U.S. patent application number 11/060980 was filed with the patent office on 2005-11-03 for alternating asymmetrical plasma generation in a process chamber.
This patent application is currently assigned to Applied Materials, Inc.. Invention is credited to Hatcher, Brian K., Holland, John P., Kropewnicki, Thomas J., Nguyen, Huong Thanh, Paterson, Alexander, Pavel, Elizabeth G., Todorow, Valentin N..
Application Number | 20050241762 11/060980 |
Document ID | / |
Family ID | 35353132 |
Filed Date | 2005-11-03 |
United States Patent
Application |
20050241762 |
Kind Code |
A1 |
Paterson, Alexander ; et
al. |
November 3, 2005 |
Alternating asymmetrical plasma generation in a process chamber
Abstract
Embodiments of the invention generally provide etch or CVD
plasma processing methods and apparatus used to generate a uniform
plasma across the surface of a substrate by modulation pulsing the
power delivered to a plurality of plasma controlling devices found
in a plasma processing chamber. The plasma generated and/or
sustained in the plasma processing chamber is created by the one or
more plasma controlling devices that are used to control, generate,
enhance, and/or shape the plasma during the plasma processing steps
by use of energy delivered from a RF power source. Plasma
controlling devices may include, for example, one or more coils
(inductively coupled plasma), one or more electrodes (capacitively
coupled plasma), and/or any other energy inputting device such as a
microwave source.
Inventors: |
Paterson, Alexander; (San
Jose, CA) ; Pavel, Elizabeth G.; (San Jose, CA)
; Todorow, Valentin N.; (Palo Alto, CA) ; Nguyen,
Huong Thanh; (San Ramon, CA) ; Kropewnicki, Thomas
J.; (San Mateo, CA) ; Hatcher, Brian K.; (San
Jose, CA) ; Holland, John P.; (San Jose, CA) |
Correspondence
Address: |
MOSER, PATTERSON & SHERIDAN, LLP
APPLIED MATERIALS, INC.
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Assignee: |
Applied Materials, Inc.
|
Family ID: |
35353132 |
Appl. No.: |
11/060980 |
Filed: |
February 18, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60566718 |
Apr 30, 2004 |
|
|
|
Current U.S.
Class: |
156/345.28 ;
216/67 |
Current CPC
Class: |
H01J 37/321 20130101;
H01J 37/32146 20130101; H01J 37/32165 20130101; H01J 37/32082
20130101; H01J 37/32091 20130101 |
Class at
Publication: |
156/345.28 ;
216/067 |
International
Class: |
C23F 001/00 |
Claims
1. A plasma chamber for plasma processing a substrate, comprising:
a first plasma controlling device in communication with a
processing region of a plasma chamber, wherein the first plasma
controlling device is connected to a first RF power source; a
second plasma controlling device in communication with the
processing region of the plasma chamber, wherein the second plasma
controlling device is connected to a second RF power source; and a
controller adapted to synchronize the amplitude modulation of the
RF power delivered to the first plasma controlling device and the
second plasma controlling device such that the shape of the
amplitude modulated waveform and overlap in time of the RF power
supplied to the first and second plasma controlling devices is
controlled to improve the uniformity of the plasma process
completed on a substrate mounted in the processing region.
2. The plasma chamber of claim 1, wherein the controller, the first
RF power source, and the second RF power source modulate the
amplitude of the RF power, and wherein modulating the amplitude of
the RF power includes synchronizing the RF power delivered to the
first and second plasma controlling devices, controlling the ratio
of power delivered to the first and second plasma controlling
devices, and controlling the shape and duration of the amplitude
modulated power.
3. The plasma chamber of claim 1, wherein the shape of the
amplitude modulated RF power supplied to the first and second
plasma controlling devices, is rectangular in shape, trapezoidal in
shape, triangular in shape or sinusoidal in shape.
4. The plasma chamber of claim 1, wherein the amplitude modulated
RF power is rectangular in shape and the amplitude modulated RF
power supplied to the second plasma controlling devices is at 0
Watts when the first plasma controlling device is at a power level
greater than 0 Watts, and the amplitude modulated RF power supplied
to the first plasma controlling devices is 0 Watts when the second
plasma controlling device is at a power level greater than 0
Watts.
5. The plasma chamber of claim 1, wherein the amplitude modulated
RF power is rectangular in shape and the amplitude modulated RF
power supplied to the first plasma devices and the second plasma
controlling device overlap an amount less than the full pulse
width.
6. The plasma chamber of claim 1, wherein the controller, the first
RF power source, and the second RF power source control the
interaction of the plasma generated by the first and second plasma
controlling devices by varying the frequency of the amplitude
modulations of the RF power.
7. The plasma chamber of claim 1, wherein the overlap in time is a
rest time between the amplitude modulations of the RF power.
8. The plasma chamber of claim 1, wherein the first plasma
controlling device is an inductive coil, an electrode or a
torroidal source.
9. The plasma chamber of claim 1, wherein the second plasma
controlling device is an inductive coil, an electrode or a
torroidal source.
10. The plasma chamber of claim 1, further comprising a pedestal
that is adapted to support the substrate, wherein the pedestal is
connected to a third RF power source that is capable of amplitude
modulation of the RF power delivered to the pedestal.
11. The plasma chamber of claim 10, further comprising a fourth RF
power source connected to the pedestal that is capable of amplitude
modulation of the RF power delivered to the pedestal, wherein the
RF frequency of the fourth RF power source is greater than the RF
frequency of the third RF power source.
12. A plasma chamber for processing a substrate, comprising: a
first plasma controlling device connected to a first RF power
source that is capable of amplitude modulation of the RF power
delivered to the first plasma controlling device; a second plasma
controlling device connected to a second RF power source that is
capable of amplitude modulation of the RF power delivered to the
second plasma controlling device; a third plasma controlling device
connected to a third RF power source that is capable of amplitude
modulation of the RF power delivered to the third plasma
controlling device; and a controller adapted to synchronize the
amplitude modulation of the RF power delivered to the first plasma
controlling device, the second plasma controlling device and the
third plasma controlling device such that the shape of the
amplitude modulated waveform and overlap in time of the RF power
supplied to the first, second and third plasma controlling devices
is controlled to improve the uniformity of the plasma process
completed on a substrate mounted in the processing region.
13. The plasma chamber of claim 12, wherein the first plasma
controlling device is an inductive coil, an electrode, or a
torroidal source.
14. The plasma chamber of claim 12, wherein the second plasma
controlling device is an inductive coil, an electrode, or a
torroidal source.
15. The plasma chamber of claim 12, wherein the third plasma
controlling device is a torroidal source, an inductive coil, or a
electrode.
16. The plasma chamber of claim 12, further comprising a pedestal
that is adapted to support the substrate, wherein the pedestal is
connected to a fourth RF power source that is capable of amplitude
modulation of the RF power delivered to the pedestal.
17. The plasma chamber of claim 16, further comprising a fifth RF
power source connected to the pedestal that is capable of amplitude
modulation of the RF power delivered to the pedestal, wherein the
RF frequency of the fifth power source is greater than the RF
frequency of the fourth RF power source.
18. The plasma chamber of claim 12, wherein the overlap in time is
a rest time between the amplitude modulations of the RF power.
19. A method of processing a substrate in a plasma chamber,
comprising: amplitude modulating the RF power delivered to a first
plasma controlling device at a first modulation pulse frequency and
at a first power level; amplitude modulating the RF power delivered
to a second plasma controlling device at a second modulation pulse
frequency and at a second power level; synchronizing the amplitude
modulation of the RF power to the first plasma controlling device
and the second plasma controlling device; and controlling the
amplitude modulation of the RF power such that the overlap in time
and the shape of the amplitude modulated RF power delivered to the
first and second plasma controlling devices is controlled to
improve the uniformity of the process completed on the
substrate.
20. The method of claim 19, wherein the first modulation pulsing
frequency and the second modulation pulsing frequency are between
about 0.1 Hz and about 100,000 Hz.
21. The method of claim 19, wherein the first RF power level and
the second RF power level are between about 0 Watts and about 5000
Watts.
22. The method of claim 19, wherein the ratio of the first RF power
level to the second RF power level or the second RF power level to
the first RF power level is between about 1:1 and about 100:1.
23. The method of claim 19, wherein the first plasma controlling
device is an inductive coil, an electrode, or a torroidal
source.
24. The method of claim 19, wherein the second plasma controlling
device is an inductive coil, an electrode or a torroidal
source.
25. The method of claim 19, wherein the amplitude modulating of the
RF power supplied to the second plasma controlling devices is less
than the first plasma controlling device at a first time, and the
RF power supplied to the first plasma controlling devices is less
than the second plasma controlling device at a second time.
26. The method of claim 19, wherein the shape of the amplitude
modulated RF power is rectangular in shape, trapezoidal in shape,
triangular in shape or sinusoidal in shape.
27. The method of claim 19, further comprising: amplitude
modulating the RF power delivered to a third plasma controlling
device at a third modulation pulsing frequency and at a third power
level; synchronizing the amplitude modulating of the RF power to
the first, second and third plasma controlling devices; and
controlling the amplitude modulation of the RF power such that the
overlap of the amplitude modulated RF power delivered to the first,
second and third plasma controlling devices is controlled to
improve the uniformity of the process completed on the
substrate.
28. A method of processing a substrate in a plasma chamber,
comprising: generating a first torroidal path of plasma that passes
near and transverse a surface of the substrate using a first
torroidal plasma controlling device; generating a second torroidal
path of plasma that passes near and transverse a surface of the
substrate using a second torroidal plasma controlling device,
wherein the first torroidal path is not coincident to the second
torroidal path; and varying the plasma density in the vicinity of
the substrate by amplitude modulating the first torroidal path of
plasma at a first modulation pulsing frequency and a first RF power
and modulation pulsing the second torroidal path of plasma at a
second modulation pulsing frequency and a second RF power as a
function of time.
29. The method of claim 28, wherein the first modulation pulsing
frequency and the second modulation pulsing frequency are between
about 0.1 Hz and about 100,000 Hz.
30. The method of claim 28, wherein the first RF power level and
the second RF power level are between about 0 Watts and about 5000
Watts.
31. The method of claim 28, wherein the ratio of the first RF power
to the second RF power level is between about 1:1 and about
100:1.
32. A method of processing a substrate in a plasma chamber,
comprising: generating a plasma over a surface of a substrate using
a first plasma controlling device; generating a plasma over a
surface of the substrate using a second plasma controlling device,
wherein the first plasma controlling device generates a plasma in a
first region near the substrate and the second plasma controlling
device generates a plasma in a second region near the substrate and
the first and second regions overlap; and varying the plasma
density generated in the first region, in the second region, and a
region between the first and second region by amplitude modulating
the RF power delivered to the first plasma controlling device and
the second plasma controlling device.
33. The method of claim 32, wherein the first modulation pulse
frequency and the second modulation pulse frequency are between
about 0.1 Hz and about 100,000 Hz.
34. The method of claim 32, wherein the first RF power level and
the second RF power level are between about 0 Watts and about 5000
Watts.
35. The method of claim 32, wherein the ratio of the first RF power
to the second RF power ev is between about 1:1 and about 100:1.
36. The method of claim 32, wherein the first plasma controlling
device is a first inductive coil and the second plasma controlling
device is a second inductive coil.
37. The method of claim 32, wherein the first plasma controlling
device is a first electrode and the second plasma controlling
device is a second electrode.
38. The method of claim 32, wherein the first plasma controlling
device is a first torroidal source and the second plasma
controlling device is a second torroidal source.
39. A method of processing a substrate in a plasma chamber,
comprising: amplitude modulating the RF power to a first plasma
controlling device at a first modulation pulse frequency and at a
first power level; amplitude modulating the RF power to a second
plasma controlling device at a second modulation pulse frequency
and at a second power level; synchronizing the amplitude modulation
of the RF power to the first plasma controlling device and the
second plasma controlling device; and varying the first and second
modulation pulse frequencies to adjust the plasma density in a
plasma chamber to compensate for a non-uniform area on a substrate
surface.
40. A method of processing a substrate in a plasma chamber,
comprising: amplitude modulating the RF power to a first plasma
controlling device at a first modulation pulse frequency and at a
first power level; amplitude modulating the RF power to a second
plasma controlling device at a second modulation pulse frequency
and at a second power level; synchronizing the amplitude modulation
of the RF power to the first plasma controlling device and the
second plasma controlling device; and controlling the shape of the
amplitude modulated RF power to the first and second plasma
controlling devices, wherein the shape of the amplitude modulated
RF power is rectangular, trapezoidal, triangular or sinusoidal.
41. A method of processing a substrate in a plasma chamber,
comprising: amplitude modulating the RF power to a first plasma
controlling device at a first modulation pulse frequency and at a
first power level; amplitude modulating the RF power to a second
plasma controlling device at a second modulation pulse frequency
and at a second power level; synchronizing the amplitude modulation
of the RF power to the first plasma controlling device and the
second plasma controlling device, controlling the shape of the
amplitude modulated RF power to the first and second plasma
controlling devices; and controlling the overlap and/or gap between
the amplitude modulated RF power to the first plasma controlling
device and the second plasma controlling device.
42. A method of processing a substrate in a plasma chamber,
comprising: amplitude modulating the RF power to a first plasma
controlling device at a first modulation pulse frequency and at a
first power level; amplitude modulating the RF power to a second
plasma controlling device at a second modulation pulse frequency
and at a second power level; synchronizing the amplitude modulation
of the RF power to the first plasma controlling device and the
second plasma controlling device, controlling the amplitude
modulation of the RF power to the first plasma controlling device
and amplitude modulation of the RF power to the second plasma
controlling device such that the power, modulation pulse frequency,
modulation pulse duration, rest time between modulation pulses, and
overlap of the modulation pulse to the first and/or second plasma
controlling devices can be varied as a function of time.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims benefit of provisional U.S. Patent
Application Ser. No. 60/566,718, filed Apr. 30, 2004, entitled
"Alternating Asymmetrical Plasma Generation In A Process Chamber,"
[Attorney Docket No. 8459L] and is herein incorporated by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the invention generally relate to plasma
processing systems and materials and apparatus for controlling
plasma uniformity in plasma processing systems.
[0004] 2. Description of the Related Art
[0005] Plasma chambers are regularly utilized in various electronic
device fabrication processes, such as etching processes, chemical
vapor deposition (CVD) processes, and other processes related to
the manufacture of electronic devices on substrates. Many ways have
been employed to generate and/or control the plasma density, shape,
and electrical characteristics in processing chambers, such as
capacitively or inductively coupled plasma chambers. An inductively
coupled RF plasma chamber typically has an inductive coil antenna
wound around the chamber and connected to a plasma source RF power
supply. A capacitively coupled plasma chamber typically has two
parallel plate electrodes, i.e., "showerhead" and substrate
support, between which plasma is generated.
[0006] Inductively coupled and capacitively coupled plasma chambers
typically have a plasma ion density distribution across the surface
of the substrate being processed that varies greatly depending upon
various processing parameters. These processing parameters, for
example, may include the type of process gas or gas mixture
introduced into the chamber, the gas pressure, and/or the energy
(e.g., RF power, etc.) delivered into the chamber to excite the gas
or gas mixture. The plasma ion density may be high, for example, at
the substrate center and low at the substrate periphery for one
process gas, while for another process gas the plasma ion density
may be low at the substrate center and high at the substrate
periphery. As a result of these types of processing
characteristics, conventional plasma chamber RF coil designs, or
electrode designs, are customized for each process or process gas
in order to provide a specific plasma uniformity across a substrate
surface in the chamber. Multiple RF coil or electrode designs,
typically two coils or electrodes, have also been implemented in
order to improve plasma uniformity in processing chambers. In these
configurations, the first RF coil or electrode is in electrical
communication with a first power supply through, for example, a
first matching network/circuit, while the second RF coil or
electrode is in electrical communication with a second RF power
supply through a second matching network/circuit. Therefore, the
respective RF power supplies and accompanying matching networks
operate to individually control the power supplied to the
respective coils or electrodes.
[0007] During conventional electronic device fabrication processing
methods, the RF power is held constant during a substrate
processing sequence. This is undesirable for some processing
sequences, because the plasma uniformity over the surface of the
substrate generated in a particular processing chamber may be
acceptable for one portion of a sequence, while causing substrate
damage during another portion of the sequence. Conventional
processing chambers may vary the ion density and uniformity by
varying pressure in the chamber (the density or flow of the process
gas into the chamber) or the power applied to the coils or
electrodes. However, varying the gas flow is also undesirable,
since the gas flow affects the plasma composition and is harder to
control due to transient effects created due to the pressure
changes. Uniformity achieved in a plasma processing chamber may
also be affected by the interaction of the electric and/or magnetic
fields generated by two or more plasma controlling devices (e.g.,
coils, electrodes, etc.) used in the plasma processing chamber. The
interaction of the fields are an inherent part of the chamber
design, and fields may interact to a greater degree or to a lesser
degree based on the configuration of the chamber hardware and
process variable settings. Overlapping fields will constructively
interfere, thus increasing the ion density in places where the
fields interact and decreasing uniformity and the ability to
control the process uniformity.
[0008] The uniformity of the generated plasma may vary as the
process conditions are varied (e.g., power, pressure, gas mixture,
etc.), the number and shape of the plasma controlling devices in
the chamber are varied, the way the plasma controlling devices are
installed and/or the inherent physical characteristics of the
plasma controlling devices and their relative position to the
surface of the substrate. To compensate for any plasma
non-uniformity, it is common to adjust the configuration of the
plasma controlling hardware and/or plasma process variables such
as, for example, a continuous power delivered to each plasma
controlling device, chamber pressure or the position of the
substrate in the plasma. Once all of the various hardware and
process related variables have been optimized, the process
uniformity may still exceed a desired value due to the interaction
of the fields (i.e., magnetic or electric fields) created when
power is delivered to a plurality of plasma controlling devices or
due to other effects caused by the interaction of the plasma
generated by the plasma controlling devices. The non-uniformity in
the process results, for example, may create a variation between
the center and edge of the substrate or an edge to edge type
variation (e.g., right-side/left-side variation, saddle shaped
variation, etc.).
[0009] Therefore, there is a need for an improved apparatus and
methods for controlling plasma uniformity, wherein the apparatus
and methods allow for plasma uniformity adjustment without
adjusting conventional processing parameters and changing hardware
configurations.
SUMMARY OF THE INVENTION
[0010] Embodiments of the invention provide an apparatus for plasma
processing a substrate, wherein the apparatus includes first and
second plasma controlling devices that are in communication with a
processing region of a plasma chamber. The first plasma controlling
device and second plasma controlling device are connected to a
first RF power source and a second RF power source, respectively. A
controller that is connected to the first RF power source and the
second RF power source controls the modulation of the amplitude of
the RF power supplied to the first plasma controlling device and
the second plasma controlling device such that the overlap in time
of the RF power supplied to the first and second plasma controlling
devices is controlled to improve the uniformity of the plasma
process completed on a substrate mounted in the processing
region.
[0011] Embodiments of the invention further provide an apparatus
for plasma processing a substrate, wherein the apparatus includes
first and second plasma controlling devices that are in
communication with a processing region of a plasma chamber. The
first plasma controlling device and second plasma controlling
device are connected to a first RF power source and a second RF
power source, respectively. A controller that is connected to the
first RF power source and the second RF power source synchronizes
and controls the amplitude modulation of the RF power supplied to
the first plasma controlling device and the second plasma
controlling device such that the power, modulation pulse frequency,
modulation pulse duration, rest time between modulation pulses, and
overlap of the modulation pulse to the first and/or second plasma
controlling devices can be varied as a function of time.
[0012] Embodiments of the invention further provide an apparatus
for plasma processing a substrate, wherein the apparatus includes
first, second and third plasma controlling devices that are in
communication with a processing region of a plasma chamber. The
first plasma controlling device, the second plasma controlling
device and the third plasma controlling device are connected to a
first RF power source, a second RF power source, and a third RF
power source, respectively. A controller that is connected to the
first RF power source, the second RF power source and third RF
power source controls the modulation of the amplitude of the RF
power supplied to the first, the second and the third plasma
controlling devices such that the overlap in time of the RF power
supplied to the first and second plasma controlling devices is
controlled to improve the uniformity of the plasma process
completed on a substrate mounted in the processing region.
[0013] Embodiments of the invention further provide a method for
processing a substrate in a plasma chamber, wherein the method
includes amplitude modulating the RF power to a first plasma
controlling device and a second plasma controlling device. The
method generally includes modulating the pulse frequency and RF
power level, to each of the plasma controlling devices,
synchronizing the amplitude modulation of the RF power to the first
plasma controlling device and the second plasma controlling device;
and controlling the amplitude modulation of the RF power such that
the overlap of the amplitude modulated RF power delivered to the
first and second plasma controlling devices is controlled to
improve the uniformity of the process completed on the
substrate.
[0014] Embodiments of the invention further provide a method for
processing a substrate in a plasma chamber, wherein the method
includes generating first and second torroidal paths of plasma,
which are not coincident, that pass near and traverse the surface
of a substrate. The method generally includes varying the plasma
density in the vicinity of the substrate by amplitude modulating
the first torroidal path of plasma at a first modulation pulsing
frequency and a first RF power and modulation pulsing the second
torroidal path of plasma at a second modulation pulsing frequency
and a second RF power as a function of time.
[0015] Embodiments of the invention further provide a method for
processing a substrate in a plasma chamber, wherein the method
includes generating a plasma over a first area of a substrate and a
second area of a substrate, wherein the first plasma controlling
device generates a plasma in a first region near the substrate and
the second plasma controlling device generates a plasma in a second
region near the substrate and the first and second regions overlap.
The method also generally includes varying the plasma density
generated in the first region, in the second region, and a region
between the first and second region by amplitude modulating the RF
power delivered to the first plasma controlling device and the
second plasma controlling device.
[0016] Embodiments of the invention further provide a method for
processing a substrate in a plasma chamber, wherein the method
includes amplitude modulating the RF power to a first plasma
controlling device and a second plasma controlling device. The
method also includes varying the modulation pulse frequency and RF
power level, to each of the plasma controlling devices and
synchronizing the amplitude modulation of the RF power to the first
plasma controlling device and the second plasma controlling device
to adjust the plasma density in the plasma chamber to compensate
for a non-uniform area on a substrate surface.
[0017] Embodiments of the invention further provide a method for
processing a substrate in a plasma chamber, wherein the method
includes amplitude modulating the RF power to a first plasma
controlling device and a second plasma controlling device. The
method also includes amplitude modulating the RF power delivered to
each of the plasma controlling devices, synchronizing the amplitude
modulation of the RF power to the first plasma controlling device
and the second plasma controlling device, and controlling the shape
of the amplitude modulated RF power, wherein the shape of the
modulated RF power is rectangular, triangular, trapezoidal or
sinusoidal.
[0018] Embodiments of the invention further provide a method for
processing a substrate in a plasma chamber, wherein the method
includes amplitude modulating the RF power to a first plasma
controlling device and a second plasma controlling device. The
method also includes amplitude modulating the RF power delivered to
each of the plasma controlling devices, synchronizing the amplitude
modulation of the RF power to the first and the second plasma
controlling devices, controlling the shape of the amplitude
modulation of the RF power, and controlling the overlap and/or gap
between the amplitude modulated RF power to the first and second
plasma controlling devices.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] So that the manner in which the above recited features of
the present invention can be understood in detail, a more
particular description of the invention, briefly summarized above,
may be had by reference to embodiments, some of which are
illustrated in the appended drawings. It is to be noted, however,
that the appended drawings illustrate only typical embodiments of
this invention and are therefore not to be considered limiting of
its scope, for the invention may admit to other equally effective
embodiments.
[0020] FIG. 1A illustrates an isometric schematic cross-sectional
view of a torroidal plasma source chamber.
[0021] FIG. 1B illustrates a schematic cross-sectional view of a
torroidal plasma source chamber.
[0022] FIG. 2A illustrates a schematic top view of a torroidal
plasma source chamber having two orthogonal plasma conduits.
[0023] FIG. 2B illustrates a cross-sectional top view of the
processing region of a torroidal plasma source in which a plasma
current is generated in the first conduit 150A only.
[0024] FIG. 2C illustrates a cross-sectional top view of the
processing region of a torroidal plasma source in which a plasma
current is generated in the second conduit 150B only.
[0025] FIG. 2D illustrates a cross-sectional top view of the
processing region of a torroidal plasma source in which a plasma
current is generated in the first conduit 150A and the second
conduit 150B.
[0026] FIG. 2E illustrates a cross-sectional top view of the
processing region of a torroidal plasma source in which a plasma
current is generated in the first conduit 150A and the second
conduit 150B and a bias is applied to the substrate pedestal
115.
[0027] FIG. 2F illustrates a cross-sectional top view of the
processing region of a torroidal plasma source in which the plasma
current generated in the first conduit 150A and the second conduit
150B are each amplitude modulated and synchronized.
[0028] FIG. 3A illustrates a cross-sectional view of an inductively
coupled plasma processing chamber.
[0029] FIG. 3B illustrates a cross-sectional view of an inductively
coupled and torroidal plasma source configuration that may adapted
for plasma processing.
[0030] FIG. 4A illustrates a cross-sectional view of a capacitively
coupled plasma processing chamber
[0031] FIG. 4B illustrates a cross-sectional view of a capacitively
coupled plasma processing chamber.
[0032] FIG. 5 illustrates a cross-sectional view of a capacitively
coupled plasma processing chamber.
[0033] FIG. 6A illustrates the composite profile of a rectangular
shaped amplitude modulation of the RF power delivered to a first
and a second plasma controlling device as a function of time as
shown in FIGS. 6B and 6C.
[0034] FIG. 6B illustrates a rectangular shaped amplitude
modulation of the RF power that is delivered to a first plasma
controlling device as a function of time.
[0035] FIG. 6C illustrates a rectangular shaped amplitude
modulation of the RF power that is delivered to a second plasma
controlling device as a function of time.
[0036] FIG. 7A illustrates the composite profile of a rectangular
shaped amplitude modulation of the RF power delivered to a first
and a second plasma controlling device as a function of time as
shown in FIGS. 7B and 7C.
[0037] FIG. 7B illustrates a rectangular shaped amplitude
modulation of the RF power that is delivered to a first plasma
controlling device as a function of time.
[0038] FIG. 7C illustrates a rectangular shaped amplitude
modulation of the RF power that is delivered to a second plasma
controlling device as a function of time.
[0039] FIG. 8A illustrates the composite profile of a rectangular
shaped amplitude modulation of the RF power delivered to a first
and a second plasma controlling device as a function of time as
shown in FIGS. 8B and 8C.
[0040] FIG. 8B illustrates a rectangular shaped amplitude
modulation of the RF power that is delivered to a first plasma
controlling device as a function of time.
[0041] FIG. 8C illustrates a rectangular shaped amplitude
modulation of the RF power that is delivered to a second plasma
controlling device as a function of time.
[0042] FIG. 9A illustrates the composite profile of a rectangular
shaped amplitude modulation of the RF power delivered to a first
and a second plasma controlling device as a function of time as
shown in FIGS. 9B and 9C.
[0043] FIG. 9B illustrates a rectangular shaped amplitude
modulation of the RF power that is delivered to a first plasma
controlling device as a function of time.
[0044] FIG. 9C illustrates a rectangular shaped amplitude
modulation of the RF power that is delivered to a second plasma
controlling device as a function of time.
[0045] FIG. 10A illustrates the composite profile of a triangular
shaped amplitude modulation of the RF power delivered to a first
and a second plasma controlling device as a function of time as
shown in FIGS. 10B and 10C.
[0046] FIG. 10B illustrates a triangular shaped amplitude
modulation of the RF power that is delivered to a first plasma
controlling device as a function of time.
[0047] FIG. 10C illustrates a triangular shaped amplitude
modulation of the RF power that is delivered to a second plasma
controlling device as a function of time.
[0048] FIG. 11A illustrates the composite profile of a sinusoidal
shaped amplitude modulation of the RF power delivered to a first
and a second plasma controlling device as a function of time as
shown in FIGS. 11B and 11C.
[0049] FIG. 11B illustrates a sinusoidal shaped amplitude
modulation of the RF power that is delivered to a first plasma
controlling device as a function of time.
[0050] FIG. 11C illustrates a sinusoidal shaped amplitude
modulation of the RF power that is delivered to a second plasma
controlling device as a function of time.
[0051] FIG. 12A illustrates a rectangular shaped amplitude
modulation of the RF power that is delivered to a plasma
controlling device with the modulated RF power waveform shown.
[0052] FIG. 12B illustrates a rectangular shaped amplitude
modulation of the RF power that is delivered to a plasma
controlling device with the modulated RF power waveform shown.
[0053] FIG. 12C illustrates a sinusoidal shaped amplitude
modulation of the RF power that is delivered to a first plasma
controlling device with the modulated RF power waveform shown.
[0054] FIG. 13A is a 49 point contour map measuring the change in
thickness of a silicon dioxide layer after plasma etching using an
orthogonal torroidal source plasma controlling device at a 1000 Hz
modulation pulse frequency.
[0055] FIG. 13B is a 49 point contour map measuring the change in
thickness of a silicon dioxide layer after plasma etching using an
orthogonal torroidal source plasma controlling device at a 2000 Hz
modulation pulse frequency.
[0056] FIG. 13C is a 49 point contour map measuring the change in
thickness of a silicon dioxide layer after plasma etching using an
orthogonal torroidal source plasma controlling device at a 15,000
Hz modulation pulse frequency.
[0057] FIG. 13D is a 49 point contour map measuring the change in
thickness of a silicon dioxide layer after plasma etching using an
orthogonal torroidal source plasma controlling device at a 25,000
Hz modulation pulse frequency.
[0058] FIG. 13E is a 49 point contour map measuring the change in
thickness of a silicon dioxide layer after plasma etching using an
orthogonal torroidal source plasma controlling device at a constant
RF power to both plasma controlling devices.
[0059] FIG. 14A illustrates an isometric schematic cross-sectional
view of a torroidal plasma source chamber having a first and a
second pedestal RF power source and a first and a second pedestal
impedance match element connected to the substrate pedestal.
[0060] FIG. 14B illustrates a cross-sectional view of an
inductively coupled plasma processing chamber having a first and a
second pedestal RF power source and a first and a second pedestal
impedance match element connected to the substrate pedestal.
[0061] FIG. 14C illustrates a cross-sectional view of a
capacitively coupled plasma processing chamber having a first and a
second pedestal RF power source and a first and a second pedestal
impedance match element connected to the substrate pedestal.
[0062] FIG. 14D illustrates a cross-sectional view of a
capacitively coupled plasma processing chamber having a first and a
second pedestal RF power source and a first and a second pedestal
impedance match element connected to the substrate pedestal.
[0063] FIG. 15 illustrates an isometric schematic cross-sectional
view of a torroidal plasma source chamber which contains a
substrate pedestal that has two electrodes embedded therein that
may be RF biased separately.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0064] Embodiments of the present invention generally provide etch
or CVD plasma processing methods and apparatus used to generate a
uniform etch or deposition profile on the surface of a substrate by
modulating the amplitude of the RF power delivered to a plurality
of plasma controlling devices associated with a plasma processing
chamber. The amplitude modulated RF power, delivered to the plasma
controlling devices, generates a uniform plasma, which thus
develops the uniform etch or deposition profile. The plasma
generated and/or sustained in the plasma processing chamber is
created by the one or more plasma controlling devices that are used
to control, generate, enhance, and/or shape the plasma during the
plasma processing steps by use of energy delivered from a RF power
source. A plasma controlling device may include, for example, one
or more coils (inductively coupled plasma), one or more electrodes
(capacitively coupled plasma), a substrate pedestal, and/or any
other energy inputting device such as a microwave source.
[0065] Embodiments of the invention are used to correct process
non-uniformities by synchronizing the amplitude modulation of the
RF power delivered to each plasma controlling device to reduce the
interaction of the field(s) created by the plasma controlling
devices, overcome inherent chamber design shortcomings, and/or
hardware installation issues. By varying the nature and extent of
interaction of the fields, and generated plasma, created by the
plasma controlling devices, a temporal and spatial variation in the
plasma density can be controlled and thus averaged over the plasma
processing time to yield a desired process result. The term
"spatial variation" in the plasma density is meant to denote a
change in the plasma density (or composition) over a localized area
of the substrate and/or a shifting, or translation, of the
generated plasma across the surface of the substrate. The term
"temporal variation" in the plasma density is meant to denote any
change in the plasma density (or composition) over a localized area
of the substrate as a function of time.
[0066] In operation, embodiments of the invention generally provide
a plasma-based electronic device fabrication processing sequence,
wherein the plasma uniformity or flux of ions and neutrals at the
surface of a substrate is varied during the processing sequence to
achieve more uniform process results on the surface of the
substrate. Therefore, embodiments of the invention allow for an
infinite number of variations in plasma and/or etch uniformity
within a processing sequence, and within recipe steps of the
processing sequence, and generally do not require any disassembly
or reconfiguration of the plasma controlling devices in order to
accomplish plasma uniformity variation. Embodiments of the
invention generally provide for varying the plasma uniformity by
modulating the amplitude of the RF power delivered to each of the
plasma controlling devices as a function of time, since the plasma
uniformity and plasma ion density are directly affected by the
magnetic field strength or electric field strength in the plasma
region of the chamber. A single recurring component of the
amplitude modulated RF power waveform, or modulation pulse, can
have an infinite number of shapes. FIGS. 12A-C illustrate three
examples of amplitude modulated RF power waveforms, or modulation
pulse 4 (or modulating waveform), and the underlying amplitude
modulated RF power 3 (or carrier). In configurations that contain
more than two plasma controlling devices, it may be possible, for
example, to vary the order of the modulation pulses delivered to
each plasma controlling device as a function of time (e.g., the
order of the modulation pulse delivered to the plasma controlling
devices need not be sequential, etc.), the length of the modulation
pulse, and the power level needed to achieve the desired uniformity
across the substrate. In various embodiments of the invention, the
frequency of the modulation pulse may vary between about 0.1 hertz
and about 100,000 hertz, but preferably varies between about 0.1
hertz and about 10,000 hertz. The power delivered to each of the
plasma controlling devices may vary between about 0 Watts to about
5000 Watts at a RF frequency of about 13.56 MHz. The frequency of
the power delivered by the RF power source is not limited to
frequencies around 13.56 MHz and may be run at frequencies between
about 0.4 MHz to greater than 10 GHz.
[0067] The amplitude modulated RF power delivered to each of the
plasma controlling devices is synchronized and controlled by use of
a controller 300 (see FIG. 3), such as a microprocessor-based
controller. The controller 300 is configured to receive inputs from
a user and/or various sensors in the plasma processing chamber and
appropriately control the plasma processing chamber components in
accordance with the various inputs and software instructions
retained in the controller's memory. The controller 300 generally
contains memory and a CPU (not shown) which are utilized by the
controller to retain various programs, process the programs, and
execute the programs when necessary. The memory (not shown) is
connected to the CPU, and may be one or more of a readily available
memory, such as random access memory (RAM), read only memory (ROM),
floppy disk, hard disk, or any other form of digital storage, local
or remote. Software instructions and data can be coded and stored
within the memory for instructing the CPU. The support circuits
(not shown) are also connected to the CPU for supporting the
processor in a conventional manner. The support circuits may
include cache, power supplies, clock circuits, input/output
circuitry, subsystems, and the like all well known in the art. A
program (or computer instructions) readable by the controller 300
determines which tasks are performable in the plasma processing
chamber. Preferably, the program is software readable by the
controller 300 and includes instructions to monitor and control the
plasma process based on defined rules and input data.
[0068] The controller 300 in conjunction with an RF power source,
for example, RF power source 180 (see FIG. 1A), is adapted to
control the amplitude modulation of the RF power delivered to each
of the plasma controlling devices. The controller 300 and the RF
power source combination are generally configured to control the
modulation pulsing characteristics, for example, modulation pulse
power level, modulation pulse width, modulation pulse overlap, rest
time or gap between modulation pulses, modulation pulse
frequencies, which are varied to achieve a desired process result.
In one embodiment, the controller 300 is adapted to synchronize the
amplitude modulated RF power delivered to each of the plasma
controlling devices. In one embodiment the amplitude modulation
control elements of the controller 300 are contained in the two or
more RF power sources. In this embodiment the RF power sources are
in communication with each other to synchronize the delivery of the
modulation pulses to each of the plasma controlling devices.
[0069] Hardware Configurations
[0070] FIG. 1A illustrates a cross-sectional view of a torroidal
plasma chamber that is useful for practicing the inventions
described herein. An exemplary torroidal plasma chamber is further
described in the U.S. Pat. No. 6,410,449, entitled "Method Of
Processing A Workpiece Using An Externally Excited Torroidal Plasma
Source", filed on Aug. 11, 2000, which is incorporated by reference
herein to the extent not inconsistent with the claimed aspects and
disclosure herein. Referring to FIG. 1, a plasma chamber 100
enclosed by a cylindrical sidewall 105 and a ceiling 110 houses a
torroidal plasma source 172 and a substrate pedestal 115 for
supporting a wafer or substrate 120. A backside gas supply 128 (not
shown) furnishes a gas, such as helium, to a gap between the
backside of the substrate 120 and the substrate pedestal 115 to
improve thermal conduction between the substrate pedestal 115 and
the substrate 120. In one embodiment, the substrate pedestal 115 is
heated and/or cooled by use of embedded heat transfer fluid lines
(not shown), or an embedded thermoelectric device (not shown), to
improve the plasma process results on the substrate 120 surface. A
process gas supply 125 furnishes process gas into the chamber 100
through one or more gas inlet nozzles 130 extending through the
sidewall 105. A vacuum pump 135 controls the pressure within the
chamber 100, typically holding the pressure below 0.5 milliTorr
(mT).
[0071] The torroidal plasma source 172, or torroidal type of plasma
controlling device, generally contains a conduit 150, a
magnetically permeable core 1015, antenna 170, an impedance match
element 175, and a RF power source 180. The antenna 170, which
includes a winding or coil section, is wound around a closed
magnetically permeable core 1015, which surrounds the conduit 150.
The closed magnetically permeable core 1015 is used to inductively
couple to the plasma generated inside the hollow conduit 150 by use
of the antenna 170, the impedance match element 175, and the RF
power source 180. In one embodiment, dynamic impedance matching may
be provided to the antenna 170 by frequency tuning, impedance
matching network tuning or frequency tuning with forward power
servoing. In an alternate embodiment an impedance match may be
achieved without the impedance match element 175 by using, instead,
a secondary winding 1120 (not shown) around the core 1015 connected
across a tuning capacitor 1130 (not shown). The capacitance of the
tuning capacitor 1130 (not shown) is selected to resonate the
secondary winding 1120 (not shown) at the frequency of the RF power
source 180. For a fixed tuning capacitor 1130 (not shown), dynamic
impedance matching may be provided.
[0072] The half-torroidal hollow tube enclosure or conduit 150
extends above the ceiling 110 in a half circle. The conduit 150,
although extending externally outwardly from ceiling 110, is
nevertheless part of the chamber and forms a wall of the chamber.
Internally the conduit 150 shares the same evacuated atmosphere as
exists elsewhere in the chamber. The conduit 150 has one open end
157 sealed around a first opening, port 155, in the chamber ceiling
110 and its other end 158 sealed around a second opening, port 160,
in the chamber ceiling 110. The two openings, port 155 and port
160, are located on generally opposite sides of the substrate
pedestal 115. The hollow conduit 150 is reentrant in that it
provides a flow path which exits the main portion of the chamber at
one opening and re-enters at the other opening. The conduit 150 may
be described herein as being half-torroidal, in that the conduit is
hollow and provides a portion of a closed path in which plasma
generated in the conduit 150 may flow across the process region
overlying the substrate pedestal 115. Notwithstanding the use of
the term "torroidal", the trajectory of the closed path as well as
the cross-sectional shape of the path or conduit 150 may be
circular or non-circular, and may be square, rectangular or any
other shape, regular or irregular.
[0073] In order to avoid edge effects at the substrate periphery,
the ports 155 and 160 are separated by a distance that exceeds the
diameter of the substrate. For example, for a 12-inch diameter
substrate, the ports 155 and 160 are about 16 to 22 inches apart.
For an 8-inch diameter substrate, the ports 155 and 160 are about
10 to 16 inches apart.
[0074] The external conduit 150 may be formed of a relatively thin
conductor such as sheet metal and may contain a first insulating
gap 152 and a second insulating gap 153 filled with an insulating
ring 154 made from a ceramic material. The insulating gaps, which
extend across and through the conduit 150, suppress eddy currents
in the sheet metal of the hollow conduit 150 and thereby facilitate
coupling of an RF inductive field into the interior of the conduit
150. An RF power source 162 applies RF bias power to the substrate
pedestal 115 and substrate 120 through an impedance match element
164. In one embodiment, dynamic impedance matching may be provided
to the substrate pedestal by frequency tuning, impedance matching
network tuning or frequency tuning with forward power servoing
which are well known in the art.
[0075] Process gases from the chamber 100 fill the hollow conduit
150. In addition, a separate process gas supply 190 may supply
process gases directly into the hollow conduit 150 through a gas
inlet 195. The RF field in the external hollow conduit 150 ionizes
the gases in the tube to produce a plasma. The RF field induced by
the magnetically permeable core 1015 is such that the plasma formed
in the conduit 150 reaches through the region between the substrate
120 and the ceiling 110 to complete a torroidal path that includes
the half-torroidal hollow conduit 150. As employed herein, the term
"torroidal" refers to the closed and solid nature of the path, but
does not refer to or limit its cross-sectional shape or trajectory,
either of which may be circular or non-circular or square or
otherwise. Plasma circulates through the complete torroidal path or
region which may be thought of as a closed plasma circuit or plasma
current path. The RF inductive field generated in the conduit 150
by the closed magnetically permeable core 1015 is closed, as are
all magnetic fields, and therefore induces a plasma current along
the closed torroidal path. The current is generally uniform along
the closed path length and alternates at the frequency of the RF
signal applied to the closed magnetically permeable core 1015 by
the RF power source 180 through the antenna 170 is varied. The
torroidal region extends across the diameter of the substrate 120
and, in certain embodiments, has a sufficient width in the plane of
the substrate so that it overlies the entire substrate surface.
[0076] FIG. 1B is a cross-sectional view of the torroidal plasma
chamber shown in FIG. 1A. The gas distribution showerhead 210
consists of a gas distribution plenum 220 connected to the gas
supply 125 and communicating with the process region 121 over the
substrate 120 through plural gas nozzle openings 230. In one
embodiment, a conductive showerhead 210, which is connected to
ground, may be used since the conductive showerhead may tend to
constrict the plasma path over the substrate surface and thereby
increases the density of the plasma current in that vicinity and it
may provide a uniform electrical potential reference or ground
plane close to and across the entire substrate surface.
[0077] FIG. 2A illustrates a top view of a pair of orthogonal
torroidal plasma sources, described below as a first torroidal
plasma source (item 172A) and a second torroidal plasma source
(item 172B). A first conduit 150A and a second conduit 150B, which
extend through their respective ports in the ceiling 110 (i.e.,
155A and 160A, and 155B and 160B) are excited by their respective
magnetically permeable cores 1015A and 1015B which are in
communication with their respective coil antennas 170A and 170B.
This embodiment creates two mutually orthogonal torroidal plasma
current paths over the substrate 120 for enhanced uniformity. The
two torroidal sources are separate and independently powered as
illustrated, but intersect in the process region 121 overlying the
substrate (not shown in this view). In other embodiments,
containing two or more torroidal plasma sources, the torroidal
plasma sources may not be orthogonal to each other, unlike what is
shown in FIG. 2A, but are placed at an angle or are otherwise
positioned relative to one another, for example, placed parallel to
each other, placed end to end, etc., which may help improve process
uniformity or improve the ease of manufacturing. In this embodiment
the two or more torroidal plasma sources may be placed in any
orientation except a coincident orientation, or overlapping
orientation, since it is generally preferred not use such an
orientation because it will derive a minimal benefit from
modulation pulsing the RF power delivered to the plasma controlling
devices. The term "coincident" is meant to describe the case where
the fields and plasma paths of two or more plasma generating
sources are directly in-line and completely overlap each other.
[0078] FIGS. 2B-2F illustrate cross-sectional top views of the
processing region 121, above the substrate surface and below the
showerhead 210. FIGS. 2B-2F also illustrate one embodiment of the
pair of orthogonal conduits having rectangular shaped conduit ports
(i.e., 155A, 155B, 160A and 160B). FIG. 2B illustrates a top view
of the processing region when RF power is applied to generate a
plasma in the first conduit, which is connected to port 155A and
port 160A. One segment of the torroidal path of a plasma generated
using a first conduit is shown as item "C".
[0079] FIG. 2C illustrates a top view of the processing region when
RF power is applied to generate a plasma in the second conduit,
which is connected to port 155B and port 160B. One segment of the
torroidal path of a plasma generated using a second conduit is
shown as item "D".
[0080] FIG. 2D illustrates a top view of the processing region when
RF power is applied to the first conduit, which is connected to
ports 155A and 160A, and the second conduit, which is connected to
ports 155B and 160B. FIG. 2D depicts a typical annular plasma path
"E" created when a plasma is being generated and/or sustained in
both the first conduit and the second conduit. Since the plasma
path "E" is not an overlapping pattern, as might be expected after
reviewing the plasma paths shown in FIGS. 2B and 2C, the annular
path "E" illustrates how the interaction of the generated plasmas
and/or generated fields can affect plasma uniformity.
[0081] FIG. 2E illustrates a top view of the processing region when
RF power is applied to the first conduit, which is connected to
ports 155A and 160A, and the second conduit, which is connected to
ports 155B and 160B, and a bias is applied to the substrate
pedestal 115. FIG. 2E illustrates how adding bias to the substrate
pedestal 115, under typical process conditions, has only a limited
effect on distributing the plasma generated in the plasma
processing chamber since the interaction of the fields and/or
generated plasma keeps a large majority of the plasma in an annular
region illustrated by the darker region shown near the annular path
"E".
[0082] FIG. 2F illustrates a top view of the processing region when
RF power is modulation pulsed to the first conduit, which is
connected to ports 155A and 160A, and the second conduit, which is
connected to ports 155B and 160B, such that the interaction between
the generated fields is reduced. FIG. 2F illustrates how modulation
pulsing the RF power creates a uniform plasma density across the
process region, and thus the surface of the substrate, by averaging
the plasma density over a sequence of modulation pulses, over a
period of time, or more generally over the plasma processing time.
A sequence of modulation pulses may be defined as an ordered set of
modulation pulses which are able to achieve a uniform processing
result on a substrate, and may be defined as the minimum number of
modulation pulses in a sequence before the sequence repeats itself.
FIGS. 6-11 illustrate embodiments of various modulation pulse
sequences having various shapes and degrees of interaction. For a
two plasma controlling device plasma processing chamber, the
shortest sequence may be a two modulation pulse sequence, such as a
modulation pulse of the RF power to the first electrode and then a
modulation pulse of the RF power to the second electrode. For a
three plasma controlling device plasma processing chamber, the
shortest sequence may be a three step sequence, for example, a
modulation pulse of the RF power to the first electrode, a
modulation pulse of the RF power to the second electrode and then a
modulation pulse of the RF power to the third electrode.
[0083] By modulation pulsing the RF power delivered to the plasma
controlling devices, the first conduit and the second conduit, it
has been found that the uniformity of the plasma process can be
improved. By adapting the hardware and processing steps, various
plasma modulation pulsing recipes can be utilized to improve the
processing uniformity. The RF power modulation pulse
characteristics may be varied, for example, at the transition
between recipe steps in a plasma processing chamber recipe, at one
or more times within individual recipe steps of a plasma processing
chamber recipe, or continuously throughout the plasma processing
process. In one embodiment, a user is able to input the desired
modulation pulse characteristics (as described above) and other
process variables, for example, chamber pressure, gas types, gas
flow rates, etc., into a recipe from which the controller 300 is
able to monitor and control all aspects of the plasma chamber
process.
[0084] FIG. 3A illustrates a cross-sectional view of a typical
inductively coupled plasma processing chamber having two RF coils
disposed on a lid of the chamber which may be used to carry out one
embodiment of the invention. The inductively coupled plasma
processing chamber generally includes a plasma chamber 10 having a
generally cylindrical sidewall 15 and a dome-shaped ceiling 20.
Other embodiments of an inductively coupled plasma processing
chamber may include a chamber lid having another shape such as
cylindrical with a flat top (coils reside on top). A gas inlet 25
supplies process gas into the plasma chamber 10. A substrate
support member or substrate pedestal 115 supports a substrate 120,
inside the plasma chamber 10. A backside gas supply 128 (not shown)
furnishes a gas, such as helium, to a gap between the backside of
the substrate 120 and the substrate pedestal 115 to improve thermal
conduction between the substrate pedestal 115 and the substrate
120. In one embodiment the substrate pedestal 115 is heated and/or
cooled by use of embedded heat transfer fluid lines (not shown), or
an embedded thermoelectric device (not shown), to improve the
plasma process results on the substrate 120 surface. An RF power
source 162 may be connected to the substrate pedestal 115 through a
conventional RF impedance match element 164. A plasma is ignited
and maintained within the plasma chamber 10 above substrate
pedestal 115 by RF power inductively coupled from a coil antenna 50
consisting of a pair of antenna loops or RF coils 52, 54, wound
around different portions of the dome-shaped ceiling. In the
embodiment shown in FIG. 3A, both loops are wound around a common
axis of symmetry coincident with the axis of symmetry of the
dome-shaped ceiling 20 and the axis of symmetry of the substrate
pedestal 115 and substrate 120. The first RF coil 52 is wound
around an outer portion of the dome-shaped ceiling 20 while the
second RF coil 54 is positioned centrally over the ceiling 20.
First and second RF coils 52, 54, as shown in FIG. 3A, are
separately connected to the respective first and second RF power
sources 60, 65 through first and second RF impedance match networks
70, 75. RF power in each RF coil 52, 54 are separately controlled.
The RF power signal applied to the first RF coil (outer antenna
loop) 52 generally affects plasma ion density near the periphery of
the substrate 120 while the RF power signal applied to the second
RF coil (inner antenna loop) 54 generally affects plasma ion
density near the center of the substrate 120. The RF power signals
delivered to each of the RF coils are adjusted or configured
relative to each other to achieve substantial uniformity of plasma
ion distribution over a substrate disposed on a substrate support
member.
[0085] In operation, the plasma processing system receives a
substrate 120 on substrate pedestal 115 for processing in plasma
chamber 10. Plasma chamber 10 may then be pulled to a predetermined
pressure/vacuum by a vacuum pump system (not shown). Once the
predetermined pressure is achieved, a process gas may be introduced
into the plasma chamber 10 by gas inlet 25, while the vacuum
pumping system continues to pump the plasma chamber 10, such that
an equilibrium processing pressure is obtained. The processing
pressure is adjustable through, for example, throttling the
communication of the vacuum system to the plasma chamber 10 or
adjusting the flow rate of the process gases being introduced into
plasma chamber 10 by gas inlet 25. Once the pressure and gas flows
are established, the respective power supplies may be activated.
Power can be independently supplied to the first RF coil 52 and
second RF coil 54, and the substrate pedestal 115. The application
of power to the first RF coil 52 and second RF coil 54 facilitates
striking of a plasma in the region immediately above the substrate
pedestal 115. The ion density of the plasma may be increased or
decreased through adjustment of the power supplied to the first RF
coil 52 and second RF coil 54 or through adjustment of the
processing pressure in plasma chamber 10, that is, through
increased/decreased flow rate of the process gas or an
increase/decrease in the chamber pumping rate.
[0086] The inductively coupled plasma processing chamber,
illustrated in FIG. 3A, depicts an embodiment having an inner
(center) and outer (edge) coil configuration. The inner and outer
coil configuration generates a plasma that will generally vary
radially, which can generally create radial bands of varying etch
rate or deposition rate that are concentric about the center of the
substrate being processed. The magnetic field strength over these
annular bands is conventionally generated by energizing one or more
coils positioned over the substrate being processed. The magnetic
field generated by the energized coils positioned above the
substrate penetrates the chamber and directly affects plasma
uniformity. The uniformity of the generated plasma may vary as the
process conditions are varied (e.g., power, pressure, gas mixture,
etc.), the way the plasma controlling devices are positioned, the
position of the substrate in the plasma and/or the inherent
physical characteristics of the plasma controlling devices. By use
of aspects of the invention, the plasma uniformity can be optimized
by modulation pulsing the RF power delivered to the plasma
controlling devices (e.g., outer coil 52, inner coil 54, substrate
pedestal, etc.) and thus reducing the interaction of the magnetic
fields and plasma that is generated when the plasma controlling
devices are energized. By use of the controller 300 the user can
define and control the process and modulation pulsing
characteristics during the plasma process. In one embodiment the
modulation pulsed RF power to each plasma controlling device and
plasma processing variables, for example, the chamber pressure, gas
mixture, and/or the position of the substrate in the plasma, are
varied to achieve a desired plasma uniformity and/or plasma
density.
[0087] FIG. 3B illustrates a cross-sectional view of an inductively
coupled plasma processing chamber 10A that contains a torroidal
plasma source 172 and a inductive coil (e.g., item 52) that are
adapted to perform a plasma process. While FIG. 3B, illustrates a
single inductive coil positioned outside the torroidal plasma
source 172, this configuration is not intended to limit the scope
of the present invention since the number, type of plasma
controlling devices, and/or position of the plasma controlling
devices is not intended to be limiting to the various aspects of
the invention described herein. In one aspect, an RF power source
162 may be connected to the substrate pedestal 115 through a
conventional RF impedance match element 164 to generate or control
the plasma in the plasma processing chamber 10A. The torroidal
plasma source 172, as described above, is adapted to generate a
plasma that is maintained over the surface of the substrate 120.
The RF coil 57, as shown in FIG. 3B, is separately connected to the
first RF power source 60 through the first RF impedance match
networks 70. The RF power delivered to the torroidal plasma source
172, substrate pedestal and/or the RF coil 57 may be separately
controlled to generate and control the plasma formed in the process
region 121. The RF power delivered to each of the plasma
controlling devices can be adjusted or configured relative to each
other to achieve substantial uniformity of plasma ion distribution
over a substrate disposed on a substrate support member. By use of
aspects of the invention, uniformity of the plasma generated in the
plasma processing chamber 10A can be optimized by modulation
pulsing the RF power delivered to the plasma controlling devices
(e.g., coil 57, torroidal plasma source 172, substrate pedestal
115, etc.) and thus reducing the interaction of the magnetic fields
and plasma that are generated when the plasma controlling devices
are energized. By use of the controller 300 the user can define and
control the process and modulation pulsing characteristics during
the plasma process. In one embodiment the modulation pulsed RF
power to each plasma controlling device and plasma processing
variables, for example, the chamber pressure, gas mixture, and/or
the position of the substrate in the plasma, are varied to achieve
a desired plasma uniformity and/or plasma density.
[0088] FIG. 4A illustrates a capacitively coupled plasma chamber
305. A sidewall 405, a ceiling 406, and a base 407 enclose the
capacitively coupled plasma chamber 305. A substrate pedestal 115,
which supports a substrate 120, mounts to the base 407 of the
capacitively coupled plasma chamber 305. A backside gas supply 128
(not shown) furnishes a gas, such as helium, to a gap between the
backside of the substrate 120 and the substrate pedestal 115 to
improve thermal conduction between the substrate pedestal 115 and
the substrate 120. In one embodiment the substrate pedestal 115 is
heated and/or cooled by use of embedded heat transfer fluid lines
(not shown), or an embedded thermoelectric device (not shown), to
improve the plasma process results on the substrate 120 surface. A
vacuum pump 135 controls the pressure within the capacitively
coupled plasma chamber 305, typically holding the pressure below
0.5 milliTorr (mT). A gas distribution showerhead 410 consists of a
gas distribution plenum 420 connected to the gas supply 125 and
communicating with the process region 121 over the substrate 120
through plural gas nozzle openings 430. The showerhead 410, made
from a conductive material (e.g., anodized aluminum, etc.), acts as
a plasma controlling device by use of the attached to a first
impedance match element 175A and a first RF power source 180A. A
second electrode 415, which is concentric to the substrate 120's
surface, is biased by a second impedance match element 175B and a
second RF power source 180B. A RF power source 162 applies RF bias
power to the substrate pedestal 115 and substrate 120 through an
impedance match element 164. A controller 300 is adapted to control
the impedance match elements (i.e., 175A, 175B, and 164), the RF
power sources (i.e., 180A, 180B, and 162) and all other aspects of
the plasma process. In one embodiment dynamic impedance matching is
provided to the substrate pedestal 115, the showerhead 410 and
second electrode 415 by frequency tuning, impedance matching
network tuning or frequency tuning with forward power servoing.
[0089] FIG. 4B illustrates a capacitively coupled plasma chamber
320. The capacitively coupled plasma chamber 320 contains all of
the same components as the chamber shown in FIG. 4A except it does
not contain the second electrode 415, the second impedance match
element 175B and the second RF power source 180B. The controller
300 is thus adapted to control the impedance match elements (i.e.,
175A and 164), the RF power sources (i.e., 180A and 162) and all
other aspects of the plasma process.
[0090] FIG. 5 illustrates a top view of another capacitively
coupled plasma processing chamber 400 which generally contains all
of the components found in FIG. 4B, and four side electrodes 450A-D
which are individually connected to their respective impedance
match element 428A-D, which are connected to their respective RF
power source 429A-D. In one embodiment, the plasma processing
chamber 400 may contain more than four side electrodes 450,
impedance match elements 428 and RF power sources 429. In another
embodiment the plasma processing chamber 400 may contain less than
four side electrodes 450, impedance match elements 428 and RF power
sources 429.
[0091] In one embodiment of the plasma processing chamber 400 the
gas distribution showerhead 410 (not shown) is not RF biased. In
this embodiment RF power is only delivered to a side electrode 450
and a substrate pedestal 115 (not shown). A controller 300 is
adapted to control the impedance match elements (i.e., 428, 164 and
175A (if biased)), the RF power sources (i.e., 429, 162 and 180A
(if biased)) and all other aspects of the plasma process.
[0092] The uniformity of the generated plasma in the capacitively
coupled plasma processing chambers 305, 320 and 400 may vary
depending on the process conditions are varied (e.g., power,
pressure, gas mixture, etc.), the way the plasma controlling
devices are positioned, the position of the substrate in the plasma
and/or the inherent physical characteristics (e.g., surface
characteristics, surface area, etc.) of the plasma controlling
devices. By use of aspects described herein, the plasma uniformity
can be optimized by modulation pulsing the power delivered to the
plasma controlling devices (e.g., showerhead 410, second electrode
415 (FIG. 4A only), substrate pedestal 115, side electrode 450,
etc.) which reduces the interaction of the electric fields and
plasma that are generated by the plasma controlling devices. By use
of the controller 300, the user is able to define and control the
process variables and modulation pulsing characteristics used
during the plasma process. In one embodiment the modulation pulsed
RF power to each plasma controlling device and plasma processing
variables, for example, the chamber pressure, gas mixture, and/or
the position of the substrate in the plasma, are varied to achieve
a desired plasma uniformity and/or plasma density.
[0093] In addition to amplitude modulating the RF power to coils,
electrodes, torroidal sources relative to each other, as described
above, in some embodiments of the invention the RF power delivered
to the substrate pedestal is modulation pulsed relative to one or
more plasma controlling devices in the chamber, for example, a
torroidal plasma source, an RF coil 52, an RF coil 54, a showerhead
210, etc. Modulation pulsing the RF power to the substrate pedestal
relative to other plasma controlling devices can: reduce RF field
interaction between the substrate pedestal and the plasma
controlling device(s), shape the plasma, control plasma bombardment
of the substrate surface, and/or vary the plasma sheath thickness
and/or voltage.
[0094] In another aspect of the invention, two or more RF power
sources are attached to the substrate pedestal 115 mounted in a
torroidal plasma processing chamber, an inductively coupled plasma
processing chamber or a capacitively coupled plasma processing
chamber. FIG. 14A illustrates an embodiment of the plasma chamber
100 in which the impedance match element 164 and the pedestal RF
power source 162 are replaced by a first impedance match element
164A, a first pedestal RF power source 162A connected to the
substrate pedestal 115, and a second impedance match element 164B,
and a second pedestal RF power source 162B connected to the
substrate pedestal 115. FIG. 14B illustrates an embodiment of the
plasma chamber 10 in which the impedance match element 164 and the
pedestal RF power source 162 are replaced by a first impedance
match element 164A, a first pedestal RF power source 162A connected
to the substrate pedestal 115, and a second impedance match element
164B, and a second pedestal RF power source 162B connected to the
substrate pedestal 115. FIG. 14C illustrates an embodiment of the
plasma chamber 305 in which the impedance match element 164 and the
pedestal RF power source 162 are replaced by a first impedance
match element 164A, a first pedestal RF power source 162A connected
to the substrate pedestal 115, and a second impedance match element
164B, and a second pedestal RF power source 162B connected to the
substrate pedestal 115. FIG. 14D illustrates an embodiment of the
plasma chamber 320 in which the impedance match element 164 and the
pedestal RF power source 162 are replaced by a first impedance
match element 164A, a first pedestal RF power source 162A connected
to the substrate pedestal 115, and a second impedance match element
164B, and a second pedestal RF power source 162B connected to the
substrate pedestal 115. In one embodiment, the first impedance
match element 164A and the first pedestal RF power source 162A
deliver RF power to the substrate pedestal at a first RF frequency
while the second impedance match element 164B and the second
pedestal RF power source 162B deliver RF power to the substrate
pedestal at a second RF frequency which is higher than the first
frequency. For example, the first RF frequency may be 13.56 MHz and
the second frequency may be 1360 MHz. In general, the RF
frequencies that may be created by the first pedestal RF power
source 162A and the second pedestal RF power source 162B may range
from about 0.4 MHz to about 10 GHz. By powering the substrate
pedestal 115 using RF energy delivered at different powers and
frequencies, the plasma sheath and substrate bias can be
controlled. In one embodiment, the RF power delivered to the
substrate pedestal 115 from the first RF power source 162A, the
second RF power source 162B, or the first and second RF power
sources (i.e., 162A and 162B) are modulation pulsed relative to
another plasma controlling devices in the chamber, for example, a
torroidal plasma source, an RF coil 52, an RF coil 54, an
showerhead 210, etc., to help reduce RF field interaction between
the various RF fields, to vary the plasma sheath thickness and/or
voltage, to shape the plasma and to control plasma bombardment of
the substrate surface. In yet another embodiment, the RF power
delivered to the substrate pedestal 115 from the first pedestal RF
power source 162A and second pedestal RF power source 162B are
modulation pulsed relative to each other to help reduce RF field
interaction between the various RF fields, vary the plasma sheath
thickness and/or voltage, shape the plasma and control plasma
bombardment of the substrate surface.
[0095] In another aspect of the invention, the substrate pedestal
115 contains two or more segmented regions that are RF biasable as
illustrated in FIG. 15. The biasable regions are generally two or
more electrodes attached or embedded in the substrate pedestal 115,
which can control or shape the generated plasma by amplitude
modulating the RF power at different RF powers and/or frequencies
to each of the biasable regions. By powering each of the biasable
regions using RF energy delivered at different powers and
frequencies, the plasma sheath and substrate bias can be controlled
over different regions of the substrate during processing. FIG. 15
illustrates an embodiment of the plasma chamber 100 which contains:
a first impedance match element 164A and a first pedestal RF power
source 162A connected to a first biasable region 115A; a second
impedance match element 164B and a second pedestal RF power source
162B connected to the first biasable region 115A; a third impedance
match element 164C and a third pedestal RF power source 162C
connected to a second biasable region 115B; and a fourth impedance
match element 164D and a fourth pedestal RF power source 162D are
connected to the second biasable region 115B. While FIG. 15
illustrates a concentric two biasable region configuration (e.g.,
biasable regions 115A and 115B) other embodiments may be oriented
in a non-concentric manner, for example, in quadrants, divided in
half, or other geometric orientations and/or number of biasable
regions as needed to achieve a desired process result. Also, while
FIG. 15 illustrates the use of a segmented substrate pedestal 115
in a plasma chamber 100 (i.e., torroidal plasma source) this
embodiment may also be used in other types of plasma processing
chambers, such as those described above. In one embodiment, the
first impedance match element 164A and the first pedestal RF power
source 162A may deliver RF power to the first biasable region 115A
at a first frequency while the second impedance match element 164B
and the second pedestal RF power source 162B may deliver RF power
to the first biasable region 115A at a second frequency which is
higher than the first frequency. In this embodiment, the third
impedance match element 164C and the third pedestal RF power source
162C may deliver RF power to the second biasable region 115B at a
third frequency, while the fourth impedance match element 164D and
the fourth pedestal RF power source 162D may deliver RF power to
the second biasable region 115B at a fourth frequency which is
higher than the third frequency. For example, the first and third
RF frequencies may be 13.56 MHz and the second and fourth
frequencies may be 1360 MHz. In general, the first, second, third
and fourth RF frequencies that may be used can each vary from about
0.4 MHz to about 10 GHz. The delivered RF power levels may be from
0 to 5000 Watts. By powering each of the biasable regions using RF
energy delivered at different RF power levels and frequencies, the
plasma sheath and substrate bias can be controlled over different
regions of the substrate during processing.
[0096] Amplitude Modulation Control
[0097] FIGS. 6-11 illustrate various embodiments of the invention
where the amount of power delivered to two plasma controlling
devices is varied as a function of time. While FIGS. 6-11
illustrate different methods of amplitude modulation of the RF
power applied to two plasma controlling devices, other embodiments
of the invention may contain more than two plasma controlling
devices. The underlying amplitude modulated RF power waveform, that
is, item 3 in FIGS. 12A-C, is not shown in FIGS. 6-11 for
clarity.
[0098] FIG. 6A illustrates the composite profile of
rectangular-shaped modulation pulses delivered to the first and
second plasma controlling devices as a function of time. The
rectangular-shaped modulation pulses delivered to the first and
second plasma controlling devices are shown in FIGS. 6B and 6C,
respectively. The modulated pulse waveform 1 in FIG. 6B illustrates
an embodiment of an amplitude modulation of the RF power delivered
to a first plasma controlling device as a function of time. The
modulated pulse waveform 2 in FIG. 6C illustrates an embodiment of
an amplitude modulation of the RF power delivered to a second
plasma controlling device as a function of time. FIGS. 6A-C
illustrate a case where the total power in the processing chamber
is kept relatively constant as a function of time but the power to
each plasma controlling device is either on or off at any given
time, except possibly during the transition to or from the peak RF
power level. In one embodiment, the peak RF power level, pulse
width (e.g., see items t.sub.1-t.sub.4), and modulation pulse
frequency of each modulation pulse may be varied from one pulse to
the next.
[0099] FIG. 7A illustrates the composite profile of a rectangular
shaped modulation pulse delivered to the first and second plasma
controlling devices as a function of time. The rectangular-shaped
modulation pulses delivered to the first and second plasma
controlling devices are shown in FIGS. 7B and 7C, respectively. The
modulated pulse waveform 1 in FIG. 7B illustrates an embodiment of
an amplitude modulation of the RF power delivered to a first plasma
controlling device as a function of time. The modulated pulse
waveform 2 in FIG. 7C illustrates an embodiment of an amplitude
modulation of the RF power delivered to a second plasma controlling
device as a function of time. In this embodiment the rectangular
modulation pulse overlaps an amount "A" and thus the fields created
by each plasma controlling device interact for only a portion of
the total modulation pulse width. To achieve a more uniform result,
the amount of overlap "A" may be varied throughout the plasma
process, from one modulation pulse to another, or as different
processing conditions are varied, such as, when the concentration
of gasses and the chamber pressure are varied.
[0100] FIG. 8A illustrates the composite profile of a
rectangular-shaped modulation pulse delivered to the first and
second plasma controlling devices as a function of time. The
rectangular-shaped modulation pulses delivered to the first and
second plasma controlling devices are shown in FIGS. 8B and 8C,
respectively. The modulated pulse waveform 1 in FIG. 8B illustrates
an embodiment of an amplitude modulation of the RF power delivered
to a first plasma controlling device as a function of time. The
modulated pulse waveform 2 in FIG. 8C illustrates an embodiment of
an amplitude modulation of the RF power delivered to a second
plasma controlling device as a function of time. In this embodiment
a rest time "B" is added between the modulation pulses. The rest
time is a period of time of about 100 microseconds or less, in
which no power is delivered to any of the plasma controlling
devices. It may be advantageous to keep the rest time short enough
that the plasma generated in the processing chamber does not
extinguish and thus does not require reignition of the plasma after
each subsequent modulation pulse is applied to a plasma controlling
device. In one embodiment, the rest time is varied throughout the
plasma process, from one modulation pulse to another, or as
different processing conditions are varied, such as the
concentration of gasses and the chamber pressure.
[0101] FIG. 9A illustrates the composite profile of a
rectangular-shaped modulation pulse delivered to the first and
second plasma controlling devices as a function of time. The
rectangular-shaped modulation pulses delivered to the first and
second plasma controlling devices are shown in FIGS. 9B and 9C,
respectively. The modulated pulse waveform 1 and 1A in FIG. 9B
illustrates an embodiment of an amplitude modulation of the RF
power delivered to a first plasma controlling device as a function
of time. The modulated pulse waveform 2 and 2A in FIG. 9C
illustrates an embodiment of an amplitude modulation of the RF
power delivered to a second plasma controlling device as a function
of time. In this embodiment, the rectangular modulation pulse
overlap and the amount of power delivered to each plasma
controlling device, after each subsequent modulation pulse, may be
varied proportionally to the power delivered to the other plasma
controlling devices (e.g., waveform 1 to 2A and waveform 2 to 1A).
In this embodiment, the fields created by each plasma controlling
device interact, but the amount of interaction is minimized from a
continuous power delivery case by varying the power of one plasma
controlling device relative to the other plasma controlling
device(s). The ratio of power delivered at any one time to the
various plasma controlling devices may range, for example, from a
ratio from about 1 to 1 to about 100 to 1, but is preferably
between about 1 to 1 and about 10 to 1.
[0102] While the embodiments illustrated in FIGS. 6-9 have
substantially equal amplitude, modulation pulse width, and
modulation pulse frequency (or period), these embodiments are not
intended to limit the scope of the invention described herein.
Modulation pulse width is generally defined as the duration of a
modulation pulse, such as the time the power is at its peak power
level (e.g., t.sub.1 and t.sub.3 in FIG. 6B), length of time the
power is off (e.g., t.sub.2 and t.sub.4 in FIG. 6B), or the length
of time the power is at some intermediate level (e.g., items 1A and
2A in FIG. 9). In other embodiments, the duration of a modulation
pulse to the two or more plasma controlling devices may be varied
throughout the plasma process, from one modulation pulse to
another, or as different processing conditions are varied. In other
embodiments, the frequency (or period) of the modulation pulse
delivered to the two or more plasma controlling devices may be
varied throughout the plasma process, from one modulation pulse to
another, or as different processing conditions are varied. In still
other embodiments, the amount of power delivered for each
subsequent modulation pulse may not be equal and may be varied
throughout the plasma process, from one modulation pulse to
another, or as different processing conditions are varied. In other
embodiments, the modulation pulse is not rectangular in shape and
may be, for example, trapezoidal, triangular, etc. in shape.
[0103] FIGS. 10 and 11 illustrate two other embodiments having a
triangular-shaped and a sinusoidal-shaped modulation pulse,
respectively. Items 1 and 2 in FIGS. 10 and 11 depict amplitude
modulation of the RF power that is delivered to a first plasma
controlling device as a function of time and delivered to a second
plasma controlling device as a function of time, respectively.
FIGS. 10 and 11 illustrate embodiments where the power delivered to
the plasma controlling devices have substantially equal amplitude,
modulation pulse width and frequency (or period). In other
embodiments, the modulation pulse width and/or frequency of a
modulation pulse to the two or more plasma controlling devices may
be varied from one modulation pulse to another, as a function of
time or from process step to process step. In still other
embodiments, the amount of power delivered to each plasma
controlling device may not be equal at any given time and may be
varied relative to one another as required. In another embodiment,
the modulation pulses overlap and/or have a rest time between each
modulation pulse. In another embodiment a multisegmented modulation
pulse is used, that is, a modulation pulse having many segments in
which the power is varied as a function of time.
[0104] Other embodiments of the invention having different
modulation pulse shapes may be devised without departing from the
basic scope of the present invention. In one embodiment, the ramp
up to the peak power and/or the ramp down from the peak power may
not be linear, as shown in FIGS. 6-11, and may be, for example, a
second order, a third order, or exponential-shaped curve. In
another embodiment, it may be advantageous to use a sequence of
modulation pulses having different shapes (e.g., rectangular and
triangular modulation pulse, sinusoidal and rectangular modulation
pulse, rectangular, triangular and sinusoidal modulation pulse,
etc.) during processing to achieve the desired uniformity. In
another embodiment, a random modulation pulse generator may be used
to control when power is delivered to each plasma controlling
device, the ratio of power delivered to each device, the shape of
the modulation pulse, modulation pulse width, and/or the frequency
(or period) of each modulation pulse in an effort to even out any
nonuniformity that may occur from delivering the modulation pulse
in a systematic way.
EXAMPLES
[0105] The following non-limiting examples are provided to further
illustrate embodiments of the invention. However, the examples are
not intended to be all-inclusive and are not intended to limit the
scope of the inventions described herein.
Example 1
[0106] Examples of different plasma processing recipes utilizing an
amplitude modulation of RF power delivered to an orthogonal two
plasma controlling device torroidal source are described below for
a silicon dioxide etching process. The general process parameters
used to etch the surface of a substrate having a silicon dioxide
thickness of 20,000 Angstroms are as follows: a chamber process
pressure of 30 mTorr, a flow rate of 60 sccm of
hexafluoro-1,3-butadiene (C.sub.4F.sub.6), a flow rate of 60 sccm
of oxygen (O.sub.2), a flow rate of 500 sccm of argon, a substrate
pedestal temperature of 20 degrees Celsius, a substrate backside
helium pressure of 25 Torr, a constant substrate pedestal bias of
2000 Watts at a RF frequency of 13.56 MHz, and a plasma processing
time of 60 seconds. All RF power delivered to the other plasma
controlling devices was delivered using dynamic impedance matching
at an RF frequency of about 13.56 MHz+/-1 MHz. The 1 sigma, or 1
standard deviation, uniformity values discussed below were measured
using a Tencor Prometrix UV 1050's 49-point contour map at a
substrate edge exclusion of 3 millimeters. The Tencor Prometrix UV
1050's 49-point contour map uniformity data was collected by
measuring the difference, or change, in the surface profile of the
substrate before and after plasma etching.
Example 1A
[0107] Using a constant RF power level of 1000 Watts to both of the
plasma controlling devices achieved an average etch rate of 3400
Angstroms/minute and a uniformity of about 8.4%.
Example 1B
[0108] An average etch rate of 4930 Angstroms/minute and uniformity
of about 1.6% was achieved using a rectangular-shaped amplitude
modulated RF power pulse sequence, as shown in FIG. 6A, where the
RF power delivered to one of the plasma controlling devices, at any
given time, was at 2000 Watts and the other plasma controlling
device was at zero Watts and the modulation pulse frequency was 0.1
Hz. The modulation pulse width was half of the period.
Example 1C
[0109] An average etch rate of 5027 Angstroms/minute and uniformity
of about 1.5% was achieved using a rectangular-shaped amplitude
modulated RF power pulse sequence, as shown in FIG. 6A, where the
RF power delivered to one of the plasma controlling devices, at any
given time, was at 2000 Watts and the other plasma controlling
device was at zero Watts and the modulation pulse frequency was 0.5
Hz. The modulation pulse width was half of the period.
Example 1D
[0110] An average etch rate of 4602 Angstroms/minute and uniformity
of about 1.2% was achieved using a rectangular-shaped amplitude
modulated RF power pulse sequence, as shown in FIG. 9A, where the
RF power delivered to one of the plasma controlling devices, at any
given time, was at 1800 Watts and the other plasma controlling
device was at 200 Watts and the modulation pulse frequency was 0.1
Hz. The modulation pulse width was half of the period.
Example 1E
[0111] An average etch rate of 4170 Angstroms/minute and uniformity
of about 2.7% was achieved using a rectangular-shaped amplitude
modulated RF power pulse sequence, as shown in FIG. 9A, where the
RF power delivered to one of the plasma controlling devices, at any
given time, was at 1600 Watts and the other plasma controlling
device was at 400 Watts and the modulation pulse frequency was 0.1
Hz. The modulation pulse width was half of the period.
Example 1F
[0112] An average etch rate of 3522 Angstroms/minute and uniformity
of about 8.7% was achieved using a rectangular-shaped amplitude
modulated RF power pulse sequence, as shown in FIG. 9A, where the
RF power delivered to one of the plasma controlling devices, at any
given time, was at 1200 Watts and the other plasma controlling
device was at 800 Watts and the modulation pulse frequency was 0.1
Hz. The modulation pulse width was half of the period.
[0113] In one aspect, by varying the frequency of the amplitude
modulation of the RF power, or the modulation pulse frequency, it
is possible to vary the plasma density across the surface of the
substrate. In one embodiment the frequency of the amplitude
modulation of the RF power is varied at various times during the
process to tailor the plasma density to match a desired etch or
deposition profile on the surface of the substrate. In cases where
the user knows the profile of the surface of the substrate prior to
processing in the plasma chamber, varying the modulation pulse
frequency during plasma processing can allow the etch or deposition
profile to be adjusted to compensate for the initial
non-uniformity. For example, in a case where the starting substrate
profile is edge thick versus the center of the substrate the
modulation pulse frequency can be varied to increase the plasma
density near the edge of the substrate relative to the center of
the substrate to assure the results of the plasma process are
uniform. Since each plasma processing chamber configuration,
process sequence, and process recipe can cause the etch or
deposition plasma density to vary from chamber to chamber, sequence
to sequence and/or recipe to recipe it is likely that an optimum
frequency to achieve a desired plasma density profile will need to
be empirically found. An example of such results are shown in
Example 2 below.
Example 2
[0114] FIGS. 13A-E illustrate examples of how varying the amplitude
modulation pulse characteristics in a plasma processing chamber can
vary the plasma density across the surface of the substrate. The
results shown below were collected using an orthogonal two plasma
controlling device torroidal source utilizing a rectangular-shaped
amplitude modulation of RF power to complete a silicon dioxide
etching process. The general process parameters used to etch the
surface of a substrate having a silicon dioxide thickness of 20,000
Angstroms are as follows: a chamber process pressure of 30 mTorr, a
flow rate of 60 sccm of hexafluoro-1,3-butadiene (C.sub.4F.sub.6),
a flow rate of 60 sccm of oxygen (O.sub.2), a flow rate of 500 sccm
of argon, a substrate pedestal temperature of 20 degrees Celsius, a
substrate backside helium pressure of 25 Torr, a constant substrate
pedestal bias of 2000 Watts at a RF frequency of 13.56 MHz, and a
plasma processing time of 60 seconds. All RF power delivered to the
other plasma controlling devices was delivered using dynamic
impedance matching at an RF frequency of about 13.56 MHz+/-1 MHz.
The same hardware configuration process configurations were used
throughout this example. The 1 sigma, or 1 standard deviation,
uniformity values described herein were measured using a Tencor
Prometrix UV 1050's 49 point contour map at a substrate edge
exclusion of 3 millimeters. The Tencor Prometrix UV 1050's 49 point
contour map uniformity data was collected by measuring the
difference, or change, in the surface profile of the substrate
before and after plasma etching.
[0115] FIGS. 13A-D illustrate Tencor Prometrix UV 1050 49-point
contour maps of the production surface of an etched silicon dioxide
layer on a substrate using a rectangular-shaped amplitude modulated
RF power, similar to the RF power modulation profiles shown in FIG.
6. In the examples shown in FIGS. 13A-D the magnitude of the
modulation pulse to one of the plasma controlling devices, at any
given time, was 2000 Watts, while the magnitude of the modulation
pulse to the other plasma controlling device was zero Watts. The
modulation pulse width used in this example was half of the period.
FIG. 13A illustrates an example where at a modulation pulse
frequency of 1000 Hz an average etch rate of 5159 Angstroms/minute
was achieved at a 49 point 1-sigma uniformity of about 1.8%. FIG.
13B illustrates an example where at a modulation pulse frequency of
2000 Hz an average etch rate of 4971 Angstroms/minute was achieved
at a 49 point 1-sigma uniformity of about 2.58%. FIG. 13C
illustrates an example where at a modulation pulse frequency of
15,000 Hz an average etch rate of 4666 Angstroms/minute was
achieved at a 49 point 1-sigma uniformity of about 4.78%. FIG. 13D
illustrates an example where at a modulation pulse frequency of
25,000 Hz an average etch rate of 3524 Angstroms/minute was
achieved at a 49 point 1-sigma uniformity of about 9.49%.
[0116] FIG. 13E illustrates a Tencor Prometrix UV 1050 49-point
contour map of an etched silicon dioxide layer on a substrate where
a constant RF power level of 1000 Watts, that is, no amplitude
modulation pulsing is delivered to each of the plasma controlling
devices. This configuration achieved an average etch rate of 3648
Angstroms/minute and a uniformity of about 10.9%. Reviewing FIGS.
13A-E one will note that by increasing the modulation pulse
frequency the etch rate towards the edge of the substrate increases
as the modulation pulse frequency increases in this orthogonal
torroidal source configuration. This effect is shown on the
49-point contour map by the annular ring of "+" symbols on the edge
of the substrate, which correspond to a greater amount of etching,
versus the "-" symbols in the center, which corresponds to a lesser
amount of etching, and the increasing uniformity values as the
frequency increases. It should be noted that other plasma
controlling device types and configurations, which generate and
shape the plasma differently than the torroidal source example
shown here, can lead to different etch or deposition rate profiles
at various different frequencies.
[0117] 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.
* * * * *