Drive element

Abstract

This drive element comprises: a substrate (101); a layered structure (110) that is formed on the substrate (101) and includes a piezoelectric layer (104), and an upper electrode layer (105) and a lower electrode layer (103) which are positioned above and below the piezoelectric layer (104); a first protective film (106) that is composed of Al2O3 and covers the entire surface of the layered structure (110); and a second protective film (107) that is warm water-resistant and covers the entire surface of the first protective film (106).

Description

Drive element

[0001] The present invention relates to a drive element that drives a movable part.

[0002] A driving element that drives a movable part is known. In this type of driving element, a piezoelectric element can be used as a driving source. For example, Patent Document 1 listed below describes a meander-type driving element that uses a piezoelectric element as a driving source. The driving part is configured by sandwiching the piezoelectric element between a lower electrode and an upper electrode. The driving part is covered with an insulating protective film.

[0003] International Publication No. 2023-162674

[0004] In the driving element described above, the protective film is formed of a moisture-resistant material. For example, the protective film is made of Al, which has excellent moisture resistance. ２ O ３ However, Al ２ O ３ Therefore, when the drive element is used in a hot and humid environment, hot water droplets may penetrate through the protective film and cause electrical problems in the drive unit.

[0005] In view of the above problems, an object of the present invention is to provide a driving element that can operate with high reliability even in a high-temperature and high-humidity environment.

[0006] A main aspect of the present invention relates to a driving element for driving a movable part. The driving element according to this aspect includes a substrate, a laminated structure formed on the substrate and including a piezoelectric layer, an upper electrode layer and a lower electrode layer disposed above and below the piezoelectric layer, and an Al ２ O ３ The laminated structure is provided with a first protective film that covers the entire surface of the laminated structure, and a warm-water-resistant second protective film that covers the entire surface of the first protective film.

[0007] In the driving element according to this aspect, the entire surface of the first protective film is covered with the hot-water-resistant second protective film, preventing the first protective film from being exposed to high-temperature hot water. Even if a humid gas such as water vapor passes through the second protective film, the gas is blocked by the moisture-resistant first protective film. Therefore, the driving element can operate reliably even in a high-temperature, high-humidity environment.

[0008] As described above, according to the present invention, it is possible to provide a driving element that can operate with high reliability even in a hot and humid environment.

[0009] The effects and significance of the present invention will become more apparent from the following description of the embodiments, however, the embodiments shown below are merely examples of how the present invention can be implemented, and the present invention is not limited to the embodiments described below.

[0010] FIG. 1 is a perspective view schematically illustrating the configuration of a driving element according to an embodiment. FIG. 2(a) is a diagram schematically illustrating a cross-sectional structure of the driving element when cut at the A-A' position in FIG. 1 according to an embodiment. FIG. 2(b) is a diagram schematically illustrating a cross-sectional structure of the driving element when cut at the B-B' position in FIG. 1 according to an embodiment. FIG. 3 is a plan view schematically illustrating an electrical connection between a driving unit and a terminal unit according to an embodiment. FIGS. 4(a) and 4(b) are diagrams schematically illustrating a cross-sectional structure according to a comparative example. FIGS. 5(a) and 5(b) are diagrams schematically illustrating a film formation process of a first protective film in a vibrating unit according to an embodiment. FIGS. 6(a) and 6(b) are diagrams schematically illustrating a film formation process of a first protective film in a fixed unit according to an embodiment. FIGS. 7(a) and 7(b) are diagrams schematically illustrating a film formation process of a first protective film and a second protective film in a vibrating unit according to a first modified example. 8(a) and 8(b) are diagrams schematically showing a film formation process of a first protective film and a second protective film in a fixed portion according to Modification Example 1. FIGS. 9(a) and 9(b) are diagrams schematically showing a film formation process of a first protective film and a second protective film in a vibrating portion according to Modification Example 2. FIGS. 10(a) and 10(b) are diagrams schematically showing a film formation process of a first protective film and a second protective film in a fixed portion according to Modification Example 2. FIG. 11 is a perspective view schematically showing a configuration of a drive element according to Modification Example 3.

[0011] However, the drawings are for illustrative purposes only and do not limit the scope of the present invention.

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. For convenience, each drawing is labeled with mutually orthogonal X, Y, and Z axes. The positive direction of the Z axis is the vertically upward direction and corresponds to the thickness direction (height direction) of the drive element 1.

[0013] This embodiment describes a driving element that scans a beam incident on a reflecting surface by rotating the reflecting surface. This driving element is mounted, for example, on an image display device that displays a predetermined image by scanning a beam. However, the device in which the driving element is mounted is not limited to this. For example, a driving element having the following configuration may be mounted on an object detection device that detects the presence or absence of an object in the projection direction of the beam and the distance to the object.

[0014] FIG. 1 is a perspective view schematically showing the configuration of a driving element 1. As shown in FIG.

[0015] The driving element 1 includes a fixed portion 10, a vibrating portion 20, a connecting portion 30, a movable portion 40, driving portions 51 and 52, wiring portions 61 and 62, and terminal portions 71 to 73. The driving element 1 has a shape symmetrical about a center C10 in a plan view.

[0016] The fixed portion 10 supports the movable portion 40 via the vibrating portion 20. A pair of fixed portions 10 and a pair of vibrating portions 20 are arranged to sandwich the movable portion 40 in the X-axis direction. The vibrating portion 20 has a meandering shape in the Y-axis direction in a plan view. That is, in one vibrating portion 20, four rectangular plate-like portions whose long sides are parallel to the Y-axis in a plan view are arranged side by side in the X-axis direction. Two adjacent plate-like portions are connected at their ends on the positive side of the Y-axis or the negative side of the Y-axis so that one vibrating portion 20 has a meandering shape in a plan view.

[0017] One end of the vibrating section 20 is connected to the fixed section 10, and the other end of the vibrating section 20 is connected to the movable section 40 via the connecting section 30. The movable section 40 is circular in plan view. The upper surface of the movable section 40 forms a reflective surface 40a. The reflective surface 40a may be formed by mirror-finishing the upper surface of the movable section 40, or a reflective film may be formed on the upper surface of the movable section 40 to form the reflective surface 40a.

[0018] The fixed part 10, the vibrating part 20, the connecting part 30 and the movable part 40 are connected by a common substrate 101 (see FIGS. 2(a) and 2(b)).

[0019] Specifically, an SOI substrate having a surface oxide film, an active layer (Si), a box layer, a base layer (Si), and a surface oxide film stacked in this order from top to bottom is etched to form the outline of the driving element 1 in a plan view. Furthermore, the box layer, the base layer, and the lower surface oxide film are removed from the SOI substrate by etching to form a common substrate 101. At this time, the box layer, the base layer, and the lower surface oxide film remain on the fixed portion 10 to ensure its thickness. The box layer, the base layer, and the lower surface oxide film remain on the vibrating portion 20 so that ribs are formed at the positive and negative ends of the Y-axis. Furthermore, the box layer, the base layer, and the lower surface oxide film remain on the outer periphery of the movable portion 40 so that ribs are formed.

[0020] Drive units 51 and 52 are alternately arranged in the region of the vibration unit 20 on the substrate 101. As will be described later with reference to Fig. 2(a) , the drive units 51 and 52 are formed by arranging an upper electrode layer 105 and a lower electrode layer 103 above and below a piezoelectric layer 104.

[0021] The upper electrode layers 105 of the two driving units 51 arranged in one vibrating unit 20 are connected to each other by a wiring unit 61 arranged on the upper surface of the substrate 101, and are further connected to the terminal unit 71 of the fixed unit 10 by the wiring unit 61.

[0022] The upper electrode layers 105 of the two drive units 52 arranged in one vibrating unit 20 are connected to each other by wiring units 62 arranged on the upper surface of the substrate 101, and are further connected to terminal units 72 of the fixed unit 10 by the wiring units 62. The lower electrode layers 103 of each of the drive units 51, 52 arranged in one vibrating unit 20 are connected to terminal units 73 of the fixed unit 10 via the wiring units 61, 62.

[0023] Therefore, by connecting terminal 73 to the ground of the drive circuit and supplying drive signals of opposite phases that oscillate positively and negatively from the drive circuit to terminals 71 and 72, drive units 51 and 52 deform in opposite directions, thereby allowing movable unit 40 to rotate repeatedly about rotation axis R10.

[0024] Fig. 2(a) is a diagram schematically showing the cross-sectional structure of the driving element 1 when cut at the position AA' in Fig. 1. Fig. 2(b) is a diagram schematically showing the cross-sectional structure of the driving element 1 when cut at the position BB' in Fig. 1.

[0025] 2(a), in the plate-shaped portion of the vibration unit 20, the drive unit 51 and the wiring unit 62 are arranged side by side in the X-axis direction on a substrate 101. In the region of the drive unit 51 and the wiring unit 62, a surface oxide film 102, a lower electrode layer 103, a piezoelectric layer 104, and an upper electrode layer 105 are stacked in this order from the bottom up. The surface oxide film 102 is the surface oxide film on the upper side of the SOI substrate described above. The substrate 101 is the active layer (Si) of the SOI substrate described above. In the region other than the region of the drive unit 51 and the wiring unit 62, the surface oxide film 102 is removed by etching.

[0026] The lower electrode layer 103 is made of, for example, platinum (Pt). The piezoelectric layer 104 is made of, for example, PZT (lead zirconate titanate: Pb(Zr,Ti)O ３ The upper electrode layer 105 is made of, for example, gold (Au). However, the materials that make up the lower electrode layer 103, the piezoelectric layer 104, and the upper electrode layer 105 are not limited to these.

[0027] In this embodiment, the surface oxide film 102, the lower electrode layer 103, the piezoelectric layer 104, and the upper electrode layer 105 form a laminated structure 110. The laminated structure 110 may further include other layers. The laminated structure 110 is covered with a first protective film 106. The first protective film 106 is further covered with a second protective film 107.

[0028] The first protective film 106 is made of a material having excellent moisture resistance. ２ O ３ It is composed of Al. ２ O ３ has excellent adhesion to gold (Au) constituting the upper electrode layer 105. ２ O ３ Therefore, when the driving element 1 is used in a high-temperature and high-humidity environment, the first protective film 106 (Al２ O ３ ) is exposed, the first protective film 106 (Al ２ O ３ ) may cause deterioration of the film quality.

[0029] To address this issue, the first protective film 106 is covered with the second protective film 107. The second protective film 107 is made of a material that is highly resistant to hot water. For example, the second protective film 107 is made of ZrO ２ However, the second protective film 107 is not limited to this, and may be made of ZrO ２ , TiO ２ , Nb ２ O ５ , CeO ２ , Ta ２ O ５ , HfO ２ , Si ３ N ４ , Y ２ O ３ , MgO, SiO ２ , MgF ２ The film may be composed of a single layer of any one of the above or a laminated film of a combination of at least two of these.

[0030] Although these materials constituting the second protective film 107 have excellent resistance to hot water, they are not as resistant to Al, which is the material of the first protective film 106. ２ O ３ On the other hand, the Al constituting the first protective film 106 has poorer moisture resistance than the Al ２ O ３ As described above, the laminated structure 110 has excellent moisture resistance but poor hot water resistance. Therefore, by covering the laminated structure 110 with the first protective film 106 and the second protective film 107, the moisture resistance and hot water resistance of the laminated structure 110 can be complementarily achieved. This allows the driving element 1 to operate with high reliability even when the driving element 1 is used in a high-temperature, high-humidity environment.

[0031] 2(b), the fixed portion 10 has terminal portions 71 to 73 arranged on a substrate 101. Similar to the laminated structure 110, the terminal portions 71 and 72 have a surface oxide film 102, a lower electrode layer 103, a piezoelectric layer 104, and an upper electrode layer 105 laminated thereon. In the areas surrounding the terminal portions 71 and 72, the upper electrode layer 105 has been removed by etching, leaving the surface oxide film 102, the lower electrode layer 103, and the piezoelectric layer 104. In the terminal portion 73, the piezoelectric layer 104 and the upper electrode layer 105 have been removed by etching, leaving the lower electrode layer 103 exposed. Here, the laminated structure 110 remains on the positive side of the terminal portion 73 along the Y axis.

[0032] The piezoelectric layer 104 near the terminal portions 71 and 72 is covered with an upper electrode layer 105 and a first protective film 106. That is, the top surface of the piezoelectric layer 104 is covered with the upper electrode layer 105 arranged in the region of the terminal portions 71 and 72 and the first protective film 106, and the side surface of the piezoelectric layer 104 is covered with the first protective film 106. Furthermore, the first protective film 106 is covered with a second protective film 107. The second protective film 107 covers the entire surface of the first protective film 106 so that the upper electrode layer 105 of the terminal portions 71 and 72 is exposed.

[0033] 2A, the laminated structure 110 on the positive side of the terminal portion 73 along the Y axis is also covered with the first protective film 106 and the second protective film 107. The lower electrode layer 103 of the terminal portion 73 is covered with the first protective film 106 and the second protective film 107 so that a portion of the lower electrode layer 103 is exposed. The second protective film 107 covers the entire surface of the first protective film 106.

[0034] 2(a), the terminal portions 71 and 72 are also covered with the first protective film 106 and the second protective film 107, and these protective films complementarily achieve moisture resistance and hot water resistance. Furthermore, the laminate structure 110 on the positive side of the terminal portion 73 along the Y axis is also covered with the first protective film 106 and the second protective film 107, and these protective films complementarily achieve moisture resistance and hot water resistance. Therefore, even when the driving element 1 is used in a high-temperature and high-humidity environment, the driving element 1 can operate with high reliability.

[0035] FIG. 3 is a plan view showing a schematic diagram of the electrical connection between the driving portions 51 and 52 and the terminal portions 71 to 73. As shown in FIG.

[0036] 3 shows the electrical connection configuration within the range of the fixed portion 10 and the vibrating portion 20 on the positive side of the X axis. The outlines of the fixed portion 10 and the vibrating portion 20 are shown by dashed lines. For convenience, the first protective film 106 and the second protective film 107 are not shown in FIG. 3. The electrical connection configuration within the range of the fixed portion 10 and the vibrating portion 20 on the negative side of the X axis is equivalent to the configuration in FIG. 3 rotated 180° about the Z axis.

[0037] In Fig. 3, layers exposed upward when the first protective film 106 and the second protective film 107 are omitted are shown with hatching similar to that in Figs. 2(a) and (b). For convenience, the wiring portions 61 and 62 are shown simply as lines rather than as layers. As shown in Fig. 2(a), the wiring portions 61 and 62 are configured with a stacked structure 110, and therefore the upper electrode layer 105 is exposed upward.

[0038] 3 , the upper electrode layers 105 of the two drive units 51 are connected in series by wiring units 61, and are further connected to terminal units 71 by the wiring units 61. The two drive units 51, the wiring units 61, and the terminal units 71 are integrally formed with a common layered structure 110. Similarly, the upper electrode layers 105 of the two drive units 52 are connected in series by wiring units 62, and are further connected to terminal units 72 by the wiring units 62. The two drive units 52, the wiring units 62, and the terminal units 72 are integrally formed with a common layered structure 110.

[0039] A lower electrode layer 103 extends over the fixed portion 10. The lower electrode layer 103 of the fixed portion 10 is integrally connected to the lower electrode layer 103 of the wiring portions 61 and 62. A piezoelectric layer 104 remains around the terminal portions 71 to 73, and an upper electrode layer 105 remains in the region of the terminal portions 71 and 72. Therefore, the region of the terminal portions 71 and 72 has the same configuration as the laminated structure 110 of the wiring portions 61 and 62. In the region of the terminal portion 73, the piezoelectric layer 104 has been removed, exposing the lower electrode layer 103.

[0040] Therefore, by connecting the lower electrode layer 103 of the terminal portion 73 to ground, the two drive portions 51 and the two drive portions 52 are connected to ground. Furthermore, by applying a drive voltage to the upper electrode layer 105 of the terminal portion 71, this drive voltage can be applied to the upper electrode layer 105 of the two drive portions 51, and by applying a drive voltage to the upper electrode layer 105 of the terminal portion 72, this drive voltage can be applied to the upper electrode layer 105 of the two drive portions 52. In this way, the piezoelectric layer 104 of each of the drive portions 51, 52 can be driven.

[0041] 2(a) shows the cross-sectional structure of the vibration section 20 (plate-shaped portion) in which the driving section 51 furthest on the positive side of the X axis in FIG. 3 is arranged, along with the cross-sectional structures of the first protective film 106 and the second protective film 107. The cross-sectional structure of the vibration section 20 (plate-shaped portion) in which the remaining driving section 51 in FIG. 3 is arranged is also the same as FIG. 2(a). Furthermore, the cross-sectional structure of the vibration section 20 (plate-shaped portion) in which the two driving sections 52 in FIG. 3 are arranged is also the same as FIG. 2(a). In this case, the driving section 51 and the wiring section 62 in FIG. 2(a) are changed to the driving section 52 and the wiring section 61.

[0042] The cross-sectional structure of each plate-like portion of the vibrating portion 20 on the negative side of the X-axis is a cross-sectional structure obtained by inverting the cross-sectional structure of Figure 2(a) in the X-axis direction. This can be easily understood from the symmetry of the pair of fixed portions 10 and the pair of vibrating portions 20.

[0043] 4A and 4B are diagrams schematically showing a cross-sectional structure according to a comparative example.

[0044] The cross-sectional structure in Figure 4(a) is the same as in Figure 2(a) when the driving element 1 is cut at the A-A' position in Figure 1, and the cross-sectional structure in Figure 4(b) is the same as in Figure 2(b) when the driving element 1 is cut at the B-B' position in Figure 1.

[0045] In the comparative example, after the first protective film 106 and the second protective film 107 are successively formed, an etching process is performed to form the terminal portion 73 and to process the end faces of the first protective film 106 and the second protective film 107. As a result, the end faces of the first protective film 106 are exposed at the positions indicated by the dotted circle in FIGS. 4(a) and 4(b). In this case, if the driving element 1 is used in a high-temperature and high-humidity environment, these end faces of the first protective film 106 will be exposed to hot water such as water droplets. As a result, the first protective film 106 (Al ２ O ３ ) may deteriorate in quality, and moisture may penetrate between the first protective film 106 and the substrate 101.

[0046] In this case, in order to prevent such moisture penetration, it is necessary to set the length of the portion of the first protective film 106 extending along the upper surface of the substrate 101 (corresponding to the bottom portion 106a in FIGS. 2(a) and 2(b)) to a certain extent. However, doing so requires reducing the width of the driving section 51 (piezoelectric layer 104) in the planar direction, which results in a decrease in the driving force of the driving section 51. In the driving element 1, it is required to increase the arrangement area (installation area) of the piezoelectric layer 104 on the substrate 101 of the vibration section 20 as much as possible to increase the driving force of the driving section 51 and to increase the driving efficiency of the movable section 40 as much as possible.

[0047] In contrast to this, in this embodiment, as shown in Figures 2(a) and (b), the entire surface of the first protective film 106, including the end faces of the first protective film 106, is covered with the second protective film 107. Therefore, even if the driving element 1 is used in a high-temperature and high-humidity environment, the first protective film 106 is not exposed to hot water such as high-temperature water droplets. Therefore, the first protective film 106 (Al ２ O ３ ) deterioration of the film quality due to hot water does not occur, and the driving element 1 can operate with high reliability even in a high-temperature and high-humidity environment.

[0048] Furthermore, because the end face of the first protective film 106 is covered by the second protective film 107 in this way, the width from this end face to the end face of the substrate 101 can be set small, and as a result, the widths W1 and W2 in FIG. 2A can be reduced. This allows the arrangement area (installation area) of the drive unit 51 to be expanded, and the drive force of the drive unit 51 to be increased. This is also true for the drive unit 52. Therefore, the drive efficiency of the movable unit 40 can be improved.

[0049] 2B can be reduced on the fixed portion 10 side for the same reason, and the installation area around the terminal portions 71 to 73 can be increased. Therefore, the width of the terminal portions 71 to 73 can be smoothly ensured.

[0050] 5(a) and 5(b) are diagrams schematically showing the film formation process of the first protective film 106 in the vibrating portion 20. Figures 6(a) and 6(b) are diagrams schematically showing the film formation process of the first protective film 106 in the fixed portion 10.

[0051] Before forming the first protective film 106, the surface oxide film 102, the lower electrode layer 103, the piezoelectric layer 104, and the upper electrode layer 105 shown in FIGS. 5(a) and 6(a) are formed on the substrate 101. These films are formed by a process similar to a well-known semiconductor film formation process. Thereafter, as shown in FIGS. 5(a) and 6(a), the first protective film 106 (Al ２ O ３ ) is formed. Here, the first protective film 106 is formed by atomic layer deposition (ALD). The thickness of the first protective film 106 is constant. The thickness of the first protective film 106 can be set to about 20 to 300 nm.

[0052] 5(b) and 6(b), a portion of the first protective film 106 is removed by an etching process. The etching process is performed by anisotropic etching. Here, the first protective film 106 is removed so that a portion of the first protective film 106 that wraps around the upper surface of the substrate 101 or the upper surface of the upper electrode layer 105 remains. As a result, a skirt portion 106a that extends along the upper surface of the substrate 101 is formed in the first protective film 106.

[0053] Distances R1 and R3 from the side surfaces of the laminated structure 110 to the end surfaces of the first protective film 106 can be set to 1 μm or more. This can improve adhesion between the first protective film 106 and the upper surface of the substrate 101. Distances R2 and R4 from the end surfaces of the first protective film 106 to the end surfaces of the substrate 101 can be set to 1 μm or more. However, as these distances increase, the installation area of ​​the laminated structure 110 (piezoelectric layer 104) decreases, and the driving efficiency decreases. For this reason, it is preferable that these distances be as small as possible and be 1 μm or more.

[0054] After the first protective film 106 is formed and processed in this manner, the second protective film 107 is formed, and then an etching process is performed on the second protective film 107. As a result, the second protective film 107 is formed as shown in FIGS. 2(a) and 2(b). The second protective film 107 also has a skirt portion 107a that extends along the upper surface of the substrate 101. The second protective film 107 may be formed by the ALD method, as with the first protective film 106. The thickness of the second protective film 107 is constant. The thickness of the second protective film 107 may be set to about 10 to 100 nm.

[0055] Here, second protective film 107 is formed so that the edge surface of second protective film 107 is flush with the edge surface of substrate 101. Therefore, the edge surface of second protective film 107 is spaced from the edge surface of first protective film 106 by 1 μm or more, which are the distances R2 and R4 in Figures 5(b) and 6(b) . This ensures a sufficient width for skirt portion 107a of second protective film 107 that wraps around the upper surface of substrate 101, and improves adhesion between second protective film 107 and substrate 101 at skirt portion 107a.

[0056] <Effects of the embodiment> According to the above embodiment, the following effects are achieved.

[0057] As shown in FIG. 2A, the driving element 1 includes a substrate 101, a laminated structure 110 formed on the substrate 101 and including a piezoelectric layer 104, an upper electrode layer 105 and a lower electrode layer 103 disposed above and below the piezoelectric layer 104, and an Al ２ O ３The laminated structure 110 is provided with a first protective film 106 that covers the entire surface of the laminated structure 110 , and a second protective film 107 that is resistant to hot water and that covers the entire surface of the first protective film 106 .

[0058] With this configuration, all surfaces of the first protective film 106, including the end faces, are covered with the hot-water-resistant second protective film 107, preventing the first protective film 106 from being exposed to high-temperature hot water. Furthermore, even if a humid gas such as water vapor passes through the second protective film 107, this gas is blocked by the highly moisture-resistant first protective film 106. Therefore, the driving element 1 can be operated with high reliability even in a high-temperature and humid environment.

[0059] As shown in Figures 1 and 2(a), the driving element 1 has driving units 51 and 52 that apply driving force to the movable unit 40, wiring units 61 and 62 connected to the driving units 51 and 52, and terminal units 71 to 73 connected to the wiring units 61 and 62 for supplying driving signals, which are arranged on a substrate 101, and a laminated structure 110 is formed in the areas of the driving units 51 and 52 and the wiring units 61 and 62.

[0060] According to this configuration, the entire surface of the laminated structure 110 of the drive units 51, 52 and the wiring units 61, 62 is covered with the first protective film 106 and the second protective film 107, so that when the drive element 1 is used in a high-temperature and high-humidity environment, electrical malfunctions can be prevented from occurring in the drive units 51, 52 and the wiring units 61, 62. Therefore, the drive element 1 can be operated with high reliability.

[0061] As shown in Figures 2(b) and 3, in the terminal portions 71 and 72, the piezoelectric layer 104, the upper electrode layer 105, and the lower electrode layer 103 extend from the wiring portions 61 and 62, and in the terminal portions 71 and 72, the entire surface of the piezoelectric layer 104 is covered with the upper electrode layer 105, the lower electrode layer 103, and the first protective film 106, and in the terminal portions 71 and 72, the entire surface of the first protective film 106 is covered with the second protective film 107.

[0062] According to this configuration, even at the terminal portions 71 and 72, the second protective film 107 prevents the first protective film 106 from being exposed to high-temperature hot water, and humid gas such as water vapor that passes through the second protective film 107 is blocked by the first protective film 106. Therefore, electrical malfunctions due to high temperature and humidity can be prevented at the terminal portions 71 and 72, and the driving element 1 can be operated with high reliability.

[0063] As shown in FIG. 2A, the end face of the second protective film 107 and the end face of the substrate 101 are flush with each other.

[0064] With this configuration, the arrangement area of ​​the piezoelectric layer 104 as a driving source can be expanded in a direction approaching the end face of the substrate 101. In other words, if the width W2 of the portion (bottom portion 107a) of the second protective film 107 that wraps around the upper surface of the substrate 101 is a predetermined dimension, aligning the end face of the second protective film 107 flush with the end face of the substrate 101 allows the position of the side of the laminated structure 110 to be shifted toward the end face of the substrate 101 compared to when the end face of the second protective film 107 is recessed inward from the end face of the substrate 101. Therefore, the arrangement area (installation area) of the piezoelectric layer 104 as a driving source can be expanded, and a greater driving force can be applied to the movable part 40.

[0065] As shown in FIGS. 2( a ), 2 ( b ), 5 ( b ), and 6 ( b ), the first protective film 106 has a skirt portion 106 a that extends along the upper surface of the substrate 101 .

[0066] This configuration can improve the adhesion between bottom portion 106a and substrate 101, thereby reliably preventing humid gas from penetrating into the interior from the boundary between first protective film 106 and the upper surface of substrate 101. Furthermore, by providing bottom portion 106a in this manner, it is possible to reliably maintain adhesion between first protective film 106 and substrate 101 even if processing variations occur in first protective film 106 during etching.

[0067] As explained with reference to Figures 5(b) and 6(b), it is preferable that the end face of the first protective film 106 (end face of the skirt portion 106a) is at least 1 μm (distances R1, R3) away from the side face of the piezoelectric layer 104.

[0068] In this way, by forming a bottom portion 106a on the first protective film 106 so that the end face of the first protective film 106 is at least 1 μm away from the side surface of the laminated structure 110, this bottom portion 106a can reliably prevent humid gas from entering the piezoelectric layer 104.

[0069] As described with reference to FIGS. 5B and 6B, the end face of the second protective film 107 is spaced apart from the end face of the first protective film 106 by 1 μm or more (distances R2 and R4).

[0070] In this way, by forming a portion of the second protective film 107 (bottom portion 107a) that wraps around the top surface of the substrate 101 so that the end face of the second protective film 107 is at least 1 μm away from the end face of the first protective film 106, this portion can reliably prevent hot water from entering the first protective film 106.

[0071] As described with reference to FIGS. 5A and 5B, the thickness of the first protective film 106 formed on the top surface and side surfaces of the laminated structure 110 is substantially uniform.

[0072] Because the first protective film 106 covers the laminated structure 110, when the laminated structure 110 is used in the driving units 51 and 52, the first protective film 106 affects the driving efficiency of the piezoelectric layer 104, which is the driving source. Therefore, from the viewpoint of the driving efficiency of the piezoelectric layer 104, it is preferable that the thickness of the first protective film 106 is as small as possible. On the other hand, from the viewpoint of moisture resistance, which is the original purpose of the first protective film 106, it is preferable that the thickness of the first protective film 106 is somewhat large. Due to these contradictory reasons, it is sufficient that the thickness of the first protective film 106 is substantially constant near the minimum film thickness that maintains coverage. This makes it possible to maintain high driving efficiency of the piezoelectric layer 104 while ensuring coverage by the first protective film 106.

[0073] As described with reference to FIGS. 2A and 2B, the thickness of the second protective film 107 formed on the upper surface and side surfaces of the first protective film 106 is substantially constant.

[0074] As with the first protective film 106, it is preferable that the thickness of the second protective film 107 be as small as possible from the viewpoint of the drive efficiency of the piezoelectric layer 104. On the other hand, from the viewpoint of the original purpose of the second protective film 107, that is, resistance to hot water, it is preferable that the thickness of the second protective film 107 be somewhat large. For these reasons, it is sufficient that the thickness of the second protective film 107 is substantially constant around the minimum film thickness that can maintain coverage. This makes it possible to maintain high drive efficiency of the piezoelectric layer 104 while ensuring coverage by the second protective film 107.

[0075] As described above, the second protective film 107 is made of ZrO ２ , TiO ２ , Nb ２ O ５ , CeO ２ , Ta ２ O ５ , HfO ２ , Si ３ N ４ , Y ２ O ３ , MgO, SiO ２ , MgF ２ The film may be a single layer of any one of the above or a laminated film of a combination of at least two of these.

[0076] By using these materials for the second protective film 107, the second protective film 107 having excellent resistance to warm water can be formed well on the surface of the first protective film 106.

[0077] 7(a) and 7(b) are diagrams schematically showing a process of forming the first protective film 106 and the second protective film 107 in the vibrating section 20 according to Modification 1. Figures 8(a) and 8(b) are diagrams schematically showing a process of forming the first protective film 106 and the second protective film 107 in the fixed section 10 according to Modification 1.

[0078] 7( a) and 8(a) show the state of the first protective film 106 after etching has been applied to the first protective film 106 formed as shown in FIGS. 5(a) and 6(a). In Modification 1, isotropic etching is used as the etching process for the first protective film 106. As a result, the end faces of the first protective film 106 have a tapered shape with the lower portion widening outward, as shown by the dashed circle in FIGS. 7(a) and 8(a).

[0079] Thereafter, similarly to the above embodiment, the second protective film 107 is formed, and then an etching process is performed on the second protective film 107. As a result, the second protective film 107 is formed as shown in FIGS. 7B and 8B. Isotropic etching is also used for the etching process here. The shape of the second protective film 107 near the end face of the first protective film 106 is tapered, reflecting the end face shape of the first protective film 106. The thicknesses of the first protective film 106 and the second protective film 107 may be similar to those of the above embodiment.

[0080] Effect of Modification Example 1 As described above, tapering the end faces of first protective film 106 improves adhesion of second protective film 107 to first protective film 106. This improves the coverage of second protective film 107 to first protective film 106.

[0081] 9(a) and 9(b) are diagrams schematically showing a film formation process of the first protective film 106 and the second protective film 107 in the vibrating section 20 according to Modification 2. Figures 10(a) and 10(b) are diagrams schematically showing a film formation process of the first protective film 106 and the second protective film 107 in the fixed section 10 according to Modification 2.

[0082] As shown in FIGS. 9A and 10A, in Modification 2, the first protective film 106 is etched so as to prevent the formation of the skirt portion 106a. This etching may be performed by anisotropic etching. Thereafter, the step of forming the second protective film 107 is performed, as in the above embodiment. As a result, the second protective film 107 is formed, as shown in FIGS. 9B and 10B.

[0083] Effect of Modification 2 According to Modification 2, the first protective film 106 does not have the bottom portion 106a, so the side surface of the laminated structure 110 can be brought closer to the end surface of the substrate 101. This allows the arrangement area (installation area) of the piezoelectric layer 104 in the drive units 51 and 52 to be expanded, and the drive efficiency of the movable unit 40 can be improved.

[0084] On the other hand, since the first protective film 106 does not have the skirt portion 106a, the coverage of the laminated structure 110 by the first protective film 106 is reduced. Therefore, in order to further improve the coverage of the laminated structure 110 and increase the reliability of the driving element 1, it is preferable that the first protective film 106 has the skirt portion 106a, as in the above embodiment. Furthermore, in consideration of masking deviation (processing variation) during the etching process for the first protective film 106, it can be said that it is preferable to provide the skirt portion 106a in the first protective film 106.

[0085] Although the above embodiment shows an example in which the present invention is applied to a meandering type driving element 1, the present invention may also be applied to driving elements of other types. For example, the present invention may be applied to a tuning fork type driving element 2 shown in FIG.

[0086] The driving element 2 includes a pair of fixed portions 201, a pair of arm portions 202, a pair of support portions 203, and a movable portion 204. As described above, these are configured on a common substrate. A driving portion 205 is disposed on the arm portion 202, and each driving portion 205 is connected to terminal portions 206, 207, and 208 by wiring portions (not shown) formed on the upper surface of the substrate. A reflective film 204a is formed on the upper surface of the movable portion 204.

[0087] The cross-sectional structure at CC' may be substantially similar to the cross-sectional structure in Figure 2(a). The cross-sectional structure at DD' may be substantially similar to the cross-sectional structure in Figure 2(b). The wiring is configured in the same manner as in the laminated structure 110, and is connected to terminal portions 206, 207 and terminal portion 208. The layer structure around terminal portions 206 to 208 may be similar to the layer structure of terminal portions 71 to 73 in Figure 3.

[0088] In the third modification, as in the above embodiment, the surfaces of the laminated structure and the layered structure around the terminal portions 206 to 208, as well as their end faces, are completely covered with the first protective film 106 and the second protective film 107. Therefore, even if the driving element 2 is used in a high-temperature and high-humidity environment, the driving element 2 can be operated with high reliability.

[0089] <Other Modifications> In the above embodiment, as shown in FIG. 2( b), the end face of the second protective film 107 and the end face of the substrate 101 are flush with each other. However, the end face of the second protective film 107 may be recessed inward relative to the end face of the substrate 101.

[0090] 2B, the side surface of the second protective film 107 can be brought closer to the end surface of the substrate 101, thereby increasing the installation area of ​​the piezoelectric layer 104. Therefore, in order to further increase the driving force of the piezoelectric layer 104, it is preferable that the end surface of the second protective film 107 is flush with the end surface of the substrate 101, as in the above embodiment.

[0091] The configuration of the meander-type driving element 1 is not limited to the configuration shown in FIG. 1 and can be modified in various ways. For example, some or all of the ribs formed on the outer periphery of the movable part 40 may be omitted, or additional ribs may be formed on the underside of the movable part 40. The connection position of the connection part 30 to the movable part 40 may also be changed from the position shown in FIG. 11. Furthermore, the layout of the wiring parts 61 and 62 and the terminal parts 71 to 73 may also be changed. The configuration of the tuning-fork-type driving element 2 shown in FIG. 11 may also be modified as appropriate.

[0092] Furthermore, the driving element does not have to scan the beam by rotating the movable part. In this case, the movable part does not have to have a reflective surface, and other members besides the reflective surface may be arranged. Furthermore, the driving of the movable part is not limited to rotation, and may be driving in the vertical direction, etc.

[0093] In addition, the embodiments of the present invention can be modified in various ways as appropriate within the scope of the technical ideas set forth in the claims.

[0094] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0095] (Technology 1) A driving element for driving a movable part, comprising: a substrate; a laminated structure formed on the substrate, the laminated structure including a piezoelectric layer, an upper electrode layer and a lower electrode layer disposed above and below the piezoelectric layer; and Al２ O ３ a first protective film that covers the entire surface of the laminated structure, and a second protective film that is resistant to hot water and covers the entire surface of the first protective film.

[0096] According to this technology, the entire surface of the first protective film is covered with the hot-water-resistant second protective film, preventing the first protective film from being exposed to high-temperature hot water. Even if humid gases such as water vapor pass through the second protective film, the gases are blocked by the highly moisture-resistant first protective film. Therefore, the driving element can operate reliably even in a high-temperature, high-humidity environment.

[0097] (Technology 2) The driving element according to Technology 1, characterized in that a driving unit that applies a driving force to the movable unit, a wiring unit connected to the driving unit, and a terminal unit that is connected to the wiring unit and supplies a driving signal are arranged on the substrate, and the laminated structure is formed in the area of ​​the driving unit and the wiring unit.

[0098] According to this technology, the entire surface of the laminated structure of the drive unit and wiring unit is covered with the first protective film and the second protective film, so that electrical problems in the drive unit and wiring unit can be prevented when the drive element is used in a high-temperature and high-humidity environment, thereby enabling the drive element to operate with high reliability.

[0099] (Technology 3) A driving element according to Technology 2, characterized in that the piezoelectric layer, the upper electrode layer, and the lower electrode layer extend from the wiring portion to the terminal portion, the entire surface of the piezoelectric layer in the terminal portion is covered with the upper electrode layer, the lower electrode layer, and the first protective film, and the entire surface of the first protective film in the terminal portion is covered with the second protective film.

[0100] According to this technology, even at the terminal portion, the second protective film prevents the first protective film from being exposed to high-temperature hot water, and humid gases such as water vapor that pass through the second protective film are blocked by the first protective film, thereby preventing electrical malfunctions at the terminal portion due to high temperature and humidity, and allowing the drive element to operate with high reliability.

[0101] (Technology 4) The driving element according to any one of technologies 1 to 3, characterized in that an end face of the second protective film and an end face of the substrate are flush with each other.

[0102] This technology allows the area where the piezoelectric layer serving as the driving source is located to be expanded in the direction toward the edge of the substrate. In other words, if the width of the portion (bottom) of the second protective film that wraps around the top surface of the substrate is a predetermined dimension, aligning the edge of the second protective film flush with the edge of the substrate allows the side of the laminated structure to be shifted toward the edge of the substrate, compared to when the edge of the second protective film is recessed inward from the edge of the substrate. This allows the area where the piezoelectric layer serving as the driving source is located to be expanded, and a greater driving force can be applied to the movable part.

[0103] (Technology 5) The driving element according to any one of Technologies 1 to 4, wherein the first protective film has a skirt portion extending along the upper surface of the substrate.

[0104] This technique can improve the adhesion between the skirt and the substrate, thereby reliably preventing humid gas from entering the interior through the boundary between the first protective film and the upper surface of the substrate.

[0105] (Technology 6) The driving element according to Technology 5, wherein the end face of the first protective film is spaced 1 μm or more from the side face of the piezoelectric layer.

[0106] In this way, by forming the bottom of the first protective film so that the end face of the first protective film is at least 1 μm away from the side face of the piezoelectric layer, the bottom can reliably prevent humid gas from entering the piezoelectric layer.

[0107] (Technology 7) The driving element according to Technology 6, wherein the end face of the second protective film is spaced 1 μm or more from the end face of the first protective film.

[0108] In this way, by forming a skirt portion on the second protective film so that the end face of the second protective film is at least 1 μm away from the end face of the first protective film, this skirt portion can reliably prevent hot water from entering the first protective film.

[0109] (Technology 8) The driving element according to any one of Technologies 5 to 7, wherein the end face of the first protective film has a tapered shape with a lower portion expanding outward.

[0110] By tapering the end face of the first protective film in this manner, the adhesion of the second protective film to the first protective film is improved, and the coverage of the second protective film to the first protective film can be improved.

[0111] (Technology 9) The driving element according to any one of Technologies 1 to 8, wherein the thickness of the first protective film formed on the top surface and the side surface of the laminated structure is substantially constant.

[0112] Because the first protective film covers the laminated structure, when the laminated structure is used in the drive section, the first protective film affects the drive efficiency of the piezoelectric layer, which is the drive source. Therefore, from the viewpoint of the drive efficiency of the piezoelectric layer, it is preferable that the thickness of the first protective film is as small as possible. On the other hand, from the viewpoint of moisture resistance, which is the original purpose of the first protective film, it is preferable that the thickness of the first protective film is relatively large. Due to these contradictory reasons, it is sufficient that the thickness of the first protective film is substantially constant near the minimum film thickness that maintains coverage. This makes it possible to maintain high drive efficiency of the piezoelectric layer while ensuring coverage by the first protective film.

[0113] (Technology 10) The driving element according to any one of Technologies 1 to 9, wherein the thickness of the second protective film formed on the upper surface and side surfaces of the first protective film is substantially constant.

[0114] As with the first protective film, the thickness of the second protective film is preferably as small as possible from the viewpoint of the drive efficiency of the piezoelectric layer. On the other hand, from the viewpoint of the warm water resistance, which is the original purpose of the second protective film, it is preferable that the thickness of the second protective film is somewhat large. For these reasons, the thickness of the second protective film should be substantially constant around the minimum film thickness that can maintain coverage. This makes it possible to maintain high drive efficiency of the piezoelectric layer while ensuring coverage by the second protective film.

[0115] (Technology 11) In the driving element according to any one of Techniques 1 to 10, the second protective film is made of ZrO ２ , TiO ２ , Nb ２ O ５ , CeO ２ , Ta ２ O ５ , HfO ２ , Si ３ N ４ , Y ２ O ３ , MgO, SiO ２ , MgF ２ a single layer film of any one of the above or a laminated film of a combination of at least two of these.

[0116] By using these materials for the second protective film, a second protective film having excellent resistance to warm water can be formed satisfactorily on the surface of the first protective film.

[0117] 1, 2 Drive element 10, 201 Fixed portion 40, 204 Movable portion 51, 52, 205 Drive portion 61, 62 Wiring portion 71 to 73, 206 to 208 Terminal portion 101 Substrate 103 Lower electrode layer 104 Piezoelectric layer 105 Upper electrode layer 106 First protective film 106a Bottom portion 107 Second protective film 107a Bottom portion 110 Laminated structure R10 Rotation axis

Claims

1. A driving element for driving a movable part, comprising: a substrate; a laminated structure formed on the substrate, the laminated structure including a piezoelectric layer, an upper electrode layer and a lower electrode layer disposed above and below the piezoelectric layer; and Al ２ O ３ a first protective film that covers the entire surface of the laminated structure, and a second protective film that is resistant to hot water and covers the entire surface of the first protective film.

2. A driving element as claimed in claim 1, characterized in that a driving section for applying a driving force to the movable section, a wiring section connected to the driving section, and a terminal section connected to the wiring section for supplying a driving signal are arranged on the substrate, and the laminated structure is formed in the area of ​​the driving section and the wiring section.

3. A driving element as described in claim 2, wherein the piezoelectric layer, the upper electrode layer and the lower electrode layer extend from the wiring portion to the terminal portion, the entire surface of the piezoelectric layer in the terminal portion is covered by the upper electrode layer, the lower electrode layer and the first protective film, and the entire surface of the first protective film in the terminal portion is covered by the second protective film.

4. The driving element according to claim 1, wherein the end face of the second protective film and the end face of the substrate are flush with each other.

5. A driving element according to claim 1, wherein the first protective film has a skirt portion extending along the upper surface of the substrate.

6. A driving element according to claim 5, wherein the end face of the first protective film is spaced 1 μm or more from the side face of the piezoelectric layer.

7. A driving element according to claim 6, wherein the end face of the second protective film is spaced 1 μm or more from the end face of the first protective film.

8. A driving element according to claim 5, wherein the end face of the first protective film has a tapered shape with the lower portion expanding outward.

9. A driving element according to claim 1, wherein the thickness of the first protective film formed on the top surface and side surfaces of the laminated structure is substantially constant.

10. A driving element according to claim 1, wherein the thickness of the second protective film formed on the upper surface and side surfaces of the first protective film is substantially constant.

11. A driving element according to any one of claims 1 to 10, wherein the second protective film is made of ZrO ２ , TiO ２ , Nb ２ O ５ , CeO ２ , Ta ２ O ５ , HfO ２ , Si ３ N ４ , Y ２ O ３ , MgO, SiO ２ , MgF ２ a single layer film of any one of the above or a laminated film of a combination of at least two of these.

Images