Base, piezoelectric device and manufacturing method of base for piezoelectric device

Abstract

To provide a base, which has a novel structure, for a piezoelectric device.SOLUTION: A base 10 comprises: a first substrate 11 consisting of a crystal; a loading pad 11b for a piezoelectric element provided on a first face 11a of the first substrate; a contact hole 11d and contact hole wiring 11e provided in the first substrate and leading from the loading pad to a second face 11c which is an opposite face of the first face; a first metal film 11f provided in a region including a peripheral region of the contact hole on the second face; a second substrate 13 consisting of the crystal; a second metal film 13b provided on a face of the second substrate at the side of the first substrate and constituting an inter-metal joint together with the first metal film; routing wiring 13e; a castellation 13f; and an external mounting terminal 13g. An opening area α of the contact hole at the side of the second face is larger than an opening area β at the side of the first face.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a base for a piezoelectric device and a piezoelectric device using the base. [Background technology]

[0002] Piezoelectric devices require a container to contain the piezoelectric element. For this reason, various containers are used or researched for quartz devices, which are a type of piezoelectric device, such as metal containers, ceramic containers, and containers made of glass or quartz. Surface-mount containers are widely used, especially for mass-produced quartz devices, as there is a high demand for surface-mount containers.

[0003] A typical example of a surface-mount type container suitable for mass production is a ceramic container. Specifically, it is a container in which a ceramic base is joined to a metal or ceramic lid. The ceramic base is typically formed by integrally firing a bottom plate made of a ceramic material and having a rectangular shape in a plan view, and a bank portion made of a ceramic material laminated on the bottom plate (see, for example, paragraph 26, FIG. 1, etc. of Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-274071 A [Patent Document 2] JP 2022-145456 A Summary of the Invention [Problem to be solved by the invention]

[0005] Currently, ceramic bases are the best bases for piezoelectric devices. However, as piezoelectric devices become thinner and smaller, there are limitations in terms of structure, precision, and cost. Therefore, a base with a new structure that can replace ceramic bases is desired. In response to this demand, an inventor associated with the applicant has proposed a base for a piezoelectric device having a structure in which two quartz substrates are bonded using metal-to-metal bonding, and a wiring structure in which wiring is arranged using the bonded boundaries and sides of the two quartz substrates (Patent Document 2). This base is promising as a base for piezoelectric devices, but further improvement of the wiring structure is desired. The present invention has been made in consideration of the above points, and therefore, an object of this application is to provide a base for a piezoelectric device having a structure in which two quartz crystal substrates are bonded using metal-to-metal bonding and also having a wiring structure, wherein the base for a piezoelectric device has an improved wiring structure, and a piezoelectric device using the same. [Means for solving the problem]

[0006] In order to achieve this object, the first invention of this application is a base for a piezoelectric device comprising a first substrate having a first surface and a second surface opposite the first surface and made of glass or quartz, a contact hole and contact hole wiring extending from the first surface to the second surface, a first metal film provided in an area including the surrounding area of ​​the contact hole on the second surface, a second substrate made of the same material as the first substrate and joined to the first substrate by intermetallic bonding, a second metal film provided on a third surface which is the surface of the second substrate facing the first substrate and cooperating with the first metal film to form the intermetallic bond, and wiring extending through the contact hole wiring, the third surface, and a side surface of the second substrate to a fourth surface which is the surface opposite the third surface of the second substrate, wherein the contact hole has a larger opening area on the second surface side than on the first surface side.

[0007] In carrying out the first invention, it is preferable that the first substrate is a flat plate having a seal pattern for sealing along the edge of the first surface of the first substrate. In this preferred embodiment, a new flat base according to the first invention can be provided. Furthermore, by using this base and a cap-shaped lid member, a new piezoelectric device consisting of a flat base and a cap-shaped lid member can be realized (see, for example, FIG. 8). In carrying out the first invention, it is preferable that the first substrate has a recess for accommodating a piezoelectric element on the first surface side and a bank portion around the recess. In this preferred embodiment, a novel base according to the first invention can be provided that can house a piezoelectric element. Furthermore, by using this base and a flat-plate lid member, a novel piezoelectric device can be realized that is composed of a base that can house a piezoelectric element and a flat-plate lid member (see FIG. 9).

[0008] In addition, the piezoelectric device which is the second invention of this application is characterized by comprising the base of the first invention, a piezoelectric element connected and fixed to a mounting pad of the base by a conductive member, and a cover member joined to the base and sealing the piezoelectric element.

[0009] According to a third aspect of the present invention, there is provided a method for manufacturing a base for a piezoelectric device, the method comprising the steps of: (a) forming a hole for a contact hole in a first substrate having a first surface and a second surface opposed thereto, the first substrate being made of glass or quartz, the hole extending from the second surface to the first surface and stopping midway in a thickness direction of the first substrate; (b) forming a first metal film for intermetallic bonding around the hole for the contact hole on the second surface; (c) forming a second metal film on the third surface of a second substrate made of the same material as the first substrate, the second metal film being adapted to cooperate with the first metal film to generate intermetallic bonds; the second metal film is adapted to cooperate with the first metal film on the third surface of the second substrate, the second metal film being ... (d) bonding the first substrate, on which the contact hole holes and the first metal film have been formed, to the second substrate, on which the second metal film has been formed, by contacting the second surface and the third surface of the first substrate and forming an intermetallic bond between the first metal film and the second metal film; (e) forming a recess for accommodating a piezoelectric element, the recess having a bottom surface connected to the contact hole, from the first surface side of the bonded structure; The present invention is characterized by comprising: Effect of the Invention

[0010] According to the base of the first invention of this application, a base for a piezoelectric device is formed having a structure in which a first substrate and a second substrate made of glass or quartz are laminated by intermetallic bonding. Moreover, a base having a structure in which a piezoelectric element mounted on the base can be connected to an external mounting terminal by a contact hole wiring provided on the first substrate, a part of the metal film used in the intermetallic bonding, and a lead wiring using castellation provided on the second substrate is realized. Moreover, since the periphery of the contact hole is surrounded by intermetallic bonding of the first metal film and the second metal film, the contact hole region, which is likely to become a bottleneck in reducing airtightness, is sealed by intermetallic bonding. Moreover, since the first substrate and the second substrate are made of the same material, they have the same physical properties such as thermal expansion coefficient, which is also advantageous in terms of airtightness. Moreover, the opening area of ​​the contact hole on the second surface side is larger than that on the first surface side. In general, the piezoelectric element is connected to the base with a silicone-based conductive adhesive. When the piezoelectric element is attached to the base, the piezoelectric element is pressed toward the base from the top surface of the piezoelectric element to improve the electrical connection between the conductive adhesive and the electrodes of the piezoelectric element. In this case, if the opening area of ​​the contact hole on the second surface side is larger than that on the first surface side, the conductive adhesive can easily reach the contact hole wiring and the second metal on the second substrate, which is expected to improve the reliability of the electrical connection of the piezoelectric element. Therefore, even in a laminated structure of a first substrate and a second substrate made of glass or quartz, airtightness is ensured and a base that allows for an improved wiring structure can be realized. In addition, the glass and quartz that make up the first and second substrates can be processed using photolithography, allowing for relatively high precision and low material costs, making it possible to realize a highly accurate and inexpensive base. Moreover, according to the piezoelectric device which is the second invention of this application, a novel piezoelectric device can be realized which uses a base having the above-mentioned novel structure. Furthermore, according to the third invention of this application, which is a method for manufacturing a base for a piezoelectric device, it is possible to easily manufacture a base related to the first invention, which has a recess for accommodating a piezoelectric element and a bank portion around the recess. [Brief description of the drawings]

[0011] [Figure 1] FIG. 2 is a diagram for explaining the base 10 of the first embodiment. [Diagram 2] 1A and 1B are diagrams for explaining the structure of the base 10 of the first embodiment, particularly the contact hole 10d and the contact hole wirings 11e and 11ea. [Diagram 3] 2A to 2C are diagrams for explaining some examples of a first metal film and a second metal film. [Figure 4] FIG. 2 is a diagram for explaining, in particular, the wiring paths of the base 10 according to the first embodiment. [Diagram 5] 11 is a diagram for explaining a base 20 according to a second embodiment. FIG. [Figure 6] 13 is a diagram for explaining a base 30 according to a third embodiment. FIG. [Figure 7] 1A and 1B are diagrams illustrating a piezoelectric device 50 according to a first embodiment. [Figure 8] 11 is a diagram illustrating a piezoelectric device 60 according to a second embodiment. FIG. [Figure 9] 10A to 10C are diagrams for explaining an example of a method for manufacturing the base 20 of the second embodiment. [Figure 10] 9 for explaining an example of a method for manufacturing the base 20 of the second embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, the embodiments of the base, piezoelectric device, and base manufacturing method of this application will be described with reference to the drawings. Note that the drawings used in the description are merely schematic illustrations to the extent that these inventions can be understood. In addition, in the drawings used in the description, similar components are indicated by the same numbers, and their explanation may be omitted. Furthermore, the shapes, dimensions, materials, etc. described in the following examples are merely preferred examples within the scope of this invention. Therefore, the present invention is not limited to the following embodiments.

[0013] 1. First embodiment of the invention (base) 1-1. Base 10 of the first embodiment 1(A) and (B) are diagrams for explaining a base 10 according to a first embodiment. In particular, Fig. 1(A) is a perspective view of the base 10, and Fig. 1(B) is an exploded perspective view showing the base 10 divided into a first substrate 11 and a second substrate 13. The base 10 of the first embodiment has a first surface 11a and an opposing second surface 11b, and is equipped with a first substrate 11 made of glass or quartz, a mounting pad 11c for a piezoelectric element (piezoelectric element 53 shown in Figure 7, etc.) provided on the first surface 11a of the first substrate 11, a contact hole 11d and contact hole wiring 11e leading from the first surface 11a to the second surface 11b, a first metal film 11f provided in a region including the surrounding region of the contact hole 11d on the second surface 11b, an insulating region 11g, and a seal pattern 11h. The base 10 further includes a second substrate 13 made of the same material as the first substrate 11 and bonded to the first substrate 11 by intermetallic bonding, a second metal film 13b provided on a third surface 13a of the second substrate 13 facing the first substrate 11 and forming an intermetallic bond together with the first metal film 11f, i.e., bonded to the first metal film 11f, a lead wiring 13e extending from the contact hole wiring 11e through the third surface 13a and the side surface 13c of the second substrate 13 to a fourth surface 13d of the second substrate 13 opposite to the third surface 13a, a castellation 13f provided on the side surface 13c of the second substrate 13 for the lead wiring 13e, and an external mounting terminal 13g (see FIG. 3) provided on the fourth surface 13d and connected to the lead wiring. Specific examples of each of the above-mentioned components will be described below.

[0014] In this example, the first substrate 11 has a rectangular planar shape and is flat. The specific material of the first substrate 11 is preferably, for example, a Z-cut or AT-cut quartz crystal plate. Both the Z-cut and AT-cut quartz crystal plates are mass-produced substrates for use in quartz crystal resonators, and therefore are advantageous in terms of cost. In addition, if the specific material of the first substrate 11 is glass, any suitable glass such as soda glass may be used.

[0015] The mounting pad 11c is connected and fixed to the piezoelectric element by a conductive adhesive or the like. The mounting pad 11c is electrically connected to the contact hole wiring 11e. The mounting pad 11c is provided at any location on the first surface 11a of the first substrate 11, with any shape according to the mounting structure of the piezoelectric element. In this example, since a structure in which the piezoelectric element is cantilevered is illustrated, the mounting pads 11c are provided in two locations near one side of the first substrate 11 and spaced apart from each other in a direction along the one side. The planar shape of the mounting pad 11c can be any shape, such as a square, a round, or an elliptical shape. The mounting pad 11c can be made of any suitable metal film, for example, a laminated film of a chromium film and a gold film.

[0016] The contact holes 11d and the contact hole wiring 11e extend from the first surface 11a to the second surface 11b of the first substrate 11, and can be formed in the first substrate 11 by using, for example, photolithography, wet etching, and film formation techniques. An example of the manufacturing method will be described later. The structure of this contact hole 11d will be described in detail with reference to Fig. 2. Fig. 2(A) is a perspective view of the base 10 similar to Fig. 1(A). Figs. 2(B) to (D) are cross-sectional views taken along lines P1-P1, P2-P2, and P3-P3 in Fig. 2(A), respectively. 2(B)-(D), particularly as shown in the partially enlarged view of Fig. 2(B), the contact hole 11d has an opening area α on the second surface 11b side of the first substrate 11 that is larger than an opening area β on the first surface 11a side. As described in detail in the section on means for solving the problems, a configuration where α>β is satisfied is expected to improve the reliability of electrical connection of the entire wiring structure between the electrode of the piezoelectric element (excitation electrode 53a shown in Fig. 7 and the like) and the external connection terminal 10g of the base 10, compared to cases where this is not the case. The planar shape of the contact hole 11d may be any shape, such as a circle, an ellipse, or a rectangle, but is typically a circle. The ratio of α to β is, for example, 1.1≦α / β≦2, and preferably 1.3≦α / β≦1.7. If α / β is too small, the above effect cannot be obtained, and if it is too large, it will be an obstacle in terms of miniaturization of the base 10 and airtight reliability. The material of the contact hole wiring 11e can be any suitable metal material, for example, similar to that of the mounting pad 11c.

[0017] In order to further improve the electrical reliability of the contact hole wiring 11e, it is preferable that the surface layer of the contact hole wiring 11e is a plating film 11ea, as shown in the enlarged view in FIG. 2(B). The plating film 11ea may be either an electrolytic plating film or an electroless plating film. The material of the plating film may be any suitable one, but for example, a nickel plating film is preferable. The plating film 11ea may be provided on the surface layer of the contact hole wiring 11e and the mounting pad 11c connected thereto. The reason for providing the plating film 11ea is as follows. The boundary between the first surface 11a and the second surface 11b of the contact hole 11d is edge-shaped, so the coverage of the wiring metal is generally poor. The contact wiring 11e is typically formed by a film formation method such as a sputtering method or a vapor deposition method, but in the case of these film formation methods, there is a limit to how thick the film can be, so the coverage of the above-mentioned boundary edge is poor. Therefore, it is preferable to provide a plating film 11ea which can provide a thicker film than a film formed by a method such as sputtering, thereby increasing the coverage of the above-mentioned edge and improving the reliability of the wiring structure. In the base 10 of the first embodiment, the two contact holes 11d are arranged in a straight line parallel to the side of the first substrate 11, but the planar position of the contact holes 11d on the first substrate 11 is not limited to this and can be changed as desired depending on the design of the piezoelectric device. For example, the contact holes 11d may be provided on a diagonal line of the first substrate 11.

[0018] The first metal film 11f is one of the members for bonding the first substrate 11 and the second substrate 13 by intermetallic bonding, and also serves as one of the sealing members for ensuring airtightness of the contact holes 11d. Therefore, in this example, the first metal film 11f is composed of three parts: a first part 11f1 having a planar shape surrounding one of the two contact holes 11d, a second part 11f2 having a planar shape surrounding the other of the two contact holes 11d, and a third part 11f3 covering the remaining area. The above three parts 11f1, 11f2, and 11f3 of the first metal film 11f need to be electrically isolated from each other, and are therefore separated by an insulating region 11g in which the metal film is removed. However, in order to increase the area of ​​intermetallic bonding with the second metal film 13b described later, it is preferable to minimize the area of ​​the insulating region 11g. On the other hand, the second metal film 13b provided on the second substrate 13 side is the other member for bonding the first substrate 11 and the second substrate 13 by metal-to-metal bonding, and also serves as the other sealing member for ensuring airtightness of the contact hole 11d. Therefore, the second metal film 13b is composed of three parts corresponding to the three parts 11f1, 11f2, and 11f3 of the first metal film 11f, and these three parts are separated by an insulating region 13h. It is preferable that the area of ​​this insulating region 13h is as small as possible, similar to the insulating region 11g.

[0019] Here, the materials of the first metal film 11f and the second metal film 13b will be described with reference to Figures 3(A) to 3(C). These figures are cross-sectional views of a laminate of the first substrate 11 (or the second substrate 13) and the first metal film 11f (or the second metal film 13b). Each of the first metal film 11f and the second metal film 13b can be made of any suitable metal film capable of performing intermetallic bonding. For example, it can be made of a laminated film of a chromium film 80a and a gold film 80b, which are laminated in this order from the first substrate side (FIG. 3(A)). In this way, the first metal film 11f and the second metal film 13b cooperate to generate intermetallic bonding between the gold films, thereby enabling intermetallic bonding between the first substrate 11 and the second substrate 13. Alternatively, each of the first metal film 11f and the second metal film 13b can be made of a laminated film of a titanium film and a gold film, which are laminated in this order from the first substrate side. More preferably, as shown in Fig. 3(B), each of the first metal film 11f and the second metal film 13b is preferably made of a three-layer laminate film including a chromium film 80a as an undercoat film, a nickel film or a nickel-tungsten alloy film 80c as an intermediate film, and a gold film 80b as an upper layer film. The configuration including a nickel film or a nickel-tungsten alloy film as an intermediate film can prevent the chromium film as an undercoat film from diffusing into the gold film as an upper layer film, so that the first metal film and the second metal film can form a better intermetallic bond. In addition, this three-layer laminate film is considered to be able to prevent the diffusion of chromium into the gold film over time. More preferably, as shown in Fig. 3(C), each of the first metal film 11f and the second metal film 13b is a five-layered metal film having a laminated film consisting of a titanium film 80d and a gold film 80e laminated on the titanium film 80d on the gold film 80b, which is the upper layer of the three-layered metal film. Even if nickel or a nickel-tungsten alloy is provided, chromium may diffuse into the gold film, but the titanium film can prevent the diffusion of chromium into the top gold film, thereby achieving better intermetallic bonding. It is considered that this five-layered laminated film can also better prevent the diffusion of chromium into gold over time.

[0020] The seal pattern 11h (FIG. 1) is for joining a lid member (lid member 51 shown in FIG. 7, etc.) described later to the base 10. The base 10 of this embodiment shows an example in which the lid member is joined to the base by a solder material, such as a gold-tin alloy. Therefore, the seal pattern 11h is made of any suitable material that is easy to join with gold-tin. The seal pattern 11h is provided with a predetermined width along the edge of the first substrate 11. In providing the seal pattern 11h on the first surface 11a of the first substrate 11, it is preferable to provide a recess 11ha having a depth equivalent to the thickness of the seal pattern 11h in the region of the first surface of the first substrate 11 where the seal pattern 11h is to be provided, as shown in Fig. 2(B), and to provide the seal pattern 11h in this recess 11ha. When it is desired to realize a low-profile piezoelectric device, the thickness of the seal pattern 11h itself may be an obstacle to achieving a low profile, but if the seal pattern 11h is embedded in the recess 11ha as in this preferred example, it is possible to prevent the thickness of the piezoelectric device from increasing due to the thickness of the seal pattern 11h.

[0021] The second substrate 13 is bonded to the first substrate by intermetallic bonding between the first metal film and the second metal film. The second substrate 13 is a flat substrate made of the same material as the first substrate 11 and has substantially the same planar shape. However, the planar shape of the second substrate 13 is slightly different from that of the first substrate 11 in that castellations 13f are provided. The castellations 13f will be described later.

[0022] The lead wiring 13e is a wiring that extends from the contact hole wiring 11e, in this embodiment, from the mounting pad 11c, through the third surface 13a and the side surface 13c of the second substrate 13, to the fourth surface 13d. However, the lead wiring 13e is formed using a part of the first metal film 11f and the second metal film 13b. Specifically, the lead wiring between the first substrate 11 and the second substrate 13 is formed by the first portion 11f1 and the second portion 11f2 of the first metal film and the second metal film 13b (13e) facing them. Note that the portion of the lead wiring 13e that extends from the side surface 13c of the second substrate 13 to the external mounting terminal 13g is formed by a metal film that is continuous with the second metal film 13b.

[0023] Next, the castellation 13f will be described with reference to FIG. 4. FIG. 4(A) is a plan view of the first substrate 11 focusing on the castellation 13f, and FIG. 4(B) is a plan view of the second substrate 13 focusing on the castellation 13f. The castellation 13f is for routing the lead-out wiring 13e to the external mounting terminal 13g (see FIG. 1). The castellation 13f is a notch-shaped recessed slightly from the edge of the second substrate 13 to the center in a part of each of the two opposing sides of the second substrate 13. Therefore, a notch 11i is provided in a portion of the first substrate 11 corresponding to the castellation 13f. Although the number of castellations is two in the illustrated example, it may be three or more.

[0024] The external mounting terminals 13g are provided on the fourth surface 13d and connected to the above-mentioned lead wiring 13e. The external mounting terminals 13g are terminals used when mounting a piezoelectric device (see Figs. 10 and 11) manufactured using the base 10 of the present invention on various electronic devices (not shown). In this example, four terminals are shown as the external mounting terminals 13g, but the number of terminals is not limited to this. In this case, two of the four terminals are non-connected (NC). In cases where the piezoelectric device has an earth structure, these non-connected terminals can also be used as earth terminals.

[0025] 1-2. Base 20 of the Second Embodiment Next, the base 20 of the second embodiment will be described with reference to Fig. 5. Fig. 5(A) is a plan view for explaining the base 20 of the second embodiment, and Figs. 5(B) to (D) are cross-sectional views of the base 20 taken along lines Q1-Q1, Q2-Q2, and Q3-Q3 in Fig. 5(A). The base 20 of the second embodiment differs from the base 10 of the first embodiment in that the first substrate 11 is provided with a recess 21a that contains a piezoelectric element, and a bank portion 21b provided around the recess 21a. The planar shape of the recess 21a is quadrangular, and may be square or rectangular depending on the shape of the piezoelectric element to be mounted in the recess 21a. The height and width of the bank portion 21b can be set to any value depending on the design of the piezoelectric element to be mounted in the recess 21a and taking into consideration the need to ensure airtightness, etc.

[0026] 1-3. Base of the third embodiment Next, the base 30 of the third embodiment will be described with reference to Fig. 6. Fig. 6(A) is a plan view for explaining the base 30 of the third embodiment, and Figs. 6(B) and (C) are cross-sectional views of the base 30 taken along the lines Q1-Q1 and Q2-Q2 in Fig. 6(A). The base 30 of the third embodiment corresponds to a modified example of the base 20 of the second embodiment having a recess 21a for containing a piezoelectric element (not shown). Specifically, when forming the recess 21a for containing the piezoelectric element in the first substrate, a method is usually used in which a predetermined area of ​​the first surface of the first substrate 21 is etched to a predetermined depth in the thickness direction of the first substrate 21 by photolithography and wet etching. However, in the case of wet etching, the bottom surface of the recess 21a is not flat to the corner, and a part of the first substrate remains in the thickness direction at the corner. If this remaining part exists, the planar dimensions of the recess 21a become smaller due to this remaining part, and the area in which the piezoelectric element can be contained becomes narrow, and as a result, the dimensions of the piezoelectric element cannot be increased. In general, the larger the area of ​​the piezoelectric element, the more improved the characteristics can be expected, so it is better that the above-mentioned remaining part does not exist. In order to solve this problem, the base 30 of the third embodiment has the following structure. That is, the recess 21a is rectangular in plan view, and is provided with a recess shape modifying portion 31 consisting of a hole facing the second substrate in a region near a pair of sides of the rectangular bottom surface of the recess. When the first substrate 21 is formed of, for example, a Z-plate of quartz, it is preferable to provide the recess shape modifying portion 31 in a region near a pair of sides parallel to the X-axis of the quartz or a pair of sides parallel to the Y-axis of the quartz, among the four sides of the rectangular bottom surface of the recess 21a. When the recess shape modifying portion 31 is provided, the side wall of this portion of the recess becomes closer to a vertical wall, so that the planar area near the side of the recess provided with the recess shape modifying portion 31 can be made larger than when the recess shape modifying portion 31 is not provided.

[0027] 2. Piezoelectric Device Embodiments Next, an embodiment of a piezoelectric device will be described. 2-1. Piezoelectric device according to the first embodiment First, a piezoelectric device 50 according to a first embodiment will be described with reference to Fig. 7. Fig. 7(A) is an exploded perspective view of the piezoelectric device 50 according to the first embodiment, and Fig. 7(B) is a cross-sectional view taken along line PP in Fig. 7(A) of a cap-shaped lid member 51 having a recess 51a for accommodating a piezoelectric element. The piezoelectric device 50 of the first embodiment includes the base 10 of the first embodiment, an AT-cut quartz crystal vibrating piece 53 as a piezoelectric element 53 mounted on the base 10, and a cap-shaped lid member 51 connected to the base 10 at the seal pattern 11h to seal the piezoelectric element 532. The bonding can be performed using a soldering material such as gold and tin. The cap-shaped lid member 51 is preferably made of metal, and is preferably a metal lid member that takes into account the linear expansion coefficients of the first and second substrates, for example, a lid member made of copper, nickel, or Kovar. Copper is most preferable in terms of the linear expansion coefficient. Note that what is indicated with 53a in FIG. 7(A) is an excitation electrode provided on the piezoelectric element 53. The piezoelectric element 53 is connected and fixed to the mounting pad 11c at the end (drawing wiring) position of the excitation electrode 53a by a conductive adhesive (not shown).

[0028] 2-2. Piezoelectric device according to the second embodiment Next, a piezoelectric device 60 according to a second embodiment will be described with reference to Fig. 8. Fig. 8(A) is an exploded perspective view of the piezoelectric device 60 according to the second embodiment, and Fig. 8(B) is a cross-sectional view of the piezoelectric device 60 taken along line QQ in Fig. 8(A). The piezoelectric device 60 of the second embodiment uses the base 20 of the second embodiment and a flat lid member 61. A piezoelectric element 53 is connected and fixed to a mounting pad 11c at the end of an excitation electrode 53a in a recess 21a of the base 20 by a conductive adhesive (not shown). The lid member 61 is connected to a seal pattern 11h provided on the top surface of the bank portion 21b of the base 20 by a solder material such as gold and tin. Each of the above-mentioned embodiments of the piezoelectric device is an example of a piezoelectric vibrator, but the invention of this application can also be applied to a piezoelectric vibrator with a temperature sensor in which a temperature sensor such as a thermistor is implemented together with a piezoelectric element, to a piezoelectric oscillator in which an oscillation circuit is implemented together with a piezoelectric element, and to a piezoelectric oscillator in which a temperature compensation circuit is implemented.

[0029] 3. Manufacturing Method Next, an embodiment of a method for manufacturing a base for a piezoelectric device, which is the third invention of the present application, will be described. This third invention relates to a method for manufacturing a base having a recess 21a for mounting a piezoelectric element, like the base 20 of the second embodiment. Moreover, in this manufacturing method, the base is manufactured in a wafer state in which a large number of the bases are arranged in a matrix. Figures 9 and 10 are process diagrams for explaining this, and in particular, are diagrams for explaining the process of forming contact holes. In Figures 9 and 10, some figures show the entire wafer, and some figures show an enlarged view of a part of the wafer.

[0030] First, a wafer 21x for forming a first substrate is prepared, which has a first surface and an opposing second surface, and is made of glass or quartz. A wafer 13x for forming a second substrate is prepared, which has a third surface as one of its main surfaces and a fourth surface as the main surface opposing the third surface, and is made of the same material as the wafer 21x for forming the first substrate. Each of the wafers 21x and 13x is, for example, a quartz wafer or a glass wafer having a circular or rectangular planar shape and a predetermined thickness. Next, in the wafer 21x for forming the first substrate, a hole 11d for a contact hole is formed, the hole being stopped midway in the thickness direction of the wafer 11x for forming the first substrate from the second surface 11b to the first surface 11a. Next, first metal films 11f1, 11f2, and 11f3 for intermetallic bonding are formed around the hole 11d for the contact hole on the second surface of the wafer 21x for forming the first substrate (FIG. 9(A)). The contact hole 11d and the first metal film can be formed by photolithography, wet etching, and film formation techniques, such as sputtering. When forming the hole 11d for the contact hole, the hole for the recess shape modifying portion 31 described in the base 30 of the third embodiment (see FIG. 10(B)) is formed, so that the manufacturing process of the base of the third embodiment can be carried out. Of course, if the recess shape modifying portion 31 is not required, it is not necessary to form the hole for the recess shape modifying portion 31. Next, second metal films 13b and 13e for generating intermetallic bonds in cooperation with the first metal film are formed on the third surface 13a of the wafer 13x for forming the second substrate (FIG. 9(B)). The second metal films 13b and 13e can be formed by photolithography, wet etching, and film formation techniques.

[0031] Next, the wafer 21x for forming the first substrate, on which the contact holes and the first metal film have been formed, and the wafer 13x for forming the second substrate, on which the second metal film has been formed, are brought into contact with the second surface 11b and the third surface 13a (FIG. 9(C)), and bonded by intermetallic bonding using the first metal film and the second metal film (FIGS. 9(D), 10(A)). Intermetallic bonding is typically performed by applying pressure and heat to the wafers 13x and 21x. The portion indicated by M in FIG. 10(A) corresponds to one base formation region. After the above bonding process, a recess 21a for accommodating a piezoelectric element is formed on the first surface 11a side of the first substrate forming wafer 21x of the structure 90 (FIG. 10(A)), the bottom of which is connected to the hole 15d for the contact hole (FIGS. 10(B) and (C)). When this process is completed, the contact hole 11d and the recess 21a are connected, and the original contact hole 11d is obtained. When a hole for the recess shape modifying portion 31 is formed, the recess shape modifying portion 31 can be formed at a predetermined position of the recess 21a (FIGS. 10(B) and (C)). Next, the contact hole wiring 11e, the plating film 11ea as required, the mounting pad 11c, the wiring 13e, and the external connection terminal 13g (see FIG. 2) are formed by photolithography, wet etching, and film formation techniques. This makes it possible to obtain a wafer 91 having a large number of the bases 20 of the second embodiment in a matrix form (FIG. 10(D)). [Explanation of symbols]

[0032] 10: Base of the first embodiment 11: First substrate 11a: 1st side 11b: 2nd side 11c: Mounting pad 11d: Contact hole 11e: Contact hole wiring 11ea: Plating film 11f, 11f1, 11f2, 11f3: First metal film 11g: Insulation area 11h: Seal pattern 11i: Notch 13: second substrate 13a: third surface 13b: Second metal film 13c: Side surface 13d: 4th side 13e: Wiring 13f: Castellation 13g: External mounting terminal 13h: insulating region 13x: wafer for forming second substrate α, β: opening area of ​​contact hole 20: Base of the second embodiment 21a: Recess 21b: bank portion 21x: wafer for forming first substrate 30: Base of the third embodiment 31: Recess shape correction part 50: Piezoelectric device according to the first embodiment 51: Cap-shaped lid member

Claims

1. a first substrate having a first surface and a second surface opposite to the first surface, the first substrate being made of glass or quartz; a contact hole and a contact hole wiring extending from the first surface to the second surface; a first metal film provided on the second surface in a region including a peripheral region of the contact hole; a second substrate made of the same material as the first substrate and joined to the first substrate by metal-to-metal bonding; a second metal film provided on a third surface of the second substrate, the third surface being a surface of the second substrate facing the first substrate, and constituting the intermetallic bond together with the first metal film; a lead-out wiring extending from the contact hole wiring through the third surface and a side surface of the second substrate to a fourth surface of the second substrate, the fourth surface being an opposite surface to the third surface of the second substrate; The base is characterized in that the contact hole has an opening area on the second surface side larger than an opening area on the first surface side.

2. 2. The base according to claim 1, wherein the surface layer of the contact hole wiring is a plating film.

3. the contact hole wiring is provided so as to extend to an area of ​​the first surface that corresponds to an edge of the contact hole, The base according to claim 1 , wherein the contact hole wiring has a surface layer made of a plating film.

4. a mounting pad for mounting a piezoelectric element on the periphery of the contact hole on the first surface; 2. The base according to claim 1, wherein the surface layers of the contact hole wiring and the mounting pads are plated films.

5. The base according to claim 1 , wherein a part of the lead wiring is the first metal film and the second metal film.

6. The base according to claim 1 , wherein the first substrate is a flat plate and is provided with a seal pattern for sealing along an edge of the first surface of the first substrate.

7. 2. The base according to claim 1, wherein the first substrate has, on the first surface side, a recess for accommodating the piezoelectric element and a bank portion around the recess.

8. the first substrate has, on the first surface side, a recess for accommodating the piezoelectric element and a bank portion around the recess; The base described in claim 1, characterized in that the recess is rectangular in a planar view, and is provided with a recess shape modification portion consisting of a hole facing toward the second substrate in a region near one set of sides of the rectangular shape of the bottom surface of the recess.

9. the first substrate is made of a quartz Z-plate, and has a recess for accommodating the piezoelectric element on the first surface side and a bank portion around the recess; The base described in claim 1, characterized in that the recess is rectangular in a planar view, and is provided with a recess shape modification portion consisting of a hole toward the second substrate in a pair of sides parallel to the Y axis of the rectangular shaped crystal on the bottom surface of the recess or in a region near a pair of sides parallel to the Y axis of the crystal.

10. The base described in claim 1, characterized in that each of the first metal film and the second metal film is a laminated film of a chromium film as a base film, a nickel film or a nickel-tungsten alloy film as an intermediate film, and a gold film as an upper layer film, or a laminated film of a titanium film as a base film and a gold film as an upper layer film.

11. Each of the first metal film and the second metal film is a laminated film including a chromium film as a base film, a nickel film or a nickel-tungsten alloy film as an intermediate film, and a gold film as an upper layer film; 2. The base according to claim 1, further comprising a laminated film on said upper film, said laminated film being made of a titanium film and a gold film laminated on said titanium film.

12. the contact holes are two contact holes, a first contact hole and a second contact hole, each of the first metal film and the second metal film includes a first portion surrounding the first contact hole in a planar manner, a second portion surrounding the second contact hole in a planar manner, and a third portion covering the remaining area; The base of claim 1 , further comprising an insulating region providing insulation between the first portion, the second portion and the third portion.

13. 2. The base according to claim 1, wherein each of the first and second substrates is made of a quartz AT plate or a quartz Z plate.

14. A piezoelectric device comprising: a base according to any one of claims 1 to 13; a piezoelectric element connected directly or indirectly to the contact hole wiring by a conductive member; and a cover member joined to the base and sealing the piezoelectric element.

15. 14. The piezoelectric device according to claim 13, wherein the piezoelectric element is an AT-cut quartz crystal resonator piece.

16. In manufacturing the base according to claim 7, A step of forming a hole for a contact hole in a first substrate having a first surface and a second surface opposite thereto, the first substrate being made of glass or quartz, the hole extending from the second surface to the first surface and stopping midway in a thickness direction of the first substrate; forming a first metal film for intermetallic bonding around a hole for the contact hole on the second surface; a step of forming a second metal film on the third surface of a second substrate, the second metal film being for generating intermetallic bonds in cooperation with the first metal film, the second substrate having a third surface as a main surface and a fourth surface as a main surface opposite the third surface and made of the same material as the first substrate; a step of bonding a first substrate on which the holes for the contact holes and the first metal film have been formed and a second substrate on which the second metal film has been formed by bringing the second surface and the third surface into contact with each other through intermetallic bonding between the first metal film and the second metal film; forming a recess for accommodating a piezoelectric element, the recess having a bottom surface connected to the contact hole, from the first surface side of the bonded structure; A method for manufacturing a base for a piezoelectric device, comprising:

17. 17. The method for manufacturing a base according to claim 16, The recess that accommodates the piezoelectric element has a rectangular shape in a plan view, A method for manufacturing a base for a piezoelectric device, characterized in that when forming a hole for the contact hole in the substrate, a hole for correcting the shape of the recess is formed toward the first surface in an area where the rectangular recess is to be formed, the area corresponding to one set of sides of the rectangular shape of the bottom surface of the recess.

Images