U.S. patent application number 12/880782 was filed with the patent office on 2012-03-15 for method for fabricating a semiconductor chip panel.
Invention is credited to Markus Fink, Edward Fuergut.
Application Number | 20120064673 12/880782 |
Document ID | / |
Family ID | 45756235 |
Filed Date | 2012-03-15 |
United States Patent
Application |
20120064673 |
Kind Code |
A1 |
Fuergut; Edward ; et
al. |
March 15, 2012 |
METHOD FOR FABRICATING A SEMICONDUCTOR CHIP PANEL
Abstract
The method includes providing a plurality of semiconductor chips
and placing the plurality of semiconductor chips on a carrier. A
compression molding apparatus is provided that includes a first
tool and a second tool. The carrier is placed on the first tool of
the compression molding apparatus and the semiconductor chips are
encapsulated in a mold material by compression molding. During
compression molding a heat transfer from the first tool to an upper
surface of the carrier is delayed.
Inventors: |
Fuergut; Edward; (Dasing,
DE) ; Fink; Markus; (Zell, DE) |
Family ID: |
45756235 |
Appl. No.: |
12/880782 |
Filed: |
September 13, 2010 |
Current U.S.
Class: |
438/127 ;
257/E21.502; 425/160 |
Current CPC
Class: |
H01L 24/97 20130101;
Y10T 29/5142 20150115; B29C 43/18 20130101; H01L 21/565
20130101 |
Class at
Publication: |
438/127 ;
425/160; 257/E21.502 |
International
Class: |
H01L 21/56 20060101
H01L021/56; B29C 43/52 20060101 B29C043/52 |
Claims
1. A method for fabricating a semiconductor chip panel, the method
comprising: providing a plurality of semiconductor chips; placing
the semiconductor chips on a carrier; providing a compression
molding apparatus comprising a first tool and a second tool;
placing the carrier on the first tool of the compression molding
apparatus; and encapsulating the semiconductor chips in a mold
material by compression molding, wherein during compression molding
a heat transfer from the first tool to an upper surface of the
carrier is delayed, wherein during the compression molding:
providing a gap between the first tool and the carrier during
compression molding, and pressing air between an upper surface of
the first tool and a lower surface of the carrier during
compression molding.
2. (canceled)
3. A method for fabricating a semiconductor chip panel, the method
comprising: providing a plurality of semiconductor chips; placing
the semiconductor chips on a carrier; providing a compression
molding apparatus comprising a first tool and a second tool,
wherein the first tool of the compression molding apparatus
comprises a plurality of pins extending from an upper surface of
the first tool and being insertable into the first tool; placing
the carrier on the first tool of the compression molding apparatus
so that the carrier is situated onto the pins so a gap is
established between a lower surface of the carrier and the upper
surface of the first tool; and encapsulating the semiconductor
chips in a mold material by compression molding, wherein during
compression molding a heat transfer from the first tool to an upper
surface of the carrier is delayed, wherein during compression
molding, a distance between the first tool and the second tool is
reduced until the pins are inserted into the first tool and the
carrier comes to rest with its lower surface at the upper surface
of the first tool.
4. (canceled)
5. The method according to claim 6, wherein the carrier is
constructed in such a way that during compression molding a heat
transfer from a lower surface of the carrier to the upper surface
of the carrier is obstructed.
6. A method for fabricating a semiconductor chip panel, the method
comprising: providing a plurality of semiconductor chips; placing
the semiconductor chips on a carrier; providing a compression
molding apparatus comprising a first tool and a second tool,
placing the carrier on the first tool of the compression molding
apparatus, wherein the carrier comprises a lower metallic layer, an
upper metallic layer, and an intermediate layer, wherein the
intermediate layer comprises a lower heat conductivity than each
one of the lower and upper metallic layers; and encapsulating the
semiconductor chips in a mold material by compression molding,
wherein during compression molding a heat transfer from the first
tool to an upper surface of the carrier is delayed.
7. The method according to claim 6, wherein a temperature of the
upper surface of the carrier rises by more than 30% during
compression molding, wherein at a start of the compression molding,
the temperature of the upper surface of the carrier is above room
temperature.
8. A method for fabricating a semiconductor chip panel, the method
comprising: providing a plurality of semiconductor chips; placing
the semiconductor chips on a carrier; providing a compression
molding apparatus comprising a first tool and a second tool;
placing the carrier on the first tool of the compression molding
apparatus; and encapsulating the semiconductor chips in a mold
material by a compression molding process, wherein during the
compression molding process a temperature of an upper surface of
the carrier rises by more than 30%, wherein during a portion of the
compression molding process blowing air between an upper surface of
the first tool and a lower surface of the carrier to form a gap
between the first tool and the carrier.
9. The method according to claim 8, wherein the temperature of the
upper surface of the carrier is below 100.degree. C. at the
beginning of the compression molding.
10. The method according to claim 8, wherein a temperature of the
first tool is increased during the compression molding.
11. The method according to claim 8, wherein a gap is provided
between the first tool and the carrier during compression
molding.
12. A method for fabricating a semiconductor chip panel, the method
comprising: providing a plurality of semiconductor chips; placing
the semiconductor chips on a carrier; providing a compression
molding apparatus comprising a first tool and a second tool,
wherein the first tool of the compression molding apparatus
comprises a plurality of pins extending from an upper surface of
the first tool and being insertable into the first tool; placing
the carrier on the first tool of the compression molding apparatus
so that the carrier is situated onto the pins and a gap is
established between a lower surface of the carrier and the upper
surface of the first tool; and encapsulating the semiconductor
chips in a mold material by a compression molding process, wherein
during the compression molding process a temperature of an upper
surface of the carrier rises by more than 30%, wherein during the
compression molding process, a distance between the first tool and
the second tool is reduced until the pins are inserted into the
first tool and the carrier comes to rest with its lower surface on
the upper surface of the first tool.
13. (canceled)
14. The method according to claim 8, wherein the carrier is
constructed in such a way that a heat transfer from a lower surface
of the carrier to the upper surface of the carrier is delayed
during compression molding.
15. The method according to claim 8, wherein the carrier comprises
a lower metallic layer, an upper metallic layer, and an
intermediate layer, wherein the intermediate layer comprises a
lower heat conductivity than each one the lower and upper metallic
layers.
16. A method for fabricating a semiconductor chip panel, the method
comprising: providing a plurality of semiconductor chips; placing
the semiconductor chips on a carrier; providing a compression
molding apparatus, the compression molding apparatus comprising a
first tool and a second tool; placing the carrier on the first tool
of the compression molding apparatus; and encapsulating the
semiconductor chips in a mold material by compression molding,
wherein at a beginning of the compression molding a temperature of
an upper surface of the carrier is above room temperature but below
100.degree. C.
17. The method according to claim 16, wherein a temperature of the
first tool is increased during compression molding.
18. The method according to claim 16, wherein a heat transfer from
the first tool to the upper surface of the carrier is delayed
during compression molding.
19. The method according to claim 16, wherein a gap is provided
between the first tool and the carrier during compression
molding.
20. The method according to claim 16, further comprising pressing
air between an upper surface of the first tool and a lower surface
of the carrier during compression molding.
21. The method according to claim 16, wherein the carrier is
constructed in such a way that a heat transfer from a lower surface
of the carrier to the upper surface of the carrier is delayed
during compression molding.
22. The method according to claim 21, wherein the carrier comprises
a lower metallic layer, an upper metallic layer, and an
intermediate layer, wherein the intermediate layer comprises a
lower heat conductivity than each one the lower and upper metallic
layers.
23. A method for fabricating a semiconductor chip panel, the method
comprising: providing a plurality of semiconductor chips; placing
the semiconductor chips on a carrier; providing a compression
molding apparatus, the compression molding apparatus comprising a
first tool and a second tool; placing the carrier on the first tool
of the compression molding apparatus; and encapsulating the
semiconductor chips in a mold material by compression molding,
wherein a temperature of the first tool is increased during
compression molding, wherein at a beginning of the compression
molding the temperature of the first tool comprises a value
T.sub.1.gtoreq.80.degree. C., and wherein during the compression
molding the temperature of the first tool is increased to a value
T.sub.2.ltoreq.180.degree. C.
24. (canceled)
25. A compression molding apparatus, comprising: a first tool and a
second tool, the first tool comprising a plurality of pins
extending from an upper surface of the first tool and being
insertable into the first tool; a first heating device to heat the
first tool; a heat flow delay element to delay heat flow to a
surface of the first tool, or alternatively a heat timer connected
with the first heating device to heat the first tool according to a
particular time function; and a first configuration in which the
first tool of the compression molding apparatus is placed adjacent
a carrier so that the carrier is situated onto the plurality of
pins so a gap is established between a lower surface of the carrier
and the upper surface of the first tool, wherein the compression
molding apparatus is configured to reduce a distance between the
first tool and the second tool during a compression molding process
until the plurality of pins are inserted into the first tool and a
carrier comes to rest with its lower surface on the upper surface
of the first tool.
26. A compression molding apparatus, comprising: a first tool and a
second tool, the first tool comprising holes configured to pass air
from a bottom side of the first tool to an opposite top side of the
first tool; a first heating device to heat the first tool; and a
heat flow delay element to delay heat flow to a surface of the
first tool, or alternatively a heat timer connected with the first
heating device to heat the first tool according to a particular
time function.
27-28. (canceled)
Description
TECHNICAL FIELD
[0001] The present invention is related to a method for fabricating
a semiconductor chip panel and a compression molding apparatus.
BACKGROUND
[0002] For fabricating semiconductor chip package devices, the
so-called Embedded Wafer Level Ball Grid Array (eWLB) technology
was developed. In particular, this technology provides a wafer
level packaging solution for semiconductor devices requiring a
higher integration level and a greater number of external contacts.
The eWLB technology is successfully enabling semiconductor
manufacturers to provide a small, high performing semiconductor
package technology with increased thermal and electrical
performance of the individual semiconductor chip package devices.
There is, however, a steady demand for an increase in performance,
yield and through-put of the packaging process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] The accompanying drawings are included to provide a further
understanding of embodiments and are incorporated in and constitute
a part of this specification. The drawings illustrate embodiments
and together with the description serve to explain principles of
embodiments. Other embodiments and many of the intended advantages
of embodiments will be readily appreciated as they become better
understood by reference to the following detailed description. The
elements of the drawings are not necessarily to scale relative to
each other. Like reference numerals designate corresponding similar
parts.
[0004] FIG. 1 shows a flow diagram of a method for fabricating a
semiconductor chip panel according to an embodiment;
[0005] FIGS. 2A-2C show schematic cross-sectional side view
representations of a compression molding apparatus in successive
stages for illustrating a method of FIG. 1 according to an
embodiment;
[0006] FIGS. 3A-3C show schematic cross-sectional side view
representations of a compression molding apparatus in successive
stages for illustrating a method of FIG. 1 according to an
embodiment;
[0007] FIG. 4 shows a schematic cross-sectional side view
representation of a carrier for illustrating a method of FIG. 1
according to an embodiment;
[0008] FIG. 5 shows a diagram plotting the temperature over time at
the adhesive tape according to an embodiment and a comparative
example;
[0009] FIG. 6 shows a flow diagram of a method for fabricating a
semiconductor chip panel according to an embodiment;
[0010] FIG. 7 shows a flow diagram of a method for fabricating a
semiconductor chip panel according to an embodiment; and
[0011] FIG. 8 shows a flow diagram of a method for fabricating a
semiconductor chip panel according to an embodiment.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0012] In the following detailed description, reference is made to
the accompanying drawings, which form part hereof, and in which is
shown by way of illustration specific embodiments in which the
invention may be practiced. In this regard, directional
terminology, such as "top", "bottom", "front", "back", "leading",
"trailing" etc., is used with reference to the orientation of the
figures being described. Because components of embodiments can be
positioned in a number of different orientations, the directional
terminology is used for purposes of illustration and is in no way
limiting. It is to be understood that other embodiments may be
utilized and structural or logical changes may be made without
departing from the scope of the present invention. The following
detailed description, therefore, is not to be taken in a limiting
sense, and the scope of the present invention is defined by the
appended claims.
[0013] The aspects and embodiments are now described with reference
to the drawings, wherein like reference numerals are generally
utilized to refer to like elements throughout. In the following
description, for purposes of explanation, numerous specific details
are set forth in order to provide a thorough understanding of one
or more aspects of the embodiments. It may be evident, however, to
one skilled in the art that one or more aspects of the embodiments
may be practiced with a lesser degree of the specific details. In
other instances, known structures and elements are shown in
schematic form in order to facilitate describing one or more
aspects of the embodiments. It is to be understood that other
embodiments may be utilized and structural or logical changes may
be made without departing from the scope of the present invention.
It should be noted further that the drawings are not to scale or
not necessarily to scale.
[0014] In addition, while a particular feature or aspect of an
embodiment may be disclosed with respect to only one of several
implementations, such feature or aspect may be combined with one or
more other features or aspects of the other implementations as may
be desired and advantageous for any given or particular
application. Furthermore, to the extent that the terms "include,"
"have," "with" or other variants thereof are used in either the
detailed description or the claims, such terms are intended to be
inclusive in a manner similar to the term "comprise." The terms
"coupled" and "connected," along with derivatives may be used. It
should be understood that these terms may be used to indicate that
two elements co-operate or interact with each other regardless of
whether they are in direct physical or electrical contact, or they
are not in direct contact with each other. Also, the term
"exemplary" is merely meant as an example, rather than the best or
optimal. The following detailed description, therefore, is not to
be taken in a limiting sense, and the scope of the present
invention is defined by the appended claims.
[0015] The devices used there, namely semiconductor chips or
semiconductor dies may include contact elements or contact pads on
one or more of their outer surfaces wherein the contact elements
serve for electrically contacting the respective device to a
wireboard, for example. The contact elements may be made from any
electrically conducting material, e.g., from a metal such as
aluminum, gold, or copper, for example, or a metal alloy, e.g.,
solder alloy, or an electrically conducting organic material, or an
electrically conducting semiconductor material.
[0016] The plurality of semiconductor chips will become packaged or
covered with an encapsulant material. The encapsulant material can
be any electrically insulating material like, for example, any kind
of mold material, any kind of epoxy material, or any kind of resin
material with or without any kind of filler materials.
[0017] In particular, when fabricating the semiconductor chips and
the packaging of the semiconductor dies with the encapsulant
material, fan-out embedded dies can be fabricated. The fan-out
embedded dies can be arranged in an array having the form, e.g., of
a wafer and is therefore often called a "re-configured wafer".
However, it should be appreciated that the fan-out embedded die
array is not limited to the form and shape of a wafer but can have
any size and shape and any suitable array of semiconductor chips
embedded therein. This technology is called extended wafer level
packaging technology. In the following the semiconductor chips
packaged with the encapsulant material will be designated with the
general term "semiconductor chip panel."
[0018] In the claims and in the following description different
embodiments of a method of fabricating a semiconductor device are
described as a particular sequence of processes or measures, in
particular, in the flow diagrams. It is to be noted that the
embodiments should not be necessarily limited to the particular
sequence described. Particular ones or all or different processes
or measures can also be conducted simultaneously or in any other
useful and appropriate sequence.
[0019] For fabricating semiconductor chip package devices,
compression molding can be used for fabricating an encapsulation
layer for embedding the plurality of semiconductor chips. To this
end, the individual semiconductor chips are placed on a carrier, in
particular by use of an adhesive tape, and a mold material can, for
example, be dispensed onto a central portion of the array of
semiconductor chips. Thereafter the carrier can then be placed in a
compression molding apparatus and within the compression molding
apparatus the dispensed mold material can be compression molded and
cured to obtain a semiconductor chip encapsulated layer panel. The
semiconductor chip panel can then be taken out of the compression
molding apparatus for further processing and finally singulating
the panel into a plurality of semiconductor chip package
devices.
[0020] It has been found by the inventors that the temperature of
the carrier and of the adhesive layer or adhesive tape attached to
the carrier is a crucial parameter in the compression molding
process. Roughly speaking, the compression molding process can be
divided into three phases which are handling, compression, and
curing. On the one hand, it is desirable to apply a relatively high
temperature to the carrier in order to accelerate the curing of the
mold material. On the other hand, a high temperature may be
disadvantageous during the compression molding process as the
adhesive properties of any adhesive layer and adhesive tape between
the semiconductor chips and the carrier will deteriorate with
rising temperature so that chips or dies are likely to be peeled
away from the underlying tape or carrier ("flying dies").
[0021] It is therefore an essential idea of the present invention
to control the temperature at an upper surface of the carrier in
such a way that the temperature is higher in the curing phase as
compared to the compression phase. To this end, appropriate
measures are taken that the temperature at the upper surface of the
carrier will start being increased at a particular point in time
during compression molding in order to reach a higher temperature
at the end of the compression molding phase when the curing phase
begins. It will thus be possible to maintain on average a
relatively low temperature at the upper surface of the carrier in
the compression molding phase and to reach a relatively high
temperature on the upper surface of the carrier at the end of the
compression molding phase and at the beginning of the curing phase.
It is well-known that for many mold materials known in the art the
hardening time or curing time increases by a factor of 2 if the
temperature increases by 10.degree. C. in the curing phase. On the
other hand, the relatively low temperature at the upper surface of
the carrier during the compression molding phase allows for stable
and reliable encapsulating of the semiconductor chips without the
danger of the chips being peeled off from the carrier due to a
temperature induced decrease of the adhesion force of the adhesion
layer or adhesion tape.
[0022] FIG. 1 shows a flow diagram of a method for fabricating a
semiconductor chip panel according to an embodiment. The method
comprises providing a plurality of semiconductor chips (s1),
placing the plurality of semiconductor chips on a carrier (s2),
providing a compression molding apparatus comprising a first tool
and a second tool (s3), placing the carrier on the first tool of
the compression molding apparatus (s4), and encapsulating the
semiconductor chips in a mold material by compression molding,
wherein during compression molding a heat transfer from the first
tool to an upper surface of the carrier is delayed (s5).
[0023] In other words, in s5 the heat transfer from the first tool
to the carrier or an upper surface thereof is artificially
obstructed so that heat can not be easily and quickly transferred
from the first tool to an upper surface of the carrier.
[0024] According to an embodiment of the method of FIG. 1, the
temperature of the first tool is held at a constant level
throughout the compression molding process.
[0025] According to an embodiment of the method of FIG. 1, a gap is
provided between the first tool and the carrier during compression
molding. In particular, the gap can be provided during a particular
partial phase of the compression molding phase, in particular, an
initial phase of the compression molding phase. The gap can be
comprised of a vacuum gap as well as a gap filled with any gaseous
medium like air. According to a particular embodiment, the first
tool of the compression molding apparatus comprises a plurality of
pins, e.g., a number of three or four pins extending from an upper
surface of the first tool and being insertable into the first tool
by a downward force exerted on the pins, wherein the method further
comprises placing the carrier on the first tool so that the carrier
is situated onto the pins so that a gap is established between a
lower surface of the carrier and an upper surface of the first
tool, and during compression molding the distance between the first
tool and second tool is continuously reduced so that the carrier is
moved by the second tool in the direction of the first tool until
the pins are inserted into the first tool and the carrier comes to
rest with its lower surface onto the upper surface of the carrier.
As long as the gap exists, heat transfer between the first tool and
the carrier will be obstructed so that, as a result, the heat
transfer from the first tool to the upper surface of the carrier
will be delayed.
[0026] According to a further embodiment, the gap will be generated
by pressing air or any other suitable gaseous medium between the
upper surface of the first tool and the lower surface of the
carrier during a partial phase of the compression molding
phase.
[0027] According to an embodiment of the method of FIG. 1, a tape
is applied onto the carrier and the plurality of semiconductor
chips is placed onto the tape.
[0028] According to an embodiment of the method of FIG. 1, the
carrier itself is constructed in such a way that during compression
molding a heat transfer from a lower surface of the carrier to an
upper surface of the carrier is obstructed. According to an
embodiment thereof, the carrier comprises a lower metallic layer,
an upper metallic layer, and an intermediate layer, wherein the
intermediate layer comprises a lower heat conductivity than each
one of the lower and upper metallic layers.
[0029] According to an embodiment of the method of FIG. 1, during
compression molding a temperature of an upper surface of the
carrier, in particular, of a tape applied onto the upper surface of
the carrier is increased, by more than 30%. More specifically, the
temperature rise can be more than 40%, 50%, 60%, 70%, 80%, 90% or
even as high as 100%.
[0030] According to an embodiment of the method of FIG. 1, at the
beginning of the compression molding the temperature of an upper
surface of the carrier, in particular, of a tape applied onto the
upper surface of the carrier, is below 100.degree. C. In
particular, this temperature can be below 95.degree. C., below
90.degree. C., below 85.degree. C., below 80.degree. C., below
75.degree. C., below 70.degree. C., below 65.degree. C., or even
below 60.degree. C.
[0031] According to an embodiment of the method of FIG. 1, during
compression molding in addition a heat transfer from the second
tool to an upper surface of the carrier is delayed. In particular,
according to an embodiment instead of holding the temperature of
the second tool from the beginning on a relatively high
temperature, the temperature of the second tool can be increased so
that there is a delay in heat transfer to the upper surface of the
carrier and the temperature on the upper surface of the carrier is
slowly increased.
[0032] Referring to FIGS. 2A-2C, shown are schematic
cross-sectional side view representations of a compression molding
apparatus in successive stages for illustrating a method for
fabricating a semiconductor chip panel according to a specific
embodiment of the embodiment of FIG. 1.
[0033] FIG. 2A shows a schematic cross-sectional representation of
the compression molding apparatus. The compression molding
apparatus 100 comprises a first tool 10, which can be a bottom
tool, and a second tool 20, which can be a top tool. The first tool
10 and the second tool 20 are moveable with respect to each other
so that they can form an inner cavity which can be sealed from the
outside environment. The second tool 20 essentially comprises
includes a stamp portion 21 which can be heated to a temperature in
the range of between 100.degree. C. and 200.degree. C. The second
tool 20 also comprises a resin clamp ring 22 which circularly
surrounds the stamp portion 21. Before initiating the compression
molding process, a release foil 23 made, for example, of ETFE
(ethylen tetra fluorethylen) or of PET (polyethylenterephtalate),
is attached to respective lower surfaces of the stamp portion 21
and the resin clamp ring 22. The first tool 10 can be heated to a
temperature in a range between 80.degree. C. and 200.degree. C. The
first tool 10 comprises a plurality of floating pins 11 which are
spring-load mounted within openings formed in the upper surface of
the first tool 10. The spring-load mounting of the pins 11 is such
that in their normal position the pins 11 extend with their upper
portion from the upper surface of the first tool 10 in the
direction of the second tool 20, but when exerting a downward
vertical force upon the pins 11, the pins 11 can be completely
vertically inserted into the holes formed within the upper surface
of the first tool 10. In an end position of the compression molding
process the resin clamp ring 22 of the second tool 20 exerts a
vertical downward force upon the pins 11 and presses them into the
first tool 10, as will be seen later. As an example, in case of a
circularly shaped first tool 10, a number of four pins 11 can be
arranged so that the pins are located in an edge portion of the
first tool 10 at equally spaced angular positions with respect to
the center of the first tool 10. A number of three pins 11 would
also be sufficient for the purpose of this embodiment.
[0034] FIG. 2B shows the compression molding apparatus 100 in the
next stage where a carrier 30 supplied with semiconductor chips 40
has been placed on the pins 11 of the first tool 10. The carrier 30
is, for example, comprised of a circular metallic substrate. Before
placing the carrier in the compression molding apparatus 100, an
adhesive tape 50 is attached to an upper surface of the carrier 30.
Thereafter a plurality of semiconductor chips 40 is placed on an
upper surface of the tape 50 by means of, for example, a
pick-and-place machine. The semiconductor chips 40 are placed
according to a predetermined arrangement with sufficient
intermediate spaces between the individual semiconductor chips 40
so as to allow the fabrication of semiconductor package devices
with desirable fan-out of the electrical contact pads. Thereafter,
a predetermined amount of mold material 60 is dispensed onto a
central portion of the carrier 30 and a respective part of the
semiconductor chips 40. Thereafter, the carrier 30 is placed onto
the pins 11 of the first tool 10 in the compression molding
apparatus 100.
[0035] In operation of the compression molding apparatus 100, the
distance between the first tool 10 and the second tool 20 is
reduced, in particular, the second tool 20 moves downward until the
resin clamp ring 22 with the underlying release foil 23 rests on an
outer ring-like edge of the carrier 30. Alternatively also the
first tool 10 can be moved upwards in the direction of the top tool
20. The inner space defined by the second tool 20 and the carrier
30 will now be evacuated and compression molding begins in a
situation in which, due to the pins 11, a gap exists between the
carrier 30 and the upper surface of the first tool 10. For this
reason, at this stage no significant heat connection exists between
the first tool 10 and the carrier 30 and therefore no significant
heat transfer will occur. Meanwhile the second tool 20 keeps on
pressing downwardly onto the carrier 30 such that the pressing
force exceeds the oppositely directed pre-load force of the springs
in the openings of the pins 11. As a result the second tool 20 will
press the carrier 30 against the spring-load forces of the pins 11
downwards until the carrier 30 will rest with its lower surface
upon the upper surface of the first tool 10.
[0036] Referring to FIG. 2C, the compression molding apparatus 100
is shown in its end position in which the carrier 30 rests with its
lower surface upon the upper surface of the first tool 10 so that
there is optimum heat connection between the first tool 10 and the
carrier 30 and the mold material 60 so that curing or hardening of
the mold material 60 can occur under optimum high temperature
conditions. After curing of the mold material 60, the compression
molding apparatus 100 can be opened and the carrier system together
with the semiconductor chip panel can be taken out.
[0037] Referring to FIGS. 3A-3C shown are schematic cross-sectional
representations of a compression molding apparatus for illustrating
a method for fabricating a semiconductor chip panel according to
FIG. 1 and according to a further embodiment. As far as the same
reference numerals are used as in the embodiment of FIGS. 2A-2C,
the same or functionally the same technical features are designated
therewith and are not repeatedly described here.
[0038] FIG. 3A shows a compression molding apparatus 200 comprising
a first tool 10 and a second tool 20. The first tool 10 includes a
plurality of through-borings 10A which are connected at their
respective lower inlet ports at the lower surface of the first tool
10 with an air supply device (not shown).
[0039] FIG. 3B shows the compression molding apparatus 200 after
placing the carrier 30 on the first tool 10 of the compression
molding apparatus 200. FIG. 3B thus depicts a situation equivalent
to that one of FIG. 2B of the previous embodiment. In the present
case no floating pins exist to hold the carrier 30 in a position
wherein a gap exists between carrier 30 and the upper surface of
first tool 10. Instead air is blown through the through-borings 10A
to form an air layer between the upper surface of first tool 10 and
the lower surface of carrier 30 so that the carrier 30 is supported
by the air layer in a small distance from the first tool 10.
[0040] In the following a scenario similar to that one of the
embodiment of FIGS. 2A-2C occurs in which the second tool 20 is
pressed downwards until the resin clamp ring 22 with the underlying
release foil 23 rests upon an outer edge of the upper surface of
carrier 30 so that afterwards a vacuum can be generated in the
inner cavity defined by second tool 20 and carrier 30 and
compression molding can be initiated. Meanwhile the second tool 20
keeps on pressing carrier 30 downward in the direction of first
tool 10 and exceeds the oppositely directed resilient force of the
air layer situated between the first tool 10 and the carrier 30. In
a final position the carrier 30 comes to rest on the upper surface
of first tool 10.
[0041] FIG. 3C is similar to the situation as shown in FIG. 2C of
the previous embodiment wherein the second tool 20 has now
completely pressed down onto the carrier 30 onto the upper surface
of the first tool 10 so that optimum heat connection is established
from first tool 10 to carrier 30 and the mold material 60.
[0042] As was shown above and explained in connection with the
embodiments of FIGS. 2A-2C and FIGS. 3A-3C, at the beginning of and
during an initial phase of the compression molding phase a gap is
established between the lower surface of carrier 30 and the upper
surface of first tool 10. The gap is schematically shown in FIG. 2C
and FIG. 3C wherein the dimensions shown in these figures are not
to scale. In fact the gap can have a height in a range between 10
.mu.m and 100 .mu.m, in particular, 30 .mu.m to 70 .mu.m, 40 .mu.m
to 60 .mu.m, or a value of or around 50 .mu.m.
[0043] Also in connection with FIGS. 2A-2C and FIGS. 3A-3C,
according to a further embodiment the first tool 10 and the second
tool 20 are held on constant temperatures each. Whereas the first
tool 10 is held at a constant temperature in a range in-between
80.degree. C. and 200.degree. C., the second tool 20 is held at a
constant temperature in a range in-between 100.degree. C. and
180.degree. C.
[0044] Referring to FIG. 4, there is shown a schematic
cross-sectional side view representation of a carrier for
illustrating a method of FIG. 1 according to an embodiment. The
carrier 300 is essentially comprised of a layer stack consisting of
a first layer 310, a second layer 320, and a third layer 330. The
second, intermediate layer 320 includes a lower heat conductivity
than each one of the first and third layers 310 and 330. The first
and third layers 310 and 330 can, for example, be comprised of
metallic layers. The carrier 300 can be used in principle in the
same way as the carriers 30 in the embodiments of FIGS. 2A-2C and
3A-3C. In this case, however, the carrier 300 itself would serve
for the delay in heat transfer from the first tool to the upper
surface of the carrier. The carrier 300 would be placed into a
compression molding apparatus together with a plurality of
semiconductor chips placed on its upper surface or on an adhesive
tape attached to its upper surface. In contrast to the embodiments
of FIGS. 2A-2C and FIGS. 3A-3C, the carrier 300 would be placed
from the beginning directly upon the first tool which could be held
on a constant temperature in the range between 80.degree. C. and
180.degree. C. The delay of heat transfer from the first tool to
the upper surface of the carrier 300 is due to the second
intermediate layer 320 of low heat conductivity. At the beginning
of the compression molding phase, i.e., when the carrier 300 was
just placed onto the first tool, the upper surface of the carrier
300 is still on a relatively low temperature as the second
intermediate layer 320 of the carrier 300 blocks the heat flow from
the first tool via the first layer 310 to the third layer 330. Only
after a certain amount of time has sufficient heat been transferred
through the second intermediate layer 320 so that the third layer
330 will at least approximately reach the temperature of the first
tool. Therefore, the carrier 300 itself serves for a delay of heat
transfer from the first tool to the upper surface of the carrier
300. In this embodiment it will thus be not necessary to establish
a gap between the carrier and the first tool as was the case in the
embodiments of FIGS. 2A-2C and FIGS. 3A-3C.
[0045] Referring to FIG. 5, there is shown a diagram plotting the
measured temperature of an adhesive tape attached to the upper
surface of the carrier versus the time in a compression molding
process for two different configurations. Two curves are shown in
the diagram of FIG. 5, one of which (open circles) is related to an
embodiment in which an air gap of a height of 50 .mu.m is
established, in particular, by one of the embodiments as shown in
FIGS. 2A-2C and FIGS. 3A-3C. The other curve (full circles) is
related to an example which does not form a part of the invention
and in which no gap and no delay in heat transfer at all is
established between the carrier and the first tool throughout the
whole compression molding process. In the diagram of FIG. 5 the
curve of the example shows an initial steep increase of the
temperature of the tape over time due to the optimum heat transfer
between the first tool and the carrier. After about 5 seconds the
curve reaches a saturation level approaching an upper temperature
close to the temperature of the first tool. This means that at the
beginning of the compression molding phase, i.e., 5 seconds after
starting to establish the vacuum, the temperature is rather high so
that the adhesion force of the tape may deteriorate together with
an increased danger of peeling off of the semiconductor chips. On
the other hand, the curve of the embodiment shows a smooth increase
of temperature so that during the compression molding phase the
danger of peeling off of the semiconductor chips or the tape can be
significantly reduced. It can be seen that at the beginning of the
compression molding phase the temperature is slightly below
60.degree. C. and the temperature rises during the compression
molding phase by almost 100% until it reaches its final level.
[0046] Referring to FIG. 6, there is shown a flow diagram of a
method for fabricating a semiconductor chip panel according to an
embodiment. The method includes providing a plurality of
semiconductor chips (s1), placing the plurality of semiconductor
chips on a carrier (s2), providing a compression molding apparatus
comprising a first tool and a second tool (s3), placing the carrier
on the first tool of the compression molding apparatus (s4), and
encapsulating the semiconductor chips in a mold material by
compression molding, wherein during compression molding a
temperature of an upper surface of the carrier rises by more than
30% (s5).
[0047] According to an embodiment, an adhesive tape is attached to
the upper surface of the carrier and the semiconductor chips are
placed onto the adhesive tape, which means that the temperature of
the adhesive tape is smoothly increased during the compression
molding phase from a relatively low level to a relatively high
level at the end of the compression molding phase.
[0048] According to an embodiment of the method of FIG. 6, the
temperature rise during the compression molding phase can also be
more than 40%, 50%, 60%, 70%, 80%, or 90%.
[0049] According to an embodiment of the method of FIG. 6, at the
beginning of the compression molding phase the temperature of an
upper surface of the carrier, in particular, the temperature of a
tape attached to the carrier, is below 100.degree. C. The
temperature can be even lower than that, in particular, below
95.degree. C., 90.degree. C., 85.degree. C., 80.degree. C.,
75.degree. C., 70.degree. C., below 65.degree. C., or below
60.degree. C.
[0050] Other embodiments of the method according to the embodiment
of FIG. 6 can be formed along the embodiments or features which
were described above in connection with FIG. 1.
[0051] Referring to FIG. 7, there is shown a flow diagram of a
method for fabricating a semiconductor chip panel according to an
embodiment. The method includes providing a plurality of
semiconductor chips (s1), placing the plurality of semiconductor
chips on a carrier (s2), providing a compression molding apparatus,
the compression molding apparatus comprising a first tool and a
second tool (s3), placing the carrier on the first tool of the
compression molding apparatus (s4), and encapsulating the
semiconductor chips in a mold material by compression molding,
wherein at the beginning of the compression molding the temperature
of an upper surface of the carrier is below 100.degree. C.
(s5).
[0052] Further embodiments of the methods of FIG. 7 can be formed
along embodiments and features as were described above in
connection with FIG. 1 or 6.
[0053] Referring to FIG. 8, there is shown a flow diagram for
illustrating a method for fabricating a semiconductor chip panel
according to an embodiment. The method includes providing a
plurality of semiconductor chips (s1), placing the plurality of
semiconductor chips on a carrier (s2), providing a compression
molding apparatus comprising a first tool and a second tool (s3),
placing the carrier on the first tool of compression molding
apparatus (s4), and encapsulating the semiconductor chips in a mold
material by compression molding, wherein during compression molding
a temperature of the first tool is increased (s5).
[0054] According to an embodiment of the method of FIG. 8, the heat
transfer from the first tool to the carrier is not artificially
obstructed or delayed as was the case in the embodiment of FIG. 1.
The temperature of the first tool can be, for example, increased in
such a way that the temperature at the upper surface of the carrier
or at the tape attached to the carrier will follow the curve of the
embodiment as shown in FIG. 5 (open circles).
[0055] According to an embodiment of the method of FIG. 8, at the
beginning of the compression molding the temperature of the first
tool can be T.sub.1.gtoreq.80.degree. C., and during the
compression molding the temperature of the first tool can be
increased to T.sub.2.ltoreq.180.degree. C.
[0056] According to an embodiment of the method of FIG. 8, during
compression molding in addition a heat transfer from the second
tool to an upper surface of the carrier is delayed. In particular,
according to an embodiment instead of holding the temperature of
the second tool from the beginning on a relatively high constant
temperature, the temperature of the second tool can be increased
from a relatively low temperature to a relatively high temperature
so that there is a delay in heat transfer to the upper surface of
the carrier and the temperature on the upper surface of the carrier
is slowly increased. More specifically, at the beginning of the
compression molding the temperature of the second tool can be
T.sub.3.gtoreq.80.degree. C., and during the compression molding
the temperature of the second tool can be increased to
T.sub.4.ltoreq.180.degree. C.
[0057] A further embodiment is directed to a compression molding
apparatus which comprises a first tool and a second tool, a first
heating device to heat the first tool, and a heat flow delay
element to delay heat flow to a surface of the first tool, or
alternatively a heat timer connected with the first heating device
to heat the first tool according to a particular time function. The
compression molding apparatus therefore either comprises a heat
flow delay element or a heat timer. If it comprises a heat flow
delay element, it may work according to a method as depicted in one
of the FIG. 1-4, 6 or 7, and if it comprises a heat timer it may
work according to a method as depicted in FIG. 8. In particular,
the heat flow delay element can, for example, be comprised of a
plurality of pins 11 as shown in FIGS. 2A-C or it can be comprised
of the through-borings 10A in the first tool 10 as depicted in
FIGS. 3A-C together with a suitable device for pressing air through
the through-borings 10A for generating an air layer above the first
tool 10. The heat flow delay element can also be comprised of a
carrier such as that depicted in FIG. 4. If a heat timer is used
instead of a heat flow delay element, the heat timer can be
adjusted such that it slowly rises the temperature of the first
tool as described, for example, in previous embodiments herein. It
is also possible to employ both a heat flow delay element and a
heat timer in a compression molding apparatus according to a
further embodiment.
* * * * *