U.S. patent application number 11/184001 was filed with the patent office on 2005-11-10 for wafer-adhering adhesive tape.
This patent application is currently assigned to THE FURUKAWA ELECTRIC CO., LTD.. Invention is credited to Ishiwata, Shinichi, Kita, Kenji, Morishima, Yasumasa.
Application Number | 20050249909 11/184001 |
Document ID | / |
Family ID | 32844217 |
Filed Date | 2005-11-10 |
United States Patent
Application |
20050249909 |
Kind Code |
A1 |
Morishima, Yasumasa ; et
al. |
November 10, 2005 |
Wafer-adhering adhesive tape
Abstract
A wafer-adhering adhesive tape, which has, on a surface of a
base, a radiation-curable removable adhesive layer, and if
necessary a die-bonding adhesive layer in order, wherein the
radiation-curable removable adhesive layer is mainly composed of an
acrylic-series copolymer having, in a principal chain, at least a
radiation-curable carbon-carbon double bond containing group, a
hydroxyl group, and a group containing a carboxyl group,
respectively, and the radiation-curable removable adhesive layer
has a gel fraction of 60% or greater.
Inventors: |
Morishima, Yasumasa; (Tokyo,
JP) ; Kita, Kenji; (Tokyo, JP) ; Ishiwata,
Shinichi; (Tokyo, JP) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Assignee: |
THE FURUKAWA ELECTRIC CO.,
LTD.
|
Family ID: |
32844217 |
Appl. No.: |
11/184001 |
Filed: |
July 19, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11184001 |
Jul 19, 2005 |
|
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|
PCT/JP04/01038 |
Feb 3, 2004 |
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Current U.S.
Class: |
428/40.1 |
Current CPC
Class: |
Y10T 428/14 20150115;
H01L 21/6836 20130101; Y10T 428/1462 20150115; Y10T 428/24926
20150115; Y10T 428/2809 20150115; Y10T 428/24364 20150115; H01L
2221/68327 20130101; H01L 21/67132 20130101; C09J 2203/326
20130101; Y10T 428/28 20150115; Y10T 428/2852 20150115; C09J 7/385
20180101 |
Class at
Publication: |
428/040.1 |
International
Class: |
B32B 009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 5, 2003 |
JP |
2003-028912 |
Claims
1. A wafer-adhering adhesive tape, having a radiation-curable
removable adhesive layer on a surface of a base, wherein the
radiation-curable removable adhesive layer is mainly composed of an
acrylic-series copolymer having, in a principal chain, at least a
radiation-curable carbon-carbon double bond containing group, a
hydroxyl group, and a group containing a carboxyl group,
respectively, and said radiation-curable removable adhesive layer
has a gel fraction of 60% or greater.
2. A wafer-adhering adhesive tape having a radiation-curable
removable adhesive layer and a die-bonding adhesive layer, in this
order, on a surface of a base, wherein the radiation-curable
removable adhesive layer is mainly composed of an acrylic-series
copolymer having, in a principal chain, at least a
radiation-curable carbon-carbon double bond containing group, a
hydroxyl group, and a group containing a carboxyl group,
respectively, and said radiation-curable removable adhesive layer
has a gel fraction of 60% or greater.
3. The wafer-adhering adhesive tape according to claim 1 or 2,
wherein the ratio of carbon-carbon double bonds contained in the
radiation-curable removable adhesive layer is 0.5 to 2.0 meq/g.
Description
TECHNICAL FIELD
[0001] The present invention relates to an adhesive tape that is
provided with a removable adhesive agent layer on one side of a
base film.
BACKGROUND ART
[0002] An assembling process of a semiconductor device, such as an
IC or the like, comprises the steps of: cutting and separating
(dicing) a semiconductor wafer and the like into respective chips,
after patterning; mounting the chips on a substrate or the like;
and sealing them with a resin or the like.
[0003] In the dicing step, a semiconductor wafer is adhered and
fixed by an adhesive tape in advance, and then it is diced along a
chip shape. In the mounting step, the chip is peeled off (picked
up) from the adhesive tape and then fixed on a substrate or the
like with an adhesive agent for adhering and fixing.
[0004] The tapes used for the above purposes include a usual
pressure-sensitive adhesive-type tape, and a tape having a reduced
adhesive force when it is hardened or cured by radiation, such as
ultraviolet (UV) rays, electronic rays, and the like. Both of these
types of tapes are required to have sufficient adhesive force so
that the tape is not peeled off from the wafer upon dicing, and
they are also required to have peeling capability to be easily
peeled off from the wafer upon picking up.
[0005] Further, in the mounting step, sufficient adhesive force is
required between the chip(s) and the substrate and the like.
[0006] There are suggested a variety of adhesive or adhesion tapes
that are equipped with both of the function of a dicing adhesive
tape used in the above process, and the function of an adhesive on
a substrate and the like, which tapes are improved in the coating
workability of the adhesive, and which simplify the whole
process.
[0007] These adhesive tapes enable a so-called direct die bonding
for, after dicing, picking up a chip with a removable adhesive
layer adhered on the rear side of the chip, mounting the chip on a
substrate or the like, and curing and adhering the chip by heating
or the like. By these adhesive tapes, the coating process of an
adhesive can be omitted.
[0008] However, the removable adhesion agent or adhesive agent used
for these adhesive tapes is in a coating liquid state with low
viscosity and low wettability to a tape base, and thus it has the
problem of poor yield. Further, the above adhesion or adhesive
agent is low in adhesion strength, compared with an existing
adhesive or bonding agent for die bonding. Thus it is difficult to
obtain reliability from the above adhesion or adhesive agent.
[0009] As means to obtain adhesion reliability and provide dicing
performance, it is proposed to use a laminate of a die bonding
adhesive layer and a dicing tape. However, this laminate-type tape
has the problem that it is difficult to control the peeling ability
between the adhesive and the dicing tape. A die bonding adhesive
with high adhesion reliability generally requires heat adhesion
upon temporarily fixing it to a wafer. However, the laminate-type
tape has the problem of increase of peeling ability between the
dicing tape and the die-bonding-sheet adhesive layer due to such a
heat adhesion, thereby causing a raise of the pickup failure ratio
after the dicing.
[0010] Further, it is also proposed that a die bond sheet is
heat-adhered to a wafer in-advance, and a dicing tape is laminated
to the die bonding adhesive layer adhered to the wafer, before use.
Also, in this case, a surface protective tape for back-grinding is
usually bonded to a side of the wafer on which no die bonding sheet
or dicing tape is bonded. To peel the surface protective tape from
the wafer by lowering the adhesive force of the surface protective
tape, a heat treatment is generally carried out. The heating
temperature is generally about 40.degree. C. or more, for example,
about 60.degree. C. Similarly to the above, this causes the problem
of increased peeling force between the die bonding adhesive layer
and the dicing tape.
DISCLOSURE OF THE INVENTION
[0011] The present invention resides in a wafer-adhering adhesive
tape, which has a radiation-curable removable adhesive layer on a
surface of a base, wherein the radiation-curable removable adhesive
layer is mainly composed of an acrylic-series copolymer having, in
a principal chain, at least a radiation-curable carbon-carbon
double bond containing group, a hydroxyl group, and a group
containing a carboxyl group, respectively, and the
radiation-curable removable adhesive layer has a gel fraction of
60% or greater.
[0012] Further, the present invention resides in a wafer-adhering
adhesive tape, which has a radiation-curable removable adhesive
layer and a die-bonding adhesive layer, in this order, on a surface
of a base, wherein the radiation-curable removable adhesive layer
is mainly composed of an acrylic-series copolymer having, in a
principal chain, at least a radiation-curable carbon-carbon double
bond containing group, a hydroxyl group, and a group containing a
carboxyl group, respectively, and the radiation-curable removable
adhesive layer has a gel fraction of 60% or greater.
[0013] Other and further features and advantages of the invention
will appear more fully from the following description.
BEST MODE FOR CARRYING OUT THE INVENTION
[0014] According to the present invention, there are provided the
following means:
[0015] (1) A wafer-adhering adhesive tape, having a
radiation-curable removable adhesive layer on a surface of a base,
wherein the radiation-curable removable adhesive layer is mainly
composed of an acrylic-series copolymer having, in a principal
chain, at least a radiation-curable carbon-carbon double bond
containing group, a hydroxyl group, and a group containing a
carboxyl group, respectively, and the radiation-curable removable
adhesive layer has a gel fraction of 60% or greater;
[0016] (2) A wafer-adhering adhesive tape, having a
radiation-curable removable adhesive layer and a die-bonding
adhesive layer, in this order, on a surface of a base, wherein the
radiation-curable removable adhesive layer is, mainly composed of
an acrylic-series copolymer having, in a principal chain, at least
a radiation-curable carbon-carbon double bond containing group, a
hydroxyl group, and a group containing a carboxyl group,
respectively, and the radiation-curable removable adhesive layer
has a gel fraction of 60% or greater; and
[0017] (3) The wafer-adhering adhesive tape according to the above
item (1) or (2), wherein the ratio of carbon-carbon double bonds
contained in the radiation-curable removable adhesive layer is 0.5
to 2.0 meq/g (milliequivalents/gram).
[0018] Herein, the term "being mainly composed of" means that a
main component of a removable adhesive component in the
radiation-curable removable adhesive layer, which layer is
comprised of the removable adhesive component, a hardening agent
and a polymerization initiator, is the acrylic-series copolymer
having a carbon-carbon double bond containing group, a hydroxyl
group, and a carboxyl group, respectively. Further, in the adhesive
tape of the present invention, 60% by mass or more of the
radiation-curable removable adhesive layer is generally composed of
the acrylic-series copolymer having a carbon-carbon double bond
containing group, a hydroxyl group, and a carboxyl group,
respectively.
[0019] Further, herein, the "removable adhesive" means an agent
capable of adhering and being removed after treatment such as
curing, while an "adhesive" means an agent capable of adhering
only. For example, the "radiation-curable removable adhesive" means
a removable adhesive capable of being removed or pealed off by
hardening by irradiation of radiation such as UV, after application
of the removable adhesive to a wafer and the like.
[0020] The present invention will be described in detail below.
[0021] The present inventors have keenly studied to solve the
above-described problems in the conventional adhesive or adhesion
tapes. As a result, the present inventors found that defective
picking-up does not occur, while maintaining sufficient adhesion
reliability, by using an adhesive tape that comprises an adhesive
or adhesion composition, which is mainly composed of an
acrylic-series polymer having at least a radiation-curable
carbon-carbon double bond containing group, a hydroxyl group, and a
group containing a carboxyl group, respectively, in a principal
chain, and which composition has a gel fraction of 60% or greater;
and, if necessary, further laminating a die-bonding adhesive layer
with the above adhesive tape. The present invention has been
accomplished based on this finding.
[0022] The wafer adhering adhesive tape of the present invention
can be made by forming a radiation curable removable adhesive layer
on a base surface, in which the removable adhesive layer is mainly
composed of the acrylic-series copolymer having at least a
radiation curable carbon-carbon double bond containing group, a
hydroxyl group and a carboxyl group-containing group, respectively,
in the principal chain, and in which the adhesive layer has a gel
fraction of 60% or greater. Further, in addition to the radiation
curable removable adhesive layer, a die-bonding adhesive layer may
be form on the base surface, and it is preferred to form the
radiation curable removable adhesive layer and the die-bonding
adhesive layer, in order, on the base surface.
[0023] The acrylic-series copolymer (hereinafter, referred to as
"acrylic copolymer (A)") having at least a radiation curable
carbon-carbon double bond containing group, a hydroxyl group, and a
group containing a carboxyl group, respectively, in the principal
chain, which copolymer can be used in the present invention, may be
any one prepared by any manner. For example, the acrylic copolymer
(A) can be obtained, by subjecting a copolymer (A1), which
comprises a (meth)acrylic acid ester, a hydroxyl group-containing
unsaturated compound, a carboxyl group-containing unsaturated
compound, and the like, to addition reaction with a compound (A2)
that has a functional group addition-reactive to a functional group
in the copolymer (A1) and that has a carbon-carbon double bond, in
which a carbon chain of the copolymer (A1) is to be a principal
chain.
[0024] As the (meth)acrylic acid ester, included are, for example,
hexyl acrylate, n-octyl acrylate, isooctyl acrylate, 2-ethylhexyl
acrylate, dodecyl acrylate, decyl acrylate, each having 6 to 12
carbon atoms, or monomers having 5 or less carbon atoms, such as
pentyl acrylate, n-butyl acrylate, isobutyl acrylate, ethyl
acrylate, and methyl acrylate, or methacrylates like these. In this
case, as the number of carbon atoms of monomers increases, the
glass transition temperature becomes lower, thereby enabling
manufacture of monomers of a desired transition temperature.
Further, besides the glass transition temperature, for the purpose
of enhancing compatibility and various performances, a low
molecular compound having a carbon-carbon double bond, such as
vinyl acetate, styrene, and acrylonitrile, can be blended within
the range of 5% by mass or less.
[0025] Examples of the hydroxyl group-containing unsaturated
compound include 2-hydroxyethyl acrylate, 2-hydroxyethyl
methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl
methacrylate, and the like.
[0026] Examples of the carboxyl group-containing unsaturated
compound include acrylic acid, methacrylic acid, and the like.
[0027] As a functional group in the above-described compound (A2)
having an addition reactive functional group and a carbon-carbon
double bond, in a case that the functional group in the copolymer
(A1) is a carboxyl group or a cyclic acid anhydride group, included
are a hydroxyl group, an epoxy group, an isocyanato group, and the
like; or in a case that the functional group in the copolymer (A1)
is a hydroxyl group, included are a cyclic acid anhydride group, an
isocyanato group, and the like; or in a case that the functional
group in the copolymer (A1) is an amino group, included is an
isocyanato group, and the like. Specific examples of the compound
(A2) include acrylic acid, methacrylic acid, cinnamic acid,
itaconic acid, fumaric acid, phthalic acid, 2-hydroxyalkyl
acrylates, 2-hydroxyalkyl methacrylates, glycol monoacrylates,
glycol monomethacrylates, N-methylol acrylamide, N-methylol
methacrylamide, allyl alcohol, N-alkylaminoethyl acrylates,
N-alkylaminoethyl methacrylates, acrylamides, methacrylamides,
maleic anhydride, itaconic anhydride, fumaric anhydride, phthalic
anhydride, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl
ether, and polyisocyanate compounds in which isocyanato groups are
partially urethanated with a monomer having a hydroxyl group or
carboxyl group and a photopolymerizable carbon-carbon double
bond.
[0028] In the synthesis of the acrylic-series copolymer (A), when
carrying out copolymerization by solution polymerization, a
ketone-series, ester-series, alcohol-series, or aromatic-series
solvent can be used as an organic solvent. Among these, a
preferable solvent is a usual good solvent for an acrylic-series
polymer, which solvent has a boiling point of 60 to 120.degree. C.
Examples of the preferable solvent include toluene, ethyl acetate,
isopropyl alcohol, benzene methylcellosolve, ethylcellosolve,
acetone, methyl ethyl ketone, and the like. As a polymerization
initiator, use may be generally made of a radical generating agent
of azobis-series, such as .alpha.,.alpha.'-azobisisobuty-
ronitrile, and organic peroxide-series, such as benzoylperoxide. At
this time, a catalyst, a polymerization inhibitor can be optionally
added, if necessary. In this way, it is possible to obtain an
acrylic-series copolymer (A) with a desired molecular weight, by
controlling a polymerization temperature and a polymerization time,
and then carrying out an addition reaction at a functional group.
As for the control of the molecular weight, it is preferred to use
a mercaptan-series or carbon tetrachloride-series solvent.
[0029] Additionally, this copolymerization is not limited to a
solution polymerization, but it may also be performed in other ways
such as bulk polymerization, suspension polymerization, and the
like.
[0030] As mentioned in the above, the acrylic-series copolymer (A)
can be obtained. In the present invention, the mass average
molecular weight of the acrylic-series copolymer (A) is preferably
about 300,000 to about 1,000,000. If the molecular weight is too
small, the cohesive force by irradiation of a radiation becomes
lesser, thus a misalignment of elements (chips) may occur easily
upon dicing the wafer, and image recognition may be difficult.
Further, to prevent this misalignment of elements as much as
possible, it is preferable that the molecular weight is 400,000 or
more. If the molecular weight is too large, there is a possibility
of gelation upon synthesis and coating. Further, as for properties
of the copolymer, since the glass transition temperature is low,
the flowability of the removable adhesive after irradiation of a
radiation is not sufficient in a case of irradiation of a radiation
not in a pattern shape but entirely, even if the molecular weight
is large. Thus, although there occurs no such problems that an
interval between elements is insufficient after stretching or that
it is difficult to recognize an image upon picking up, the
molecular weight is more preferably 900,000 or less. Herein, the
molecular weight in the present invention means a mass average
molecular weight in terms of polystyrene.
[0031] Further, in the present invention, an amount to be
introduced of a photopolymerizable carbon-carbon double bond in the
acrylic-series copolymer (A) may be varied according, for example,
to use conditions thereof such as a UV irradiation amount and the
like, and it is not limited, as long as it reaches an amount to
give the effect of sufficiently lowering the adhesive force after
radiation curing. The amount of the photopolymerizable
carbon-carbon double bond to be introduced is preferably 0.5 to 2.0
meq/g, more preferably 0.8 to 1.5 meq/g. If the double bond amount
is too small, the effect of reducing the adhesive ability after
irradiation of a radiation becomes smaller. If the double bond
amount is too large, the flowability of the removable adhesive
after irradiation of a radiation is insufficient, thereby to make
insufficient intervals between the resultant elements after
stretching and make it difficult for each element to recognize an
image upon picking up, in some cases. In this case, further, the
acrylic-series copolymer (A) itself may be insufficient in
stability and may be made difficult to manufacture.
[0032] In the present invention, the gel fraction of the
radiation-curable removable adhesive layer can be controlled by the
average molecular weight of the acrylic-series copolymer (A) and
the amount of the hardening agent to be blended. The gel fraction
is 60% or greater, and more preferably 80% or greater. If the gel
fraction is too small, the removable adhesive component may be
slightly moved on the contact interface, thus making it difficult
to obtain stability on the peeling force with the lapse of
time.
[0033] Further, the acrylic-series copolymer (A) has a hydroxyl
group and a carboxyl group-containing group, each of which is
unreacted, in the principal chain. It is preferable that the
acrylic-series copolymer (A) has a hydroxyl group so that a
hydroxyl group value is from 5 to 10, more preferably from 20 to
70, since the adhesive ability after irradiation of a radiation is
reduced, to thus further decrease the risk of picking-up mistakes.
Further, it is preferable that the acrylic-series copolymer (A) has
a carboxyl group so that an acid value is from 0.5 to 30, since the
tape recovery (restoration) ability is improved, to thus make it
easy to cope with a tape housing-type mechanism for a used tape.
The acid value is more preferably 1 to 10. In the meanwhile, if the
hydroxyl group value of the acrylic-series copolymer (A) is too
low, the adhesive ability after irradiation of a radiation is not
sufficiently reduced, or if too high, the flowability of the
removable adhesive after irradiation of a radiation is damaged.
Further, if the acid value is too low, the tape recovery ability is
not sufficiently improved, or if too high, the flowability of the
removable adhesive is damaged.
[0034] Further, in case of hardening the radiation-curable
removable adhesive layer for use in the present invention by
ultraviolet irradiation, as an additional component, if necessary,
use can be made of a photo polymerization initiator, such as
isopropyl benzoin ether, isobutyl benzoin ether, benzophenone,
Michler's ketone, chlorothioxanthone, dodecyl thioxanthone,
dimethyl thioxanthone, diethyl thioxanthone, benzyl dimethyl ketal,
.alpha.-hydroxycyclohexyl phenyl ketone,
2-hydroxymethylphenylpropane, and the like. The amount of the photo
polymerization initiator to be blended is preferably 0.01 to 5 mass
parts, to 100 mass parts of the acrylic-series polymer.
[0035] Further, the radiation curable removable adhesive layer may
contain, if necessary, another additional component including, for
example, a hardening agent such as a polyisocyanate compound and
the like. The amount of the hardening agent to be blended is
preferably 0.5 to 10 mass parts, to 100 mass parts of the
acrylic-series polymer that is the main component.
[0036] The thickness of the radiation-curable removable adhesive
layer is preferably 5 to 50 .mu.m.
[0037] The base that can be used in the present invention may be a
film of any material having a radiation transmission ability.
Examples of the film include those made, for example, of a
homopolymer or copolymer of an .alpha.-olefin, such as
polyethylene, polypropylene, an ethylene/propylene copolymer,
polybuten, an ethylene/vinyl acetate copolymer, an
ethylene/acrylate copolymer, or an ionomer; an engineering plastic,
such as polyethylene terephthalates, a polycarbonate, or
poly(methyl methacrylate); or a thermoplastic elastomer, such as
polyurethane, styrene/ethylene/buten, or a penten-series copolymer.
Alternately, a mixture or double or higher layer of two or more
kinds selected from the above compound group may be used.
[0038] The thickness of the base film to be used is preferably 50
to 200 .mu.m.
[0039] By laminating the thus-obtained adhesive tape and a
die-bonding adhesive, it is possible to make the wafer-adhering
adhesive tape with higher performance. As the die-bonding adhesive,
an acrylic/epoxy-series die bonding adhesive or the like can be
used. By heat adhering the wafer-adhering adhesive tape to a
semiconductor wafer, sufficient adhesive ability is obtained in the
dicing step so not to peel off or remove the wafer, the die-bonding
adhesive layer, the radiation-curable removable adhesive layer, and
the base film each other. On the other hand, when picking up, the
removable adhesive layer can be easily peeled off from chips
attached to the die-bonding adhesive layer via radiation
hardening.
[0040] Further, the similar effects can be exhibited by adhering
the adhesive tape of the present invention, to the die-bonding
adhesive layer side of the wafer with the die-bonding adhesive film
attached thereto.
[0041] The peeling force of the die-bonding adhesive layer and the
radiation-curable removable adhesive layer upon dicing is
preferably 0.5 to 10 N/25 mm, and the peeling force between the
chip attached to the die-bonding adhesive layer and the tape
attached with the removable adhesive layer after irradiation of a
radiation is preferably 0.5 to 0.05 N/25 mm.
[0042] In one preferable example of the present invention, the
radiation curable removable adhesive layer and the die-bonding
adhesive layer are formed on the surface of a base, in this order
from the base side. In the die-bonding adhesive layer in the
present invention, for example, a bonding adhesive gent which is
usually used for die-bonding, such as a film-like bonding adhesive
mainly composed of an epoxy resin, can be used. The thickness of
the die-bonding adhesive layer is preferably 5 to 50 .mu.m.
[0043] The wafer-adhering adhesive tape of the present invention
has sufficient adhesive ability that the radiation-curable
removable adhesive layer is not peeled off from a die-bonding
adhesive layer and a wafer, when dicing; it allows easy removal of
the removable adhesive layer and a chip attached to the die-bonding
adhesive layer by radiation and hardening, when picking up; and it
gives sufficient adhesive ability between the resultant chip and a
substrate or the like, when mounting; thereby it enables a
so-called direct die bonding
[0044] Further, the wafer-adhering adhesive tape of the present
invention can be used as a dicing tape upon dicing, and it can be
used with the adhesive layer easily peeled off upon mounting,
thereby to enable a direct die-bonding, and the wafer-adhering
adhesive tape is excellent in storage stability. Further, when a
die bonding sheet is heat-adhered to a wafer in advance and a
dicing tape is laminated onto a die-bonding adhesive layer bonded
to the wafer before use, the wafer-adhering adhesive tape of the
present invention can be preferably used as the above dicing tape.
Further, according to the wafer-adhering adhesive tape of the
present invention, an interval between elements is sufficiently
made after stretching, while obtaining the effects of reducing
adhesive force after radiation hardening.
[0045] The present invention will be described in more detail based
on the examples given below, but the present invention is not meant
to be limited by these examples.
EXAMPLES
Examples 1 to 4
[0046] (Synthesis of Acrylic-Series Copolymer A)
[0047] A copolymer was prepared by solution radical polymerization
of 65 mass parts of butyl acrylate, 25 mass parts of 2-hydroxyethyl
acrylate, and 10 mass parts of acrylic acid, as raw materials.
Then, to the thus-obtained copolymer, 2-isocyanatethyl methacrylate
was added dropwise and reacted therewith, to prepare a copolymer A.
In this manner, the amount of 2-isocyanatethyl methacrylate to be
added dropwise and the reaction time of the solution radical
polymerization are properly adjusted, to prepare copolymers A1 to
A5, respectively, which were different in carbon-carbon double bond
amounts and molecular weights.
[0048] (Preparation of a Wafer Adhering Adhesive Tape)
[0049] To the copolymers A1 to A5, a polyisocyanate compound (trade
name: Coronet L, produced by Japan Polyurethane) as a hardening
agent, and .alpha.-hydroxycyclohexyl phenyl ketone as a photo
polymerization initiator were admixed in a mixing ratio, as shown
in the following Table 1, to thereby obtain a radiation-curable
removable adhesive, respectively.
[0050] Each of the removable adhesives was coated on a high-density
polyethylene resin film (100 .mu.m) such that the removable
adhesive thickness after drying would be 10 .mu.m, to prepare an
adhesive tape, respectively. Each of these adhesive tapes and a
film-like adhesive (for die bonding) mainly composed of an epoxy
resin with 25-.mu.m thickness were laminated at a room temperature,
to prepare respective wafer-adhering adhesive tapes of Examples 1
to 4 and Comparative Example 1, as shown in Table 1.
[0051] (Properties Test)
[0052] As for the following properties 1 to 6 of the thus-prepared
wafer adhering adhesive tapes, tests were carried out as described
below. The test results are also shown in Table 1.
[0053] 1. Gel Fraction
[0054] About 0.05 g of the removable adhesive layer was weighed,
dipped in 50 ml of xylene for 24 hours at 120.degree. C., then the
resultant xylene was filtered through a stainless-steel metallic
net of 200 meshes and insoluble constituents on the metallic net
were dried for 120 minutes at 110.degree. C. Then, the mass of the
dried insoluble constituents was weighted, to estimate the gel
fraction by the formula shown below:
Gel Fraction (%)=(Mass of insoluble constituents/Mass of weighed
removable adhesive layer).times.100
[0055] 2. Removable Adhesive Double Bond Amount
[0056] The amount of carbon-carbon double bond contained in about
10 g of the heated and dried removable adhesive was measured and
quantitatively determined by a mass increasing method by bromine
addition reaction in a dark place in vacuo.
[0057] 3. Expandability (Interval Between Elements)
[0058] The above-prepared wafer-adhering adhesive tape was heat
adhered to a wafer for 10 seconds at 80.degree. C., then a silicon
wafer of a diameter of 5 inches was full-cut into a size of 3
mm.times.3 mm, and the thus-cut wafer was subjected to
ultraviolet-radiation hardening (irradiation not on a pattern shape
but on the entire wafer). Then, the resultant wafer was stretched
in a wafer expanding machine (air pressure: 2.0 kg/cm.sup.2), and
the lengths of element intervals in longitudinal and transverse
directions upon being stretched were measured, to estimate the
average values. The lengths of element intervals included a blade
thickness of 40 .mu.m upon dicing.
[0059] The expandability is evaluated as below, based on the size
(q) of element interval.
[0060] ".largecircle.": q 100 .mu.m: Image recognition of the
element can be carried out satisfactorily.
[0061] ".DELTA.": 100 .mu.m>q 80 .mu.m: It is difficult to carry
out image recognition of the element.
[0062] ".times.": q<80 .mu.m: It is impossible to carry out
image recognition of the element.
[0063] 4. Picking-up Success Ratio
[0064] The above-prepared wafer-adhering adhesive tape was heat
adhered to a wafer for 10 seconds at 80.degree. C., and then
diced-to 10 mm.times.10 mm. Afterwards, ultraviolet rays of 200
mJ/cm.sup.2 were irradiated to the removable adhesive layer by an
air-cooling-type high-pressure mercury lamp (80 W/cm, irradiation
distance: 10 cm). Then a picking-up test was carried out by a die
bonder machine (produced by NEC Machinery, trade name: CPS-100 FM),
to obtain a picking-up success ratio at 100 picked-up chips.
[0065] 5. Peeling Ability (Peeling Force)
[0066] Peeling ability before and after UV irradiation were
measured according to JIS Z0237 (UV irradiation amount: 1000
mJ/cm.sup.2). The wafer-adhering adhesive tape was heat adhered to
a mirror surface of a silicon wafer heated to 80.degree. C., and
then the peeling force between the die-bonding adhesive layer and
the adhesive tape was measured. The test was carried out under the
conditions of a peeling angle of 90.degree. and a peeling speed of
50 mm/min.
[0067] 6. Storage Stability
[0068] The above-prepared wafer-adhering adhesive tape was heat
adhered to a wafer for 10 seconds at 80.degree. C., and diced to 10
mm.times.10 mm. Afterwards, ultraviolet rays of 200 mJ/cm.sup.2
were irradiated to the removable adhesive layer by an
air-cooling-type high-pressure mercury lamp (80 W/cm, irradiation
distance: 10 cm). Then, after the thus-irradiated wafer-adhering
adhesive tape was stood for 2 weeks under room temperature
conditions (25.degree. C., 60% RH), the picking-up success ratio
was obtained. Storage stability is evaluated and shown with this
picking-up success ratio (%).
1 TABLE 1 Example Example Example Example Comparative 1 2 3 4
Example 1 Kind of copolymer A1 A2 A3 A4 A5 Acid value (mgKOH/g) 5.9
5.6 6.9 5.0 6.0 Hydroxyl group value (mgKOH/g) 55 34 40 34 50
Amount of copolymer to be used 100 100 100 100 100 (mass parts)
Amount of hardening agent to be used 2 3 1.5 2 3 (mass parts)
Amount of photo polymerization 1 1 1 1 1 initiator to be used (mass
parts) Gel fraction (%) 90.5 91.3 68.2 86.7 50.8 Removable adhesive
double bond 0.6 1.5 1.1 2.4 1.5 amount (meq/g) Expandability
(element interval) .largecircle. .largecircle. .largecircle.
.DELTA. .largecircle. Picking-up success ratio (%) 100 100 100 100
100 Peeling ability before UV irradiation 1.20 1.31 1.29 1.13 1.34
(N/25 mm) Peeling ability after UV irradiation 0.21 0.11 0.16 0.14
0.21 (N/25 mm) Storage stability (%) 100 100 100 100 54
[0069] As can be seen from Table 1, Examples 1 to 3 according to
the present invention showed that, in addition to that both of the
picking-up success ratio and the storage stability were each 100%,
the expandability was also good. Further, Example 4 indicated that
the element interval upon expansion was slightly poor, but the
picking-up success ratio and the storage stability were each 100%.
Contrary to these, Comparative Example 1 showed that the storage
stability was conspicuously poor.
[0070] From these results, it can be understood that the
wafer-adhering adhesive tape of the present invention can be used
as a dicing tape upon dicing, and it can be used with the adhesive
layer easily peeled off upon mounting, to thereby enable a direct
die-bonding, and that the inventive wafer-adhering adhesive tape is
excellent in storage stability.
[0071] Separately, an example of the wafer-adhering adhesive tape,
in which the ratio of a carbon-carbon double bond contained in the
radiation-curable removable adhesive layer was too low, was
prepared and tested in the same manner as Example 1, excepted that
the ratio of carbon-carbon double bond was changed to 0.3 meq/g. As
a result, the picking-up success ratio obtained in this example was
25%. At this time, the peeling forces before and after UV
irradiation were 1.42 N/25 mm and 0.4 N/25 mm, respectively.
Example 5
[0072] The removable adhesive same as that in Example 1 was coated
on a high-density polyethylene resin film (thickness: 100 .mu.m)
such that the adhesive thickness after drying would be 10 .mu.m, to
prepare an adhesive tape. Separately, a silicon wafer of 5-inch
diameter, on which a surface protective tape for grinding was
attached, was provided. To a ground surface of the wafer, on which
surface no protective tape was attached, a film-like adhesive (for
die bonding) with 25-.mu.m thickness was heat adhered for 10
seconds at 80.degree. C. The above-prepared adhesive tape was
attached to a (die-bonding) adhesive layer attached to the wafer.
Then, the resultant silicon wafer adhered with the adhesive tape
was subjected to heat treatment for 100 seconds at 60.degree. C.,
to peel off the surface protective tape from the wafer.
[0073] Afterwards, in the same manner as to Example 1, this silicon
wafer was full-cut into a size of 3 mm.times.3 mm, UV-irradiation
hardened, and expanded, and then subjected to the picking-up test.
As a result, good expandability and picking-up property, as in
Example 1, were exhibited. Further, it was found that the storage
stability of the adhesive tape was also good.
[0074] As seen from above, when a die-bonding sheet is heat adhered
to a wafer in advance and then the adhesive tape of the present
invention is adhered and laminated to the resultant die-bonding
adhesive layer attached to the wafer, the adhesive tape of the
present invention can also be preferably used.
INDUSTRIAL APPLICABILITY
[0075] The wafer-adhering adhesive tape of the present invention is
preferable, for example, as a semiconductor wafer-adhering adhesive
tape that is used in an adhering process for fixing a wafer or the
like, dicing it, and lap-jointing it with a substrate or a
semiconductor chip, when a semiconductor device, such as a silicon
wafer or the like, is manufactured.
[0076] Having described our invention as related to the present
embodiments, it is our intention that the invention not be limited
by any of the details of the description, unless otherwise
specified, but rather be construed broadly within its spirit and
scope as set out in the accompanying claims.
* * * * *