U.S. patent application number 11/417445 was filed with the patent office on 2007-10-25 for high temperature anodic bonding apparatus.
Invention is credited to Raymond C. Cady, John Joseph III Costello, Alexander Lakota, William Edward Lock, John Christopher Thomas.
Application Number | 20070246450 11/417445 |
Document ID | / |
Family ID | 38618501 |
Filed Date | 2007-10-25 |
United States Patent
Application |
20070246450 |
Kind Code |
A1 |
Cady; Raymond C. ; et
al. |
October 25, 2007 |
High temperature anodic bonding apparatus
Abstract
An anodic bonding apparatus includes: a first bonding plate
mechanism operable to engage a first material sheet, and to provide
at least one of controlled heating, voltage, and cooling thereto; a
second bonding plate mechanism operable to engage a second material
sheet, and to provide at least one of controlled heating, voltage,
and cooling thereto; a pressure mechanism operatively coupled to
the first and second bonding plate mechanisms and operable to urge
the first and second bonding plate mechanisms toward one another to
achieve controlled pressure of the first and second material sheets
against one another along respective surfaces thereof; a control
unit operable to produce control signals to the first and second
bonding plate mechanisms and the pressure mechanism to provide
heating, voltage, and pressure profiles sufficient to achieve
anodic bonding between the first and second material sheets.
Inventors: |
Cady; Raymond C.;
(Horseheads, NY) ; Lakota; Alexander; (Kanona,
NY) ; Lock; William Edward; (Horseheads, NY) ;
Thomas; John Christopher; (Elmira, NY) ; Costello;
John Joseph III; (Painted Post, NY) |
Correspondence
Address: |
CORNING INCORPORATED
SP-TI-3-1
CORNING
NY
14831
US
|
Family ID: |
38618501 |
Appl. No.: |
11/417445 |
Filed: |
May 3, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60793976 |
Apr 21, 2006 |
|
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|
Current U.S.
Class: |
219/250 ;
438/455 |
Current CPC
Class: |
H01L 21/67144 20130101;
H01L 21/67092 20130101; H01L 21/76254 20130101; H01L 21/67121
20130101 |
Class at
Publication: |
219/250 ;
438/455 |
International
Class: |
D06F 75/26 20060101
D06F075/26 |
Claims
1. An anodic bonding apparatus, comprising: a first bonding plate
mechanism operable to engage a first material sheet, and to provide
at least one of controlled heating, voltage, and cooling thereto; a
second bonding plate mechanism operable to engage a second material
sheet, and to provide at least one of controlled heating, voltage,
and cooling thereto; a pressure mechanism operatively coupled to
the first and second bonding plate mechanisms and operable to urge
the first and second bonding plate mechanisms toward one another to
achieve controlled pressure of the first and second material sheets
against one another along respective surfaces thereof; a control
unit operable to produce control signals to the first and second
bonding plate mechanisms and the pressure mechanism to provide
heating, voltage, and pressure profiles sufficient to achieve
anodic bonding between the first and second material sheets.
2. The anodic bonding apparatus of claim 1, wherein the first
material sheet is at least one of a glass substrate and a glass
ceramic substrate, and the second material sheet is a donor
semiconductor wafer.
3. The anodic bonding apparatus of claim 1, wherein the heating
profile includes at least a peak temperature of at least one of the
first and second material sheets of greater than about 600.degree.
C.
4. The anodic bonding apparatus of claim 1, wherein the heating
profile includes at least a peak temperature of at least one of the
first and second material sheets of between about 600.degree. C.
and 1000.degree. C.
5. The anodic bonding apparatus of claim 1, wherein the heating
profile includes at least a peak temperature of at least one of the
first and second material sheets of greater than about 1000.degree.
C.
6. The anodic bonding apparatus of claim 1, wherein the voltage
profile includes at least a peak voltage of at least one of the
first and second material sheets of between about 100 volts DC to
about 2000 volts DC.
7. The anodic bonding apparatus of claim 6, wherein at least one
of: the voltage profile includes at least a peak voltage difference
of between about 1000 volts DC and about 2000 volts DC between the
first material sheet and the second material sheet; one of the
first and second material sheets are at ground potential; and the
peak voltage difference is attained by applying a positive voltage
potential to one of the first and second material sheets and a
negative voltage potential to the other of the first and second
material sheets.
8. The anodic bonding apparatus of claim 1, wherein the pressure
profile includes at least a peak pressure between the first and
second material sheets of between about 1 pound per square inch
(psi) and 100 psi.
9. The anodic bonding apparatus of claim 1, wherein the pressure
profile includes at least a peak pressure between the first and
second material sheets of about 20 psi.
10. The anodic bonding apparatus of claim 1, wherein the control
unit is operable to produce control signals to at least one of the
first and second bonding plate mechanisms to provide an active
cooling profile to the first and second material sheets sufficient
to facilitate separation of an exfoliation layer from one of the
first and second material sheets that has been bonded to the other
of the first and second material sheets.
11. The anodic bonding apparatus of claim 10, wherein the cooling
profile provides at least one of differing rates of cooling and
differing levels of cooling to the first and second material
sheets.
12. An anodic bonding apparatus, comprising: a first bonding plate
mechanism operable to engage a first material sheet, and to provide
at least one of controlled heating and voltage thereto; a second
bonding plate mechanism operable to engage a second material sheet,
and to provide at least one of controlled heating and voltage
thereto; and a lift and press mechanism operatively coupled to the
first bonding plate mechanism and operable to urge the first and
second bonding plate mechanisms toward one another to achieve
controlled pressure of the first and second material sheets against
one another along respective surfaces thereof to assist in the
anodic bonding of same.
13. The anodic bonding apparatus of claim 12, wherein: the first
and second bonding plate mechanisms each include a bearing
surfaces, each bearing surface defining a bearing plane for
engaging a respective one of the first and second material sheets;
and the lift and press mechanism is operable to impart a
controllable force on the first bonding plate mechanism, the
controllable force being substantially perpendicular to the bearing
plane thereof.
14. The anodic bonding apparatus of claim 13, wherein the lift and
press mechanism includes a bellows actuator operable to impart the
controllable force in response to variations in fluid pressure
provided to the actuator.
15. The anodic bonding apparatus of claim 14, wherein the fluid is
a gas.
16. The anodic bonding apparatus of claim 13, wherein the lift and
press mechanism is operable to provide: a first actuator function
imparting a coarse displacement of the first bonding plate
mechanism to move the first bonding plate mechanism toward the
second bonding plate mechanism; and a second actuator function
imparting the controllable force to the first bonding plate
mechanism.
17. The anodic bonding apparatus of claim 16, wherein the lift and
press mechanism includes a piston-driven actuator operable to
provide the first actuator function.
18. The anodic bonding apparatus of claim 16, wherein the lift and
press mechanism includes a bellows actuator operable to provide the
second actuator function.
19. The anodic bonding apparatus of claim 16, wherein the first
actuator function results in initial contact between the first and
second material sheets along the respective surfaces thereof.
20. The anodic bonding apparatus of claim 16, wherein the lift and
press mechanism includes: first and second actuators operable to
provide the first and second actuator functions, respectively,
wherein the first and second actuators are in axial alignment with
the first bonding plate mechanism.
21. The anodic bonding apparatus of claim 20, wherein the first and
second actuators are disposed such that actuation of the first
actuator imparts the coarse displacement of both the second
actuator and the first bonding plate mechanism.
22. The anodic bonding apparatus of claim 21, wherein actuation of
the second actuator does not impart any displacement of the first
actuator.
23. An anodic bonding apparatus, comprising: a first bonding plate
mechanism operable to engage a first material sheet and a second
bonding plate mechanism operable to engage a second material sheet,
the first and second bonding plate mechanisms each including a
bearing surface, each bearing surface defining a bearing plane for
engaging a respective one of the first and second material sheets;
and an open and close mechanism operatively coupled to the second
bonding plate mechanism and operable to: (i) assist, when in a
closed orientation, in achieving controlled pressure of the first
and second material sheets against one another along respective
surfaces thereof; and (ii) provide a dual motion opening profile,
where a first motion separates the second bonding plate mechanism
from the first bonding plate mechanism in a direction substantially
perpendicular to the respective bearing planes thereof, and a
second motion tilts the second bonding plate mechanism away from
the first bonding plate mechanism such that the bearing plane of
the second bonding plate mechanism is oblique to the bearing plane
of the first bonding plate mechanism.
24. The anodic bonding apparatus of claim 23, wherein the bearing
planes of the first and second bonding plate mechanisms remain
substantially parallel throughout substantially all of the first
opening motion of the second bonding plate mechanism.
25. The anodic bonding apparatus of claim 23, wherein the open and
close mechanism includes: a lift assembly operable to extend and
retract in a direction substantially perpendicular to the bearing
plane of the first bonding plate mechanism; and a mount plate
having first and second ends, the second bonding plate mechanism
being disposed toward the first end thereof, and the mount plate
being pivotally coupled to the lift assembly at a position
intermediate to the first and second ends.
26. The anodic bonding apparatus of claim 25, wherein: the open and
close mechanism includes one or more stop arms extending in
substantially parallel orientation to the lift assembly and
slideably engaged at first ends thereof with the second end of the
mount plate; and the stop arms permits movement of the second end
of the mount plate as the lift assembly extends for limited travel
during the first motion such that the second bonding plate
mechanism separates away from the first bonding plate mechanism in
the direction substantially perpendicular to the respective bearing
planes thereof.
27. The anodic bonding apparatus of claim 26, wherein the one or
more stop arms are operable to prohibit movement of the second end
of the mount plate beyond the limited travel such that continued
extension of the lift assembly produces a lever action at the
second end of the mount plate about the pivot coupling of the mount
plate and the lift assembly.
28. The anodic bonding apparatus of claim 27, wherein the lever
action at the second end of the mount plate tilts the second
bonding plate mechanism away from the first bonding plate
mechanism.
29. The anodic bonding apparatus of claim 27, wherein retraction of
the lift assembly from the open orientation of the first and second
bonding plate mechanisms tilts the second bonding plate mechanism
toward the first bonding plate mechanism via the lever action at
the second end of the mount plate.
30. The anodic bonding apparatus of claim 29, wherein the
retraction of the lift assembly is operable to cause the second end
of the mount plate to reach the limited travel movement such that
continued retraction of the lift assembly such that the second
bonding plate mechanism separates away from the first bonding plate
mechanism in the direction substantially perpendicular to the
respective bearing planes thereof.
31. An anodic bonding apparatus, comprising: a first bonding plate
mechanism operable to engage the first material sheet, and to
provide at least one of controlled heating, voltage, and cooling
thereto; a second bonding plate mechanism operable to engage the
second material sheet, and to provide at least one of controlled
heating, voltage, and cooling thereto; and a spacer mechanism
including a plurality of movable shim assemblies, the spacer
mechanism being coupled to the first bonding plate mechanism, and
being operable to symmetrically move the shim assemblies toward and
between the first and second material sheets to prevent peripheral
edges of the first and second material sheets from touching one
another.
32. The apparatus of claim 31, wherein the first material sheet is
at least one of a glass substrate and a glass ceramic substrate,
and the second material sheet is a donor semiconductor wafer.
33. The apparatus of claim 31, wherein the spacer mechanism is of
substantially annular construction and includes: a mount ring
fixedly coupled with respect to the first bonding plate mechanism;
and a swivel ring rotationally coupled to the mount ring, wherein
the plurality of shim assemblies are slideably coupled to the mount
ring such that they may move synchronously into and/or out of a
space between the first and second material sheets in response to
forward and rearward rotation of the swivel ring.
34. The apparatus of claim 33, wherein: the swivel ring includes
one or more cams disposed at a peripheral edge thereof; the
respective shim assemblies each include one or more cam guides that
engage the one or more cams of the swivel ring such that when the
swivel ring rotates the shim assemblies move synchronously into
and/or out of the space between the first and second material
sheets.
35. The apparatus of claim 34, wherein the swivel ring includes one
cam slot for each shim assembly, each cam slot spiraling away from
a center of the spacer mechanism.
36. The apparatus of claim 31, wherein: the first and second
bonding plate mechanisms each include a bearing surface, each
bearing surface defining a bearing plane for engaging a respective
one of the first and second material sheets; and the spacer
mechanism is operable such that the shim assemblies move
substantially parallel to at least the bearing surface of the first
bonding plate mechanism to interpose between or move out from
between the first and second material sheets.
37. The apparatus of claim 31, wherein the spacer mechanism is
operable to move the shim assemblies between the first and second
material sheets in order to enable bonding only in a central region
of the first and second material sheets.
38. The apparatus of claim 37, wherein the spacer mechanism is
operable to move the shim assemblies out from between the first and
second material sheets after bonding has been achieved in the
central region of the first and second material sheets.
39. The apparatus of claim 37, further comprising at least one
preload plunger having at least an electrode extending through an
aperture of the first bonding plate mechanism, the electrode being
operable to electrically connect to the first material sheet.
40. The apparatus of claim 39, wherein the preload plunger is
operable to bias against and move the first material sheet against
the second material sheet in the central region thereof.
41. The apparatus of claim 40, wherein the preload plunger is
operable to provide a seed voltage to the first material sheet to
induce bonding between the first and second material sheets in the
central region thereof.
42. An apparatus, comprising: a first bonding plate mechanism
operable to engage a material sheet, and to provide at least one of
controlled heating, voltage, and cooling thereto; a second bonding
plate mechanism operable to engage an embossing tool having
micro-structures thereon, and to provide at least one of controlled
heating, voltage, and cooling thereto; a pressure mechanism
operatively coupled to the first and second bonding plate
mechanisms and operable to urge the first and second bonding plate
mechanisms toward one another to achieve controlled pressure of the
embossing tool against the material sheet along respective surfaces
thereof; a control unit operable to produce control signals to the
first and second bonding plate mechanisms and the pressure
mechanism to provide a heating profile sufficient to cause the
material sheet to flow into the micro-structures of the embossing
tool.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to U.S. Provisional Patent
Application Ser. No. 60/793,976, filed Apr. 21, 2006 by Raymond C.
Cady, entitled "A BONDING PLATE MECHANISM FOR USE IN ANODIC
BONDING," now pending, which is incorporated herein by reference in
its entirety.
BACKGROUND
[0002] The present invention relates to an apparatus for
manufacturing, for example, a semiconductor-on-insulator (SOI)
structure using an anodic bonding technique.
[0003] To date, the semiconductor material most commonly used in
semiconductor-on-insulator structures has been silicon, and the
abbreviation "SOI" has been applied to such structures. SOI
technology is becoming increasingly important for high performance
thin film transistors, solar cells, and displays, such as, active
matrix displays.
[0004] For ease of presentation, the following discussion will at
times refer to SOI structures, however, such references to this
particular type of structure are made to facilitate the explanation
of the invention and are not intended to, and should not be
interpreted as, limiting the invention's scope in any way. The SOI
abbreviation is used herein to refer to semiconductor-on-insulator
structures in general, including, but not limited to,
silicon-on-insulator structures. Similarly, the SOG abbreviation is
used to refer to semiconductor-on-glass structures in general,
including, but not limited to, silicon-on-glass structures. The SOG
nomenclature is also intended to include
semiconductor-on-glass-ceramic structures, including, but not
limited to, silicon-on-glass-ceramic structures. The abbreviation
SOI encompasses SOG structures.
[0005] SOI structures may include a thin layer of substantially
single crystal silicon (generally 0.1-0.3 microns in thickness) on
an insulating material. Various ways of obtaining SOI structures
include: (i) bonding a single crystal silicon wafer to another
silicon wafer on which an oxide layer of SiO.sub.2 has been grown;
(ii) ion-implantation methods to form a buried oxide layer in the
silicon wafer; (iii) ion-implantation methods to separate
(exfoliate) a thin silicon layer from a silicon donor wafer and
bond same to another silicon wafer.
[0006] U.S. Pat. No. 5,374,564 discloses a process for obtaining a
single crystal silicon film on a substrate using a thermal process.
A semiconductor donor wafer having a planar face is subject to the
following steps: (i) implantation by bombardment of a face of the
wafer by means of ions creating a layer of gaseous micro-bubbles
defining a lower region constituting the mass of the donor wafer
and an upper region constituting a relatively thin exfoliation
layer; (ii) contacting the planar face of the wafer with a
stiffener constituted by at least one rigid material layer; and
(iii) a third stage of heat treating the assembly of the wafer and
the stiffener at a temperature above that at which the ion
bombardment was carried out and sufficient to create a pressure
effect in the micro-bubbles and a separation between the thin film
and the mass of the substrate. Notably, this process does not
generally work with glass or glass-ceramic substrates because much
higher temperatures are required for bonding some glass and
glass-ceramic substrates.
[0007] U.S. Patent Application No.: 2004/0229444 discloses a
process that produces a SOG structure, the entire disclosure of
which is hereby incorporated by reference. The steps include: (i)
exposing a silicon donor wafer surface to hydrogen ion implantation
to create an exfoliation layer having a bonding surface; (ii)
bringing the bonding surface of the silicon donor wafer into
contact with a glass substrate; (iii) applying pressure,
temperature and voltage to the silicon donor wafer and the glass
substrate to facilitate bonding therebetween; and (iv) cooling the
structure to a common temperature to facilitate separation of the
glass substrate and the exfoliation layer of silicon from the
silicon donor wafer.
[0008] The SOG structure resulting from the process disclosed in
U.S. Patent Application No.: 2004/0229444 may include, for example,
a glass substrate, and a semiconductor layer bonded thereto. The
specific material of the semiconductor layer may be in the form of
a substantially single-crystal material. The word "substantially"
is used in describing the semiconductor layer to take account of
the fact that semiconductor materials normally contain at least
some internal or surface defects either inherently or purposely
added, such as lattice defects or a few grain boundaries. The word
"substantially" also reflects the fact that certain dopants may
distort or otherwise affect the crystal structure of bulk
semiconductor.
[0009] For the purposes of discussion, it may be assumed that the
semiconductor layers discussed herein may be formed from silicon.
It is understood, however, that the semiconductor material may be a
silicon-based semiconductor or any other type of semiconductor,
such as, the III-V, II-IV, II-IV-V, etc. classes of semiconductors.
Examples of these materials include: silicon (Si), germanium-doped
silicon (SiGe), silicon carbide (SiC), germanium (Ge), gallium
arsenide (GaAs), GaP, and InP. The glass substrate may be formed
from an oxide glass or an oxide glass-ceramic. Although not
required, the SOG structures described herein may include an oxide
glass or glass-ceramic. By way of example, the glass substrate may
be formed from glass substrates containing alkaline-earth ions,
such as, substrates made of CORNING INCORPORATED GLASS COMPOSITION
NO. 1737 or CORNING INCORPORATED GLASS COMPOSITION NO. EAGLE
2000.TM.. These glass materials have particular use in, for
example, the production of liquid crystal displays.
[0010] It has been discovered by the present inventors that a good
quality anodic bond between the thin exfoliation semiconductor
layer (e.g., silicon) and certain substrates, such as some glass
and glass ceramic substrates, requires careful control of a number
of process variables. These variables include one or more of:
temperature (especially high temperatures approaching and/or
exceeding 1000.degree. C.); pressure (between the semiconductor
layer and the substrate); voltage (to induce electrolysis);
atmospheric conditions (e.g., vacuum or non-vacuum); cooling
profiles (to induce exfoliation); mechanical separation enhancement
(e.g., to assist in exfoliation); etc. Conventional techniques for
the anodic bonding of a semiconductor layer to a glass or
glass-ceramic substrate do not adequately address the above process
variables. For example, the temperature limit of conventional
anodic bonding processes is about 600.degree. C.
[0011] Thus, there are needs in the art for new apparatuses that
can achieve improvement in the anodic bonding process, e.g., by
controlling one or more of the process variables above.
SUMMARY OF THE INVENTION
[0012] In accordance with one or more embodiments of the present
invention, an anodic bonding apparatus includes: a first bonding
plate mechanism operable to engage a first material sheet, and to
provide at least one of controlled heating, voltage, and cooling
thereto; a second bonding plate mechanism operable to engage a
second material sheet, and to provide at least one of controlled
heating, voltage, and cooling thereto; a pressure mechanism
operatively coupled to the first and second bonding plate
mechanisms and operable to urge the first and second bonding plate
mechanisms toward one another to achieve controlled pressure of the
first and second material sheets against one another along
respective surfaces thereof; a control unit operable to produce
control signals to the first and second bonding plate mechanisms
and the pressure mechanism to provide heating, voltage, and
pressure profiles sufficient to achieve anodic bonding between the
first and second material sheets.
[0013] In accordance with one or more further embodiments of the
present invention, an anodic bonding apparatus includes: a first
bonding plate mechanism operable to engage a first material sheet,
and to provide at least one of controlled heating and voltage
thereto; a second bonding plate mechanism operable to engage a
second material sheet, and to provide at least one of controlled
heating and voltage thereto; and a lift and press mechanism
operatively coupled to the first bonding plate mechanism and
operable to urge the first and second bonding plate mechanisms
toward one another to achieve controlled pressure of the first and
second material sheets against one another along respective
surfaces thereof to assist in the anodic bonding of same.
[0014] In accordance with one or more further embodiments of the
present invention, an anodic bonding apparatus includes: a first
bonding plate mechanism operable to engage a first material sheet
and a second bonding plate mechanism operable to engage a second
material sheet, the first and second bonding plate mechanisms each
including a bearing surface, each bearing surface defining a
bearing plane for engaging a respective one of the first and second
material sheets; and an open and close mechanism operatively
coupled to the second bonding plate mechanism and operable to: (i)
assist, when in a closed orientation, in holding the upper bonding
plate mechanism in position with respect to the lower bonding plate
mechanism such that movement of the lower bonding plate mechanism
toward the upper bonding plate mechanism achieves controlled
pressure of the first and second material sheets against one
another along respective surfaces thereof; and (ii) provide a dual
motion opening profile, where a first motion separates the second
bonding plate mechanism from the first bonding plate mechanism in a
direction substantially perpendicular to the respective bearing
planes thereof, and a second motion tilts the second bonding plate
mechanism away from the first bonding plate mechanism such that the
bearing plane of the second bonding plate mechanism is oblique to
the bearing plane of the first bonding plate mechanism.
[0015] In accordance with one or more further embodiments of the
present invention, an anodic bonding apparatus includes: a first
bonding plate mechanism operable to engage the first material
sheet, and to provide at least one of controlled heating, voltage,
and cooling thereto; a second bonding plate mechanism operable to
engage the second material sheet, and to provide at least one of
controlled heating, voltage, and cooling thereto; and a spacer
mechanism including a plurality of movable shim assemblies, the
spacer mechanism being coupled to the first bonding plate
mechanism, and being operable to symmetrically move the shim
assemblies toward and between the first and second material sheets
to prevent peripheral edges of the first and second material sheets
from touching one another.
[0016] In accordance with one or more further embodiments of the
present invention, a bonding plate mechanism (for use in anodic
bonding of first and second material sheets together) includes: a
base including first and second spaced apart surfaces; a thermal
insulator supported by the second surface of the base and operable
to impede heat transfer to the base; a heating disk directly or
indirectly coupled to the insulator and operable to produce heat in
response to electrical power; and a thermal spreader directly or
indirectly coupled to the heating disk and operable to at least
channel heat from the heating disk, and impart voltage, to the
first material sheet, wherein the heat and voltage imparted to the
first material sheet are in accordance with respective heating and
voltage profiles to assist in the anodic bonding of the first and
second material sheets.
[0017] In accordance with one or more further embodiments of the
present invention, a bonding plate mechanism (for use in anodic
bonding of first and second material sheets together) includes: a
base including first and second spaced apart surfaces; a heating
disk directly or indirectly coupled to the base and operable to
produce heat in response to electrical power, wherein the heater
disk includes a plurality of heating zones operable to provide an
edge loss temperature compensation feature, wherein the heat
imparted to the first material sheet is in accordance with a
heating profile to assist in the anodic bonding of the first and
second material sheets.
[0018] In accordance with one or more further embodiments of the
present invention, a bonding plate mechanism (for use in anodic
bonding of first and second material sheets together) includes: a
heating disk including first and second spaced apart surfaces and
operable to produce heat in response to electrical power; a thermal
spreader directly or indirectly coupled to the second surface of
the heating disk and operable to at least channel heat from the
heating disk, and impart voltage, to the first material sheet; and
at least one cooling channel in thermal communication with the
first surface of the heater disk and being operable to carry
cooling fluid to remove heat from the first material sheet through
the thermal spreader and heater disk, wherein the heat and voltage
imparted to the first material sheet are in accordance with
respective heating and voltage profiles to assist in the anodic
bonding of the first and second material sheets, and the cooling
imparted to the first material sheet is in accordance with a
cooling profile to assist in separating, from the first material
sheet, an exfoliation layer that has been bonded to the second
material sheet.
[0019] In accordance with one or more further embodiments of the
present invention, a bonding plate mechanism (for use in anodic
bonding of first and second material sheets together) includes: a
base including first and second spaced apart surfaces and an
aperture therethrough; a heating disk supported by, and thermally
insulated from, the base and operable to produce heat in response
to electrical power, the heating disk including an aperture
therethrough; a thermal spreader directly or indirectly coupled to
the heating disk and operable to at least channel heat from the
heating disk, and impart a bonding voltage, to the first material
sheet, the thermal spreader including an aperture therethrough; and
a preload plunger having an electrode extending through the
apertures of the base, the heating disk, and the thermal spreader,
the electrode being operable to electrically connect to the first
material sheet when it contacts the thermal spreader.
[0020] Other aspects, features, advantages, etc. will become
apparent to one skilled in the art when the description of the
invention herein is taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] For the purposes of illustrating the various aspects of the
invention, there are shown in the drawings forms that are presently
preferred, it being understood, however, that the invention is not
limited to the precise arrangements and instrumentalities
shown.
[0022] FIG. 1 is a perspective view of an embodiment of the bonding
apparatus of the present invention in a partially closed
configuration;
[0023] FIG. 2 is a front elevational view of the bonding apparatus
of FIG. 1 in an open configuration;
[0024] FIG. 3 is a front elevational view of the bonding apparatus
of FIG. 1 in a partially closed configuration;
[0025] FIG. 4A is a front elevational view of the bonding apparatus
of FIG. 1 in a closed configuration;
[0026] FIG. 4B is a side elevational view of the bonding apparatus
of FIG. 1 in a closed configuration;
[0027] FIG. 5 is a partially exploded perspective view of the
bonding apparatus of FIG. 1;
[0028] FIG. 6 is a perspective view of an embodiment of a lift and
press mechanism suitable for use in the bonding apparatus of FIG. 1
(and/or one or more other embodiments);
[0029] FIG. 7 is a perspective view of an embodiment of an/open and
close mechanism suitable for use in the bonding apparatus of FIG. 1
(and/or one or more other embodiments);
[0030] FIG. 8A is a perspective view of an embodiment of an upper
(or lower) bonding plate mechanism suitable for use in the bonding
apparatus of FIG. 1 (and/or one or more other embodiments);
[0031] FIG. 8B is a cross-sectional view of the bonding plate
mechanism of FIG. 8A taken through line 8B-8B;
[0032] FIG. 9A is a perspective view of a heater element suitable
for use with the upper (or lower) bonding plate mechanism of FIG.
8A or other embodiments;
[0033] FIG. 9B is a perspective view of an alternative heater
element suitable for use with the upper (or lower) bonding plate
mechanism of FIG. 8A or other embodiments;
[0034] FIG. 10 is an exploded perspective view of the bonding plate
mechanism of FIG. 8A;
[0035] FIG. 11A is a top plan view of the bonding plate mechanism
of FIG. 8A;
[0036] FIG. 11B is a cross-sectional view of the bonding plate
mechanism of FIG. 11A taken though line 11B-11B;
[0037] FIG. 11C is a cross-sectional view of the bonding plate
mechanism of FIG. 11A taken though line 11C-11C;
[0038] FIG. 12A is a side elevational view of a preload plunger
suitable for use with the bonding plate mechanism of FIG. 8A
(and/or one or more other embodiments);
[0039] FIG. 12B is a cross-sectional view of the preload plunger of
FIG. 12A taken though line 12B-12B;
[0040] FIG. 13 is a cross-sectional view of upper and lower bonding
plate mechanisms suitable for use in the bonding apparatus of FIG.
1 (and/or one or more other embodiments);
[0041] FIG. 14 is a perspective view of an embodiment of a spacer
mechanism suitable for use in the bonding apparatus of FIG. 1
(and/or one or more other embodiments);
[0042] FIG. 15 is an exploded view of a thermocouple in a
pre-loaded mounting fixture suitable for use with the bonding plate
mechanism of FIG. 8A (and/or one or more other embodiments);
[0043] FIG. 16 is a perspective view of an alternative embodiment
of an upper (or lower) bonding plate mechanism suitable for use in
the bonding apparatus of FIG. 1 (and/or one or more other
embodiments);
[0044] FIG. 17 is an exploded view of the bonding plate mechanism
of FIG. 16;
[0045] FIG. 18 is an exploded view of a heater disk suitable for
use with the bonding plate mechanism of FIG. 16 (and/or one or more
other embodiments);
[0046] FIG. 19 is a cross-sectional view of the bonding plate
mechanism of FIG. 16;
[0047] FIG. 20 is a cross-sectional view of an alternative
embodiment of an upper (or lower) bonding plate mechanism suitable
for use in the bonding apparatus of FIG. 1 (and/or one or more
other embodiments);
[0048] FIG. 21 is an exploded perspective view of the bonding plate
mechanism of FIG. 20;
[0049] FIG. 22 is a side elevational view of the bonding apparatus
of FIG. 1 disposed within an atmospheric control chamber;
[0050] FIG. 23 is a block diagram illustrating the structure of an
SOG device that may be produced using the bonding apparatus of FIG.
1;
[0051] FIGS. 24-26 are block diagrams illustrating intermediate
structures that may be formed and/or operated upon using the
bonding apparatus of FIG. 1;
[0052] FIG. 27 is a block diagram illustrating a final SOG
structure that may be formed using the bonding apparatus of FIG. 1;
and
[0053] FIG. 28 is a block diagram of the bonding apparatus of FIG.
1 adapted for a micro-structure embossing application.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
[0054] With reference to the drawings, wherein like numerals
indicate like elements, there is shown in FIG. 1 a perspective view
of a bonding apparatus 10 in accordance with one or more
embodiments of the present invention. In this embodiment, the
bonding apparatus is an integrated processing system capable of
anodically bonding two material sheets of an SOI structure at
temperatures above conventional bonding temperatures, e.g., above
600.degree. C. and approaching and/or exceeding 1000.degree. C. (It
is noted that the bonding apparatus 10 is also capable of anodic
bonding at conventional temperatures.) For purposes of illustration
(but not limitation), an SOI structure will be described herein as
a suitable work piece upon which the bonding apparatus 10 operates
(e.g., in producing the SOI structure). Also for purposes of
discussion (but not limitation), the particular SOI structure
discussed hereinbelow as a work piece will be an SOG structure
formed by bonding a semiconductor donor wafer (such as a silicon
wafer) to a glass (or glass ceramic) substrate and exfoliating a
silicon layer from the silicon donor wafer such that it remains
bonded to the glass substrate.
[0055] The bonding apparatus 10 includes the following components:
a lift and press mechanism 100, an open and close mechanism 200, a
spacer mechanism 300, an upper bonding plate mechanism 400, and a
lower bonding plate mechanism 500. These main components are
coupled to one another and the combination is supported by a base
plate 12 and support frame 14. A control unit (not shown), which
may include one or more closed control loops, is operable to
control the various elements of the bonding apparatus 10 (e.g., by
way of a computer program) as will be discussed in more detail
below.
[0056] Although the operation of the bonding apparatus 10 and
certain specific bonding processes will be described in more detail
later in this document, a brief introduction of such operation will
now be presented. In FIG. 1, the bonding apparatus 10 is in a
closed orientation whereby the upper bonding plate mechanism 400
closely overlies the lower bonding plate mechanism 500. As seen in
FIG. 2, the upper bonding plate mechanism 400 is operable to rotate
upward and away from the lower bonding plate mechanism 500 to
permit insertion of the two material sheets (e.g., a silicon donor
wafer and a glass substrate) to be bonded together into the
apparatus 10. Again, for the purposes of discussion, the silicon
donor wafer is assumed to include an exfoliation layer to be bonded
to the glass substrate and later separated from the silicon donor
wafer.
[0057] In this example, it is assumed that the silicon donor wafer
contacts the upper bonding plate mechanism 400, while the glass
substrate contacts the lower bonding plate mechanism 500 during the
bonding process. For example, the glass substrate may be set down
on the lower bonding plate mechanism 500 and the silicon donor
wafer may be set atop the glass substrate so that it will be in a
position to contact the upper bonding plate mechanism 400 (when the
apparatus 10 is closed). (It is understood, however that this
orientation may be reversed without departing from the scope of
various embodiments of the invention.) In alternative embodiments,
the silicon donor wafer may be coupled to the upper bonding plate
mechanism 400, for example by clips, chuck mechanisms, vacuum, etc.
when the upper bonding plate mechanism 400 is in the open
position.
[0058] In general, the upper bonding plate mechanism 400 is
operable to provide at least one of controlled heating, voltage,
and cooling to the silicon donor wafer, while the lower bonding
plate mechanism 500 is operable to provide at least one of
controlled heating, voltage, and cooling to the glass substrate.
The lift and press mechanism 100 is operatively coupled to the
upper and lower bonding plate mechanisms 400, 500 and is operable
to urge the first and second bonding plate mechanisms 400, 500
toward one another to achieve controlled pressure of the silicon
donor wafer against the glass substrate along respective surfaces
(i.e., an interface) thereof. The control unit is operable to
produce control signals to the upper and lower bonding plate
mechanisms 400, 500 and the lift and press mechanism 100 to provide
heating, voltage, and pressure profiles sufficient to achieve
anodic bonding between the silicon donor wafer and the glass
substrate. The control unit is also operable to produce control
signals to the upper and/or the lower bonding plate mechanisms 400,
500 to actively cool same and facilitate separation of the
exfoliation layer from the silicon donor wafer after bonding.
[0059] As shown in FIG. 2, after the upper bonding plate mechanism
400 rotates upward and away from the lower bonding plate mechanism
500 and the silicon donor wafer and the glass substrate are
inserted therebetween, the upper bonding plate mechanism 400 is
operable to rotate downward (via the open and close mechanism 200)
such that the upper and lower bonding plate mechanisms 400, 500 are
spaced apart. Thus, when the silicon donor wafer is set atop the
glass substrate, the upper bonding plate mechanism 400 will be
spaced apart from the silicon donor wafer. Alternatively, if the
silicon donor wafer is coupled to the upper bonding plate mechanism
400 (e.g., by the aforementioned clips, chuck, vacuum, etc.), the
silicon donor wafer and the glass substrate will be spaced apart.
If the latter approach is employed, separate heating of the silicon
donor wafer and the glass substrate to specific temperatures (which
may approach and/or exceed 1000.degree. C.) may commence by way of
controlled energizing of the respective upper and lower bonding
plate mechanisms 400, 500. If the former approach is employed,
separate heating may commence after full closure of the bonding
apparatus 10.
[0060] As shown in FIGS. 4A and 4B, the silicon donor wafer and the
glass substrate may contact one another under the controlled
actuation of the lift and press mechanism 100. The lift and press
mechanism 100 raises the lower bonding plate mechanism 500 (and the
glass substrate) into position such that controlled heating and
pressure between the silicon donor wafer and the glass substrate
may be achieved. The silicon donor wafer and the glass substrate
are also subject to a differential voltage potential of about 1750
volts DC imposed by the respective upper and lower bonding plate
mechanisms 400, 500. The pressure, temperature differential, and
voltage differential are applied for a controlled period of time.
Thereafter, the voltage is brought to zero and the silicon donor
wafer and the glass substrate are permitted to cool (which may
involve active cooling), which at least initiates the separation of
the exfoliation layer from the silicon donor wafer. Although not
believed likely, if the separation between the exfoliation layer
and the silicon donor wafer is not complete from the cooling
process, one or more mechanical or other mechanisms may be used to
assist in the exfoliation process.
[0061] A more detailed discussion of the respective elements of the
bonding apparatus 10 will now be described. FIG. 5 is a
perspective, partially exploded, view of the bonding apparatus 10.
Thus, the specific components of the lift and press mechanism 100,
the open and close mechanism 200, the spacer mechanism 300, and the
upper and lower bonding plate mechanisms 400, 500 are easily
discerned.
[0062] With further reference to FIG. 6, an embodiment of the lift
and press mechanism 100 will now be discussed. The lift and press
mechanism 100 is coupled to the lower bonding plate mechanism 500
and is operable to urge the upper and lower bonding plate
mechanisms 400, 500 toward one another to achieve controlled
pressure of the silicon donor wafer and the glass substrate against
one another along respective surfaces thereof to assist in the
anodic bonding of same. In this embodiment, the lift and press
mechanism 100 is operable to permit two basic movements of the
lower bonding plate mechanism 500: (i) pre-loading movement in
which the lower bonding plate mechanism 500 moves the glass
substrate vertically toward the upper bonding plate mechanism 400
to achieve initial pre-load positioning of the upper and lower
bonding plate mechanisms 400, 500 (and thus the glass substrate and
the silicon donor wafer); and (ii) pressure loading movement in
which the glass substrate is pressed against the silicon donor
wafer at a controlled pressure (which may also permit
self-alignment between the glass substrate and the silicon donor
wafer for substantially uniform pressure distribution).
[0063] The lift and press mechanism 100 includes a base 102, a
first actuator 104, a second actuator 106, and a lower mount 108.
The base 102 includes an upper surface 110 and a lower surface 112.
The first actuator 104 may be coupled to the lower surface 112 of
the base 102, while the second actuator 106 may be coupled to the
upper surface 110 of the base 102. The lower mount 108 is coupled
to the second actuator 106 such that the second actuator 106 is
interposed between the base 102 and the lower mount 108.
[0064] The base 102 is slideable with respect to a plurality of
guide posts 114, 116, 118. (Although three guide posts are shown, a
lesser or greater number of guide posts may be employed.) By way of
example, the base 102 may include respective guide bushings 120,
122, 124 (where bushing 124 is not visible), whereby the respective
guide posts 114, 116, 118 are coaxially disposed within the
respective guide bushings 120, 122, 124 such that the guide posts
114, 116, 118 may slide longitudinally within the guide bushings
120, 122, 124. The respective guide posts 114, 116, 118 may be
anchored to the base plate 12 of the bonding apparatus 10 by way of
fasteners 130.
[0065] In accordance with one or more embodiments, actuation of the
first actuator 104 may achieve the aforementioned pre-loading
movement in which the lower bonding plate mechanism 500 moves via
the lower mount 108 toward the upper bonding plate mechanism 400 to
achieve initial pre-load positioning of the upper and lower bonding
plate mechanisms 400, 500 (and thus the glass substrate and the
silicon donor wafer). This pre-load movement may be a coarse
displacement of the lower bonding plate mechanism 500 toward the
upper bonding plate mechanism 400. The first actuator 104 and the
second actuator 106 may be mounted in axial alignment with the
lower bonding plate mechanism 500 such that the actuation of the
first actuator 104 imparts the coarse displacement of both the
second actuator 106 and the lower bonding-plate mechanism 500.
[0066] More particularly, the first actuator 104 may include a
shaft 104A that is operable to move the first actuator 104 upward
and downward. The shaft 104A may be driven by way of any suitable
device, such as an electromechanical solenoid, a hydraulic piston
arrangement, etc. Upward and downward movement of the first
actuator 104 may cause corresponding movement of the base 102,
whereby the planar orientation of the base 102 is maintained by way
of the guide posts 114, 116, 118 as they slide within the guide
bushings 120, 122, 124. The movement of the base 102 results in
corresponding movements of the second actuator 106, the lower mount
108, and the lower bonding plate mechanism 500. The movement of the
first actuator 104 by way of the shaft 104A may be mechanically,
electrically, and/or hydraulically limited such that the preloading
movement of the lower bonding plate mechanism 500 is controlled. As
shown in FIG. 6, the limited movement may be measured by the
distance D between the respective fasteners 130 and the guide
bushings 120, 122, 124 as compared with a substantially zero or
resting distance therebetween as illustrated in FIG. 3.
[0067] The second actuator 106 of the lift and press mechanism 100
is operable to impart a controllable force (e.g., fine movement as
compared with the aforementioned coarse movement) on the lower
bonding plate mechanism 500, where the controllable force is
substantially perpendicular to the bearing surface (i.e., the
surface that contacts the glass substrate) of the lower bonding
plate mechanism 500. As the bearing surface of the upper bonding
plate mechanism 400 is parallel to the bearing surface of the lower
bonding plate mechanism 500, the second actuator 106 of the lift
and press mechanism 100 ensures that no (or minimal) lateral forces
are applied as between the silicon donor wafer and the glass
substrate, which might cause scraping or other impediments to the
quality of the anodic bond.
[0068] The second actuator 106 may be a bellows actuator that is
operable to move the lower mount 108 upward and downward in
response to changing the internal fluid pressure (e.g., liquid or
gas pressure) of the bellows. The second actuator 106 may be
independently controlled (with respect to the first actuator 104)
in order to achieve the aforementioned pressure loading movement in
which the glass substrate is pressed against the silicon donor
wafer. Careful control of the second actuator 106 by way of the
control unit (e.g., control of the pressure within the bellows) may
be employed to establish the proper pressure (psi) as between the
glass substrate and the silicon donor wafer for anodic bonding.
Further, employing a bellows in second actuator 106 permits the
lower mount 108, the lower bonding plate mechanism 500, and the
glass substrate to float or self-align with respect to the upper
bonding plate mechanism 400 (and the silicon donor wafer).
[0069] The lift and press mechanism 100 may also include a
plurality of mounting elements, such as upwardly directed posts 140
that are coupled to the lower mount 108. The mounting elements 140
are operable to engage and retain the spacer mechanism 300 as will
be discussed in more detail later in this description.
[0070] As best seen in FIG. 5, the lift and press mechanism 100 may
also include a position sensor 150 coupled to the lower mount 108
and/or the lower bonding plate mechanism 500. The position sensor
150 is operable to provide an output signal to the control
mechanism indicating to what extent the lower bonding plate
mechanism 500 has been moved. For example, the output signal of the
position sensor 150 may provide an indication of whether the
aforementioned coarse displacement of the lower bonding plate
mechanism 500 (toward the upper bonding plate mechanism 400) has
taken place. This may provide an indication of when to initiate
heating, preload pressure and seed voltage application, etc. The
output signal of the position sensor 150 may additionally or
alternatively provide an indication of the velocity and/or
acceleration of the lower bonding plate mechanism 500. Those
skilled in the art will appreciate that the position, velocity,
acceleration, etc. of the lower bonding plate mechanism 500 may be
computed by the control unit based on one or more position
measurements obtained from the output signal of the position sensor
150 and a time base. By way of example, the position sensor may be
implemented using a linear voltage differential transformer (LVDT),
which provides a varying amplitude output signal as a function of a
movable core of the transformer.
[0071] An embodiment of the open and close mechanism 200 will now
be discussed with further reference to FIG. 7. In this embodiment,
the open and close mechanism 200 includes a lift assembly 202, an
actuator assembly 204, a tilt assembly 206, and a mount plate 208.
The open and close mechanism 200 is coupled to the upper bonding
plate mechanism 400 (not shown in FIG. 7, see FIGS. 1 and 5) and is
operable to: (i) assist, when in a closed orientation, in holding
the upper bonding plate mechanism 400 in position with respect to
the lower bonding plate mechanism 500 such that movement of the
lower bonding plate mechanism 500 toward the upper bonding plate
mechanism 400 achieves controlled pressure of the silicon donor
wafer against the glass substrate; and (ii) provide a dual motion
opening profile, where a first motion separates the upper bonding
plate mechanism 400 from the lower bonding plate mechanism 500 in a
direction substantially perpendicular to the respective bearing
planes thereof, and a second motion tilts the upper bonding plate
mechanism 400 away from the lower bonding plate mechanism 500 such
that the bearing plane of the upper bonding plate mechanism 400 is
oblique to the bearing plane of the lower bonding plate mechanism
500.
[0072] As to the dual motion opening profile, the lift assembly
202, the actuator assembly 204, the tilt assembly 206, and the
mount plate 208 cooperate to achieve two basic movements: (i) a
vertical movement of the mount plate 208 with respect to the base
plate 12; and (ii) a tilt movement to permit the mount plate 208 to
rotate upward with respect to the base plate 12. Noting that the
upper bonding plate mechanism 400 is operable to couple to the
mount plate 208, the rotation of the mount plate 208 permits access
(as discussed above) for inserting the silicon donor wafer and the
glass substrate into the bonding apparatus 10 between the upper and
lower bonding plate mechanisms 400, 500. The vertical movement of
the mount plate 208 (and the upper bonding plate mechanism 400)
permits an initial separation motion as between the upper and lower
bonding plate mechanisms 400, 500 that is substantially purely
vertical. This permits separation without sideways scraping that
might otherwise damage the SOG structure. These features will be
discussed in more detail below.
[0073] The lift assembly 202 includes a base 210, a guide shaft
212, and a guide bushing 214. The base 210 is operable to connect
directly or indirectly to the base plate 12 and to provide a rigid
reference from which the lift and tilt motions may be launched. The
guide shaft 212 is operatively coupled to the base 210 and extends
vertically toward the tilt assembly 206 and the mount plate 208.
The guide bushing 214 is operable to slidingly engage the guide
shaft 212. As will be discussed in more detail below, the sliding
movement of the guide bushing 214 with respect to the guide shaft
212 causes the vertical movement and the rotational movement of the
mount plate 208. The guide bushing 214 includes a fastening plate
216 that is operable to permit a mechanical linkage to the actuator
assembly 204.
[0074] The actuator assembly 204 is operable to provide vertical
force to the fastening plate 216 of the guide bushing 214, such
that controlled sliding of the guide bushing 214 is achieved, again
to obtain the lift and tilt motions of the mount plate 208. In one
embodiment, the actuator assembly 204 may include a jack 230, such
as a Duff-Norton jack, a shaft 232 linked to the jack 230, and a
coupling element 234 connected to the fastening plate 216 of the
guide bushing 214. In one or more embodiments, the Duff-Norton jack
230 is operable such that application of a rotational force on a
shaft 236 causes a vertical movement of the shaft 232 and a
resultant vertical movement of the guide bushing 214. The actuation
of the jack 230 may be controlled via the control unit, such as by
employing an electrical motor to turn the shaft 236.
[0075] The mount plate 208 may include a first end 240 that is
operable to engage the upper bonding plate mechanism 400, and a
second end 242 that is operatively coupled to the tilt assembly
206. In this embodiment, the tilt assembly 206 includes a hinge
plate 250 that couples the mount plate 208 to the lift assembly 202
(which will be discussed in more detail below). The tilt assembly
206 also includes first and second stop arms 252, 254 and a
pivoting linkage 258 of the hinge plate 250 to the mount plate 208.
The stop arms 252, 254 are coupled to the base plate 12 at first
ends thereof, and are coupled to the mount plate 208 at second ends
thereof. The stop arms 252, 254 may be rotationally coupled to the
base plate 12 at the first ends such that vertical movement thereof
(with respect to the base plate 12) is prevented but pivotable
movement of the second ends about the first ends is permitted. Each
of the stop arms 252, 254 include a slot 256 that is operable to
receive a corresponding roller or post 244 extending laterally from
the second end 242 of the mount plate 208.
[0076] The mount plate 208 is operatively coupled to the hinge
plate 250 by way of the pivoting linkage 258. More particularly,
the hinge plate 250 includes a block 260 that extends at least
partially into an aperture 245 of the mount plate 208. The pivoting
linkage 258 permits the mount plate 208 to swivel or pivot about
the pivoting linkage 258. The aperture 245 may be sized and shaped
such that the block 260 may swivel within the aperture 245 without
interference.
[0077] In response to actuation of the jack 230 (for example, via
applying a rotational force to the shaft 236), the shaft 232 may
raise/lower the guide bushing 214. In the orientation shown, the
guide bushing 214 raises in response to the aforementioned
actuation, thereby imparting vertical movement (upward) to the
hinge plate 250. In response, the hinge plate 250 applies a
vertical force to the mount plate 208 by way of the block 260 and
pivoting linkage 258. Notably, the mount plate 208 moves by way of
the block 260 in a manner such that the bearing planes of the upper
and lower bonding plate mechanisms 400, 500 remain substantially
parallel throughout substantially all of a limited travel of the
upper bonding plate mechanism 400 during the lift motion.
[0078] The vertical force applied to the mount plate 208 by way of
the hinge plate 250 causes the rollers or pins 244 of the mount
plate 208 to move upward within the respective slots 256 of the
respective stop arms 252, 254. The mount plate 208 will, therefore,
rise vertically away from the base plate 12 while maintaining a
substantially parallel relationship thereto. The vertical upward
movement (or lift), while maintaining a substantially parallel
orientation with respect to the base plate 12, will continue for
limited travel, i.e., until the rollers or pins 244 of the mount
plate 208 engage an upper limit within the slots 256. When the
rollers or pins 244 reach this limit, a continued upward force on
the mount plate 208 by the block 260 causes the first end 240 of
the mount plate 208 to tilt upward in response to a rotational
movement about the pivoting linkage 258. (Slight pivoting movement
of the stop arms 252, 254 about the first ends thereof is permitted
to account for lateral movement of the mount plate 208 in response
to pivoting about the pivoting linkage 258.) The degree to which
the mount plate 208 tilts may be adjusted by way of stops 257
located at the ends of the respective stop arms 252, 254. By way of
example, the stops 257 may include threaded rods and nuts, where
the threaded rods may be turned into and out of the associated slot
256 by varying amounts. This adjustment in the usable lengths of
the slots 256 permit a change in the permissible travel of the
rollers or pins 244 and in the degree to which the mount plate 208
tilts.
[0079] A reversal of the actuator assembly 204 results in the mount
plate 208 tilting downward to its substantially parallel
orientation with the base plate 12, followed by a vertical movement
downward where the mount plate 208 maintains a substantially
parallel relationship with the base plate 12. The parallel
orientation of the mount plate 208 may be adjusted by way of one or
more stops 259 of the hinge plate 250. For example, the stops 259
may include threaded bolts that may be threaded into and out of the
hinge plate 250 to provide an adjustable resting position for the
mount plate 208.
[0080] The first end 240 of the mount plate 208 also preferably
includes a plurality of locks 246 that are operable to engage and
couple to upper ends 114A, 116A, 118A of the guide posts 114, 116,
118 of the lift and press mechanism 100 (see FIG. 6). By way of
example, the locks 246 may be implemented utilizing threaded bolts
that may be manipulated manually. When the mount plate 208 lowers
to the position shown in FIGS. 4A, 4B, the locks 246 ensure that
the upward pressure on the silicon donor wafer and the upper
bonding plate mechanism 400 may be countered by the mount plate 208
without exposing the lift assembly 202, the actuator assembly 204
or the tilt assembly 206 to excessive force.
[0081] The first end 240 of the mount plate 208 also includes a
plurality of apertures through which various wires, cables, and
conduits may pass as will be discussed in more detail
hereinbelow.
[0082] Reference is now made to FIGS. 8A and 8B, which provide
further details regarding the upper bonding plate mechanism 400.
FIG. 8A is a perspective view of the upper bonding plate mechanism
400, while FIG. 8B is a cross-sectional view thereof. Owing to the
symmetry of the bonding apparatus 10, it is noted that the
functional and/or structural details of the upper bonding plate
mechanism 400 may readily be applied to the lower bonding plate
mechanism 500 (as will be discussed below).
[0083] The primary components of the upper bonding plate mechanism
400 include a base 402, an insulator 404, a back plate 406, a
heater disk 408, and a thermal spreader 410. The primary functions
of the upper bonding plate mechanism 400 include heating the
silicon donor wafer, providing pressure to the silicon donor wafer,
providing a voltage potential to the silicon donor wafer, and
cooling the silicon donor wafer.
[0084] The heating function originates at the heater disk 408 and
is operable to provide temperatures lower or greater than about
600.degree. C., and may approach or exceed temperatures of
1,000.degree. C. This embodiment of the upper bonding plate
mechanism 400 is also operable to provide the heat uniformly to
within +/-0.5% of the controlled set-point across substantially the
entire silicon donor wafer.
[0085] The pressure imparted to the silicon donor wafer by the
upper bonding plate mechanism 400 is substantially uniformly
distributed over the wafer by way of the thermal spreader 410,
which provides a counter-force to the upward pressure by the glass
substrate (imparted by the lower bonding plate mechanism 500). This
results in a pressure profile at the interface of the silicon donor
wafer and the glass substrate suitable for anodic bonding. By
controlling the upward pressure imparted by the lower bonding plate
mechanism 500 (e.g., under the control of the control unit) the
pressure profile may include at least a peak pressure of between
about 1 pound per square inch (psi) to 100 psi. Lower pressures of
between about 10 to 50 psi (for example, about 20 psi) are believed
advantageous as they are less likely to crack the silicon donor
wafer or the glass substrate.
[0086] As discussed above, the silicon donor wafer and the glass
substrate are subject to a differential voltage potential of about
1750 volts DC, which is imposed by the respective upper and lower
bonding plate mechanisms 400, 500. It is noted that this voltage
potential may be achieved by: (i) applying a voltage potential to
one of the silicon donor wafer and the glass substrate (while
grounding the other); or by (ii) applying respective voltage
potentials to both the silicon donor wafer and the glass substrate
(such as a positive voltage potential to the silicon donor wafer
and a negative voltage potential to the glass substrate). Thus, the
ability of the upper bonding plate mechanisms 400 to impart a
voltage potential (other than ground) to the silicon donor wafer is
an optional feature. If a bonding voltage potential (other than
ground) is applied to the silicon donor wafer by the upper bonding
plate mechanism 400, such may be distributed by the thermal
spreader 410 substantially uniformly over the entire surface of the
wafer.
[0087] While the present invention is not limited by any theory of
operation, it is noted that there may be a general relationship
between bonding voltage, temperature, time, and material
properties. For example, as the bonding voltage decreases, the
temperature, time and/or amount of conductivity ions (e.g., of the
glass substrate) may be increased to at least tend toward the same
bonding result. The relationship also holds when the temperature,
time and/or amount of conductivity ions are the independent
variable. The bonding voltage potential between the silicon donor
wafer and the glass substrate may be in the range of about 100
volts DC (or lower) to about 2000 volts DC (or greater) and may be
measured using peak, average, RMS, or other measurement
conventions. For certain type of glass substrates a bonding voltage
in the range of about 1000 volts DC to about 2000 volts DC is
suitable.
[0088] If active cooling of the silicon donor wafer is desired,
such may be achieved utilizing controlled fluid flow through the
upper bonding plate mechanism 400. These and other features of the
upper bonding plate mechanism 400 will be discussed in more detail
below.
[0089] The base 402 of the upper bonding plate mechanism 400 is of
substantially cylindrical construction and defines an interior
volume for receiving the insulator 404. By way of example, the base
402 may be formed from a machinable glass ceramic (e.g., MACOR),
which provides structural integrity as well as high temperature
capabilities. Other suitable materials may additionally or
alternatively be employed to form the base 402. The insulator 404
is operable to limit or impede heat flow from the heater disk 408
into the base 402 (and other portions of the bonding apparatus 10).
By way of example, the insulator 404 may be formed from a ceramic
foam insulating material, such as 40% dense fused silica. Other
suitable insulating materials may additionally or alternatively be
employed. The insulator 404 should provide significant insulating
capabilities inasmuch as the heater disk 408 is operable to attain
temperatures of 600.degree. C. or more, such as reaching or
exceeding 1,000.degree. C. It is noted that insufficient insulation
that would permit significant heat flow into the base 402 could
have catastrophic consequences in terms of the proper operation of
other portions of the bonding apparatus 10. In addition, a
relatively high degree of insulation as between the base 402 and
the heater disk 408 insures a relatively low thermal inertia of the
upper bonding plate mechanism 400, which assists in achieving rapid
thermal cycling capabilities.
[0090] The back plate 406 is insulated from the base 402 by way of
the insulator 404. The back plate 406 is operable to provide at
least one cooling channel 420 through which cooling fluid may flow
when it is desirable to actively reduce the temperature of the SOG
structure, specifically the silicon donor wafer. By way of example,
the back plate 406 may be formed from hot pressed boron nitride
(HBN) in order to withstand high temperatures and relatively rapid
changes in temperature (as is the case when cooling fluid is
introduced into the channel 420). Other suitable materials may
additionally or alternatively by employed to form the back plate
406. At least one inlet tube 422 is operable to introduce cooling
fluid into the channel 420, while at least one outlet tube 424 (not
viewable in FIG. 8B, but see FIG. 11B, as will be discussed below)
is operable to remove the cooling fluid from the channel 420. A
heat exchanger (not shown) may be employed to cool the cooling
fluid prior to reintroducing same into the inlet tube 422.
[0091] Active cooling may be achieved by controlling the
temperature and flow rate of the cooling fluid through the channel
420 using the control unit. For example, the cooling profile of the
upper bonding plate mechanism 400 may be actively controlled (e.g.,
by the control unit) to provide at least one of differing rates of
cooling and differing levels of cooling (e.g., dwells) to the
silicon donor wafer. It is believed that providing differing
cooling profiles to the silicon donor wafer and the glass
substrate, respectively, facilitates better separation of the
exfoliation layer from the silicon donor wafer. Notably, the active
cooling feature of the upper bonding plate mechanism 400 is
optional as the differential cooling profiles as between the
silicon donor wafer and the glass substrate, respectively, may be
achieved through active cooling of the glass substrate (and not the
silicon donor wafer) via the lower bonding plate mechanism 500 (as
will be discussed in more detail below).
[0092] A cap ring 426 (see FIG. 8B) is operable to maintain the
insulator 404 in position within the base 402 as well as to provide
a recess within which the heater disk 408 may be disposed. The cap
ring 426 may be formed from a machinable glass ceramic (such as the
aforementioned MACOR).
[0093] The heater disk 408 is operable to generate heat in response
to electrical excitation (voltage and current), while also
providing electrical insulation properties such that the potential
applied to the silicon donor wafer is not applied to the back plate
406 or the base 402. Indeed, the relatively high voltage potential
applied to the silicon donor wafer should be confined. Thus, the
heater disk 408 may be formed from a material that exhibits
substantial electrical insulting properties and substantial thermal
conductivity. One such suitable material is pyrolytic boron nitride
(PBN).
[0094] With reference to FIGS. 9A and 9B, two examples of heater
disk designs are illustrated that are suitable for implementing the
heater disk 408. FIG. 9A is a perspective view of a first heater
disk 408A, while FIG. 9B is a perspective view of an alternative,
second heater disk 408B. As substantially uniform heating is
desired, the heater disks 408A, 408B may include thermal edge loss
compensation, such that the tendency for outer portions of the
heater disks 408A, 408B to run cooler than the central portions
thereof may be managed. In the embodiments shown, the thermal edge
loss compensation of the heater disks 408A, 408B may be achieved
using two heating zones, one substantially centrally located and
the other in the form of an annular ring around the central zone.
The heating zones may be implemented using respective heating
elements.
[0095] The heater disk 408A of FIG. 9A includes two separate
heating elements 409A and 409B, where heating element 409B is
substantially centrally located and heating element 409A is in the
form of an annular ring around heating element 409B. Each heating
element 409A, 409B includes a pair of terminals 411A, 411B to which
respective power sources may be connected. The voltage and current
excitation from the respective power sources to the heater elements
409A and 409B of the heater disk 408A may be separately controlled
via the control unit such that the respective temperatures of the
two heating zones may be separately regulated and compensation of
thermal edge loss may be achieved.
[0096] The heating elements 409A and 409B may be formed from
pyrolytic graphite (PG), THERMAFOIL, etc. THERMOFOIL material is a
thin, flexible material having heating properties, which include an
etched foil resistive element laminated between layers of flexible
insulation. While THERMOFOIL may exhibit better reliability in a
vacuum environment, non-vacuum environments (which may include one
or more oxidizing agents, such as air environments) are also
contemplated herein. In a non-vacuum atmosphere, the heating
elements 409A and 409B may be formed from INCONEL, which includes a
family of high strength austenitic nickel-chromium-iron alloys that
have good anti-corrosion and heat-resistance properties.
[0097] In one or more embodiments, the heater elements 409A and
409B may be vertically offset to assist in thermal edge loss
compensation. For example, the heater element 409B in the central
zone may be located toward a bottom side of the heater disk 408A,
while the heater element 409A in the annular zone may be disposed
at or toward the upper side of the heater disk 408A. This reduces
the thermal resistance between the heater element 409A at the
periphery of the heater disk 408A and the silicon donor wafer as
compared with the thermal resistance between the heater element
409B at the center of the heater disk 408A and the silicon donor
wafer. The offset feature may be achieved, for example, by
interposing a spacer element (not shown), e.g., a sheet of
material, between the heater elements 409A, 409B. This may also
permit the terminals 411B to exit laterally rather than downward as
illustrated in FIG. 9A.
[0098] The heater disk 408B of FIG. 9B includes an integrally
formed, contiguous heating element that operates as if having
separate heating elements 409C, 409D. In particular, the widths
(and/or the thickness) of the resistive material used to form the
heating element is varied depending on its location within the
heater disk 408B. For example, the width of the heating element at
peripheral positions 409C is lower than the width of the heating
element at central positions 409D. Varying the width of the heating
element changes the resistance of (and thus the heating
characteristics) of the heating element as a function of position.
By varying the resistance of the integrated heating element as a
function of position from a central region of the heater disk 408B,
only a single voltage and current excitation is needed to achieve
the thermal edge loss compensation. Indeed, the integrated heater
element will respond (heat) differently in response to the
excitation voltage and current due to the varying resistance of
same in regions 409C and 409D.
[0099] Irrespective of the heater element construction, the
resistance of the heating element(s) may be on the order of about
10-20 Ohms (e.g., about 15 Ohms). To achieve the aforementioned
heating levels of about 600.degree. C. to 1000.degree. C., a
voltage of about 220 volts (AC) may be applied across the heating
elements, which causes a heat dissipation on the order of about
3250 Watts RMS.
[0100] In one or more embodiments, the heater disk 408 exhibits
relatively low thermal inertia, due at least in part by the choice
of materials and construction. The heater disk may measure about 2
mm thick using the materials and construction details discussed
above. The relatively low thickness (as compared with prior art
heating elements measuring 1-2 inches thick) contributes to a lower
thermal mass and thermal inertia, which assists in achieving rapid
thermal cycling capabilities.
[0101] The thermal spreader 410 is in thermal communication with
the heater disk 408 and is operable to integrate the heating
profile presented by the heater disk 408 such that a more uniform
presentation of heat is imparted to the silicon donor wafer. The
thermal spreader 410 may be both electrically and thermally
conductive, as it is in direct contact with the silicon donor wafer
and facilitates heating the wafer and applying the aforementioned
high voltage thereto.
[0102] Among the materials that may be employed to implement the
thermal spreader 410, electrically conductive graphite is
desirable, such as THERMAFOIL. In a non-vacuum atmosphere (e.g.,
air), the thermal spreader 410 may be formed from other materials
that may exhibit better reliability in oxidizing environments, such
as a non-oxidizing electro-thermal conductive element, copper with
a non-oxidizing coating (such as electroless nickel, platinum,
molybdenum, tantalum, etc.), THERMOFOIL with a non-oxidizing
coating (such as electroless nickel, platinum, molybdenum,
tantalum, etc.), silicon carbide (which may or may not be coated)
KEVLAR with a metal coating (such as electroless nickel, platinum,
molybdenum, tantalum, etc.).
[0103] In one or more embodiments, the thermal spreader 410 also
exhibits relatively low thermal inertia, due again at least in part
by the choice of materials and construction. The thermal spreader
410 may measure about 0.5-6 mm thick using the materials and
construction details discussed above.
[0104] The relatively low thicknesses of the heater disk 408 and
the thermal spreader 410, coupled with the high insulation
properties exhibited by the insulator 404 and other material
choices discussed above, contribute to very low thermal mass and
thermal inertia of the upper bonding plate mechanism 400. Thus, the
upper bonding plate mechanism 400 may heat a material sheet from
room temperature to about 1000.degree. C. in about 2 minutes and
cool same to room temperature in about 10 minutes or less. This is
in comparison to prior art substrate heaters, which may take about
one-half hour to one hour to elevate a material sheet from room
temperature to only about 600.degree. C., and may take about 20
minutes to cool the material sheet to room temperature.
[0105] The control unit is operable to program the upper bonding
plate mechanism 400 to follow any desired heat-up or cool down ramp
and dwell at any desired processing temperature.
[0106] As shown in FIG. 8A, the upper bonding plate mechanism 400
may include an aperture 450 that permits access to the silicon
donor wafer during the bonding process, for example to impart a
pre-charge voltage to the wafer. This optional feature will be
discussed in further detail later in this description.
[0107] FIG. 10 illustrates an exploded view of the upper bonding
plate mechanism 400 (excluding the base 402 and the insulator 404).
As shown in the exploded view, the upper bonding plate mechanism
400 is a multi-layer assembly including a support ring 430, a
gasket 432, the back plate 406, a gasket 434, the heater disk 408,
and the thermal spreader 410. The support ring 430 provides a
support for the back plate 406 and for the gasket 432. The back
plate 406 is sandwiched between the gasket 432 and the gasket 434,
which operate to prevent the cooling fluid from leaking as it flows
through the channels 420. Among the materials from which the
gaskets 432, 434 may be formed, the GRAFOIL ring material is
desirable because it exhibits suitable sealing and heat resistant
properties. The heater disk 408 overlies the gasket 434 and the
thermal spreader 410 is disposed above the heater disk 408. The
respective layers of the upper bonding plate mechanism 400 may be
coupled to one another utilizing bolts.
[0108] In one or more embodiments, the back plate 406 may include a
single, contiguous channel 420 or multiple separate channels 420.
As illustrated in FIG. 10, the back plate 406 includes two separate
channels 420, which each receive cooling fluid via respective
inlets 406A, 406B, and emit the cooling fluid via a shared outlet
406C. The dual cooling channels 420 ensure more even cooling across
the thermal spreader 410 (and thus the silicon donor wafer).
[0109] Notably, the thermal spreader 410 includes a plurality of
fins 436 that extend radially outward from a peripheral edge of the
thermal spreader 410. The fins 436 provide a peripheral surface
that is utilized to maintain the thermal spreader 410 in position
and to provide a connection to a high voltage source. As best seen
in FIG. 8B, the fins 436 are engaged by respective retainer clips
440 and prevent the thermal spreader 410 from moving. Preferably,
the retainer clips 440 are formed from a machinable glass ceramic
(e.g., MACOR), such that they provide electrical insulation and
good structural integrity.
[0110] As discussed above, the upper bonding plate mechanism 400
may optionally include the aperture 450, which may be implemented
by way of separate apertures 450 of the base 402, the insulator
404, the back plate 406, the heating disk 408, and the thermal
spreader 410. The aperture 450 may be centrally located such that
access to a central region of the silicon donor wafer (e.g., the
center thereof) may be obtained. A use of the access to the silicon
donor wafer provided by the aperture 450 will be discussed in more
detail below.
[0111] Reference is now made to FIGS. 11A, 11B, and 11C, which
illustrates further structural and functional aspects of the upper
bonding plate mechanism 400. FIGS. 11B and 11C are cross-sectional
views taken through lines 11B-11B and 11C-11C, respectively. As
best seen in FIG. 11C, excitation voltage and current may be
applied to the heater disk 408 by way of terminals 452, which
extend through the base 402, the insulator 404, and the back plate
406. The number of terminals 452 will depend on how many heating
elements are employed in the heating disk 408 and how the heating
elements are implemented. As discussed above, in one or more
embodiments, two heating elements may be employed for which the
excitation voltages and current may be separately controlled via
the control unit such that the temperatures of the two heating
zones may be tightly regulated. Alternatively, the heating elements
may be integrated (using variable resistance) such that a single
excitation voltage may be employed for temperature regulation and
edge loss compensation.
[0112] As best seen in FIG. 11B, respective fluid couplings 460 may
be connected to the inlet tube(s) 422 and the outlet tube 424 to
permit the connection of a fluid source (not shown) to the upper
bonding plate mechanism 400. Notably, the inlet tube 422 and outlet
tube 424 extend far enough from the base 402 to pass through
apertures in the mount plate 208.
[0113] As best seen in FIGS. 11B and 11C, a relatively high voltage
potential (e.g., as compared to the heater voltage) may be applied
to the thermal spreader 410 by way of high voltage terminal 453,
which extends through the base 402, the insulator 404, the back
plate 406, and the heater disk 408. As discussed above, the voltage
applied to the thermal spreader 410 (which may be between about
1000 to 2000 volts DC) is employed to assist in the anodic bonding
of the silicon donor wafer to the glass substrate.
[0114] Although not shown, the upper bonding plate mechanism 400
may also include one or more vacuum conduits that extend to the
thermal spreader 410, through the base 402, the insulator 404, the
back plate 406, and the heater disk 408. If employed, the vacuum
conduits permit the application of a vacuum to the silicon donor
wafer when it is placed against the thermal spreader 410 such that
the wafer will be coupled to the thermal spreader 410 when the
upper bonding plate mechanism 400 is in the upwardly rotated (open)
position, as shown in FIG. 2. Application of the vacuum may be
achieve using a conventional vacuum source (not shown) that is
controlled via the control unit or manually by an operator of the
bonding apparatus 10.
[0115] As discussed above, the upper bonding plate mechanism 400
may optionally include the aperture 450 to permit access to the
silicon donor wafer during the bonding process. When the aperture
450 is employed, a preferred use thereof is to permit a preload
pressure and/or seed voltage to be applied to the silicon donor
wafer prior to application of the bonding voltage. The purpose of
the preload pressure and seed voltage is to initiate anodic bonding
in a localized area of the interface between the silicon donor
wafer and the glass substrate prior to application of the bonding
voltage, which facilitates anodic bonding across substantially the
entire area of the interface. The seed voltage may be of the same
or different magnitude as the bonding voltage, however, a lower or
equal voltage is believed to be superior, e.g., about 750-1000
volts DC. The aperture 450 may be centrally located such that the
initial anodic bonding occurs at or near a central region of the
interface between the silicon donor wafer and the glass
substrate.
[0116] Reference is now made to FIGS. 12A, 12B, and 13, which
illustrate a suitable apparatus for achieving aforementioned
preload pressure and seed voltage functionality. FIG. 12A
illustrates a side view of a preload plunger 470 that is operable
to engage the upper bonding plate mechanism 400 and extend through
the aperture 450 thereof to mechanically and electrically
communicate with the silicon donor wafer. FIG. 12B is a
cross-sectional view of the preload plunger 470 of FIG. 12A, while
FIG. 13 is a cross-sectional view of the upper and lower bonding
plate mechanisms 400, 500 with the preload plunger 470 coupled to
the upper bonding plate mechanism 400. The preload plunger 470
includes a housing 472 having a proximal end 474 and a distal end
476. An electrical terminal 478 is disposed at the proximal end of
the housing 474 and provides a means for connecting a voltage
source from which the preload potential is obtained. A plunger 480
is partially disposed within the housing 472 and extends through
the distal end 476 of the housing 472. The plunger 480 is slideable
within the housing 472, in a telescoping fashion. The plunger 480
includes a stop 482 at one end to prevent the plunger 480 from
passing all the way through the distal end 476 and becoming
disengaged from the housing 472. An electrode 484 is coaxially
disposed within the plunger 480, where a tip 486 of the electrode
484 extends beyond an end of the plunger 480. (As will be discussed
in more detail below, the tip 486 engages the silicon donor
wafer.)
[0117] A first compression spring 488 mechanically and electrically
couples the electrode 484 and the terminal 478 such that the
slideable movement of the plunger 480 does not disturb the
electrical connection between the terminal 478 and the electrode
484. The first compression spring 488 also urges or biases the
electrode 484 (and the plunger 480) forward such that the stop 482
engages the housing 472. A second compression spring 490 also urges
the plunger 480 forward such that the stop 482 engages the housing
472 and biases the plunger 480 and the electrode 484 in an extended
orientation. An axially directed force on the electrode 484 and the
plunger 480 is absorbed by the respective compression springs 488,
490 such that the tip 486 of the electrode 484 is biased toward and
maintains an electrical connection with the silicon donor wafer.
The electrode 484 thus delivers the seed voltage to the silicon
donor wafer. In one or more embodiments, the electrode 484 may
slide within the plunger 480, such that the plunger 480, itself, is
also biased toward and applies (alone or in combination with the
electrode 484) the preload pressure on the silicon donor wafer.
[0118] In a preferred embodiment, the tip 486 of the electrode 484
extends below the thermal spreader 410 of the upper bonding plate
mechanism 400 such that it contacts the silicon donor wafer when
the lift and press 100 mechanism coarsely displaces the lower
bonding plate mechanism 500 toward the upper bonding plate
mechanism 400 (i.e., as shown in FIGS. 4A-4B before the bonding
apparatus 10 is fully closed). Thus, application of the preload
pressure and seed voltage may initiate the anodic bonding of the
silicon donor wafer and the glass substrate before full pressure,
temperature, and voltage is applied.
[0119] Similar to the application of the bonding voltage to the
silicon donor wafer and the glass substrate, the seed voltage
potential may be achieved by: (i) applying a voltage potential to
one of the silicon donor wafer and the glass substrate (while
grounding the other); or by (ii) applying respective voltage
potentials to both the silicon donor wafer and the glass substrate.
Thus, even if initial bonding in a localized area of the interface
between the silicon donor wafer and the glass substrate is desired,
the ability of the upper bonding plate mechanisms 400 to impart the
seed voltage potential to the silicon donor wafer is an optional
feature. Indeed, as will be discussed later in this description,
the seed voltage potential may be applied to the glass substrate by
way of the lower bonding plate mechanism 500 (while grounding the
silicon donor wafer).
[0120] While the preload pressure and seed voltage may be applied
as discussed above, it is desirable to limit the contact area of
the silicon donor wafer and the glass substrate while the preload
pressure and seed voltage are applied in order to limit the area
over which pre-bonding is permitted. In this regard, the spacer
mechanism 300 may be used in combination with the aforementioned
preload plunger 470. In general, the spacer mechanism 300 is
coupled to the lower bonding plate mechanism 500 (see FIGS. 1 and
5) and is operable to prevent peripheral edges of the silicon donor
wafer and the glass substrate from touching one another when
pre-bonding is achieved in the central region thereof. After the
pre-bonding is achieved, the spacer mechanism 300 permits the
silicon donor wafer and the glass substrate to touch one another
(including the peripheral edges thereof) for the full bonding
procedure to be carried out.
[0121] Reference is now made to FIG. 14, which is a perspective
view of the spacer mechanism 300. The spacer mechanism 300 is
operable to mechanically assist in holding the peripheral regions
of the silicon donor wafer and the glass substrate away from one
another during the application of the preload pressure and seed
voltage. In one or more embodiments, the spacer mechanism 300 is
operable to provide symmetrical (multi-position) shim action as
between the silicon donor wafer and the glass substrate.
[0122] The spacer mechanism 300 is of substantially annular
construction and includes a mount ring 302, a swivel ring 304, and
a plurality of shim assemblies 306. The mount ring 302 is of
substantially annular construction including a central aperture 308
and a peripheral edge 310. A plurality of mounting elements (such
as apertures) 312 are disposed about the peripheral edge 310 and
are of complementary construction as the mounting elements 140,
which may be upwardly directed posts 140 (see FIGS. 1, 5, and 6).
The size, shape and positions of the mounting elements 140 and 312
are such that the mount ring 302 may be coupled to the lower mount
108 of the lift and press mechanism 100. In the illustrated
embodiment, the mount ring 302 cannot rotate with respect to the
lower mount 108 of the lift and press mechanism 100.
[0123] The swivel ring 304 is also of substantially annular
construction and further defines the central aperture 308. The
swivel ring 304 is rotationally coupled to the mount ring 302 and,
therefore, may rotate with respect to the mount ring 302 and the
lower mount 108 of the lift and press mechanism 100. The swivel
ring 304 includes a plurality of cams 320 (e.g., cam slots)
disposed at a peripheral edge thereof, which may include one such
cam 320 for each of the shim assemblies 306. One of the cams 320A
is a geared cam, including a plurality of teeth that are of a pitch
that corresponds with a gear 142 of a stepper motor 144 of the lift
and press mechanism 100 (see FIG. 6). As the stepper motor 144
turns the gear 142, the swivel ring 304 rotates with respect to the
mount ring 302 and the lower mount 108 of the lift and press
mechanism 100. The control unit may provide drive excitation to the
stepper motor 144 to obtain precise rotational movement of the
swivel ring 304.
[0124] Each shim assembly 306 may include a shim 330 coupled to a
slide block 332. The shim 330 is sized and shaped to fit between,
and separate, the silicon donor wafer and the glass substrate. The
shim is operable to achieve radial inward and outward movement with
respect to a center area of the spacer mechanism 300 (and thus a
central area of the interface between the silicon donor wafer and
the glass substrate). This radial movement is achieved by way of
slideable engagement between the slide block 332 and the mount ring
302. For example, each shim assembly may include one or more guide
bushings 334 that slidingly engage a corresponding one or more pins
336. The pins 336 may extend radially away from the peripheral edge
310 of the mount ring 302 such that sliding movement of the guide
bushings 334 along the pins 336 results in the aforementioned
radial movement of the slide block 332 and the shim 330.
[0125] Each slide block 332 also includes a cam guide (not
visible), such as a roller or post, that engages the respective cam
slot 320. Rotation of the swivel ring 304 (via actuation of the
stepper motor 144) applies radial forces to the respective slide
blocks 332 such that they slide in a controlled fashion along the
posts 336 (via the guide bushings 334). Thus, all the shims 330
move in symmetric motion, which prevents any uneven frictional
loads as between the silicon donor wafer and the glass substrate.
It is noted that the rotation of the swivel ring 304 may be
achieved using other actuation means, such as a pneumatic cylinder,
linear motor, solenoid arrangement, etc.
[0126] The shims 330 are preferably electrically insulated such
that the voltage potential(s) of the SOG are not permitted to
couple to the mount ring 302 and other portions of the bonding
apparatus 10. For example, the slide blocks 332 may be formed with
ceramic material. The mount ring 302 and swivel ring 304 may be
positioned below the high heat zone of the lower bonding plate
mechanism 500, which protects them from excessive heat input.
[0127] As best seen in FIG. 11A, the upper bonding plate mechanism
400 may include one or more further apertures to permit access to
the heater disk 408. By way of example, a first aperture 454 may
permit the insertion of a thermocouple through the assembly such
that it may thermally engage the heater disk 408 and provide a
temperature feedback signal to the control unit (which permits
tight temperature regulation of the heater disk 408 and the silicon
donor wafer). It is noted that the aperture 454 extends from the
rear of the upper bonding plate mechanism as viewed in FIG. 11A and
is thus shown in dashed line. A second aperture 456 (also from the
rear) may also be included that provides additional access to the
heater disk 408 for further thermal regulation. Notably, the first
aperture 454 is disposed in the area of the central heating element
of the heater disk 408, while the second aperture 456 is disposed
at or near the annular heating element of the heater disk 408. This
permits independent feedback and control of the energizing signals
to the respective central and annular heating elements (unless they
are integrally formed), thereby permitting compensation for thermal
edge effects as well as overall temperature regulation.
[0128] FIG. 15 is a perspective view of a thermocouple assembly 494
that may be employed to extend through the apertures 454, 456 and
engage the heater disk 408. The thermocouple assembly 494 includes
a standard thermocouple plug 495, a spring assembly 496, and a
probe 498. The probe 498 is operatively urged forward by the spring
assembly 496 such that it is biased against the heater disk 408,
thereby insuring suitable thermal conductivity therebetween.
[0129] The structural details of one or more embodiments of the
lower bonding plate mechanism 500 will now be described. The
primary functions of the lower bonding plate mechanism 500 are
complimentary to those of the upper bonding plate mechanism 400,
namely, heating the glass substrate, providing pressure to the
glass substrate, providing a voltage potential to the glass
substrate, and cooling the glass substrate.
[0130] In accordance with one or more embodiments, the lower
bonding plate mechanism 500 may include any number of the features
of the embodiments of the upper bonding plate mechanism 400
described above. For example, in the embodiment illustrated in FIG.
13, the upper and lower bonding plate mechanisms 400, 500 are
substantially the same, except the upper bonding plate mechanism
400 employs the aperture 450 and pre-load plunger 470, while the
lower bonding plate mechanism 500 does not.
[0131] The heating function of the lower bonding plate mechanism
500 is operable to provide temperatures lower or greater than about
600.degree. C., which may approach or exceed temperatures of
1,000.degree. C. The lower bonding plate mechanism 500 may be
operable to provide heat uniformly to within +/-0.5% of the
controlled set-point across substantially the entire glass
substrate. The voltage potential (about 1,750 volts DC) may
optionally be applied to the glass substrate by the lower bonding
plate mechanism 500, and may be distributed substantially uniformly
over the entire surface of the substrate. Alternative embodiments
of the lower bonding plate mechanism 500 may provide for active
cooling of the glass substrate utilizing controlled fluid flow.
[0132] While the embodiment of the lower bonding plate mechanism
500 illustrated in FIGS. 16-21 contains similar features as the
upper bonding plate mechanism 400 discussed above, the lower
bonding plate mechanism 500 may also include some different
features. FIG. 16 is a perspective view of the lower bonding plate
mechanism 500, while FIG. 17 is an exploded view thereof. The
primary components of the lower bonding plate mechanism 500 include
a base 502, an insulator 504, a heater disk 508, and a thermal
spreader 510. These elements are disposed within, coupled to, or
supported by a housing 506, which may be formed for example from
stainless steel.
[0133] The base 502 is coupled to a lower portion of the housing
506, thereby forming a substantially cylindrical structure defining
an interior volume for receiving the insulator 504. By way of
example, but not limitation, the base 502 may be formed from a
machinable ceramic material (e.g., Cotronics 902 machinable alumina
silicate), which provides structural integrity as well as high
temperature capabilities. The insulator 504 is operable to limit
heat flow from the heater disk 508 into the base 502, housing 506
and other portions of the bonding apparatus 10. By way of example,
but not limitation, the insulator 504 may be formed from a ceramic
foam insulating material, such as 40% dense fused silica. The
temperature insulating properties of the insulator 504 should
prevent heat flow from the heater disk 508 into the base 502 (and
other components) and provide a relatively low thermal inertia of
the lower bonding plate mechanism 500 (for rapid thermal cycling
capabilities).
[0134] The heater disk 508 and the insulator 504 may be bonded
together using a ceramic adhesive, such as Cotronics RESBOND
905.
[0135] The heater disk 508 is operable to generate heat in response
to electrical excitation (voltage and current), while also
providing electrical insulation properties such that any voltage
potential directly or indirectly applied to the glass substrate is
not applied to the base 502 or housing. Thus, the heater disk 508
may be formed from a material that exhibits substantial electrical
insulting properties and substantial thermal conductivity.
[0136] With reference to FIG. 18, the heater disk 508 may be formed
from a resistive heater layer 508A sandwiched between two (or more)
electrical insulating layers 508B. By way of example, and not
limitation, the resistive heater layer 508A may be formed from
THERMAFOIL rolled graphite and the electrical insulating layers
508B may be formed from fused silica. The resistive heater layer
508A and the electrical insulating layers 508B may be bonded
together using a ceramic adhesive, such as Cotronics RESBOND 905
(which exhibits low thermal expansion characteristics).
[0137] As substantially uniform heating is desired, the heater disk
508 may include thermal edge loss compensation. In this embodiment,
the heater disk 508 may include two heating zones, one
substantially centrally located and the other in the form of an
annular ring around the central zone. The heating zones may be
implemented within the resistive heater layer 508A. For example,
the respective heating zones may be formed by varying respective
widths of resistive material as the material spirals outward from a
center of the layer 508A. This results in a varying resistance (and
thus the heating characteristics) of the material depending on the
radial distance of same from the center of the layer 508A. This
permits use of a single voltage and current excitation to achieve
the thermal edge loss compensation because the heater element will
respond (heat) differently to the excitation voltage and current
due to the differences in the resistance as a function of radial
position.
[0138] The voltage and current excitation to the resistive heater
layer 508A is provided by a power source (not shown) and controlled
by the control unit to achieve temperature regulation (which may
employ feedback control as discussed below). The control unit may
be operable to program the lower bonding plate mechanism 500 to
follow any desired heat-up or cool down ramp and dwell at any
desired processing temperature. Terminals 552 (FIGS. 16-17) and
terminals 508C (FIG. 18) permit electrical connections from the
power source to the resistive heater layer 508A.
[0139] The thermal spreader 510 is in thermal communication with
the heater disk 508 and is operable to integrate the heating
profile presented by the heater disk 508 such that a more uniform
presentation of heat is imparted to the glass substrate. The
thermal spreader 510 may be both electrically and thermally
conductive, as it is in direct contact with the glass substrate and
facilitates heating the substrate and optionally applying a bonding
voltage thereto. Again, the bonding voltage applied to the silicon
donor wafer and the glass substrate may be achieved by: (i)
applying a voltage potential to one of the silicon donor wafer and
the glass substrate (while grounding the other); or by (ii)
applying respective voltage potentials to both the silicon donor
wafer and the glass substrate. Thus, the ability of the lower
bonding plate mechanism 500 to impart a voltage potential (other
than ground) to the glass substrate is an optional feature. If a
bonding voltage potential (other than ground) is applied to the
glass substrate by the lower bonding plate mechanism 500, such may
be distributed substantially uniformly over the entire surface of
the substrate, and may be in the range of about 1,750 volts DC.
[0140] Among the materials that may be employed to implement the
thermal spreader 510, electrically conductive graphite is
desirable, such as THERMAFOIL. Terminal 553 permits electrical
connection from the high voltage power source (not shown) to the
thermal spreader 510. The control unit may be operable to program
the voltage level from the high voltage power source to attain the
desired voltage (such as 1750 volts DC).
[0141] Reference is now also made to FIG. 19, which illustrates
further structural and functional aspects of the lower bonding
plate mechanism 500. As shown, the lower bonding plate mechanism
500 may optionally include an aperture 550 that permits access to
the glass substrate during the bonding process, for example to
impart a preload pressure and/or seed voltage to the substrate. It
is noted that this optional feature need not be employed, but may
provide advantageous operation as will be discussed below. When the
aperture 550 is employed, a preferred use thereof is to permit a
preload pressure and/or seed voltage to be applied to the glass
substrate prior to application of the bonding voltage and full
bonding pressure. As discussed above with respect to the upper
bonding plate mechanism 400, the purpose of the preload pressure
and seed voltage is to initiate anodic bonding in a localized area
of the interface between the silicon donor wafer and the glass
substrate prior to application of the bonding voltage, which
facilitates anodic bonding across substantially the entire area of
the interface. The seed voltage may be of the same or different
magnitude as the bonding voltage, however, a lower or equal voltage
is believed to be superior, e.g., about 750-1000 volts DC.
[0142] By way of example, a preload plunger 570 may be employed to
achieve the aforementioned pre-charge functionality. The preload
plunger 570 may be of substantially the same construction as the
preload plunger 470 discussed above with respect to FIGS. 12A-12B.
The preload plunger 570 is operable to engage the lower bonding
plate mechanism 500 and extend through the aperture 550 thereof to
electrically and mechanically communicate with the glass substrate.
An electrode 584 of the preload plunger 570 engages the glass
substrate at least to impart the seed voltage. A plunger of the
preload plunger 570 is coaxially disposed about the electrode 584
and may alone (or in combination with the electrode 584) apply the
preload pressure.
[0143] The lower bonding plate mechanism 500 may include one or
more further apertures to permit the insertion of a thermocouple
through the assembly such that it may thermally engage the heater
disk 508 and provide a temperature feedback signal to the control
unit (which permits tight temperature regulation of the heater disk
508 and the glass substrate). The structure and location of the
aperture(s) for the thermocouples (and the thermocouple itself) may
be substantially the same as those discussed above with respect to
the upper bonding plate mechanism 400.
[0144] Reference is now made to FIGS. 20-21, which illustrate
alternative functionality that may be employed in one or more
further embodiments of a lower bonding plate mechanism. FIG. 20 is
a cross-sectional view of the lower bonding plate mechanism 500A
employing an active cooling feature. FIG. 21 is an exploded view of
the lower bonding plate mechanism 500A of FIG. 20. In this
embodiment, the insulator 504A of the lower bonding plate mechanism
500A includes one or more cooling channels 520 through which
cooling fluid may flow when it is desirable to reduce the
temperature of the SOG structure, specifically the glass substrate
thereof. For example, the cooling channel 520 may extend spirally
from a center of the insulator 504A toward the peripheral edge
thereof. The channel(s) 520 may be machined into the surface of the
insulator 504A. An inlet tube 522 is operable to introduce cooling
fluid into the channels 520, while an outlet tube 524 is operable
to remove the cooling fluid from the channels 520. A heat exchanger
(not shown) may be employed to cool the cooling fluid prior to
reintroducing same into the inlet tube 522. Active cooling may be
achieved by controlling the temperature and flow rate of the
cooling fluid through the channels 520 using the control unit. As
illustrated in FIG. 13, appropriate fluid couplings 560 may be
connected to the inlet tube 522 and the outlet tube 524 to permit
the connection of a fluid source (not shown) to the lower bonding
plate mechanism 500.
[0145] With reference to FIG. 22, the bonding apparatus 10 may be
disposed in an atmospheric chamber to provide control of
atmospheric conditions of the bonding environment, such as vacuum,
gas atmospheres (such as hydrogen, nitrogen, etc.), and other
conditions. Notably, the bonding apparatus 10 may operate in a
non-vacuum atmosphere (e.g., an atmosphere that may include one or
more oxidizing agents) without degradation of the various
components thereof, especially the bonding plate mechanisms 400,
500.
[0146] Further details regarding the operation of the bonding
apparatus 10 will now be described with reference to FIGS. 23-27.
FIG. 23 illustrates a final SOG structure 600, while FIGS. 24-27
illustrate intermediate structures thereof produced using one or
more embodiments of the bonding apparatus 10. With reference to
FIG. 24, prior to introducing materials into the bonding apparatus
10, an implantation surface 621 of a donor semiconductor wafer 620
is prepared, such as by polishing, cleaning, etc. to produce a
relatively flat and uniform implantation surface 621 suitable for
bonding to the glass or glass-ceramic substrate 602 (FIG. 23). For
the purposes of discussion, the semiconductor wafer 620 may be a
substantially single crystal Si wafer, although as discussed above
any other suitable semiconductor conductor material may be
employed.
[0147] An exfoliation layer 622 is created by subjecting the
implantation surface 621 to an ion implantation process to create a
weakened region below the implantation surface 621 of the donor
semiconductor wafer 620, which defines the exfoliation layer 622.
By way of example, the implantation surface 621 may be subject to
hydrogen ion implantation, or other rare earth ions, such as boron,
helium, etc. The donor semiconductor wafer 620 may be treated to
reduce, for example, the hydrogen ion concentration on the
implantation surface 621. For example, the donor semiconductor
wafer 620 may be washed and cleaned and the implantation donor
surface 621 of the exfoliation layer 622 may be subject to mild
oxidation. The mild oxidation treatments may include treatment in
oxygen plasma, ozone treatments, treatment with hydrogen peroxide,
hydrogen peroxide and ammonia, hydrogen peroxide and an acid or a
combination of these processes. It is expected that during these
treatments hydrogen terminated surface groups oxidize to hydroxyl
groups, which in turn also makes the surface of the silicon wafer
hydrophilic. The treatment may be carried out at room temperature
for the oxygen plasma and at temperature between 25-150.degree. C.
for the ammonia or acid treatments. Appropriate surface cleaning of
the glass substrate 602 (and the exfoliation layer 622) may be
carried out.
[0148] Assuming that the bonding apparatus 10 is in an initial
orientation whereby the upper bonding plate mechanism 400 is
rotated upward (as in FIG. 2), the donor semiconductor wafer 620
and the glass substrate 602 are inserted into the bonding apparatus
10. In this example, it is assumed that the glass substrate 602 is
placed down and held via gravity to the lower bonding plate
mechanism 500 and the donor semiconductor wafer 620 is placed atop
the glass substrate 602. When application of a preload pressure and
seed voltage to initiate bonding in a central region of the donor
semiconductor wafer 620 and the glass substrate 602 is desired, the
spacer mechanism 300 may be activated prior to the donor
semiconductor wafer 620 being placed atop the glass substrate 602.
As discussed with respect to FIGS. 6 and 14, the stepper motor 144
may rotate the gear 142, such that the swivel ring 304 rotates with
respect to the mount ring 302, thereby driving the shims 330 to
overlie peripheral portions of the glass substrate 602. The donor
semiconductor wafer 620 may then be placed atop the shims 330 such
that the shims 330 are interposed between the donor semiconductor
wafer 620 and the glass substrate 602. Thus, the donor
semiconductor wafer 620 and the glass substrate 602 will be spaced
apart by the thickness of the shims 330.
[0149] Next, the upper bonding plate mechanism 400 is operable to
rotate downward (via the open and close mechanism 200) such that
the upper and lower bonding plate mechanisms 400, 500 are spaced
apart in parallel orientation. More particularly, as discussed
above with respect to FIG. 7, the jack 230 is actuated via
manipulating the shaft 236, which results in lowering the shaft
232, the guide bushing 214, and the hinge plate 250. The lowering
of the hinge plate 250 causes the mount plate 208 to pivot about
the pivot linkage 258 such that the mount plate 208 and the upper
bonding plate mechanism 400 tilt downward until the mount plate 208
engages the stops 259 of the hinge plate 250. At this point, the
upper bonding plate mechanism 400 is in substantially parallel
orientation with respect to the lower bonding plate mechanism 500.
Continued downward movement of the hinge plate 250 results in the
locks 246 engaging the ends 114A, 116A, 118A of the guide posts
114, 116, 118 of the lift and press mechanism 100 (FIG. 6). The
operator may then engage the locks 246 into the guide posts 114,
116, 118 of the lift and press mechanism 100. The locks 246 ensure
that upward pressure on the donor semiconductor wafer 620 and the
upper bonding plate mechanism 400 may be countered by the mount
plate 208 without exposing the lift and press mechanism 100 to
excessive force.
[0150] The lift and press mechanism 100 may then impart coarse
displacement of the lower bonding plate mechanism 500 (and the
glass substrate 602 and donor semiconductor wafer 620) toward the
upper bonding plate mechanism 400. As the electrode 484 of the
preload plunger 470 extends below the thermal spreader 410 of the
upper bonding plate mechanism 400, it contacts the donor
semiconductor wafer 620 when the lift and press 100 mechanism
coarsely displaces the lower bonding plate mechanism 500 toward the
upper bonding plate mechanism 400. As the shims 330 of the spacer
mechanism 300 prevent the peripheral edges of the donor
semiconductor wafer 620 and the glass substrate 602 from touching
one another, the preload plunger 470 will tend to bow the donor
semiconductor wafer 620 such that the central portion thereof
touches the glass substrate 602. Thus, application of the preload
pressure and seed voltage may initiate the anodic bonding of the
donor semiconductor wafer 620 and the glass substrate 602 before
full pressure, temperature, and voltage is applied.
[0151] Following the initial bonding of the central portions of the
donor semiconductor wafer 620 and the glass substrate 602, the
spacer mechanism 300 may be commanded to withdraw the shims 330.
The control unit may command the stepper motor 144 to rotate the
gear 142 such that the swivel ring 304 rotates with respect to the
mount ring 302, thereby withdrawing the shims 330 from between the
donor semiconductor wafer 620 and the glass substrate 602. The
shims 330 move in symmetric motion, which prevents any uneven
friction loads as between the donor semiconductor wafer 620 and the
glass substrate 602. Advantageously, if the bonding process is
taking place in a vacuum, the bonding of the central portions of
the donor semiconductor wafer 620 and the glass substrate 602
followed by withdrawal of the shims 330 permits any gasses from
between the donor semiconductor wafer 620 and the glass substrate
602 to be evacuated. Thus, the likelihood of gas (e.g., air)
impeding a proper bond between the donor semiconductor wafer 620
and the glass substrate 602 may be reduced.
[0152] With reference to FIG. 25, the glass substrate 602 may be
bonded to the exfoliation layer 622 using the anodic (electrolysis)
process by bringing the glass substrate and the donor semiconductor
wafer 620 into direct contact and subjecting them to the
temperature, voltage and pressure using the bonding apparatus 10 as
discussed above. The bonding apparatus 10 may operate under the
control of the computer program (running on a processor of the
control unit) to achieve the desired anodic bonding. Thus, it is
contemplated that the computer program causes the various
mechanisms of the bonding apparatus 10 to operate in the manner
discussed herein to achieve the anodic bonding.
[0153] The exfoliation layer 622 of the donor semiconductor wafer
620, and the glass substrate 602 are heated under a differential
temperature gradient. The glass substrate 602 may be heated to a
higher temperature (via the lower bonding plate mechanism 500) than
the donor semiconductor wafer 620 and exfoliation layer 622 (via
the upper bonding plate mechanism 400). By way of example, the
temperature difference between the glass substrate 602 and the
donor semiconductor wafer 620 (and the exfoliation layer 622) may
be anywhere between about 6.degree. C. to about 200.degree. C. or
more. This temperature differential is desirable for a glass having
a coefficient of thermal expansion (CTE) matched to that of the
donor semiconductor wafer 620 (such as matched to the CTE of
silicon) since it facilitates later separation of the exfoliation
layer 622 from the semiconductor wafer 620 due to thermal stresses.
The glass substrate 602 and the donor semiconductor wafer 620 may
be taken to a temperature within about +/-650.degree. C. of the
strain point of the glass substrate 602.
[0154] Mechanical pressure is also applied to the intermediate
assembly. The pressure range may be: between about 1 to about 100
pounds per square inch (psi), between about 6 to about 50 psi, or
about 20 psi. Although application of higher pressures, e.g.,
pressures at or above 100 psi are possible, such pressures should
be used cautiously as they might cause breakage of the glass
substrate 602. As discussed above with respect to FIGS. 4A, 4B, and
6, the donor semiconductor wafer 620 and the glass substrate 602
may contact one another under the controlled actuation of the lift
and press mechanism 100. The second actuator 106 of the lift and
press mechanism 100 raises the lower mount 108, the lower bonding
plate mechanism 500, and the glass substrate 602 into position such
that controlled heating and pressure between the donor
semiconductor wafer 620 and the glass substrate 602 may be
achieved.
[0155] A voltage is also applied across the intermediate assembly,
for example with the donor semiconductor wafer 620 at a positive
potential and the glass substrate 602 at a lower potential. The
application of the voltage potential causes alkali or alkaline
earth ions in the glass substrate 602 to move away from the
semiconductor/glass interface further into the glass substrate 602.
This accomplishes two functions: (i) an alkali or alkaline earth
ion free interface is created; and (ii) the glass substrate 602
becomes very reactive and bonds strongly to the exfoliation layer
622 of the donor semiconductor wafer 620 with the application of
heat at relatively low temperatures.
[0156] The pressure, temperature differential, and voltage
differential are applied for a controlled period of time (e.g.,
approximately 6 hr or less). Thereafter, the high level voltage
potential is brought to zero and the donor semiconductor wafer 620
and the glass substrate 602 are permitted to cool to at least
initiate the separation of the exfoliation layer 622 from the donor
semiconductor wafer 620. The cooling process may involve active
cooling, whereby cooling fluid is introduced into one or both of
the upper and lower bonding plate mechanisms 400, 500. In one or
more embodiment, the active cooling profile may involve cooling the
donor semiconductor wafer 620 and the glass substrate 602 at
different profiles (e.g., cooling rates, dwells and/or levels) to
impact the degree and quality of the exfoliation process.
[0157] As illustrated in FIG. 26, after separation the resulting
structure may include the glass substrate 602 and the exfoliation
layer 622 of semiconductor material bonded thereto. In order to
access this structure, the locks 246 are disengaged from the guide
posts 114, 116, 118 and the jack 230 is actuated (for example, via
applying a rotational force to the shaft 236), such that the shaft
232 may raises the guide bushing 214 and the hinge plate 250
applies a vertical force to the mount plate 208 by way of the block
260 and pivoting linkage 258 (FIGS. 6-7). The upper bonding plate
mechanism 400 will, therefore, rise vertically away from the lower
bonding plate mechanism 500 while maintaining a substantially
parallel relationship thereto. A continued upward force on the
mount plate 208 causes the upper bonding plate mechanism 400 to
tilt upward in response to a rotational movement about the pivoting
linkage 258. The intermediate structures of the SOG may then be
extracted from the bonding apparatus 10.
[0158] Any unwanted or rough semiconductor material may be removed
from the surface 623 via thinning and/or polishing techniques,
e.g., via CMP or other techniques known in the art to obtain the
semiconductor layer 604 on the glass substrate 602 as illustrated
in FIG. 27.
[0159] It is noted that the donor semiconductor wafer 620 may be
reused to continue producing other SOG structures 600.
[0160] In accordance with one or more further embodiments of the
present invention, the bonding apparatus 10 may be employed to
emboss micro-structures in a substrate, such as glass, glass
ceramic, ceramic, etc. Conventional approaches to producing
replicated patterns on substrates such as glass have employed
additive processes (e.g. using UV cured polymers), or subtractive
processes (e.g. chemical etching, Reactive Ion Etching). These
convention approaches are not desirable in every application;
indeed, polymer structures are very versatile but may not have the
desired material properties, and etching methods can produce fine
structures but are often very slow and costly. In accordance with
one of more aspects of the present invention, however, patterns are
impressed/embossed into a substrate from a master tool through
heating. The master tool is constructed from material that is
structurally rigid and has a melting point above that of the
substrate. The tool and/or substrate are heated to level(s) where
the substrate flows into micro-structures of the tool. Thereafter,
the components are cooled and separated.
[0161] In one or more embodiments, the bonding apparatus 10 may be
adapted to rapidly heat the tool and/or substrate (e.g., glass)
allowing for high throughput. The aforementioned active cooling
features, controlled compression features, vacuum atmosphere, etc.
of the bonding apparatus 10 may also increase throughput.
[0162] With reference to FIG. 28, the bonding apparatus 10 may be
operable to receive a tool 700 having micro-structures 701 (e.g.,
in the nanometer scale) disposed on at least one surface thereof.
The micro-structures on the tool 700 are the reverse of those
desired to be embossed onto the substrate 702. By way of example,
the tool 700 may be coupled to the lower bonding plate mechanism
500 and the substrate 702 (e.g., a glass substrate) may be placed
atop the tool 700. Alternatively, the substrate 702 may be coupled
to the lower bonding plate mechanism 500 and the tool 700 may be
placed atop the substrate 702. In a further alternative embodiment,
the tool 700 may be clipped or otherwise fastened to the upper
bonding plate mechanism 400. Respective GRAFOIL gaskets 704A, 704B
may be interposed between the upper/lower bonding plate mechanisms
400, 500 and the substrate 702/tool 700.
[0163] The bonding apparatus 10 may then be closed (as discussed
above) and the temperature taken above the Tg of the glass
substrate 702. The pattern or structure is thus transferred from
the tool 700 to the glass substrate 702. The replication process
may be conducted under high pressure from the controlled pressure
features of the bonding apparatus 10 as described above.
Alternatively, gravity and atmospheric pressure may be employed to
facilitate the flow of the glass substrate 702 into the
micro-structures 710 of the tool 700.
[0164] The tool 700 may be constructed of material that will not
change structurally at temperatures elevated to, or above the flow
temperature of the substrate 702, such as the Tg of a glass
substrate. By way of example, fused silica may be employed to
implement the tool 700. The micro-structures 701 may be formed in
the tool 700 by Reactive Ion Etching (RIE). A surface treatment of
the tool 700 and/or substrate 702 may also be employed, such as a
diamond coating.
[0165] 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.
* * * * *