U.S. patent application number 12/975521 was filed with the patent office on 2012-02-16 for automated thermal slide debonder.
This patent application is currently assigned to SUSS MICROTEC INC. Invention is credited to JAMES HERMANOWSKI.
Application Number | 20120037307 12/975521 |
Document ID | / |
Family ID | 44149429 |
Filed Date | 2012-02-16 |
United States Patent
Application |
20120037307 |
Kind Code |
A9 |
HERMANOWSKI; JAMES |
February 16, 2012 |
AUTOMATED THERMAL SLIDE DEBONDER
Abstract
An improved apparatus for debonding temporary bonded wafers
includes a debonder, a cleaning module and a taping module. A
vacuum chuck is used in the debonder for holding the debonded
thinned wafer and remains with the thinned debonded wafer during
the follow up processes steps of cleaning and mounting onto a
dicing tape. In one embodiment the debonded thinned wafer remains
onto the vacuum chuck and is moved with the vacuum chuck into the
cleaning module and then the taping module. In another embodiment
the debonded thinned wafer remains onto the vacuum chuck and first
the cleaning module moves over the thinned wafer to clean the wafer
and then the taping module moves over the thinned wafer to mount a
dicing tape onto the wafer.
Inventors: |
HERMANOWSKI; JAMES;
(WATERBURY, VT) |
Assignee: |
SUSS MICROTEC INC
WATERBURY
VT
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20110146901 A1 |
June 23, 2011 |
|
|
Family ID: |
44149429 |
Appl. No.: |
12/975521 |
Filed: |
December 22, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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61289634 |
Dec 23, 2009 |
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Current U.S.
Class: |
156/249 ;
156/499; 156/536 |
Current CPC
Class: |
H01L 21/67132 20130101;
H01L 21/6838 20130101; H01L 2221/68331 20130101; H01L 21/6719
20130101; H01L 21/67207 20130101; Y10T 156/15 20150115; Y10T
156/1944 20150115; H01L 21/6836 20130101; H01L 2221/68318 20130101;
H01L 2924/30105 20130101; H01L 21/67748 20130101; H01L 21/67745
20130101; H01L 21/68742 20130101; Y10T 156/1132 20150115 |
Class at
Publication: |
156/249 ;
156/536; 156/499 |
International
Class: |
B32B 38/10 20060101
B32B038/10 |
Claims
1. An apparatus for processing a temporary bonded wafer pair
comprising a device wafer and a carrier wafer, said apparatus
comprising: a debonder for debonding the device wafer from the
carrier wafer; a cleaning module for cleaning the debonded device
wafer; a taping module for applying a tape onto the debonded device
wafer; a vacuum chuck wherein said vacuum chuck is used in the
debonder during the debonding for holding the device wafer and
comprises means for holding the debonded device wafer; and means
for moving the vacuum chuck with the debonded device wafer into and
out of the cleaning module and into and out of the taping
module.
2. The apparatus of claim 1 wherein said debonder comprises a top
chuck assembly, a bottom chuck assembly, a static gantry supporting
the top chuck assembly, an X-axis carriage drive supporting the
bottom chuck assembly and an X-axis drive control configured to
drive horizontally the X-axis carriage drive and the bottom chuck
assembly from a loading zone to a process zone under the top chuck
assembly and from the process zone back to the loading zone, and
wherein said bottom chuck assembly comprises said vacuum chuck.
3. The apparatus of claim 2 wherein said top chuck assembly
comprises: a top support chuck bolted to the static gantry; a
heater support plate in contact with the bottom surface of the top
support chuck; said heater being in contact with the bottom surface
of the heater support plate; a top wafer plate in contact with the
heater; a Z-axis drive for moving the top wafer plate in the
Z-direction and placing the top wafer plate in contact with the
unbonded surface of the carrier wafer; and a plate leveling system
for leveling the top wafer plate and for providing wedge error
compensation of the top wafer plate.
4. The apparatus of claim 2 further comprising a lift pin assembly
for raising and lowering said wafer pair onto the bottom chuck
assembly.
5. The apparatus of claim 2 wherein said bonder further comprises a
base plate supporting the X-axis carriage drive and the static
gantry and wherein said base plate comprises one of a honeycomb
structure with vibration isolation supports or a granite plate.
6. The apparatus of claim 2 further comprising means for twisting
the device wafer at the same time said horizontal motion is
initiated.
7. The apparatus of claim 2 wherein said X-axis carriage drive
comprises an air bearing carriage drive.
8. The apparatus of claim 2 wherein said debonder further comprises
two parallel lateral carriage guidance tracks guiding said X-axis
carriage drive in its horizontal motion along the X-axis.
9. The apparatus of claim 2 wherein said carrier wafer is held by
said top chuck assembly via vacuum pulling.
10. The apparatus of claim 3, wherein said plate leveling system
comprises three guide shafts connecting said heater to said top
support chuck and three pneumatically actuated split clamps.
11. The apparatus of claim 3, wherein said heater comprises two
independently controlled concentric heating zones configured to
heat wafers having a diameter of 200 or 300 millimeters,
respectively.
12. The apparatus of claim 1 further comprising: a bonder for
temporary bonding the wafer pair; and a wafer thinning module for
thinning the device wafer of the temporarily bonded wafer pair.
13. An apparatus for processing a temporary bonded wafer pair
comprising a device wafer and a carrier wafer, said apparatus
comprising; a debonder for debonding the device wafer from the
carrier wafer; a cleaning module for cleaning the debonded device
wafer, wherein the cleaning module comprises means for moving over
the debonded wafer in the debonder for cleaning the debonded wafer;
a taping module for applying a tape onto the debonded device wafer,
wherein the taping module comprises means for moving over the
debonded wafer in the debonder for applying the tape onto the
debonded wafer; and a vacuum chuck used in the debonder and
comprising means for holding the debonded device wafer during
debonding, cleaning and taping.
14. The apparatus of claim 13 wherein said debonder comprises a top
chuck assembly, a bottom chuck assembly, a static gantry supporting
the top chuck assembly, an X-axis carriage drive supporting the
bottom chuck assembly and an X-axis drive control configured to
drive horizontally the X-axis carriage drive and the bottom chuck
assembly from a loading zone to a process zone under the top chuck
assembly and from the process zone back to the loading zone, and
wherein said bottom chuck assembly comprises said vacuum chuck.
15. The apparatus of claim 14 wherein said top chuck assembly
comprises: a top support chuck bolted to the static gantry; a
heater support plate in contact with the bottom surface of the top
support chuck; said heater being in contact with the bottom surface
of the heater support plate; a top wafer plate in contact with the
heater; a Z-axis drive for moving the top wafer plate in the
Z-direction and placing the top wafer plate in contact with the
unbonded surface of the carrier wafer; and a plate leveling system
for leveling the top wafer plate and for providing wedge error
compensation of the top wafer plate.
16. The apparatus of claim 14 further comprising a lift pin
assembly for raising and lowering said wafer pair onto the bottom
chuck assembly.
17. The apparatus of claim 14 wherein said bonder further comprises
a base plate supporting the X-axis carriage drive and the static
gantry and wherein said base plate comprises one of a honeycomb
structure with vibration isolation supports or a granite plate.
18. The apparatus of claim 14 further comprising means for twisting
the device wafer at the same time said horizontal motion is
initiated.
19. The apparatus of claim 14 wherein said X-axis carriage drive
comprises an air bearing carriage drive.
20. The apparatus of claim 14 wherein said debonder further
comprises two parallel lateral carriage guidance tracks guiding
said X-axis carriage drive in its horizontal motion along the
X-axis.
21. The apparatus of claim 14 wherein said carrier wafer is held by
said top chuck assembly via vacuum pulling.
22. The apparatus of claim 15, wherein said plate leveling system
comprises three guide shafts connecting said heater to said top
support chuck and three pneumatically actuated split clamps.
23. The apparatus of claim 15, wherein said heater comprises two
independently controlled concentric heating zones configured to
heat wafers having a diameter of 200 or 300 millimeters,
respectively.
24. The apparatus of claim 13 further comprising: a bonder for
temporary bonding the wafer pair; and a wafer thinning module for
thinning the device wafer of the temporarily bonded wafer pair.
25. A method for debonding and processing two via an adhesive layer
temporary bonded wafers, comprising: providing a debonder
comprising a top chuck assembly, a bottom chuck assembly, a static
gantry supporting the top chuck assembly, an X-axis carriage drive
supporting the bottom chuck assembly and an X-axis drive control
configured to drive horizontally the X-axis carriage drive and the
bottom chuck assembly from a loading zone to a process zone under
the top chuck assembly and from the process zone back to the
loading zone, and wherein said bottom chuck assembly comprises a
vacuum chuck; loading a wafer pair comprising a carrier wafer
bonded to a device wafer via an adhesive layer upon said bottom
chuck assembly at the loading zone oriented so that the unbonded
surface of the device wafer is in contact with the bottom chuck
assembly; driving said X-axis carriage drive and said bottom chuck
assembly to the process zone under the top chuck assembly; placing
the unbonded surface of the carrier wafer in contact with the top
chuck assembly and holding said carrier wafer by said top chuck
assembly; heating said carrier wafer with a heater comprised in
said top chuck assembly to a temperature around or above said
adhesive layer's melting point; initiating horizontal motion of
said X-axis carriage drive along the X-axis by said X-axis drive
control while heat is applied to said carrier wafer and while said
carrier wafer is held by said top chuck assembly and said device
wafer is held by said bottom chuck assembly and thereby causing the
device wafer to separate and slide away from the carrier wafer;
moving said vacuum chuck with said debonded device wafer into a
cleaning module and removing any residual adhesive off said device
wafer; moving said vacuum chuck with said cleaned debonded device
wafer into a taping module and applying a tape onto a surface of
the debonded device wafer; and removing the taped debonded device
wafer from the vacuum chuck and placing it into a device wafer
cassette.
26. The method of claim 25 wherein said residual adhesive is
removed by using a solvent and applying spin cleaning
techniques.
27. The method of claim 25, wherein said top chuck assembly further
comprises: a top support chuck bolted to the static gantry; a
heater support plate in contact with the bottom surface of the top
support chuck; said heater being in contact with the bottom surface
of the heater support plate; a top wafer plate in contact with the
heater; a Z-axis drive for moving the top wafer plate in the
Z-direction and placing the top wafer plate in contact with the
unbonded surface of the carrier wafer; and a plate leveling system
for leveling the top wafer plate and for providing wedge error
compensation of the top wafer plate.
28. A method for debonding and processing two via an adhesive layer
temporary bonded wafers, comprising: providing a chamber comprising
a top chuck assembly, a bottom chuck assembly, an X-axis carriage
drive supporting the bottom chuck assembly and an X-axis drive
control configured to drive horizontally the X-axis carriage drive
and the bottom chuck assembly from a loading zone to a process zone
and from the process zone back to the loading zone and wherein said
bottom chuck assembly comprises a vacuum chuck; loading a wafer
pair comprising a carrier wafer bonded to a device wafer via an
adhesive layer upon said bottom chuck assembly at the loading zone
oriented so that the unbonded surface of the device wafer is in
contact with the bottom chuck assembly; driving said X-axis
carriage drive and said bottom chuck assembly to the process zone
and placing said the top chuck assembly on top of said bottom chuck
assembly; placing the unbonded surface of the carrier wafer in
contact with the top chuck assembly and holding said carrier wafer
by said top chuck assembly; heating said carrier wafer with a
heater comprised in said top chuck assembly to a temperature above
said adhesive layer's melting point; initiating horizontal motion
of said X-axis carriage drive along the X-axis by said X-axis drive
control while heat is applied to said carrier wafer and while said
carrier wafer is held by said top chuck assembly and said device
wafer is held by said vacuum chuck and thereby causing the device
wafer to debond and slide away from the carrier wafer; moving said
top chuck assembly with the debonded carrier wafer away from the
process zone; moving a cleaning module into the chamber over said
debonded device wafer and removing any residual adhesive off said
device wafer; moving said cleaning module out of the chamber after
any residual adhesive is removed off said device wafer; moving a
taping module into the chamber over said debonded and cleaned
device wafer and applying a tape to a surface of the debonded
device wafer; and removing the taped debonded device wafer from the
bottom chuck assembly and placing it into a device wafer
cassette.
29. The method of claim 28 wherein said residual adhesive is
removed by using a solvent and applying spin cleaning
techniques.
30. The method of claim 28, wherein said top chuck assembly further
comprises: a top support chuck bolted to the static gantry; a
heater support plate in contact with the bottom surface of the top
support chuck; said heater being in contact with the bottom surface
of the heater support plate; a top wafer plate in contact with the
heater; a Z-axis drive for moving the top wafer plate in the
Z-direction and placing the top wafer plate in contact with the
unbonded surface of the carrier wafer; and a plate leveling system
for leveling the top wafer plate and for providing wedge error
compensation of the top wafer plate.
Description
CROSS REFERENCE TO RELATED CO-PENDING APPLICATIONS
[0001] This application claims the benefit of U.S. provisional
application Ser. No. 61/289,634 filed Dec. 23, 2009 and entitled
"AUTOMATED THERMAL SLIDE DEBONDER", the contents of which are
expressly incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to an apparatus for temporary
semiconductor wafer bonding and debonding, and more particularly to
an industrial-scale apparatus for temporary wafer bonding and
debonding that comprises an automated thermal slide debonder.
BACKGROUND OF THE INVENTION
[0003] Several semiconductor wafer processes include wafer thinning
steps. In some applications the wafers are thinned down to a
thickness of less than 100 micrometers for the fabrication of
integrated circuit (IC) devices. Thin wafers have the advantages of
improved heat removal and better electrical operation of the
fabricated IC devices. In one example, GaAs wafers are thinned down
to 25 micrometers to fabricate power CMOS devices with improved
heat removal. Wafer thinning also contributes to a reduction of the
device capacitance and to an increase of its impedance, both of
which result in an overall size reduction of the fabricated device.
In other applications, wafer thinning is used for 3D-Integration
bonding and for fabricating through wafer vias.
[0004] Wafer thinning is usually performed via back-grinding and/or
chemical mechanical polishing (CMP). CMP involves bringing the
wafer surface into contact with a hard and flat rotating horizontal
platter in the presence of a liquid slurry. The slurry usually
contains abrasive powders, such as diamond or silicon carbide,
along with chemical etchants such as ammonia, fluoride, or
combinations thereof. The abrasives cause substrate thinning, while
the etchants polish the substrate surface at the submicron level.
The wafer is maintained in contact with the abrasives until a
certain amount of substrate has been removed in order to achieve a
targeted thickness.
[0005] For wafer thicknesses of over 200 micrometers, the wafer is
usually held in place with a fixture that utilizes a vacuum chuck
or some other means of mechanical attachment. However, for wafer
thicknesses of less than 200 micrometer and especially for wafers
of less than 100 micrometers, it becomes increasingly difficult to
mechanically hold the wafers and to maintain control of the
planarity and integrity of the wafers during thinning. In these
cases, it is actually common for wafers to develop microfractures
and to break during CMP.
[0006] An alternative to mechanical holding of the wafers during
thinning involves attaching a first surface of the device wafer
(i.e., wafer processed into a device) onto a carrier wafer and
thinning down the exposed opposite device wafer surface. The bond
between the carrier wafer and the device wafer is temporary and is
removed (i.e., debonded) upon completion of the thinning processing
steps.
[0007] Several temporary bonding techniques have been suggested
including using of adhesive compounds that are chemically dissolved
after processing or using of adhesive tapes or layers that are
thermally or via radiation decomposed after processing. Most of
these adhesive-based temporary bonding techniques are followed by a
thermal slide debonding process where the device wafer and the
carrier wafer are held by vacuum chucks while heat is applied to
the bonded wafer pair and the wafers slide apart from each other.
In the current thermal slide debonding process the separated
thinned device wafer is held via a secondary support mechanism for
further processing. This secondary support mechanism usually adds
cost and complications to the processing equipment. It is desirable
to reduce the added cost and complications.
SUMMARY OF THE INVENTION
[0008] An improved apparatus for temporary wafer bonding and
debonding 100 includes a temporary bonder 110, a wafer thinning
station 120, a debonder 150, a cleaning module 170 and a taping
module 180, as shown in FIG. 2 and FIG. 3. Usually a secondary
carrier is used for moving the thinned wafer from the debonder 120
to the cleaning 170 and taping 180 modules. The present invention
eliminates the need for a secondary carrier by allowing a vacuum
chuck 152 used in the thermal slide debonder 150 to remain with the
thinned wafer 20 during the follow up processes steps of cleaning
(52) and mounting onto a dicing tape (53). In one embodiment the
thinned wafer 20 remains onto the vacuum chuck 152 and is moved
with the vacuum chuck 152 into the various process stations, shown
in FIG. 2. In another embodiment the thinned wafer 20 remains onto
the vacuum chuck 152 and the various process stations 170, 180 move
over the thinned wafer 20 to perform the various process steps,
shown in FIG. 3.
[0009] In general, in one aspect, the invention features an
apparatus for processing a temporary bonded wafer pair comprising a
device wafer and a carrier wafer. The apparatus includes a debonder
for debonding the device wafer from the carrier wafer after it has
been thinned, a cleaning module for cleaning the debonded thinned
device wafer, a taping module for applying a tape onto the debonded
thinned device wafer and a vacuum chuck. The vacuum chuck is used
in the debonder and includes means for holding the debonded thinned
device wafer. The apparatus also includes means for moving the
vacuum chuck with the debonded thinned device wafer into and out of
the cleaning module and into and out of the taping module.
[0010] In general, in another aspect, the invention features an
apparatus for processing a temporary bonded wafer pair comprising a
device wafer and a carrier wafer. The apparatus includes a debonder
for debonding the device wafer from the carrier wafer after it has
been thinned, a cleaning module for cleaning the debonded thinned
device wafer, a taping module, and a vacuum chuck used in the
debonder and including means for holding the debonded thinned
device wafer during debonding, cleaning and taping. The cleaning
module includes means for moving over the debonded thinned wafer in
the debonder for cleaning the debonded thinned wafer. The taping
module includes means for moving over the debonded thinned wafer in
the debonder for applying the tape onto the debonded thinned
wafer.
[0011] Implementations of these aspects of the invention may
include one or more of the following features. The debonder
includes a top chuck assembly, a bottom chuck assembly, a static
gantry supporting the top chuck assembly, an X-axis carriage drive
supporting the bottom chuck assembly and an X-axis drive control
configured to drive horizontally the X-axis carriage drive and the
bottom chuck assembly from a loading zone to a process zone under
the top chuck assembly and from the process zone back to the
loading zone, and the bottom chuck assembly includes the vacuum
chuck. The top chuck assembly includes a top support chuck bolted
to the static gantry, a heater support plate in contact with the
bottom surface of the top support chuck, a heater being in contact
with the bottom surface of the heater support plate, a top wafer
plate in contact with the heater, a Z-axis drive for moving the top
wafer plate in the Z-direction and placing the top wafer plate in
contact with the unbonded surface of the carrier wafer and a plate
leveling system for leveling the top wafer plate and for providing
wedge error compensation of the top wafer plate. The apparatus
further includes a lift pin assembly for raising and lowering the
wafer pair onto the bottom chuck assembly. The bonder further
includes a base plate supporting the X-axis carriage drive and the
static gantry and the base plate includes one of a honeycomb
structure with vibration isolation supports or a granite plate. The
apparatus further includes means for twisting the device wafer at
the same time the horizontal motion is initiated. The X-axis
carriage drive includes an air bearing carriage drive. The debonder
further includes two parallel lateral carriage guidance tracks
guiding the X-axis carriage drive in its horizontal motion along
the X-axis. The carrier wafer is held by the top chuck assembly via
vacuum pulling. The plate leveling system includes three guide
shafts connecting the heater to the top support chuck and three
pneumatically actuated split clamps. The heater includes two
independently controlled concentric heating zones configured to
heat wafers having a diameter of 200 or 300 millimeters,
respectively. The apparatus further includes a bonder for temporary
bonding the wafer pair and a wafer thinning module for thinning the
device wafer of the temporarily bonded wafer pair.
[0012] In general, in another aspect, the invention features a
method for debonding and processing two via an adhesive layer
temporary bonded wafers. The method includes the following steps.
First, providing a bonder comprising a top chuck assembly, a bottom
chuck assembly, a static gantry supporting the top chuck assembly,
an X-axis carriage drive supporting the bottom chuck assembly and
an X-axis drive control configured to drive horizontally the X-axis
carriage drive and the bottom chuck assembly from a loading zone to
a process zone under the top chuck assembly and from the process
zone back to the loading zone. The bottom chuck assembly comprises
a vacuum chuck. Next, loading a wafer pair comprising a carrier
wafer bonded to a device wafer via an adhesive layer upon the
bottom chuck assembly at the loading zone oriented so that the
unbonded surface of the device wafer is in contact with the bottom
chuck assembly. Next, driving the X-axis carriage drive and the
bottom chuck assembly to the process zone under the top chuck
assembly. Next, placing the unbonded surface of the carrier wafer
in contact with the top chuck assembly and holding the carrier
wafer by the top chuck assembly. Next, heating the carrier wafer
with a heater comprised in the top chuck assembly to a temperature
around or above the adhesive layer's melting point. Next,
initiating horizontal motion of the X-axis carriage drive along the
X-axis by the X-axis drive control while heat is applied to the
carrier wafer and while the carrier wafer is held by the top chuck
assembly and the device wafer is held by the bottom chuck assembly
and thereby causing the device wafer to separate and slide away
from the carrier wafer. Next, moving the vacuum chuck with the
debonded thinned device wafer into a cleaning station and removing
any residual adhesive off the device wafer and then moving the
vacuum chuck with the cleaned debonded thinned device wafer into a
taping module and applying a tape to a surface of the debonded
thinned device wafer. Finally, removing the taped debonded device
wafer from the vacuum chuck and placing it into a device wafer
cassette. The residual adhesive is removed by using a solvent and
applying spin cleaning techniques. The top chuck assembly further
includes a top support chuck bolted to the static gantry, a heater
support plate in contact with the bottom surface of the top support
chuck, a heater being in contact with the bottom surface of the
heater support plate, a top wafer plate in contact with the heater,
a Z-axis drive for moving the top wafer plate in the Z-direction
and placing the top wafer plate in contact with the unbonded
surface of the carrier wafer and a plate leveling system for
leveling the top wafer plate and for providing wedge error
compensation of the top wafer plate.
[0013] In general, in another aspect, the invention features a
method for debonding and processing two via an adhesive layer
temporary bonded wafers. The method includes the following steps.
First, providing a chamber comprising a top chuck assembly, a
bottom chuck assembly, an X-axis carriage drive supporting the
bottom chuck assembly and an X-axis drive control configured to
drive horizontally the X-axis carriage drive and the bottom chuck
assembly from a loading zone to a process zone and from the process
zone back to the loading zone. Next, loading a wafer pair
comprising a carrier wafer bonded to a device wafer via an adhesive
layer upon the bottom chuck assembly at the loading zone oriented
so that the unbonded surface of the device wafer is in contact with
the bottom chuck assembly. Next, driving the X-axis carriage drive
and the bottom chuck assembly to the process zone and placing the
top chuck assembly on top of the bottom chuck assembly. Next,
placing the unbonded surface of the carrier wafer in contact with
the top chuck assembly and holding the carrier wafer by the top
chuck assembly. Next, heating the carrier wafer with a heater
comprised in the top chuck assembly to a temperature around or
above the adhesive layer's melting point. Next, initiating
horizontal motion of the X-axis carriage drive along the X-axis by
the X-axis drive control while heat is applied to the carrier wafer
and while the carrier wafer is held by the top chuck assembly and
the device wafer is held by the bottom chuck assembly and thereby
causing the device wafer to debond and slide away from the carrier
wafer. Next, moving the top chuck assembly with the debonded
carrier wafer away from the process zone. Next, moving a cleaning
station module into the chamber over the debonded device wafer and
removing any residual adhesive off the device wafer. Next, moving
the cleaning station module out of the chamber after any residual
adhesive is removed off the device wafer. Next, moving a taping
module into the chamber over the debonded and cleaned device wafer
and applying a tape to a surface of the debonded device wafer and
then removing the taped debonded device wafer from the bottom chuck
assembly and placing it into a device wafer cassette. The residual
adhesive is removed by using a solvent and applying spin cleaning
techniques. The top chuck assembly further includes a top support
chuck bolted to the static gantry, a heater support plate in
contact with the bottom surface of the top support chuck, a heater
being in contact with the bottom surface of the heater support
plate, a top wafer plate in contact with the heater, a Z-axis drive
for moving the top wafer plate in the Z-direction and placing the
top wafer plate in contact with the unbonded surface of the carrier
wafer and a plate leveling system for leveling the top wafer plate
and for providing wedge error compensation of the top wafer
plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] Referring to the figures, wherein like numerals represent
like parts throughout the several views:
[0015] FIG. 1 is an overview schematic diagram of a prior art
temporary wafer bonder and debonder system;
[0016] FIG. 1A is a schematic diagram of temporary wafer bonding
process A and debonding process A performed in bonder 210 and
debonder 150' of FIG. 1, respectively;
[0017] FIG. 1B depicts a schematic cross-sectional view of the
temporary bonder 210 of FIG. 1 and a list of the process steps for
performing the temporary wafer bonding process 60a of FIG. 1A;
[0018] FIG. 2 and FIG. 2A are overview diagrams of one embodiment
of the temporary wafer bonder system with an automated thermal
slide debonder 150 of this invention where chuck 152 moves from
station to station;
[0019] FIG. 3 and FIG. 3A are overview diagrams of another
embodiment of the automated thermal slide debonder 150 of this
invention where the various process stations move over chuck
152;
[0020] FIG. 4 depicts a view of chuck 152 of FIG. 2;
[0021] FIG. 5 depicts the temporary wafer bonder 210 of FIG. 2;
[0022] FIG. 6 depicts a schematic cross-sectional schematic view of
the temporary wafer bonder of FIG. 5;
[0023] FIG. 7 depicts a cross-sectional view of the temporary wafer
bonder of FIG. 5 perpendicular to the load direction;
[0024] FIG. 8 depicts a cross-sectional view of the temporary wafer
bonder of FIG. 5 in line with the load direction;
[0025] FIG. 9 depicts the top chuck leveling adjustment in the
temporary wafer bonder of FIG. 5;
[0026] FIG. 10 depicts a cross-sectional view of the top chuck of
the temporary wafer bonder of FIG. 5;
[0027] FIG. 11 depicts a detailed cross-sectional view of the
temporary wafer bonder of FIG. 5;
[0028] FIG. 12 depicts a wafer centering device with the
pre-alignment arms in the open position;
[0029] FIG. 13 depicts wafer centering device of FIG. 12 with the
pre-alignment arms in the closed position;
[0030] FIG. 14 depicts an overview diagram of the thermal slide
debonder of FIG. 2;
[0031] FIG. 15 depicts a cross-sectional view of the top chuck
assembly of the debonder of FIG. 14;
[0032] FIG. 16 depicts a cross-sectional side view of the debonder
of FIG. 14;
[0033] FIG. 17A, FIG. 17B depict the thermal slide debonder
operational steps.
DETAILED DESCRIPTION OF THE INVENTION
[0034] Referring to FIG. 1, an apparatus for temporary wafer
bonding 100 includes a temporary bonder 210, a wafer thinning
module 120, a thermal slide debonder 150', a wafer cleaning station
170 and a wafer taping station 180. Bonder 210 facilitates the
temporary bonding processes 60a, shown in FIG. 1A and debonder 150'
facilitates the thermal slide debonding processes 60b, shown in
FIG. 1A.
[0035] Referring to FIG. 1A, temporary bond process 60a includes
the following steps. First, device wafer 20 is coated with a
protective coating 21 (62), the coating is then baked and chilled
(63) and then the wafer is flipped (64). A carrier wafer 30 is
coated with an adhesive layer 31 (65) and then the coating is baked
and chilled (66). In other embodiments, a dry adhesive film is
laminated onto the carrier wafer, instead of coating an adhesive
layer. Next, the flipped device wafer 20 is aligned with the
carrier wafer 30 so that the surface of the device wafer with the
protective coating 20a is opposite to the surface of the carrier
wafer with the adhesive layer 30a (67) and then the two wafers are
bonded (68) in the temporary bonder module 210, shown in FIG. 1B.
The bond is a temporary bond between the protective layer 21 and
the adhesive layer 31. In other embodiments, no protective coating
is applied onto the device wafer surface and the device wafer
surface 20a is directly bonded with the adhesive layer 31. Examples
of device wafers include GaAs wafers, silicon wafers, or any other
semiconductor wafer that needs to be thinned down to less than 100
micrometers. These thin wafers are used in military and
telecommunication applications for the fabrication of power
amplifiers or other power devices where good heat removal and small
power factor are desirable. The carrier wafer 30 is usually made of
a non-contaminating material that is thermally matched with the
device wafer, i.e., has the same coefficient of thermal expansion
(CTE). Examples of carrier wafer materials include silicon, glass,
sapphire, quartz or other semiconductor materials. The diameter of
the carrier wafer 30 is usually the same as or slightly larger than
the diameter of the device wafer 20, in order to support the device
wafer edge and prevent cracking or chipping of the device wafer
edge. In one example, the carrier wafer thickness is about 1000
micrometers and the total thickness variation (TTV) is 2-3
micrometers. Carrier wafers are recycled and reused after they are
debonded from the device wafer. In one example, adhesive layer 31
is an organic adhesive WaferBOND.TM. HT-10.10, manufactured by
Brewer Science, Missouri, USA. Adhesive 31 is applied via a spin-on
process and has a thickness in the range of 9 to 25 micrometers.
The spin speed is in the rage of 1000 to 2500 rpm and the spin time
is between 3-60 second. After the spin-on application, the adhesive
layer is baked for 2 min at a temperature between 100.degree. C. to
150.degree. C. and then cured for 1-3 minutes at a temperature
between 160.degree. C. to 220.degree. C. WaferBOND.TM. HT-10.10
layer is optically transparent and is stable up to 220.degree. C.
The bonded wafer stack 10 is placed in a thinning module 120. After
the thinning 120 of the exposed device wafer surface 20b the
carrier wafer 30 is debonded via the debond process 60b, shown in
FIG. 1A. Debond process 60b, includes the following steps. First
heating the wafer stack 10 until the adhesive layer 31 softens and
the carrier wafer 30 slides off from the thinned wafer (69). The
WaferBOND.TM. HT-10.10 debonding time is less than 5 minutes. The
thinned wafer 20 is then moved to a cleaning station 170 where any
adhesive residue is stripped away (52) and then the thinned wafer
20 is moved to a taping station 180 placed in a dicing frame 25
(53).
[0036] The temporary bonding (68) of the carrier wafer 30 to the
device wafer 20 takes place in temporary bonder module, 210.
Referring to FIG. 1B, the device wafer 20 is placed in a fixture
chuck and the fixture chuck is loaded in the chamber 210. The
carrier wafer 30 is placed with the adhesive layer facing up
directly on the bottom chuck 210a and the two wafers 20, 30 are
stacked and aligned. The top chuck 210b is lowered down onto the
stacked wafers and a low force is applied. The chamber is evacuated
and the temperature is raised to 200.degree. C. for the formation
of the bond between the protective coating layer 21 and the
adhesive layer 31. Next, the chamber is cooled and the fixture with
the bonded wafer stack 10 is unloaded.
[0037] The debond process 60b is a thermal slide debond process and
includes the following steps, shown in FIG. 1A. The bonded wafer
stack 10 is heated causing the adhesive layer 31 to become soft.
The carrier wafer is then twisted around axis 169 and then slid off
the wafer stack under controlled applied force and velocity (69).
The separated device wafer 20 is then moved into the cleaning
station 170 and cleaned (52) and then it is moved into the taping
station 180 where it is mounted onto a dicing frame 25 (53).
[0038] In cases where the thinned device wafer is thicker than
about 100 micrometers usually no additional support is needed for
moving the thinned wafer 20 from the thermal slide debonder 150 to
the further processing stations 170, 180. However, in cases where
the thinned device wafer 20 is thinner than 100 micrometers a
secondary support mechanism is required to prevent breaking or
cracking of the thinned device wafer. Currently, the secondary
support mechanism includes an electrostatic carrier or a carrier
comprising a Gelpak.TM. acrylic film on a specially constructed
wafer. As was mentioned above, these secondary support mechanism
add complications and cost to the process.
[0039] The present invention eliminates the need for a secondary
carrier by allowing a vacuum chuck 152 used in the thermal slide
debonder 150 to remain with the thinned wafer 20 during the follow
up processes steps of cleaning (52) and mounting onto a dicing tape
(53). In one embodiment the thinned wafer 20 remains onto the
vacuum chuck 152 and is moved with the vacuum chuck into the
various process stations. In another embodiment the thinned wafer
20 remains onto the vacuum chuck 152 and the various process
stations 170, 180 move over the thinned wafer 20 to perform the
various process steps.
[0040] Referring to FIG. 2 and FIG. 2A, the bonded wafer pair 10 is
loaded into the vacuum chuck 152 (shown in FIG. 4 and FIG. 14) of
debonder 150 and the thermal debonding process 60b is applied. The
vacuum chuck 152 with the debonded device wafer 20 moves into the
cleaning station 170 where a solvent is used to clean the residual
adhesive off the wafer via a spin cleaning technique. Next, the
chuck 152 with the cleaned device wafer 20 moves to the taping
station 180 where a tape/frame assembly is attached to the thinned
device wafer 20 surface. Finally, the taped thinned wafer 20 is
moved to a cassette and the carrier wafer 30 is moved to a
different cassette.
[0041] Referring to FIG. 3 and FIG. 3A, in another embodiment, the
thinned wafer stack 10 is placed in the vacuum chuck 152 and the
chuck 152 is loaded in a chamber 122. Next, thermal slide debonder
150 moves into position over the vacuum chuck 152 with the bonded
wafer pair 10 and performs the thermal debonding process 60b. Next,
the thermal slide debonder 150 moves out of the chamber 122 and the
cleaning module 170 moves into the chamber 122 and cleans the
residual adhesive off the device wafer 20. Once the cleaning step
is completed, the cleaning module 170 is removed and the taping
module 180 is moved over the thinned and cleaned device wafer 20
and applies the tape/frame assembly onto the device wafer 20.
Finally, the taped thinned device wafer 20 is moved to a cassette
and the carrier wafer 30 is moved to a different cassette.
[0042] Referring to FIG. 5-FIG. 11, temporary bond module 210
includes a housing 212 having a load door 211, an upper block
assembly 220 and an opposing lower block assembly 230. The upper
and lower block assemblies 220, 230 are movably connected to four
Z-guide posts 242. In other embodiments, less than four or more
than four Z-guide posts are used. A telescoping curtain seal 235 is
disposed between the upper and lower block assemblies 220, 230. A
temporary bonding chamber 202 is formed between the upper and lower
assemblies 220, 230 and the telescoping curtain seal 235. The
curtain seal 235 keeps many of the process components that are
outside of the temporary bonding chamber area 202 insulated from
the process chamber temperature, pressure, vacuum, and atmosphere.
Process components outside of the chamber area 202 include guidance
posts 242, Z-axis drive 243, illumination sources, mechanical
pre-alignment arms 460a, 460b and wafer centering jaws 461a, 461b,
among others. Curtain 235 also provides access to the bond chamber
202 from any radial direction.
[0043] Referring to FIG. 7, the lower block assembly 230 includes a
heater plate 232 supporting the wafer 20, an insulation layer 236,
a water cooled support flange 237 a transfer pin stage 238 and a
Z-axis block 239. Heater plate 232 is a ceramic plate and includes
resistive heater elements 233 and integrated air cooling 234.
Heater elements 233 are arranged so the two different heating zones
are formed. A first heating zone 233B is configured to heat a 200
mm wafer or the center region of a 300 mm wafer and a second
heating zone 233A is configured to heat the periphery of the 300 mm
wafer. Heating zone 233A is controlled independently from heating
zone 233B in order to achieve thermal uniformity throughout the
entire bond interface 405 and to mitigate thermal losses at the
edges of the wafer stack. Heater plate 232 also includes two
different vacuum zones for holding wafers of 200 mm and 300 mm,
respectively. The water cooled thermal isolation support flange 237
is separated from the heater plate by the insulation layer 236. The
transfer pin stage 238 is arranged below the lower block assembly
230 and is movable supported by the four posts 242. Transfer pin
stage 238 supports transfer pins 240 arranged so that they can
raise or lower different size wafers. In one example, the transfer
pins 240 are arranged so that they can raise or lower 200 mm and
300 mm wafers. Transfer pins 240 are straight shafts and, in some
embodiments, have a vacuum feed opening extending through their
center, as shown in FIG. 11. Vacuum drawn through the transfer pin
openings holds the supported wafers in place onto the transfer pins
during movement and prevents misalignment of the wafers. The Z-axis
block 239 includes a precision Z-axis drive 243 with ball screw,
linear cam design, a linear encoder feedback 244 for submicron
position control, and a servomotor 246 with a gearbox, shown in
FIG. 8.
[0044] Referring to FIG. 9, the upper block assembly 220 includes
an upper ceramic chuck 222, a top static chamber wall 221 against
which the curtain 235 seals with seal element 235a, a 200 mm and a
300 mm membrane layers 224a, 224b, and three metal flexure straps
226 arranged circularly at 120 degrees. The membrane layers 224a,
224b, are clamped between the upper chuck 222 and the top housing
wall 213 with clamps 215a, 215b, respectively, and form two
separate vacuum zones 223a, 223b designed to hold 200 mm and 300 mm
wafers, respectively, as shown in FIG. 10. Membrane layers 224a,
224b are made of elastomer material or metal bellows. The top
ceramic chuck 222 is highly flat and thin. It has low mass and is
semi-compliant in order to apply uniform pressure upon the wafer
stack 10. The top chuck 222 is lightly pre-loaded with membrane
pressure against three adjustable leveling clamp/drive assemblies
216. Clamp/drive assemblies 216 are circularly arranged at 120
degrees. The top chuck 222 is initially leveled while in contact
with the lower ceramic heater plate 232, so that it is parallel to
the heater plate 232. The three metal straps 226 act a flexures and
provide X-Y-T (Theta) positioning with minimal Z-constraint. The
clamp/drive assemblies 216 also provide a spherical Wedge Error
Compensating (WEC) mechanism that rotates and/or tilts the ceramic
chuck 222 around a center point corresponding to the center of the
supported wafer without translation.
[0045] The loading and pre-alignment of the wafers is facilitated
with the mechanical centering device 460, shown in FIG. 12.
Centering device 460 includes two pre-alignment arms 460a, 460b,
shown in the open position in FIG. 12 and in the closed position in
FIG. 13. At the ends of each arm 460a, 460b there are mechanical
jaws 461a, 461b. The mechanical jaws 461a, 461b have tapered
surfaces 462 and 463 that conform to the curved edge of the 300 mm
wafer and 200 mm wafer, respectively.
[0046] Referring to FIG. 14, thermal slide debonder 150 includes a
top chuck assembly 151, a bottom chuck assembly 152, a static
gantry 153 supporting the top chuck assembly 151, an X-axis
carriage drive 154 supporting the bottom chuck assembly 152, a lift
pin assembly 155 designed to raise and lower wafers of various
diameters including diameters of 200 mm and 300 mm, and a base
plate 163 supporting the X-axis carriage drive 154 and gantry
153.
[0047] Referring to FIG. 15, the top chuck assembly 151 includes a
top support chuck 157 bolted to gantry 153, a heater support plate
158 in contact with the bottom surface of the top support chuck
157, a top heater 159 in contact with the bottom surface of the
heater plate 158, a Z-axis drive 160 and a plate leveling system
for leveling the upper wafer plate/heater bottom surface 164. The
plate leveling system includes three guide shafts 162 that connect
the top heater 159 to the top support chuck 157 and three
pneumatically actuated split clamps 161. The plate leveling system
provides a spherical Wedge Error Compensating (WEC) mechanism that
rotates and/or tilts the upper wafer plate 164 around a center
point corresponding to the center of the supported wafer without
translation. The heater 159 is a steady state heater capable to
heat the supported wafer stack 10 up to 350.degree. C. Heater 159
includes a first heating zone configured to heat a 200 mm wafer or
the center region of a 300 mm wafer and a second heating zone
configured to heat the periphery of the 300 mm wafer. The first and
second heating zones are controlled independently from each other
in order to achieve thermal uniformity throughout the entire bond
interface of the wafer stack and to mitigate thermal losses at the
edges of the wafer stack. The heater support plate 158 is water
cooled in order to provide thermal isolation and to prevent the
propagation of any thermal expansion stresses that may be generated
by the top heater 159.
[0048] Referring to FIG. 16, the bottom chuck 152 is made of a low
thermal mass ceramic material and is designed to slide along the
X-axis 149 on top of the air bearing carriage drive 154. The
carriage drive 154 is guided in this X-axis motion by two parallel
lateral carriage guidance tracks 156. Bottom chuck 152 is also
designed to rotate along its Z-axis 169. A Z-axis rotation by a
small angle (i.e., twisting) is used to initiate the separation of
the wafers, as will be described below. The base plate 163 is
vibration isolated. In one example, base plate is made of granite.
In other examples base plate 156 has a honeycomb structure and is
supported by pneumatic vibration isolators (not shown).
[0049] Referring to FIG. 17A, FIG. 17B, the debonding operation
with the thermal slide debonder 150 of FIG. 16 includes the
following steps. First, the temporary bonded wafer stack 10 is
loaded on the primary lift pins 155 arranged so that the carrier
wafer 30 is on the top and the thinned device wafer 20 is on the
bottom (171). Next, the wafer stack 10 is lowered so that the
bottom surface of the thinned device wafer 20 is brought into
contact with the bottom chuck 152 (172). The bottom chuck 152 is
then moved along the 165a direction until it is under the top
heater 159 (174). Next, the Z-axis 160 of the top chuck 151 moves
down and the bottom surface 164 of the top heater 159 is brought
into contact with the top surface of the carrier wafer 30 and then
air is floated on top heater 159 and carrier wafer 30 until the
carrier wafer stack 30 reaches a set temperature. When the set
temperature is reached, vacuum is pulled on the carrier wafer 30 so
that is held by the top chuck assembly 151 and the guide shafts 162
are locked in the split clamps 162 (175). At this point the top
chuck 151 is rigidly held while the bottom chuck 152 is compliant
and the thermal slide separation is initiated (176) by first
twisting the bottom chuck 152 and then moving the X-axis carriage
154 toward the 165b direction away from the rigidly held top chuck
assembly 151 (177). The debonded thinned device wafer 20 is carried
by the X-axis carriage 154 on top of chuck 152 to the unload
position. Next, chuck 152 with the thinned debonded wafer 20 is
moved to stations 170 and 180 for cleaning and taping, respectively
(178). Alternatively, stations 170 and 180 are moved over chuck 152
with the debonded wafer 20 for cleaning and taping to take place
(179).
[0050] Several embodiments of the present invention have been
described. Nevertheless, it will be understood that various
modifications may be made without departing from the spirit and
scope of the invention. Accordingly, other embodiments are within
the scope of the following claims.
* * * * *