U.S. patent application number 13/420266 was filed with the patent office on 2012-09-27 for method for manufacturing semiconductor chip, adhesive film for semiconductor, and composite sheet using the film.
Invention is credited to Keiichi Hatakeyama, Youji Katayama, Tsutomu Kitakatsu, Yuuki Nakamura.
Application Number | 20120244347 13/420266 |
Document ID | / |
Family ID | 39863823 |
Filed Date | 2012-09-27 |
United States Patent
Application |
20120244347 |
Kind Code |
A1 |
Nakamura; Yuuki ; et
al. |
September 27, 2012 |
METHOD FOR MANUFACTURING SEMICONDUCTOR CHIP, ADHESIVE FILM FOR
SEMICONDUCTOR, AND COMPOSITE SHEET USING THE FILM
Abstract
There is an adhesive film for a semiconductor for use in a
method for manufacturing a semiconductor chip. The method includes
preparing a laminated body having a semiconductor wafer, an
adhesive film for a semiconductor and dicing tape laminated in that
order. The adhesive film for a semiconductor has a tensile breaking
elongation of less than 5%, and the tensile breaking elongation is
less than 110% of the elongation at maximum load. The semiconductor
wafer is partitioned into multiple semiconductor chips and notches
are formed from the semiconductor wafer side so that at least a
portion of the adhesive film for a semiconductor remains uncut in
its thickness direction. The method also includes stretching out
the dicing tape in a direction so that the multiple semiconductor
chips are separated apart, to separate the adhesive film for a
semiconductor along the notches.
Inventors: |
Nakamura; Yuuki;
(Hitachi-shi, JP) ; Kitakatsu; Tsutomu;
(Hitachi-shi, JP) ; Katayama; Youji; (Hitachi-shi,
JP) ; Hatakeyama; Keiichi; (Tsukuba-shi, JP) |
Family ID: |
39863823 |
Appl. No.: |
13/420266 |
Filed: |
March 14, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12594634 |
Dec 11, 2009 |
8232185 |
|
|
PCT/JP2008/056361 |
Mar 31, 2008 |
|
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13420266 |
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Current U.S.
Class: |
428/343 ;
524/538 |
Current CPC
Class: |
H01L 2924/01045
20130101; H01L 24/73 20130101; H01L 2224/73265 20130101; H01L
2924/10253 20130101; H01L 2924/01005 20130101; H01L 24/83 20130101;
B23K 2103/172 20180801; H01L 2224/29006 20130101; H01L 21/6835
20130101; H01L 2221/68327 20130101; H01L 2224/274 20130101; H01L
2924/01015 20130101; H01L 2924/3512 20130101; H01L 2924/09701
20130101; H01L 2224/92247 20130101; H01L 2924/0665 20130101; H01L
2924/01006 20130101; H01L 2224/48091 20130101; B23K 2101/40
20180801; H01L 2924/014 20130101; H01L 2924/15788 20130101; C09J
201/00 20130101; H01L 21/6836 20130101; H01L 2924/01077 20130101;
H01L 2924/10253 20130101; H01L 2224/48227 20130101; H01L 25/50
20130101; H01L 2924/01027 20130101; H01L 2924/01033 20130101; H01L
2924/01004 20130101; B23K 2103/50 20180801; H01L 2924/01029
20130101; H01L 2924/15747 20130101; H01L 21/78 20130101; H01L
2924/181 20130101; H01L 2224/2919 20130101; H01L 2224/2919
20130101; H01L 2224/48091 20130101; H01L 2224/73265 20130101; H01L
2924/01051 20130101; H01L 2924/01082 20130101; H01L 2224/32225
20130101; H01L 2924/01013 20130101; B23K 26/40 20130101; H01L
2224/92247 20130101; H01L 2924/12042 20130101; H01L 2924/181
20130101; H01L 2924/0102 20130101; H01L 2224/83191 20130101; H01L
2924/12042 20130101; H01L 2924/07802 20130101; H01L 2224/32145
20130101; B23K 26/53 20151001; H01L 2924/15788 20130101; H01L
2224/73265 20130101; H01L 2924/01012 20130101; H01L 24/27 20130101;
Y10T 428/28 20150115; B23K 26/364 20151001; H01L 2924/15747
20130101; H01L 2221/68336 20130101; B28D 5/0082 20130101; H01L
2924/01047 20130101; H01L 2224/92247 20130101; H01L 2924/0665
20130101; H01L 21/67132 20130101; H01L 2924/10329 20130101; H01L
2224/8385 20130101; H01L 2924/00012 20130101; H01L 2224/73265
20130101; H01L 2224/32145 20130101; H01L 2224/48227 20130101; H01L
2224/32225 20130101; H01L 2924/00 20130101; H01L 2924/00 20130101;
H01L 2224/73265 20130101; H01L 2924/0665 20130101; H01L 2924/00
20130101; H01L 2924/00014 20130101; H01L 2924/00 20130101; H01L
2224/48227 20130101; H01L 2924/00 20130101; H01L 2924/00 20130101;
H01L 2224/32225 20130101; H01L 2924/00 20130101; H01L 2924/00012
20130101; H01L 2924/00012 20130101; H01L 2224/48227 20130101; H01L
2224/48227 20130101; H01L 2924/00 20130101; H01L 2224/32145
20130101; H01L 2924/00012 20130101 |
Class at
Publication: |
428/343 ;
524/538 |
International
Class: |
C09J 7/02 20060101
C09J007/02; C09J 163/00 20060101 C09J163/00; C09J 179/08 20060101
C09J179/08; B32B 37/02 20060101 B32B037/02; B32B 38/04 20060101
B32B038/04 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 5, 2007 |
JP |
P2007-099344 |
Aug 6, 2007 |
JP |
P2007-204338 |
Claims
1. An adhesive film for a semiconductor for use in a method for
manufacturing a semiconductor chip comprising the steps of:
preparing a laminated body having a semiconductor wafer, an
adhesive film for a semiconductor and dicing tape laminated in that
order, the adhesive film for a semiconductor having a tensile
breaking elongation of less than 5%, the tensile breaking
elongation being less than 110% of the elongation at maximum load,
the semiconductor wafer being partitioned into multiple
semiconductor chips and notches being formed from the semiconductor
wafer side so that at least a portion of the adhesive film for a
semiconductor remains uncut in its thickness direction, and
stretching out the dicing tape in a direction so that the multiple
semiconductor chips are separated apart, to separate the adhesive
film for a semiconductor along the notches, wherein the adhesive
film for a semiconductor has a tensile breaking elongation of less
than 5% and the tensile breaking elongation of less than 110% of
the elongation at maximum load.
2. The adhesive film for a semiconductor according to claim 1,
which can be attached to a semiconductor wafer at 100.degree. C. or
below.
3. The adhesive film for a semiconductor according to claim 1,
which comprises a thermoplastic resin, a thermosetting component
and a filler, a filler content being less than 30% by mass with
respect to the mass of the adhesive film for a semiconductor.
4. A composite sheet comprising the adhesive film for a
semiconductor according to claim 1, and dicing tape laminated on
one side of the adhesive film for a semiconductor.
5. An adhesive film for a semiconductor for use in a method for
manufacturing a semiconductor chip comprising the steps of:
preparing a laminated body having a semiconductor wafer, an
adhesive film for a semiconductor and dicing tape laminated in that
order, the adhesive film for a semiconductor having a tensile
breaking elongation of less than 5% and the tensile breaking
elongation being less than 110% of the elongation at maximum load,
with reformed sections formed in the semiconductor wafer by laser
working along lines for division of the semiconductor wafer into
multiple semiconductor chips, and stretching out the dicing tape in
a direction so that the multiple semiconductor chips are separated
apart, to partition the semiconductor wafer into multiple
semiconductor chips while partitioning the adhesive film for a
semiconductor along the reformed sections, wherein the adhesive
film for a semiconductor has a tensile breaking elongation of less
than 5% and the tensile breaking elongation of less than 110% of
the elongation at maximum load.
6. The adhesive film for a semiconductor according to claim 5,
which can be attached to a semiconductor wafer at 100.degree. C. or
below.
7. The adhesive film for a semiconductor according to claim 5,
which comprises a thermoplastic resin, a thermosetting component
and a filler, a filler content being less than 30% by mass with
respect to the mass of the adhesive film for a semiconductor.
8. A composite sheet comprising the adhesive film for a
semiconductor according to claim 5 and dicing tape laminated on one
side of the adhesive film for a semiconductor.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application is a Divisional application of U.S.
application Ser. No. 12/594,634 filed Oct. 5, 2009, and claims
priority from International Application PCT/JP2008/056361 filed
Mar. 31, 2008, Japanese Application No. JP2007-099344 filed on Apr.
5, 2007, and Japanese Application No. JP2007-204338 filed on Aug.
6, 2007, the contents of each of which are hereby incorporated by
reference into this application.
TECHNICAL FIELD
[0002] The present invention relates to a method for manufacturing
a semiconductor chip, and to an adhesive film for a semiconductor
and a composite sheet using the film.
BACKGROUND ART
[0003] When a semiconductor chip is mounted on a supporting member,
silver paste is conventionally used, for the most part, as the die
bonding material to bond the semiconductor chip with the supporting
member. However, as semiconductor chips become smaller with higher
performance and the supporting members used also become smaller and
more miniaturized, methods that employ silver pastes are presenting
problems including paste bleed-out and wire bonding troubles due to
sloping of the semiconductor chip. In recent years, therefore,
adhesive films (adhesive films for semiconductors) have come to be
used in place of silver pastes.
[0004] Systems used to obtain semiconductor devices using adhesive
films include short bar attachment systems and wafer back-side
attachment systems.
[0005] In a short bar attachment system, short bars are cut out by
cutting or punching from a reel-shaped adhesive film and the short
bars of the adhesive film are bonded to a supporting member.
Individuated semiconductor chips are joined to the supporting
member by a separate dicing step, via the adhesive film bonded to
the supporting member. A semiconductor device is then obtained, if
necessary by a wire bond step, sealing step, or the like. In short
bar attachment systems, however, a special assembly apparatus is
necessary to cut out the adhesive film into short bars and bond
them to the supporting member, and therefore production cost has
been higher than methods using silver paste.
[0006] In a wafer back-side attachment system, first an adhesive
film and dicing tape are attached in that order to the back side of
a semiconductor wafer. The semiconductor wafer is diced for
partitioning into a plurality of semiconductor chips, and the
adhesive film is cut for each semiconductor chip. Next, the
semiconductor chips are picked up together with the adhesive films
laminated on their back sides, and the semiconductor chips are
bonded to supporting members through the adhesive films. A
semiconductor device is then obtained by further steps such as
heating, curing and wire bonding. A wafer back-side attachment
system does not require an assembly apparatus for individuation of
the adhesive film, and a conventional assembly apparatus used for
silver paste may be used either in its original form or with part
of the apparatus modified by addition of a heating plate or the
like. Among methods that employ adhesive films, therefore, this
method has been of interest with the aim of helping to limit
production cost.
[0007] Methods proposed for dicing semiconductor wafers, on the
other hand, include stealth dicing, in which a semiconductor wafer
is irradiated with laser light to selectively create reformed
sections inside the semiconductor wafer, and the semiconductor
wafer is cut along the reformed sections (Patent documents 1 and
2). In this method, dicing tape is stretched to apply stress to the
semiconductor wafer, and the semiconductor wafer is partitioned
into multiple semiconductor chips along the reformed sections.
[0008] [Patent document 1] Japanese Unexamined Patent Publication
No. 2002-192370 [0009] [Patent document 2] Japanese Unexamined
Patent Publication No. 2003-338467
DISCLOSURE OF THE INVENTION
Problems to be Solved by the Invention
[0010] Wafer back-side attachment systems require the adhesive film
to be cut simultaneously during semiconductor wafer dicing.
However, when the semiconductor wafer and adhesive film are
simultaneously cut by ordinary dicing methods employing a diamond
blade, cracking occurs on the side surfaces of the cut
semiconductor chips (chip cracks), and the adhesive film becomes
raised on the cut surfaces, producing numerous burrs. The presence
of such chip cracks and burrs tends to result in cracking of the
semiconductor chips during their pickup, thus lowering the
yield.
[0011] The stealth dicing method mentioned above can potentially
inhibit the extent of chip cracks and burrs produced with dicing.
However, it is known that when the semiconductor wafers are
partitioned by stretching dicing tape after creating reformed
sections in the semiconductor wafers by laser working, it is
difficult to completely separate the adhesive film for a
semiconductor simply by stretching of the dicing tape, while it is
also difficult to obtain high semiconductor chip yields in
practice.
[0012] It is an object of the present invention to provide a method
that allows semiconductor chips to be obtained from a semiconductor
wafer at high yield, while sufficiently inhibiting generation of
chip cracks and burrs. It is another object of the invention to
provide an adhesive film for a semiconductor and composite sheet
that can be suitably used in the method.
Means for Solving the Problems
[0013] According to one aspect, the invention relates to a method
for manufacturing a semiconductor chip. The manufacturing method of
the invention comprises a step of preparing a laminated body having
a semiconductor wafer, an adhesive film for a semiconductor and
dicing tape laminated in that order, the adhesive film for a
semiconductor having a tensile breaking elongation of less than 5%,
the tensile breaking elongation being less than 110% of the
elongation at maximum load, the semiconductor wafer being
partitioned into multiple semiconductor chips, and notches being
formed from the semiconductor wafer side so that at least a portion
of the adhesive film for a semiconductor remains uncut in its
thickness direction, and a step of stretching out the dicing tape
in a direction so that the multiple semiconductor chips are
separated apart, to separate the adhesive film for a semiconductor
along the notches.
[0014] According to the manufacturing method of the invention, a
laminated body is prepared with the adhesive film for a
semiconductor connected instead of being completely cut. Stretching
out of the dicing tape also causes the adhesive film for a
semiconductor to be partitioned. According to this method, the
adhesive film for a semiconductor having the aforementioned
specified tensile breaking elongation is employed to allow
semiconductor chips to be obtained from a semiconductor wafer at
high yield while sufficiently inhibiting generation of chip cracks
and burrs.
[0015] The method for manufacturing a semiconductor chip according
to the invention may also comprise a step of preparing a laminated
body having a semiconductor wafer, an adhesive film for a
semiconductor and dicing tape laminated in that order, the adhesive
film for a semiconductor having a tensile breaking elongation of
less than 5% and the tensile breaking elongation being less than
110% of the elongation at maximum load, with reformed sections
formed in the semiconductor wafer by laser working along lines for
division of the semiconductor wafer into multiple semiconductor
chips, and a step of stretching out the dicing tape in a direction
so that the multiple semiconductor chips are separated apart, to
partition the semiconductor wafer into multiple semiconductor chips
while partitioning the adhesive film for a semiconductor along the
reformed sections.
[0016] In the manufacturing method of the invention, the
semiconductor wafer is partitioned after forming reformed sections
in the semiconductor wafer by laser working, and therefore
generation of chip cracks and burrs is satisfactorily prevented
compared to conventional methods that employ dicing blades or the
like. Furthermore, since the method employs an adhesive film for a
semiconductor having the aforementioned specified tensile
characteristics, the adhesive film for a semiconductor is
efficiently and reliably partitioned by stretching out of the
dicing tape, allowing semiconductor chips to be obtained at high
yield as a result.
[0017] The adhesive film for a semiconductor preferably comprises a
thermoplastic resin, a thermosetting component and a filler, and
has a filler content of less than 30% by mass with respect to the
mass of the adhesive film for a semiconductor. Reducing the filler
content somewhat while imparting the specified tensile
characteristic to the adhesive film for a semiconductor will
inhibit reflow cracks after mounting.
[0018] In the manufacturing methods described above, the step of
preparing the laminated body preferably includes a step of
attaching the adhesive film for a semiconductor onto the
semiconductor wafer at a temperature of not higher than 100.degree.
C. Attachment of the adhesive film for a semiconductor to the
semiconductor wafer while maintaining a relatively low temperature
of the adhesive film for a semiconductor will satisfactorily
prevent warping of the semiconductor wafer and damage resulting
from the thermal history of the dicing tape or backgrind tape.
[0019] According to another aspect, the invention relates to an
adhesive film for a semiconductor. The adhesive film for a
semiconductor according to the invention has a tensile breaking
elongation of less than 5% and the tensile breaking elongation of
less than 110% of the elongation at maximum load. By employing such
an adhesive film for a semiconductor in the manufacturing method of
the invention described above, it is possible to obtain
semiconductor chips from a semiconductor wafer at high yield while
sufficiently inhibiting generation of chip cracks and burrs.
[0020] Such an adhesive film for a semiconductor according to the
invention is preferably attachable to a semiconductor wafer at
100.degree. C. or below.
[0021] The adhesive film for a semiconductor according to the
invention preferably comprises a thermoplastic resin, a
thermosetting component and a filler, where a filler content is
less than 30% by mass with respect to the mass of the adhesive film
for a semiconductor. Reducing the filler content somewhat while
imparting the specified tensile characteristics to the adhesive
film for a semiconductor will further inhibit reflow cracks.
[0022] According to yet another aspect, the invention relates to a
composite sheet comprising an adhesive film for a semiconductor
according to the invention as described above, and dicing tape
laminated on one side of the adhesive film for a semiconductor. By
using such a composite sheet it is possible to further efficiently
obtain a semiconductor chip and semiconductor device by simple
steps.
Effect of the Invention
[0023] According to the invention it is possible to obtain a high
yield of semiconductor chips from a semiconductor wafer while
sufficiently inhibiting generation of chip cracks and burrs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is an end view showing a method for manufacturing a
semiconductor chip according to a first embodiment.
[0025] FIG. 2 is an end view showing a method for manufacturing a
semiconductor chip according to a first embodiment.
[0026] FIG. 3 is an end view showing a method for manufacturing a
semiconductor chip according to a first embodiment.
[0027] FIG. 4 is an end view showing a method for manufacturing a
semiconductor chip according to a first embodiment.
[0028] FIG. 5 is an end view showing a method for manufacturing a
semiconductor chip according to a first embodiment.
[0029] FIG. 6 is an end view showing a method for manufacturing a
semiconductor chip according to a second embodiment.
[0030] FIG. 7 is an end view showing a method for manufacturing a
semiconductor chip according to a second embodiment.
[0031] FIG. 8 is an end view showing a method for manufacturing a
semiconductor chip according to a second embodiment.
[0032] FIG. 9 is an end view showing a method for manufacturing a
semiconductor chip according to a second embodiment.
[0033] FIG. 10 is a cross-sectional view showing an embodiment of a
semiconductor device.
[0034] FIG. 11 is a view showing a stress-strain curve for a
tensile test of an adhesive film for a semiconductor.
[0035] FIG. 12 is a view showing a stress-strain curve for a
tensile test of an adhesive film for a semiconductor.
[0036] FIG. 13 is a view showing a stress-strain curve for a
tensile test of an adhesive film for a semiconductor.
[0037] FIG. 14 is a schematic view of a measuring apparatus used
for a chip pull off test.
EXPLANATION OF SYMBOLS
[0038] 1: Semiconductor wafer, 1a: reformed section, 2: adhesive
film for a semiconductor, 3: dicing tape, 4: dicing blade, 5:
division line, 7: wiring-attached base, 8: bonding wire, 9: sealing
resin layer, 10, 10a, 10b: semiconductor chips, 20: laminated body,
40: notch, 100: semiconductor device.
BEST MODE FOR CARRYING OUT THE INVENTION
[0039] Preferred embodiments of the invention will now be described
in detail. However, the present invention is not limited to the
embodiments described below.
First Embodiment
[0040] FIGS. 1, 2, 3, 4 and 5 are end views showing a method for
manufacturing a semiconductor chip according to a first embodiment.
The method for manufacturing a semiconductor chip according to this
embodiment comprises a step of preparing a laminated body 20
obtained by laminating a semiconductor wafer 1, an adhesive film
for a semiconductor 2 and dicing tape 3 in that order (FIG. 1), a
step of forming notches 40 in the laminated body 20 from one side
of the semiconductor wafer 1 (FIGS. 2 and 3), a step of
partitioning the adhesive film for a semiconductor 2 along the
notches 40 (FIG. 4), and a step of pickup of semiconductor chips 10
together with the adhesive film for a semiconductor 2 (FIG. 5).
[0041] The laminated body 20 in FIG. 1 is prepared by a method in
which an adhesive film for a semiconductor 2 and dicing tape 3 are
attached in that order on the back side of a semiconductor wafer 1,
or a composite sheet obtained by laminating the adhesive film for a
semiconductor 2 and dicing tape 3 is attached to the back side of
the semiconductor wafer 1 with the adhesive film for a
semiconductor 2 facing the semiconductor wafer 1 side.
[0042] The semiconductor wafer 1 used is a wafer comprising
single-crystal silicon, or polycrystalline silicon, a ceramic, or a
compound semiconductor composed of gallium-arsenic. The dicing tape
3 is not particularly restricted so long as it has a sufficient
adhesive property to allow anchoring onto an anchoring ring, and
can be stretched out so that the adhesive film for a semiconductor
2 is partitioned. Vinyl chloride-based tape, for example, may be
used as the dicing tape. The adhesive film for a semiconductor 2
will be described in detail below.
[0043] When the adhesive film for a semiconductor 2 or a composite
sheet comprising it is attached to the semiconductor wafer 1, the
temperature of the adhesive film for a semiconductor is preferably
kept at 0-100.degree. C. Attachment of the adhesive film for a
semiconductor 2 at such a relatively low temperature will
satisfactorily prevent warping of the semiconductor wafer 1 and
damage resulting from the thermal history of the dicing tape or
backgrind tape. From the same viewpoint, the temperature is more
preferably 15.degree. C.-95.degree. C. and even more preferably
20.degree. C.-90.degree. C.
[0044] A dicing blade 4 is used to form notches 40 in the laminated
body 20 from the semiconductor wafer 1 side, in such a manner that
the semiconductor wafer 1 is partitioned into multiple
semiconductor chips 10 while leaving a portion uncut in the
direction of thickness of the adhesive film for a semiconductor 2
(FIG. 2). In other words, the semiconductor wafer 1 is completely
cut while the adhesive film for a semiconductor 2 is half-cut along
the lines on which the semiconductor wafer 1 is cut.
[0045] FIG. 3 is a magnified end view showing the area near a notch
40 formed in the laminated body 20. "Half-cut" means that the
thickness T1 of the adhesive film for a semiconductor 2 and the
depth T2 to which the adhesive film for a semiconductor 2 is
notched satisfy the relationship T2/T1<1. T2/T1 is preferably
1/5-4/5, more preferably 1/4-3/4 and even more preferably 1/3-2/3.
A smaller T2 will tend to prevent generation of burrs when the
adhesive film for a semiconductor 2 is partitioned along the
notches 40, but will also tend to interfere with complete
partitioning of the adhesive film for a semiconductor 2 even by
stretching of the dicing tape 3 and increasing the thrusting height
during pickup of the semiconductor chip 10. A larger T2 will tend
to facilitate complete segmentation of the die bond film even with
a low amount of stretching of the dicing tape (also referred to
hereunder as "expanding volume"), and even with a low thrusting
height during pickup of the semiconductor chip 10. However, an
excessively large T2 will tend to reduce the effect against burrs
and lower the yield for production of semiconductor devices.
[0046] After forming the notches 40, the dicing tape 3 is stretched
out in a direction such that the multiple semiconductor chips 10
are separated apart, i.e. in the direction along the main side of
the dicing tape 3 (the direction of the arrow in FIG. 2), to
partition the adhesive film for a semiconductor 2 (FIG. 4). As a
result, the semiconductor chips 10 and the adhesive film-attached
semiconductor chips having the adhesive film for a semiconductor 2
attached thereover become arranged on the dicing tape 3.
[0047] The expanding volume is the difference between the width
(maximum width) of the dicing tape 3 after stretching R.sub.1 and
the initial width (maximum width) of the dicing tape 3 R.sub.0 (see
FIG. 2). The expanding volume is preferably 2 mm-10 mm, more
preferably 2 mm-8 mm and even more preferably 2 mm-7 mm. Since the
notches formed in the adhesive film for a semiconductor 2 as in
this embodiment serve as starting points for cutting, the expanding
volume may be reduced compared to a situation where the adhesive
film for a semiconductor 2 is completely uncut, as in the second
embodiment described hereunder.
[0048] After the dicing tape 3 has been stretched out, the
semiconductor chips 10 are picked up together with the adhesive
film for a semiconductor 2 attached onto the back side thereof
(FIG. 5). The dicing tape 3 may be pushed up to a prescribed height
from the side opposite the semiconductor chips 10, at the locations
where the semiconductor chips 10 are to be picked up. The picked-up
semiconductor chips 10 are mounted onto supporting members or the
like using the adhesive film for a semiconductor 2 attached on
their back sides as die bonding materials. The steps after pickup
will be described below.
[0049] The adhesive film for a semiconductor 2 will now be
described in detail.
[0050] The adhesive film for a semiconductor 2 has, as a feature, a
relatively short tensile breaking elongation. The adhesive film for
a semiconductor 2 does not yield in a tensile test, or breaks
immediately after yielding at maximum load. With such tensile
characteristics, the adhesive film for a semiconductor 2 will be
resistant to raising of the ruptured surface when rupture occurs
due to tensile stress, so that generation of burrs can be
satisfactorily prevented.
[0051] More specifically, the tensile breaking elongation of the
adhesive film for a semiconductor 2 is preferably less than 5%. The
tensile breaking elongation of the adhesive film for a
semiconductor 2 is preferably less than 110% with respect to the
elongation at maximum load in a tensile test. The adhesive film for
a semiconductor 2 with such tensile characteristics can be
efficiently and reliably separated with low expanding volume.
[0052] With a tensile breaking elongation of 5% or greater, it will
be necessary for the expanding volume of the dicing tape 3 to be
greater than usual for complete separation of the adhesive film for
a semiconductor 2. A proportion of 110% or greater for the tensile
breaking elongation with respect to the elongation under maximum
load corresponds to a long yield state or proneness to necking, and
this will make it difficult to completely separate the adhesive
film for a semiconductor 2 while preventing burrs.
[0053] From the same viewpoint, the tensile breaking elongation is
more preferably less than 4% and even more preferably less than
3.5%. Similarly, the ratio of the tensile breaking elongation to
the elongation under maximum load is more preferably less than 108%
and even more preferably less than 105%. This ratio is a minimum of
100%, when the tensile breaking elongation and the elongation under
maximum load are equal.
[0054] The maximum stress, maximum load elongation and tensile
breaking elongation are determined by using a test strip with a
width of 5 mm, a length of 50 mm and a thickness of 25 .mu.m, cut
out from the adhesive film for a semiconductor in the B-stage
state, for a tensile test under the following conditions, in an
environment at 25.degree. C.
Tensile tester: 100N autograph "AGS-100NH" by Shimadzu Length
between chucks (at start of test): 30 mm Pull rate: 5 mm/min
[0055] The maximum load, length between chucks at maximum load and
length between chucks at the time of rupture are read from a
stress-strain curve obtained by the tensile test, and these values
and the measured value for the cross-sectional area of the sample
are used to calculate the maximum stress, maximum load elongation
and tensile breaking elongation by the following formula.
Maximum stress (Pa)=maximum load (N)/cross-sectional area of sample
(m.sup.2)
Elongation at maximum load (%)={(length between chucks at maximum
load (mm)-30)/30}.times.100
Tensile breaking elongation (%)={(length between chucks at the time
of rupture (mm)-30)/30}.times.100
[0056] Normally, measurement is made for several test pieces, and
the average value is recorded as the tensile characteristic of the
adhesive film for a semiconductor. From the viewpoint of
reproducibility the tensile test is preferably carried out under
the conditions described above, but the conditions may be altered
to other conditions that give substantially the same test
results.
[0057] The adhesive film for a semiconductor 2 preferably comprises
a thermoplastic resin, a thermosetting component and a filler. By
constructing the adhesive film for a semiconductor 2 with these
components and appropriately adjusting the types of components and
their amounts, it is possible to obtain an adhesive film for a
semiconductor 2 having the tensile characteristics specified
above.
[0058] The thermoplastic resin in the adhesive film for a
semiconductor preferably has a glass transition temperature (Tg) of
not higher than 60.degree. C. A thermoplastic resin with heat
resistance of 300.degree. C. or above is also preferred. As
specific examples of preferred thermoplastic resins there may be
mentioned polyimide resins, polyamideimide resins, phenoxy resins,
acrylic resins, polyamide resins and urethane resins. These may be
used alone or in combinations of two or more. Polyimide resins are
particularly preferred among those mentioned above. By using a
polyimide resin it is possible to easily impart the tensile
characteristic described above to the adhesive film for a
semiconductor 2 while maintaining a reasonably small filler
content.
[0059] A thermosetting component is a component that can be
hardened when it undergoes crosslinking under heating, and for
example, it may be composed of a thermosetting resin and its curing
agent. The thermosetting resin may be any known one and is not
particularly restricted, but preferred are epoxy resins and imide
compounds with at least two thermosetting imide groups in the
molecule, from the viewpoint of convenience as a semiconductor
peripheral material (availability of high purity product, variety
and easily controllable reactivity). An epoxy resin will normally
be used together with an epoxy resin curing agent.
[0060] An epoxy resin is preferably a compound having two or more
epoxy groups. From the viewpoint of curability and cured
properties, it is preferably a phenol glycidyl ether-type epoxy
resin. As examples of phenol glycidyl ether-type epoxy resins there
may be mentioned condensation products of bisphenol A, bisphenol
AD, bisphenol S, bisphenol F or halogenated bisphenol A with
epichlorohydrin, as well as phenol-novolac resin glycidyl ether,
cresol-novolac resin glycidyl ether and bisphenol A-novolac resin
glycidyl ether. Novolac-type epoxy resins (glycidyl ethers of
cresol-novolac resins, glycidyl ethers of phenol-novolac resins,
and the like) are preferred among those mentioned above because
they have high cured crosslink density and can increase the
adhesive strength of the hot film. They may be used alone or in
combinations of two or more.
[0061] As examples of epoxy resin curing agents there may be
mentioned phenol-based compounds, aliphatic amines, alicyclic
amines, aromatic polyamines, polyamides, aliphatic acid anhydrides,
alicyclic acid anhydrides, aromatic acid anhydrides,
dicyandiamides, organic acid dihydrazides, boron trifluoride amine
complexes, imidazoles and tertiary amines. Phenol-based compounds
are preferred among these, with phenol-based compounds having two
or more phenolic hydroxyl groups being especially preferred. More
specifically, naphthol-novolac resins and trisphenol-novolac resins
are preferred. Using these phenol-based compounds as epoxy resin
curing agents can effectively reduce contamination of the chip
surfaces and devices during heating for package assembly, as well
as generation of outgas that is a cause of odor.
[0062] The filler content may also be adjusted to control the
tensile characteristic of the adhesive film for a semiconductor. A
high filler content will tend to lower the tensile breaking
elongation, while also tending to reduce the ratio of the tensile
breaking elongation to the elongation at maximum load. Appropriate
use of a filler can produce effects such as improved handleability,
increased thermal conductivity, modified melt viscosity and
thixotropic properties.
[0063] For such purposes, the filler is preferably an inorganic
filler. More specifically, preferred inorganic fillers contain one
or more inorganic materials selected from the group consisting of
aluminum hydroxide, magnesium hydroxide, calcium carbonate,
magnesium carbonate, calcium silicate, magnesium silicate, calcium
oxide, magnesium oxide, alumina, aluminum nitride, aluminum borate
whiskers, boron nitride, crystalline silica, amorphous silica and
antimony oxide. Alumina, aluminum nitride, boron nitride,
crystalline silica and amorphous silica are preferred for increased
thermal conductivity. To adjust the melt viscosity and impart a
thixotropic property, aluminum hydroxide, magnesium hydroxide,
calcium carbonate, magnesium carbonate, calcium silicate, magnesium
silicate, calcium oxide, magnesium oxide, alumina, crystalline
silica and amorphous silica are preferred. Alumina, silica,
aluminum hydroxide and antimony oxide are preferred for increased
humidity resistance. Different types of fillers may also be used in
combination.
[0064] A high filler content will tend to lower the tensile
breaking elongation while raising the elastic modulus and
increasing the breaking strength, but will also tend to lower the
adhesion, resulting in reduced reflow crack resistance. In
particular, it will be more prone to tearing during reflow between
semiconductor chips and an adherend with irregularities formed in
the surface, such as an organic board. A high filler content will
also tend to lower the resistance in reliability testing under
high-temperature, high-humidity environments, such as HAST testing.
In addition, increasing the filler content will tend to increase
the temperature at which the adhesive film for a semiconductor can
attach to semiconductor wafers. In consideration of the above, the
filler content is preferably less than 30% by mass and more
preferably less than 25% by mass with respect to the total mass of
the adhesive film for a semiconductor. It is more preferably less
than 20% by mass.
[0065] The adhesive film for a semiconductor 2 is preferably
attachable to a semiconductor wafer as the adherend, at 100.degree.
C. or below. The adhesive film for a semiconductor is considered to
be attachable to a semiconductor wafer if the peel strength at the
interface between the adhesive film for a semiconductor and the
semiconductor wafer is at least 20 N/m when the adhesive film for a
semiconductor kept at the prescribed temperature is attached to the
semiconductor wafer. The adhesive film for a semiconductor may be
attached to the semiconductor wafer, for example, using a hot roll
laminator set to a temperature of 100.degree. C. or below. The peel
strength is measured in an atmosphere at 25.degree. C., with a pull
angle of 90.degree. and a pull speed of 50 mm/min. By reducing the
filler content or using a thermoplastic resin with a low Tg, for
example, it is possible to obtain an adhesive film for a
semiconductor that can be attached to a semiconductor wafer at
100.degree. C. or below. The adhesive film for a semiconductor 2 is
preferably attachable to the semiconductor wafer at a temperature
of not higher than 95.degree. C. and more preferably not higher
than 90.degree. C.
[0066] The adhesive film for a semiconductor 2 preferably has the
heat resistance and humidity resistance required for mounting of a
semiconductor chip onto a semiconductor chip mounting supporting
member. It should therefore pass a reflow crack resistance test.
The reflow crack resistance of the adhesive film for a
semiconductor can be evaluated based on the adhesive strength. In
order to obtain satisfactory reflow crack resistance, the peel
strength is preferably at least 1.0 kg/cm initially, and at least
0.5 kg/cm after standing for 48 hours in an atmosphere at
85.degree. C./85%, when the adhesive film for a semiconductor is
attached to a semiconductor wafer with a 4.times.2 mm square
bonding area. The initial peel strength is more preferably at least
1.3 kg/cm and even more preferably 1.5 kg/cm. The peel strength
after standing for 48 hours in an atmosphere at 85.degree. C./85%
is more preferably at least 0.7 kg/cm and even more preferably at
least 0.8 kg/cm.
[0067] The adhesive film for a semiconductor 2 may be obtained by a
method in which, for example, a coating solution comprising a
thermoplastic resin, a thermosetting component, a filler and an
organic solvent which dissolves or disperses the foregoing is
coated onto a base film, and the organic solvent is removed from
the coating solution on the base film by heating.
[0068] The organic solvent is not particularly restricted so long
as it allows uniform dissolution and dispersion of the materials,
and as examples there may be mentioned dimethylformamide,
dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide,
diethyleneglycol dimethyl ether, toluene, benzene, xylene, methyl
ethyl ketone, tetrahydrofuran, ethylcellosolve, ethylcellosolve
acetate, butylcellosolve, dioxane, cyclohexanone and ethyl acetate.
These may be used alone or in combinations of two or more.
[0069] The base film is not particularly restricted so long as it
can withstand the heating used for removal of the organic solvent.
As examples of base films there may be mentioned polyester films,
polypropylene films, polyethylene terephthalate films, polyimide
films, polyetherimide films, polyether naphthalate films and
methylpentene films. A multilayer film comprising two or more of
these films may also be used as the base film. The surface of the
base film may be treated with a release agent which is
silicone-based, silica-based or the like. After removal of the
organic solvent, the base film may be used by itself as the support
of the adhesive film for a semiconductor without removal.
[0070] The adhesive film for a semiconductor may be stored and used
as a composite sheet attached to dicing tape. Using such a
composite sheet can simplify the semiconductor device production
process.
Second Embodiment
[0071] FIGS. 6, 7, 8 and 9 are end views showing a method for
manufacturing a semiconductor chip according to a second
embodiment. The method according to this embodiment comprises a
step of preparing a laminated body 20 obtained by laminating a
semiconductor wafer 1, an adhesive film for a semiconductor 2 and
dicing tape 3 in that order (FIGS. 6-8), a step of stretching out
the dicing tape 3 in a direction such that the plurality of
semiconductor chips 10 separate from each other, to partition the
adhesive film for a semiconductor 2 as the semiconductor wafer 1 is
partitioned into a plurality of semiconductor chips 10 (FIG. 9),
and a step of pickup of the semiconductor chips 10 together with
the adhesive film for a semiconductor 2.
[0072] The step of preparing the laminated body 20 comprises a step
of laser working to form reformed sections 1a inside the
semiconductor wafer 1 along lines 50 that demarcate the
semiconductor wafer 1 into multiple semiconductor chips 10
(hereinafter referred to as "division lines") (FIG. 6), a step of
attaching an adhesive film for a semiconductor 2 onto the
semiconductor wafer 1 in which the reformed sections 1a have been
formed (FIG. 7), and a step of attaching dicing tape 3 onto the
adhesive film for a semiconductor 2 (FIG. 8).
[0073] In the step of forming the reformed sections 1a by laser
working, a laser 90 is irradiated along division lines 50 (FIG.
6(b)). The laser working may be carried out under conditions
commonly employed for known "stealth dicing" methods. The laser
working forms reformed sections 1a inside the semiconductor wafer
1.
[0074] Next, the adhesive film for a semiconductor 2 and dicing
tape 3 are attached in that order onto the semiconductor wafer 1 as
shown in FIGS. 7 and 8, to obtain a laminated body 20.
[0075] The steps for obtaining the laminated body 20 are not
limited to the order of this embodiment. For example, the reformed
sections may be formed by laser working after the adhesive film for
a semiconductor has been attached onto the semiconductor wafer.
[0076] After the laminated body 20 has been obtained, the dicing
tape 3 is stretched out in a direction such that the plurality of
semiconductor chips 10 separate apart (direction of the arrow in
FIG. 8(b)), to partition the semiconductor wafer 1 into multiple
semiconductor chips 10 while also partitioning the adhesive film
for a semiconductor 2 along the reformed sections 1a (FIG. 9).
[0077] According to this embodiment, the semiconductor wafer 1 and
adhesive film for a semiconductor 2 are partitioned by stretching
the dicing tape, without cutting with a dicing blade. This method
does not require simultaneous cutting of the semiconductor wafer 1
and adhesive film for a semiconductor 2 with a dicing blade and can
therefore increase the speed of individuation of the semiconductor
wafer while inhibiting generation of burrs.
[0078] For this embodiment, the expanding volume of the dicing tape
3 is preferably 5-30 mm, more preferably 10-30 mm and even more
preferably 10-20 mm. If the expanding volume is less than 5 mm it
will tend to be difficult to completely separate the semiconductor
wafer 1 and adhesive film for a semiconductor 2, while if it is
greater than 30 mm, tearing will tend to occur at sections other
than the sections along the division lines.
[0079] For this embodiment, the speed at which the dicing tape 3 is
stretched out (the expanding speed) is preferably 10-1000 mm/sec,
more preferably 10-100 mm/sec and even more preferably 10-50
mm/sec. If the expanding speed is less than 10 mm/sec it will tend
to be difficult to completely separate the semiconductor wafer 1
and adhesive film for a semiconductor 2, while if it is greater
than 1000 mm/sec, tearing will tend to occur at sections other than
the sections along the division lines.
[0080] The semiconductor chips 10, that are obtained by the first
embodiment or second embodiment as explained above and are picked
up together the adhesive film for a semiconductor 2, are used to
construct a semiconductor element such as an IC or LSI. For
example, the semiconductor chips 10 are bonded onto supporting
members via the adhesive film for a semiconductor 2 attached on
their back sides. As examples for the supporting members there may
be mentioned lead frames such as 42 alloy lead frames and copper
lead frames, boards obtained by impregnating a resin film, nonwoven
glass fabric or glass woven fabric formed from an epoxy resin,
polyimide-based resin, maleimide-based resin or the like with a
thermosetting resin such as an epoxy resin, polyimide-based resin
or maleimide-based resin and curing the resin, as well as glass
boards and ceramic boards of alumina and the like.
[0081] The semiconductor chips may also be bonded together via the
adhesive film for a semiconductor. FIG. 10 is a cross-sectional
view showing an embodiment of a semiconductor device obtained by
such a method. The semiconductor device 100 shown in FIG. 10
comprises a wiring-attached base (supporting member) 7, a
semiconductor chip 10a bonded to the wiring-attached base 7 via the
adhesive film for a semiconductor 2, and a semiconductor chip 10b
bonded to the semiconductor chip 10a via the adhesive film for a
semiconductor 2. The semiconductor chips 10a and 10b are connected
to the wiring of the wiring-attached base 7 by bonding wire 8. The
semiconductor chips 10a and 10b are sealed by a sealing resin layer
9 in which they are embedded.
[0082] Bonding between the semiconductor chip and supporting member
and between the semiconductor chips is accomplished, for example,
by heating at 60-300.degree. C. for 0.1-300 seconds with the
adhesive film for a semiconductor sandwiched between the
semiconductor chip and supporting member or between the
semiconductor chips.
[0083] When the adhesive film for a semiconductor 2 contains a
thermosetting resin, the bonded semiconductor chips are preferably
heated to promote adhesion and curing of the adhesive film for a
semiconductor onto the adherend, for increased joint strength. The
heating may be appropriately adjusted according to the composition
of the adhesive film, and it will normally be 60-220.degree. C. for
0.1-600 minutes. When resin sealing is carried out, the heating in
the curing step for the sealing resin may be utilized.
EXAMPLES
[0084] The present invention will now be explained in greater
detail by examples. However, the present invention is not limited
to the examples described below.
1. Formation of Adhesive Films for Semiconductor
Example 1
[0085] After placing 1,3-bis(3-aminopropyl)tetramethyldisiloxane
(0.1 mol) as a diamine and 150 g of N-methyl-2-pyrrolidone as the
solvent in a 500 ml 4-necked flask equipped with a thermometer,
stirrer and calcium chloride tube, the mixture was stirred at
60.degree. C. Upon dissolution of the diamine, small portions of
1,10-(decamethylene)bis(trimellitate dianhydride)(0.02 mol) and
4,4'-oxydiphthalic dianhydride (0.08 mol) were added and reaction
was conducted at 60.degree. C. for 3 hours. This was followed by
heating at 170.degree. C. while blowing in N.sub.2 gas, and removal
of the water in the system over a period of 3 hours by azeotropic
distillation together with part of the solvent. The NMP solution of
the polyimide resin obtained by removal of the water was used to
form an adhesive film.
[0086] To the NMP solution containing the polyimide resin obtained
as described above (containing 100 parts by weight of polyimide
resin) there were added 4 parts by weight of a cresol-novolac-type
epoxy resin (product of Tohto Kasei Co., Ltd.), 2 parts by weight
of
4,4'-[1-[4-[1-(4-hydroxyphenyl)-1-methylethyl]phenyl]ethylidene]bisphenol
(product of Honshu Chemical Industry) and 0.5 part by weight of
tetraphenylphosphoniumtetraphenyl borate (product of Tokyo Chemical
Industry Co., Ltd.). There were further added a boron nitride
filler (product of Mizushima Ferroalloy Co., Ltd.) at 12 wt % with
respect to the total solid weight and AEROSIL filler R972 (product
of Nippon Aerosil Co., Ltd.) at 3 wt % with respect to the total
solid weight, and the mixture was thoroughly kneaded to obtain a
varnish. The prepared varnish was coated onto a release-treated
polyethylene terephthalate film and heated at 80.degree. C. for 30
minutes and then at 120.degree. C. for 30 minutes, after which the
polyethylene terephthalate film was peeled off at room temperature
(25.degree. C.) to obtain an adhesive film with a thickness of 25
.mu.m.
Example 2
[0087] An NMP solution of a polyimide resin was obtained in the
same manner as Example 1, except that
1,3-bis(3-aminopropyl)tetramethyldisiloxane (0.06 mol) and
4,9-dioxadecane-1,12-diamine (0.04 mol) were used as diamine
components. The obtained NMP solution of the polyimide resin was
used to form an adhesive film in the same manner as Example 1.
Example 3
[0088] An adhesive film was formed in the same manner as Example 1,
except that the boron nitride filler was used at 57 wt %.
Comparative Examples 1-3
[0089] There were prepared DF-402 as the adhesive film for
Comparative Example 1, DF-470 as the adhesive film for Comparative
Example 2 and DF-443 as the adhesive film for Comparative Example 3
(all die bond films by Hitachi Chemical Co., Ltd.).
Comparative Example 4
[0090] After placing etherdiamine 2000 (product of BASF) (0.03
mol), 1,12-diaminododecane (0.07 mol) and 150 g of
N-methyl-2-pyrrolidone in a 500 ml 4-necked flask equipped with a
thermometer, stirrer and calcium chloride tube, the mixture was
stirred at 60.degree. C. After dissolution of the diamine,
2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (0.1
mol) was added in small portions. After reaction at 60.degree. C.
for 1 hour, it was heated at 170.degree. C. while blowing in
N.sub.2 gas, and the water was removed by azeotropic distillation
together with part of the solvent. The NMP solution of the
polyimide resin obtained by removal of the water was used to form
an adhesive film. An adhesive film was formed in the same manner as
Example 1, except that the obtained solution was used and the boron
nitride filler content was 25 wt % with respect to the total solid
weight.
Comparative Example 5
[0091] An adhesive film was formed in the same manner as
Comparative Example 4, except that the boron nitride filler was
used at 47 wt %.
2. Evaluation of Adhesive Film
[0092] (1) Maximum Stress, Maximum Load Elongation and Tensile
Breaking Elongation
[0093] A test strip (width: 5 mm, length: 50 mm) cut out from the
adhesive film in the B-stage state was used for a tensile test. The
maximum stress, maximum load elongation and tensile breaking
elongation were determined from the obtained stress-strain curve,
based on the following formulas. The tensile test was conducted
using a tensile tester (100N autograph, AGS-100NH by Shimadzu)
under conditions with an atmosphere at 25.degree. C., a length
between chucks of 30 mm at the start of the test and a pull rate of
5 mm/min.
Maximum stress (Pa)=maximum load (N)/cross-sectional area of sample
(m.sup.2)
Elongation at maximum load (%)=[(length between chucks at maximum
load (mm)-30)/30].times.100
Tensile breaking elongation (%)=[(length between chucks at the time
of rupture (mm)-30)/30].times.100
[0094] FIG. 11 is a view showing the stress-strain curve for the
adhesive film of Example 1, FIG. 12 is the same for Example 2, and
FIG. 13 is the same for Comparative Example 1. In the views,
elongation (mm)=length between chucks-30. The maximum load
elongation is calculated from the elongation corresponding to the
maximum load Pmax, and the tensile breaking elongation is
calculated from the elongation E at the moment at which the load
has fallen to 0, after the test piece has ruptured.
[0095] (2) Wafer Attachment Temperature
[0096] A peel test was conducted in which a hot roll laminator (0.3
m/min, 0.3 MPa) heated to a prescribed temperature was used to
attach an adhesive film with a width of 10 mm to a semiconductor
wafer and then the adhesive film was pulled off in a 25.degree. C.
atmosphere at a pull angle of 90.degree. and a pull speed of 50
mm/min, to determine the peel strength. The peel test was conducted
using a UTM-4-100 TENSILON by Toyo Baldwin. The preset temperature
of the hot roll laminator was raised from 40.degree. C., 10.degree.
C. at a time, and the lowest temperature among the hot roll
laminator temperatures at which peel strength of 20 N/m or greater
was obtained was recorded as the wafer attachment temperature.
[0097] (3) Peel Strength (Chip Pull-Off Strength)
[0098] A silicon wafer with a thickness of 400 .mu.m was half-cut
from the surface side to a depth of 250 .mu.m and split by force
applied in the back-side direction, to prepare 4 mm.times.2 mm
silicon chips having 150 .mu.m-wide raised edges on the perimeter.
An adhesive film cut out to a size of 4 mm.times.2 mm was
sandwiched between the silicon chips and 42 alloy lead frame. A
load of 200 gf was applied to the entire section and contact bonded
therewith at 160.degree. C. for 5 seconds, and then heated at
180.degree. C. for 60 minutes for postcuring of the adhesive film.
The chip pull-off strength during heating at 260.degree. C. for 20
seconds was then measured using the measuring apparatus 15 shown in
FIG. 14 with a modified push-pull gauge. The measuring apparatus 15
comprised a heating plate 14, a die pad 13 mounted on the heating
plate 14, and a push-pull gauge 12. The sample was placed on the
die pad 13 of the measuring apparatus 15, and the push-pull gauge
12 was hooked onto the raised edge of the silicon chip to measure
the chip peel strength. The peel strength of each sample was
measured initially, and after high-temperature, high-humidity
treatment for 48 hours in an environment of 85.degree. C., 85% RH.
This measurement allows the surface adhesive strength of the
adhesive film to be measured. A higher numerical value corresponds
to greater resistance to reflow crack formation.
[0099] (4) Reflow Crack Resistance
[0100] An adhesive film-attached silicon chip comprising a silicon
chip cut to a 5 mm square and an adhesive film attached thereto was
bonded to a circuit board having wiring formed on the surface of a
polyimide film (25 .mu.m thickness) as the base. A separate 5
mm-square adhesive film-attached silicon chip was then bonded to
this silicon chip.
[0101] Treatment of ten obtained samples was carried out twice, the
treatment comprising passing each sample through an IR reflow
furnace set so that the surface temperature reached 260.degree. C.
and the temperature was held for 20 seconds, and then allowing it
to stand at room temperature (25.degree. C.) for cooling. Cracks in
the treated samples were observed visually and with an acoustic
microscope, to confirm the presence of any board/chip or chip/chip
cracks. The reflow crack resistance was evaluated on the following
scale, based on the observation results.
A: No cracks found in any of the samples. C: Cracks occurred in one
or more samples.
TABLE-US-00001 TABLE 1 Comp. Comp. Comp. Comp. Comp. Units Ex. 1
Ex. 2 Ex. 3 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Filler content wt % 15 15
60 9 10 40 28 50 Film thickness .mu.m 25 25 25 25 25 25 25 25 Wafer
attachment temperature .degree. C. 90 80 150 140 120 160 40 140
Tensile Maximum stress MPa 42.7 45.9 22.6 60.0 54.0 23.2 0.7 5.0
properties Maximum load % 2.9 2.5 2.3 3.9 3.9 12.2 306.2 185.0
elongation Tensile breaking % 3.0 2.5 2.4 10.3 14.4 13.0 311.6
201.0 elongation Tensile breaking % 104 101 104 264 370 106 102 108
elongation/Maximum load elongation Chip Initial kg/ 1.7 1.7 0.5 2.0
2.0 1.1 1.6 1.3 pull-off After 85.degree. C./85%/48 h 4 .times. 2
1.2 1.1 0.2 1.4 1.5 0.6 1.0 0.7 strength mm Reflow Board/chip -- A
A C A A C A C crack Chip/chip -- A A C A A A A A resistance
[0102] (5) Tear Resistance, Chip Cracks and Burrs
[0103] Each of the adhesive films produced in the examples and
comparative examples described above was attached onto a
semiconductor wafer, and the semiconductor wafer was partitioned
into semiconductor chips by methods of "full-cutting",
"half-cutting" or "laser dicing" described hereunder, after which
the tear resistance of the adhesive film and occurrence of chip
cracks and burrs were confirmed. Vinyl chloride-based tape (90
.mu.m thickness) was used as the dicing tape for all of the
methods.
[0104] Full-Cutting
[0105] A hot roll laminator (DM-300H by JCM, 0.3 m/min, 0.3 MPa)
was used to attach each adhesive film to a 50 .mu.m-thick
semiconductor wafer at the wafer attachment temperature listed in
Table 1. Next, dicing tape was laminated onto the adhesive film
under conditions with a hot plate temperature of 80.degree. C., to
prepare a dicing sample. A stainless steel ring was attached around
the perimeter of the dicing tape, and a DFD-6361 by DISCO was used
to cut the dicing sample. The cutting was performed with a
single-cut system in which working is completed with a single
blade, under conditions with an NBC-ZH104F-SE 27HDBB blade, a blade
rotation rate of 45,000 rpm and a cutting speed of 50 mm/s. The
blade height (cutting depth) during cutting was 80 .mu.m, as a
height allowing complete cutting of the adhesive film. Next, the
dicing tape was stretched out with an expanding apparatus, with the
ring in an anchored state. The expanding speed was 10 mm/s and the
expanding volume was 3 mm.
[0106] Half-Cutting
[0107] A test was conducted under the same conditions as
full-cutting, except that the blade height (cutting depth) was 100
.mu.m, as a height leaving a 10 .mu.m-thick section of the die bond
film uncut.
[0108] Laser Dicing
[0109] The semiconductor wafer (50 .mu.m thickness) was subjected
to laser irradiation to form reformed sections therein along the
lines demarcating the semiconductor chips. Adhesive film and dicing
tape were then attached in that order, by the same procedure as for
full-cutting, and a stainless steel ring was attached around the
outer periphery of the dicing tape. Next, the dicing tape was
stretched out with an expanding apparatus, with the ring in an
anchored state. The expanding speed was 30 mm/s and the expanding
volume was 15 mm.
[0110] Tear R was Ob Esistance
[0111] After stretching out the dicing tape, the presence of any
tearing of the adhesive film served with an optical microscope, the
length of the completely cleaved section as a proportion of the
total length of the cut surface was determined, and the proportion
was classified according to the scale shown below to evaluate the
tear resistance. The tear resistance was not evaluated for
full-cutting, since the adhesive film was cut with a dicing
blade.
AA: .gtoreq.98%
A: .gtoreq.90%
B: .gtoreq.50% and <90%
C: <50%
[0112] Chip Cracking
[0113] After stretching out the dicing tape, the condition of chip
cracking was observed with an optical microscope. The length of
chip cracks formed on the side of the semiconductor chip opposite
the adhesive film was classified according to the scale shown below
to evaluate the condition of chip cracking.
AA: <5 .mu.m
A: .gtoreq.5 .mu.m and <10 .mu.m
B: .gtoreq.10 and <25 .mu.m
C: .gtoreq.25 .mu.m
[0114] Burrs
[0115] After stretching out the dicing tape, the semiconductor
chips were picked up together with the adhesive film. The edges of
the adhesive film-attached semiconductor chips that had been picked
up were observed with an optical microscope to confirm the
condition of burrs.
AA: Burr lengths of <20 .mu.m A: Burr lengths of .gtoreq.20
.mu.m and <40 .mu.m B: Burr lengths of .gtoreq.40 and <100
.mu.m C: Burr lengths of .gtoreq.100 .mu.m
TABLE-US-00002 TABLE 2 Comp. Comp. Comp. Comp. Comp. Units Ex. 1
Ex. 2 Ex. 3 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Full- Expanding mm 3 3 3
3 3 3 3 3 cutting volume Chip -- B B B B B B C C cracks Burrs -- B
B B B B B C C Half- Expanding mm 3 3 3 3 3 3 3 3 cutting volume
Tear -- AA AA AA C C A C C resistance Chip -- A A A -- -- A -- --
cracks Burrs -- AA AA AA -- -- AA -- -- Laser Expanding mm 15 15 15
15 15 15 15 15 dicing volume Tear -- AA AA AA C C C C C resistance
Chip -- AA AA AA -- -- -- -- -- cracks Burrs -- AA AA AA -- -- --
-- --
[0116] The adhesive films of the examples, which had tensile
breaking elongations of less than 5% and tensile breaking
elongation/elongation at maximum load ratios of less than 110%,
exhibited satisfactory tear resistance with both half-cutting and
laser dicing, while the generation of chip cracks and burrs was
also sufficiently minimized. The adhesive films of Examples 1 and 2
which had filler contents of less than 30% by mass were attachable
to semiconductor wafers at 100.degree. C. or below, and were highly
superior in terms of reflow crack resistance.
[0117] In contrast, the adhesive films of the comparative examples,
which had tensile breaking elongations of 5% or greater or tensile
breaking elongation/elongation at maximum load ratios of 110% or
greater, did not always exhibit sufficient tear resistance and did
not allow manufacturing of semiconductor chips at high yield.
Comparative Example 3 exhibited relatively high tear resistance
with half-cutting, but the tear resistance with laser dicing was
inadequate.
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