U.S. patent application number 10/429768 was filed with the patent office on 2004-11-11 for method system and computer readable medium for monitoring the status of a chamber process.
This patent application is currently assigned to TOKYO ELECTRON LIMITED. Invention is credited to Ludviksson, Audunn.
Application Number | 20040221957 10/429768 |
Document ID | / |
Family ID | 33416117 |
Filed Date | 2004-11-11 |
United States Patent
Application |
20040221957 |
Kind Code |
A1 |
Ludviksson, Audunn |
November 11, 2004 |
Method system and computer readable medium for monitoring the
status of a chamber process
Abstract
A method system and computer readable medium for monitoring a
process performed in a process chamber includes performing the
process in the chamber, generating light in the chamber, and
detecting transmission properties of the light through a window of
the chamber. A status of the process is monitored based the
detected transmission properties of the light through the window.
The process performed in the chamber may be a conditioning,
cleaning or production process for a semiconductor, and may include
generating a plasma, CVD or wet etching.
Inventors: |
Ludviksson, Audunn;
(Scottsdale, AZ) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
TOKYO ELECTRON LIMITED
Tokyo
JP
|
Family ID: |
33416117 |
Appl. No.: |
10/429768 |
Filed: |
May 6, 2003 |
Current U.S.
Class: |
156/345.24 |
Current CPC
Class: |
H01J 37/32935 20130101;
C23F 1/00 20130101; G01N 21/71 20130101; G01N 21/59 20130101; H01J
37/32862 20130101; H01L 21/67253 20130101 |
Class at
Publication: |
156/345.24 |
International
Class: |
C23F 001/00 |
Claims
1. A method of monitoring a process performed in a process chamber,
comprising: performing the process in the chamber; generating light
in the chamber; detecting transmission properties of the light
through a window of the chamber having a layer of material thereon;
and monitoring a status of the process based on changes in the
detected transmission properties that are caused by the process
changing a state of the layer of material.
2. The method of claim 1, wherein the performing a process
comprises conditioning the chamber for a semiconductor production
process.
3. The method of claim 2, wherein the conditioning comprises
generating a plasma in the chamber.
4. The method of claim 2, wherein the conditioning comprises
performing chemical vapor deposition in the chamber.
5. The method of claim 2, wherein the conditioning the chamber
comprises forming the layer of material on an interior surface of
the window.
6. The method of claim 1, wherein the performing a process
comprises cleaning an interior surface of the chamber.
7. The method of claim 6, wherein the cleaning comprises performing
a wet etching cleaning process in the chamber to remove material
from the interior surface of the chamber.
8. The method of claim 6, wherein the cleaning comprises performing
a dry etching cleaning process in the chamber to remove material
from the interior surface of the chamber.
9. The method of claim 1, wherein the performing a process
comprises performing a production process on a semiconductor
substrate in the chamber.
10. The method of claim 9, wherein the performing a production
process comprises generating a plasma in the chamber.
11. The method of claim 9, wherein the performing a production
process comprises performing chemical vapor deposition in the
chamber.
12. The method of claim 1, wherein the generating light comprises
generating light from a light source.
13. The method of claim 12, wherein the generating light from a
light source comprises generating light at a predetermined
wavelength based on the process performed in the chamber.
14. The method of claim 1, wherein the generating light comprises
generating light from the process performed in the chamber.
15. The method of claim 14, wherein the generating light comprises
generating light from a plasma generated in the chamber.
16. The method of claim 1, wherein the detecting transmission
properties comprises detecting an intensity of the light through
the window of the chamber.
17. The method of claim 1, wherein the detecting transmission
properties comprises detecting a wavelength of the light through
the window of the chamber.
18. The method of claim 17, wherein the detecting a wavelength
comprises detecting a predetermined wavelength based on the process
performed in the chamber.
19. The method of claim 1, wherein the detecting transmission
properties comprises performing optical emission spectroscopy on
the light emitted through the window of the chamber.
20. The method of claim 1, wherein the monitoring comprises
comparing the detected transmission property with prerecorded
transmission property data correlated to the process performed in
the chamber.
21. The method of claim 20, further comprising determining an
endpoint of the process performed in the chamber based on the
comparing step.
22. The method of claim 20, further comprising determining a phase
change point of the process performed in the chamber based on the
comparing step.
23. The method of claim 20, further comprising determining an
abnormal condition of the process performed in the chamber based on
the comparing step.
24. The method of claim 1, further comprising controlling the
process performed in the chamber based on the monitored status of
the process.
25. The method of claim 24, wherein the controlling comprises at
least one of stopping the process and changing parameters of the
process.
26. The method of claim 1, wherein the light generated is infrared
light and the method further comprises monitoring absorption of
infrared light by material on a surface of the window.
27. The method of claim 2, wherein: the detecting comprises
detecting an intensity of the light through the window having the
layer of material thereon; the monitoring comprises comparing the
detected intensity with a predetermined threshold intensity
correlated to an endpoint of the conditioning process; and the
method further comprises stopping the conditioning process when the
detected intensity is less than or equal to the threshold
intensity.
28. The method of claim 27, wherein the predetermined threshold
intensity is one of a fixed intensity quantity and an intensity
ratio representing a proportion of the intensity detected at the
start of the conditioning process.
29. The method of claim 6, wherein: the detecting comprises
detecting an intensity of the light through the window having the
layer of material thereon; the monitoring comprises comparing the
detected intensity with a predetermined threshold intensity
correlated to an endpoint of the cleaning process; and the method
further comprises stopping the cleaning process when the detected
intensity is more than or equal to the threshold intensity.
30. The method of claim 27, wherein the predetermined threshold
intensity is one of a fixed intensity quantity and an intensity
ratio representing a proportion of the intensity detected at the
start of the cleaning process.
31. A method of monitoring a process performed in a process
chamber, comprising: step for performing the process in the
chamber; step for generating light in the chamber; step for
detecting transmission properties of the light through a window of
the chamber having a layer of material thereon; and step for
monitoring a status of the process based on changes in the detected
transmission properties that are caused by the process changing a
state of the layer of material.
32. A computer readable medium containing program instructions for
execution on a computer system, which when executed by the computer
system, cause the computer system to perform the steps of:
performing the process in the chamber; generating light in the
chamber; detecting transmission properties of the light through a
window of the chamber having a layer of material thereon; and
monitoring a status of the process based on changes in the detected
transmission properties that are caused by the process changing a
state of the layer of material.
33. A system for monitoring a process performed in a process
chamber, comprising: a light generating device configured to
generate light in the chamber; a detector configured to detect
transmission properties of the light through a layer of material on
a window of the chamber; and a monitoring device configured to
monitor a status of the process based on changes in the detected
transmission properties that are caused by the process changing a
state of the layer of material.
34. The system of claim 33, further comprising a plasma generating
device configured to generate a plasma in the chamber.
35. The system method of claim 33, further comprising a deposition
device configured to perform chemical vapor deposition in the
chamber.
36. The system of claim 33, further comprising a holding device
configured to hold a semiconductor substrate to be processed in the
chamber.
37. The system of claim 33, wherein the light generating device
comprises a device for generating a plasma in the chamber.
38. The system of claim 33, wherein the light generating device
comprises a light source.
39. The system of claim 38, wherein the light source comprises a
light source configured to generate light at a predetermined
wavelength based on the process performed in the chamber.
40. The system of claim 33, wherein the detector comprises a device
configured to detect an intensity of the light through the window
of the chamber.
41. The system of claim 33, wherein the detector comprises a device
configured to detect a wavelength of the light through the window
of the chamber.
42. The system of claim 41, wherein the detector comprises a device
configured to detect a predetermined wavelength based on the
process performed in the chamber.
43. The system of claim 33, wherein the detector comprises a device
configured to perform optical emission spectroscopy on the light
emitted through the window of the chamber.
44. The system of claim 33, wherein said monitoring device
comprises a controller comprising: a memory configured to store
prerecorded transmission property data correlated to the process
performed in the chamber; and a processor configured to compare the
detected transmission property with the prerecorded transmission
property data.
45. The system of claim 44, wherein the processor is configured to
determine an endpoint of the process performed in the chamber based
on a result of the compare function.
46. The system of claim 44, wherein the processor is configured to
determine a phase change point of the process performed in the
chamber based on the compare function.
47. The system of claim 44, wherein the processor is configured to
determine an abnormal condition of the process performed in the
chamber based on the compare function.
48. The system of claim 44, wherein the controller is configured to
control the process performed in the chamber based on the status of
the process monitored.
49. The system of claim 48, wherein the controller is configured to
control the process by performing at least one of stopping the
process and changing parameters of the process.
50. The system of claim 33, wherein: the detector comprises a
device configured to detect an intensity of the light through the
window; the monitoring device comprises a device configured to
compare the detected intensity with a predetermined threshold
intensity correlated to an endpoint of a conditioning process
performed in the chamber; and the system further comprises a
controller configured to stop the conditioning process when the
detected intensity is less than or equal to the threshold
intensity.
51. The system of claim 50, wherein the monitoring device is
configured to compare the detected intensity to one of a fixed
intensity quantity and an intensity ratio representing a proportion
of the intensity detected at the start of the conditioning
process.
52. The system of claim 33, wherein: the detector comprises a
device configured to detect an intensity of the light through the
window; the monitoring device comprises a device configured to
compare the detected intensity with a predetermined threshold
intensity correlated to an endpoint of a cleaning process performed
in the chamber; and the system further comprises a controller
configured to stop the cleaning process when the detected intensity
is more than or equal to the threshold intensity.
53. The system of claim 52, wherein the monitoring device is
configured to compare the detected intensity to one of a fixed
intensity quantity and an intensity ratio representing a proportion
of the intensity detected at the start of the cleaning process.
54. A system for monitoring a process performed in a process
chamber, comprising: means for generating light in the chamber;
means for detecting transmission properties of the light through a
window of the chamber having a layer of material thereon; and means
for monitoring status of the process based changes in the detected
transmission properties that are caused by the process changing a
state of the layer of material.
55. The method of claim 7, wherein the dry etching cleaning process
comprises performing a plasma process in the chamber to remove
material from the interior surface of the chamber.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to chamber
processing, and more particularly to monitoring a process performed
in a processing chamber.
[0003] 2. Discussion of the Background
[0004] Many semiconductor fabrication processes are performed in
process chambers such as plasma etch chambers, plasma deposition
chambers, chemical vapor deposition chambers, atomic layer
deposition chambers, etc. Chamber conditioning processes (also
referred to as passivation processes) are commonly implemented in
semiconductor fabrication to prepare process chambers for optimal
performance. For example, chamber conditioning processes may be
carried out following chamber cleaning, after an extended chamber
idle period, or before a first chamber production process. When
used with plasma chambers, chamber conditioning processes typically
involve using a "conditioning plasma" in the plasma chamber for a
predetermined length of time to prepare, or "condition", the
chamber for the performance of plasma processes with production
wafers. The parameters of the conditioning process (e.g., RF power,
chamber and substrate temperature, feed gas composition, and
pressure) are usually maintained at or near the parameters of the
corresponding production process for which the chamber is being
conditioned. In this manner, conditioning processes can help ensure
that all processes performed in a process chamber produce results
within a desired range.
[0005] The ability of process chamber conditioning processes to
deposit polymers or other materials on the inner surfaces of the
chamber, can be particularly important when conditioning process
chambers after a cleaning procedure. In semiconductor
manufacturing, process chambers are periodically cleaned to remove
contaminants that collect on the inner surface of the process
chamber during processing. The chamber cleaning processes may be
carried out using wet cleaning methods (i.e., processes that use
liquid etchant solutions to remove materials from the inner surface
of the chamber) or dry cleaning methods (e.g., processes that use
plasmas to remove materials from the chamber inner surface).
Regardless of the type of cleaning process used, trace residues of
the chemicals used in the cleaning process may remain on the inner
surfaces of the chamber after the cleaning procedures. In chamber
conditioning processes, new layers of polymeric materials, or other
materials, may be deposited on the inner surfaces of the process
chamber to block these residues, as well as other contaminants,
thereby reducing contamination during subsequent processing.
[0006] Conditioning processes may also be used to replace some
materials removed by cleaning processes in order to improve initial
process chamber behavior in subsequent chamber processing. In
plasma processing chambers, the deposited polymeric layers may act
as insulators that can affect the coupling condition of plasmas
formed in the chamber. Since the plasma process parameters are
typically designed to account for the insulating effects of these
polymeric layers, any plasma processes performed in the absence of
such layers may not produce the desired results (e.g., because of
direct coupling of the plasma to the chamber walls). Conditioning
processes performed after cleaning may be used to deposit a
polymeric layer having insulating properties similar to the
polymeric layers deposited during normal processing and
sufficiently thick to help ensure that the plasmas formed in
subsequent etch process behave as intended.
[0007] Conditioning processes can be performed on several wafers or
sets of wafers. The extent of conditioning can be monitored by
periodically analyzing the wafers during the conditioning procedure
to determine process compliance. However, conditioning processes
that are carried out for long time periods can involve the use of a
large numbers of test wafers, which results in large startup
expense. Alternatively, the extent of conditioning can be carried
out for a fixed time period that has proven to provide production
process compliance. However, because the effectiveness of the
conditioning process is not actually monitored, the fixed time
period may be unnecessarily long in order to account for varying
conditioning times required to achieve process compliance for
different runs of a conditioning process. This results in
unacceptable reduction in manufacturing time for the chamber.
Similarly, cleaning processes are often unmonitored and therefore
may be carried out for a long time period during which the chamber
is unusable.
SUMMARY OF THE INVENTION
[0008] An object of the present invention is to reduce or solve any
or all of the above-described problems.
[0009] Another object of the present invention is to provide a
useful method for monitoring the status of a process in a process
chamber.
[0010] Yet another object of the present invention is to provide a
cost effective and accurate method of monitoring a chamber
conditioning process.
[0011] Yet another object of the present invention is to provide a
cost effective and accurate method of monitoring a chamber cleaning
process.
[0012] These and other objects of the present invention may be
provided by a method system and computer readable medium for
monitoring a process performed in a process chamber. The method on
which the system and computer readable medium are based includes
performing the process in the chamber, generating light in the
chamber, detecting transmission properties of the light through a
window of the chamber, and monitoring a status of the process based
the detected transmission properties of the light through the
window. The process performed in the chamber may be a conditioning,
cleaning or production process for a semiconductor, and may include
generating a plasma, CVD or wet etching.
[0013] The light may be generated from the process performed in the
chamber, or from a light source, in which case the generated light
may be a predetermined wavelength based on the process performed in
the chamber. The transmission properties detected through the
window of the chamber may be intensity and/or wavelength of the
light, in which case a predetermined wavelength may be detected
based on the process performed in the chamber. Detecting
transmission properties may also be performed by optical emission
spectroscopy on the light emitted through the window of the
chamber.
[0014] Monitoring may be performed by comparing the detected
transmission property with prerecorded transmission property data
correlated to the process performed in the chamber. An endpoint,
phase change point or abnormal condition of the process performed
in the chamber may be determined based on the comparing performed
by the monitoring. The process in the chamber may also be
controlled based on the monitored status of the process.
Controlling may include at least one of stopping the process and
changing parameters of the process.
[0015] In a specific aspect of the invention, the process performed
in the chamber is a conditioning process, detecting includes
detecting an intensity of the light through the window, and
monitoring includes comparing the detected intensity with a
predetermined threshold intensity correlated to an endpoint of the
conditioning process. The conditioning process is stopped when the
detected intensity is less than or equal to the threshold
intensity. The predetermined threshold intensity may be one of a
fixed intensity quantity and an intensity ratio representing a
proportion of the intensity detected at the start of the
conditioning process.
[0016] In another specific aspect of the invention, the process
performed in the chamber is a cleaning process, detecting includes
detecting an intensity of the light through the window, and
monitoring includes comparing the detected intensity with a
predetermined threshold intensity correlated to an endpoint of the
cleaning process. The cleaning process is stopped when the detected
intensity is more than or equal to the threshold intensity. The
predetermined threshold intensity is one of a fixed intensity
quantity and an intensity ratio representing a proportion of the
intensity detected at the start of the cleaning process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] A more complete appreciation of the invention and many of
the attendant advantages thereof will be readily obtained as the
same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings, wherein:
[0018] FIG. 1 shows a simplified block diagram of a system for
processing an object in a processing chamber in accordance with an
embodiment of the present invention;
[0019] FIG. 2 is a process flow chart showing a method of
monitoring a process performed on an object in a chamber in
accordance with an embodiment of the present invention;
[0020] FIG. 3 is a process flow chart showing a method of
monitoring a chamber conditioning process in accordance with an
embodiment of the present invention;
[0021] FIG. 4 is a graph showing a correlation of light intensity
to conditioning process time for a particular conditioning process
in accordance with an embodiment of the invention;
[0022] FIG. 5 is a process flow chart showing a method of
monitoring a chamber cleaning process in accordance with an
embodiment of the present invention;
[0023] FIG. 6 is a graph showing a correlation of light intensity
to cleaning process time for a particular cleaning process in
accordance with an embodiment of the invention; and
[0024] FIG. 7 illustrates a computer system upon which an
embodiment of the present invention may be implemented.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0025] Referring now to the drawings, wherein like reference
numerals designate identical or corresponding parts throughout the
several views, FIG. 1 shows a simplified block diagram of a system
for processing an object in a processing chamber in accordance with
an embodiment of the present invention. As seen in FIG. 1, the
processing system includes chamber 12, light source 14, optical
detector 16, vacuum pump 18 and controller 20. The chamber 12
includes an object holder 22 for holding an object 24 in the
processing space 26. In the embodiment of FIG. 1, the chamber 12
includes an input mechanism 28 for inputting gasses and/or other
matter represented by arrows 30 into the chamber 12 to process the
object 24. The chamber further includes window 32 having an
interior surface 34 and an exterior surface adjacent to the light
source 14, and window 36 having interior surface 38 and an exterior
surface adjacent to the optical monitoring system 16.
[0026] In one embodiment of the invention, the object to be
processed 24 is a semiconductor substrate and the processing system
10 is used as a plasma processing system, a chemical vapor
deposition system, or any other processing system for processing a
semiconductor substrate. In the case of plasma processing,
processing chamber 12 can facilitate the formation of a process
plasma in the process space 26 adjacent to the substrate 24. The
processing system 10 can be configured to process various
substrates (i.e. 200 mm substrates, 300 mm substrates, or larger).
In the semiconductor processing embodiment, the vacuum pump system
18 is used to provide a reduced pressure atmosphere in processing
chamber 12, and the input mechanism 28 is a gas injection assembly
that introduces process gas to the processing chamber 12. The gas
injection system can include a showerhead, wherein the process gas
is supplied to the process space 26 through a gas injection plenum,
a series of baffle plates, and a multi-orifice showerhead gas
injection plate. The substrate 24 can be transferred into and out
of plasma processing chamber 12 through a slot valve and chamber
feed-through via a robotic substrate transfer system where it is
received by substrate lift pins housed within object holder 22 (not
shown) and mechanically translated by devices housed therein. Once
the substrate 24 is received from a substrate transfer system, it
is lowered to an upper surface of the object holder 22, which may
include an electrostatic clamping system for affixing the substrate
to the object holder 22.
[0027] Windows 32 and 36 are light transmissive windows that allow
light to enter or exit the chamber 12. The light source 14 is
positioned adjacent to window 32 so as to generate light in the
chamber by directing the light through the window 32. Light source
14 is a device for generating electromagnetic waves at optical
wavelengths in any or all of the ultraviolet, visible or infrared
wavelength ranges. For example, the light source 14 may be a light
emitting diode (LED), laser, ultraviolet light or any other device
for generating visible or non-visible light. Optical detector 16 is
positioned adjacent to window 36 so as to detect light that passes
from the interior of the chamber through the window 36. Such light
can be generated by a process, such as a plasma process, occurring
in the chamber, or by the light source 14, as will be further
described below.
[0028] The optical detector is preferably able to detect a broad
range of optical wavelengths that may be generated by a plasma
process or the light source 14. In one embodiment, the light source
14 is an infrared (IR) light source and the optical detector 16 is
capable of detecting changes in IR light intensity, in the
wavelength range of about 2 microns to about 15 microns, due to IR
light absorption by molecular vibrations of materials deposited on
the surfaces 38 and 34 of the light transmissive window 32 and 36,
respectively. The optical detector 16 may be a simple detection
device such as a photomultiplier tube, a CCD or other solid state
detector that provides signals representative of the detected light
to controller 20, or may incorporate tools, such as a spectrometer,
for analyzing optical signals. One example of optical detector 16
is a S2000 Miniature Fiber Optic Spectrometer that performs optical
emission spectroscopy (OES), available from Ocean Optics Inc.,
Dunedin, Fla. The S2000 can measure UV-VIS-Shortwave Near-IR light
with wavelengths from 200 to 1100 nm.
[0029] Controller 20 is a processing device for monitoring and
controlling the components of the processing system 10 to perform a
desired process in the chamber 12. Thus, in the embodiment of FIG.
1, controller 20 is coupled to and can exchange information with
the processing chamber 12, light source 14, optical detector 16,
vacuum pump 18 and gas injection system 28. Controller 20 may be
implemented as a special purpose component that includes a
microprocessor, a memory, and a digital I/O port capable of
generating control voltages sufficient to communicate and activate
inputs to the processing system 10 as well as monitor outputs from
the processing system 10. One example of controller 20 is a DELL
PRECISION WORKSTATION 610TM, available from Dell Corporation,
Dallas, Tex. Alternatively, the controller 20 may be implemented as
a general purpose computer such as the computer system of FIG. 7. A
computer program stored in the memory of the controller 20 can be
utilized to control the components of a processing system 10
according to a desired process, and to perform any functions
associated with monitoring the process.
[0030] It is to be understood that the system in FIG. 1 is for
exemplary purposes only, as many variations of the specific
hardware and software used to implement the present invention will
be readily apparent to one having ordinary skill in the art. For
example, the functionality of the optical detector 16 and the
controller 20 may be combined in a single device. To implement
these variations as well as other variations, a single computer
(e.g., the computer system of FIG. 7) may be programmed to perform
special purpose functions of the controller 20 or any of the
devices shown in FIG. 1. On the other hand, two or more programmed
computers may be substituted for the controller or other devices
shown in FIG. 1. Principles and advantages of distributed
processing, such as redundancy and replication, may also be
implemented as desired to increase the robustness and performance
of the system, for example.
[0031] FIG. 2 is a process flow chart showing a method of
monitoring a process performed on an object in a chamber in
accordance with an embodiment of the present invention. As seen in
this figure, the method begins at step 202 with the performance of
a process within the chamber. The process may be any preparation or
production process that is performed in a chamber and affects the
light transmission properties of a chamber window. For example, the
process may be any type of deposition or cleaning process performed
on an object in a chamber, or may be a chamber conditioning or
cleaning process used to prepare the chamber for semiconductor
processing. In addition, the chamber process of step 202 may
generate light within the chamber 12, such as with a plasma
process, or may be a non light generating process such as dry
cleaning or CVD. Where the process does not generate light, a
separate light generation step must be performed as will be
described below. Moreover, specific examples of the present
invention used to monitor chamber conditioning and cleaning
processes will be further described with respect to FIGS. 3-6
below.
[0032] Once the process is performed in the chamber, light is
generated in the chamber as shown in step 204. As indicated above,
the light may be generated by the process occurring in the chamber
itself, or by light being directed from light source 14 into the
chamber 12. Where the light is generated by directing light from
the source 14, it is to be understood that the light may be
generated either before or after the process begins. In addition, a
combination of plasma generated light and light generated by the
light source 14 may be used. Where light is generated in the
chamber by the source 14, a particular wavelength of light may be
selected in accordance with the process to be monitored. For
example, light at longer wavelengths (e.g., visible) is less
affected (less reduction in transmission) by a coating on a window
36 than light at shorter wavelengths (e.g., UV). The selection of
the generated wavelength used to monitor the conditioning process
can therefore be based on the thickness of the coating and the
intensity of the transmitted light signal.
[0033] In step 206, the optical detector 16 detects transmission of
the light through the transmissive window 36. Detection step 204
may include detection of light intensity, wavelength, a combination
of wavelength and intensity or any other property of the light that
may be useful in monitoring a process in the chamber 12. In step
208, the process performed in the chamber 12 is monitored based on
detected transmission properties of the light through the
transmissive window 36. During processing in the chamber, materials
used for processing tend to be deposited or removed from the window
surfaces 34 and 38 (and other surfaces inside the process chamber),
or may change in material composition during the process. This
alters the light transmission properties of the windows 34 and 38
as the process continues in the chamber 12. The present inventors
have discovered that this change in transmission properties can be
detected by detector 16 and correlated to a status of the process
performed in the chamber 12.
[0034] For example, a production process that deposits or removes
materials on the surfaces 34 and 38 may include several process
milestones such as process phase start points where parameters of
the process are changed, or a process endpoint where the overall
process is stopped. For a particular process, process milestones
can be correlated to a threshold light intensity detected through
the transmission window 36 as the process deposits or removes
material on the surfaces 34 and 38. The process can then be
monitored by comparing the light intensity detected by the optical
detector 16 through the window 36 with the predetermined threshold.
When a threshold intensity corresponding to a process milestone is
detected, the process is controlled to perform functions associated
with the milestone. As another example, changes in the transmission
properties of the window 36 may be used to detect abnormal
conditions in the process performed in the chamber. Detection of
different wavelengths of light emitted from the chamber may
indicate different material compositions present on the interior
wall of the chamber. The existence of such materials may be
correlated to process problems that can be detected and corrected
early in the process. The results of these monitoring methods can
then be used to control the process occurring in the chamber.
[0035] Thus, the present inventors have discovered that the status
of process materials on the interior surfaces of the chamber may be
detected based on the changes in light transmission properties of
windows of the chamber. Specifically, as the layer of material on
the windows is built up, removed, or changes composition during
processing of an object in the chamber, the intensity or wavelength
of light detected through the window changes. This change in light
intensity or wavelength can be correlated to a status of the
process thereby allowing monitoring of process status by detecting
the light properties during future runs of the same process in the
chamber. This monitoring technique can be performed for a variety
of chamber processes such as the processing of semiconductor
wafers.
[0036] FIG. 3 is a process flow chart showing a method of
monitoring a chamber conditioning process in accordance with an
embodiment of the present invention. In step 302, the chamber
conditioning process is performed in the chamber. The conditioning
process may be a plasma generating conditioning process or a
non-plasma generating conditioning process, such as a CVD
conditioning process. In step 304, light is generated in the
chamber 12 by a light source such as the source 14 and/or by the
process itself if the process is capable of generating light. The
light generated in the chamber 12 is transmitted through the window
36 and the intensity of the light is detected by optical detector
16 as shown by step 306. The intensity is detected for at least one
wavelength of the generated light and, as discussed above, the
wavelength to be detected may be selected based on the
characteristics of the conditioning process performed in the
chamber 12.
[0037] In the embodiment of FIG. 3, the light intensity is
monitored to determine an endpoint of the conditioning process. In
one embodiment, correlation of the light intensity to a status of
the conditioning process is accomplished by an initial conditioning
process performed while detecting light intensity and monitoring
the test wafers for production process compliance. For example,
test wafers can be monitored for a desired etch rate, etch
selectivity, deposition rate, quality of deposited films, etc.
during the conditioning process, and the detected threshold light
intensity recorded when such requirements are met. This threshold
intensity can then be used to detect the endpoint for the
correlated process without the need for test wafers for future runs
of the correlated conditioning process. The threshold intensity may
be a fixed intensity value, or a ratio of measured light intensity
and initial light intensity (measured at the start of the
conditioning process). Moreover, the transmissive window 36 is
preferably cleaned or replaced prior to a conditioning process in
order to maximize the amount of light that reaches the optical
detector 16 at the start of the conditioning process.
[0038] FIG. 4 is a graph showing a correlation of light intensity
to conditioning process time for a particular conditioning process
in accordance with an embodiment of the invention. As seen by the
light intensity curve 402, the detected light intensity generally
decreases as the conditioning process takes place, due to the
buildup of polymer and other materials on the surface 38 of window
36, for example. Where light source 14 is used to generate light
for the conditioning process, the decrease in intensity is also due
to buildup on the surface 34 of window 32. While the curve 402 in
FIG. 4 shows a substantially linear decrease in light intensity, it
is to be understood that the intensity curve depends on the
characteristics of the conditioning process and may be nonlinear.
As also seen in FIG. 4, a threshold intensity point 404 is recorded
that corresponds the light intensity detected at the time when the
test wafers show production process compliance. Other milestones in
the conditioning process may also be recorded in the correlation
graph.
[0039] Returning to FIG. 3, as the light intensity is detected in
step 306 during the conditioning process, a processor in the
controller 20 compares the detected light intensity with stored
correlation data as shown by step 308. In decision block 310, the
controller 20 determines whether the detected intensity is less
than or equal to the predetermined threshold intensity recorded in
the correlation data. Where the threshold intensity is not yet
detected, the extent of conditioning is not completed and,
therefore, the monitoring process returns to step 302 where
conditioning continues. When the threshold light intensity is
detected, the extent of conditioning is sufficient for production
process requirements and, therefore, the chamber conditioning
process is stopped as shown by step 312 and the monitoring process
ends.
[0040] Thus, the chamber conditioning process can be monitored and
an endpoint determined by detecting changes in the transmission
properties of the light through a chamber window. As noted in the
background section above, conditioning of a semiconductor
processing chamber has conventionally been performed for a fixed
period of time, or based on monitoring of test wafers. The present
inventors have discovered that use of a detected threshold
intensity can provide a more reliable determination of the process
endpoint than the time method conventionally used because the time
required to reach test wafer compliance may change for different
runs of the same conditioning process. Therefore, the present
invention can prevent the need for long conditioning process times
conventionally performed to ensure conditioning is complete.
Moreover, after the light intensity is correlated with the a
particular process, there is no further need to use costly test
wafers to repeat the conditioning process.
[0041] FIG. 5 is a process flow chart showing a method of
monitoring a chamber cleaning process in accordance with an
embodiment of the present invention. In step 502, the chamber
cleaning process is performed in the chamber. The cleaning process
may be a dry cleaning process, a dry plasma generating process, or
a wet non-plasma generating process. In step 504, light is
generated in the chamber 12 by a light source such as the source 14
and/or by the process itself if the process is capable of
generating light. The light generated in the chamber 12 is
transmitted through the window 36 and the intensity of the light is
detected by optical detector 16 as shown by step 506. The intensity
is detected for at least one wavelength of the generated light and,
as discussed above, the wavelength to be detected may be selected
based on the characteristics of the conditioning process performed
in the chamber 12.
[0042] In the embodiment of FIG. 5, the light intensity is
monitored to determine an endpoint of the cleaning process. In one
embodiment, correlation of the light intensity to a status of the
cleaning process is accomplished by an initial cleaning process
performed while detecting light intensity and monitoring the
chamber for cleanliness. Alternatively, the light intensity
detected through the window 36 can be recorded when the window 36
is new and unused, and this intensity value used to establish an
acceptable threshold intensity corresponding to a level of
cleanliness required for a desired process. This threshold
intensity can then be used to detect the endpoint for the cleaning
process without the need for monitoring the cleanliness of the
chamber by other methods. The threshold intensity may be a fixed
intensity value preferably corresponding to a new window, or a
ratio of measured light intensity and initial light intensity
(measured at the start of the cleaning process).
[0043] FIG. 6 is a graph showing a correlation of light intensity
to cleaning process time for a particular cleaning process in
accordance with an embodiment of the invention. As seen by the
light intensity curve 602, the detected light intensity generally
increases as the cleaning process takes place, due to the removal
of polymer and other materials from the surface 38 of window 36,
for example. Where light source 14 is used to generate light for
the conditioning process, the increase in intensity is also due to
removal of material from the surface 34 of window 32. While the
curve 602 in FIG. 6 shows a substantially linear increase in light
intensity, it is to be understood that the intensity curve depends
on the characteristics of the cleaning process and may be
nonlinear. As also seen in FIG. 6, a threshold intensity point 604
is recorded that corresponds the light intensity detected at the
time when the window 36 is known to be at an acceptably clean level
for a desired process. Other milestones in the cleaning process may
also be recorded in the correlation graph. In this regard, it is to
be understood that an acceptable level of cleanliness may vary
depending on the production process to be performed in the chamber.
Thus, the graph of FIG. 6 may plot several threshold points for a
particular cleaning process that correspond to acceptable
cleanliness levels for different production processes.
[0044] Returning to FIG. 5, as the light intensity is detected in
step 506 during the cleaning process, a processor in the controller
20 compares the detected light intensity with stored correlation
data as shown by step 508. In decision block 510, the controller 20
determines whether the detected intensity is less than or equal to
the predetermined threshold intensity recorded in the correlation
data. Where the threshold intensity is not yet detected, the extent
of cleaning is not acceptable and the monitoring process returns to
step 502, where cleaning continues. Where the threshold light
intensity is detected, the extent of cleaning is sufficient for
production process requirements and, therefore, the chamber
cleaning process is stopped as shown by step 512 and the monitoring
process ends.
[0045] Thus, the chamber cleaning process can be monitored and an
endpoint determined by detecting changes in the transmission
properties of the light through a chamber window. As noted in the
background section above, cleaning of a semiconductor processing
chamber has conventionally been performed for a fixed period of
time based on past experience for the cleaning process. The present
inventors have discovered that use of a detected threshold
intensity provides a more reliable determination of the cleaning
process endpoint than the time method conventionally used because
the time required to achieve an acceptable level of cleanliness may
vary for different runs of the same cleaning process. Therefore,
the present invention can prevent the need for long cleaning
process times conventionally performed to ensure cleaning is
complete.
[0046] FIG. 7 illustrates a computer system 1201 upon which an
embodiment of the present invention may be implemented. The
computer system 1201 may be used as the controller 12 to perform
any or all of the functions of the controller described above. The
computer system 1201 includes a bus 1202 or other communication
mechanism for communicating information, and a processor 1203
coupled with the bus 1202 for processing the information. The
computer system 1201 also includes a main memory 1204, such as a
random access memory (RAM) or other dynamic storage device (e.g.,
dynamic RAM (DRAM), static RAM (SRAM), and synchronous DRAM
(SDRAM)), coupled to the bus 1202 for storing information and
instructions to be executed by processor 1203. In addition, the
main memory 1204 may be used for storing temporary variables or
other intermediate information during the execution of instructions
by the processor 1203. The computer system 1201 further includes a
read only memory (ROM) 1205 or other static storage device (e.g.,
programmable ROM (PROM), erasable PROM (EPROM), and electrically
erasable PROM (EEPROM)) coupled to the bus 1202 for storing static
information and instructions for the processor 1203.
[0047] The computer system 1201 also includes a disk controller
1206 coupled to the bus 1202 to control one or more storage devices
for storing information and instructions, such as a magnetic hard
disk 1207, and a removable media drive 1208 (e.g., floppy disk
drive, read-only compact disc drive, read/write compact disc drive,
compact disc jukebox, tape drive, and removable magneto-optical
drive). The storage devices may be added to the computer system
1201 using an appropriate device interface (e.g., small computer
system interface (SCSI), integrated device electronics (IDE),
enhanced-IDE (E-IDE), direct memory access (DMA), or
ultra-DMA).
[0048] The computer system 1201 may also include special purpose
logic devices (e.g., application specific integrated circuits
(ASICs)) or configurable logic devices (e.g., simple programmable
logic devices (SPLDs), complex programmable logic devices (CPLDs),
and field programmable gate arrays (FPGAs)).
[0049] The computer system 1201 may also include a display
controller 1209 coupled to the bus 1202 to control a display 1210,
such as a cathode ray tube (CRT), for displaying information to a
computer user. The computer system includes input devices, such as
a keyboard 1211 and a pointing device 1212, for interacting with a
computer user and providing information to the processor 1203. The
pointing device 1212, for example, may be a mouse, a trackball, or
a pointing stick for communicating direction information and
command selections to the processor 1203 and for controlling cursor
movement on the display 1210. In addition, a printer may provide
printed listings of data stored and/or generated by the computer
system 1201.
[0050] The computer system 1201 performs a portion or all of the
processing steps of the invention in response to the processor 1203
executing one or more sequences of one or more instructions
contained in a memory, such as the main memory 1204. Such
instructions may be read into the main memory 1204 from another
computer readable medium, such as a hard disk 1207 or a removable
media drive 1208. One or more processors in a multi-processing
arrangement may also be employed to execute the sequences of
instructions contained in main memory 1204. In alternative
embodiments, hard-wired circuitry may be used in place of or in
combination with software instructions. Thus, embodiments are not
limited to any specific combination of hardware circuitry and
software.
[0051] As stated above, the computer system 1201 includes at least
one computer readable medium or memory for holding instructions
programmed according to the teachings of the invention and for
containing data structures, tables, records, or other data
described herein. Examples of computer readable media are compact
discs, hard disks, floppy disks, tape, magneto-optical disks, PROMs
(EPROM, EEPROM, flash EPROM), DRAM, SRAM, SDRAM, or any other
magnetic medium, compact discs (e.g., CD-ROM), or any other optical
medium, punch cards, paper tape, or other physical medium with
patterns of holes, a carrier wave (described below), or any other
medium from which a computer can read.
[0052] Stored on any one or on a combination of computer readable
media, the present invention includes software for controlling the
computer system 1201, for driving a device or devices for
implementing the invention, and for enabling the computer system
1201 to interact with a human user (e.g., print production
personnel). Such software may include, but is not limited to,
device drivers, operating systems, development tools, and
applications software. Such computer readable media further
includes the computer program product of the present invention for
performing all or a portion (if processing is distributed) of the
processing performed in implementing the invention.
[0053] The computer code devices of the present invention may be
any interpretable or executable code mechanism, including but not
limited to scripts, interpretable programs, dynamic link libraries
(DLLs), Java classes, and complete executable programs. Moreover,
parts of the processing of the present invention may be distributed
for better performance, reliability, and/or cost.
[0054] The term "computer readable medium" as used herein refers to
any medium that participates in providing instructions to the
processor 1203 for execution. A computer readable medium may take
many forms, including but not limited to, non-volatile media,
volatile media, and transmission media. Non-volatile media
includes, for example, optical, magnetic disks, and magneto-optical
disks, such as the hard disk 1207 or the removable media drive
1208. Volatile media includes dynamic memory, such as the main
memory 1204. Transmission media includes coaxial cables, copper
wire and fiber optics, including the wires that make up the bus
1202. Transmission media also may also take the form of acoustic or
light waves, such as those generated during radio wave and infrared
data communications.
[0055] Various forms of computer readable media may be involved in
carrying out one or more sequences of one or more instructions to
processor 1203 for execution. For example, the instructions may
initially be carried on a magnetic disk of a remote computer. The
remote computer can load the instructions for implementing all or a
portion of the present invention remotely into a dynamic memory and
send the instructions over a telephone line using a modem. A modem
local to the computer system 1201 may receive the data on the
telephone line and use an infrared transmitter to convert the data
to an infrared signal. An infrared detector coupled to the bus 1202
can receive the data carried in the infrared signal and place the
data on the bus 1202. The bus 1202 carries the data to the main
memory 1204, from which the processor 1203 retrieves and executes
the instructions. The instructions received by the main memory 1204
may optionally be stored on storage device 1207 or 1208 either
before or after execution by processor 1203.
[0056] The computer system 1201 also includes a communication
interface 1213 coupled to the bus 1202. The communication interface
1213 provides a two-way data communication coupling to a network
link 1214 that is connected to, for example, a local area network
(LAN) 1215, or to another communications network 1216 such as the
Internet. For example, the communication interface 1213 may be a
network interface card to attach to any packet switched LAN. As
another example, the communication interface 1213 may be an
asymmetrical digital subscriber line (ADSL) card, an integrated
services digital network (ISDN) card or a modem to provide a data
communication connection to a corresponding type of communications
line. Wireless links may also be implemented. In any such
implementation, the communication interface 1213 sends and receives
electrical, electromagnetic or optical signals that carry digital
data streams representing various types of information.
[0057] The network link 1214 typically provides data communication
through one or more networks to other data devices. For example,
the network link 1214 may provide a connection to another computer
through a local network 1215 (e.g., a LAN) or through equipment
operated by a service provider, which provides communication
services through a communications network 1216. The local network
1214 and the communications network 1216 use, for example,
electrical, electromagnetic, or optical signals that carry digital
data streams, and the associated physical layer (e.g., CAT 5 cable,
coaxial cable, optical fiber, etc). The signals through the various
networks and the signals on the network link 1214 and through the
communication interface 1213, which carry the digital data to and
from the computer system 1201 maybe implemented in baseband
signals, or carrier wave based signals. The baseband signals convey
the digital data as unmodulated electrical pulses that are
descriptive of a stream of digital data bits, where the term "bits"
is to be construed broadly to mean symbol, where each symbol
conveys at least one or more information bits. The digital data may
also be used to modulate a carrier wave, such as with amplitude,
phase and/or frequency shift keyed signals that are propagated over
a conductive media, or transmitted as electromagnetic waves through
a propagation medium. Thus, the digital data may be sent as
unmodulated baseband data through a "wired" communication channel
and/or sent within a predetermined frequency band, different than
baseband, by modulating a carrier wave. The computer system 1201
can transmit and receive data, including program code, through the
network(s) 1215 and 1216, the network link 1214, and the
communication interface 1213. Moreover, the network link 1214 may
provide a connection through a LAN 1215 to a mobile device 1217
such as a personal digital assistant (PDA) laptop computer, or
cellular telephone.
[0058] Obviously, numerous modifications and variations of the
present invention are possible in light of the above teachings. It
is therefore to be understood that within the scope of the appended
claims, the invention may be practiced otherwise than as
specifically described herein. For example, the process steps
described herein and recited in the claims may be performed in a
sequence other than the sequence in which they are described or
listed herein. As should be understood by one of ordinary skill in
the art, only those process steps necessary to the performance of a
later process steps are required to be performed before the later
process step is performed.
* * * * *