JP5813177B2 - Elastic wave device and circuit board - Google Patents

Description

The present invention relates to a surface acoustic wave (SAW) device or a piezoelectric thin film resonator (F).
The present invention relates to an acoustic wave device such as a BAR (Film Bulk Acoustic Resonator) and a circuit board .

  2. Description of the Related Art A so-called wafer level package (WLP: Wafer.Level Package) type acoustic wave device for the purpose of downsizing is known. This WLP type acoustic wave device has a piezoelectric substrate, an excitation electrode provided on the piezoelectric substrate, and a cover for sealing the excitation electrode.

  Further, the upper surface of the cover is used as, for example, a space for arranging a terminal or a space for providing a reinforcing member made of a metal material for preventing deformation of the vibration space of the excitation electrode (for example, Patent Document 1).

JP 2007-142770 A

  In a WLP type acoustic wave device that is smaller than the conventional acoustic wave device, the area of the upper surface of the cover is small, and if a terminal or the like is arranged on the upper surface of the cover, there is almost no room for space. Therefore, in order to satisfy the demand for further downsizing of the acoustic wave device, measures such as reducing the terminal and measures such as reducing the margin between the terminal and the reinforcing member are necessary.

  However, various problems arise with such measures. For example, if the terminal is made small, the mounting strength of the acoustic wave device will be reduced, and if the margin between the terminal and the reinforcing member is made small, a short circuit will occur between the terminal and the reinforcing member. Is more likely to occur.

  Therefore, a WLP type acoustic wave device corresponding to downsizing that is unlikely to cause the above-described problems is desired.

An elastic wave device according to one aspect of the present invention includes a substrate that propagates an elastic wave, an excitation electrode that generates the elastic wave, which is disposed on a main surface of the substrate, and a main surface of the substrate. And a cover having a frame portion surrounding the excitation electrode and a lid portion disposed on the frame portion , the cover being electrically connected to the excitation electrode disposed in a region overlapping the frame portion. The frame portion is located inside the outer periphery of the substrate when viewed in plan, and the lid portion has an outer periphery that is the outer periphery of the frame portion . It has an extended region located outside.

  The elastic wave device having the above-described configuration is provided with an extended region on the second main surface of the cover, so that the entire structure can be reduced in size while terminals for electrically connecting the excitation electrode to an external circuit, In addition, a space for arranging a reinforcing layer or the like formed on the cover as a reinforcing member for preventing deformation of the vibration space of the excitation electrode can be secured on the second main surface of the cover. As a result, for example, a reduction in the mounting strength of the acoustic wave device can be suppressed without reducing the area of the terminal more than necessary. Alternatively, it is possible to prevent a short circuit between the terminal and the reinforcing layer without unnecessarily reducing the margin between the terminal and the reinforcing layer.

1 is an external perspective view of a SAW device according to an embodiment of the present invention. FIG. 2A is a plan view of the SAW device of FIG. 1, and FIG. 2B is a plan view of the SAW device of FIG. It is sectional drawing in the III-III line of Fig.2 (a). It is an expanded sectional view of the part shown by M of FIG. (A) to (d) are cross-sectional views illustrating a method for manufacturing the SAW device of FIG. (A) to (d) are cross-sectional views illustrating a method for manufacturing the SAW device of FIG. (A) to (c) is a cross-sectional view illustrating a method of manufacturing the SAW device of FIG. It is an expanded sectional view of the part corresponding to Drawing 4 showing the modification of the SAW device shown in Drawing 1.

<Structure of SAW device>
FIG. 1 is an external perspective view of a SAW device 1 according to an embodiment of the present invention, and FIGS. 2A and 2B are plan views of the SAW device 1. FIG. 2B is a plan view of the cover 5 with the lid 17 removed. FIG. 3 is a cross-sectional view taken along the line III-III in FIG.

  The SAW device 1 is a so-called WLP type SAW device. The SAW device 1 includes a substrate 3, an excitation electrode 2 disposed on the main surface 3 a of the substrate 3, a cover 5 that protects the excitation electrode 2, a plurality of terminals 7 that are exposed from the cover 5, and an upper surface of the cover 5. The reinforcing layer 4 is disposed.

  Signals are input to the SAW device 1 via any of the plurality of terminals 7. The input signal is filtered by the SAW device 1. Then, the SAW device 1 outputs the filtered signal via any of the plurality of terminals 7. For example, the SAW device 1 is mounted with a plurality of terminals 7 by being resin-sealed in a state of being placed on the mounting surface with a surface on the cover 5 facing a mounting surface such as a circuit board (not shown). It is mounted while connected to the pads on the surface.

  The substrate 3 is formed of a piezoelectric substrate. For example, the substrate 3 is a rectangular parallelepiped single crystal substrate having piezoelectricity such as a lithium tantalate single crystal or a lithium niobate single crystal. The planar shape of the substrate 3 may be appropriately set. For example, the substrate 3 is a rectangle having a predetermined direction (Y direction) as a longitudinal direction. Although the magnitude | size of the board | substrate 3 may be set suitably, for example, thickness is 0.2 mm-0.5 mm, and the length of 1 side is 0.5 mm-2 mm.

  Various electrodes and wirings such as the excitation electrode 2 and the connection wiring 11 are provided on the main surface 3 a of the substrate 3.

  A conductor layer 13 is attached to a back surface 3b which is a surface opposite to the main surface 3a of the substrate 3. By attaching the conductor layer 13 to the back surface 3b, excess charges accumulated in the substrate 3 are discharged, and the characteristics of the SAW device as a filter can be stabilized. Note that the back surface of the substrate 3 may be exposed without providing the conductor layer 13.

  The excitation electrode 2 is for generating SAW. As shown in FIG. 2B, the excitation electrode 2 includes a plurality of comb-like IDT electrodes having a plurality of electrode fingers, and reflector electrodes arranged at both ends of the plurality of IDT electrodes. By arranging the excitation electrode 2 on the main surface of the piezoelectric substrate 3, for example, a dual mode SAW resonator filter or the like is configured. FIG. 2B is a schematic diagram, and actually, a plurality of pairs of comb-like electrodes having a larger number of electrode fingers are provided. In addition, a plurality of excitation electrodes 2 may be connected by a system such as a series connection or a parallel connection, and a ladder-type SAW filter or the like may be configured. The excitation electrode 2 is made of an Al alloy such as an Al—Cu alloy.

  Excitation electrode 2 is connected to terminal 7 via connection wiring 11 and through conductor 9. The connection wiring 11 is made of, for example, the same material as that of the excitation electrode 2 and is made of an Al alloy such as an Al—Cu alloy. Further, the thickness of the wiring connection 11 may be made larger than the thickness of the excitation electrode 2 in order to reduce the wiring resistance of the connection wiring 11.

  Various electrodes and wirings such as the excitation electrode 2 formed on the main surface 3a of the substrate 3 are covered with a protective layer 14 as shown in the sectional view of FIG. The protective layer 14 contributes to the prevention of oxidation of various electrodes and wirings provided on the main surface 3a of the substrate 3 such as the excitation electrode 2. The protective layer 14 is formed of, for example, a material having an insulating property and a mass that is light enough not to affect the propagation of the SAW. For example, the protective layer 14 is made of silicon oxide, silicon nitride, silicon, or the like.

  A cover 5 for protecting various electrodes and wirings arranged on the main surface 3 a of the substrate 3 and securing the vibration space 6 of the excitation electrode 2 is arranged on the main surface 3 a of the substrate 3. The planar shape of the cover 5 is, for example, the same as the planar shape of the substrate 3 and is rectangular. The cover 5 is formed slightly smaller than the main surface 3a of the substrate 3 so that the outer peripheral portion of the main surface 3a of the substrate 3 is exposed when viewed in plan.

  The cover 5 includes a frame portion 15 stacked on the main surface 3 a of the substrate 3 and a lid portion 17 stacked on the frame portion 15. An opening 16 is formed in the frame portion 15. The opening 16 is provided in a portion that overlaps the excitation electrode 2 when the frame 15 is viewed in plan. In other words, the inner wall of the frame portion 15 surrounds the excitation electrode 2. When the opening 16 is closed by the lid 17, the vibration space 6 is formed between the main surface 3 a of the substrate 3 and the cover 5.

The frame portion 15 is configured by a layer having a substantially constant thickness. The thickness of the frame portion 15 is, for example, 10 μm to 30 μm. The lid portion 17 is composed of a layer having a substantially constant thickness. The thickness of the lid part 17 is, for example, 10 μm to 30 μm.

  The frame portion 15 and the lid portion 17 are made of, for example, a photosensitive resin. The photosensitive resin is, for example, a urethane acrylate-based, polyester acrylate-based, or epoxy acrylate-based resin that is cured by radical polymerization of an acryl group or a methacryl group.

  The frame portion 15 and the lid portion 17 may be formed of the same material or may be formed of different materials. In the figure, for convenience of explanation, the boundary line between the frame portion 15 and the lid portion 17 is clearly shown. However, in an actual product, the frame portion 15 and the lid portion 17 are formed of the same material and are integrally formed. It may be.

  The vibration space 6 is a cavity provided in the cover 5, and is provided on the upper surface of the excitation electrode 2. Since the vibration space 6 is provided on the upper surface of the excitation electrode 2, the SAW generated by the excitation electrode 2 can easily propagate through the substrate 3. As shown in FIG. 2B, the vibration space 6 is formed in a generally rectangular shape in plan view. Further, as shown in the cross-sectional view of FIG. 3, the corner portion on the lid portion 17 side of the vibration space 6, that is, the portion on the lid portion 17 side of the inner wall surface of the frame portion 15 is curved. Thereby, even when a large pressure is applied to the SAW device 1 from the outside during resin molding, the lid portion 17 can be prevented from being bent. The size and number of the vibration spaces 6 may be set as appropriate. FIG. 2B shows an example in which only one vibration space 6 is provided. For example, when a plurality of excitation electrodes 2 are provided, a plurality of vibration spaces 6 are provided for each of the plurality of excitation electrodes 2. May be.

  As shown in FIG. 3, a through conductor 9 is provided so as to penetrate the cover 5 in the height direction. The through conductor 9 is disposed near the end of the connection wiring 11. The through conductor 9 has a columnar first columnar portion 9a penetrating the frame portion 15 in the height direction, and a columnar second columnar portion 9b penetrating the lid portion 17 in the height direction.

  The cross-sectional shape when the first pillar 9a is cut in a direction parallel to the main surface 3a of the substrate 3 is, for example, a circular shape. Moreover, the 1st pillar part 9a inclines inside as the side surface goes from the 1st main surface 5a of the cover 5 to the 2nd main surface 5b. Similarly to the first columnar portion 9a, the second columnar portion 9b has a circular cross-sectional shape when cut in a direction parallel to the main surface 3a of the substrate 3, for example, and its side surface is the first main portion of the cover 5. It inclines inside as it goes to the 2nd main surface 5b from the surface 5a.

  When the SAW device 1 is mounted on an external circuit board or the like, a force that pulls out the through conductor 9 may act. However, by inclining the side surface of the through conductor 9 as described above, the side surface of the through conductor 9 is inclined. It is possible to suppress the through conductor 9 from being pulled out from the substrate 3 as compared with the case where the through conductor 9 is not. Further, external moisture or the like may enter from the gap between the side surface of the through conductor 9 and the cover 5, and when it reaches the vibration space 6, the filter characteristics are deteriorated. By inclining the side surface, the moisture intrusion path length can be made longer than that in which the side surface of the penetrating conductor 9 is not inclined, so that there is an advantage that deterioration of the filter characteristics can be suppressed. FIG. 3 shows an example in which the inclination angle of the side surface of the first columnar portion 9a with respect to the main surface 3a of the substrate 3 is larger than the inclination angle of the side surface of the second columnar portion 9b with respect to the main surface 3a of the substrate 3. However, the inclination angle may be appropriately changed. For example, the same inclination angle may be used for the first column portion 9a and the second column portion 9b.

Moreover, in the connection part of the 1st pillar part 9a and the 2nd pillar part 9b, the cross-sectional area by the side of the 1st pillar part 9a of the 2nd pillar part 9b is the disconnection by the side of the 2nd pillar part 9b of the 1st pillar part 9a. It is larger than the area. Thereby, a level | step difference is formed in the side surface in the connection part of the 1st pillar part 9a of the penetration conductor 9, and the 2nd pillar part 9b. By providing a stepped portion on the side surface of the through conductor 9 in this way, it is possible to lengthen the water intrusion path that can enter from between the side surface of the through conductor 9 and the cover 5, and to enter the vibration space 6. It is possible to suppress the deterioration of the filter characteristics due to.

  The through conductor 9 is formed by, for example, copper plating, and a plating base layer (not shown) is provided between the through conductor 9 and the cover 5. The plating base layer is made of, for example, titanium or copper.

  A connection reinforcing layer 8 is provided between the through conductor 9 and the connection wiring 11. The connection reinforcing layer 8 is for reinforcing the connection wiring 11 formed relatively thin and strengthening the connection between the connection wiring 11 and the through conductor 9. The connection reinforcing layer 8 has, for example, a three-layer structure in which chromium, nickel, and gold are stacked in this order from the main surface 3a side.

  On the other hand, a terminal 7 is connected to an exposed portion of the through conductor 9 from the cover 5. The terminal 7 is formed by, for example, copper plating. When the terminal 7 and the through conductor 9 are formed by copper plating, both can be formed integrally.

  For example, the terminal 7 is formed to be slightly larger than the end surface of the second column portion 9b so as to cover the end surface of the second column portion 9b exposed from the lid portion 17 of the second column portion 9b. The part is laminated on the cover 5. The shape of the terminal 7 in plan view is, for example, a circle.

  A reinforcing layer 4 is disposed on the second main surface 5b of the cover 5 on which the terminals 7 are disposed, as shown in FIGS. The reinforcing layer 4 is for reinforcing the strength of the cover 5. For example, after mounting the SAW device 1 on an external circuit board or the like, the entire SAW device 1 may be resin-molded, and a large pressure is applied to the SAW device 1 when resin-molding. Even in this case, the cover 5 can be prevented from being deformed by providing the reinforcing layer 4. As a result, the shape of the vibration space 6 can be prevented from being greatly distorted, so that the reliability of the SAW device 1 can be improved.

  The reinforcing layer 4 is made of a material having a higher Young's modulus than the material constituting the cover 5. For example, the Young's modulus of the cover 5 is 0.5 to 1.0 GPa, whereas the Young's modulus of the reinforcing layer 4 is 100 to 250 GPa. As a specific material, for example, when a resin material is used as the cover 5, a metal material can be used as the reinforcing layer 4. The thickness of the reinforcing layer 4 is, for example, 1 to 50 μm. The reinforcing layer 4 is formed over a relatively wide range of the cover 5. From the viewpoint of preventing deformation of the vibration space 6, the reinforcing layer 4 vibrates so as to cover at least the entire vibration space 6 when the cover 5 is seen through the plane. It is preferable that it be formed larger than the space 6. The reinforcing layer 4 is not connected to the terminal 7 and is in an electrically floating state.

  FIG. 4 is an enlarged view of a region M circled in FIG. As shown in FIG. 4, the outer peripheral edge 12 of the first main surface 5 a that is the surface of the cover 5 on the main surface 3 a side of the substrate 3 is located inside the outer peripheral edge 13 of the main surface 3 a of the substrate 3. . In the manufacturing process of the SAW device 1, when the piezoelectric wafer to be the substrate 3 is diced, a crack or the like may occur on the main surface 3 a of the substrate 3 from the side surface to the inside. It has been confirmed that the cover 5 easily peels when it reaches. Therefore, as shown in FIG. 3, the outer peripheral edge 12 of the first main surface 5 a of the cover 5 is positioned on the inner side of the outer peripheral edge 13 of the main surface 3 a of the substrate 3, whereby the side surface of the substrate 3 and the cover 5 Compared with the case where the side surfaces are flush with each other, the cracks generated on the main surface 3a of the substrate 3 are less likely to reach the cover 5, and therefore the peeling of the cover 5 from the substrate 3 can be suppressed. Further, the side surface 15c of the frame portion 15 constituting the side surface of the lower side of the cover 5 (the main surface 3a side of the substrate 3) is inclined outwardly from the first main surface 5a toward the second main surface 5b. . Accordingly, the outer peripheral edge 12 of the first main surface 5a of the cover 5 is made smaller than the main surface 3a of the substrate 3 without making the area of the upper surface (surface on the second main surface 5b side) of the frame portion 15 unnecessarily small. It can be located inside. Therefore, even when the outer peripheral edge 12 of the first main surface 5a of the cover 5 is positioned inside the outer peripheral edge 13 of the main surface 3a of the substrate 3, the upper surface of the frame portion 15 does not become extremely small. The space for arranging the lid portion 17 stacked on the frame portion 15 is sufficiently secured.

  A distance d1 from the outer peripheral edge 13 of the main surface 3a of the substrate 3 to the outer peripheral edge 12 of the first main surface 5a of the cover 5 is set to 5 μm to 30 μm, for example.

  Further, the second main surface 5b of the cover 5 has an extended region 10 located outside the outer peripheral edge 12 of the first main surface 5a. By providing such an extended region 10 on the second main surface 5b, the area of the second main surface 5b is increased. Therefore, various members are provided on the second main surface 5b while reducing the overall structure of the SAW device 1. Space for placement can be secured. Thereby, for example, the area of the terminal 7 disposed on the second main surface 5b can be increased, and the mounting strength of the SAW device 1 can be increased. Or the margin between the terminal 7 and the reinforcement layer 4 can be enlarged, and it can suppress that a short circuit generate | occur | produces between the terminal 7 and the reinforcement layer 4. FIG.

  The extended region 10 is formed by inclining outward the side surface 17c of the lid portion 17 from the first main surface 5a toward the second main surface 5b. In other words, in the cross-sectional view of FIG. 4, the extended region 10 is located outward from the outer peripheral edge 12 of the first main surface 5 a among the adjacent sides of the right triangle having the inclined side surface 17 c of the lid portion 17 as the hypotenuse. Part. The width d2 of the expansion region 10 is set to 1 μm to 20 μm, for example.

  The external angle α formed between the inclined side surface 17c of the lid portion 17 and the line L1 parallel to the main surface 3a of the substrate 3 is formed between the second column portion 9b and the line L1 parallel to the main surface 3a of the substrate 3. The inner angle is larger than the angle β. By making the angles α and β different from each other in this way, a larger internal stress is generated in the region between the side surface of the cover 5 and the through conductor 9 than in the case where the angles α and β are the same. Can be suppressed. When the angle α is compared with the angle β, the angle α is larger than the angle β. Thereby, the expansion region 10 can be provided while improving the effect of suppressing the through conductor 9 from being pulled out of the substrate 3. The angle α is set to 45 ° to 88 °, for example. Note that the angle α is the main surface of the substrate 3 and a straight line connecting one end and the other end of the side surface 17c when the region including the side surface 17c and the second columnar portion 9b of the lid portion 17 is observed by a cross-sectional SEM photograph. This is an angle measured from an angle formed by a straight line along 3a. Similarly, when the region including the side surface 17c of the lid portion 17 and the second column portion 9b is observed by the cross-sectional SEM photograph, the angle β is a straight line connecting one end and the other end of the side surface of the second column portion 9b. This is an angle obtained by measuring an angle formed by a straight line along the main surface 3 a of the substrate 3.

  The extended region 10 is formed over the entire outer periphery of the second main surface 5b. In FIG. 2A, the outer peripheral edge 12 of the first main surface 5a is indicated by a broken line. That is, the part located outside the outer peripheral edge 12 shown by the broken line in the second main surface 5b is the extended region 10. As shown in FIG. 2A, the extended region 10 may be provided over the entire outer periphery of the second main surface 5b, or may be provided partially, for example, only around the terminal 7. .

  According to the SAW device 1 described above, the outer peripheral edge 12 of the first main surface 5a of the cover 5 is located on the inner side of the outer peripheral edge 13 of the main surface 3a of the substrate 3, and the first main surface 5b By providing the extended region 10 positioned outside the outer peripheral edge 12 of the main surface 5a, the area of the upper surface of the cover 5 is expanded while reducing the overall structure of the SAW device 1, and the terminals 7 and A sufficient space for arranging the reinforcing layer 4 can be secured.

<Method for Manufacturing SAW Device>
Next, a method for manufacturing the SAW device 1 will be described with reference to FIGS. 5 to 7
These are schematic cross-sectional views for explaining a method for manufacturing the SAW device 1.

  As shown in FIG. 5A, first, a large substrate 33 having a first region A1 and a second region A2 adjacent to the first region A1 is prepared. The large substrate 33 is, for example, a piezoelectric wafer such as a lithium tantalate single crystal or a lithium niobate single crystal. In the figure, the boundary between the first area A1 and the second area A2 is indicated by a boundary line L2.

On the main surface 33a of the large substrate 33, various electrodes and wirings such as the excitation electrode 2 and the connection wiring 11 are formed in each of the first element region A1 and the second element region A2. Specifically, first, a metal layer is formed on the main surface 33a of the large substrate 33 by a thin film forming method such as a sputtering method, a vapor deposition method or a CVD (Chemical Vapor Deposition) method. Next, the metal layer is patterned by a photolithography method using a reduction projection exposure machine (stepper) and an RIE (Reactive Ion Etching) apparatus. Thereby, the excitation electrode 2 and the connection wiring 11 are formed.

  When various electrodes and wirings such as the excitation electrode 2 and the connection conductor 11 are formed, as shown in FIG. 5B, the protective layer 14 and the connection reinforcing layer 8 are formed. Either the protective layer 14 or the connection reinforcing layer 8 may be formed first. For example, first, a thin film to be the protective layer 14 is formed by a thin film forming method such as a CVD method or a vapor deposition method so as to cover the excitation electrode 2 and the connection wiring 11. Next, a part of the thin film is removed by photolithography so that a portion of the connection wiring 11 at the position where the through conductor 9 is disposed is exposed. Thereby, the protective layer 14 is formed. Next, a metal layer is formed on the exposed portion of the connection wiring 11 from the protective layer 14 and the protective layer 14 by vapor deposition or the like, and the metal layer on the protective layer 14 is removed by lift-off or photolithography. The Thereby, the connection reinforcing layer 8 is formed.

  When the protective layer 14 and the connection reinforcing layer 8 are formed, the frame portion 15 is formed as shown in FIGS. 5C to 6A.

  Specifically, first, as shown in FIG. 5 (c), on the main surface 3a of the large substrate 3, the frame portion constituting layer 35 constituting the frame portion 15 is formed with the first element region A1 and the second element region A2. It is formed so as to straddle the boundary part. The frame portion constituting layer 35 is formed, for example, by attaching a film formed of a negative type photoresist. Thereafter, the large substrate 33 on which the frame portion constituting layer 35 is formed is subjected to heat treatment. Thereby, the adhesion strength between the frame portion constituting layer 35 and the large substrate 33 can be increased.

  Next, as shown in FIG. 5D, the frame component layer 35 is irradiated with light L such as ultraviolet rays through the photomask 40. That is, an exposure process is performed. The photomask 40 is configured, for example, by forming a light shielding layer 39 on a transparent substrate 38. The light shielding layer 39 is disposed at a position corresponding to the position where the frame portion constituting layer 35 is to be removed. That is, they are arranged at positions corresponding to the vibration space 6, the through conductor 9, and the dicing line, respectively. Each light shielding layer has a different width, the light shielding layer corresponding to the vibration space 6 is the largest, and the width of the light shielding layer corresponding to the through conductor is the smallest. The width of the light shielding layer corresponding to the dicing line is smaller than the width of the light shielding layer corresponding to the vibration space 6 and larger than the width of the light shielding layer corresponding to the through conductor. The exposure may be projection exposure, proximity exposure, or contact exposure.

Thereafter, as shown in FIG. 6A, development processing is performed to leave a portion irradiated with light in the frame portion constituting layer 35 and remove a portion not irradiated with light. Thereby, the opening part 36 used as the vibration space 6 and the 1st hole part 41 in which the 1st pillar part 9a is arrange | positioned are formed in the frame structure layer 35. FIG. At the same time, a first groove 42 serving as a dicing line is formed at the boundary between the first element region A1 and the second element region A2. That is, the frame part 15 is formed.

  At the edge of the region where the light L of the frame portion constituting layer 35 is irradiated, the irradiated light L is diverged to the region where the light L of the frame portion constituting layer 35 is not irradiated. Light does not reach the surface 33a side sufficiently. Therefore, the edge portion of the region where the light of the frame portion constituting layer 35 is irradiated is removed without the main surface 33a side of the large substrate 33 being sufficiently cured. As a result, the first hole 41, the first groove 42, and the opening 36 are formed in a tapered shape (forward tapered shape) whose diameter increases toward the main surface 33a.

  In addition, the angles of the tapered surfaces of the opening 36, the first hole 41, and the first groove 42 with respect to the main surface 33a are different. The difference in the angle of the tapered surface with respect to the main surface 33a is caused by the difference in various conditions when patterning the frame portion constituting layer 35 by the photolithography method. In particular, the inventors of the present application have confirmed that the width and shape of the light shielding layer of the photomask corresponding to each of the opening 36, the first hole 41, and the first groove 42 greatly affects the difference in the angle of the tapered surface. Yes. Specifically, the angle of the tapered surface with respect to the main surface 33a tends to be smaller as the width of the light shielding layer 39 of the photomask 40 is smaller. In addition, the angle of the tapered surface with respect to the main surface 33a tends to be smaller when the outer periphery of the light shielding layer 39 of the photomask 40 is curved than when the outer periphery is linear.

  Therefore, when comparing the respective tapered surfaces of the opening 36, the first hole 41, and the first groove 42, the width of the corresponding light shielding layer 39 is the smallest and the outer periphery of the planar shape is circular. The angle of the tapered surface of the one hole portion 41 with respect to the main surface 33a is the smallest.

  When the first hole portion 41, the opening portion 36, and the first groove portion 42 are formed, the lid portion 17 is formed as shown in FIGS. 6 (b) to 6 (d).

  Specifically, first, as shown in FIG. 6 (b), the lid portion constituting layer 37 constituting the lid portion 17 is formed on the frame portion 15 at the boundary portion between the first element region A1 and the second element region A2. It is formed so as to straddle. The lid component layer 37 is formed, for example, by attaching a film formed of a negative photoresist. By forming the lid component layer 37, the opening 36 of the frame portion 15 is closed, and the vibration space 6 is configured. In addition, it is preferable that the frame part constituent layer 35 and the lid part constituent layer 37 are joined by heating.

  Next, as shown in FIG. 6C, light L such as ultraviolet rays is irradiated to the lid constituting layer 37 through the photomask 50. That is, an exposure process is performed. Similar to the photomask 40, the photomask 50 is configured by forming a light shielding layer 52 on a transparent substrate 51. The light shielding layer 52 is disposed at a position corresponding to a position where the lid constituting layer 37 is to be removed. That is, it is disposed at a position corresponding to the through conductor 9 and a position corresponding to the dicing line. For example, the photomask 50 has a configuration in which the portion corresponding to the vibration space 6 in the light shielding layer 39 is removed from the photomask 40. The exposure may be projection exposure, proximity exposure, or close exposure.

  Thereafter, as shown in FIG. 6D, development processing is performed to leave a portion irradiated with light and remove a portion not irradiated with light from the lid constituting layer 37. As a result, a second hole portion 43 and a second groove portion 44 in which the second pillar portion 9 b is disposed are formed in the lid portion constituting layer 37. That is, the lid portion 17 is formed. By forming the lid portion 17, the cover 5 including the frame portion 15 and the lid portion 17 is completed. The first hole 41 and the second hole 43 are connected to form a through conductor hole, and the first groove 42 and the second groove 44 are connected to form a dicing line.

  Comparing the second groove 44 and the second hole 43 formed in the lid constituting layer 37, the angle of the tapered surface of the second groove 44 with respect to the principal surface 33a and the principal surface 33a of the tapered surface of the second hole 43 are compared. The angle with respect to is different. Specifically, the angle of the tapered surface of the second hole 43 with respect to the major surface 33a is smaller than the angle of the tapered surface of the second groove portion 44 with respect to the major surface 33a. This is mainly because the width of the light shielding layer 52 corresponding to the second hole 43 is smaller than the width of the light shielding layer 52 of the photomask 50 corresponding to the second groove 44 and corresponds to the second groove 44 in plan view. This is because the edge of the light shielding layer 52 is linear, whereas the edge of the light shielding layer 52 corresponding to the second hole 43 is circular.

  Further, comparing the connected first hole 41 and second hole 43, the angle of the tapered surface of the first hole 41 with respect to the major surface 33a is the angle of the tapered surface of the second hole 42 with respect to the major surface 33a. Greater than angle. Similarly, the angle of the tapered surface of the first groove portion 42 with respect to the major surface 33a is larger than the angle of the tapered surface of the second groove portion 44 with respect to the major surface 33a of the connected first groove portion 42 and second groove portion 44 as well. The difference in angle is that the light shielding layer 39 corresponding to the first hole portion 41 and the light shielding layer 52 corresponding to the second hole portion 43 have different widths, and the frame portion constituting layer 35 and the lid portion constituting layer. This is due to the difference in hardness from 37. Specifically, the frame constituting layer 35 when performing photolithography is in a harder state than the lid constituting layer 37. This difference in hardness is caused by, for example, whether or not heat treatment is performed before photolithography. The term “hardness” as used herein refers to that measured as Young's modulus.

  By forming the first groove portion 42 and the second groove portion 44 having tapered surfaces inclined at a predetermined angle with respect to the main surface 33a by the above-described method, the extension region 10 is formed on the second main surface 5b of the cover 5. Can be formed.

  When the cover 5 is formed, the through conductor 9 and the terminal 7 are formed as shown in FIGS. 7 (a) and 7 (b). Specifically, a plating base layer (not shown) is first formed so as to cover the exposed portion of the cover 5. In addition to the exposed portion of the cover 5, the plating base layer is also formed on the bottom surface of the first hole portion 41 and the bottom surface of the first groove portion 42. The plating base layer is preferably formed of Ti—Cu or the like by, for example, sputtering or flash plating.

  The plating resist layer 55 is formed on the plating base layer. The plating resist layer 55 is formed on the substrate by a technique such as spin coating. In the plating resist layer 55, a terminal hole 57 is formed on the second hole 43, and a reinforcing layer hole 54 is formed in a region where the reinforcing layer 4 is formed. The terminal hole portion 57 has a diameter larger than that of the second hole portion 43, and the depth (thickness of the plating resist layer 57) is equal to or greater than the thickness of the terminal 7. The reinforcing layer hole 54 is formed to be larger than the vibration space 6 so as to include the entire vibration space 6 when viewed through the plane, and the depth thereof is set to be the same size as the terminal hole 57. . The terminal hole 57 and the reinforcing layer hole 54 are formed by, for example, photolithography.

  On the other hand, the first groove part 42 and the second groove part 44 are filled with a resist layer 55 for plating. Here, since the extended region 10 is provided on the second main surface 5 b of the cover 5, the flatness of the upper surface of the plating resist layer 55 buried in the first groove portion 42 and the second groove portion 44 is improved. For example, when the extended region 10 is not provided, such as when the inner peripheral surfaces of the first hole portion 42 and the second hole portion 44 are perpendicular to the main surface 33a of the large-sized substrate 33, plating is performed. It has been confirmed that a depression is easily formed near the center of the upper surface of the resist layer 55. If a depression is generated in the vicinity of the center of the upper surface of the plating resist 55 layer as described above, the outer peripheral portion of the plating resist layer 55 is distorted, and as a result, the terminal 7 formed using the plating resist layer 55 as a guide. Will be distorted. On the other hand, when the extended region 10 is provided on the second main surface 5 b of the cover 5, the extended region 10 serves as a support for the plating resist layer 55, and a depression is generated near the center of the upper surface of the plating resist layer 55. It becomes difficult. Therefore, the flatness of the upper surface of the plating resist layer 55 is improved, and the outer peripheral portion of the plating resist layer 55 can be prevented from being distorted. As a result, the terminal 7 with less distortion can be formed, and the mounting stability of the SAW device 1 is provided.

Next, as shown in FIG. 7B, a plating method is applied to the plating base layer exposed from the plating resist layer 55. As a result, the first hole 42, the second hole 44, the terminal hole 57, and the reinforcing layer hole 54 are filled with metal. The metal to be filled is, for example, copper. Then, the first pillar portion 9a is formed by the metal filled in the first hole portion 41, the second pillar portion 9b is formed by the metal filled in the second hole portion 43, and the terminal hole portion 57 is filled. The terminal 7 is formed of a metal. In the terminal hole portion 57, it is not necessary to fill the metal up to the surface of the plating resist layer 55, and it is sufficient that the metal is filled to an appropriate depth of the terminal hole portion 57. Alternatively, after the metal is filled higher than the surface of the plating resist layer 55, planarization may be performed by chemical mechanical polishing (CMP) or the like until the terminal 7 has a predetermined thickness.

  The plating method may be selected as appropriate, but the electroplating method is preferable. This is because the electroplating method has a high degree of freedom in the height of the columnar terminals 7 and has good adhesion to the plating base layer.

  Thereafter, the plating resist layer 57 is removed. Thereafter, as shown in FIG. 7C, the SAW device 1 is formed by cutting the large substrate 33 with the dicing blade 60 along the boundary L2 between the first element region A1 and the second element region A2. .

  In the above embodiment, the SAW device 1 is an example of the acoustic wave device of the present invention. The frame portion constituting layer 35 and the lid portion constituting layer 37 are examples of the cover constituting layer of the present invention.

  The present invention is not limited to the above embodiment, and may be implemented in various aspects.

  The elastic wave device is not limited to the SAW device. For example, the acoustic wave device may be a piezoelectric thin film resonator. In the acoustic wave device, the protective layer 14, the connection reinforcing layer 8, and the conductor layer 13 may be omitted, or conversely, other appropriate layers may be formed. For example, in the embodiment, a resin layer that covers the conductor layer 13 may be provided. By providing a resin layer covering the conductor layer 13, there is an advantage that marking becomes easy.

  FIG. 8 is a cross-sectional view of a portion corresponding to FIG. The extended region 10 in the modified example is formed by disposing the preliminary layer 19 on the lid portion 17 and positioning the end portion of the preliminary layer 19 outside the side surface of the frame portion 15. As shown in this modification, the extended region 10 is not limited to the one formed by inclining the side surface of the cover 5.

1. Surface acoustic wave device (elastic wave device)
2 ... excitation electrode 3 ... substrate 4 ... reinforcing layer 5 ... cover 5a ... first main surface 5b ... second main surface 6 ... vibration space 7 ... terminal 8 ... Connection reinforcement layer 9 ... Penetration conductor 10 ... Expansion region 11 ... Connection wiring

Claims (13)

A substrate that propagates elastic waves;
An excitation electrode arranged on a main surface of the substrate for generating the elastic wave;
A cover having a frame portion disposed on the main surface of the substrate and surrounding the excitation electrode, and a cover portion disposed on the frame portion;
The cover has a through conductor disposed in a region overlapping the frame portion and electrically connected to the excitation electrode;
The frame portion is located on the inner side of the outer periphery of the substrate when the outer peripheral edge is viewed in plan view.
The lid may have a extension area outer peripheral edge located outside the outer periphery of the frame portion,
The frame portion and the elastic wave device wherein lid ing from photosensitive resin.   2. The elastic wave device according to claim 1, wherein in the extension region, the outer peripheral edge of the lid portion is located on an upper surface of the lid portion. The substrate further includes a protective film covering the excitation electrode,
The elastic wave device according to claim 1, wherein the cover is disposed on the protective film.   The said frame part is an elastic wave apparatus in any one of Claims 1-3 comprised by the material different from the said cover part. Having a vibration space surrounded by the substrate and the cover, and having a reinforcing layer disposed on the cover at a position overlapping the vibration space;
The elastic wave device according to any one of claims 1 to 4 , wherein the reinforcing layer is made of a material having a Young's modulus higher than that of the material constituting the cover. The elastic wave device according to claim 5 , wherein the reinforcing layer is made of a resin material or a metal material. The elastic wave device according to any one of claims 1 to 6 , comprising a plurality of vibration spaces surrounded by the substrate and the cover. The elastic wave device according to any one of claims 1 to 7 , wherein the lid portion further includes a preliminary layer disposed on the lid portion. The acoustic wave device according to claim 8 , wherein the lid portion includes the extended region as a part of the preliminary layer. Side surface of the lid, the elastic wave device according to any one of claims 1 to 9 is inclined outwardly toward the opposite side of the substrate from the substrate side. The elastic wave device according to any one of claims 1 to 10 , wherein the extended region is arranged over the entire outer periphery of the lid portion. The elastic wave device according to any one of claims 1 to 11 ,
A circuit board having an external board on which the acoustic wave device is mounted. The circuit board according to claim 1 2, further comprising a resin for molding the elastic wave device.