U.S. patent application number 14/391607 was filed with the patent office on 2015-04-30 for method and apparatus for adjusting operating parameters of a vacuum pump arrangement.
The applicant listed for this patent is EDWARDS LIMITED. Invention is credited to Jack Raymond Tattersall, Neil Turner.
Application Number | 20150114476 14/391607 |
Document ID | / |
Family ID | 46546266 |
Filed Date | 2015-04-30 |
United States Patent
Application |
20150114476 |
Kind Code |
A1 |
Turner; Neil ; et
al. |
April 30, 2015 |
Method and Apparatus for Adjusting Operating Parameters of a Vacuum
Pump Arrangement
Abstract
A method for adjusting operating parameters of a vacuum pump
arrangement includes determining characteristics of a gas flowing
through the vacuum pump arrangement; and setting operating
parameters of the vacuum pump arrangement based on the determined
characteristics of the first gas. A controller can be configured to
perform the method for adjusting the operating parameters of the
vacuum pump arrangement in accordance with the characteristics of
the gas.
Inventors: |
Turner; Neil; (Godalming,
GB) ; Tattersall; Jack Raymond; (Bonbeach,
AU) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EDWARDS LIMITED |
Crawley, West Sussex |
|
GB |
|
|
Family ID: |
46546266 |
Appl. No.: |
14/391607 |
Filed: |
April 23, 2013 |
PCT Filed: |
April 23, 2013 |
PCT NO: |
PCT/GB2013/051025 |
371 Date: |
October 9, 2014 |
Current U.S.
Class: |
137/2 ;
137/565.23 |
Current CPC
Class: |
F04D 19/046 20130101;
F04D 27/005 20130101; Y10T 137/0324 20150401; Y10T 137/86083
20150401; F04D 27/00 20130101; F04C 28/28 20130101; F05C 2251/04
20130101; F04C 28/02 20130101; F04C 25/02 20130101; F04C 2220/30
20130101; F04C 23/005 20130101 |
Class at
Publication: |
137/2 ;
137/565.23 |
International
Class: |
F04C 25/02 20060101
F04C025/02; F04D 27/00 20060101 F04D027/00; F04C 28/02 20060101
F04C028/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 18, 2012 |
GB |
1208735.9 |
Claims
1. A method of adjusting operating parameters of a vacuum pump
arrangement, comprising: determining characteristics of a first gas
flowing through the vacuum pump arrangement; and setting operating
parameters of the vacuum pump arrangement based on the determined
characteristics of the first gas.
2. The method of claim 1, wherein the determining characteristics
of the first gas comprises a step for the vacuum pump arrangement
to receive a signal indicative of the characteristics.
3. The method of claim 2, wherein the signal is provided from a
process tool upstream of the vacuum pump arrangement.
4. The method of claim 2, wherein the signal is generated by a
sensor in a foreline connecting a process tool to the vacuum pump
arrangement downstream thereof.
5. The method of claim 4, wherein the senor is configured to make
direct or indirect measurements of thermal conductivity of the
first gas.
6. The method of claim 1, wherein the determining characteristics
of the first gas comprises: monitoring a property of the vacuum
pump arrangement, as the vacuum pump arrangement pumps the first
gas therethrough; and determining the characteristics of the first
gas based on the monitored property.
7. The method of claim 6, wherein the property is a power
consumption pattern.
8. The method of claim 1, wherein the vacuum pump arrangement
comprises a booster pump and a backing pump serially connected to a
process chamber in a manner that the booster pump is downstream of
the process chamber and upstream of the backing pump.
9. The method of claim 8, wherein the determining characteristics
of the first gas comprises determining whether a power consumption
of the booster pump at a given moment is above a first
predetermined threshold.
10. The method of claims 8, wherein the determining characteristics
of the first gas comprises determining whether a power consumption
of the backing pump at the given moment is below a predetermined
second threshold, if the power consumption of the booster pump at
the given moment is above the first predetermined threshold.
11. The method of claim 10, wherein the determining characteristics
of the first gas comprises designating the first gas as a heavy gas
if the power consumption of the backing pump is below the second
predetermined threshold and the power consumption of the booster
pump is above the first predetermined threshold at the given
moment.
12. The method of claims 10, wherein the operating parameters are
set to be heavy gas operating parameters in accordance with
characteristics of the heavy gas if the power consumption of the
backing pump is below the second predetermined threshold and the
power consumption of the booster pump is above the first
predetermined threshold at the given moment.
13. The method of claim 10, wherein the determining characteristics
of the first gas comprises designating the first gas as a hydrogen
rich gas if the power consumption of the backing pump is above the
second predetermined threshold and the power consumption of the
booster pump is above the first predetermined threshold at the
given moment.
14. The method of claim 10, wherein the operating parameters are
set to be hydrogen operating parameters in accordance with
characteristics of the hydrogen rich gas if the power consumption
of the backing pump is above the second predetermined threshold and
the power consumption of the booster pump is above the first
predetermined threshold at the given moment.
15. The method of claims 13, wherein the hydrogen operating
parameters have a power limit for the vacuum pump arrangement
higher than that of the heavy gas operating parameters.
16. The method of claims 13, wherein the hydrogen operating
parameters have a temperature limit for the vacuum pump arrangement
higher than that of the heavy gas operating parameters.
17. The method of claim 12, wherein the determining characteristics
of the first gas comprises determining whether the power
consumption of the booster pump is below a third predetermined
threshold.
18. The method of claim 17, wherein the determining characteristics
of the first gas comprises determining whether the booster pump
exceeds a predetermined speed threshold, if the power consumption
of the booster pump is below the third predetermined threshold.
19. The method according to any of claims 17, wherein the operating
parameters are set to be hydrogen operating parameters in
accordance with characteristics of the hydrogen rich gas, if the
booster pump exceeds the predetermined speed threshold and the
power consumption of the booster pump is below the third
predetermined threshold.
20. The method according to claim 7, wherein the power consumption
pattern comprises a relationship between a power consumption of the
vacuum pump arrangement and an inlet pressure of the vacuum pump
arrangement.
21. The method according to claim 7, wherein the power consumption
pattern comprises a relationship between a power consumption of the
vacuum pump arrangement and a pump speed of the vacuum pump
arrangement.
22. The method according to claim 7, wherein the power consumption
pattern comprises a relationship between a power consumption of the
vacuum pump arrangement and a temperature of the vacuum pump
arrangement.
23. An apparatus comprising: a process tool having a process
chamber; a vacuum pump arrangement for evacuating the process
chamber; and a controller configured to set operating parameter of
the vacuum pump arrangement in response to information representing
characteristics of a first gas flowing through the vacuum pump
arrangement.
24. The apparatus of claim 23, wherein the information is in a form
of a signal generated by the process tool.
25. The apparatus of claim 24, wherein the signal is generated by a
sensor in a foreline connecting the process tool to the vacuum pump
arrangement downstream thereof.
26. The apparatus of claim 25, wherein the senor is configured to
make direct or indirect measurements of thermal conductivity of the
first gas.
27. The apparatus of claim 23, wherein the information is in a form
of a monitored property of the vacuum pump arrangement.
28. The apparatus of claim 27, wherein the monitored property
comprises a power consumption pattern.
29. The apparatus of claim 28, wherein the vacuum pump arrangement
comprises a booster pump and a backing pump serially connected to a
process chamber in a manner that the booster pump is downstream of
the process chamber and upstream of the backing pump.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This Application is a Section 371 National Stage Application
of International Application No. PCT/GB2013/051025, filed Apr. 23,
2013, which is incorporated by reference in its entirety and
published as WO 2013/171454 A1 on Nov. 21, 2013 and which claims
priority of British Application No. 1208735.9, filed May 18,
2012.
BACKGROUND
[0002] This invention relates to a method and/or apparatus for
adjusting the operating parameters of a vacuum pump arrangement,
and more particularly to a method and/or apparatus for
self-adjusting the power or temperature limits of the vacuum pump
arrangement based on the thermal characteristics of the gas flowing
through the vacuum pump arrangement.
[0003] A system used in semiconductor or other industrial
manufacturing processes typically includes, among other things, a
process tool, a vacuum pump arrangement having a booster pump and a
backing pump, and an abatement device. In semiconductor
manufacturing applications, the process tool typically includes a
process chamber, in which a semiconductor wafer is processed into a
predetermined structure. The vacuum pump arrangement is connected
to the process tool for evacuating the process chamber to create a
vacuum environment in the process chamber in order for various
semiconductor processing techniques to take place. The gas
evacuated from the process chamber by the vacuum pump arrangement
might be directed to the abatement device, which destroys or
decomposes harmful or toxic components of the gas before it is
released to the environment.
[0004] Many semiconductor processing techniques are associated with
injecting various gases into the process chamber at different
steps. Hydrogen is one of the commonly used gases in processes,
such as Metalorganic Chemical Vapor Deposition (MOCVD), Plasma
Enhanced Chemical Vapor Deposition (PECVD), and silicon epitaxy.
The gases that are rich in hydrogen often exhibit very different
characteristics from those including heavier gaseous components.
The gas with a large proportion of hydrogen tends to have a high
thermal conductivity, whereas the gas with a large proportion of
heavy gaseous components tends to have a lower thermal
conductivity. When the hydrogen rich gas is pumped through a vacuum
pump, the temperature differential between the rotor and the stator
tends to be smaller than that when the gas contains a large
proportion of heavy gaseous components. As a result, there is a
lower risk for a vacuum pump pumping the hydrogen rich gas to seize
due to a clash between the rotor and the stator caused by thermal
expansion, as opposed to a vacuum pump pumping heavy gases.
[0005] Despite the well controlled risk of pump seizure, vacuum
pumps used in semiconductor manufacturing processes are often not
driven as hard as they can be. Besides hydrogen, other heavier
gases are also present in various steps in many semiconductor
manufacturing process cycles. In order to accommodate those heavier
gases, the power limits of the vacuum pumps are often set
conservatively in order to avoid pump seizure caused by a clash
between the rotor and the stator. As a result, the vacuum pumps
tend to be underutilized.
[0006] Moreover, setting temperature limits for vacuum pumps based
on the thermal characteristics of the heavy gases tends to cause
frequent nuisance tripping when the vacuum pumps are pumping
hydrogen rich gases. The temperature of a vacuum pump is almost
always monitored from the outside of the pump casing, whereas the
critical temperatures inside the vacuum pump are inferred from the
outside temperature. It is a common industry practice to set the
limit conservatively based on the outside temperature of the vacuum
pump in order to avoid the internal temperatures exceeding a
predetermined safety level. Due to the high thermal conductivity of
hydrogen, the temperature differential between the outside and the
inside of the vacuum pump tends to be smaller when the vacuum pump
is pumping the hydrogen rich gas as opposed to the heavy gases.
Because the internal temperature of a vacuum pump tends to be
higher than the temperature on the outside, a limit set based on
the thermal characteristics of the heavy gases might be too
conservative for hydrogen-rich pumped gases. When the vacuum pump
is pumping the hydrogen rich gas, such limit can be easily
exceeded, while there is little risk for the pump to seize. This
leads to nuisance tripping or a false alarm being triggered.
[0007] Conventionally, it might be possible to adjust the
rotational speed of the vacuum pumps in response to the state of
the process chamber. An example can be found in U.S. Pat. No.
6,739,840, which is directed to a method for controlling the vacuum
pumps based on a signal provided by an upstream process tool that
indicates whether or not the process chamber is in operation for
the purpose of reducing the power consumption of the vacuum pumps.
However, such a method does not take into account the chemistry and
other characteristics of the gases evacuated from the process
chamber for the purpose of extracting maximum performance out of
the vacuum pumps. Neither does it provide the capability of
adjusting the power and/or temperature limits of the vacuum pumps
based on the signal generated by the process tool.
[0008] As such, what is needed is a method and/or apparatus for
adjusting the operating parameters of the vacuum pump based on the
thermal characteristics of the gas currently flowing through the
vacuum pump.
[0009] The Summary is provided to introduce a selection of concepts
in a simplified form that are further described in the Detail
Description. This Summary is not intended to identify key features
or essential features of the claimed subject matter, nor is it
intended to be used as an aid in determining the scope of the
claimed subject matter.
SUMMARY
[0010] The disclosure is directed to a method for adjusting
operating parameters of a vacuum pump arrangement, comprising:
determining characteristics of a first gas flowing through the
vacuum pump arrangement; and setting operating parameters of the
vacuum pump arrangement based on the determined characteristics of
the first gas.
[0011] The disclosure is also directed to an apparatus comprising:
a process tool having a process chamber; a vacuum pump arrangement
for evacuating the process chamber; and a controller configured to
set operating parameters of the vacuum pump arrangement in response
to information representing characteristics of a first gas flowing
through the vacuum pump arrangement.
[0012] The construction and method of operation of the invention,
however, together with additional objectives and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
[0013] The Summary is provided to introduce a selection of concepts
in a simplified form that are further described in the Detail
Description. This Summary is not intended to identify key features
or essential features of the claimed subject matter, nor is it
intended to be used as an aid in determining the scope of the
claimed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 illustrates a schematic view of a system where a
process chamber, a booster pump, and a backing pump are connected
in series in accordance with some embodiments of the invention.
[0015] FIG. 2 illustrates a flow chart showing a method for
self-adjusting the operating parameters of the booster pump and the
backing pump in accordance with some embodiments of the
invention.
[0016] FIG. 3 illustrates a graph comparing the power consumption
curves of the vacuum pumps in various conditions in accordance with
some embodiments of the invention.
DETAILED DESCRIPTION
[0017] This disclosure is directed to a method and/or apparatus for
adjusting the operating parameters of a vacuum pump arrangement in
response to a signal indicative of the thermal characteristics of
the gas being evacuated from a process tool upstream of the vacuum
pump arrangement, or a determination of the thermal characteristics
of the gas flowing through the vacuum pump arrangement based on
power consumption patterns of the vacuum pump arrangement. The
operating parameters of the vacuum pump arrangement can be adjusted
in response to the signal received by the vacuum pump arrangement
from a process tool that indicates the chemistry and thermal
characteristics of the gas being evacuated from the process tool.
Absent such signal, the thermal characteristics of the gases can be
determined by analyzing the power consumption patterns, since
different gases generate different power consumption patterns as
they flow through the vacuum pump arrangement.
[0018] FIG. 1 illustrates a schematic view of a system 10 where a
process chamber 12 and a vacuum pump arrangement 20 are connected
in series in accordance with some embodiments of the invention. The
vacuum pump arrangement 20 draws gases out of the process chamber
12 and creates a vacuum environment in it to carry out certain
processes, such as depositions, etching, ion implantation, epitaxy,
etc. The gases can be introduced into the process chamber 12 from
one or more gas sources, such as the ones designated by 14a and 14b
in this figure. The gas sources 14a and 14b can be connected to the
process chamber 12 via control valves 16a and 16b, respectively.
The timing of introducing various gases into the process chamber
can be controlled by selectively turning on or off the control
valves 16a and 16b. The flow rates of the gases introduced from the
gas sources 14a and 14b into the process chamber 12 can be
controlled by adjusting the fluid conductance of the control valves
16a and 16b. As discussed above, many semiconductor processing
techniques, such as MOCVD, PECVD, and silicon epitaxy, often inject
hydrogen rich gases into the process chamber 12 at one step, and
other heavier gases at other steps. By "hydrogen rich," it is
understood that the hydrogen component in the gas is 50% or more in
mole fraction or 7% or more in mass fraction.
[0019] The vacuum pump arrangement 20 includes a booster pump 22
and a backing pump 24 connected in series. The inlet of the booster
pump 22 is connected to the outlet of the process chamber 12. The
outlet of the booster pump 22 is connected to the inlet of the
backing pump 24. The outlet of the backing pump 24 might be
connected to an abatement device (not shown in the figure) where
the exhaust gases emitted from the backing pump 24 are treated in
order to reduce the harmful impact the exhaust gases might have on
the environment. Sensors (not shown in the figure) can be
implemented in the vacuum pump arrangement 20 to collect data of
various measurements, such as the temperatures, power consumptions,
pump speeds, etc., of the booster pump 22 and the backing pump 24.
Sensors can also be implemented to measure the gas pressures at the
inlets and/or outlets of the booster pump 22 and/or the backing
pump 24. A controller 30 can be implemented to adjust the
parameters of the vacuum pump arrangement 20 in response to a
signal indicating the chemistry and thermal characteristics of the
gas being evacuated from the process chamber 12. Such signal might
be generated by a process tool incorporating the process chamber
12, or a remote host computer monitoring and controlling the
process tool via a local area network or the Internet. Such signal
might indicate a change of process recipe in the process chamber
12, and causes the controller 30 to adjust the parameters of the
vacuum pump arrangement 20 accordingly. Additionally, one or more
sensors (not shown) disposed on the foreline connecting the chamber
12 and vacuum pump arrangement 20 can be employed to determine the
nature or characteristic of the gas being evacuated from the
chamber 12.
[0020] Alternatively, the controller 30 can be implemented in the
vacuum pump arrangement 20 in the form of a control circuit, which
can analyze the data to obtain power consumption patterns of the
vacuum pump arrangement 20, and set the operating parameters of the
vacuum pump arrangement 20 according to the power consumption
patterns.
[0021] FIG. 2 illustrates a flow chart 100 showing a method for
self-adjusting the operating parameters of the vacuum pump
arrangement 20 in accordance with some embodiments of the
invention. FIG. 3 illustrates an exemplary graph comparing the
power consumption curves of the booster pump 22 and the backing
pump 24 in various conditions. Referring to FIGS. 2 and 3,
initially at step 102, the booster pump 22 and backing pump 24 are
set at the hydrogen operating parameters suitable for pumping gases
that are rich in hydrogen. The hydrogen operating parameters
compared to the heavy gas operating parameters can have higher
power or temperature limits. As discussed above, the hydrogen rich
gas has a high thermal conductivity, which leads to a low
temperature differential between the inside and outside of a vacuum
pump, and therefore permits the vacuum pump to be driven
harder.
[0022] Step 104 determines whether the power consumption of the
booster pump is greater than a first predetermined threshold. If
the power consumption is below the first predetermined threshold,
the process goes back to the beginning of step 104. If the power
consumption is above the first predetermined threshold, the process
proceeds to step 106. Step 106 determines whether the power
consumption of the backing pump is below a second predetermined
threshold. If the power consumption is above the second
predetermined threshold, the process goes back to the beginning of
step 104. If the power consumption is below the second
predetermined threshold, the process proceeds to step 108 where the
booster pump and the backing pump are set to the heavy gas
operating parameters.
[0023] As shown in FIG. 3, the power consumption curve of the
booster pump pumping hydrogen is designated by 202, whereas the
power consumption curve of the booster pump pumping air is
designated by 204. The power consumption curve of the backing pump
pumping hydrogen is designated by 208, whereas the power
consumption curve of the backing pump pumping air is designated by
206. Here, hydrogen and air are used as the proxies of the hydrogen
rich gas and heavy gas, respectively, for the purposes of
explaining the process illustrated in FIG. 2. The x-axis represents
the gas pressure at the inlet of the vacuum pump arrangement that
is constructed by the serially connected booster pump and backing
pump. The y-axis represents the power consumptions of the booster
pump and the backing pump. The first and second predetermined
thresholds are represented by horizontal lines designated by 210
and 212, respectively. At pressure P1, if hydrogen is pumped
through the booster pump and the backing pump, the power
consumption of the booster pump will fall below the first
predetermined threshold 210, and the hydrogen operating parameters
will remain unchanged. However, if air is pumped through the
booster pump and the backing pump, at pressure P1, the power
consumption of the booster pump will be higher than the first
predetermined threshold 210, while the power consumption of the
backing pump will be below the second predetermined threshold 212.
As such, the booster pump and the backing pump will be set to the
heavy gas operating parameters.
[0024] After the booster pump and the backing pump are set to the
heavy gas operating parameters at step 108, the process proceeds to
step 110 where the power consumption of the booster pump is
compared to a third predetermined threshold. If the power
consumption of the booster pump is above the third predetermined
threshold, the process goes back to the beginning of the step 110.
If the power consumption of the booster pump is below the third
predetermined threshold, the process proceeds to step 112 where the
speed of the booster pump is compared to a predetermined speed
threshold. If the speed of the booster pump is slower than the
predetermined speed threshold, the process goes back to the
beginning of step 110. If the speed of the booster pump exceeds the
predetermined speed threshold, the process goes back to step 102
where the booster pump and the backing pump are reset to the
hydrogen operating parameters.
[0025] As shown in FIG. 3, the third predetermined threshold is
represented by a horizontal line designated by 214. There are two
regions in the graph where the power consumptions of the booster
pump are below the third predetermined threshold, namely region 220
where the pressure is below P2 and region 222 where the pressure is
above P3. If the booster pump is in region 220, its speed would
exceed the predetermined speed threshold, and therefore it would be
safe to reset the booster pump and the backing pump back to the
hydrogen operating parameters. However, if the booster pump is in
region 222, its speed would be slower than the predetermined speed
threshold, due to the high pressure at the inlets of the pumps. In
such condition, it is not safe to reset the pumps to the hydrogen
operating parameters, because they would drive the pumps too hard,
therefore risking their exceeding the safety limits.
[0026] The disclosed method is capable of adjusting the parameters
of the vacuum pump arrangement based on the data collected from the
vacuum pump arrangement. If it is determined that the hydrogen rich
gas is being pumped through the vacuum pump arrangement, the
hydrogen operating parameters will be employed to drive the vacuum
pump arrangement harder than when the heavy gas operating
parameters are used. This enables the vacuum pump arrangement to
operate at a greater capacity, without risking the vacuum pump
arrangement exceeding its power or temperature limits.
[0027] Alternatively, the operating parameters of the vacuum pump
arrangement can be adjusted in response to a signal indicating the
chemistry and thermal characteristics of the gas being evacuated
from the process chamber to the vacuum pump arrangement. As shown
in FIG. 1, the controller 30 can be configured to adjust the
operating parameters in response to such signal. The controller 30
can be implemented as a stand-alone device or an integral part of
the vacuum pump arrangement 20. In some embodiments of the
invention, the signal might be generated by the process tool
incorporating the process chamber 12. In some other embodiments of
the invention, the signal might be generated by a host computer
remotely monitoring and controlling both the process tool and the
vacuum pump arrangement via a local area network, or the Internet.
Also, the signal might be generated by one or more sensors disposed
in the foreline between the chamber and vacuum pump
arrangement.
[0028] In some semiconductor manufacturing processes, a vacuum pump
arrangement is used to pump both the hydrogen rich gas and the
heavy gas at various steps. Conventionally, if the vacuum pump
arrangement is designed according to the hydrogen gas flow, the
size of the vacuum pump arrangement would need to be large in order
to avoid pump seizure when it pumps the heavy gases. Unlike the
conventional designs, the disclosed method and apparatus enables
the vacuum pump arrangement to adjust or self-adjust its power or
temperature limits in response to the thermal characteristics of
the gas flowing through the arrangement. Thus, it enables the
vacuum pump arrangement to be made in a smaller size, without
compromising on its pumping capacity when it pumps the hydrogen
rich gas or risking seizure when it pumps the heavy gas.
[0029] In addition to using the relationship between the power
consumption and the inlet gas pressure to determine the thermal
characteristics of the gas flowing through a vacuum pump
arrangement, other relationships can also be used to make the
determination. For example, the relationship between the power
consumption and the pump speed might be used to determine the
thermal characteristics of the gas flowing through the vacuum pump
arrangement. As another example, the relationship between the power
consumption and temperature of the pumps might be used to determine
the thermal characteristics of the gas flowing through the vacuum
pump arrangement. It is understood that setting the operating
parameters of the vacuum pump arrangement based on those
relationships can be achieved by applying the process illustrated
in FIG. 2, with certain modifications accounting for the different
curve patterns in those relationships. It is asserted that those
modifications are within the scope of the present disclosure.
[0030] Although the invention is illustrated and described herein
as embodied in one or more specific examples, it is nevertheless
not intended to be limited to the details shown, since various
modifications and structural changes may be made therein without
departing from the spirit of the invention and within the scope and
range of equivalents of the claims. Accordingly, it is appropriate
that the appended claims be construed broadly and in a manner
consistent with the scope of the invention, as set forth in the
following claims.
* * * * *