U.S. patent application number 15/431610 was filed with the patent office on 2017-06-08 for acoustic wave device and method for producing same.
The applicant listed for this patent is KYOCERA CORPORATION. Invention is credited to Yoshihiro OOKUBO.
Application Number | 20170163241 15/431610 |
Document ID | / |
Family ID | 44066603 |
Filed Date | 2017-06-08 |
United States Patent
Application |
20170163241 |
Kind Code |
A1 |
OOKUBO; Yoshihiro |
June 8, 2017 |
ACOUSTIC WAVE DEVICE AND METHOD FOR PRODUCING SAME
Abstract
An acoustic wave device comprises a substrate and an acoustic
wave element on one main surface of the substrate. Side surfaces of
the substrate comprises a protruding portion which protrudes out at
a side of an another main surface closer than a side with the one
main surface side.
Inventors: |
OOKUBO; Yoshihiro;
(Higashiomi-shi, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
KYOCERA CORPORATION |
Kyoto-shi |
|
JP |
|
|
Family ID: |
44066603 |
Appl. No.: |
15/431610 |
Filed: |
February 13, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14629373 |
Feb 23, 2015 |
9584095 |
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15431610 |
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13498815 |
Mar 28, 2012 |
8963655 |
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PCT/JP2010/071154 |
Nov 26, 2010 |
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14629373 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H03H 9/10 20130101; B05D
3/12 20130101; H03H 9/1071 20130101; H03H 9/25 20130101; H03H 3/08
20130101; H03H 9/02629 20130101; B05D 1/38 20130101; H03H 9/171
20130101; Y10T 83/0524 20150401; H03H 3/02 20130101 |
International
Class: |
H03H 9/25 20060101
H03H009/25; H03H 9/10 20060101 H03H009/10; H03H 3/08 20060101
H03H003/08; H03H 9/17 20060101 H03H009/17; H03H 3/02 20060101
H03H003/02 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 27, 2009 |
JP |
2009-269576 |
Claims
1. An acoustic wave device, comprising: a substrate and an acoustic
wave element on one main surface of the substrate, wherein a side
surface of the substrate comprises a protruding portion which
protrudes out at a side of an another main surface closer than a
side of the one main surface.
2. The acoustic wave device according to claim 1, wherein when the
side surface of the substrate are divided in a thickness direction
into two regions of a first region at the side of the one main
surface and a second region at the side of the another main
surface, the protruding portion is provided in the second
region.
3. The acoustic wave device according to claim 2, wherein the
protruding portion is provided along an outer circumference of the
other main surface and over the entire outer circumference.
4. The acoustic wave device according to claim 1, wherein the
protruding portion is formed tapered to spread more outward toward
a position near the other main surface.
5. The acoustic wave device according to claim 1, further
comprising: a resin film which covers the side surface of the
substrate at the part at the side of the one main surface other
than the protruding portion, abuts against the protruding portion
from the side of the one main surface, and is softer than the
substrate.
6. The acoustic wave device according to claim 5, further
comprising: a cover which is provided on the one main surface and
seals the acoustic wave element, wherein a side surface of the
cover which is located at an inner side away from the side surface
of the substrate and which forms a step with the substrate, and the
resin film is provided and straddles the side surface of the cover
from the side surface of the substrate and abuts against the step
from the side of the one main surface.
7. The acoustic wave device according to claim 1, wherein: the side
surface of the substrate at the side of the one main surface other
than the protruding portion and the surface of the protruding
portion facing the side direction of the substrate are cut surfaces
formed by surfaces cut by a blade.
8. A method for manufacturing an acoustic wave device, comprising:
a first cutting step of forming a groove portions which partition a
plurality of acoustic wave devices by cutting with a first blade
one main surface side portion of a wafer which the plurality of
acoustic wave elements are provided on one main surface and a
second cutting step of cutting an other main surface side portion
of the wafer along the groove portions with a second blade having a
thinner blade thickness than the first blade, and separating the
wafer.
9. The method for manufacturing an acoustic wave device according
to claim 8, further comprising: a step of filling resin in the
groove portions after the first cutting step and before the second
cutting step.
10. The method for manufacturing an acoustic wave device according
to claim 8, further comprising: a step of forming a resin layer on
the other main surface of the wafer before the first cutting step,
wherein the resin layer is not cut in the first cutting step, and
the resin layer is cut in the second cutting step.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional of U.S. application Ser.
No. 14/629,373 filed on Feb. 23, 2015, which is a divisional of
U.S. application Ser. No. 13/498,815 filed on Mar. 28, 2012 and
issued as U.S. Pat. No. 5,963,655, which is a 371 National Stage
Application of International Application no. PCT/JP2010/071154
filed on Nov. 26, 2010 which claims the benefit of Japanese
Application no. 2009-269576 filed on Nov. 27, 2009. The contents of
each of the above applications are incorporated by reference herein
in their entirety.
TECHNICAL FIELD
[0002] The present invention relates to an acoustic wave device
such as a surface acoustic wave (SAW) device or a film bulk
acoustic resonator (FBAR) or the like and a method of producing the
same.
BACKGROUND ART
[0003] An acoustic wave device having a substrate and an acoustic
wave element provided on a main surface of the substrate is known.
Patent literature 1 discloses an acoustic wave device improved in
shock resistance by covering side surfaces or a back surface (main
surface on the side opposite to the main surface having an acoustic
wave element provided thereon) of the substrate by a resin.
[0004] An acoustic wave device is sometimes impacted from a side
direction of the substrate at the time of transport during the
period from manufacture to mounting etc. Note that, Patent
Literature 1 refers to the shock resistance, but does not
particularly take note of impact from a side direction of the
substrate. As a result, the acoustic wave device of Patent
Literature 1 is not a particularly preferred aspect against impact
from the side direction of a substrate.
[0005] Accordingly, it is preferable that an acoustic wave device
capable of improving the shock resistance from a side direction of
a substrate and a method of production of the same be provided.
[0006] Patent literature 1: Japanese Patent Publication (A) No.
2008-5464
SUMMARY OF INVENTION
[0007] An acoustic wave device according to an embodiment of the
present invention has a substrate and an acoustic wave element on
one main surface of the substrate. On the side surface of the
substrate, a protruding portion is provided which protrudes out
from the side surfaces at a side of the other main surface compared
with a side of the one main surface.
[0008] A method of production of an acoustic wave device according
to an embodiment of the present invention has a first cutting step
of cutting a wafer, on one main surface of which a plurality of
acoustic wave elements are provided, at the part of that one main
surface side by a first blade so as to form groove portions which
partition a plurality of acoustic wave devices and a second cutting
step of cutting the wafer at the part of the other main surface
side along the groove portions by a second blade having a thinner
blade thickness than the first blade so as to separate the
wafer.
[0009] According to the above constitution and procedure, when
shock is applied to a side surface of an acoustic wave device at
the time of transport etc. of the acoustic wave device, the
protruding portion is more easily impacted. On the other hand, for
maintaining the performance of the acoustic wave device, rather
than maintaining the shape of the part at the other main surface
side, maintaining the shape of the part at the one main surface
side on which the acoustic wave element is provided is more
important. Accordingly, this means that the acoustic wave device is
improved in shock resistance from the side direction of the
substrate as a whole. Therefore, the maintenance of shape of the
acoustic wave element and maintenance of adhesion between the cover
and the substrate are improved.
BRIEF DESCRIPTION OF DRAWINGS
[0010] FIG. 1 is a perspective view showing an appearance of a SAW
device according to a first embodiment of the present
invention.
[0011] FIG. 2 is a perspective view schematically showing the SAW
device of FIG. 1 partially cut away.
[0012] FIG. 3 is a conceptual cross-sectional view along the line
III-III in FIG. 1.
[0013] FIGS. 4A, 4B, 4C and 4D are cross-sectional views for
explaining a method of production of the SAW device in FIG. 1.
[0014] FIGS. 5A , 5B and 5D are cross-sectional views showing a
continuation of FIG. 4D.
[0015] FIGS. 6A, 6B, 6C and 6D are cross-sectional views showing a
continuation of FIG. 5C.
[0016] FIGS. 7A, 7B and 7C are cross-sectional views showing
protruding portions according to first to third modifications.
DESCRIPTION OF EMBODIMENTS
[0017] Below, a SAW device according to an embodiment of the
present invention is explained with reference to the drawings. Note
that, the drawings used in the following explanation are schematic.
Dimensions and ratios etc. on the drawings do not always coincide
with the actual ones.
(Constitution of SAW Device)
[0018] FIG. 1 is a perspective view of the appearance of a SAW
device 1 according to an embodiment of the present invention.
[0019] The SAW device 1 is constituted by a so-called wafer level
package (WLP) type SAW device. The SAW device 1 is formed in a
general block shape as a whole. At one surface of the block, a
plurality of terminals 3 are exposed. The number and arrangement
positions of the plurality of terminals 3 are suitably set in
accordance with the configuration of the electronic circuit inside
the SAW device 1. The present embodiment illustrates a case where
six terminals 3 are arranged along an outer edge of one
surface.
[0020] The SAW device 1 receives as input a signal through any of
the plurality of terminals 3. The input signal is filtered by the
SAW device 1. Then, the SAW device 1 outputs the filtered signal
through any of the plurality of terminals 3. The SAW device 1 is
for example mounted on the mounting surface of a not shown circuit
board or the like with the surface at which the plurality of
terminals 3 are exposed made to face that mounting surface and is
sealed by a resin in that state. Due to this, it is mounted in a
state with the terminals 3 connected to the terminals on the
mounting surface.
[0021] FIG. 2 is a perspective view showing the SAW device 1
partially cut away. Further, FIG. 3 is a cross-sectional view taken
along the line III-III in FIG. 1.
[0022] The SAW device 1 has a substrate 5 and SAW elements 7
provided on the substrate 5. Further, for the purpose of protection
etc. of the SAW elements 7, the SAW device 1 has a cover 9 covering
the SAW elements 7, a resin film 11 covering side surfaces of the
substrate 5, a back surface electrode 13 provided on the substrate
5 at the side opposite to the SAW element 7 side, and a resin layer
15 laminated on the back surface electrode 13.
[0023] The substrate 5 is constituted by a piezoelectric substrate.
Specifically, for example, the substrate 5 is a single crystal
substrate having a piezoelectric property such as a lithium
tantalite single crystal, lithium niobate single crystal, or the
like. The substrate 5 is generally formed in a thin block shape and
has a first main surface 5a, a second main surface 5b (FIG. 3) on
the back surface side of the same, and side surfaces 5c facing the
sides (outer circumference side) of the first main surface 5a and
second main surface 5b. On the side surfaces 5c, a protruding
portion 5d protruding outward from the side surfaces 5c is
formed.
[0024] The protruding portion 5d is provided along the outer
circumference of the second main surface 5b over the entire outer
circumference. In other words, it is also possible to grasp that
the protruding portion 5d is formed by the side surfaces 5c being
expanded at the parts at the second main surface 5b sides and
possible to grasp that it is formed by parts which remain without
being cut away when cutting away the piezoelectric substrate 3 at
the first main surface 5a side over the entire outer circumference.
The cross-sectional shape (cross-sectional shape shown in FIG. 3)
of the protruding portion 5d is generally rectangular. Further, the
protruding portion 5d is provided in a "second region" when equally
dividing the side surfaces 5c in the vertical direction into two
into a first region (region on first main surface 5a side) and a
second region (region on second main surface 5b side).
[0025] The length of one side of the substrate 5 is for example 0.5
mm to 2 mm. The thickness of the substrate 5 is for example 0.2 mm
to 0.5 mm. The amount of protrusion of the protruding portion 5d is
for example 5 to 10 .mu.m. The thickness of the protruding portion
5d is for example 25 to 50 .mu.m.
[0026] Each SAW element 7 is an element for filtering a signal
which is input to the SAW device 1. The SAW element 7 is provided
on the first main surface 5a. The SAW element 7 has a pair of
comb-shaped electrodes (IDT electrodes) 17. Each comb-shaped
electrode 17 has a bus bar 17a (FIG. 2) extending in the
propagation direction (X-direction) of the SAW in the substrate 5
and a plurality of electrode fingers 17b extending from the bus bar
17a in a direction (Y-direction) perpendicular to the above
propagation direction. The comb-shaped electrodes 17 are provided
so that their electrode fingers 17b mesh with each other.
[0027] Note that, FIG. 2 and FIG. 3 are schematic views, so show
one pair of comb-shaped electrodes 17 each having several electrode
fingers 17b. In actuality, two or more pairs of comb-shaped
electrodes each having a number of electrode fingers larger than
this may be provided. Further, a ladder type SAW filter, double
mode SAW resonator filter, or the like may be constituted by a
plurality of SAW elements 7 connected in serial connection,
parallel connection, or other method. The SAW elements 7 are formed
by for example Al alloy such as Al-Cu alloy or the like.
[0028] The cover 9 has a frame 19 surrounding the SAW elements 7 in
a plan view of the first main surface 5a and has a lid 21 closing
the opening of the frame 19. Further, the spaces surrounded by the
first main surface 5a (strictly speaking, a protective film 29
which is explained later), frame 19, and lid 21 form vibration
spaces S for facilitating the propagation of the SAW. Note that,
the vibration spaces S may be provided in suitable numbers and
shapes. The present application illustrates a case where two
vibration spaces S are provided.
[0029] The frame 19 is comprised of a layer having a generally
constant thickness in which one or more openings which become
vibration spaces S are formed. In the present embodiment, two
vibration spaces S are provided. The thickness of the frame 19
(height of the vibration spaces S) is for example several .mu.m to
30 .mu.m. The lid 21 is constituted by a layer having a generally
constant thickness which is laminated on the frame 19. The
thickness of the lid 21 is for example several pm to 30 .mu.m.
[0030] The planar shape of the cover 9 is similar to the planar
shape of the substrate 5 and is rectangular in the present
embodiment. The cover 9 has for example a generally equivalent area
with the first main surface 5a and covers generally the entire
surface of the first main surface 5a. However, the cover 9 is a bit
smaller than the first main surface 5a, so steps is formed between
the side surfaces 5c and the side surfaces 9c of the cover 9. The
steps is formed over the entire circumference of the first main
surface 5a. The size of the steps is for example 5 to 20 .mu.m.
[0031] The frame 19 and lid 21 are formed by for example a
photosensitive resin. The photosensitive resin is for example a
urethane acrylate-based, polyester acrylate-based, or epoxy
acrylate-based resin which is cured by radical polymerization of
acryl groups, methacryl groups, or the like.
[0032] The frame 19 and lid 21 may be formed by the same material
or may be formed by materials different from each other. In the
present example, for convenience of explanation, the borderline
between the frame 19 and the lid 21 is clearly indicated. However,
in an actual product, the frame 19 and lid 21 may be formed by the
same material and formed integrally as well.
[0033] The resin film 11 covers the side surfaces 5c at the parts
at the first main surface 5a side other than the protruding portion
5d and the side surfaces 9c of the cover 9. The resin film 11 is
provided so as to bury the steps caused by the protruding portion
5d and the step between the substrate 5 and the cover 9 so that the
outer shape of the SAW device 1 constituted by the substrate 5,
cover 9, and resin film 11 becomes a block shape. That is, the
resin film 11 covers the entire surfaces of the side surfaces 5c at
the parts at the first main surface 5a side other than the
protruding portion 5d and the entire surfaces of the side surfaces
9c. Further, outer circumferential surface 11e of the resin film 11
is flush with the top face 5e of the protruding portion 5d, and end
surface 11a of the resin film 11 on the first main surface 5a side
is flush with the top face 9a of the cover 9.
[0034] The resin film 11 is formed by for example a novolac-based
resin, epoxy resin, Biphenol resin, or polyimide resin. The resin
film 11 has a lower Young's modulus than the substrate 5. That is,
the resin film 11 is softer than the substrate 5 and easily absorbs
shock.
[0035] The back surface electrode 13 covers the entire surface of
the second main surface 5b. The thickness of the back surface
electrode 13 is for example 1 .mu.m to several .mu.m. The back
surface electrode 13 is formed by for example an Al alloy such as
an Al-Cu alloy or the like. The charges formed in the substrate 5
due to temperature change etc. flow to the back surface electrode
13, whereby pyroelectric breakdown of the SAW elements 7 is
suppressed.
[0036] The resin layer 15 covers the entire surface of the second
main surface 5b (back surface electrode 13). The thickness of the
resin layer 15 is for example 25 .mu.m to 50 .mu.m. The resin layer
15 is formed by for example a thermosetting resin such as an epoxy
resin or the like. The resin layer 15 has a lower Young's modulus
than the substrate 5 in the same way as the resin film 11.
[0037] The terminals 3 are formed standing at the first main
surface 5a and are exposed at the upper surface 9a of the cover 9
through holes 9h formed in the cover 9. Specifically, the holes 9h
penetrate through the frame 19 and lid 21 in directions facing the
first main surface 5a at the outsides of the vibration spaces
S.
[0038] The first main surface 5a is provided with lines 23 (FIG. 2)
connected to the SAW elements 7 and a plurality of pads 25
connected to the lines 23. The terminals 3 are connected to the SAW
elements 7 by being provided on the pads 25.
[0039] As shown in FIG. 3, on the first main surface 5a, a
conductive layer 27 and a protective film 29 covering the
conductive layer 27 are provided.
[0040] The conductive layer 27 forms the SAW elements 7, at least a
part of the lines 23 (FIG. 2), and at least a part of the pads 25.
The conductive layer 27 is formed by for example an Al alloy such
as an Al-Cu alloy or the like. Its thickness is for example 100 to
300 nm.
[0041] The protective film 29 contributes to prevention of
oxidation etc. of the conductive layer 27. The protective film 29
is formed by for example a material which has an insulating
property and has a mass light enough so as not to influence the
propagation of the SAW. For example, the protective film 29 is
formed by silicon oxide (SiO2 etc.), silicon nitride, silicon or
the like. The thickness of the protective film 29 is for example
about 1/10 (10 nm to 30 mm) of the thickness of the conductive
layer 27 or equal to or more than the thickness of the conductive
layer 27 (100 nm to 300 nm).
[0042] The protective film 29 is for example provided over
generally the entire first main surface 5a, while the cover 9 is
laminated over the protective film 29. Further, also the part of
the resin film 11 which is on the first main surface 5a is
laminated over the protective film 29. On the other hand, at the
positions of arrangement of the terminals 3, the protective film 29
is removed so that the pads 25 are exposed from the protective film
29.
[0043] Note that, strictly speaking, the cover 9 is not directly
provided on the first main surface 5a, but is provided on the
protective film 29 or the like. In the present example, even in a
case where predetermined members, layers, etc. are indirectly
provided on the main surface of the substrate 5 in this way and are
not directly provided on the main surface of the substrate 5, it is
sometimes expressed so that these predetermined members, layers,
etc. are provided on the main surface of the substrate 5. This is
true for the word "laminate" as well.
[0044] On the first main surface 5a, other than this, an insulation
film which is laminated on the conductive layer 27 or protective
film 29, another conductive layer which is laminated on the
conductive layer 27 with the insulation film interposed
therebetween and forms a part of the lines 23, a connection
strengthening layer which forms upper layer portions of the pads 25
and strengthens the connection between the pads 25 and the
terminals 3, and so on may be provided as well.
(Method of Production of SAW Device)
[0045] FIG. 4A to FIG. 6D are cross-sectional views for explaining
the method of production of the SAW device 1. The steps are
advanced in order from FIG. 4A to FIG. 6D.
[0046] The steps explained below are realized in a so-called "wafer
process". That is, a mother board (wafer 31) which is later divided
to form the substrates 5 is formed with a thin film, processed by
photolithography, etc., then is diced to form a large number of SAW
devices in parallel.
[0047] Note, in FIG. 4A to FIG. 5C, only parts corresponding to one
SAW device 1 are shown. Further, in FIG. 6A to FIG. 6D, only parts
corresponding to three SAW devices 1 are shown. The conductive
layer, insulation layer, etc. change in shapes along with the
progress in the process. However, common notations are used before
and after the changes. In the same way, notations of the first main
surface 5a and second main surface 5b of the substrate 5 are
assigned to the first main surface and second main surface of the
wafer 31.
[0048] As shown in FIG. 4A, first, on the first main surface 5a of
the substrate 5, a conductive layer 27 is formed. Specifically,
first, the thin film forming method such as the sputtering method,
vapor deposition method, CVD (chemical vapor deposition) method, or
the like is used to form a metal layer which becomes the conductive
layer 27 on the first main surface 5a. Next, the metal layer is
patterned by photolithography etc. using a reduced protrusion
exposure machine (stepper) and RIE (reactive ion etching) device.
Therefore, a conductive layer 27 including the SAW elements 7, at
least a part of the lines 23, and at least a part of the pads 25 is
formed.
[0049] Next, as shown in FIG. 4B, the protective film 29 is formed.
Specifically, first, a thin film which becomes the protective film
29 is formed by the thin film forming method such as the CVD method
or vapor deposition method or the like. Next, parts of the thin
film are removed by the photolithography method so that parts of
the conductive layer 27 which constitute the pads 25 are exposed.
Accordingly, the protective film 29 is formed.
[0050] After the protective film 29 is formed, as shown in FIG. 4C,
a thin film which becomes the frame 19 is formed. The thin film is
formed by for example adhesion of a film formed by a photosensitive
resin or a thin film forming method the same as that for the
protective film 29 etc.
[0051] After the thin film which becomes the frame 19 is formed, as
shown in FIG. 4D, the photolithography method is used to remove
parts of the thin film and form openings which becomes the
vibration spaces S and lower side portions of the holes 9h.
Further, groove portions are formed along the dicing lines, and
side surfaces of the frame 19 are formed as well. That is, the
frame 19 is formed from the thin film. Note that, the
photolithography may be either of the positive type or the negative
type.
[0052] After the frame 19 is formed, as shown in FIG. 5A, the lid
21 is formed by the same method as the method of formation of the
frame 19. Specifically, first, a thin film which becomes the lid 21
is formed. The thin film is formed by for example adhesion of a
film formed by a photosensitive resin. By laminating the thin film
on the frame 19, the openings of the frame 19 are closed, and the
vibration spaces S are constituted.
[0053] Next, by the photolithography method, parts of the thin film
are removed, and upper side portions of the holes 9h are formed.
Further, groove portions are formed along the dicing lines, and
side surfaces of the frame 19 are formed. That is, the lid 21 is
formed from the thin film. Note that, the photolithography may be
either of the positive type or negative type.
[0054] After the lid 21 is formed, as shown in FIG. 5D, terminals 3
are formed. Specifically, first, a base layer 33 is formed over the
upper face 9a of the cover 9 and the inside of the holes 9h. The
base layer 33 is a metal layer and is formed by for example the
sputtering method.
[0055] Next, on the base layer 33, a resist layer 37 is formed. The
resist layer 37 is for example formed by having a thin film formed
on the substrate by a spin coating method or other technique and
having that thin film patterned by the photolithography method. By
removal of parts of the thin film by patterning, the base layer 33
is exposed at the holes 9h and their peripheral parts.
[0056] After that, the electroplating method is used to cause a
metal to deposit on the exposed parts of the base layer 33.
Accordingly, solid parts 35 are formed.
[0057] After the solid parts 35 are formed, as shown in FIG. 5C,
the parts of the base layer 33 covered by the resist layer 37 and
the resist layer 37 are removed. Therefore, the terminals 3 are
formed. That is, the surface parts of the terminals 3 are
constituted by the base layer 33, and internal parts (majority) of
the terminals 3 are constituted by the solid parts 35. Note that,
in FIG. 3, illustration of the base layer 33 is omitted.
[0058] After that, on the second main surface 5b, the back surface
electrode 13 and resin layer 15 are sequentially formed (FIG. 5C).
Specifically, the back surface electrode 13 is formed by the thin
film forming method such as the sputtering method, vapor deposition
method, CVD method, or the like. The resin layer 15 is formed by
for example adhering a resin sheet to the back surface electrode
13, and then thermosetting it. Note that, the resin layer 15 may be
formed by a potting method or printing method as well.
[0059] After the resin layer 15 is formed, as shown in FIG. 6A, the
resin layer 15 of the wafer state SAW devices 1 and a dicing tape
39 are bonded.
[0060] Next, as shown in FIG. 6D, a first blade 41 is used to the
portions of the wafer 31 on the first main surface 5a side along
the dicing lines. Accordingly, groove portions 31a partitioning a
plurality of SAW devices 1 are formed.
[0061] After the groove portions 31a are formed, as shown in FIG.
6C, resin constituting the resin film 11 is filled in the groove
portions 31a. The resin is filled by using for example a dispenser
43. Further, the filled resin is cured by heating.
[0062] After the resin is filled and hardened, as shown in FIG. 6D,
a second blade 45 having a thinner blade thickness than the first
blade 41 is used to cut the wafer-state SAW devices 1 along the
groove portions 31a from the first main surface 5a side.
Specifically, the resin filled in the groove portions 31a, parts of
the wafer 31 at the second main surface 5b side, the back surface
electrode 13, and the resin layer 15 are cut at schematically the
center of the groove portions 31a.
[0063] Therefore, the plurality of SAW devices 1 are separated from
each other. Further, due to the difference of blade thickness
between the first blade 41 and the second blade 45, the protruding
portions 5d are formed. For example, when the blade thickness of
the first blade 41 is 50 .mu.m and the blade thickness of the
second blade is 40 .mu.m, the amount of protrusion of the
protruding portions 5d is (50-40)/2=5 .mu.m.
[0064] Note that, the first blade 41 is for example a fixed
abrasive type blade and has a plurality of fixed abrasive grains
41a and a connecting material 41b holding the plurality of fixed
abrasive grains 41a. In the same way, the second blade 45 has a
plurality of fixed abrasive grains 45a and a connecting material
45b holding the plurality of fixed abrasive grains 45a.
[0065] The material of the abrasive grains, particle size, the
density of the abrasive grains, the material of the connecting
material, and blade thickness may be suitably selected. Part of the
conditions other than the blade thickness may be shared between the
first blade 41 and the second blade 45. For example, between the
first blade 41 and the second blade 45, the material of the
abrasive grains, particle size, and the density of abrasive grains
are shared, but the type of the connecting material is different.
As the connecting material 41b, one suitable for cutting a
piezoelectric substrate (substrate 5) is selected, while as the
connecting material 45b, one suitable for cutting a resin (at least
one of the resin film 11 and resin layer 15) is selected.
[0066] According to the above embodiment, each SAW device 1 has a
substrate 5 and SAW elements 7 on the first main surface 5a of the
substrate 5. On the side surfaces 5c of the substrate 5, a
protruding portion 5d is provided at the second main surface 5b
side compared with the first main surface 5a.
[0067] Accordingly, at the time of transport etc. of the SAW device
1, when shock is applied to a side surface 5c, the protruding
portion 5d is more easily impacted than the part of the side
surface 5c at the first main surface 5a side. On the other hand,
for maintaining the performance of the SAW device 1, rather than
maintaining the shape of the part at the second main surface 5b
side, maintaining the shape of the part at the first main surface
5a side is more important. Accordingly, this means that the SAW
device 1 is improved in shock resistance from the side direction of
the substrate 5 as a whole. Specifically, by strengthening of
protection of the substrate 5 at the part at the first main surface
5a side against shock from the side, maintenance of the shape of
the SAW elements 7 (maintenance of filter precision) and
maintenance of adhesion between the cover 9 and the substrate 5
(protective film 29) (antioxidation effect of conductive layer) are
improved. Note that, Patent Literature 1 does not disclose the idea
of protecting the first main surface 5a side against the impact
from the side surface with priority over the second main surface 5b
side.
[0068] The protruding portion 5d is provided along the outer
circumference of the second main surface 5b. Accordingly, it is
possible to strengthen the protection of the first main surface 5a
side against impact from various directions parallel to the first
main surface 5a. Further, as explained with reference to FIG. 6B
and FIG. 6D, the protruding portion 5d can be formed by a simple
and convenient method of changing the cutting width at the time of
dicing, for example, the protruding portion 5d can be formed by
using the first blade 41 and second blade 45 having different blade
thicknesses.
[0069] The SAW device 1 has the resin layer 11 which covers the
side surfaces 5c at the parts of the first main surface 5a side
other than the protruding portion 5d, abuts against the protruding
portion 5d from the first main surface 5a side, and is softer than
the substrate 5. Accordingly, due to the resin film 11, shock with
respect to a side surface 5c can be absorbed, and protection of the
parts of the SAW device 1 at the first main surface 5a side can be
strengthened. Note that, a "resin film 11 which is softer than the
substrate 5" means "softer" when compared in Young's modulus. That
is, the resin film 11 has a smaller Young's modulus than the
substrate 5. Further, the protruding portion 5d functions as a
stopper which limits movement of the resin film 11 to the second
main surface 5b side, whereby peeling of the resin film 11 from the
side surfaces 5c is suppressed.
[0070] The resin film 11 may also be formed so that its side
surfaces are located at the inner side compared with the protruding
portion 5d. In other words, the protruding portion 5d may be formed
so that it protrudes outward compared with the side surfaces of the
resin film 11. Due to this, when an object having a surface
parallel to a side surface strikes a SAW device 1 from the side
direction of the substrate 5, that object strikes the protruding
portion 5d, so propagation of a large impact to the first main
surface 5a of the SAW device 1 can be suppressed. On the other
hand, when a pointed object that does not contact the protruding
portion 5d strikes the SAW device 1 from the side direction of the
substrate 5, the shock at the time of impact is eased by the resin
film 11, so propagation of a large shock to the first main surface
5a of the SAW device 1 can again be suppressed.
[0071] The SAW device 1 has the cover 9 which is provided on the
first main surface 5a and seals the SAW elements 7. The side
surfaces 9c of the cover 9 form steps by being positioned at the
inner sides from the side surfaces 5c of the substrate 5. The resin
film 11 is provided so as to straddle the side surfaces 9c of the
cover 9 from the side surfaces 5c of the substrate 5 and abuts
against the steps from the first main surface 5a side. Accordingly,
by covering of mating parts of the cover 9 and substrate 5
(strictly speaking, protective film 29) by the resin film 11,
invasion of moisture from the mating parts and peeling of the cover
9 from the substrate 5 are suppressed. Further, the steps formed by
the cover 9 and substrate 5 function as stoppers which limit
movement of the resin film 11 to the second main surface 5b side,
so peeling of the resin film 11 from the side surface 9c and side
surface 5c is suppressed.
[0072] Further, the method of production of the SAW device 1 has a
first cutting step (FIG. 6B) of cutting the wafer 31, on the first
main surface 5a of which a plurality of SAW elements 7 are
provided, at the parts of the first main surface 5a sides by the
first blade 41 so as to form groove portions 31a for partitioning
the plurality of SAW devices 1. Further, this method of production
has a second cutting step (FIG. 6D) of cutting the wafer 31 at
parts of the second main surface 5b sides along the groove portions
31a by the second blade 45 having a thinner blade thickness than
the first blade 41 so as to separate the wafer 31.
[0073] Accordingly, the protruding portions 5d can be simply
formed. Further, blades which are different from each other are
used in the two steps, therefore blades suitable for the steps can
be used. For example, in the first cutting step (FIG. 6B), cutting
is carried out at a high speed by cutting by the first blade 41
having the large particle size, while in the second cutting step
(FIG. 6D), chipping, which easily occurs when a blade passes
through a wafer, can be suppressed by cutting by the second blade
45 having a small particle size.
[0074] The method of production of the SAW device 1 further has a
step (FIG. 6C) of filling resin in the groove portions 31a after
the first cutting step (FIG. 6B) and before the second cutting step
(FIG. 6D). Accordingly, the above-mentioned resin film 11 which
covers the side surfaces 5c at the first main surface 5a side other
than the protruding portion 5d and adheres to the protruding
portion 5d can be simply constituted.
[0075] The method of production of the SAW device 1 further has a
step (FIG. 5C) of forming the resin layer 15 on the second main
surface 5b of the wafer 31 before the first cutting step (FIG. 6B).
The resin layer 15 is not cut in the first cutting step (FIG. 6B),
but the resin layer 15 is cut in the second cutting step (FIG. 6D).
Accordingly, by selecting as the first blade 45 one suitable for
cutting the piezoelectric substrate and as the second blade 45
selecting one suitable for cutting the resin layer 15, chipping and
cracks in the second main surface 5b can be suppressed.
[0076] FIG. 7A to FIG. 7C are cross-sectional views showing first
to third modifications of the protruding portion 5d. The protruding
portions 5d of the first to third modifications are formed tapered
so as to spread further outward toward the second main surface 5b
side. In other words, the protruding portions 5d of the first to
third modifications protrude out further the more toward the second
main surface 5b sides (the closer in position to the second main
surfaces 5b).
[0077] More specifically, in the first modification shown in FIG.
7A, the protruding portion 5d is formed so that its cross-sectional
shape becomes a generally right triangle. In the second
modification shown in FIG. 7B, the protruding portion 5d is formed
so that its cross-sectional shape becomes generally trapezoidal. In
the third modification shown in FIG. 7C, the protruding portion 5d
is formed so that the cross-sectional shape of the part at the
first main surface 5a side is generally rectangular (square) and
the cross-sectional shape of the part at the second main surface 5b
side is generally trapezoidal. The angle of inclination of the
tapered surface (5e) of the protruding portion 5d relative to the
side surface 5c (defined as 0.degree. when the tapered surface is
parallel to the side surface 5c) is for example 5.degree. to
40.degree..
[0078] Note that, in the first to third modifications, the
protruding portion 5d may be provided along the outer circumference
of the second main surface 5b, the resin film 11 which abuts
against the protruding portion 5d from the first main surface 5a
side may be provided, and so on in the same way as the above
embodiment.
[0079] The protruding portion 5d in the first modification can
relieve stress concentration at the base of the protruding portion
5d at the first main surface 5a side compared with the protruding
portion 5d in the above embodiment, while can cause the positions
where impact occurs to concentrate at the second main surface 5b
side. Further, compared with the protruding portion 5d in the above
embodiment, the protruding portions 5d in the second and third
modifications can cause the positions where impact occurs to
concentrate at the second main surface 5b side. The protruding
portions 5d in the first to third modifications can be formed by
for example forming the entire second blade 45 or its outer
circumferential edge to be tapered.
EXAMPLES
[0080] For the substrates 5 in the above embodiment and first
modification, concrete dimensions etc. were set and simulations
were performed concerning impact. Specifically, this was as
follows:
Simulation Conditions
[0081] Basic dimensions of substrate 5 [0082] Lx (see FIG. 2) =0.6
mm [0083] Ly (see FIG. 2) =0.8 mm [0084] Lz (see FIG. 2) =0.2
mm
[0085] Dimensions of protruding portion 5d [0086] d1 (see FIG. 2
and FIG. 7A) =0.0075 mm [0087] d2 (see FIG. 2 and FIG. 7A) =0.037
mm
[0088] Young's modulus of substrate 5:230 GPa (assuming LiTaO3)
[0089] Poisson's ratio of substrate 5:0.3 (assuming LiTaO3)
[0090] Density of substrate 5:7450 kg/m3 (assuming LiTaO3)
[0091] Assumed situation: A situation was assumed where the
substrate 5 was dropped in a Y-direction (see FIG. 2) and struck an
XZ surface (surface perpendicular to Y-direction). A velocity at
the time of impact of 3.2 m/s and an acceleration at the time of
impact of 9.8 m/s2 (gravitational acceleration) were assumed.
Computation Method
[0092] The finite element method was used to calculate the stress
distribution in the substrate 5 in time sequence.
[0093] That is, when dropping the substrate 5 in the Y-direction,
the protruding portion 5d impacts the XZ surface whereby stress is
generated at the protruding portion 5d. This stress is propagated
to the entire substrate 5 along with the elapse of time. This
situation was reproduced and the stress of each part of the
substrate 5 at each point of time was examined.
Evaluation Method
[0094] The maximum stress generated at the first main surface 5a
was extracted.
[0095] Reason: This is because, as explained above, for maintenance
of performance of the SAW device 1, it is considered that
maintaining the shape of the part at the first main surface 5a side
is more important than maintaining the shape of the part at the
second main surface 5b side. Further, it is considered that the
influence of the maximum value is greater than the mean value of
stress.
[0096] Note that, the position of generation and point of time of
generation in the first main surface 5a of the maximum stress which
is generated in the first main surface 5a differ according to the
simulation conditions.
Simulation Results
[0097] Case of the protruding portion 5d in the above embodiment
[0098] Maximum stress in first main surface 5a:2.8.times.108 Pa
[0099] Case of protruding portion 5d in the first modification
[0100] Maximum stress in first main surface 5a:2.5.times.108 Pa
[0101] It was confirmed from the simulation results that the
maximum value of stress generated in the first main surface 5a was
smaller in the case where the protruding portion 5d was tapered so
as to further protrude outward toward the second main surface 5b
side than the case where the protruding portion 5d was
rectangular.
[0102] The present invention is not limited to the above embodiment
and modifications and may be executed in various ways.
[0103] The acoustic wave device is not limited to a SAW device. For
example, the acoustic wave device may be a film bulk acoustic
resonator. Further, the acoustic wave device may be a boundary
acoustic wave device utilizing a boundary acoustic wave.
[0104] In the acoustic wave device, the resin film (11), back
surface electrode (13), resin layer (15), and protective film (29)
may be omitted. Conversely, other suitable layers etc. may be
formed. Further, in the case of the boundary acoustic wave device,
an acoustic wave device can be prepared without provision of
vibration spaces S.
[0105] Further, the shape of the protruding portion 5d is not
limited to the above explained ones. For example, the protruding
portion 5d may be formed so as to gradually become broader from the
first main surface 3a of the piezoelectric substrate 3 toward the
second main surface 3b. In other words, the protruding portion 5d
may be provided so that the shape of the piezoelectric substrate 3
becomes generally trapezoidal when viewing it from the side
surface.
[0106] The cutting of the wafer is not limited to cutting carried
out by using a blade. For example, the cutting may be carried out
by using a laser. Further, a plurality of methods may be combined.
For example, the first cutting step may be carried out by using a
blade and the second cutting step may be carried out by using a
laser.
[0107] Note that, in the SAW device, whether a side surface (5c) at
the one main surface side (5a) other than the protruding portion
(5d) and the surface (5e) of the protruding portion facing the side
direction of the substrate are formed by surfaces cut by a blade
can be identified by for example observation of the surfaces by an
SEM (scanning electron microscope). For example, when a wafer is
cut by a blade, straight (strictly speaking, arc-shaped) grooves
which are formed by cutting by abrasive grains and are parallel to
the main surface is formed in the side surface, therefore these
grooves can be observed by the SEM.
[0108] The cutting in the second cutting step (FIG. 6D) need not be
carried out from one main surface 5a side (side cut in the first
cutting step) or may be carried out from the other main surface 5b
side.
[0109] In the filling step (FIG. 6C) of resin which forms the resin
film 11, the resin need not be filled up to the upper surface 9a of
the cover 9. For example, the resin may be filled up to one main
surface 5a of the substrate 5 or a part lower than it, or may be
filled up to the upper face of the cover or a part lower than
it.
REFERENCE SIGNS LIST
[0110] 1 . . . SAW device (acoustic wave device), 5 . . .
substrate, 5a . . . first main surface (one main surface), 5b . . .
second main surface (other main surface), 5c . . . side surface, 5d
. . . protruding portion, and 7 . . . SAW element (acoustic wave
element).
* * * * *