U.S. patent application number 15/685787 was filed with the patent office on 2017-12-07 for inductively coupled plasma source with multiple dielectric windows and window supporting structure.
The applicant listed for this patent is Applied Materials, Inc.. Invention is credited to Ankur Agarwal, Ajit Balakrishna, Douglas A. Buchberger, James D. Carducci, Kenneth S. Collins, Leonid Dorf, Richard Fovell, Jason A. Kenney, Andrew Nguyen, Kartik Ramaswamy, Shahid Rauf.
Application Number | 20170350018 15/685787 |
Document ID | / |
Family ID | 49945556 |
Filed Date | 2017-12-07 |
United States Patent
Application |
20170350018 |
Kind Code |
A1 |
Nguyen; Andrew ; et
al. |
December 7, 2017 |
Inductively Coupled Plasma Source with Multiple Dielectric Windows
and Window Supporting Structure
Abstract
A plasma reactor enclosure has a metallic portion and a
dielectric portion of plural dielectric windows supported on the
metallic portion, each of the dielectric windows extending around
an axis of symmetry. Plural concentric coil antennas are disposed
on an external side of the enclosure, respective ones of the coil
antennas facing respective ones of the dielectric windows.
Inventors: |
Nguyen; Andrew; (San Jose,
CA) ; Collins; Kenneth S.; (San Jose, CA) ;
Ramaswamy; Kartik; (San Jose, CA) ; Rauf; Shahid;
(Pleasanton, CA) ; Carducci; James D.; (Sunnyvale,
CA) ; Buchberger; Douglas A.; (Livermore, CA)
; Agarwal; Ankur; (Fremont, CA) ; Kenney; Jason
A.; (Sunnyvale, CA) ; Dorf; Leonid; (San Jose,
CA) ; Balakrishna; Ajit; (Sunnyvale, CA) ;
Fovell; Richard; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Applied Materials, Inc. |
Santa Clara |
CA |
US |
|
|
Family ID: |
49945556 |
Appl. No.: |
15/685787 |
Filed: |
August 24, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13666280 |
Nov 1, 2012 |
|
|
|
15685787 |
|
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|
|
61673937 |
Jul 20, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
C23C 14/28 20130101;
H01J 37/32834 20130101; H01J 37/321 20130101; H05H 1/46 20130101;
B01J 12/002 20130101; H01J 37/32733 20130101; C23F 1/08 20130101;
H01J 37/3211 20130101 |
International
Class: |
C23F 1/08 20060101
C23F001/08; C23C 14/28 20060101 C23C014/28; B01J 12/00 20060101
B01J012/00; H05H 1/46 20060101 H05H001/46; H01J 37/32 20060101
H01J037/32 |
Claims
1-20. (canceled)
21. A plasma reactor comprising: an enclosure having an axis of
symmetry and a workpiece support within the enclosure, the
workpiece support and the enclosure defining a processing region,
the enclosure including a cylindrical metallic portion, a
cylindrical dielectric window extending around the said axis of
symmetry and supported on the metallic portion, a bottom edge of
the cylindrical dielectric window positioned above the workpiece
support such that a workpiece on the workpiece support is supported
below the bottom edge, a metallic plate having a central opening
and supported on the cylindrical dielectric window, and a
disk-shaped dielectric window supported on the plate and extending
around the said axis of symmetry and overlying the central opening,
a bottom face of the disk-shaped dielectric window positioned above
a top edge of the cylindrical dielectric window, an inner diameter
of cylindrical dielectric window being greater than an outer
diameter of the disk-shaped dielectric window; and a plural
concentric coil antennas disposed on an external side of said
enclosure, the plural concentric coil antennas including a first
coil antenna positioned above and facing the disk-shaped window,
and a second coil antenna surrounding and facing the cylindrical
dielectric window.
22. The plasma reactor of claim 21, wherein the disk-shaped
dielectric window has a circular edge portion supported on an edge
of said central opening.
23. The plasma reactor of claim 21, wherein the metallic plate
provides an annular top gas plate having a peripheral portion
supported on the cylindrical dielectric window.
24. The plasma reactor of claim 23, wherein the top gas plate has
plural gas injection orifices circularly arranged about the
peripheral portion.
25. The plasm reactor of claim 24, further comprising a center gas
disperser in a center of said disk-shaped dielectric window and
disposed to introduce gas into the processing region.
26. The plasma reactor of claim 21, wherein the metallic plate
abuts the top edge of the cylindrical dielectric window.
27. The plasma reactor of claim 21, the metallic plate comprises a
planar bottom surface extending inwardly from the top edge of the
cylindrical dielectric window.
28. The plasma reactor of claim 21, wherein the metallic plate
extends radially outward past the dielectric window.
29. The plasma reactor of claim 28, comprising at least one
insulator extending axially through the metallic plate, and an
axial conductor extending through the insulator and connected to
the second coil antenna to supply RF power to the second coil
antenna.
30. The plasma reactor of claim 21, comprising a third coil
antenna, the third coil antenna disposed over and facing the
disk-shaped dielectric window and concentric and surrounding the
first coil antenna.
31. The plasma reactor of claim 21, further comprising a first
heater layer on the disk-shaped dielectric window.
32. The plasma reactor of claim 31, further comprising a second
heater layer on the cylindrical dielectric window.
33. The plasma reactor of claim 21, wherein the workpiece support
comprises a pedestal and a post to hold the pedestal above a bottom
of the processing region.
34. The plasma reactor of claim 33, wherein the cylindrical
metallic portion extends to the bottom of the processing region.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. application
Serial No. 13/666,280, filed Nov. 1, 2012, which claims the benefit
of U.S. Provisional Application Serial No. 61/673,937, filed Jul.
20, 2012, the disclosures of which are incorporated by
reference.
BACKGROUND
Field
[0002] Embodiments of the present invention are generally concerned
with a plasma processing reactor chamber for processing workpieces,
in which plasma is generated by inductive coupling of RF power to
process gases inside the chamber.
Description of the Related Art
[0003] Electronic devices such as integrated circuits, flat panel
displays and the like, are fabricated by a series of processes, in
which thin film layers are deposited on substrates and etched into
desired patterns. The process steps may include plasma-enhanced
reactive ion etching (RIE), plasma-enhanced chemical vapor
deposition (CVD), plasma-enhanced physical vapor deposition
(PVD).
[0004] Uniform distribution of etch rate or deposition rate across
the entire surface of the substrate is essential for successful
fabrication. Such uniformity is becoming more difficult to achieve,
as substrate size is increasing and device geometry is shrinking.
In particular, inductively coupled plasma sources can have two
concentrically arranged coil antennas over the chamber ceiling, so
that uniformity of etch rate distribution can be optimized by
adjusting the different RF power levels delivered to the different
coil antennas. As workpiece diameter and chamber diameter increase,
we have found this approach is not adequate, as the larger size
increases the difficultly of attaining the requisite process
uniformity. Various sources of process non-uniformity, such as
chamber design asymmetries, temperature distribution
non-uniformities and gas distribution control become more
important.
SUMMARY
[0005] A plasma reactor includes an enclosure having an axis of
symmetry and a workpiece support within the enclosure, the
workpiece support and the enclosure defining a processing region.
The enclosure includes a metallic portion and a dielectric portion
including plural dielectric windows supported on the metallic
portion, each of the dielectric windows extending around the axis
of symmetry, the enclosure having a diameter greater than the
diameter of at least one of the dielectric windows. Plural
concentric coil antennas are disposed on an external side of the
enclosure, respective ones of the coil antennas facing respective
ones of the dielectric windows. Respective RF power sources are
coupled to respective ones of the coil antennas.
[0006] In one embodiment, a first one of the dielectric windows
includes a disk-shaped dielectric window, the enclosure having a
diameter greater than the diameter of the disk-shaped dielectric
window. A second one of the dielectric windows is a cylindrical
dielectric window. The cylindrical dielectric window is below a
plane of the disk-shaped dielectric window.
[0007] In an embodiment, the metallic portion includes: (a) a
cylindrical chamber body wall surrounding the cylindrical
dielectric window, and (b) an annular top gas plate including a
peripheral portion supported on the chamber body wall, and a
central opening through the annular top gas plate, wherein the
disk-shaped dielectric window includes a circular edge portion
supported on an edge of the central opening.
[0008] The disk-shaped dielectric window has a diameter less than
the diameter of the chamber body wall. A gap separates the chamber
body wall from the disk-shaped dielectric window, the peripheral
portion of the top gas plate spanning the gap and the disk-shaped
dielectric window is suspended over the central opening of the top
gas plate.
[0009] In an embodiment, first and second ones of the coil antennas
are concentrically disposed over the disk-shaped dielectric window,
and a third one of the coil antennas has a diameter exceeding a
diameter of the cylindrical dielectric window and surrounds the
cylindrical dielectric window.
[0010] The plasma reactor may further include a center gas
disperser in a center of the disk-shaped dielectric ceiling and
disposed to spray gas into the processing region, and the top gas
plate may include: (a) plural gas injection orifices circularly
arranged about the peripheral portion, (b) plural gas supply ports,
and (c) a first hierarchy of equal length recursive gas flow paths
from a first one of the gas supply ports to the plural gas
injection orifices.
[0011] The center gas disperser may include a pair of opposing
input ports, the reactor further including at least a pair of
opposing gas flow conduits extending radially across the
disk-shaped dielectric window to the opposing input ports of the
center gas disperser. And, the top gas plate further includes a
second hierarchy of equal length recursive gas flow paths from a
second one of the gas supply ports to the pair of gas flow
conduits.
[0012] The plasma reactor may further include a first heater layer
on the disk-shaped dielectric window and including a radially outer
portion and plural fingers extending radially inwardly from the
radially outer portion. In an embodiment, the pair of opposing gas
flow conduits is enclosed in respective ones of the plural fingers
of first heater layer. The plasma reactor may further include a
second heater layer on the cylindrical dielectric window, the
second heater layer including a grid of axial fingers.
[0013] In an embodiment, the plasma reactor further includes: (a) a
cylindrical shield coaxial with the axis of symmetry and located
between the first and second coil antennas and facing an inner
radial portion of the disk-shaped dielectric window, (b) a top fan
plenum in a central air flow path including having an axial path
passing through an interior of the cylindrical shield and a radial
path extending across a surface of the disk-shaped dielectric
window, and (c) plural intake fans coupled to the top fan plenum.
In one embodiment, an annular air flow plate overlies the
disk-shaped dielectric window and has a center air flow aperture
open to the interior of the cylindrical shield and forming a top
boundary of the radial path of the central air flow path. The
annular air flow plate confines the radial path to regions between
the plural fingers of the first heater layer.
[0014] In an embodiment, a side air flow passage is defined between
the cylindrical dielectric window and cylindrical chamber body side
wall, and the plasma reactor further includes: (a) a side fan
plenum at an axial location between the top fan plenum and the
cylindrical dielectric window, the side fan plenum open to the side
air flow passage and including plural side fan plenum openings, and
(b) plural exhaust fans at the plural side fan plenum openings.
[0015] An embodiment further includes: (a) an RF power feed
assembly coupled to the plural coil antennas and including plural
conductive legs, (b) a ground plate extending radially and having
openings through which respective ones of the legs extend, the
ground plate providing a boundary between an upper region in which
at least some of the plural conductive legs are distributed
asymmetrically and a lower region in which the respective ones the
legs are distributed symmetrically with respect to the axis of
symmetry. and (c) wherein the ground plate includes a circular
center aperture aligned with the axial path of the central air flow
path.
[0016] A first temperature sensor may be provided at the
disk-shaped dielectric window and a second temperature sensor may
be provided at the cylindrical dielectric window, with a controller
coupled to the first and second temperature sensors, the controller
being coupled to govern levels of power delivered respectively to
the first heater layer, the second heater layer, the plural intake
fans, the plural exhaust fans, and to respective ones of the coil
antennas. In an embodiment, the controller is programmed to control
the power levels delivered to the first heater layer and the plural
intake fans in response to an output of the first temperature
sensor. The controller is further programmed to control the power
levels delivered to the second heater layer and the plural exhaust
fans in response to an output of the second temperature sensor.
[0017] In one embodiment, the plasma reactor further includes an
exhaust chamber assembly, the exhaust chamber assembly including:
(a) an exhaust chamber wall defining an evacuation region at a side
of the workpiece support opposite the processing region, the
exhaust chamber assembly having an exhaust pump port symmetrically
located relative to the axis of symmetry, and (b) plural axial
exhaust passages between the processing region and the evacuation
region, and symmetrically distributed with respect to the axis of
symmetry.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] So that the manner in which the exemplary embodiments of the
present invention are attained can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to the embodiments thereof which are
illustrated in the appended drawings. It is to be appreciated that
certain well known processes are not discussed herein in order to
not obscure the invention.
[0019] FIG. 1 is a cut-away view of a plasma reactor of an
embodiment the invention.
[0020] FIG. 1A is an enlarged view of an upper section of the
reactor of FIG. 1.
[0021] FIG. 1B is an enlarged view of a lower section of the
reactor of FIG. 1.
[0022] FIG. 2 illustrates an inner zone inductive RF power
applicator of the reactor of FIG. 1.
[0023] FIG. 3 illustrates an intermediate or middle zone inductive
RF power applicator of the reactor of FIG. 1.
[0024] FIG. 4 illustrates an outer zone inductive RF power
applicator of the reactor of FIG. 1.
[0025] FIG. 5 illustrates a conductive RF power feeder for the RF
power applicator of FIG. 3.
[0026] FIG. 6 illustrates a conductive RF power feeder for the RF
power applicator of FIG. 4.
[0027] FIG. 7 is a cut-away cross-sectional view of a portion of a
lid assembly of the reactor of FIG. 1.
[0028] FIG. 8 is a plan view of a heater layer covering a
disk-shaped dielectric window of the lid assembly of FIG. 7.
[0029] FIG. 9 is an orthographic projection of a heater layer
covering a cylindrical dielectric window depicted with the lid
assembly of FIG. 7.
[0030] FIG. 10 is a plan view of the lid assembly of FIG. 7.
[0031] FIG. 11A is a plan view corresponding to FIG. 10 depicting
gas flow passages in a gas flow plate of the lid assembly.
[0032] FIG. 11B is a view of an opposite side of the gas flow plate
of FIGS. 7 and 11A.
[0033] FIG. 12 is a plan view corresponding to FIG. 10 and
depicting gas flow paths to a center hub.
[0034] FIG. 12A is an orthographic projection corresponding to a
portion of FIG. 12 depicting encasement of a gas flow conduit in a
portion of the heater layer of FIG. 8.
[0035] FIG. 12B is a cut-away elevational view corresponding to
FIG. 12A.
[0036] FIG. 13 is an enlarged cut-away view of a center gas
disperser of the reactor of FIG. 1.
[0037] FIG. 14 is a plan view of the center gas disperser of FIG.
13.
[0038] FIG. 15 is a cross-sectional view taken along lines 15-15 of
FIG. 14.
[0039] FIG. 16 is a cross-sectional view taken along lines 16-16 of
FIG. 14.
[0040] FIG. 17 is a cross-sectional view taken along lines 17-17 of
FIG. 1B.
[0041] FIG. 18 is a cross-sectional view taken along lines 18-18 of
FIG. 1B.
[0042] FIG. 19 is a view corresponding to FIG. 1A and depicting
cooling air flow paths.
[0043] FIGS. 20A and 20B are block diagrams of alternative
embodiments of RF power sources for the RF power applicators of
FIG. 1A.
[0044] FIG. 21 is a block diagram of a control system controlling
the reactor of FIG. 1.
[0045] To facilitate understanding, identical reference numerals
have been used, where possible, to designate identical elements
that are common to the figures. It is contemplated that elements
and features of one embodiment may be beneficially incorporated in
other embodiments without further recitation. It is to be noted,
however, that the appended drawings illustrate only exemplary
embodiments of this invention and are therefore not to be
considered limiting of its scope, for the invention may admit to
other equally effective embodiments.
DETAILED DESCRIPTION
[0046] A plasma reactor 10 depicted in FIG. 1 includes an upper
portion 20 depicted in the enlarged view of FIG. 1A and a lower
portion 30 depicted in the enlarged view of FIG. 1B. Referring to
FIGS. 1, 1A and 1B, the plasma reactor 10 includes a plasma
processing chamber 100 having a side wall 105 and a lid assembly
110. The side wall 105 has an axially symmetrical shape, such as a
cylinder. The side wall 105 includes an axially symmetrical (e.g.,
cylindrical) dielectric side window 106 and a chamber liner 107,
which may be formed of metal. A workpiece support 115 inside the
chamber 100 includes a pedestal 120 having a workpiece support
surface 121 facing the lid assembly 110 for holding a workpiece
122, and a post 125 supporting the pedestal 120. A processing
region 101 of the chamber 100 is confined by the lid assembly 110,
the pedestal 120 and the side wall 105. The pedestal 120 may
include an insulated internal electrode 130. Optionally, an
electrostatic chucking (ESC) voltage and/or RF plasma bias power
may be supplied to the internal electrode 130 via a cable 132
extending through the post 125. The cable 132 may be coupled to an
RF bias power source (such as an RF impedance match network and/or
an RF power generator) as an RF bias feed to the electrode 130. The
cable 132 may be provided as a coaxial transmission line, which may
be rigid (or flexible), or as a flexible coaxial cable.
[0047] Plasma source power is inductively coupled into the
processing region 101 by a set of coil antennas, including an inner
coil antenna 140, a middle coil antenna 150 and an outer or side
coil antenna 160, all of which are concentrically disposed with
respect to each other and are coaxial with the axis of symmetry of
the side wall 105. The lid assembly 110 includes a disk-shaped
dielectric window 112 through which the inner and middle coil
antennas 140 and 150 inductively couple RF plasma source power into
the processing region 101. The disk-shaped dielectric window 112 is
coaxial with the side wall 105 and has a disk-plane parallel with
the plane of the workpiece support surface 121. The side coil
antenna 160 inductively couples RF plasma source power into the
processing region 101 through the cylindrical dielectric side
window 106.
[0048] Referring to FIGS. 1A and 2, in one embodiment, the inner
coil antenna 140 includes four wire conductors 140-1 through 140-4,
each one helically wound about a constant radius along an arc
length of 180 degrees, their ends being staggered (i.e., offset
along a circumferential direction) at uniformly spaced 90 degree
intervals, as depicted in FIG. 2. Uniform and symmetrical
distribution of RF power to the wire conductors 140-1 through 140-4
is provided by an RF current distributor in the form of an inverted
metal bowl 142 having a circular bottom edge 144 contacting the top
ends of each of the wire conductors 140-1 through 140-4, and a lid
146 connected to an inner RF feed rod 148. The bottom ends of the
four wire conductors 140-1 through 140-4 are grounded by connection
to an inner ground shield 149 (FIG. 1A) in the form of a
cylindrical metal sleeve coaxial with the coil antenna 140 and
lying between the inner and middle coil antennas 140 and 150. The
inner ground shield 149 provides a uniform and symmetrical
distribution of ground current from the four wire conductors 140-1
through 140-4, and further provides RF shielding or isolation
between the inner and middle coil antennas 140 and 150, by
suppressing mutual inductance between them. This enhances
independent control of the inner and middle coil antennas 140,
150.
[0049] Referring to FIGS. 1A and 3, in one embodiment, the middle
coil antenna 150 includes four wire conductors 150-1 through 150-4,
each one helically wound about a constant radius along an arc
length of 180 degrees, their ends being staggered at uniformly
spaced 90 degree intervals, as depicted in FIG. 3. Uniform and
symmetrical distribution of RF power to the wire conductors 150-1
through 150-4 is provided by an RF current distributor in the form
of a cylindrical metal sleeve 152 having a circular bottom edge 154
contacting the top ends of each of the wire conductors 150-1
through 150-4, and a circular top edge 156 connected to a circular
array of four axial RF feed rods 158. RF power is fed to the RF
feed rods 158 by a conductor structure depicted in FIG. 5, which is
described later in this specification.
[0050] Referring again to FIG. 1A, the bottom ends of the four wire
conductors 150-1 through 150-4 are grounded by connection to a
middle ground shield 159. The middle ground shield 159 may be in
the form of a cylinder. However, in one embodiment depicted in
dashed line in FIG. 1A, the top of the middle ground shield 159 is
a metal ring 159-1 coaxial with the coil antenna 150. Four
conductive legs 159a through 159d (of which only the legs 159a and
159c can be seen in the view of FIG. 1A) extend axially downward
from the ring 159-1 and have bottom ends contacting the bottom ends
of the four conductors 150-1 through 150-4. The middle ground
shield 159 provides a uniform and symmetrical distribution of
ground current from the four wire conductors 150-1 through
150-4.
[0051] Referring to FIGS. 1A and 4, the side coil antenna 160 is
disposed below the plane of the disk shaped dielectric window 112
and surrounds the cylindrical dielectric side window 106. In one
embodiment, the side coil antenna 160 includes eight wire
conductors 160-1 through 160-8, each one helically wound about a
constant radius along an arc length of 90 degrees, their ends being
staggered at uniformly spaced 45 degree intervals, as depicted in
FIG. 4. Uniform and symmetrical distribution of RF power to the
wire conductors 160-1 through 160-8 is provided by an RF current
distributor in the form of an inverted metal bowl 162 (FIG. 1A)
having a circular bottom edge 164 attached to respective axial
conductors 161-1 through 161-8 (of which only the axial conductors
161-1 and 161-5 are visible in the view of FIG. 1A) contacting the
top ends of the wire conductors 160-1 through 160-8 respectively.
The inverted metal bowl 162 further has a circular top edge 166
connected to a circular array of eight uniformly spaced axial RF
feed rods 168. A cylindrical outer chamber wall 170 surrounds the
side coil antenna 160 and is grounded. The bottom ends of the eight
wire conductors 160-1 through 160-8 are grounded by connection to
the outer chamber wall 170. While the described embodiments include
direct connection to ground of the coil antennas 140, 150 and 160
by the ground shields 149 and 159 and the outer chamber wall 170,
respectively, the connection to ground may not need to be a direct
connection, and instead the connection to ground may be through
elements such as capacitors, for example.
[0052] Referring to FIG. 5, the four axial RF feed rods 158
associated with the middle coil antenna 150 extend to four radial
RF feed rods 172 connected to a common axial feed rod 174.
Referring to FIG. 6, the eight axial RF feed rods 168 associated
with the side coil antenna 160 extend to eight radial RF feed rods
176 connected to a common axial feed rod 178. The axial RF feed rod
148, the common axial feed rod 174 and the common axial feed rod
178 couple RF power to the respective coil antennas 140, 150 and
160. The power may be supplied from a common RF source or from
different RF sources such as RF matches (RF impedance match
networks) 180 and 182. As will be described below with reference to
FIG. 20B, an RF impedance match network may be employed having dual
outputs in order to drive two of the coil antennas with a first RF
generator, while a second RF generator and a second RF impedance
match network drives the third coil antenna. Alternatively, as will
be described below with reference to FIG. 20A, three RF generators
may separately drive the three coil antennas through three
respective RF impedance match networks. In yet another embodiment,
a single RF power generator may drive all three coil antennas
through an RF impedance matching network having three outputs. In
some implementations of the foregoing embodiments, the RF power
levels applied to the different coil antennas may be separately
adjusted in order to control radial distribution of plasma ion
density. While described embodiments include the three coil
antennas 140, 150 and 160, other embodiments may include only one
or two of the three described coil antennas 140, 150 and 160.
[0053] Only the axial RF feed rod 148 is symmetrically located at
the axis of symmetry of the side wall 105, while the axial feed
rods 174 and 178 are located off-center, as depicted in FIGS. 1A, 5
and 6. This feature is asymmetrical. The axial RF feed rods 148,
158 and 168 are arrayed symmetrically relative to the axis of
symmetry of the side wall 105. A generally disk-shaped conductive
ground plate 184 generally parallel with the workpiece support
surface 121 contains openings through which the axial RF feed rods
148, 158 and 168 extend. The ground plate 184 provides separation
between an upper region containing the non-symmetrically arranged
axial feed rods 174 and 178 (and an upper portion of the RF feed
rod 148 which is symmetrically located), and a lower region
containing only symmetrical features such as the axial RF feed rods
148, 158 and 168. The RF feed rods 148, 158 and 168 are
electrically insulated from the ground plate 184. The ground plate
184 electromagnetically shields the processing region 101 from the
effects of the asymmetric features above the ground plate 184, and
also prevents skew effects in plasma processing of the workpiece
122.
[0054] Referring to FIGS. 1 and 7, the disk-shaped dielectric
window 112 has a diameter less than the diameter of the outer
chamber wall 170. The window 112 is supported at its periphery by
an annular top gas plate 200 (described later in this
specification) that spans the gap between the outer chamber wall
170 and the window 112, while maintaining the space below the
window 112 free of structure that would otherwise inhibit inductive
coupling of RF power into the processing region 101. The chamber
diameter is therefore not limited by the diameter of the
disk-shaped dielectric window 112. The inner and middle coil
antennas 140 and 150 (coextensive with the disk-shaped dielectric
window 112) may control plasma ion density distribution within an
intermediate zone of a diameter smaller than that of the workpiece
or wafer 122. Plasma density in an outer zone is governed by the
side coil antenna 160 through the cylindrical dielectric window
106. This affords control of plasma ion density distribution across
the entire wafer without requiring a concomitant increase in
diameter of the disk-shaped dielectric window 112.
[0055] As referred to above, the annular top gas plate 200 supports
the disk-shaped dielectric window 112 and spans the gap or distance
between the outer chamber wall 170 and the periphery of the
disk-shaped dielectric window 112. The top gas plate 200 includes
an annulus 202 surrounding an opening 204. A top inner edge 202a of
the annulus 202 underlies and supports an outer edge 112a of the
dielectric window 112 and surrounds the opening 204. A bottom outer
edge 202b of the annulus 202 rests on the outer chamber wall 170.
The opening 204 faces the disk-shaped dielectric window 112. The
axial conductors 161-1 through 161-8 (of the outer coil antenna
160) extend through respective insulators 171 in the top gas plate
200.
[0056] The disk-shaped dielectric window 112 and the cylindrical
dielectric side window 106 are heated and have their respective
temperatures controlled independently of one another. They are
heated and cooled independently, by cooling from a fan system
described later in this specification and by independent heater
elements now described. A flat heater layer 220 depicted in FIGS.
1A, 7 and 8 overlies the disk-shaped dielectric window 112. The
heater layer 220 is in the form of a disk-shaped Faraday shield,
having an outer annulus 222 and plural radial fingers 224 extending
radially inwardly from the outer annulus 222, the radial fingers
224 being separated from one another by evenly spaced apertures
226. The spacing of the radial fingers 224 (defining the width of
the apertures 226) is sufficient to permit inductive coupling of RF
power through the heater layer 220. The heater layer 220 is
symmetrical with respect to the axis of the side wall 105. In the
illustrated example, there are 24 radial fingers 224, although any
suitable number of fingers may be employed. The heater layer 220 is
heated electrically by an internal electrically resistive element
229 (FIG. 7) within the heater layer 220.
[0057] A cylindrical Faraday shield layer 230 depicted in FIGS. 1A
and 9 is disposed between the cylindrical dielectric window 106 and
the outer coil antenna 160, and surrounds the cylindrical
dielectric side window 106. The cylindrical Faraday shield layer
230 has upper and lower cylindrical rings 232, 234, and plural
axial legs 236 extending axially between the upper and lower
cylindrical rings 232, 234 and being separated by evenly spaced
gaps 238. The cylindrical Faraday shield layer 230 may be heated
electrically by an internal element (such as a heater layer 231
shown in FIGS. 1A and 7 within or contacting with the Faraday
shield layer 230.
[0058] Process gas is injected into the processing region 101 by a
central dual-zone ceiling gas injector 300 (FIG. 1A) and a circular
array of peripheral (side) gas injectors 310 (FIG. 7). The ceiling
gas injector 300 is located at the center of the disk-shaped
dielectric window 112. The peripheral gas injectors 310 are
supported on the top gas plate 200 near the side wall 106.
[0059] Referring to FIGS. 7, 10 and 11A, the lid assembly 110
includes an annular gas flow plate 320. The heater layer or Faraday
shield 220 is held on the gas flow plate 320 by a spring plate 322
as shown in FIG. 7. The gas flow plate 320 has three gas input
ports 321a, 321b, 321c (FIG. 10). The gas flow plate 320 provides
recursive gas flow paths from the input port 321a to a first zone
of the dual zone ceiling gas injector 300, recursive gas flow paths
from the input port 321b to the other zone of the dual zone gas
injector 300, and recursive gas flow paths from the gas input port
321c to the side gas injectors 310. The side gas injectors 310 are
fed through respective gas ports 312 in the bottom surface of the
gas flow plate 320 visible in the bottom view of FIG. 11B. The
recursive gas flow paths provide uniformly distributed gas flow
path lengths to different gas injection zones. Uniformity control
of the gas distribution can also be enhanced by the recursive gas
flow paths.
[0060] Referring to FIG. 11A, a first set or hierarchy of recursive
gas flow paths 330 in the gas flow plate 320 feeds gas to the side
gas injectors 310 through the gas ports 312. The first set of
recursive gas flow paths 330 includes a half-circular gas flow path
or channel 331. The gas injection port 321c is coupled to the
midpoint of the half-circular gas flow channel 331. The gas flow
path 331 extends around half a circle and feeds at its ends the
midpoints of a pair of arcuate gas flow paths 332 each extending a
quarter circle, which in turn feed at their respective ends the
midpoints of four arcuate gas flow paths 334 each extending around
an eighth circle. The four arcuate gas flow paths 334 feed at their
ends the midpoints of eight arcuate gas flow paths 336 each
extending around a sixteenth of a circle. The ends of the gas flow
paths 336 feed the gas ports 312 for gas flow to the side gas
injectors 310.
[0061] Referring to FIG. 12, gas flow to one zone of the dual zone
gas injector 300 is carried in a pair of opposing radial gas flow
lines 340, 342 overlying the disk-shaped dielectric window 112. Gas
flow to the other zone of the dual zone gas injector 300 is carried
in a second pair of opposing radial gas flow lines 344, 346
overlying the disk-shaped dielectric window 112 and disposed at
right angles to the first pair of radial gas flow lines 340, 342.
Connection from the four radial gas flow lines 340, 342, 344, 346
to the dual zone gas injector 300 is provided by a gas flow hub 350
axially coupled to the dual zone gas injector 300.
[0062] Referring again to FIG. 11A, a half-circular gas flow
channel 353 provides uniform distribution of gas flow from the gas
input port 321b to the outer ends of the first pair of radial gas
flow lines 340, 342. A quarter-circular gas flow channel 357
provides gas flow from the input port 321b to the midpoint of the
half-circular gas flow channel 354. A half-circular gas flow
channel 355 provides uniform gas flow from the gas input port 321a
to the outer ends of the second pair of radial gas flow lines 344,
346.
[0063] As depicted in FIGS. 12, 12A and 12B, each of the four
radial gas flow lines 340, 342, 344, 346 overlying the disk-shaped
dielectric window 112 may be enclosed in a respective one of the
radial fingers 224 of the heater layer 220.
[0064] As previously described with reference to FIGS. 1 and 12,
the gas flow hub 350 provides coupling between the four radial gas
flow lines 340, 342, 344, 346 and the dual zone gas injector 300.
One example of the dual zone gas injector 300 is depicted in FIG.
13. The dual zone gas injector 300 of FIG. 13 includes a center gas
disperser 302 having an axial inner annular channel 302-1 extending
axially and dispersing gas to a radially inner zone A, and a middle
gas disperser 304 having a slanted middle annular channel 304-1
dispersing gas to a radially outer zone B. The gas flow hub 350 is
now described with reference to FIGS. 13, 14, 15 and 16. The hub
350 has four gas inlet ports 352, 354, 356 and 358 oriented at
right angles to one another and connectable to the four radial gas
flow lines 340, 342, 344, 346 as indicated in dashed line. The gas
inlet ports 352 and 354 feed respective pairs of split gas
distribution lines 360, 362, respectively, that terminate at four
equally spaced points along a circular inner distribution channel
366 that is in registration with the axial inner annular channel
302-1 of the dual zone gas injector 300. The gas inlet ports 356
and 358 feed respective pairs of split gas distribution lines 370,
372, respectively, that terminate at four equally spaced points
along a circular middle distribution channel 374 that is in
registration with the axial middle annular channel 304-1 of the
dual zone gas injector 300.
[0065] Referring again to the bottom view of FIG. 11B, in one
embodiment, optional cooling passages 390 may be provided in the
gas flow plate 320, in the form of a circular supply passage 390a
and a circular return passage 390b forming a continuous path.
External coolant ports 392a and 392b provided connection of the
supply and return passages 390a, 390b to an external coolant source
(not illustrated in FIG. 11B). Optionally, internal coolant
passages may be provided in the outer chamber body wall 170 and fed
through a coolant input port.
[0066] Referring to FIGS. 1 and 1B, the chamber liner 107 is
enclosed within a lower chamber body 400 including a cylindrical
lower chamber body side wall 405 and a lower chamber body floor
410. The lower chamber body side wall 405 and the lower chamber
body floor 410 enclose an evacuation region 411. The chamber liner
107 includes an upper cylindrical section 107-1 and a lower annular
grid 107-2 in the form of an inverted truncated cone. A vacuum pump
440 is disposed in a vacuum pump opening 410a in the floor 410 and
is centered relative to the axis of symmetry of the side wall 105.
A containment wall 415 coaxial with the workpiece support 115 and a
flexible bellows 417 extending between the pedestal 120 and the
containment wall 415 enclose the workpiece support 115 in an
internal central space 419. The central space 419 is isolated from
the volume evacuated by the vacuum pump 440, including the
evacuation region 411 and the processing region 101. Referring to
FIGS. 1B, 17, 18 and 19, there are three hollow radial struts 420
defining radial access passages 421 spaced at 120 degree intervals
extending through the chamber body side wall 405 and providing
access to the central space 419. Three axial exhaust passages 430
are defined between the three radial struts 420. Different
utilities may be provided through different ones of the radial
access passages 421, including the RF power cable 132 connected to
the electrode 130, heater voltage supply lines connected to heater
elements in the workpiece support 115, an electrostatic chucking
voltage supply line connected to the electrode 130, coolant supply
lines and helium supply lines for backside helium gas channels in
the workpiece support surface 121, for example. A workpiece support
lift actuator 450 is fixed with respect to the chamber body and
moves the workpiece support 115 axially. The workpiece support lift
actuator 450 may be used to vary the distance between the workpiece
122 and the lid assembly 110. Varying this distance varies the
distribution of plasma ion density. Movement of the lift actuator
may be used to improve uniformity of distribution of process (e.g.,
etch) rate across the surface of the workpiece 122. The lift
actuator 450 may be controlled by the user through a programmable
controller, for example.
[0067] The axially centered exhaust assembly including the vacuum
pump opening 410a and the axial exhaust passages 430 avoids
asymmetries or skew in processing distribution across the workpiece
122. The annular grid 107-2 masks the processing region 101 from
the discontinuities or effects of the radial struts 420. The
combination of the axially centered exhaust assembly with the
symmetrical distribution of RF current flow below the ground plate
184 minimize skew effects throughout the processing region 101 and
enhance process uniformity in the processing region 101.
[0068] FIG. 19 depicts cooling air flow through the upper section
20 of FIG. 1A. Referring to FIGS. 1A and 19, a chamber body side
wall 406 surrounds the lid assembly 110. A lower plenum wall 500 in
the form of a truncated cone, for example, is mounted between the
top edge of the chamber body side wall 406 and the peripheral edge
of the ground plate 184, to enclose a lower plenum 502. A circular
array of exhaust fans 504 are mounted in respective openings 506 in
the lower plenum wall 500.
[0069] The ground plate 184 has a center opening 600 that is
co-extensive with the inner ground shield 149. A cylindrical plenum
center wall 606 is coextensive with the center opening 600. A
plenum plate 610 overlies the plenum center wall 606. A return
chamber 612 is enclosed between a return chamber side wall 608, the
plenum plate 610, the ground plate 184 and the center wall 606. The
return chamber side wall 608 includes air flow screen sections 609.
Openings 614 through the ground plate 184 permit air flow between
the lower plenum 502 and the return chamber 612.
[0070] An upper plenum 650 is enclosed between a top plate 655 and
the plenum plate 610 by an upper plenum side wall 660 in the form
of a truncated cone. Plural intake fans 665 are mounted at
respective openings 667 in the upper plenum side wall 660.
[0071] The intake fans 665 draw air into the upper plenum 650 which
flows down through the central opening formed by the center wall
606, the ground plate opening 600 and the middle grounded shield
149. An annular air flow plate 670 overlying the disk-shaped
dielectric window 112 confines the air flow between the plate 670
and the window 112. This air may flow through the apertures 226 of
the Faraday shield 220 of FIG. 8, for example. Alternatively (or in
addition), the air may be confined in a gap 671 between the air
flow plate 670 and the window 112. Downward air flow through the
cylindrical shield 149 enters the space within the aperture 226
through a central opening of the plate 670 and flows radially
outwardly over the disk-shaped dielectric window 112 and enters the
lower plenum 502. From the lower plenum 502, the air escapes into
the return chamber 612, from which it may exit through the screen
sections 609 of the return chamber side wall 608. Thus, the intake
fans 665 provide cooling for the disk-shaped dielectric window
112.
[0072] The exhaust fans 504 provide cooling for the cylindrical
dielectric window 106. The exhaust fans 504 draw air through intake
ports 680 in the lower chamber side wall 170 and past the
cylindrical dielectric window 106. By operating the intake fans 665
independently from the exhaust fans 504, the different heat loads
on the different dielectric windows 106 and 112 may be compensated
independently, for accurate temperature control of each window.
[0073] FIG. 20A depicts one embodiment of an RF source for the
three coil antennas 140, 150, 160, the RF source having independent
RF generators 740-1, 740-2, 740-3, and RF impedance matching
networks 742-1, 742-1, 742-3 for the respective coil antennas 140,
150, 160. FIG. 20B depicts an embodiment in which the inner and
middle coil antennas 140, 150 are driven from a single RF generator
750-1 through an RF impedance matching network 180 having dual
outputs. The dual output RF impedance matching network 180 may
facilitate differential control of the power levels applied to the
inner and middle coil antennas 140, 150. The outer coil antenna 160
is driven by an RF generator 750-2 through an RF impedance matching
network 182. The dual output RF impedance matching network 180
functions as two separate RF power sources, so that there are a
total of three RF power sources in the system. In each of the
foregoing embodiments, the RF impedance match networks may be
disposed on the top plate 655 as depicted in FIG. 1A.
[0074] FIG. 21 depicts a control system for controlling the plasma
reactor of FIG. 1. The control system is responsive to temperature
sensors at different locations within the plasma reactor, such as a
temperature sensor 106' at or in the cylindrical dielectric window
106, and a temperature sensor 112' at or in the disk-shaped
dielectric window 112. The control system includes a programmable
controller 800 which may be implemented as a microprocessor, for
example. The controller 800 has an input 802 for receiving the
output of the temperature sensor 106' and an input 804 for
receiving the output of the temperature sensor 112'. The controller
800 has independent command outputs, including an output 806
governing the speed of the intake fans 665, an output 808 governing
the speed of the exhaust fans 504, an output 810 governing the flow
rate of coolant to the coolant port 392a in the gas flow plate 320,
an output 812 governing the power level to the electric heater 229
near the dielectric window 112, and an output 814 governing the
power level to the electric heater 231 at the cylindrical
dielectric window 106.
[0075] The controller 800 in one embodiment is programmed to govern
the outputs 808-814 in response to the inputs 802, 804 to maintain
the windows 106, 112 at respective target temperatures that may be
furnished by a user to controller inputs 816 and 818. The
controller 800 may be programmed to operate in the manner of a
feedback control loop to minimize the difference between the user
input 816 and the sensor input 802, and to minimize the difference
between the user input 818 and the sensor input 804.
[0076] As described above, some of the advantageous effects of
various ones of the foregoing embodiments include symmetrical
distribution of RF power to the coil antennas for enhanced plasma
distribution symmetry. Shielding of the coils from asymmetrical RF
current feed structures reduces skew effects in plasma
distribution. Shielding of the coil antennas from one another
enhances independent control of the coil antennas, for superior
control of plasma density distribution. Symmetrical chamber exhaust
in combination with the symmetrical coil antennas provides a high
density plasma source with symmetrical plasma distribution.
Separate dielectric windows for different RF coils enables
independent thermal control of the different dielectric windows.
Separately supporting the different dielectric windows at or over
the processing region enables the chamber diameter to be increased
beyond the diameter of each individual dielectric window,
facilitating a large increase in chamber diameter. The moveable
workpiece support electrode in combination with symmetrical coil
antenna(s) allows superior control over center-to-edge plasma
density distribution with a minimized asymmetrical non-uniformity
component. The moveable workpiece support electrode in combination
with symmetrical coil antenna(s) and in further combination with
the symmetrical chamber exhaust allows even better control over
center-to-edge plasma density distribution with minimized
asymmetrical non-uniform component.
[0077] 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.
* * * * *