U.S. patent application number 15/679099 was filed with the patent office on 2017-11-30 for substrate support assembly.
The applicant listed for this patent is Applied Materials, Inc.. Invention is credited to Kadthala Ramaya Narendrnath, Vijay D. Parkhe.
Application Number | 20170345691 15/679099 |
Document ID | / |
Family ID | 50880108 |
Filed Date | 2017-11-30 |
United States Patent
Application |
20170345691 |
Kind Code |
A1 |
Parkhe; Vijay D. ; et
al. |
November 30, 2017 |
SUBSTRATE SUPPORT ASSEMBLY
Abstract
An electrostatic chuck comprises a ceramic body having a first
surface and a second surface that is on an opposite side of the
ceramic body to the first surface, the ceramic body comprising a
through-hole between the first surface and the second surface. The
electrostatic chuck further comprises a thermally conductive base
that supports the ceramic body and comprises a second hole that
lines up with the through-hole, wherein the second hole is to
fluidly couple to a source of heat transfer gas. The electrostatic
chuck further comprises a bonding layer between the ceramic body
and the thermally conductive base, the bonding layer comprising a
space between an opening of the through-hole on the second surface
and the gas introduction path.
Inventors: |
Parkhe; Vijay D.; (San Jose,
CA) ; Narendrnath; Kadthala Ramaya; (San Jose,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Applied Materials, Inc. |
Santa Clara |
CA |
US |
|
|
Family ID: |
50880108 |
Appl. No.: |
15/679099 |
Filed: |
August 16, 2017 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15613061 |
Jun 2, 2017 |
|
|
|
15679099 |
|
|
|
|
13842044 |
Mar 15, 2013 |
9685356 |
|
|
15613061 |
|
|
|
|
61735895 |
Dec 11, 2012 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y10T 156/10 20150115;
H01L 21/67109 20130101; H01L 21/6831 20130101; H01J 37/32715
20130101; Y10T 279/23 20150115 |
International
Class: |
H01L 21/67 20060101
H01L021/67; H01J 37/32 20060101 H01J037/32; H01L 21/683 20060101
H01L021/683 |
Claims
1. An electrostatic chuck comprising: a ceramic body having a first
surface and a second surface that is on an opposite side of the
ceramic body to the first surface, the ceramic body comprising a
through-hole between the first surface and the second surface; a
thermally conductive base that supports the ceramic body and
comprises a second hole that lines up with the through-hole,
wherein the second hole is to fluidly couple to a source of heat
transfer gas; and a bonding layer between the ceramic body and the
thermally conductive base, the bonding layer comprising a space
between an opening of the through-hole on the second surface and an
opening of the second hole.
2. The electrostatic chuck of claim 1, wherein the bonding layer is
formed from at least one of a silicone-based compound or an
acrylic-based compound.
3. The electrostatic chuck of claim 2, wherein at least one of the
silicone-based compound or the acrylic-based compound comprises at
least one of metal fillers or ceramic fillers.
4. The electrostatic chuck of claim 3, wherein: the metal fillers
are selected from a group consisting of Al, Mg, Ta and Ti; and the
ceramic fillers are selected from a group consisting of
Al.sub.2O.sub.3, MN and TiB.sub.2.
5. The electrostatic chuck of claim 1, further comprising: a
gasket, disposed on the first surface or the second surface of the
ceramic body, that encircles the through-hole.
6. The electrostatic chuck of claim 5, wherein the gasket comprises
a fluoro-polymer.
7. The electrostatic chuck of claim 5, wherein the gasket comprises
a fluoro-polymer compressible o-ring.
8. The electrostatic chuck of claim 5, wherein the gasket is a
cured liquid polymer.
9. The electrostatic chuck of claim 5, wherein the gasket is
between the ceramic body and the thermally conductive base.
10. The electrostatic chuck of claim 1, wherein the ceramic body
has a first ceramic material composition, the electrostatic chuck
further comprising: a plasma resistant protective layer comprising
a bulk sintered ceramic article having a second ceramic material
composition that is different from the first ceramic material
composition; and a metal bond layer between the first surface of
the ceramic body and the plasma resistant protective layer.
11. The electrostatic chuck of claim 10, wherein the metal bond
layer comprises: a first metal layer; a second metal layer; and a
third metal layer between the first metal layer and the second
metal layer, the third metal layer comprising a combination of at
least two different metals.
12. The electrostatic chuck of claim 10, further comprising: a
third hole in the plasma resistant protective layer that lines up
with the through-hole.
13. The electrostatic chuck of claim 10, wherein a thickness of the
metal bond layer is approximately 5-20 mil and a thickness of the
plasma resistant protective layer is approximately 200-900
microns.
14. The electrostatic chuck of claim 10, further comprising: a
gasket, disposed on the ceramic body between the ceramic body and
the plasma resistant protective layer, wherein the gasket encircles
the through-hole.
15. The electrostatic chuck of claim 10, wherein the second ceramic
material composition is selected from a group consisting of
Y.sub.xAl.sub.yO.sub.z and a ceramic compound comprising
Y.sub.4Al.sub.2O.sub.9 and a solid-solution of
Y.sub.2O.sub.3--ZrO.sub.2.
16. The electrostatic chuck of claim 1, wherein the through-hole
has a diameter of 5-7 mm.
17. The electrostatic chuck of claim 1, further comprising: an
electrode embedded in the ceramic body; and an electrode
connection, formed in the ceramic body, to electrically connect the
electrode to at least one of a power source or a radio frequency
source, the electrode connection comprising a hole filled with an
electrically conductive material.
18. The electrostatic chuck of claim 1, further comprising: a
porous ceramic plug in the through-hole that plugs the
through-hole, wherein the porous ceramic plug permits a flow of
helium through the porous ceramic plug but prevents arcing of
flowed plasma within the through-hole.
19. The electrostatic chuck of claim 1, further comprising: a
gasket at an outer perimeter of the first surface or the second
surface of the ceramic body.
20. The electrostatic chuck of claim 1, wherein: the ceramic body
comprises MN or Al.sub.2O.sub.3; and the thermally conductive base
comprises Al or stainless steel.
Description
RELATED APPLICATIONS
[0001] This patent application is a continuation application of
U.S. patent application Ser. No. 15/613,061, filed Jun. 2, 2017,
which is a divisional application of U.S. patent application Ser.
No. 13/842,044, filed Mar. 15, 2013, which claims the benefit under
35 U.S.C. .sctn.119(e) of U.S. Provisional Application No.
61/735,895, filed Dec. 11, 2012. U.S. patent application Ser. Nos.
13/842,044 and 15/613,061 are herein incorporated by reference.
TECHNICAL FIELD
[0002] Some embodiments of the present invention relate, in
general, to a substrate support assembly such as an electrostatic
chuck that has a plasma resistant protective layer. Other
embodiments relate to reactive multi-layer foils and the
manufacture of reactive multi-layer foils.
BACKGROUND
[0003] In the semiconductor industry, devices are fabricated by a
number of manufacturing processes producing structures of an
ever-decreasing size. Some manufacturing processes such as plasma
etch and plasma clean processes expose a substrate support (e.g.,
an edge of the substrate support during wafer processing and the
full substrate support during chamber cleaning) to a high-speed
stream of plasma to etch or clean the substrate. The plasma may be
highly corrosive, and may corrode processing chambers and other
surfaces that are exposed to the plasma.
[0004] Additionally, traditional electrostatic chucks include a
ceramic puck silicone bonded to a metal cooling plate. The Ceramic
puck in such traditional electrostatic chucks is manufactured by a
multi-step manufacturing process that can be costly to form an
embedded electrode and heating elements.
[0005] Reactive multilayer foils (referred to herein as reactive
foils) are used to form a metal bond between substrates.
Traditional reactive foil is manufactured in flat featureless
sheets. Traditional reactive foil is typically not appropriate for
bonding substrates having non-flat surfaces. Additionally, if the
traditional reactive foil is used to bond substrates having surface
features, the reactive foil is machined (e.g., by laser drilling,
chemical etching, etc.) to form corresponding features in the
reactive foil. Such machining can induce a heat load on the
reactive foil and cause the reactive foil to ignite. Moreover,
traditional reactive foil has a preset size such as 9 inch squares.
When the traditional reactive foil is used to bond substrates that
are larger than the reactive foil, then multiple sheets of reactive
foil are used to perform the bonding. This commonly introduces
leakage paths such as cracks, grooves, lines, etc. between the
reactive foil sheets, and causes the resultant metal bond to not be
vacuum sealed.
SUMMARY
[0006] In one embodiment, an electrostatic chuck includes a ceramic
body and a thermally conductive base bonded to a lower surface of
the ceramic body. The ceramic body may be bonded to the thermally
conductive base by a metal bond or by a silicone bond. The
electrostatic chuck is fabricated with a protective layer bonded to
an upper surface of the ceramic body by a metal bond, the
protective layer comprising a bulk sintered ceramic article.
[0007] In another embodiment, reactive foil is manufactured. A
template having one or more surface features is provided.
Alternating nanoscale layers of aluminum and nickel are deposited
onto the template to form a reactive foil sheet. The reactive foil
sheet is removed from the template. The resultant reactive foil
sheet has one or more foil features corresponding to one or more
surface features.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The present invention is illustrated by way of example, and
not by way of limitation, in the figures of the accompanying
drawings in which like references indicate similar elements. It
should be noted that different references to "an" or "one"
embodiment in this disclosure are not necessarily to the same
embodiment, and such references mean at least one.
[0009] FIG. 1 depicts a sectional view of one embodiment of a
processing chamber;
[0010] FIG. 2 depicts an exploded view of one embodiment of a
substrate support assembly;
[0011] FIG. 3 depicts a side view of one embodiment of a substrate
support assembly;
[0012] FIG. 4 depicts an exploded side view of one embodiment of a
substrate support;
[0013] FIG. 5 illustrates one embodiment of a process for
manufacturing an electrostatic chuck;
[0014] FIG. 6 illustrates another embodiment of a process for
manufacturing an electrostatic chuck; and
[0015] FIG. 7 illustrates one embodiment of a process for
performing a metal bonding process.
[0016] FIG. 8 illustrates one embodiment of a process for
manufacturing reactive foil having preformed foil features.
[0017] FIG. 9A illustrates deposition of nanoscale metal layers
onto a template having surface features.
[0018] FIG. 9B illustrates a reactive foil sheet having preformed
foil features.
[0019] FIG. 10A illustrates deposition of nanoscale metal layers
onto a non-planar template.
[0020] FIG. 10B illustrates a non-planar reactive foil sheet.
[0021] FIG. 11 illustrates interlocking reactive foil sheets.
DETAILED DESCRIPTION OF EMBODIMENTS
[0022] Embodiments of the present invention provide a substrate
support assembly (e.g., an electrostatic chuck) having a protective
layer formed over a ceramic body of the substrate support assembly.
The protective layer may provide plasma corrosion resistance for
protection of the ceramic body. The protective layer may be a bulk
sintered ceramic article (e.g., a ceramic wafer) that is metal
bonded to the ceramic body using a nano-bonding technique. Various
bonding materials such as In, Sn, Ag, Au, Cu and their alloys could
be used along with a reactive foil.
[0023] In one embodiment, the ceramic body is a bulk sintered
ceramic body (e.g., another ceramic wafer). When the ceramic body
does not include a chucking electrode, the metal bond may function
as a chucking electrode for the electrostatic chuck. The ceramic
body may additionally be metal bonded to a thermally conductive
base by another metal bond. The thermally conductive base may
include heating elements as well as channels that can be used to
regulate temperature by flowing liquid for heating and/or cooling.
The metal bond between the thermally conductive base and the
ceramic body provides a good thermal contact, and enables the
thermally conductive base to heat and cool the ceramic body, the
protective layer and any substrate held by the electrostatic chuck
during processing. Embodiments provide an electrostatic chuck that
can be as much as 4x cheaper to manufacture than conventional
electrostatic chucks. Moreover, embodiments provide an
electrostatic chuck that can adjust temperature rapidly and that is
plasma resistant. The electrostatic chuck and a substrate being
supported may be heated or cooled quickly, with some embodiments
enabling temperature changes of 2.degree. C./s or faster. This
enables the electrostatic chuck to be used in multi-step processes
in which, for example, a wafer may be processed at 20-30.degree. C.
and then rapidly ramped up to 80-90.degree. C. for further
processing. The embodiments described herein may be used for both
Columbic electrostatic chucking applications and Johnson Raybek
chucking applications.
[0024] In another embodiment, reactive foil is manufactured that
has preformed surface features. The reactive foil may be
manufactured by depositing alternating nanoscale layers of two
reactive materials such as aluminum and nickel onto a template that
has surface features. The surface features of the template may
correspond to surface features of one or more substrates that the
reactive foil will be used to bond. For example, if the one or more
substrates have holes in them, then the template may have steps
corresponding to the holes. These steps may cause reactive foil
formed on the template to have preformed holes that correspond to
the holes in the substrate.
[0025] FIG. 1 is a sectional view of one embodiment of a
semiconductor processing chamber 100 having a substrate support
assembly 148 disposed therein. The substrate support assembly 148
has a protective layer 136 of a bulk ceramic that has been metal
bonded to a ceramic body of the substrate support assembly 148. The
metal bond may include a combination of metals, such as a
combination of indium, tin, aluminum, nickel and one or more
additional metals (e.g., such as gold or silver). The metal bonding
process is described in greater detail below.
[0026] The protective layer may be a bulk ceramic (e.g., a ceramic
wafer) such as Y.sub.2O.sub.3 (yttria or yttrium oxide),
Y.sub.4Al.sub.2O.sub.9 (YAM), Al.sub.2O.sub.3 (alumina)
Y.sub.3Al.sub.5O.sub.12 (YAG), YAlO3 (YAP), Quartz, SiC (silicon
carbide) Si.sub.3N.sub.4 (silicon nitride) Sialon, Minn. (aluminum
nitride), AlON (aluminum oxynitride), TiO.sub.2 (titania),
ZrO.sub.2 (zirconia), TiC (titanium carbide), ZrC (zirconium
carbide), TiN (titanium nitride), TiCN (titanium carbon nitride)
Y.sub.2O.sub.3 stabilized ZrO.sub.2 (YSZ), and so on. The
protective layer may also be a ceramic composite such as
Y.sub.3Al.sub.5O.sub.12 distributed in Al.sub.2O.sub.3 matrix,
Y.sub.2O.sub.3--ZrO.sub.2 solid solution or a SiC--Si.sub.3N.sub.4
solid solution. The protective layer may also be a ceramic
composite that includes a yttrium oxide (also known as yttria and
Y.sub.2O.sub.3) containing solid solution. For example, the
protective layer may be a ceramic composite that is composed of a
compound Y.sub.4Al.sub.2O.sub.9 (YAM) and a solid solution
Y.sub.2-xZr.sub.xO.sub.3 (Y.sub.2O.sub.3--ZrO.sub.2 solid
solution). Note that pure yttrium oxide as well as yttrium oxide
containing solid solutions may be doped with one or more of
ZrO.sub.2, Al.sub.2O.sub.3, SiO.sub.2, B.sub.2O.sub.3,
Er.sub.2O.sub.3, Nd.sub.2O.sub.3, Nb.sub.2O.sub.5, CeO.sub.2,
Sm.sub.2O.sub.3, Yb.sub.2O.sub.3, or other oxides. Also note that
pure Aluminum Nitride as well as doped Aluminum Nitride with one or
more of ZrO.sub.2, Al.sub.2O.sub.3, SiO.sub.2, B.sub.2O.sub.3,
Er.sub.2O.sub.3, Nd.sub.2O.sub.3, Nb.sub.2O.sub.5, CeO.sub.2,
Sm.sub.2O.sub.3, Yb.sub.2O.sub.3, or other oxides may be used.
Alternatively, the protective layer may be sapphire or MgAlON.
[0027] The protective layer may be a sintered ceramic article that
was produced from a ceramic powder or a mixture of ceramic powders.
For example, the ceramic composite may be produced from a mixture
of a Y.sub.2O.sub.3 powder, a ZrO.sub.2 powder and an
Al.sub.2O.sub.3 powder. The ceramic composite may include
Y.sub.2O.sub.3 in a range of 50-75 mol %, ZrO.sub.2 in a range of
10-30 mol % and Al.sub.2O.sub.3 in a range of 10-30 mol %. In one
embodiment, the HPM ceramic composite contains approximately 77%
Y.sub.2O.sub.3, 15% ZrO.sub.2 and 8% Al.sub.2O.sub.3. In another
embodiment, the ceramic composite contains approximately 63%
Y.sub.2O.sub.3, 23% ZrO.sub.2 and 14% Al.sub.2O.sub.3. In still
another embodiment, the HPM ceramic composite contains
approximately 55% Y.sub.2O.sub.3, 20% ZrO.sub.2 and 25%
Al.sub.2O.sub.3. Relative percentages may be in molar ratios. For
example, the HPM ceramic composite may contain 77 mol %
Y.sub.2O.sub.3, 15 mol % ZrO.sub.2 and 8 mol % Al.sub.2O.sub.3.
Other distributions of these ceramic powders may also be used for
the ceramic composite.
[0028] The processing chamber 100 includes a chamber body 102 and a
lid 104 that enclose an interior volume 106. The chamber body 102
may be fabricated from aluminum, stainless steel or other suitable
material. The chamber body 102 generally includes sidewalls 108 and
a bottom 110. An outer liner 116 may be disposed adjacent the side
walls 108 to protect the chamber body 102. The outer liner 116 may
be fabricated and/or coated with a plasma or halogen-containing gas
resistant material. In one embodiment, the outer liner 116 is
fabricated from aluminum oxide. In another embodiment, the outer
liner 116 is fabricated from or coated with yttria, yttrium alloy
or an oxide thereof.
[0029] An exhaust port 126 may be defined in the chamber body 102,
and may couple the interior volume 106 to a pump system 128. The
pump system 128 may include one or more pumps and throttle valves
utilized to evacuate and regulate the pressure of the interior
volume 106 of the processing chamber 100.
[0030] The lid 104 may be supported on the sidewall 108 of the
chamber body 102. The lid 104 may be opened to allow excess to the
interior volume 106 of the processing chamber 100, and may provide
a seal for the processing chamber 100 while closed. A gas panel 158
may be coupled to the processing chamber 100 to provide process
and/or cleaning gases to the interior volume 106 through a gas
distribution assembly 130 that is part of the lid 104. Examples of
processing gases may be used to process in the processing chamber
including halogen-containing gas, such as C.sub.2F.sub.6, SF.sub.6,
SiCl.sub.4, HBr, NF.sub.3, CF.sub.4, CHF.sub.3, CH.sub.2F.sub.3,
Cl.sub.2 and SiF.sub.4, among others, and other gases such as
O.sub.2, or N.sub.2O. Examples of carrier gases include N.sub.2,
He, Ar, and other gases inert to process gases (e.g., non-reactive
gases). The gas distribution assembly 130 may have multiple
apertures 132 on the downstream surface of the gas distribution
assembly 130 to direct the gas flow to the surface of the substrate
144. Additionally, the gas distribution assembly 130 can have a
center hole where gases are fed through a ceramic gas nozzle. The
gas distribution assembly 130 may be fabricated and/or coated by a
ceramic material, such as silicon carbide, Yttrium oxide, etc. to
provide resistance to halogen-containing chemistries to prevent the
gas distribution assembly 130 from corrosion.
[0031] The substrate support assembly 148 is disposed in the
interior volume 106 of the processing chamber 100 below the gas
distribution assembly 130. The substrate support assembly 148 holds
the substrate 144 during processing. An inner liner 118 may be
coated on the periphery of the substrate support assembly 148. The
inner liner 118 may be a halogen-containing gas resist material
such as those discussed with reference to the outer liner 116. In
one embodiment, the inner liner 118 may be fabricated from the same
materials of the outer liner 116.
[0032] In one embodiment, the substrate support assembly 148
includes a mounting plate 162 supporting a pedestal 152, and an
electrostatic chuck 150. In one embodiment, the electrostatic chuck
150 further includes a thermally conductive base 164 bonded to an
electrostatic puck 166 by a metal or silicone bond 138.
Alternatively, a simple ceramic body may be used instead of the
electrostatic puck 166, as will be described in greater detail with
reference to FIG. 3. An upper surface of the electrostatic puck 166
is covered by the protective layer 136 that is metal bonded to the
electrostatic puck 166. In one embodiment, the protective layer 136
is disposed on the upper surface of the electrostatic puck 166. In
another embodiment, the protective layer 136 is disposed on the
entire surface of the electrostatic chuck 150 including the outer
and side periphery of the thermally conductive base 164 and the
electrostatic puck 166. The mounting plate 162 is coupled to the
bottom 110 of the chamber body 102 and includes passages for
routing utilities (e.g., fluids, power lines, sensor leads, etc.)
to the thermally conductive base 164 and the electrostatic puck
166.
[0033] The thermally conductive base 164 and/or electrostatic puck
166 may include one or more optional embedded heating elements 176,
embedded thermal isolators 174 and/or conduits 168, 170 to control
a lateral temperature profile of the support assembly 148. The
conduits 168, 170 may be fluidly coupled to a fluid source 172 that
circulates a temperature regulating fluid through the conduits 168,
170. The embedded isolator 174 may be disposed between the conduits
168, 170 in one embodiment. The heater 176 is regulated by a heater
power source 178. The conduits 168, 170 and heater 176 may be
utilized to control the temperature of the thermally conductive
base 164, thereby heating and/or cooling the electrostatic puck 166
and a substrate (e.g., a wafer) being processed. The temperature of
the electrostatic puck 166 and the thermally conductive base 164
may be monitored using a plurality of temperature sensors 190, 192,
which may be monitored using a controller 195.
[0034] The electrostatic puck 166 and/or protective layer may
further include multiple gas passages such as grooves, mesas and
other surface features, that may be formed in an upper surface of
the puck 166 and/or the protective layer. The gas passages may be
fluidly coupled to a source of a heat transfer (or backside) gas,
such as He via holes drilled in the puck 166. In operation, the
backside gas may be provided at controlled pressure into the gas
passages to enhance the heat transfer between the electrostatic
puck 166 and the substrate 144.
[0035] In one embodiment, the electrostatic puck 166 includes at
least one clamping electrode 180 controlled by a chucking power
source 182. In alternative embodiments, the metal bond may function
as the clamping electrode. Alternatively, the protective layer may
include an embedded clamping electrode (also referred to as a
chucking electrode). The electrode 180 (or other electrode disposed
in the puck 166 or protective layer) may further be coupled to one
or more RF power sources 184, 186 through a matching circuit 188
for maintaining a plasma formed from process and/or other gases
within the processing chamber 100. The sources 184, 186 are
generally capable of producing an RF signal having a frequency from
about 50 kHz to about 3 GHz and a power of up to about 10,000
Watts. In one embodiment, an RF signal is applied to the metal
base, an alternating current (AC) is applied to the heater and a
direct current (DC) is applied to the chucking electrode.
[0036] FIG. 2 depicts an exploded view of one embodiment of the
substrate support assembly 148. The substrate support assembly 148
depicts an exploded view of the electrostatic chuck 150 and the
pedestal 152. The electrostatic chuck 150 includes the
electrostatic puck 166 or other ceramic body, as well as the
thermally conductive base 164 attached to the electrostatic puck
166 or ceramic body. The electrostatic puck 166 or other ceramic
body has a disc-like shape having an annular periphery 222 that may
substantially match the shape and size of the substrate 144
positioned thereon. In one embodiment, the electrostatic puck 166
or other ceramic body may be fabricated by a ceramic material.
Suitable examples of the ceramic materials include aluminum oxide
(Al.sub.2O.sub.3), aluminum nitride (AlN), titanium oxide (TiO),
titanium nitride (TiN), silicon carbide (SiC) and the like. In one
embodiment, the ceramic body is a bulk sintered ceramic, which may
be in the form of a wafer.
[0037] The thermally conductive base 164 attached below the
electrostatic puck 166 or ceramic body may have a disc-like main
portion 224 and an annular flange 220 extending outwardly from a
main portion 224 and positioned on the pedestal 152. In one
embodiment, the thermally conductive base 164 may be fabricated by
a metal, such as aluminum or stainless steel or other suitable
materials. Alternatively, the thermally conductive base 164 may be
fabricated by a composite of ceramic, such as an aluminum-silicon
alloy infiltrated SiC or Molybdenum to match a thermal expansion
coefficient of the ceramic body. The thermally conductive base 164
should provide good strength and durability as well as heat
transfer properties. An upper surface of the protective layer 136
may have an outer ring 216, multiple mesas 210 and channels 208,
212 between the mesas.
[0038] FIG. 3 illustrates a cross sectional side view of the
electrostatic chuck 150. Referring to FIG. 3, the thermally
conductive base 164 is coupled to a ceramic body 302 by a first
metal bond 304. The ceramic body 302 may be a bulk sintered ceramic
such as aluminum oxide (Al.sub.2O.sub.3), aluminum nitride (AlN),
titanium oxide (TiO), titanium nitride (TiN), silicon carbide (SiC)
and the like. The ceramic body 302 may be provided, for example, as
a thin ceramic wafer. In one embodiment, the ceramic body has a
thickness of about 1 mm. The ceramic body 302 may have an electrode
connection 306 formed therein (e.g., by drilling a hole through the
ceramic body and filling the hole with an electrically conductive
material. The electrode connection 306 may connect a metal bond
that functions as a clamping electrode to a chucking power source
and/or to an RF source.
[0039] The first metal bond 304 facilitates thermal energy exchange
between the ceramic body 302 and the thermally conductive base 164
and may reduce thermal expansion mismatch therebetween. The metal
base 164 may include multiple conduits (e.g., an inner conduit 168
and an outer conduit 170) through which fluids may be flowed to
heat or cool the electrostatic chuck 150 and a substrate 144. The
metal base 164 may additionally include one or more embedded
heaters 176, which may be resistive heating elements.
[0040] The first metal bond 304 mechanically bonds the thermally
conductive base 164 to the ceramic body 302. In one embodiment, the
metal bonding material 304 includes tin and/or indium.
Alternatively, other metals may be used. Additionally, the first
metal bond 304 may include a thin layer of aluminum and nickel
(e.g., having a thickness of about 2-4 mil in one embodiment)
between two layers of other metals (e.g., between two layers of
tin). In one embodiment, the thin layer is initially a reactive
multi-layer foil (referred to herein as a reactive foil) composed
of alternating nanoscale layers of reactive materials such as
aluminum and nickel. During a room temperature metal bonding
process, the reactive foil may be activated (e.g., ignited),
creating a near instantaneous reaction generating upwards of 1500
degrees C. This may cause upper and lower layers of metal, which
act as a solder, to melt and reflow to bond the thermally
conductive base 164 to the ceramic body 302. In one embodiment, the
reactive foil is NanoFoil.RTM., manufactured by Indium Corporation
of America.
[0041] The electrostatic chuck 150 additionally includes a
protective layer 136 that is coupled to the ceramic body 302 by a
second metal bond 308. The protective layer 136 may be provided,
for example, as a thin ceramic wafer. Mesas (not shown) may be
formed on a surface of the protective layer, and the protective
layer and ceramic body may include holes for the flow of helium and
holes for lift pins. Such holes may be formed before or after the
protective layer 136 is bonded to the ceramic body. The second
metal bond 308 may be substantially similar to the first metal bond
304, and may have been generated using a room temperature bonding
process (e.g., using an ignitable reactive foil). In one
embodiment, the reactive foil has preformed foil features that
correspond to surface features of the protective layer and/or the
ceramic body. For example, the reactive foil may have preformed
holes that correspond to helium holes and lift pin holes in the
protective layer. Reactive foil having preformed foil features is
described in greater detail below with reference to FIGS.
8A-11.
[0042] In one embodiment, both the first metal bond 304 and the
second metal bond 308 are formed at the same time. For example, the
entire structure may be pressed together in a fixture, and reactive
foil between the thermally conductive base and ceramic body may be
activated at approximately the same time as reactive foil between
the protective layer and the ceramic body to form both metal bonds
in parallel. Bond thickness may be approximately 25 microns to 500
microns (e.g., 150 to 250 microns in one embodiment).
[0043] The thickness of protective layer 136 may be selected to
provide desired dielectric properties such as a specific breakdown
voltage. In one embodiment, when the electrostatic chuck is to be
used in a Columbic mode, the protective layer has a thickness of
between about 150-500 microns (and about 200-300 microns in one
example embodiment). If the electrostatic chuck is to be used in a
Johnson Raybek mode, the protective layer may have a thickness of
around 1 mm.
[0044] As mentioned above, the protective layer 136 is a bulk
sintered ceramic. In one embodiment, the protective layer is a
ceramic composite as described above, which has a high hardness
that resists wear (due to relative motion because of thermal
property mismatch between substrate & the puck) during plasma
processing. In one embodiment, the ceramic composite provides a
Vickers hardness (5 Kgf) between about 5 GPa and about 11 GPa. In
one embodiment, the ceramic composite provides a Vickers hardness
of about 9-10 GPa. Additionally, the ceramic composite may have a
density of around 4.90 g/cm3, a flexural strength of about 215 MPa,
a fracture toughness of about 1.6 MPam.sup.1/2, a Youngs Modulus of
about 190 GPa, a thermal expansion of about 8.5.times.10.sup.-6/K
(20-900.degree. C.), a thermal conductivity of about 3.5 W/mK, a
dielectric constant of about 15.5 (measured at 20.degree. C. 13.56
MHz), a dielectric loss tangent of about 11.times.10-4 (20.degree.
C. 13.56 MHz), and a volume resistivity of greater than 10.sup.15
.OMEGA.cm at room temperature in one embodiment.
[0045] In another embodiment, the protective layer is YAG. In
another embodiment, the protective layer is sapphire. In still
another embodiment, the protective layer is yttrium aluminum oxide
(Y.sub.xAl.sub.yO.sub.z).
[0046] A gasket 310 may be disposed at a periphery of the
electrostatic chuck 150 between the protective layer 136 and the
ceramic body 302. In one embodiment, the gasket 310 is a
fluoro-polymer compressible o-ring. In another embodiment, the
gasket is a liquid polymer that cures under pressure to form the
gasket. The gasket 310 provides a protective seal that protects the
metal bond 308 from exposure to plasma or corrosive gases. A
similar gasket may encircle and protect the first metal bond 304.
Note also that a similar type of gasket 314 may be used to seal off
and separate the electrode connection 306 from the first metal bond
304.
[0047] A quartz ring 146, or other protective ring, surrounds and
covers portions of the electrostatic chuck 150. The substrate 144
is lowered down over the electrostatic puck 166, and is held in
place via electrostatic forces.
[0048] If the electrostatic chuck 150 is to be used for Columbic
chucking, then the thickness of the protective layer (dielectric
above the electrode) may be about 200 microns to about 1 mm. If the
electrostatic shuck 150 is to be used for Johnson Raybek chucking,
then the thickness of the protective layer may be about 1 mm to
about 1.5 mm.
[0049] FIG. 4 illustrates a cross sectional side view of one
embodiment of an electrostatic chuck 400. The electrostatic chuck
400 has a ceramic body 410 metal bonded to a protective layer 415
by a metal bond 420 and further bonded to a metal plate 455 by a
silicone bond or other bond 496. In one embodiment, the ceramic
body has a thickness of about 3 mm. The ceramic body 410 may
include one or more heating elements 418. In one embodiment, the
ceramic body 410 includes an electrode embedded therein. In another
embodiment (as shown), an electrode 485 may be embedded in the
protective layer 415. In yet another embodiment, a metal bond 420
may at as an electrode. In one embodiment, an upper portion 492 of
the protective layer 415 that lies above the electrode 485 has a
thickness of greater than 200 micron (e.g., 5 mil in one
embodiment). The thickness of the upper portion 492 of the
protective layer 415 may be selected to provide desired dielectric
properties such as a specific breakdown voltage.
[0050] After the protective layer 415 is placed (and ground to a
final thickness in some embodiments), mesas 418 are formed on an
upper surface of the protective layer 415. The mesas 418 may be
formed, for example, by bead blasting or salt blasting the surface
of the protective layer 415. The mesas may be around 3-50 microns
tall (about 10-15 in one embodiment) and about 200 microns in
diameter in some embodiments.
[0051] Additionally, multiple holes 475 are drilled through the
ceramic body 410 and/or protective layer 415. These holes 475 may
be drilled before or after the protective layer 415 is bonded to
the ceramic base 410, and holes in the protective layer 415 may
line up with holes in the ceramic body 410 and/or base 455. In one
embodiment, holes are drilled through the protective layer 415,
ceramic body 410 and base 455 after the bonding is performed.
Alternatively, holes may be drilled separately and then aligned
prior to bonding. The holes may line up with preformed holes in a
reactive foil used to form the metal bond 420 between the ceramic
body 410 and protective layer 415. In one embodiment, gaskets 490
are placed or formed at a perimeter of the metal bond 420 and where
the holes 475 meet the metal bond 420. The gaskets formed around
the holes 475 may be omitted in some implementations in which the
metal bond 420 is not used as an electrode. In one embodiment, the
holes 475 have a diameter of about 4-7 mil. In one embodiment, the
holes are formed by laser drilling. The holes 475 may deliver a
thermally conductive gas such as helium to valleys or conduits
between the mesas 418. The helium (or other thermally conductive
gas) may facilitate heat transfer between a substrate and the
electrostatic chuck 400. It is also possible to deposit the mesas
418 on top of substrate support (e.g., onto the protective layer
415). Ceramic plugs (not shown) may fill the holes. The ceramic
plugs may be porous, and may permit the flow of helium. However,
the ceramic plugs may prevent arcing of flowed plasma.
[0052] FIG. 5 illustrates one embodiment of a process 500 for
manufacturing an electrostatic chuck. At block 505 of process 500,
a ceramic body is provided. The provided ceramic body may be a
ceramic wafer. The ceramic wafer may have undergone some
processing, such as to form an electrode connector, but may lack
heating elements, cooling channels, and an embedded electrode.
[0053] At block 510, a lower surface of the ceramic body is bonded
to a thermally conductive base by performing a metal bonding
process to form a first metal bond. At block 515, a bulk sintered
ceramic protective layer is bonded to an upper surface of the
ceramic body by the metal bonding process to form a second metal
bond. The protective layer may be a ceramic wafer having a
thickness of about 700 microns to about 1-2 mm. The metal bonding
process is described with reference to FIG. 7. In one embodiment,
the upper surface of the ceramic body is polished flat before
bonding it to the protective layer. At block 520, the second metal
bond is coupled to a sealed electrode connection. This coupling may
occur as a result of the metal bonding process that forms the
second metal bond.
[0054] At block 525, a surface of the protective layer is ground
down to a desired thickness. The protective layer may be a
dialectic material over a clamping electrode, and so the desired
thickness may be a thickness that provides a specific breakdown
voltage (e.g., about 200-300 microns in one embodiment).
[0055] At block 530, mesas are formed on an upper surface of the
protective layer. At block 535, holes are formed in the protective
layer and the ceramic body (e.g., by laser drilling). Note that the
operations of block 530 may be performed after bonding the
protective layer to the ceramic body (as shown), or may be
performed prior to such bonding. Plugs may then be formed in the
holes. In an alternative embodiment, the ceramic body may be bonded
to the base after the mesas are formed, after the holes are formed
and/or after the protective layer is bonded.
[0056] FIG. 6 illustrates another embodiment of a process for
manufacturing an electrostatic chuck. At block 605 of process 600,
a ceramic body is provided. The provided ceramic body may be a
ceramic puck that includes one or more heating elements. The
ceramic puck may or may not include an embedded electrode.
[0057] At block 610, a lower surface of the ceramic body is bonded
to a thermally conductive base. The bond may be a silicone bond in
one embodiment. In another embodiment, the bonding material may be
a thermal conductive paste or tape having at least one of an
acrylic based compound and silicone based compound. In yet another
embodiment, the bonding material may be a thermal paste or tape
having at least one of an acrylic based compound and silicone based
compound, which may have metal or ceramic fillers mixed or added
thereto. The metal filler may be at least one of Al, Mg, Ta, Ti, or
combination thereof and the ceramic filler may be at least one of
aluminum oxide (Al.sub.2O.sub.3), aluminum nitride (AlN), titanium
diboride (TiB.sub.2) or combination thereof.
[0058] At block 615, a bulk sintered ceramic protective layer is
bonded to an upper surface of the ceramic body by a metal bonding
process to form a metal bond. The metal bonding process is
described with reference to FIG. 7.
[0059] At block 620, a surface of the protective layer is ground
down to a desired thickness. The protective layer may be a
dialectic material over a clamping electrode, and so the desired
thickness may be a thickness that provides a specific breakdown
voltage.
[0060] At block 625, mesas are formed on an upper surface of the
protective layer. At block 630, holes are formed in the protective
layer and the ceramic body (e.g., by laser drilling). In an
alternative embodiment, the ceramic body may be bonded to the base
after the mesas are formed, after the holes are formed or after the
protective layer is bonded.
[0061] FIG. 7 illustrates one embodiment for performing a metal
bonding process. At block 705, a surface of a first body is coated
with a first metal layer. The metal layer may be tin, indium or
another metal. At block 710, a surface of a second body is coated
with a second metal layer. The first body and second body may be,
for example, a protective layer, a ceramic body or a thermally
conductive base. For ceramic bodies (e.g, the ceramic body or
protective layer), coating the surface with a metal layer may
include first forming a titanium layer on the surface. Titanium has
properties that cause it to form strong bonds with ceramics (such
as by forming bonds with oxygen molecules in ceramics). A metal
layer may then be formed over the titanium.
[0062] The metal layer may be tin or indium, for example. If tin is
used for the metal layer, then processes of below 250 degrees C.
may be performed using the electrostatic chuck since tin has a
melting temperature of 250 degrees C. If indium is used for the
metal layer, then processes of below 150 degrees C. may be
performed using the electrostatic chuck since indium has a melting
temperature of 150 degrees C. If higher temperature processes are
to be performed, than a metal having a higher melting temperature
should be used for the metal layers. The titanium layer and the
subsequent metal layer may be formed by evaporation,
electroplating, sputtering, or other metal deposition or growth
techniques. Alternatively, the first metal layer may be a first
sheet of solder (e.g., a sheet of tin or indium) that is positioned
against the first body, and the second metal layer may be a second
sheet of solder that is positioned against the second body. In one
embodiment, the first metal layer and second metal layer are each
approximately 1-20 mils thick (e.g., 25-100 microns in one
embodiment).
[0063] At block 715, a gasket is applied on a periphery of the
coated surface of the first body or second body. The gasket will
protect the coated surface from interaction with corrosive gases or
plasmas. In one embodiment, the gasket is a compressible o-ring.
Alternatively, the gasket may be a liquid that cures under pressure
to form the gasket.
[0064] At block 720, the coated surface of the first body is
positioned against the coated surface of the second body with a
reactive foil therebetween. In one embodiment, the reactive foil is
approximately 50-150 microns thick. At block 725, pressure is
applied to compress the first body against the second body. The
pressure may be about 50 pounds per square inch (PSI) in one
embodiment. While the pressure is applied, at block 730 the
reactive foil is activated. The reactive foil may be activated by
providing a small burst of local energy, such as by using optical,
electrical or thermal energy sources. Ignition of the reactive foil
causes a chemical reaction that produces a sudden and momentary
localized burst of heat up to about 1500 degrees C., which melts
the first and second metal layers, causing them to reflow into a
single metal bond. This nano-bonding technique for forming a metal
bond precisely delivers localized heat that does not penetrate the
bodies being bonded. Since the bodies are not heated, the bodies
may have a significant mismatch in coefficients of thermal
expansion (CTE) without a detrimental effect (e.g., without
inducing stress or warping).
[0065] FIG. 8 illustrates one embodiment of a process 800 for
manufacturing a reactive foil sheet having preformed foil features.
At block 805 of process 800, a template having surface features is
provided. The template may be any rigid material in one embodiment.
The template may have a substantially planar surface, with one or
more surface features. Alternatively, the template may have a
non-planar surface with or without surface features.
[0066] The surface features may include positive steps (e.g.,
standoffs) and/or negative steps (e.g., holes or trenches) in a
surface of the template. The steps may have a height or depth that
is sufficient to cause a first portion of a deposited reactive foil
sheet that covers the step to be discontiguous with a second
portion of the reactive foil sheet that covers a remainder of the
template. For example, standoffs may have a height of about 1-25
mm, and holes/trenches may have a depth of about 1-25 mm In one
particular embodiment, the steps have a height or depth of about
2-10 mm Instead, deposited reactive foil may have the shape of the
non-planar regions.
[0067] The surface features may also include non-planar regions
such as bumps, dips, curves, and so forth. These surface features
may not cause any portions of a deposited reactive foil sheet to be
discontiguous with other portions of the reactive foil sheet.
[0068] At block 810, alternating nanoscale layers of at least two
reactive materials are deposited onto the template to form a
reactive foil sheet. In one embodiment, the reactive materials are
metals that are sputtered onto the template. The reactive materials
may also be formed by evaporation, electroplating, or other metal
deposition or growth techniques. Thousands of alternating layers of
the two reactive materials may be deposited onto the template. Each
layer may have a thickness on the scale of one nanometer to tens of
nanometers. In one embodiment, the reactive foil is approximately
10-500 microns thick, depending on the number of nanoscale layers
that the reactive foil includes. In a further embodiment, the
reactive foil is about 50-150 microns thick.
[0069] In one embodiment, the two reactive materials are aluminum
(Al) and nickel (Ni), and the reactive foil is a stack of Al/Ni
layers. Alternatively, the two reactive materials may be aluminum
and titanium (Ti) (producing a stack of Al/Ti layers), titanium and
boron (B) (producing a stack of Ti/B layers), copper (Cu) and
nickel (producing a stack of Cu/Ni layers) or titanium and
amorphous silicon (Si) (producing a stack of Ti/Si layers). Other
reactive materials may also be used to form the reactive foil.
[0070] For some surface features, a height or depth of the surface
feature may cause a portion of a deposited reactive foil sheet to
be discontiguous with other portions of the reactive foil sheet. In
many cases, this discontinuity is intended. However, if no
discontinuity is desired, then an angle of the template with
regards to a deposition source may be controlled to eliminate any
such discontinuity. In one embodiment, the template is rotated
and/or the angle of the template with relation to the deposition
source is changed during the deposition process. In another
embodiment, multiple deposition sources having different locations
are used. The arrangement of the deposition sources may be set to
maximize coverage of a non-planar surface and/or surface features
while minimizing thickness variations in the alternating
layers.
[0071] At block 815, the reactive foil sheet is removed from the
template. The reactive foil sheet may have a weak mechanical bond
to the template, enabling the reactive foil to be removed from the
template without tearing. The reactive foil sheet may have foil
features that correspond to surface features of the template. For
example, the reactive foil sheet may have voids corresponding to
the regions of the template that had steps. Additionally, the
reactive foil sheet may have non-planar (e.g., three dimensional)
features corresponding to three dimensional features in the
template. The features may have various sizes and shapes. The
preformed foil features may correspond to surface features of one
or more substrates that the reactive foil is designed to bond.
Accordingly, the formed reactive foil may be production worthy. For
example, the reactive foil may be set in place on a substrate
having surface features and energized to create a metal bond
without first machining the reactive foil to accommodate the
surface features.
[0072] FIG. 9A illustrates deposition of nanoscale metal layers
onto a template 900 having surface features. The template 900 has a
substantially planar surface 905 with three surface features 910,
915, 922. Surface features 910 and 915 are steps having a height
920. The height 920 is sufficiently tall to cause nanoscale metal
layers deposited 925 onto the features 910, 915 to be discontiguous
with nanoscale metal layers deposited 925 onto a remainder of the
template's surface 905. Surface feature 922 is a non-planar (e.g.,
three dimensional) feature. Metal layers 925 deposited onto feature
922 are contiguous with metal layers deposited onto the remainder
of the template's surface 905.
[0073] FIG. 9B illustrates a reactive foil sheet 950 having
preformed foil features 960, 965, 970. The reactive foil sheet 950
is formed by depositing alternating nanoscale metal layers onto
template 900 of FIG. 9A. The reactive foil sheet 950 is
substantially planar. However, reactive foil sheet 950 includes a
non-planar feature 970 caused by deposition over surface feature
922 of template 900. Foil features 960 and 965 are voids in
reactive foil sheet 950, and correspond to surface features 910,
920 of template 900.
[0074] FIG. 10A illustrates deposition of nanoscale metal layers
onto a template 1000 having a non-planar surface 1005. The template
1000 may have a three dimensional shape as shown, or may have any
other three dimensional shape. FIG. 10B illustrates a non-planar
reactive foil sheet 1050 having a three dimensional shape that
matches the three dimensional shape of template 1000. This three
dimensional shape may correspond to a three dimensional shape of
two substrates that the reactive foil will be used to bond
together. Accordingly, the reactive foil sheet 1050 may be place
onto one of the substrates in an orientation and position that
causes a shape and any features of the reactive foil sheet 1050 to
line up with a shape and features of the substrate. The second
substrate may then be placed over the reactive foil sheet, and the
reactive foil sheet may be ignited. Because the reactive foil sheet
has a shape that matches the substrates that it will bond, the
reactive foil sheet will not be deformed or torn. This may minimize
or eliminate leakage paths that might otherwise be caused by
attempting to use a planar reactive foil sheet to bond non-planar
surfaces.
[0075] The reactive foil sheets with preformed features described
herein may be used to bond any two substrates. The reactive foil
sheets may be particularly useful for applications in which a room
temperature, rapid bond is to be formed without vacuum and between
substrates having surface features. For example, the reactive foil
may be used to bond an electrostatic puck with helium holes to a
cooling base plate. The reactive foil sheets described herein may
also be used to bond a protective layer over a showerhead, which
may have thousands of gas distribution holes as well as divots
and/or standoffs around the gas distribution holes. The reactive
foil sheets may also be used to bond semiconductor devices, solar
devices, and other devices.
[0076] FIG. 11 illustrates a continuous reactive foil 1100 formed
of interlocking reactive foil sheets 1105, 1110, 1115, 1120. The
perimeters of the reactive foil sheets 1105-1120 may have a
tessellating puzzle shape that enables the reactive foil sheets
1105-1120 to interlock. The tessellating puzzle shape may be formed
by depositing alternating nanoscale metal layers over a template
having a step around a perimeter of the template with the
tessellating puzzle shape. Accordingly, the above described process
800 may be used to create interlocking reactive foil sheets. These
interlocking reactive foil sheets enable any sized substrate to be
bonded using a metal bonding process without introducing leakage
pathways.
[0077] The preceding description sets forth numerous specific
details such as examples of specific systems, components, methods,
and so forth, in order to provide a good understanding of several
embodiments of the present invention. It will be apparent to one
skilled in the art, however, that at least some embodiments of the
present invention may be practiced without these specific details.
In other instances, well-known components or methods are not
described in detail or are presented in simple block diagram format
in order to avoid unnecessarily obscuring the present invention.
Thus, the specific details set forth are merely exemplary.
Particular implementations may vary from these exemplary details
and still be contemplated to be within the scope of the present
invention.
[0078] Reference throughout this specification to "one embodiment"
or "an embodiment" means that a particular feature, structure, or
characteristic described in connection with the embodiment is
included in at least one embodiment. Thus, the appearances of the
phrase "in one embodiment" or "in an embodiment" in various places
throughout this specification are not necessarily all referring to
the same embodiment. In addition, the term "or" is intended to mean
an inclusive "or" rather than an exclusive "or." When the term
"about" or "approximately" is used herein, this is intended to mean
that the nominal value presented is precise within .+-.10%.
[0079] Although the operations of the methods herein are shown and
described in a particular order, the order of the operations of
each method may be altered so that certain operations may be
performed in an inverse order or so that certain operation may be
performed, at least in part, concurrently with other operations. In
another embodiment, instructions or sub-operations of distinct
operations may be in an intermittent and/or alternating manner In
one embodiment, multiple metal bonding operations are performed as
a single step.
[0080] It is to be understood that the above description is
intended to be illustrative, and not restrictive. Many other
embodiments will be apparent to those of skill in the art upon
reading and understanding the above description. The scope of the
invention should, therefore, be determined with reference to the
appended claims, along with the full scope of equivalents to which
such claims are entitled.
* * * * *