U.S. patent application number 11/190941 was filed with the patent office on 2005-11-24 for vacuum pumping system and method for monitoring of the same.
This patent application is currently assigned to Kabushiki Kaisha Toshiba. Invention is credited to Nakao, Takashi, Tanaka, Masayuki, Ushiku, Yukihiro.
Application Number | 20050260081 11/190941 |
Document ID | / |
Family ID | 19090273 |
Filed Date | 2005-11-24 |
United States Patent
Application |
20050260081 |
Kind Code |
A1 |
Tanaka, Masayuki ; et
al. |
November 24, 2005 |
Vacuum pumping system and method for monitoring of the same
Abstract
A vacuum pumping system includes: an evacuation conduit, having
a sequence of monitoring zones serially assigned in an exhaust
direction; sensors respectively provided to the monitoring zones
and independently detecting the conditions of the monitoring zones;
heaters respectively provided to the monitoring zones and being
paired with the sensors; and a control unit receiving data signals
from the sensors, comparing the data signals with a threshold
value, and when the data signals from a specific sensor exceed the
threshold value, selectively supplying heating power to a heater of
the monitoring zone where the specific sensor is provided.
Inventors: |
Tanaka, Masayuki;
(Kanagawa-ken, JP) ; Nakao, Takashi;
(Kanagawa-ken, JP) ; Ushiku, Yukihiro;
(Kanagawa-ken, JP) |
Correspondence
Address: |
FINNEGAN, HENDERSON, FARABOW, GARRETT & DUNNER
LLP
901 NEW YORK AVENUE, NW
WASHINGTON
DC
20001-4413
US
|
Assignee: |
Kabushiki Kaisha Toshiba
|
Family ID: |
19090273 |
Appl. No.: |
11/190941 |
Filed: |
July 28, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11190941 |
Jul 28, 2005 |
|
|
|
10224255 |
Aug 21, 2002 |
|
|
|
Current U.S.
Class: |
417/282 ;
417/207; 417/279; 417/292; 417/53 |
Current CPC
Class: |
C23C 16/4412
20130101 |
Class at
Publication: |
417/282 ;
417/053; 417/207; 417/279; 417/292 |
International
Class: |
F04B 049/00; F04B
001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 31, 2001 |
JP |
P2001-263533 |
Claims
1-10. (canceled)
11. A method for monitoring an evacuation conduit comprising:
evacuating a reactive gas and a reaction by-product of the reactive
gas by the evacuation conduit having a plurality of monitoring
zones serially arranged in an evacuation direction; independently
detecting respective conditions of the monitoring zones by sensors
provided respectively to the monitoring zones; receiving respective
data signals from the sensors; comparing the data signals with a
threshold value; and selectively supplying heating power to only a
heater of the monitoring zone where the specified sensor is
arranged, when the data signals from a specific sensor exceeds the
threshold value.
12. The method of claim 11, wherein one of the respective
conditions is a vibration.
13. The method of claim 11, wherein one of the respective
conditions is a temperature.
14. A method for monitoring an evacuation conduit comprising:
evacuating a reactive gas and a reaction by-product of the reactive
gas, by the evacuation conduit, including a first valve connected
to a suction side piping of a specific evacuation element, a
branching vacuum piping having an exhaust side piping connected to
the first valve, a second valve connected to other exhaust side
piping of the branching vacuum piping, a bypass piping having a
suction side piping connected to the second valve; detecting a
condition of the specific evacuation element by sensors connected
to at least one of the suction side piping of the specific
evacuation element, the exhaust side piping of the specific
evacuation element, and the main body of the specific evacuation
element; and receiving data signals from the sensors, comparing the
data signals with a threshold value, and when the data signals from
a specific sensor exceeds the threshold value, supplying
respectively signals for closing the first valve and opening the
second valve to the first and second valves.
15. The method of claim 14, wherein one of the respective
conditions is a vibration.
16. The method of claim 14, wherein one of the respective
conditions is a temperature.
17. The method of claim 14, further comprising a spare evacuation
element in-between the second valve and the bypass piping, and a
third and fourth valve, which are respectively connected to exhaust
piping of the bypass piping and the specific evacuation
element.
18. The method of claim 17, wherein one of the respective
conditions is a vibration.
19. The method of claim 17, wherein one of the respective
conditions is a temperature.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon and claims the benefit of
priority from prior Japanese Patent Application 2001-263533 filed
on Aug. 31, 2001; the entire contents of which are incorporated by
reference herein.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a vacuum pumping system,
which is used in general industry or in a semiconductor
manufacturing equipment. In particular, it is related to a vacuum
pumping system, which provides improved longevity through failure
prevention thereof.
[0004] 2. Description of the Related Art
[0005] Problems of the conventional vacuum pumping system often
utilized in general industry or in many semiconductor manufacturing
equipments will be described. As an example, problems relating to
the vacuum pumping system, which is used in a low-pressure chemical
vapor deposition (LPCVD) equipment, specifically a tandem pump
system, which is used in a LPCVD equipment for a silicon nitride
film (Si.sub.3N.sub.4 film), will be described.
[0006] Conventionally, deposition of a silicon nitride film through
a LPCVD method involves the chemical reaction of dichlorosilane
(SiH.sub.2Cl.sub.2) gas, which is used as a silicon source, and
ammonia (NH.sub.3) gas, which is used as a nitride species, under
low pressure conditions at approximately 800.degree. C. to deposit
a silicon nitride film upon a silicon (Si) substrate. In addition
to generating the silicon nitride, the chemical reaction produces
the reaction by-products of ammonium chloride (NH.sub.4Cl) gas and
hydrogen (H.sub.2) gas. The hydrogen in gas phase is evacuated
through the vacuum pumping system utilizing the LPCVD equipment. On
the other hand, since the temperature within the reactor is
approximately 800.degree. C. and it is under low pressure
conditions of several 100 Pa or less at the time of formation, the
ammonium chloride is also in the gas phase. The LPCVD equipment
typically has a trap for collecting solid phase by-products,
disposed between a LPCVD chamber and the vacuum pumping system.
[0007] However, it is impossible to completely collect the solid
phase by-products with the trap since pressure at the location of
the trap is low. Accordingly, the ammonium chloride that has not
been collected reaches the vacuum pumping system. The vacuum
pumping system generates an approximately five digits difference in
pressure before and after the evacuation pump, where there is
approximately 0.1 Pa of pressure on the upstream side and
atmospheric pressure on the downstream side under such operational
performance. While the ammonium chloride is in a gas phase at the
time of formation, it begins to solidify within the evacuation pump
as the pressure increases due to gas compression therein. At the
portions where solidification has begun, exhaust conductance
decreases due to reduction of the pipe radius, and solidification
is further accelerated there. In other words, localized
solidification that has begun in one portion rapidly accelerates,
and the pipes ultimately are blocked, or adhesion to the rotating
portions happens making rotation impossible, thereby making the
vacuum pumping system fail. Failure of the vacuum pumping system
maybe caused by catastrophic failure in just one portion, resulting
in an vacuum pumping system with a remarkably short life span.
SUMMARY OF THE INVENTION
[0008] A first aspect of the present invention inheres in a vacuum
pumping system including: an evacuation conduit, having a sequence
of monitoring zones serially assigned in an exhaust direction;
sensors respectively provided to the monitoring zones and
independently detecting the conditions of the monitoring zones;
heaters respectively provided to the monitoring zones and being
paired with the sensors; and a control unit receiving data signals
from the sensors, comparing the data signals with a threshold
value, and when the data signals from a specific sensor exceed the
threshold value, selectively supplying heating power to a heater of
the monitoring zone where the specific sensor is provided.
[0009] A second aspect of the present invention inheres in a vacuum
pumping system, being connected such that a group of evacuation
elements regulate a fixed evacuation direction, including: a
specific evacuation element included among the group of the
evacuation elements; a first valve connected to a suction side
piping of the specific evacuation element; a branching vacuum
piping, having an exhaust side piping connected to the first valve;
a second valve connected to other exhaust side piping of the
branching vacuum piping; a bypass piping having a suction side
piping connected to the second valve; other evacuation elements
connecting one of the suction side piping to an exhaust side piping
of the specific evacuation element, and the other suction side
piping to an exhaust side piping of the bypass piping; sensors
connected to at least one of the suction side piping of the
specific evacuation element, the exhaust side piping of the
specific evacuation element, and a main body of the specific
evacuation element; and a control unit receiving data signals from
the sensors, comparing the data signals with a threshold value, and
when the data signals exceed the threshold value, respectively
supplying signals for closing the first valve and opening the
second valve to the first and second valves.
[0010] A third aspect of the present invention inheres in a method
for monitoring an evacuation conduit including: evacuating a
reactive gas and a reaction by-product of the reactive gas by the
evacuation conduit having a plurality of monitoring zones serially
arranged in an evacuation direction; independently detecting
respective conditions of the monitoring zones by sensors provided
respectively to the monitoring zones; receiving respective data
signals from the sensors; comparing the data signals with a
threshold value; and selectively supplying heating power to only a
heater of the monitoring zone where the specified sensor is
arranged, when the data signals from a specific sensor exceeds the
threshold value.
[0011] A fourth aspect of the present invention inheres in a method
for monitoring an evacuation conduit including: evacuating a
reactive gas and a reaction by-product of the reactive gas, by the
evacuation conduit, including a first valve connected to a suction
side piping of a specific evacuation element, a branching vacuum
piping having an exhaust side piping connected to the first valve,
a second valve connected to other exhaust side piping of the
branching vacuum piping, a bypass piping having a suction side
piping connected to the second valve; detecting a condition of the
specific evacuation element by sensors connected to at least one of
the suction side piping of the specific evacuation element, the
exhaust side piping of the specific evacuation element, and the
main body of the specific evacuation element; and receiving data
signals from the sensors, comparing the data signals with a
threshold value, and when the data signals from a specific sensor
exceeds the threshold value, supplying respectively signals for
closing the first valve and opening the second valve to the first
and second valves.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1 is a block diagram showing the concept of a vacuum
pumping system according to a first embodiment of the present
invention;
[0013] FIG. 2 is a block diagram schematically showing in more
detail the vacuum pumping system according to the first embodiment
of the present invention;
[0014] FIG. 3 is a block diagram schematically showing a vacuum
pumping system according to a second embodiment of the present
invention; and
[0015] FIG. 4 is a block diagram schematically showing a vacuum
pumping system according to other embodiments of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0016] Various embodiments of the present invention will be
described with reference to the accompanying drawings. It is to be
noted that the same or similar reference numerals are applied to
the same or similar parts and elements throughout the drawings, and
the description of the same or similar parts and elements will be
omitted or simplified.
FIRST EMBODIMENT
[0017] As shown in FIG. 1, a vacuum pumping system according to the
first embodiment of the present invention encompasses an evacuation
conduit 2, which has a plurality of monitoring zones Z.sub.1,
Z.sub.2, Z.sub.3, . . . , Z.sub.m serially arranged in the exhaust
direction; sensors 101, 102, 103, . . . , 104, which are
respectively provided to the monitoring zones Z.sub.1, Z.sub.2,
Z.sub.3, . . . , Z.sub.m and each independently detect the
condition of the corresponding zones of the evacuation conduit 2
therein; heaters 201, 202, 203, . . . , 204, which are paired with
the sensors 101, 102, 103, . . . , 104 and respectively provided to
the monitoring zones Z.sub.1, Z.sub.2, Z.sub.3, . . . , Z.sub.m;
and a control unit 1, which respectively receives data signals
D.sub.1, D.sub.2, D.sub.3, . . . , D.sub.m from the sensors 101,
102, 103, . . . , 104, compares these data signals D.sub.1,
D.sub.2, D.sub.3, . . . , D.sub.m with a threshold value, and when
a data signal D.sub.J (J:1-m) from a particular sensor exceeds the
threshold value, selectively supplies heating power to only the
heater of the monitoring zone the specific sensor is arranged
therein. The heating power can be directly supplied to the heaters
201, 202, 203, . . . , 204 from the control unit 1. On the
contrary, the necessary heating power can be indirectly supplied by
power units, each connected to the heaters 201, 202, 203, . . . ,
204, as shown in FIG. 1. That is, the necessary heater control
signals C.sub.1, C.sub.2, C.sub.3, . . . , C.sub.m from the control
unit 1 are respectively supplied to the power units so as to supply
heating power to the heaters 201, 202, 203, . . . , 204.
[0018] More specifically, in the vacuum pumping system according to
the first embodiment of the present invention, the evacuation
conduit 2 has a large variety of and a plurality of sensors 101,
102, 103, . . . , 104, which constantly monitor its condition,
mounted thereon. The group of a large variety and a plurality of
sensors 101, 102, 103, . . . , 104 constantly sends to the control
unit 1 the condition of the evacuation conduit 2. Temperature
gauges, pressure gauges, flowmeters, ammeters/voltmeters or
vibration gauges may be considered as the sensors 101, 102, 103, .
. . , 104. A comparator, which compares the received data signals
D.sub.1, D.sub.2, D.sub.3, . . . , D.sub.m with the threshold
value, is provided within the control unit 1. Analog comparison
with the threshold value may be made, or alternatively, comparison
may be made with a digital circuit.
[0019] In the case of comparing with a digital circuit, information
from the group of the sensors 101, 102, 103, . . . , 104 passes
through an A/D converter, which is provided to the output circuit
of the sensors 101, 102, 103, . . . , 104, and is concentrated in
the control unit 1 as digital signals. Otherwise, it may be
structured such that they are transmitted to the control unit 1 as
analog signals, passed through an installed A/D converter of an
input circuit of the control unit 1, so as to be input into the
comparator after being transformed into digital signals. Employing
either method, the information D.sub.1, D.sub.2, D.sub.3 . . . ,
D.sub.m from the group of the sensors 101, 102, 103, . . . , 104 is
collected by the control unit 1. For performing further detailed
diagnosis/analysis of the information D.sub.1, D.sub.2, D.sub.3, .
. . , D.sub.m, a central processing unit (CPU) may be installed.
The CPU is controlled in conformity with predetermined
software.
[0020] In this manner, the control unit 1 diagnoses/analyzes the
information D.sub.1, D.sub.2, D.sub.3, . . . , D.sub.m from the
group of sensors 101, 102, 103, . . . , 104, and controls the group
of the heaters 201, 202, 203, . . . , 204 based on the results.
[0021] In FIG. 2, a portion of the evacuation conduit 2 of the
LPCVD equipment for Si.sub.3N.sub.4 films is illustrated. The
evacuation conduit 2 has a plurality of evacuation elements 21, . .
. , 24, 25, 26, 27 serially connected in the exhaust direction from
the upstream side. The evacuation elements are a backing pump
(mechanical booster pump) a first stage main pump (omitted from the
drawing), a second stage main pump (omitted from the drawing), a
third stage main pump 24, a first stage gas cooler 25, a fourth
stage main pump 26, a second stage gas cooler 27, a fifth stage
main pump (omitted from the drawing), and a third stage gas cooler
(omitted from the drawing) respectively. The evacuation elements
21, . . . , 24, 25, 26, 27 are connected to each other through
vacuum piping 32, . . . , 34, 35, 37, 38, 39. In FIG. 2, similarly
to FIG. 1, a plurality of monitoring zones are assigned to the
evacuation elements 21, . . . , 24, 25, 26, 27. In addition,
sensors 111, 112, . . . , 121, 122, 123, 124, 125, 126, 127, 128,
which independently detect the condition of the evacuation conduit
2 in the monitoring zones, respectively, and heaters 211, 212, 213,
221, 222, 223, 224, 225, 226, 227, 228, 229, which are paired with
these sensors 111, 112, . . . , 121, 122, 123, 124, . . . , 127,
128 and are respectively provided to the monitoring zones, are
arranged corresponding to these monitoring zones. In the following,
the sensors 111, 112, . . . , 121, 122, 123, 124, 125, 126, 127,
128 are described as being temperature gauges such as thermocouples
or semiconductor thermometers. However, it should be noted that as
long as change in the condition of the evacuation conduit 2 can be
detected, the sensors 111, 112, . . . , 121, 122, 123, 124, 125,
126, 127, 128 are not limited to being temperature gauges. The
control unit 1 receives the respective data signals from the
sensors 111, 112, . . . , 121, 122, 123, 124, 125, 126, 127, 128,
compares these data signals to the threshold value, and in the case
where a data signal from a specific sensor exceeds the threshold
value, operates so as to selectively supply heating power to only
the heater in the monitoring zone where the specific sensor is
arranged. Thus, the sensors 111, 112, . . . , 121, 122, 123, 124,
125, 126, 127, 128 and the control unit 1 are connected to each
other by wiring 311, 312, . . . , 321, 322, 323, 324, 325, 326, 327
,328. Furthermore, the heaters 211, 212, . . . , 221, 222, 223,
224, 225, 226, 227, 228, 229 and the control unit 1 are connected
to each other by wiring, however, in FIG. 2, of these, only the
wiring 423, 424, 425 connected to the heaters 223, 224, 225 are
shown in the drawing.
[0022] During the LPCVD method for the silicon nitride film using
dichlorosilane (SiH.sub.2Cl.sub.2) and ammonia (NH.sub.3) as source
gases, ammonium chloride (NH.sub.4Cl) gas, a reaction by-product,
is generated as a result. Normally, a trap, which collects these
unreacted source gases (reactive gases) and the reaction by-product
(NH.sub.4Cl) from the reaction of the source gases, is inserted
between the evacuation conduit 2 and the CVD reactor (chamber) in
the LPCVD equipment. It is impossible for the trap to completely
collect the reaction by-product due to low pressure. The reaction
by-product that is not collected reaches the evacuation conduit 2.
The pressure in the evacuation conduit 2, which has the plurality
of evacuation elements 21, . . . , 24, 25, 26, 27, increases from
approximately 0.1 Pa to normal atmospheric pressure due to the
compression of the gas. The reaction by-product exists as a gas
under low pressure conditions; it begins to solidify in accordance
with the sublimation curve of the phase diagram as the pressure
increases. Within the pump, since the pressure changes from several
hundred Pa to the normal atmospheric pressure through repeated
compression of the gas, the gaseous reaction by-product within the
exhaust gas begins to solidify in the evacuation conduit 2 as the
pressure increases. If the solidification begins in the piping of
the evacuation conduit 2, the volume of the piping or the gas
coolers 25, 27 decreases, and the exhaust conductance decreases.
The pressure further increases in the portions of the reaction
by-product solidifying/adsorbing, whereby as a result, the
temperature begins to rise.
[0023] In the control unit 1, the threshold values (permissible
values) are set so as to permit the temperature to rise up to
approximately a certain degree Celsius in each of the plurality of
monitoring zones of the evacuation conduit 2. The threshold values
are determined based upon control information, which takes into
account the starting condition of the LPCVD equipment and the
operating status of the evacuation conduit 2 accumulated up to the
present. In the first embodiment, the temperature rise threshold
value is set to "a rise of 10.degree. C. from the initial
condition". When the rise in temperature reaches the threshold
value, the control unit 1 supplies power to only the heater on the
corresponding monitoring zone in the heaters 211, 212, . . . , 221,
222, 223, 224, 225, 226, 227, 228, 229, which are attached inside
the plurality of monitoring zones of the evacuation conduit 2,
selectively raising the temperature of only the corresponding
monitoring zone.
[0024] For example, it is assumed that clogging at the piping 35 on
the suction side of the first stage gas cooler 25 disposed in
upstream begins due to adhesion of the reaction by-product, and a
rise in temperature occurs. As previously mentioned, there are
three stages of gas coolers in all. In this case, the heater 223
for the piping 35 on the suction side of the first stage gas cooler
25, the heater 225 for the piping 38 on the exhaust side and the
heater 224 for the outer wall portion of the first stage gas cooler
25 are heated to 180.degree. C. The preset temperature of the
heaters 223, 225, 224 is the temperature at which ammonium chloride
sublimes. Accordingly, since a reaction by-product generated by a
LPCVD equipment of other material has different properties, the
LPCVD equipment for the other material requires setting a
temperature corresponding to the reaction by-product. By raising
the temperature of the heaters 223, 225 and 224, adhesion of the
reaction by-product at the first stage gas cooler 25 stops
progressing any further.
[0025] By continuing to perform a semiconductor manufacturing
process, adhesion and clogging in other monitoring zones progresses
and thus changes arise in the condition of the evacuation conduit
2. Similar to the aforementioned processing, the control unit 1
raises the temperature of the corresponding heater in the heaters
211, 212, . . . , 221, 222, 223, 224, 225, 226, 227, 228, 229 to
180.degree. C. when the change in the evacuation conduit 2
condition exceeds the threshold value, which is set for a newly
clogged monitoring zone. Successively, dispersing the
solidified/adsorbed reaction by-product is possible by repeating
the same process (operation).
[0026] Conventionally, solidification drastically accelerates in
the portions where the reaction by-product has begun to adhere,
becoming a catastrophic failure that makes the pump fail. However,
according to the first embodiment, it is possible to suppress
further adhesion in the portion where clogging has begun,
dispersing the reaction by-product to other monitoring zones. Thus,
the life span of the LPCVD equipment may be lengthened.
SECOND EMBODIMENT
[0027] In the first embodiment, a method for suppressing adhesion
of a reaction by-product, which is generated in a portion of the
monitoring zones of the evacuation pump system, by heating specific
monitoring zones Z1, Z2, Z3, . . . , Zm, however, other methods are
also possible.
[0028] FIG. 3, similar to FIG. 2, shows a portion of an evacuation
conduit 2, which has a backing pump (mechanical booster pump) 21, a
main pump first stage (omitted from the drawing), a main pump
second stage (omitted from the drawing), a main pump third stage
24, a first stage gas cooler 25, a fourth stage main pump 26, a gas
cooler second stage 27, a main pump fifth stage (omitted from the
drawing), and a gas cooler third stage (omitted from the drawing),
serially connected in the evacuation direction from the upstream
side. A group of the plurality of evacuation elements 21, . . . ,
24, 25, 26, 27 are connected through vacuum piping 32, . . . , 34,
35, 37, 38, 39 so as to define a fixed evacuation direction. The
evacuation conduit 2 is described by focusing on the gas cooler
first stage as a specific evacuation element 25. A first valve 50
is connected to a suction side piping 37 of the gas cooler first
stage (specific evacuation element) 25. One exhaust side piping of
a branch vacuum piping 35 is connected to the first valve 50. A
second valve 51 is connected to the other exhaust side piping of
the branch vacuum piping 35. The suction side piping of a bypass
piping 36 is connected to the second valve 51. One suction side
piping of the main pump fourth stage as another evacuation element
26 is connected to an exhaust side piping 38 of the first stage gas
cooler 25. The other suction side piping of the fourth stage main
pump (another evacuation element) 26 is connected to the exhaust
side piping of the bypass piping 36.
[0029] Here, sensors 122, 123, 124 are provided to the suction side
piping 37 of the first stage first stage gas cooler 25, the main
frame of the first stage gas cooler 25, and the exhaust side piping
28 of the first stage gas cooler 25. As with the first embodiment,
the second embodiment is described with temperature gauges as the
sensors. The control unit 1 receives data signals from these
sensors 122, 123, 124, compares the data signals with the threshold
value, and when these data signals exceed the threshold value,
respectively supplies to the first valve 50 and second valve 51
signals for closing the first valve 50 and opening the second valve
51. Consequently, the sensors 122, 123, 124 and the control unit 1
are connected to each other by the wiring 322, 323 and 324.
Furthermore, the first valve 50 and second valve 51 are connected
to the control unit 1 via respective wiring 450 and 451. In order
to open and close the first valve 50 and second valve 51 in
conformity with electrical signals from the control unit 1, the
first valve 50 and second valve 51 may be magnetic valves or
pneumatic valves which operate by air pressure. In the case of the
pneumatic valves, the air pressure respectively supplied to the
first valve 50 and second valve 51 may be controlled by a pneumatic
piping system, which is connected to the first valve 50 and second
valve 51. More specifically, the first valve 50 and second valve 51
may be controlled to open and close by driving the magnetic valves,
which control the pneumatic piping system, in conformity with
electrical signals from the control unit 1.
[0030] In this manner, the method depending on the provision of the
bypass piping 36 may also allow for lengthening of the evacuation
conduit 2 life span. In the initial condition where clogging has
not occurred, the first valve 50 is in an open status and the
second valve 51 is in a closed status. In other words, gas passes
through the first stage gas cooler 25. In the LPCVD equipment for
Si.sub.3N.sub.4 films, the upstream side first stage gas cooler 25
often clogs up. If the rise in temperature due to clogging exceeds
the threshold value, the control unit 1 closes the first valve 50
and simultaneously opens the second valve 51. The exhaust gas
passes through the bypass piping 36 and flows into the fourth stage
main pump 26. Namely, if it is conventional, when clogging of the
first stage gas cooler 25 occurs, replacement of the entire
evacuation conduit 2 is necessary; however, by allowing operation
of the portions where clogging has not occurred using the bypass
piping 36, lengthening the evacuation conduit 2 life span becomes
possible.
[0031] It should be noted that the evacuation elements other than
the first stage gas cooler 25, such as the backing pump (mechanical
booster pump) 21, the first stage main pump (omitted from the
drawing), the second stage main pump (omitted from the drawing),
the third stage main pump 24, the fourth stage main pump 26, the
second stage gas cooler 27, the fifth stage main pump (omitted from
the drawing), and the third stage gas cooler (omitted from the
drawing), may also be provided automatic valves for switching to
the bypass piping.
OTHER EMBODIMENTS
[0032] The present invention has been described through the first
and second embodiments as mentioned above, however the descriptions
and drawings that constitute a portion of this disclosure should
not be perceived as limiting this invention. Various modified
examples of the embodiments, alternative embodiments, working
examples and operational techniques will become clear to persons
skilled in the art from this disclosure.
[0033] For example, the structure may have other evacuation
elements further arranged on the bypass piping 36 side of FIG. 3,
which is used in the description of the second embodiment
previously described. FIG. 4 is a structure related to a modified
example of the second embodiment of the present invention, wherein
a spare gas cooler 28 is further arranged on the bypass piping 36
side of FIG. 3. In other words, as shown in FIG. 4, the first valve
50 is connected to the suction side piping 37 of the first stage
gas cooler 25, and one of the exhaust side piping of the branch
vacuum piping 35 is connected to the first valve 50. The second
valve 51 is connected to the other exhaust side piping of the
branch vacuum piping 35. A suction side piping of the spare gas
cooler 28 is connected to the second valve 51 via a bypass piping
41. A fourth valve 53 is connected to the exhaust side of the spare
gas cooler 28 via a bypass piping 42. A third valve 52 is connected
to an exhaust side piping 38 of the first stage gas cooler 25, and
via the third valve 52, one of the suction side piping of the main
pump fourth stage is connected thereto. A bypass piping 43 is
connected to the fourth valve 53 exhaust side, and the bypass
piping 43 is connected to the other suction side piping of the
fourth stage main pump 26.
[0034] Similar to FIG. 3, sensors 122, 123,124 are provided to the
suction side piping 37 of the first stage gas cooler 25, the main
body of the first stage gas cooler 25, and the exhaust side piping
38 of the first stage gas cooler 25. As the first embodiment, the
second embodiment is described with the sensors being temperature
gauges. The control unit 1 receives data signals from these sensors
122, 123 and 124, compares the data signals with the threshold
value, and when data signals exceed the threshold value,
respectively supplies to the first valve 50, second valve 51, third
valve 52 and fourth valve 53 signals for closing the first valve 50
and the third valve 52 and opening the second valve 51 and the
fourth valve 53. Consequently, the sensors 122, 123, 124 are
connected to the control unit 1 via the wiring 322, 323 and 324.
Furthermore, the first valve 50, second valve 51, third valve 52
and fourth valve 53 are connected to the control unit 1 via
respective the wiring 450, 451, 452 and 453. The fact that in order
to open and close the first valve 50, second valve 51 third valve
52 and fourth valve 53 in conformity with electrical signals from
the control unit 1, the first valve 50, second valve 51 third valve
52 and fourth valve 53 may be magnetic valves or pneumatic valves,
which operate by air pressure, is similar to the case of FIG.
3.
[0035] As shown in FIG. 4, since the spare gas cooler 28 is
provided between the bypass piping 41 and 42, it is possible to
switch over the exhaust channel so that the spare gas cooler 28 is
used when clogging of the first stage gas cooler 25 occurs. Then,
after switching over to the exhaust channel that uses the spare gas
cooler 28, a vacuum flange (omitted from the drawing), which is
provided at the portion of the suction side piping 37 and exhaust
side piping 38 of the first stage gas cooler 25, is opened, and the
first stage gas cooler 25 where clogging occurred there may be
overhauled. If both sides or one side of the vacuum flange is
connected with a bellows, the disassembling procedure is easy.
After overhaul is complete, the first stage gas cooler 25 is once
again inserted to the exhaust channel at the vacuum flange (omitted
from the drawing) portion of the suction side piping 37 and exhaust
side piping 38. By doing as such, next, if clogging on the spare
gas cooler 28 side occurs, contrary to the aforementioned, the
first valve 50 and third valve 52 are opened, and signals for
closing the second valve 51 and fourth valve 53 may be respectively
transmitted to the first valve 50, second valve 51, third valve 52
and fourth valve 53 from the control unit 1. For this purpose, a
sensor is arranged in the spare gas cooler 28, which is omitted
from the drawing. In other words, the first stage gas cooler 25 and
spare gas cooler 28 may be formed with a symmetrical structure.
[0036] As such, by making the first stage gas cooler 25 and the
spare gas cooler 28 be symmetrically formed, when clogging occurs
in one, it may be switched over to the other, and the gas cooler
where clogging occurred may be overhauled. Accordingly, with the
evacuation conduit 2 in an operating state, the clogging may be
resolved, allowing for the further lengthening of the evacuation
conduit 2 life span.
[0037] It should be noted that the evacuation elements other than
the first stage gas cooler 25, such as the backing pump (mechanical
booster pump) 21, the first stage main pump (omitted from the
drawing), the second stage main pump (omitted from the drawing),
the third stage main pump 24, the fourth stage main pump 26, the
second stage gas cooler 27, the fifth stage main pump (omitted from
the drawing), and the third stage gas cooler (omitted from the
drawing), may also be formed with symmetrical structures.
[0038] Various modifications will become possible for those skilled
in the art after receiving the teachings of the present disclosure
without departing from the scope thereof. Accordingly, the present
invention naturally includes various embodiments not specifically
mentioned herein. Therefore, the technical scope of the present
invention may be limited only by the scope of the patent claims
deemed reasonable from the above description.
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