and 813b in a direction along the outer edge of the first contact hole 811a. Note that in this embodiment, the first contact hole 811a has a semicircular opening, but it may be circular as in the third embodiment. Also, in this embodiment, the second and third contact holes 812a and 813a correspond to other contact holes.

[0066] And the first wiring layer 81b is also disposed at the end portions 812b and 813b of the first to third contact holes 811a to 813a. Therefore, as shown in FIGS. 14 to 16, the portion disposed on the piezoelectric film 50 and the portion disposed in the first to third contact holes 811a to 813a are configured to have a portion connected by a single step portion D.

[0067] According to the present embodiment described above, as the contact holes 81a for the intermediate electrode film, the first to third contact holes 811a to 813a having different widths are formed. Also, as the contact holes 82a for the lower electrode film, the first to third contact holes 821a to 823a having different widths are formed. Therefore, the same effects as those of the first embodiment can be obtained.

[0068] (1) In this embodiment, the second and third contact holes 812a and 813a are shaped along a part of the outer edge of the first contact hole 811a, and have end portions 812b and 813b in the direction along this outer edge. And the wiring layer 81b is also disposed at the end portions 812b and 813b, so that the portion disposed on the piezoelectric film 50 and the portion disposed on the first to third contact holes 811a to 813a are connected by a single step portion D. Therefore, even if the first wiring layer 81b is connected to the intermediate electrode film 62 via any of the first to third contact holes 811a to 813a, the number of step portions D is the same, and variation in the wiring resistance of the first wiring layer 81b can be suppressed.

[0069] (Modification of the Fourth Embodiment) A modification of the above fourth embodiment will be described. In the above fourth embodiment, as shown in FIGS. 17 and 18, the opening of the first contact hole 811a may be rectangular. And as shown in FIG. 17, the second and third contact holes 812a and 813a may be substantially U-shaped along a part of the outer edge of the first contact hole 811a. Also, as shown in FIG. 18, the second and third contact holes 812a and 813a may be substantially L-shaped along a part of the outer edge of the first contact hole 811a.

[0070] (Other Embodiments) Although the present disclosure has been described in accordance with the embodiments, it is understood that the present disclosure is not limited to the embodiments and structures. The present disclosure includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, and further other combinations and forms including only one element, more than one, or less than one of them, are within the scope and thinking range of the present disclosure.

[0071] For example, each of the above embodiments can also be applied to other piezoelectric sensors that do not have the vibrating portion 20 instead of the piezoelectric sensor having the vibrating portion 20. Also, the piezoelectric film 50 may be made of AlN or the like.

[0072] Also, in each of the above embodiments, the shape of the slit 41 can be appropriately changed, and the vibration region 22 may be in a doubly supported state.

[0073] Furthermore, in each of the above embodiments, the number of layers of the piezoelectric film 50 and the number of layers of the electrode film 60 can be appropriately changed. And, in each of the above embodiments, the number of contact holes 81a for the intermediate electrode film may be two, or may be four or more. Similarly, in each of the above embodiments, the number of contact holes 82a for the lower electrode film may be two, or may be four or more.

[0074] Also, in the above-described third and fourth embodiments, the first to third contact holes 811a to 813a may have different opening areas.

[0075] [Disclosure of the present invention] The above-described present disclosure can be grasped, for example, from the viewpoints shown below.

[0076] [First viewpoint] A piezoelectric sensor, an electrode film (61, 62), a piezoelectric film (50) laminated on the electrode film and having contact holes (81a, 82a) formed to expose the electrode film, and a wiring layer (81b, 82b) disposed in the contact holes and electrically connected to the electrode film, wherein a plurality of the contact holes are formed so as to overlap the same electrode film in a normal direction with respect to a plane direction of the piezoelectric film, the plurality of contact holes have different lengths (d1 to d3) in one direction in the plane direction of the piezoelectric film, and the greater the length in the one direction, the deeper the depth, the electrode film is exposed from the bottom of one of the plurality of contact holes, The wiring layer is disposed in each of the plurality of contact holes and is electrically connected to a portion of the electrode film that is exposed from the contact hole, a piezoelectric sensor.

[0077] [Second aspect] The piezoelectric sensor according to the first aspect, wherein the openings of the plurality of contact holes have equal areas.

[0078] [Third aspect] The piezoelectric sensor according to the first or second aspect, wherein the plurality of contact holes are formed in a concentric frame shape with one contact hole as a reference contact hole.

[0079] [Fourth aspect] The plurality of contact holes have one contact hole as a reference contact hole, and when a contact hole different from the reference contact hole is used as another contact hole, in the normal direction, the other contact hole is formed along a part of the outer edge of the reference contact hole, the other contact hole has ends (812b, 813b) in a direction along the outer edge, The piezoelectric sensor according to the first or second aspect, wherein the wiring layer is also disposed at the ends.

[0080] [Fifth aspect] The piezoelectric sensor according to any one of the first to fourth aspects, wherein the piezoelectric film is made of scandium aluminum nitride.

Explanation of reference numerals

[0081] 50 Piezoelectric film 61, 62 Electrode film 81a, 82a Contact hole 81b, 82b Wiring layer d1~d3 Lengths in the first direction

Claims

1. A piezoelectric sensor, comprising: electrode films (61, 62); a piezoelectric film (50) laminated on the electrode films and having contact holes (81a, 82a) formed thereon to expose the electrode films; and wiring layers (81b, 82b) disposed in the contact holes and electrically connected to the electrode films. A plurality of the contact holes are formed so as to overlap the same electrode film in a normal direction with respect to a plane direction of the piezoelectric film. The plurality of contact holes have different lengths (d1 to d3) in one direction in the plane direction of the piezoelectric film, and the greater the length in the one direction, the deeper the depth. The electrode film is exposed from the bottom of one of the plurality of contact holes. The wiring layers are disposed in respective ones of the plurality of contact holes and are electrically connected to a portion of the electrode film exposed from the contact holes, the piezoelectric sensor.

2. The piezoelectric sensor according to claim 1, wherein openings of the plurality of contact holes have equal areas.

3. The piezoelectric sensor according to claim 1 or 2, wherein the plurality of contact holes are formed in a concentric frame shape with one contact hole as a reference contact hole.

4. When the plurality of contact holes have one contact hole as a reference contact hole and other contact holes different from the reference contact hole, in the normal direction, the other contact holes are formed along a part of an outer edge of the reference contact hole. The other contact holes have ends (812b, 813b) in a direction along the outer edge. The piezoelectric sensor according to claim 1 or 2, wherein the wiring layer is also disposed at the ends.

5. The piezoelectric sensor according to claim 1, wherein the piezoelectric film is made of scandium aluminum nitride.

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