Substrate for piezoelectric device, method for manufacturing same, and piezoelectric device

Abstract

The invention provides a pedestal having a novel structure for a piezoelectric device, a method of manufacturing the same, and a piezoelectric device. The base (10) includes: a first substrate (11) including a crystal; a mounting pad (11c) for a piezoelectric element provided on the first surface (11a) of the first substrate; a contact hole (11d) and a contact hole line (11e) which are provided in the first substrate and which extend from the mounting pad to a second surface (11b) which is the opposite surface to the first surface; a first metal film (11f) provided in a region of the second surface including a peripheral region of the contact hole; a second substrate (13) containing a crystal; a second metal film (13b) which is provided on the first substrate-side surface of the second substrate, and which constitutes an inter-metal bonding together with the first metal film; a guide line (13e); a castellated portion (13f); and an external mounting terminal (13g). The opening area (alpha) of the contact hole on the second surface side is larger than the opening area (beta) on the first surface side.

Description

Technical Field

[0001] The present invention relates to a base for a piezoelectric device, a method for manufacturing the same, and a piezoelectric device using the base. Background Art

[0002] In a piezoelectric device, a container for enclosing a piezoelectric element is essential. Therefore, in a crystal device, which is a type of piezoelectric device, various containers such as metal containers, ceramic containers, and containers using glass or crystal are used or studied. In particular, in mass-produced crystal devices, the demand for surface-mounted crystal devices is high, so surface-mounted containers are often used.

[0003] A representative container suitable for surface mounting and mass production is a ceramic container. Specifically, it is a container formed by joining a ceramic base with a metal or ceramic cover. Typically, the ceramic base is formed by calcining a bottom plate made of ceramic material and having a rectangular shape in a plan view and a bank part made of ceramic material stacked on the bottom plate as a whole (for example, paragraphs 26, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 67, 68, 69, 70, 71, 72, 73, 74, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 101, 102, 103, 104, 105, 106, 107, 108, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 121, 122, 123, 124, 125, 126, 127, 128, 129, 130, 131, 132, 133, 134, 135, 136, 137, 13 Figure 1 wait).

[0004] [Prior art literature]

[0005] [Patent Document]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2007-274071

[0007] [Patent Document 2] Japanese Patent Application Publication No. 2022-145456 Summary of the invention

[0008] [Problems to be solved by the invention]

[0009] At present, ceramic bases are the most excellent bases for piezoelectric devices. However, as piezoelectric devices become thinner and smaller, there are limits in terms of structure, precision, and cost. Therefore, a base with a novel structure that can replace ceramic bases is desired.

[0010] In order to meet the above requirements, the inventors of the present application proposed a base for a piezoelectric device having a structure in which two crystal substrates are joined together using metal-to-metal bonding, and having a circuit structure in which circuits are configured using the joining boundary or side surfaces of the two crystal substrates (Patent Document 2).

[0011] The above-mentioned base can be expected to be used as a base for a piezoelectric device, but further improvement in the circuit structure is desired.

[0012] The present invention is made in view of the above aspects. Therefore, the purpose of this application is to provide a base for a piezoelectric device and a piezoelectric device using the same. The base for the piezoelectric device has a structure in which two crystal substrates are joined together using metal-to-metal bonding, and has a circuit structure, and achieves an improvement in the circuit structure.

[0013] [Technical means to solve the problem]

[0014] In order to achieve the above-mentioned purpose, according to the base for a piezoelectric device as the first invention of the present application, it is characterized in that it includes: a first substrate, having a first surface and a second surface facing the first surface, and comprising glass or crystal; a contact hole and a contact hole circuit, extending from the first surface to the second surface; a first metal film, arranged in an area of ​​the second surface including the surrounding area of ​​the contact hole; a second substrate, comprising the same material as the first substrate, and joined to the first substrate by metal-to-metal bonding; a second metal film, arranged on a surface of the second substrate on the first substrate side, i.e., a third surface, cooperating with the first metal film to form the metal-to-metal bonding; and a guide circuit, reaching the opposite surface of the third surface of the second substrate, i.e., a fourth surface, via the contact hole circuit, the third surface and the side surface of the second substrate, the opening area of ​​the second surface side of the contact hole being larger than the opening area of ​​the first surface side.

[0015] When implementing the first invention, it is preferred that the first substrate is a flat plate, and a sealing pattern for sealing is included along the edge of the first surface of the first substrate. In the case of the preferred example, a novel base of the first invention can be provided, which is a flat base. Furthermore, by using the base and a cap-shaped cover member, a novel piezoelectric device including a flat plate base and a cap-shaped cover member can be realized (for example, see Figure 8 (A) Figure 8 (B)).

[0016] When implementing the first invention, it is preferred that the first substrate has a recessed portion for accommodating the piezoelectric element and a bank around the recessed portion on the first surface side. In the case of the preferred example, a novel base of the first invention can be provided, which is a base capable of housing a piezoelectric element. Furthermore, by using the base and a flat cover member, a novel piezoelectric device including a base capable of housing a piezoelectric element and a flat cover member can be realized (see Fig. 9 (A)~ Fig. 9 (D)).

[0017] In addition, according to the piezoelectric device of the second invention of the present application, it is characterized by including: the base of the first invention; a piezoelectric element, which is connected to the mounting pad of the base through a conductive member; and a cover member, which is bonded to the base to seal the piezoelectric element.

[0018] In addition, according to a method for manufacturing a base for a piezoelectric device as a third invention of the present application, it is characterized in that when manufacturing the base of the first invention and being a base including a recess for accommodating a piezoelectric element and a bank around the recess, the method includes the following steps:

[0019] (a) forming a hole for a contact hole on a first substrate having a first surface and a second surface facing the first surface and made of glass or crystal, the hole extending from the second surface toward the first surface and stopping halfway in the thickness direction of the first substrate;

[0020] (b) forming a first metal film for metal-to-metal bonding around the hole for the contact hole on the second surface;

[0021] (c) forming a second metal film for producing an intermetallic bond in cooperation with the first metal film on the third surface of a second substrate having one of its principal surfaces defined as a third surface and a principal surface opposite to the third surface defined as a fourth surface and comprising the same material as the first substrate;

[0022] (d) a step of bringing the second surface and the third surface into contact with each other and bonding the first substrate on which the hole for the contact hole and the first metal film are formed to the second substrate on which the second metal film is formed, through the metal bonding between the first metal film and the second metal film; and

[0023] (e) forming a recessed portion that accommodates the piezoelectric element and has a bottom surface connected to the hole for the contact hole from the first surface side of the bonded structure.

[0024] [Effects of the Invention]

[0025] According to the base of the first invention of the present application, a base for a piezoelectric device having the following structure is formed, wherein a first substrate and a second substrate including glass or crystal are stacked by metal-to-metal bonding. Furthermore, a base having the following structure is realized, wherein the piezoelectric element mounted on the base can be connected to an external mounting terminal through a contact hole circuit provided on the first substrate, a part of a metal film used in the metal-to-metal bonding, and a guide circuit provided on the second substrate and using a castellated portion. Furthermore, the contact hole is surrounded by the metal-to-metal bonding formed by the first metal film and the second metal film, so that the contact hole region which is prone to being the key to reduced airtightness is sealed by the metal-to-metal bonding. Furthermore, the first substrate and the second substrate are made of the same material, and therefore have the same physical properties such as the coefficient of thermal expansion, which is also advantageous for airtightness in this respect.

[0026] Moreover, the opening area on the second surface side of the contact hole is larger than the opening area on the first surface side. Generally speaking, the piezoelectric element is connected to the base through a silicone-based conductive adhesive. Furthermore, when the piezoelectric element is bonded to the base, in order to ensure good electrical connection between the conductive adhesive and the electrode of the piezoelectric element, the piezoelectric element is pressed from the upper surface of the piezoelectric element toward the base side. At this time, if the contact hole has a larger opening area on the second surface side than the opening area on the first surface side, the conductive adhesive is also likely to spread to the contact hole circuit or the second metal on the second substrate, so it can be expected that the reliability of the electrical connection of the piezoelectric element will be improved.

[0027] Therefore, even with a stacked structure of a first substrate and a second substrate made of glass or crystal, a base can be realized that ensures airtightness and achieves an improved circuit structure.

[0028] In addition, the glass and crystal constituting the first substrate and the second substrate can be processed by photolithography technology, so they can be processed with relatively high precision, and the material cost is relatively cheap. Therefore, a high-precision and cheap base can be realized.

[0029] In addition, according to the piezoelectric device as the second invention of the present application, a novel piezoelectric device using the base having the novel structure can be realized.

[0030] According to the invention of the method for manufacturing a piezoelectric device base as the third invention of the present application, the base of the first invention having the recess for accommodating the piezoelectric element and the bank around the recess can be easily manufactured. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 (A) Figure 1 (B) is a diagram for explaining the base 10 according to the first embodiment.

[0032] Figure 2 (A)~ Figure 2 (D) is a diagram for explaining the structure of the base 10 according to the first embodiment, particularly the contact hole 11d, the contact hole line 11e, and the plating film 11ea.

[0033] Figure 3 (A)~ Figure 3 (C) is a diagram for explaining some examples of the first metal film and the second metal film.

[0034] Figure 4 (A) Figure 4 (B) is a diagram for explaining the base 10 of the first embodiment, particularly the line path.

[0035] Figure 5 (A)~ Figure 5(D) is a diagram for explaining the base 20 according to the second embodiment.

[0036] Figure 6 (A)~ Figure 6 (C) is a diagram for explaining a base 30 according to the third embodiment.

[0037] Figure 7 (A) Figure 7 (B) is a diagram for explaining the piezoelectric device 50 according to the first embodiment.

[0038] Figure 8 (A) Figure 8 (B) is a diagram for explaining a piezoelectric device 60 according to the second embodiment.

[0039] Fig. 9 (A)~ Fig. 9 (D) is a diagram for explaining an example of a method for manufacturing the susceptor 20 according to the second embodiment.

[0040] Fig.10 (A)~ Fig.10 (D) is a continuation of the example of the method for manufacturing the base 20 according to the second embodiment. Fig. 9 (A)~ Fig. 9 Figure 5.

[0041] [Explanation of Symbols]

[0042] 10: Base / Base of the First Embodiment

[0043] 11: First substrate

[0044] 11a: Side 1

[0045] 11b: Side 2

[0046] 11c: Mounting pad / Mounting pad for piezoelectric element

[0047] 11d: Contact hole / hole for contact hole

[0048] 11e: Contact hole line

[0049] 11ea: coating film

[0050] 11f: First metal film

[0051] 11f1: First part / Part / First metal film

[0052] 11f2: Second part / Part / First metal film

[0053] 11f3: Part III / Part I Metal Film

[0054] 11g: Insulation area

[0055] 11h: Seal pattern

[0056] 11ha: concave part

[0057] 11i: Incision

[0058] 13: Second substrate

[0059] 13a: Side 3

[0060] 13b: Second metal film

[0061] 13c: Side

[0062] 13d: The fourth side

[0063] 13e: Guide Line

[0064] 13f: Castellations

[0065] 13g: External mounting terminal

[0066] 13h: Insulated area

[0067] 13x: Wafer / wafer for forming the second substrate

[0068] 20: Base / base of the second embodiment

[0069] 21: First substrate

[0070] 21a: concave part

[0071] 21b: Embankment

[0072] 21x: Wafer / wafer for forming the first substrate

[0073] 30: Base / base of the third embodiment

[0074] 31: Concave shape correction part

[0075] 50: Piezoelectric device according to the first embodiment

[0076] 51: Cap-shaped cover member / cover member

[0077] 51a: concave part

[0078] 53: Piezoelectric element / AT-cut crystal vibrator

[0079] 53a: Excitation electrode

[0080] 60: Piezoelectric device according to the second embodiment

[0081] 61: Cover member

[0082] 80a: Chrome film

[0083] 80b, 80e: Gold film

[0084] 80c: Nickel film or nickel-tungsten alloy film

[0085] 80d: Titanium film

[0086] 90: Structure

[0087] M: Partial

[0088] PP, P1-P1, P2-P2, P3-P3, QQ, Q1-Q1, Q2-Q2, Q3-Q3: lines

[0089] α, β: contact hole opening area / opening area DETAILED DESCRIPTION

[0090] Hereinafter, with reference to the accompanying drawings, embodiments of the inventions of the base, piezoelectric device, and method for manufacturing the base of the present application will be described. In addition, the various figures used for the description are only schematically represented to the extent that these inventions can be understood. In addition, in the various figures used for the description, the same components are marked with the same numbers and represented, and their descriptions are sometimes omitted. In addition, the shapes, sizes, materials, etc. described in the following embodiments are only preferred examples within the scope of the present invention. Therefore, the present invention is not limited to the following embodiments.

[0091] 1. Embodiments of the first invention (base)

[0092] 1-1. Base 10 of First Embodiment

[0093] Figure 1 (A) Figure 1 (B) is a diagram for explaining the base 10 of the first embodiment. Figure 1 (A) is a three-dimensional view of the base 10, Figure 1 (B) is an exploded perspective view showing the base 10 divided into a first substrate 11 and a second substrate 13 .

[0094] The base 10 of the first embodiment includes: a first substrate 11 having a first surface 11a and a second surface 11b facing the first surface 11a and comprising glass or crystal; a piezoelectric element ( Figure 7 (A) Figure 7 A mounting pad 11c for the piezoelectric element 53) shown in (B) is arranged on the first surface 11a of the first substrate 11; a contact hole 11d and a contact hole line 11e extend from the first surface 11a to the second surface 11b; a first metal film 11f is arranged in an area of ​​the second surface 11b including the surrounding area of ​​the contact hole 11d; an insulating area 11g; and a sealing pattern 11h.

[0095] Furthermore, the base 10 includes: a second substrate 13, which includes the same material as the first substrate and is bonded to the first substrate 11 through an intermetallic bonding; a second metal film 13b, which is provided on a surface of the second substrate 13 on the first substrate 11 side, i.e., a third surface 13a, and is bonded to the first metal film 11f together with the first metal film 11f to form an intermetallic bonding; a guide line 13e, which reaches a fourth surface 13d of the second substrate 13, which is the opposite surface to the third surface 13a, from the contact hole line 11e via the third surface 13a and the side surface 13c of the second substrate 13; a castellated portion 13f, which is provided on the side surface 13c of the second substrate 13 for guiding the line 13e; and an external mounting terminal 13g (refer to Figure 3 (A)~ Figure 3 (C)), which is disposed on the fourth surface 13d and connected to the guide line. Specific examples of the above-mentioned components are described below.

[0096] In the case of this example, the first substrate 11 is a flat plate having a square planar shape. The specific material of the first substrate 11 is preferably a Z-cut plate or an AT-cut plate of crystal. The Z-cut plate and the AT-cut plate of crystal are substrates produced in large quantities for crystal resonators, respectively, and therefore are also cost-effective. In addition, when the specific material of the first substrate 11 is glass, any preferred glass such as soda glass can be used.

[0097] The mounting pad 11c is used to connect and fix the piezoelectric element by means of a conductive adhesive or the like. The mounting pad 11c is electrically connected to the contact hole circuit 11e. A mounting pad 11c of any shape corresponding to the mounting structure of the piezoelectric element is provided at any position on the first surface 11a of the first substrate 11. In the case of this example, a structure in which the piezoelectric element is held by a cantilever is illustrated, and therefore mounting pads 11c are provided near one side of the first substrate 11 and at two locations spaced apart from each other in the direction along the side. The planar shape of the mounting pad 11c can be set to any shape such as a square, a circle, an ellipse, etc. The mounting pad 11c can include any preferred metal film, such as a laminated film of a chromium film and a gold film.

[0098] The contact hole 11d and the contact hole line 11e extend from the first surface 11a to the second surface 11b of the first substrate 11 and can be formed on the first substrate 11 using, for example, photolithography, wet etching and film forming techniques. An example of the manufacturing method will be described later.

[0099] Reference Figure 2 (A)~ Figure 2 (D) describes the details of the structure of the contact hole 11d. Figure 2 (A) is related to Figure 1 (A) is a perspective view of the same base 10. Figure 2 (B)~ Figure 2 The (D) are along Figure 2 Cross-sectional views along the line P1-P1, line P2-P2, and line P3-P3 in (A).

[0100] like Figure 2 (B)~ Figure 2 (D), especially Figure 2 As shown in the partial enlarged view in (B), regarding the contact hole 11d, the opening area α on the second surface 11b side of the first substrate 11 is larger than the opening area β on the first surface 11a side. The reason is that if the structure is α>β, the electrode ( Figure 7 (A) Figure 7 The reliability of the electrical connection of the entire circuit structure between the excitation electrode 53a) shown in (B) and the external mounting terminal 13g of the base 10 is improved.

[0101] The planar shape of the contact hole 11d may be any shape such as a circle, an ellipse, or a square, but is typically preferably a circle. The ratio of α to β may be, 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 becomes an obstacle in terms of miniaturization or airtight reliability of the base 10. In addition, the constituent material of the contact hole line 11e may include, for example, any preferred metal material similar to the mounting pad 11c.

[0102] In addition, in order to further improve the electrical reliability of the contact hole circuit 11e, as shown in FIG. Figure 2 As shown in the enlarged view in (B), the surface layer of the contact hole circuit 11e is preferably a plated film 11ea. As the plated film 11ea, it can be any one of an electrolytic plated film and an electroless plated film. The material of the plated film can also be set to any preferred material, for example, it is preferably a nickel-plated film. In addition, the plated film 11ea can also be provided on the surface layer of the contact hole circuit 11e and the mounting pad 11c connected thereto. The reason for providing the plated film 11ea is as follows. Since the boundary between the contact hole 11d and the first surface 11a or the second surface 11b becomes an edge shape, the coverage of the circuit metal is usually poor. The contact hole circuit 11e is typically formed by a film forming method such as sputtering or evaporation, but in the case of these film forming methods, there is a limit even if the film thickness is thickened, so the coverage of the boundary edge is poor. Therefore, it is preferred to provide a plated film 11ea that can obtain a thicker film than a film formed by a sputtering method or the like, thereby improving the coverage of the edge and achieving an improvement in the reliability of the circuit structure.

[0103] In addition, 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 arbitrarily changed according to the design of the piezoelectric device. For example, it can also be set at a position on the diagonal line of the first substrate 11.

[0104] The first metal film 11f is one of the members for joining the first substrate 11 and the second substrate 13 by metal-to-metal bonding, and has a role as one of the sealing members for ensuring the airtightness of the contact hole 11d. Therefore, in the case of this example, the first metal film 11f includes three parts, namely, a first part 11f1, a second part 11f2, and a third part 11f3. The first part 11f1 has a planar shape surrounding one of the two contact holes 11d, the second part 11f2 has a planar shape surrounding the other of the two contact holes 11d, and the third part 11f3 is used for the area other than these. In addition, the three parts 11f1, 11f2, and 11f3 of the first metal film 11f need to be electrically separated, and are therefore separated by an insulating region 11g formed by removing the metal film. However, in order to increase the metal-to-metal bonding area with the second metal film 13b described later, the area of ​​the insulating region 11g is preferably set to the minimum necessary limit.

[0105] On the other hand, the second metal film 13b provided on the second substrate 13 side is another member for bonding the first substrate 11 and the second substrate 13 by metal-to-metal bonding, and has a function as another sealing member for ensuring the airtightness of the contact hole 11d. Therefore, the second metal film 13b includes three parts corresponding to the three parts 11f1, 11f2 and 11f3 of the first metal film 11f, and these three parts are separated by the insulating region 13h. Similar to the insulating region 11g, the area of ​​this insulating region 13h is preferably set to the minimum necessary limit.

[0106] Here, refer to Figure 3 (A)~ Figure 3 (C) describes the materials of the first metal film 11f and the second metal film 13b. In addition, 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).

[0107] The first metal film 11f and the second metal film 13b may each include any preferred metal film capable of metal-to-metal bonding. For example, they may include a laminated film ( 80a , 80b ) of a chromium film and a gold film stacked in order from the first substrate side. Figure 3In this way, the first metal film 11f and the second metal film 13b cooperate to produce metal-to-metal bonding between the gold films, thereby achieving metal-to-metal bonding between the first substrate 11 and the second substrate 13. Alternatively, the first metal film 11f and the second metal film 13b may each include a stacked film of a titanium film and a gold film stacked in sequence from the first substrate side.

[0108] More preferably, the first metal film 11f and the second metal film 13b are respectively Figure 3 (B) shows a laminated film having a three-layer structure including a chromium film 80a as a base film, a nickel film or a nickel-tungsten alloy film 80c as an intermediate film, and a gold film 80b as an upper film. The reason is that if the structure includes a nickel film or a nickel-tungsten alloy film as an intermediate film, the chromium film as the base film can be prevented from diffusing into the gold film as the upper film, so that the metal-to-metal bonding between the first metal film and the second metal film can be performed more effectively. In addition, it is believed that if the laminated film has this three-layer structure, the diffusion of chromium into the gold film can also be prevented over time.

[0109] More preferably, the first metal film 11f and the second metal film 13b are respectively as follows Figure 3 (C) shows a five-layer structure of the metal film, wherein the five-layer structure is formed by a laminated film including a titanium film 80d and a gold film 80e laminated on the titanium film 80d on the upper film of the three-layer structure of the metal film, that is, the gold film 80b. The reason is that even if nickel or a nickel-tungsten alloy is provided, there is a situation where chromium diffuses into the gold film. Therefore, the titanium film can prevent chromium from diffusing into the uppermost gold film, thereby enabling better metal-to-metal bonding. In addition, in the case of this five-layer structure of the laminated film, it is also believed that the diffusion of chromium into gold can be further prevented over time.

[0110] Seal pattern 11h( Figure 1 (A) Figure 1 (B)) is used to cover the cover member ( Figure 7 (A) Figure 7 The cover member 51 shown in (B) is bonded to the base 10. The base 10 of this embodiment shows an example in which the cover member is bonded to the base by a soldering material such as a gold-tin alloy. Therefore, the seal pattern 11h includes any preferred material that is easy to bond with gold-tin. The seal pattern 11h is provided along the edge of the first substrate 11 with a predetermined width.

[0111] Furthermore, when the seal pattern 11h is provided on the first surface 11a of the first substrate 11, it is preferable that Figure 2As shown in (B), a recess 11ha having a depth equal to the thickness of the seal pattern 11h is preferably provided in the region where the seal pattern 11h is provided on the first surface of the first substrate 11, and the seal pattern 11h is provided in the recess 11ha. The reason for this is that, when a low-profile piezoelectric device is desired, the thickness of the seal pattern 11h itself sometimes hinders the low-profile, but if the seal pattern 11h is buried in the recess 11ha as in the preferred example, the thickness of the piezoelectric device can be prevented from increasing due to the thickness of the seal pattern 11h.

[0112] The second substrate 13 is bonded to the first substrate by metal bonding between the first metal film and the second metal film. The second substrate 13 is a flat plate made of the same material and substantially the same planar shape as the first substrate 11. However, the second substrate 13 is provided with a castellated portion 13f relative to the first substrate 11, and in this respect, the planar shape is somewhat different. The castellated portion 13f will be described later.

[0113] The guide line 13e is a line extending from the contact hole line 11e, in the case of the present embodiment, from the mounting pad 11c via the third surface 13a and the side surface 13c of the second substrate 13 to the fourth surface 13d. The guide line 13e is formed by using a part of the first metal film 11f and the second metal film 13b. Specifically, the guide line 13e between the first substrate 11 and the second substrate 13 includes a first part 11f1 and a second part 11f2 of the first metal film and a second metal film 13b (13e) facing these parts. In addition, the part of the guide line 13e from the side surface 13c of the second substrate 13 to the external mounting terminal 13g includes a metal film continuous with the second metal film 13b.

[0114] Next, refer to Figure 4 (A) Figure 4 (B) describes the castellated portion 13f. Figure 4 (A) is a plan view of the first substrate 11 focusing on the castellated portion 13f. Figure 4 (B) is a plan view of the second substrate 13 focusing on the castellated portion 13f. The castellated portion 13f is used to guide the guide line 13e to the external mounting terminal 13g (see Figure 1 (A) Figure 1 (B)). The castellations 13f are formed into a cutout shape slightly recessed from the edge of the second substrate 13 toward the center at a portion of each of the two opposing sides of the second substrate 13. Therefore, a cutout 11i is provided at a portion of the first substrate 11 corresponding to the castellations 13f. In addition, in the example shown in the figure, the number of castellations is set to two, but it may be three or more.

[0115] The external mounting terminal 13g is provided on the fourth surface 13d and connected to the guide line 13e. The external mounting terminal 13g is a piezoelectric device manufactured using the base 10 of the present invention (see Figure 7 (A) Figure 7 (B) Figure 8 (A) Figure 8 (B)) is a terminal used when it is mounted on various electronic devices (not shown). In this example, four terminals are shown as external mounting terminals 13g, but the number of terminals is not limited to this. In addition, in this case, two of the four terminals are examples of non-connection (NoConnection, NC). In the case where the piezoelectric device has a grounding structure, these non-connected terminals can also be used as grounding terminals.

[0116] 1-2. Base 20 of Second Embodiment

[0117] Next, refer to Figure 5 (A)~ Figure 5 (D) of the present invention will now be described the base 20 according to the second embodiment. Figure 5 (A) is a plan view of a base 20 for explaining the second embodiment. Figure 5 (B)~ Figure 5 (D) is along Figure 5 (A) is a cross-sectional view of the base 20 taken along line Q1-Q1, line Q2-Q2, and line Q3-Q3.

[0118] The base 20 of the second embodiment is different from the base 10 of the first embodiment in that the first substrate 11 includes a recess 21a containing a piezoelectric element and a bank 21b provided around the recess 21a. The planar shape of the recess 21a is set to be a square shape, and can be a square shape or a rectangular shape depending on the shape of the piezoelectric element installed in the recess 21a. The height or width of the bank 21b can be set to an arbitrary value according to the design of the piezoelectric element installed in the recess 21a, and in consideration of ensuring airtightness, etc.

[0119] 1-3. Base 30 of the Third Embodiment

[0120] Next, refer to Figure 6 (A)~ Figure 6 (C) The base 30 of the third embodiment is described. Figure 6 (A) is a plan view of a base 30 for explaining the third embodiment. Figure 6 (B) Figure 6 (C) is along Figure 6 (A) is a cross-sectional view of the base 30 taken along line Q1-Q1 and line Q2-Q2.

[0121] The base 30 of the third embodiment is equivalent to a modified example of the base 20 of the second embodiment having a recess 21a for enclosing a piezoelectric element (not shown). Specifically, when a recess 21a for enclosing a piezoelectric element is formed on a 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 along 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 will not become a flat surface until the corner, and a part of the first substrate will remain in the thickness direction at the corner. If the residual part exists, the plane size of the recess 21a becomes smaller due to the residual part, and the area that can enclose the piezoelectric element becomes narrower, resulting in the inability to increase the size of the piezoelectric element. Generally speaking, if the piezoelectric element has a large area, it is expected that the characteristics will be improved, so it is preferable that there is no residual part. In order to solve the above problem, the base 30 of the third embodiment includes the following structure.

[0122] That is, the concave portion 21a is a square shape in a plan view, and includes a concave shape correction portion 31 including a hole facing the second substrate side in a vicinity of a set of sides of the square shape of the bottom surface of the concave portion. When the first substrate 21 is formed of a Z plate of crystal, for example, the concave shape correction portion 31 is preferably included in a vicinity of a set of sides parallel to the X axis of the crystal or a set of sides parallel to the Y axis of the crystal among the four sides of the square shape of the bottom surface of the concave portion 21a. If the concave shape correction portion 31 is provided, since the side wall of the concave portion is close to a vertical wall, the plane area near the side portion of the concave portion provided with the concave shape correction portion 31 can be increased compared with a case where the concave shape correction portion 31 is not provided.

[0123] 2. Implementation of piezoelectric devices

[0124] Next, embodiments of the piezoelectric device will be described.

[0125] 2-1. Piezoelectric device according to first embodiment

[0126] First, refer to Figure 7 (A) Figure 7 (B) describes the piezoelectric device 50 according to the first embodiment. Figure 7 (A) is a perspective view showing the piezoelectric device 50 according to the first embodiment in an exploded manner. Figure 7 (B) is a cap-shaped cover member 51 having a recess 51a for accommodating a piezoelectric element. Figure 7 (A) PP line profile.

[0127] The piezoelectric device 50 of the first embodiment includes the base 10 of the first embodiment, an AT-cut crystal vibrating piece 53 as a piezoelectric element 53 mounted on the base 10, and a cap-shaped cover member 51 connected to the base 10 at the position of the sealing pattern 11h in order to seal the piezoelectric element 53. The joining can be performed using a soldering material such as gold tin. The cap-shaped cover member 51 is preferably made of metal, and is preferably a metal cover member taking into account the linear expansion coefficient of the first substrate and the second substrate, such as a cover member made of copper, nickel or Kovar. If the linear expansion coefficient is taken into consideration, copper is most preferred. In addition, Figure 7 Reference numeral 53a in (A) denotes an excitation electrode included in the piezoelectric element 53. The piezoelectric element 53 is connected and fixed to the mounting pad 11c at the end portion (lead-out line) of the excitation electrode 53a by a conductive adhesive (not shown).

[0128] 2-2. Piezoelectric device according to second embodiment

[0129] Next, refer to Figure 8 (A) Figure 8 (B) describes the piezoelectric device 60 according to the second embodiment. Figure 8 (A) is a perspective view showing an exploded view of a piezoelectric device 60 according to the second embodiment. Figure 8 (B) is the piezoelectric device 60 along Figure 8 Cross-sectional view of line QQ in (A).

[0130] The piezoelectric device 60 of the second embodiment uses the base 20 of the second embodiment and a flat cover member 61. The piezoelectric element 53 is connected and fixed to the mounting pad 11c at the end of the excitation electrode 53a in the recess 21a of the base 20 by a conductive adhesive (not shown). The cover member 61 is connected to the seal pattern 11h provided on the top surface of the bank 21b of the base 20 by a soldering material such as gold tin.

[0131] The various embodiments of the piezoelectric device are examples of piezoelectric vibrators, but the invention of the present application can also be applied to a piezoelectric vibrator with a temperature sensor in which a piezoelectric element and a temperature sensor such as a thermistor are installed together, a piezoelectric oscillator in which a piezoelectric element and an oscillation circuit are installed together, and a piezoelectric oscillator in which a temperature compensation circuit is installed.

[0132] 3. Implementation of the manufacturing method

[0133] Next, an embodiment of a method for manufacturing a base for a piezoelectric device as the third invention of the present application is described. The 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. In the manufacturing method, the base is manufactured in a wafer state in which a plurality of bases are arranged in a matrix. Fig. 9 (A)~ Fig. 9 (D) Fig.10 (A)~ Fig.10 (D) is a process diagram for explaining the process, particularly a diagram for explaining the process of forming a contact hole. Fig. 9 (A)~ Fig. 9 (D) Fig.10 (A)~ Fig.10 In (D), a partial view shows the entire wafer, and a partial view shows a portion of the wafer in an enlarged manner.

[0134] First, a wafer 21x for forming a first substrate having a first surface and a second surface facing the first surface and made of glass or crystal is prepared. In addition, a wafer 13x for forming a second substrate having one of the principal surfaces as the third surface and the principal surface facing the third surface as the fourth surface and made of the same material as the wafer 21x for forming the first substrate is prepared. In addition, for these wafers 21x and 13x, a crystal wafer or a glass wafer having a circular or square planar shape and a predetermined thickness is used, respectively.

[0135] Next, a hole 11d for a contact hole is formed on the wafer 21x for forming the first substrate, the hole extending from the second surface 11b toward the first surface 11a and stopping halfway in the thickness direction of the wafer 21x for forming the first substrate. Next, a first metal film 11f1, a first metal film 11f2, and a first metal film 11f3 ( Fig. 9 (A)).

[0136] The formation of the contact hole 11d and the formation of the first metal film can be performed by photolithography technology, wet etching technology, and film formation technology. As the film formation technology, for example, sputtering is suitable.

[0137] Furthermore, when forming the hole 11d for the contact hole, the hole for the concave shape correction portion 31 described in the base 30 of the third embodiment (see Fig.10 (B)), the manufacturing process of the base of the third embodiment can be implemented. Of course, when the recessed shape correction part 31 is not required, it is not necessary to form a hole for the recessed shape correction part 31.

[0138] Next, second metal films 13b and 13e (13e) for forming metal-to-metal bonding together 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 technology, wet etching technology, and film formation technology.

[0139] Next, the second surface 11b and the third surface 13a are brought into contact ( Fig. 9 (C)) and the first substrate forming chip 21x on which the holes for contact holes and the first metal film are formed is joined to the second substrate forming chip 13x on which the second metal film is formed by metal-to-metal bonding based on the first metal film and the second metal film ( Fig. 9 (D) Fig.10 (A)). Metal-to-metal bonding is typically performed by pressurizing and heating the wafer 13x and the wafer 21x. Fig.10 The portion indicated by M in (A) corresponds to a base forming area.

[0140] After the bonding is completed, the structure 90 ( Fig.10 On the first surface 11a side of the wafer 21x for forming the first substrate (A)), a concave portion 21a (21a) is formed to accommodate the piezoelectric element and the bottom surface of which is connected to the hole 11d for the contact hole. Fig.10 (B) Fig.10 (C)). When the above process is completed, the contact hole 11d is connected to the recess 21a, and the original contact hole 11d is obtained. In the case where the hole with the recess shape correction part 31 is formed, the recess shape correction part 31 can be formed at a predetermined position of the recess 21a ( Fig.10 (B) Fig.10 (C)).

[0141] Next, the contact hole circuit 11e, the plating film 11ea as needed, the mounting pad 11c, the guide circuit 13e, and the external mounting terminal 13g are formed by photolithography technology, wet etching technology, and film forming technology (see Figure 2 (A)~ Figure 2 Thus, a wafer 21x having a plurality of the susceptors 20 of the second embodiment in a matrix shape can be obtained ( Fig.10 (D)).

Claims

1. A base, characterized in that include: A first substrate having a first surface and a second surface facing the first surface, and comprising glass or crystal; A contact hole and a contact hole circuit extending from the first surface to the second surface; A first metal film is provided in a region of the second surface including a peripheral region of the contact hole; A second substrate, comprising the same material as the first substrate, and bonded to the first substrate by metal-to-metal bonding; a second metal film, disposed on a surface of the second substrate on the side of the first substrate, i.e., a third surface, and forming the metal-to-metal joint together with the first metal film; as well as A guide line extends from the contact hole line through the third surface and the side surface of the second substrate to the fourth surface of the second substrate which is the opposite surface of the third surface. An opening area of ​​the contact hole on the second surface side is larger than an opening area of ​​the contact hole on the first surface side.

2. The base according to claim 1, characterized in that: The surface layer of the contact hole circuit is a plating film.

3. The base according to claim 1, characterized in that: The contact hole circuit is also provided over a region of the first surface corresponding to an edge of the contact hole. The surface layer of the contact hole circuit is a plating film.

4. The base according to claim 1, characterized in that: comprising a mounting pad for mounting a piezoelectric element around the contact hole of the first surface, The surface layers of the contact hole circuit and the mounting pad are plated films.

5. The base according to claim 1, characterized in that: A portion of the guiding circuit is the first metal film and the second metal film.

6. The base according to claim 1, characterized in that The first substrate is a flat plate, and includes a sealing pattern along an edge of the first surface of the first substrate for sealing.

7. The base according to claim 1, characterized in that The first substrate has a recessed portion for accommodating the piezoelectric element and a bank portion around the recessed portion on the first surface side.

8. The base according to claim 1, characterized in that The first substrate has a recessed portion for accommodating the piezoelectric element and a bank portion around the recessed portion on the first surface side. The recessed portion has a square shape in a plan view, and includes a recessed portion shape correction portion including a hole facing the second substrate in a region near a set of sides of the square shape on a bottom surface of the recessed portion.

9. The base according to claim 1, characterized in that: The first substrate includes a Z-plate of crystal, and has a recessed portion for accommodating the piezoelectric element and a bank portion around the recessed portion on the side of the first surface. The recess is square in plan view, and a region near a group of sides of the square parallel to the X-axis of the crystal or a group of sides parallel to the Y-axis of the crystal on the bottom surface of the recess includes a recess shape correction portion including a hole facing the second substrate.

10. The base according to claim 1, characterized in that The first metal film and the second metal film are respectively a stacked 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 film, or a stacked film of a titanium film as a base film and a gold film as an upper film.

11. The base according to claim 1, characterized in that The first metal film and the second metal film are respectively laminated films 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 film. The upper layer film includes a stacked film including a titanium film and a gold film stacked on the titanium film.

12. The base according to claim 1, characterized in that The contact holes are a first contact hole and a second contact hole, The first metal film and the second metal film respectively include a first portion, a second portion and a third portion, the first portion surrounds the first contact hole on a plane, the second portion surrounds the second contact hole on a plane, and the third portion is responsible for the area outside of the first portion, and, The base includes an insulating region for insulating the first portion, the second portion, and the third portion.

13. The base according to claim 1, characterized in that The first substrate and the second substrate include a crystal AT plate or a crystal Z plate respectively.

14. A piezoelectric device, characterized in that include: A base according to any one of claims 1 to 13; A piezoelectric element is directly or indirectly connected to the contact hole circuit through a conductive member; and a cover member engaged with the base to seal the piezoelectric element.

15. The piezoelectric device according to claim 14, characterized in that: The piezoelectric element is an AT-cut crystal vibrating plate.

16. A method for manufacturing a base for a piezoelectric device, characterized in that: When manufacturing the base according to claim 7, the following steps are included: A step of forming a hole for a contact hole on a first substrate having a first surface and a second surface facing the first surface and made of glass or crystal, wherein the hole extends from the second surface toward the first surface and stops halfway in the thickness direction of the first substrate; forming a first metal film for metal bonding around the hole for the contact hole on the second surface; forming a second metal film for forming an intermetallic bond with the first metal film on the third surface of a second substrate having one of its principal surfaces as the third surface and a principal surface facing the third surface as the fourth surface and made of the same material as the first substrate; A step of bringing the second surface and the third surface into contact with each other and bonding the first substrate on which the hole for the contact hole and the first metal film are formed and the second substrate on which the second metal film is formed, through metal-to-metal bonding based on the first metal film and the second metal film; as well as A step of forming a recessed portion that accommodates a piezoelectric element and has a bottom surface connected to the hole for the contact hole from the first surface side of the bonded structure.

17. The method for manufacturing a base for a piezoelectric device according to claim 16, wherein: The concave portion for accommodating the piezoelectric element is square in plan view. When forming the hole for the contact hole in the first substrate, a hole for correcting the shape of the recess is formed in a region where the rectangular recess is to be formed and which is a bottom surface of the recess and corresponds to a group of sides of the rectangular shape and faces the first surface.

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