Piezoelectric resonant devices

Abstract

The resonant frequency of a piezoelectric element changes depending on various factors. [Solution] The piezoelectric resonant device comprises a substrate 110 having a first surface 1110, electrode pads 1131 and 1132 located on the first surface, a MEMS element 150 having a second surface (upper surface 1500) located on the first surface, connection pads 151 and 152 located on the second surface, and a resonant portion 153 exposed on the second surface and electrically connected to a second connection conductor, and bonding wires 181 and 182 electrically connecting the connection pads. The connection pads and bonding wires are located outside the range obtained by extending the range of the resonant portion in a predetermined direction in a plan view when the first surface is viewed from above.

Description

[[TECHNICAL FIELD]]

[0001] The present disclosure relates to a piezoelectric resonant device. [[BACKGROUND ART]]

[0002] In recent years, for piezoelectric resonant devices that vibrate a piezoelectric element at a resonant frequency to output signals, there is a technology that uses an element having a MEMS (Micro Electro Mechanical Systems) structure (MEMS element) that employs a semiconductor element such as silicon instead of quartz.

[0003] The resonant frequency of a piezoelectric element can vary depending on various factors. For example, as shown in Patent Document 1, there is a piezoelectric vibrating device in which a shield for reducing the influence of external noise is properly positioned. [[PRIOR ART DOCUMENT]] [[PATENT DOCUMENT]]

[0004] [[Patent Document 1]] Japanese Unexamined Patent Publication No. 2019-97105 [[Summary of Invention]] [[Means for Solving the Problems]]

[0005] One aspect of the present disclosure provides a base, and a MEMS element located on said base, said MEMS element comprises resonant means that can vibrate in a predetermined mode and comprises a silicon layer, a peripheral portion that has a silicon layer continuous with the silicon layer of said resonant means, is located around said resonant means, and holds said resonant means so as to allow vibration thereof, and a support portion joined to said peripheral portion and said base, supports said peripheral portion, and comprises a silicon substrate, which is a piezoelectric resonant device. [[Brief Description of Drawings]]

[0006] [Figure 1A] This is an overall perspective view of a piezoelectric resonant device with the cover removed, looking at the side where the cover is connected. [Figure 1B] This is an overall perspective view of a piezoelectric resonant device with the cover removed, looking at the side opposite to where the cover is attached. [Figure 2A] This is a plan view of the piezoelectric resonant device with its cover removed. [Figure 2B] This is a cross-sectional view of a piezoelectric resonant device with its cover removed. [Figure 3] This is a cross-sectional view illustrating the MEMS element, including the resonant region, in more detail. [Figure 4A] This is a cross-sectional view showing a modified example 1 of a piezoelectric resonant device. [Figure 4B] This is a cross-sectional view showing a modified example 2 of a piezoelectric resonant device. [Figure 4C] This is a cross-sectional view showing a modified example 3 of the piezoelectric resonant device. [Figure 5A] This is a cross-sectional view showing a modified example 4 of the piezoelectric resonant device. [Figure 5B] This is a cross-sectional view showing a modified example 5 of the piezoelectric resonant device. [Figure 6] This is a plan view showing the piezoelectric resonant device in modified example 6 with the cover removed. [Figure 7] This is an overall perspective view of modified piezoelectric resonant device 7 with the cover removed. [Modes for carrying out the invention]

[0007] The embodiments will be described below with reference to the drawings. Figures 1A and 1B are overall perspective views of the piezoelectric resonant device 1 of this embodiment with the cover 120 removed. Figure 1A shows the side where the cover 120 is joined, and Figure 1B shows the side opposite to where the cover 120 is joined.

[0008] The piezoelectric resonant device 1 comprises a base 100 and a MEMS element 150, etc. The base 100 comprises a substrate 110 and a cover 120, etc. The substrate 110 is divided into a frame portion 1101 and a base portion 1102, and has a housing portion 111 and through holes 115, etc. A frame-shaped metallized layer 112, electrode pads 113, and external connection pads 114 are located bonded to the substrate 110. The housing portion 111 is a concave region located on one surface on the side to which the cover 120 is bonded, that is, on the upper surface in the z direction. The MEMS element 150 is located within the housing portion 111. The frame portion 1101 consists of the upper open surface of the housing portion 111 and the surface opposite to the open surface, which is the mounting surface 1110 (first surface) for the MEMS element 150, that is, the surfaces connecting the open surface and the mounting surface 1110, and in this case, each surface is parallel to the z direction. The base portion 1102 is the portion of the substrate 110 below the housing portion 111 and the frame portion 1101, i.e., in the -z direction, and includes the mounting surface 1110 described above. A frame-shaped metallized layer 112, which is a conductive layer, is positioned in a frame shape at the joint surface of the frame portion 1101 with the lid 120 (the end surface on the open surface side). The frame-shaped metallized layer 112 is joined to the lid 120 via a sealing material such as silver solder. While not strictly limited, the dimensions of this substrate 110 are approximately 0.6 to 10.0 mm on each side in the xy plane, and approximately 0.2 to 2.0 mm in thickness in the z direction. Here, the x direction is defined as the longitudinal direction of the base body 100.

[0009] The electrode pads 113 (first connecting conductors) are positioned in pairs in the y-direction on the mounting surface 1110 of the housing section 111. The electrode pads 113 are, for example, rectangular in shape with the same size and orientation in a plan view. The electrode pads 113 are connected to external connecting pads 114, for example, external connecting pads 1141 and 1144, respectively. The electrode pads 113 are formed on the mounting surface 1110 by plating or the like, for example, a thin gold film layer. Alternatively, the electrode pads 113 may be formed convexly from the mounting surface by screen printing or the like.

[0010] The external connection pads 114 are external electrodes that are joined to an external surface, such as a module substrate. Here, the external connection pads 114 are located at the four corners of the substrate bottom surface, which is opposite to the mounting surface 1110 of the base 1102. If the required number of external connection pads 114 is less than four, they may be omitted as appropriate. The external connection pads 114 connected to the MEMS element 150 may, for example, be connected to a drive circuit and act as an oscillator by applying a voltage signal of a predetermined frequency to the MEMS element 150.

[0011] The MEMS element 150 is positioned in the -x direction relative to the electrode pad 113 on the mounting surface 1110 of the housing 111. The MEMS element 150 is bonded to the mounting surface 1110 via an adhesive member 170. The adhesive member 170 is, for example, a resin-based adhesive that has insulating properties. The adhesive member 170 may be made of an epoxy resin containing alumina or the like. The particle size of the filler in the adhesive member 170 is, for example, 1 to 10 μm. This ensures that the MEMS element 150 is mounted stably without tilting.

[0012] The MEMS element 150 is electrically connected to two electrode pads 1131 (third connection point) and electrode pad 1132 (fourth connection point) by two conductive bonding wires 181 (first wiring conductor) and 182 (second wiring conductor). Bonding wires 181 and 182 are collectively referred to as bonding wire 180 (wiring conductor). The material of bonding wire 180 is not particularly limited, but for example, it is gold (Au). The bonding wire 180 is connected by ultrasonic bonding using, for example, a wire bonder with a capillary. Here, the bonding of the bonding wire 180 to the MEMS element 150 is the first bonding, and the bonding to the electrode pad 113 is the second bonding. However, the order of bonding can be reversed to reduce the pressure applied to the MEMS element 150 during ultrasonic bonding.

[0013] The substrate 110 comprises a ceramic material, such as an aluminum oxide sintered body, an aluminum nitride sintered body, a mullite sintered body, or a glass-ceramic sintered body. The lid 120 is made of a conductive metal, and hermetically seals the housing portion 111 by being bonded to the frame-shaped metallization layer 112. A conductive sealing material such as gold-tin (AuSn) or silver solder is used for the sealing. The lid 120 suppresses propagation of external noise into the housing portion 111 by being grounded. The lid 120 is electrically connected to the through-hole 115 of the substrate 110 via the conductive sealing member and the frame-shaped metallization layer 112. The through-hole 115 penetrates the substrate 110 in the z-direction and is connected to one or two of the external connection pads 114 on the bottom surface of the substrate. When the external connection pad 114 is grounded, the lid 120 is brought into a grounded state. Note that the frame portion 1101 may have a plate-shaped conductive plate instead of the through-hole 115, and form part of a path for electrically connecting the lid 120 and the external connection pad 114.

[0014] The frame-shaped metallization layer 112 is made of a conductive metal and is formed by printing on the bonding surface of the frame portion 1101. At least exposed surfaces of conductive portions such as the frame-shaped metallization layer 112, the electrode pads 113, and the external connection pads 114 may be coated with a plating layer of nickel and / or gold. For example, nickel plating is formed on the exposed surface to a thickness of 1 to 20 μm, and a gold plating layer is formed on the nickel plating layer to a thickness of 0.1 to 3.0 μm. This can suppress oxidative corrosion on the surface, and also enables easy and firm connection between the frame-shaped metallization layer 112 located on the upper surface of the substrate 110, which is an insulating substance, and the lid 120, which is a metal conductor. In addition, the lid 120 can be appropriately connected to the bonding wire 180, which is a gold wire, and transmit signals with low resistance.

[0015] FIG. 2A is a plan view of the piezoelectric resonance device 1 with the lid 120 removed. FIG. 2B is a cross-sectional view taken along section line AA in the plan view of FIG. 2A.

[0016] As described above, the two electrode pads 1131 and 1132 are positioned side by side in the y-direction near the edge of the mounting surface 1110 where the x-component is greatest. The electrode pads 1131 and 1132 are positioned approximately symmetrically with respect to the center line Sy of the substrate 110 in the y-direction. The connection point C3 between electrode pad 1131 and bonding wire 181, and the connection point C4 between electrode pad 1132 and bonding wire 182 are also in approximately the same position in the x-direction. That is, the second reference line S2 passing through connection points C3 and C4 is parallel to the y-axis, and the midpoint of connection points C3 and C4 approximately coincides with the center line Sy. Here, connection point C3 is defined as the predetermined third position of electrode pad 1131. Also, connection point C4 is defined as the predetermined fourth position of electrode pad 1132. Note that the expressions "parallel," "points or points and lines coincide," and "identical" used here and thereafter do not need to be strictly defined. A slight deviation from the designed position is acceptable.

[0017] In a plan view, the electrode pads 1131 and 1132 overlap with the through conductors 1161 and 1162, respectively, which penetrate the base 1102. The through conductors 1161 and 1162 have a first end and a second end. The first end is connected to the electrode pads 1131 and 1132, and the second end is connected to the external connection pads 1141 and 1144. Here, the through conductors 1161 and 1162 are described as extending only in the z direction, but they may also extend within the base 1102 in the x and y directions, for example, connecting electrode pad 1131 to external connection pad 1142.

[0018] The MEMS element 150 has a connection pad 151 (first connection part) and a connection pad 152 (second connection part) and a resonant part 153 on its upper surface (second surface), that is, the surface opposite to the surface joined to the mounting surface by the adhesive member 170. The resonant part 153 has a resonant means 1531. The upper surface of the resonant means 1531 is exposed to the upper surface (second surface) of the MEMS element 150, supported by a node, and is capable of vibrating in a predetermined mode with the node as the fixed end. As described later, the resonant means 1531 has an upper electrode and a lower electrode on the upper side, i.e., the +z side, and on the lower side, i.e., the -z side, respectively, and each electrode is electrically connected to the connection pads 151 and 152. Here, the connection pad 151 is connected to the upper electrode via wiring 154. The connection pad 152 is connected to the lower electrode inside the MEMS element 150.

[0019] The connecting pads 151 and 152 are located near the end of the MEMS element 150 where the x-component is greatest, and are collectively referred to as the second connecting conductor. The connecting pads 151 and 152 are the connection ends of the MEMS element 150 that are connected to the electrode pads 1131 and 1132 by the bonding wire 180 as described above. The uppermost surfaces of the connecting pads 151 and 152 may be made of gold (Au), for example. The connecting pad 151 is located in a position corresponding to the electrode pad 1131 in the y-direction, here between the electrode pad 1131 and the resonant portion 153, and the bonding wire 181 is connected to it. The connecting pad 152 is located in a position corresponding to the electrode pad 1132 in the y-direction, here between the electrode pad 1132 and the resonant portion 153, and is connected to the bonding wire 182. The connection points C1 and C2 of the bonding wires 181 and 182 at connection pads 151 and 152 are located in approximately the same position in the x-direction and are located approximately symmetrically with respect to the center line Sy in the y-direction. That is, the first reference line S1 passing through connection points C1 and C2 is parallel to the y-axis, and the midpoints of these connection points C1 and C2 coincide approximately with the center line Sy. Also, the y-coordinates of connection points C1 and C3 are approximately the same, and the y-coordinates of connection points C2 and C4 are approximately the same. Therefore, the bonding wire 181, i.e., the line connecting connection points C1 and C3, and the bonding wire 182, i.e., the line connecting connection points C2 and C4, extend parallel to the x-direction in a plan view, i.e., perpendicular to the y-direction. Here, connection point C1 is defined as a predetermined first position on connection pad 151, and connection point C2 is defined as a predetermined second position on connection pad 152. The bonding wires 181 and 182 do not need to extend in the shortest distance in the x-direction, i.e., in a straight line; some slack is acceptable, and there may be a slight deviation or bend in the y-direction from the straight line extending in the x-direction in a plan view, but they should not have excessive slack. Here, the bonding wires 181 and 182 are designed so that they do not hang down and come into contact with the upper edge of the MEMS element 150.

[0020] Here, the center or center of gravity of the resonant portion 153 lies on the center line Sy. As a result, the resonant portion 153, the connecting pads 151 and 152, the bonding wires 181 and 182, and the electrode pads 1131 and 1132 are all symmetrical with respect to the center line Sy.

[0021] The MEMS element 150 is, for example, a rectangle whose longitudinal direction is along the x-direction, which is the longitudinal direction of the substrate 100, but is not limited to this. The shape of the resonant portion 153 can be changed in various ways depending on the output frequency, so the resonant portion 153 may be positioned in an optimal orientation according to its shape. On the upper surface of the MEMS element 150, there is a small space 155 near the edge in the -x direction that does not overlap with the resonant portion 153, that is, on the opposite side of the connection pads 151 and 152 from the resonant portion 153. This space 155 is used as the adsorption space for an adsorption device that adsorbs and holds the MEMS element 150 when it is placed and mounted on the mounting surface. The size of space 155 should be within a range of suction force that is not too strong and does not damage the MEMS element 150, and should be greater than a predetermined area on which the adsorption device can adsorb the MEMS element 150. For example, it may be 100 μm in the x direction and less than the width of the MEMS element 150 in the y direction, for example, 450 μm for a MEMS element 150 with a width of 600 to 800 μm. Space 155 should be a flat surface on the upper surface of the MEMS element 150 that can be adsorbed, and may include markings such as the product serial number.

[0022] The adhesive member 170 is not only adhered to the back surface of the MEMS element 150, facing the mounting surface 1110, but also extends beyond the outer edge of the MEMS element 150 in a plan view. For example, when the bonding wires 181 and 182 are joined at connection points C1 and C2, respectively, a large force is applied to the MEMS element 150 from above. At this time, the entire MEMS element 150 is stably joined and fixed, and the elasticity of the adhesive member 170 absorbs the force in a balanced manner, suppressing damage to the MEMS element 150. Note that the adhesive member 170 may be attached to the entire surface of the MEMS element 150 facing the mounting surface 1110, or there may be some areas on the opposing surface where the adhesive member 170 is not attached.

[0023] Furthermore, connection points C1 and C3 are determined such that the distance L1 between them (each connection position) in a plan view is smaller than the distance L2 between connection point C3 and the edge of the mounting surface 1110 in the +x direction, i.e., the frame portion 1101. Since the positions of connection points C1 and C2 in the x direction are equal, and the positions of connection points C3 and C4 in the x direction are equal, in this case, similarly, the distance between connection points C2 and C4 (each connection position) is L1, which is equal to the distance between connection points C1 and C3. Also, the distance from connection point C4 to the frame portion 1101 in the +x direction is L2. Since approximately equal lengths of bonding wires 181 and 182 are dispensed by the wire bonder described above, the lengths of bonding wires 181 and 182 are also approximately equal. In this way, by keeping the lengths of bonding wires 181 and 182 from being unnecessarily long and making them equal in length, it becomes possible to transmit signals with low loss and uniformity in bonding wires, which are thinner than other parts and tend to have higher losses.

[0024] Figure 3 is a cross-sectional view illustrating the MEMS element 150, including the resonant portion 153, in more detail. Here, the cross-section at the cross-sectional line BB in Figure 2A is shown.

[0025] The MEMS element 150 consists of a handling layer 1501, an insulating layer 1502, a doping layer 1503 (lower electrode), a piezoelectric layer 1504 (piezoelectric material), and an upper electrode 1505, which are stacked in order from the -z side.

[0026] The handling layer 1501 includes a silicon substrate and is bonded to the mounting surface 1110 of the substrate 110 by an adhesive member 170. The adhesive member 170 extends beyond the edge of the handling layer 1501, forming fillet portions 1701 and 1702.

[0027] The insulating layer 1502 is a silicon dioxide (SiO2) layer. The insulating layer 1502 may have a very small thickness. This insulating layer 1502 is removed in the area of ​​the resonant region 153. Here, the handling layer 1501 and the insulating layer 1502 are combined to form a semiconductor substrate.

[0028] The doped layer 1503 is a silicon layer that has been p-doped. The amount of doping here is much greater than that in typical semiconductor devices, for example, one to two orders of magnitude larger. As a result, the doped layer 1503 behaves effectively as a conductor and functions as a lower electrode.

[0029] A portion of the doped layer 1503 is separated from the other components in areas other than the nodes, making it capable of vibration.

[0030] The piezoelectric layer 1504 is a thin film layer of a piezoelectric member that has a correspondence between physical shape changes and electrical signals. Here, the piezoelectric layer 1504 is a thin film layer of aluminum nitride (AlN) that deforms in response to the applied voltage between the upper electrode 1505 and the doped layer 1503, or generates a voltage between the upper electrode 1505 and the doped layer 1503 corresponding to the amount of deformation due to external pressure, etc.

[0031] The upper electrode 1505 is located in contact with the upper side of the piezoelectric layer 1504 and is electrically connected to the connection pad 151 via wiring 154. The upper electrode 1505 is, for example, an aluminum (Al) layer.

[0032] Thus, in the area of ​​the resonant region 153 that does not have an insulating layer 1502, the laminated structure of the doped layer 1503, piezoelectric layer 1504, and upper electrode 1505 is separated from the lower handling layer 1501, and in a plan view, each layer is separated from the surrounding area in the xy plane except for node portions not shown, forming a resonant means 1531. As a result, this resonant means 1531 can generate vibrations at the resonant frequency.

[0033] The adhesive member 170 includes, for example, an epoxy resin. The upper end positions of the fillet portions 1701 and 1702 of the adhesive member 170 are lower than the upper end position of the insulating layer 1502 (lower end position of the doped layer 1503) on the side surface of the MEMS element 150, i.e., the surface perpendicular to the xy plane, and are usually below the upper end position of the handling layer 1501. Therefore, they do not come into contact with the doped layer 1503, the piezoelectric layer 1504, and the upper electrode 1505, nor do they come into contact with the upper surface of the MEMS element 150.

[0034] When the adhesive member 170 is made of epoxy resin, if the adhesive member 170 comes into contact with the dope layer 1503, sodium (Na), iron (Fe), and other impurities such as manganese (Mn), nickel (Ni), titanium (Ti), and phosphorus (P) contained in the epoxy resin may migrate to the dope layer 1503, potentially changing its conductivity.

[0035] Furthermore, the operating environment of the piezoelectric resonant device 1 may not be constant. When the temperature of the piezoelectric resonant device 1, i.e., the MEMS element 150, changes, the adhesive member 170 expands / contracts. If the adhesive member 170 is in contact with the dope layer 1503, the piezoelectric layer 1504, or the upper electrode 1505, the expansion / contraction of the adhesive member 170 will apply unnecessary stress to these dope layers 1503, piezoelectric layer 1504, or upper electrode 1505, causing a change in their frequency characteristics.

[0036] On the other hand, the adhesive member 170 has fillet portions 1701 and 1702 and is bonded to the side surface of the handling layer 1501 of the MEMS element 150, thereby improving the adhesive strength of the MEMS element 150.

[0037] Therefore, in the piezoelectric resonant device 1, the upper ends of the fillet portions 1701 and 1702 of the adhesive member 170 are positioned so that they do not come into contact with the doped layer 1503, thereby reducing changes in the conductivity and frequency characteristics of the MEMS element 150 while fixing the MEMS element 150 to the mounting surface 1110.

[0038] The resonant frequency of the resonant means 1531 depends not only on the characteristics of the piezoelectric layer 1504, but also on the characteristics of each part, such as the size, i.e., area and thickness, of the doped layer 1503 and the upper electrode 1505, as well as the surrounding node members (not shown). In other words, the resonant frequency is determined only after the MEMS element 150 is mounted on the piezoelectric resonant device 1. That is, there may be some deviation from the expected resonant frequency depending on the mounting condition. Therefore, in the piezoelectric resonant device 1, adjustments are made to the resonant means 1531 after mounting by thinning the upper electrode 1505 on the exposed upper surface to bring it closer to the desired resonant frequency.

[0039] In the piezoelectric resonant device 1, the resonant frequency is changed by surface processing using an ion laser, such as an argon laser, to make the upper electrode 1505 thinner than when it was mounted. At this time, the ion laser is scanned in a predetermined direction, in this case the scanning direction Ss, and the upper electrode 1505 is thinned almost uniformly. Therefore, if the bonding wire 180 and / or connection pads 151 and 152 are on the extension of the scanning direction Ss, they may also be scraped and damaged. For this reason, in the piezoelectric resonant device 1, the positional relationship of each component is determined so that the bonding wire 180 or connection pads 151 are not on the scanning line.

[0040] The scanning direction Ss is such that the range passing through the resonant means 1531 is the same between scans. Generally, it is determined along the longitudinal direction of the rectangular resonant portion 153 in a plan view, but is not limited to this. The scanning direction Ss may be perpendicular to the longitudinal direction, or it may be inclined at a predetermined angle with respect to the longitudinal direction. Here, as shown in Figures 1A, 1B, 2A, and 2B, the connection pads 151 and 152, in this case connection points C1 and C2, are located near the end of the MEMS element 150 where the x component is largest, and the resonant portion 153 is located at a position where the x component is smaller than these. That is, by determining the scanning direction Ss along the y direction, this scanning direction Ss becomes parallel to the direction in which the connection pads 151 and 152, i.e., the connection points C1 and C2 are aligned, and the scan lines that run multiple times across the width of the resonant means 1531 in the x direction while shifting the scanning position in the x direction on the resonant portion 153 do not overlap the connection pads 151 and 152 in a plan view. Furthermore, the resonant section 153 has its longitudinal direction in the y-direction.

[0041] Furthermore, at positions where the x-component is greater than that of the MEMS element 150, the electrode pads 1131 and 1132, and in this case the connection points C3 and C4, are aligned in the y-direction. That is, the scanning direction Ss is also parallel to the direction in which the electrode pads 1131 and 1132, and in this case the connection points C3 and C4, are aligned. Therefore, the electrode pads 1131 and 1132 do not overlap with the scan line in a plan view. In addition, the bonding wire 181 connecting electrode pad 1131 and connection pad 151, and the bonding wire 182 connecting electrode pad 1132 and connection pad 152, are also positioned so as not to overlap with the scan line in a plan view.

[0042] In other words, the connecting pads 151 and 152, the electrode pads 1131 and 1132, and the bonding wires 181 and 182 are all located outside the range of the resonant portion 153 extended in the scanning direction.

[0043] The procedure for obtaining the piezoelectric resonant device 1 from the above-described substrate 100 and MEMS element 150 is as follows. First, an adhesive member 170 is applied to the mounting position of the MEMS element 150 on the substrate 100. The MEMS element 150, which has been adsorbed by a suction device, is moved relative to the mounting position of the MEMS element 150, and the MEMS element 150 is bonded to the mounting surface 1110 by pressing or the like.

[0044] A wire bonder is used to bond a bonding wire 181 between the connection pad 151 and the electrode pad 1131, and a bonding wire 182 is used to bond a bonding wire 182 between the connection pad 152 and the electrode pad 1132.

[0045] While monitoring the voltage between connection pads 151 and 152, or between electrode pads 1131 and 1132, or between external connection pads 1141 and 1144, the ion gun is scanned to abrade the surface of the resonant section 153 and adjust the resonant frequency. This adjustment may be repeated multiple times. Once the adjustment is complete, the lid 120 and the frame-shaped metallized layer 112 are joined together.

[0046] Figures 4A to 4C are cross-sectional views showing modified examples 1 to 3 of the piezoelectric resonant device 1, respectively. These cross-sections are identical to those shown in Figure 2B.

[0047] In the piezoelectric resonant devices 1 of Modified Examples 1 to 3, resin members 185, 185a, and 185b are located in at least a portion of the space between the bonding wires 181 and 182 between the connection pads 151 and 152 of the MEMS element 150 and the electrode pad 113 of the substrate 100 in the x-direction, and the mounting surface 1110. In the piezoelectric resonant device 1 of Modified Example 1 shown in Figure 4A, the resin member 185 occupies the entire space between the connection pad 151 and the electrode pad 1131 in the x-direction. In the area overlapping with the bonding wires 181 and 182 in a plan view, the maximum height of the resin member 185 in the z-direction, i.e., the maximum distance from the mounting surface 1110, is greater than or equal to the height of the connection pads 151 and 152 of the MEMS element 150 in the z-direction, and the resin member 185 is in contact with or covers the edge of the MEMS element 150. Since the gold material of the bonding wire 181 is particularly susceptible to damage from contact with sharp edges, it is preferable to maintain a wiring position that does not come into contact with the edges of the MEMS element 150. The bonding wire 181 may be in contact with the resin member 185, but it is not required. In this case, the bonding wire 181 should be joined after the resin member 185 has been placed on the base 100.

[0048] The resin members 185 to 185b can be selected without damaging the bonding wires 181 and 182, and with appropriate consideration given to some or all of their durability, volatility, and corrosiveness. For example, they may be epoxy resin or polyimide resin. Alternatively, they may be made of any other material that is an insulating material with higher elasticity compared to ceramic materials, etc., and does not interfere with signal transmission.

[0049] In the piezoelectric resonant device 1 of the modified example 2 shown in Figure 4B, the resin member 185a has at least a portion of the bonding wire 181 located inside it. Here, the portion of the bonding wire 181 that connects to the electrode pad 1131 is also located inside the resin member 185a, but is not limited to this. Also, here, contrary to the above embodiment, the connection of the bonding wire 181 to the electrode pad 1131 is shown as first bonding, and the connection to the connecting pad 151 is shown as second bonding, but is not limited to this. In this case, the resin member 185a can be placed on the substrate after the bonding wire 181 has been bonded to the electrode pad 1131 and the connecting pad 151. Alternatively, instead of the bonding wire 181 being embedded inside the resin member 185a, the resin member 185a may have a groove that is open upward, i.e., in the +z direction, and the bonding wire 181 may extend within this groove.

[0050] In the piezoelectric resonant device 1 of the modified example 3 shown in Figure 4C, the resin member 185b occupies only a portion of the space between the electrode pad 113 and the connecting pad 151 that is in contact with the MEMS element 150. The height of the resin member 185b in the z direction is greater than the height of the MEMS element 150. Also, the area near the upper end of the resin member 185b in the z direction is gently curved. Similar to the resin member 185 in the modified example 1 described above, the resin member 185b is positioned and shaped in such a way that the edge of the MEMS element 150 and the bonding wire 181 are unlikely to come into contact. That is, even if the bonding wire 181 is slightly loose, it will come into contact with the area near the upper end of the resin member 185, making it unlikely to come into contact with the edge of the MEMS element 150.

[0051] Figures 5A and 5B are cross-sectional views showing modified examples 4 and 5 of the piezoelectric resonant device 1, respectively. These cross-sections are also cut along the same cross-sectional line AA as the cross-section shown in Figure 2B, and the cross-sections that include the connection positions of the bonding wire 182 to the electrode pad 1132 and the connection positions to the connecting pad 152 have a similar structure. In the piezoelectric resonant device 1 of the modified example 4 shown in Figure 5A, the mounting surface 1110 of the housing portion 111 has a projection 1111 perpendicular to the mounting surface 1110, and the electrode pad 1131 is located on the projection 1111. The electrode pad 113 on the projection 1111 may have an underlayer (not shown) of various well-known materials, such as nickel (Ni) or chromium (Cr), between the projection 1111 and the Au thin film. The projection is formed, for example, using a mold. That is, the shape of the projection should be included in the mold used to form the base portion 1102.

[0052] Here, the electrode pad 113 and the surface of the connecting pad 151 are located at approximately the same distance from the mounting surface 1110. That is, the height of the connection point of the bonding wire 181 with the electrode pad 113 and the connecting pad 151 is approximately equal. This makes it easier to crimp and fix the bonding wire 181 by the wire bonder. In addition, the bonding wire 181 is shortened by the amount by which its length in the z direction is reduced. Furthermore, the bonding wire 181 is less likely to sag when it reaches a height that makes contact with the corner of the MEMS element 150.

[0053] Even in this case, the MEMS element 150 may have a resin member at its corner. Also, in this case, since the bonding wire 180 may come into contact with the corner of the electrode pad 113 to the same extent as the MEMS element 150, the electrode pad 113 may also have a resin member at its MEMS element 150 side, i.e., the -x side corner.

[0054] In the piezoelectric resonant device 1 of Modification 5 shown in Figure 5B, the corners of the bonding wire 181 in the direction of extension at the MEMS element 150a are rounded or beveled. This reduces damage caused by right-angle corners even if the bonding wire 181 becomes loose and comes into contact with the MEMS element 150a. The same applies to the bonding wire 182.

[0055] In this case as well, a resin member may be present on the mounting surface 1110. Furthermore, the electrode pad 113 may be positioned on the projection. Additionally, the corner of the electrode pad 113 facing the MEMS element 150, i.e., the corner in the -x direction, may be rounded or beveled.

[0056] Figure 6 is a plan view showing the state in which the cover 120 has been removed in a modified example 6 of the piezoelectric resonant device 1.

[0057] In this modified example 6 of the piezoelectric resonant device 1, the adhesive members 171a to 171d that bond the MEMS element 150 to the mounting surface extend beyond the MEMS element 150 only at the four corners of the MEMS element 150. In other words, the adhesive members do not necessarily need to extend in a fillet-like manner from all directions of the MEMS element 150 as the adhesive member 170 in the above embodiment; as long as they extend outward at at least each corner, the MEMS element 150 can be fixed stably and flexibly.

[0058] While it is not necessary for the entire surface between the MEMS element 150 and the mounting surface to be covered by adhesive, in addition to the four corners mentioned above, adhesive may also be applied to positions that overlap with, for example, the connection pads 151 and 152, particularly the connection points C1 and C2.

[0059] Figure 7 is an overall perspective view of modified example 7 of the piezoelectric resonant device 1 with the cover 120 removed.

[0060] In this modified example 7 of the piezoelectric resonant device 1, the substrate 110a is a flat plate, and the lid 120a has a concave housing portion 121. In this case, the frame-shaped metallized layer 112 may be formed first on the portion of the lid 120a corresponding to the frame portion of the housing portion 121, and then bonded to the substrate 110a. The electrode pads 113, bonding wires 180, and MEMS element 150 on the substrate 110a are all housed inside the housing portion 121.

[0061] As described above, the piezoelectric resonant device 1 of this embodiment comprises a substrate 100 having a mounting surface 1110, electrode pads 1131 and 1132 located on the mounting surface 1110, a MEMS element 150 having an upper surface 1500 located on the mounting surface 1110, connection pads 151 and 152 located on the upper surface 1500, and a resonant portion 153 exposed on the upper surface 1500 and electrically connected to the connection pads 151 and 152, and bonding wires 181 and 182 that electrically connect the electrode pads 1131 and 1132 and the connection pads 151 and 152. The electrode pads 1131 and 1132, the connection pads 151 and 152 and the bonding wires 181 and 182 are located outside the range of the resonant portion 153 extended in the scanning direction of the ion gun during its adjustment, when viewed from above on the mounting surface 1110 in a plan view. In the piezoelectric resonant device 1 using the MEMS element 150, by positioning the resonant portion 153 so that it is exposed on the upper surface 1500 of the MEMS element 150, the resonant frequency of the resonant portion 153 can be adjusted to a desired value according to the mounting conditions after mounting the resonant portion 153, with ease and accuracy compared to crystal oscillators and the like. In this case, the piezoelectric resonant device 1 allows for easy connection of the connection pads 151 and 152 and the electrode pads 1131 and 1132 by wire bonding. Furthermore, when scanning the exposed surface of the resonant portion 153 with an ion gun to adjust the thickness by scraping the surface, the output of the ion gun is likely to damage the bonding wires 181 and 182, the electrode pads 1131 and 1132, and the connection pads 151 and 152. To suppress this damage and / or to facilitate the control of an ion gun or the like for suppressing damage, the piezoelectric resonant device 1 may be arranged and shaped such that the bonding wires 181, 182, electrode pads 1131, 1132, and connecting pads 151, 152 are all located outside the range of the resonant portion 153 extended in the scanning direction. With such a structure, the piezoelectric resonant device 1 can be easily adjusted for resonant frequency.

[0062] Furthermore, the connecting pads 151 and 152 are located between the electrode pad 113 and the resonant portion 153. With this arrangement, the bonding wire 180 is not located in a range with a smaller x-component than the connecting pads 151 and 152 (i.e., the resonant portion 153, etc.), so the bonding wire 180 can safely and efficiently connect the connecting pads 151 and 152 to the electrode pad 113.

[0063] Furthermore, the connection pad has connection pad 151 and connection pad 152 at different positions. The electrode pad 113 has electrode pad 1131 and electrode pad 1132 at different positions. The bonding wire 180 has a bonding wire 181 that connects connection pad 151 and electrode pad 1131, and a bonding wire 182 that connects connection pad 152 and electrode pad 1132. The first reference line S1 passing through a predetermined first position of connection pad 151, for example, connection point C1, and a predetermined second position of connection pad 152, for example, connection point C2, is parallel to the scanning direction. By arranging the connection pads 151 and 152 parallel to the scanning direction in this manner, the adjustment process of the resonant section 153 by the ion gun can be easily and safely prevented from affecting the connection pads 151 and 152.

[0064] Furthermore, the scanning direction is parallel to the second reference line S2 passing through a predetermined third position of electrode pad 1131, for example, connection point C3, and a predetermined fourth position of electrode pad 1132, for example, connection point C4. By positioning the electrode pads 1131 and 1132 parallel to the scanning direction in this way, the influence of the adjustment process of the resonant section 153 by the ion gun is easily and safely prevented from affecting the connection pads 151 and 152. In addition, by aligning the connection pads 151 and 152 parallel to the scanning line, their positional relationship becomes easier, and the bonding of the bonding wires 181 and 182 also becomes easier and more efficient.

[0065] Furthermore, the MEMS element 150 has its resonant portion 153 centered on a line passing through the midpoints of the first and second positions and the midpoints of the third and fourth positions. In this way, the resonant portion 153, connecting pads 151 and 152, and electrode pads 1131 and 1132 are positioned symmetrically with respect to the y-direction, allowing signals to be transmitted evenly between the electrode pads 1131 and 1132 and the resonant portion 153 in an efficient positional relationship. This also facilitates the formation of the piezoelectric resonant device 1.

[0066] Furthermore, the distance between the first reference line S1 and the second reference line S2 is smaller than the distance between the second reference line S2 and the edge of the mounting surface 1110 in the x-direction perpendicular to the second reference line S2, i.e., the frame portion 1101. In this way, the distance between the connecting pads 151, 152 and the electrode pads 1131, 1132 is made smaller than the range in which they can be positioned on the mounting surface 1110, and by bringing these pads closer together, the bonding wire 180 can be made smaller than necessary, and the pads can be connected compactly. This reduces damage to the bonding wire 180 and also reduces signal strength loss due to the bonding wire 180.

[0067] Furthermore, the distance between connection points C1 and C3 of bonding wire 181 is equal to the distance between connection points C2 and C4 of bonding wire 182. In this way, by connecting points of the same distance in the xy plane with bonding wires 181 and 182, the distances of bonding wires 181 and 182 can also be made approximately equal. This allows for uniform signal transmission through bonding wires 181 and 182.

[0068] Furthermore, the lines connecting the first and third positions, and the lines connecting the second and fourth positions, are perpendicular to the scanning direction, respectively. In this way, because the bonding wires 181 and 182 extend straight away from the resonant section 153 in a plan view, the pads can be efficiently connected with short bonding wires 181 and 182.

[0069] Furthermore, the scanning direction is either along the longitudinal direction of the resonant section 153 or perpendicular to the longitudinal direction. By performing the adjustment operation while scanning in a direction along the sides of the rectangle, the adjustment operation time between each scan can be made equal, allowing for easy and uniform adjustment in a single process. In addition, it is not necessary to perform an unnecessarily large number of scans.

[0070] Furthermore, the mounting surface 1110 has projections 1111. The electrode pads 1131 and 1132 are located on the projections 1111. The surfaces of the electrode pads 1131 and 1132 and the surfaces of the connecting pads 151 and 152 are located at the same distance from the mounting surface 1110. By aligning the heights of the electrode pads 1131 and 1132 with the connecting pads 151 and 152 in this way, the connection of the bonding wires 181 and 182 becomes easier, and it is also possible to prevent the bonding wires 181 and 182 from hanging down too much and hitting the corners of the MEMS element 150 or other components, thereby preventing damage.

[0071] Furthermore, in a plan view, a resin member 185 is positioned between the electrode pads 1131 and 1132 and the connecting pads 151 and 152, and at least a portion of the space between the bonding wires 181 and 182 and the mounting surface 1110. Even if the bonding wires 181 and 182 hang down, they are in contact with and supported by this resin member 185, which helps to suppress contact with the MEMS element 150, especially the corners, thus making it less likely for the bonding wires 181 and 182 to be damaged.

[0072] Furthermore, in a plan view, at positions where the resin members 185, 185a, and 185b overlap with the bonding wires 181 and 182, the maximum distance from the mounting surface 1110 is greater than or equal to the distance between the mounting surface 1110 and the upper surfaces 1500 of the connecting pads 151 and 152. In other words, the bonding wires 181 and 182 are more likely to come into contact with the resin members 185, 185a, and 185b before they hit the corners of the MEMS element 150, and are supported by these resin members 185, 185a, and 185b, effectively preventing damage from hitting the corners of the MEMS element 150.

[0073] Furthermore, the resin members 185, 185a, and 185b cover the corners of the MEMS element 150, i.e., the edges of the upper surface 1500, at least between the electrode pads 1131, 1132 and the connecting pads 151, 152. This significantly reduces the possibility of the bonding wires 181, 182 directly contacting the corners of the MEMS element 150, thereby minimizing the possibility of damaging the bonding wires 181, 182.

[0074] Furthermore, the bonding wire 180 is located inside the resin member 185a in at least a portion of the space between the electrode pad 113 and the connecting pads 151 and 152. In this way, the bonding wire 180 is covered at least in part by the resin member 185a, which suppresses unnecessary movement of the bonding wire 180 and reduces problems such as damage to it.

[0075] Furthermore, the upper surface 1500 of the MEMS element 150 has a space 155 that is larger than a predetermined area corresponding to the size of the suction port of the suction device, in a position that does not overlap with the connection pads 151, 152, the resonant portion 153, and the bonding wires 181, 182 in a plan view. As a result, the piezoelectric resonant device 1 can easily obtain appropriate mounting accuracy while avoiding damage to the resonant portion 153 and excessive load due to suction when attaching the MEMS element 150 to the substrate 100.

[0076] Furthermore, space 155 is located on the upper surface 1500, opposite the connection pads 151 and 152 to the resonant portion 153. In this way, suction occurs at a position far from not only the resonant portion 153 but also the connection pads 151 and 152, and the MEMS element 150 is transported to the mounting position on the substrate 100, so problems with the MEMS element 150 during movement to the mounting position can be sufficiently reduced.

[0077] Furthermore, the MEMS element 150 is bonded to the mounting surface 1110 via adhesive members 170. In a plan view, the adhesive members 170 extend outward at least beyond the corners of the MEMS element 150. In this way, the adhesive members 170 stably fix at least the four corners of the MEMS element 150, effectively suppressing damage to the MEMS element 150, particularly the resonant portion 153, due to pressure applied during installation of the MEMS element 150 and during ultrasonic bonding of the bonding wire 180.

[0078] Furthermore, the MEMS element 150 has the following components stacked in order from the mounting surface 1110 upwards, that is, above the mounting surface 1110 and in order closest to the mounting surface 1110: the semiconductor substrate including the handling layer 1501 and the insulating layer 1502, the doped layer 1503 which is the lower electrode, the piezoelectric layer 1504, and the upper electrode 1505. The upper end position of the adhesive member 170 on the side surface of the MEMS element 150 is lower than the upper end position of the semiconductor substrate. In other words, the fillet portions 1701 and 1702 that result from the adhesive member 170 protruding from the lower surface of the MEMS element 150 do not need to come into contact with the conductive portion and the piezoelectric layer 1504 located in the upper part of the laminated structure of the MEMS element 150. This allows the MEMS element 150 to be bonded to the mounting surface 1110 within a range that is less likely to cause problems such as short circuits, and also suppresses further deviations in frequency characteristics such as the resonant frequency, and changes in the conductivity of conductive portions such as the doped layer 1503.

[0079] Furthermore, at least the surface material of the electrode pads 1131, 1132 and the connecting pads 151, 152 is gold. This suppresses corrosion reactions and reduces resistance losses, thereby enabling proper signal transmission.

[0080] The above embodiments are illustrative examples, and various modifications are possible. For example, in the above embodiment, the case in which the housing 111 is sealed with the lid 120 and the MEMS element 150 is used as an oscillator was described. However, the external connection pad may be connected to a predetermined detection circuit and used as a detection unit to detect acceleration, etc. Alternatively, a substance may be able to come into contact with or be deposited on the resonant portion 153 of the MEMS element 150, either directly or via a predetermined coating, and the detection unit may be able to detect the contact frequency or the weight of the deposited substance using a detection circuit, etc. For example, when using the MEMS element 150 as a gas sensor, the resonant frequency is measured before placing the MEMS element 150 in the measurement target area. This is the resonant frequency in the absence of the gas to be detected, i.e., the reference frequency. Subsequently, the MEMS element 150 is placed in the measurement target area and its resonant frequency is measured. By comparing this resonant frequency with the above reference frequency, the presence or absence of the gas to be detected can be determined.

[0081] Furthermore, in the above embodiment, the connection between the connection pads 151 and 152 of the MEMS element 150 and the electrode pads 1131 and 1132 was made using bonding wires, but the invention is not limited to this, and any conductive wiring material in general may be used.

[0082] Furthermore, in the above embodiment, the electrode pads 1131, 1132 and the connecting pads 151, 152 were described as being rectangular in shape with the same size and orientation in a plan view, but they do not have to be rectangular, nor do they have to be the same orientation or size. If they are not rectangular in a plan view, they may be circular, for example, or they may be rectangular with some or all of the corners cut off or rounded. Even if the size and / or shape are different, the connection points C1, C2 and C3, C4 may be in the same position in the x direction. Also, the electrode pads 1131, 1132 may be arranged so that the x coordinates of the centroids are equal. Also, the connecting pads 151, 152 may be arranged so that the x coordinates of the centroids are equal.

[0083] Furthermore, in this example, the connection points C1 to C4 with each bonding wire 180 were designated as the 1st to 4th positions for the connection pads 151 and 152 and the electrode pads 1131 and 1132, respectively. However, the designated positions may be the center of gravity or the center position of each pad, as long as the setting method is consistent.

[0084] Furthermore, at least one of the first reference line S1 and the second reference line S2 does not have to be parallel to the scanning direction. If it is difficult to position them symmetrically with respect to the center line Sy depending on the shape of the resonant section 153, they may be adjusted as appropriate. Also, depending on these positional relationships, the lengths or the distance in the x-direction of the bonding wires 181 and 182 do not have to be equal, and the bonding wires 181 and 182 do not have to extend along the x-direction in a plan view.

[0085] Furthermore, the upper electrode 1505 may have a protective layer on its upper surface. This helps to prevent oxidation or abrasion of the upper electrode 1505. The protective layer may be made of, for example, AlN.

[0086] Furthermore, the uppermost surface of the upper electrode 1505 may be made of gold (Au).

[0087] Furthermore, the specific configurations, processing operations, and procedures shown in the above embodiments may be modified as appropriate without departing from the spirit of this disclosure. The scope of the present invention includes the scope of the invention as described in the claims and its equivalents. [Industrial applicability]

[0088] This disclosure can be used in piezoelectric resonant devices. [Explanation of Symbols]

[0089] 1. Piezoelectric Resonance Device 100 base 110, 110a substrate 1101 Frame section 1102 Base 111 Detention Unit 1110 Mounting surface 1111 Protrusion 113, 1131, 1132 electrode pads 112 Frame-shaped metallized layer 113, 1131, 1132 electrode pads 114, 1141~1144 External connection pads 115 Through Hole 1161, 1162 Through conductor 120, 120a lid body 121 Storage Unit 150, 150a MEMS element 1500 Top 1501 Handling Layer 1502 Insulating layer 1503 Dope layer 1504 Piezoelectric layer 1505 Upper electrode 151, 152 Connection Pads 153 Resonance section 1531 Resonance means 154 Wiring 155 spaces 170, 171a~171d Adhesive material 180, 181, 182 bonding wires 185, 185a, 185b Resin components C1~C4 Connection points S1 1st reference line S2 2nd reference line Ss scanning direction Sy center line

Claims

1. Substrate and, The substrate comprises a MEMS element located on the substrate, The aforementioned MEMS element is A resonant means having a silicon layer that can vibrate in a predetermined mode, A peripheral portion having a silicon layer continuous with the silicon layer of the resonant means, located around the resonant means, and holding the resonant means so that it can vibrate, The surrounding portion and the base body are joined together, and the surrounding portion is supported, and the support portion includes a silicon substrate. Piezoelectric resonant device.

2. The support portion supports the peripheral portion on the first side of the resonant means and on the second side located opposite to the first side of the resonant means in the first direction. The piezoelectric resonant device according to claim 1.

3. The surrounding portion has a first holding portion located on the third side of the resonant means and a second holding portion located on the fourth side in a second direction perpendicular to the first direction. The piezoelectric resonant device according to claim 2.

4. The surrounding portion encloses the entire circumference of the resonant means, The support portion supports the entire surrounding portion. The piezoelectric resonant device according to claim 1.

5. The surrounding portion and the support portion extend to the outer edge of the MEMS element. The piezoelectric resonant device according to claim 1.

6. The thickness of the silicon layer of the resonant means is the same as the thickness of at least a portion of the surrounding area. The piezoelectric resonant device according to claim 1.

7. The surrounding portion has multiple layers, Among the aforementioned multiple layers, the silicon layer is the thickest. The piezoelectric resonant device according to claim 1.

8. The support portion further includes an adhesive member for bonding the silicon substrate and the base body, The silicon substrate is thicker than the adhesive member. The piezoelectric resonant device according to claim 1.

9. The adhesive member has insulating properties. The piezoelectric resonant device according to claim 8.

10. The adhesive member is resin and A filler containing alumina, The piezoelectric resonant device according to claim 8.

11. The adhesive member has a fillet portion and covers a part of the side surface of the silicon substrate at the outer edge of the MEMS element. The piezoelectric resonant device according to claim 8.

12. The substrate includes ceramic, The piezoelectric resonant device according to claim 1.

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