U.S. patent application number 10/589748 was filed with the patent office on 2008-08-28 for vacuum apparatus.
This patent application is currently assigned to Foundation for Advancement of International Science. Invention is credited to Tadahiro Ohmi.
Application Number | 20080206072 10/589748 |
Document ID | / |
Family ID | 34857851 |
Filed Date | 2008-08-28 |
United States Patent
Application |
20080206072 |
Kind Code |
A1 |
Ohmi; Tadahiro |
August 28, 2008 |
Vacuum Apparatus
Abstract
An object of this invention is to provide a vacuum apparatus
used in the field of semiconductor production and capable of
suppressing power consumption. The vacuum apparatus comprises
vacuum containers (10, 11, 12, 13, 14, and 15) having gas inlets
and gas outlets, vacuum pumps of at least one stage for
depressurizing the inside of the vacuum containers or maintaining
the inside of the container in a depressurized state, and
compressors (4c, 5c, 6c, 7c, 8c, and 9c) connected to the discharge
ports of the vacuum pumps (4b, 5b, 6b, 7b, 8b, and 9b) on the last
stage among the vacuum pumps and having capacities having
capability of depressurizing the input sides thereof.
Inventors: |
Ohmi; Tadahiro; (Miyagi,
JP) |
Correspondence
Address: |
FOLEY AND LARDNER LLP;SUITE 500
3000 K STREET NW
WASHINGTON
DC
20007
US
|
Assignee: |
Foundation for Advancement of
International Science
|
Family ID: |
34857851 |
Appl. No.: |
10/589748 |
Filed: |
February 14, 2005 |
PCT Filed: |
February 14, 2005 |
PCT NO: |
PCT/JP05/02151 |
371 Date: |
August 17, 2006 |
Current U.S.
Class: |
417/251 ;
415/169.1; 418/9 |
Current CPC
Class: |
F04C 18/16 20130101;
F04C 2220/10 20130101; F04C 23/003 20130101; F04C 23/001 20130101;
F04B 37/14 20130101; F04C 2220/30 20130101; F04C 25/02
20130101 |
Class at
Publication: |
417/251 ;
415/169.1; 418/9 |
International
Class: |
F04B 37/16 20060101
F04B037/16 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 17, 2004 |
JP |
2004-39597 |
Claims
1. A vacuum apparatus comprising: a vacuum container having a gas
inlet and a gas outlet; a vacuum pump of at least one stage
connected to said gas outlet of said vacuum container for
depressurizing the inside of said vacuum container or maintaining
the inside of said vacuum container in a depressurized state; and a
compressor connected to a discharge port of the last-stage vacuum
pump of said at least one-stage vacuum pump and having capability
of depressurizing an input side of said compressor.
2. A vacuum apparatus according to claim 1, wherein the number of
vacuum pump stages is set to one stage or a plurality of stages
depending on a gas amount introduced into said vacuum
container.
3. A vacuum apparatus according to claim 1, wherein the number of
vacuum pump stages is set to the plurality of stages.
4. A vacuum apparatus according to any one of claims 1 to 3,
further comprising a gas recovery apparatus for recovering a gas
discharged from said last-stage vacuum pump for re-use of said gas;
and wherein said compressor is a gas recovery compressor in said
gas recovery apparatus.
5. A vacuum apparatus comprising a container to be depressurized
having a gas inlet and a gas outlet, vacuum pumps of a plurality of
stages connected to said container for depressurizing the inside of
said container and maintaining the inside of said container in a
depressurized state, and a gas recovery apparatus for recovering a
gas discharged from the last-stage vacuum pump of said vacuum pumps
for re-use of said gas; wherein said vacuum apparatus further
comprises a gas recovery compressor connected to a discharge port
of said last-stage vacuum pump and having depressurization
capability for assisting a depressurization operation of said
last-stage vacuum pump and suppressing back diffusion from said
discharge port.
6. A vacuum apparatus according to claim 5, wherein a supply amount
of a gas introduced into said container is smaller than a
predetermined amount, and said last-stage vacuum pump is omitted, a
gas discharged from the vacuum pump at the stage prior to the last
stage being recovered and reused by said gas recovery apparatus,
and said gas recovery compressor being connected to a discharge
port of said vacuum pump at the stage prior to the last stage.
7. A vacuum apparatus comprising: a container to be depressurized
having a gas inlet and a gas outlet; a first vacuum pump for
maintaining the inside of said container to be depressurized; a
second vacuum pump connected at a subsequent stage of said first
vacuum pump; a third vacuum pump connected at a subsequent stage of
said second vacuum pump; and a compressor having depressurization
capability and connected to said third vacuum pump.
8. A vacuum apparatus according to claim 7, wherein said first
vacuum pump is a turbomolecular pump or a thread groove pump, and
said second vacuum pump is a booster pump, said third vacuum pump
being a dry pump.
9. A vacuum apparatus according to claim 7 or 8, further comprising
a gas recovery apparatus for recovering a gas discharged from said
third vacuum pump for re-use of said gas, wherein said compressor
is a gas recovery compressor in said gas recovery apparatus.
10. A vacuum apparatus comprising: a container to be depressurized
having a gas inlet and a gas outlet and introduced with a gas in a
supply amount smaller than a predetermined amount; a first vacuum
pump for maintaining the inside of said container to be
depressurized; a second vacuum pump connected at a subsequent stage
of said first vacuum pump; and a compressor having depressurization
capability and connected to said second vacuum pump.
11. A vacuum apparatus according to claim 10, wherein said first
vacuum pump is a turbomolecular pump or a thread groove pump, and
said second vacuum pump is a booster pump.
12. A vacuum apparatus according to claim 10 or 11, further
comprising a gas recovery apparatus for recovering a gas discharged
from said second vacuum pump for re-use of said gas, wherein said
compressor is a gas recovery compressor in said gas recovery
apparatus.
13. A vacuum apparatus according to any one of claims 1, 5, 7 or
10, wherein the vacuum pump connected to said compressor is a screw
pump.
14. A vacuum apparatus according to any one of claims 1, 5, 7 or
10, wherein said compressor and the vacuum pump to which said
compressor is connected are co-operated in series.
Description
TECHNICAL FIELD
[0001] This invention relates to a vacuum apparatus and, in
particular, relates to a vacuum apparatus for use in the field of
manufacturing semiconductor devices, flat panel display devices, or
the like.
BACKGROUND ART
[0002] vacuum apparatus have been used in the semiconductor
manufacturing field and many other industrial fields.
[0003] The vacuum apparatus generally comprises a vacuum container
and vacuum pumps for keeping the inside of the vacuum container in
a vacuum or depressurized state.
[0004] The vacuum apparatus is disposed in a clean room and is
configured to perform predetermined processing while introducing
and exhausting a predetermined process gas into and from the vacuum
container.
[0005] A vacuum apparatus of this type having vacuum pumps of a
plurality of stages for use in the manufacturing field of a
semiconductor device manufacturing apparatus is disclosed, for
example, in Patent Document 1.
[0006] In the conventional vacuum apparatus of this type, a high
vacuum pump as a first vacuum pump is connected to a reaction
chamber in order to bring the inside of the reaction chamber into a
depressurized or vacuum state, and a booster pump as a second
vacuum pump and a back pump as a third vacuum pump are respectively
arranged at a subsequent stage of the high vacuum pump.
[0007] Generally, use is made, as the high vacuum pump, of a high
vacuum pump that operates in a molecular flow region of ultimate
pressure (10.sup.-7 Torr or less). Specifically, a turbomolecular
pump or a thread groove pump is generally used as the high vacuum
pump.
[0008] The turbomolecular pump and the thread groove pump each
generally have a low allowable back pressure of 1 Torr or less
(specifically 0.5 Torr or less) while the pumping speed is high
even with a small size. Therefore, there is/are provided, at the
subsequent stage of the high vacuum pump, an intermediate/low
vacuum pump or intermediate/low vacuum pumps in one or two stages
which each operate at a relatively low back pressure while the
ultimate pressure is relatively low.
[0009] For example, in the case where vacuum pumps are provided in
two stages at the subsequent stage of the high vacuum pump, a
booster pump or the like is provided subsequent to the high vacuum
pump as an intermediate vacuum pump and, further, a back pump
(Roots-type back pump or the like) is provided subsequent to the
booster pump as a low vacuum pump that operates at a relatively low
back pressure while the ultimate pressure is low.
[0010] In many cases, a gas exhausted from the reaction chamber is
discarded. However, particularly when a noble gas such as krypton
or xenon is used for plasma excitation, or the like, the expensive
noble gas is normally recovered. In this case, the discharge side
of the back pump is connected to a compressor of a recovery
apparatus. The compressor of the conventional recovery apparatus
merely accumulates an input gas, increases its pressure, and
discharges it.
[0011] As described above, in a vacuum apparatus for use in the
manufacture of a semiconductor device manufacturing apparatus, use
is generally made of two or three vacuum pumps in multistages with
respect to one reaction chamber (vacuum container). These vacuum
pumps often have mutually different structures as described above,
but are all driven by electric motors. Accordingly, in the vacuum
apparatus of this type where the number of vacuum pumps used is
large, the power consumption increases. Since the power consumption
of the vacuum apparatus resultantly affects the manufacturing cost
of the semiconductor device manufacturing apparatus, it is desired
to reduce the power consumption.
[0012] Particularly, since the last-stage low vacuum pump (back
pump) among the multistage vacuum pumps is required to have a large
capacity, the power consumption thereof is also large. Therefore,
it is effective and desirable to suppress the power consumption of
the back pump for a reduction in power consumption of the entire
vacuum apparatus and thus a reduction in manufacturing cost of the
semiconductor device manufacturing apparatus.
[0013] Herein, the reasons of the large power consumption of the
back pump are firstly that since its discharge side is the
atmosphere (the atmospheric pressure is 760 Torr), the exhaust
operation should always be carried out (even when the reaction
chamber is not operated) in order to prevent back diffusion to the
inlet side from the atmospheric side and secondly that although a
depressurized gas enters from the inlet side, the gas does not go
out into the atmosphere unless its pressure is increased to the
atmospheric pressure or more.
[0014] Patent Document 1:
Japanese Unexamined Patent Application Publication (JP-A) No.
2002-39061
DISCLOSURE OF THE INVENTION
Problem to be Solved by the Invention
[0015] Therefore, it is an object of this invention to provide a
vacuum apparatus and a vacuum pump that can suppress the power
consumption.
Means for Solving the Problem
[0016] According to this invention, there is obtained a vacuum
apparatus characterized by comprising a vacuum container having a
gas inlet and a gas outlet, a vacuum pump of at least one stage
connected to the gas outlet of the vacuum container for
depressurizing the inside of the vacuum container or maintaining
the inside of the vacuum container in a depressurized state, and a
compressor connected to a discharge port of the last-stage vacuum
pump of the at least one-stage vacuum pump and having capability of
depressurizing an input side of the compressor.
[0017] The number of vacuum pump stages is set to one stage or a
plurality of stages depending on a gas amount introduced into the
vacuum container or the capability of the vacuum pump.
[0018] In this invention, it is preferable that a gas recovery
apparatus for recovering a gas discharged from the last-stage
vacuum pump for re-use of said gas be provided and the compressor
be a gas recovery compressor in the gas recovery apparatus.
[0019] Further, according to this invention, there is obtained a
vacuum apparatus comprising a container to be depressurized having
a gas inlet and a gas outlet, mechanical vacuum pumps of a
plurality of stages connected to the container for depressurizing
the inside of the container and maintaining the inside of the
container in a depressurized state, and a gas recovery apparatus
for recovering a gas discharged from the last-stage vacuum pump for
re-use of said gas, the vacuum apparatus characterized by
comprising a gas recovery compressor connected to a discharge port
of the last-stage vacuum pump and having depressurization
capability for assisting a depressurization operation of the
last-stage vacuum pump and suppressing back diffusion from the
discharge port.
[0020] When a supply amount of a gas introduced into the container
to be depressurized is smaller than a predetermined amount (in this
case, the pumping speed of the gas recovery compressor relatively
increases, thereby enabling evacuation to a predetermined back
pressure or less of the preceding-stage vacuum pump), the
last-stage vacuum pump is omitted, a gas discharged from the vacuum
pump at the stage prior to the last stage is recovered and reused
by the gas recovery apparatus, and the gas recovery compressor is
connected to a discharge port of the vacuum pump at the stage prior
to the last stage.
[0021] The vacuum pumps in the plurality of stages may comprise a
first vacuum pump, a second vacuum pump connected at a subsequent
stage of the first vacuum pump, and a third vacuum pump connected
at a subsequent stage of the second vacuum pump and, in this case,
it is preferable that the first vacuum pump be a turbomolecular
pump or a thread groove pump, the second vacuum pump be a booster
pump, and the third vacuum pump be a dry pump. When a supply amount
of an introducing gas is smaller than a predetermined amount (in
this case, the pumping speed of the gas recovery compressor
relatively increases, thereby enabling evacuation to a
predetermined back pressure or less of the preceding-stage vacuum
pump), the third vacuum pump is omitted and the compressor having
the depressurization capability is connected to the second vacuum
pump.
[0022] It can also be said that the compressor additionally
attached to the discharge port of the last-stage pump, particularly
the discharge port exposed to the atmospheric side, has the
function of a vacuum pump.
Effect of the Invention
[0023] In the vacuum apparatus according to this invention, since
the gas recovery compressor having the function of a vacuum pump or
having the depressurization capability is connected to the
discharge port of the last-stage vacuum pump, the compressor
assists the depressurization operation of the last-stage vacuum
pump (i.e. since the compressor having the depressurization
capability reduces the pressure at the discharge port of the
last-stage vacuum pump, the last-stage vacuum pump is not required
to increase the pressure of the sucked gas to the atmospheric
pressure or more) and suppresses back diffusion from the discharge
port of the last-stage vacuum pump and, hence, it is possible to
suppress the power consumption of the last-stage vacuum pump as
compared with conventional and, as a result, it is possible to
reduce the manufacturing cost of a semiconductor device
manufacturing apparatus or the like.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] [FIG. 1] is a schematic diagram showing a semiconductor
manufacturing vacuum apparatus according to an embodiment of this
invention.
[0025] [FIG. 2], (a) and (b) are sectional views showing a screw
pump as a last-stage vacuum pump of the vacuum apparatus according
to the embodiment of this invention.
[0026] [FIG. 3] is a diagram showing the relationship between the
inlet pressure and the power consumption of the pump along with
that of a comparative example for explaining the operation and
effect of this invention.
DESCRIPTION OF SYMBOLS
[0027] 1, 2, 3 high vacuum pump [0028] 4a, 5a, 6a, 7a, 8a, 9a
booster pump [0029] 4b, 5b, 6b, 7b, 8b, 9b back pump [0030] 4c, 5c,
6c, 7c, 8c, 9c compressor [0031] 10, 11, 12 reaction chamber [0032]
13, 14 load lock chamber [0033] 15 transfer chamber [0034] 25 male
rotor [0035] 26 female rotor [0036] 27, 28 rotation shaft [0037]
31, 32 timing gear [0038] 33 water cooling jacket [0039] 42 main
casing [0040] 43 end plate [0041] 46, 55 auxiliary casing [0042] 56
inlet port [0043] 57 discharge port
[0044] B gas recovery apparatus
BEST MODE FOR CARRYING OUT THE INVENTION
[0045] Hereinbelow, an embodiment of a vacuum apparatus of this
invention will be described with reference to the drawings.
EMBODIMENT 1
[0046] Referring to FIG. 1, this vacuum apparatus comprises a
plurality of reaction chambers 10, 11, and 12, high vacuum pumps 1,
2, and 3 as first vacuum pumps one or a plurality of which are
arranged for each of the reaction chambers 10, 11, and 12 in order
to bring the inside thereof into a depressurized or vacuum state,
and booster pumps 4a, 5a, and 6a as second vacuum pumps and back
pumps 4b, 5b, and 6b as third vacuum pumps that are arranged at
subsequent stages of the high vacuum pumps, respectively.
[0047] Further, valves 22, 23, and 24 are provided between the high
vacuum pumps 1, 2, and 3 and the booster pumps 4a, 5a, and 6a,
respectively.
[0048] There are further provided load lock chambers 13 and 14 for
transferring processing objects such as wafers to the reaction
chambers 10, 11, and 12 and a transfer chamber 15 provided therein
with a robot (transfer apparatus) that transfers the processing
objects, brought into the load lock chamber 13, into the reaction
chambers 10, 11, and 12 and transfers them from the reaction
chambers 10, 11, and 12 into the load lock chamber 14.
[0049] A booster pump 8a, a back pump 8b, and a compressor 8c are
connected to the load lock chamber 13, a booster pump 7a, a back
pump 7b, and a compressor 7c are connected to the load lock chamber
14, and a booster pump 9a and a back pump 9b are connected to the
transfer chamber 15, thereby being capable of bringing those
chambers into depressurized or vacuum states, respectively.
[0050] Further, although not illustrated, the reaction chambers 10,
11, and 12 are each provided with a gas inlet and heating means
such as a heater to thereby carry out predetermined processing such
as film formation while introducing a predetermined gas under
heating.
[0051] In the figure, symbols A1 denote pipes between the high
vacuum pumps 1, 2, and 3 and the booster pumps 4a, 5a, and 6a,
respectively, while symbols A2 denote pipes between the reaction
chambers 10, 11, and 12 and the high vacuum pumps 1, 2, and 3,
respectively. Further, in the figure, symbol R denotes a clean
room.
[0052] In the state where this vacuum apparatus is on standby, the
transfer chamber 15 and the reaction chambers 10, 11, and 12 are
each held in a depressurized or vacuum state.
[0053] Then, a cassette with a plurality of processing objects such
as wafers placed therein is brought into the load lock chamber 13
from the atmosphere outside the system and the load lock chamber 13
is evacuated.
[0054] Subsequently, a gate valve (not illustrated) between the
load lock chamber 13 and the transfer chamber 15 is opened and the
processing object transfer robot uses its transfer arm to pick up
one of the processing objects from the cassette and transfer it
into the transfer chamber 15.
[0055] Thereafter, a gate valve (not illustrated) between the
reaction chamber 10 and the transfer chamber 15 is opened and the
processing object is placed on a stage in the reaction chamber 10
by the use of the transfer arm.
[0056] Then, after the predetermined processing such as film
formation, the processed object is transferred into the other
reaction chamber 11 or 12 or the load lock chamber 14 by the use of
the transfer arm.
[0057] Then, after the processing, the processed object is finally
transferred to the exterior from the load lock chamber 14.
[0058] In the system shown in FIG. 1, use is made, as the high
vacuum pump, of a high vacuum pump that operates in a molecular
flow region of ultimate pressure (10.sup.-7 Torr or less).
Specifically, a turbomolecular pump or a thread groove pump is used
as the high vacuum pump.
[0059] The turbomolecular pump and the thread groove pump each
generally have a low allowable back pressure of 1 Torr or less
(specifically 0.5 Torr or less) while the pumping speed is high
even with a small size. Therefore, there is/are provided, at the
subsequent stage of the high vacuum pump, an intermediate/low
vacuum pump or intermediate/low vacuum pumps in one or two stages
which each operate at a relatively low back pressure while the
ultimate pressure is relatively low.
[0060] For example, in the case where vacuum pumps are provided in
two stages at the subsequent stage of the high vacuum pump, a
booster pump or the like is provided subsequent to the high vacuum
pump as an intermediate vacuum pump and, further, a back pump
(Roots-type back pump or the like) is provided subsequent to the
booster pump as a low vacuum pump that operates at a relatively low
back pressure while the ultimate pressure is low.
[0061] In this invention, the back pumps 4b, 5b, 6b, 7b, 8b, and 9b
serving as the vacuum pumps at the last stage in FIG. 1 are
respectively provided with gas recovery apparatuses B incorporated
with compressors 4c, 5c, and 6c each having a vacuum pump function
that can assist the depressurization operation by the back pump or
suppress back diffusion from a discharge port of the back pump and
compressors 7c, 8c, and 9c each having the vacuum pump
function.
[0062] In the embodiment 1 of this invention, the back pumps 4b,
5b, 6b, 7b, 8b, and 9b in FIG. 1 have screw pumps,
respectively.
[0063] Referring to FIG. 2, (a) and (b), a male rotor 25 and a
female rotor 26 of the screw pump are received in a main casing 42
and rotatably supported by bearings 35 and 36 attached to an end
plate 43 sealing the main casing 42 on its one end side and
bearings 37 and 38 attached to an auxiliary casing 46,
respectively.
[0064] Timing gears 31 and 32 accommodated in the auxiliary casing
46 are mounted on rotation shafts 27 and 28 of the male and female
rotors 25 and 26, respectively, and a gap between the male rotor 25
and the female rotor 26 is adjusted so that both rotors do not
contact each other. Further, a motor M is attached to the rotation
shaft of the male rotor 25 through a coupling or speed change gear.
It is configured that the rotation of the motor M is transmitted to
the male rotor 25 and rotates the female rotor 26 through the
timing gears 31 and 32.
[0065] An auxiliary casing 55 provided with an inlet port 56 is
attached to the main casing 42 on its one end side. Further, the
end plate 43 of the main casing 42 is formed with a discharge port
57 for discharging a gas compressed by the male rotor 25 and the
female rotor 26.
[0066] Since the main casing 42, the compressed gas, and so on rise
in temperature due to the compression of the gas, a cooling jacket
33 is formed on the outside of the main casing 42. A coolant such
as water is circulated in the cooling jacket 33 to thereby cool the
main casing 42, the compressed gas, and so on.
[0067] In the screw pump thus configured, when the male rotor 25 is
driven by the motor M, the female rotor 26 is rotationally driven
through the timing gears 31 and 32. Then, following the rotation of
the male rotor 25 and the female rotor 26, a gas from the
corresponding one of the upper-stage booster pumps 4a, 5a, 6a, 7a,
8a, and 9a (FIG. 1) is sucked through the inlet port 56 into a
working chamber formed by the male rotor 25, the female rotor 26,
and the main casing 42. The sucked gas is discharged through the
discharge port 57 while being compressed following the rotation of
the male rotor 25 and the female rotor 26.
[0068] Herein, this vacuum apparatus is provided with the gas
recovery apparatuses B incorporated with the compressors 4c, 5c,
and 6c and the compressors 7c, 8c, and 9c having the vacuum pump
function and connected to the discharge ports 57 of the screw pumps
4b, 5b, 6b, 7b, 8b, and 9b for suppressing the back diffusion
through the discharge ports 57 from the exterior near the
atmospheric pressure to thereby reduce the power consumption.
[0069] As a result of this, the back diffusion through the back
pumps 4b, 5b, 6b, 7b, 8b, and 9b is largely reduced, thereby
enabling a large reduction in power consumption. The ultimate
pressure of the compressor (4c, 5c, 6c, 7c, 8c, or 9c) having the
vacuum pump function can be reduced to approximately 300 Torr.
[0070] FIG. 3 shows the results of examining the relationship
between the pressure at the inlet port 56 of the screw pump and the
power consumption of the screw pump when the screw pumps were used
as the back pumps 4b, 5b, 6b, 7b, 8b, and 9b in the vacuum
apparatus shown in FIG. 1. In this examination, the measurement was
carried out in the case where the exhaust was performed with the
compressors 4c, 5c, 6c, 7c, 8c, and 9c, having the vacuum pump
function, connected to the discharge ports of the back pumps 4b,
5b, 6b, 7b, 8b, and 9b and in the case where no compressor having
the vacuum pump function was connected to any of the back pumps 4b,
5b, 6b, 7b, 8b, and 9b.
[0071] As clear from FIG. 3, with respect to the screw pump having
the compressor with the vacuum pump function, the power consumption
is low overall regardless of the inlet pressure as compared with
the screw pump having no compressor with the vacuum pump function.
Particularly, when the inlet pressure is 10 Torr or less, the screw
pump having the compressor with the vacuum pump function is reduced
in power consumption by approximately 50% as compared with the
screw pump having no compressor with the vacuum pump function.
[0072] In other words, in the case where the screw pumps are
applied as the back pumps 4b, 5b, and 6b of the vacuum apparatus
shown in FIG. 1, a higher effect is achieved when no gas is
introduced into any of the reaction chambers 10, 11, and 12 (FIG.
1).
[0073] The number of stages of the vacuum pumps in the vacuum
apparatus according to this invention is not limited to the
multistage structure but may be two stages or one stage. That is, a
vacuum pump (last-stage vacuum pump) to be connected with a
compressor is not limited to a back pump in a multistage structure
but may be a second-stage vacuum pump in a two-stage structure or a
first-stage vacuum pump in a single-stage structure as long as the
back pressure thereof is within a pressure range over which the
effect of the compressor appears. Further, this vacuum pump may be
one of various types of vacuum pumps such as the Roots type.
[0074] Description will next be given in detail of the fact that
the last-stage back pump 4b can be omitted when the supply amount
of the gas introduced into the reaction chamber 10 in FIG. 1 is
smaller than a predetermined amount.
[0075] The predetermined amount of the gas supply in this case is
determined based on various conditions, particularly the process
pressure, the performance (back pressure, pumping speed, etc.) of
the booster pump 4a, and the performance (pressure, pumping speed,
etc.) of the compressor 4c. For example, assuming that the process
pressure is 5 Torr, the booster pump 4a has the performance with
the back pressure being 200 Torr and the pumping speed being 2000
L/min, and the compressor 4c has the performance with the pressure
being 200 Torr and the pumping speed being 50 L/min, since the
performance of the booster pump 4a is not exhibited unless the back
pressure of the booster pump 4a is set to 200 Torr or less, it is
necessary that the pressure at a discharge port of the booster pump
4a be evacuated to 200 Torr or less by the compressor 4c. Since, in
this event, an equation of "introducing gas amount.times.760 Torr
(atmospheric pressure)/pumping speed 50 L/min of the compressor
4c=200 Torr (back pressure of the booster pump 4a)" is established,
the maximum introducing gas amount is derived to be 13 L/min
through calculation of this equation. When the reaction chamber 10
with this introducing gas amount of 13 L/min is evacuated by the
booster pump 4a (back pressure 200 Torr, pumping speed 2000 L/min),
the chamber pressure becomes "introducing gas amount 13
L/min.times.760 Torr (atmospheric pressure)/pumping speed 2000
L/min of the booster pump 4a=5 Torr" and, hence, the introducing
gas amount of 13 L/min can be flown if the process pressure is 5
Torr or less. That is, under the foregoing conditions, when the
supply amount of the gas introduced into the reaction chamber 10 is
13 L/min or less, the last-stage back pump 4b can be omitted and
further the high vacuum pump 1 can also be omitted, wherein the
reaction chamber 10 can be evacuated by the booster pump (second
vacuum pump) 4a and the compressor 4c.
INDUSTRIAL APPLICABILITY
[0076] In the foregoing embodiment, the description has been made
of the semiconductor device manufacturing vacuum apparatus.
However, the use of the vacuum apparatus of this invention is not
limited to a semiconductor device manufacturing apparatus but it
can be used in every industrial field that requires
depressurization.
* * * * *