Refrigeration – Low pressure cold trap process and apparatus
Reexamination Certificate
2000-02-15
2001-05-22
Capossela, Ronald (Department: 3744)
Refrigeration
Low pressure cold trap process and apparatus
C417S901000
Reexamination Certificate
active
06233948
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a cryopump control apparatus for controlling a plurality of cryopumps.
Conventionally, cryopumps have been used for evacuation of the interior of a vacuum chamber in semiconductor manufacturing systems or the like. A cryopump of this type is made up by, in a two-stage expansion type refrigerator equipped with expansion cylinders of two stages, attaching a first cryo-panel to a first expansion cylinder of the first stage, further attaching a second cryo-panel to a second expansion cylinder of the second stage, closely fitting activated carbon to the inside of the second cryo-panel, and by covering the first and second cryo-panels as a whole with a casing.
With regard to the cryopump having such a makeup, an opening at a front end of the casing is fitted to a discharge port of a vacuum chamber via a gate valve. Then, water vapor within the vacuum chamber is frozen and collected, and discharged, by the first cryo-panel cooled to 50 K-80 K, and nitrogen gas, oxygen gas, argon gas and the like within the vacuum chamber are condensed and discharged by the second cryo-panel cooled to 10 K-20 K, and moreover hydrogen gas within the vacuum chamber is adsorbed and discharged by the activated carbon.
When the first and second cryo-panels are filled with the above accumulated substances such as hydrogen, oxygen and nitrogen, the first and second cryo-panels are increased in temperature and a nitrogen purge valve is opened so that nitrogen is introduced into the casing, by which a regeneration process of discharging the collected and adsorbed substances is carried out. Further, a cooldown process of cooling the first and second cryo-panels to a low temperature of 20 K is carried out.
In this connection, the discharging process, the regeneration process and the cooldown process in the cryopump are fulfilled by controlling, with an exclusive programmable processor (hereinafter, referred to simply as processor), the supply or discharge of high-pressure helium gas with respect to the two-stage expansion type refrigerator from or to a helium compressor, the turn-on and -off of heaters attached to the first and second cryo-panels, the monitoring of detection signals derived from a thermometer, a pressure gauge and a vacuum gauge, and the opening and closing of various valves.
In semiconductor manufacturing factories, when different processes such as sputtering and etching processes are carried out sequentially on semiconductor wafers, for example, a cluster tool in which process chambers for the respective processes are combined together is used. Further, the plurality of chambers are evacuated by independent cryopumps, respectively, thus making it necessary to control the evacuation process, the regeneration process and the cooldown process in the individual cryopumps according to their respective wafer processes and in correlation with one another.
Therefore, in conventional control apparatuses for cryopumps, a plurality of cryopumps are controlled in the following manner. For example, in the case of an electronically controlled cryopump disclosed in Japanese Patent Publication No. 2873031, exclusive processors
2
a
-
2
c
are provided for a plurality of cryopumps
1
a
-
1
c
, respectively, as shown in FIG.
10
. Then, a processor
2
a
for one cryopump
1
a
is connected with an exclusive line
4
to a host computer
3
that controls the whole system. Further, a processor
2
b
for the cryopump
1
b
is connected to the processor
2
a
with an exclusive line
5
, while a processor
2
c
for the cryopump
1
c
is connected to the processor
2
b
with an exclusive line
6
.
In this arrangement, control instructions from the host computer
3
to all the cryopumps
1
a
-
1
c
are transmitted to the processors
2
a
-
2
c
of the cryopumps
1
a
-
1
c
, respectively. Whereas an instruction, for example, to the processor
2
c
for the cryopump
1
c
is transmitted via the processors
2
a
,
2
b
, this is intended to facilitate the expanded provision of cryopumps, which is essentially nothing more than that an instruction is transmitted from the host computer
3
directly to the processor
2
c.
However, the above conventional electronically controlled cryopump has the following problems. That is, in the case of simultaneously controlling, for example, three cryopumps
1
a
-
1
c
, exclusive processors
2
having the same functions need to be provided for the cryopumps
1
a
-
1
c
, respectively. This is wasteful and lead to an increase in cost, as a problem.
Also, in the case where controlling objects per cryopump
1
are one power switch, two motor-operated valves, one valve motor, two heaters, one pressure gauge and one vacuum gauge, the host computer
3
and one cryopump
1
are connected to each other with eight control lines. Therefore, for simultaneous control of three cryopumps
1
a
-
1
c
,
24
(=8×3) control lines are wired from the host computer
3
, causing a complexity as another problem.
Accordingly, an object of the present invention is to provide a cryopump control apparatus which eliminates the need of providing exclusive processors for individual cryopumps in controlling a plurality of cryopumps, allowing cost reduction and wiring simplification to be achieved.
In order to achieve the object, there is provided a cryopump control apparatus for controlling a plurality of cryopumps, comprising:
a communication conversion section and an I/O conversion section both of which are provided in each of the plurality of cryopumps;
a processor for controlling the plurality of cryopumps; and
a communication network for connecting the processor and the communication conversion sections of the cryopumps to each other, wherein
the processor controls the individual cryopumps by performing data exchange with the communication conversion sections of the respective cryopumps via the communication network.
With this constitution, the processor performs data exchange with the communication conversion sections provided in the plurality of cryopumps, respectively, via the communication network, by which the plurality of cryopumps are controlled. In this way, a plurality of cryopumps are controlled by one processor without mounting exclusive processors on the cryopumps, respectively.
In one embodiment of the present invention, the communication network is formed into a hierarchical structure.
With this embodiment, a communication network can be easily built in the case where a plurality of groups of cryopumps are controlled by one processor or where some cryopumps are additionally provided as an expansion.
In one embodiment of the present invention, the apparatus comprises a compressor unit in which a communication conversion section and an I/O conversion section are provided, and which supplies a compressed refrigerant to the individual cryopumps, wherein
the communication conversion section of the compressor unit is connected to the communication network.
With this embodiment, the compressor unit for supplying high-pressure refrigerant gas to the plurality of cryopumps is also controlled via the communication network. This makes it possible to eliminate the exclusive line for connecting the processor and the compressor unit with each other.
In one embodiment of the present invention, the communication network is connected to a host computer.
With this embodiment, the control over the processor by the host computer that controls the whole system is also implemented via the communication network, making it possible to eliminate the exclusive line for connecting the host computer and the processor to each other. Also, the cryopumps, the compressor unit and the processor can be connected to the communication network in this order according to the closeness to the host computer, by which the wiring to the cryopumps, the compressor unit and the processor can be further simplified. Moreover, the evacuation system with the cryopumps can be incorporated into the network of the system controlled by the host computer.
In one embodiment of the pre
Morishita Hiroyuki
Uosaki Satoru
Birch & Stewart Kolasch & Birch, LLP
Capossela Ronald
Daikin Industries Ltd.
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