U.S. patent application number 10/782300 was filed with the patent office on 2005-06-23 for tuned potential pedestal for mask etch processing apparatus.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Collins, Kenneth S., Mak, Alfred W., Nguyen, Khiem, Sahin, Turgut, Satitpunwaycha, Peter.
Application Number | 20050133166 10/782300 |
Document ID | / |
Family ID | 34681603 |
Filed Date | 2005-06-23 |
United States Patent
Application |
20050133166 |
Kind Code |
A1 |
Satitpunwaycha, Peter ; et
al. |
June 23, 2005 |
Tuned potential pedestal for mask etch processing apparatus
Abstract
The present invention generally provides an improved pedestal
for supporting a substrate. The pedestal has greatest application
during a plasma etching process, such as for a quartz photomask, or
"reticle." The pedestal defines a body, and a substrate support
base along an upper surface of the body. The substrate support base
has an outer edge, and an intermediate substrate support ridge for
receiving and supporting the substrate. At least a portion of the
substrate support base outside of the intermediate substrate
support ridge is fabricated from a dielectric material. The purpose
is to couple greater RF power through the reticle in order to
enhance the plasma etching process.
Inventors: |
Satitpunwaycha, Peter;
(Sunnyvale, CA) ; Nguyen, Khiem; (San Jose,
CA) ; Mak, Alfred W.; (Union City, CA) ;
Collins, Kenneth S.; (San Jose, CA) ; Sahin,
Turgut; (Cupertino, CA) |
Correspondence
Address: |
MOSER, PATTERSON & SHERIDAN, LLP
APPLIED MATERIALS, INC.
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
34681603 |
Appl. No.: |
10/782300 |
Filed: |
February 18, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60531062 |
Dec 19, 2003 |
|
|
|
Current U.S.
Class: |
156/345.51 |
Current CPC
Class: |
H01J 37/321 20130101;
H01J 2237/2001 20130101; H01L 21/68735 20130101; H01L 21/67069
20130101; H01L 21/68785 20130101 |
Class at
Publication: |
156/345.51 |
International
Class: |
C23F 001/00 |
Claims
1. A pedestal for supporting a substrate in a plasma etching
chamber, comprising: a body, the body being configured to receive
an RF power; and a substrate support base along an upper surface of
the body, the substrate support base having an outer edge, and an
intermediate substrate support ridge for receiving and supporting
the substrate; and wherein at least a portion of the substrate
support base outside of the intermediate substrate support ridge is
fabricated from a dielectric material.
2. The pedestal of claim 1, wherein the portion of the substrate
support base within the substrate support ridge is fabricated from
a metallic material.
3. The pedestal of claim 2, wherein the portion of the substrate
support base fabricated from a dielectric material is formed by
placing a layer of dielectric material along a top surface of the
substrate support base outside of the substrate support ridge in
order to form a dielectric ring.
4. The pedestal of claim 3, wherein the substrate support ridge is
fabricated from a metallic material.
5. The pedestal of claim 3, wherein the dielectric material is
fabricated from materials selected from the group consisting of a
polymeric material, a ceramic material, and combinations
thereof.
6. The pedestal of claim 2, wherein the portion of the substrate
support base fabricated from a dielectric material defines
substantially the entire thickness of the substrate support base
outside of the substrate support ridge.
7. The pedestal of claim 6, wherein the substrate support ridge is
fabricated from a metallic material.
8. The pedestal of claim 6, wherein the dielectric material is
fabricated from materials selected from the group consisting of a
polymeric material, a ceramic material, and combinations
thereof.
9. The pedestal of claim 1, further comprising a cover configured
to be received on the substrate support base.
10. A pedestal for supporting a reticle in a plasma etching
chamber, comprising: a body, the body being configured to receive
an RF power; a reticle support base along an upper surface of the
body, the reticle support base having an outer edge, and an
intermediate reticle support ridge for receiving and supporting the
reticle; and wherein at least a portion of the reticle support base
outside of the intermediate substrate support ridge is fabricated
from a dielectric material.
11. The pedestal of claim 10, wherein: the portion of the reticle
support base within the reticle support ridge is fabricated from a
metallic material; the reticle support ridge is fabricated from a
metallic material; and
12. The pedestal of claim 10, wherein the dielectric material is
fabricated from at least one of a polymeric material and a ceramic
material.
13. The pedestal of claim 12, wherein the portion of the reticle
support base fabricated from a dielectric material is formed by
placing a layer of dielectric material along a top surface of the
reticle support base outside of the reticle support ridge in order
to form a dielectric ring.
14. The pedestal of claim 12, wherein the portion of the reticle
support base fabricated from a dielectric material defines
substantially the entire thickness of the reticle support base
outside of the reticle support ridge
15. A plasma etching chamber having a pedestal therein for
supporting a reticle, comprising: a chamber body defining a base
wall, a side wall and a dome; a gate along the side wall for
permitting a reticle to be moved into the plasma etching chamber;
and a reticle support member for supporting a reticle within the
plasma etching chamber during processing, the reticle support
member comprising: a body, the body being configured to receive an
RF power; a reticle support base along an upper surface of the
body, the reticle support base having an outer edge, and an
intermediate reticle support ridge for receiving and supporting the
reticle; and wherein at least a portion of the reticle support base
outside of the intermediate substrate support ridge is fabricated
from a dielectric material.
16. The chamber of claim 15, wherein: the portion of the reticle
support base within the reticle support ridge is fabricated from a
metallic material; the reticle support ridge is fabricated from a
metallic material; and
17. The chamber of claim 16, wherein the dielectric material is
fabricated from at least one of a polymeric material and a ceramic
material.
18. The chamber of claim 17, wherein the portion of the reticle
support base fabricated from a dielectric material is formed by
placing a layer of dielectric material along a top surface of the
reticle support base outside of the reticle support ridge in order
to form a dielectric ring.
19. The chamber of claim 17, wherein the portion of the reticle
support base fabricated from a dielectric material defines
substantially the entire thickness of the reticle support base
outside of the reticle support ridge
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] The present application claims priority to previously filed
provisional patent application Ser. No. 60/531,062, filed Dec. 19,
2003, entitled "Tuned Potential Pedestal for Mask Etch Processing
Apparatus." The provisional application is incorporated herein by
referenced in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention generally relates to the fabrication
of integrated circuits. More specifically, the invention relates to
an apparatus for manufacturing a photomask, or "reticle," useful in
manufacturing semiconductors.
[0004] 2. Description of the Related Art
[0005] Integrated circuits (IC) are manufactured by forming
discrete semiconductor devices on a surface of a semiconductor
substrate. An example of such a substrate is a silicon (Si) or
silicon dioxide (SiO.sub.2) wafer. To interconnect the devices on
the substrate, a multi-level network of interconnect structures is
formed. Material is deposited on the substrate in layers and
selectively removed in a series of controlled steps.
[0006] Increasing circuit densities have placed additional demands
on processes used to fabricate semiconductor devices. For example,
as circuit densities increase, the widths of vias, contacts and
other features, as well as the dielectric materials between them,
decrease to sub-micron dimensions. However, the thickness of the
dielectric layers remains substantially constant, with the result
that the aspect ratios for the features, i.e., their height divided
by width, increases. Reliable formation of high aspect ratio
features is important to the success of sub-micron technology and
to the continued effort to increase circuit density and the quality
of individual substrates and die.
[0007] Reliable formation of high aspect ratio features with
desired critical dimensions requires precise patterning and
subsequent etching of the substrate. A technique commonly used to
form precise patterns on substrates is photolithography. The
technique generally involves the direction of light energy through
a lens, or "reticle" and onto the substrate. In conventional
photolithographic processes, a photoresist material is first
applied on a substrate layer to be etched. In the context of
optical resists, the resist material is sensitive to light energy,
such as ultraviolet or laser sources. The resist material defines a
polymer that is tuned to respond to the specific wavelength of
light used, and to different exposing sources.
[0008] After the resist is deposited onto the substrate, the light
source is actuated to emit ultraviolet (UV) light or low X-ray
light, for example, directed at the resist-covered substrate. The
selected light source chemically alters the composition of the
photoresist material. However, the photoresist layer is only
selectively exposed. In this respect, a photomask, or "reticle," is
positioned between the light source and the substrate being
processed. The photomask is patterned to contain the desired
configuration of features for the substrate. The patterned
photomask causes the light energy to strike the resist material in
accordance with the pattern.
[0009] Photolithographic reticles are fabricated from an optically
transparent material, such as quartz (i.e., silicon dioxide,
SiO.sub.2). The reticle includes a pattern of opaque material that
inhibits the light from exposing portions of the substrate in
accordance with the desired pattern. A thin opaque layer of metal,
typically chromium, is disposed on the surface of the reticle. This
light-shielding layer is patterned to correspond to the features to
be transferred to the substrate, such as transistors or polygates.
The metallic material is patterned using conventional laser or
electron beam patterning equipment to define the critical
dimensions to be transferred to the metal layer. The metal layer is
then etched to remove the metal material not protected by the
patterned resist, thereby exposing the underlying quartz material
and forming a patterned photomask layer. Photomask layers thus
allow light to pass therethrough in a precise pattern onto the
substrate surface.
[0010] In photolithography, the exposed material may either be a
positive resist or a negative resist. In a positive resist, the
exposed resist material on the substrate is removed, while in a
negative resist, the unexposed portions are removed. Removal is
typically by a chemical process to expose an underlying substrate
material. The exposed underlying substrate material may then be
etched to form patterned features in the substrate surface while
the retained resist material remains as a protective coating for
the unexposed underlying substrate material. In this manner,
contacts, vias, or interconnects may be formed by exposing the
resist to a pattern of light through a photolithographic reticle
having a photomask layer disposed thereon.
[0011] In an iterative convergence, the method for fabricating a
patterned reticle itself involves a deposition and subsequent
etching process. In this respect, a metal layer is first deposited
on a top surface of a glass reticle. Thereafter, selected portions
of the metal layer are removed through etching. Various types of
etching processes are used for etching the metal layer from a
reticle. One such etching method is known as plasma etching. In
order to perform plasma etching, a glass reticle is first placed
within a process chamber. More specifically, the glass reticle is
placed on a pedestal. In a plasma etching process, the pedestal
serves as a cathode. To this end, the metallic pedestal is given RF
power. Power applied to the pedestal creates a substrate bias in
the form of a negative voltage on the upper surface of the reticle.
This negative voltage is used to attract ions from a plasma formed
above the reticle in the chamber. The plasma is formed by the
application of power to one or more inductive coils at the top of
the chamber. The inductive coils generate and sustain the plasma
above the pedestal and reticle. Thus, a voltage drop is induced
across the pedestal that draws ions to the upper surface of the
reticle, thereby etching a metallic layer.
[0012] Because the reticle is formed from a material having a low
dielectric constant, e.g., glass or quartz, the amount of RF power
that is coupled through the reticle is low. This inhibits the gas
plasma in reacting with the reticle surface. This limitation is
compounded by a gap typically existing between the reticle and the
supporting pedestal therebelow. In addition, when the surface area
of the pedestal is large compared to the reticle area, the RF power
may preferentially couple to other regions of the pedestal,
producing a loss of RF power. Further, it has been observed that
the use of a pedestal cover, e.g., cover ring and capture ring,
fabricated from a dielectric material is inadequate to lessen the
power coupled through the region of the pedestal that is not
immediately below the reticle.
[0013] Therefore, there is a need for a plasma etching apparatus
that aids in the chemical reaction between a gas plasma and a
reticle. In addition, there is a need for a pedestal fabricated
from a material that does not contribute to the power loss across
the reticle during a plasma etching procedure.
SUMMARY OF THE INVENTION
[0014] The present invention generally provides an improved
pedestal for supporting a substrate and related substrate support
hardware. The pedestal has greatest application during a plasma
etching process, such as for a quartz photomask, or "reticle."
[0015] The pedestal defines a body, and a base along on an upper
surface of the body. The body receives an RF power during substrate
processing. The substrate support base has an outer edge, and an
intermediate substrate support ridge for receiving and supporting
the substrate. At least a portion of the substrate support base
outside of the intermediate substrate support ridge is fabricated
from a dielectric material, or material having a lower dielectric
constant than the remaining support base. An example is quartz.
Quartz has a lower dielectric constant than the materials typically
used for fabricating the pedestal body or cover, e.g., alumina. The
placement of quartz allows greater RF power to be coupled through
the reticle, thereby enhancing the plasma etching process. It also
provides greater control over the relative amount of RF power
coupled through the reticle.
[0016] In one aspect, a layer of dielectric material is placed
along the top of the support base of the pedestal body. In another
embodiment, the entire cross-sectional thickness of the support
base that encompasses the supporting ridge is fabricated from a
dielectric material. In one embodiment, a separate substrate
support assembly is disposed on the base to facilitate the transfer
of the substrate onto and off of the pedestal, with the substrate
support assembly being fabricated from a dielectric material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to the appended drawings. It is to be
noted, however, that the appended drawings illustrate only typical
embodiments of this invention and are, therefore, not to be
considered limiting of its scope.
[0018] FIG. 1 is a cross-sectional view of a plasma etching chamber
as might contain the pedestal of the present invention. The chamber
shown in FIG. 1 is exemplary.
[0019] FIG. 2 presents an exploded perspective view of the
substrate support member of FIG. 1.
[0020] FIG. 3 shows a perspective cutaway view of one embodiment of
a pedestal of the present invention.
[0021] FIG. 4 provides a cross-sectional schematic view of a
pedestal of the present invention. A portion fabricated from a
dielectric material is shown.
[0022] FIG. 5 presents a cross-sectional schematic view of a
pedestal of the present invention, in an alternate embodiment. A
portion fabricated from a dielectric material is again shown.
DETAILED DESCRIPTION OF THE INVENTION
[0023] Aspects of the invention will be described below in
reference to an inductively coupled plasma etch chamber. Suitable
inductively coupled plasma etch chambers include the Decoupled
Plasma Source (DPS.TM.) chamber available from Applied Materials,
Inc., of Santa Clara, Calif., or the ETEC Tetra.TM. photomask etch
chamber available from ETEC of Hayward, Calif. A two-coil chamber,
such as the Tetra II.TM. decoupled plasma source chamber available
from Applied Materials, Inc. may also be employed. Other process
chambers may be used including, for example, capacitively coupled
parallel plate chambers and magnetically enhanced ion etch
chambers, as well as inductively coupled plasma etch chambers of
different designs. Although the processes are advantageously
performed with the DPS.TM. processing chamber, the description in
conjunction with the DPS.TM. processing chamber is illustrative and
should not be construed or interpreted to limit the scope of
aspects of the invention.
[0024] In order to perform plasma etching, a substrate, e.g., a
glass reticle, is placed within a processing chamber. An example of
such a chamber is schematically shown in FIG. 1. The process
chamber 100 of FIG. 1 has a substrate support member 200 disposed
therein, and a substrate handler blade 300 positioned adjacent
thereto. Substrates 222 are shown positioned on both the substrate
support member 200 and the handler blade 300.
[0025] The processing chamber 100 is configured to receive a
substrate 222, such as a glass reticle to be processed through
plasma etching. The substrate 222 enters and exits the chamber 100
through a gate 161. The gate 161 serves as a port, and also
isolates the chamber 100 environment during reticle processing. The
substrate 222 is transported via a substrate cassette, using the
substrate handling blade 300. The substrate handling blade 300
transfers the substrate 222 between a separate transfer chamber
(not shown) and various processing chambers. In this respect, it is
understood that the reticle fabrication process involves multiple
steps, and that different steps are typically conducted in
different chambers that mechanically cooperate with the substrate
handling blade 300. An example of such a processing system is a
Centura.TM. processing system available from Applied Materials,
Inc. of Santa Clara, Calif.
[0026] The process chamber 100 generally includes a cylindrical
side wall 162. The side wall 162 helps define the chamber body, and
also supports the gate 161. The chamber 100 is also defined by a
chamber bottom 167, and an energy transparent ceiling or lid 163.
An inductive coil 176 is disposed around at least a portion of the
lid 163. The chamber body 162 and chamber bottom 167 of the chamber
100 can be made from a metal, such as anodized aluminum. The lid
163 is fabricated from an energy transparent material such as a
ceramic or other dielectric material.
[0027] As mentioned above, the chamber 100 holds a substrate
support member 200. The support member 200 supports the substrate
222 during processing. A plasma zone 164 is defined by the process
chamber 100 above an upper surface of the substrate support member
200. During processing, process gases are introduced into the
plasma etch chamber 100 through a gas distributor 172. The gas
distributor 172 is peripherally disposed about the substrate
support member 200. The gas distributor 172 is shown
illustratively, and may be disposed in other configurations, such
as disposed at the top of lid 163. Process gases and etchant
byproducts may be exhausted from the process chamber 100 through an
exhaust system (not shown). An optional cooling line 184 is
provided in the pedestal 200. for controlling the pressure in the
plasma etch chamber 100. An endpoint measurement device may
optionally be included to determine the endpoint of a process
performed in the chamber 100.
[0028] With respect to the substrate support member 200 itself, the
support member 200 defines a pedestal for the substrate 222 during
processing. The support member 200 first comprises a body 206. The
body 206 has an upper surface that defines a substrate support base
210 (seen in FIG. 2). In one arrangement, the substrate support
base 210 is a separate piece mounted on an upper surface of the
body 206. An optional substrate supporting assembly 215 is
preferably provided over the base 210 to aid in transporting the
substrate 222 into and out of the chamber 100. The substrate
supporting assembly 215 is shown in detail in FIG. 2. Only the
capture ring 216 of the supporting assembly 215 is seen in FIG.
1.
[0029] Referring back to FIG. 1, the body 206 of the substrate
support member 200 is mounted on a bulk head assembly, or shaft,
102. In the embodiment shown, the body 206 is stationary in the
chamber 100; however, in an alternative embodiment, the body 206
(or a portion of the body 206) may be moveable within the chamber
100. In one arrangement, the body 206 of the substrate support
member 200 is mounted on a stainless steel base 104. The base 104
is typically disposed on the bottom of the processing chamber (not
shown in FIG. 2), with the bulk head assembly 102 mounted through
the bottom of the processing chamber 100 and coupled to the body
206. The substrate support member 200 is adapted to maintain vacuum
isolation between the interior of the chamber 100 and the outside
environment. Power, electrical controls, and backpressure gases may
be provided to the substrate support member 200 via the shaft
102.
[0030] FIG. 2 presents an exploded perspective view of one
embodiment of a substrate support member 200. From FIG. 2, the body
206 and support base 210 are more clearly seen. It can also be seen
that a cathode 112 is disposed in the support base 210. The cathode
112 may optionally vertically extend above the surface of the body
206. The cathode 112 is electrically coupled to an electrode power
supply 178 to generate a capacitive electric field in the plasma
etch chamber 100. Typically an RF voltage is applied to the cathode
112 while the chamber body 162 is electrically grounded. Power
applied to the pedestal 200 creates a substrate bias in the form of
a negative voltage on the upper surface of the substrate 222. This
negative voltage is used to attract ions from the plasma formed in
the chamber 100 to the upper surface of the substrate 222. The
capacitive electric field forms a bias which accelerates
inductively formed plasma species toward the substrate 222 to
provide a more vertically oriented anisotropic etching of the
substrate 222.
[0031] Channels 211 (three are shown) are also disposed through the
body 206, and house internally movable lift pins 214 therein. As
will be discussed further below, the lift pins 214 engage the lower
surface of a capture ring 220 to move the capture ring 220
vertically within the chamber 100 relative to the cover ring 216.
The body 206 may comprise a temperature controlled base adapted to
regulate the temperature of the substrate support assembly 215, and
thus, a substrate 222 disposed thereon. The body 206 can be made of
a material inert to the process formed in the processing chamber
including, for example, aluminum oxide, or aluminum, and substrate
support assembly 215 components can be made of aluminum or aluminum
oxide. The body 206 may include fluid channels, heating elements,
e.g., resistive heating elements or other temperature control
members.
[0032] In the support member arrangement of FIG. 2, the substrate
support member 200 includes a separate substrate supporting
assembly 215. The substrate supporting assembly 215 generally
includes a cover ring 216 and a capture ring 220.
[0033] Referring first to the cover ring 216, the cover ring 216 is
preferably a circular ring having an upper surface 219 and support
shoulders 218. The substrate supports 218 define shoulders for
receiving a substrate (not shown). In one arrangement, the
substrate supports 218 define opposing raised surfaces 221, 223
that each includes an inner sloped surface for receiving a
substrate. A central opening 225 is formed in the upper surface 219
of the cover ring 216. The two raised surfaces 221, 223 are
generally disposed on opposing sides of the central opening 225.
The first raised surface 221 defines an essentially linear raised
surface extending along the length of one side of the central
opening 225. The second raised surface 223 defines an arcuate
raised surface 221 having an outer diameter 224 and an inner
diameter 226. The outer diameter 224 generally matches the radius
of the cover ring 216, while the inner diameter 226 conforms to the
geometry of the central bore 225 along one or more sides of the
bore 225. The upper surface 219 and the raised surfaces 221, 223
may be monolithic or may be made of separate components connected
together.
[0034] The capture ring 220 defines an arcuate base plate having an
inner diameter 207 and an outer diameter 202. A central bore 206 is
formed within the inner diameter 207 of the capture ring 220. The
diameters 207, 202 of the capture ring 220 are not continuous, but
retain an opening that serves as part of the bore 206. As with the
cover ring 216, the capture ring 220 includes substrate supports
204, 205. The substrate supports 204, 205 generally follow the
inner diameter 207 of the capture ring 220. In the arrangement of
FIG. 2, the supports 204, 205 define shoulders disposed along the
inner perimeter 207. The substrate supports 204, 205 and the base
plate 202 form a substrate receiving area. The shoulders 204, 205
and the base plate 202 are adapted to mate with the substrate
supports 218 on the cover ring 216. When the capture ring 220 is
rested upon the cover ring 216, the substrate supports 205 for the
capture ring 220 are co-planar with the substrate supports 218 for
the cover ring. The capture ring 220 is dimensioned to rest on the
cover ring 216 without covering the two raised surfaces 221, 222 on
the cover ring 216. Together, the substrate supports 205, 218 may
then seamlessly receive a substrate (not shown).
[0035] The capture ring 220 moves vertically above the cover ring
216. In operation, the lift pins 214 move the capture ring 220
vertically above the cover ring 216 during substrate transfer, and
then lower the capture ring 220 onto the cover ring 216 for
substrate processing. The use of lift pins in the semiconductor
fabrication business is known, and those of ordinary skill in the
art will understand from this disclosure how the lift pins may be
fabricated.
[0036] Channels 217 are formed through the cover ring 216 to enable
the lift pins 214 disposed through the body 206 to move
therethrough and lift the capture ring 220 vertically. The vertical
movement imparted by the lift pins 214 is used to lift the capture
ring 220 to effectuate substrate transfer between the substrate
handler blade 300 and the capture ring 220. The lift pins 214 move
the capture ring 220 vertically above the cover ring 216 during
substrate transfer, and then lower the capture ring 220 onto the
cover ring 216 for substrate processing.
[0037] To begin processing, the reticle 222 (or other substrate) is
positioned on the surface of the pedestal 200. Etch gases are then
introduced into the chamber 100. To this end, a process gas source
supplies gas, such as an oxygen based gas, through a gas input line
172. In the arrangement of FIG. 1, the input line 172 feeds gas
into the side of the lid 163. However, gas may also be introduced
through nozzles (not shown) in the top of the lid 163. Chamber
pressure is controlled by a closed-loop pressure control system
(not shown).
[0038] As gas is injected into the chamber 100, a gas plasma is
created. Plasma is formed by the application of power to one or
more inductive coils 176 at the top of the lid 163. In the chamber
100 of FIG. 1, two RF coils 176 are used, with one being an outer
coil and one being an inner coil. A power supply 177 and matching
network is used to apply power to the inductive coils 176. The
inductive coils 176 generate and sustain the plasma above the
pedestal 200 and substrate 222. In one arrangement, approximately
125 Watts is applied to the coils 176 at a frequency of about 13.56
MHz, to produce and maintain an oxygen-comprising plasma over the
surface of the reticle 222. In one arrangement for a dual coil
system, approximately 400 Watts is applied to the coils 176 at a
frequency of about 13.56 MHz, to produce and maintain a
chlo7rine-and-oxygen-comprising plasma over the surface of the
reticle 222. For a single coil system, the coils may provide a DC
bias of about 340 to 410 Volts on the reticle surface.
[0039] FIG. 3 shows a perspective cutaway view of one embodiment of
a pedestal 300 of the present invention. The pedestal 300 is
configured to receive and support a substrate in a plasma etching
chamber. Preferably, the substrate is a photolithographic reticle,
and the chamber is a plasma etching chamber, such as the chamber
shown in FIG. 1, and discussed above.
[0040] The pedestal first comprises a body 306. In the arrangement
of FIG. 3, the body 306 is a generally cylindrical object, though
other shapes may be employed. The body 306 includes an upper
surface 310 that serves as a substrate support base. In the
arrangement shown in FIG. 3, the support base 310 has a radial
outer diameter 324. The base 310 also has an intermediate shoulder
326 that forms a four-sided support ridge 325. The support ridge
325 serves to support the reticle above the pedestal 300 during
processing. The support ridge 325 is preferably fabricated from a
metallic material. The term "support ridge" means any raised
surface feature of any height or shape along the support base 310
that contacts and supports a substrate 222 during processing.
[0041] The support base 310 is typically configured to receive a
cover (not shown) to further support a reticle during processing.
The cover may be configured to operate as the substrate support
assembly 215 described above.
[0042] In the novel pedestal 300 of the present invention, at least
a portion of the body 306 is fabricated from a dielectric material.
In the cutaway view of FIG. 3, the dielectric material portion of
the body 306 is shown at 318. Dielectric material 318 is
selectively used in the upper surface 310 so as to define a
dielectric ring generally about the perimeter of the body 306. The
dielectric material 318 is placed outside of the contact point,
e.g., support ridge 326, for the reticle 222 on the pedestal 300.
The dielectric material portion 318 of the body 306 may comprise
two or more separate components (not shown) joined together to form
the dielectric portion 318 of the body 306. The two or more
dielectric members may be fabricated from materials having
different dielectric properties. The benefit of using material of
different dielectric properties is to control the relative amount
of RF power coupled through the reticle, as the thickness and
dielectric property of the reticle substrate, e.g., quartz, is
fixed.
[0043] The dielectric material portion 318 of the body 306 may be
of different thicknesses. This is demonstrated in the schematic
embodiments shown in FIGS. 4 and 5. FIG. 4 provides a
cross-sectional view of a pedestal 300' of the present invention.
The pedestal 300' is shown schematically. Likewise, FIG. 5 presents
a cross-sectional view of a pedestal 300' of the present invention,
in an alternate embodiment. The pedestal 300" is again shown
schematically. In each view, a reticle 222 is shown being supported
on the respective pedestal 300', 300". Further, in each view a
cover 315 is provided. The cover 315 may be configured in
accordance with the cover 215 shown in the exploded view of FIG. 2.
The cover 315 is preferably fabricated from a dielectric material.
The use of different dielectric material thickness is to adjust or
control the relative RF power coupled to the reticle. One benefit
of using a dielectric material is it enables the use of two control
knobs, that is knobs for dielectric constant and thickness. This,
in turn, enables the operator to change the relative amounts of RF
that goes into the reticle versus the RF power that goes to the
pedestal area surrounding the reticle. The dielectric thickness and
type may be such that the relative amount is the same for uniform
power distribution, or different if needed for compensating for the
etch process.
[0044] Dielectric material is shown at 318 in both FIG. 4 and in
FIG. 5. In FIG. 4, the dielectric material 318 resides along the
top of the upper support base 306. In FIG. 5, the dielectric
material 318 defines substantially the entire thickness of the
upper support base 306. In either instance, the dielectric material
318 is preferably placed outside of the contact point for the
reticle 222 on the pedestal 300.
[0045] As can be seen, the pedestals 300, 300', 300" place
dielectric material along a periphery of the upper substrate
support body 306. The dielectric material 318 may be polymeric or
ceramic. An example of a polymeric material is Ardel.TM.
polyarylate material manufactured by Amoco polymers. Another
example is Vespel.TM. polyimide from DuPont. Still another example
is a plastic material sold under the trade name Ultem.TM.. Yet
another example is a synthetic rubber material. An example of a
suitable ceramic material is aluminum oxide. Another example of an
acceptable dielectric material is quartz. The selected use of
dielectric material 318 has the effect of changing the amount of RF
power coupling into the reticle during a plasma etching procedure.
In this respect, during a plasma etching procedure, the body 306
receives power, such as an RF power. By using dielectric material
on the periphery of the body, the potential drop across the
pedestal is changed to have a value less than the region where the
reticle rests, i.e., inside of the substrate support ridge 326. The
portion of the pedestal 300 within the substrate support ridge 326
remains metallic in order to efficiently conduct waste heat away
from the reticle 222.
[0046] While the foregoing is directed to embodiments of the
present invention, other and further embodiments of the invention
may be devised without departing from the basic scope thereof, and
the scope thereof is determined by the claims that follow.
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