U.S. patent application number 09/863685 was filed with the patent office on 2002-01-10 for contact heating device.
This patent application is currently assigned to KYOCERA CORPORATION. Invention is credited to Arima, Hiroyuki, Shimozuru, Hideaki, Turumaru, Takafumi, Yokoyama, Kiyoshi.
Application Number | 20020003137 09/863685 |
Document ID | / |
Family ID | 26592604 |
Filed Date | 2002-01-10 |
United States Patent
Application |
20020003137 |
Kind Code |
A1 |
Yokoyama, Kiyoshi ; et
al. |
January 10, 2002 |
Contact heating device
Abstract
There is provided a bonding heater used to package a
semiconductor chip on a multilayer substrate, which has
adaptability to various chip sizes, with an excellent maintenance
characteristics, with undesirable displacement of the chip at the
time of mounting a semiconductor chip being made as small as
possible and also with a temperature rise time to a desired
temperature being shortened. This bonding heater is constituted by
a ceramic tool for pressing an object to be heated, a ceramic
heater for heating the tool, a heat insulating member for
transferring heat generated by the ceramic heater mainly to the
tool side and a holder for integrating these members and connecting
these members to another member, and the tool, ceramic heater, heat
insulating member and holder are detachably bonded.
Inventors: |
Yokoyama, Kiyoshi;
(Kokubu-shi, JP) ; Turumaru, Takafumi;
(Kokubu-shi, JP) ; Arima, Hiroyuki; (Kokubu-shi,
JP) ; Shimozuru, Hideaki; (Kokubu-shi, JP) |
Correspondence
Address: |
HOGAN & HARTSON L.L.P.
500 S. GRAND AVENUE
SUITE 1900
LOS ANGELES
CA
90071-2611
US
|
Assignee: |
KYOCERA CORPORATION
|
Family ID: |
26592604 |
Appl. No.: |
09/863685 |
Filed: |
May 22, 2001 |
Current U.S.
Class: |
219/243 ;
219/536; 219/542 |
Current CPC
Class: |
H01L 21/67103 20130101;
B23K 3/0471 20130101; H01L 24/75 20130101; H05B 1/00 20130101; H01L
2924/12042 20130101; H01L 2224/81193 20130101; H01L 24/81 20130101;
H01L 2924/12042 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
219/243 ;
219/542; 219/536 |
International
Class: |
H05B 003/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 25, 2000 |
JP |
2000-154917 |
Jun 29, 2000 |
JP |
2000-195729 |
Claims
What is claimed is:
1. A contact heating device comprising: a ceramic tool for pressing
an object to be heated; a ceramic heater for heating the tool in
contact therewith; a heat insulating member for supporting and
thermally shielding the ceramic heater; and a holder for supporting
the heat insulating member and holding these element of the contact
heating device, wherein the tool, ceramic heater, heat insulating
member and holder are detachably bonded.
2. The contact heating device according to claim 1, wherein the
tool is fixed by vacuum suction by the ceramic heater.
3. The contact heating device according to claim 2, wherein the
ceramic heater is threadedly fixed to the heat insulating member
and the heat insulating member threadedly fixed to the holder.
4. The contact heating device according to claim 2, wherein a ring
groove is formed in the ceramic heater surface and first suction
through holes which penetrate through the heat insulating member
and holder so as to be communicated with the ring groove are
disposed.
5. The contact heating device according to claim 2, wherein a
second suction through hole which opens in the tool surface and is
penetratingly communicated with the tool, ceramic heater, heat
insulating member and holder is disposed.
6. The contact heating device according to claim 1, wherein a
thermal conductivity of the tool is 100 W/m.multidot.K or more and
a thermal conductivity of the ceramic heater is 10 W/m.multidot.K
or more.
7. The contact heating device according to claim 1, wherein thermal
expansion coefficients of the tool, ceramic heater, heat insulating
member and holder are 6.times.10.sup.-6/K or less.
8. The contact heating device according to claim 1, wherein the
heat insulating member and/or holder is provided with a cooling
path through which a coolant is allowed to flow therein.
9. The contact heating device according to claim 8, wherein the
cooling path comprises: a groove, through which the coolant is
allowed to flow, which is formed in the bonding surface of the heat
insulating member adjacent to the ceramic heater; and a cooling
hole which is communicated with the groove and penetratingly formed
through the heat insulating member and holder, to promote cooling
of the ceramic heater.
10. The contact heating device according to claim 8, wherein the
cooling path comprises: a groove which is formed in the bonding
surface of the holder adjacent to the heat insulating; and a
cooling hole which is penetratingly formed through the holder and
communicated with the groove, to cool the holder.
11. The contact heating device according to claim 8, wherein the
coolant is a gas.
12. The contact heating device according to claim 6, wherein
porosity of the heat insulating member is 30% or less.
13. The contact heating device according to claim 6, wherein a
thermal conductivity of the heat insulating member is 5
W/m.multidot.K or less.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a contact heating device
for heating an object to be heated in contact therewith such as a
die bonding heater or the like used when a semiconductor bare chip
is mounted on a substrate.
[0003] 2. Prior Art
[0004] As a packaging method for mounting a semiconductor bare chip
on a circuit substrate, the ACF bonding method is known, by which
pad electrodes on a chip and those on a substrate are bonded by
using a resin-based adhesive such as an anisotropic conductive film
or the like. As another mounting method, the flip chip bonding
method, by which pad electrodes on a chip and those on a substrate
are bonded by using low melting braze material such as Au--Si,
Au--Sn alloys or the like, is also utilized for manufacturing
multiple chip modules.
[0005] As shown in FIG. 5A, in the flip chip bonding method, a
semiconductor chip 8 is placed on a multi-layered substrate 85, a
pressing tool 910 fixedly bonded to a bonding heater 92 is brought
into contact with an upper surface of the chip 8 and then the chip
is pressed while heated. The semiconductor chip 8 is brazed on the
substrate 85 by melting solders 82, 87 between pad electrodes 81,
86. After cooling, bonding of the pad electrodes 81, 86 and wiring
are completed and the semiconductor chip 8 is fixed oil the
substrate 85. After this operation, the pressing tool 910 is
separated from the semiconductor chip 8 and moved to another
semiconductor chip 8. The pressing tool 910 captures the chip to
carry out the same bonding operation.
[0006] As characteristics of a bonding heater 92, firstly, it is
required to efficiently transfer necessary and sufficient heat to
the bond material via a semiconductor chip 8 in order to soften or
melt bond material such as solders 82, 87 used for bonding of bump
electrodes or the like.
[0007] Secondly, from the viewpoint of production efficiency, it is
important that time for a temperature rise to a required
temperature and time for a temperature fall after bonding until the
bond material is solidified are both short.
[0008] Thirdly, since pressure as well as heat is applied when a
semiconductor chip 8 is bonded, the bonding heater 92 and tool 910
are required to have mechanical strength and abrasion
resistance.
[0009] To achieve these performances, the bonding heater 92 is
constituted by a sintered body composed of a small amount of
heat-resistant metal such as titanium, molybdenum or the like as a
sintering additive and diamond particles (for example, a diamond
sintered body, as disclosed in Japanese Patent Laid-Open
Publication No. 11-240762) and utilized as a tool 910. This is a
pulse heater method, in which large pulse current is allowed to
flow in the heat-resistant metal itself such as titanium,
molybdenum or the like contained in the tool in order to heat the
tool.
[0010] Japanese Patent Laid-Open Publication No. 10-134938
discloses a bonding heater shown in FIG. 5B. The heater is composed
of a ceramic head 91 (or tool) and a ceramic holder 94 for
connecting the head 91 to another member. Here, a thermal
conductivity of the head 91 is made higher than that of the holder
94. The head 91 is fixedly bonded to a ceramic heater 92 by using a
high melting point glass bonding layer 911. Glass material of this
bonding layer 911 has a composition consisting of a combination of
any selecting from silicon nitride, aluminum nitride, alumina,
silicon oxide, zirconia, alkaline-earth metal oxide and rare-earth
element oxide and has a high melting point of 1500-1800.degree.
C.
[0011] To accelerate a temperature fall, in Japanese Patent
Laid-Open Publication No. 11-339929, use of a water cooling jacket
is proposed to improve a temperature fall speed which is slow due
to cooling by standing. As shown in FIG. 6, the water cooling
jacket 96 is embedded in a holder body 95 and forcibly cools the
holder 94, thereby indirectly cooling the bonding heater 92 and
tool 91 provided to the heater holder 94.
[0012] While, microcomputers requiring a small size, high density
and high speed processing such as a portable telephone, mobile
computer and the like are rapidly being further widespread, higher
performances are being achieved. Under these circumstances, more
highly integrated semiconductor chip packaging and miniaturization
are further required. Along with this, semiconductor chips have a
more variety of sizes and arc required to be mounted on
multi-layered packaging substrates.
[0013] In the conventional bonding heater as shown in an example in
FIG. SA, as described above, a bonding heater 92 and tool 910 are
integrally bonded to each other. In an example in FIG. 5B as well,
a ceramic heater 92 and a head 91 are completely bonded by a
bonding material 911. Therefore, such conventional bonding heaters
are not adaptable to chips having different chip sizes. In
addition, even if only either the tool 91 and 910 or bonding heater
92 is damaged, both of these need to be replaced.
[0014] In the bonding heater 92, the tool 91 and 910 needs to have
a uniform surface temperature over the surface area in order to
uniformly bond pad electrodes on the whole surface of a
semiconductor chip 8. However, the conventional bonding heater 92
has a disadvantage that the temperature of a peripheral portion of
the tool 91 and 910 lowers due to heat dissipation into air.
[0015] Since location accuracy of mounting or the like in
semiconductor chip packaging significantly affects performances of
electronic equipment, deformation of the contact heating device
itself due to thermal expansion is also a problem. When the contact
heating device employs a pulse heater method, large current pulses
are applied to a resistor composed of titanium or molybdenum for a
rapid temperature rise. As a result, the heater itself is vibrated
and the actually mounted position is displaced from the position
where the semiconductor chip 8 is originally located. This
displacement significantly affects performances of the electronic
equipment on which the semiconductor chip is mounted.
[0016] On the other hand, in a constant heater method, in which the
heater is continuously used, when the heater is used at a
temperature of 500.degree. C., the temperature of the holder 94
rises to 100-150.degree. C. However, since the holder 94 is
composed of metallic material, a warpage occurs due to a
temperature distribution generated in the holder 94. Consequently,
accuracy of semiconductor chip mounting location is
deteriorated.
[0017] The bonding heater 6 is also required to speed up a
temperature rise and temperature fall to shorten the work tact. In
particular, in the above flip chip process, the temperature needs
to be rapidly increased to a prescribed temperature to soften the
bond material and position the semiconductor chip B. However, it
takes a long time to heating up the bonding heater 6 using
heat-resistant metal such as titanium, molybdenum or the like to a
prescribed temperature.
[0018] Furthermore, the bonding heater 7 is required to shorten
time required for cooling to shorten the work tact. For example,
time for a use temperature fall from 400.degree. C. to 100.degree.
C. needs to be 10 seconds or less. However, in the bonding heater 6
using heat-resistant metal such as titanium, molybdenum or the
like, time required to cooling, for example, from 400.degree. C. to
100.degree. C. is 20 seconds or longer even if a water cooling
jacket 14 is used as shown in FIG. 6.
SUMMARY OF THE INVENTION
[0019] Accordingly, an object of the present invention is to
provide a contact heating device which can be assembled so that
each element can be individually replaced if either a ceramic
heater or tool is damaged.
[0020] Another object of the present invention is to provide a
contact heating device capable of making a temperature of a tool
contact surface uniform.
[0021] Another object of the present invention is to provide a
contact heating device which does not vibrate so that a
semiconductor chip is not displaced and precisely positioned during
soldering operation.
[0022] Another object of the present invention is to provide a
contact heating device capable of being rapidly heated to a
prescribed temperature to shorten heating tine.
[0023] Another object of the present invention is to provide a
contact heating device further capable of being rapidly cooled
after heated to shorten cooling time.
[0024] A contact heating device of the present invention is
constituted by a ceramic tool for pressing an object to bc heated,
a ceramic heater for heating the tool, a heat insulating member for
transferring heat generated by the ceramic heater mainly to the
tool side and a holder for integrating these members and connecting
these members to another member and is characterized in that the
tool, ceramic heater, heat insulating member and holder are
detachably bonded.
[0025] The present invention can provide a contact heating device
which can bond semiconductor chips in various sizes by detachably
bonding the tool, ceramic heater, heat insulating member and holder
and can be easily maintained even if a ceramic heater or tool
portion in use is damaged.
[0026] In the present invention, the tool is preferably fixed by
vacuum suction by the ceramic heater to make each element
detachable. On the other hand, the ceramic heater can be threadedly
fixed to the heat insulating member and the heat insulating member
is threadedly fixed to the holder.
[0027] As such vacuum suction means, a ring groove is formed in the
ceramic heater surface and communicated to first suction through
holes which are disposed penetratingly through the heat insulating
member. A second suction through hole can also be disposed which
opens in the tool surface and penetrates through the tool, ceramic
heater, heat insulating member and holder.
[0028] In the contact heating device of the present invention, a
heat insulating member and/or holder is provided with a coolant
path so that a coolant is allowed to flow at the time of cooling
the ceramic heater in order to directly cool the heater quickly,
thereby achieving a rapid temperature fall. Furthermore, since a
temperature rise is suppressed by cooling the heat insulating
member and holder, thermal deformation of the heat insulating
member and holder is made extremely small to decrease packaging
accuracy of the chip on the substrate.
[0029] As such cooling means, a cooling path allowing a coolant to
flow in the heat insulating member and/or holder can be provided. A
groove in which the coolant is allowed to flow may be formed in the
bonding surface of the ceramic heater and heat insulating member,
and at least one cooling hole communicated with the groove can also
be penetratingly formed through the heat insulating member to
accelerate cooling of the ceramic heater. A groove may also be
formed in the bonding surface of the holder so that the grooves is
communicated with a cooling hole which is penetratingly formed in
the holder to cool the holder.
[0030] It is preferable that a thermal conductivity of the tool is
100 W/m.multidot.K or higher and that the thermal conductivity of
the ceramic heater is 10 W/m.multidot.K or higher. On the other
hand, a thermal conductivity of the heat insulating member is
preferably made 5 W/m.multidot.K or lower to achieve a uniform
temperature of the tool surface and rapid heating.
[0031] The tool, ceramic heater, heat insulating member and holder
preferably have a thermal expansion coefficient of
6.times.10.sup.-6/K or lower in order to prevent thermal
deformation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] Preferred embodiments of the present invention will be
described below in detail with reference to the drawings, in
which:
[0033] FIG. 1 is a perspective view showing a contact heating
device according to an embodiment of the invention viewed from
below;
[0034] FIG. 2 is an exploded view showing the contact heating
device according to the embodiment of the invention shown in FIG.
1;
[0035] FIG. 3 is a side view showing a contact heating device
according to another embodiment of the invention;
[0036] FIG. 4 is a side view showing a contact heating device
according to another embodiment of the invention in which a cooling
medium path is disposed in the holder,
[0037] FIG. 5A shows a conventional contact heating device being
used at the time of bonding;
[0038] FIG. 5B is a cross section of the conventional contact
heating device; and
[0039] FIG. 6 shows a conventional contact heating device provided
with a water cooling jacket.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0040] As shown in FIGS. 1 and 2, a contact heating device of the
present invention is provided with a ceramic tool 1 for pressing an
object to be heated in contact therewith, a ceramic heater 2 for
heating the tool 1, a heat insulating member 3 and a holder 4 for
integrating these components and connecting these components to a
supporting member of a bonding device. These elements are
detachably bonded to the holder.
[0041] The heat insulating member 3 is provided between the ceramic
heater 2 and holder 4 and transfers heat generated by the ceramic
heater 2 mainly to the tool 1 side in order to reduce thermal
conduction to the holder 4. The heat insulating member 3 is
detachably fixed on a surface of the holder 4 in a mechanical
manner. The ceramic heater 2 is detachably fastened to the heat
insulating member 3. Consequently, the ceramic heater 2, heat
insulating member 3 and holder 4 are integrated so as to be
individually replaceable.
[0042] In this embodiment, the tool 1 is vacuum-adsorbed to the
ceramic heater 2 as described later. The tool 1 heats a
semiconductor chip by transferring heat to the semiconductor chip
in contact therewith. The tool 1 fixedly vacuum-adsorbs the
semiconductor chip as described later.
[0043] As a mechanically bonding method, the exploded view of FIG.
2 shows an example of a contact heating device in which the ceramic
heater 2 is threadedly fixed to the heat insulating member 3 with
bolts 6 and the heat insulating member is threadedly fixed to the
holder with bolts 5.
[0044] The holder 4 is a rectangular solid base block provided with
flat outer surfaces and the heat insulating member 3 is fixed on
one surface 40 thereof. The heat insulating member 3 includes a
flange 31 of which one surface 30 is placed on the surface 40 of
the holder 4 and a stage 32 on which the ceramic heater 2 is
fixedly placed thereon. In this example, bolt through holes 51
penetrate through the flange 31 at four corners while bolting
hole.9 52 are threaded and opened at sites corresponding thereto on
the upper surface of the holder 4. The heat insulating member 3 is
placed on the upper surface of the holder 4 and fixed by screwing
bolts 5 into the bolting holes 52 through the bolt through holes
51.
[0045] The heat insulating member 3 is provided with a ceramic
heater 2 placing surface on the front surface 33 thereof and the
ceramic heater 2 is fixed by bolts 6.
[0046] The ceramic heater 2 has a shape of a plate in which a
heating element is embedded therein and has a pair of leads 21
electrically connected to the heating element in a plate surface
direction. Projected portions 24 are provided on both sides in the
horizontal direction and bolt through holes 61 are opened. Bolting
holes 62 corresponding to the bolt through holes 61 are threaded
into projected portions 34 provided in the horizontal direction of
the stage 32 of the insulating member 3. The ceramic heater 2 is
placed on the stage 32 of the insulating member 3 and fixed by
inserting a pair of holts 6, 6 into the bolt through holes 61 of
the ceramic heater 2 and screwing into the bolting holes 62 in the
stage of the insulating member 3.
[0047] In this example, while the tool 1 is attracted and fixed to
the ceramic heater 2 by vacuum suction, the tool 1 can hold and
move a semiconductor chip by vacuum suction and press the chip
while heating. In this example, the tool 1 has a thin plate shape
and a cruciform through hole 71b is formed at a central position. A
few kinds of outer shapes and surfaces of the tool 1 are prepared
to match shapes of semiconductor chips to be adsorbed.
[0048] In a contact heating device shown in FIG. 2, a ring groove
72a is formed in the front surface 20 of the ceramic heater 2 and
first suction through holes 73a, 74a penetrating through the heat
insulating member 3 and holder 4 so as to be communicated with this
ring groove 72a so that the ceramic heater 2 fixes the tool 1 by
vacuum suction.
[0049] Specifically, to adsorb the tool 1, a ring groove 72a is
carved in the tool 1 surface and portions of the ring groove 72a
penetrates through to the rear. A pair of through holes 73a, 73a
for vacuum suction are provided in the insulating member 3 so as to
be communicated with these penetrated portions. Similarly, through
holes 74a, 74a communicated with these through holes 73a, 13a are
provided in the holder 4. In the holder 4, the through holes 74a,
74a are connected to an external suction device snot shown) and the
rear surface 10 of the tool 1 is fixedly adsorbed to the front
surface 20 of the ceramic heater 2 by vacuum suction by the ring
groove 72a.
[0050] Furthermore, in this contact heating device, a second
suction through hole opens in the front surface 11 of the tool 1
and is penetratingly communicated with the tool 1, ceramic heater
2, heat insulating member 3 and holder 4, so that the tool can in
turn attract and lift semiconductor chips. In this example, the
second through holes 71b, 72b, 73b, 74b are penetratingly formed so
that the tool 1, ceramic heater 2, insulating member 3 and holder 4
are communicated with each other. After assembly, the holder 4 is
sucked by another external suction device (not shown) by the
through hole so that the semiconductor chip can be fixedly adsorbed
on the end surface of the tool 1. The aperture in the front surface
11 of the tool is formed in a cruciform shape for convenient
suction.
[0051] In addition to the above method utilizing bolting and vacuum
suction, bonding means using a detachable adhesive can be utilized
in the contact heating device. A method of fixing by sandwiching
the above members by metallic or ceramic plates from sides can also
be employed.
[0052] FIG. 3 shows a contact heating device in which the
aforementioned members are fixed only by vacuum suction. This
device has a structure obtained by stacking a tool 1, ceramic
heater 2, heat insulating member 3 and holder 4. First suction
through holes 72a, 73a, 74a for adsorbing the tool 1 (head) are
disposed in the ceramic heater 2, heat insulating member 3 and
holder 4, respectively, so as to be communicated with each
other.
[0053] The embodiment in FIG. 3 shows that a third suction through
hole 74d for adsorbing the heat insulating member 3 penetrates
through and that the aperture thereof is opposed to the bottom
surface 30 (rear surface) of the heat insulating member 3. In this
figure, fourth suction through holes 73e, 74e for adsorbing the
ceramic heater 2 are further formed penetratingly through the heat
insulating member 3 and holder 4, respectively. These elements 1,
2, 3, 4 are vacuum-adsorbed by these suction through holes and
integrally held.
[0054] Thus, since the respective elements 1, 2, 3, 4 are only
mechanically connected and can be separated, the device can be
applied to various semiconductor chip sizes of different dimensions
only by replacing the tool 1 and ceramic heater 2. Furthermore, if
any one of the elements is damaged, only the damaged member needs
to be replaced.
[0055] Another embodiment of the present invention relates to a
contact heating device provided with cooling means. In this
embodiment, the cooling means includes means for accelerating
cooling of the ceramic heater at the time of a temperature fall,
thereby increasing a temperature fall speed. Furthermore, the
cooling means includes means for preventing a temperature rise of
the holder to prevent deformation thereof.
[0056] As cooling means for increasing a temperature fall speed
according to the present invention, as shown in FIG. 4, a pair of
shallow grooves are formed with a clearance therebetween in the
heat insulating member 3 surface. When the ceramic heater 2 is
bonded, a pair of gaps 73d, 73d are provided between the heat
insulating member 3 and ceramic heater 2. Cooling hole 73c
penetrating through the heat insulating member 3 open to these gaps
73d, 73d and these cooling holes 73c are communicated with cooling
holes 74c penetrating through the holder 4. The spaces 3d and
cooling holes 73c, 74c constitute a coolant path. At the time of
cooling after heating the heater, a gas as a coolant is allowed to
flow through the cooling holes 74c, 73c through the gaps 73d to
directly and forcibly cool the ceramic heater 2. Consequently, the
ceramic heater 2 can be cooled in a shorter time than by a
conventional indirect cooling method.
[0057] It is preferable that two or more of the cooling holes 73c,
74c having a diameter of 1-5 mm are provided. The height h of the
gap 73d is preferably 0.5-2 mm. The spaces are open to the side
surfaces and a gas as the coolant is evenly diffused to the outer
surroundings. It is not preferable that the space has a height h of
less than 0.5 mm since a pressure loss is increased due to the gas
flow, thereby requiring pre-load of the gas. It is not preferable
either that the height is 2 mm or more since the volume of the gap
73d is increased and the gas is replaced slowly, thereby making
cooling slow.
[0058] Furthermore, since the gaps 73d are formed between the
ceramic heater 2 and heat insulating member 3, the contact area
between the ceramic heater 2 and heat insulating member 3 is
reduced 20% or more. Thus, heat transfer to the heat insulating
member 3 side is reduced, thereby increasing a temperature rise
speed of this ceramic heater 2.
[0059] Cooling means for preventing thermal deformation of the
holder 4 to improve mounting accuracy will be described below. To
prevent thermal deformation of the contact heating device, it is
effective to minimize heating of the holder 4 composed of metallic
material. Therefore, shallow grooves 74f, which are coolant paths,
are provided in a contact surface 40 of the holder 4 brought into
contact with the heat insulating member 3 and a mounting surface 41
of the holder 4 to be mounted to a device. A gas as a cooling
medium is supplied from a gas supply hole 74g. The heat insulating
member 3 and holder 4 are cooled by allowing the gas in the grooves
74f, 74f formed in the upper and lower surfaces thereof. Air
flowing in the grooves 74f is gradually diffused from a bonding
surface of the holder 4 and heat insulating member 3 or a bonding
surface of the holder 4 and a supporting member of a bonding
device.
[0060] Consequently, even when the ceramic heater 2 is used as a
constant heater, which is continuously used at a high temperature
of about 500.degree. C., both the heat insulating member 3 and
holder 4 can be maintained at a low temperature of about 50.degree.
C., thereby preventing thermal deformation. This groove 74f for
cooling has similar effects when formed not in the both surfaces of
the heat insulating member 3 and holder 4, but inside thereof.
[0061] As a coolant gas, gases such as air, nitrogen gas, carbonic
acid gas and the like can be used. Carbonic acid gas is an
excellent coolant due to its large heat capacity. When an open
system is employed for exhaustion, air is preferably used as a
coolant from the viewpoint of safety. A flow rate of the gas is
preferably about 300-50000 normal cm.sup.3/min per path.
[0062] In the contact heating device of the present invention, it
is preferable that a thermal conductivity of the tool 1 is 100
W/m.multidot.K or higher and that a thermal conductivity of the
ceramic heater 2 is 10 W/m.multidot.K or higher. Such a thermal
conductivity is determined because the problem can be solved that
the temperature of a peripheral portion of the tool 910 is low due
to heat dissipation into air in the conventional bonding heater 92
shown in FIG. 5A. In FIG. 1 of the present invention, a temperature
fall of the peripheral portion of the tool 1 due to heat
dissipation into air can be prevented by increasing a thermal
conductivity of the tool 1 and ceramic heater 2 to the
aforementioned range. At the same time, heat generated by the
ceramic heater 2 can be efficiently supplied to the tool 1 side and
the temperature fall of the peripheral portion of the tool 1 can be
prevented by employing the heat insulating member 3 having a lower
thermal conductivity than that of the ceramic heater.
[0063] Since a tool 1 having a thermal conductivity lower than 100
W/m.multidot.K has a large temperature distribution therein, a
temperature distribution on a semiconductor chip becomes large and
thereby variations of solder chip bonding can occur. In addition, a
ceramic heater 2 having a thermal conductivity lower than 10
W/m.multidot.K is not preferable since the temperature distribution
on the surface thereof becomes large and variations in the
temperature distribution on the semiconductor chip occur.
[0064] Furthermore, the thermal expansion coefficient of the tool
1, ceramic heater 2, heat insulating member 3 and holder 4 is
preferably 6.times.10.sup.-6/K or lower. By setting such a low
thermal expansion coefficient, displacement due to expansion or
contraction at the time of heating or cooling of each element can
be reduced and displacement at the time of semiconductor chip
mounting, which is a problem in the conventional pulse heater
method, can be reduced.
[0065] Furthermore, the thermal conductivity of the heat insulating
member 3 is preferably 5 W/m.multidot.K or lower. Since such a heat
insulating member 3 restricts heat transfer to the holder side and
thereby heat is transferred to the ceramic tool 1 side, performance
of heating the tool 1 can be improved and time to soften and melt a
bond material solder alloy or conductive adhesive for bonding a
semiconductor chip and circuit substrate can be shortened.
[0066] Materials meeting thermal requirements of the above elements
of the contact heating device of the present invention are
described below. As the tool 1 for pressing an object to be heated,
a sintered body containing aluminium nitride, silicon carbide or
the like as a main ingredient is used. These aluminum nitride
sintered body and silicon carbide sintered body can have a thermal
conductivity of 100 W/m.multidot.K or higher and a thermal
expansion coefficient 6.times.10.sup.-6/K or lower.
[0067] The aluminum nitride sintered body can contain Al.sub.2O,
Y.sub.2O.sub.3, Yb.sub.2O.sub.3 or the like as a sintering
additive. To manufacture the tool 1 from aluminum nitride ceramic,
an aluminium nitride powder and a desired sintering additive powder
such as A1.sub.2O.sub.3, Y.sub.2O.sub.3, Yb.sub.2O.sub.3 or the
like are adjusted to prepare a desired composition and mixed with
the balls of alumina or silicon nitride in a ball mill, vibrating
mill or the like to increase mixing efficiency with a non-aqueous
solvent such as methanol, IPA or the like. The obtained aluminium
nitride slurry is passed through a sieve of about 200 meshes, dried
by a explosion-proof drier at about 120.degree. C. for about 24
hours and then passed through a sieve of about 40 meshes. The
obtained aluminium nitride is granulated by mixing a desired
organic binder and employing a method of spray drying, dry-type or
wet-type granulating. The granulated substances are formed into a
molded body by a press or CIP molding process, and then the organic
binder is removed at about 500-700.degree. C. The obtained molded
body is sintered in the presence of nitrogen at about
1800-2000.degree. C. In another method, the granulated substances
may be directly sintered by hot pressing in which molding and
sintering are performed at the same time in a carbon die.
[0068] To obtain a tool from a silicon carbide sintered body,
0.2-4.0 weight % of boron carbide or, as required, 0.5-5 weight %
of rare-earth element oxide is added to silicon carbide and
sintered in vacuum at 1900-2100.degree. C.
[0069] It is preferable to use a ceramic heater 2 having a heating
resistor buried in a ceramic containing silicon nitride, silicon
carbide, alumina, aluminium nitride or the like as a main
ingredient. For example, silicon carbide is used to obtain a
sintered body by containing B, C or the like as a sintering
additive. When silicon nitride is used, a sintered body containing
Y.sub.2O.sub.3, Al.sub.2O.sub.3, Yb.sub.2O.sub.2 or the like as a
sinterinq additive is used. When silicon carbide or silicon nitride
is used, a ceramic heater 2 having a thermal conductivity of 10
W/m.multidot.K or higher and a thermal expansion coefficient of
6.times.10.sup.-6/K or lower can be obtained.
[0070] To manufacture a ceramic heater 2, the above sintering
additive is blended to the silicon nitride powder or silicon
carbide powder to prepare a desired composition and mixed with
Al.sub.2O.sub.3 media with a non-aqueous solvent such as methanol,
IPA or the like by a ball mill, vibrating mill or the like. The
obtained slurry is dried by a drier at about 120.degree. C. and
then passed through a sieve of about 40 meshes.
[0071] A desired organic binder is mixed with the mixture powder
obtained here by a method such as a spray drying method or the like
and a desired shape is obtained by press or CIP molding. The molded
body is debinded at about 500-700.degree. C. and sintered at about
1800-2000.degree. C. in the presence of nitrogen to obtain a plate
of silicon nitride or silicon carbide. The silicon nitride or
silicon carbide plate may be sintered by hot pressing in which
molding and sintering are directly performed at the same time in a
carbon die.
[0072] The silicon nitride or silicon carbide plate so obtained is
utilized as a ceramic heater as described below. When silicon
carbide is used in a ceramic heater 2, the silicon carbide be used
as a heating element by passing current through the silicon carbide
itself due to its characteristics as semiconductor.
[0073] On the other hand, when silicon nitride is utilized in a
ceramic heater 2, a heating element is formed due to its insulating
characteristic. A conductive ceramic or metallic resistance heating
element such as W/Mo, WC or the like is-printed on the of surface
of or inside silicon nitride and then the heating element is
printed on the silicon nitride later or at the same time as
sintering of the silicon nitride in a reducing atmosphere or the
like to integrate these. The metal lead wire is brazed to the
heating element composed of conductive ceramic or metal by using
braze material such as AgCu, Ag, Cu or the like and this brazed
metal lead wire is energetized.
[0074] For example, in a ceramic heater 2 containing silicon
nitride as a main ingredient, a silicon nitride powder, rare-earth
element oxide such as Y.sub.2O.sub.3, Yb.sub.2O.sub.3 or the like
and desired sintering additive powder such as Al.sub.2O.sub.3,
SiO.sub.2 or the like are adjusted to prepare a desired
composition. Then, a heating resistor pattern containing high
melting point metal such as W, Mo or the like or carbide thereof as
a main ingredient and lead electrodes are printed on the molded
body molded under a pressure of 1 ton/cm.sup.2. Then, onto the
molded body is stacked and boded another molded body which is
subjected to hot press at 1650-1750.degree. C. or fired at
1700-1850.degree. C. in a nitrogen atmosphere of 10 atmosphere or
more to obtain a sintered body. The main surfaces of the combined
bodies are ground with precise dimensions and the lead electrode
portion is separately ground to expose the lead electrode.
Electrode metal fittings are connected by braze material to obtain
a ceramic heater 2.
[0075] To manufacture a ceramic heater 2 containing alumina as a
main ingredient, an alumina powder and material to which an
appropriate amount of SiO.sub.2, MgO and CaO as a sintering
additive are added are mixed. A heating resistor containing one or
more kinds from W, Mo and Re as a main ingredient and electrode
lead portion are printed on a surface of an tape cast alumina tape
to form an electrode pad on the rear surface of the electrode lead
portion. Then, a through hole is formed and brought into conduction
by filling an paste having the same material therein as that of the
electrode lead portion. After another aluminum nitride tape is
stacked and bonded on the heating resistor, a sintered body is
obtained by firing in a reducing atmosphere at 1500-1600.degree. C.
After the electrode pad is plated with nickel, electrode metal
fittings are connected by brazing to obtain a ceramic heater 2.
[0076] To manufacture a ceramic heater containing aluminium nitride
as a main ingredient, an appropriate amount of rare-earth element
oxide such as Y.sub.2O.sub.3, Yb.sub.2O.sub.3 or the like and
alkaline-earth oxide such as CaO, MgO or the like as sintering
additives are mixed with an aluminium nitride powder. A heating
resistor containing one or more kinds from W, Mo, Re and carbide
thereof or nitride thereof as a main ingredient and an electrode
lead portion are printed on a surface of a tape cast aluminium
nitride tape to form an electrode pad on the rear surface of the
electrode lead portion. Then, a through hole is formed and brought
into conduction by filling an paste having the same material
therein as that of the electrode lead portion. After another
alumina tape is stacked and bonded on the heating resistor, a
sintered body is obtained by sintering in a vacuum or nitrogen
atmosphere at 1700-1950.degree. C. After the electrode pad is
subjected to Ni plating, electrode metal fittings are connected by
brazing to obtain a ceramic heater 2.
[0077] AuCu, AuNi or AgCu braze material can be used as braze
material used for brazing the ceramic heater 2.
[0078] Mullite ceramic or mullite-cordierite ceramic having
porosity of about 5-30% can be used as the heat insulating member
3. When the heat insulating member 3 having this porosity is
sintered while dispersing resin beads in the generated body, a
sintered body satisfying strength and heat insulation at the same
time can be obtained. If simply only a porous sintered body needs
to be obtained, a porous heat insulating member can be obtained by
sintering at a temperature lower than a sintering temperature or
sintering by using material having a large grain size.
[0079] Thus, a heat insulating member 3 having a thermal
conductivity of 5 W/m.multidot.K or lower and a thermal expansion
coefficient or 6.times.10.sup.-6/K or lower can be obtained.
[0080] As a holder for integrating the component members except for
the ceramic tool 1 and connecting these members to another member,
for example, invar alloy having a thermal expansion coefficient of
6.times.10.sup.-6/K or lower by adjusting the amount of added Ni
can be used.
EXAMPLE 1
[0081] Here, the adaptability and maintenance characteristics to
different semiconductor chip sizes were compared between the
contact heating device of the present invention and a conventional
contact heating device.
[0082] The ceramic heater of the present invention was manufactured
as described below according to the structure shown in the
embodiment of the present invention as shown in FIGS. 1 and 2.
[0083] A tool 1 having a rectangular external shape of 24.times.24
mm and a thickness of 2 mm was obtained by mixing an aluminium
nitride powder containing Yb.sub.2O.sub.3 as a sintering additive
with a binder and pressing in a die, sintering in a nitrogen
atmosphere at 1900.degree. C. and machining by surface grinding. A
cruciform through hole 71 was penetratingly formed at the central
portion of the tool 1.
[0084] To obtain a ceramic heater, a silicon nitride or aluminium
nitride powder containing Yb.sub.2O.sub.3 as a sintering additive
was mixed with a binder and subjected to press molding to obtain
square molded bodies of 50 mm. A tungsten carbide WC paste was
printed on one molded body as a heating element and another molded
body was combined to obtain an aggregate by placing the WC paste
between these two molded bodies.
[0085] The aggregate was hot pressed at 1700-1800.degree. C. to
obtain sintered bodies of, respectively, silicon nitride and
aluminum nitride, incorporated with a WC heating element. These
were processed by using a surface grinder or ultrasonic machine to
obtain a heater having an external shape of 24.times.24 mm and a
thickness of 3 mm and bolt through holes 61 penetrated on both
sides. Then, pad electrodes 21, a second through hole 72b and a
ring groove 72a for vacuum suction were formed to obtain a ceramic
heater 2.
[0086] A heat insulating member 3 was formed by processing porous
mullite material by using a surface grinder or ultrasonic machine
so that the dimensions thereof matched those of the ceramic heater
2. Bolt through holes 51 and bolting holes 62 for fastening the
heater were punched and first and second through holes 73a, 73b for
vacuum suction were further punched at prescribed positions. The
thermal conductivity of the heat insulating member 3 was changed by
adjusting the porosity.
[0087] A holder 4 was prepared by processing FeNi alloy (invar
alloy) containing much Ni by a surface grinder or ultrasonic
machine so that the dimensions thereof matched those of the heat
insulating member 3. Bolting holes 52 were threaded at corners by
machining and first and second through holes 74a, 74b for vacuum
suction were formed at the central portion.
[0088] The thermal expansion coefficient of the holder 4 was
changed by changing the Ni content in the alloy.
[0089] The conventional contact heating device was obtained by
bonding a ceramic heater 92 and head 16 with bond material 911 as
shown in FIG. 5B and fixing this to the holder 94.
[0090] Table 1 shows comparison of adaptability and maintenance
characteristics to various semiconductor chip sizes between these
sample.
1 TABLE 1 Adaptability to semiconductor chips Maintenance Pulse
heater Adaptable to specific Heater and tool replac chip size only
ed simultaneously Embodiment Adaptable to various chip Heater and
tool can be sizes separately replaced.
[0091] In the contact heating device of the present invention shown
in-FIGS. 1 and 2, a ceramic tool 1 for pressing an object to be
heated and a ceramic heater 2 for heating the tool 1 are provided
separatably and a heat insulating member 3 for transferring heat to
the ceramic tool 1 side and holder 4 are mechanically fastened by
bolts 5. Therefore, the tool can respond to various semiconductor
chip sizes. In maintenance as well, the tool and ceramic heater can
be separately replaced. Thus, the separatable contact heating
device of the present invention solves the problem that the
conventional fixed type contact heating device cannot respond to
various semiconductor chip sizes and that if any of the tool and
ceramic heater is damaged, both of them need to be replaced.
EXAMPLE 2
[0092] In this example, the relationship of a thermal conductivity
of the ceramic heater 2 and tool 1 to a temperature distribution on
a semiconductor chip 8 heated by a contact heating device using the
same was investigated.
[0093] The thermal conductivity of the tool 1 was adjusted by
adjusting the contents of Yb.sub.2O.sub.3 and aluminium nitride.
The thermal expansion coefficient of the ceramic heater 2 was
changed by selecting silicon nitride or aluminium nitride to be
used as a ceramic heater 2. The thermal conductivity thereof was
changed by changing the composition of silicon nitride or aluminium
nitride and Yb.sub.2O.sub.3, in this example, the thermal
conductivity of the ceramic tool 1 was set to be 100 W/m.multidot.K
or higher and that of the ceramic heater 2 was set to be 10
W/m.multidot.K or higher. In this example, the temperature of a
peripheral portion of the tool 1 fell and heat generated by the
ceramic heater 2 could be supplied at the same time due to heat
dissipation into air by increasing the thermal conductivity of the
tool 1 and ceramic heater 2. The temperature distribution on the
semiconductor chip was measured by a thermoviewer while changing
the thermal conductivity of the tool 1 and ceramic heater 2 and
prevention of a temperature fall in the peripheral portion of the
tool 1 was compared.
[0094] The results are shown in Table 2.
2 TABLE 2 Heat conductivity Temperature W/m.K distribution Sample
Heater Tool .DELTA.T (.degree. C.) Sample 1 9 90 9 Sample 2 20 110
4 Sample 3 9 110 7 Sample 4 20 90 8 Comparative -- -- 30
[0095] This example shows that temperature differences between the
highest temperature point and lowest point were all 10.degree. C.
or less on the semiconductor chip. In particular, the temperature
difference was made 5.degree. C. or less by setting the thermal
conductivity of the ceramic tool 1 to be 100 W/m.multidot.K or
higher and that of the ceramic heater 2 to be 10 W/m.multidot.K or
higher.
[0096] On the other hand, the temperature difference between the
highest temperature point and lowest point on the semiconductor
chip was as large as 30.degree. C. in the conventional pulse
heater, in which the temperature was rapidly increased by passing
large current through titanium or molybdenum.
EXAMPLE 3
[0097] In this example, the thermal expansion coefficients of all
the ceramic tool 1, ceramic heater 2, heat insulating member 3 and
holder 4 were set to be as low as 6.times.10.sup.-6/K or lower. By
reducing change in dimensions of each component member in the
heating and cooling processes, displacement of a semiconductor chip
with respect to the substrate upon mounting a semiconductor chip
was compared with that in the case of employing a conventional
pulse heater method. The displacement of the chip was measured by
using a laser interferometer.
[0098] The results are shown in Table 3.
3 TABLE 3 Thermal expansion coefficient (.times.10.sup.-6/K)
insulating Displace- Tool Heater material Holder ment (.mu.m)
Sample 1 4.5 3.2 3.2 5.0 9 Sample 2 4.5 4.4 3.2 5.0 10 Sample 3 4.5
3.2 3.2 6.5 18 Comparative -- -- -- -- 40
[0099] In this example, displacement of the semiconductor chip was
20 micron or less in all cases. In particular, displacement could
be made 10 nm or less by setting the thermal expansion coefficients
of all the ceramic tool 1, ceramic heater 2, heat insulating member
3 and holder 4 to be as low as 6.times.10.sup.-6/K or lower. This
is great improvement as compared with the conventional pulse
heater, in which the displacement was 40 micron.
EXAMPLE 4
[0100] In this example, a temperature rise time from heat
generation by the ceramic heater to 25-350.degree. C. was evaluated
in relation to a thermal conductivity of the heat insulating member
3. The thermal conductivities of samples were changed to 1, 2, 4
and 6 W/m.multidot.K by adjusting porosity of the heat insulating
member 3 and the heat insulating member was manufactured as
described in Example 1. A pulse heater was used for comparison.
[0101] The results are shown in Table 4.
4 TABLE 4 Heat conductivity (W/m.K) Temp. rise of insulating
material rate (s) Sample 1 6 1.9 Sample 2 4 1.4 Sample 3 2 1.1
Sample 4 1 1.0 Comparative -- 3.2
[0102] In the conventional pulse heater, the temperature rise time
until the adhesive was softened was 3.2 seconds. On the other hand,
in the samples of the Example in which the thermal conductivities
of the heat insulating member 3 were set to be within a range of
1-6 W/m.multidot.K, the temperature rise time was 2 seconds or
shorter. It was found that the temperature rise time could be made
1.5 seconds or shorter by setting 5 W/m.multidot.K or lower.
EXAMPLE 5
[0103] Here, the cooling speed was compared between the contact
heating device of the present invention and conventional contact
heating device. The contact heating device using the ceramic heater
of the present invention shown in FIGS. 1 and 4 and the
conventional bonding heater shown in FIG. 5B were prepared.
[0104] An aluminum nitride powder containing Yb.sub.2O.sub.3 as a
sintering additive was mixed with a binder, subjected to press
molding in a die, sintered in a nitrogen atmosphere at 1900.degree.
C. and machined by a surface grinder to obtain a rectangular tool 1
having an area of 24.times.24 mm and a thickness of 2 mm.
[0105] A silicon nitride powder or aluminium nitride powder
containing Yb.sub.2O.sub.3 as a sintering additive is mixed with a
binder and then subjected to press molding to obtain a 50-mm square
molded bodies of silicon nitride or aluminium nitride. Then, a WC
paste is printed as a heating resistor and hot pressing is
performed at 1700-1800.degree. C. while sandwiching the WC paste
with another 50-mm square molded body of silicon nitride or
aluminium nitride to obtain a sintered body incorporating WC as a
heating resistor. The heat generation unit was made 24.times.24 in
shape and 3 mm in thickness by using a surface grinder or
ultrasonic machine and bolting holes were formed on both sides.
Further, legs for an electrode lead portion, vacuum suction holes
and vacuum suction groove were formed to obtain a ceramic heater 2.
The heat insulating member 3 was manufactured by processing porous
mullite material by a surface grinder or ultrasonic machine so that
the dimensions thereof matched those of the heater 2. The thermal
conductivity of the heat insulating member 3 was changed by
adjusting porosity.
[0106] A holder 4 was formed by processing Fe--Ni Invar alloy by
using a surface grinder or ultrasonic machine so that the
dimensions thereof matched those of the heat insulating member 3.
The thermal expansion coefficient of the holder 4 was changed by
changing the Ni content in the alloy.
[0107] The contact heating device of the present invention was
manufactured by mechanically fastening a ceramic tool 1 for
pressing an object to be heated, a ceramic heater 2 containing
ceramic as a main ingredient for heating the tool, a heat
insulating member 3 for transferring heat generated by the ceramic
heater 2 mainly to the ceramic tool side and a holder 4 for
integrating the respective component members and connecting these
members to another member by using bolts 5 or the like.
[0108] As shown in FIG. 4, two gaps 73d having a height h of 0.5 mm
were provided between the heat insulating member 3 and ceramic
heater 2 to form a coolant path. Air was allowed to flow through
this path as a coolant in order to directly and forcibly cool the
ceramic heater 2.
[0109] As shown in FIG. 6, in the conventional contact heating
device, the bonding heater 92 and head 91 were attached to the
heater holder 94 and this was fixed to a holder 95 incorporating a
water cooling jacket 96 to obtain a contact heating device.
[0110] Then, the cooling speed of the ceramic heater 2 was compared
between these samples.
[0111] The results are shown in Table 5.
5 TABLE 5 Temperature fall time (s) in temperature range of
400.degree. C.-100.degree. C. 400.degree. C.-200.degree. C. Example
8.0 3.5 Comparative example 30 18
[0112] As shown in Table 5, cooling times from 400.degree. C. to
100.degree. C. and from 400.degree. C. to 200.degree. C. required
by the conventional example were 30 seconds and 18 seconds,
respectively. On the other hand, the cooling times required by the
Example of the present invention were 8 seconds and 3.8 seconds,
respectively. Thus, it was found that the cooling time could be
shortened to 10 seconds or less.
EXAMPLE 6
[0113] Here, reduction of thermal deformation due to cooling of the
heat insulating member 3 and holder 4 was shown. By using aluminium
nitride having a thermal expansion coefficient of
4.5.times.30.sup.-6/K as a ceramic tool 1, silicon nitride having a
thermal expansion coefficient of 3.2.times.10.sup.-6/K and
aluminium nitride having a thermal expansion coefficient of
4.5.times.10.sup.-6/K as a ceramic heater 2, silicon nitride having
a thermal expansion coefficient of 3.2.times.10.sup.-6/K as a heat
insulating member 3 and invar alloy having a thermal expansion
coefficient of 5.0.times.10.sup.-6/K as a holder 4, three kinds of
contact heating devices were prepared as described in Example 5 as
shown in Table 6 and air was allowed to flow at a rate of 2000
Ncm.sup.3/min through the cooling holes to cool the heat insulating
member 3 and holder 4.
[0114] A conventional contact heating device shown in FIG. 6 was
used for comparison.
[0115] Evaluation was performed by measuring displacement of the
semiconductor chip mounted product by using a laser interferometer
after subjecting the ceramic heater 2 to 100 cycles of temperature
rises and falls between 100.degree. C. and 500.degree. C.
[0116] The results are shown in Table 6.
6 TABLE 6 Thermal expansion coefficient (.times. 10.sup.-6/K)
insulating Displacement Tool Heater material Holder (.mu.m) Sample
1 4.5 3.2 3.2 5.0 9 Sample 2 4.5 4.5 3.2 5.0 10 Sample 3 4.5 3.2
3.2 5.0 18 Comparative -- -- -- -- 40 example
[0117] As shown in Table 6, in a semiconductor chip mounted product
of the comparative example using the conventional contact heating
device, displacement of 40 .mu.m occurred as compared with the
initial state. On the other hand, the samples 1-3 of the Example of
the present invention had displacement of 20 .mu.m or less. It was
found that displacement could be reduced by cooling the heat
insulating member 3 and holder 4. When the conventional contact
heating device was used, the temperature of the holder 4 rose to
130.degree. C. However, it was found that the holder 4 of the
samples 1-3 of the Example of the present invention rose to
50-60.degree. C., that is, the temperature rise could be largely
restricted.
* * * * *