U.S. patent application number 13/191950 was filed with the patent office on 2012-02-02 for film for flip chip type semiconductor back surface and its use.
This patent application is currently assigned to NITTO DENKO CORPORATION. Invention is credited to Fumiteru ASAI, Goji SHIGA, Naohide TAKAMOTO.
Application Number | 20120028416 13/191950 |
Document ID | / |
Family ID | 45527155 |
Filed Date | 2012-02-02 |
United States Patent
Application |
20120028416 |
Kind Code |
A1 |
TAKAMOTO; Naohide ; et
al. |
February 2, 2012 |
FILM FOR FLIP CHIP TYPE SEMICONDUCTOR BACK SURFACE AND ITS USE
Abstract
The present invention relates to a film for flip chip type
semiconductor back surface, which is to be disposed on a back
surface of a semiconductor element flip chip-connected onto an
adherend, the film for flip chip type semiconductor back surface
including an adhesive layer and a protective layer laminated on the
adhesive layer, in which the protective layer is constituted of a
heat-resistant resin having a glass transition temperature of
200.degree. C. or more or a metal.
Inventors: |
TAKAMOTO; Naohide; (Osaka,
JP) ; SHIGA; Goji; (Osaka, JP) ; ASAI;
Fumiteru; (Osaka, JP) |
Assignee: |
NITTO DENKO CORPORATION
Osaka
JP
|
Family ID: |
45527155 |
Appl. No.: |
13/191950 |
Filed: |
July 27, 2011 |
Current U.S.
Class: |
438/113 ;
257/E21.599; 428/343; 428/411.1; 428/473.5; 428/500; 428/704 |
Current CPC
Class: |
H01L 2224/13144
20130101; H01L 2224/814 20130101; H01L 2924/14 20130101; H01L
2224/81815 20130101; H01L 2924/12042 20130101; H01L 2224/814
20130101; H01L 2224/13111 20130101; H01L 2224/8191 20130101; H01L
2224/13111 20130101; Y10T 428/28 20150115; H01L 2224/13144
20130101; H01L 2224/81024 20130101; H01L 2224/16225 20130101; H01L
2224/16227 20130101; H01L 2224/81193 20130101; Y10T 428/31504
20150401; H01L 21/6836 20130101; H01L 2224/13147 20130101; H01L
24/81 20130101; H01L 2924/12042 20130101; H01L 2224/13111 20130101;
Y10T 428/2804 20150115; H01L 2221/68327 20130101; H01L 2924/01047
20130101; H01L 2224/13147 20130101; H01L 2224/81007 20130101; H01L
23/3164 20130101; H01L 2924/01047 20130101; H01L 2924/00 20130101;
H01L 2924/00014 20130101; H01L 2924/01083 20130101; H01L 2924/00014
20130101; H01L 2924/00014 20130101; H01L 2924/014 20130101; H01L
2924/01029 20130101; H01L 2924/00 20130101; H01L 2924/00014
20130101; H01L 2924/14 20130101; H01L 2221/68377 20130101; Y10T
428/31721 20150401; Y10T 428/31855 20150401 |
Class at
Publication: |
438/113 ;
428/343; 428/473.5; 428/500; 428/704; 428/411.1; 257/E21.599 |
International
Class: |
H01L 21/78 20060101
H01L021/78; B32B 27/00 20060101 B32B027/00; B32B 7/12 20060101
B32B007/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 29, 2010 |
JP |
2010-170807 |
Claims
1. A film for flip chip type semiconductor back surface, which is
to be disposed on a back surface of a semiconductor element flip
chip-connected onto an adherend, the film for flip chip type
semiconductor back surface comprising an adhesive layer and a
protective layer laminated on the adhesive layer, wherein the
protective layer comprises a heat-resistant resin having a glass
transition temperature of 200.degree. C. or more or a metal.
2. The film for flip chip type semiconductor back surface according
to claim 1, wherein the heat-resistant resin is at least one
selected from the group consisting of a polyimide, a polyphenylene
sulfide, a polysulfone, a polyether imide, a polyether ketone and a
polyether ether ketone.
3. The film for flip chip type semiconductor back surface according
to claim 2, wherein the heat-resistant resin is a polyimide.
4. The film for flip chip type semiconductor back surface according
to claim 1, wherein the metal is at least one selected from the
group consisting of aluminum, alumite, stainless steel, iron,
titanium, tin and copper.
5. The film for flip chip type semiconductor back surface according
to claim 1, wherein a surface of the protective layer facing the
adhesive layer has been subjected to a surface activation
treatment.
6. The film for flip chip type semiconductor back surface according
to claim 5, wherein the surface activation treatment is at least
one treatment selected from the group consisting of a plasma
treatment, an ozone water treatment, an ultraviolet ozone treatment
and an ion beam treatment.
7. A dicing tape-integrated film for semiconductor back surface,
which comprises: a dicing tape comprising a base material and a
pressure-sensitive adhesive layer laminated on the base material,
and the film for flip chip type semiconductor back surface
according to claim 1, which is laminated on the pressure-sensitive
adhesive layer so that the protective layer faces the
pressure-sensitive adhesive layer.
8. A method for producing a semiconductor device, the method
comprising: attaching a semiconductor wafer onto the film for flip
chip type semiconductor back surface in the dicing tape-integrated
film for semiconductor back surface according to claim 7, dicing
the semiconductor wafer to form a semiconductor element, peeling
the semiconductor element together with the film for flip chip type
semiconductor back surface from the pressure-sensitive adhesive
layer of the dicing tape, adhering a flux to a connecting member
for an adherend in the semiconductor element, and flip
chip-connecting the semiconductor element onto the adherend.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a film for flip chip type
semiconductor back surface and to a dicing tape-integrated film for
semiconductor back surface using the same. The film for flip chip
type semiconductor back surface is used for protecting the back
surface of a semiconductor element such as a semiconductor chip and
for enhancing the strength thereof. Moreover, the invention relates
to a method for producing a semiconductor device using the dicing
tape-integrated film for semiconductor back surface.
BACKGROUND OF THE INVENTION
[0002] Recently, thinning and miniaturization of a semiconductor
device and its package have been increasingly demanded. Therefore,
as the semiconductor device and its package, flip chip type
semiconductor devices in which a semiconductor element such as a
semiconductor chip is mounted (flip chip-connected) on a substrate
by means of flip chip bonding have been widely utilized. In such
flip chip connection, a semiconductor chip is fixed to a substrate
in a form where the circuit face of the semiconductor chip is
opposed to the electrode-formed face of the substrate. In such a
semiconductor device or the like, there may be a case where the
back surface of the semiconductor chip is protected with a
protective film to prevent the semiconductor chip from damaging or
the like (see, Patent Document 1). The film for back surface may be
laser-marked to increase the product discrimination ability thereof
(see, Patent Document 2). [0003] Patent Document 1:
JP-A-2007-158026 [0004] Patent Document 2: JP-A-2008-166451
[0005] As a typical procedure of flip chip connection, a solder
bump and the like formed on a semiconductor chip surface to which a
film for back surface is bonded are immersed in a flux, thereafter,
the bump is brought into contact with an electrode formed on a
substrate (a solder bump is further formed on the electrode as
needed), and finally, the solder bump is allowed to melt to reflow
connect the solder bump to the electrode. The flux has been used
for the purposes of cleaning or oxidation prevention of the solder
bump, improvement of solder wettability, and the like, at the time
of soldering. By the procedure described above, good electrical
connection between the semiconductor chip and the substrate can be
formulated.
[0006] The flux is usually allowed to adhere to only the bump
portion herein. However, the flux adheres to the film for back
surface attached to a semiconductor chip back surface in some cases
depending on working conditions. Then, when the reflow connection
is performed while the flux adheres to the film for back surface,
flux-derived stains occur on a surface of the film for back surface
to cause a fear of deteriorating appearance properties or laser
marking properties.
[0007] The invention has been made in consideration of the
foregoing problem, and an object thereof is to provide a film for
flip chip type semiconductor back surface, which can prevent the
occurrence of stains even when a flux adheres thereto and can
produce a semiconductor device having excellent appearance
properties, a dicing tape-integrated film for semiconductor back
surface using the same, and a method for producing the
semiconductor device.
[0008] In order to solve the foregoing problem, the present
inventors have made investigations. As a result, the inventors have
found that a film for flip chip type semiconductor back surface,
which can prevent the occurrence of flux-derived stains and can
produce a semiconductor device having excellent appearance
properties, can be provided by employing the following
constitution, and have completed the invention.
[0009] Namely, the present invention provides a film for flip chip
type semiconductor back surface, which is to be disposed on a back
surface of a semiconductor element flip chip-connected onto an
adherend, the film for flip chip type semiconductor back surface
comprising an adhesive layer and a protective layer laminated on
the adhesive layer, wherein the protective layer comprises a
heat-resistant resin having a glass transition temperature of
200.degree. C. or more or a metal.
[0010] In the film for semiconductor back surface, a layer composed
of a heat-resistant resin having a glass transition temperature of
200.degree. C. or more or a metal is formed as a protective layer,
so that a flux component is finally evaporated without entering the
protective layer, at reflow for flip chip bonding. As a result, the
occurrence of the flux-derived stains on the film for semiconductor
back surface can be prevented. The reason for such stain inhibition
is estimated as follows, although it is not sure. When the flux
adheres to the film for back surface having no protective layer, a
molecular structure of the resin constituting the film for back
surface is largely loosened at a reflow temperature. It becomes
therefore easy for the flux component to enter the film for back
surface, and the flux component finally remains in a state where
both are partially compatible, resulting in the occurrence of the
stains. On the other hand, in the film for semiconductor back
surface of the invention, the protective layer composed of the
heat-resistant resin having a glass transition temperature of
200.degree. C. or more or the metal is provided. Accordingly, a
micro structure (the molecular structure or an atomic structure) in
the protective layer is inhibited from being loosened or not
substantially loosened even at the reflow temperature, whereby the
flux component is inhibited from entering the protective layer. The
flux remaining on a surface of the film for semiconductor back
surface is evaporated by heating at reflow. As a result, the
occurrence of the flux-derived stains is prevented.
[0011] The above-mentioned heat-resistant resin is preferably at
least one selected from the group consisting of a polyimide, a
polyphenylene sulfide, a polysulfone, a polyether imide, a
polyether ketone and a polyether ether ketone. These resins can
efficiently prevent the occurrence of the flux-derived stains
because of their easy availability, rigid molecular structure and
extremely high glass transition temperature. Of these, polyimide is
preferred as the heat-resistant resin.
[0012] The above-mentioned metal is preferably at least one
selected from the group consisting of aluminum, alumite, stainless
steel, iron, titanium, tin and copper. These metals can exhibit not
only an effect of preventing the occurrence of the flux-derived
stains, but also excellent laser marking properties.
[0013] When a surface of the above-mentioned protective layer
facing the adhesive layer has been subjected to a surface
activation treatment, adhesive force between the protective layer
and the adhesive layer can be improved. Accordingly, both can be
prevented from being peeled in production steps of a semiconductor
device and at the time of use as a product after the production,
and a semiconductor device having high reliability can be
produced.
[0014] The above-mentioned surface activation treatment is
preferably at least one treatment selected from the group
consisting of a plasma treatment, an ozone water treatment, an
ultraviolet ozone treatment and an ion beam treatment. By these
treatments, surface activation can be efficiently performed, even
when the protective layer is composed of any one of the
heat-resistant resins and the metals.
[0015] The present invention further provides a dicing
tape-integrated film for semiconductor back surface, which
comprises: a dicing tape comprising a base material and a
pressure-sensitive adhesive layer laminated on the base material,
and the above-mentioned film for flip chip type semiconductor back
surface, which is laminated on the pressure-sensitive adhesive
layer so that the protective layer faces the pressure-sensitive
adhesive layer.
[0016] In the dicing tape-integrated film for semiconductor back
surface having the above-mentioned constitution, the dicing tape
and the film for flip chip type semiconductor back surface are
integrally formed. Accordingly, the dicing tape-integrated film of
this type can be used in a dicing step of dicing a semiconductor
wafer to produce a semiconductor element, and also in a subsequent
picking up step. That is to say, in the case where the dicing tape
is attached to a back surface of the semiconductor wafer prior to
the dicing step, the above-mentioned film for semiconductor back
surface can also be attached thereto, so that a step of attaching
only the film for semiconductor back surface thereto (a
semiconductor back surface film attaching step) is not required. As
a result, the number of process steps may be reduced. Moreover, the
back surface of the semiconductor wafer or the semiconductor
element formed by dicing is protected by the film for semiconductor
back surface with the adhesive layer. Accordingly, in the dicing
step and subsequent steps (such as the picking up step), damage of
the semiconductor element can be reduced or prevented, and the
occurrence of the flux-derived stains at flip chip bonding can be
prevented, thereby being able to produce a semiconductor device
having excellent appearance properties.
[0017] The present invention furthermore provides a method for
producing a semiconductor device, the method comprising: attaching
a semiconductor wafer onto the film for flip chip type
semiconductor back surface in the above-mentioned dicing
tape-integrated film for semiconductor back surface, dicing the
semiconductor wafer to form a semiconductor element, peeling the
semiconductor element together with the film for flip chip type
semiconductor back surface from the pressure-sensitive adhesive
layer of the dicing tape, adhering a flux to a connecting member
for an adherend in the semiconductor element, and flip
chip-connecting the semiconductor element onto the adherend.
[0018] In the production method, the film for flip chip type
semiconductor back surface on which the protective layer is formed
is used, so that the occurrence of the flux-derived stains on the
film for semiconductor back surface can be prevented in the flip
chip bonding step, and the semiconductor device having excellent
appearance properties can be efficiently produced.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is a cross-sectional schematic view showing one
embodiment of a dicing tape-integrated film for semiconductor back
surface of the invention.
[0020] FIG. 2 is a cross-sectional schematic view showing one
embodiment of a film for flip chip type semiconductor back surface
of the invention.
[0021] FIGS. 3A to 3D are cross-sectional schematic views showing
one embodiment of a method for producing a semiconductor device
using a dicing tape-integrated film for semiconductor back surface
of the invention.
DESCRIPTION OF REFERENCE NUMERALS AND SIGNS
[0022] 1 Dicing Tape-Integrated Film for Semiconductor Back Surface
[0023] 2 Film for Semiconductor Back Surface [0024] 21 Adhesive
Layer [0025] 22 Protective Layer [0026] 3 Dicing Tape [0027] 31
Base Material [0028] 32 Pressure-Sensitive Adhesive Layer [0029] 33
Part Corresponding to Semiconductor Wafer-Attaching Part [0030] 4
Semiconductor Wafer [0031] 5 Semiconductor Chip [0032] 51 Bump
Formed on the Circuit Face Side of Semiconductor Chip 5 [0033] 6
Adherend [0034] 61 Conductive Material for Connection Adhered to
Connection Pad of Adherend 6
BEST MODE FOR CARRYING OUT THE INVENTION
[0035] Embodiments of the invention will be described with
reference to the drawings, but the invention is not restricted to
these embodiments. Incidentally, in the drawings in the present
specification, parts that are unnecessary for the description are
omitted, and there are parts shown by magnifying, minifying or the
like in order to make the description easy.
(Dicing Tape-Integrated Film for Semiconductor Back Surface)
[0036] FIG. 1 is a cross-sectional schematic view showing one
embodiment of a dicing tape-integrated film for semiconductor back
surface according to the invention. As shown in FIG. 1, the dicing
tape-integrated film 1 for semiconductor back surface (hereinafter
sometimes also referred to as "dicing tape-integrated semiconductor
back surface protective film", "film for semiconductor back surface
with dicing tape", or "semiconductor back surface protective film
with dicing tape") comprises a dicing tape 3 including a
pressure-sensitive adhesive layer 32 formed on a base material 31,
and a film 2 for flip chip type semiconductor back surface
(hereinafter sometimes referred to as "film for back surface",
"film for semiconductor back surface" or "semiconductor back
surface protective film") provided on the pressure-sensitive
adhesive layer. As described later, the film 2 for semiconductor
back surface includes an adhesive layer and a protective layer
laminated on this adhesive layer.
[0037] Also, as shown in FIG. 1, the dicing tape-integrated film
for semiconductor back surface of the invention may be so designed
that the film 2 for semiconductor back surface is formed only on
the part 33 corresponding to the semiconductor wafer-attaching
part; however, the film for semiconductor back surface may be
formed over the whole surface of the pressure-sensitive adhesive
layer 32, or the film for semiconductor back surface may be formed
on the part larger than the part 33 corresponding to the
semiconductor wafer-attaching part but smaller than the whole
surface of the pressure-sensitive adhesive layer 32. Incidentally,
the surface of the film 2 for semiconductor back surface (surface
to be attached to the back surface of wafer) may be protected with
a separator or the like until the film is attached to wafer back
surface. The followings sequentially describes the film for
semiconductor back surface and the dicing tape-integrated film for
semiconductor back surface in detail.
(Film for Flip Chip Type Semiconductor Back Surface)
[0038] FIG. 2 is a cross-sectional schematic view showing one
embodiment of a film for flip chip type semiconductor back surface
of the invention. The film 2 for flip chip type semiconductor back
surface has a film-shaped configuration, and includes an adhesive
layer 21 and a protective layer 22 laminated on the adhesive layer
21. The adhesive layer 21 is usually in an uncured state (including
a semi-cured state) in the shape of the dicing tape-integrated film
for semiconductor back surface as a product, and is thermally cured
after the dicing tape-integrated film for semiconductor back
surface is attached to the semiconductor wafer.
[0039] Moreover, the light transmittance with a visible light
(visible light transmittance, wavelength: 400 to 800 nm) in the
film 2 for semiconductor back surface is not particularly
restricted but is, for example, preferably in the range of 20% or
less (0 to 20%), more preferably 10% or less (0 to 10%), and
particularly preferably 5% or less (0 to 5%). When the film 2 for
semiconductor back surface has a visible light transmittance of
more than 20%, there is a concern that the transmission of the
light may adversely influence the semiconductor element. The
visible light transmittance (%) can be controlled by the kind and
content of the resin components of the film 2 for semiconductor
back surface, the kind and content of the coloring agent (such as
pigment or dye), the content of the inorganic filer, and the
like.
[0040] The visible light transmittance (%) of the film 2 for
semiconductor back surface can be determined as follows. Namely, a
film 2 for semiconductor back surface having a thickness (average
thickness) of 20 .mu.m itself is prepared. Then, the film 2 for
semiconductor back surface is irradiated with a visible light
having a wavelength of 400 to 800 nm in a prescribed intensity
[apparatus: a visible light generating apparatus manufactured by
Shimadzu Corporation [trade name "ABSORPTION SPECTRO PHOTOMETER"],
and the intensity of transmitted visible light is measured.
Further, the visible light transmittance (%) can be determined
based on intensity change before and after the transmittance of the
visible light through the film 2 for semiconductor back surface. In
this regard, it is also possible to derive visible light
transmittance (%; wavelength: 400 to 800 nm) of the film 2 for
semiconductor back surface having a thickness of 20 .mu.m from the
value of the visible light transmittance (%; wavelength: 400 to 800
nm) of the film 2 for semiconductor back surface whose thickness is
not 20 .mu.m. In the invention, the visible light transmittance (%)
is determined in the case of the film 2 for semiconductor back
surface having a thickness of 20 .mu.m, but the film for
semiconductor back surface according to the invention is not
limited to one having a thickness of 20 .mu.m.
(Adhesive Layer)
[0041] The adhesive layer 21 is preferably formed of at least a
thermosetting resin, and more preferably formed of at least a
thermosetting resin and a thermoplastic resin. Further, a thermal
curing-accelerating catalyst may be allowed to be contained in the
resin constituting the adhesive layer 21. The adhesive layer is
formed of at least the thermosetting resin, thereby being able to
effectively exhibit an adhesive function thereof.
[0042] Examples of the thermoplastic resin include natural rubber,
butyl rubber, isoprene rubber, chloroprene rubber, an
ethylene-vinyl acetate copolymer, an ethylene-acrylic acid
copolymer, an ethylene-acrylic acid ester copolymer, a
polybutadiene resin, a polycarbonate resin, a thermoplastic
polyimide resin, a polyamide resin such as 6-nylon and 6,6-nylon, a
phenoxy resin, an acrylic resin, a saturated polyester resin such
as PET (polyethylene terephthalate) or PBT (polybutylene
terephthalate), a polyamideimide resin, or a fluorine resin. The
thermoplastic resin may be employed singly or in a combination of
two or more kinds. Among these thermoplastic resins, an acrylic
resin containing a small amount of ionic impurities, having high
heat resistance and capable of securing reliability of a
semiconductor element is especially preferable.
[0043] The acrylic resins are not particularly restricted, and
examples thereof include polymers containing one kind or two or
more kinds of esters of acrylic acid or methacrylic acid having a
straight chain or branched alkyl group having 30 or less carbon
atoms, preferably 4 to 18 carbon atoms, more preferably 6 to 10
carbon atoms, and especially 8 or 9 carbon atoms as component(s).
Namely, in the invention, the acrylic resin has a broad meaning
also including a methacrylic resin. Examples of the alkyl group
include a methyl group, an ethyl group, a propyl group, an
isopropyl group, an n-butyl group, a t-butyl group, an isobutyl
group, a pentyl group, an isopentyl group, a hexyl group, a heptyl
group, a 2-ethylhexyl group, an octyl group, an isooctyl group, a
nonyl group, an isononyl group, a decyl group, an isodecyl group,
an undecyl group, a dodecyl group (lauryl group), a tridecyl group,
a tetradecyl group, a stearyl group, and an octadecyl group.
[0044] Moreover, other monomers for forming the acrylic resins
(monomers other than the alkyl esters of acrylic acid or
methacrylic acid in which the alkyl group is one having 30 or less
carbon atoms) are not particularly restricted, and examples thereof
include carboxyl group-containing monomers such as acrylic acid,
methacrylic acid, carboxylethyl acrylate, carboxylpentyl 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)methylacrylate; 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; and phosphoric acid group-containing monomers such as
2-hydroxyethylacryloyl phosphate. In this regard, the (meth)acrylic
acid means acrylic acid and/or methacrylic acid, (meth)acrylate
means acrylate and/or methacrylate, (meth)acryl means acryl and/or
methacryl, etc., which shall be applied over the whole
specification.
[0045] Moreover, examples of the thermosetting resin include, in
addition to an epoxy resin and a phenol resin, an amino resin, an
unsaturated polyester resin, a polyurethane resin, a silicone resin
and a thermosetting polyimide resin. The thermosetting resin may be
employed singly or in a combination of two or more kinds. As the
thermosetting resin, an epoxy resin containing only a small amount
of ionic impurities which corrode a semiconductor element is
suitable. Also, the phenol resin is suitably used as a curing agent
of the epoxy resins.
[0046] The epoxy resin is not particularly restricted and, for
example, a difunctional epoxy resin or a polyfunctional epoxy resin
such as a bisphenol A type epoxy resin, a bisphenol F type epoxy
resin, a bisphenol S type epoxy resin, a brominated bisphenol A
type epoxy resin, a hydrogenated bisphenol A type epoxy resin, a
bisphenol AF type epoxy resin, a biphenyl type epoxy resin, a
naphthalene type epoxy resin, a fluorene type epoxy resin, a phenol
novolak type epoxy resin, an o-cresol novolak type epoxy resin, a
trishydroxyphenylmethane type epoxy resin and a tetraphenylolethane
type epoxy resin, or an epoxy resin such as a hydantoin type epoxy
resin, a trisglycidylisocyanurate type epoxy resin or a
glycidylamine type epoxy resin may be used.
[0047] As the epoxy resin, among those exemplified above, a novolak
type epoxy resin, a biphenyl type epoxy resin, a
trishydroxyphenylmethane type epoxy resin, and a
tetraphenylolethane type epoxy resin are preferable. This is
because these epoxy resins have high reactivity with a phenol resin
as a curing agent and are superior in heat resistance and the
like.
[0048] Furthermore, the above-mentioned phenol resin acts as a
curing agent of the epoxy resin, and examples thereof include
novolak type phenol resins such as phenol novolak resins, phenol
aralkyl resins, cresol novolak resins, tert-butylphenol novolak
resins, and nonylphenol novolak resins; resol type phenol resins;
and polyoxystyrenes such as poly-p-oxystyrene. The phenol resin may
be employed singly or in a combination of two or more kinds. Among
these phenol resins, phenol novolak resins and phenol aralkyl
resins are especially preferable. This is because connection
reliability of the semiconductor device can be improved.
[0049] The mixing ratio of the epoxy resin to the phenol resin is
preferably made, for example, such that the hydroxyl group in the
phenol resin becomes 0.5 to 2.0 equivalents per equivalent of the
epoxy group in the epoxy resin component. It is more preferably 0.8
to 1.2 equivalents. That is, when the mixing ratio becomes outside
the range, a curing reaction does not proceed sufficiently, and the
characteristics of the epoxy resin cured product tends to
deteriorate.
[0050] The content of the above-mentioned thermosetting resin is
preferably from 5% by weight to 90% by weight, more preferably from
10% by weight to 85% by weight, and still more preferably from 15%
by weight to 80% by weight, based on all the resin components in
the adhesive layer. The thermosetting shrinkage can be easily
controlled to 2% by volume or more by adjusting the above-mentioned
content to 5% by weight or more. Further, when an encapsulation
resin is thermally cured, the adhesive layer can be fully thermally
cured, and surely adhered and fixed to the back surface of the
semiconductor element, which makes it possible to produce the flip
chip type semiconductor device with no peeling. On the other hand,
the warpage of a package (PKG: flip chip type semiconductor device)
can be inhibited by adjusting the above-mentioned content to 90% by
weight or less.
[0051] Not specifically defined, the thermal curing-accelerating
catalyst for the epoxy resin and the phenol resin may be suitably
selected from known thermal curing-accelerating catalysts. One or
more thermal curing-accelerating catalysts may be used here either
singly or as combined. As the thermal curing-accelerating catalyst,
for example, an amine-based curing-accelerating catalyst, a
phosphorus-based curing-accelerating catalyst, an imidazole-based
curing-accelerating catalyst, a boron-based curing-accelerating
catalyst, or a phosphorus-boron-based curing-accelerating catalyst
can be used.
[0052] The adhesive layer 21 is particularly suitably formed of a
resin composition containing an epoxy resin and a phenolic resin or
a resin composition containing an epoxy resin, a phenolic resin,
and an acrylic resin. Since these resins contain only a small
amount of ionic impurities and have high heat resistance,
reliability of semiconductor elements can be secured.
[0053] It is important that the adhesive layer 21 has adhesiveness
(close adhesiveness) to the back surface (non-circuit-formed face)
of semiconductor wafer. The adhesive layer 21 can be, for example,
formed of a resin composition containing an epoxy resin as a
thermosetting resin component. In case where the adhesive layer 21
is cured beforehand to some degree, at its preparation, it is
preferable to add a polyfunctional compound capable of reacting
with the functional group or the like at the molecular chain end of
the polymer as a crosslinking agent. Thereby, adhesive
characteristics under high temperature can be enhanced and
improvement of the heat resistance of the film can be achieved.
[0054] The adhesive force of the adhesive layer 21 to semiconductor
wafer (23.degree. C., peeling angle of 180 degrees, peeling rate of
300 mm/min) is preferably within a range of from 0.5 N/20 mm to 15
N/20 mm, more preferably from 0.7 N/20 mm to 10 N/20 mm. When the
adhesive force is at least 0.5 N/20 mm, then the film can be
adhered to semiconductor wafer and semiconductor element with
excellent adhesiveness and is free from film swelling or the like
adhesion failure. In addition, in dicing of semiconductor wafer,
the chips can be prevented from flying out. On the other hand, when
the adhesive force is at most 15 N/20 mm, then it facilitates
peeling from the dicing tape.
[0055] The crosslinking agent is not particularly restricted and
known crosslinking agents can be used. Specifically, for example,
not only isocyanate-based crosslinking agents, epoxy-based
crosslinking agents, melamine-based crosslinking agents, and
peroxide-based crosslinking agents but also urea-based crosslinking
agents, metal alkoxide-based crosslinking agents, metal
chelate-based crosslinking agents, metal salt-based crosslinking
agents, carbodiimide-based crosslinking agents, oxazoline-based
crosslinking agents, aziridine-based crosslinking agents,
amine-based crosslinking agents, and the like may be mentioned. As
the crosslinking agent, an isocyanate-based crosslinking agent or
an epoxy-based crosslinking agent is suitable. The crosslinking
agent may be employed singly or in a combination of two or more
kinds.
[0056] Examples of the isocyanate-based crosslinking agents include
lower aliphatic polyisocyanates such as 1,2-ethylene diisocyanate,
1,4-butylene diisocyanate, and 1,6-hexamethylene diisocyanate;
alicyclic polyisocyanates such as cyclopentylene diisocyanate,
cyclohexylene diisocyanate, isophorone diisocyanate, hydrogenated
tolylene diisocyanate, and hydrogenated xylylene diisocyanate; and
aromatic polyisocyanates such as 2,4-tolylene diisocyanate,
2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and
xylylene diisocyanate. In addition, a trimethylolpropane/tolylene
diisocyanate trimer adduct [a trade name "COLONATE L" manufactured
by Nippon Polyurethane Industry Co., Ltd.], a
trimethylolpropane/hexamethylene diisocyanate trimer adduct [a
trade name "COLONATE HL" manufactured by Nippon Polyurethane
Industry Co., Ltd.], and the like are also used. Moreover, examples
of the epoxy-based crosslinking agents include
N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidylaniline,
1,3-bis(N,N-glycidylaminomethyl)cyclohexane, 1,6-hexanediol
diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene
glycol diglycidyl ether, propylene glycol diglycidyl ether,
polyethylene glycol diglycidyl ether, polypropylene glycol
diglycidyl ether, sorbitol polyglycidyl ether, glycerol
polyglycidyl ether, pentaerythritol polyglycidyl ether,
polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether,
trimethylolpropnane polyglycidyl ether, adipic acid diglycidyl
ester, o-phthalic acid diglycidyl ester,
triglycidyl-tris(2-hydroxyethyl)isocyanurate, resorcin diglycidyl
ether, and bisphenol-S-diglycidyl ether, and also epoxy-based
resins having two or more epoxy groups in the molecule.
[0057] The amount of the crosslinking agent to be used is not
particularly restricted and can be appropriately selected depending
on the degree of the crosslinking. Specifically, it is preferable
that the amount of the crosslinking agent to be used is usually 7
parts by weight or less (for example, 0.05 to 7 parts by weight)
based on 100 parts by weight of the polymer component
(particularly, a polymer having a functional group at the molecular
chain end). When the amount of the crosslinking agent is larger
than 7 parts by weight based on 100 parts by weight of the polymer
component, the adhesive force is lowered, so that the case is not
preferred. From the viewpoint of improving the cohesive force, the
amount of the crosslinking agent is preferably 0.05 parts by weight
or more based on 100 parts by weight of the polymer component.
[0058] In the invention, instead of the use of the crosslinking
agent or together with the use of the crosslinking agent, it is
also possible to perform a crosslinking treatment by irradiation
with an electron beam, UV light, or the like.
[0059] The above-mentioned adhesive layer 21 may be colored. When
the protective layer is transparent, the colored adhesive layer can
exhibit excellent appearance properties through the protective
layer, which makes it possible to obtain the semiconductor device
having value-added appearance. The colored film for semiconductor
back surface can also accentuate marking on the transparent
protective layer, so that marking can be performed to impart
various kinds of information such as literal information and
graphical information to a face on the non-circuit side of the
semiconductor element or the semiconductor device using the
semiconductor element by utilizing any of various marking methods
such as a printing method and a laser marking method, through the
film for semiconductor back surface. In particular, by controlling
the color of coloring, it becomes possible to visually observe the
information (such as literal information and graphical information)
imparted by marking with excellent visibility. Moreover, when the
adhesive layer is colored, the dicing tape and the film for
semiconductor back surface can be easily distinguished from each
other, so that workability and the like can be improved.
Furthermore, for example, as the semiconductor device, it is also
possible to classify products thereof by color. In the case where
the film for semiconductor back surface is colored (in the case
where the film is neither colorless nor transparent), the color
shown by coloring is not particularly restricted. However, for
example, dark colors such as black, blue and red are preferred, and
black is especially suitable.
[0060] In the present embodiment, dark color basically means a dark
color having L*, defined in L*a*b* color space, of 60 or smaller (0
to 60), preferably 50 or smaller (0 to 50), and more preferably 40
or smaller (0 to 40).
[0061] Moreover, black color basically means a black-based color
having L*, defined in L*a*b* color space, of 35 or smaller (0 to
35), preferably 30 or smaller (0 to 30), and more preferably 25 or
smaller (0 to 25). In this regard, in the black color, each of a*
and b*, defined in the L*a*b* color space, can be suitably selected
according to the value of L*. For example, both of a* and b* are
within the range of preferably -10 to 10, more preferably -5 to 5,
and further preferably -3 to 3 (particularly 0 or about 0).
[0062] In the present embodiment, L*, a*, and b* defined in the
L*a*b* color space can be determined by a measurement with a color
difference meter (a trade name "CR-200" manufactured by Minolta
Ltd; color difference meter). The L*a*b* color space is a color
space recommended by the Commission Internationale de l'Eclairage
(CIE) in 1976, and means a color space called CIE1976 (L*a*b*)
color space. Also, the L*a*b* color space is defined in Japanese
Industrial Standards in JIS Z8729.
[0063] At coloring of the adhesive layer 21, according to an
objective color, a colorant (coloring agent) can be used. As such a
colorant, various dark-colored colorants such as black-colored
colorants, blue-colored colorants, and red-colored colorants can be
suitably used and black-colored colorants are more suitable. The
colorant may be any of pigments and dyes. The colorant may be
employed singly or in combination of two or more kinds. In this
regard, as the dyes, it is possible to use any forms of dyes such
as acid dyes, reactive dyes, direct dyes, disperse dyes, and
cationic dyes. Moreover, also with regard to the pigments, the form
thereof is not particularly restricted and can be suitably selected
and used among known pigments.
[0064] In particular, when a dye is used as a colorant, the dye
becomes in a state that it is homogeneously or almost homogeneously
dispersed by dissolution in the adhesive layer 21, so that the film
for semiconductor back surface (as a result, the dicing
tape-integrated film for semiconductor back surface) having a
homogeneous or almost homogeneous color density can be easily
produced. Accordingly, when a dye is used as a colorant, the film
for semiconductor back surface in the dicing tape-integrated film
for semiconductor back surface can have a homogeneous or almost
homogeneous color density and can enhance a marking property and an
appearance property.
[0065] The black-colored colorant is not particularly restricted
and can be, for example, suitably selected from inorganic
black-colored pigments and black-colored dyes. Moreover, the
black-colored colorant may be a colorant mixture in which a
cyan-colored colorant (blue-green colorant), a magenta-colored
colorant (red-purple colorant), and a yellow-colored colorant
(yellow colorant) are mixed. The black-colored colorant may be
employed singly or in a combination of two or more kinds. Of
course, the black-colored colorant may be used in combination with
a colorant of a color other than black.
[0066] Specific examples of the black-colored colorant include
carbon black (such as furnace black, channel black, acetylene
black, thermal black, or lamp black), graphite, copper oxide,
manganese dioxide, azo-type pigments (such as azomethine azo
black), aniline black, perylene black, titanium black, cyanine
black, active charcoal, ferrite (such as non-magnetic ferrite or
magnetic ferrite), magnetite, chromium oxide, iron oxide,
molybdenum disulfide, a chromium complex, a composite oxide type
black pigment, and an anthraquinone type organic black pigment.
[0067] In the invention, as the black-colored colorant,
black-colored dyes such as C.I. Solvent Black 3, 7, 22, 27, 29, 34,
43, 70, C.I. Direct Black 17, 19, 22, 32, 38, 51, 71, C.I. Acid
Black 1, 2, 24, 26, 31, 48, 52, 107, 109, 110, 119, 154, and C.I.
Disperse Black 1, 3, 10, 24; black-colored pigments such as C.I.
Pigment Black 1, 7; and the like can also be utilized.
[0068] As such black-colored colorants, for example, a trade name
"Oil Black BY", a trade name "Oil Black BS", a trade name "Oil
Black HBB", a trade name "Oil Black 803", a trade name "Oil Black
860", a trade name "Oil Black 5970", a trade name "Oil Black 5906",
a trade name "Oil Black 5905" (manufactured by Orient Chemical
Industries Co., Ltd.), and the like are commercially available.
[0069] Examples of colorants other than the black-colored colorant
include cyan-colored colorants, magenta-colored colorants, and
yellow-colored colorants. Examples of the cyan-colored colorants
include cyan-colored dyes such as C.I. Solvent Blue 25, 36, 60, 70,
93, 95; C.I. Acid Blue 6 and 45; cyan-colored pigments such as C.I.
Pigment Blue 1, 2, 3, 15, 15:1, 15:2, 15:3, 15:4, 15:5, 15:6, 16,
17, 17:1, 18, 22, 25, 56, 60, 63, 65, 66; C.I. Vat Blue 4, 60; and
C.I. Pigment Green 7.
[0070] Moreover, among the magenta colorants, examples of
magenta-colored dye include C.I. Solvent Red 1, 3, 8, 23, 24, 25,
27, 30, 49, 52, 58, 63, 81, 82, 83, 84, 100, 109, 111, 121, 122;
C.I. Disperse Red 9; C.I. Solvent Violet 8, 13, 14, 21, 27; C.I.
Disperse Violet 1; C.I. Basic Red 1, 2, 9, 12, 13, 14, 15, 17, 18,
22, 23, 24, 27, 29, 32, 34, 35, 36, 37, 38, 39, 40; C.I. Basic
Violet 1, 3, 7, 10, 14, 15, 21, 25, 26, 27 and 28.
[0071] Among the magenta-colored colorants, examples of
magenta-colored pigment include C.I. Pigment Red 1, 2, 3, 4, 5, 6,
7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 21, 22, 23, 30,
31, 32, 37, 38, 39, 40, 41, 42, 48:1, 48:2, 48:3, 48:4, 49, 49:1,
50, 51, 52, 52:2, 53:1, 54, 55, 56, 57:1, 58, 60, 60:1, 63, 63:1,
63:2, 64, 64:1, 67, 68, 81, 83, 87, 88, 89, 90, 92, 101, 104, 105,
106, 108, 112, 114, 122, 123, 139, 144, 146, 147, 149, 150, 151,
163, 166, 168, 170, 171, 172, 175, 176, 177, 178, 179, 184, 185,
187, 190, 193, 202, 206, 207, 209, 219, 222, 224, 238, 245; C.I.
Pigment Violet 3, 9, 19, 23, 31, 32, 33, 36, 38, 43, 50; C.I. Vat
Red 1, 2, 10, 13, 15, 23, 29 and 35.
[0072] Moreover, examples of the yellow-colored colorants include
yellow-colored dyes such as C.I. Solvent Yellow 19, 44, 77, 79, 81,
82, 93, 98, 103, 104, 112, and 162; yellow-colored pigments such as
C.I. Pigment Orange 31, 43; C.I. Pigment Yellow 1, 2, 3, 4, 5, 6,
7, 10, 11, 12, 13, 14, 15, 16, 17, 23, 24, 34, 35, 37, 42, 53, 55,
65, 73, 74, 75, 81, 83, 93, 94, 95, 97, 98, 100, 101, 104, 108,
109, 110, 113, 114, 116, 117, 120, 128, 129, 133, 138, 139, 147,
150, 151, 153, 154, 155, 156, 167, 172, 173, 180, 185, 195; C.I.
Vat Yellow 1, 3, and 20.
[0073] Various colorants such as cyan-colored colorants,
magenta-colored colorants, and yellow-colorant colorants may be
employed singly or in a combination of two or more kinds,
respectively. In this regard, in the case where two or more kinds
of various colorants such as cyan-colored colorants,
magenta-colored colorants, and yellow-colorant colorants are used,
the mixing ratio (or blending ratio) of these colorants is not
particularly restricted and can be suitably selected according to
the kind of each colorant, an objective color, and the like.
[0074] In the case where the adhesive layer 21 is colored, the
colored form is not particularly restricted. The adhesive layer 21
may be, for example, a single-layer film-shaped article added with
a coloring agent. Moreover, the adhesive layer 21 may be a
laminated film where a resin layer formed of at least a
thermosetting resin and a coloring agent layer are at least
laminated. In this regard, in the case where the adhesive layer 21
is a laminated film of the resin layer and the coloring agent
layer, the adhesive layer 21 in the laminated form preferably has a
laminated form of a resin layer/a coloring agent layer/a resin
layer. In this case, two resin layers at both sides of the coloring
agent layer may be resin layers having the same composition or may
be resin layers having different composition.
[0075] Into the adhesive layer 21, other additives can be suitably
blended according to the necessity. Examples of the other additives
include an extender, an antiaging agent, an antioxidant, and a
surfactant, in addition to a filler, a flame retardant, a
silane-coupling agent, and an ion-trapping agent.
[0076] The filler may be any of an inorganic filler and an organic
filler, but is preferably an inorganic filler. Incorporating the
other filler such as an inorganic filler thereinto makes it
possible to impart electroconductivity to the adhesive layer 21, to
enhance the thermal conductivity of the adhesive layer 21 and to
control the elasticity of the adhesive layer 21. The adhesive layer
21 may be electroconductive or non-electroconductive. The inorganic
filler includes various inorganic powders of, for example, ceramics
such as silica, clay, gypsum, calcium carbonate, barium sulfate,
beryllium oxide; metals such as aluminium, copper, silver, gold,
nickel, chromium, lead, tin, zinc, palladium, solder; their alloys
and other carbon. One or more such fillers may be used here either
singly or as combined. As the filler, preferred is silica, and more
preferred is fused silica. Preferably, the average particle size of
the inorganic filler is within a range of from 0.1 .mu.m to 80
.mu.m. The average particle size of the inorganic filler is
determined with a laser diffraction particle sizer.
[0077] The blending amount of the filler (in particular, inorganic
filler) is preferably 80 parts by weight or less (0 part by weight
to 80 parts by weight) and more preferably 0 part by weight to 70
parts by weight based on 100 parts by weight of the organic resin
components.
[0078] Examples of the flame retardant include antimony trioxide,
antimony pentoxide, and brominated epoxy resins. The flame
retardant may be employed singly or in a combination of two or more
kinds. Examples of the silane coupling agent include
.beta.-(3,4-epoxycyclohexyl)ethyltrimethoxysilane,
.gamma.-glycidoxypropyltrimethoxysilane, and
.gamma.-glycidoxypropylmethyldiethoxysilane. The silane coupling
agent may be employed singly or in a combination of two or more
kinds. Examples of the ion-trapping agent include hydrotalcites and
bismuth hydroxide. The ion-trapping agent may be employed singly or
in a combination of two or more kinds.
[0079] Incidentally, in the case where the adhesive layer 21 is
formed of a resin composition containing a thermosetting resin such
as an epoxy resin, the adhesive layer 21 is in a state that the
thermosetting resin is uncured or partially cured at a stage before
the film is applied to a semiconductor wafer. In this case, after
it is applied to the semiconductor wafer (specifically, usually, at
the time when the encapsulating material is cured in the flip chip
bonding step), the thermosetting resin in the adhesive layer 21 is
completely or almost completely cured.
[0080] As above, since the adhesive layer 21 is in a state that the
thermosetting resin is uncured or partially cured even when the
film contains the thermosetting resin, the gel fraction of the
adhesive layer 21 is not particularly restricted but is, for
example, suitably selected from the range of 50% by weight or less
(0 to 50% by weight) and is preferably 30% by weight or less (0 to
30% by weight) and particularly preferably 10% by weight or less (0
to 10% by weight). The gel fraction of the adhesive layer 21 can be
measured by the following measuring method.
[0081] <Gel Fraction Measuring Method>
[0082] About 0.1 g of a sample is sampled from the adhesive layer
21 and precisely weighed (weight of sample) and, after the sample
is wrapped in a mesh-type sheet, it is immersed in about 50 mL of
toluene at room temperature for 1 week. Thereafter, a
solvent-insoluble matter (content in the mesh-type sheet) is taken
out of the toluene and dried at 130.degree. C. for about 2 hours,
the solvent-insoluble matter after drying is weighed (weight after
immersion and drying), and a gel fraction (% by weight) is then
calculated according to the following expression (a).
Gel fraction(% by weight)=[(Weight after immersion and
Drying)/(Weight of sample)].times.100 (a)
[0083] The gel fraction of the adhesive layer 21 can be controlled
by the kind and content of the resin components and the kind and
content of the crosslinking agent and besides, heating temperature,
heating time and the like.
[0084] In the invention, in the case where the adhesive layer 21 is
a film-shaped article formed of a resin composition containing a
thermosetting resin such as an epoxy resin, close adhesiveness to a
semiconductor wafer can be effectively exhibited.
[0085] Incidentally, since cutting water is used in the dicing step
of the semiconductor wafer, the adhesive layer 21 absorbs moisture
to have a moisture content of a normal state or more in some cases.
When flip chip bonding is performed with still maintaining such a
high moisture content, water vapor remains at the adhesion
interface between the adhesive layer 21 and the semiconductor wafer
or its processed body (semiconductor) and lifting is generated in
some cases. Therefore, by constituting the adhesive layer 21 as a
configuration in which a core material having a high moisture
permeability is provided on each surface thereof, water vapor
diffuses and thus it becomes possible to avoid such a problem. From
such a viewpoint, a multilayered structure in which the adhesive
layer is formed at one surface or both surfaces of the core
material may be used as the adhesive layer 21. Examples of the core
material include films (e.g., polyimide films, polyester films,
polyethylene terephthalate films, polyethylene naphthalate films,
polycarbonate films, etc.), resin substrates reinforced with a
glass fiber or a plastic nonwoven fiber, silicon substrates, and
glass substrates.
[0086] The thickness (total thickness in the case of the laminated
film) of the adhesive layer 21 is not particularly restricted but
can be, for example, suitably selected from the range of about 2
.mu.m to 200 .mu.m. Furthermore, the thickness is preferably about
3 .mu.m to 160 .mu.m, more preferably about 4 .mu.m to 100 .mu.m,
and particularly about 5 .mu.m to 80 .mu.m.
[0087] The tensile storage elastic modulus of the above-mentioned
adhesive layer 21 in an uncured state at 23.degree. C. is
preferably 1 GPa or more (for example, 1 GPa to 50 GPa), more
preferably 2 GPa or more, and particularly preferably 3 GPa or
more. Incidentally, in the case where the adhesive layer 21 is
formed of the resin composition containing the thermosetting resin,
the thermosetting resin is usually in an uncured or partially cured
state, as described above. Accordingly, the elastic modulus of the
adhesive layer 21 at 23.degree. C. is usually the tensile storage
elastic modulus at 23.degree. C. in a state where the thermosetting
resin is uncured or partially cured.
[0088] Here, the adhesive layer 21 may be either a single layer or
a laminated film where a plurality of layers are laminated. In the
case of the laminated film, the tensile storage elastic modulus is
sufficiently 1 GPa or more (e.g., 1 GPa to 50 GPa) as the whole
laminated film in an uncured state. Also the tensile storage
elastic modulus (23.degree. C.) of the adhesive layer in an uncured
state can be controlled by suitably setting up the kind and content
of the resin components (thermoplastic resin and/or thermosetting
resin) or the kind and content of a filler such as a silica filler.
In the case where the adhesive layer 21 is a laminated film where a
plurality of layers are laminated (in the case where the adhesive
layer has a form of the laminated layer), as the lamination form,
is not particularly limited. Moreover, between the adhesive layer
and the protective layer, other layers (an intermediate layer, a
light-shielding layer, a reinforcing layer, a colored layer, a base
material layer, an electromagnetic wave-shielding layer, a heat
conductive layer, a pressure-sensitive adhesive layer, etc.) may be
provided.
[0089] The tensile storage elastic modulus is determined by
preparing the film-shaped adhesive layer 21 in an uncured state
without lamination onto the dicing tape 3 and measuring elastic
modulus in a tensile mode under conditions of a sample width of 10
mm, a sample length of 22.5 mm, a sample thickness of 0.2 mm, a
frequency of 1 Hz, and a temperature elevating rate of 10.degree.
C./minute under a nitrogen atmosphere at a prescribed temperature
(23.degree. C.) using a dynamic viscoelasticity measuring apparatus
"Solid Analyzer RS A2" manufactured by Rheometrics Co. Ltd. and the
measured elastic modulus is regarded as a value of tensile storage
elastic modulus obtained.
[0090] Preferably, the surface of the adhesive layer which is
opposite to the surface thereof that faces the protective layer is
protected with a separator (release liner) (not shown in figures).
The separator has a function as a protective material for
protecting the adhesive layer until it is practically used.
Further, in the dicing tape-integrated film 1 for semiconductor
back surface, the separator may further serve as the supporting
base material in transferring the film 2 for semiconductor back
surface onto the pressure-sensitive adhesive layer 32 of the base
material of the dicing tape. The separator is peeled off when a
semiconductor wafer is attached onto the film for semiconductor
back surface. As the separator, a film of polyethylene or
polypropylene, as well as a plastic film (such as polyethylene
terephthalate), a paper or the like whose surface is coated with a
releasing agent such as a fluorine-based releasing agent or a
long-chain alkyl acrylate-based releasing agent can also be used.
The separator can be formed by a conventionally known method.
Moreover, the thickness or the like of the separator is not
particularly restricted.
[0091] In case where the film for semiconductor back surface 2 is
not laminated with the dicing tape 3, the adhesive layer 21 may be
wound up along with one separator having a release layer on both
sides thereof, into a roll in which it is protected with the
separator having a release layer on both surfaces thereof; or it
may be protected with a separator having a release layer on at
least one surface thereof.
[0092] Moreover, as the adhesive layer 21, one having lower
moisture absorbance is more preferred. Specifically, the moisture
absorbance is preferably 1% by weight or less and more preferably
0.8% by weight or less. By regulating the moisture absorbance to 1%
by weight or less, the generation of voids between the adhesive
layer 21 and the semiconductor element can be suppressed or
prevented in the reflow step. The moisture absorbance is a value
calculated from a weight change before and after the adhesive layer
21 is allowed to stand under an atmosphere of a temperature of
85.degree. C. and a humidity of 85% RH for 168 hours. In the case
where the adhesive layer 21 is formed of a resin composition
containing a thermosetting resin, the moisture absorbance means a
value obtained when the film after thermal curing is allowed to
stand under an atmosphere of a temperature of 85.degree. C. and a
humidity of 85% RH for 168 hours. Moreover, the moisture absorbance
can be regulated, for example, by changing the amount of the
inorganic filler to be added.
[0093] Moreover, as the adhesive layer 21, one having a smaller
ratio of volatile matter is more preferred. Specifically, the ratio
of weight decrease (weight decrease ratio) of the adhesive layer 21
after heating treatment is preferably 1% by weight or less and more
preferably 0.8% by weight or less. The conditions for the heating
treatment are, for example, a heating temperature of 250.degree. C.
and a heating time of 1 hour. By regulating the weight decrease
ratio to 1% by weight or less, for example, the generation of
cracks in a flip chip type semiconductor device can be suppressed
or prevented in the reflow step. The weight decrease ratio can be
regulated, for example, by adding an inorganic substance capable of
reducing the crack generation at lead-free solder reflow. In the
case where the adhesive layer 21 is formed of a resin composition
containing a thermosetting resin component, the weight decrease
ratio is a value obtained when the adhesive layer 21 after thermal
curing is heated under conditions of a temperature of 250.degree.
C. and a heating time of 1 hour.
(Protective Layer)
[0094] The above-mentioned protective layer 22 is laminated on the
adhesive layer 21 in a film form, and is composed of the
heat-resistant resin having a glass transition temperature of
200.degree. C. or more or the metal. In the film for flip chip type
semiconductor back surface, the protective layer is provided as
described above, so that the occurrence of the flux-derived stains
at flip chip bonding can be prevented.
[0095] The heat-resistant resin constituting the protective layer
22 is not particularly restricted, as long as the heat-resistant
resin has a glass transition temperature of 200.degree. C. or more,
and resins so-called super engineering plastics can be suitably
used. Examples thereof include polyphenylene sulfides (PPS),
polyimides (PI), polyether imides (PEI), polyarylates (PAR),
polysulfones (PSF), polyether sulfones (PES), polyether ether
ketones (PEEK), liquid crystal polymers (LCP),
polytetrafluoroethylene (PTFE) and the like. Of these, at least one
selected from the group consisting of polyimides, polyphenylene
sulfides, polysulfones, polyether imides, polyether ketones and
polyether ether ketones is preferred, and polyimides are
particularly preferred, from the viewpoints of easy availability
and the prevention of the occurrence of the flux-derived stains.
Herein, the glass transition temperature (Tg) of the heat-resistant
resin can be determined as follows. The tensile storage elastic
modulus and the tensile loss elastic modulus of the heat-resistant
resin are determined by preparing a sample of the heat-resistant
resin and measuring the storage elastic modulus and the loss
elastic modulus in a tensile mode under conditions of a sample
width of 10 mm, a sample length of 22.5 mm, a sample thickness of
0.2 mm, a frequency of 1 Hz, and a temperature elevating rate of
10.degree. C./minute under a nitrogen atmosphere at a prescribed
temperature (23.degree. C.) using a dynamic viscoelasticity
measuring apparatus "Solid Analyzer RS A2" manufactured by
Rheometrics Co. Ltd. Then, tan .delta.=(loss elastic
modulus)/(storage elastic modulus) was calculated using the
obtained values of the tensile storage elastic modulus and the
tensile loss elastic modulus and regarded as the glass transition
temperature (Tg) of the heat-resistant resin.
[0096] The metal constituting the protective layer 22 is not
particularly restricted. For example, at least one selected from
the group consisting of aluminum, alumite, stainless steel, iron,
titanium, tin and copper is preferred in terms of laser marking
properties. Of these, aluminum is particularly preferred in
consideration of easy processing, laser marking properties and the
like.
[0097] The thickness of the protective layer 22 can be
appropriately determined in consideration of processability and the
like. The thickness thereof is usually within the range of 2 to 200
.mu.l, preferably from 3 to 100.mu.m, more preferably from 4 to 80
.mu.m, and particularly preferably from 5 to 50 .mu.m.
[0098] When the protective layer 22 is composed of the
heat-resistant resin, the protective layer 22 may be colored.
Further, when the protective layer 22 is composed of the metal, a
coloring layer may be provided on a surface of the protective layer
22. As methods for coloring the protective layer 22, the
above-mentioned methods for coloring the adhesive layer can be
suitably employed.
(Method for Producing Film for Flip Chip Type Semiconductor Back
Surface)
[0099] First, the adhesive layer 21 can be formed, for example, by
utilizing a conventional method of mixing the thermosetting resin
such as an epoxy resin, the thermoplastic resin such as an acrylic
resin as needed, and a solvent, other additives and the like as
needed to prepare a resin composition, and forming the composition
to a film-shaped layer. Specific examples thereof include a method
including applying the above-mentioned resin composition onto an
appropriate separator (such as release paper), and drying the
composition (heat treating as needed and drying the composition, in
the case where thermal curing is required) to form the adhesive
layer. Further, when the adhesive layer is directly formed on the
pressure-sensitive adhesive layer of the dicing tape, the
film-shaped adhesive layer can be formed by a method of applying
the above-mentioned resin composition onto the pressure-sensitive
adhesive layer 32 of the dicing tape, a method of transferring the
adhesive layer formed on the separator onto the pressure-sensitive
adhesive layer 32, or the like. The above-mentioned resin
composition may be either a solution or a dispersion. Incidentally,
when thermal curing is performed in forming the film 2 for
semiconductor back surface, it is important to perform thermal
curing to such a degree that a partially cured state is obtained.
However, it is preferred to perform no thermal curing.
[0100] Then, the film for flip chip type semiconductor back surface
can be prepared by attaching the resulting adhesive layer to the
protective layer separately prepared. As the protective layer, a
commercially available heat-resistant resin or metal foil is
satisfactorily used. Further, for example, when a polyimide film is
employed as the protective layer, the polyimide film can be formed
by applying a solution of polyamic acid to a heat-resistant
supporting base material and performing imidation at about 300 to
500.degree. C. Furthermore, in the case of the metal protective
layer, a thin metal film may be directly formed by performing
sputtering or the like on the adhesive layer. Attaching conditions
of the adhesive layer and the protective layer are not particularly
restricted, and examples thereof include conditions of an attaching
angle of 100 to 140.degree., a pressure of 0.1 to 0.5 MPa and a
speed of 5 to 20 mm/s.
(Dicing Tape)
[0101] The dicing tape 3 includes a base material 31 and a
pressure-sensitive adhesive layer 32 formed on the base material
31. Thus, it is sufficient that the dicing tape 3 has a
configuration in which the base material 31 and the
pressure-sensitive adhesive layer 32 are laminated.
(Base Material)
[0102] The base material (supporting base material) can be used as
a supporting material for the pressure-sensitive adhesive layer and
the like. The base material 31 preferably has a radiation
ray-transmitting property. As the base material 31, for example,
suitable thin materials, e.g., paper-based base materials such as
paper; fiber-based base materials such as fabrics, non-woven
fabrics, felts, and nets; metal-based base materials such as metal
foils and metal plates; plastic base materials such as plastic
films and sheets; rubber-based base materials such as rubber
sheets; foamed bodies such as foamed sheets; and laminates thereof
[particularly, laminates of plastic based materials with other base
materials, laminates of plastic films (or sheets) each other, etc.]
can be used. In the invention, as the base material, plastic base
materials such as plastic films and sheets can be suitably
employed. Examples of raw materials for such plastic materials
include olefinic resins such as polyethylene (PE), polypropylene
(PP), and ethylene-propylene copolymers; copolymers using ethylene
as a monomer component, such as ethylene-vinyl acetate copolymers
(EVA), ionomer resins, ethylene-(meth)acrylic acid copolymers, and
ethylene-(meth)acrylic acid ester (random, alternating) copolymers;
polyesters such as polyethylene terephthalate (PET), polyethylene
naphthalate (PEN), and polybutylene terephthalate (PBT); acrylic
resins; polyvinyl chloride (PVC); polyurethanes; polycarbonates;
polyphenylene sulfide (PPS); amide-based resins such as polyamides
(Nylon) and whole aromatic polyamides (aramide); polyether ether
ketones (PEEK); polyimides; polyetherimides; polyvinylidene
chloride; ABS (acrylonitrile-butadiene-styrene copolymers);
cellulose-based resins; silicone resins; and fluorinated
resins.
[0103] In addition, the materials for the base material 31 include
polymers such as crosslinked materials of the foregoing resins. The
plastic films may be used without stretching or may be used after
subjected to a uniaxial or biaxial stretching treatment, if
necessary. According to the resin sheet to which thermal
contraction property is imparted by a stretching treatment or the
like, the adhered area between the pressure-sensitive adhesive
layer 32 and the film for semiconductor back surface 2 is reduced
by thermal contraction of the base material 31 after dicing and
thus the recovery of the semiconductor chip can be facilitated.
[0104] A commonly used surface treatment, e.g., a chemical or
physical treatment such as a chromate treatment, ozone exposure,
flame exposure, exposure to high-voltage electric shock, or an
ionized radiation treatment, or a coating treatment with an
undercoating agent e.g., a pressure-sensitive adhesive substance to
be mentioned later) may be applied onto the surface of the base
material 31 in order to enhance close adhesiveness with the
adjacent layer, holding properties, and the like.
[0105] As the base material 31, the same kind or different kinds of
materials can be suitably selected and used and, if necessary,
several kinds of materials can be blended and used. Moreover, to
the base material 31, for imparting antistatic ability, a vapor
deposition layer of a conductive substance having a thickness of
about 30 to 500 angstrom, which is composed of a metal, alloy or an
oxide thereof, can be formed on the base material 31. The base
material 31 may be a single layer or a multilayer of two or more
thereof.
[0106] The thickness (total thickness in the case of the laminated
layer) of the base material 31 is not particularly restricted and
can be appropriately selected depending on strength, flexibility,
intended purpose of use, and the like. For example, the thickness
is generally 1,000 .mu.m or less (e.g., 1 .mu.m to 1,000 .mu.m),
preferably 10 .mu.m to 500 .mu.m, further preferably 20 .mu.m to
300 .mu.m, and particularly preferably about 30 .mu.m to 200 .mu.m
but is not limited thereto.
[0107] Incidentally, the base material 31 may contain various
additives (a coloring agent, a filler, a plasticizer, an antiaging
agent, an antioxidant, a surfactant, a flame retardant, etc.)
within the range where the advantages and the like of the invention
are not impaired.
(Pressure-Sensitive Adhesive Layer)
[0108] The pressure-sensitive adhesive layer 32 is formed of a
pressure-sensitive adhesive and has a pressure-sensitive
adhesiveness. Not specifically defined, the pressure-sensitive
adhesive may be suitably selected from known pressure-sensitive
adhesives. Concretely, as the pressure-sensitive adhesive, for
example, those having the above-mentioned characteristics are
suitably selected from known pressure-sensitive adhesives such as
acrylic pressure-sensitive adhesives, rubber-based
pressure-sensitive adhesives, vinyl alkyl ether-based
pressure-sensitive adhesives, silicone-based pressure-sensitive
adhesives, polyester-based pressure-sensitive adhesives,
polyamide-based pressure-sensitive adhesives, urethane-based
pressure-sensitive adhesives, fluorine-based pressure-sensitive
adhesives, styrene-diene block copolymer-based pressure-sensitive
adhesives, and creep characteristics-improved pressure-sensitive
adhesives prepared by incorporating a thermofusible resin having a
melting point of not higher than 200.degree. C. to the
above-mentioned pressure-sensitive adhesive (for example, see JP-A
56-61468, JP-A-61-174857, JP-A-63-17981, JP-A-56-13040, herein
incorporated by reference), and are used herein. As the
pressure-sensitive adhesive, also usable here are radiation-curable
pressure-sensitive adhesives (or energy ray-curable
pressure-sensitive adhesives) and thermally expandable
pressure-sensitive adhesives. One or more such pressure-sensitive
adhesives may be used here either singly or as combined.
[0109] As the pressure-sensitive adhesive, preferred for use herein
are acrylic pressure-sensitive adhesives and rubber-based
pressure-sensitive adhesives, and more preferred are acrylic
pressure-sensitive adhesives. The acrylic pressure-sensitive
adhesives include those comprising, as the base polymer, an acrylic
polymer (homopolymer or copolymer) of one or more
alkyl(meth)acrylates as monomer component(s).
[0110] The alkyl(meth)acrylate for the acrylic pressure-sensitive
adhesive includes, for example, methyl(meth)acrylate,
ethyl(meth)acrylate, propyl(meth)acrylate, isopropyl(meth)acrylate,
butyl(meth)acrylate, isobutyl(meth)acrylate, s-butyl
(meth)acrylate, t-butyl(meth)acrylate, pentyl(meth)acrylate,
hexyl(meth)acrylate, heptyl(meth)acrylate, octyl(meth)acrylate,
2-ethylhexyl(meth)acrylate, isooctyl (meth)acrylate,
nonyl(meth)acrylate, isononyl(meth)acrylate, decyl(meth)acrylate,
isodecyl(meth)acrylate, undecyl(meth)acrylate,
dodecyl(meth)acrylate, tridecyl (meth)acrylate,
tetradecyl(meth)acrylate, pentadecyl(meth)acrylate, hexadecyl
(meth)acrylate, heptadecyl(meth)acrylate, octadecyl(meth)acrylate,
nonadecyl (meth)acrylate, eicosyl(meth)acrylate, etc. As the
alkyl(meth)acrylate, preferred are those in which the alkyl group
has from 4 to 18 carbon atoms. In the alkyl (meth)acrylate, the
alkyl group may be linear or branched.
[0111] The acrylic polymer may contain, if desired, a unit
corresponding to any other monomer component copolymerizable with
the above-mentioned alkyl(meth)acrylate (copolymerizable monomer
component), for the purpose of improving the cohesive force, the
heat resistance and the crosslinkability thereof. The
copolymerizable monomer component includes, for example, carboxyl
group-containing monomers such as (meth)acrylic acid (acrylic acid,
methacrylic acid), carboxyethyl acrylate, carboxypentyl acrylate,
itaconic acid, maleic acid, fumaric acid, crotonic acid; acid
anhydride group-containing monomers such as maleic anhydride,
itaconic anhydride; hydroxyl group-containing monomers such as
hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate,
hydroxybutyl(meth)acrylate, hydroxyhexyl (meth)acrylate,
hydroxyoctyl(meth)acrylate, hydroxydecyl(meth)acrylate,
hydroxylauryl(meth)acrylate, (4-hydroxymethylcyclohexyl)methyl
methacrylate; sulfonic acid group-containing monomers such as
styrenesulfonic acid, allylsulfonic acid,
2-(meth)acrylamide-2-methylpropanesulfonic acid,
(meth)acrylamide-propanesulfonic acid, sulfopropyl(meth)acrylate,
(meth)acryloyloxynaphthalenesulfonic acid; phosphoric acid
group-containing monomers such as 2-hydroxyethyl acryloylphosphate;
(N-substituted) amide monomers such as (meth)acrylamide,
N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide,
N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide;
aminoalkyl (meth)acrylate monomers such as
aminoethyl(meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate,
t-butylaminoethyl(meth)acrylate; alkoxyalkyl(meth)acrylate monomers
such as methoxyethyl(meth)acrylate, ethoxyethyl(meth)acrylate;
cyanoacrylate monomers such as acrylonitrile, methacrylonitrile;
epoxy group-containing acrylic monomers such as
glycidyl(meth)acrylate; styrene monomers such as styrene,
.alpha.-methylstyrene; vinyl ester monomers such as vinyl acetate,
vinyl propionate; olefin monomers such as isoprene, butadiene,
isobutylene; vinyl ether monomers such as vinyl ether;
nitrogen-containing monomers such as N-vinylpyrrolidone,
methylvinylpyrrolidone, vinylpyridine, vinylpiperidone,
vinylpyrimidine, vinylpiperazine, vinylpyrazine, vinylpyrrole,
vinylimidazole, vinyloxazole, vinylmorpholine, N-vinylcarbonamides,
N-vinylcaprolactam; maleimide monomers such as
N-cyclohexylmaleimide, N-isopropylmaleimide, N-laurylmaleimide,
N-phenylmaleimide; itaconimide monomers such as
N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide,
N-octylitaconimide, N-2-ethylhexylitaconimide,
N-cyclohexylitaconimide, N-laurylitaconimide; succinimide monomers
such as N-(meth)acryloyloxymethylenesuccinimide,
N-(meth)acryloyl-6-oxyhexamethylenesuccinimide,
N-(meth)acryloyl-8-oxyoctamethylenesuccinimide; acryl glycolate
monomers such as polyethylene glycol (meth)acrylate, polypropylene
glycol (meth)acrylate, methoxyethylene glycol (meth)acrylate,
methoxypolypropylene glycol (meth)acrylate; acrylate monomers
having a hetero ring, a halogen atom, a silicone atom or the like
such as tetrahydrofurfuryl(meth)acrylate, fluoro(meth)acrylate,
silicone (meth)acrylate; polyfunctional monomers such as hexanediol
di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate,
(poly)propylene glycol di(meth)acrylate, neopentylglycol
di(meth)acrylate, pentaerythritol di(meth)acrylate,
trimethylolpropane tri(meth)acrylate, pentaerythritol
tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate,
epoxyacrylate, polyester acrylate, urethane acrylate,
divinylbenzene, butyl di(meth)acrylate, hexyl di(meth)acrylate,
etc. One or more these copolymerizable monomer components may be
used here either singly or as combined.
[0112] The radiation-curable pressure-sensitive adhesive (or energy
ray-curable pressure-sensitive adhesive) (composition) usable in
the invention includes, for example, an internal-type
radiation-curable pressure-sensitive adhesive comprising, as the
base polymer, a polymer having a radical-reactive carbon-carbon
double bond in the polymer side chain, main chain or main chain
terminal, and a radiation-curable pressure-sensitive adhesive
prepared by incorporating a UV-curable monomer component or
oligomer component in a pressure-sensitive adhesive. The thermally
expandable pressure-sensitive adhesive also usable here includes,
for example, those comprising a pressure-sensitive adhesive and a
foaming agent (especially thermally expandable microspheres).
[0113] In the invention, the pressure-sensitive adhesive layer 32
may contain various additives (e.g., a tackifying resin, a coloring
agent, a thickener, an extender, a filler, a plasticizer, an
antiaging agent, an antioxidant, a surfactant, a crosslinking
agent, etc.) within the range where the advantages of the invention
are not impaired.
[0114] The crosslinking agent is not particularly restricted and
known crosslinking agents can be used. Specifically, as the
crosslinking agent, not only isocyanate-based crosslinking agents,
epoxy-based crosslinking agents, melamine-based crosslinking
agents, and peroxide-based crosslinking agents but also urea-based
crosslinking agents, metal alkoxide-based crosslinking agents,
metal chelate-based crosslinking agents, metal salt-based
crosslinking agents, carbodiimide-based crosslinking agents,
oxazoline-based crosslinking agents, aziridine-based crosslinking
agents, amine-based crosslinking agents, and the like may be
mentioned, and isocyanate-based crosslinking agents and epoxy-based
crosslinking agents are suitable. The crosslinking agent may be
employed singly or in a combination of two or more kinds.
Incidentally, the amount of the crosslinking agent to be used is
not particularly restricted.
[0115] Examples of the isocyanate-based crosslinking agents include
lower aliphatic polyisocyanates such as 1,2-ethylene diisocyanate,
1,4-butylene diisocyanate, and 1,6-hexamethylene diisocyanate;
alicyclic polyisocyanates such as cyclopentylene diisocyanate,
cyclohexylene diisocyanate, isophorone diisocyanate, hydrogenated
tolylene diisocyanate, and hydrogenated xylylene diisocyanate; and
aromatic polyisocyanates such as 2,4-tolylene diisocyanate,
2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and
xylylene diisocyanate. In addition, a trimethylolpropane/tolylene
diisocyanate trimer adduct [a trade name "COLONATE L" manufactured
by Nippon Polyurethane Industry Co., Ltd.], a
trimethylolpropane/hexamethylene diisocyanate trimer adduct [a
trade name "COLONATE HL" manufactured by Nippon Polyurethane
Industry Co., Ltd.], and the like are also used. Moreover, examples
of the epoxy-based crosslinking agents include
N,N,N',N'-tetraglycidyl-m-xylenediamine, diglycidylaniline,
1,3-bis(N,N-glycidylaminomethyl)cyclohexane, 1,6-hexanediol
diglycidyl ether, neopentyl glycol diglycidyl ether, ethylene
glycol diglycidyl ether, propylene glycol diglycidyl ether,
polyethylene glycol diglycidyl ether, polypropylene glycol
diglycidyl ether, sorbitol polyglycidyl ether, glycerol
polyglycidyl ether, pentaerythritol polyglycidyl ether,
polyglycerol polyglycidyl ether, sorbitan polyglycidyl ether,
trimethylolpropnane polyglycidyl ether, adipic acid diglycidyl
ester, o-phthalic acid diglycidyl ester,
triglycidyl-tris(2-hydroxyethyl) isocyanurate, resorcin diglycidyl
ether, and bisphenol-S-diglycidyl ether, and also epoxy-based
resins having two or more epoxy groups in the molecule.
[0116] In place of using the crosslinking agent or along with the
crosslinking agent in the invention, the pressure-sensitive
adhesive layer may be crosslinked through irradiation with electron
rays or UV rays.
[0117] The pressure-sensitive adhesive layer 32 can be, for
example, formed by utilizing a commonly used method including
mixing a pressure-sensitive adhesive and optional solvent and other
additives and then shaping the mixture into a sheet-like layer.
Specifically, for example, there may be mentioned a method
including applying a mixture containing a pressure-sensitive
adhesive and optional solvent and other additives on the base
material 31; a method including applying the foregoing mixture on
an appropriate separator (such as a release paper) to form a
pressure-sensitive adhesive layer 32 and then transferring
(transcribing) it on the base material 31; or the like.
[0118] The adhesive force of the pressure-sensitive adhesive layer
32 of the dicing tape 3 to the film for flip chip type
semiconductor back surface 2 (23.degree. C., peeling angle of 180
degrees, peeling rate of 300 mm/min) is preferably within a range
of from 0.02 N/20 mm to 10 N/20 mm, more preferably from 0.05 N/20
mm to 5 N/20 mm. When the adhesive force is at least 0.02 N/20 mm,
then the semiconductor chips may be prevented from flying away in
dicing semiconductor wafer. On the other hand, when the adhesive
force is at most 10 N/20 mm, then it facilitates peeling of
semiconductor chips in picking up them, and prevents the
pressure-sensitive adhesive from remaining
[0119] Incidentally, in the invention, the film 2 for flip-chip
type semiconductor back surface or the dicing tape-integrated film
1 for semiconductor back surface can be made to have an antistatic
function. Owing to this configuration, the circuit can be prevented
from breaking down due to the generation of electrostatic energy at
the time adhesion and at the time of peeling thereof or due to
charging of a semiconductor wafer or the like by the electrostatic
energy. Imparting of the antistatic function can be performed by an
appropriate manner such as a method of adding an antistatic agent
or a conductive substance to the base material 31, the
pressure-sensitive adhesive layer 32, and the film for
semiconductor back surface 2, or a method of providing a conductive
layer composed of a charge-transfer complex, a metal film, or the
like onto the base material 31. As these methods, a method in which
an impurity ion having a fear of changing quality of the
semiconductor wafer is difficult to generate is preferable.
Examples of the conductive substance (conductive filler) to be
blended for the purpose of imparting conductivity, improving
thermal conductivity, and the like include a sphere-shaped, a
needle-shaped, or a flake-shaped metal powder of silver, aluminum,
gold, copper, nickel, a conductive alloy, or the like; a metal
oxide such as alumina; amorphous carbon black, and graphite.
However, the film for semiconductor back surface 2 is preferably
non-conductive from the viewpoint of having no electric
leakage.
[0120] Moreover, the film 2 for flip-chip type semiconductor back
surface or the dicing tape-integrated film 1 for semiconductor back
surface may be formed in a form where it is wound as a roll or may
be formed in a form where the sheet (film) is laminated. For
example, in the case where the film has the form where it is wound
as a roll, the film is wound as a roll in a state that the film 2
for semiconductor back surface or the laminate of the film 2 for
semiconductor back surface and the dicing tape 3 is protected by a
separator according to needs, whereby the film can be prepared as a
film 2 for semiconductor back surface or a dicing tape-integrated
film 1 for semiconductor back surface in a state or form where it
is wound as a roll. In this regard, the dicing tape-integrated film
1 for semiconductor back surface in the state or form where it is
wound as a roll may be constituted by the base material 31, the
pressure-sensitive adhesive layer 32 formed on one surface of the
base material 31, the film 2 for semiconductor back surface formed
on the pressure-sensitive adhesive layer 32, and a releasably
treated layer (rear surface treated layer) formed on the other
surface of the base material 31.
[0121] Incidentally, the thickness of the dicing tape-integrated
film 1 for semiconductor back surface (total thickness of the
thickness of the film for semiconductor back surface and the
thickness of the dicing tape including the base material 31 and the
pressure-sensitive adhesive layer 32) can be, for example, selected
from the range of 25 .mu.m to 1,600 .mu.m, and it is preferably
from 30 .mu.m to 850 .mu.m, more preferably 35 .mu.m to 500 .mu.m,
and particularly preferably 50 .mu.m to 330 .mu.m.
[0122] In this regard, in the dicing tape-integrated film 1 for
semiconductor back surface, by controlling the ratio of the
thickness of the film 2 for semiconductor back surface to the
thickness of the pressure-sensitive adhesive layer 32 of the dicing
tape 3 or the ratio of the thickness of the film 2 for
semiconductor back surface to the thickness of the dicing tape
(total thickness of the base material 31 and the pressure-sensitive
adhesive layer 32), a dicing property at the dicing step, a
picking-up property at the picking-up step, and the like can be
improved and the dicing tape-integrated film for semiconductor back
surface 1 can be effectively utilized from the dicing step of the
semiconductor wafer to the flip chip bonding step of the
semiconductor chip.
(Producing Method of Dicing Tape-Integrated Film for Semiconductor
Back Surface)
[0123] The producing method of the dicing tape-integrated film for
semiconductor back surface according to the present embodiment is
described while using the dicing tape-integrated film for
semiconductor back surface 1 shown in FIG. 1 as an example. First,
the base material 31 can be formed by a conventionally known
film-forming method. Examples of the film-forming method include a
calendar film-forming method, a casting method in an organic
solvent, an inflation extrusion method in a closely sealed system,
a T-die extrusion method, a co-extrusion method, and a dry
laminating method.
[0124] Next, the pressure-sensitive adhesive composition is applied
to the base material 31 and dried thereon (and optionally
crosslinked under heat) to form the pressure-sensitive adhesive
layer 32. The coating system includes roll coating, screen coating,
gravure coating, etc. The pressure-sensitive adhesive composition
may be directly applied to the base material 31 to form the
pressure-sensitive adhesive layer 32 on the base material 31; or
the pressure-sensitive adhesive composition may be applied to a
release sheet or the like of which the surface has been processed
for lubrication, to form the pressure-sensitive adhesive layer 32
thereon, and the pressure-sensitive adhesive layer 32 may be
transferred onto the base material 31. With that, the dicing tape 3
is formed having the pressure-sensitive adhesive layer 32 formed on
the base material 31.
[0125] The dicing tape-integrated film 1 for semiconductor back
surface according to the invention can be obtained by transferring
the film 2 for flip chip type semiconductor back surface prepared
by the above-mentioned procedure onto the pressure-sensitive
adhesive layer 32 of the resulting dicing tape 3. In this case, the
film 2 for semiconductor back surface is transferred to the dicing
tape 3 in such a manner that the protective layer 22 of the film 2
for semiconductor back surface faces the pressure-sensitive
adhesive layer 32.
[0126] The dicing tape-integrated film 1 for semiconductor back
surface of the invention can be suitably used at the production of
a semiconductor device including the flip chip connection step.
Namely, the dicing tape-integrated film 1 for semiconductor back
surface of the invention is used at the production of a flip
chip-mounted semiconductor device and thus the flip chip-mounted
semiconductor device is produced in a condition or form where the
film 2 for semiconductor back surface of the dicing tape-integrated
film 1 for semiconductor back surface is attached to the back
surface of the semiconductor chip. Therefore, the dicing
tape-integrated film 1 for semiconductor back surface of the
invention can be used for a flip chip-mounted semiconductor device
(a semiconductor device in a state or form where the semiconductor
chip is fixed to an adherend such as a substrate by a flip chip
bonding method).
[0127] The film 2 for semiconductor back surface is usable also for
flip chip-mounted semiconductor devices (semiconductor devices in a
state or form where a semiconductor chip is fixed to the adherend
such as a substrate or the like in a flip chip bonding method),
like in the dicing tape-integrated film 1 for semiconductor back
surface.
(Semiconductor Wafer)
[0128] The semiconductor wafer is not particularly restricted as
long as it is a known or commonly used semiconductor wafer and can
be appropriately selected and used among semiconductor wafers made
of various materials. In the invention, as the semiconductor wafer,
a silicon wafer can be suitable used.
(Production Process of Semiconductor Device)
[0129] The process for producing a semiconductor device according
to the invention will be described referring to FIGS. 3A to 3D.
FIGS. 3A to 3D are cross-sectional schematic views showing a
process for producing a semiconductor device in the case where a
dicing tape-integrated film for semiconductor back surface 1 is
used.
[0130] According to the above-mentioned semiconductor device
production method, the semiconductor device can be produced using
the above-mentioned dicing tape-integrated film 1 for semiconductor
back surface. Specifically, the method comprises at least a step of
attaching a semiconductor wafer onto the film for flip chip type
semiconductor back surface in the dicing tape-integrated film for
semiconductor back surface, a step of dicing the semiconductor
wafer to form a semiconductor element, a step of peeling the
semiconductor element together with the film for flip chip type
semiconductor back surface from the pressure-sensitive adhesive
layer of the dicing tape, a step of adhering a flux to a connecting
member for an adherend in the semiconductor element, and a step of
flip chip-connecting the semiconductor element onto the
adherend.
(Mounting Step)
[0131] First, as shown in FIG. 3A, a separator optionally provided
on the film 2 for semiconductor back surface of the dicing
tape-integrated film 1 for semiconductor back surface is suitably
peeled off and the semiconductor wafer 4 is attached onto the film
2 for semiconductor back surface to be fixed by adhesion and
holding (mounting step). On this occasion, the film 2 for
semiconductor back surface is in an uncured state (including a
semi-cured state). Moreover, the dicing tape-integrated film 1 for
semiconductor back surface is attached to the back surface of the
semiconductor wafer 4. The back surface of the semiconductor wafer
4 means a face opposite to the circuit face (also referred to as
non-circuit face, non-electrode-formed face, etc.). The attaching
method is not particularly restricted but a method by press bonding
is preferred. The press bonding is usually performed while pressing
with a pressing means such as a pressing roll.
(Dicing Step)
[0132] Next, as shown in FIG. 3B, the semiconductor wafer 4 is
diced. Thereby, the semiconductor wafer 4 is cut into a prescribed
size and individualized (is formed into small pieces) to produce
semiconductor chips 5. The dicing is performed according to a
normal method from the circuit face side of the semiconductor wafer
4, for example. Moreover, the present step can adopt, for example,
a cutting method called full-cut that forms a slit reaching the
dicing tape-integrated film 1 for semiconductor back surface. The
dicing apparatus used in the present step is not particularly
restricted, and a conventionally known apparatus can be used.
Further, since the semiconductor wafer 4 is adhered and fixed by
the dicing tape-integrated film 1 for semiconductor back surface
having the film for semiconductor back surface, chip crack and chip
fly can be suppressed, as well as the damage of the semiconductor
wafer 4 can also be suppressed. In this regard, when the film 2 for
semiconductor back surface is formed of a resin composition
containing an epoxy resin, generation of adhesive extrusion from
the adhesive layer of the film for semiconductor back surface can
be suppressed or prevented at the cut surface even when it is cut
by dicing. As a result, re-attachment (blocking) of the cut
surfaces themselves can be suppressed or prevented and thus the
picking-up to be mentioned below can be further conveniently
performed.
[0133] In the case where the dicing tape-integrated film 1 for
semiconductor back surface is expanded, the expansion can be
performed using a conventionally known expanding apparatus. The
expanding apparatus has a doughnut-shaped outer ring capable of
pushing the dicing tape-integrated film 1 for semiconductor back
surface downward through a dicing ring and an inner ring which has
a diameter smaller than the outer ring and supports the dicing
tape-integrated film for semiconductor back surface. Owing to the
expanding step, it is possible to prevent the damage of adjacent
semiconductor chips through contact with each other in the
picking-up step to be mentioned below.
(Picking-Up Step)
[0134] In order to collect the semiconductor chip 5 that is adhered
and fixed to the dicing tape-integrated film 1 for semiconductor
back surface, picking-up of the semiconductor chip 5 is performed
as shown in FIG. 3C to peel the semiconductor chip 5 together with
the film 2 for semiconductor back surface from the dicing tape 3.
The method of picking-up is not particularly restricted, and
conventionally known various methods can be adopted. For example,
there may be mentioned a method including pushing up each
semiconductor chip 5 from the base material 31 side of the dicing
tape-integrated film 1 for semiconductor back surface with a needle
and picking-up the pushed semiconductor chip 5 with a picking-up
apparatus. In this regard, the back surface of the picked-up
semiconductor chip 5 is protected with the film 2 for semiconductor
back surface.
(Flip Chip Connection Step)
[0135] The picked-up semiconductor chip 5 is fixed to an adherend
such as a substrate by a flip chip bonding method (flip chip
mounting method) as shown in FIG. 3D. Specifically, the
semiconductor chip 5 is first fixed to the adherend 6 according to
a usual manner in a form where a circuit face (also referred to as
a front face, a circuit-pattern formed face, an electrode-formed
face or the like) is opposed to the adherend 6. For example, a bump
51 formed as the connecting member on the circuit face side of the
semiconductor chip 5 is brought into contact with the flux to allow
the flux to adhere to the bump 51. Then, the bump 51 of the
semiconductor chip 5 is brought into contact with a conductive
material (such as solder) 61 for connection adhered to a connection
pad of the adherend 6, and the bump 51 and the conductive material
are melted under pressure, whereby electric connection between the
semiconductor chip 5 and the adherend 6 can be secured and the
semiconductor chip 5 can be fixed to the adherend 6 (flip chip
bonding step). On this occasion, gaps are formed between the
semiconductor chip 5 and the adherend 6, and the distance between
the gaps is generally from about 30 to 300 .mu.m. Incidentally,
after the flip chip bonding (flip chip connection) of the
semiconductor chip 5 to the adherend 6, it is important that the
flux remaining on the opposing faces of the semiconductor chip 5
and the adherend 6 or in the gaps therebetween is removed by
washing, followed by filling the gaps with an encapsulating
material (such as an encapsulating resin) to perform
encapsulation.
[0136] As the adherend 6, various substrates such as lead frames
and circuit boards (such as wiring circuit boards) can be used. The
material of the substrates is not particularly restricted and there
may be mentioned ceramic substrates and plastic substrates.
Examples of the plastic substrates include epoxy substrates,
bismaleimide triazine substrates, and polyimide substrates.
[0137] In the flip chip bonding step, the material of the bump and
the conductive material is not particularly restricted and examples
thereof include solders (alloys) such as tin-lead-based metal
materials, tin-silver-based metal materials,
tin-silver-copper-based metal materials, tin-zinc-based metal
materials, and tin-zinc-bismuth-based metal materials, and
gold-based metal materials and copper-based metal materials.
[0138] Incidentally, in the flip chip bonding step, the conductive
material is melted to connect the bump at the circuit face side of
the semiconductor chip 5 and the conductive material on the surface
of the adherend 6. The temperature at the melting of the bump and
the conductive material is usually about 260.degree. C. (e.g.,
250.degree. C. to 300.degree. C.). The dicing tape-integrated film
for semiconductor back surface of the invention can be made to have
thermal resistance capable of enduring the high temperature in the
flip chip bonding step by forming the film for semiconductor back
surface with an epoxy resin or the like.
[0139] In the present step, it is preferred to wash the opposing
face (electrode-formed face) between the semiconductor chip 5 and
the adherend 6 and the gaps. The washing liquid to be used at the
washing is not particularly restricted and examples thereof include
organic washing liquids and aqueous washing liquids. The film for
semiconductor back surface in the dicing tape-integrated film for
semiconductor back surface of the invention has solvent resistance
against the washing liquid and has substantially no solubility to
these washing liquid. Therefore, as mentioned above, various
washing liquids can be employed as the washing liquid and the
washing can be achieved by any conventional method without
requiring any special washing liquid.
[0140] In the semiconductor device production method of the
invention, the flip chip bonding step is performed using the film
for semiconductor back surface provided with the protective layer,
so that the flux for soldering does not remain in the film for
semiconductor back surface, even when the flux adheres to the back
surface of the semiconductor chip, thereby being able to prevent
the occurrence of the flux-derived stains.
[0141] Next, an encapsulation step is performed for encapsulating
the gaps between the flip chip-bonded semiconductor chip 5 and the
adherend 6. The encapsulation step is performed using an
encapsulating resin. The encapsulation conditions on this occasion
are not particularly restricted but the curing of the encapsulating
resin is usually carried out at 175.degree. C. for 60 seconds to 90
seconds. However, in the invention, without limitation thereto, the
curing may be performed at a temperature of 165 to 185.degree. C.
for several minutes, for example. By the thermal treatment in this
step, not only the encapsulating resin but also the film for
semiconductor back surface 2 is also thermally cured at the same
time. Accordingly, both the encapsulating resin and the film for
semiconductor back surface 2 are cured and shrunk with the
procedure of the thermal curing. As a result, the stress to be
given to the semiconductor chip 5 owing to the curing shrinkage of
the encapsulating resin can be cancelled or relaxed through curing
shrinkage of the film for semiconductor back surface 2. Moreover,
in the step, the film for semiconductor back surface 2 can be
completely or almost completely thermally cured and can be attached
to the back surface of the semiconductor element with excellent
close adhesiveness. Further, the film for semiconductor back
surface 2 according to the invention can be thermally cured
together with the encapsulating material in the encapsulation step
even when the film is in an uncured state, so that it is not
necessary to newly add a step for thermal curing of the film for
semiconductor back surface 2.
[0142] The encapsulating resin is not particularly restricted as
long as the material is a resin having an insulating property (an
insulating resin) and may be suitably selected and used among known
encapsulating materials such as encapsulating resins. The
encapsulating resin is preferably an insulating resin having
elasticity. Examples of the encapsulating resin include resin
compositions containing an epoxy resin. As the epoxy resin, there
may be mentioned the epoxy resins exemplified in the above.
Furthermore, the encapsulating resin composed of the resin
composition containing an epoxy resin may contain a thermosetting
resin other than an epoxy resin (such as a phenol resin) or a
thermoplastic resin in addition to the epoxy resin. Incidentally, a
phenol resin can be utilized also as a curing agent for the epoxy
resin and, as such a phenol resin, there may be mentioned phenol
resins exemplified in the above.
[0143] According to the semiconductor device (flip chip-mounted
semiconductor device) manufactured using the dicing tape-integrated
film 1 for semiconductor back surface or the film 2 for
semiconductor back surface, the film for semiconductor back surface
is attached to the back surface of the semiconductor chip, and
therefore, laser marking can be applied with excellent visibility.
In particular, even when the marking method is a laser marking
method, laser marking can be applied with an excellent contrast
ratio, and it is possible to observe various kinds of information
(for example, literal information and graphical information)
applied by laser marking with good visibility. At the laser
marking, a known laser marking apparatus can be utilized. Moreover,
as the laser, it is possible to utilize various lasers such as a
gas laser, a solid-state laser, and a liquid laser. Specifically,
as the gas laser, any known gas lasers can be utilized without
particular limitation but a carbon dioxide laser (CO.sub.2 laser)
and an excimer laser (ArF laser, KrF laser, XeCl laser, XeF laser,
etc.) are suitable. As the solid-state laser, any known solid-state
lasers can be utilized without particular limitation but a YAG
laser (such as Nd:YAG laser) and a YVO.sub.4 laser are
suitable.
[0144] Since the semiconductor device produced using the dicing
tape-integrated film 1 for semiconductor back surface or the film 2
for semiconductor back surface of the invention is a semiconductor
device mounted by the flip chip mounting method, the device has a
thinned and miniaturized shape as compared with a semiconductor
device mounted by a die-bonding mounting method. Thus, the
semiconductor devices can be suitably employed as various
electronic devices and electronic parts or materials and members
thereof. Specifically, as the electronic devices in which the flip
chip-mounted semiconductor devices of the invention are utilized,
there may be mentioned so-called "mobile phones" and "PHS",
small-sized computers [e.g., so-called "PDA" (handheld terminals),
so-called "notebook-sized personal computer", so-called "Net Book
(trademark)", and so-called "wearable computers", etc.],
small-sized electronic devices having a form where a "mobile phone"
and a computer are integrated, so-called "Digital Camera
(trademark)", so-called "digital video cameras", small-sized
television sets, small-sized game machines, small-sized digital
audio players, so-called "electronic notepads", so-called
"electronic dictionary", electronic device terminals for so-called
"electronic books", mobile electronic devices (portable electronic
devices) such as small-sized digital type watches, and the like.
Needless to say, electronic devices (stationary type ones, etc.)
other than mobile ones, e.g., so-called "desktop personal
computers", thin type television sets, electronic devices for
recording and reproduction (hard disk recorders, DVD players,
etc.), projectors, micromachines, and the like may be also
mentioned. In addition, electronic parts or materials and members
for electronic devices and electronic parts are not particularly
restricted and examples thereof include parts for so-called "CPU"
and members for various memory devices (so-called "memories", hard
disks, etc.).
EXAMPLES
[0145] The following will illustratively describe preferred
Examples of the invention in detail. However, the invention is not
limited to the following Examples unless it exceeds the gist
thereof. Moreover, part in each example is a weight standard unless
otherwise stated.
<Preparation of Adhesive Layer>
[0146] 113 parts of an epoxy resin (trade name: "Epicoat 1004",
manufactured by JER Co., Ltd.), 121 parts of a phenol resin (trade
name: "Milex XLC-4L", manufactured by Mitsui Chemicals, Inc.), 246
parts of spherical silica (trade name: "SO-25R", manufactured by
Admatechs Co., Ltd.), 5 parts of dye 1 (trade name: "OIL GREEN
502", manufactured by Orient Chemical Industries Co., Ltd.) and 5
parts of dye 2 (trade name: "OIL BLACK BS", manufactured by Orient
Chemical Industries Co., Ltd.) based on 100 parts of an acrylic
ester-based polymer mainly composed of ethyl acrylate-methyl
methacrylate (trade name: "Paracron W-197CM", manufactured by
Negami Chemical Industrial Co., Ltd.) were dissolved in methyl
ethyl ketone to prepare an adhesive composition solution having a
solid concentration of 23.6% by weight.
[0147] This adhesive composition solution was applied onto a
release-treated film as a release liner (separator), which was
formed of a 50 .mu.m-thick polyethylene terephthalate film
subjected to a silicone release treatment, and then dried at
130.degree. C. for 2 minutes to prepare an adhesive layer A having
a thickness (average thickness) of 10 .mu.m.
Example 1
<Preparation of Film for Semiconductor Back Surface>
[0148] The resulting adhesive layer A was attached to a 10
.mu.m-thick aluminum foil (manufactured by Toyo Aluminum K.K.,
1N30) as a protective layer under conditions of an attaching angle
of 120.degree., a pressure of 0.2 MPa and a speed of 10 mm/s to
prepare a film for semiconductor back surface.
Example 2
<Preparation of Film for Semiconductor Back Surface>
[0149] The resulting adhesive layer A was attached to a 12.5
.mu.m-thick polyimide film (Apical, manufactured by Kaneka
Corporation, glass transition temperature (Tg): 240.degree. C.) as
a protective layer under conditions of an attaching angle of
120.degree., a pressure of 0.2 MPa and a speed of 10 mm/s to
prepare a film for semiconductor back surface.
Comparative Example 1
[0150] In accordance with the procedure of "Preparation of Adhesive
Layer" described above, an adhesive layer having a thickness
(average thickness) of 20 .mu.m was prepared, and this adhesive
layer was used as a film for semiconductor back surface without
being provided with a protective layer.
<Preparation of Dicing Tape-Integrated Film for Semiconductor
Back Surface>
[0151] Each of the films for semiconductor back surface obtained in
Examples and Comparative Example was attached onto a
pressure-sensitive adhesive layer of a dicing tape (trade name:
"V-8-T", manufactured by Nitto Denko Corporation, average thickness
of base material: 65 .mu.m, average thickness of pressure-sensitive
adhesive layer: 10 .mu.m) by using a hand roller to prepare a
dicing tape-integrated film for semiconductor back surface.
(Evaluation of Flux Staining Property)
[0152] A semiconductor wafer (diameter: 8 inches, thickness: 0.6
mm, silicon mirror wafer) was subjected to a back surface polishing
treatment, and a mirror wafer having a thickness of 0.2 mm was used
as a work. After the separator was peeled from the dicing
tape-integrated film for semiconductor back surface, the mirror
wafer (work) was attached onto the film for semiconductor back
surface at 70.degree. C. by roll pressing. Incidentally,
semiconductor wafer polishing conditions and attaching conditions
were as follows:
(Semiconductor Wafer Polishing Conditions)
[0153] Polishing apparatus: trade name: "DFG-8560", manufactured by
DISCO Corporation Semiconductor wafer: 8 inches in diameter (back
surface polishing from a thickness of 0.6 mm to a thickness of 0.2
mm)
(Attaching Conditions)
[0154] Attaching apparatus: trade name: "MA-3000III", manufactured
by Nitto Seiki Co., Ltd. Attaching speed: 10 mm/min Attaching
pressure: 0.15 MPa Stage temperature in attaching: 70.degree.
C.
[0155] A drop of a flux (RM-26-20, manufactured by TAMURA
Corporation) was dropped with a dropper onto the film for
semiconductor back surface attached to the semiconductor wafer, and
a reflow step was performed under lead solder conditions defined by
JEDEC. The flux staining property was evaluated, taking as "good"
the case where no stain occurred and as "poor" the case where a
stain occurred. The results thereof are shown in Table 1.
(Reflow Conditions)
[0156] Temperature: the peak temperature was 260.degree. C. Time:
the time at the peak temperature was 30 seconds.
TABLE-US-00001 TABLE 1 Flux Staining Protective Layer Property
Example 1 Aluminum Good Example 2 polyimide Good Comparative Not
provided Poor Example 1
[0157] As apparent from Table 1, no flux-derived stain occurred in
the dicing tape-integrated films for semiconductor back surface
according to Examples 1 and 2, and the appearance properties of the
films for semiconductor back surface was good. On the other hand,
flux-derived stains occurred in the film for semiconductor back
surface of Comparative Example 1, resulting in showing poor
appearance properties.
[0158] 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.
[0159] This application is based on Japanese patent application No.
2010-170807 filed Jul. 29, 2010, the entire contents thereof being
hereby incorporated by reference.
* * * * *