U.S. patent application number 11/757452 was filed with the patent office on 2009-12-24 for pressure-sensitive adhesive sheet for dicing and method for processing processed material using the same.
This patent application is currently assigned to Nitto Denko Corporation. Invention is credited to Shouji YAMAMOTO.
Application Number | 20090317633 11/757452 |
Document ID | / |
Family ID | 38198573 |
Filed Date | 2009-12-24 |
United States Patent
Application |
20090317633 |
Kind Code |
A2 |
YAMAMOTO; Shouji |
December 24, 2009 |
Pressure-Sensitive Adhesive Sheet for Dicing and Method for
Processing Processed Material Using the Same
Abstract
The present invention intends to provide a pressure-sensitive
adhesive sheet for dicing which inhibits the generation of fibrous
scraps and has good expandability. The present invention relates to
a pressure-sensitive adhesive sheet for dicing, which includes a
base material and at least one pressure-sensitive adhesive layer
disposed on at least one surface the base material, in which the
base material contains a polymer having a random copolymer block,
and the random copolymer block contains a block (I) containing, as
a main constitutional unit, a constitutional unit represented by
the following structural formula (A):
--(CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.2)-- (A) and a block (II)
containing, as a main constitutional unit, a constitutional unit
represented by the following structural formula (B): ##STR1##
Inventors: |
YAMAMOTO; Shouji;
(Ibaraki-shi, Osaka, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
UNITED STATES
202-293-7060
202-293-7860
SUGHRUE@SUGHRUE.COM
|
Assignee: |
Nitto Denko Corporation
1-2, Shimohozumi 1-chome
Ibaraki-shi, Osaka
JP
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20070281152 A1 |
December 6, 2007 |
|
|
Family ID: |
38198573 |
Appl. No.: |
11/757452 |
Filed: |
June 4, 2007 |
Current U.S.
Class: |
428/343; 442/149;
442/151 |
Current CPC
Class: |
Y10T 428/31917 20150401;
Y10T 428/28 20150115; C09J 7/241 20180101; C09J 2203/326 20130101;
Y10T 428/31913 20150401; C09J 2453/006 20130101; Y10T 428/31924
20150401; Y10T 442/2754 20150401; Y10T 442/2738 20150401; H01L
21/6836 20130101; H01L 2221/68327 20130101; Y10T 428/31909
20150401; Y10T 428/31931 20150401 |
Class at
Publication: |
428/343; 442/149;
442/151 |
International
Class: |
B32B 27/04 20060101
B32B027/04; B32B 27/12 20060101 B32B027/12; B32B 7/12 20060101
B32B007/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 2, 2006 |
JP |
2006-154717 |
Claims
1. A pressure-sensitive adhesive sheet for dicing, which comprises
a base material and at least one pressure-sensitive adhesive layer
disposed on at least one surface the base material, wherein the
base material contains a polymer having a random copolymer block,
and wherein the random copolymer block contains: a block (I)
containing, as a main constitutional unit, a constitutional unit
represented by the following structural formula (A):
--(CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.2)-- (A) and a block (II)
containing, as a main constitutional unit, a constitutional unit
represented by the following structural formula (B): ##STR5##
2. The pressure-sensitive adhesive sheet according to claim 1,
wherein the block (I) and the block (II) are each contained in an
amount within a range of from 30 to 70% by weight based on the
weight of the polymer.
3. The pressure-sensitive adhesive sheet according to claim 1,
wherein the block (I) is a random copolymer block including the
constitutional unit represented by the structural formula (A) and
the constitutional unit represented by the structural formula (B),
and wherein the constitutional unit represented by the structural
formula (A) is contained in an amount within a range of from 65 to
95% by weight, and the constitutional unit represented by the
structural formula (B) is contained in an amount within a range of
from 5 to 35% by weight.
4. The pressure-sensitive adhesive sheet according to claim 1,
wherein the block (II) is a random copolymer block including the
constitutional unit represented by the structural formula (A) and
the constitutional unit represented by the structural formula (B),
and wherein the constitutional unit represented by structural
formula (A) is contained in an amount within a range of from 5 to
35% by weight, and the constitutional unit represented by
structural formula (B) is contained in an amount within a range of
from 65 to 95% by weight.
5. The pressure-sensitive adhesive sheet according to claim 1,
wherein the base material has a crystallinity of from 10 to 50% by
weight.
6. The pressure-sensitive adhesive sheet according to claim 1,
wherein the base material is composed of a monolayer film, and
contains the polymer in an amount of 50% by weight or more based on
the total weight of the base material.
7. The pressure-sensitive adhesive sheet according to claim 1,
wherein the base material is composed of a multilayer film, and at
least one layer of the multilayer film contains the polymer in an
amount of 50% by weight or more based on the total weight of the
layer.
8. The pressure-sensitive adhesive sheet according to claim 1,
wherein the pressure-sensitive adhesive layer contains a
radiation-curable adhesive.
9. The pressure-sensitive adhesive sheet according to claim 1,
wherein the base material is a base material obtainable by
polymerizing 1,3-butadiene as a main raw material monomer of the
block (I) and 1,2-butadiene as a main raw material monomer of the
block (II), followed by conducting a hydrogenation.
10. A method for processing a processed material, which comprises
performing dicing of the processed material to which a
pressure-sensitive adhesive sheet for dicing is stuck, thereby
forming pieces of the processed material, wherein the
pressure-sensitive adhesive sheet comprises a base material and at
least one pressure-sensitive adhesive layer disposed on at least
one surface the base material, wherein the base material contains a
polymer having a random copolymer block, and wherein the random
copolymer block contains: a block (I) containing, as a main
constitutional unit, a constitutional unit represented by the
following structural formula (A):
--(CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.2)-- (A) and a block (II)
containing, as a main constitutional unit, a constitutional unit
represented by the following structural formula (B): ##STR6##
11. The method according to claim 10, which further comprises
expanding the pressure-sensitive adhesive sheet after the dicing,
and then picking up the pieces of the processed material after the
dicing from the pressure-sensitive adhesive sheet.
12. The method according to claim 10, wherein the processed
material is a semiconductor element.
13. A piece of a processed material obtainable by the method
according to claim 10.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a pressure-sensitive
adhesive sheet for dicing. Further, the invention relates to a
method of performing dicing by using the pressure-sensitive
adhesive sheet for dicing and to small pieces of a processed
material obtainable by the dicing. The pressure-sensitive adhesive
sheet for dicing of the invention is particularly useful as a
pressure-sensitive adhesive sheet for dicing a semiconductor wafer,
which is used for fixing the processed material such as the
semiconductor wafer when the processed material such as the
semiconductor wafer is cut and separated (diced) and when small
pieces of the processed material which have been cut and separated
are expanded and separated (picked up). For example, the
pressure-sensitive adhesive sheet for dicing of the invention can
be used as a pressure-sensitive adhesive sheet for dicing a silicon
semiconductor, a pressure-sensitive adhesive sheet for dicing a
compound semiconductor, a pressure-sensitive adhesive sheet for
dicing a semiconductor package, a pressure-sensitive adhesive sheet
for dicing glass, and the like.
BACKGROUND OF THE INVENTION
[0002] Conventionally, a semiconductor wafer made of silicon,
gallium, arsenic or the like is produced in a state having a large
diameter, then cut and separated (diced) into small element pieces,
and further transferred to a mounting step. In this case, the
semiconductor wafer is subjected to respective steps of a dicing
step, a washing step, an expanding step, a pickup step and a
mounting step in a state where the semiconductor wafer is stuck
onto the pressure-sensitive adhesive sheet and retained thereby. As
the above-mentioned pressure-sensitive adhesive sheet, there has
been generally used a sheet in which an acrylic adhesive of about 1
to 200 .mu.m in thickness is applied onto a base material composed
of a plastic film.
[0003] The above-mentioned dicing step is usually performed using a
round blade (dicing blade) which moves with rotating. In that case,
cutting with the round blade is performed so that the blade reaches
an inside of the base material of the pressure-sensitive adhesive
sheet for dicing which retains the semiconductor package. At this
time, when cutting is performed into the inside of the base
material of the pressure-sensitive adhesive sheet, the plastic film
itself as the base material generates fibrous scraps thereof. When
the fibrous scraps are adhered to a side of a semiconductor chip,
the semiconductor chip is mounted in a state where the fibrous
scraps are adhered. As a result, the fibrous scraps have caused a
problem of a significant reduction in quality of an electronic
circuit.
[0004] As a means for solving such a problem, for example,
JP-A-5-156214 (patent document 1) proposes a wafer sticking sheet
using an ethylene-methacrylate copolymer as a base material.
However, although this wafer sticking sheet inhibits the generation
of fibrous scraps in some degree, it does not satisfy a level which
is endurable in the dicing step performed for obtaining further
highly reliable semiconductor devices.
[0005] Further, JP-A-5-211234 (patent document 2) discloses a
pressure-sensitive adhesive sheet for wafer sticking using a
polyolefinic film irradiated with an electron ray or a .gamma.-ray
at 1 to 80 MRad as a base material film. However, in this
pressure-sensitive adhesive sheet for wafer sticking, the damage of
the base material film caused by the radiation is extensive, and it
is difficult to obtain a film excellent in appearance. Moreover, a
great deal of cost is required in the production of the base
material film.
[0006] Furthermore, JP-A-2003-257893 (patent document 3) discloses
a pressure-sensitive adhesive sheet for dicing using a base
material film which contains an olefinic thermoplastic elastomer
containing propylene and ethylene and/or an .alpha.-olefin having 4
to 8 carbon atoms as polymerization components and having a melting
point peak temperature of 120.degree. C. to 170.degree. C., and an
ethylenic polymer containing ethylene as a main polymerization
component. However, this pressure-sensitive adhesive sheet for
dicing has the trade-off relation that the occurrence of whiskers
can be reduced by an increase in the ratio of propylene contained
in the base material film, whereas expandability is deteriorated.
Namely, the above-mentioned constitution can inhibit the occurrence
of fibrous scraps, but it is necessary to sacrifice expandability
to some degree.
[0007] Furthermore, as a means for solving the problem of
expandability, for example, JP-A-2-215528 (patent document 4)
discloses a multilayer film for dicing in which a thermoplastic
resin having rubber elasticity and an ethylenic resin layer are
laminated with each other through a pressure-sensitive adhesive
layer or directly. Further, it is described that the thermoplastic
resin having rubber elasticity is a polybutene-1, polyurethane or
polyester elastomer, or a saturated thermoplastic elastomer having
a crystallinity of 5% to 50% and an average molecular weight of
80,000 or more, which is obtained by hydrogenating a
1,2-polybutadiene, styrene-butadiene-styrene or
styrene-isoprene-styrene block copolymer. However, although this
multilayer film for dicing improves expandability, a lot of fibrous
scraps are generated in dicing. Accordingly, it is difficult to
produce a semiconductor chip which secures high reliability.
[0008] Patent Document 1: JP-A-5-156214
[0009] Patent Document 2: JP-A-5-211234
[0010] Patent Document 3: JP-A-2003-257893
[0011] Patent Document 4: JP-A-2-215528
SUMMARY OF THE INVENTION
[0012] The invention intends to solve the problems associated with
the conventional techniques as described above, and an object of
the invention is to provide a pressure-sensitive adhesive sheet for
dicing which inhibits the generation of fibrous scraps and has good
expandability. Further, another object of the invention is to
provide a method for processing a processed material, using the
pressure-sensitive adhesive sheet for dicing. Furthermore, a
further object of the invention is to provide a small piece of the
processed material which is obtainable by the dicing method.
[0013] The present inventors have found that the above-mentioned
objects can be achieved by using a polymer having a specific
polymerization regularity as a constituent material of a base
material film, thus arriving at completion of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic cross-sectional view showing an
outline of a pressure-sensitive adhesive sheet for dicing according
to one embodiment of the invention.
DESCRIPTION OF REFERENCE NUMERALS AND SIGNS
[0015] 10: Pressure-sensitive adhesive sheet for dicing [0016] 11:
Base material film (base material) [0017] 12: Pressure-sensitive
adhesive layer [0018] 13: Separator
DETAILED DESCRIPTION OF THE INVENTION
[0019] Namely, in order to solve the above-mentioned problems, the
present invention relates to the following (1) to (9).
[0020] (1) A pressure-sensitive adhesive sheet for dicing, which
comprises a base material and at least one pressure-sensitive
adhesive layer disposed on at least one surface the base
material,
[0021] wherein the base material contains a polymer having a random
copolymer block, and
[0022] wherein the random copolymer block contains:
[0023] a block (I) containing, as a main constitutional unit, a
constitutional unit represented by the following structural formula
(A): --(CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.2)-- (A)
[0024] and a block (II) containing, as a main constitutional unit,
a constitutional unit represented by the following structural
formula (B): ##STR2##
[0025] (2) The pressure-sensitive adhesive sheet according to (1),
wherein the block (I) and the block (II) are each contained in an
amount within a range of from 30 to 70% by weight based on the
weight of the polymer.
[0026] (3) The pressure-sensitive adhesive sheet according to (1),
wherein the block (I) is a random copolymer block including the
constitutional unit represented by the structural formula (A) and
the constitutional unit represented by the structural formula (B),
and
[0027] wherein the constitutional unit represented by the
structural formula (A) is contained in an amount within a range of
from 65 to 95% by weight, and the constitutional unit represented
by the structural formula (B) is contained in an amount within a
range of from 5 to 35% by weight.
[0028] (4) The pressure-sensitive adhesive sheet according to (1),
wherein the block (II) is a random copolymer block including the
constitutional unit represented by the structural formula (A) and
the constitutional unit represented by the structural formula (B),
and
[0029] wherein the constitutional unit represented by structural
formula (A) is contained in an amount within a range of from 5 to
35% by weight, and the constitutional unit represented by
structural formula (B) is contained in an amount within a range of
from 65 to 95% by weight.
[0030] (5) The pressure-sensitive adhesive sheet according to (1),
wherein the base material has a crystallinity of from 10 to 50% by
weight.
[0031] (6) The pressure-sensitive adhesive sheet according to (1),
wherein the base material is composed of a monolayer film, and
contains the polymer in an amount of 50% by weight or more based on
the total weight of the base material.
[0032] (7) The pressure-sensitive adhesive sheet according to (1),
wherein the base material is composed of a multilayer film, and at
least one layer of the multilayer film contains the polymer in an
amount of 50% by weight or more based on the total weight of the
layer.
[0033] (8) The pressure-sensitive adhesive sheet according to (1),
wherein the pressure-sensitive adhesive layer contains a
radiation-curable adhesive.
[0034] (9) The pressure-sensitive adhesive sheet according to (1),
wherein the base material is a base material obtainable by
polymerizing 1,3-butadiene as a main raw material monomer of the
block (I) and 1,2-butadiene as a main raw material monomer of the
block (II), followed by conducting a hydrogenation.
[0035] According to the above-mentioned constitution, the base
material is constituted to include a random copolymer block having
block (I) and block (II), so that it becomes possible to control
the degree of crystallinity of the base material. As a result, the
generation of fibrous scraps can be inhibited by controlling the
crystallinity so as not to be excessively decreased, whereas a
decrease in extension can be prevented by controlling the
crystallinity so as not to be excessively increased. That is to
say, the above-mentioned constitution can provide the
pressure-sensitive adhesive sheet for dicing excellent in balance
between inhibition of the generation of fibrous scraps and
improvement in expandability.
[0036] The contents of the above-mentioned block (I) and block (II)
are each preferably within a range of from 30 to 70% by weight
based on the weight of the above-mentioned polymer.
[0037] When the content of the block (I) exceeds 70% by weight, or
when the content of the block (II) is less than 30% by weight,
extensibility is unfavorably decreased by an excessive increase in
crystallinity of the base material, whereby expandability is
decreased in some cases. Further, when the content of the block (I)
is less than 30% by weight, or when the content of the block (II)
exceeds 70% by weight, fibrous scraps are unfavorably generated in
some cases by an excessive decrease in crystallinity of the base
material.
[0038] It is preferred that the above-mentioned block (I) is a
random copolymer block of a constitutional unit represented by the
above-mentioned structural formula (A) and a constitutional unit
represented by the above-mentioned structural formula (B), and that
the content of the constitutional unit represented by the
above-mentioned structural formula (A) is within a range of from 65
to 95% by weight, and the content of the constitutional unit
represented by the above-mentioned structural formula (B) is within
a range of from 5 to 35% by weight.
[0039] Further, it is preferred that the above-mentioned block (II)
is a random copolymer block of a constitutional unit represented by
the above-mentioned structural formula (A) and a constitutional
unit represented by the above-mentioned structural formula (B), and
that the content of the constitutional unit represented by the
above-mentioned structural formula (A) is within a range of from 5
to 35% by weight, and the content of the constitutional unit
represented by the above-mentioned structural formula (B) is within
a range of from 65 to 95% by weight.
[0040] The crystallinity of the above-mentioned base material is
preferably from 10 to 50% by weight. The crystallinity is a value
measured using X-ray diffraction.
[0041] The above-mentioned base material is preferably composed of
a monolayer film, and preferably contains the above-mentioned
polymer in an amount of 50% by weight or more based on the total
weight of the base material.
[0042] The above-mentioned base material is preferably composed of
a multilayer film, and at least one layer of the multilayer film
preferably contains the above-mentioned polymer in an amount of 50%
by weight or more based on the total weight of the layer.
[0043] The above-mentioned pressure-sensitive adhesive layer
preferably contains a radiation-curable adhesive.
[0044] In the case that the radiation-curable adhesive is contained
in the pressure-sensitive adhesive layer, it is possible to
decrease adhesive force of the pressure-sensitive adhesive layer by
irradiation of a radiation. As a result, when a processed material
is cut and separated to form small pieces of the processed
material, followed by separation of the small pieces from the
pressure-sensitive adhesive sheet for dicing, the separation can be
easily performed.
[0045] The above-mentioned base material is preferably a base
material obtainable by polymerizing 1,3-butadiene as a main raw
material monomer of the block (I) and 1,2-butadiene as a main raw
material monomer of the block (II), followed by conducting a
hydrogenation.
[0046] According to the base material having the above-mentioned
constitution, in block (I) containing the above-mentioned
structural formula (A) as a main constitutional unit, polybutadiene
having the structure of structural formula (A) by hydrogenation
shows a structure similar to that of polyethylene. Moreover, the
abundance ratio of the above-mentioned structural formula (B) is
small, so that regularity is little disrupted, which makes it easy
to induce crystallization in block (I).
[0047] On the other hand, in block (II) containing the
above-mentioned structural formula (B) as a main constitutional
unit, polybutadiene having the structure of structural formula (B)
by hydrogenation shows a structure similar to that of polybutene.
Moreover, the abundance ratio of the above-mentioned structural
formula (A) is small, so that regularity is little disrupted, which
makes it easy to induce crystallization in block (II). Accordingly,
different from an ordinary hydrogenated product of a copolymer
including 1,2-butadiene and 1,3-butadiene, a base material
containing a random copolymer block having high crystallinity can
be obtained.
[0048] Further, the present invention relates to the following (10)
to (12).
[0049] (10) A method for processing a processed material, which
comprises performing dicing of the processed material to which a
pressure-sensitive adhesive sheet for dicing is stuck, thereby
forming pieces of the processed material,
[0050] wherein the pressure-sensitive adhesive sheet comprises a
base material and at least one pressure-sensitive adhesive layer
disposed on at least one surface the base material,
[0051] wherein the base material contains a polymer having a random
copolymer block, and
[0052] wherein the random copolymer block contains:
[0053] a block (I) containing, as a main constitutional unit, a
constitutional unit represented by the following structural formula
(A): --(CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.2)-- (A)
[0054] and a block (II) containing, as a main constitutional unit,
a constitutional unit represented by the following structural
formula (B): ##STR3##
[0055] (11) The method according to (10), which further comprises
expanding the pressure-sensitive adhesive sheet after the dicing,
and then picking up the pieces of the processed material after the
dicing from the pressure-sensitive adhesive sheet.
[0056] (12) The method according to (10), wherein the processed
material is a semiconductor element.
[0057] According to the above-mentioned method, the processed
material is diced using the pressure-sensitive adhesive sheet for
dicing which is capable of inhibiting the generation of fibrous
scraps from the base material, so that adhesion of fibrous scraps
to the small pieces of the processed material after dicing can be
decreased. Accordingly, significant deterioration of quality of the
small pieces of the processed material can be inhibited, whereby
the yield can be thus improved.
[0058] Further, in the above-mentioned method, the above-mentioned
pressure-sensitive adhesive sheet for dicing is expanded after the
dicing has been performed, and small pieces of the processed
material after cutting can be picked up from the pressure-sensitive
adhesive sheet for dicing.
[0059] The pressure-sensitive adhesive sheet for dicing used in
this method inhibits the generation of fibrous scraps and has good
expandability, so that the spacing between the small pieces of the
processed material which are adjacent to each other can be
sufficiently secured when the pressure-sensitive adhesive sheet for
dicing is expanded, thereby being able to prevent the small pieces
of the processed material from causing damaging to each other in
the course of picking up. Thus, the yield can be further
improved.
[0060] As the above-mentioned processed material, a semiconductor
element can be used.
[0061] Furthermore, the present invention relates to the following
(13).
[0062] (13) A piece of a processed material obtainable by the
method according to (10).
[0063] The invention accomplishes advantages as described below
according to the means described above.
[0064] Namely, according to the pressure-sensitive adhesive sheet
for dicing of the invention, since a base material containing a
random copolymer block of block (I) containing the above-mentioned
structural formula (A) as a main constitutional unit and block (II)
containing the above-mentioned structural formula (B) as a main
constitutional unit is employed, it is possible to control the
degree of crystallinity of the base material. As a result, the
pressure-sensitive adhesive sheet for dicing excellent in balance
between inhibition of the generation of fibrous scraps and
expandability can be provided.
[0065] Further, according to the method for processing a processed
material of the invention, since the processed material is
processed using the above-mentioned adhesive sheet for dicing, the
generation of fibrous scraps is inhibited in dicing the processed
material and good expandability is exerted in expanding. As a
result, adhesion of fibrous scraps to small pieces of the processed
material is inhibited. Thus, the yield can be improved, and the
production cost can be decreased.
[0066] The pressure-sensitive adhesive sheet for dicing according
to one embodiment of the invention will be illustrated in detail
below with reference to FIG. 1. FIG. 1 is a schematic
cross-sectional view showing an outline of the pressure-sensitive
adhesive sheet for dicing (hereinafter referred to as the
pressure-sensitive adhesive sheet) according to one embodiment of
the invention. As shown in FIG. 1, the pressure-sensitive adhesive
sheet 10 has a constitution in which a pressure-sensitive adhesive
layer 12 and a separator 13 are laminated on one surface of a base
material film (base material) 11 in this order.
[0067] The pressure-sensitive adhesive sheet may take an
appropriate form depending on its application, such as a sheet form
or a roll form. For example, in the case of a dicing application of
a semiconductor wafer, one previously cut to a specified form can
be preferably used. In this embodiment, a description is given
taking as an example the sheet in which the pressure-sensitive
adhesive layer 12 is provided on only one surface of the base
material film 11, but the invention should not be construed as
being limited thereto. For example, the pressure-sensitive adhesive
layers 12 may be provided on both surfaces of the base material
film 11.
[0068] The base material film 11 sustains the strength of the
pressure-sensitive adhesive sheet 10. The base material film 11
includes a polymer having a random copolymer block. The random
copolymer block has block (I) and block (II). Further, block (I)
contains a constitutional unit represented by the following
structural formula (A):
--(CH.sub.2--CH.sub.2--CH.sub.2--CH.sub.2)-- (A) as a main
constitutional unit, and block (II) contains a constitutional unit
represented by the following structural formula (B): ##STR4## as a
main constitutional unit.
[0069] When the base material film 11 is composed of a monolayer
film, the above-mentioned polymer having the random copolymer block
is preferably contained in an amount of 50% by weight or more. On
the other hand, when the base material film 11 is composed of a
multilayer film, at least one layer of the multilayer film
preferably contains the above-mentioned polymer in an amount of 50%
by weight or more.
[0070] The block (I) containing the constitutional unit represented
by the above-mentioned structural formula (A) as a main
constitutional unit is formed using, for example, 1,3-butadiene as
a main constitutional monomer, and the block (II) containing the
constitutional unit represented by the above-mentioned structural
formula (B) as a main constitutional unit is formed using, for
example, 1,2-butadiene as a main constitutional monomer.
[0071] The contents of the above-mentioned block (I) and block (II)
are each preferably within the range of 30 to 70% by weight based
on the weight of the random copolymer. When the content of the
block (I) exceeds 70% by weight, or when the content of the block
(II) is less than 30% by weight, extensibility is unfavorably
decreased by an excessive increase in crystallinity of the base
material, whereby expandability is decreased in some cases.
Further, when the content of the block (I) is less than 30% by
weight, or when the content of the block (II) exceeds 70% by
weight, fibrous scraps are unfavorably generated in some cases by
an excessive decrease in crystallinity of the base material.
[0072] The constitutional unit represented by the above-mentioned
structural formula (B) may be contained in the above-mentioned
block (I). In this case, it is preferred that the content of the
constitutional unit represented by the above-mentioned structural
formula (A) is within a range of from 65 to 95% by weight, and that
the constitutional unit represented by the above-mentioned
structural formula (B) is within a range of from 5 to 35% by
weight.
[0073] The constitutional unit represented by the above-mentioned
structural formula (A) may be contained in the above-mentioned
block (II). In this case, it is preferred that the content of the
constitutional unit represented by the above-mentioned structural
formula (A) is within a range of from 5 to 35% by weight, and that
the constitutional unit represented by the above-mentioned
structural formula (B) is within a range of from 65 to 95% by
weight.
[0074] The above-mentioned polymer has high stereoregularity due to
the structure thereof, and crystallization in the random copolymer
block is liable to occur. Accordingly, the above-mentioned polymer
has relatively high crystallinity. The crystallinity of the
above-mentioned base material film 11 is preferably from 10 to 50%
by weight. When the crystallinity is less than 10% by weight,
fibrous scraps are unfavorably generated in some cases. On the
other hand, when the crystallinity exceeds 50% by weight,
expandability is deteriorated to unfavorably cause breakage of the
base material film 11 in expanding in some cases.
[0075] In order to enhance adhesion and retention to an adjacent
layer, a surface of the base material film 11 may be subjected to a
conventional surface treatment, for example, chemical or physical
treatment such as chromic acid treatment, ozone exposure, flame
exposure, high-pressure electric shock exposure or ionized
radiation treatment, or coating treatment with a primer (for
example, an adhesive material described later).
[0076] In order to impart antistatic ability to the base material
film 11, a deposited layer (about 30 to 500 angstroms in thickness)
made of a conductive material such as a metal, an alloy or an oxide
thereof may be provided on the above-mentioned base material film
11. The base material film 11 may be either a monolayer or a
multilayer including two or more kinds of layers. When the
pressure-sensitive adhesive layer 12 described later is of a
radiation-curable type, there is used a layer which allows a
radiation such as an X-ray, an ultraviolet ray or an electron beam
to at least partially permeate.
[0077] Although the thickness of the base material film 11 can be
appropriately determined without any particular limitation, it is
generally about from 10 to 300 .mu.m, preferably about from 25 to
200 .mu.m, and more preferably about from 30 to 200 .mu.m.
[0078] In the base material film 11, various additives, for
example, a softener such as mineral oil, a filler such as calcium
carbonate, silica, talc, mica or clay, an antioxidant, a light
stabilizer, an antistatic agent, a lubricant, a dispersing agent
and a neutralizing agent may be optionally blended. Further, the
base material film 11 may be optionally subjected to uniaxial or
biaxial stretching treatment. Furthermore, the base material film
11 can be optionally subjected to a conventional physical or
chemical treatment such as matting treatment, corona discharge
treatment or primer treatment.
[0079] The base material film 11 may be produced, for example, in
the following manner. That is to say, a random copolymer having the
structural formula (A) as a main constitutional unit is first
produced in the presence of 65 to 95% by weight of 1,3-butadiene
and 5 to 35% by weight of 1,2-butadiene. Then, a random copolymer
having the structural formula (B) as a main constitutional unit is
produced in the presence of 65 to 95% by weight of 1,2-butadiene
and 5 to 35% by weight of 1,3-butadiene. Thereafter, hydrogenation
is performed under specified conditions to remove remaining double
bonds, thereby preparing a material for forming the base material
film 11. In this regard, the preparation method of the material for
forming the base material film 11 should not be construed as being
limited to the above.
[0080] Film formation of the base material film 11 can be performed
by a conventional film forming method, using the above-mentioned
forming material. As the film forming method, there is exemplified,
for example, calender film formation, casting film formation,
inflation extrusion, T-die extrusion or the like.
[0081] As the adhesive constituting the pressure-sensitive adhesive
layer 12, there can be used a pressure-sensitive adhesive which has
been generally used. Specifically, there may be used various
adhesives such as a rubber-based adhesive, an acrylic adhesive, a
silicone-based adhesive, a polyester-based adhesive and a polyvinyl
acetate-based adhesive. As the above-mentioned adhesive, preferred
is a (meth)acrylic adhesive having a (meth)acrylic polymer as a
base polymer, in terms of adhesiveness to a semiconductor wafer or
a semiconductor package as the processed material, cleaning
properties of a semiconductor wafer or the like with ultrapure
water or an organic solvent such as an alcohol, and the like. As
the (meth)acrylic polymer, there is ordinarily used a polymer of an
alkyl (meth)acrylate or a copolymer thereof with a copolymerizable
monomer. As a main monomer of the (meth)acrylic polymer, preferred
is an alkyl (meth)acrylate whose homopolymer has a glass transition
temperature of 20.degree. C. or less. In this regard, the alkyl
(meth)acrylate means an alkyl acrylate and/or an alkyl
methacrylate, and the term (meth) used in the present specification
unexceptionally has the same meaning.
[0082] Examples of the above-mentioned (meth)acrylic polymers
include (meth)acrylic polymers in which one or two or more of alkyl
esters of (meth)acrylic acid (for example, alkyl esters having 1 to
30 carbon atoms, particularly straight-chain or branched alkyl
esters having 4 to 18 carbon atoms, such as a methyl ester, an
ethyl ester, a propyl ester, an isopropyl ester, a butyl ester, an
isobutyl ester, a s-butyl ester, a t-butyl ester, a pentyl ester,
an isopentyl ester, a hexyl ester, a heptyl ester, an octyl ester,
a 2-ethylhexyl ester, an isooctyl ester, an isononyl ester, a decyl
ester, an isodecyl ester, an undecyl ester, a dodecyl ester, a
tridecyl ester, a tetradecyl ester, a hexadecyl ester, an octadecyl
ester and an eicocyl ester), cycloalkyl esters of (meth)acrylic
acid (for example, a cyclopentyl ester and a cyclohexyl ester),
hydroxyalkyl esters of (meth)acrylic acid (for example, a
hydroxyethyl ester, hydroxybutyl ester and a hydroxyhexyl ester),
glycidyl (meth)acrylate, (meth)acrylic acid, itaconic acid, maleic
anhydride, (meth)acrylic acid amide, (meth)acrylic acid
N-hydroxymethylamide, alkylaminoalkyl esters of (meth)acrylic acid
(for example, dimethylaminoethyl methacrylate and t-butylaminoethyl
methacrylate), vinyl acetate and styrene are used as monomer
components.
[0083] In order to modify cohesion force, adhesiveness or the like,
the above-mentioned (meth)acrylic polymer may contain a unit
corresponding to another monomer component copolymerizable with the
above-mentioned alkyl ester or cycloalkyl ester of (meth)acrylic
acid, according to the necessity. Examples of such monomer
components include carboxyl group-containing monomers such as
acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate,
carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric
acid and crotonic acid; acid anhydride monomers such as maleic
anhydride and itaconic anhydride; hydroxyl group-containing
monomers such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl
(meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl
(meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl
(meth)acrylate, 12-hydroxylauryl (meth)acrylate and
(4-hydroxymethylcyclohexyl)methyl (meth)acrylate; sulfonic acid
group-containing monomers such as styrenesulfonic acid,
allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic
acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl
(meth)acrylate and (meth)acryloyloxynaphthalenesulfonic acid;
phosphoric acid-containing monomers such as 2-hydroxyethylacryloyl
phosphate; acrylamide, acrylonitrile and the like. These
copolymerizable monomer components can be used either alone or as a
mixture of two or more thereof. The amount of these copolymerizable
monomers used is preferably 30% by weight or less, and more
preferably 15% by weight or less, based on the total monomer
components.
[0084] Further, the above-mentioned (meth)acrylic polymer may also
contain a multifunctional monomer or the like as a monomer
component for copolymerization according to the necessity, in order
to crosslink this polymer. Self-sustaining properties of the
pressure-sensitive adhesive layer is improved by crosslinking the
base polymer, so that large deformation of the pressure-sensitive
adhesive sheet can be prevented, which makes it easy to maintain a
flat plate form of the pressure-sensitive adhesive sheet 10.
[0085] Examples of the multifunctional monomers include hexanediol
di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate,
(poly)propylene glycol di(meth)acrylate, neopentyl glycol
di(meth)acrylate, pentaerythritol di(meth)acrylate,
trimethylolpropane tri(meth)acrylate, pentaerythritol
tri(meth)acrylate dipentaerythritol hexa(meth)acrylate, epoxy
(meth)acrylate, polyester (meth)acrylate, and urethane
(meth)acrylate. These multifunctional monomers can also be used
either alone or as a mixture of two or more thereof. The amount of
the multifunctional monomer is preferably 30% by weight or less
based on the total monomer components, in terms of adhesive
characteristics and the like.
[0086] The above-mentioned (meth)acrylic polymer is obtained by
polymerizing a single monomer or a mixture of two or more kinds of
monomers. Polymerization can be conducted by any system of solution
polymerization, emulsion polymerization, bulk polymerization,
suspension polymerization and photopolymerization. In particular,
when polymerization is conducted by irradiation of a radiation such
as an ultraviolet ray or an electron beam, it is preferred that a
liquid composition obtained by blending the monomer component and a
photopolymerization initiator with a urethane (meth)acrylate-based
oligomer is cast and photopolymerized, thereby synthesizing the
(meth)acrylic polymer.
[0087] The above-mentioned urethane (meth)acrylate-based oligomer
has a number average molecular weight of about 500 to 100,000,
preferably 1,000 to 30,000, and is a bifunctional compound having
an ester diol as a main skeleton. Further, the examples of the
monomer components include morpholine (meth)acrylate, isobonyl
(meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl
(meth)acrylate, and methoxylated cyclodecatriene (meth)acrylate.
The mixing ratio of the urethane (meth)acrylate-based oligomer to
the monomer component is preferably from 95:5 to 5:95, and more
preferably from 50:50 to 70:30. When the content of the urethane
(meth)acrylate-based oligomer is high, the viscosity of the liquid
composition increases to cause the tendency of polymerization to
become difficult.
[0088] In terms of contamination prevention and the like of the
processed material, it is preferred that the content of a low
molecular weight material in the pressure-sensitive adhesive layer
12 is low. In view of this, the number average molecular weight of
the (meth)acrylic polymer is preferably about from 200,000 to
3,000,000, and more preferably about from 250,000 to 1,500,000.
[0089] Further, in order to increase the number average molecular
weight of the (meth)acrylic polymer as the base polymer, an
external crosslinking agent may also be appropriately employed in
the above-mentioned adhesive. Specific means of external
crosslinking methods include a method of adding a so-called
crosslinking agent such as a polyisocyanate compound, a melamine
resin, a urea resin an epoxy resin or a polyamine carboxyl
group-containing polymer and allowing it to react. When the
external crosslinking agent is used, the amount thereof used is
appropriately determined depending on the balance with the base
polymer to be crosslinked, and further depending on its application
as an adhesive. In general, it is preferably blended in an amount
of about 1 to 5 parts by weight based on 100 parts by weight of the
above-mentioned base polymer. Further, various additives such as a
tackifier and an antiaging agent which have hitherto been known, as
well as the above-mentioned components, may be optionally used in
the adhesive.
[0090] Furthermore, as the above-mentioned adhesive, the
radiation-curable adhesive can be used. As the radiation-curable
adhesive, there can be used one having a radiation-curable
functional group such as a carbon-carbon double bond and showing
adhesion, without any particular limitation. As the
radiation-curable adhesive, desirable is an ultraviolet-curable
adhesive which decreases in adhesive force by ultraviolet
irradiation. According to such a pressure-sensitive adhesive layer
12, the pressure-sensitive adhesive sheet 10 can be easily
separated by ultraviolet irradiation after a back-grinding step or
a dicing step.
[0091] The ultraviolet-curable adhesive can be constituted, for
example, by a homopolymer of the above-mentioned (meth)acrylic acid
ester or a copolymer thereof with a copolymerizable comonomer (an
acrylic polymer), an ultraviolet-curable component (which may be
one obtained by adding a carbon-carbon double bond to a side chain
of the above-mentioned acrylic polymer), a photopolymerization
initiator, and optional conventional additives such as a
crosslinking agent, a tackifier, a filler, an antiaging agent and a
coloring agent.
[0092] The above-mentioned ultraviolet-curable component may be any
one, so long as it is a monomer, oligomer or polymer having a
carbon-carbon double bond in the molecule thereof and curable by
radical polymerization. Specific examples thereof include esters of
polyvalent alcohols and (meth)acrylic acid, such as a urethane
oligomer, urethane (meth)acrylate, tetramethylolmethane
tetra(meth)acrylate, trimethylolpropane tri(meth)acrylate,
pentaerythritol tri(meth)acrylate, pentaerythritol
tetra(meth)acrylate, dipentaerythritol monohydroxy
penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate,
1,4-butanediol di(meth)acrylate, tetraethylene glycol
di(meth)acrylate and 1,6-hexanediol di(meth)acrylate; acrylate
oligomers; and isocyanurate or isocyanurate compounds such as
2-propenyl-di-3-butenyl cyanurate,
2-hydroxyethylbis(2-acryloxyethyl) isocyanurate and
tris(2-methacryloxyethyl) isocyanurate. When the
ultraviolet-curable polymer having a carbon-carbon double bond on
the side chain of the polymer is employed as an acrylic polymer, it
is unnecessary to particularly add the above-mentioned
ultraviolet-curable component. The amount of the
ultraviolet-curable monomer or oligomer component blended is, for
example, about from 20 to 200 parts by weight, and preferably about
from 50 to 150 parts by weight, based on 100 parts by weight of the
base polymer such as the (meth)acrylic polymer constituting the
adhesive.
[0093] Further, examples of the radiation-curable adhesives
include, in addition to the addition type radiation curable
adhesive described above, an internal type radiation-curable
adhesive using as the base polymer a polymer having a carbon-carbon
double bond on a side chain of the polymer, in a main chain thereof
or at a terminal end of the main chain. The internal type
radiation-curable adhesive is not required to contain the oligomer
component or the like as a low molecular weight component, or does
not contain it in large amounts, so that the oligomer component or
the like does not move in the adhesive with time. Accordingly, the
pressure-sensitive adhesive layer 12 having a stable layer
structure can be formed.
[0094] As the above-mentioned carbon-carbon double bond-containing
base polymer, there can be used one having a carbon-carbon double
bond and having adhesion property without any particular
limitation. As such a base polymer, preferred is one having the
(meth)acrylic polymer as a basic skeleton. Examples of the basic
acrylic polymer skeleton include the (meth)acrylic polymers
exemplified above.
[0095] When the carbon-carbon double bond is introduced into the
polymer side chain in the above-mentioned (meth)acrylic polymer,
molecular design becomes easy. A method for introducing the
carbon-carbon double bond is not particularly limited, and various
methods can be employed. For example, there is mentioned a method
of previously copolymerizing a functional group-containing monomer
with the (meth)acrylic polymer, and then allowing a compound having
a functional group reactable with the above functional group and
the carbon-carbon double bond to react by condensation or addition
while maintaining radiation curability of the carbon-carbon double
bond.
[0096] Examples of combinations of these functional groups include
a carboxylic acid group and an epoxy group, a carboxylic acid group
and an aziridyl group, and a hydroxyl group and an isocyanate
group. Among these combinations of the functional groups, the
combination of a hydroxyl group and an isocyanate group is suitable
from the viewpoint of easy tracing of the reaction. Further, by
combining these functional groups, the functional group may be
either on the side of the (meth)acrylic polymer or on the side of
the above-mentioned compound, so long as it is such a combination
that the above-mentioned carbon-carbon bond-containing
(meth)acrylic polymer is formed. However, in the above-mentioned
preferred combination, the case where the (meth)acrylic polymer has
the hydroxyl group and the above-mentioned compound has the
isocyanate group is suitable. In this case, examples of the
carbon-carbon double bond-containing isocyanate compounds include
methacryloyl isocyanate, 2-methacryloyloxyethyl isocyanate, and
m-isopropenyl-.alpha.,.alpha.-dimethylbenzyl isocyanate. Further,
examples of the (meth)acrylic polymers include the hydroxy
group-containing monomers exemplified above, and copolymers
obtained by copolymerizing ether-based compounds such as
2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether and
diethylene glycol monovinyl ether.
[0097] As the above-mentioned internal type radiation-curable
adhesive, the above-mentioned carbon-carbon double bond-containing
base polymer (particularly, the (meth)acrylic polymer) may be used
solely. Further, the above-mentioned radiation-curable monomer or
oligomer component may be blended in such a degree that the
characteristics are not deteriorated. The amount of the
radiation-curable oligomer component or the like blended is usually
30 parts by weight or less, and preferably 10 parts by weight or
less, based on 100 parts by weight of the base polymer.
[0098] The above-mentioned polymerization initiator may be any one,
so long as it is a substance which cleaves by irradiation of an
ultraviolet ray having an appropriate wavelength acting as a
trigger for the polymerization reaction to form a radical. Specific
examples thereof include benzoin alkyl ethers such as benzoyl
methyl ether, benzoin isopropyl ether and benzoin isobutyl ether;
aromatic ketones such as benzyl, benzoin, benzophenone and
.alpha.-hydroxycyclohexyl phenyl ketone; aromatic ketals such as
benzyl dimethyl ketal; polyvinyl benzophenone; and thioxanthones
such as chlorothioxanthone, dodecylthioxanthone,
dimethylthioxanthone and diethylthioxanthone. The amount of the
polymerization initiator blended is about from 0.1 to 20 parts by
weight, and preferably from 1 to 10 parts by weight, based on 100
parts by weight of the base polymer such as the (meth)acrylic
polymer or the like constituting the adhesive.
[0099] On the other hand, examples of the above-mentioned
heat-releasable adhesives include a heat foaming type adhesive in
which fine heat-expandable particles are blended with a general
pressure-sensitive adhesive. The pressure-sensitive adhesive layer
12 foams or expands by heating the pressure-sensitive adhesive
containing the fine heat-expandable particles after the object of
adhering an article has been attained, to change a surface of the
pressure-sensitive adhesive layer 12 to an uneven form, thus
decreasing adhesive force by a decrease in adhered area with an
adherend, which makes the article easily separable. This has
therefore been used for a wide variety of purposes, such as fixing
in processing electronic parts, materials therefor or the like and
physical distribution such as conveyance.
[0100] There is no particular limitation on the fine
heat-expandable particles, and various inorganic or organic
heat-expandable microspheres can be selected to use so that a
combination of microspheres having different release initiation
temperatures, a low release initiation temperature and a high
release initiation temperature, is obtained. The difference in
release separation temperature between these two types of
heat-expandable microspheres can be appropriately determined
depending on processing accuracy such as temperature-sensitive
characteristics of the heat-expandable microspheres. However, the
difference between these temperatures is set generally from 20 to
70.degree. C., and preferably from 30 to 50.degree. C.
[0101] In the heat foaming type adhesive, the adhered area
decreases by foaming of the fine heat-expandable particles due to
heat to make separation easy. The average particle size of the fine
heat-expandable particles is preferably about from 1 to 25 .mu.m,
more preferably from 5 to 15 .mu.m, and particularly preferably
about 10 .mu.m.
[0102] As the fine heat-expandable particles, a material expandable
under heating can be used without any particular limitation.
However, fine heat-expandable particles obtained by
microencapsulating a heat-expandable material are preferably used
in terms of an easy mixing operation and the like. For example,
they may be used any one, so long as they are microspheres in which
a material easily gasified by heating, such as isobutane, propane
or pentane, is encapsulated in shells having elasticity. The
above-mentioned shells are usually formed by a thermoplastic
material, a thermofusible material, a material which bursts by heat
expansion or the like. The materials for forming the
above-mentioned shells include, for example, a vinylidene
chloride-acrylonitrile copolymer, polyvinyl alcohol, polyvinyl
butyral, polymethyl methacrylate, polyacrylonitrile polyvinylidene
chloride, and polysulfone. The heat-expandable microcapsules have
an advantage of excellent dispersion mixability with the
above-mentioned adhesive. Commercially available products of the
heat-expandable microcapsules include, for example, Microsphere
(trade name: manufactured by Matsumoto Yushi-Seiyaku Co., Ltd.). In
addition, a heat expansion aid may be optionally added.
[0103] For the amount of the fine heat-expandable particles
(heat-expandable microcapsules) blended with the above-mentioned
adhesive, an amount which can decrease its adhesive force can be
appropriately determined depending on the kind of the
above-mentioned pressure-sensitive adhesive layer 12. In general,
the fine heat-expandable particles are blended in an amount which
can maintain the thickness of the pressure-sensitive adhesive layer
12 containing the fine heat-expandable particles to 60% or more,
preferably 70% or more, and more preferably 80% or more, of the
thickness thereof immediately after heat expansion. Further, the
amount thereof is about from 1 to 100 parts by weight, preferably
from 5 to 40 parts by weight, and more preferably from 10 to 20
parts by weight, based on 100 parts by weight of the base
polymer.
[0104] The thickness of the pressure-sensitive adhesive layer 12 is
preferably about from 1 .mu.m to 200 .mu.m, and more preferably
about from 3 .mu.m to 50 .mu.m, in terms of compatibility of
adhesion fixability with releasability. Further, the adhesive force
of the pressure-sensitive adhesive layer 12 is not particularly
limited, so long as it is within the range in which the
pressure-sensitive adhesive layer is finally easily separable from
a support wafer. For example, the value of the 180.degree. peel
adhesive force to a semiconductor wafer is preferably within a
range of 1 to 30 N/10 mm, and more preferably within a range of 5
to 20 N/10 mm.
[0105] The formation of the pressure-sensitive adhesive layer 12 on
the base material film 11 is performed, for example, by applying an
adhesive-containing composition, followed by drying (performing
heat crosslinking as needed). Coating systems include roll coating,
screen coating, and gravure coating. Further, coating may be
directly made on the base material, or the composition may be
applied onto release paper whose surface is subjected to release
treatment, followed by transfer thereof to the base material.
Subsequently, the separator 13 described later is stuck onto the
surface of the pressure-sensitive adhesive layer 12, whereby the
pressure-sensitive adhesive sheet 10 according to this embodiment
can be obtained.
[0106] When the pressure-sensitive adhesive layer 12 is composed of
the radiation-curable adhesive such as the ultraviolet-curable
adhesive, the base material film 11 is required to have sufficient
radiation permeability, because the pressure-sensitive adhesive
layer 12 is irradiated with a radiation before or after dicing.
[0107] The above-mentioned separator 13 may be optionally provided
for label processing or for the purpose of smoothing the surface of
the pressure-sensitive adhesive layer 12. Constituent materials of
the separator 13 include paper, a film of a synthetic resin such as
polyethylene, polypropylene or polyethylene terephthalate, and the
like. In order to enhance releasability from the pressure-sensitive
adhesive layer 12, release treatment such as silicone treatment,
long-chain alkyl treatment or fluorine treatment may be optionally
performed to a surface of the separator 13. Further, ultraviolet
prevention treatment may be optionally performed so that the
pressure-sensitive adhesive sheet does not react with environmental
ultraviolet rays. The thickness of the separator 13 is usually
about from 10 to 200 .mu.m, and preferably about from 25 to 100
.mu.m.
[0108] A processing method of a processed material using the
pressure-sensitive adhesive sheet 10 according to this embodiment
will be described below. In the following description, the case
where a semiconductor wafer is used as the processed material is
taken as an example.
[0109] The pressure-sensitive adhesive sheet 10 of the invention is
stuck onto the semiconductor wafer such as a semiconductor part (a
mounting step), and then, mainly used in a dicing step and a pickup
step. In the mounting step, the pressure-sensitive adhesive sheet
10 is laminated on the semiconductor wafer so that the
pressure-sensitive adhesive layer 12 is stuck onto the
semiconductor wafer, and pressed with a pressing means such as a
pressure roll. Further, sticking can also be performed by
laminating the semiconductor wafer and the pressure-sensitive
adhesive sheet 10 as described above in a pressurizable container
(for example, an autoclave), and pressurizing the inside of the
container. In this case, the pressure-sensitive adhesive sheet 10
may be stuck onto the semiconductor wafer while pressing with the
pressing means. Further, sticking can also be performed in a vacuum
chamber in the same manner as described above. Although the
sticking temperature in sticking is not limited at all, it is
preferably from 20 to 80.degree. C.
[0110] The dicing step is performed for cutting the semiconductor
wafer to individual pieces to produce semiconductor chips (small
pieces of a processed material). The dicing is performed, for
example, from the circuit face side of the semiconductor wafer by a
conventional method. In the dicing step, a blade is allowed to
rotate at high speed, and the semiconductor wafer is cut therewith
to a specified size. Further, in this step, there can be used, for
example, a cutting system called full cutting where cutting is
performed into the pressure-sensitive adhesive sheet 10. A dicing
apparatus used in this step is not particularly limited, and
conventional may be used. Further, the semiconductor wafer is
adhered and fixed by the pressure-sensitive adhesive sheet 10, so
that chip cracking and chip flying can be inhibited, and breakage
of the semiconductor wafer can also be inhibited.
[0111] Then, the pressure-sensitive adhesive sheet 10 is expanded.
The expanding is performed using a conventional expanding
apparatus, after the pressure-sensitive adhesive sheet 10 has been
optionally irradiated with a radiation. The expanding apparatus
includes a doughnut-shaped outer ring which can push the
pressure-sensitive adhesive sheet 10 downward through a dicing
ring, and an inner ring which has a diameter smaller than that of
the outer ring and supports the pressure-sensitive adhesive sheet
10. In this embodiment, the pressure-sensitive adhesive sheet 10
excellent in expandability is used, so that the spacing between the
semiconductor chips adjacent to each other can be sufficiently
increased without breakage of the base material film 11. As a
result, at the time of picking up, the semiconductor chips can be
prevented from coming into contact with each other to damage.
[0112] The semiconductor chip is picked up for separating the
semiconductor chip adhered and fixed to the pressure-sensitive
adhesive sheet 10. A pickup method is not particularly limited, and
various conventional methods can be employed. Examples thereof
include a method of pushing up the individual semiconductor chip
from the pressure-sensitive adhesive sheet 10 side with a needle,
and picking up the pushed-up semiconductor chip with a pickup
apparatus.
[0113] When the pressure-sensitive adhesive sheet 10 having the
radiation-curable adhesive layer or the heat-releasable adhesive
layer is used herein, the pressure-sensitive adhesive layer 12 may
be subjected to irradiation of a radiation or heat treatment. By
doing so, adhesion is decreased thereby intending to make pickup
easy. In the case of the radiation-curable adhesive layer,
conditions such as irradiation intensity and irradiation time at
the time of irradiation of a radiation are not particularly
limited, and may be appropriately set as needed. Further, in the
case of heat-releasable adhesive layer, the pressure-sensitive
adhesive layer expands by heat-foaming or heat-expandable component
upon heating thereof, whereby the adhered area with the
semiconductor chip can be significantly decreased. Accordingly, the
adhesive force of the pressure-sensitive adhesive sheet 10 to the
semiconductor chip is decreased, which makes it easy to separate
the pressure-sensitive adhesive sheet 10 from the semiconductor
chip. As a result, the pickup become possible without damaging the
semiconductor chip. Heating conditions such as heating temperature
and heating time at the time when the heat treatment is conducted
are not particularly limited, and may be appropriately set as
needed.
[0114] In the above description, the description of the
pressure-sensitive adhesive sheet according to the invention was
given taking as an example the case where the semiconductor wafer
was used as the processed material. However, the pressure-sensitive
adhesive sheet for dicing according to the invention should not be
construed as being limited thereto, and is also applicable for
dicing of a semiconductor package, a glass, a ceramic or the
like.
EXAMPLES
[0115] Preferred examples of the invention will be illustratively
described in detail below. However, materials, amounts thereof
blended and the like described in the examples are for illustrative
purpose only, and do not intend to limit the scope of the invention
thereto only, unless otherwise specified.
Example 1
[0116] As a base material, there was used RB film (trade name,
thickness: 100 .mu.m) manufactured by JSR Corporation. The
above-mentioned base material is a hydrogenated polybutadiene film,
and the composition ratio of block (I) containing the
above-mentioned structural formula (A) as a main constitutional
component to block (II) containing the above-mentioned structural
formula (B) as a main constitutional component in the whole film
polymer is 50:50 in terms of weight ratio. The ratio of the
above-mentioned structural formula (A) to the above-mentioned
structural formula (B) contained in block (I) is 80:20 in terms of
weight ratio, and the ratio of the above-mentioned structural
formula (A) to the above-mentioned structural formula (B) contained
in block (II) is 20:80 in terms of weight ratio. The crystallinity
of the base material measured by X-ray diffraction was 30%.
[0117] To a solution containing an acrylic copolymer having a
weight average molecular weight of 500,000 which was obtained by
copolymerizing 90 parts by weight of butyl acrylate and 10 parts by
weight of acrylic acid in toluene by a conventional method, there
were added 80 parts by weight of dipentaerythritol hexaacrylate
(Kayarad DPHA (trade name) manufactured by Nippon Kayaku Co., Ltd),
5 parts by weight of a photopolymerization initiator (Irgacure 184
(trade name) manufactured by Ciba Specialty Chemicals) and 5 parts
by weight of a polyisocyanate compound (Colonate (trade name)
manufactured by Nippon Urethane Co., Ltd.) to prepare an acrylic
ultraviolet-curable adhesive solution.
[0118] The adhesive solution prepared above was applied onto a
corona-treated surface of the base material and crosslinked by heat
at 80.degree. C. for 10 minutes to form an ultraviolet-curable
pressure-sensitive adhesive layer having a thickness of 10 .mu.m.
Then, a separator was stuck to the pressure-sensitive adhesive
layer side to prepare an ultraviolet-curable pressure-sensitive
adhesive sheet for dicing.
Comparative Example 1
[0119] In this Comparative Example, an ultraviolet-curable adhesive
sheet for dicing was prepared in the same manner as in Example 1
with the exception that a base material film obtained by forming an
ethylene-methacrylic acid copolymer (MFR=2.0) to a film having a
thickness of 100 .mu.m by a T-die extrusion method was used as the
base material.
Comparative Example 2
[0120] In this Comparative Example, an ultraviolet-curable adhesive
sheet for dicing was prepared in the same manner as in Example 1
with the exception that a base material film obtained by forming an
olefinic thermoplastic elastomer (Zelas 5053 (trade name)
manufactured by Mitsubishi Chemical Corporation) (MFR=6.8) to a
film having a thickness of 100 .mu.m by a T-die extrusion method
was used as the base material.
[0121] Evaluation Tests
[0122] The respective pressure-sensitive adhesive sheets for dicing
obtained in Example and Comparative Examples were evaluated by the
following methods:
[0123] (1) Evaluation of Dicing Properties
[0124] A six-inch semiconductor wafer having a thickness of 350
.mu.m was mounted on the pressure-sensitive adhesive sheet for
dicing, and then diced under the following conditions:
[0125] <Dicing Conditions>
[0126] Dicer: DFD-651 manufactured by DISCO Co., Ltd.
[0127] Blade: NBC-ZH2050 27HEDD manufactured by DISCO Co., Ltd.
[0128] Number of Revolutions of Blade: 45,000 rpm
[0129] Dicing Rate: 100 mm/sec
[0130] Dicing Depth: 30 .mu.m in the base film
[0131] Dicing Size: 2.5 mm.times.2.5 mm
[0132] Cut mode: Down cut
[0133] After dicing, the state of the occurrence of fibrous scraps
on a surface of each semiconductor chip obtained by cutting of the
semiconductor wafer was observed under an optical microscope (at
200-fold magnification). In this observation, the number of fibrous
scraps was counted for each size of the fibrous scraps. The results
thereof are shown in the following Table 1.
[0134] (2) Evaluation of Expandability
[0135] After dicing, the pressure-sensitive adhesive sheet for
dicing was subjected to ultraviolet irradiation with an ultraviolet
irradiator. Then, expanding was performed with a die bonder under
the following conditions;
[0136] <Expanding Conditions>
[0137] Die Bonder: GPS-100 manufactured by NEC Machinery
Corporation
[0138] Shape of Inner Ring: E-bearing type
[0139] Pull-Down Amount: 7 mm, 12 mm
[0140] It was visually observed whether breakage of the
pressure-sensitive adhesive sheet for dicing occurred or not by
expanding. The results thereof are shown in the following Table
1.
[0141] Results
[0142] As seen from the following Table 1, it was confirmed that no
fibrous scraps were generated in the pressure-sensitive adhesive
sheet for dicing of Example 1. Further, it was also confirmed that
the pressure-sensitive adhesive sheet for dicing did not break at
the time of expanding. That is to say, it was found that the
pressure-sensitive adhesive sheet for dicing according to Example 1
could inhibit the generation of fibrous scraps, and was also
excellent in expandability. In contrast, the pressure-sensitive
adhesive sheet for dicing of Comparative Example 1 did not break
when the pull-down amount was 7 mm, but broke when the pull-down
amount was 12 mm. Further, it was confirmed that fibrous scraps
were also generated. Furthermore, in the pressure-sensitive
adhesive sheet for dicing of Comparative Example 2, no fibrous
scraps were generated, but it was confirmed that the base material
film broke in the course of expanding. TABLE-US-00001 TABLE 1
Number of Fibrous Scraps for Occurrence Each Size (.mu.m) of
Breakage in Each Crystallinity Less than From 100 500 .mu.m
Pull-Down Amount (%) 100 .mu.m to 500 .mu.m or more 7 mm 12 mm
Example 1 30 0 0 0 Not Not occurred occurred Comparative 12 100 or
100 or 67 Not Occurred Example 1 more more occurred Comparative 45
0 0 0 Occurred Occurred Example 2
[0143] While the present invention has been described in detail and
with reference to specific embodiments thereof, it will be apparent
to one skilled in the art that various changes and modifications
can be made therein without departing from the scope thereof.
[0144] This application is based on Japanese patent application No.
2006-154717 filed Jun. 2, 2006, the entire contents thereof being
hereby incorporated by reference.
[0145] Further, all references cited herein are incorporated in
their entireties.
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