U.S. patent application number 14/937477 was filed with the patent office on 2016-03-17 for dual plasma volume processing apparatus for neutral/ion flux control.
The applicant listed for this patent is Lam Research Corporation. Invention is credited to Andrew D. Bailey III, Rajinder Dhindsa, Alexei Marakhtanov.
Application Number | 20160079039 14/937477 |
Document ID | / |
Family ID | 45555213 |
Filed Date | 2016-03-17 |
United States Patent
Application |
20160079039 |
Kind Code |
A1 |
Dhindsa; Rajinder ; et
al. |
March 17, 2016 |
Dual Plasma Volume Processing Apparatus for Neutral/Ion Flux
Control
Abstract
A semiconductor wafer processing apparatus includes a first
electrode exposed to a first plasma generation volume, a second
electrode exposed to a second plasma generation volume, and a gas
distribution unit disposed between the first and second plasma
generation volumes. The first electrode is defined to transmit
radiofrequency (RF) power to the first plasma generation volume,
and distribute a first plasma process gas to the first plasma
generation volume. The second electrode is defined to transmit RF
power to the second plasma generation volume, and hold a substrate
in exposure to the second plasma generation volume. The gas
distribution unit includes an arrangement of through-holes defined
to fluidly connect the first plasma generation volume to the second
plasma generation volume. The gas distribution unit also includes
an arrangement of gas supply ports defined to distribute a second
plasma process gas to the second plasma generation volume.
Inventors: |
Dhindsa; Rajinder; (San
Jose, CA) ; Marakhtanov; Alexei; (Albany, CA)
; Bailey III; Andrew D.; (Pleasanton, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Lam Research Corporation |
Fremont |
CA |
US |
|
|
Family ID: |
45555213 |
Appl. No.: |
14/937477 |
Filed: |
November 10, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12850559 |
Aug 4, 2010 |
9184028 |
|
|
14937477 |
|
|
|
|
Current U.S.
Class: |
438/5 ; 118/723R;
156/345.29; 438/714; 438/758 |
Current CPC
Class: |
H01J 37/32715 20130101;
H01L 22/26 20130101; H01L 21/67069 20130101; H01L 21/6831 20130101;
H01L 21/67259 20130101; H01J 37/32449 20130101; H01J 37/32091
20130101; H01J 37/32834 20130101; H01J 37/32697 20130101 |
International
Class: |
H01J 37/32 20060101
H01J037/32; H01L 21/683 20060101 H01L021/683; H01L 21/66 20060101
H01L021/66; H01L 21/67 20060101 H01L021/67 |
Claims
1. A semiconductor wafer processing apparatus, comprising: an
electrostatic chuck having a top surface configured to hold a
substrate; a gas distribution unit positioned above and spaced
apart from the electrostatic chuck, the gas distribution unit
having a bottom surface oriented in a substantially parallel
orientation with the top surface of the electrostatic chuck, a
space between the top surface of the electrostatic chuck and the
bottom surface of the gas distribution unit forming a lower plasma
generation volume, the gas distribution unit configured to receive
and distribute a process gas to the lower plasma generation volume,
the gas distribution unit including an arrangement of through-holes
extending from the bottom surface of the gas distribution unit to a
top surface of the gas distribution unit; an outer lower structural
member configured to circumscribe the gas distribution unit and
support the gas distribution unit in its position above and spaced
apart from the electrostatic chuck; a showerhead electrode
positioned above and spaced apart from the gas distribution unit,
the showerhead electrode having a bottom surface oriented in a
substantially parallel orientation with the top surface of the gas
distribution unit, a space between the bottom surface of the
showerhead electrode and the top surface of the gas distribution
unit forming an upper plasma generation volume; an outer upper
structural member configured to circumscribe the showerhead
electrode and support the showerhead electrode in its position
above and spaced apart from the gas distribution unit; an exhaust
channel configured to extend in a radial direction outward from a
perimeter of the upper plasma generation volume, the exhaust
channel configured to circumscribe the upper plasma generation
volume and extend radially outward between the outer upper
structural member and the outer lower structural member; and a
throttle ring configured to move vertically within a conformally
defined recessed region within the outer upper structural member so
as to extend vertically into the exhaust channel by a controlled
amount of distance.
2. The semiconductor wafer processing apparatus as recited in claim
1, wherein the exhaust channel is configured to have a
substantially uniform vertical height along its extent in the
radial direction with an exception of a location beneath the
throttle ring.
3. The semiconductor wafer processing apparatus as recited in claim
1, further comprising: a first insulating ring configured to
circumscribe an outer perimeter of the showerhead electrode, the
first insulating ring disposed within a horizontal slot formed
within the outer upper structural member, the first insulating ring
configured to extend along a portion of a vertical height of the
showerhead electrode, the first insulating ring configured to
physically contact the outer perimeter of the showerhead
electrode.
4. The semiconductor wafer processing apparatus as recited in claim
3, wherein the first insulating ring has a tapered bottom surface
extending downward and away from the bottom surface of the
showerhead electrode.
5. The semiconductor wafer processing apparatus as recited in claim
3, further comprising: a second insulating ring configured to
circumscribe the outer perimeter of the showerhead electrode, the
second insulating ring disposed on a top surface of the first
insulating ring, the second insulating ring positioned between the
outer perimeter of the showerhead electrode and the outer upper
structural member, the second insulating ring configured to extend
along a remainder of the vertical height of the showerhead
electrode located above the first insulating ring, the second
insulating ring positioned to contact both the showerhead electrode
and the outer upper structural member.
6. The semiconductor wafer processing apparatus as recited in claim
1, wherein a first portion of the arrangement of through-holes
extend from the bottom surface of the gas distribution unit to the
top surface of the gas distribution unit in an angled direction
relative to a reference direction that extends perpendicularly
between the top and bottom surfaces of the gas distribution
unit.
7. The semiconductor wafer processing apparatus as recited in claim
6, wherein an angle of the first portion of the arrangement of
through-holes relative to the reference direction is sufficiently
large to prevent an uninterrupted line-of-sight in the reference
direction through the gas distribution unit.
8. The semiconductor wafer processing apparatus as recited in claim
6, wherein a second portion of the arrangement of through-holes
extend from the bottom surface of the gas distribution unit to the
top surface of the gas distribution unit in the reference
direction.
9. The semiconductor wafer processing apparatus as recited in claim
8, wherein the first and second portions of the arrangement of
through-holes are distributed in a substantially uniformly mixed
manner across the gas distribution unit.
10. The semiconductor wafer processing apparatus as recited in
claim wherein the throttle ring is configured to provide a complete
shutoff of flow from the upper plasma generation volume through the
exhaust channel when the throttle ring is fully lowered into the
exhaust channel.
11. The semiconductor wafer processing apparatus as recited in
claim 1, wherein the outer lower structural member is rigidly
connected to the electrostatic chuck.
12. The semiconductor wafer processing apparatus as recited in
claim 11, wherein the outer lower structural member includes an
upper horizontal portion, a lower horizontal portion, and a
vertical portion extending between the lower horizontal portion and
the upper horizontal portion, and wherein the upper horizontal
portion is sealed against an outer perimeter of the gas
distribution unit, and wherein the lower horizontal portion is
sealed against an outer perimeter of the electrostatic chuck, and
wherein each of the upper horizontal portion, the lower horizontal
portion, and the vertical portion of the outer lower structural
member forms an impermeable barrier except for a set of slotted
exhaust channels formed through the lower horizontal portion,
wherein the set of slotted exhaust channels form fluid flow
pathways out of the lower plasma generation volume.
13. The semiconductor wafer processing apparatus as recited in
claim 12, further comprising: a pressure control ring disposed
below the set of slotted exhaust channels, the pressure control
ring configured as a horizontally oriented annular-shaped solid
disc that is movable in a controlled manner in a vertical direction
toward and away from the set of slotted exhaust channels.
14. The semiconductor wafer processing apparatus as recited in
claim 13, wherein the pressure control ring is configured to
provide a complete shutoff of flow from the lower plasma generation
volume through the set of slotted exhaust channels when the
pressure control ring is fully raised to contact the lower
horizontal portion of the outer lower structural member.
15. A method for processing a semiconductor wafer, comprising:
placing a semiconductor wafer on a top surface of an electrostatic
chuck within a semiconductor wafer processing apparatus, wherein
the semiconductor wafer process apparatus includes: a gas
distribution unit positioned above and spaced apart from the
electrostatic chuck, the gas distribution unit having a bottom
surface oriented in a substantially parallel orientation with the
top surface of the electrostatic chuck, a space between the top
surface of the electrostatic chuck and the bottom surface of the
gas distribution unit forming a lower plasma generation volume, the
gas distribution unit configured to receive and distribute a
process gas to the lower plasma generation volume, the gas
distribution unit including an arrangement of through-holes
extending from the bottom surface of the gas distribution unit to a
top surface of the gas distribution unit, and an outer lower
structural member configured to circumscribe the gas distribution
unit and support the gas distribution unit in its position above
and spaced apart from the electrostatic chuck, and a showerhead
electrode positioned above and spaced apart from the gas
distribution unit, the showerhead electrode having a bottom surface
oriented in a substantially parallel orientation with the top
surface of the gas distribution unit, a space between the bottom
surface of the showerhead electrode and the top surface of the gas
distribution unit forming an upper plasma generation volume, and an
outer upper structural member configured to circumscribe the
showerhead electrode and support the showerhead electrode in its
position above and spaced apart from the gas distribution unit, and
an exhaust channel configured to extend in a radial direction
outward from a perimeter of the upper plasma generation volume, the
exhaust channel configured to circumscribe the upper plasma
generation volume and extend radially outward between the outer
upper structural member and the outer lower structural member, and
a throttle ring configured to move vertically within a conformally
defined recessed region within the outer upper structural member so
as to extend vertically into the exhaust channel by a controlled
amount of distance; operating the electrostatic chuck to hold the
substrate; flowing a first process gas through the showerhead
electrode into the upper plasma generation volume; supplying
radiofrequency power to the showerhead electrode to transform the
first process gas into a plasma within the upper plasma generation
volume, wherein reactive constituents of the plasma within the
upper plasma generation volume travel through the arrangement of
through-holes within the gas distribution unit and into the lower
plasma generation volume; flowing a second process gas through the
gas distribution unit into the lower plasma generation volume; and
supplying radiofrequency power to the electrostatic chuck to
transform the second process gas into a plasma within the lower
plasma generation volume.
16. The method as recited in claim 15, further comprising:
controlling a vertical position of the throttle ring within the
conformally defined recessed region within the outer upper
structural member so as to control an amount of flow from the upper
plasma generation volume through the exhaust channel.
17. The method as recited in claim 16, further comprising:
operating a pressure manometer to measure a pressure within the
upper plasma generation volume; generating feedback signals for
controlling the vertical position of the throttle ring; and using
the generated feedback signals to control the vertical position of
the throttle ring to provide active control of the pressure within
the upper plasma generation volume.
18. The method as recited in claim 15, wherein the outer lower
structural member includes a set of slotted exhaust channels that
form fluid flow pathways out of the lower plasma generation volume,
and wherein the semiconductor wafer process apparatus includes a
pressure control ring disposed below the set of slotted exhaust
channels, the pressure control ring configured as a horizontally
oriented annular-shaped solid disc that is movable in a controlled
manner in a vertical direction toward and away from the set of
slotted exhaust channels, the method further comprising controlling
a vertical position of the pressure control ring so as to control
an amount of flow from the lower plasma generation volume through
the set of slotted exhaust channels.
19. The method as recited in claim 18, further comprising: fully
lowering the throttle ring within the exhaust channel to shut off
flow from the upper plasma generation volume through the exhaust
channel, such that exhaust from the upper plasma generation volume
is forced to flow through the arrangement of through-holes within
the gas distribution unit and through the lower plasma generation
volume and through the set of slotted exhaust channels past the
pressure control ring.
20. The method as recited in claim 18, further comprising: fully
raising the pressure control ring to contact the outer lower
structural member to shut off flow from the lower plasma generation
volume through the set of slotted exhaust channels, such that
exhaust from the lower plasma generation volume is forced to flow
through the arrangement of through-holes within the gas
distribution unit and through the upper plasma generation volume
and through the exhaust channel past the throttle ring.
Description
CLAIM OF PRIORITY
[0001] This application is a continuation application under 35
U.S.C. 120 of prior U.S. application Ser. No. 12/850,559, filed
Aug. 4, 2010, the disclosure of which is incorporated herein by
reference in its entirety for all purposes.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0002] This application is related to U.S. patent application Ser.
No. 12/850,552, filed on Aug. 4, 2010, the disclosure of which is
incorporated herein by reference in its entirety for all
purposes.
BACKGROUND OF THE INVENTION
[0003] Current plasma processing systems used in semiconductor
wafer fabrication rely on highly interdependent control parameters
to control radical separation, radical flux, ion energy, and ion
flux delivered to the wafer. For example, current plasma processing
systems attempt to achieve necessary radical separation, radical
flux, ion energy, and ion flux by controlling a single plasma
generated in the presence of the wafer. Unfortunately, chemistry
dissociation and radical formation are coupled to ion production
and plasma density and often do not work in concert to achieve the
desired plasma processing conditions.
[0004] For example, it is difficult in current plasma processing
systems to obtain higher chemical dissociation and lower ion
density simultaneously in the same plasma, as the higher chemical
dissociation requires application of higher power which in turn
causes generation of higher ion density. Also, in current plasma
processing systems, the high interdependence of the control
parameters limits smaller technology node application processing
windows and/or manufacturing capability. Given the foregoing, there
is a need for a plasma processing system that provides for
independent control of radical/neutral flux relative to ion
flux.
SUMMARY OF THE INVENTION
[0005] In one embodiment, a semiconductor wafer processing
apparatus is disclosed. The apparatus includes a first electrode
exposed to a first plasma generation volume. The first electrode is
defined to transmit radiofrequency (RF) power to the first plasma
generation volume. The first electrode is further defined to
distribute a first plasma process gas to the first plasma
generation volume. The apparatus also includes a second electrode
exposed to a second plasma generation volume. The second electrode
is defined to transmit RF power to the second plasma generation
volume. The second electrode is further defined to hold a substrate
in exposure to the second plasma generation volume. The apparatus
further includes a gas distribution unit disposed between the first
plasma generation volume and the second plasma generation volume.
The gas distribution unit is defined to include an arrangement of
through-holes that each extend through the gas distribution unit to
fluidly connect the first plasma generation volume to the second
plasma generation volume. The gas distribution unit is further
defined to include an arrangement of gas supply ports defined to
distribute a second plasma process gas to the second plasma
generation volume.
[0006] In another embodiment, a system for semiconductor wafer
processing is disclosed. The system includes a chamber defined to
have an interior cavity and an exhaust port that provides for fluid
connection of the interior cavity to an exhaust pump. The system
also includes a dual plasma processing apparatus disposed within
the interior cavity of the chamber. The dual plasma processing
apparatus includes an upper plasma chamber that includes an upper
plasma generation volume. The dual plasma processing apparatus also
includes a showerhead electrode defined above the upper plasma
generation volume to supply a first plasma process gas and RF power
to the upper plasma generation volume. The dual plasma processing
apparatus also includes a lower plasma chamber that includes a
lower plasma generation volume. The dual plasma processing
apparatus also includes a gas distribution unit disposed between
the upper and lower plasma generation volumes. The gas distribution
unit is defined to supply a second plasma process gas to the lower
plasma generation volume. The gas distribution unit is further
defined to provide controlled fluid communication between the upper
and lower plasma generation volumes. The system further includes a
chuck disposed within the interior cavity of the chamber below the
lower plasma generation volume. The chuck is defined to hold a
substrate in exposure to the lower plasma generation volume. The
chuck is further defined to supply RF power to the lower plasma
generation volume. Each of the upper and lower plasma chambers is
respectively defined to exhaust the upper and lower plasma
generation volumes into the interior cavity of the chamber.
[0007] In another embodiment, a gas distribution unit is disclosed.
The gas distribution unit includes a plate formed to separate an
upper plasma generation volume from a lower plasma generation
volume. An upper surface of the plate provides a lower boundary of
the upper plasma generation volume. A lower surface of the plate
provides an upper boundary of the lower plasma generation volume.
The plate includes an arrangement of through-holes that each extend
through the plate from the upper surface of the plate to the lower
surface of the plate, so as to fluidly connect the upper plasma
generation volume to the lower plasma generation volume. The plate
also includes interior gas supply channels that are fluidly
connected to an arrangement of gas supply ports defined on the
lower surface of the plate to distribute a plasma process gas to
the lower plasma generation volume.
[0008] Other aspects and advantages of the invention will become
more apparent from the following detailed description, taken in
conjunction with the accompanying drawings, illustrating by way of
example the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 shows a semiconductor wafer processing apparatus, in
accordance with one embodiment of the present invention;
[0010] FIG. 2 shows a bottom view of the showerhead electrode, in
accordance with one embodiment of the present invention;
[0011] FIG. 3A shows a bottom view of the gas distribution unit, in
accordance with one embodiment of the present invention;
[0012] FIG. 3B shows a top view of the gas distribution unit, in
accordance with one embodiment of the present invention;
[0013] FIG. 3C shows a gas supply port cross-section, in accordance
with one embodiment of the present invention;
[0014] FIG. 3D shows a cross-section of a through-hole defined to
extend through the gas distribution unit and an angle, in
accordance with one embodiment of the present invention;
[0015] FIG. 4A shows a flow control plate disposed on the upper
surface of the gas distribution unit, in accordance with one
embodiment of the present invention;
[0016] FIG. 4B shows a top view of the flow control plate
positioned such that a hole pattern defined therein allows for flow
through all through-holes defined within the underlying gas
distribution unit, in accordance with one embodiment of the present
invention;
[0017] FIG. 4C shows a top view of the flow control plate
positioned such that the hole pattern defined therein allows for
flow through only angled through-holes defined within the
underlying gas distribution unit, in accordance with one embodiment
of the present invention;
[0018] FIG. 4D shows a top view of a flow control plate assembly
defined by a number of concentric rotatable flow control plates, in
accordance with one embodiment of the present invention; and
[0019] FIG. 5 shows the chamber of FIG. 1 with an upper plasma and
a lower plasma, in accordance with one embodiment of the present
invention.
DETAILED DESCRIPTION
[0020] In the following description, numerous specific details are
set forth in order to provide a thorough understanding of the
present invention. It will be apparent, however, to one skilled in
the art that the present invention may be practiced without some or
all of these specific details. In other instances, well known
process operations have not been described in detail in order not
to unnecessarily obscure the present invention.
[0021] A semiconductor wafer processing apparatus is disclosed
herein to enable decoupling of radical generation on neutral
species from ion generation within plasma, such that the
radical/neutral species can be independently controlled relative to
the charged ion species during semiconductor wafer processing. The
apparatus includes an upper, i.e., downstream, plasma generation
volume in which the radical/neutral species are generated without
concern with regard to associated ion generation. The apparatus
also includes a lower plasma generation volume within which a
separate plasma of appropriate ion density is generated in exposure
to a substrate, i.e., wafer. The radical/neutral species within the
upper plasma generation volume are flowed in a controlled manner
through a gas distribution unit to the lower plasma generation
volume, thereby providing the radical/neutral species constituents
for wafer processing.
[0022] The radical/neutral species are allowed to travel from the
upper plasma generation volume to the lower plasma generation
volume through the gas distribution unit which separates the upper
and lower plasma generation volumes. However, ions generated in the
upper plasma generation volume are prevented by the gas
distribution unit from traveling to the lower plasma generation
volume. Thus, the gas distribution unit serves as an ion filter.
The radical/neutral species contributed from the upper plasma
generation volume are used for wafer processing in the lower plasma
generation volume. The ions generated in the lower plasma
generation volume represent the charged species used for wafer
processing.
[0023] The upper and lower plasma generation volumes are
independently controllable, such that the radical/neutral flux
contributed for wafer processing is generated independently from
the ionic plasma generated in exposure to the wafer. Therefore, the
upper and lower plasma generation volumes of the apparatus
disclosed herein, provide for decoupling of radical/neutral flux
from ion flux during wafer processing. Thus, the radical/neutral
species can be controlled separate from the ion flux.
[0024] FIG. 1 shows a semiconductor wafer processing apparatus, in
accordance with one embodiment of the present invention. The
apparatus includes a chamber 100 formed by a top plate 100A, a
bottom plate 100B, and walls 100C. In one embodiment, the walls
100C form a contiguous cylindrical shaped wall 100C. In other
embodiments, the walls 100C can have other configurations, so long
as an interior cavity 100D of the chamber 100 can be isolated from
an external environment outside the chamber 100. A number of seals
139 are disposed between the chamber top plate 100A, bottom plate
100B, and walls 100C to facilitate isolation of the interior cavity
100D of the chamber 100 from the external environment.
[0025] In various embodiments, the top plate 100A, bottom plate
100B, and walls 100C of the chamber 100 can be formed of a metal
that is a good conductor of electricity and heat, and that is
chemically compatible with the process gases to which the interior
cavity 100D is to be exposed during wafer processing. For example,
in various embodiments, metals such as aluminum, stainless steel,
or the like, maybe used to form the chamber 100 components. Also,
the seals 139 can be elastomeric seals or consumable metallic
seals, or any other type of seal material, so long as the seals 139
are chemically compatible with processing materials to which the
interior cavity 100D will be exposed, and so long as the seals 139
provide sufficient isolation of the interior cavity 100D from the
external environment outside the chamber 100.
[0026] It should be appreciated that in other embodiments, one or
more additional plates or members can be disposed outside any one
or more of the top plate 100A, bottom plate 100B, or walls 100C, as
necessary to satisfy chamber 100 deployment-specific conditions or
other considerations. Additionally, the top plate 100A, bottom
plate 100B, and/or walls 100C can be fastened to these additional
plates or members as appropriate for the particular implementation.
The chamber 100 structure, including the top plate 100A, bottom
plate 100B and walls 100C, is formed of an electrically conducting
material and is electrically connected to a reference ground
potential.
[0027] The chamber 100 includes an exhaust port 135 which provides
for fluid connection of the interior cavity 100D to an external
exhaust pump 137, such that a negative pressure can be applied
through the exhaust port 135 to remove gases and/or particulates
from within the interior cavity 100D. In one embodiment, the
chamber 100 also includes a gate valve 102 formed within a section
of the chamber wall 100C to enable insertion of a wafer 113 into
the interior cavity 100D, and corresponding removal of the wafer
113 from the interior cavity 100D. In its closed position, the gate
valve 102 is defined to maintain isolation of the interior cavity
100D from the external environment. In various embodiments, the
exhaust pump 137 can be implemented in different ways, so long as
the exhaust pump 137 is capable of applying a suction at the
exhaust port 135 to draw a fluid flow from the interior cavity 100D
of the chamber 100.
[0028] A dual plasma processing apparatus is disposed within the
interior cavity 100D of the chamber 100. The dual plasma processing
apparatus includes an upper plasma chamber 112 that includes an
upper plasma generation volume 103. The dual plasma processing
apparatus also includes a lower plasma chamber 114 that includes a
lower plasma generation volume 109. The upper and lower plasma
chambers 112/114 are physically and fluidly connected by a gas
distribution unit 115, which is disposed to separate the upper and
lower plasma generation volumes 103/109.
[0029] The upper plasma chamber 112 is formed in part by an outer
structural member 104 defined around a periphery of the upper
plasma chamber 112 and connected to the top plate 100A. The upper
plasma chamber 112 also includes a showerhead electrode 101
disposed above the upper plasma generation volume 103 within the
outer structural member 104. The showerhead electrode 101 is
fastened to the top plate 100A by way of an insulating member 141.
The insulating member 141 is defined to provide electrical
insulation. However, the insulating member 141 is also defined to
provide thermal conduction between the showerhead electrode 101 and
other components which interface with the insulating member
141.
[0030] During operation, radiofrequency (RF) power is transmitted
from an RF power source 105 to the showerhead electrode 101. In one
embodiment, the RF power source 105 is defined to provide RF power
at multiple frequencies. In one embodiment, frequencies of the RF
power source 105 are set within a range extending from 1 kHz to 100
MHz. In another embodiment, frequencies of the RF power source 105
are set within a range extending from 400 kHz to 60 MHz. The plasma
density is controlled primarily by the RF power source 105.
[0031] Additionally, in one embodiment, the showerhead electrode
101 is connected to a DC bias source 120 to enable control of
plasma potential within the upper plasma generation volume 103
independent of the plasma density. The DC bias source 120 is
defined to control a bias of the showerhead electrode 101 at
various voltage settings extending upward from ground. In one
embodiment, the DC bias source 120 of the showerhead electrode 101
can be defined to operate in a pulsed manner to synchronize the
plasma in the upper plasma generation volume 103 with the plasma in
the lower plasma generation volume 109. More specifically, this
pulsed control of the DC bias source 120 can be used to control a
time-dependent voltage differential between the plasmas in the
upper and lower plasma generation volumes 103 and 109.
[0032] A heater 143 is disposed above and in contact with both the
insulating member 141 and the outer structural member 104. The
heater 143 is also secured to the top plate 100A. Additionally, a
number of cooling channels 145 are defined within the top plate
100A. A coolant fluid is flowed through the cooling channels 145 to
draw heat away from the top plate 100A. In one embodiment, the
coolant fluid is water. However, other embodiments may utilize
coolant fluids other than water, so long as the coolant fluid is
chemically compatible with the material of the top plate 100A. In
one embodiment, thermocouple measured temperature feedback from
various portions of the chamber 100 is used to control the
temperature of the top plate 100A via the heater 143 and cooling
channels 145. By way of the heater 143 and the cooling channels
145, a temperature of the showerhead electrode 101, and hence upper
plasma generation volume 103, can be controlled.
[0033] The showerhead electrode 101 is electrically isolated from
the outer structural member 104 by insulating rings 147. In one
embodiment, the insulating rings 147 and/or the insulating member
141 are formed of quartz. In other embodiments, the insulating
rings 147 and/or the insulating member 141 can be formed of a
material other than quartz so long as the material provides for
electrical insulation while also providing for thermal
conduction.
[0034] FIG. 2 shows a bottom view of the showerhead electrode 101,
in accordance with one embodiment of the present invention. The
showerhead electrode 101 includes an arrangement of gas supply
ports 121 defined to supply plasma process gas to the upper plasma
generation volume 103. The plasma process gas is supplied from one
or more plasma process gas supply sources 116 to the showerhead
electrode 101. It should be understood that in some embodiments the
gas supply sources 116 represent multiple gas supplies and/or gas
boxes that provide for selection of appropriate gases and/or gas
mixtures for flow through the showerhead electrode 101. The
showerhead electrode 101 is defined to transmit RF power to the
first plasma process gas as its flows through the showerhead
electrode 101 to the arrangement of gas supply ports 121 for
distribution to the upper plasma generation volume 103.
[0035] In various embodiments the showerhead electrode 101 can be
formed of metal that is a good conductor of electricity and heat,
and that is chemically compatible with the processes to be
conducted in the upper plasma generation volume 103, such as
aluminum, stainless steel, or the like. In one embodiment, portions
of the showerhead electrode 101 that are exposed to plasma in the
upper plasma generation volume 103 are protected by a covering of
plasma resistant material. In one embodiment, the plasma resistant
material is formed as a coating. In another embodiment, the plasma
resistant material is formed as a protective structure, e.g.,
plate, that conformally covers the showerhead electrode 101. In
either of these embodiments, the plasma resistant material is
secured to the showerhead electrode 101 to ensure adequate
electrical and thermal conduction between the plasma resistant
material and the showerhead electrode 101. In various embodiments,
the plasma resistant coating/covering used to protect the
showerhead electrode 101 can be formed of silicon, silicon carbide,
silicon oxide, yttrium oxide, or the like.
[0036] In one embodiment, such as that depicted in FIG. 2, the gas
supply ports 121 of the showerhead electrode 101 are arranged in a
number of concentric radial zones 101 A, 101B, 101C facing toward
the upper plasma generation volume 103. The gas supply ports 121
within each concentric radial zone 101A, 101B, 101C are plumbed to
a respective gas flow control device 201A, 201B, 201C, such that
supply of the plasma process gas to each concentric radial zone
101A, 101B, 101C is independently controllable. It should be
appreciated that the independent control of the plasma process gas
supply to the multiple concentric gas supply zones 101A, 101B, 101C
of the showerhead electrode 101 provides for increased
center-to-edge plasma uniformity control. Although the example
embodiment of FIG. 2 shows three concentric gas supply zones 101A,
101B, 101C, it should be understood that the showerhead electrode
101 can be defined to include more or less independently
controllable gas supply zones. For example, in another embodiment,
the showerhead electrode 101 is defined to include two
independently controllable concentric gas supply zones.
[0037] As previously discussed, the showerhead electrode 101 forms
an upper surface of the upper plasma generation volume 103, with
the gas distribution unit 115 forming the lower surface of the
upper plasma generation volume 103. In one embodiment, the gas
distribution unit 115 provides a ground electrode for the upper
plasma generation volume 103. In one embodiment, the showerhead
electrode 101 and the gas distribution unit 115 form an approximate
one-to-one power-to-ground surface area.
[0038] In the embodiment of FIG. 1 with the showerhead electrode
101, the upper plasma chamber 112 is a capacitively coupled plasma
chamber. In this embodiment, a vertical distance across the upper
plasma generation volume 103, as measured perpendicularly between
the lower surface of the showerhead electrode 101 and the upper
surface of the gas distribution unit 115, is set within a range
extending from about 1 cm to about 5 cm. In one embodiment, this
vertical distance across the upper plasma generation volume 103 is
about 2 cm. In another embodiment, the showerhead electrode 101 can
be functionally replaced by an induction coil, such that the upper
plasma chamber 112 is an inductively coupled plasma chamber. In
this embodiment, the vertical distance across the upper plasma
generation volume 103 can be up to about 12 cm.
[0039] The lower plasma chamber 114 is formed in part by an outer
structural member 106 defined around a periphery of the lower
plasma chamber 114. In one embodiment, the outer structural member
106 of the lower plasma chamber 114 is rigidly connected to the
outer structural member 104 of the upper plasma chamber 112 by a
number of structural linking members, such that the outer
structural member 106 of the lower plasma chamber 114 effectively
hangs from the top plate 100A by way of the outer structural member
104 of the upper plasma chamber 112. In this embodiment, the
structural linking members can extend through the exhaust channel
125, but are defined to avoid adverse disruption of fluid flow
through the exhaust channel 125.
[0040] The gas distribution unit 115 is disposed between the upper
plasma generation volume 103 and the lower plasma generation volume
109. The gas distribution unit 115 is defined as a plate formed to
separate the upper plasma generation volume 103 from the lower
plasma generation volume 109, such that an upper surface of the gas
distribution unit 115 plate provides a lower boundary of the upper
plasma generation volume 103, and such that a lower surface of the
gas distribution unit 115 plate provides an upper boundary of the
lower plasma generation volume 109.
[0041] The gas distribution unit 115 is held in a fixed position by
the outer structural member 106 of the lower plasma chamber 114.
The gas distribution unit 115 is defined to supply a plasma process
gas to the lower plasma generation volume 109 through an
arrangement of gas supply ports 119. The gas distribution unit 115
is further defined to include an arrangement of through-holes 117
to provide controlled fluid communication between the upper plasma
generation volume 103 and the lower plasma generation volume 109.
Each of the through-holes 117 extends through the gas distribution
unit 115 plate from its upper surface to its lower surface.
[0042] FIG. 3A shows a bottom view of the gas distribution unit
115, in accordance with one embodiment of the present invention.
Each of the gas supply ports 119 and through-holes 117 are defined
in open fluid communication through the lower surface of the gas
distribution unit 115. The arrangement of gas supply ports 119 is
interspersed between the arrangement of through-holes 117. The gas
supply ports 119 are plumbed through the gas distribution unit 115
to one or more plasma process gas supply sources 118, such that no
direct fluid communication exists between the gas supply ports 119
and the through-holes 117 within the gas distribution unit 115.
[0043] FIG. 3B shows a top view of the gas distribution unit 115,
in accordance with one embodiment of the present invention. Each of
the through-holes 117 is defined in open fluid communication
through the upper surface of the gas distribution unit 115.
However, the gas supply ports 119 are not fluidly exposed through
the upper surface of the gas distribution unit 115. Therefore, the
gas supply ports 119 are defined to flow plasma process gas into
only the lower plasma generation volume 109. In contrast, the
through-holes 117 are defined to enable fluid communication between
the upper and lower plasma generation volumes 103/109. Fluid flow
through the through-holes 117 of the gas distribution unit 115 is
controlled primarily by a pressure differential between the upper
plasma generation volume 103 and the lower plasma generation volume
109.
[0044] It should be understood that the gas distribution unit 115
serves as a RF return path electrode, plasma process gas manifold,
fluid flow baffle plate, and ion filter. In various embodiments the
gas distribution unit 115 can be formed of metal that is a good
conductor of electricity and heat, and that is chemically
compatible with the processes to be conducted in the upper and
lower plasma generation volumes 103/109, such as aluminum,
stainless steel, silicon, silicon carbide, silicon oxide, yttrium
oxide, or essentially any other material that provides adequate
plasma resistance, electrical conduction, and thermal conduction
for the plasma processes to which it is exposed.
[0045] In various embodiments, the gas distribution unit 115 is
connected to its own DC bias source 124 and/or RF power source 122
to enable the gas distribution unit 115 to provide an appropriate
ground return path for the RF power sources 105 and 111, while also
providing appropriate bias to affect ions generated in the upper
plasma generation volume 103. The RF power source 122 can also be
defined to provide RF power at multiple frequencies. Additionally,
in one embodiment, electrodes 130 are embedded within the gas
distribution unit 115 and are connected to the DC bias source 124
to provide bias voltage for influencing ions generated in the upper
plasma generation volume 103. In one embodiment, the embedded
electrodes 130 within the gas distribution unit 115 are defined
around the through-holes 117, such that bias voltage applied to the
embedded electrodes 130 can be used to either accelerate or
decelerate ions passing through the through-holes 117. Also, in one
embodiment, the embedded electrodes 130 within the gas distribution
unit 115 are defined in multiple separately controllable zones,
with each zone connected to its own DC bias source 124. This
embodiment enables independent regional biasing across the gas
distribution unit 115, to provide for independent regional ion
control across the gas distribution unit 115.
[0046] In one embodiment, portions of the gas distribution unit 115
that are exposed to plasma in either the upper or lower plasma
generation volumes 103/109 are protected by a covering of plasma
resistant material. In one embodiment, the plasma resistant
material is formed as a coating. In another embodiment, the plasma
resistant material is formed as a protective structure, e.g.,
plate, that conformally covers the gas distribution unit 115. In
either of these embodiments, the plasma resistant material is
secured to the gas distribution unit 115 to ensure adequate
electrical and thermal conduction between the plasma resistant
material and the gas distribution unit 115. In the embodiment of
the plasma resistant protective structure, the protective structure
may be secured to the gas distribution unit 115 by a pressure
differential between the upper and lower plasma generation volumes
103/109, by a number of fasteners, or by a combination thereof. In
various embodiments, the plasma resistant coating/protective
structure used to protect the gas distribution unit 115 can be
formed of silicon, silicon carbide, silicon oxide, yttrium oxide,
or essentially any other material that provides adequate plasma
resistance, electrical conduction, and thermal conduction for the
plasma processes to which it is exposed.
[0047] The gas distribution unit 115 is defined as a swappable
component. Different versions/configurations of the gas
distribution unit 115 can be defined to have different arrangements
of the gas supply ports 119 and through-holes 117. Additionally, in
the event that plasma deteriorates the gas distribution unit 115 or
its functionality, the gas distribution unit 115 can be
replaced.
[0048] Each of the gas supply ports 119 and through-holes 117 is
defined to optimize fluid flow through it, while simultaneously
preventing adverse intrusion of plasma into it. Fluid flow and
plasma intrusion through/into each of the gas supply ports 119 and
though-holes 117 is directly proportional to its size. Therefore,
it is necessary to define each of the gas supply ports 119 and
though-holes 117 such that its size is small enough to prevent
adverse plasma intrusion into it, while remaining large enough to
provide adequate fluid flow through it. In various embodiments, the
diameter of the gas supply ports 119 is sized within a range
extending from about 0.1 mm to about 3 mm. In various embodiments,
the diameter of the through-holes 117 is sized within a range
extending from about 0.5 mm to about 5 mm. It should be understood,
however, that in various embodiments the gas supply ports 119 and
through-holes 117 can be respectively defined with essentially any
diameter size, so long as the diameter size provides for adequate
fluid flow there through while simultaneously providing for
adequate suppression of plasma intrusion therein.
[0049] Because the fluid flow pressure to the gas supply ports 119
is directly controllable, it is possible to define the gas supply
ports 119 to have a small enough size to essentially prevent plasma
intrusion into the gas supply ports 119. However, it is appropriate
to avoid defining the gas supply ports 119 so small as to cause
supersonic fluid flow through the gas supply ports 119. To avoid
supersonic fluid flow from the gas supply ports 119, the gas supply
ports 119 can be defined to have a diffuser shape at their exit
from the lower surface of the gas distribution unit 115. FIG. 3C
shows a gas supply port 119 cross-section, in accordance with one
embodiment of the present invention. The gas supply port 119 is
shown to have a diffuser shape 307 at its exit location from the
gas distribution unit 115.
[0050] The gas distribution unit 115 includes interior gas supply
channels 126 fluidly connected to the arrangement of gas supply
ports 119. These interior gas supply channels 126 are fluidly
connected to one or more plasma process gas supply sources 118. It
should be understood that the interior gas supply channels 126 and
associated gas supply ports 119 are defined between the arrangement
of through-holes 117 such that the plasma process gas is
distributed to the lower plasma generation volume 109 and is not
distributed to the upper plasma generation volume 103. In one
embodiment, the plasma process gas supply sources 118 for the lower
plasma generation volume 109 are separate from the plasma process
gas supply sources 116 for the upper plasma generation volume 103,
such that flow rates of plasma process gases to the upper and lower
plasma generation volumes 103/109 are independently controllable.
In one embodiment, one or more shared plasma process gas supply
sources can be used for both the upper and lower plasma generation
volumes 103/109. However, in this embodiment, the plasma process
gas flows from each shared plasma process gas supply is separately
controlled for each of the upper and lower plasma generation
volumes 103/109, respectively. Also, it should be understood that
in some embodiments the gas supply sources 118 represent multiple
gas supplies and/or gas boxes that provide for selection of
appropriate gases and/or gas mixtures for flow through the gas
distribution unit 115.
[0051] In one embodiment, such as depicted in FIG. 3A, the interior
gas supply channels 126 within the gas distribution unit 115 are
defined to fluidly separate the arrangement of gas supply ports 119
into multiple concentric regions/zones 115A, 115B, 115C across the
lower surface of the gas distribution unit 115, such that flow
rates of the plasma process gas to the gas supply ports 119 within
each of the multiple concentric regions/zones 115A, 115B, 115C can
be separately controlled. In one embodiment, the gas supply ports
119 within each concentric radial region/zone 115A, 115B, 115C are
plumbed to a respective gas flow control device 305A, 305B, 305C,
such that supply of the plasma process gas to each concentric
radial region/zone 115A, 115B, 115C is independently
controllable.
[0052] Separation of the gas supply ports 119 into independently
controllable multiple concentric regions/zones 115A, 115B, 115C
provides for center-to-edge gas supply control within the lower
plasma generation volume 109, which in turn facilitates
center-to-edge plasma uniformity control within the lower plasma
generation volume 109. Although the example embodiment of FIG. 3A
shows three concentric gas supply regions/zones 115A, 115B, 115C,
it should be understood that the gas distribution unit 115 can be
defined to include more or less independently controllable gas
supply regions/zones. For example, in another embodiment, the gas
distribution unit 115 is defined to include two independently
controllable concentric gas supply regions/zones.
[0053] In one embodiment, the number of through-holes 117 is larger
than the number gas supply ports 119, to provide for adequate
radical/neutral flow from the upper plasma generation volume 103 to
the lower plasma generation volume 109. Also, the through-holes 117
can be defined to have a larger size than the gas supply ports 119,
to provide for adequate radical/neutral flow from the upper plasma
generation volume 103 to the lower plasma generation volume 109.
However, as previously discussed, the size of the through-holes 117
is limited to prevent adverse plasma intrusion from either the
upper or lower plasma generation volumes 103/109 into the
through-holes 117.
[0054] In one embodiment, some or all of the through-holes 117 are
defined to extend at an angle through the gas distribution unit.
FIG. 3D shows a cross-section of a through-hole 117 defined to
extend through the gas distribution unit 115 and an angle 303, in
accordance with one embodiment of the present invention. The
through-hole 117 is defined to extend from the upper surface 302 of
the gas distribution unit 115 to the lower surface 304 of the gas
distribution unit 115 at the angle 303 offset from a reference
direction 301 that extends perpendicularly between the upper and
lower surfaces 302/304 of the gas distribution unit 115.
[0055] The through-holes 117 are angled to increase the probability
that charged constituents, i.e., ions, within the upper plasma
generation volume 103 will encounter the electrically grounded gas
distribution unit 115 as they travel through the through-hole 117,
so as to be removed from radical/neutral flux passing through the
gas distribution unit 115 by way of the through-holes 117. In one
embodiment, the angle 303 is sufficiently large to prevent an
uninterrupted line-of-sight within the through-hole 117 through the
gas distribution unit 115 in the reference direction 301.
[0056] In one embodiment, all through-holes 117 within the gas
distribution unit 115 are angled to ensure that essentially none of
the ions generated within the upper plasma generation volume 103
are allowed to pass through the gas distribution unit 115 to the
lower plasma generation volume 109. This embodiment provides for an
essentially pure radical/neutral flux introduction into the lower
plasma generation volume 109 by way of the through-holes 117. In
another embodiment, a portion of the through-holes 117 are angled
with a remainder of through-holes 117 defined to extend in a
substantially straight manner coincident with the reference
direction 301. This embodiment provides for some ions to be mixed
with the radical/neutral flux that flows from the upper plasma
generation volume 103 to the lower plasma generation volume 109. In
this embodiment, the number and distribution of straight
through-holes 117 relative to angled through-holes 117 can be
defined to achieve a desired ion concentration within the
radical/neutral flux.
[0057] In one embodiment, a flow control plate is disposed on the
upper surface of the gas distribution unit 115 to control which
through-holes 117 are exposed to the upper plasma generation volume
103. FIG. 4A shows a flow control plate 401 disposed on the upper
surface 302 of the gas distribution unit 115, in accordance with
one embodiment of the present invention. In one embodiment, the
flow control plate 401 is defined as a disc having a thickness 403
within a range extending from about 3 mm to about 6 mm. The flow
control plate 401 disc is defined to have a diameter sufficient to
cover the through-holes 117 through which flow is to be controlled.
In one embodiment, the flow control plate 401 disc is defined to
have a diameter that covers the upper surface of the gas
distribution unit 115 so as to maintain a uniform exposure of the
plasma in the upper plasma generation volume 103 to the RF return
path provided by the gas distribution unit 115.
[0058] In one embodiment, the flow control plate 401 is formed of
an electrically and thermally conductive material, and is secured
to the gas distribution unit 115 to ensure adequate electrical and
thermal conduction between the flow control plate 401 and the gas
distribution unit 115. In one embodiment, the flow control plate
401 may be secured to the gas distribution unit 115 by a pressure
differential between the upper and lower plasma generation volumes
103/109, by a number of fasteners, or by a combination thereof.
Also, in various embodiments, the flow control plate 401 can be
covered and protected by a plasma resistant coating such as that
discussed above with regard to the gas distribution unit 115.
[0059] In one embodiment, multiple patterns of holes are defined
through the flow control plate 401. Each of the multiple patterns
of holes within the flow control plate 401 aligns with a different
set of through-holes 117 within the gas distribution unit 115.
Disposal of the flow control plate 401 on the upper surface of the
gas distribution unit 115 at a particular rotational position of
the flow control plate 401 relative to the upper surface of the gas
distribution unit 115 corresponds to alignment of a particular one
of the multiple patterns of holes within the flow control plate 401
with its corresponding set of through-holes 117 within the gas
distribution unit 115. Each of the multiple patterns of holes that
extends through the flow control plate 401 is defined to expose a
different number or a different spatial pattern of through-holes
117 within the gas distribution unit 115. Therefore,
radical/neutral flow through the flow control plate 401, and hence
through the gas distribution unit 115, can be controlled by setting
the flow control plate 401 at a particular rotational position
relative to the upper surface of the gas distribution unit 115.
[0060] In one embodiment, the flow control plate 401 is defined to
include a pattern of holes that provides for shutoff of the
through-holes 117 that extend straight through the gas distribution
unit 115 in the reference direction 301, thereby enabling shutoff
of ion flow through the gas distribution unit 115. FIG. 4B shows a
top view of the flow control plate 401 positioned such that a hole
405 pattern defined therein allows for flow through all
through-holes 117 defined within the underlying gas distribution
unit 115, in accordance with one embodiment of the present
invention. FIG. 4C shows a top view of the flow control plate 401
positioned such that the hole 405 pattern defined therein allows
for flow through only angled through-holes 117 defined within the
underlying gas distribution unit 115, in accordance with one
embodiment of the present invention. Also, in other embodiments,
the multiple patterns of holes 405 in the flow control plate 401
are defined to provide for different spatial patterns of
radical/neutron flow through the gas distribution unit 115.
[0061] FIG. 4D shows a top view of a flow control plate assembly
401A defined by a number of concentric rotatable flow control
plates 407A, 407B, 407C, in accordance with one embodiment of the
present invention. Each concentric rotatable flow control plate
407A, 407B, 407C can be set independently to provide center-to-edge
control over which through-holes 117 are open or closed within the
gas distribution unit 115. Specifically, the flow control plate
assembly 401A includes a central disc 407A and a number of
concentric rings 407B/407C, disposed in a concentric manner on the
upper surface of the gas distribution unit 115. It should be
understood that the particular configuration of FIG. 4D is provided
by way of example. Other embodiments may include a different number
of concentric rotatable flow control plates than what is shown in
FIG. 4D.
[0062] Each of the central disc 407A and the number of concentric
rings 407B/407C respectively include multiple patterns of holes
405A/405B/405C extending there through.
[0063] Each of the multiple patterns of holes 405A/405B/405C aligns
with a different set of through-holes 117 within the gas
distribution unit 115, such that disposal of each of the central
disc 407A and the concentric rings 407B/407C on the upper surface
of the gas distribution unit 115, at a particular rotational
position relative to the upper surface of the gas distribution unit
115, corresponds to alignment of a particular one of the multiple
patterns of holes 405A/405B/405C with its corresponding set of
through-holes 117 within the gas distribution unit 115. Each of the
multiple patterns of holes 405A/405B/405C extending through the
central disc 407A and the concentric rings 407B/407C is defined to
expose a different number or a different spatial pattern of
through-holes 117 within the gas distribution unit 115.
[0064] With reference back to FIG. 1, a chuck 107 is disposed
within the interior cavity 100D of the chamber 100 below the lower
plasma generation volume 109. In one embodiment, the chuck 107 is
cantilevered from the wall 100C of the chamber 100. In one
embodiment, the chuck 107 is an electrostatic chuck and provides an
electrode for transmitting RF power to the lower plasma generation
volume 109. The chuck 107 is defined to hold a substrate 113, i.e.,
wafer 113, in exposure to the lower plasma generation volume 109.
In one embodiment, a wafer edge ring 149 is disposed on the chuck
107 about the periphery of a substrate 113 receiving/holding area
on the chuck 107. In various embodiments, the wafer edge ring is
formed of quartz or silicon. Also, in one embodiment, a conductor
148 is disposed below the wafer edge ring 149, and is connected to
drive DC bias through the wafer edge ring 149. The chuck 107 is
also defined to include a configuration of cooling channels and/or
heating elements, so as to enable temperature control of the
substrate 113 and the lower plasma generation volume 109.
[0065] The chuck 107 is defined to move vertically within the
interior cavity 100D, as indicated by arrows 123. In this manner,
the chuck 107 can be lowered to receive/provide the substrate 113
through the gate valve 102, and can be raised to form the lower
surface of the lower plasma generation volume 109. Also, a vertical
distance across the lower plasma generation volume 109, as measured
perpendicular to both the chuck 107 and the gas distribution unit
115, can be set and controlled by controlling the vertical position
of the chuck 107. The vertical distance across the lower plasma
generation volume 109 can be set to achieve a sufficient
center-to-edge plasma uniformity and density, and can also be set
to avoid printing on the wafer 113 by jets of gas flowing from the
gas supply ports 119 and/or through-holes 117. In various
embodiments, the vertical distance across the lower plasma
generation volume 109 can be set within a range extending from
about 1 cm to about 5 cm, or from about 2 cm to about 3.6 cm.
[0066] The chuck 107 is further defined to supply RF power from an
RF power source 111 to the lower plasma generation volume 109, such
that chuck 107 serves as an electrode for the lower plasma
generation volume 109. It should be understood that the RF power
source 111 of the lower plasma chamber is separate and independent
from the RF power source 105 of the upper plasma chamber.
Therefore, the RF power supplied to the upper and lower plasma
generation volumes 103/109 can be separately and independently
controlled. In one embodiment, the RF power source 111 is defined
to provide RF power and multiple frequencies. For example, the RF
power source 111 can be defined to provide RF power at frequencies
of 2 MHz, 27 MHz, and 60 MHz. It should be understood that each of
the RF power sources 105/111 for the upper and lower plasma
chambers 112/114, respectively, are connected through their own
matching networks to enable transmission of the RF power to the
showerhead electrode 101 and the chuck 107, respectively. As
previously discussed, in one embodiment, the gas distribution unit
115 serves as a reference ground electrode in the RF power return
path for both the upper and lower plasma generation volumes
103/109.
[0067] The upper plasma chamber is defined to include an exhaust
channel 125 through which gases within the upper plasma generation
volume 103 are exhausted into the interior cavity 100D of the
chamber 100. The exhaust channel 125 is defined to circumscribe the
upper plasma generation volume 103 outside a radial periphery of
the showerhead electrode 101 and outside of a radial periphery of
the gas distribution unit 115. In this configuration, the exhaust
channel 125 extends in a radial direction between a lower surface
of the outer structural member 104 of the upper plasma chamber and
upper surfaces of both the gas distribution unit 115 and outer
structural member 106 of the lower plasma chamber.
[0068] A pressure throttle ring 127 is defined to move within the
exhaust channel 125 to throttle a fluid flow, i.e., flow of gases,
from the upper plasma generation volume 103 through the exhaust
channel 125 to the interior cavity 100D of the chamber 100. In one
embodiment, the pressure throttle ring 127 is defined to move
vertically within a conformally defined recessed region within the
outer structural member 104 of the upper plasma chamber 112. In
this embodiment, the pressure throttle ring 127 can be moved in a
controlled manner down into the exhaust channel 125 to reduce a
flow area through the exhaust channel 125 and thereby throttle the
fluid flow from the upper plasma generation volume 103. In one
embodiment, the pressure throttle ring 127 is defined to enable a
complete shutoff of flow from the upper plasma generation volume
103 through the exhaust channel 125 into the interior cavity 100D
of the chamber 100.
[0069] It should be understood that the pressure throttle ring 127
configuration depicted in FIG. 1 is one example embodiment of its
implementation. In other embodiments, the pressure throttle ring
127 can be implemented in different ways, so long as the pressure
throttle ring 127 provides for control of fluid flow through the
exhaust channel 125. Also, in one embodiment, a pressure manometer
is disposed to measure the pressure within the upper plasma
generation volume 103. In this embodiment, this measured pressure
within the upper plasma generation volume 103 is used to generate
feedback signals for controlling the position of the pressure
throttle ring 127, which in turn provides active control of the
pressure within the upper plasma generation volume 103.
[0070] The lower plasma chamber is defined to include a set of
slotted exhaust channels 129 through which gases within the lower
plasma generation volume 109 are exhausted into the interior cavity
100D of the chamber 100. The set of slotted exhaust channels 129 is
defined to circumscribe the lower plasma generation volume 109
outside a radial periphery of the chuck 107 and outside of a radial
periphery of the gas distribution unit 115. In one embodiment, as
depicted in FIG. 1, the set of slotted exhaust channels 129 is
defined in a horizontally oriented portion of the outer structural
member 106 of the lower plasma chamber 114 located at a vertical
position near a top surface of the chuck 107 upon which the
substrate 113 is held. In this embodiment, the set of slotted
exhaust channels 129 extends vertically through the horizontally
oriented portion of the outer structural member 106 of the lower
plasma chamber 114.
[0071] A pressure control ring 131 is defined to move toward and
away from the set of slotted exhaust channels 129 to throttle a
fluid flow, i.e., flow of gases, from the lower plasma generation
volume 109 through the set of slotted exhaust channels 129 into the
interior cavity 100D of the chamber 100. In one embodiment, the
pressure control ring 131 is defined as a horizontally oriented
annular-shaped disc which is movable in a vertical direction toward
and away from the set of slotted exhaust channels 129. The pressure
control ring 131 is defined to cover the set of slotted exhaust
channels 129 (on the interior cavity 100D side) when placed against
the set of slotted exhaust channels 129, i.e., when placed against
a lower surface of the horizontally oriented portion of the outer
structural member 106 within which the set of slotted exhaust
channels 129 is formed.
[0072] Fluid flow from the lower plasma generation volume 109
through the set of slotted exhaust channels 129 to the interior
cavity 100D of the chamber 100 can be throttled, i.e., controlled,
through vertical movement of the pressure control ring 131 toward
and away from the set of slotted exhaust channels 129. In one
embodiment, the pressure control ring 131 is defined to enable a
complete shutoff of flow from the lower plasma generation volume
109 through the set of slotted exhaust channels 129 into the
interior cavity 100D of the chamber 100. Also, in one embodiment, a
pressure manometer is disposed to measure the pressure within the
lower plasma generation volume 109. In this embodiment, this
measured pressure within the lower plasma generation volume 109 is
used to generate feedback signals for controlling the position of
the pressure control ring 131, which in turn provides active
control of the pressure within the lower plasma generation volume
109.
[0073] It should be understood that both the upper plasma chamber
112 and the lower plasma chamber 114 enclose respective confined
plasmas. A confined plasma is beneficial in that its residence time
can be controlled by controlling volume, pressure, and flow within
the plasma region, i.e., within the upper and lower plasma
generation volumes 103/109. The plasma residence time affects the
dissociation process, which is a factor in radical/neutron
formation. The upper and lower plasma generation volumes 103/109
are small and well-controlled with regard to pressure and
temperature.
[0074] As previously discussed, the upper and lower plasma chambers
112/114 have their own respective RF power sources/controls,
pressure controls, temperature controls, plasma process gas
sources/controls, and gas flow controls. In various embodiments, a
pressure within the upper plasma processing volume 103 can be
controlled within a range extending from about 100 mTorr to about 1
Torr, or from about 200 mTorr to about 600 mTorr. In various
embodiments, a pressure within the lower plasma processing volume
109 can be controlled within a range extending from about 5 mTorr
to about 100 mTorr, or from about 10 mTorr to about 30 mTorr.
[0075] FIG. 5 shows the chamber 100 of FIG. 1 with an upper plasma
501 and a lower plasma 503, in accordance with one embodiment of
the present invention. The process gases from the upper plasma 501
are exhausted from the upper plasma generation volume 103 through
the exhaust channel 125 into the interior cavity 100D of the
chamber 100, as indicated by arrows 505. The process gases from the
lower plasma 503 are exhausted from the lower plasma generation
volume 109 through the set of slotted exhaust channels 129 into the
interior cavity 100D of the chamber 100, as indicated by arrows
507. Process gases are exhausted from the interior cavity 100D of
the chamber 100 through the exhaust port 135 as indicated by arrow
509.
[0076] It should be understood that the independent control of the
upper and lower plasma chambers 112/114 provides for extensive
possibilities with regard to wafer processing recipes, particularly
concerning the independent control of radical/neutral flux relative
to ion flux. A couple of example wafer processes are provided
below. However, it should be understood that the example wafer
processes disclosed herein are provided as examples only and in no
way represent any limitation on use of the dual plasma processing
chamber 100 disclosed herein.
[0077] In one example embodiment, the chamber 100 is used to
perform a wafer process that utilizes high fluorine radical/neutral
flux with low dissociation of CxFy (C4F8, C4F6, etc.) in the wafer
processing plasma. In this example embodiment, a mixture of Ar and
NF3 is supplied as the plasma process gas to the upper plasma
generation volume 103. The upper plasma generation volume 103 is
operated at high pressure and high RF frequency (60 MHz). The high
fluorine radical/neutral flux is generated in the upper plasma
generation volume 103 and is flowed through the through-holes 117
of the gas distribution unit 115. The ions generated in the upper
plasma processing volume 103 are filtered by the gas distribution
unit 115.
[0078] Also, in this example embodiment, a mixture Ar and CxFy gas
is supplied as the plasma process gas to the lower plasma
generation volume 109. The lower plasma generation volume 109 is
operated at low pressure and low to medium RF frequency (2 MHz and
27 MHz). The low RF frequency of the lower plasma generation volume
109 corresponds to low dissociation of CxFy in the plasma exposed
to the wafer 113. It should be appreciated that the high power
required in the upper plasma generation volume 103 to generate the
necessary fluorine radical/neutral flux would cause high
dissociation of CxFy if applied to the lower plasma generation
volume 109. Therefore, the dual plasma chamber 100 enables
performance of the above described process.
[0079] In another example embodiment, the chamber 100 is used to
perform a wafer process that utilizes high dissociation of CxFy
(C4F8, C4F6, etc.) in a high pressure volume with a high density Ar
plasma in a low pressure volume. In this example embodiment, a
mixture of CxFy and Ar is supplied as the plasma process gas to the
upper plasma generation volume 103. The upper plasma generation
volume 103 is operated at high pressure and high RF frequency (60
MHz) to cause high dissociation of CxFy. The highly dissociated
CxFy generated in the upper plasma generation volume 103 flows
through the through-holes 117 of the gas distribution unit 115. The
ions generated in the upper plasma processing volume 103 are
filtered by the gas distribution unit 115. Also, in this example
embodiment, Ar gas is supplied as the plasma process gas to the
lower plasma generation volume 109. The lower plasma generation
volume 109 is operated at low pressure and low to medium RF
frequency (2 MHz and 27 MHz) to generate a high density Ar plasma
with high ion flux.
[0080] In one operational embodiment, the pressure control ring 131
of the lower plasma chamber 114 is closed, and the upper plasma
chamber 112 is set in an exhaust only configuration. In this
embodiment, a plasma is not generated in the upper plasma
generation volume 103. In this embodiment, plasma process gas flows
through the gas supply ports 119 of the gas distribution unit 115
into the lower plasma generation volume 109. Also in this
embodiment, plasma process gas exhausts from lower plasma
generation volume 109 through the through-holes 117 of the gas
distribution unit 115 into the upper plasma generation volume 103,
and then out the exhaust channel 125 into the interior cavity 100D
of the chamber 100.
[0081] This operational embodiment provides for axial pump in and
pump out of plasma process gases to/from the lower plasma
generation volume 109. In this embodiment, accurate pressure
uniformity control can be achieved across the wafer 113, because
gases are pumped out vertically as opposed to radially. It should
be appreciated that radial pump out of exhaust gases causes a
radial pressure distribution across wafer 113. This embodiment also
allows for accurate control of residence time in low flow
applications, such as atomic layer deposition or atomic layer
etching in which short plasma residence time, e.g., less than a
millisecond, is required.
[0082] It should be appreciated that the dual plasma chamber 100 is
defined to decouple radical/neutral flux generation/application
from ionic plasma generation/application. Also, in one embodiment,
the lower plasma chamber 114 can be inactive, i.e., exhaust only,
such that radical/neutral flux from the upper plasma chamber 112
can be applied to the wafer 113 without exposing the wafer 113 to a
plasma.
[0083] While this invention has been described in terms of several
embodiments, it will be appreciated that those skilled in the art
upon reading the preceding specifications and studying the drawings
will realize various alterations, additions, permutations and
equivalents thereof. It is therefore intended that the present
invention includes all such alterations, additions, permutations,
and equivalents as fall within the true spirit and scope of the
invention.
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