U.S. patent application number 13/970447 was filed with the patent office on 2014-02-27 for dual wafer spin coating.
This patent application is currently assigned to Tessera, Inc.. The applicant listed for this patent is Tessera, Inc.. Invention is credited to Belgacem Haba, Craig Mitchell, Ilyas Mohammed, Vage Oganesian, Piyush Savalia.
Application Number | 20140057370 13/970447 |
Document ID | / |
Family ID | 46232792 |
Filed Date | 2014-02-27 |
United States Patent
Application |
20140057370 |
Kind Code |
A1 |
Oganesian; Vage ; et
al. |
February 27, 2014 |
DUAL WAFER SPIN COATING
Abstract
A method of bonding a first substrate and a second substrate
includes the steps of rotating first substrate with an adhesive
mass thereon, and second substrate contacting the mass and
overlying the first substrate, controlling a vertical height of a
heated control platen spaced apart from and not contacting the
second substrate so as to control a temperature of the adhesive
mass, so as to at least one of bond the first and second substrates
in alignment with one another, or achieve a sufficiently planar
adhesive interface between the first and second substrates.
Inventors: |
Oganesian; Vage; (Palo Alto,
CA) ; Haba; Belgacem; (Saratoga, CA) ;
Mohammed; Ilyas; (Santa Clara, CA) ; Savalia;
Piyush; (San Jose, CA) ; Mitchell; Craig; (San
Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tessera, Inc. |
San Jose |
CA |
US |
|
|
Assignee: |
Tessera, Inc.
San Jose
CA
|
Family ID: |
46232792 |
Appl. No.: |
13/970447 |
Filed: |
August 19, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12974611 |
Dec 21, 2010 |
8512491 |
|
|
13970447 |
|
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Current U.S.
Class: |
438/7 |
Current CPC
Class: |
H01L 21/67092 20130101;
H01L 22/12 20130101 |
Class at
Publication: |
438/7 |
International
Class: |
H01L 21/66 20060101
H01L021/66 |
Claims
1. A method of bonding a first substrate and a second substrate,
comprising: while rotating first substrate with an adhesive mass
thereon, and second substrate contacting the mass and overlying the
first substrate, controlling temperature of the adhesive mass, so
as to at least one of: bond the first and second substrates in
alignment with one another, or achieve a sufficiently planar
adhesive interface between the first and second substrates.
2. The method as claimed in claim 1, wherein the method further
comprises: receiving a first signal representative of a position of
second substrate while rotating the first substrate with the
adhesive mass thereon; using the first signal to generate a control
signal; and using the control signal to adjust the vertical height
of the second substrate.
3. The method as claimed in claim 2, wherein the step of using the
control signal is performed so as to bond the first and second
substrates in alignment with one another.
4. The method as claimed in claim 2, wherein the step of using the
control signal is performed so as to achieve a sufficiently planar
adhesive interface between the first and second substrates.
5. The method of claim 2, wherein the first signal is
representative of a misalignment of the second substrate in a
direction parallel to the top surface of the first substrate.
6. The method of claim 2, wherein the step of receiving a first
signal includes generating the first signal by detecting positions
of fiducials of the first and second rotating substrates.
7. The method of claim 2, wherein the step of receiving a first
signal includes generating the first signal by detecting positions
of notches of the first and second rotating substrates.
8-13. (canceled)
14. The method as claimed in claim 1, wherein the step of
controlling the temperature includes changing the vertical height
of a heated control platen while rotating the first and second
substrates with the adhesive mass therebetween.
15. The method as claimed in claim 1, further comprising admitting
a gas through an inlet during said rotating.
16. The method as claimed in claim 1, further comprising evacuating
a volume surrounding said first and second substrates at least one
of prior to or during said rotating.
17. A method of bonding substrates, comprising: while rotating a
first substrate with an adhesive mass thereon, and a second
substrate contacting the mass and overlying the first substrate,
receiving a first signal representative of a difference in relative
position of the first and second substrates; using the first signal
to generate a control signal and using the control signal to
control a movement of a control platen adjacent to but spaced apart
from the second substrate so as to control a temperature of the
adhesive mass and at least one of: bond the first and second
substrates in alignment with one another, or achieve a sufficiently
planar adhesive interface between the first and second
substrates.
18. The method of claim 17, wherein the movement includes a
rotational movement.
19. The method of claim 17, wherein the movement includes a
vertical movement.
20. (canceled)
21. (canceled)
22. The method of claim 17, wherein the control signal controls a
rate of rotation of the control platen.
23. The method of claim 17, wherein the first signal is
representative of a difference in relative position between the
first and second substrates.
24. The method of claim 17, wherein the first signal is
representative of rotational misalignment between the first and
second substrates.
25. The method of claim 17, wherein the first signal is
representative of a misalignment of the first substrate in a
direction parallel to the top surface of the second substrate.
26. The method of claim 23, wherein the step of receiving a first
signal includes generating the first signal by detecting positions
of fiducials of the first and second rotating substrates.
27. The method of claim 23, wherein the step of receiving a first
signal includes generating the first signal by detecting positions
of notches of the first and second rotating substrates. wherein
notches in the first substrate and second substrate are used to
determine the relative position between the first and second
substrates.
28. (canceled)
29. (canceled)
30. A method of bonding a first wafer and a second wafer,
comprising: rotating the first wafer with an adhesive mass thereon,
contacting the second wafer with the adhesive mass; adjusting the
position of second wafer relative to the first wafer so as to
control a movement of air or gas between second wafer and a control
platen, so as to at least one of: bond the first and second
substrates in alignment with one another, or achieve a sufficiently
planar adhesive interface between the first and second wafers.
31. (canceled)
32. (canceled)
Description
BACKGROUND OF THE INVENTION
[0001] In the fabrication of microelectronic assemblies, it may be
necessary to bond two or more substrates such as semiconductor
wafers together. Some existing methods of bonding require the
application of a bonding material to one or both substrates, such
as wafers, then heating the bonding material to cause it to flow,
and eventually curing the bonding material to form a bond. Various
methods exist for performing each of these steps. Nonetheless,
despite all of the effort which has been devoted to improving upon
bonding techniques for two or more substrates, there are unmet
needs for further improvements.
SUMMARY OF THE INVENTION
[0002] The presently disclosed methods are directed to improving
upon techniques for bonding two or more substrates. Among others,
the present invention discloses methods of bonding at least two
substrates that can help to achieve better alignment between two
substrates, as well as provide for a sufficiently planar bonding
material interface between the first and second substrates.
[0003] In one aspect of the present invention, a method of bonding
a first substrate and a second substrate is disclosed that includes
the steps of while rotating a first substrate with an adhesive mass
thereon, and second substrate contacting the mass and overlying the
first substrate, controlling a vertical height of a heated control
platen spaced apart from and not contacting the second substrate so
as to control a temperature of the adhesive mass, so as to at least
one of bond the first and second substrates in alignment with one
another, or achieve a sufficiently planar adhesive interface
between the first and second substrates.
[0004] In one embodiment of this aspect of the invention, the
method further includes receiving a first signal representative of
a position of second substrate while rotating the first substrate
with the adhesive mass thereon; using the first signal to generate
a control signal; and using the control signal to adjust the
vertical height of the second substrate.
[0005] In another embodiment of this aspect of the invention, the
step of using the control signal is performed so as to bond the
first and second substrates in alignment with one another.
[0006] In another embodiment of this aspect of the invention, the
step of using the control signal is performed so as to achieve a
sufficiently planar adhesive interface between the first and second
substrates.
[0007] In another embodiment of this aspect of the invention, the
first signal is representative of a misalignment of the second
substrate in a direction parallel to the top surface of the first
substrate.
[0008] In another embodiment of this aspect of the invention, the
step of receiving a first signal includes generating the first
signal by detecting positions of fiducials of the first and second
rotating substrates.
[0009] In another embodiment of this aspect of the invention, the
step of receiving a first signal includes generating the first
signal by detecting positions of notches of the first and second
rotating substrates.
[0010] In another embodiment of this aspect of the invention, the
heated control platen rotates.
[0011] In another embodiment of this aspect of the invention, the
method further includes controlling the rotation of the heated
control platen so as to influence the movement of the second
wafer.
[0012] In another embodiment of this aspect of the invention, the
step of controlling the rotation of the heated control platen
adjusts a position of the second wafer in at least one of a
direction parallel to or a direction transverse to the surface of
the first wafer.
[0013] In another embodiment of this aspect of the invention, the
heated control platen has a central portion overlying the second
substrate and a wall extending from the central portion so as to
create a chamber.
[0014] In another embodiment of this aspect of the invention, the
wall extends adjacent the edge of the second substrate.
[0015] In another embodiment of this aspect of the invention, the
wall extends adjacent the edge of the first substrate.
[0016] In another embodiment of this aspect of the invention, the
step of controlling the vertical height of the heated control
platen includes changing the vertical height of the heated control
platen while rotating the first and second substrates with the
bonding material therebetween.
[0017] In another embodiment of this aspect of the invention, the
method further includes admitting a gas through an inlet during
said rotating.
[0018] In another embodiment of this aspect of the invention, the
method further includes evacuating a volume surrounding said first
and second substrates at least one of prior to or during said
rotating.
[0019] In another aspect of the present invention, a method of
bonding substrates includes the steps of while rotating a first
substrate with an adhesive mass thereon, and a second substrate
contacting the mass and overlying the first substrate, receiving a
first signal representative of a position of the second substrate;
using the first signal to generate a control signal and using the
control signal to control a movement of a control platen adjacent
to the second substrate so as to at least one of: bond the first
and second substrates in alignment with one another, or achieve a
sufficiently planar adhesive interface between the first and second
substrates.
[0020] In one embodiment of this aspect of the present invention,
the movement includes a rotational movement.
[0021] In another embodiment of this aspect of the invention, the
movement includes a vertical movement.
[0022] In another embodiment of this aspect of the invention, the
movement only includes a vertical movement.
[0023] In another embodiment of this aspect of the invention, the
control platen does not rotate.
[0024] In another embodiment of this aspect of the invention, the
control signal controls a rate of rotation of the control
platen.
[0025] In another embodiment of this aspect of the invention, the
first signal is representative of a difference in relative position
between the first and second substrates.
[0026] In another embodiment of this aspect of the invention, the
first signal is representative of rotational misalignment between
the first and second substrates.
[0027] In another embodiment of this aspect of the invention, the
first signal is representative of a misalignment of the first
substrate in a direction parallel to the top surface of the second
substrate.
[0028] In another embodiment of this aspect of the invention, the
step of receiving a first signal includes generating the first
signal by detecting positions of fiducials of the first and second
rotating substrates.
[0029] In another embodiment of this aspect of the invention, the
step of receiving a first signal includes generating the first
signal by detecting positions of notches of the first and second
rotating substrates, wherein notches in the first substrate and
second substrate are used to determine the relative position
between the first and second substrates.
[0030] In another embodiment of this aspect of the invention, the
step of using the control signal is performed so as to bond the
first and second substrates in alignment with one another.
[0031] In another embodiment of this aspect of the invention, the
step of using the control signal is performed so as to achieve a
sufficiently planar adhesive interface between the first and second
substrates.
[0032] In another aspect of the present invention, a method of
bonding a first wafer and a second wafer includes the steps of
while rotating first wafer with an adhesive mass thereon, and
second wafer contacting the mass and overlying the first substrate,
receiving a first signal representative of a position of second
wafer; using the first signal to generate a control signal, and
using the control signal to adjust the position of second wafer by
controlling a vertical height of a control platen adjacent to
second wafer so as to control a movement of air or gas between
second wafer and a control platen, so as to at least one of: bond
the first and second substrates in alignment with one another, or
achieve a sufficiently planar adhesive interface between the first
and second wafers.
[0033] In another embodiment of this aspect of the invention, the
step of using the control signal is performed so as to bond the
first and second wafers in alignment with one another.
[0034] In another embodiment of this aspect of the invention, the
step of using the control signal is performed so as to achieve a
sufficiently planar adhesive interface between the first and second
wafers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 (1(a)-1(h)) depicts a method of spin-coating in
accordance with an embodiment of the invention.
[0036] FIG. 2A depicts an alternate embodiment of the wafers shown
in FIG. 1.
[0037] FIG. 2B depicts an alternate embodiment of the wafers shown
in FIG. 1.
[0038] FIG. 3 depicts an alternate embodiment of a method of
spin-coating in accordance with an embodiment of the invention.
[0039] FIG. 4 depicts an alternate embodiment of a method of
spin-coating in accordance with an embodiment of the invention.
[0040] FIG. 5 depicts an alternate embodiment of a method of
spin-coating in accordance with an embodiment of the invention.
[0041] FIG. 6 depicts an alternate embodiment of a method of
spin-coating in accordance with an embodiment of the invention.
DETAILED DESCRIPTION
[0042] It is often necessary to bond two or more substrates
together. The inventors have determined that the spin coating
process is one process that can accomplish bonding of such
substrates together. During the spin coating process, a substrate,
e.g., a wafer, can be placed on a platen and a bonding material can
be deposited thereon. A second substrate can be stacked on top of
the bonding material. Subsequent rotation of the platen causes both
wafers to rotate and increasing the temperatures causes the bonding
material to be deposited across the surfaces of the wafers.
[0043] Through testing, the inventors have determined, however,
that use of the spin coating process presents several challenges.
During the bonding process, the first and second substrates are
subject to movement in six degrees of freedom: movement along the
x, y, and z axis, as well as rotation, pitch, and roll. Due to the
numerous degrees of freedom, it can be difficult to distribute the
bonding material evenly between surfaces of the substrates. Also,
particular challenges exist in achieving proper alignment of the
edges of the first and second substrates.
[0044] Distribution of the bonding material is dependent upon
temperature and the resulting viscosity of the bonding material. If
the bonding material does not flow properly, it becomes difficult
to evenly distribute the bonding material. This occurs when the
bonding material is too viscous to allow centrifugal force to
evenly distribute the bonding material across the surfaces of the
substrates.
[0045] Rotation of the first and second substrates relative to one
another during the spin-coating process can also present alignment
problems. The first substrate may rotate at a rate which is faster
or slower than the second substrate. Alternatively, the first and
second substrates may not rotate along the same axis if the first
and second substrates begin to move relative to one another. As a
result of the differing movements of the first and second
substrates, it can be difficult to perfectly align the first and
second wafers together.
[0046] Embodiments of the invention described herein can provide
improved ways of bonding substrates using the spin coating process
so as to achieve an at least substantially planar interface between
the substrates. In addition, substrates can be bonded together in a
manner which improves alignment of the substrates relative to one
another. For example, features such as conductive pads on
respective wafers can be aligned within alignment tolerances.
[0047] FIG. 1 represents a method of bonding at least two
substrates together in accordance with an exemplary embodiment of
the present invention. Substrates utilized in the methods described
herein typically have a coefficient of thermal expansion of less
than 10 parts per million/.degree. C. One or more of the substrates
may include a layer of monocrystalline semiconductor material, such
as silicon, gallium arsenide or other semiconductor material. Such
substrate can embody active circuit elements, i.e., electronic
devices such as transistors or diodes, which may be connected
together in the form of integrated circuits. One or more of the
substrates may be in the form of a wafer, such as an active device
wafer embodying active circuit elements or a "blank," e.g.,
unpatterned semiconductor or dielectric wafer. Alternatively, a
substrate may consist essentially of dielectric material.
[0048] Referring now to FIG. 1(a), a first substrate, such as first
wafer 10 is shown. First wafer 10 has a top surface 12 and a bottom
surface 8. First wafer 10 includes contacts 20 and active circuitry
22. Dicing lanes 23 extend along boundaries of individual chips of
the first wafer 10. Although not required, at least one notch 14
may be formed on first wafer 10. As shown, notch 14 may be formed
along at least a portion of an outer edge 16 of first wafer 10. In
this embodiment, notch 14 extends inwardly from an edge 16 of first
wafer 10 adjacent the bottom surface 8.
[0049] Turning now to FIG. 1(b), first wafer 10 may be placed onto
a first platen 26 of a spin coating machine or spinner (not shown)
(FIG. 1(e)). When positioned, the bottom surface 8 of first wafer
10 may overlie a major surface 28 of first platen 26. In this
embodiment, although not required, first platen 26 may be capable
of being heated to a desired temperature via a heating element (not
shown). The platen 26 can include or consist essentially of metal
or other thermally conductive material, although any suitable
material capable of conducting heat may be used.
[0050] As shown in FIG. 1(c), a bonding material 30 may be placed
or deposited on the top surface 12 of first wafer 10. The bonding
material 30 may be any type of material capable of providing a bond
between two substrates. For example, adhesive material, dielectric
material, or the like may be used. In one embodiment, an adhesive
polymeric material, such as epoxy, may be used.
[0051] Referring now to FIG. 1(d), a second substrate, such as
second wafer 40 may be provided. In another embodiment, second
wafer 40 may be a blank wafer. Second wafer may have a notch 44
extending inwardly from the outer edge 46 of second wafer 40. In
one embodiment, second wafer 40, like the first wafer 10, may
embody active circuit elements and have contacts exposed at a major
surface, e.g., bottom surface 38.
[0052] Turning now to FIG. 1(e), second wafer 40 may be positioned
to overlie the bonding material 30 and first wafer 10. As shown,
the bottom surface 38 of second wafer 40 contacts the bonding
material 30 and faces the top surface 12 of first wafer 10 above
the top surface 28 of first platen 26. Second wafer 40 will be
positioned a distance H2 from first wafer 10 that can be defined by
the height or thickness of the bonding material 30.
[0053] A second platen 50 may be positioned over first platen 26,
as well as the first and second wafers 10, 40. Second platen 50 may
be formed of metal, but any other material capable of conducting
heat may also be utilized. The second platen may have an outer
surface 52 and an inner surface 54. Unlike first platen 26, in one
embodiment, second platen 50 may include a central portion 56 with
a wall 58 extending circumferentially therefrom. In this
embodiment, the wall 58 extends at least as far as the bottom
surface 8 of first platen 26. The shape of first platen 26 helps to
create an area or environment within the interior of the wall 58.
The shape of second platen 50 can help to regulate the temperature
and/or airflow about the first wafer 10, second wafer 40 and
bonding material 30, during the spin-coating process, as discussed
in more detail below.
[0054] Referring now to FIG. 1(f), first platen 26 may be rotated
in a clockwise or counter-clockwise direction, thereby causing both
first wafer 10 and second wafer 40 to rotate. Second platen 50,
which in this embodiment operates as a control platen, may be
heated to increase the temperature of the environment within wall
58. When the temperature of the second platen 50 is increased, the
temperature of the bonding material 30 also increases, causing the
bonding material 30 to flow. Due to the rotation of the first and
second platens and the increased flowability of the bonding
material 30, centrifugal force can distribute the bonding material
30 between the top surface 12 of first wafer 10 and the bottom
surface 38 of second wafer 40.
[0055] As the bonding material 30 begins to flow, the height or
thickness of the bonding material 30 is reduced. When this happens,
the thickness or height H2' (FIG. 1(f)) of the bonding material 30
is less than the initial thickness or height H2 (FIG. 1(e)) of the
bonding material 30 prior to an increase in temperature of the
bonding material 30. As a result, the distance H1' (FIG. 1(f))
between the top surface of second wafer 40 and the inner surface 54
of second platen 50 is greater than the original distance H1 (FIG.
1(e)) between second platen 50 and second wafer 40.
[0056] Second platen 50 can be considered a control platen which
can be used to regulate the area or environment within its wall 58.
In this embodiment, second platen 50 helps to control temperature.
First, the second platen 50 may be heated or cooled when it is
desired to increase or decrease the temperature needed to increase
or decrease flowability and/or viscosity of the bonding material
30. Heating of the second platen can be accomplished by any one of
several ways, such as by heating the second platen 50 with a heat
cartridge in thermal communication therewith. Alternative methods
of heating may include resistive heating, use of thermoelectricity,
or other known methods. Second, the structure of the second platen
aids in achieving a desired temperature. Among other structural
improvements, because the wall 58 of the second platen encloses a
certain limited space or environment, it is easier to maintain that
space or environment at a desired temperature, as compared to
maintaining a specific temperature in a much larger space. Third,
as shown by the arrow A in FIG. 1(g), second platen 50 may be
capable of moving upward or downward. The ability of the heated
second platen 50 to move closer to and/or away from the first and
second wafers 10, 40, as well as the bonding material 30, allows
for better control over the temperature of the bonding material 30
and its viscosity during the bonding process. This is because the
heated second platen 50 can be brought closer to or further away
from the bonding material 30 to increase or decrease the
temperature of the bonding material 30.
[0057] As shown in FIG. 1(g), second platen 50 may be moved closer
to second wafer 40, such that the adjusted height or distance
A.sub.H1' between second platen 50 and the top surface 42 of second
wafer 40 is less than the initial height or distance H1 (FIG.
1(e)). The ability of second platen 50 to move or adjust relative
to the first and second wafers 10,40 aids in creating an
environment within the interior of second platen 50 which allows
for the bonding material 30 to reach or remain at a certain desired
temperature that allows for the uniform distribution of the bonding
material 30. In one embodiment, the temperature prior to bonding is
up to 50.degree. C. In one example in which it is desirable to
maintain the bonding material at a temperature of about 80.degree.
C., maintaining the temperature of the first and second wafers via
the second platen can help achieve this.
[0058] As previously discussed, during the spinning process, first
wafer 10, which is connected to the first platen 26, may sometimes
rotate at a slightly different rate than second wafer 40. For
example, the second wafer 40 may rotate at a slightly lower rate
than the first wafer 10 due, in part, to inertia and that the
bonding material 30, while uncured, permits the second wafer 40 to
slip relative to first wafer 10. As a result, the first and second
wafers 10,40 could become misaligned when bonded together. The
presence of notches on the wafer as described herein can permit
addressing misalignment of the first and second wafers 10,40 during
the bonding process.
[0059] In this embodiment, although not required, to ensure that
first wafer 10 and second wafer 40 are properly aligned with one
another, notches 14 on first wafer 10 and notches 44 on second
wafer 40 can be utilized. Notches 14,44 are visible from the edge
of the respective first and second wafers 10, 40. A secondary
device (not shown), such as a spectroscope, can be used to
determine whether the notches 14,44 are aligned with one another.
For example, if the spectroscope indicates that the notches 14,44
are not aligned, the operator may determine that it is necessary to
adjust second platen 50 in an upward or downward direction to
create a condition wherein notches 14,44 can be aligned. This
determination can be made by observing the effects of moving second
platen 50 upward or downward. For example, if it is necessary for
second wafer 40 to rotate at a greater speed, the platen may be
moved closer to the bonding material 30, so as to increase
flowability of the bonding material and minimize the amount of
resistance caused by the bonding material 30. Alternatively, it may
be desired to slow down the speed of rotation of second wafer 40,
in which case it may be desired to move second platen 50 further
away from the first and second wafers 10,40 so as to reduce the
temperature in the environment and the flowability of the bonding
material 30. In alternative embodiments, as discussed herein,
movement of the second platen 50 may be automatically adjusted by a
control system that will compensate for the needed changes in
temperature that will result in the desired flowability of the
bonding material 30.
[0060] Referring to FIG. 1(h), once the bonding material 30 has
been distributed across the surfaces of the first and second wafers
10,40, the bonding material 30 may be cured. Thereafter, the bonded
first and second wafers 10,40 may be removed from the spinner. As
shown, first wafer 10 and second wafer 40 are now bonded together
by the bonding material 30 interposed therebetween. The bonded
wafers may then be cut into individual units along the dicing lanes
23, each unit including a portion of each of the first and second
wafers 10,40.
[0061] Turning to FIGS. 2A and 2B, an alternative embodiment of
bonding is shown. It is to be appreciated that throughout the
description of FIGS. 2A and 2B, as well as throughout the
application, similar reference numerals will be used to indicate
similar elements. In this embodiment, instead of just one notch on
a wafer, any alternative form of notches or notch arrangements may
be utilized. In FIG. 2A, instead of only one notch on the wafer,
more than one notch may be included on a wafer. As shown, four
notches 214 may be dispersed along the outer edge 215 of the wafer
210. The notches may be similar in shape to the notches 14,44 shown
in FIGS. 1(a) and 1(d). Alternatively, as shown in FIG. 2B, there
may be two notches 214 which are triangular in shape. It is to be
appreciated that notches may be placed on the wafers 210 in any
manner, shape, or pattern desired.
[0062] Referring now to FIG. 3, an alternative embodiment of the
present invention is shown. In this embodiment, there is shown a
first platen 326, a bonding material 330 overlying the first wafer
310, a second wafer 340 overlying the bonding material 330, and a
second platen 350 that overlies first wafer 310, bonding material
330, and second wafer 340. This embodiment is similar to FIG. 1(g),
except that a separate control system 391 may be utilized to
automatically determine whether it is necessary for second platen
350 to move upward or downward and/or whether to increase the
temperature of the second platen 350. As shown, the control system
391 may include a detecting unit 392 and an adjustment unit 394.
The detecting unit 392 may include sensors 390 capable of detecting
and determining the position of the notches 314,344. The adjustment
unit can then determine whether the notches 314,344 are aligned
with one another and/or how much misalignment exists between the
notch 314 of the first wafer 310 and the notch 344 of the second
wafer 340. Once the detecting unit 392 detects the positions of the
first and second wafers, the detecting unit 392 will send one or
more signals to the adjustment unit. The adjustment unit can then
determine whether the notches 314,344 are aligned with one another
and/or any offset of the notches 314,344 relative to one another.
The adjustment unit 394 will then determine whether it is necessary
for the second platen 350 to be moved in an upward or downward
direction. For example, if it is determined that the notches
314,340 are not aligned, the adjustment unit 394 may then make a
determination that it is necessary to increase the temperature of
the environment to increase the flowability of the bonding material
30. To do so, the adjustment unit can provide a control signal
causing a mechanism (not shown) coupled to the second platen 350 to
cause the second control platen 350 to move downward toward the
second wafer 340, thereby increasing the temperature of the bonding
material 330 and causing the bonding material 330 to flow more
readily. In contrast, if the notches 314,344 are aligned, the
adjustment unit will make a determination that it is not necessary
to move the second platen 350 at all.
[0063] The adjustment unit 394 may also be capable of adjusting the
second platen 350 to regulate the temperature within the
environment contained within second platen 350 and the resulting
flowability of the bonding material 330, as opposed to or in
addition to ensuring proper alignment of the notches 314,344. In
one embodiment, at least one temperature sensor 393 may be
positioned on the second platen 350. The temperature sensor 393 may
be capable of determining the temperature of the second wafer
340.
[0064] In one embodiment, the control system 391 may be operated so
that the temperature of the second wafer 340 is maintained at or
close to the temperature of the first wafer 310 throughout the
bonding process. In this way, increases or decreases in the
temperature of the first wafer 310 are followed by the second wafer
50 340, so as to maintain a flowability and desired characteristics
of the bonding material.
[0065] In another embodiment, the control system 391 may be
operated so that the temperature of the second wafer 340 is
maintained in accordance with a predetermined profile over time. In
such embodiment, the system might control the second wafer 340
temperature so as to match the temperature called for by the
predetermined profile at different points in time. However, in such
a case, control over the second wafer 340 temperature might not be
in direct relation to the temperature of the bottom wafer.
[0066] During operation, when it is determined that the temperature
of the second wafer 340 needs to change, the adjustment unit 394
can determine whether the position of the control platen may need
to move closer or farther from the second wafer 340 and can
determine whether the temperature of the second platen 350 should
increase or decrease (e.g., by control of a heating element
attached to second platen 350).
[0067] Referring now to FIG. 4, another alternative embodiment is
shown. This embodiment is similar to FIG. 3, except that here, as
indicated by the arrows, both first platen 426 and second platen
450 rotate. Either or both first platen 426 and second platen 450
may be heated. As previously discussed, alignment of the second
wafer 440 and first wafer 410 will be affected by the rotation rate
of the second wafer 440 relative to the first wafer 410. In this
embodiment, rotation of the second wafer 440 can be controlled by
movement of second platen 450 based upon principles of
aerodynamics. The rate of rotation of second platen 450 relative to
the second wafer 440 can cause the second wafer 440 to accelerate
or decelerate. For example, if second platen 450 is rotating at a
lower speed than second wafer 440 or not rotating and is moved
toward the second wafer 440, such that the distance H1 between
second platen 450 and second wafer 440 is reduced, the rate of
rotation of the second wafer 440 decelerates. However, if the
second platen is rotating faster than the second wafer, its motion
can influence the second wafer's motion and cause it to rotate
faster than its current speed. Other combinations of rotational and
vertical movement are possible. For example, moving the second
platen 450 to a distance further away from the second wafer 440 may
have the effect of reducing the influence of the first platen's 426
rotation on the rotation of the second wafer. Therefore, moving the
second platen 450 further away when the second platen 450 is
rotating more slowly than the second wafer 340 can cause the
rotation of the second 340 wafer to accelerate.
[0068] A control system 491 may be used to automatically adjust a
position or temperature of the second platen 450, or both position
and temperature. The control system 491 may include a detecting
unit 492 and an adjustment unit 494. A detecting unit 492 can
determine the relative rate of rotation of the second wafer 440
relative to the first wafer 410. If the rate of rotation of the
second wafer 440 relative to the first wafer 410 is not the same,
the detection unit 492 can send a signal to the adjustment unit
494, causing an adjustment in motion or position of the second
platen 450. If the rate of rotation of the second wafer 440 needs
to be adjusted, the adjustment unit 494 can send a control signal
to second platen 450 to cause the second platen 450 to rotate
faster or more slowly, to move upward or downward. Such movement
will accelerate or decelerate the rotation of the second wafer 440.
In contrast, if the rate of rotation of the second wafer 440 needs
to be decreased, the adjustment unit can send a control signal to
second platen 450 to move second platen 450 downward or closer to
the second wafer 440. Such movement will decelerate rotation of the
second wafer 440.
[0069] Referring to FIG. 5, another alternative embodiment of FIG.
3 is shown. Like the embodiment of FIG. 3, only first platen 526
rotates. Second platen 550 is stationary, but includes openings
596, 598. The opening 596 may be connected to a source of gas which
can enter through the opening to adjust the volume of gas adjacent
or surrounding the wafers 510,540. The opening 598 may be connected
to a pump which permits air or gas within the volume defined by
second platen to be withdrawn. This allows for an alternate form of
aerodynamic control over spinning of the second wafer 540. Instead
of rotating second platen 550, as in the previous embodiment, the
amount of air within the area defined by second platen 550 can be
regulated. Thus, when it is desired to adjust the speed of rotation
of the second wafer 540 relative to the first wafer, air or gas can
be admitted or withdrawn through the openings 596, 598.
Additionally, the distance H1 between the second platen 550 and the
second wafer 540 can be adjusted to further increase or decrease
the rotation of the second wafers 40.
[0070] Referring now to FIG. 6, another embodiment of the present
invention is shown. Here, once the bonding material 630 has been
completely cured or partially cured, second bonding material 630
may be deposited on the top surface of the second wafer.
Thereafter, a third wafer 640 may be provided and positioned to
overlie the bonding material 630, the first and second wafers
610,640, and the second bonding material 630. Changing the
viscosity of the bonding material 630 may then be initiated using
any of the aforementioned processes alone or in combination with
one another. In one example, only first platen 626 may rotate.
Second platen 650 may be used to control temperature and rotation
of the third wafer 640 based upon the distance of the inner surface
654 of second platen 650 relative to the top surface 642 of the
third wafer 640.
[0071] As in the previous embodiments, the second platen 650 may be
controlled by a control system, that may include a detecting unit
692 and an adjustment unit 694. The detecting unit 692 may include
sensors 690A, 690B, 690C which are capable of detecting the
position of the notches 614, 644, 644'. Additionally, at least one
temperature sensor 692 may be positioned on the second platen 650
that is capable of determining the temperature of the second wafer
640 and/or the volume adjacent to or surrounding the wafers
610,640,640' and/or the specific temperature of the bonding
material 630,630'. Once the detecting unit 692 makes a
determination regarding temperature and/or alignment of the wafers,
the detecting unit 692 will send a signal to the adjustment unit
694. The adjustment unit 694 will then determine what adjustment to
make in temperature and/or alignment of first, second, and third
wafers 610, 640, 640'. The adjustment unit 694 will then send a
control signal to the second platen 650 which may cause the control
platen to move upward or downward relative to wafer 640'.
Additionally, the control signal may require increasing or
decreasing the heat applied to the second platen 650.
[0072] Although the invention herein has been described with
reference to particular embodiments, it is to be understood that
these embodiments are merely illustrative of the principles and
applications of the present invention. It is therefore to be
understood that numerous modifications may be made to the
illustrative embodiments and that other arrangements may be devised
without departing from the spirit and scope of the present
invention as defined by the appended claims.
* * * * *