U.S. patent application number 14/867240 was filed with the patent office on 2017-03-30 for plasma reactor for processing a workpiece with an array of plasma point sources.
The applicant listed for this patent is APPLIED MATERIALS, INC.. Invention is credited to Praburam Gopalraja, Steven Lane, Srinivas D. Nemani, Kartik Ramaswamy, Lawrence Wong, Yang Yang.
Application Number | 20170092470 14/867240 |
Document ID | / |
Family ID | 58409895 |
Filed Date | 2017-03-30 |
United States Patent
Application |
20170092470 |
Kind Code |
A1 |
Ramaswamy; Kartik ; et
al. |
March 30, 2017 |
PLASMA REACTOR FOR PROCESSING A WORKPIECE WITH AN ARRAY OF PLASMA
POINT SOURCES
Abstract
A plasma source consisting of an array of plasma point sources
that controls generation of charged particles and radicals
spatially and temporally over a user defined region.
Inventors: |
Ramaswamy; Kartik; (San
Jose, CA) ; Wong; Lawrence; (San Jose, CA) ;
Lane; Steven; (Porterville, CA) ; Yang; Yang;
(Los Gatos, CA) ; Nemani; Srinivas D.; (Sunnyvale,
CA) ; Gopalraja; Praburam; (San Jose, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
APPLIED MATERIALS, INC. |
Santa Clara |
CA |
US |
|
|
Family ID: |
58409895 |
Appl. No.: |
14/867240 |
Filed: |
September 28, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01J 37/32422 20130101;
H01J 37/3211 20130101; H01J 37/32449 20130101; H01J 37/32357
20130101; H01J 37/3244 20130101; H01J 2237/3323 20130101; H01J
37/32091 20130101; H01J 2237/334 20130101; H01J 37/32568 20130101;
H01H 1/46 20130101 |
International
Class: |
H01J 37/32 20060101
H01J037/32 |
Claims
1. A plasma reactor comprising: a processing chamber and a
workpiece support in said processing chamber, said chamber
comprising a lower ceiling facing said workpiece support; an upper
ceiling overlying and facing said lower ceiling and a gas
distributor overlying said upper ceiling; plural cavity walls
defining plural cavities between said upper and lower ceilings,
said gas distributor comprising plural gas flow paths to respective
ones of said plural cavities; plural outlet holes in said lower
ceiling aligned with respective ones of said plural cavities;
respective power applicators adjacent respective ones of said
plural cavities, a power source, plural power conductors coupled to
respective ones of said power applicators, and a power distributor
coupled between said power source and said plural power
conductors.
2. The plasma reactor of claim 1 wherein said plural cavity walls
comprise dielectric cavity walls.
3. The plasma reactor of claim 1 wherein said power source
comprises an RF power generator and wherein each one of said
respective power applicators is separated from an interior of a
corresponding one of said plural cavities by the corresponding one
of said plural cavity walls.
4. The plasma reactor of claim 3 wherein said power applicator
comprises an electrode for capacitively coupling RF power into the
corresponding one of said plural cavities.
5. The plasma reactor of claim 4 wherein said electrode surrounds a
section of the corresponding one of said plural cavities.
6. The plasma reactor of claim 3 wherein said power applicator
comprises a coil antenna for inductively coupling RF power into the
corresponding one of said plural cavities.
7. The plasma reactor of claim 6 wherein said coil antenna
comprises a conductor coiled around a section of the corresponding
one of said plural cavities.
8. The plasma reactor of claim 1 wherein said power source is a
D.C. power generator, each one of said power applicators comprises
an electrode for D.C. discharge, and wherein each one of said
cavity walls is configured to expose a corresponding electrode to
an interior of a corresponding one of said plural cavities.
9. The plasma reactor of claim 1 wherein said power distributor
comprises plural switches coupled between an output of said power
source and respective ones of said power conductors.
10. The plasma reactor of claim 9 further comprising a processor
controlling said plural switches individually in accordance with
user-defined instructions.
11. The plasma reactor of claim 1 further comprising: a process gas
source and a gas distributor comprising plural valves coupled
between said process gas source and respective ones of said plural
cavities.
12. The plasma reactor of claim 11 wherein said process gas source
comprises plural gas sources of different gas species, wherein
respective ones of said plural valves are coupled between
respective ones of said plural gas sources and respective ones of
said plural cavities.
13. The plasma reactor of claim 12 further comprising a processor
controlling said plural valves individually in accordance with
user-defined instructions.
14. The plasma reactor of claim 9 further comprising: a process gas
source and a gas distributor comprising plural valves coupled
between said process gas source and respective ones of said plural
cavities.
15. The plasma reactor of claim 14 wherein said process gas source
comprises plural gas sources of different gas species, wherein
respective ones of said plural valves are coupled between
respective ones of said plural gas sources and respective ones of
said plural cavities.
16. The plasma reactor of claim 15 further comprising a processor
controlling said plural valves individually and controlling said
plural switches individually in accordance with user-defined
instructions.
17. The plasma reactor of claim 1 further comprising a remote
plasma source coupled to deliver plasma by-products to said plural
cavities.
18. The plasma reactor of claim 1 wherein said processing chamber
further comprises a cylindrical side wall below said lower ceiling,
said reactor further comprising an inductively coupled plasma
source comprising a coil antenna wound around said cylindrical side
wall and an RF power generator coupled to said coil antenna through
an impedance match.
19. A plasma reactor comprising: a processing chamber and a
workpiece support in said processing chamber; a gas distributor
overlying said workpiece support; plural cavity walls defining
plural cavities underlying said gas distributor, said gas
distributor comprising plural gas flow paths to respective ones of
said plural cavities; respective power applicators adjacent
respective ones of said plural cavities, a power source, plural
power conductors coupled to respective ones of said power
applicators, and a power distributor coupled between said power
source and said plural power conductors; and a process gas source
and a gas distributor comprising plural valves coupled between said
process gas source and respective ones of said plural cavities.
20. A method of processing a workpiece in a plasma reactor
comprising an array of plasma point sources distributed over a
surface of the workpiece, comprising: performing a plasma process
on the workpiece; observing a non-uniformity in a spatial
distribution of process rate across the surface of the workpiece;
and reducing said non-uniformity by performing at least one of: (a)
adjusting an apportionment of plasma source power levels among said
array of plasma point sources, or (b) adjusting an apportionment of
gas flows among said array of plasma point sources.
Description
BACKGROUND
[0001] Technical Field
[0002] The disclosure concerns plasma processing of a workpiece
such as a semiconductor wafer, and reduction in process
non-uniformities.
[0003] Background Discussion
[0004] In conventional plasma processing, the processed wafers may
suffer from local non uniformities--due non-uniform stress,
non-uniform film composition (for a deposition process),
non-uniform CD's (critical dimensions of features) due to different
etch environments. This could be due to differences among incoming
wafers or differences in the characteristic of the processing
chamber (e.g., in a carousel style processing chamber where the
rotating wafer sees a leading edge and a trailing edge radical
dwell time difference or different local temperature).
SUMMARY
[0005] A plasma reactor comprises: a processing chamber and a
workpiece support in the processing chamber, the chamber comprising
a lower ceiling facing the workpiece support; an upper ceiling
overlying and facing the lower ceiling and a gas distributor
overlying the upper ceiling; plural cavity walls defining plural
cavities between the upper and lower ceilings, the gas distributor
comprising plural gas flow paths to respective ones of the plural
cavities; plural outlet holes in the lower ceiling aligned with
respective ones of the plural cavities; and respective power
applicators adjacent respective ones of the plural cavities, a
power source, plural power conductors coupled to respective ones of
the power applicators, and a power distributor coupled between the
power source and the plural power conductors.
[0006] In one embodiment, the plural cavity walls comprise
dielectric cavity walls.
[0007] In a further embodiment, the power source comprises an RF
power generator and wherein each one of the respective power
applicators is separated from an interior of a corresponding one of
the plural cavities by the corresponding one of the plural cavity
walls.
[0008] In one embodiment, the power applicator comprises an
electrode for capacitively coupling RF power into the corresponding
one of the plural cavities. In this embodiment, each electrode may
surround a section of the corresponding one of the plural
cavities.
[0009] In another embodiment, the power applicator comprises a coil
antenna for inductively coupling RF power into the corresponding
one of the plural cavities. In this embodiment, the coil antenna
may comprise a conductor coiled around a section of the
corresponding one of the plural cavities.
[0010] In a yet further embodiment, the power source is a D.C.
power generator, each one of the power applicators comprises an
electrode for D.C. discharge, and wherein each one of the
dielectric cavity walls is configured to expose the corresponding
electrode to the interior of the corresponding one of the plural
cavities.
[0011] In one embodiment, the power distributor comprises plural
switches coupled between an output of the power generator and
respective ones of the power conductors.
[0012] In one embodiment, the plasma reactor further comprises a
processor controlling the plural switches individually in
accordance with user-defined instructions.
[0013] In one embodiment, the plasma reactor further comprises a
process gas source and a gas distributor comprising plural valves
coupled between the process gas source and respective ones of the
plural cavities. The process gas source may comprise plural gas
sources of different gas species, wherein respective ones of the
plural valves are coupled between respective ones of the plural gas
sources and respective ones of the plural cavities. In one
embodiment, the plasma reactor further comprises a processor
controlling the plural valves individually in accordance with
user-defined instructions.
[0014] In one embodiment, the plasma reactor further comprises a
remote plasma source coupled to deliver plasma by-products to the
plural cavities.
[0015] In one embodiment, the processing chamber further comprises
a cylindrical side wall, the reactor further comprising an
inductively coupled plasma source comprising a coil antenna wound
around the cylindrical side wall and an RF power generator coupled
to the coil antenna through an impedance match.
[0016] In one embodiment, a plasma reactor comprises: a processing
chamber and a workpiece support in the processing chamber; a gas
distributor overlying the workpiece support; plural cavity walls
defining plural cavities underlying the gas distributor, the gas
distributor comprising plural gas flow paths to respective ones of
the plural cavities; respective power applicators adjacent
respective ones of the plural cavities, a power source, plural
power conductors coupled to respective ones of the power
applicators, and a power distributor coupled between the power
source and the plural power conductors; and a process gas source
and a gas distributor comprising plural valves coupled between the
process gas source and respective ones of the plural cavities.
[0017] In a further embodiment, a method of processing a workpiece
in a plasma reactor comprising an array of plasma point sources
distributed over a surface of the workpiece, comprises: performing
a plasma process on the workpiece; observing a non-uniformity in a
spatial distribution of process rate across the surface of the
workpiece; and reducing the non-uniformity by performing at least
one of:
(a) adjusting an apportionment of plasma source power levels among
the array of plasma point sources, or (b) adjusting an
apportionment of gas flows among the array of plasma point
sources.
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. 1A is a simplified diagram of a first embodiment having
an array of plasma point sources.
[0020] FIG. 1B is an enlarged plan view of a plasma point source in
the embodiment of FIG. 1A.
[0021] FIGS. 2A and 2B depict different arrangements of an array of
plasma point sources.
[0022] FIG. 3 depicts an embodiment in which the plasma point
sources employ plasma D.C. discharge.
[0023] FIG. 4 depicts an embodiment in which the plasma point
sources employ inductive coupling.
[0024] FIG. 5 depicts a modification of the embodiment of FIG. 1A
employing a remote plasma source.
[0025] FIG. 6 depicts a modification of the embodiment of FIG. 4
employing a remote plasma source.
[0026] FIG. 7 depicts a modification of the embodiment of FIG. 1A
having a chamber-wide inductively coupled source in addition to the
array of plasma point sources.
[0027] 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
Introduction
[0028] A plasma source consists of a multitude or array of
independently controlled local plasma point sources, which allows
the spatial and temporal control of charged particle species
(electrons, negative and positive ions) and radicals over a user
defined region.
[0029] Using a plasma source that enables spatial and temporal
control enables correction of local non-uniformities. This may be
accomplished by switching ON or OFF plasma generation in different
plasma point sources where the charged particles and radicals are
generated. Alternatively or in addition, this may be accomplished
by changing process gas flows to the different plasma point
sources. For example, the gas flow may be switched ON or OFF and/or
the gas mixture for each plasma point source may be changed. The
user can select the gas to be ionized or broken down in the local
plasma point source. The user can further select the time or
duration of the discharge.
[0030] One can alter the local discharge chemistry by either
operating in parallel different gas chemistries in different
simultaneous local gas discharges (spatial control) or by
alternating gas chemistry locally in the same local discharge.
[0031] One can subject the entire workpiece (wafer) to a constant
negative DC bias but attract ions locally to implant, or etch or
deposit.
[0032] The array of plasma point sources can be combined with a
conventional non-local plasma source (such as a capacitively
coupled large electrode plasma source or an inductively coupled
plasma source) and, in real time, correct for local
non-uniformities in plasma generation.
[0033] The array of plasma point sources can be combined with a
remote plasma source (e.g., a remote radical source). The radical
processing step could be followed by a plasma treatment step where
one can vary the composition and local dwell time. Past solutions
have focused on local variation of temperature by varying current
through local heating elements in the substrate holders.
Embodiments described herein add to the existing solution, and
enable local chemistries, and affect the generation of charged
particles and radicals rather than depending upon only temperatures
to speed up reactions.
Embodiments
[0034] FIGS. 1A and 1B depict an embodiment having multiple plasma
point sources 90 that are capacitively coupled using an RF
frequency. The point sources 90 can be arranged in various
configurations, such as circular (FIG. 2A) or pie shaped (FIG. 2B).
The embodiment of FIG. 1A includes a process chamber body 100
having a processing zone 92 enclosed by a cylindrical side wall
102, a lower ceiling 104 and a floor 106. A workpiece support 94
supports a workpiece 96 within the processing zone 92. A vacuum
pump 108 may be coupled to the processing zone 92 through the floor
106. An upper ceiling 110 supported on an upper cylindrical side
wall 126 overlies the lower ceiling 104 and supports a gas
distributor 112. The lower ceiling 104 includes an array of gas
outlet holes 114. In the embodiment of FIG. 1A, the point sources
90 are an array of cylindrical cavities 115 enclosed by dielectric
cylindrical cavity walls 116, each being parallel to an axis of
symmetry of the cylindrical side wall 102 and aligned with a
respective one of the gas outlet holes 114. The dielectric
cylindrical cavity walls 116 are ringed by respective cylindrical
electrodes 118.
[0035] Each plasma point source 90 is local, in that the area of
each gas outlet hole 114 is small relative to the area of the lower
ceiling 104 or the upper ceiling 110 or relative to the diameter of
the chamber body 100. In one embodiment, the area of each gas
outlet hole 114 does not exceed 5% of the area of the lower ceiling
104 or the upper ceiling 110 or area of the chamber body 100.
[0036] In the illustrated embodiment of FIGS. 1A and 1B, the shape
of each gas outlet opening 114 is circular and conforms with the
shape of the cylindrical cavity 115. However, in other embodiments,
each gas outlet hole 114 may be of any shape and may not conform
with the shape of the cylindrical cavity 115. For example, each gas
outlet hole 114 may be of a non-circular shape (e.g., elliptical)
or may be of a polygonal shape or a linear slot shape or
combinations of some of the foregoing shapes. If the shape of the
gas outlet hole 114 does not conform with the cylindrical cavity
115, then an adapter (not illustrated) may be introduced to provide
a gas seal between the gas outlet hole 114 and the cylindrical
cavity 115, in one embodiment.
[0037] The upper ceiling 110 has an array of gas inlet openings 119
each aligned with a respective one of the cylindrical cavities 115.
The gas distributor 112 furnishes process gases into the
cylindrical cavities 115 through the gas inlet openings 119.
Individual power conductors 120 conduct power to individual ones of
the respective cylindrical electrodes 118. A power distributor 122
distributes power to the power conductors 120 from a power source
124. In one embodiment, the power source 124 is an alternating
current (AC) power generator or a radio frequency (RF) power
generator with an RF impedance match. In related embodiments, the
frequency of the power source 124 may be any from D.C. to UHF, for
example. In one embodiment, plasma is produced in the cylindrical
cavities 115 by capacitive coupling of RF power from the
cylindrical electrodes 118 through the dielectric cylindrical
cavity walls 116 into the cylindrical cavities 115. The lower
ceiling 104 isolates the cylindrical electrodes 118 from
plasma.
[0038] The gas distributor 112 receives different gas species from
plural gas supplies 250 and apportions different gas mixtures to
different ones of the cylindrical cavities 115 through the
respective gas inlet openings 119 in accordance with different
user-specified gas recipes for the different cylindrical cavities
115. For example, the gas distributor 112 may include an array of
gas valves 252 individually controlled by a processor 254 in
accordance with user-defined instructions that define gas mixtures
for the individual cylindrical cavities 115. The array of gas
valves 252 is coupled between the plural gas supplies 250 and the
gas inlet openings 119 to the cylindrical cavities 115.
[0039] The power distributor 122, in one embodiment, controls the
power supplied to each power conductor 120 individually. For
example, the power distributor 122 may include an array of
electrical switches 262 individually controlled by the processor
254 in accordance with user-defined instructions. The power may be
controlled by pulse width modulation, and the user-defined
instructions may define individual on/off durations (or duty
cycles) of power for the individual cylindrical cavities 115. The
array of electrical switches 262 is coupled between the power
source 124 and the power conductors 120.
[0040] In a first embodiment, the lower ceiling 104 is formed of a
dielectric material while the upper ceiling 110 is formed of a
conductive material. In a second embodiment, the lower ceiling 104
is adjacent a lower plate 190 formed of a conductive material, and
both the lower plate 190 and the upper ceiling 110 are grounded. In
this way, the plasma source is located between two grounded plates,
namely the lower plate 190 and the upper ceiling 110.
[0041] FIG. 3 depicts an embodiment in which plasma is produced by
a D.C. discharge, and the power source 124 is a D.C. power
generator. Each of the dielectric cylindrical cavity walls 116 is
terminated above the corresponding one of the cylindrical
electrodes 118. This feature can directly expose each cylindrical
electrode 118 to plasma to facilitate the D.C. discharge.
[0042] FIG. 4 depicts a modification of the embodiment of FIG. 1A,
in which the cylindrical electrodes 118 are replaced by individual
inductive coils 210, to produce an inductively coupled plasma
within each cylindrical cavity 115. Each inductive coil 210 is
wrapped around a bottom section of the corresponding cylindrical
dielectric wall 116, as depicted in FIG. 4. In the embodiment of
FIG. 4, a changing magnetic field generates a changing electric
field in the cylindrical cavity 115 which in turn generates a
closed turn oscillating plasma current.
[0043] FIG. 5 depicts another modification of the embodiment of
FIG. 1A that includes a remote plasma source 220 and a radical
distribution plate 280. The radical distribution plate 280 directs
radicals from the remote plasma source 220 into the individual
cylindrical cavities 115. The remote plasma source 220 may include
a plasma source power applicator 222 driven by a power source 224.
The remote plasma source 220 may further include controlled gas
sources 226 containing precursors of desired radical species. There
are some processes in which chemically active radicals generated
remotely play a critical role in the processing of wafers. However,
there may be a need to follow the radical treatment with a plasma
treatment step. Having a spatially and temporally controllable
plasma source helps in addressing radical non-uniformity. In the
case of radicals which are short lived (recombine into inert
neutrals), having a controllable plasma density can help regenerate
important radicals.
[0044] FIG. 6 depicts a modification of the embodiment of FIG. 4
that includes a remote plasma source 220 and a radical distribution
plate 280. In the embodiment of FIG. 6, the remote plasma source
220 is combined with the inductively coupled plasma sources (i.e.,
the inductively coupled coils 210) of FIG. 4. The inductively
coupled plasma sources (the coils 210) enable operation in
different (lower) pressure regimes (e.g., below 25 mTorr), compared
to the capacitively coupled plasma source of the embodiment of FIG.
1A.
[0045] FIG. 7 depicts a modification of the embodiment of FIG. 1A,
in which the array of plasma point sources 90 is combined with a
larger non-local inductively coupled plasma source. The non-local
inductively coupled plasma source of FIG. 7 includes a helically
wound coil antenna 240 surrounding the cylindrical side wall 102.
The helically wound coil antenna 240 is driven by an RF power
generator 242 through an RF impedance match 244. In the embodiment
of FIG. 7, the cylindrical side wall 102 is formed of a
non-metallic material to enable inductive coupling of RF power
through the cylindrical side wall 102. The lower plate 190 protects
the individual plasma point sources (corresponding to the
individual cylindrical cavities 115) from the larger inductively
coupled plasma source (corresponding to the helically wound coil
antenna 240).
[0046] The individual plasma point sources 90 (corresponding to the
individual cylindrical cavities 115) are individually controllable.
The enables spatial and temporal control of plasma distribution.
Such control may be exercised in such a manner as to reduce plasma
distribution non-uniformity.
Control Modes:
[0047] The power source 124 can power each plasma point source 90
in different modes. In a first mode, each plasma point source 90
dissipates a fixed amount of power and the control system switches
on or off the power furnished to the plasma point source using the
array of electrical switches 262. In one example, each point source
dissipates a constant amount of about 3 watts when it is on. The
array of electrical switches 262 essentially apply the power to
individual plasma point sources 90 on command. The plasma density
is a function of how many plasma point sources 90 are turned on. In
this manner, the net power delivered to each plasma point source 90
may be controlled by pulse width modification.
[0048] In a second mode, what is controlled is the level of power
delivered to each plasma point source 90. Also, gas composition to
individual plasma point sources 90 (or groups of plasma point
sources 90) can be varied by the gas distributor 112. Thus, the
different plasma point sources 90 need not have the same gas
discharge composition. Each plasma point source 90 has a fixed
address. The power and/or gas flow to each plasma point source 90
can be targeted to turn on or off individually.
[0049] In accordance with one method, the spatial distribution of
process rate across the surface of the workpiece is measured. The
non-uniformities in the process rate distribution are compensated
by establishing a spatial distribution of ON/OFF duty cycles of
power supplied to the array of plasma point sources 90 that is in
effect an inverse of the measured process rate spatial
distribution. In other words, the distribution of ON/OFF power duty
cycles has maxima in locations where the measured process rate
distribution has minima and has minima where the measured process
rate distribution has maxima.
[0050] In accordance with another method, the non-uniformities in
the process rate distribution are compensated by establishing a
spatial distribution of ON/OFF duty cycles of process gas flows
supplied to the array of plasma point sources 90 that is in effect
an inverse of the measured process rate spatial distribution. In
other words, the distribution of ON/OFF gas flow duty cycles has
maxima in locations where the measured process rate distribution
has minima and has minima where the measured process rate
distribution has maxima.
Advantages:
[0051] A primary advantage is complete control spatially and
temporally of the generation of charged particles and energetic
radicals. This enables spatial and temporal control over
distribution of local charged particles and energetic radicals.
[0052] 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.
* * * * *