U.S. patent application number 09/902788 was filed with the patent office on 2002-01-10 for automatic reference-pressure balance method.
This patent application is currently assigned to Globitech, Inc.. Invention is credited to Kenney, Danny, Lindberg, Keith.
Application Number | 20020002856 09/902788 |
Document ID | / |
Family ID | 26735748 |
Filed Date | 2002-01-10 |
United States Patent
Application |
20020002856 |
Kind Code |
A1 |
Kenney, Danny ; et
al. |
January 10, 2002 |
Automatic reference-pressure balance method
Abstract
The present invention provides a system and method for
calibrating pressure sensors associated with chambers in a
processing facility. The system calibrates the pressure sensors
while the chamber are open to each other, such as through an open
slit valve or vacuum sealed door. Maintaining the pressure in the
chambers relative to each other prevents a rush of gases,
condensate or other foreign materials into an adjacent chamber that
may occur when the pressure between the chambers is not equalized.
This prevents contamination of the materials being processed, and
eliminates the need for system shutdown to calibrate sensors. Also,
since calibration occurs every time the slit valve is open, the
calibration is real-time and does not allow the pressure
differential between the chambers to become too great.
Inventors: |
Kenney, Danny; (Sherman,
TX) ; Lindberg, Keith; (Sherman, TX) |
Correspondence
Address: |
Rudolph J. Buchel, Jr.
Jones, Day, Reavis & Pogue
2727 N. Harwood Street
P.O. Box 660623
Dallas
TX
75201
US
|
Assignee: |
Globitech, Inc.
|
Family ID: |
26735748 |
Appl. No.: |
09/902788 |
Filed: |
July 11, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09902788 |
Jul 11, 2001 |
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09378881 |
Aug 23, 1999 |
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6279373 |
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09378881 |
Aug 23, 1999 |
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09137354 |
Aug 20, 1998 |
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60056821 |
Aug 22, 1997 |
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Current U.S.
Class: |
73/1.63 |
Current CPC
Class: |
G01L 27/002 20130101;
G01L 27/007 20130101 |
Class at
Publication: |
73/1.63 |
International
Class: |
G01L 027/00 |
Claims
What is claimed is:
1. A method for maintaining a consistent pressure between two
chambers in a processing facility, wherein the two chambers have a
slit valve there between, the method comprising the steps of:
determining when the slit valve is open; measuring a pressure of
the first chamber while the slit valve is open; measuring a
pressure of the second chamber while the slit valve is open;
calibrating first and second pressure sensors, associated with the
first and second chambers, respectively, relative to each other
while the slit valve is open; and closing the slit valve when the
pressure sensors have been calibrated relative to each other.
2. The method of claim 1 wherein the slit valve is a vacuum-sealed
door.
3. The method of claim 1 wherein the calibrating is performed by
changing a reading value of the first pressure sensor to be in
accordance with the second pressure sensor.
4. The method of claim 3 wherein the second chamber is a transfer
chamber connecting the first chamber to a third chamber.
5. The method of claim 3 further comprising: monitoring the change
of the reading value of the first sensor; and determining if the
change indicates a faulty system.
6. A method for maintaining a consistent pressure in a processing
facility having a transfer chamber used to transfer materials to
and from a process chamber, wherein the two chambers have a valve
there between, the method comprising the steps of: determining when
the valve is open; measuring a pressure of the transfer chamber
while the valve is open; measuring a pressure of the processing
chamber while the valve is open; calibrating a pressure sensor on
the processing chamber relative to a pressure sensor on the
transfer chamber while the valve is open; and closing the valve
when the pressure sensors on the processing chamber and transfer
chamber are relatively calibrated.
7. The method of claim 6 wherein the transfer chamber is also used
to transfer materials to and from a loading chamber, the transfer
chamber and loading chamber having a second valve there between,
the method further comprising: determining when the second valve is
open; measuring a pressure of the transfer chamber while the second
valve is open; measuring a pressure of the loading chamber while
the second valve is open; calibrating a pressure sensor on the
loading chamber relative to the pressure sensor on the transfer
chamber while the second valve is open; and closing the second
valve when the pressure sensors on the loading chamber and transfer
chamber are relatively calibrated.
8. An automated system for controlling processing of a product in a
processing facility, said system compromising: first, second, and
third chambers; first, second, and third pressure sensors
associated with the first, second, and third chambers,
respectively, for measuring a pressure inside each chamber; first,
second, and third exhaust lines connected to the first, second, and
third chamber, respectively; first, second, and third pressure
restriction control valves connected to the first, second, and
third exhaust lines, respectively; a first material transfer valve
connecting the first chamber to the second chamber; a second
material transfer valve connecting the second chamber to the third
chamber a control module connected to the first and second material
transfer valves, the first, second and third pressure sensors, the
first, second and third variable restriction control valves, and
the first, second and third chambers, the control module including
processing capabilities for performing the steps of: measuring the
pressure in the first and second chamber while the first material
transfer valve is closed; adjusting the first and second variable
restriction control valves until the first and second pressure
sensors have similar readings while the first material transfer
valve is closed; and calibrating the first pressure sensor to
generate a reading similar to that of the second pressure sensor
when the first material transfer valve is open.
9. The system described in claim 8 wherein the first and second
material transfer valves are vacuum-sealed doors.
10. The system described in claim 8 wherein the transfer chamber
includes a robot for handling of the materials being processed.
11. The system described in claim 8 wherein the control module also
includes processing capabilities for: detecting a fault in the
system by monitoring the adjustment of the first pressure sensor
over a period of adjustments.
12. The system described in claim 8 wherein the control module also
includes processing capabilities for: measuring the pressure in the
second and third chambers while the second material transfer valve
is closed; adjusting the second and third variable restriction
control valves until the second and third pressure sensors have
similar readings while the second material transfer valve is
closed; and calibrating the third pressure sensor attached to the
third chamber to generate a reading similar to that of the second
pressure sensor when the second material transfer valve is
open.
13. The system described in claim 12 wherein the control module
also includes processing capabilities for: detecting a fault in the
system by monitoring the adjustment of the first, second, and third
pressure sensors over a period of adjustments.
14. The system described in claim 13 wherein the control module
also includes processing capabilities for: determining that the
fault is associated with the third chamber if only the third sensor
requires significant adjustment over the period of adjustments.
15. The system described in claim 13 wherein the control module
also includes processing capabilities for: determining that the
fault is associated with the second chamber if both the first and
third sensors require significant adjustment over the period of
adjustments.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation in part of patent
application Ser. No. 09/137,354, filed Aug. 20, 1998 which claims
priority from U.S.
[0002] Provisional Patent Application Ser. No. 60/056,821, filed
Aug. 22, 1997.
TECHNICAL FIELD
[0003] This invention relates generally to semiconductor processing
and, more particularly, to a system and method for calibrating gas
or liquid pressure during wafer processing.
BACKGROUND
[0004] Contamination of materials is a factor in many manufacturing
processes, and is of particular concern in the fabrication of
integrated circuits.
[0005] In general, integrated circuit technology is based on the
ability to form numerous transistor structures on a single
semiconductor substrate. Typically, multiple integrated circuits
will be formed on a single silicon wafer, the wafer providing the
semiconductor substrate for the circuits. The intricacy of the
circuits and the large number of steps involved in the fabrication
make it essential that each of the process steps be tightly
controlled and meet very stringent specifications to prevent any
type of contamination. To increase the purity and hence the quality
and reliability of manufacturing processes, most are done in sealed
rooms or chambers, where the environment, including temperature,
pressure and purity of liquids or gases introduced can be
controlled. One of the biggest sources of contamination occurs when
the product being manufactured is transferred from one area of the
manufacturing process to the next, which necessitates opening a
door or valve to introduce the material into the next chamber or
room. When the door or valve is open, if there is a pressure
differential between the chambers, the potential for contamination
is increased. Processing fluid and/or gas will rush from the
chamber with the higher pressure to the chamber with the lower
pressure to equalize the pressure, bringing solids and liquids
along with the gas, which may cause such problems as condensation
and particulate contamination on the material being
manufactured.
[0006] The solutions used to mitigate the above-identified problem
have included: reducing the amount of time that the door or valve
is opened to reduce the amount of contaminants that enter the
chamber; making the transfer in two stages; utilizing an
intermediate or transfer chamber into which only one of the other
chambers is opened at a given time; placing calibrated pressure
sensors in each chamber; and tying the pressure sensors into the
valve-opening mechanisms in both chambers to obtain a desired,
consistent pressure balance before the valve between the chambers
is opened. However, these solutions, separately or in combination,
do not always adequately resolve the aforementioned problems.
[0007] Even minimizing the time the door or valve is open will
result in some contamination, especially if the pressure is not
equalized between the two chambers before opening the door or
valve. One of the biggest problems in equalizing the pressure is
keeping the pressure sensors calibrated, as sensors tend to drift
in calibration over time. If the pressure sensor in either chamber
is out of calibration, the pressure between the two chambers will
not actually be equal, and when the door or valve is open, the gas
will rush from the higher to lower pressure chamber to equalize the
pressure. The effective drift of the pressure sensors is actually
doubled if the two sensors drift calibration in opposite
directions. If a sensor has drifted, process overseers are
generally unaware of the problem until a rush of gas between the
chambers has occurred, resulting in contamination of a manufactured
product. In order to re-calibrate sensors that have drifted, the
manufacturing process generally has to be shut down, and the sensor
taken off-line to be calibrated, resulting in production
down-time.
[0008] U.S. Pat. No. 5,808,175 issued Sep. 15, 1998 to Shen-Yan
Chang discloses a method of temporarily, manually mounting a
second, in-line calibrated sensor to the same chamber for the
purpose of monitoring or correcting the first sensor. However,
Chang only utilizes the second sensor for comparison to the
readings obtained from the first sensor for the same chamber, to
determine if it needs replacing. If there is drift in the sensors
used to read the pressure in different chambers, a situation may
still occur wherein the pressure differential between two chambers
is such that a rush of gas and contaminants occurs when the door or
valve between the two chambers is opened.
[0009] It would, therefore, be desirable to be able to provide a
method and apparatus wherein the pressure in the two chambers
between which materials are being transferred can be kept equal so
that there will not be a rush of gas between the two chambers when
the door or valve is opened.
SUMMARY
[0010] The present invention overcomes the above outlined problems
and a technical advance is achieved by a system and method that
equalizes and calibrates the pressure of two or more chambers on
either side of a valve (door) during operation. In one embodiment,
the method is performed each time the valve is opened. When the
valve is opened, the pressure in the chambers will equalize. After
the pressure in the chambers has equalized, pressure readings from
sensors mounted in each chamber are calibrated relative to each
other.
[0011] In some embodiments, the pressure readings are sent to a
control module. The control module evaluates the readings taken
from the sensors and adjusts them to match each other.
[0012] In some embodiments, there may be an intermediate, or
transfer chamber between a process chamber and a loading chamber.
The sensor readings from the process and loading chambers are
adjusted to match the sensor readings of the transfer chamber. As a
result, all the chambers will be calibrated with the transfer
chamber, and therefore with each other.
[0013] Since calibration occurs every time the valve is open, the
pressure differential between the chambers never becomes too great.
As a result, there is little if any fluid flow (e.g., a flow
processing gases and/or contaminants) between the chambers and a
very clean chamber environment is maintained.
[0014] Also, because the relative calibration is done during actual
use, the system does not have to be shut down to perform
calibration routines. This, of course, results in increased
productivity and cycle time.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a diagram of an exemplary processing facility that
utilizes a transfer chamber between operational chambers.
[0016] FIG. 2 is a diagram of an exemplary processing facility that
does not utilize a transfer chamber between operational
chambers.
[0017] FIG. 3 is a method flow diagram showing the steps taken in
calibrating the pressure sensors.
[0018] FIG. 4 is a diagram of two chambers of FIG. 1, separated by
a valve.
[0019] FIG. 5 is a diagram of the two chambers of FIG. 4 showing
the pressure in each chamber being calibrated relative to the other
chamber while the valve is open.
DETAILED DESCRIPTION
[0020] Referring to FIG. 1, reference numeral 10 designates a
portion of an integrated circuit processing facility including two
loading chambers 12, 14, a transfer chamber 16, and two process
chambers 18, 20. Loading chambers are typically used for loading
and unloading one or more materials for processing. Processing
chambers are typically used for performing processing operations,
and may include additional components for varying the temperature
of the chamber or for adding processing fluids and/or constituents
into the chamber. Transfer chambers are often used as an
intermediate chamber between loading chambers and processing
chambers, and may include a robot arm or some equivalent device for
moving materials between the different chambers. To facilitate
processing and maintain a clean environment, the different chambers
must be hermetically sealed from each other at particular
times.
[0021] The loading chambers 12, 14 are connected to the transfer
chamber 16 through slit valves 22, 24, respectively. Likewise, the
process chambers 18, 20 are connected to the transfer chamber 16
through slit valves 26, 28, respectively. Connected to the transfer
chamber 16 is an exhaust line 40 with a variable restriction
control valve 42 used for controlling the pressure in the chamber.
Likewise, connected to the loading and process chambers 12, 14, 18,
20 are exhaust lines 44, 46, 48, 50 with variable restriction
control valves 52, 54, 56, 58, respectively. Each of the variable
restriction control valves 42, 52, 54, 56, 58 is controlled by a
control module 60.
[0022] The control module 60 receives pressure readings from
pressure sensors (e.g. transducers) 62, 64, 66, 68, 70 connected to
loading chambers 12 and 14, transfer chamber 16, and process
chambers 18, 20, respectively. Furthermore, the control module 60
is informed of the status (open or closed) of slit valves 22, 24,
26, and 28 through monitor lines 72, 74, 76, 78 respectively.
[0023] In operation, the control module 60 reads the pressure of
the loading chamber 12 through the pressure sensor 64 and the
transfer chamber 16 through the pressure sensor 62. The control
module 60 then equalizes the pressure in the two chambers 16 and 12
by adjusting the variable restriction control valves 42 and 52
accordingly. As a result, the pressure in the loading chamber 12
matches that of the transfer chamber 16. Every time that the slit
valve 22 is open between the chambers, the control module 60
calibrates the pressure sensors 62 and 64 relative to each other.
The same process is performed every time the slit valve 24, 26, or
28 is open between the transfer chamber 16 and the loading or
process chamber 14, 18, or 20, respectively. In a configuration of
the system that utilizes a transfer chamber 16, such as that shown
in FIG. 1, the pressure sensors for the chambers on either side of
the transfer chamber are calibrated in reference to the pressure
sensor for the transfer chamber so that it will be accurate
regardless of which chamber connecting into it is opened at any one
time.
[0024] Referring now to FIG. 2, the reference numeral 80 designates
a portion of an integrated circuit processing facility with a
direct chamber-to-chamber connection, including a loading chamber
12, and a process chamber 18. In this embodiment, the loading
chamber 12 and the process chamber 18 are similar to those
described in FIG. 1, except that no intermediate transfer chamber
exists there between. The loading chamber 12 is connected to the
process chamber 18 through the valve 22. Connected to the loading
chamber 12 is an exhaust line 44 with a variable restriction
control valve 52, used for controlling the pressure in the chamber.
Likewise, connected to the process chamber 18 is exhaust line 48
with variable restriction control valve 56. Each of the variable
restriction control valves 52, 56 is controlled by a control module
60.
[0025] The control module 60 receives pressure readings from
pressure sensors (e.g. transducers) 64, 68 connected to the loading
chamber 12 and the process chamber 18, respectively. Furthermore,
the control module 60 is informed of the status (e.g. open or
closed) of the slit valve 22 through the monitor line 72.
[0026] In operation, the control module 60 reads the pressure of
the loading chamber 12 through the pressure sensor 64 and the
process chamber 18 through the pressure sensor 68. The control
module 60 then equalizes the pressure in the two chambers 12 and 18
by adjusting the variable restriction control valves 52 and 56
accordingly so the pressure in the loading chamber 12 10 matches
that of the process chamber 18. Every time that the slit valve 22
is open between the chambers, and after the pressure of the two
chamber has equalized, the control module 60 calibrates the
pressure sensors 64 and 68 relative to each other.
[0027] Referring to FIG. 3, a calibration method 100 may be
performed on a sensor inside the system 10 (FIG. 1). For the sake
of example, the calibration method 100 is used after a wafer 82 is
placed in the loading chamber 12 and is ready to be transferred to
the transfer chamber 16. FIG. 4 shows a magnified portion of the
system 10 for discussion with the present example.
[0028] Referring also to FIG. 4, a wafer 82 is in the loading
chamber 12, ready for transfer to the next chamber 16 through the
slit valve 22. At step 102, it is determined if the wafer 82 is
ready for transfer to the next chamber. Since in the present
example, the wafer is in the loading chamber 12, step 102
determines that the chamber has been properly closed and sealed. At
step 104, the control module 60 equalizes the pressure between the
loading chamber 12 and the next chamber (the transfer chamber, in
the present example) 16. The control module 60 will not open the
slit valve 22 until the pressure between loading chamber 12 and
transfer chamber 16 is equalized. Specifically, the control module
60, using readings obtained from pressure sensors 62 and 64, will
equalize the pressure in the transfer chamber 16 and loading
chamber 12 by adjusting the variable restriction control valves 42
and 52, connected to the exhaust lines 40 and 44 respectively.
[0029] Referring now to FIGS. 3 and 5, at step 106, when the
control module 60 receives readings from the pressure sensors 62
and 64 that indicate the pressures in the loading chamber 12 and
transfer chamber 16 are equal, execution proceeds to step 108. The
control module 60 sends a signal to the slit valve 22 to open, as
shown in FIG. 5. The wafer 82 will then be shifted to the transfer
chamber 16 through the slit valve 22.
[0030] While the slit valve 22 is open for the transfer of
material, if there is any difference in the actual pressure between
the loading chamber 12 and transfer chamber 16, it will be
equalized automatically. At step 110, the control module 60 will
then check the readings on the pressure sensors 62 and 64. At step
112, a determination is made as to whether the pressure sensors 62,
64 are calibrated relative to each other. If so, then execution
proceeds to step 114 where the slit valve 22 is closed and
processing continues on in a normal progression.
[0031] If at step 112 the pressure sensors 62, 64 read differently,
execution proceeds to step 116 where the sensors are calibrated
relative to each other. In one embodiment, the pressure sensor 64
is calibrated to the pressure sensor 62. By so doing, all of the
pressure sensors 64, 66, 68, 70 (FIG. 1) will eventually be
calibrated relative to pressure sensor 62 and thus to each other.
It may be desirable, on a periodic basis, to calibrate pressure
sensor 62 to a reference measurement. However, even this
calibration has been simplified because only one sensor needs to be
calibrated. Execution then returns to step 110. It is understood,
however, that the control module 60 may have certain error modules
so that the method will not continually loop to step 110 if the
pressure sensors cannot be properly calibrated.
[0032] Because the pressure in the two chambers is known to be
equal while the slit valve 22 is open, calibrating the sensors 62
and 64 relative to each other eliminates the potential for a rush
of processing fluid and constituents between the chambers the next
time the valve is open. Also, because the process of relative
calibration is performed every time the slit valve 22 is opened, a
variation of no more than 0.01-0.02 Torr should occur between any
two calibrations. This is an improvement over the prior art, where
variations of 5 Torr or greater between chambers would be common
because of the infrequency of calibration.
[0033] Furthermore, because the relative calibration is done during
actual use, the system does not have to be shut down to perform
calibration routines quite as often as conventional systems. This,
of course, results in increased productivity and cycle time.
[0034] Further still, the control module 60 can maintain a history
of calibrations to determine if any of the pressure sensors must be
repeatedly calibrated. This may indicate that the particular
pressure sensor or corresponding chamber is faulty. Likewise, if a
majority of the pressure sensors must be repeatedly calibrated,
this may indicate that the pressure sensor for the transfer chamber
16, or corresponding chamber, is faulty.
[0035] Although the invention has been described with reference to
specific embodiments, such as the manufacture of integrated circuit
semiconductors, this description is not meant to be construed in a
limited sense. The invention can be used in a variety of processes.
Also, different types of valves and chamber may equally benefit
from the present invention. Various modifications of the disclosed
embodiments, as well as alternative embodiments of the inventions
will become apparent to persons skilled in the art upon reference
to the description of the invention. It is, therefore, contemplated
that the appended claims will cover such modifications that fall
within the scope of the invention.
* * * * *