U.S. patent application number 09/252236 was filed with the patent office on 2001-05-31 for vacuum exhaust system.
Invention is credited to KAWAMURA, TAKESHI, NIIMURA, YASUHIRO.
Application Number | 20010001950 09/252236 |
Document ID | / |
Family ID | 12930186 |
Filed Date | 2001-05-31 |
United States Patent
Application |
20010001950 |
Kind Code |
A1 |
KAWAMURA, TAKESHI ; et
al. |
May 31, 2001 |
VACUUM EXHAUST SYSTEM
Abstract
A vacuum exhaust system can improve the operating efficiency of
the vacuum exhaust system while reducing the system cost, to
quickly attain a vacuum in the auxiliary chambers without
increasing the size of the vacuum pumps. The vacuum exhaust system
comprises a first pumping section and a second pumping section
disposed downstream of and in series with the first pumping
section. A main exhaust passage is provided to communicate a main
chamber with a suction port of the first pumping section, and an
auxiliary exhaust passage is provided to communicate an auxiliary
chamber with a suction port of the second pumping section.
Inventors: |
KAWAMURA, TAKESHI;
(KAWASAKI-SHI, JP) ; NIIMURA, YASUHIRO;
(AYASE-SHI, JP) |
Correspondence
Address: |
ARMSTRONG,WESTERMAN, HATTORI,
MCLELAND & NAUGHTON, LLP
1725 K STREET, NW, SUITE 1000
WASHINGTON
DC
20006
US
|
Family ID: |
12930186 |
Appl. No.: |
09/252236 |
Filed: |
February 18, 1999 |
Current U.S.
Class: |
118/715 |
Current CPC
Class: |
C23C 16/54 20130101;
C23C 16/4412 20130101 |
Class at
Publication: |
118/715 |
International
Class: |
C23C 016/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 18, 1998 |
JP |
52984/1998 |
Claims
What is claimed is:
1. A vacuum exhaust system for evacuating a main chamber and at
least one associated auxiliary chamber comprising: a first pumping
section; a second pumping section disposed downstream of and in
series with said first pumping section; a main exhaust passage
communicating said main chamber with a suction port of said first
pumping section; and at least one auxiliary exhaust passage
communicating said auxiliary chamber with a suction port of said
second pumping section.
2. A vacuum exhaust system according to claim 1, wherein said at
least one auxiliary exhaust passage comprises a shut-off valve.
3. A vacuum exhaust system according to claim 1, wherein said first
pumping section and said second pumping section share a common
drive motor to constitute a multi-stage vacuum pump.
4. A vacuum exhaust system according to claim 1, wherein said first
pumping section and said second pumping section are individually
provided with respective drive sections.
5. A vacuum exhaust system according to claim 1, further comprising
a control section for controlling rotation speed of said first or
second pumping sections so as to obtain a minimum fluctuation in
pressure, according to a pressure measured inside said main
chamber.
6. A vacuum exhaust system according to claim 1, wherein said a
plurality of said auxiliary chambers are provided to said main
chamber.
7. A vacuum exhaust system according to claim 1, wherein said
auxiliary chamber is a load lock chamber.
8. A vacuum exhaust system for evacuating a main chamber and a
plurality of associated auxiliary chambers, said plurality of
auxiliary chambers having a connecting passage connecting each
other which can be opened or closed to equalize pressure in said
auxiliary chambers.
9. A vacuum exhaust system according to claim 8, wherein said
auxiliary chambers comprise at least one load lock chamber.
10. A vacuum exhaust system according to claim 8, further
comprising a control section for controlling said connecting
passage to open and close before one of said auxiliary chambers are
evacuated.
11. A method for exhausting a main chamber and at least one
associated auxiliary chamber comprising: disposing a second pumping
section downstream of and in series with a first pumping section;
communicating said main chamber with a suction port of said first
pumping section through a main exhaust passage; communicating said
at least one auxiliary chamber with a suction port of said second
pumping section through an auxiliary exhaust passage; and opening
said auxiliary exhaust passage so as to apply evacuation ability of
said second pumping section to evacuation of said auxiliary
chamber.
12. A method according to claim 11, wherein said first pumping
section and said second pumping section share a common drive motor
to constitute a multi-stage vacuum pump.
13. A method according to claim 11, wherein said first pumping
section and said second pumping section are individually provided
with respective drive sections.
14. A method according to claim 11, further comprising controlling
rotation speed of said first or second pumping sections so as to
obtain a minimum fluctuation in pressure, according to a pressure
measured inside said main chamber.
15. A method according to claim 11, wherein said a plurality of
said auxiliary chambers are provided to said main chamber.
16. A method according to claim 11, wherein said auxiliary chamber
is a load lock chamber.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a vacuum exhaust system for
use in evacuating a processing chamber for advanced products such
as semiconductor devices, for example.
[0003] 2. Description of the Related Art
[0004] A conventional arrangement of a vacuum exhaust system used
in semiconductor device manufacturing processes to evacuate a
processing chamber for carrying out such process as etching and
chemical vapor deposition (CVD) of semiconductor wafers is shown in
FIG. 8. A main chamber (processing chamber) 10 is connected on both
sides to auxiliary chambers (load lock chambers) 12a, 12b, for
loading and unloading purposes through respective gates 14. Each
auxiliary chamber 12a, 12b is isolated from or open to the external
environment by a gate 15.
[0005] The main chamber 10 is connected to a vacuum pump 18 through
an exhaust path 16 having a valve 20, and each auxiliary chamber
12a, 12b is connected similarly to a vacuum pump 24 through an
exhaust path 22 having a valve 26. It has been customary to use
rotary oil pumps for the vacuum pumps 18, 24, but lately, dry pumps
are used primarily for this type of work.
[0006] In this type of apparatus, in order to access the main
chamber 10 while it is under vacuum, loading or unloading of a
workpiece into the main chamber 10 requires that an auxiliary
chamber 12 be evacuated first, and the gate 14 opened next so as to
avoid exposing the main chamber 10 to external atmosphere. This is
done to prevent the main chamber 10 and associated piping from
contamination as well as to improve productivity by shortening the
time for re-starting.
[0007] In such conventional systems, a vacuum pump is provided for
each chamber to evacuate individual chambers, therefore, working
efficiency of each vacuum pumps is low. If the number of main
chambers 10 is increased in an effort to raise productivity, it
leads to a problem that the number of vacuum pumps need to be
increased, leading ultimately to a large size facility and higher
running costs. If an attempt is made to shorten the time for
evacuating the auxiliary chambers, a higher capacity for each pump
is required, thus aggravating the above problems even further.
SUMMARY OF THE INVENTION
[0008] It is an object of the present invention to provide a vacuum
exhaust system to enable as much sharing of vacuum pumps as
possible, to improve the operating efficiency of the vacuum exhaust
system while reducing the system cost, or to quickly attain a
vacuum in the auxiliary chambers without increasing the size of the
vacuum pumps.
[0009] The object has been achieved in a vacuum exhaust system for
evacuating a main chamber and at least one associated auxiliary
chamber comprising: a first pumping section; a second pumping
section disposed downstream of and in series with the first pumping
section; a main exhaust passage communicating the main chamber with
a suction port of the first pumping section; at least one auxiliary
exhaust passage communicating the auxiliary chamber with a suction
port of the second pumping section.
[0010] Accordingly, the main chamber can be evacuated with two
pumping sections arranged in series, and the auxiliary chambers are
evacuated with one of the pumping sections, thereby increasing the
operating efficiency of each pumping section while keeping the
capacity of each pump as small as practicable.
[0011] The first and second pumping sections may share a common
drive motor. Accordingly, one multi-stage vacuum pump can manage
the task of evacuating an entire processing system so that the
number of vacuum pumps can be reduced compared with a case of
providing a vacuum pump for each auxiliary chamber. However, the
first pumping section and the second pumping section may be
provided with individual drive sections.
[0012] The pumping sections may be controlled so as to obtain a
minimum fluctuation in pressure, according to a pressure measured
inside the main chamber. Accordingly, pressure changes can be held
to a minimum in the main chamber which is an important chamber for
processing advanced products such as semiconductor devices.
[0013] Another aspect of the invention is a vacuum exhaust system
for evacuating a main chamber and a plurality of associated
auxiliary chambers, the plurality of auxiliary chambers having a
connecting passage connecting each other which can be opened or
closed to equalize pressure in the auxiliary chambers. Accordingly,
vacuum environment present inside an auxiliary chambers can be
utilized to lower the pressure of another auxiliary chamber which
may be at an atmospheric pressure so that evacuation time can be
significantly reduced to improve the operating efficiency of the
overall evacuation operation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a schematic diagram of a first embodiment of the
vacuum exhaust system of the present invention;
[0015] FIG. 2 is a time-chart showing the control steps for the
first system shown in FIG. 1;
[0016] FIG. 3 is a schematic diagram of a variation of the first
system;
[0017] FIG. 4 is a schematic diagram of another embodiment of the
vacuum exhaust system of the present invention;
[0018] FIG. 5 is a time-chart showing the control steps for the
second system shown in FIG. 4;
[0019] FIG. 6 is a variation of the second system;
[0020] FIG. 7 is a schematic diagram of a third embodiment of the
vacuum exhaust system of the present invention; and
[0021] FIG. 8 is a schematic diagram of a conventional vacuum
exhaust system.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0022] Preferred embodiments will be presented in the following
with reference to the drawings.
[0023] FIGS. 1 and 2 relate to a first embodiment of the vacuum
exhaust system of the present invention, which includes, as in the
conventional systems, a main chamber 10 for carrying out processes
such as etching and CVD of semiconductor wafers. An auxiliary
chamber 12a is attached, through a gate 14a, to the main chamber 10
on the loading-side, and an auxiliary chamber 12b is attached,
through a gate 14b, to the main chamber 10 on the unloading-side.
Each of the auxiliary chambers 12a, 12b is isolated from and
connected to the outside atmosphere through respective gates 15a,
15b.
[0024] To exhaust three chambers 10, 12a, 12b, one two-stage pump
34 is used. The two-stage pump 34 has a first pumping section 30a
on the upstream side, and a second pumping section 30b on the
downstream side. The pumping sections 30a, 30b share a common shaft
connected to a variable-speed motor 32. The two-stage pump 34 is
provided with a suction port 34a, and an exhaust port 34b, and an
intermediate port 34c opening at a location between the pumping
section 30a, 30b. The exhaust passage 16 for the main chamber 10 is
connected through a valve 20 to the suction port 34a, and the
exhaust passages 22a, 22b, respectively, for auxiliary chambers
12a, 12b, are connected though respective valves 26a, 26b to the
intermediate port 34c.
[0025] As shown in FIG. 2, performance of the two-stage pump 34 is
designed so as to enable exhaustion of the main chamber 10 at a
first rotation speed n.sub.1, and to enable exhaustion of the main
chamber 10 and one of the auxiliary chamber 12a, 12b concurrently
at a second rotation speed n.sub.2 which is larger than n.sub.1.
This exhaustion system is provided with a control section 38 to
control the operating parameters such as on/off and rotational
speed for the variable speed motor 32 according to output signal
from a pressure sensor 36 provided inside the main chamber 10.
Speed control can be effected by following a certain pre-selected
pattern in sequence or by feedback control to follow signals output
from the sensor 36.
[0026] Operation of the vacuum exhaust system in first embodiment
will be explained with reference to FIG. 2 showing the
time-sequence of a processing workpiece. First, the gate 15a is
opened to load the workpiece into the auxiliary chamber 12a, and
the gate 15a is closed. Next, valves 26a, 20 are opened and the
pump 34 is operated at the higher second speed n.sub.2, and the
rotation speed is gradually reduced back to the first speed n.sub.1
during a time interval (t.sub.1-t.sub.2) so that the auxiliary
chamber 12a and the main chamber 10 are both evacuated. After the
main chamber 10 reaches a required pressure, workpiece processing
operation can be started.
[0027] While the processing is proceeding in the main chamber 10,
the auxiliary chamber 12b will also be evacuated. The pump 34 is
operated at the higher second speed n.sub.2 and the rotation speed
is gradually reduced back to the first speed n.sub.1 during a time
interval (t.sub.2-t.sub.3). After the auxiliary chamber 12b is
exhausted, the pump 34 is operated at the first speed n.sub.1 to
complete the processing in the main chamber 10 during a time
interval (t.sub.3-t.sub.4).
[0028] Next, the gate 14b is opened to unload the processed
workpiece from the main chamber 10 to the auxiliary chamber 12b at
time t.sub.4. During the processing interval in the main chamber
10, a new workpiece is placed inside the auxiliary chamber 12b by
opening the gate 15a, so that the interior pressure is at an
atmospheric pressure. At this point, the steps from time t.sub.1
are repeated. In the meantime, the gate 15b is opened to remove the
processed workpiece from inside the auxiliary chamber 12b.
[0029] By following the steps described above, the embodied
exhaustion system enables to operate the system with one pump by
suitably switching the evacuation process among the main chamber
and the auxiliary chambers thereby reliably maintaining the
required load locking functions. And since the emphasis is placed
on exhausting the main chamber by using a multi-stage pump,
lowering of gas exhausting capability of the main chamber is
avoided.
[0030] In the above case, although the rotation speed was
controlled sequentially according to a pre-determined pattern, it
is permissible to use a feedback control according to signals
output from a pressure sensor 36. When valves 26a, 20 are opened to
evacuate the auxiliary chamber 12a and the main chamber 10, opening
of the valve 26a causes the pressure in the mid-chamber 35 of the
pump 34 to increase, and the pump capacity is lowered so that the
interior pressure in the main chamber 10 is also increased. To
avoid such critical pressure fluctuation in the main chamber 10,
the interior pressure can be monitored by a pressure sensor 36 so
as to control the rotation-speed of the pump 34 at a speed between
the second speed n.sub.2 and the first speed n.sub.1.
[0031] FIG. 3 shows a variation of the first embodiment, which uses
two individual pumps connected in series. A first stage booster
pump 42 is connected in series with a second stage main pump 46.
Each pump is driven by separate variable speed motors 40, 44, whose
speeds can be controlled separately by a control section 38.
[0032] The exhaust passage 16 of the main chamber 10 is connected
through a valve 20 to a suction port 42a of the booster pump 42,
and the exhaust port of booster pump 42 and the suction port of
main pump 46 are connected through a connecting pipe 50 having an
intermediate port 52. The exhaust passages 22a, 22b of the
auxiliary chambers 12a, 12b are connected through the valves 26a,
26b to the intermediate port 52. Operational characteristics of
this embodiment system are the same as those in the first case, and
their explanations will be omitted.
[0033] In this example also, the rotation speed of the pump can be
feedback controlled using the output signals from a pressure sensor
36. In this example, rotation speed of main pump 46 and booster
pump 42 can be controlled independently to enable more precise
control of the pressure.
[0034] FIG. 4 is a schematic diagram of another embodiment of the
vacuum exhaust system. This system includes: a connecting passage
60 to connect both auxiliary chambers 12a, 12b shown in FIG. 1 to
equalize the vacuum pressure; and a valve 62 for opening or closing
the connecting passage 60. The valve 62 is controlled by a control
section 38 to open in advance when either the auxiliary chamber 12a
or 12b is exhausted.
[0035] The embodied vacuum exhaust system is used, for example,
when exhausting the auxiliary chamber 12a after it has been loaded
with a workpiece so that it is at an atmospheric pressure, in a way
that the valve 62 is opened before the valve 26a is opened to
evacuate with the multi-stage pump 34 (at time t.sub.5). At this
time, the auxiliary chamber 12b has a processed workpiece passed
from the main chamber so that its interior pressure is maintained
at some low pressure. Therefore, by opening the valve 62, air flows
from the auxiliary chamber 12a to auxiliary chamber 12b so that
both chambers attain a common pressure intermediate between an
atmospheric pressure and vacuum.
[0036] After this stage, valve 62 is closed, and as in FIG. 1, pump
34 is operated at a higher second speed n.sub.2 (at time t.sub.6)
to exhaust both auxiliary chamber 12a and main chamber 10. In this
case, because the initial pressure in the auxiliary chamber is less
than an atmospheric pressure, the length of time required to
exhaust the auxiliary chamber is reduced compared with the system
shown in FIG. 1. In the auxiliary chamber 12b, gate 15b is opened
and the processed workpiece is withdrawn. This system thus allows
to utilize the reduced-pressure environment of the auxiliary
chamber 12b, which is normally discarded to waste, to shorten the
evacuation time of the auxiliary chamber 12a. This feature further
contributes to increasing the operating efficiency of the overall
vacuum exhaust system.
[0037] Similarly, when exhausting the auxiliary chamber 12b, valve
62 is first opened temporarily (time t.sub.7) to introduce the
vacuum environment in the auxiliary chamber 12a before an
unprocessed workpiece has been loaded into the auxiliary chamber
12b (time t.sub.7-t.sub.8) so that auxiliary chamber 12b can be
reduced in pressure, and then the multi-stage pump 34 is operated
at a fast speed. Thus, the exhaustion time for the auxiliary
chamber 12b can be shortened.
[0038] FIG. 6 shows a variation of the system shown in FIG. 4. This
system is based on the variation based on the third embodiment
shown in FIG. 3, and includes a connecting path 60 and a valve 62
which is designed to be opened before evacuating either of the
auxiliary chamber 12a or 12b.
[0039] FIG. 7 shows a third embodiment, and includes auxiliary
chambers 12a, 12b having dedicated exhaust passages 22a, 22b,
provided with respective vacuum pump 24a, 24b respectively,
connected with connecting passage 60, and within the connecting
passage 60, a valve 62 which is designed to open prior to
evacuating either auxiliary chamber 12a or 12b. This system also
enables to utilize waste vacuum, as in the systems shown in FIGS. 3
and 6, to shorten the exhaustion time required to evacuate the
auxiliary chambers 12a, 12b.
* * * * *