U.S. patent application number 09/777599 was filed with the patent office on 2001-08-16 for process for producing semiconductor chip.
This patent application is currently assigned to Lintec Corporation. Invention is credited to Ebe, Kazuyoshi, Noguchi, Hayato.
Application Number | 20010014492 09/777599 |
Document ID | / |
Family ID | 18554067 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010014492 |
Kind Code |
A1 |
Noguchi, Hayato ; et
al. |
August 16, 2001 |
Process for producing semiconductor chip
Abstract
A process for producing semiconductor chips, comprising the
following steps. A semiconductor wafer having a surface overlaid
with circuits is provided. An arrangement wherein a back of the
semiconductor wafer is fixed on a dicing tape and wherein a
pressure sensitive adhesive double coated sheet is stuck to a
circuit surface of the semiconductor wafer is formed. The pressure
sensitive adhesive double coated sheet comprises a shrinkable base
having its both sides overlaid with pressure sensitive adhesive
layers. At least one of the layers is composed of an energy
radiation curable pressure sensitive adhesive. The semiconductor
wafer together with the pressure sensitive adhesive double coated
sheet is diced by each circuit to thereby form semiconductor chips.
The semiconductor chips are fixed on a transparent hard plate by
adherence of the pressure sensitive adhesive layer of the pressure
sensitive adhesive double coated sheet remote from the
semiconductor chips. The dicing tape is stripped from the
semiconductor chips. The pressure sensitive adhesive double coated
sheet, on its transparent hard plate side, is irradiated with
energy radiation. The shrink base of the pressure sensitive
adhesive double coated sheet is shrunk, and the semiconductor chips
are picked up. In the working of a semiconductor wafer into
extremely reduced thickness, semiconductor chips can be produced
with high yield without suffering from damaging of semiconductor
chips such as chip splitting or cracking.
Inventors: |
Noguchi, Hayato; (Urawa-shi,
JP) ; Ebe, Kazuyoshi; (Minamisaitama-gun,
JP) |
Correspondence
Address: |
Russell D. Orkin
700 Koppers Building
436 Seventh Avenue
Pittsburgh
PA
15219-1818
US
|
Assignee: |
Lintec Corporation
|
Family ID: |
18554067 |
Appl. No.: |
09/777599 |
Filed: |
February 6, 2001 |
Current U.S.
Class: |
438/118 ;
257/E21.599 |
Current CPC
Class: |
H01L 21/6836 20130101;
H01L 2221/68327 20130101; H01L 21/78 20130101 |
Class at
Publication: |
438/118 |
International
Class: |
H01L 021/44 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 7, 2000 |
JP |
2000-28702 |
Claims
What is claimed is:
1. A process for producing semiconductor chips, comprising the
steps of: providing a semiconductor wafer having a surface equipped
(overlaid) with circuits; forming an arrangement wherein a back of
the semiconductor wafer is fixed on a dicing tape and wherein a
pressure sensitive adhesive double coated sheet is stuck to a
circuit surface of the semiconductor wafer, said pressure sensitive
adhesive double coated sheet comprising a shrinkable base having
its both sides overlaid with pressure sensitive adhesive layers, at
least one of said pressure sensitive adhesive layers composed of an
energy radiation curable pressure sensitive adhesive; dicing the
semiconductor wafer together with the pressure sensitive adhesive
double coated sheet by each circuit to thereby form semiconductor
chips; fixing the semiconductor chips on a transparent hard plate
by adherence of the pressure sensitive adhesive layer of the
pressure sensitive adhesive double coated sheet remote from the
semiconductor chips; stripping the dicing tape from the
semiconductor chips; irradiating the pressure sensitive adhesive
double coated sheet, from the transparent hard plate side, with
energy radiation; shrinking the shrinkable base of the pressure
sensitive adhesive double coated sheet; and picking the
semiconductor chips up.
2. The process as claimed in claim 1, wherein both the pressure
sensitive adhesive layers of the pressure sensitive adhesive double
coated sheet are composed of an energy radiation curable pressure
sensitive adhesive.
3. The process as claimed in claim 1 or 2, wherein, after the
stripping of the dicing tape from the semiconductor chips but
before the irradiating of the pressure sensitive adhesive double
coated sheet, from the transparent hard plate side, with energy
radiation, backs of the semiconductor chips exposed by the
stripping of the dicing tape are ground.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a process for producing
semiconductor chips. More particularly, the present invention
relates to a process for producing semiconductor chips with high
yield without suffering from damaging of semiconductor chips.
BACKGROUND OF THE INVENTION
[0002] In recent years, the spread of IC cards is being promoted,
and accordingly the reduction of the thickness thereof is
increasingly demanded. Thus, it is now needed to reduce the
thickness of semiconductor chips from the conventional about 350
.mu.m to 50-100 .mu.m or less.
[0003] In the production of the above semiconductor chips, it is
common practice to first fix a semiconductor wafer on a pressure
sensitive adhesive sheet known as a dicing tape, subsequently
perform required processing (dicing, etc.) to thereby form
semiconductor chips and thereafter pick up the semiconductor chips
while thrusting them up by applying a thrust pin to the back (base
side) of the dicing tape. However, the semiconductor chips of
reduced thickness are so brittle that they are occasionally damaged
by the impact of the thrusting.
[0004] The applicant, in Japanese Patent Application No.
11(1999)-109806, has proposed a technique utilizing a pressure
sensitive adhesive double coated sheet including a heat shrink
base. In this technique, first a semiconductor wafer is fixed on a
hard plate by means of the pressure sensitive adhesive double
coated sheet, and subsequently required processing is performed to
thereby form the semiconductor wafer into semiconductor chips.
Thereafter, the pressure sensitive adhesive double coated sheet is
heated to thereby effect a heat shrink of the base of the double
coated sheet with the result that the pressure sensitive adhesive
layer of the double coated sheet is deformed. The deformation of
the pressure sensitive adhesive layer reduces the area of contact
of the semiconductor chips with the pressure sensitive adhesive
layer to thereby result in reduction of adherence. This facilitates
the pickup of the semiconductor chips. However, in this process, it
is requisite to dice the semiconductor wafer from back thereof. In
the event of chip cracking, it is likely to occur at the circuit
surface thereof to thereby invite the danger of lowering the yield
of semiconductor chips.
OBJECT OF THE INVENTION
[0005] The present invention has been made in view of the above
state of the prior art. Thus, it is an object of the present
invention to provide a process for producing semiconductor chips
with high yield while avoiding the damaging of semiconductor chips,
such as chip splitting or cracking, while working the semiconductor
wafer having extremely reduced thickness.
SUMMARY OF THE INVENTION
[0006] The process for producing semiconductor chips according to
the present invention comprises the steps of:
[0007] providing a semiconductor wafer having a surface overlaid
with circuits;
[0008] forming an arrangement wherein a back of the semiconductor
wafer is fixed on a dicing tape and wherein a pressure sensitive
adhesive double coated sheet is stuck to a circuit surface of the
semiconductor wafer, this pressure sensitive adhesive double coated
sheet comprising a shrinkable base having its both sides overlaid
with pressure sensitive adhesive layers, at least one of these
pressure sensitive adhesive layers composed of an energy radiation
curable pressure sensitive adhesive;
[0009] dicing the semiconductor wafer together with the pressure
sensitive adhesive double coated sheet by each circuit to thereby
form semiconductor chips;
[0010] fixing the semiconductor chips on a transparent hard plate
by adherence of the pressure sensitive adhesive layer of the
pressure sensitive adhesive double coated sheet remote from the
semiconductor chips;
[0011] stripping the dicing tape from the semiconductor chips;
[0012] irradiating the pressure sensitive adhesive double coated
sheet, from the transparent hard plate side, with energy
radiation;
[0013] shrinking the shrinkable base of the pressure sensitive
adhesive double coated sheet; and
[0014] picking the semiconductor chips up.
[0015] In the present invention, it is preferred that both the
pressure sensitive adhesive layers of the pressure sensitive
adhesive double coated sheet be composed of an energy radiation
curable pressure sensitive adhesive. Further, in the present
invention, it is preferred that, after the stripping of the dicing
tape from the semiconductor chips but before the irradiating of the
pressure sensitive adhesive double coated sheet, from the
transparent hard plate side, with energy radiation, backs of the
semiconductor chips exposed by the stripping of the dicing tape are
ground.
[0016] The above present invention enables producing semiconductor
chips of extremely reduced thickness in high production efficiency
while minimizing the damaging thereof.
BRIEF DESCRIPTION OF THE DRAWING
[0017] FIGS. 1 to 6 show the steps to be performed in the process
for picking up semiconductor chips according to the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The present invention will be described in greater detail
below with reference to the appended drawings.
[0019] In the present invention, referring first to FIG. 1,
semiconductor wafer 1 having a surface overlaid with circuits is
provided, and a back of the semiconductor wafer is fixed on dicing
tape 2. Pressure sensitive adhesive double coated sheet 10 is stuck
to a circuit surface of the semiconductor wafer in order to protect
the circuit surface.
[0020] Formation of circuits on a surface of a semiconductor wafer
is accomplished by customary means such as the etching or the
lift-off technique. After the circuit formation, the back of the
semiconductor wafer may be ground so as to regulate the thickness
thereof to desirable one.
[0021] Various pressure sensitive adhesive tapes having commonly
been employed in the dicing of semiconductor wafers can be used
without any particular limitation as the dicing tape 2. In
particular, a dicing tape comprising base 2a and, overlaid thereon,
pressure sensitive adhesive layer 2b which is curable upon exposure
to energy radiation (energy rays or energy beams) is preferably
used in the present invention.
[0022] The periphery of the dicing tape 2 is secured to circular or
rectangular ring frame 3.
[0023] The pressure sensitive adhesive double coated sheet 10 for
use in the present invention, as described in detail below,
comprises shrink base 11 having its both sides overlaid with
pressure sensitive adhesive layers 12a, 12b. At least one of the
pressure sensitive adhesive layers 12a, 12b is composed of an
energy radiation curable pressure sensitive adhesive. The energy
radiation curable pressure sensitive adhesive is preferably used in
the side of pressure sensitive adhesive layer 12a to which the
semiconductor wafer 1 is stuck. The energy radiation curable
pressure sensitive adhesive layer has the property of curing upon
being exposed to energy radiation with the result that the
adherence to semiconductor chips is reduced.
[0024] Upper surface of the pressure sensitive adhesive layer 12b
not stuck to the semiconductor wafer 1 may be overlaid with release
liner 13 for protecting the pressure sensitive adhesive layer.
[0025] The arrangement of FIG. 1 can be realized through various
courses including various pretreatments to be performed in the
processing of semiconductors. Therefore, what courses have been
taken for the realization of the above arrangement are not
particularly limited in the present invention.
[0026] For example, the arrangement of FIG. 1 is realized by first
sticking the dicing tape 2 to the back of one semiconductor wafer 1
and securing the periphery of the dicing tape 2 to the ring frame 3
and thereafter sticking the pressure sensitive adhesive double
coated sheet 10 to the circuit surface of the semiconductor wafer
1.
[0027] Alternatively, the arrangement of FIG. 1 may be realized by
first sticking the pressure sensitive adhesive double coated sheet
10 to the circuit surface of the semiconductor wafer 1 and
thereafter fixing the back of one semiconductor wafer 1 on the
dicing tape 2 and securing the periphery of the dicing tape 2 to
the ring frame 3.
[0028] Subsequently in the present invention, referring to FIG. 2,
the semiconductor wafer 1 in the state of having the pressure
sensitive adhesive double coated sheet 10 stuck thereto is diced
circuit by circuit to thereby form semiconductor chips 4. Thus, for
facilitating the recognition of circuit pattern at the time of
dicing, it is preferred that all the base 11, pressure sensitive
adhesive layers 12a, 12b and release liner 13 which constitute the
pressure sensitive adhesive double coated sheet 10 are transparent.
Various dicing devices having commonly been employed in the art can
be used in this dicing without any particular limitation.
[0029] After the dicing, referring to FIG. 4, the semiconductor
chips 4 are fixed on transparent hard plate 5 by adherence of the
pressure sensitive adhesive layer 12b of the pressure sensitive
adhesive double coated sheet 10. When the release liner 13 is stuck
onto the pressure sensitive adhesive layer 12b, the release liner l
13 is removed in advance to thereby expose the pressure sensitive
adhesive layer 12b and thereafter the semiconductor chips 4 are
fixed on the transparent hard plate 5 by means of the pressure
sensitive adhesive layer 12b. The release liner 13 can be stripped
from the pressure sensitive adhesive layer 12b by, for example, the
method in which, referring to FIG. 3, pressure sensitive adhesive
sheet 6 with a diameter larger than that of the semiconductor wafer
1 is stuck to the entire surface of the release liner 13 and
thereafter a peeling strength is applied to the pressure sensitive
adhesive sheet 6.
[0030] The fixing of the semiconductor chips 4 on the transparent
hard plate 5 is performed while the semiconductor chips 4 are stuck
to the dicing tape 2. Therefore, the alignment of the semiconductor
chips is maintained. Before or after the fixing of the
semiconductor chips 4 on the transparent hard plate 5, the
periphery of the dicing tape 2 is preferably cut so that the
diameter of the dicing tape 2 conforms to that of the semiconductor
wafer. This removes excess portion of the dicing tape 2 to thereby
enable enhancing operation efficiency.
[0031] After the fixing of the semiconductor chips 4 on the
transparent hard plate 5, the dicing tape 2 is stripped from the
backs of the semiconductor chips 4. The stripping of the dicing
tape 2 is appropriately performed in conformity with the properties
of employed tape. As in the stripping of the release liner 13, a
pressure sensitive adhesive sheet may be stuck to the entire
surface of the dicing tape 2, followed by peeling the pressure
sensitive adhesive sheet from the dicing tape. When, in particular,
the dicing tape 2 comprises energy radiation curable pressure
sensitive adhesive layer 2b, the stripping off of the dicing tape 2
can be facilitated by irradiating the dicing tape 2 from its base
2a side with energy radiation to thereby reduce the adhesive
strength of the energy radiation curable pressure sensitive
adhesive layer 2b.
[0032] When the dicing tape 2 is stripped off, the backs of the
semiconductor chips 4 are exposed as shown in FIG. 5. Thus, in this
stage, the semiconductor chips 4 may further be processed according
to necessity. For example, the backs of the individual
semiconductor chips 4 may be ground so as to reduce the thickness
of the semiconductor chips 4.
[0033] Thereafter, the pressure sensitive adhesive double coated
sheet 10, from the side of transparent hard plate 5, is exposed to
energy radiation. The exposing to energy radiation may be performed
over the entire surface of the pressure sensitive adhesive double
coated sheet 10 or on a spot basis on portions where semiconductor
chips to be picked up are secured.
[0034] The energy radiation passes through the transparent hard
plate 5, the pressure sensitive adhesive layer 12b and the base 11
and reaches the energy radiation curable pressure sensitive
adhesive layer 12a. Accordingly, when ultraviolet radiation is used
as the energy radiation, transparent pressure sensitive adhesive
layer 12b and transparent base 11 are employed. The energy
radiation curable pressure sensitive adhesive layer 12a is cured by
the exposure to energy radiation, so that the adherence thereof is
reduced or vanished to thereby enable stripping of the
semiconductor chips 4.
[0035] The exposure to energy radiation is performed by common
means such as an ultraviolet lamp or a high pressure mercury lamp.
When portions of the pressure sensitive adhesive double coated
sheet 10 are exposed to energy radiation, a condensing (converging)
lens, a reflecting mirror or the like can be employed.
[0036] In the present invention, the pressure sensitive adhesive
double coated sheet 10 is heated after or simultaneously with the
exposure to energy radiation. The heating is performed by, for
example, a hot plate or a heater. The heating may also be performed
on a spot basis with the use of heat rays. The exposure to heat
rays is performed on a spot basis on portions where semiconductor
chips to be picked up are secured and where have been or are
exposed to energy radiation.
[0037] The exposure to heat rays is performed by a halogen lamp, a
xenon lamp or a high pressure mercury lamp. For spot exposure, a
condensing (converging) lens or a reflecting mirror can be
employed. The exposure to heat rays may be performed from the side
of transparent hard plate 5 or the side of semiconductor chips
4.
[0038] When any of the above measures is employed, it is preferred
that the heating be carried out so that the temperature of the
pressure sensitive adhesive double coated sheet 10 is raised to
especially about 100-300.degree. C., still especially about
150-200.degree. C.
[0039] The high pressure mercury lamp can simultaneously function
as an energy radiation source and as a heat ray source.
Accordingly, the spot exposure to energy radiation and heat rays
can be simultaneously accomplished by the use of the high pressure
mercury lamp. In the use of the high pressure mercury lamp, the
exposure is performed from the side of transparent hard plate
5.
[0040] Referring now to FIG. 6, the above heating causes the
pressure sensitive adhesive double coated sheet 10 to deform to
thereby reduce the area of contact of the semiconductor chips 4
with the pressure sensitive adhesive layer 12a of the pressure
sensitive adhesive double coated sheet 10. Thus, the pickup of the
semiconductor chips 4 is facilitated. The use of the shrinkable
base 11 promotes the deformation of the pressure sensitive adhesive
double coated sheet 10.
[0041] As mentioned above, the heating causes the pressure
sensitive adhesive double coated sheet 10 to deform to thereby
reduce the area of contact of the semiconductor chips 4 with the
pressure sensitive adhesive layer 12a. Furthermore, the adhesive
force of the pressure sensitive adhesive layer 12a is lowered by
exposure to energy radiation. As a result, the semiconductor chips
4 can be easily picked up by common means such as a suction collet.
Thus, selective pickup of semiconductor chips can be effected, and
operation efficiency can be enhanced.
[0042] The pressure sensitive adhesive double coated sheet 10 for
use in the present invention will now be described. The pressure
sensitive adhesive double coated sheet 10 comprises shrinkable base
11 having its both sides overlaid with pressure sensitive adhesive
layers 12a, 12b.
[0043] The base 11, although not particularly limited as long as it
is shrinkable, can be selected from among, for example, films of
polyethylene, polypropylene, polybutene, polybutadiene,
polymethylpentene, polyvinyl chloride, vinyl chloride copolymers,
polyethylene terephthalate, polybutylene terephthalate,
polyurethanes, ethylene/vinyl acetate copolymer, ionomer resins,
ethylene/(meth)acrylic acid copolymer, ethylene/(meth)acrylic ester
copolymers, polystyrene polycarbonate and fluororesin, films
produced by crosslinking these and films composed of laminates
thereof. Furthermore, according to necessity, use can be made of
films produced by coloring the above films. These films may be
produced by extrusion or casting. The thickness of the base is
generally in the range of 5 to 300 .mu.m, preferably 10 to 200
.mu.m.
[0044] Of the above films, heat shrinkable films are preferably
employed as the base in the present invention.
[0045] The shrinkage factor (shrinkage ratio) of the shrinkable
film preferably employed in the present invention is preferably in
the range of 10 to 90%, still preferably 20 to 80%.
[0046] The shrinkage factor (SF) of the shrinkable film is
calculated from the dimension before shrinkage and the dimension
after shrinkage by the formula: 1 SF = ( Dim . before shrink ) - (
Dim . after shrink ) ( Dim . before shrink ) .times. 100
[0047] The above shrinkage factor values are those calculated from
the dimensions of film measured before and after heating at
120.degree. C.
[0048] In particular, it is preferred that uniaxially or biaxially
oriented films of polyethylene, polypropylene, polyethylene
terephthalate or the like be used as the heat shrinkable film.
[0049] The shrinkable film may be a laminate of films whose
shrinkage factors are different from each other. When the laminate
composed of films whose shrinkage factors are different from each
other is used as the base 11, a protrudent deformation is likely to
occur on the lower shrinkage factor side, so that the sticking of
the semiconductor chips 4 is only made by point contacts to thereby
extremely facilitate the removement of the semiconductor chips
4.
[0050] In the use of the above pressure sensitive adhesive double
coated sheet 10, as aforementioned, the energy radiation curable
pressure sensitive adhesive layer is irradiated with energy
radiation after the completion of requisite steps. When ultraviolet
radiation is used as the energy radiation, all the films
constituting the shrinkable base 11 must be permeable for
ultraviolet ray.
[0051] The pressure sensitive adhesive double coated sheet 10
comprises the shrinkable base 11 having its both sides overlaid
with pressure sensitive adhesive layers 12a, 12b, at least one (one
or both) of the pressure sensitive adhesive layers composed of an
energy radiation curable pressure sensitive adhesive. It is
preferred that the pressure sensitive adhesive layer 12a stuck to
the semiconductor wafer 1 (or semiconductor chips 4) is composed of
an energy radiation curable pressure sensitive adhesive. Although
it is also preferred that the other pressure sensitive adhesive
layer 12b stuck to the transparent hard plate 5 is composed of an
energy radiation curable pressure sensitive adhesive, this is not
inevitably requisite as long as the pressure sensitive adhesive
layer 12a is composed of an energy radiation curable pressure
sensitive adhesive.
[0052] When both the pressure sensitive adhesive layers 12a, 12b
are composed of energy radiation curable pressure sensitive
adhesives, these energy radiation curable pressure sensitive
adhesives are preferably selected so that the elastic modulus of
pressure sensitive adhesive layer 12a having been cured (elastic
modulus 12a) is higher than the elastic modulus of pressure
sensitive adhesive layer 12b having been cured (elastic modulus
12b). The elastic modulus 12a is preferably at least two times the
elastic modulus 12b, still preferably at least five times the
elastic modulus 12b.
[0053] The above selection of the elastic moduli of pressure
sensitive adhesive layers 12a, 12b having been cured promotes the
thermal deformation of pressure sensitive adhesive double coated
sheet 10 and facilitates the detachment of semiconductor chips
4.
[0054] The energy radiation curable pressure sensitive adhesive
generally comprises an acrylic pressure sensitive adhesive and an
energy radiation polymerizable compound as main components.
[0055] The acrylic pressure sensitive adhesive for use in the
present invention comprises a copolymer of a monomer consisting
mainly of an acrylic acid alkyl ester or a methacrylic acid alkyl
ester, and increases the adherence and cohesive strength of energy
radiation curable pressure sensitive adhesive before curing.
[0056] For example, low-molecular-weight compounds having in the
molecule thereof at least two photopolymerizable carbon to carbon
double bonds that can be converted into a three-dimensional network
structure by light irradiation as disclosed in Japanese Patent
Laid-open Publication Nos. 60(1985)-196,956 and 60(1985)-223,139
are widely used as the energy radiation polymerizable compounds to
be incorporated in the energy radiation curable pressure sensitive
adhesives. Specific examples thereof include trimethylolpropane
triacrylate, pentaerythritol triacrylate, pentaerythritol
tetraacrylate, dipentaery-thritol monohydroxypentaacrylat- e,
dipentaerythritol hexaacrylate, 1,4-butylene glycol diacrylate,
1,6-hexanediol diacrylate, polyethylene glycol diacrylate and
commercially available oligoester acrylates.
[0057] Furthermore, besides the above acrylate compounds, urethane
acrylate oligomers can be used as the energy radiation
polymerizable compounds. Urethane acrylate oligomers can be
obtained by first reacting a polyester or polyether polyol compound
with a polyisocyanate compound such as 2,4-tolylene diisocyanate,
2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene
diisocyanate or diphenylmethane-4,4-diisocyanate to thereby obtain
an isocyanate terminated urethane prepolymer and by thereafter
reacting the obtained isocyanate terminated urethane prepolymer
with a hydroxyl group containing acrylate or methacrylate, for
example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate,
2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate,
polyethylene glycol acrylate or polyethylene glycol
methacrylate.
[0058] With respect to the blending ratio of energy radiation
polymerizable compound to acrylic pressure sensitive adhesive in
the energy radiation curable pressure sensitive adhesive, it is
preferred that 50 to 200 parts by weight of the energy radiation
polymerizable compound is used per 100 parts by weight of the
acrylic pressure sensitive adhesive. In this instance, the initial
adhesive strength of the obtained pressure sensitive adhesive sheet
is large, and the adhesive strength is sharply dropped upon
irradiation of the pressure sensitive adhesive layer with energy
radiation. Accordingly, the peeling at the interface of the
semiconductor chips 4 and the acrylic energy radiation curable
pressure sensitive adhesive layer 12a is facilitated to thereby
enable picking up of the semiconductor chips 4.
[0059] The energy radiation curable pressure sensitive adhesive
layer may be composed of an energy radiation curable copolymer
having an energy radiation polymerizable group as a side chain.
This energy radiation curable copolymer simultaneously exhibits
satisfactory adherence and energy radiation curability properties.
Details of the energy radiation curable copolymer having an energy
radiation polymerizable group as a side chain are described in, for
example, Japanese Patent Laid-open Publication Nos. 5(1993)-32946
and 8(1996)-27239.
[0060] The above acrylic energy radiation curable pressure
sensitive adhesive possesses satisfactory adhesive strength to the
semiconductor chips 4 before exposure to energy radiation, and the
adhesive strength is extremely decreased upon exposure to energy
radiation. That is, the acrylic energy radiation curable pressure
sensitive adhesive enables securing the semiconductor chips 4 with
satisfactory adhesive strength before exposure to energy radiation,
but, after exposure to energy radiation, enables easily detaching
the semiconductor chips 4 therefrom.
[0061] The other pressure sensitive adhesive layer 12b can be
formed from various conventional pressure sensitive adhesives.
These pressure sensitive adhesives are not limited at all. As
examples thereof, there can be mentioned peelable pressure
sensitive adhesives based on rubbers, acrylics, silicones,
polyurethanes and polyvinyl ethers. However, in the present
invention, it is preferred that the pressure sensitive adhesive
layer 12b also be composed of the above energy radiation curable
pressure sensitive adhesive.
[0062] Although depending on the type of material constituting the
pressure sensitive adhesive layer, the thickness of each of the
pressure sensitive adhesive layers 12a, 12b is generally in the
range of about 3 to 100 .mu.m, preferably about 10 to 50 .mu.m.
[0063] Transparent resin films, for example, a film of a polyolefin
such as polyethylene or polypropylene and a polyethylene
terephthalate film are used as the optionally employed release
liner 13.
[0064] As the transparent hard plate 5, there can be employed, for
example, a glass plate, a quartz plate or a plastic plate such as a
plate of acrylic, polyvinyl chloride, polyethylene terephthalate,
polypropylene or polycarbonate. The hardness, defined by ASTM D
883, of the transparent hard plate 5 is preferably at least 70 MPa.
The thickness of the transparent hard plate 5, although depending
on the properties of the material used therein, is generally in the
range of about 0.1 to 10 mm. Those which are permeable for energy
radiation and heat rays for use in the present invention are used
as the transparent hard plate 5.
EFFECT OF THE INVENTION
[0065] As apparent from the foregoing, the present invention
provides the process for producing semiconductor chips with high
yield while minimizing the damaging of semiconductor chips, even if
the thickness thereof is extremely reduced, and while avoiding the
chip cracking on the circuit side of the semiconductor chips.
EXAMPLE
[0066] The present invention will further be illustrated below with
reference to the following Examples which in no way limit the scope
of the invention.
Example 1
[0067] [Production of Pressure Sensitive Adhesive Double Coated
Sheet]
[0068] 1(1) 100 parts by weight of an acrylic pressure sensitive
adhesive (copolymer of 91 parts by weight of n-butyl acrylate and 9
parts by weight of acrylic acid), 120 parts by weight of urethane
acrylate oligomer (weight average molecular weight: about 10,000,
produced by Dainichiseika Color And Chemicals Manufacturing Company
Limited), 2 parts by weight of isocyanate crosslinking agent (trade
name: Coronate L, produced by Nippon Polyurethane Co., Ltd.) and 2
parts by weight of initiator for energy radiation curing reaction
(.alpha.-hydroxycyclohexyl phenyl ketone) were mixed together,
thereby obtaining an energy radiation curable pressure sensitive
adhesive composition (the elastic modulus thereof after ultraviolet
irradiation was 1.5.times.10.sup.8 Pa).
[0069] 1(2) A 38 .mu.m thick polyethylene terephthalate film having
undergone a release treatment using a silicone release agent was
coated with the pressure sensitive adhesive composition obtained in
the step 1(1) above so that the thickness of the coating was 15
.mu.m and heated at 100.degree. C. for 1 min. Thus, an energy
radiation curable pressure sensitive adhesive layer was formed.
Thereafter, the energy radiation curable pressure sensitive
adhesive layer was stuck to a heat shrink polyethylene
terephthalate film (having a thickness of 25 .mu.m and a shrinkage
factor of 65% at 120.degree. C.). Thus, there was obtained a sheet
having its one side overlaid pressure sensitive adhesive layer.
[0070] 1(3) Separately, a 38 .mu.m thick polyethylene terephthalate
film having undergone a release treatment using a silicone release
agent was coated with a pressure sensitive adhesive composition
(the elastic modulus thereof after ultraviolet irradiation was
9.0.times.10.sup.8 Pa), produced in the same manner as in the step
1(1) except that 50 parts by weight of urethane acrylate oligomer
(weight average molecular weight: about 1000) was employed, so that
the thickness of the coating was 15 .mu.m and heated at 100.degree.
C. for 1 min. Thus, another energy radiation curable pressure
sensitive adhesive layer was formed.
[0071] 1(4) The heat shrink polyethylene terephthalate film side of
the sheet having its one side overlaid pressure sensitive adhesive
layer, obtained in the step 1(2) above, was stuck to the pressure
sensitive adhesive layer formed on the PET film in the step 1(3)
above, thereby obtaining a pressure sensitive adhesive double
coated sheet.
[0072] [Production of Semiconductor Chips]
[0073] Dicing tape (Adwill D-218, manufactured by Lintec
Corporation) was stuck to an unpolished surface of a silicon wafer
of 6 inch diameter and 750 .mu.m thickness. The above produced
pressure sensitive adhesive double coated sheet (pressure sensitive
adhesive layer of step 1-(3)) was stuck to a specular surface of
the silicon wafer. The polyethylene terephthalate film (38 .mu.m)
as a release liner remained stuck to the pressure sensitive
adhesive layer of pressure sensitive adhesive double coated sheet
which was not stuck to the silicon wafer. In this arrangement, the
wafer together with the pressure sensitive adhesive double coated
sheet was diced into 10 mm squares by the use of dicing device
(AWD-4000B, manufactured by Tokyo Seimitsu Co., Ltd.). The
polyethylene terephthalate film was stripped off with the use of
pressure sensitive adhesive sheet for stripping (Adwill S-6,
manufactured by Lintec Corporation). The thus exposed pressure
sensitive adhesive layer (pressure sensitive adhesive layer of step
1-(1) above) was stuck to a transparent hard plate (700 .mu.m thick
glass). The dicing tape was cut so that the diameter of the dicing
tape conformed with that of the wafer. The dicing tape on its base
side was irradiated with ultraviolet rays by the use of ultraviolet
irradiator (RAD-2000/m8, manufactured by Lintec Corporation), and
the dicing tape was stripped off. The thus exposed unpolished
surfaces of semiconductor chips were ground by means of back
grinder (DFG-840, manufactured by Disco Corporation) so that the
thickness of the semiconductor chips became 30 .mu.m.
[0074] Thereafter, the glass side was exposed to ultraviolet rays,
and the whole was allowed to stand still on a hot plate of
160.degree. C. for 5 min. The semiconductor chips were detached
from the pressure sensitive adhesive double coated sheet. The
detachment was easily accomplished without chip damaging.
Example 2
[0075] The same procedure as in Example 1 was repeated except that,
without the use of the hot plate, spot exposure (output: 300 W,
distance: 10 cm, and exposure time: 5 sec) was performed chip by
chip by employing a xenon lamp and by condensing heat rays into a 5
mm diameter. The semiconductor chips at portions having been
exposed to heat rays were detached. The detachment was easily
accomplished without chip damaging.
* * * * *