U.S. patent application number 11/264235 was filed with the patent office on 2006-03-16 for apparatus, method and system for monitoring chamber parameters associated with a deposition process.
Invention is credited to Terry L. Gilton, Mark A. Jaso.
Application Number | 20060054497 11/264235 |
Document ID | / |
Family ID | 32736041 |
Filed Date | 2006-03-16 |
United States Patent
Application |
20060054497 |
Kind Code |
A1 |
Jaso; Mark A. ; et
al. |
March 16, 2006 |
Apparatus, method and system for monitoring chamber parameters
associated with a deposition process
Abstract
Apparatus and methods for measuring characteristics of a
metallic target as well as other interior surfaces of a sputtering
chamber. The apparatus includes a sensor configured to emit an
energy beam toward a surface of interest and to detect an energy
beam therefrom, the detected energy beam being indicative of
parameters of a characteristic of interest of the surface of
interest. Quantitative and qualitative characteristics of interest
may be determined. A sputtering system including the apparatus and
operable according to the methods of the invention is also
disclosed.
Inventors: |
Jaso; Mark A.; (Fairfax
Station, VA) ; Gilton; Terry L.; (Boise, ID) |
Correspondence
Address: |
TRASK BRITT
P.O. BOX 2550
SALT LAKE CITY
UT
84110
US
|
Family ID: |
32736041 |
Appl. No.: |
11/264235 |
Filed: |
November 1, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10609297 |
Jun 27, 2003 |
6974524 |
|
|
11264235 |
Nov 1, 2005 |
|
|
|
10352699 |
Jan 27, 2003 |
6811657 |
|
|
10609297 |
Jun 27, 2003 |
|
|
|
Current U.S.
Class: |
204/192.13 ;
204/298.03 |
Current CPC
Class: |
C23C 14/54 20130101;
C23C 14/543 20130101; C23C 14/3407 20130101; H01J 37/3482 20130101;
C23C 14/564 20130101 |
Class at
Publication: |
204/192.13 ;
204/298.03 |
International
Class: |
C23C 14/00 20060101
C23C014/00; C23C 14/32 20060101 C23C014/32 |
Claims
1. An apparatus for measuring at least one characteristic of a
surface in a chamber, the apparatus comprising: a sensor configured
to emit a first energy beam relative to an evaluation surface,
detect a second energy beam therefrom and provide an output signal
from which at least one characteristic associated with the
evaluation surface may be determined; and an arm coupled to the
sensor, the arm configured to transport the sensor relative to the
surface.
2. The apparatus of claim 1, wherein the evaluation surface is a
surface in the chamber selected from the group consisting of a
target surface, a chamber wall, a pedestal positioned proximate the
target surface, and a substrate disposed on the pedestal.
3. The apparatus of claim 1, wherein the at least one
characteristic of the evaluation surface is selected from the group
consisting of erosion of the evaluation surface, roughness of the
evaluation surface, a presence of asperities on the evaluation
surface, a composition of deposits on the evaluation surface, and a
concentration of deposits on the evaluation surface.
4. The apparatus of claim 1, wherein the first energy beam
comprises a visible light beam, an ultraviolet light beam, an
infrared light beam, a radio frequency beam, a microwave beam or an
ultrasound beam.
5. The apparatus of claim 1, further comprising a pedestal
positioned proximate a target surface, the target surface
comprising the evaluation surface in the chamber, wherein the
sensor and the arm coupled thereto are configured, positioned and
sized to enter a gap between the target surface and the pedestal,
wherein the arm is further configured to transport the sensor into
the gap without contacting the pedestal or the target surface.
6. The apparatus of claim 1, wherein the sensor comprises: a
transceiver configured to emit the first energy beam toward the
evaluation surface and to detect a first portion of the second
energy beam; and at least one first detector configured to detect a
second portion of the second energy beam.
7. The apparatus of claim 6, wherein the first portion of the
second energy beam comprises a coherently reflected portion of the
first energy beam from the evaluation surface, and the second
portion of the second energy beam comprises a scattered portion of
the first energy beam from the evaluation surface.
8. The apparatus of claim 6, further comprising an imaging device
configured to direct the first portion of the second energy beam to
the transceiver and to direct the second portion of the second
energy beam to the at least one first detector.
9. The apparatus of claim 6, wherein the transceiver comprises a
second detector and a source element configured to emit the first
energy beam.
10. The apparatus of claim 1, further comprising: a transmitter
optically coupled to the sensor, the transmitter configured to
transmit the first energy beam to the sensor; and a spectrometer
optically coupled to the sensor, the spectrometer configured to
generate sensory signals related to spectra of the second energy
beam incident thereon.
11. The apparatus of claim 10, wherein the spectrometer is selected
from the group consisting of a Raman spectrometer and an infrared
absorption spectrometer.
12. The apparatus of claim 10, wherein the spectrometer comprises:
a first mirror; a second mirror configured to move relative to the
first mirror; a beam splitter interposed between the first mirror
and the second mirror; and a receiver configured to generate the
sensory signals.
13. A method for measuring surface characteristics, the method
comprising: selectively positioning a sensor relative to an
evaluation surface; illuminating a portion of the evaluation
surface with a first energy beam; detecting a second energy beam
from the portion of the evaluation surface illuminated; and
analyzing the second energy beam to determine at least one
characteristic of the evaluation surface.
14. The method of claim 13, wherein the at least one characteristic
of the evaluation surface is selected from the group consisting of
erosion of the evaluation surface, roughness of the evaluation
surface, a presence of asperities on the evaluation surface, a
composition of deposits on the evaluation surface, and a
concentration of deposits on the evaluation surface.
15. The method of claim 13, wherein selectively positioning the
sensor comprises moving the sensor to a location proximate the
portion of the evaluation surface.
16. The method of claim 13, wherein selectively positioning the
sensor comprises inserting the sensor into a gap between a target
surface and a pedestal positioned proximate the target surface.
17. The method of claim 13, wherein selectively positioning the
sensor comprises placing the sensor proximate a window outside the
sputtering chamber.
18. The method of claim 17, further comprising emitting the first
energy beam into the sputtering chamber through the window.
19. The method of claim 13, wherein detecting the second energy
beam further comprises: detecting a coherently reflected portion of
the energy beam; and detecting a scattered portion of the energy
beam.
20. The method of claim 19, further comprising collecting the
coherently reflected portion of the energy beam and the scattered
portion of the energy beam into a plurality of optical fibers.
21. The method of claim 19, wherein illuminating the portion of the
evaluation surface with the energy beam comprises emitting a
coherent light beam from the sensor.
22. The method of claim 21, wherein emitting the coherent light
beam comprises collimating the coherent light beam as it exits an
optical fiber.
23. The method of claim 13, wherein illuminating the portion of the
evaluation surface with the first energy beam comprises
illumination with a visible light beam, an ultraviolet light beam,
an infrared light beam, a radio frequency beam, a microwave beam or
an ultrasound beam.
24. The method of claim 13, wherein detecting the second energy
beam comprises receiving at least a Raman scattered light beam as
the second energy beam.
25. The method of claim 13, wherein analyzing the second energy
beam further comprises performing a spectral analysis.
26. The method of claim 25, wherein performing the spectral
analysis comprises employing Raman spectroscopy.
27. The method of claim 25, wherein performing the spectral
analysis comprises employing a Fourier-transform analysis.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of application Ser. No.
10/609,297, filed Jun. 27, 2003, pending, which is a
continuation-in-part of U.S. patent application Ser. No.
10/352,699, entitled "Device for Measuring the Profile of a Metal
Film Sputter Deposition Target, and System and Method Employing
Same," filed Jan. 27, 2003, now U.S. Pat. No. 6,811,657, issued
Nov. 2, 2004, the disclosure of which is incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates generally to sputter
deposition of materials on substrate surfaces. More specifically,
the present invention relates to methods and apparatus for
measuring characteristics of a sputtering target and other surfaces
within a sputtering vacuum chamber.
[0004] 2. State of the Art
[0005] A thin film of metallic material may be deposited on a
substrate using a sputter deposition process wherein a metallic
target is attacked with ions, causing atoms or small particles of
the target to be ejected from the target and deposited on the
substrate surface. FIG. 1 illustrates a cross-sectional schematic
of a conventional sputtering apparatus 10 comprising a vacuum
chamber 12 having inner chamber walls 13, a gas inlet 14 and a gas
outlet 16. The vacuum chamber 12 may further include a window 15
comprising a material that is transparent to predetermined
wavelengths of electromagnetic radiation. The sputtering apparatus
10 further comprises a substrate support pedestal 24 and a metallic
target 22 attached to a sputtering cathode assembly 18, each
located within the vacuum chamber 12. The pedestal 24 may be
configured to secure a substrate 26 thereto with a biasable
electrostatic chuck, a vacuum chuck, a clamping structure, or a
combination of methods. The substrate 26 may be transported to and
from the pedestal 24 manually or with a robotic arm or blade (not
shown).
[0006] During the sputtering process, the vacuum chamber 12 is
filled with an inert gas, such as argon, through the gas inlet 14
and then reduced to a near vacuum through the gas outlet 16. The
target 22 is negatively charged to cause electrons to be emitted
from an exposed surface 23 of the target 22 and move toward an
anode (not shown). A portion of the moving electrons strike atoms
of the inert gas, causing the atoms to become positively ionized
and move towards the negatively charged target 22. The electrons,
inert gas atoms, and ions form a plasma which is typically
intensified and confined over the target surface 23 by a magnetic
field generated by a magnet assembly 20 located proximate the
target 22. The magnet assembly 20 may comprise one or more
permanent magnets or electromagnets located behind and/or to the
side of the target 22. A portion of the ions discharging from the
plasma strikes the target surface 23 at a high velocity, causing
atoms or small particles of the target 22 material to be ejected
from the target surface 23. The ejected atoms or small particles
then travel through the vacuum chamber 12 until they strike a
surface, such as the surface of the substrate 26, forming a thin
metallic film thereon.
[0007] Residue deposits comprising the ejected atoms or small
particles and byproducts are also deposited on the inner chamber
walls 13 and other surfaces within the sealed vacuum chamber 12
during the deposition process. The accumulation of the residue
deposits on the inner chamber walls 13 may be a source of
contamination as a plurality of substrates 26 is successively
processed in the vacuum chamber 12. Thus, the vacuum chamber 12
must be opened to atmosphere and cleaned after a predetermined
amount of operation time has elapsed under vacuum or when
contamination is detected on a substrate 26 that has undergone the
deposition process. Opening and cleaning the vacuum chamber 12 is
costly and time consuming. Therefore, it would be advantageous to
clean the vacuum chamber 12 only when a predetermined amount of
residue deposits have accumulated on the inner chamber walls 13 and
other surfaces within the vacuum chamber 12.
[0008] The magnetic field formed over the target surface 23 by the
magnet assembly 20 confines the electrons emitted from the target
22 to an area near the target surface 23. This greatly increases
the electron density and the likelihood of collisions between the
electrons and the atoms of the inert gas in the space near the
target surface 23. Therefore, there is a higher rate of ion
production in plasma regions near the target surface 23 where the
magnetic field intensity is stronger. Varying rates of ion
production in different plasma regions causes the target surface 23
to erode unevenly. Typically, the configuration of the magnet
assembly 20 produces a radial variation of thick and thin areas, or
grooves, within a diameter of the target surface 23. FIG. 2
illustrates a cross-sectional perspective view of a typical erosion
profile of a cylindrical metallic target 22, such as the metallic
target 22 shown in FIG. 1, which has been used in a sputtering
process. FIG. 2 illustrates a target surface 23 before erosion has
occurred as well as an eroded target surface 32 that has eroded
unevenly across the length of a diameter of the target 22. Due to
the geometry of a magnetic field surrounding the target 22, the
target surface 32 has eroded nearly symmetrically about a center
line 30 dividing the length of the diameter.
[0009] Referring now to FIGS. 1 and 2, the target 22 may comprise a
rare metal, such as gold, platinum, palladium or silver, or may
comprise, for example, aluminum, titanium, tungsten or any other
target material conventionally employed in the semiconductor
industry. Therefore, it is advantageous to consume as much of the
target 22 material during sputter deposition processes as possible
before replacing an eroded target 22. Further, replacing an eroded
target 22 before the end of its useful life may be a difficult and
time-consuming task. However, it is important to replace the target
22 before a groove "punches through" the target 22 material and
exposes portions of the cathode assembly 18 to erosion, causing
damage to the cathode assembly 18 and contaminating the sputtering
apparatus 10. For example, the target 22 material in the area of
grooves 28 shown in FIG. 2 may erode before the remainder of the
target 22 material and expose the cathode assembly 18 to ionic
bombardment from the surrounding plasma.
[0010] It may also be advantageous to replace or condition the
sputtering target 22 when certain characteristics of the target
surface 23 become degraded during the sputtering process. For
example, the smoothness of the target surface 23 may degrade over
time. The roughened target surface 23 may affect the consistency of
the deposition formation on the substrate 26 and may also be an
indication of the amount of target 22 consumption. Therefore, it
may be advantageous to replace the target 22 when the target
surface 23 reaches a predetermined roughness level.
[0011] As another example of degraded target surface 23
characteristics, certain targets 22, such as targets 22 comprising
Ag.sub.2Se (hereinafter "silver selenide"), may exhibit hair-like
growths or asperities (not shown) during the sputtering process. A
portion of the asperities may be ejected from the target surface 23
during the plasma ion bombardment and land on substrate 26, forming
defects therein. Typically, by the time the asperities have grown
on the target surface 23 so as to create noticeable defects on the
substrate 26, the target 22 is no longer useful and must be
replaced. Therefore, to avoid forming defects on the substrate 26
and to prolong the useful life of the target 22, it may be
advantageous to detect the asperities while the vacuum chamber 12
is under vacuum.
[0012] The useful life of a metallic sputtering target 22 is
typically estimated by determining the cumulative deposition time
for the target 22. A deposition time is chosen in an attempt to
guarantee that the target 22 material will never be completely
removed at any given location and may take into account the
thickness of the target 22, the material used for the target 22,
and the effect of intensifying and confining the plasma over the
target surface 23 by a magnetic field generated by the magnet
assembly 20 in a predetermined configuration. However, if the
characteristics of the plasma distribution change due, for example,
to reconfiguring the magnet assembly 20 to produce a magnetic field
with a different geometry, the erosion of the target surface 23 may
be changed and could result in localized enhanced metal removal and
the possible punching through of target 22 to the cathode assembly
18 before the expiration of the estimated deposition time.
[0013] Directly measuring the characteristics of the target surface
23 or the vacuum chamber 12 is difficult and time consuming.
Opening the vacuum chamber 12 to inspect the target surface 23 or
inner chamber walls 13 requires several hours of idle time while
the vacuum chamber 12 is baked out under post-vacuum inspection.
Accurate measurement of the target surface 23 while the sputtering
apparatus 10 is under vacuum is difficult because the gap distance
d between the target 22 and the pedestal 24 may be as small as 25
millimeters. Typical measurement devices are too large to be
inserted into the gap between the target 22 and the pedestal 24 to
profile the target surface 23 while the vacuum chamber 12 is under
vacuum. Further, measurement devices placed near the target 22
during a sputtering process may be damaged by exposure to metal
deposition.
[0014] In view of the above-noted shortcomings in the art, it would
be advantageous to prevent contamination from residue deposits on
the inner chamber walls 13 and other surfaces and to prevent
premature replacement, over-consumption or degradation of the
target 22 by providing a technique and device to measure the inner
chamber walls 13 and the target surface 23 while the vacuum chamber
12 is under vacuum.
BRIEF SUMMARY OF THE INVENTION
[0015] The present invention, in a number of embodiments, relates
to methods and apparatus for measuring the characteristics of a
metallic sputtering target and other surfaces within a sputtering
chamber.
[0016] An apparatus according to one embodiment of the present
invention may comprise a sensor configured to emit a first energy
beam toward a target surface and to detect a second energy beam
emitted from the target surface. The sensor may be coupled to a
thin profile arm configured to move or transport the sensor over
the target surface between the target and a substrate support
pedestal to a plurality of measurement locations. The arm may be
configured to attach to a robotic device. The sensor and the arm
are configured, positioned and sized to be inserted into a narrow
gap existing between the target surface and the pedestal. The arm
may also be configured to remove the sensor from the gap and to
shield the sensor during a sputtering process.
[0017] In another embodiment of the present invention, the sensor
may comprise a source element configured to emit a collimated light
beam and at least one detector. According to one aspect of the
invention, the at least one detector is arranged as a linear array
of detection elements and the source element is positioned so as to
emit the collimated light beam at an acute angle with respect to
the linear array. The linear array is positioned relative to the
source element so as to be illuminated by a reflection of the
collimated light beam. The distance from the sensor to the target
surface or the percentage of target erosion may be calculated by
determining the location in the array of the detection element or
elements illuminated by the reflection of the collimated light
beam. According to another aspect of the invention, the at least
one detector may be configured, positioned and sized to collect a
coherent reflection of the collimated light beam and a substantial
portion of scattered light beams from the target surface. The
roughness of the target surface may be calculated by comparing the
coherent reflection and scattered light beams. According to a
further aspect of the invention, the sensor may comprise a source
configured to emit an energy beam substantially parallel to the
target surface toward the at least one detector. The presence of
asperities on the target surface may be detected by analyzing the
energy beam after passing proximate to the target surface.
[0018] An apparatus according to yet another embodiment of the
present invention may comprise a sensor configured to emit a first
energy beam toward a surface in a chamber and to detect a second
energy beam emitted from the surface to analyze residue deposits
thereon. The sensor may be coupled to a thin profile arm configured
to move or transport the sensor proximate to the surface.
Alternatively, the sensor may be positioned outside the chamber and
configured to emit the energy beam through a window in the chamber.
The sensor may be configured to perform a spectral analysis on the
second energy beam.
[0019] In yet another embodiment of the present invention, a sensor
may comprise a transmitter optically coupled to a source collimator
configured to collimate a light beam as it exits an optical fiber.
The sensor may further comprise a receiver optically coupled to one
or more collection collimators, each collection collimator being
configured to collect a light beam incident thereon into a
corresponding optical fiber.
[0020] The present invention, in additional embodiments, also
encompasses a sputter deposition system incorporating the sensors
of the present invention and methods of measuring surface
characteristics.
[0021] One method according to the present invention comprises
emitting an energy beam, illuminating a first location on a target
surface, detecting a reflection of the energy beam from the first
location, and analyzing the detected reflection of the energy beam
to determine a distance from the point of emission to the first
location. Another method according to the present invention
comprises detecting a coherently reflected portion of an energy
beam from a target surface, detecting a scattered portion of the
energy beam, and relating the coherently reflected portion and the
scattered portion to a surface roughness. Yet another method
according to the present invention comprises emitting an energy
beam substantially parallel to a target surface, measuring a change
to the energy beam, and relating the change to a presence of
asperities on the target surface. A further method according to the
present invention comprises performing a spectral analysis on an
energy beam received from a surface.
[0022] Other features and advantages of the present invention will
become apparent to those of ordinary skill in the art through
consideration of the ensuing description, the accompanying
drawings, and the appended claims.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0023] In the drawings, which illustrate what are currently
considered to be best modes for carrying out the invention:
[0024] FIG. 1 is a cross-sectional side view schematic of a
sputtering apparatus;
[0025] FIG. 2 is a cross-sectional perspective side view of an
erosion profile of a cylindrical, metallic target;
[0026] FIGS. 3A-3C are cross-sectional side view schematics
according to the present invention of a portion of a sputtering
apparatus comprising a sensor configured, sized and positioned to
be inserted between a target surface and a pedestal or near a
vacuum chamber wall;
[0027] FIG. 4 is a top view schematic of a sensor configured to
measure the erosion of a sputtering target surface according to one
embodiment of the present invention;
[0028] FIG. 5 is a side view schematic of the sensor of FIG. 4 and
a portion of a sputtering apparatus;
[0029] FIG. 6 is a top view schematic of a sensor comprising a
transceiver and detectors, the sensor configured to the roughness
of a sputtering target surface according to another embodiment of
the present invention;
[0030] FIG. 7 is a side view schematic of the transceiver of FIG. 6
and a roughened target surface;
[0031] FIG. 8 is a partial side view schematic of the sensor of
FIG. 6 and the roughened target surface shown in FIG. 7;
[0032] FIG. 9 is a top view schematic of a sensor configured to
detect asperities on a sputtering target surface according to yet
another embodiment of the present invention;
[0033] FIG. 10 is a side view schematic of the sensor of FIG. 9 and
a portion of a target surface having asperities;
[0034] FIG. 11 is a block diagram of a sputter deposition system
comprising a sensor assembly according to one embodiment of the
present invention;
[0035] FIGS. 12A-12C are block diagrams of sensor assemblies
according to one embodiment of the present invention; and
[0036] FIG. 13 is a block diagram of a receiver suitable for use in
the sensor assembly of FIG. 12C.
DETAILED DESCRIPTION OF THE INVENTION
[0037] FIGS. 3A-3C each illustrate a cross-sectional schematic
according to the present invention of a portion of a sputtering
apparatus, such as the sputtering apparatus 10 shown in FIG. 1,
wherein a sensor 50 is positioned relative to a surface of an inner
chamber wall 13, a surface of pedestal 24 or surface 23 of target
22 to be analyzed. As shown in FIG. 3A, a sensor 50 coupled to a
thin profile arm 44 is configured and sized to be inserted into a
gap between a target 22 and a pedestal 24. The arm 44 may be
configured to detachably attach to a chamber robot 40 configured to
translate the sensor 50 over the target surface 23, or at least a
portion thereof. The chamber robot 40 may further be configured to
protect the sensor 50 during the sputtering process by removing the
sensor 50 from the sputtering area or by shielding the sensor 50.
The arm 44 may be interconnected to the chamber robot 40 through an
articulating arm 42 configured to provide movement in at least one
plane. In another embodiment of the present invention, the sensor
50 may detachably attach to a substrate pickup arm (not shown)
connected to the chamber robot 40 and configured to transport a
substrate (not shown) to and from the pedestal 24 using a pickup
device (not shown), such as a clamp, vacuum chuck or electrostatic
chuck, to attach the substrate thereto. In yet another embodiment,
the sensor 50 may be configured to attach directly to the pickup
device.
[0038] As shown in FIG. 3A, the sensor 50 is sized, positioned and
configured to measure the characteristics of the target surface 23
by transmitting a signal 46 toward the target 22 and receiving a
reflected or emitted signal 48 from the target surface 23. The
transmitted signal 46 may be an energy beam selected from the group
comprising a visible light beam, an ultraviolet light beam, an
infrared (hereinafter "IR") light beam, a radio frequency
(hereinafter "RF") beam, a microwave beam and an ultrasound beam.
To profile the target surface 23, the chamber robot 40 may be
configured to position the sensor 50 at a plurality of locations
relative to the target surface 23. Further, the sensor 50 may be
configured, such as by using a multiplexor, to scan a portion (as
opposed to a single point) on the target surface 23 while
positioned at one location relative to the target surface 23.
[0039] As shown in FIG. 3B, the sensor 50 may be sized, positioned
and configured to measure the characteristics of the pedestal 24 by
transmitting the signal 46 toward the pedestal 24 and receiving the
reflected or emitted signal 48 from the pedestal 24. Alternatively,
although not shown in FIG. 3B, the sensor 50 may be positioned and
configured to measure the characteristics of the substrate 26 shown
in FIG. 1 or deposits thereon. For example the sensor 50 may be
configured to detect deposition defects on the substrate 26 or to
detect when the deposition process is complete.
[0040] As shown in FIG. 3C, the sensor 50 is sized, positioned and
configured to measure the characteristics of an inner chamber wall
13 by transmitting the signal 46 toward the inner chamber wall 13
and receiving the reflected or emitted signal 48 from the inner
chamber wall 13. Similarly, the sensor 50 may be sized, positioned
and configured to measure the characteristics of any surface in the
vacuum chamber 12. Alternatively, although not shown in FIGS.
3A-3C, the sensor 50 may be positioned outside the vacuum chamber
12 and configured to pass the transmitted signal 46 through the
window 15 shown in FIG. 1 such that the transmitted signal 46 may
reflect off one or more surfaces within the vacuum chamber 12 and
exit the vacuum chamber 12 as reflected or emitted signal 48
through the same window 15, or a different window (not shown).
[0041] The surface characteristics measured by the sensor 50 shown
in FIGS. 3A-3C may be obtained, for example, through spectroscopy
techniques utilizing the absorption, emission, or scattering of
electromagnetic radiation by atoms or molecules on the surface
being analyzed to qualitatively or quantitatively study the atoms
or molecules, or to analyze physical processes occurring on the
surface. Referring to FIG. 3C, spectroscopy may be used to measure
the amount and composition of residue deposits on the inner chamber
wall 13. In one embodiment of the present invention, the signal 46
transmitted toward the inner chamber wall 13 is an IR light beam
and the absorption spectrum of the residue deposits on the inner
chamber wall 13 is measured using IR absorption spectroscopy. IR
absorption spectroscopy is the measurement of the wavelength and
intensity of the absorption of the IR light by the inner chamber
wall 13 and the residue deposits thereon. As discussed in relation
to FIG. 12C below, Fourier-transform infrared (hereinafter "FTIR")
spectroscopy may be used, for example, to measure the absorption
spectrum using Fourier-transform techniques and a Michelson
interferometer.
[0042] In another embodiment of the present invention, Raman
spectroscopy is used to measure the amount and composition of
residue deposits on the inner chamber wall 13. When the transmitted
signal 46 illuminates the surface of the inner chamber wall 13, a
portion of the transmitted signal 46 is scattered in various
directions. Light scattered due to vibrations in molecules or
optical phonons in solids is Raman scattered light. When the
transmitted signal 46 strikes the inner chamber wall 13 or the
residue deposits thereon, the light is scattered elastically (i.e.,
Rayleigh scattering) and inelastically (i.e., Raman scattering),
generating Stokes and anti-Stokes lines. In the present embodiment,
the reflected or emitted signal 48 represents a Raman scattered
beam. Raman spectroscopy is the measurement of the wavelength and
intensity of the inelastically scattered light of reflected or
emitted signal 48 from the inner chamber wall 13 or the residue
deposits thereon. The Raman scattered light of reflected or emitted
signal 48 occurs at wavelengths that are shifted from the
transmitted signal 46 by the energies of molecular vibrations.
Raman spectroscopy may provide structure determination,
multicomponent qualitative analysis, and quantitative analysis of
the residue deposits on the inner chamber wall 13. The mechanism of
Raman scattering is different from that of IR absorption.
Therefore, Raman spectroscopy and IR absorption spectroscopy may
each be used to provide complementary information about the residue
deposits on the inner chamber wall 13.
[0043] Returning to FIG. 3A, to determine the amount of erosion at
any location on the target surface 23, the reflected or emitted
signal 48 may be analyzed to determine a relative distance between
the sensor 50 and the target surface 23. It may not be necessary to
measure the relative distance between the sensor 50 and the target
surface 23 at every point on the target surface 23. Due to the
radial symmetry of the erosion of the target surface 23, it is only
necessary to determine the relative distance between the sensor 50
and the target surface 23 at points located linearly between the
center line 30 of the target surface 23 and an outside edge 25 of
the target surface 23, as shown in FIG. 2. Thus, measuring the
relative distance between the sensor 50 and the target surface 23
approximately every ten millimeters linearly between the center
line 30 and an outside edge 25 may provide sufficient resolution to
prevent punching through a target 22 having a diameter of
approximately thirty centimeters.
[0044] In one embodiment of the present invention, the relative
distance between the sensor 50 and the target surface 23 is
measured by measuring the time delay between the emission of the
transmitted signal 46 and detection of the reflected or emitted
signal 48, multiplying the measured time delay by the speed of the
transmitted signal 46 and dividing by two. In another embodiment,
the distance between the sensor 50 and the target surface 23 may be
determined by indirectly establishing the time delay by measuring a
phase difference between the transmitted signal 46 and the
reflected or emitted signal 48. In a phase measurement sensor 50,
the transmitted signal 46 may comprise a modulated signal. In yet
another embodiment, the transmitted signal 46 may be a pulsed
signal and the reflected or emitted pulse signal 48 may be detected
only during a predetermined time window such that increased time
delay between transmission and detection causes less of the pulse
to be detected. Thus, the detected power level of the reflected or
emitted pulse signal 48 is inversely proportional to the distance
traveled. Other embodiments for measuring the distance between the
sensor 50 and the target surface 23, as presently known in the art,
may also be employed.
[0045] FIG. 4 illustrates a top view schematic of a sensor 52
according to one embodiment of the present invention. The sensor 52
is attached to a thin profile arm 44, such as the arm 44 shown in
FIG. 3A. Sensor 52 comprises a source element 54 and a detector
array 55. The source element 54 has a thin profile so as to fit
between the target 22 and the pedestal 24, as shown in FIG. 3A. The
source element 54 is configured to generate a collimated light
beam. By way of example only, and not by limitation, the source
element 54 may comprise a laser diode. Alternatively, the source
element 54 may comprise a collimator, such as a lens, configured to
collimate or focus light exiting an optical fiber to a desired beam
diameter or spot size. As will be seen below, the collimated light
emitted from the source element 54 minimizes extraneous reflections
and enhances signal detection. Use of a collimated light beam as an
energy beam is currently preferred, although the invention is not
so limited.
[0046] The detector array 55 comprises a plurality of detectors or
detector elements 56 (ten shown) disposed side by side in a linear
array, each detector 56 having a thin profile so as to fit between
the target 22 and the pedestal 24, as shown in FIG. 3A. Each
detector 56 in the detector array 55 is configured to produce an
electronic sensory signal related to the magnitude of the radiation
received thereon. By way of example only, and not by limitation,
each detector may comprise a photodiode or a charge coupled device
(hereinafter "CCD"). Alternatively, each detector 56 in the
detector array 55 may comprise a collimator, such as a lens,
configured to collect light into an optical fiber.
[0047] FIG. 5 illustrates a side view schematic of the sensor 52
and arm 44 shown in FIG. 4. As shown in FIG. 5, the source element
54 is positioned so as to emit a transmitted beam 60 at a
predetermined transmission angle .alpha. in relation to the arm 44.
Although not shown, it may also be advantageous to position each
detector 56 of the detector array 55 at an angle in relation to the
arm 44 so as to align with a corresponding reflected beam, such as
reflected beams 62, 66 and 72.
[0048] FIG. 5 also illustrates the sensor 52 positioned in relation
to a portion of a target 22, such as the target 22 shown in FIG. 2.
The number of detectors 56 in the detector array 55 and the
position of each detector 56 relative to the source element 54 are
dependent upon the distance between the sensor 52 and the target
22. For illustration purposes, three surfaces 23, 32, 70 are
referenced in FIG. 5 corresponding to different target 22 erosion
states. The first target surface 23 corresponds to a new or unused
target 22 that has not yet been exposed to a sputtering process.
The transmitted beam 60 illuminates the new target surface 23 and
reflects back toward the detector array 55 as reflected beam 62. To
configure the dimensions of the detector array 55, the vertical
distance z between the new target surface 23 and the sensor 52 may
be predetermined. Thus, assuming the incident angle .beta. of the
transmitted beam 60 and the reflected angle .beta.' of the
reflected beam 62 are equal, the distance x between the source
element 54 and the nearest detector 56 in the detector array 55
(i.e., the detector 56 illuminated by the reflected beam 62) is
given by: x = 2 .times. ( z tan .times. .times. .alpha. ) ( 1 )
##EQU1##
[0049] The next target surface 32 shown in FIG. 5 corresponds to a
target 22 that has been used in a sputtering process wherein
approximately one-third of the target 22 material has been eroded.
As discussed above in relation to FIG. 2, the target surface 32 has
eroded unevenly. The transmitted beam 60, now represented by dashed
line 64, illuminates the eroded target surface 32 and reflects back
toward the detector array 55 as reflected beam 66. The reflected
beam 66 illuminates a detector 56 in the detector array 55 located
approximately one-third of the distance between the detector 56
located nearest the source element 54 and the detector 56 located
farthest from the source element 54. Therefore, it may be
determined that approximately one-third of the target 22 material
has been eroded at the measured location along the target surface
32.
[0050] The next target surface 70 shown in FIG. 5 corresponds to
the interface between the target 22 and the cathode assembly 18, as
shown in FIG. 1. The transmitted beam 60, now represented by dashed
line 68, illuminates the target interface surface 70 and reflects
back toward the detector array 55 as reflected beam 72. The
reflected beam 72 illuminates a detector 56 in the detector array
55 located farthest from the source element 54. Thus, it may be
determined that substantially all of the target 22 material has
been eroded at the measured location along the target interface
surface 70. As discussed above, use of the present invention to
detect target consumption prevents the target interface surface 70
from being punched through and exposing portions of the cathode
assembly 18 to erosion from the sputtering process. Therefore, it
may be advantageous to replace the target 22 before the target
interface surface 70 is detected.
[0051] FIG. 6 illustrates a top view schematic of a sensor 80
according to another embodiment of the present invention. The
sensor 80 is attached to a thin profile arm 44, such as the arm 44
shown in FIG. 3A. The sensor 80 comprises a transceiver 82 and a
two-dimensional detector matrix 86 comprising a plurality of
detectors 84 (24 shown). The transceiver 82 and the detectors 84
each have a thin profile so as to fit between the target 22 and the
pedestal 24, as shown in FIG. 3A. As shown in FIG. 6, the
transceiver 82 is positioned in row 87 of the detector matrix 86.
Each detector 84 in the detector matrix 86 is configured to produce
an electronic sensory signal related to the magnitude of the
radiation received thereon. By way of example only, and not by
limitation, each detector 84 may comprise a photodiode or a CCD.
Alternatively, each detector 84 may comprise a collimator, such as
a lens, configured to collect light into an optical fiber.
[0052] FIG. 7 illustrates a side view schematic of the transceiver
82 shown in FIG. 6 positioned in relation to a portion of a target
surface 88. As shown in FIGS. 7 and 8, the target surface 88 has
roughened during a deposition process. The transceiver 82 comprises
a source element 92 and a detector 94. The transceiver 82 may also
comprise a light-directing element 96, such as a mirror. The source
element 92 is configured to transmit a coherent light beam 97 of
wavelength .lamda. toward the roughened target surface 88. Use of a
collimated coherent light beam as an energy beam is presently
preferred, although the invention is not so limited. By way of
example only, and not by limitation, the source element 92 may
comprise a laser diode. Alternatively, the source element may
comprise a collimator, such as a lens, configured to collimate or
focus coherent light exiting an optical fiber to a desired beam
diameter or spot size.
[0053] A first portion of the transmitted coherent light beam 97 is
coherently reflected by the roughened target surface 88 in the
specular direction back toward the transceiver 82 as reflected
coherent beam 98 (offset for illustration only). The reflected
coherent beam 98 is directed to the detector 94 by the
light-directing element 96 where the power of the reflected
coherent beam 98 is measured. By way of example only, and not by
limitation, the detector 94 may comprise a photodiode or a CCD.
Alternatively, the detector 94 may comprise a collimator, such as a
lens, configured to collect the coherent light into an optical
fiber.
[0054] FIG. 8 illustrates a side view schematic of the sensor 80
and arm 44 shown in FIG. 6. FIG. 8 also illustrates the sensor 80
positioned in relation to a portion of the roughened target surface
88. For illustrative purposes, FIG. 8 shows a cross-sectional view
of the sensor 80 along row 87 of the detector matrix 86. As
discussed above in relation to FIG. 7, the transceiver 82 is
positioned and configured to illuminate a portion of the roughened
target surface 88 with the transmitted coherent light beam 97 and
to detect the reflected coherent beam 98. A second portion of the
transmitted coherent light beam 97 is reflected and scattered by
the roughened target surface 88 in a three-dimensional cone-like
direction back toward the detectors 84 in the detector matrix 86 as
scattered light beams 90 (four beams shown). The dimensions of the
detector matrix 86 are configured and positioned to detect a
substantial portion of the scattered light beams 90.
[0055] The roughness of the target surface 88 may be expressed as a
root-mean-square surface roughness (hereinafter "RMS_Roughness")
and may be determined as a function of the wavelength .lamda. of
the transmitted coherent light beam 97, the detected power of the
reflected coherent beam 98, and the detected power of the scattered
light beams 90. From the detected coherent reflected beam 98 power
(hereinafter "P.sub.Coherent") and the detected scattered light 90
power (hereinafter "P.sub.Scattered"), a scattering ratio is given
by: Scattering .times. .times. Ratio = P Scattered P Scattered + P
Coherent ( 2 ) ##EQU2##
[0056] The ratio of the RMS_Roughness divided by the wavelength
.lamda. of the transmitted coherent light beam 97, or
RMS_Roughness/.lamda., is related to the scattering ratio in
equation (2). If the target surface 88 is relatively smooth,
P.sub.Coherent will be large compared to P.sub.Scattered. Thus, the
scattering ratio will be relatively small and the ratio
RMS_Roughness/.lamda. will also be relatively small. As the target
surface 88 becomes increasingly rough, P.sub.Scattered increases
and P.sub.Coherent approaches zero. Thus, the scattering ratio
becomes increasingly large and the ratio RMS_Roughness/.lamda. will
also become increasingly large. Thus, for a given wavelength
.lamda. of the transmitted coherent light beam 97, the
RMS_Roughness may be characterized.
[0057] FIG. 9 illustrates a top view schematic of a sensor 100
according to another embodiment of the present invention. The
sensor 100 is attached to a thin profile arm 44, such as the arm 44
shown in FIG. 3A. The sensor 100 comprises a source element 102 and
a detector 104. The source element 102 and the detector 104 each
have a thin profile so as to fit between the target 22 and the
pedestal 24, as shown in FIG. 3A. The source element 102 is
configured to generate an energy beam. By way of example only, and
not by limitation, the source element 102 may comprise a laser
diode. Alternatively, the source element 102 may comprise a
collimator configured to collimate or focus light exiting an
optical fiber to a desired beam diameter or spot size. The detector
104 is configured to produce an electronic sensory signal related
to the magnitude of the energy beam received thereon. By way of
example only, and not by limitation, the detector 104 may comprise
a photodiode or a CCD. Alternatively, the detector 104 may comprise
a collimator, such as a lens, configured to collect light into an
optical fiber.
[0058] FIG. 10 illustrates a side view schematic of the sensor 100
shown in FIG. 9 positioned in relation to a portion of a target
surface 110. As shown in FIG. 10, the target surface 110 comprises
a plurality of asperities 112 that have grown thereon during a
deposition process. As discussed above, the target surface 110 may
comprise silver selenide or any target material which manifests
protrusion defects. As shown in FIG. 10, the source element 102 is
positioned and configured to emit an energy beam 114 substantially
parallel to the target surface 110 toward the detector 104. The
sensor 100 is configured and positioned such that the energy beam
114 illuminates or otherwise interacts with a portion of the
asperities 112. Thus, it may be advantageous to move the sensor 100
in a plane perpendicular to the target surface 110 as well as in a
plane parallel to the target surface 110. The presence of the
asperities 112 on the target surface 110 is detected by an
interruption of the energy beam 114 by a portion of the asperities
112 between the source element 102 and the detector 104. Similarly,
the presence of the asperities 112 may be detected by a reduction
in the intensity or power of the detected energy beam 114 caused by
interactions with a portion of the asperities 112. Alternatively,
the presence of the asperities 112 may be detected by measuring the
roughness of the target surface 110 as described above in relation
to FIGS. 6-8.
[0059] FIG. 11 is a block diagram of a sputter deposition system
180 according to the present invention. The sputter deposition
system 180 comprises a controller 182 electrically coupled to
chamber circuitry 190, a sensor assembly 200, an input device 184,
an output device 186 and a data storage device 188. The controller
182 is configured to communicate an electronic transmit signal to
the sensor assembly 200. Upon receipt of the transmit signal from
the controller 182, the sensor assembly 200 is configured to
transmit a beam of energy. The sensor assembly 200 is configured to
generate electronic sensory signals related to the magnitude of an
emitted, reflected or scattered energy beam received thereon. The
controller 182 is configured to receive and analyze the sensory
signals.
[0060] Referring to FIGS. 1 and 11, the sensor assembly 200 may be
located substantially within the vacuum chamber 12. Alternatively,
the sensor assembly 200 may be located substantially outside of the
vacuum chamber 12 or partially outside the vacuum chamber 12. For
example, the sensor assembly 200, or a portion thereof, may be
located outside of the vacuum chamber 12 and configured to transmit
the energy beam through the window 15. Similarly, the sensor
assembly 200 may be configured to receive the emitted, reflected or
scattered energy beam as it exits the same window 15 or a different
window (not shown).
[0061] The controller 182 may be configured to interface with the
chamber circuitry 190, including chamber robot circuitry 192, to
control the position of the sensor assembly 200 or a portion
thereof relative to a surface in the vacuum chamber 12, the
placement and removal of a substrate 26 on the pedestal 24, sputter
processing times, and other sputtering process and vacuum chamber
12 operations. The controller 182 may further be configured to
perform computer functions such as executing software to perform
desired calculations and tasks.
[0062] The input device 184 may include, by way of example only, an
Internet or other network connection, a mouse, a keypad or any
device that allows an operator to enter data into the controller
182. The output device 186 may include, by way of example only, a
printer or a video display device. The data storage device 188 may
include, by way of example only, drives that accept hard and floppy
discs, tape cassettes, CD-ROM or DVD-ROM.
[0063] The sensor assembly 200 may comprise a sensor (not shown)
such as the sensors discussed above or the embodiments disclosed
below in FIGS. 12A-13. For example, the sensor assembly 200 may
comprise the sensor 52 attached to the arm 44 shown in FIGS. 4 and
5. Referring to FIGS. 4, 5 and 11, the controller 182 is configured
to communicate an electronic transmit signal to the source element
54. Upon receipt of the transmit signal from the controller 182,
the source element 54 is configured to transmit a beam of
collimated light. The beam of collimated light may be a pulsed beam
of collimated light. Each detector 56 is configured to generate an
electronic sensory signal related to the magnitude of the radiation
received thereon. The controller 182 is configured to receive and
compare each of the sensory signals to determine which one of the
detectors 56 was illuminated with the greatest magnitude of
radiation. The controller 182 may be configured to receive the
sensory signals during a predefined time window in relation to the
communication of the transmit signal to the source element 54.
[0064] The controller 182 is further configured to determine the
relative distance from the sensor 52 to a target surface 23, 32,
70. As described above in relation to FIG. 5, the controller 182
may be configured to estimate the relative amount of erosion at a
location along the target surface 23, 32, 70 according to the
relative position of the detector 56 in the detector array 55
illuminated with the greatest amount of radiation. For example, if
a detector 56 located at the center of the detector array 55 is
determined by the controller 182 to be illuminated by a reflected
beam, then the controller 182 may be configured to estimate that
half of the target 22 material has been eroded at the position
along the target surface 23, 32, 70 being measured. Alternatively,
the distance from the sensor 52 to the target surface 23, 32, 70
may be determined as a function of the transmission angle .alpha.
and the distance between the source element 54 and the detector 56
being illuminated. For example, if the transmission angle .alpha.
and the distance x between the source element 54 and the nearest
detector 56 in FIG. 5 are known, then equation (1) above may be
used (assuming the incident angle .beta. of the transmitted beam 60
and the reflected angle .beta.' of the reflected beam 62 are equal)
to determine the distance z between the sensor 52 and the target
surface 23 as: z = x .function. ( tan .times. .times. .alpha. 2 ) (
3 ) ##EQU3##
[0065] FIGS. 12A-12C illustrate block diagrams of sensor assemblies
202, 230, and 260, suitable for use as the sensor assembly 200
shown in FIG. 11. The sensor assemblies 202, 230, 260 shown in
FIGS. 12A-12C employ fiber optics to reduce the size of a portion
of the sensor assemblies 202, 230, 260 to be positioned within a
sealed chamber (not shown), such as the vacuum chamber 12 shown in
FIG. 1. FIG. 12A illustrates a block diagram of sensor assembly 202
according to one embodiment of the present invention. The sensor
assembly 202 comprises a source element 210 and a plurality of
reception elements 212 (four shown) attached to a thin profile arm
214, such as the arm 44 shown in FIGS. 4 and 5. The source element
210 comprises a collimator, such as a lens, configured to collimate
or focus light exiting an optical fiber 216 to a desired beam
diameter or spot size. Each reception element 212 comprises a
collimator, such as a lens, configured to collect light incident
thereon into an optical fiber assembly 218. The sensor assembly 202
further comprises a transmitter 204 coupled to the source element
210 through the optical fiber 216 and a receiver 206 coupled to
each of the plurality of reception elements 212 through the optical
fiber assembly 218. The optical fiber assembly 218 comprises a
plurality of optical fibers, each optical fiber configured to
couple to one reception element 212.
[0066] Referring to FIGS. 11 and 12A, the transmitter 204 is
configured to receive a transmit signal from the controller 182 and
to transmit a beam of collimated light to the source element 210
through the optical fiber 216. The beam of collimated light may be
a pulsed beam of collimated light. For each reception element 212,
the receiver 206 is configured to receive a light beam through the
optical fiber assembly 218 and to generate an electronic sensory
signal related to the magnitude of the radiation collected at the
respective reception element 212. The receiver 206 is further
configured to transmit each of the sensory signals to the
controller 182. The controller 182 is configured to receive and
compare each of the sensory signals to determine which one of the
reception elements 212 was illuminated with the greatest magnitude
of radiation. The controller 182 may be configured to receive the
sensory signals during a predefined time window in relation to the
communication of the transmit signal to the source element 210 from
the transmitter 204. The controller 182 is further configured to
determine the relative distance from the source element 210 to an
object (not shown), as described above.
[0067] FIG. 12B illustrates a block diagram of sensor assembly 230
according to another embodiment of the present invention. The
sensor assembly 230 comprises an imaging device 236, a transceiver
238 and a scattered light reception element 240 attached to a thin
profile arm 242. The imaging device 236 may comprise a lens. The
transceiver 238 is configured to emit a coherent light beam 250 and
to receive a reflected coherent light beam 251 (offset for
illustration only). The transceiver 238 comprises a source
collimator (not shown), such as a lens, configured to collimate or
focus the coherent light beam 250 exiting an optical fiber 244 to a
desired beam diameter or spot size. The transceiver 238 also
comprises a coherent light reception element (not shown). The
transceiver 238 may also comprise a light-directing element (not
shown), such as a mirror, configured to direct the coherent light
beam 250 from the source collimator out of the transceiver 238
and/or to direct the reflected coherent light beam 251 into the
transceiver 238 to the coherent light reception element. The
coherent light reception element in the transceiver 238 and the
scattered light reception element 240 each comprise a collimator,
such as a lens, configured to collect light incident thereon into
an optical fiber assembly 246. The sensor assembly 230 further
comprises a transmitter 232 coupled to the transceiver 238 through
the optical fiber 244 and a receiver 234 coupled to the transceiver
238 and to the scattered light reception element 240 through the
optical fiber assembly 246.
[0068] Referring to FIGS. 11 and 12B, the transmitter 232 is
configured to receive a transmit signal from the controller 182 and
to transmit the coherent light beam 250 to the transceiver 238
through the optical fiber 244 where the source collimator emits the
coherent light beam 250 through the imaging device 236. The imaging
device 236 is configured to direct the reflected coherent light
beam 251 to the transceiver 238 where it is passed to the receiver
234 through the optical fiber assembly 246. The imaging device 236
is further configured to direct scattered light beams 252 (two
shown) to the scattered light reception element 240 where they are
passed to the receiver 234 through the optical fiber assembly 246.
The receiver 234 is configured to generate an electronic sensory
signal in response to each of the received reflected coherent light
beam 251 and scattered light beams 252. The receiver 234 is further
configured to transmit each of the sensory signals to the
controller 182. The controller 182 is configured to receive and
analyze the sensory signals as described above in relation to FIGS.
6-8 to determine the roughness of a surface (not shown) illuminated
by the coherent light beam 250.
[0069] FIG. 12C illustrates a block diagram of sensor assembly 260
according to yet another embodiment of the present invention. The
sensor assembly 260 comprises a source element 266 and a reception
element 268 attached to a thin profile arm 270. The source element
266 comprises a collimator, such as a lens, configured to collimate
or focus light exiting an optical fiber 272 to a desired beam
diameter or spot size. The reception element 268 also comprises a
collimator, such as a lens, configured to collect emitted,
reflected or scattered light incident thereon into an optical fiber
274. The sensor assembly 260 further comprises a transmitter 262
coupled to the source element 266 through the optical fiber 272 and
a spectrometer 264 coupled to the reception element 268 through the
optical fiber 274.
[0070] Referring to FIGS. 11 and 12C, the transmitter 262 is
configured to receive a transmit signal from the controller 182 and
to transmit a beam of collimated light to the source element 266
through the optical fiber 272. The beam of collimated light may
comprise multiple wavelengths. The spectrometer 264 is configured
to receive the collected light incident upon the reception element
268 through the optical fiber 274 and to analyze the collected
light using spectroscopy techniques. The spectrometer 264 is
further configured to generate electronic sensory signals related
to the spectroscopic analysis and to transmit the sensory signals
to the controller 182. The controller 182 is configured to receive
the sensory signals and to correlate the sensory signals to spectra
previously stored in a database in the data storage device 188.
Thus, the sensory signals may be correlated to compositional data
to determine elemental, isotropic and structural characteristics of
a surface (not shown) illuminated by the transmitted beam of
collimated light. For example, as discussed above, the sensory
signals may be correlated to determine the amount and composition
of residue deposits on the inner chamber wall 13 shown in FIG.
3C.
[0071] The spectrometer 264 shown in FIG. 12C employs a Michelson
interferometer. However, the scope of the present invention
includes all spectrometers and spectroscopy techniques presently
known in the art. The spectrometer 264 comprises a beam splitter
280, a moving mirror 282, a fixed mirror 284 and a receiver 286. As
an example of one spectroscopy technique suitable for use with the
present invention, the spectrometer 264 may be used with
Fourier-transform techniques to perform FTIR spectroscopy on the
collected light incident upon the reception element 268. In this
example, it is assumed that the collimated light beam transmitted
by source element 266 is an IR light beam and that the collected
light incident upon the reception element 268 is a reflection of
the IR light beam from a surface, such as the inner chamber wall 13
shown in FIG. 3C. The reflected IR light beam exiting the optical
fiber 274 is directed onto the beam splitter 280. The beam splitter
280 directs approximately half of the reflected IR light beam to
the moving mirror 282 and approximately half of the reflected IR
light beam to the fixed mirror 284. After reflecting off the moving
mirror 282 and the fixed mirror 284, the components of the
reflected IR light beam are recombined by the beam splitter 280 and
directed to the receiver 286. The moving mirror 282 and the fixed
mirror 284 produce constructive and destructive interference in the
recombined IR light beam which is detected by the receiver 286. The
receiver 286 is configured to convert the detected interference
into sensory signals, which are then analyzed by the controller 182
in FIG. 11 to determine the concentration and composition of the
surface being analyzed.
[0072] As another example of a spectroscopy technique suitable for
use with the present invention, the spectrometer 264 may be used to
perform Raman spectroscopy on the collected light incident upon the
reception element 268. In this example, it is assumed that the
collimated light beam transmitted by source element 266 comprises
multiple wavelengths and that the collected light incident upon the
reception element 268 is Raman scattered light from a surface
illuminated with the collimated light beam, such as the inner
chamber wall 13 shown in FIG. 3C. In this example, the Raman
scattered light is processed by the spectrometer 264 as described
above. However, the Raman scattered light undergoes additional
Raman spectroscopy once it reaches the receiver 286. FIG. 13
illustrates a receiver 300, such as the receiver 286 shown in FIG.
12C, configured to perform Raman spectroscopy.
[0073] The receiver 300 comprises a first lens 306, a grating 308,
a second lens 310, and a detector 312. The Raman scattered light is
directed onto the grating 308 by the first lens 306. The grating
308 disperses the Raman scattered light through the second lens 310
where it is focused onto the detector 312. The detector 312 may be
selected from the group comprising a CCD camera, an intensified CCD
detector, a charge injection device, a photomultiplier tube
detector array, a photodiode array (hereinafter "PDA"), an
intensified PDA, or an avalanche photodiode array. The detector 312
is configured to generate sensory signals representative of the
Raman spectra received thereon. The sensory signals are then
analyzed by the controller 182 in FIG. 11 and compared to Raman
spectra previously stored in a database in the data storage device
188. Thus, structural analysis, multicomponent qualitative
analysis, and quantitative analysis may be performed to determine
the characteristics of the surface being analyzed.
[0074] While the invention may be susceptible to various
modifications and alternative forms, specific embodiments have been
shown by way of example in the drawings and have been described in
detail herein. However, it should be understood that the invention
is not intended to be limited to the particular forms disclosed.
Rather, the invention includes all modifications, equivalents, and
alternatives falling within the spirit and scope of the invention
as defined by the following appended claims.
* * * * *