U.S. patent application number 14/722794 was filed with the patent office on 2015-10-01 for method for bonding semiconductor wafers using a molecular bonding apparatus.
The applicant listed for this patent is Soitec. Invention is credited to Marcel Broekaart, Ionut Radu.
Application Number | 20150279830 14/722794 |
Document ID | / |
Family ID | 42699871 |
Filed Date | 2015-10-01 |
United States Patent
Application |
20150279830 |
Kind Code |
A1 |
Broekaart; Marcel ; et
al. |
October 1, 2015 |
METHOD FOR BONDING SEMICONDUCTOR WAFERS USING A MOLECULAR BONDING
APPARATUS
Abstract
The present invention relates to an apparatus for the
manufacture of semiconductor devices wherein the apparatus includes
a bonding module that has a vacuum chamber to provide bonding of
wafers under pressure below atmospheric pressure; and a loadlock
module connected to the bonding module and configured for wafer
transfer to the bonding module. The loadlock module is also
connected to a first vacuum pumping device configured to reduce the
pressure in the loadlock module to below atmospheric pressure. The
bonding and loadlock modules remain at a pressure below atmospheric
pressure while the wafer is transferred from the loadlock module
into the bonding module.
Inventors: |
Broekaart; Marcel; (Theys,
FR) ; Radu; Ionut; (Crolles, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Soitec |
Crolles Cedex |
|
FR |
|
|
Family ID: |
42699871 |
Appl. No.: |
14/722794 |
Filed: |
May 27, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13624470 |
Sep 21, 2012 |
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14722794 |
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12888251 |
Sep 22, 2010 |
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13624470 |
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Current U.S.
Class: |
156/285 |
Current CPC
Class: |
H01L 21/67092 20130101;
B32B 2309/65 20130101; H01L 25/50 20130101; H01L 2924/0002
20130101; B32B 2309/64 20130101; H01L 2924/0002 20130101; B32B
38/1858 20130101; H01L 2924/00 20130101; Y10T 156/10 20150115; B32B
2309/68 20130101 |
International
Class: |
H01L 25/00 20060101
H01L025/00 |
Claims
1. A method for bonding semiconductor wafers, the method
comprising: evacuating a vacuum chamber of a bonding module to
below atmospheric pressure; transferring at least a first wafer and
a second wafer from an external environment to a loadlock module
that is connected to the bonding module; evacuating the loadlock
module to below atmospheric pressure after transferring at least
the first wafer and the second wafer to the loadlock module;
transferring at least the first wafer and the second wafer from the
evacuated loadlock module to the evacuated vacuum chamber of the
bonding module while retaining the bonding and loadlock modules at
a pressure below atmospheric pressure; positioning the first wafer
on a first bonding chuck and a positioning the second wafer on a
second bonding chuck, respectively; and moving the first wafer and
the second wafer toward each other by movement of the first and/or
second bonding chuck such that a main surface of the first wafer
and a main surface of the second wafer locally come sufficiently
close to each other to allow bonding to be initiated.
2. The method according to claim 1, further comprising positioning
the first wafer and the second wafer vertically or within
10.degree. of a vertical position on the first and the second
bonding chuck, respectively.
3. The method according to claim 1, further comprising adjusting a
vacuum pressure of the vacuum chamber after transferring at least
the first wafer and the second wafer from the evacuated loadlock
module to the evacuated vacuum chamber of the bonding module.
4. A method for bonding semiconductor wafers, the method
comprising: evacuating a vacuum chamber of a bonding module;
transferring at least a first wafer and a second wafer from an
external environment to a loadlock module; evacuating the loadlock
module to below atmospheric pressure after transferring at least
the first wafer and the second wafer to the loadlock module; and
transferring at least the first wafer and the second wafer from the
evacuated loadlock module to the evacuated vacuum chamber of the
bonding module by a robot device while retaining the bonding and
loadlock modules at a pressure or pressures below atmospheric
pressure.
5. The method according to claim 4, further comprising: positioning
the first wafer on a first bonding chuck and positioning the second
wafer on a second bonding chuck; and moving the first wafer and the
second wafer toward each other by movement of the first bonding
chuck and/or the second bonding chuck such that a main surface of
the first wafer and a main surface of the second wafer come
sufficiently close to each other to allow bonding of the first
wafer and the second wafer to be initiated.
6. The method according to claim 5, further comprising orienting
the first wafer and the second wafer in a vertical orientation or
within 10.degree. of the vertical orientation on the first bonding
chuck and the second bonding chuck, respectively, and allowing the
bonding of the first wafer and the second wafer to be initiated
while the first wafer and the second wafer are oriented in the
vertical orientation or within 10.degree. of the vertical
orientation.
7. The method of claim 2, wherein the first wafer and the second
wafer are maintained in a vertical position or within 10.degree. of
the vertical position while moving the first wafer and the second
wafer toward each other by movement of the first and/or second
bonding chuck such that the main surface of the first wafer and the
main surface of the second wafer come sufficiently close to each
other to allow bonding to be initiated.
8. The method of claim 1, wherein the loadlock module comprises a
multi wafer storage system, and wherein the method further
comprises storing a plurality of wafers in the multi wafer storage
system at a pressure below atmospheric pressure, prior to
transferring the plurality of wafers into the bonding module for
bonding.
9. The method of claim 1, further comprising transferring the
bonded first and second wafers from the bonding module to another
loadlock module, and subsequently removing the bonded first and
second wafers from the another loadlock module, and wherein the
bonded first and second wafers are not exposed to atmospheric
pressure from the time the first wafer and the second wafers are
transferred from the external environment to the loadlock module
until the time the bonded first and second wafers are removed from
the another loadlock module.
10. The method of claim 1, wherein moving the first wafer and the
second wafer toward each other by movement of the first and/or
second bonding chuck such that a main surface of the first wafer
and a main surface of the second wafer locally come sufficiently
close to each other to allow bonding to be initiated comprises
locating the first wafer and the second wafer at a predetermined
distance to each other, and releasing the first wafer from the
first bonding chuck and/or releasing the second wafer from the
second bonding chuck at the predetermined distance.
11. The method of claim 10, further comprising locally applying a
force to at least one of the first wafer and the second wafer such
that they locally become sufficiently close to each other at the
location at which the force is applied to initiate bonding.
12. The method of claim 1, wherein moving the first wafer and the
second wafer toward each other by movement of the first and/or
second bonding chuck such that a main surface of the first wafer
and a main surface of the second wafer locally come sufficiently
close to each other to allow bonding to be initiated comprises
locating the first wafer and the second wafer at a predetermined
distance to each other, and subsequently locally decreasing a
clamping force applied by at least one of the first and second
bonding chucks such that the first wafer and the second wafer
locally become sufficiently close to each other to initiate
bonding.
13. The method of claim 1, further comprising gradually releasing
the first wafer from the first bonding chuck and/or gradually
releasing the second wafer from the second bonding chuck.
14. The method of claim 1, wherein the bonding of the first and
second wafers comprises molecular bonding of the first and second
wafers.
15. The method of claim 1, wherein evacuating the vacuum chamber of
the bonding module to below atmospheric pressure comprises reducing
the pressure within the vacuum chamber to a pressure in a range
extending from 0.01 mbars and 10 mbars.
16. The method of claim 15, wherein evacuating the loadlock module
to below atmospheric pressure comprises reducing the pressure
within the loadlock module to a pressure in a range extending from
1 mbars to 10 mbars.
17. The method of claim 16, further comprising maintaining the
first and second wafers at room temperature while allowing the
bonding to be initiated.
18. The method of claim 1, wherein transferring at least the first
wafer and the second wafer from the evacuated loadlock module to
the evacuated vacuum chamber of the bonding module comprises
transferring at least the first wafer and the second wafer from the
evacuated loadlock module directly to the evacuated vacuum chamber
through a closable gate.
19. The method of claim 1, further comprising controlling a
propagation speed of a bonding wave between the first wafer and the
second wafer upon allowing initiation of the bonding.
20. The method of claim 4, further comprising positioning the first
wafer and the second wafer in a vertical position, moving the first
wafer and the second wafer toward each other in the vertical
position, and initiating molecular bonding between the first wafer
and the second wafer.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. patent application
Ser. No. 13/624,470, filed Sep. 21, 2012, pending, which is a
continuation of U.S. patent application Ser. No. 12/888,251, filed
Sep. 22, 2010, abandoned, the disclosure of each of which is hereby
incorporated herein in its entirety by this reference.
FIELD
[0002] The present invention relates to an apparatus for the
manufacture of semiconductor devices wherein the apparatus
comprises a bonding module for the molecular bonding of wafers.
BACKGROUND
[0003] Three-dimensional (3-D) integrated circuit technology where
circuit structures formed on several silicon-on-insulator (SOI)
substrates are bonded together and integrated into a 3-D circuit
with dense-vertical connections becomes of increasing importance in
modern semiconductor technology (see, for example, paper by Burns
et al., entitled A Wafer-Scale 3-D Circuit Integration Technology,
IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 53, NO. 10, October
2006, pages 2507-2516). The building blocks of the 3-D circuit
integration technology are fully depleted SOI (FDSOI) circuit
fabrication, precision wafer-wafer alignment, low-temperature
wafer-wafer oxide bonding (molecular bonding, oxide fusion
bonding), and electrical connection of the circuit structures with
dense vertical interconnections. When compared to conventional bump
bond technology, the wafer-scale 3-D technology offers higher
density vertical interconnections and reduced system power.
[0004] Molecular bonding of wafers requires that the surfaces of
the same are sufficiently smooth, free of particles or
contamination, and that they are sufficiently close to each other
to allow contact to be initiated, typically at a distance of less
than a few manometers at a point of initiation. The contact will be
initiated at a local point where the two wafer surfaces have the
closest approach to each other: no pressing forces need to be
applied to the wafers. In this case, the forces of attraction
between the two surfaces are sufficiently high to cause propagation
from this location of a "bonding wave" and molecular adhesion
(bonding induced by all of the forces of attraction--Van Der Waals
forces--of the electronic interaction between the atoms or the
molecules of the two surfaces of the wafers that are to be bonded).
By the term "bonding wave" it is referred to the front of the bond
or the molecular adhesion spreading from the point of initiation
and corresponding to the dissemination of the forces of attraction
(Van Der Waals forces) from the point of initiation over the entire
surface of close contact between the two wafers (bonding
interface).
[0005] However, molecular bonding faces the severe problems of
bonding interface defects, wafer misalignment and wafer overlay
defects due to heterogeneous distortions which appear in the
transfer layer during its assembly with the receiving substrate.
Such distortions are not the result of elementary transformations
(translation, rotation or combinations thereof) that could
originate in inaccurate assembly of the substrates
(misalignment).
[0006] These distortions result from non-homogeneous deformations
that appear in the layer while it is being assembled with the final
substrate. In fact, such distortions can lead to variations in
position which may be in the order of several hundred manometers or
even microns. Since these distortions are not homogenous, it is not
possible to correct completely these misalignment errors during
subsequently performed photolithography steps. Thereby non or
dysfunctional semiconductor devices may result.
[0007] In view of the above and in spite of the recent
technological progress there is a need for an apparatus for the
manufacture of semiconductor devices that provide molecular bonding
of wafers for 3D integrated circuit technology with sufficient
accuracy, in particular, alignment and suppression of bonding
interface defects, as well as a high through-put.
SUMMARY
[0008] The present invention relates to an apparatus for the
manufacture of semiconductor devices comprising a bonding module
comprising a vacuum chamber to provide bonding of wafers under a
pressure below atmospheric pressure; and a loadlock module
connected to the bonding module and configured and dimensioned for
wafer transfer to the bonding module and connected to a first
vacuum pumping device configured to reduce the pressure in the
loadlock module to below atmospheric pressure.
[0009] The apparatus may further comprising a second vacuum pumping
device connected via a control valve to the vacuum chamber of the
bonding module and configured to reduce the pressure in the vacuum
chamber of the bonding module below atmospheric pressure. The
apparatus provides external access to the loadlock module and has
the loadlock module connected to the bonding module by gates,
wherein the loadlock module comprises a first gate that can be
opened and closed for receipt of a wafer from an external
environment and a second gate that can be opened and closed for
transfer of a wafer from the loadlock module to the bonding
module.
[0010] The apparatus may also have a larger loadlock module,
wherein the loadlock module comprises a multi wafer storage system
for storing multiple wafers to be transferred to the bonding
module.
[0011] The apparatus may further comprise at least one additional
loadlock module connected to the bonding module and configured and
dimensioned to receive one or more bonded wafers from the bonding
module.
[0012] The apparatus also has chucks that can hold and move the
first and second wafers, wherein the bonding module comprises at
least a first moveable bonding chuck configured and dimensioned to
hold a first wafer and a second moveable bonding chuck different
from the first bonding chuck and configured and dimensioned to hold
a second wafer different from the first wafer. The first and second
bonding chucks are configured to hold the first and the second
wafer, respectively, in a within less than 10.degree. of a vertical
position within less than 10.degree. with respect to a horizontal
plane whereupon the bonding module is located, and the first
bonding chuck and/or the second bonding chuck is made of metal or
ceramics that resists bending and bowing. The first bonding chuck
and second bonding chuck can be configured and dimensioned to hold
first and second wafers that are at least 300 mm in diameter.
[0013] The apparatus can further comprise a control unit configured
to control the first and the second bonding chucks to move towards
each other, and to locate the first and the second wafers at a
predetermined distance to each other, release the first and the
second wafers at the predetermined distance, and to initiate local
application of a force to at least one of the first and the second
wafers such that they locally become that close to each other that
bonding is initiated. The apparatus can also further comprise a
control unit configured to control the first and the second bonding
chucks to move towards each other to locate the first and the
second wafers at a predetermined distance to each other and,
subsequently, locally decreasing the clamping force applied by the
first and/or second bonding chucks in order to hold the first and
second water, respectively, such that the first and the second
wafers locally become that close to each other that bonding is
initiated.
[0014] The apparatus can have a control unit, wherein the control
unit is configured to control gradual or non-gradual release of the
first and/or second wafer, wherein the first and the second wafer
become sufficiently close to each other at an initial location that
bonding is initiated.
[0015] The invention also relates to a manufacturing system
comprising the apparatus as described above, and further comprising
a load port module configured and dimensioned to introduce a wafer
into the manufacturing system; a plasma module configured to
perform a plasma treatment of a surface of the wafer introduced in
the manufacturing system; a cleaning module configured to clean the
surface of the wafer; and a moveable robot device configured and
dimensioned to transport the wafer from one of either the load port
module, plasma module, cleaning module, and loadlock module to any
other one of these modules. The present invention also relates to a
method for bonding semiconductor wafers, comprising the steps of
evacuating a vacuum chamber of a bonding module; transferring at
least a first wafer and a second wafer from an external environment
to a loadlock module that is connected to the bonding module;
evacuating the loadlock module after transfer of at least the first
and second wafers to the loadlock module; transferring at least the
first and second wafers from the evacuated loadlock module to the
evacuated vacuum chamber of the bonding module; positioning the
first wafer and a second wafer on a first and a second bonding
chuck, respectively; and moving the first and the second wafer
towards each other by movement of the first and/or second bonding
chuck such that a main surface of the first wafer and a main
surface of the second wafer locally come sufficiently close to each
other to allow bonding to be initiated. The method may also further
comprise controlling the first and second bonding chucks with a
control unit to either unclamp the first and second wafers in a
gradual or non-gradual manner. The method also involves positioning
a first wafer and a second wafer, wherein the first and the second
wafers are positioned in a vertically or within less than
10.degree. of a vertical position within less than 10.degree. with
respect to a horizontal plane whereupon the bonding module is
located on the first and the second bonding chuck, respectively,
and moved into a vertical the position and sufficiently close to
each another to allow bonding to be initiated. The method may
further comprise adjusting the vacuum of the vacuum chamber after
transfer of at least the first wafer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 illustrates an example of the inventive apparatus for
the manufacture of a semiconductor device comprising a bonding
module and a load lock module connected to the bonding module.
[0017] FIG. 2 illustrates an example of a bonding module according
to the present invention.
[0018] FIG. 3 illustrates an example of a manufacturing system
comprising the apparatus illustrated in FIG. 1.
[0019] FIG. 4 illustrates a preferred embodiment in which a second
loadlock module is connected to the bonding module to improve wafer
throughput.
DETAILED DESCRIPTION
[0020] The present invention addresses the above-mentioned need
and, accordingly, relates to an apparatus for the manufacture of
semiconductor devices comprising a bonding module comprising a
vacuum chamber to provide bonding of wafers under a pressure below
atmospheric pressure, and a loadlock module connected to the
bonding module and configured for wafer transfer to the bonding
module and connected to a first vacuum pumping device configured to
reduce the pressure in the loadlock module below atmospheric
pressure.
[0021] According to the invention molecular bonding of wafers is
performed in an evacuated vacuum chamber of a bonding module. Since
the bonding is performed under (partial) vacuum, bonding interface
defects, such as edge voids, can be significantly suppressed
without affecting the bonding strength. In addition, wafers are
transferred from the evacuated loadlock module to the vacuum
chamber of the bonding module thereby significantly increasing the
throughput as compared to the prior art. Since the loadlock module
provides the wafers to the bonding module at vacuum pressure close
to the low-pressure of the evacuated vacuum chamber of the bonding
module, switching of the bonding module from vacuum pressure to
atmospheric pressure and vice versa between two bonding steps
(bonding step and step of transfer of at least one wafer from the
loadlock module to the bonding module) is avoided. The bonding
module and loadlock module are air tight, so as to be seal against
the external atmospheric pressure, in order to maintain a vacuum
pressure below one atmosphere during evacuation, transfer and
bonding.
[0022] The loadlock module is evacuated by a first pumping device,
for example, to a pressure between about 5 mbars to below
atmospheric pressure (below 1 bar), or more preferably, to a
pressure in the range of 1 mbars to 10 mbars. The vacuum chamber of
the bonding module is, for example, evacuated by a second pumping
device to a pressure in the range of 0.01 mbars to 10 mbars, or
more preferably, 0.1 mbars to 5 mbars. It is also noted that the
temperature in the vacuum chamber is kept at room temperature in
order to avoid deformation of the wafers due to thermal expansion
of the wafer semiconductor material. The first and/or the second
pumping devices can be connected to the loadlock module and the
vacuum chamber of the bonding module, respectively, by respective
separate control valves provided to control the desired degree of
vacuum. For both the first and the second pumping device a
multi-stage rotary vane pump can be provided, for example.
[0023] It is noted that the bonding module encloses all means and
devices necessary for the aligned wafer bonding process under
vacuum, and is, thus, hermetically closed from the environment. The
loadlock module may be configured to receive and transfer to the
bonding module one wafer at a time or it may be configured to
receive multiple wafers at the same time that can be stored in a
multi wafer storing system provided in the loadlock module. In the
former case, the size of the loadlock module can be minimized such
that the vacuum of the vacuum chamber of the bonding module is not
heavily affected by opening a gate separating the bonding module
from the loadlock module during wafer transfer. In the latter case,
the throughput can be increased.
[0024] In particular, the loadlock module may comprise a first gate
that can be opened and closed for receipt of a wafer and a second
gate that can be opened and closed for transfer of a wafer from the
loadlock module to the bonding module. After the wafer is received
in the loadlock module via the opened first gate and the first gate
is closed again the first pumping device can start evacuating the
loadlock module.
[0025] According to an embodiment of the inventive apparatus at
least one additional loadlock module connected to the bonding
module and configured to receive one or more wafers or wafer stacks
that were already bonded in the bonding module is provided in order
to even further increase the throughput by allowing a first
loadlock module to act as a source of unbonded wafers and the
second loadlock module to act as a receiver of bonded wafers.
[0026] The bonding module may comprise at least a first moveable
bonding chuck configured to hold a first wafer and a second
moveable bonding chuck different from the first bonding chuck and
configured to hold a second wafer different from the first water. A
robot means or devices can be provided inside the bonding module
that is configured to grip the wafers from the loadlock system and
position them on the bonding chuck. Gripping can be achieved by
mechanical means, electrostatic means or vacuum (if the clamping
vacuum is well below the operating vacuum level of the vacuum
chamber of the bonding module). The robotic device can also include
any arms, joints, translational or rotational motion devices,
positioning sensors and actuators known to those in the art.
[0027] Two movable bonding chucks, positioned face to face, to
support and clamp the wafers may be provided inside the vacuum
chamber of the boning module. The chucks are movable in translation
and rotation in order to be able to position and align the two
wafers in front to each other. Each bonding chuck shall be provided
with a planarity as good as possible because it has been determined
that chuck bow is one of the main reasons for overlay defects.
According to an embodiment the chucks are made of metal or
ceramics, which resist bending and bowing, and cannot be easily
deformed and maintain the planarity of the wafer. Bow of the chucks
(maximum deviation from a median plane) should preferably be below
1 micron or even below 0.1 micron.
[0028] The first and second bonding chucks can be configured,
dimensioned and orientated to hold the first and the second wafer,
respectively, in a vertically or within less than 10.degree. of a
vertical position within less than 10.degree. with respect to a
horizontal plane whereupon the bonding module is located. Each
wafer has two main surfaces and four side surfaces. According to
this example, the main surfaces of the wafers are orientated almost
vertically with respect to a horizontal plane whereupon the bonding
module is located. In particular, the main surfaces of the wafers
are orientated inclined to the horizontal plane whereupon the
bonding module is located with an angle of less than about
10.degree., more particularly, with an angle of less than about
5.degree., and even more preferably, with an angle of at most about
1.degree.. By this orientation, deformation (overlay errors) of the
wafers due to their own weight can be avoided and even large wafers
of more than 300 mm in diameter can reliably be processed.
[0029] The apparatus may also include a control unit for
controlling operation of different modules of the apparatus as well
as the transfer of wafers from one module to another by means of
the robotic devices.
[0030] If required by the application, an optical positioning
system can be provided in the bonding module that is operated to
identify the exact position of alignment marks on the wafers, and
the two chucks are then moved in translation and rotation to align
the wafers in accordance with the identified alignment marks.
[0031] The actual molecular (oxide fusion) bonding process can be
controlled by the above-mentioned control unit according to
different alternatives. According to a first embodiment, the
clamping is released to free the two wafers from their chuck, and
an additional force is applied locally to cause intimate contact
(in terms of the acting molecular forces) of the wafers and
initiate the bonding wave propagation. This additional force should
be minimized, for instance below 5 N or even below 1 N, so that no
deformation of the wafer results. Thus, the inventive apparatus may
further comprise a control unit configured to control the first and
the second bonding chucks to move to each other to locate the first
and the second wafers at a predetermined distance to each other,
release the first and the second wafers at the predetermined
distance and to initiate local application of a force by an
appropriate local force application means or device to at least one
of the first and the second wafers such that they locally become
that close to each other that bonding is initiated. Here and in the
following it is understood that bonding is initiated by molecular
forces acting between the main surfaces of the wafers that have
approached or been positioned closely to each other and are to be
bonded.
[0032] According to a second embodiment, the intimate contact is
first created, and then the un-clamping of the wafer is performed
gradually. Intimate contact, in terms of the acting molecular
forces, can be created by slightly deforming locally at least one
of the wafers while bringing the two wafers in contact to each
other. Deformation can be realized by locally decreasing the
clamping force that retains the wafer to the chuck. Once intimate
contact has been created, the un-clamping is performed gradually to
control the propagation speed of the bonding wave. According to a
third embodiment, un-clamping is performed non-gradually rather
than gradually without any control of the bonding wave propagation.
The latter approach is easier to implement.
[0033] Accordingly, the apparatus according to the present
invention may further comprise a control unit configured to control
the first and the second bonding chucks to move to each other to
locate the first and the second wafers at a predetermined distance
to each other, and subsequently, locally decreasing the clamping
force applied by the first and/or second bonding chucks in order to
hold the first and second wafer, respectively, such that the first
and the second wafers locally become close enough to each other
that bonding is initiated.
[0034] The control unit may be configured to control gradual or
non-gradual release of the first and/or second wafer, wherein the
first and the second wafer become sufficiently close to each other
at an initial location that bonding is initiated, where the wafers
are sufficiently close when the surfaces of the wafers are less
than a few manometers from each other, or the forces of attraction
between the two surfaces are sufficiently high to cause propagation
from this location of a "bonding wave" and molecular adhesion.
[0035] The present invention, moreover, provides a manufacturing
system (see also detailed discussion below) comprising the
apparatus of one of the above-described examples and further
comprising a load port module configured to introduce a wafer from
an external environment in the manufacturing system; a plasma
module configured to perform a plasma treatment of a surface of the
wafer introduced in the manufacturing system; a cleaning module
configured to clean the surface of the wafer; and a moveable robot
means or device configured and dimensioned to transport the wafer
from one of the load port module, plasma module, cleaning module,
and loadlock module to another one of these modules.
[0036] One or more plasma modules can be provided for activating
one or both of the main surfaces of wafers. The cleaning module
cleans and/or brushes the surfaces of the wafers that are to be
bonded to each other in the bonding module. The robot means is a
device suitably configured and dimensioned to manipulate and
transfer the wafers from the load port to any individual module,
and also from any one module to any other. The robot in a preferred
embodiment moves along a robot moving area, to enable the transfer
of the wafer from one place to another. The system may also include
a control unit controlling operation of the individual modules and
transfer of the wafers by the robotic devices.
[0037] The present invention also relates to a method for the
bonding of semiconductor wafers, comprising the steps of evacuating
a vacuum chamber of a bonding module; transferring at least a first
wafer to a loadlock module that is connected to the bonding module;
evacuating the loadlock module after transfer of at least the first
wafer to the loadlock module; transferring at least the first wafer
from the evacuated loadlock module to the evacuated vacuum chamber
of the bonding module; optionally adjusting the vacuum of the
vacuum chamber after transfer of the at least the first wafer if
this is desired due to quality reasons of the bonded wafers;
positioning the first wafer and a second wafer on a first and a
second bonding chuck, respectively; and moving the first and the
second wafer to each other by movement of the first and/or second
bonding chuck such that a main surface of the first wafer and a
main surface of the second wafer locally come that close to each
other that bonding is initiated.
[0038] In particular, the first and the second wafers can be
positioned in a vertically or within less than 10.degree. of a
vertical position with respect to a horizontal plane whereupon the
bonding module is located on the first and the second bonding
chuck, respectively, and moved in that vertical position that close
to each other that bonding is initiated.
[0039] Additional features and advantages of the present invention
will be described with reference to the drawings. In the
description, reference is made to the accompanying figures that are
meant to illustrate preferred embodiments of the invention. It is
understood that such embodiments do not represent the full scope of
the invention, and only represent particular examples of present
invention.
[0040] As shown in FIG. 1, the apparatus of the present invention
according to a particular example comprises a bonding module 1 and
a loadlock module 2. Bonding is performed in a vacuum chamber of
the bonding module 1. The vacuum in the vacuum chamber of the
bonding module 1 is established by a vacuum pump 3 that is
connected to the vacuum chamber of the bonding module 1 via a
conduit or vacuum manifold having a control valve 4. Similarly a
vacuum can be provided in the loadlock module 2 by another vacuum
pump 5 that is connect by conduit or vacuum manifold having another
control valve 6 to the loadlock module 2. Moreover, the loadlock
module 2 comprises a first gate 7 that is opened when a wafer is
transferred from the loadlock module 2 to the bonding module 1 and
a second gate 8 that is opened when a wafer is transferred by a
robot to the loadlock module 2 from outside the bonding and
loadlock modules.
[0041] The loadlock module 2 may be configured as a one-wafer
transfer module providing one single wafer at the same time to the
bonding module 1 or may include a multi wafer storing systems for
receiving multiple wafers via the second gate 8 from an external
environment and storing the same and, then, providing these
multiple wafers to the bonding module 1 at the same time.
[0042] According to the present invention after one or more wafers
have been loaded into the loadlock module 2 and the second gate 8
has been closed (the first gate 7 is kept closed during the loading
procedure), the loadlock module 2 is evacuated to some
predetermined pressure. Evacuation may be provided by the pumping
device 5 at a rate of between 2.5 and 1,000 m.sup.3/h, in
particular, more than 500 m.sup.3/h. The loadlock module 2 is
evacuated for example, to a pressure of about 5 mbars to some
hundred mbar or to below atmospheric pressure (where 1 bar=100,000
Pa=0.987 atm). The vacuum chamber of the bonding module 1 is, for
example, evacuated to a pressure in the range of 0.01 mbars to 10
mbars, or more preferably, 0.1 mbars to 5 mbars.
[0043] After evacuation, the one or more wafers are transferred
upon opening of the first gate 7 to the vacuum chamber of the
bonding module 1 that was already evacuated by the first pumping
device 3, such as a multi-stage rotary vane pump. Since during this
transfer of the one or more wafers from the loadlock module 2 to
the bonding module 1 the bonding module is not exposed to
atmospheric pressure, only a relatively slight adjustment of the
pressure of the vacuum chamber of the bonding module 1 is necessary
if at all after completion of the wafer transfer and closing of the
first gate 7. Thus, the throughput can significantly be increased,
since the bonding module 1 does not cycle completely between
atmospheric pressure and the operating vacuum pressure.
[0044] It is noted that the throughput can be even further
increased when another loadlock module 2' is provided, for example,
on the left-hand-side of the bonding module 1 of FIG. 1 and
connected to the bonding module 1 by another gate 7' to receive the
already bonded wafers. The loadlock module 2' can be used to output
the bonded wafers from the bonding module 1 to the loadlock module
2', where the bonded wafers can then be passed to the external
environment through another gate 8', while the bonding module 1 and
loadlock module 2 remain under vacuum. In this case, the other
loadlock module 2' is evacuated before transfer of the bonded
wafers from the bonding module 1.
[0045] In FIG. 2, an example of the bonding module 1 according to
the present invention is illustrated. The bonding module comprises
a vacuum chamber 1 and is connected to a pumping device (not shown)
as described with reference to FIG. 1. In addition, the bonding
module comprises an optical system 9 that allows determining the
exact position of alignment marks on the surfaces of the wafers to
be bonded in the bonding module 1. The optical system 9 is only
necessary if the two wafers need to be perfectly aligned. This is
the case when the two wafers present micro-components. The term
micro-components is meant to mean elements that result from
technical steps carried out on or in the layers that must be
positioned with precision. Thus, the micro-components may be active
or passive components, a mere contact point, or interconnections,
like copper contact and interconnects. In the case of the process
comprising only that of bonding one wafer with micro-components
onto a virgin support wafer the alignment step may be skipped, and
thus provision of the optical system 9 are not necessary.
[0046] Furthermore, the bonding module 1 is provided with a first
bonding chuck 10 and a second bonding chuck 11 that clamp a first
wafer 12 and a second wafer 13, respectively. The bonding chucks 10
and 11 may be made of metal or ceramics to maintain planarity of
the wafers 12 and 13. Whereas in FIG. 2 the bonding chucks 10 and
11 are shown to hold the wafers 12 and 13 with their horizontally
orientated main surfaces face-to-face, the bonding chucks 10 and 11
may advantageously be arranged to hold the wafers 12 and 13 with
their vertically orientated main surfaces face-to-face. In this
case, deformation of the wafers due to their own weight can be
avoided.
[0047] In the example shown in FIG. 2, the optical system 9 is
electrically coupled to a control unit 14 that is computing the
displacement of the bonding chucks 11 and 12 in the plane of
alignment and in rotation in order to perfectly align the two
wafers 12 and 13. Moreover, the control unit 14 controls movement
of the bonding chucks 11 and 12 towards each other until the wafers
12 and 13 come into contact for molecular bonding.
[0048] FIG. 3 illustrates an example of a manufacturing system 20
comprising the apparatus illustrated in FIG. 1. In particular, the
manufacturing system 20 comprises a bonding module 1, such as for
example, the bonding module 1 shown in FIG. 2, and two loadlock
modules 2 and 2'. The manufacturing system 20 includes a load port
21 for introducing wafers into the manufacturing system 20. A robot
device 22 is configured and dimensioned to manipulate and transfer
the wafers from the load port 21 to any individual module of the
manufacturing system 20, and also from one module to the other. The
robot is moving along a robot moving area that may be predetermined
(indicated by dashed lines), to enable the transfer of the wafer
from one place or module to another.
[0049] In addition, the manufacturing system 20 comprises at least
one plasma station 23 for activating one or two main surfaces of
the wafers introduced into the manufacturing system 20. In order to
minimize the surface preparation time, a second plasma station
could be added, if the wafer processing requires that both main
surfaces of the wafers need to be activated. Alternatively, the
same plasma station 23 can be used to treat both main surfaces. A
first cleaning station 24 is provided to clean a bonding main
surface of a first wafer and a second cleaning station 25 is
provided to clean a bonding main surface of a second wafer.
[0050] The manufacturing system 20, further comprises a control
unit (not shown in FIG. 3) for controlling the robot device 22 for
transporting wafers in the manufacturing system 20. For example,
the control unit may control the robot means or device 22 to pick a
first wafer from load port 21 and transport it to plasma station
23; pick a second wafer from load port 21 and transport it to
cleaning station 25; pick the first wafer from plasma station 23
and transport it to cleaning station 24; pick the second wafer from
cleaning station 25 and transport it to loadlock module 2'; pick
the first wafer from cleaning station 24 and transport it to
loadlock module 2; and pick bonded first and second wafers after
they have been processed in the bonding module 1 from the loadlock
module 2 or 2' and transport it to the load port 21.
[0051] All previously discussed embodiments are not intended as
limitations but serve as examples illustrating features and
advantages of the invention. It is to be understood that some or
all of the above described features can also be combined in
different ways.
* * * * *