Surface acoustic wave device and manufacturing method therefor

Abstract

In a surface acoustic wave device, a conductor pattern is located on a main surface of a piezoelectric substrate and includes a surface acoustic wave element pattern, a pad and a feed line that is electrically connected to the pad and extends up to an outer peripheral edge of the main surface. The piezoelectric substrate and a cover are bonded to each other with a support layer therebetween that includes a frame extending along the outer peripheral edge of the main surface so that a gap is provided between the frame and the outer peripheral edge and includes a pad adjacent portion on the pad. Thus, a closed space is surrounded by the piezoelectric substrate, the cover and the frame. The support layer further includes a reinforcement portion that intersects a feed line at or near an intersection portion in which a separated portion of the frame that is separated from the pad adjacent portion intersects the feed line.

Claims

1. A surface acoustic wave device comprising: a piezoelectric substrate including a main surface; a conductor pattern located on the main surface and including a surface acoustic wave element pattern, a pad and a feed line that is electrically connected to the pad and extends up to an outer peripheral edge of the main surface; a support layer including a frame that is located on the main surface and has a frame-shaped structure that extends along the outer peripheral edge of the main surface and so that a gap is provided between the frame and the outer peripheral edge, and a pad adjacent portion that is located on the pad; a cover that is bonded to the support layer and faces the main surface; and a through conductor that is electrically connected to the pad and is located inside a through hole that penetrates through the pad adjacent portion of the support layer in a direction in which the main surface is viewed in plan; wherein a closed space is provided and surrounded by the piezoelectric substrate, the cover and the support layer; the feed line includes a separated feed line that intersects a separated portion of the frame that is separated from the pad adjacent portion; and the support layer further includes a reinforcement portion that is located on the main surface and intersects the separated feed line close to the separated portion.

2. The surface acoustic wave device according to claim 1, wherein the reinforcement portion is located on an outer side of the frame; and a width of the reinforcement portion, which is a dimension in a direction in which the reinforcement portion intersects the separated feed line, progressively becomes larger toward the frame.

3. The surface acoustic wave device according to claim 1, wherein the reinforcement portion is located on an outer side of the frame; and a width of the reinforcement portion, which is a dimension in a direction in which the reinforcement portion intersects the separated feed line, becomes larger in a stepwise manner toward the frame.

4. The surface acoustic wave device according to claim 1, wherein the reinforcement portion is located outside the frame and is separated from the frame.

5. The surface acoustic wave device according to claim 1, wherein the reinforcement portion is integrated with the frame on an outer side of the frame.

6. The surface acoustic wave device according to claim 1, wherein the reinforcement portion includes a plurality of reinforcement portions provided only in portions of the support layer.

7. The surface acoustic wave device according to claim 1, wherein the reinforcement portion includes a plurality of reinforcement portions integrated with the frame on an outer same of the frame.

8. The surface acoustic wave device according to claim 7, wherein a width of each of the reinforcement portions, which is a dimension in a direction in which the plurality of reinforcement portions intersect the separated feed line, progressively becomes larger toward the frame.

9. The surface acoustic wave device according to claim 7, wherein the reinforcement portion is integrated with the frame on an outer same of the frame, and a width of the reinforcement portion, which is a dimension in a direction in which the plurality of reinforcement portions intersect the separated feed line, progressively becomes larger in a stepwise manner toward the frame.

10. The surface acoustic wave device according to claim 7, wherein the separated feed line is one of a single layer feed line and a two layer feed line.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a sectional view of a surface acoustic wave device according to Preferred Embodiment 1 of the present invention.

(2) FIG. 2 is a sectional view of the surface acoustic wave device according to Preferred Embodiment 1 of the present invention.

(3) FIGS. 3A and 3B are plan views illustrating a manufacturing step for the surface acoustic wave device according to Preferred Embodiment 1 of the present invention.

(4) FIGS. 4A and 4B are plan views illustrating a manufacturing step for the surface acoustic wave device according to Preferred Embodiment 1 of the present invention.

(5) FIG. 5 is a sectional view illustrating a manufacturing step for the surface acoustic wave device according to Preferred Embodiment 1 of the present invention.

(6) FIG. 6 is a sectional view illustrating a manufacturing step for the surface acoustic wave device according to Preferred Embodiment 1 of the present invention.

(7) FIG. 7 is a sectional view illustrating a manufacturing step for the surface acoustic wave device according to Preferred Embodiment 1 of the present invention.

(8) FIG. 8 is a sectional view illustrating a manufacturing step for the surface acoustic wave device according to Preferred Embodiment 1 of the present invention.

(9) FIG. 9 is an enlarged sectional view of an important portion of the surface acoustic wave device according to Preferred Embodiment 1 of the present invention.

(10) FIG. 10 is an enlarged sectional view of an important portion of the surface acoustic wave device according to Modification 1 of a preferred embodiment of the present invention.

(11) FIG. 11 is an enlarged sectional view of an important portion of the surface acoustic wave device according to Modification 1 of a preferred embodiment of the present invention.

(12) FIG. 12 is an enlarged sectional view of an important portion of the surface acoustic wave device according to Modification 2 of a preferred embodiment of the present invention.

(13) FIG. 13 is an enlarged sectional view of an important portion of the surface acoustic wave device according to Modification 3 of a preferred embodiment of the present invention.

(14) FIGS. 14A and 14B are plan views illustrating a modification of a manufacturing step for the surface acoustic wave device.

(15) FIG. 15 is a sectional view of a surface acoustic wave device (related art example 1).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(16) Hereafter, preferred embodiments of the present invention will be described while referring to FIGS. 1 to 14.

(17) Preferred Embodiment 1

(18) A surface acoustic wave device 10 according to Preferred Embodiment 1 of the present invention will be described while referring to FIGS. 1 to 8.

(19) FIG. 1 is a sectional view of the surface acoustic wave device 10. FIG. 2 is a sectional view taken along line A-A in FIG. 1. FIG. 1 is a sectional view taken along line B-B in FIG. 2. As illustrated in FIG. 1 and FIG. 2, in the surface acoustic wave device 10, in outline, a support layer 30 is located on a main surface 11a of a piezoelectric substrate 11 and a cover 40 is bonded to the support layer 30. More detailed description will be given later, but, on the main surface 11a of the piezoelectric substrate 11, a conductor pattern includes metal films 13a and 13b, through conductors 50, which penetrate through the support layer 30 and the cover 40, are provided, and solder bumps 54, which define and function as external terminals, are provided on the cover 40.

(20) As illustrated in FIG. 2, the support layer 30 includes a frame 32 that has a frame-shaped structure so as to extend along an outer peripheral edge 11x of the main surface 11a of the piezoelectric substrate 11 and so that a gap is provided between the frame 32 and the outer peripheral edge 11x, pad adjacent portions 34 that each surround the circumference of a corresponding through conductor 50 and reinforcement portions 36. The frame 32 includes separated portions 32a that are separated from the pad adjacent portions 34 and integrated portions 32b that are integrated with the pad adjacent portions 34. A closed space 10x surrounded by the support layer 30 is provided between the piezoelectric substrate 11 and the cover 40.

(21) The surface acoustic wave device 10 can be manufactured with the steps illustrated in FIGS. 3A to 8 using the wafer piezoelectric substrate 11. FIG. 3A and FIG. 4A are plan views of the piezoelectric substrate 11 and a boundary line of a region (individual substrate region) corresponding to one substrate is indicated by a chain line. FIG. 3B and FIG. 4B are sectional views taken along line X-X in FIGS. 3A and 4A. FIGS. 5 to 8 are sectional views similar to FIGS. 3B and 4B.

(22) (a) Conductor Pattern Formation Step

(23) As illustrated in FIGS. 3A and 3B, a conductor pattern including surface acoustic wave element patterns 12a to 12d, which include IDT electrodes and reflectors, pads 14a to 14j, feed lines 18a to 18j that are electrically connected to the pads 14a to 14j and wiring lines that are electrically connected between IDT electrodes of the surface acoustic wave element patterns 12a to 12d, between IDT electrodes of the surface acoustic wave element patterns 12a to 12d and the pads 14a to 14j and so forth is formed on the main surface 11a of the wafer piezoelectric substrate. The feed lines 18a to 18j intersect the boundary line 19 and are electrically connected between pads of adjacent individual substrate regions.

(24) For example, the metal films 13a and 13b and insulating films 13c are formed on the main surface 11a of the piezoelectric substrate 11, which is a lithium tantalate (LiTaO.sub.3) substrate or a lithium niobate (LiNbO.sub.3) substrate, for example, and patterning is performed using a photolithography technique or an etching technique. In order to form wiring lines in three dimensions, the insulating films 13c are interposed between the metal films 13a and 13b.

(25) (b) Support Layer Formation Step

(26) Next, as illustrated in the plan view of FIGS. 4A and 4B, the support layer 30 is formed on the main surface 11a of the piezoelectric substrate. The support layer 30 includes the frame 32, which is formed so as to extend along the boundary line 19 and so that a gap is provided between itself and the boundary line 19, the pad adjacent portions 34, which are formed on the pads 14a to 14j and in which through holes 34a to 34j are formed through which the pads 14a to 14j are exposed, and the reinforcement portions 36, which will be described in more detail later.

(27) The support layer 30 is formed in a certain shape by, for example, applying a photosensitive polyimide-based resin to the entirety of the main surface 11a of the piezoelectric substrate 11 and then removing unwanted portions by using a photolithography technique.

(28) (b) Cover Formation Step

(29) Next, as illustrated in the sectional view of FIG. 5, the cover 40 is bonded to the top of the support layer 30. For example, a resin sheet such as one including a non-photosensitive epoxy-based resin film that can be subjected to a low temperature curing process is adhered to the top of the support layer 30 by lamination.

(30) (d) Through Hole Formation Step

(31) Next, as illustrated in the sectional view of FIG. 6, through holes 42, which are continuous with the through holes 34a to 34j in the support layer 30, are formed in the cover 40 by laser processing for example, thus causing the pads 14a to 14j to be exposed.

(32) The cover 40 in which the through holes 42 have been formed may be bonded to the top of the support layer 30 in the cover formation step after forming the through holes 42 in the cover 40.

(33) In addition, the through holes 34a to 34j in the support layer 30 need not necessarily be formed in the support layer formation step. In other words, the through holes 42 and the through holes 34a to 34j, which are continuous with each other, may be formed at the same time in the cover 40 and the support layer 30 by laser processing, for example, after bonding the cover 40 and the support layer 30 to each other.

(34) (d) Through Conductor Formation Step

(35) Next, as illustrated in the sectional view of FIG. 7, the through conductors 50 are formed by filling the through holes 42 and 34a to 34j with a metal (such as Cu or Ni) by performing electroplating and Au films with a thickness of about 0.05 m to about 0.1 m, for example, are formed on the surfaces of the through conductors 50 as underbump metal layers 52.

(36) (e) External Terminal Formation Step

(37) Next, as illustrated in the sectional view of FIG. 8, spherical solder bumps 54 are formed by printing a solder paste such as SnAgCu on top of the underbump metal layers 52 via a metal mask, heating the solder paste at a temperature at which the solder paste melts such as about 260 C., for example, to make the solder adhere to the Au films, and removing flux by using a flux cleaning agent.

(38) (e) Substrate Division Step

(39) Next, dicing processing is performed in which the piezoelectric substrate 11 is cut using a dicing blade along the boundary line 19. The piezoelectric substrate 11 is divided into individual substrates through the dicing processing so as to complete the surface acoustic wave device 10 illustrated in FIG. 1.

(40) In the surface acoustic wave device 10 manufactured through the above-described steps, the feed lines 18a to 18j are cut when the dicing processing is performed and therefore extend up to the outer peripheral edge 11x of the main surface 11a of the piezoelectric substrate 11.

(41) Among the feed lines 18a to 18j illustrated in FIGS. 3A and 3B and FIGS. 4A and 4B, the feed line 18j, which is electrically connected to the pad 14j arranged in the center of the main surface 11a of the piezoelectric substrate 11, is a separated feed line that intersects a separated portion 32a of the frame 32 of the support layer 30 that is separated from the pad adjacent portions 34. Hereafter, the feed line 18j will also be referred to as a separated feed line 18j.

(42) FIG. 9 is an enlarged sectional view of an important portion of FIG. 2. As illustrated in FIG. 2 and FIG. 9, the reinforcement portion 36 of the support layer 30 is adjacent to an intersection portion 32x of the frame 32 of the support layer 30, the separated portion 32a, which is separated from the pad adjacent portions 34, and the separated feed line 18j intersecting each other in the intersection portion 32x, and the reinforcement portion 36 is formed so as to be integrated with the frame 32 on the outer side of the frame 32.

(43) Reduction of the sealing property of the closed space 10x is prevented by the reinforcement portions 36. In other words, the separated feed line 18j may peel off from the main surface 11a of the piezoelectric substrate 11 when the aggregate substrate is cut by dicing processing, and in such a case, stress may act on the separated portion 32a of the support layer 30 from the separated feed line 18j that has peeled off from the main surface 11a causing peeling off from the main surface 11a. As a result, the adhesion between the separated feed line 18j, the frame 32 of the support layer 30 and the main surface 11a of the piezoelectric substrate 11 is reduced and the airtight state of the closed space 10x may be reduced. Accordingly, when the reinforcement portions 36 are added, peeling off of the separated feed line 18j is able to be stopped in front of the frame 32 by the reinforcement portion 36 and reduction of the sealing property of the closed space 10x is suppressed or prevented.

(44) The frame 32 of the support layer 30 is formed so that a gap is provided between itself and the boundary line 19 in order that clogging up of the dicing blade is avoided and the dicing processing is able to be efficiently performed. On the other hand, the reinforcement portions 36 of the support layer are only formed in portions of the support layer 30 and therefore it is not likely that clogging up of the dicing blade will occur. Consequently, the reinforcement portions 36 may be formed so as to reach the boundary line 19.

(45) If the reinforcement portions of the support layer 30 have a shape that makes it possible for stress acting on the separated feed line 18j when the separated feed line 18j is cut by the dicing processing to be released, it is possible to suppress or prevent reduction of the sealing property of the closed space 10x and therefore, for example, the reinforcement portions 36 is able to have shapes such as those in FIGS. 10 to 13. FIGS. 10 to 13 are enlarged sectional views similar to FIG. 9.

(46) Modification 1

(47) As illustrated in FIGS. 10 and 11, reinforcement portions 36a and 36b of Modification 1 of a preferred embodiment of the present invention are preferably integrated with the frame 32 on the outer side of the frame 32 such that the width of the reinforcement portions 36a and 36b (dimension in vertical direction in FIG. 10 and FIG. 11), which is the dimension in a direction in which they intersect the separated feed line 18j, becomes progressively larger toward the frame 32. In this case, stress in a direction in which the separated feed line 18j extends (lateral direction in FIG. 10 and FIG. 11) acting at the time of the dicing processing is released in a direction different to the direction in which the separated feed line 18j extends by the reinforcement portions 36a and 36b. Cross sections 36p and 36q of the reinforcement portions 36a and 36b on the two sides of the separated feed line 18j have a convex shape or a concave shape, but may instead have a linear shape.

(48) Modification 2

(49) As illustrated in FIG. 12, a reinforcement portion 36c of Modification 2 of a preferred embodiment of the present invention is preferably integrated with the frame 32 on the outer side of the frame 32 such that the width of the reinforcement portion 36c, which is a dimension in a direction in which the reinforcement portion 36c intersects the separated feed line 18j (dimension in vertical direction in FIG. 12), becomes larger in a stepwise manner toward the frame 32. In this case, stress in a direction in which the separated feed line 18j extends (lateral direction in FIG. 12) acting at the time of the dicing processing is released in a direction different to the direction in which the separated feed line 18j extends by the reinforcement portion 36c.

(50) Modification 3

(51) As illustrated in FIG. 13, a reinforcement portion 36d of Modification 3 of a preferred embodiment of the present invention is preferably located outside the frame 32 so as to be separated from the frame 32. In this case, peeling off of the separated feed line 18j is able to be stopped in front of the frame 32 by the reinforcement portion 36d and reduction of the sealing property of the closed space 10x is suppressed or prevented. The reinforcement portion 36d illustrated in FIG. 13 which is separated from the frame 32 can be combined with Modification 1 or Modification 2. More specifically, the reinforcement portion 36d, which is separated from the frame 32, may be formed so as to become larger in a stepwise manner toward the frame 32.

(52) As described above, when a reinforcement portion having a shape that allows stress acting in a direction in which a separated feed line peels off is formed and located on the separated feed line, peeling off of the feed line from a piezoelectric substrate during dicing processing is significantly reduced or prevented and reduction of the sealing property of a closed space can be suppressed or prevented.

(53) In addition, the present invention is not limited to the above-described preferred embodiments and modifications thereto, and can be modified in various ways. More specifically, it is not necessary to form the separated feed line 18j of two layers by stacking the separated feed line 18j on the feed line 18i as in the case of the separated feed line 18j illustrated in FIGS. 3A and 3B. That is, the separated feed line 18j may be formed by being extracted from a one layer feed line as illustrated in FIGS. 14A and 14B.

(54) While preferred embodiments of the present invention have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present invention. The scope of the present invention, therefore, is to be determined solely by the following claims.