Piezoelectric Device

Abstract

To provide a piezoelectric device capable of avoiding current leakage.SOLUTION: A piezoelectric device 1 comprises: a seed layer 4; a first conductive film 5 that is arrayed on the seed layer 4 in the state of contact with a top surface 4a of the seed layer 4; a piezoelectric film 6 that is arrayed on the first conductive film 5 in the state of contact with a top surface 5a of the first conductive film 5; a second conductive film 7 that is arrayed on the piezoelectric film 6; and an insulation part 8 that is provided within a trench 9 passing through the piezoelectric film 6 and the first conductive film 5 and that is higher in electrical resistivity than the piezoelectric film 6.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a piezoelectric device. [Background technology]

[0002] Patent document 1 discloses a piezoelectric device comprising a base material, a first conductive film disposed on the base material, a piezoelectric film disposed on the first conductive film, and a second conductive film disposed on the piezoelectric film. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-59770 A Summary of the Invention [Problem to be solved by the invention]

[0004] Two first conductive films are disposed on the upper surface of a base material with a gap between them. A piezoelectric film is disposed continuously on and in contact with the upper surfaces of the two first conductive films and the upper surface of a portion of the base material located between the two first conductive films. Two second conductive films are disposed on the piezoelectric films with a gap between them. When manufacturing a piezoelectric device having such a structure, one continuous piezoelectric film is formed across the upper surfaces of different materials.

[0005] In this case, the formation of the piezoelectric film is disturbed at the joints of different materials and at the parts where the piezoelectric layers grown on each material join together. As a result, the crystallinity of the piezoelectric material deteriorates or cracks occur in the part of the piezoelectric film located between the two first conductive films. As a result, when at least one of a laminated part in which one first conductive film, a piezoelectric film, and one second conductive film are laminated and a laminated part in which the other first conductive film, a piezoelectric film, and the other second conductive film are laminated is used as a piezoelectric element, a current leak occurs between the first conductive film and the second conductive film of each laminated part, or between the two first conductive films.

[0006] This problem occurs not only when the piezoelectric device has one piezoelectric film, but also when the piezoelectric device has multiple piezoelectric films. That is, this problem occurs when the piezoelectric film is disposed between two conductive films in a piezoelectric device in which two conductive films are disposed with a gap between them and a piezoelectric film is disposed on each of the two conductive films.

[0007] In view of the above, an object of the present invention is to provide a piezoelectric device that can avoid the current leakage that occurs in the above case. [Means for solving the problem]

[0008] In order to achieve the above object, according to the invention described in claim 1, The piezoelectric device is Base material (4, 16, 14) and a first conductive film (5, 17, 15) that is disposed on the base material and in contact with the upper surface (4a, 16a, 14a) of the base material and is made of a conductive material; a piezoelectric film (6, 18, 16) made of a piezoelectric material and disposed on the first conductive film in contact with the upper surface (5a, 17a, 15a) of the first conductive film; A second conductive film (7, 19, 17) disposed on the piezoelectric film and made of a conductive material; From the top surface of the second conductive film A trench (9, 25) extending through the piezoelectric film and the first conductive film 、2 7) and an insulating part (8, 21) having a higher electrical resistivity than the piezoelectric film. 、23 ) and 、 The insulating portion is made of an insulating material embedded inside the trench, and is embedded from the bottom of the trench to the same level as the top surface of the second conductive film. .

[0009] According to this, the insulation between the first conductive film and the piezoelectric film stacked on one side of the insulating section and the first conductive film and the piezoelectric film stacked on the other side of the insulating section is ensured by the insulating section. That is, the piezoelectric film is not disposed between the two first conductive films. This makes it possible to avoid current leakage that occurs in the portion of the piezoelectric film located between the two first conductive films when the piezoelectric film is disposed between the two first conductive films, unlike the present invention.

[0010] Also, claims 2 According to the invention described in The piezoelectric device is A base material (14); a first conductive film (15) made of a conductive material and disposed on the base material in contact with the upper surface (14a) of the base material; a first piezoelectric film (16) made of a piezoelectric material and disposed on the first conductive film in contact with an upper surface (15a) of the first conductive film; a second conductive film (17) disposed on the first piezoelectric film and made of a conductive material; a second piezoelectric film (18) made of a piezoelectric material and disposed on the second conductive film in contact with an upper surface (17a) of the second conductive film; a third conductive film (19) disposed on the second piezoelectric film and made of a conductive material; From the top surface of the third conductive film A trench (25, 25) that penetrates at least the second piezoelectric film and the second conductive film. 7) An insulating portion (21, 2) is provided inside the second piezoelectric film and has a higher electrical resistivity than the second piezoelectric film. 3) And equipped with 、 The insulating portion is embedded from the bottom of the trench to the same level as the top surface of the third conductive film. .

[0011] According to this, the insulation between the second conductive film and the second piezoelectric film laminated on one side of the insulating part and the second conductive film and the second piezoelectric film laminated on the other side of the insulating part is ensured by the insulating part. That is, the second piezoelectric film is not disposed between the two second conductive films. This makes it possible to avoid current leakage that occurs in the portion of the second piezoelectric film located between the two second conductive films when the second piezoelectric film is disposed between the two second conductive films, unlike the present invention.

[0012] The reference symbols in parentheses attached to each component indicate an example of the correspondence between the component and specific components described in the embodiments described below. [Brief description of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view of a piezoelectric device according to a first embodiment. [Figure 2A] 3A to 3C are cross-sectional views illustrating a manufacturing process of the piezoelectric device according to the first embodiment. [Figure 2B] 2B is a cross-sectional view showing a manufacturing process of the piezoelectric device subsequent to FIG. 2A. [Figure 2C] 2C is a cross-sectional view showing a manufacturing process of the piezoelectric device subsequent to FIG. 2B. [Diagram 3] 4 is a cross-sectional view of a piezoelectric device of Comparative Example 1. FIG. [Figure 4] FIG. 5 is a cross-sectional view of a piezoelectric device according to a second embodiment. [Figure 5A] 5A to 5C are cross-sectional views illustrating a manufacturing process of the piezoelectric device according to the second embodiment. [Figure 5B] 5B is a cross-sectional view showing a manufacturing process of the piezoelectric device subsequent to FIG. 5A. [Figure 5C] 5C is a cross-sectional view showing a manufacturing process of the piezoelectric device subsequent to FIG. 5B. [Figure 5D] 5D is a cross-sectional view showing a manufacturing process of the piezoelectric device subsequent to FIG. 5C. [Figure 5E] 5B is a cross-sectional view showing a manufacturing process of the piezoelectric device subsequent to FIG. 5D. [Figure 6] FIG. 11 is a cross-sectional view of a piezoelectric device according to a third embodiment. [Figure 7]FIG. 11 is a cross-sectional view of a piezoelectric device according to a fourth embodiment. [Figure 8] FIG. 13 is a cross-sectional view of a piezoelectric device according to a fifth embodiment. [Figure 9A] 13A to 13C are cross-sectional views illustrating a manufacturing process for the piezoelectric device according to the fifth embodiment. [Figure 9B] 9B is a cross-sectional view showing a manufacturing process of the piezoelectric device subsequent to FIG. 9A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0015] (First embodiment) 1 is applied to sensors, actuators, etc. The piezoelectric device 1 includes a substrate 2, an insulating film 3, a seed film 4, a first conductive film 5, a piezoelectric film 6, a second conductive film 7, and an insulating portion 8.

[0016] The substrate 2 is made of silicon (i.e., Si) or the like. The insulating film 3 is disposed on the substrate 2 in contact with the upper surface 2a of the substrate 2. The insulating film 3 is a film made of an insulating material. Examples of the insulating material constituting the insulating film 3 include silicon oxide (i.e., SiO 2 ) etc.

[0017] The seed film 4 is disposed on the insulating film 3 in contact with the upper surface 3a of the insulating film 3. The seed film 4 is used to improve the orientation (i.e., crystallinity) of the materials constituting the first conductive film 5 and the piezoelectric film 6 formed on the seed film 4.

[0018] The first conductive film 5 is a film made of a conductive material. The first conductive film 5 is disposed on the seed film 4 in contact with the upper surface 4a of the seed film 4. Therefore, in this embodiment, the seed film 4 is a base for the first conductive film 5.

[0019] The piezoelectric film 6 is disposed on the first conductive film 5 in contact with the upper surface 5a of the first conductive film 5. The piezoelectric film 6 is a film made of a piezoelectric material. In this embodiment, the piezoelectric material is scandium aluminum nitride (i.e., ScAlN). The material constituting the seed film 4 is aluminum nitride (i.e., AlN). Note that other piezoelectric materials such as AlN and lead zirconate titanate (i.e., PZT) may also be used as the piezoelectric material. When AlN is used as the piezoelectric material, AlN is used as the material constituting the seed film 4.

[0020] The second conductive film 7 is disposed on the piezoelectric film 6 in contact with the upper surface 6a of the piezoelectric film 6. The second conductive film 7 is a film made of a conductive material. The conductive material constituting each of the first conductive film 5 and the second conductive film 7 is a metal material containing as a main component any one of molybdenum, titanium, platinum, aluminum, ruthenium, etc. Materials other than metal materials may also be used as the conductive material. The conductive material constituting the second conductive film 7 is the same as the conductive material constituting the first conductive film 5, but may be different.

[0021] The insulating portion 8 is provided inside a trench 9 that penetrates from the upper surface 7a of the second conductive film 7 through the piezoelectric film 6 and the first conductive film 5. A bottom 9a of the trench 9 is located in the seed film 4. The insulating portion 8 has a higher electrical resistivity than the piezoelectric film 6. The electrical resistivity is a volume resistivity. The electrical resistivity of the insulating portion 8 is 10 8 The insulating portion 8 is made of an insulating material embedded inside the trench 9. The insulating material is embedded from the bottom 9a of the trench 9 to the same position as the upper surface 7a of the second conductive film 7. The insulating material for the insulating portion 8 is, for example, SiO 2 , silicon nitride (ie, SiN), and the like.

[0022] In the piezoelectric device 1 of this embodiment, the laminated portion A1 on one side, in which the first conductive film 51 on one side of the insulating portion 8 of the first conductive film 5, the piezoelectric film 61 on one side of the insulating portion 8 of the piezoelectric film 6, and the second conductive film 71 on one side of the insulating portion 8 of the second conductive film 7 are laminated, can be used as a piezoelectric element. When the laminated portion A1 on one side is used as a piezoelectric element, the first conductive film 51 on one side is used as a lower electrode, and the second conductive film 71 on one side is used as an upper electrode.

[0023] Furthermore, the other side of the laminated portion A2 in which the first conductive film 52 on the other side of the insulating portion 8 of the first conductive film 5, the piezoelectric film 62 on the other side of the insulating portion 8 of the piezoelectric film 6, and the second conductive film 72 on the other side of the insulating portion 8 of the second conductive film 7 are laminated can be used as a piezoelectric element. The other side of the insulating portion 8 is opposite to the one side of the insulating portion 8. When the other side of the laminated portion A2 is used as a piezoelectric element, the other side of the first conductive film 52 is used as a lower electrode, and the other side of the second conductive film 72 is used as an upper electrode.

[0024] The first conductive film 51 on one side and the first conductive film 52 on the other side are separated and insulated by an insulating portion 8 therebetween. The second conductive film 71 on one side and the second conductive film 72 on the other side are separated and insulated by an insulating portion 8 therebetween.

[0025] Depending on how the laminate part A1 on one side and the laminate part A2 on the other side are used, the second conductive film 71 on one side and the second conductive film 72 on the other side may be electrically connected by a wiring part (not shown). Also, one of the laminate part A1 on one side and the laminate part A2 on the other side may be used as a piezoelectric element, and the other of the laminate part A1 on one side and the laminate part A2 on the other side may not be used as a piezoelectric element.

[0026] Next, a method for manufacturing the piezoelectric device 1 of this embodiment will be described.

[0027] First, as shown in Fig. 2A, a laminate 10 is formed in which a substrate 2, an insulating film 3, a seed film 4, a first conductive film 5, a piezoelectric film 6, and a second conductive film 7 are laminated. In forming this laminate 10, the insulating film 3, the seed film 4, and the first conductive film 5 are deposited on the substrate 2 in the order described. Then, a piezoelectric film 6 is deposited on the first conductive film 5 in contact with an upper surface 5a of the first conductive film 5. Then, a second conductive film 7 is deposited on the piezoelectric film 6 in contact with an upper surface 6a of the piezoelectric film 6.

[0028] 2B, a trench 9 is formed penetrating the second conductive film 7, the piezoelectric film 6, and the first conductive film 5 from the upper surface 7a of the second conductive film 7. A bottom 9a of the trench 9 is located in the seed film 4. The trench 9 is formed by photolithography and etching. As an etching method, a method according to the materials constituting the second conductive film 7, the piezoelectric film 6, and the first conductive film 5 is adopted.

[0029] 2C, an insulating material is embedded inside the trench 9 to form the insulating portion 8. In this manner, the piezoelectric device 1 of the present embodiment is manufactured.

[0030] The effects of this embodiment will be described in comparison with a piezoelectric device 1A of Comparative Example 1 shown in Fig. 3. The piezoelectric device 1A of Comparative Example 1 does not include the insulating portion 8 of this embodiment. In the piezoelectric device 1A of Comparative Example 1, two first conductive films 51, 52 are disposed on a seed film 4 with a space between them. The piezoelectric film 6 is disposed continuously on the two first conductive films 51, 52 and at a position between the two first conductive films 51, 52.

[0031] In the manufacturing method of the piezoelectric device 1A of Comparative Example 1, two first conductive films 51, 52 are formed with a gap between them on the seed film 4. Then, one continuous piezoelectric film 6 is formed across the upper surfaces 5a of the two first conductive films 51, 52 and the upper surface 4a of the portion of the seed film 4 that is located between the two first conductive films 51, 52. In this manner, one continuous piezoelectric film 6 is formed across the upper surfaces of different materials.

[0032] In this case, the formation of the piezoelectric film 6 is disturbed at the joints of different materials, or at the portions where the piezoelectric layers grown on each material join together. Therefore, in the portion of the piezoelectric film 6 located between the two first conductive films 51 and 52, the crystallinity of the piezoelectric material deteriorates, or cracks B1, B2, B3, and B4 occur. As a result, when one laminated portion A1 in which one first conductive film 51, the piezoelectric film 6, and one second conductive film 71 are laminated, and the other laminated portion A2 in which the other first conductive film 52, the piezoelectric film 6, and the other second conductive film 72 are laminated, respectively, are used as piezoelectric elements, a current leak C1 occurs from the first conductive films 51 and 52 to the second conductive films 71 and 72. Or, a current leak C2 occurs between the two first conductive films 51 and 52.

[0033] In contrast, the piezoelectric device 1 of this embodiment includes a seed film 4, a first conductive film 5, a piezoelectric film 6, a second conductive film 7, and an insulating portion 8. The piezoelectric film 6 is disposed on the first conductive film 5 in contact with an upper surface 5a of the first conductive film 5. The insulating portion 8 is provided inside a trench 9 that penetrates the piezoelectric film 6 and the first conductive film 5, and has a higher electrical resistivity than the piezoelectric film 6.

[0034] In this piezoelectric device 1, the first conductive film 5, the piezoelectric film 6, and the second conductive film 7 located on one side of the insulating section 8 constitute one side of the laminated section A1 in which the conductive film and the piezoelectric film are laminated. The first conductive film 5, the piezoelectric film 6, and the second conductive film 7 located on the other side of the insulating section 8 constitute the other side of the laminated section A2 in which the conductive film and the piezoelectric film are laminated. The insulating section 8 ensures insulation between the first conductive film 5 and the piezoelectric film 6 of the laminated section A1 on one side and the first conductive film 5 and the piezoelectric film 6 of the laminated section A2 on the other side. In other words, the piezoelectric film 6 is not disposed between the two first conductive films 5. This makes it possible to avoid current leakage occurring in the piezoelectric device 1A of Comparative Example 1.

[0035] Furthermore, the piezoelectric film 6 is formed in contact with only the upper surface 5a of the first conductive film 5 out of the upper surface 4a of the seed film 4 and the upper surface 5a of the first conductive film 5. When the piezoelectric film 6 is formed, the piezoelectric film 6 is formed in contact with only the upper surface of one type of material. Therefore, good crystallinity of the piezoelectric material constituting the piezoelectric film 6 can be ensured.

[0036] The manufacturing method of the piezoelectric device 1 of this embodiment can be modified as follows. In preparing the laminate 10, a laminate 10 not having the second conductive film 7 is prepared. In forming the trench 9, the trench 9 is formed so as to penetrate the piezoelectric film 6 and the first conductive film 5 from the upper surface 6a of the piezoelectric film 6. An insulating material is then embedded inside the trench 9 to form the insulating portion 8. Thereafter, the second conductive film 7 is formed over the upper surfaces of the piezoelectric film 6 and the insulating portion 8. The second conductive film 7 is patterned.

[0037] The manufacturing method of the piezoelectric device 1 of this embodiment can be modified as follows. In forming the trench 9, the trench 9 may be formed so as to penetrate the second conductive film 7, the piezoelectric film 6, the first conductive film 5, and the seed film 4, with the bottom 9a of the trench 9 located in the insulating film 3. An insulating material is then filled into the trench 9 to form the insulating portion 8. As a result, the seed film 4 is divided into one side seed film 4 located on one side of the insulating portion 8 and the other side seed film 4 located on the other side of the insulating portion 8.

[0038] In the piezoelectric device 1 of this embodiment, the insulating portion 8 is made of an insulating material embedded inside the trench 9. However, the insulating portion 8 may be made of air present inside the trench 9, i.e., a space. The electrical resistivity of air is 1.3×10 at 20° C. 16 ~3.3×10 16 It is greater than or equal to Ω·m.

[0039] Furthermore, the piezoelectric device 1 of this embodiment includes a seed film 4. However, the piezoelectric device 1 does not necessarily need to include the seed film 4. In this case, the first conductive film 5 is disposed on the insulating film 3 in contact with the upper surface 3a of the insulating film 3. The insulating film 3 is a base material for the first conductive film 5.

[0040] Second embodiment The piezoelectric device 11 of this embodiment shown in Fig. 4 is applied to a bimorph sensor. Such a sensor may be a highly sensitive sensor such as a piezoelectric microphone. The piezoelectric device 11 includes a substrate 12, an insulating film 13, and a laminated structure D1.

[0041] The substrate 12 has a space 121. The substrate 12 is made of the same material as the substrate 2 of the first embodiment. The insulating film 13 is disposed on the substrate 12 in contact with an upper surface 12a of the substrate 12. The insulating film 13 is made of the same material as the insulating film 3 of the first embodiment.

[0042] The laminated structure D1 is disposed straddling both the insulating film 13 and the space 121. The portion of the laminated structure D1 located above the space 121 is suspended and can vibrate. This portion is the sensing portion. The portions of the laminated structure D1 located above the insulating film 13 and the substrate 12 are supported by the insulating film 13 and the substrate 12. In this manner, the laminated structure D1 is in a cantilevered state.

[0043] The laminated structure D1 is a laminate of a piezoelectric film and a conductive film. Specifically, the laminated structure D1 is a laminated structure in which a seed film 14, a first conductive film 15, a first piezoelectric film 16, a second conductive film 17, a second piezoelectric film 18, and a third conductive film 19 are laminated from bottom to top in this order.

[0044] The seed film 14 is used to improve the crystallinity of the material constituting the first conductive film 15 and the first piezoelectric film 16. The seed film 14 is composed of the same material as the seed film 4 of the first embodiment. The seed film 14 is a base for the first conductive film 15. The first conductive film 15 is disposed on the seed film 14 in contact with the upper surface 14a of the seed film 14. The first conductive film 15 is a film composed of a conductive material. The first piezoelectric film 16 is disposed on the first conductive film 15 in contact with the upper surface 15a of the first conductive film 15. The first piezoelectric film 16 is a film composed of a piezoelectric material.

[0045] The second conductive film 17 is disposed on the first piezoelectric film 16 in contact with the upper surface 16a of the first piezoelectric film 16. The second conductive film 17 is a film made of a conductive material. The second piezoelectric film 18 is disposed on the second conductive film 17 in contact with the upper surface 17a of the second piezoelectric film 17. The second piezoelectric film 18 is a film made of a piezoelectric material. The third conductive film 19 is disposed on the second piezoelectric film 18 in contact with the upper surface 18a of the second piezoelectric film 18. The third conductive film 19 is a film made of a conductive material.

[0046] The portion of the laminated structure D1 where the first conductive film 15, the first piezoelectric film 16, the second conductive film 17, the second piezoelectric film 18, and the third conductive film 19 are laminated can be used as a piezoelectric element. When this portion is used as a piezoelectric element, the first conductive film 15 is used as a lower electrode, the second conductive film 17 is used as an intermediate electrode, and the third conductive film 19 is used as an upper electrode.

[0047] The conductive materials constituting the first conductive film 15, the second conductive film 17, and the third conductive film 19 are the same as the conductive materials constituting the first conductive film 5 and the second conductive film 7 in the first embodiment. The material constituting the first conductive film 15, the material constituting the second conductive film 17, and the material constituting the third conductive film 19 are the same or may be different.

[0048] The piezoelectric material constituting each of the first piezoelectric film 16 and the second piezoelectric film 18 is the same as the piezoelectric material constituting the piezoelectric film 6 of the first embodiment. Note that the material constituting the first piezoelectric film 16 and the material constituting the second piezoelectric film 18 are the same or may be different.

[0049] The multilayer structure D1 has a first insulating portion 21, a second insulating portion 22, a third insulating portion 23, and a fourth insulating portion 24.

[0050] The first insulating portion 21 is provided inside the first trench 25. The first trench 25 penetrates the first piezoelectric film 16 and the first conductive film 15 from the upper surface 16a of the first piezoelectric film 16. A bottom 25a of the first trench 25 is located in the first piezoelectric film 16. The first insulating portion 21 has a higher electrical resistivity than the second piezoelectric film 18. The first insulating portion 21 is made of an insulating material embedded inside the first trench 25. The insulating material is embedded from the bottom 25a of the trench 25 to the same position as the upper surface 19a of the third conductive film 19.

[0051] The second insulating portion 22 is provided inside the second trench 26. The second trench 26 penetrates the first piezoelectric film 16 and the first conductive film 15 from the upper surface 16a of the first piezoelectric film 16 at a position away from the first trench 25 in the planar direction DR1 of the laminated structure portion D1. The planar direction DR1 is a direction along the upper surface 16a of the first piezoelectric film 16. The bottom 26a of the second trench 26 is located in the seed film 14. The second trench 26 does not penetrate the third conductive film 19, the second piezoelectric film 18, and the second conductive film 17. The second insulating portion 22 has a higher electrical resistivity than the first piezoelectric film 16. The second insulating portion 22 is composed of an insulating material embedded inside the second trench 26. The insulating material is embedded from the bottom 26a of the second trench 26 to the same position as the upper surface 16a of the first piezoelectric film 16.

[0052] The third insulating portion 23 is provided inside the third trench 27. The third trench 27 penetrates from the upper surface 19a of the third conductive film 19 through the third conductive film 19, the second piezoelectric film 18, the second conductive film 17, the first piezoelectric film 16, and the first conductive film 15 at a position away from each of the first trench 25 and the second trench 26 in the planar direction DR1. A bottom 27a of the third trench 27 is located in the seed film 14. The third insulating portion 23 has a higher electrical resistivity than the second piezoelectric film 18 and the first piezoelectric film 16. The third insulating portion 23 is composed of an insulating material embedded inside the third trench 27. The insulating material is embedded from the bottom 27a of the third trench 27 to the same position as the upper surface 19a of the third conductive film 19.

[0053] The insulating material constituting each of the first insulating portion 21, the second insulating portion 22, and the third insulating portion 23 is SiO 2 , SiN, etc. The first insulating portion 21, the second insulating portion 22, and the third insulating portion 23 are made of the same insulating material, but may be made of different materials.

[0054] The fourth insulating portion 24 is provided inside the fourth trench 28. The fourth trench 28 penetrates the third conductive film 19, the second piezoelectric film 18, and the second conductive film 17 from the upper surface 19a of the third conductive film 19 at a position away from each of the first trench 25, the second trench 26, and the third trench 27 in the planar direction DR1, but does not penetrate the first piezoelectric film 16. A bottom 28a of the fourth trench 28 is located in the first piezoelectric film 16. The fourth insulating portion 24 has a higher electrical resistivity than the second piezoelectric film 18. The fourth insulating portion 24 is composed of air present inside the fourth trench 28.

[0055] Next, a method for manufacturing the piezoelectric device 11 of this embodiment will be described. First, as shown in FIG. 5A, a laminate is formed in which a substrate 12, an insulating film 13, a seed film 14, a first conductive film 15, and a first piezoelectric film 16 are laminated. In forming this laminate, the insulating film 13, the seed film 14, and the first conductive film 15 are deposited on the substrate 12 in this order. No space 121 is formed on this substrate 12. Then, the first piezoelectric film 16 is deposited on the first conductive film 15 in contact with the upper surface 15a of the first conductive film 15.

[0056] 5B, a second trench 26 is formed. The second trench 26 penetrates the first piezoelectric film 16 and the first conductive film 15 from the upper surface 16a of the first piezoelectric film 16. A bottom 26a of the second trench 26 is located in the seed film 14. The second trench 26 is formed by photolithography and etching. As an etching method, a method according to the materials constituting the first piezoelectric film 16 and the first conductive film 15 is adopted.

[0057] 5C, an insulating material is filled into the second trench 26 to form the second insulating portion 22. After the upper surface 22a of the second insulating portion 22 is planarized by CMP or the like, the second conductive film 17 is formed across the upper surface 16a of the first piezoelectric film 16 and the upper surface 22a of the second insulating portion 22. Then, the second piezoelectric film 18 is formed on the second conductive film 17 in contact with the upper surface 17a of the second conductive film 17. Then, the third conductive film 19 is formed on the second piezoelectric film 18 in contact with the upper surface 18a of the second piezoelectric film 18. Then, the space portion 121 of the substrate 12 is formed by photolithography and etching the substrate 12 and the insulating film 13.

[0058] Next, as shown in FIG. 5D, a first trench 25 and a fourth trench 28 are formed at a position away from the second trench 26 in the planar direction DR1. The first trench 25 and the fourth trench 28 are away from each other in the planar direction DR1. The first trench 25 and the fourth trench 28 penetrate the third conductive film 19, the second piezoelectric film 18, and the second conductive film 17 from the upper surface 19a of the third conductive film 19. The bottoms 25a and 28a of the first trench 25 and the fourth trench 28 are located in the first piezoelectric film 16. The first trench 25 and the fourth trench 28 are formed by photolithography and etching. As an etching method, a method according to the materials constituting the third conductive film 19, the second piezoelectric film 18, and the second conductive film 17 is adopted.

[0059] Further, a third trench 27 is formed at a position away from each of the first, second, and fourth trenches 25, 26, and 28 in the planar direction DR1. The third trench 27 penetrates from the upper surface 19a of the third conductive film 19 through the third conductive film 19, the second piezoelectric film 18, the second conductive film 17, the first piezoelectric film 16, and the first conductive film 15. A bottom 27a of the third trench 27 is located in the seed film 14. The third trench 27 is formed by photolithography and etching. As an etching method, a method according to the materials constituting each of the third conductive film 19, the second piezoelectric film 18, the second conductive film 17, the first piezoelectric film 16, and the first conductive film 15 is adopted.

[0060] 5E, an insulating material is filled into the first trench 25 to form the first insulating portion 21. An insulating material is filled into the third trench 27 to form the third insulating portion 23. No insulating material is filled into the fourth trench 28. The fourth insulating portion 24 is formed by the air inside the fourth trench 28. In this manner, the piezoelectric device 11 of the present embodiment is manufactured.

[0061] The timing for forming the space 121 in the substrate 12 can be changed. For example, as shown in Fig. 5A, the space 121 may be formed after the stack is formed and before the second trench 26 is formed. Moreover, the space 121 may be formed after the first to fourth trenches 25 to 28 are formed.

[0062] In the piezoelectric device 11 of this embodiment, the floating portion of the laminated structure D1 vibrates due to the sensing target such as sound pressure. As a result, a tensile stress is applied to one of the first piezoelectric film 16 and the second piezoelectric film 18, and a compressive stress is applied to the other of the first piezoelectric film 16 and the second piezoelectric film 18. At this time, charges are extracted from each of the first piezoelectric film 16 and the second piezoelectric film 18 via the first conductive film 15, the second conductive film 17, and the third conductive film 19, thereby detecting the sensing target.

[0063] In the piezoelectric device 11 of this embodiment, the second conductive film 17 is disposed on the first piezoelectric film 16, which serves as a base material, in contact with an upper surface 16a of the first piezoelectric film 16. The second piezoelectric film 18 is disposed on the second conductive film 17 in contact with an upper surface 17a of the second conductive film 17. The third conductive film 19 is disposed on the second piezoelectric film 18.

[0064] The first insulating portion 21 is provided inside the first trench 25 penetrating the second piezoelectric film 18 and the second conductive film 17. With this, the first insulating portion 21 ensures insulation between the second conductive film 17 and the second piezoelectric film 18 on one side of the first insulating portion 21 and the second conductive film 17 and the second piezoelectric film 18 on the other side of the first insulating portion 21. The second conductive film 17 and the second piezoelectric film 18 on one side of the first insulating portion 21 correspond to the first conductive film 5 and the piezoelectric film 6 on one side of the insulating portion 8 of the first embodiment. The second conductive film 17 and the second piezoelectric film 18 on the other side of the first insulating portion 21 correspond to the first conductive film 5 and the piezoelectric film 6 on the other side of the insulating portion 8 of the first embodiment. The third conductive film 19 corresponds to the second conductive film 7 of the first embodiment. Therefore, the same effect as in the first embodiment is obtained.

[0065] Further, the fourth insulating portion 24 is provided inside a fourth trench 28 penetrating the second piezoelectric film 18 and the second conductive film 17. Accordingly, the fourth insulating portion 24 ensures insulation between the second conductive film 17 and the second piezoelectric film 18 on one side of the fourth insulating portion 24 and the second conductive film 17 and the second piezoelectric film 18 on the other side of the fourth insulating portion 24. The second conductive film 17 and the second piezoelectric film 18 on one side of the fourth insulating portion 24 correspond to the first conductive film 5 and the piezoelectric film 6 on one side of the insulating portion 8 of the first embodiment. The second conductive film 17 and the second piezoelectric film 18 on the other side of the fourth insulating portion 24 correspond to the first conductive film 5 and the piezoelectric film 6 on the other side of the insulating portion 8 of the first embodiment. Therefore, the same effect as the first embodiment can be obtained.

[0066] Further, the third insulating portion 23 is provided inside the third trench 27 penetrating the second piezoelectric film 18 and the second conductive film 17. According to this, the third insulating portion 23 ensures insulation between the second conductive film 17 and the second piezoelectric film 18 on one side of the third insulating portion 23 and the second conductive film 17 and the second piezoelectric film 18 on the other side of the third insulating portion 23. The second conductive film 17 and the second piezoelectric film 18 on one side of the third insulating portion 23 correspond to the first conductive film 5 and the piezoelectric film 6 on one side of the insulating portion 8 of the first embodiment. The second conductive film 17 and the second piezoelectric film 18 on the other side of the third insulating portion 23 correspond to the first conductive film 5 and the piezoelectric film 6 on the other side of the insulating portion 8 of the first embodiment. Therefore, the same effect as the first embodiment can be obtained.

[0067] Moreover, the first conductive film 15 is in contact with an upper surface 14a of the seed film 14 serving as a base material and is disposed on the seed film 14. The first piezoelectric film 16 is in contact with an upper surface 15a of the first conductive film 15 and is disposed on the first conductive film 15. The second conductive film 17 is disposed on the first piezoelectric film 16.

[0068] The second insulating portion 22 is provided inside a second trench 26 penetrating the first piezoelectric film 16 and the first conductive film 15. With this, the second insulating portion 22 ensures insulation between the first conductive film 15 and the first piezoelectric film 16 on one side of the second insulating portion 22 and the first conductive film 15 and the first piezoelectric film 16 on the other side of the second insulating portion 22. The first conductive film 15 and the first piezoelectric film 16 on one side of the second insulating portion 22 correspond to the first conductive film 5 and the piezoelectric film 6 on one side of the insulating portion 8 of the first embodiment. The first conductive film 15 and the first piezoelectric film 16 on the other side of the second insulating portion 22 correspond to the first conductive film 5 and the piezoelectric film 6 on the other side of the insulating portion 8 of the first embodiment. Therefore, the same effect as the first embodiment can be obtained.

[0069] The third insulating portion 23 is provided inside a third trench 27 penetrating the first piezoelectric film 16 and the first conductive film 15. As a result, the third insulating portion 23 ensures insulation between the first conductive film 15 and the first piezoelectric film 16 on one side of the third insulating portion 23 and the first conductive film 15 and the first piezoelectric film 16 on the other side of the third insulating portion 23. The first conductive film 15 and the first piezoelectric film 16 on one side of the third insulating portion 23 correspond to the first conductive film 5 and the piezoelectric film 6 on one side of the insulating portion 8 of the first embodiment. The first conductive film 15 and the first piezoelectric film 16 on the other side of the third insulating portion 23 correspond to the first conductive film 5 and the piezoelectric film 6 on the other side of the insulating portion 8 of the first embodiment. Therefore, the same effect as the first embodiment can be obtained.

[0070] In addition, the piezoelectric device 11 of this embodiment has the following effects. Highly sensitive sensors are used to detect minute changes. Therefore, in a piezoelectric device applied to a highly sensitive sensor, even a small amount of cracks in the piezoelectric film leads to fatal deterioration of the sensor characteristics. In general, in the manufacture of a bimorph type piezoelectric device in which a first piezoelectric film and a second piezoelectric film are laminated, the surface on which the second piezoelectric film is formed is less uniform when the second piezoelectric film, which is the upper layer, is formed than when the first piezoelectric film, which is the lower layer, is formed. Therefore, cracks are more likely to occur in the second piezoelectric film than in the first piezoelectric film. Therefore, in order to apply a bimorph type piezoelectric device to a highly sensitive sensor, it is particularly necessary to suppress cracks in the second piezoelectric film.

[0071] Therefore, the piezoelectric device 11 of this embodiment includes the first, third, and fourth insulating parts 21, 23, and 24. When the second piezoelectric film 18 is formed at the positions of the first, third, and fourth insulating parts 21, 23, and 24, cracks are likely to occur in the second piezoelectric film 18 at those positions. According to the piezoelectric device 11 of this embodiment, the first, third, and fourth insulating parts 21, 23, and 24 are arranged in the parts where cracks are likely to occur. Therefore, it is possible to suppress the occurrence of cracks in the second piezoelectric film 18. Therefore, when the second piezoelectric film 18 is arranged between two second conductive films 17, it is possible to avoid current leakage occurring in the part of the second piezoelectric film 18 located between the two second conductive films 17.

[0072] Moreover, according to the piezoelectric device 11 of this embodiment, the third insulating portion 23 is located inside the third trench 27 penetrating the first piezoelectric film 16 and the second piezoelectric film 18. This, unlike this embodiment, makes it possible to reduce the number of manufacturing steps in forming the third insulating portion 23, compared to a case in which a trench penetrating the first piezoelectric film 16 and a trench penetrating the second piezoelectric film 18 are separately formed. Furthermore, this, unlike this embodiment, makes it possible to avoid the problem of misalignment of the two trenches, which occurs when a trench penetrating the first piezoelectric film 16 and a trench penetrating the second piezoelectric film 18 are separately formed in forming the third insulating portion 23.

[0073] Furthermore, according to the piezoelectric device 11 of this embodiment, the first insulating portion 21 and the second insulating portion 22 are arranged at different positions in the planar direction DR1. Here, in the sensing portion located above the space portion 121 of the laminated structure portion D1, it is considered that the position of the first conductive film 15 and the position of the second conductive film 17 are made different in the planar direction DR1 in order to ensure strength. By arranging the first insulating portion 21 and the second insulating portion 22 at different positions in the planar direction DR1, it is possible to deal with the case where the position of the first conductive film 15 and the position of the second conductive film 17 are made different in the planar direction DR1.

[0074] Although the piezoelectric device 11 of the present embodiment includes both the first insulating portion 21 and the second insulating portion 22, it may include only the first insulating portion 21 of the first insulating portion 21 and the second insulating portion 22. Even in this case, by providing the first insulating portion 21, it is possible to suppress the occurrence of cracks in the second piezoelectric film 18.

[0075] Furthermore, in the method for manufacturing the piezoelectric device 11 of this embodiment, the first trench 25 and the third trench 27 are formed after the third conductive film 19 is formed. However, the first trench 25 and the third trench 27 are formed, and then the first insulating portion 21 and the third insulating portion 23 are formed. Thereafter, the third conductive film 19 may be formed and the third conductive film 19 may be patterned.

[0076] Third embodiment As shown in FIG. 6, the piezoelectric device 11A of this embodiment includes an insulating amorphous film 31. The amorphous film 31 is disposed continuously above both the second insulating portion 22 and the first piezoelectric film 16. The amorphous film 31 contacts the upper surface 22a of the second insulating portion 22 and the upper surface 16a of the first piezoelectric film 16. The amorphous film 31 is made of the same material as the second insulating portion 22 (for example, SiO 2). The second conductive film 17 is in contact with an upper surface 31a of the amorphous film 31 and is disposed continuously at a position directly above both the second insulating portion 22 and the first piezoelectric film 16. A bottom 25a of the first trench 25 is located in the amorphous film 31. The other configuration of the piezoelectric device 11A is the same as that of the piezoelectric device 11 of the second embodiment.

[0077] When the second conductive film 17 is formed in contact with both the upper surface 22a of the second insulating portion 22 and the upper surface 16a of the first piezoelectric film 16, as in the piezoelectric device 11 of the second embodiment, a difference in crystallinity occurs between the portion of the second conductive film 17 located directly above the second insulating portion 22 and the portion of the second conductive film 17 located directly above the first piezoelectric film 16.

[0078] In contrast, in the manufacture of piezoelectric device 11A of this embodiment, second conductive film 17 is formed in contact with upper surface 31a of amorphous film 31 and continuously at positions directly above both second insulating portion 22 and first piezoelectric film 16. This makes it possible to reduce the difference in crystallinity between portion 171 of second conductive film 17 located directly above second insulating portion 22 and portion 172 of second conductive film 17 located directly above first piezoelectric film 16. As a result, the crystallinity of second piezoelectric film 18 formed in contact with upper surface 17a of second conductive film 17 can be made closer to uniform.

[0079] Furthermore, in the piezoelectric device 11A of this embodiment, the amorphous film 31 is made of the same material as the second insulating portion 22. This allows the second insulating portion 22 and the amorphous film 31 to be formed consecutively in the manufacture of the piezoelectric device 11A. In other words, both the second insulating portion 22 and the amorphous film 31 can be formed in a single process.

[0080] The amorphous film 31 may be made of a material different from that of the second insulating portion 22. In this case, the second insulating portion 22 may be made of, for example, SiO 2 The amorphous film 31 is made of SiN. Further, between the amorphous film 31 and each of the second insulating portion 22 and the first piezoelectric film 16, other films may be disposed.

[0081] (Fourth embodiment) As shown in FIG. 7, the piezoelectric device 11B of this embodiment includes a second seed film 32. The second seed film 32 is disposed continuously at a position directly above both the second insulating portion 22 and the first piezoelectric film 16. The second seed film 32 contacts the upper surface 22a of the second insulating portion 22 and the upper surface 16a of the first piezoelectric film 16. The seed film 14 described in the second embodiment is the first seed film 14 in this embodiment. The second seed film 32 is made of the same material as the first seed film 14. In this embodiment, the piezoelectric material constituting the first piezoelectric film 16 and the second piezoelectric film 18 is ScAlN. The material constituting the first seed film 14 and the second seed film 32 is AlN.

[0082] The second conductive film 17 is in contact with the upper surface 32a of the second seed film 32 and is disposed continuously at a position directly above both the second insulating portion 22 and the first piezoelectric film 16. The other configuration of the piezoelectric device 11B is the same as that of the piezoelectric device 11 of the second embodiment. According to the piezoelectric device 11B of this embodiment, the same effects as those of the third embodiment can be obtained.

[0083] Furthermore, in the piezoelectric device 11B of this embodiment, the insulating material constituting the first, second and third insulating portions 21, 22 and 23 is the same material as the material constituting the first seed film 14. This allows the formation of the first seed film 14, the formation of the second insulating portion 22 and the formation of the second seed film 32 to be carried out successively in the manufacture of the piezoelectric device 11B.

[0084] The insulating material constituting the second insulating portion 22 is the same as the material constituting the first seed film 14, and the insulating material constituting the first and third insulating portions 21, 23 may be different from the material constituting the first seed film 14. Also, the insulating material constituting the first, second and third insulating portions 21, 22, 23 may be different from the material constituting the first seed film 14. Also, another film may be disposed between each of the second insulating portion 22 and the first piezoelectric film 16 and the second seed film 32.

[0085] Fifth embodiment As shown in FIG. 8, the piezoelectric device 11C of this embodiment includes an oxide layer 41 provided on the sidewall portion 27b of the third trench 27. That is, the oxide layer 41 constitutes the sidewall portion 27b. The oxide layer 41 is in contact with the third insulating portion 23. The oxide layer 41 is in contact with each of the first conductive film 15, the first piezoelectric film 16, the second conductive film 17, the second piezoelectric film 18, and the third conductive film 19. The oxide layer 41 contains the same elements as the elements constituting each of the first conductive film 15, the first piezoelectric film 16, the second conductive film 17, the second piezoelectric film 18, and the third conductive film 19.

[0086] The oxide layer 41 and the third insulating portion 23 are formed as follows. As shown in FIG. 9A, a third trench 27 is formed in the same manner as in the second embodiment. At this time, etching is performed using a resist pattern 42 formed by photolithography as a mask. At this stage, a sidewall portion 27b of the third trench 27 is composed of the first conductive film 15, the first piezoelectric film 16, the second conductive film 17, the second piezoelectric film 18, and the third conductive film 19.

[0087] Thereafter, as shown in Fig. 9B, an oxidation treatment is performed on the sidewall of third trench 27. The oxidation treatment is, for example, a heat treatment in a state in which oxygen is present inside third trench 27. As a result, an oxide layer 41 is formed on sidewall portion 27b. That is, sidewall portion 27b is composed of oxide layer 41. Thereafter, an insulating material is filled inside third trench 27, thereby forming third insulating portion 23 shown in Fig. 8.

[0088] Other configurations of the piezoelectric device 11C are the same as those of the piezoelectric device 11 of the second embodiment. Therefore, the same effects as those of the second embodiment can be obtained. Furthermore, according to the piezoelectric device 11C of this embodiment, the following effects can be obtained.

[0089] According to the piezoelectric device 11C of this embodiment, since the oxide layer 41 is provided on the side wall portion 27b, the electrical insulation of the side wall portion 27b is improved. Moreover, since the third insulating portion 23 is in contact with the oxide layer 41, the adhesion between the third insulating portion 23 and the side wall portion 27b is improved.

[0090] The oxide layer 41 may be provided on the sidewalls of the first trench 25 and the second trench 26, not limited to the third trench 27.

[0091] (Other embodiments) The present invention is not limited to the above-mentioned embodiment, and can be appropriately modified within the scope of the claims, and includes various modified examples and modifications within the equivalent scope. In addition, the above-mentioned embodiments are not unrelated to each other, and can be appropriately combined unless the combination is clearly impossible. In addition, in each of the above-mentioned embodiments, it goes without saying that the elements constituting the embodiment are not necessarily essential, except when they are specifically stated to be essential or when they are clearly considered to be essential in principle. In addition, in each of the above-mentioned embodiments, when referring to the material, shape, positional relationship, etc. of the components, etc., they are not limited to the material, shape, positional relationship, etc., except when they are specifically stated or when they are limited to a specific material, shape, positional relationship, etc. in principle. [Explanation of symbols]

[0092] 4 Seed layer 5 First conductive film 6 Piezoelectric film 7 Second conductive film 8 Insulation 9. Trench

Claims

1. 1. A piezoelectric device, comprising: Base material (4, 16, 14); a first conductive film (5, 17, 15) disposed on the base material in contact with an upper surface (4a, 16a, 14a) of the base material and made of a conductive material; a piezoelectric film (6, 18, 16) that is disposed on the first conductive film in contact with an upper surface (5a, 17a, 15a) of the first conductive film and is made of a piezoelectric material; A second conductive film (7, 19, 17) disposed on the piezoelectric film and made of a conductive material; an insulating portion (8, 21, 23) provided inside a trench (9, 25, 27) penetrating the piezoelectric film and the first conductive film from an upper surface of the second conductive film, the insulating portion having an electrical resistivity higher than that of the piezoelectric film; A piezoelectric device, wherein the insulating portion is composed of an insulating material embedded inside the trench, and is embedded from the bottom of the trench to a position flush with an upper surface of the second conductive film.

2. 1. A piezoelectric device, comprising: A base material (14); a first conductive film (15) disposed on the base material in contact with an upper surface (14a) of the base material and made of a conductive material; a first piezoelectric film (16) that is disposed on the first conductive film in contact with an upper surface (15a) of the first conductive film and is made of a piezoelectric material; a second conductive film (17) disposed on the first piezoelectric film and made of a conductive material; a second piezoelectric film (18) that is disposed on the second conductive film in contact with an upper surface (17a) of the second conductive film and is made of a piezoelectric material; a third conductive film (19) disposed on the second piezoelectric film and made of a conductive material; an insulating portion (21, 23) provided inside a trench (25, 27) that penetrates at least the second piezoelectric film and the second conductive film from an upper surface of the third conductive film, and having an electrical resistivity higher than that of the second piezoelectric film; A piezoelectric device, wherein the insulating portion is embedded from the bottom of the trench to a position flush with an upper surface of the third conductive film.

3. The piezoelectric device of claim 2 , wherein the trench (27) penetrates through the second piezoelectric film, the second conductive film, the first piezoelectric film, and the first conductive film.

4. the insulating portion is a first insulating portion (21) provided in a first trench (25) that penetrates the second piezoelectric film and the second conductive film but does not penetrate the first piezoelectric film; The piezoelectric device of claim 2, further comprising a second insulating portion (22) disposed within a second trench (26) that penetrates the first piezoelectric film and the first conductive film but does not penetrate the second conductive film, at a position away from the first trench in a direction along an upper surface (16a) of the first piezoelectric film.

5. The insulating portion is a first insulating portion (21) provided in a first trench (25) that penetrates the second piezoelectric film and the second conductive film but does not penetrate the first piezoelectric film as the trench. The piezoelectric device is a second insulating portion (22) provided inside a second trench (26) at a position away from the first trench in a direction along an upper surface (16a) of the first piezoelectric film, the second insulating portion penetrating the first piezoelectric film and the first conductive film but not penetrating the second conductive film; 3. The piezoelectric device of claim 2, further comprising: a third insulating portion (23) provided inside a third trench (27) penetrating the second piezoelectric film, the second conductive film, the first piezoelectric film, and the first conductive film, at a position away from each of the first trench and the second trench in a direction along an upper surface of the first piezoelectric film.

6. The piezoelectric device includes an insulating amorphous film (31) disposed continuously above both the second insulating portion and the first piezoelectric film, 6. The piezoelectric device according to claim 4, wherein the second conductive film is in contact with an upper surface (31a) of the amorphous film and is disposed continuously at a position directly above both the second insulating portion and the first piezoelectric film.

7. The piezoelectric device according to claim 6 , wherein the second insulating portion and the amorphous film are made of the same type of insulating material.

8. the undercoat material is a first seed film (14) that improves the crystallinity of materials constituting the first conductive film and the first piezoelectric film; The piezoelectric device includes a second seed film (32) disposed directly above and in succession with both the second insulating portion and the first piezoelectric film, the second seed film being made of the same material as the first seed film; The piezoelectric device according to claim 4 or 5, wherein the second conductive film is in contact with an upper surface (32) of the second seed film and is continuously disposed at a position directly above both the second insulating portion and the first piezoelectric film.

9. The piezoelectric device according to claim 8 , wherein the second insulating portion is made of the same material as the first seed film.

10. A piezoelectric device according to any one of the preceding claims, comprising an oxide layer (41) on the sidewalls of the trench.

11. The piezoelectric device according to claim 1 , wherein the piezoelectric material is ScAlN.

Images