U.S. patent application number 11/427318 was filed with the patent office on 2008-01-03 for low power rf tuning using optical and non-reflected power methods.
Invention is credited to James P. Cruse, Theresa Kramer Guarini, Jeffrey Charles Pierce.
Application Number | 20080003702 11/427318 |
Document ID | / |
Family ID | 38877170 |
Filed Date | 2008-01-03 |
United States Patent
Application |
20080003702 |
Kind Code |
A1 |
Cruse; James P. ; et
al. |
January 3, 2008 |
Low Power RF Tuning Using Optical and Non-Reflected Power
Methods
Abstract
Aspects of the present invention include methods and apparatuses
that may be used for monitoring and adjusting plasma in a substrate
processing system by using a plasma data monitoring assembly. For
example, an optical instrument adapted to measure properties of
light over a specific portion of the electromagnetic spectrum may
be used to detect one or more wavelength intensities from the
plasma. Then, an electronic device, for example a computer software
may analyze the wavelength intensities and a match circuit may then
be adjusted. In this way, consistent plasma may be obtained. In
other embodiments, the present invention may utilize the
relationship between chamber pressure, substrate temperature, coil
currents and/or the plasma in order to adjust and maintain a
repeatable plasma process.
Inventors: |
Cruse; James P.; (San Jose,
CA) ; Guarini; Theresa Kramer; (San Jose, CA)
; Pierce; Jeffrey Charles; (Santa Clara, CA) |
Correspondence
Address: |
PATTERSON & SHERIDAN, LLP
3040 POST OAK BOULEVARD, SUITE 1500
HOUSTON
TX
77056
US
|
Family ID: |
38877170 |
Appl. No.: |
11/427318 |
Filed: |
June 28, 2006 |
Current U.S.
Class: |
438/7 ;
257/E21.525 |
Current CPC
Class: |
H01L 21/67253 20130101;
H01L 21/67069 20130101; H01L 22/20 20130101 |
Class at
Publication: |
438/7 |
International
Class: |
H01L 21/00 20060101
H01L021/00 |
Claims
1. A method for monitoring plasma in a substrate processing system,
comprising: monitoring reflected electromagnetic radiation
reflected from a plasma within a chamber; associating the reflected
electromagnetic radiation to an RF power within the processing
system; and adjusting a matching circuit to maintain a repeatable
plasma condition.
2. The method of claim 1, wherein the electromagnetic radiation
reflected from the plasma source may have a wavelength between
about 200 nm and about 800 nm and the substrate processing system
is adapted to detect the wavelength.
3. The method of claim 1, wherein the monitoring the reflected
electromagnetic radiation is performed by utilizing an
interferometer.
4. The method of claim 1, wherein the monitoring the reflected
electromagnetic radiation is performed by utilizing a
spectrometer.
5. The method of claim 1, wherein the adjusting the match circuit
is performed before and after processing of the substrate.
6. The method of claim 1, wherein the substrate processing system
is a plasma nitridation chamber.
7. The method of claim 1, wherein the RF power has an effective
power of about 5 Watts to about 30 KWatts.
8. The method of claim 1, wherein the reflected electromagnetic
radiation is optical.
9. A method for controlling a plasma in a substrate processing
system, comprising: Controlling a first set of wavelength
intensities of reflected electromagnetic radiation reflected from a
plasma within a chamber before processing of first set of one or
more substrates; associating the first wavelength intensity of
reflected electromagnetic radiation to an RF power within the
processing system; adjusting a matching circuit based on the
reflected electromagnetic radiation; processing the first set of
one or more substrates in the substrate processing system;
controlling a second a set of wavelength intensities of reflected
electromagnetic radiation reflected from a plasma within a chamber;
associating the second wavelength intensity of reflected
electromagnetic radiation to an RF power within the processing
system; and adjusting a matching circuit based on the first or the
second set of reflected electromagnetic radiation, while processing
a second set of one or more substrates.
10. The method of claim 9, wherein the second set of wavelength
intensities are selected based on substrate type or process
recipe.
11. The method of claim 9, wherein the first set of one or more
substrates and the second set of one or more substrates are of
different types.
12. The method of claim 9, wherein the electromagnetic radiation
reflected from the plasma source may have a wavelength between
about 200 nm and about 800 nm and the substrate processing system
is adapted to detect the wavelength.
13. The method of claim 9, wherein the controlling the reflected
electromagnetic radiation is performed by utilizing an
interferometer.
14. The method of claim 9, wherein the controlling the reflected
electromagnetic radiation is performed by utilizing a
spectrometer.
15. The method of claim 9, wherein the adjusting the match circuit
is performed before and after performing a service maintenance.
16. The method of claim 9, wherein the substrate processing system
is a plasma nitridation chamber.
17. The method of claim 9, wherein the RF power has an effective
power of about 5 Watts to about 30 KWatts.
18. Apparatus for monitoring a plasma in a substrate processing
system, comprising: a plasma chamber; an RF power source; an RF
matching circuit, wherein the RF matching circuit is controllable;
a plasma data monitoring assembly for acquiring data related to the
plasma, wherein the plasma data collecting assembly is disposed
within the processing chamber; and a computer, wherein the computer
comprises a software program adapted to model a relationship
between the data collected by the plasma data monitoring assembly
and the RF power and is capable of providing values for
controllable elements in the RF match circuit for a repeatable
process.
19. The apparatus of claim 18, wherein the plasma data monitoring
assembly further comprising: a first reactance element; and a
second reactance element;
20. The apparatus of claim 18, wherein the plasma data monitoring
assembly further comprises a third reactance element.
21. The apparatus of claim 18, wherein the plasma data monitoring
assembly is an interferometer.
22. The apparatus of claim 18, wherein the plasma data monitoring
assembly is an spectrometer.
23. The apparatus of claim 18, wherein the substrate processing
system is a plasma nitridation chamber.
24. The method of claim 18, wherein the monitoring data assembly is
adapted to detect electromagnetic radiation reflected from the
plasma with wavelengths between about 200 nm and about 800 nm.
25. The method of claim 18, wherein the RF power has an effective
power of about 5 KWatts to about 30 KWatts.
26. Apparatus for monitoring a plasma in a substrate processing
system, comprising: a plasma chamber; an RF power source; an RF
matching circuit, wherein the RF matching circuit is controllable;
and a computer, wherein the computer comprises a data monitoring
assembly adapted to model a relationship between the data collected
by the data monitoring assembly and the RF power and is capable of
providing values for controllable elements in the RF match circuit
for a repeatable process.
27. The apparatus of claim 26, wherein the data collected is coil
current;
28. The apparatus of claim 26, wherein the data collected is
electron density.
29. The apparatus of claim 26, wherein the data collected is
electron-neutron ratio.
30. The apparatus of claim 26, wherein the data collected is a
temperature of a substrate.
31. The apparatus of claim 25, wherein the data collected is
related to the plasma generated within the chamber.
32. The apparatus of claim 26, wherein the data collected comprises
two or more elements from the group consisting of electromagnetic
radiation reflected from the plasma source, coil current, electron
density, substrate temperature and electron-neutron ratio.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to methods and
apparatuses for use in substrate processing. More specifically, the
present invention relates to plasma monitoring methods and
apparatuses for use in substrate processing using different
processes, such as a Plasma Nitridation process and others.
[0003] 2. Description of the Related Art
[0004] Integrated circuits have evolved into complex devices that
can include millions of components (e.g., transistors, capacitors,
resistors, and the like) on a single chip. The evolution of chip
designs continually requires faster circuitry and greater circuit
density. The demands for greater circuit density necessitate a
reduction in the dimensions of the integrated circuit components.
The minimal dimensions of features of such devices are commonly
referred to in the art as critical dimensions. The critical
dimensions generally include the minimal widths of the features,
such as lines, columns, openings, spaces between the lines, and
device/film thickness and the like. As these critical dimensions
shrink, accurate measurement and process control becomes more
difficult.
[0005] Importantly, in some cases, monitoring of implantation
processes and controlling material thickness remain to be a
challenge in substrate device processing. For example, one problem
associated with a conventional plasma process used in the
manufacture of substrates is the lack of an ability to accurately
monitor the formation of plasma and thereby accurately controlling
the plasma state in a plasma chamber operating with lower powers.
One known method used to control a process attempts to achieve
optimum power in a chamber by using a match circuit to transform
the impedance of the plasma to a value that equals or matches the
characteristic impedance of the line through which RF power is
delivered to the chamber. At the match point, optimum power is
delivered into the plasma and little power is reflected back toward
the RF supply. In this method, tuning the match circuit, which is
controlled by a detector, is accomplished by varying the variable
reactance elements within the match circuit based on the power
detected by a detector. Unfortunately, the impedance of plasma is a
complex and highly variable function of many process parameters and
thus requires constant monitoring and adjustment by the detector.
In addition, in some cases, the generator may not be capable of
controlling lower powers and thus the plasma may fluctuate during
substrate processing.
[0006] Therefore, there is a need in the art for an improved method
and apparatus for substrate monitoring and process control during
the manufacture of integrated circuits.
SUMMARY OF THE INVENTION
[0007] One embodiment of the present invention provides a method
for monitoring plasma in a substrate processing system, comprising
monitoring reflected electromagnetic radiation reflected from a
plasma within a chamber, associating the reflected electromagnetic
radiation to an RF power within the processing system, and
adjusting a matching circuit to maintain a repeatable plasma
condition.
[0008] Another embodiment of the present invention provides a
method for controlling a plasma in a substrate processing system,
comprising Controlling a first set of wavelength intensities of
reflected electromagnetic radiation reflected from a plasma within
a chamber before processing of first set of one or more substrates,
associating the first wavelength intensity of reflected
electromagnetic radiation to an RF power within the processing
system, adjusting a matching circuit based on the reflected
electromagnetic radiation, processing the first set of one or more
substrates in the substrate processing system, controlling a second
a set of wavelength intensities of reflected electromagnetic
radiation reflected from a plasma within a chamber, and associating
the second wavelength intensity of reflected electromagnetic
radiation to an RF power within the processing system, and
adjusting a matching circuit based on the first and the second set
of reflected electromagnetic radiation, while processing a second
set of one or more substrates.
[0009] Another embodiment of the present invention provides an
apparatus for monitoring a plasma in a substrate processing system,
comprising a plasma chamber, an RF matching circuit, wherein the RF
matching circuit is controllable, a plasma data monitoring assembly
for acquiring data related to the plasma, wherein the plasma data
collecting assembly is disposed within the processing chamber, and
a computer, wherein the computer comprises a software program
adapted to model a relationship between the data collected by the
plasma data monitoring assembly and the RF power and is capable of
providing values for controllable elements in the RF match circuit
for a repeatable process.
[0010] Another embodiment of the present invention provides an
apparatus for monitoring a plasma in a substrate processing system,
comprising a plasma chamber, an RF power source, an RF matching
circuit, wherein the RF matching circuit is controllable, and a
computer, wherein the computer comprises a data monitoring assembly
adapted to model a relationship between the data collected by the
data monitoring assembly and the RF power and is capable of
providing values for controllable elements in the RF match circuit
for a repeatable process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] 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.
[0012] FIG. 1 illustrates an exemplary schematic diagram of a
processing system having one embodiment of the present
invention;
[0013] FIG. 2 illustrates another exemplary schematic diagram of a
processing system with an sensor for plasma monitoring;
[0014] FIG. 3 illustrates a cross section of the chamber wall of
the system of FIG. 2 having an optical sensor;
[0015] FIG. 4 illustrates a schematic of the tuning circuit in
communication with a spectrometer according to an embodiment of the
present invention;
[0016] FIG. 5 illustrates a diagram of a match peak find according
to an embodiment of the present invention;
[0017] FIG. 6 illustrates a diagram of a match peak find according
to another embodiment of the present invention; and
[0018] FIG. 7 illustrates a flow diagram of a processing method
according to an embodiment of the present invention.
DETAILED DESCRIPTION
[0019] Embodiments of the present invention provide methods and
apparatuses that may be utilized to monitor and adjust the plasma
in a substrate processing system by using a plasma data monitoring
assembly, such as an optical instrument adapted to measure
properties of light over a portion of the electromagnetic spectrum.
For example, in one embodiment, a method may be realized by
utilizing wavelength intensities sensitive to RF power that are
generated within a chamber. Then, an electronic device, for example
a computer software may analyze the wavelength intensities and a
match circuit may then be adjusted. In this way, consistent (i.e.,
repeatable) plasma condition may be obtained. In other embodiments,
the present invention may utilize the relationship between chamber
pressure, substrate temperature, coil currents, electron-neutron
ratio, electron density, electron energy and/or the plasma in order
to adjust and maintain a consistent plasma process.
[0020] While the following description of the system is described
with reference to a plasma processing chamber (e.g., a Plasma
Nitridation Chamber), the same techniques may be applied to other
applications and systems, such as substrate etch chambers and
others, wherein plasma is generated.
[0021] Although, the present invention is described with reference
to a plasma nitridation chamber (e.g., Decoupled Plasma Nitridation
(DPN) chamber), it is to be noted that the plasma of the plasma
nitridation process may be generated by various ionizing power
sources, which may, for example, include an inductively coupled
power source, a capacitatively coupled power source, a surface wave
power source, an electronic cyclotron resonance source (ECR
source), magnetron or modified magnetron-type sources, or other
sources that may be used to facilitate plasma generation in a
processing chamber.
[0022] FIG. 1 illustrates a schematic, cross-sectional diagram of
one illustrative embodiment of a substrate processing system 100
for fabricating integrated devices suitable for use with the
present invention. The substrate processing system 100 generally
includes a plasma processing module, such as a reactor module 101.
One illustrative embodiment of a reactor module 101 that can be
used to performed the steps of the present invention is a Decoupled
Plasma Nitridation (DPN) process reactor, made by Applied Materials
located in Santa Clara, Calif.
[0023] In one embodiment, the reactor module 101 includes a process
chamber 110, a Radio Frequency (RF) power source 118 (e.g., plasma
power source), and a controller 140. The process chamber 110 may
also include a substrate support pedestal 116 within a body (wall)
130, which may be made of a conductive material. The chamber 110 is
supplied with a dielectric ceiling 120. In the depicted embodiment,
the ceiling 120 is substantially flat. Other embodiments of the
process chamber 110 may have other types of ceilings, e.g., a
curved or domed ceiling. A lid (not shown) may be additionally
provided to house and protect additional components of the reactor
101 as well as form a shield for RF radiation. Above the ceiling
120 is disposed an antenna comprising at least one inductive coil
element 112 (two co-axial elements 112 are shown). The inductive
coil element 112 is coupled, through a first matching network
(e.g., match circuit(s)) 119, to an RF power source 118. In other
embodiments, the reactor module 101 may include a plurality of
match circuits each having one or more outputs connecting to the
coil element 112. In another embodiment, the match network 119 may
have a single output connecting to the coil element 112. In any
case, the plasma source 118 typically is capable of producing up to
3000 W at 13.56 MHz.
[0024] A controller 140 is coupled to the various components of the
substrate processing substrate processing system 100 to facilitate
control of, for example, the processing, monitoring plasma,
adjusting the power and frequency of the power supply and other
automated functions as described herein. The controller 140 may
include a central processing unit (CPU) 144, a memory 142, and
support circuits 146 for the CPU 144. The controller may facilitate
control of the components of the chamber 110 and the nitridation
process. The controller 140 may be one of any form of
general-purpose computer processor that can be used in an
industrial setting for controlling various chambers and
sub-processors. The memory 142, or computer-readable medium of the
CPU 144 may be one or more of 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.
The support circuits 146 are coupled to the CPU 144 for supporting
the processor in a conventional manner. These circuits include
cache, power supplies, clock circuits, input/output circuitry and
subsystems, and the like. The inventive method may be stored in the
memory 142 as a software routine (e.g., low power RF tuning
software). The software routine may also be stored and/or executed
by a second CPU (not shown) that is remotely located from the
hardware being controlled by the CPU 144. Alternatively, in another
embodiment, the inventive method may be stored in computer 195
and/or controller 140.
[0025] In a basic operation (e.g., a substrate implant operation),
a substrate 114 is placed on the pedestal 116 and process gases are
supplied from a gas panel 138 through entry ports 126 to form a
gaseous mixture 150. The gaseous mixture 450 is ignited into a
plasma 155 in the chamber 110 by applying power from the plasma
source 118 and 122 to the inductive coil element 412. The pressure
within the interior of the chamber 110 is controlled using a
throttle valve 127 and a vacuum pump 136. Typically, the chamber
wall 130 is coupled to an electrical ground 134. The temperature of
the wall 430 is controlled using liquid-containing conduits (not
shown) that run through the wall 430.
[0026] The temperature of the substrate 114 may be controlled by
stabilizing a temperature of the support pedestal 116. In one
embodiment, helium gas from a gas source 148 is provided via a gas
conduit 149 to channels (not shown) formed in the pedestal surface
under the substrate 114. The helium gas is used to facilitate heat
transfer between the pedestal 416 and the substrate 114. During
processing, the pedestal 116 may be heated by a resistive heater
(not shown) within the pedestal to a steady state temperature and
then the helium gas facilitates uniform heating of the substrate
114. Using such thermal control, the substrate 114 may be
maintained at a temperature between about 20 to 350 degrees
Celsius.
[0027] The RF power source may operate at any suitable frequency,
for example, 13.56 MHz. In one embodiment, the power is operated at
radio frequency and the power modulation frequency may be typically
turned on and off at KHz frequencies. For example, in one
embodiment, The RF power source 118 may continuously operate at
13.56 MHz while the RF power source 118 may be pulsed at a
frequency of about 1 KHz to about 50 KHz. In other embodiments, the
RF power source 118 may continuously operate without pulsing. The
peak RF power is typically set between about 50 watts to about 3000
watts. In some embodiments, effective power (duty cycle multiplied
by the source power) may range from about 10 watts to about 30
watts. The duty cycle of the modulations (or pulses) may be between
about 2% to about 90% and the ionizing power may be varied between
about 0% and about 100% to generate the desired mean temperature of
the constituents of the plasma. It is contemplated that a Direct
Current power source (DC power source) may be utilized in some
embodiments of the present invention.
[0028] In one embodiment, a nitrogen-containing gas, such as
N.sub.2 or NH.sub.3 at a flow rate of about 50 sccm to about 20 slm
may be introduced to the chamber for processing a substrate located
within the chamber. In addition to the nitrogen-containing gas, an
inert gas, such as He, Ar, Ne (neon), Kr (krypton) or Xe (xenon),
may be used to sustain the plasma and to modify the electron
temperature within the chamber. In one embodiment, the inert gas
flow rate is between about 0 sccm and about 20 slm. The plasma
nitridation process is typically operated at pressure between about
1 mTorr to about 1 Torr.
[0029] In order to monitor and adjust the plasma generated by a low
power RF device (e.g., RF power source 118), the present invention
may utilize a device, which is capable of detecting the
electromagnetic radiation generated by a plasma within the chamber.
Electromagnetic radiation may be a visible light, infrared light,
UV light and the like.
[0030] In one embodiment, a monitoring system 182 is capable of
detecting the radiated electromagnetic radiation by utilizing
interferomtery. In another embodiment, the monitoring system 182 is
adapted to monitor the plasma by utilizing spectroscopy (e.g.,
optical spectroscopy). In one embodiment, the monitoring system 180
detects a single wavelength of electromagnetic radiation from the
plasma. In other embodiments, the monitoring system 182 may detect
a plurality of wavelengths of electromagnetic radiation with
various intensities from the plasma. In some aspects, detecting a
plurality of wavelengths of electromagnetic radiation may be used
advantageously, since the detected electromagnetic radiation waves
may behave differently for different wavelengths when monitoring
the plasma. In one embodiment, electromagnetic radiation waves
having wavelengths of between about 200 nm and about 800 nm and in
some cases, between 800 nm and 1700 nm, may be used depending on
the sources used to generate a plasma within the chamber. In other
embodiments, an average of a plurality of wavelengths may be used
to monitor the plasma and yet in other embodiments, one or more
wavelengths in addition to one or more non-RF related parameters
may be utilized to monitor and/or control the plasma. The
monitoring system 182 is capable of using non-reflective RF
parameters, spectral and non-spectral parameters in order to
monitor and control the plasma.
[0031] Depending on the species of gases (e.g., nitrogen) used to
generate plasma, a particular wavelength may be selected to monitor
the plasma. For example, for a 1.sup.st neg N.sub.2.sup.+, an
optical filter may be used in order to detect and monitor
wavelengths of about 337.13 nm or of about 391.44 nm.
Alternatively, for a 1.sup.st pos N.sub.2, a wavelength of about
590.60 nm or of about 601.36 nm is monitored. Examples of typic
gases that may be used for plasma processing may include N.sub.2,
H.sub.2, He, O.sub.2, CO.sub.2, CH.sub.4 and the like. Thus, the
selected wavelengths may vary.
[0032] In one embodiment, the monitoring system 182 may include a
spectrometer 156, a sensor 190 and a computer 195. In one
embodiment, the computer 195 and controller 140 may be one and the
same. However, in one embodiment, the controller 140 is used for
controlling the chamber activities, while, the computer 195 is used
for controlling the plasma monitoring, data collection and
analysis. The computer 195 may include a low power RF tuning module
(e.g., low power RF tuning software 180). The low power RF tuning
software 180 may include an executable program module, for example
a Dynamic Link Library (DLL) that performs one or more low power RF
tuning functions at runtime. The low power RF tuning software 180
may also be stored and/or executed by a second CPU (not shown) that
is remotely located from the hardware being controlled by the
computer 195. In another embodiment, the low power RF tuning
software 180 may be stored in controller 140 and/or computer 195.
In other embodiments, the low power RF tuning software 180 may be
located in spectrometer 256 or RF power source 118 or in the match
network 119. Alternatively, the low power RF tuning software may be
included in one or more computers placed within any of the
substrate processing's subsystems such as RF power source 118 and
the like.
[0033] FIG. 2 illustrates one embodiment of the present invention
with an exemplary schematic diagram of a processing system
(processing system 200) with an optical port sensor for plasma
monitoring. As shown, a monitoring system 280 may utilize a
spectrometer 256 to collect the radiation from the generated plasma
within the chamber. A fiber optical splitter 292 may split the
radiation into discrete wavelengths, and detect the intensity of
the radiation at each discrete wavelength. In one embodiment, the
spectrometer 256 may include an input slit, a diffraction grating
(or optical prism), a diffraction grating controller and a detector
array to collect the incoming radiation. In one embodiment the
spectrometer 256 is used to scan across a range of wavelengths of
the emitted radiation as a function of time to monitor and control
the process. A sensor 290 is adapted to detect a plurality of
wavelengths. Suitable sensors used to measure the various
wavelengths may include the following classes of sensors, for
example, a photovoltaic, a photoconductive, a
photoconductive-junction, a photoemissive diode, a photomultiplier
tube, a thermopile, a bolometer, a pyroelectric sensor or other
like detectors. When using sensor detectors of this type, it may be
advantageous to use filters to limit desired wavelengths that are
detected. In one embodiment as shown in FIG. 3, sensor 290 may be
placed next to a window such that it is in direct view of plasma
region through a chamber wall 299. Alternatively, a sensor may be
inserted or it may be fully enclosed within the processing chamber
(not shown). In either case, a fiber optic cable may be used to
transfer the detected signals to a controller, for processing, in
order to obtain desired processing data used to control the
plasma.
[0034] In one embodiment, the optical interface between the sensor
device 290 and the spectrometer 256 may be provided using a
fiber-optic array 264. The fiber optic array 264 is generally a
bundle of optical fibers (detector fibers) that are connected to
the spectrometer 256. In one embodiment, the fiber optic array 264
has a combined diameter of about 0.2 millimeters to about 1
millimeter. The size of the fibers may also vary to assist in the
collection of the reflected light. For example, the detector fibers
connected to the spectrometer 256 may have a diameter of about 300
microns. In another embodiment, the fiber optic array 164 may
include a single source fiber or an array of source fibers coupled
to the spectrometer 256 without the need for separate detector
fibers.
[0035] In operation, light reflected from the illuminated region
(the plasma) 248 is detected and guided by the detector 290 to the
spectrometer 256. The spectrometer 256 detects a broad spectrum of
wavelengths of light, enabling the intensities of the plasma to be
observed using a wavelength having a strong reflectance signal
and/or using multiple wavelengths. It is contemplated that, more
generally, any analyzer capable of analyzing the reflected light is
used to provide data via a serial cable to the computer 295.
[0036] Although only one spectrometer is illustrated in FIG. 2, it
is contemplated that in other embodiments, one or more fixed
spectrometers and/or one or more variable spectrometers or a
combination thereof may be integrated within the substrate
processing system 100 for plasma monitoring.
[0037] In one embodiment, output from the spectrometer 256 is
delivered to the computer 295 or to the controller 240 for analysis
and may be used as data to monitor and adjust the plasma within the
chamber as discussed herein. The computer 295 may be a general
purpose computer or a special purpose computer and generally is
configured with similar components as used by the controller 240
described above. In one embodiment, the output from the computer
295 is delivered to the controller 240 so that necessary process
adjustments may be made. In another embodiment, the computer 295
and controller 240 may be the same device, containing all the
required software and hardware components necessary to control the
process and analyze the spectral information. In either case, the
controller 240 or the computer 295 or any other computers embedded
within the processing system may be adapted to include a low power
RF tuning module (e.g., low power RF tuning software) for
monitoring a process and in particular, for low power RF tuning as
discussed below.
[0038] FIG. 4 illustrates a schematic of the tuning circuit in
communication with a spectrometer according to an embodiment of the
present invention. As shown, an RF match section 419 includes a
variable capacitor C.sub.1 connected in series to an input
capacitor C and an input inductor L with RF input 422. The RF match
section may also include a second variable capacitor C.sub.2 which
is connected across the capacitor C.sub.1 and ground. The
capacitance of C.sub.1 and/or C.sub.2 may be intentionally and
repeatedly changed by motors 422, and 443 of a servo unit 444. In
other embodiments, both capacitors C.sub.1 and C.sub.2 may include
movable capacitance plates such that the orientation of which are
controlled by motors 442 and 444 of a servo unit 444. A controller
440, in communication with a low power RF tuning module and
computer 495, coupled to the servo unit and the spectrometer 456,
monitors the generated plasma within the chamber and based on the
reflected intensity, controls the operation of motors 40 and 42. In
this way, the controller controls the values of the variable
capacitors C.sub.1 and C.sub.2. For example, in one embodiment, the
controller may adjust these values to provide for a maximum
intensity for a particular wavelength in order to ensure that a
consistent plasma is generated. It is also noted that the match
circuit may include other elements (e.g., other reactance
elements), in addition to the elements shown in FIG. 4.
[0039] In other embodiments, a plurality of match circuits in
communication with one or more motors may be utilized to maintain a
consistent plasma. In addition, it is contemplated that the match
circuit(s) may be located in RF power source 418. In other
embodiments, the frequency of the RF power source may be varied
instead of varying the capacitance of the match circuit in order to
tune the adjusted in order to control the plasma in the chamber.
For example, in one embodiment, the frequency of the RF power
source 418 may be varied from 13.56 MHz to up to about 13.6 MHz or
down to about 13.5 Mhz in order to adjust the plasma in the
chamber. It is also contemplated that the controller may control
the values of the variable capacitors C.sub.1 and C.sub.2 of the
match circuit in addition to the frequency of the RF power source
to maintain a consistent plasma.
[0040] FIG. 5 illustrates a diagram of a match peak find according
to an embodiment of the present invention. As illustrated, a
normalized broadband wavelength is compared with reflected power
(Pref (W)) and accordingly, a series capacitor is varied. The low
power RF tuning software is adapted to select series values that
provide for a maximum normalized broadband wavelength where the
Pref is minimized. Then, the selected value is used to compare and
adjust the series value. For example, when the low power RF tuning
software is run, the system will find the optimum series value for
a given capacitor by finding the series setting which maximizes a
user selected parameter.
[0041] In some embodiments, depending on the process and/or
substrate type used for processing in the substrate processing
chamber 100, different wavelengths may be selected. For example,
after processing a substrate under a first processing recipe, a
different wavelength may be selected for plasma monitoring for a
second substrate process recipe. In some cases, a different
wavelength may be used for different substrate types processed in
the substrate processing system.
[0042] Other embodiments of the present invention may provide
methods and apparatuses that may be utilized to monitor and adjust
the plasma in a substrate processing system by using a relationship
between one or more non-reflected power methods, such as chamber
pressure, substrate temperature, coil currents and/or voltage,
electron-neutron mass ratio, phase and others in order to adjust
and maintain a consistent plasma process. For example, in one
embodiment, the substrate processing system 100 may provide for a
consistent plasma by selecting a series value that corresponds to a
maximum inner coil current.
[0043] FIG. 6 illustrates a diagram of a match peak find according
to another embodiment of the present invention. As illustrated, the
inner coil current (e.g., Current (2)) is compared with a series
capacitor. The low power RF tuning software 180 is adapted to
select series values that provide for a maximum coil current. Then
the selected value is used to compare and/or adjust the series
value. For example, when the low power RF tuning software is run,
the system will find the optimum series value for a given capacitor
(e.g., shunt capacitor) by choosing a series setting which
maximizes a user selected parameter (e.g., Current (2)). It is
contemplated that more than one variable may be monitored in order
to adjust and maintain a consistent plasma. For example, in one
embodiment, optimum match settings may correspond to the series and
shut values at which, the reflected power is at minimum, the inner
coil current and/or the wavelength intensities of a broadband
electromagnetic reflect are at a maximum.
[0044] In other embodiments, the present invention may be used as a
monitoring device to monitor the plasma. For example, the substrate
processing system may monitor an expected response (e.g., a
predetermined wavelength intensity). The computer 195 may monitor
the reflected electromagnetic radiation and once a predetermined
deviation from the expected response is detected, an alert may be
sent to a computer system. In other embodiments, the computer 195
may utilize a dynamic loop and continually adjust the tuning
circuits to maintain a predetermined wavelength intensity.
[0045] FIG. 7 illustrates operations 700 according to an
implementation of the present invention. The operations of 700 may
be performed, for example, by the controller 140. Moreover, various
steps in the methods set forth below need not be performed or
repeated on the same controller. These operations may be performed
before and/or after processing of one or more substrates.
Alternatively, in some cases, after cleaning of the substrate
processing chamber, one or more of the following steps may be
performed. In addition, the operations 600 may be understood with
occasional reference to FIGS. 1, 4, 5 and 6.
[0046] The operations begin, at step 720, where plasma is generated
within the substrate processing system 100. A substrate 114 may be
placed on the pedestal 116 and process gases are supplied from a
gas panel 138 through entry ports 126 to form a gaseous mixture
150. The gaseous mixture 150 is ignited into plasma in the chamber
110 by applying power from the RF power source 118 to the inductive
coil element 112.
[0047] At step 740, the light reflected from the plasma may be
detected and/or collected by a signal monitoring device via sensor
190 in the form of a light signal(s) and the signal may be
transmitted by a signal cable 164 to the spectrometer 156. Then,
the signal may be analyzed by the spectrometer 156 and the computer
195. At step 760, a low power RF tuning module (e.g., low power RF
tuning software 180) may use one or more of such signals as input
data and adjust the matching circuit, for example, by adjusting
C.sub.1 and/or C.sub.2. In some embodiments, the analyzed results
can be used to generate control commands to tune the plasma and
adjust the matching circuit. In addition, the control commands may
control the reactor chamber via controller 140. In order to monitor
and adjust the plasma in a substrate processing system 100, the
system may utilize a plasma data collecting assembly, adapted to
measure properties of light over a specific portion of the
electromagnetic spectrum.
[0048] In other embodiments, the present invention may utilize the
relationship between chamber pressure, substrate temperature, or
antenna current and the plasma in order to adjust and maintain a
consistent plasma process. For example, the plasma monitoring
assembly may monitor current through the outer antenna and the
current through inner antenna (e.g., coil currents) in order to
monitor and adjust the plasma. A current sensor may be used in the
processing system to monitor and report the sensed current to the
computer. Then, the low power RF tuning software may monitor the
sensed current in the coils and accordingly adjust the series value
to find an RF match peak. For example, the low power RF tuning
software may sequence through a number of series values and monitor
and/or record a decrease in the current. Then, after a predefined
number of decreasing steps, locate a peak value. In one embodiment,
the value may be recorded and used as a reference point for future
tuning runs.
[0049] In some embodiments of the present invention, optimum match
settings may correspond to the series and shut capacitor values
where the reflected power is minimum, inner coil current is maximum
and a broadband signal intensity is maximum. In addition, in other
embodiments, the controller may monitor variables such as coil
currents, broadband signal intensities, reflected power, chamber
pressure and substrate temperature alone or in combination in order
to provide for an optimum match settings. It is noted the present
invention may utilize other parameters that can be mapped to plasma
repeatability. In addition, it is also contemplated that other
measurable characteristics of plasma may be used to provide for
desired match settings.
[0050] Embodiments of the present invention provide methods and
apparatuses that may be utilized to monitor and adjust the plasma
in a substrate processing system. By using a plasma data monitoring
assembly, information about the plasma may be monitored and then
plasma may be adjusted. In some embodiments, a method may be
realized by utilizing wavelength intensities sensitive to RF power
that are generated within a chamber. Then, an electronic device,
for example a computer software may analyze the wavelength
intensities and a match circuit may then be adjusted. In this way,
consistent plasma may be obtained. In other embodiments, the
present invention may utilize the relationship between chamber
pressure, coil currents, substrate temperature, and the plasma in
order to adjust and maintain a consistent (e.g., repeatable) plasma
process.
[0051] Although the embodiments disclosed above, which incorporate
the teachings of the present invention, have been shown and
described in detail herein, those skilled in the art can readily
devise other varied embodiments which still incorporate the
teachings and do not depart from the spirit of the invention.
* * * * *