Gas separation – Combined or convertible
Reexamination Certificate
2000-08-01
2003-04-29
Simmons, David A. (Department: 1724)
Gas separation
Combined or convertible
C055S385200, C055S445000, C055S446000, C055S457000, C055S502000, C096S416000, C096S420000
Reexamination Certificate
active
06554879
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a trap apparatus for use in an evacuating system for evacuating a vacuum chamber for a semiconductor fabrication apparatus or the like.
2. Description of the Related Art
A conventional evacuating system will be described below with reference to FIG.
16
. In
FIG. 16
, a hermetically sealed chamber
201
comprises a process chamber for use in a semiconductor fabrication process such as an etching apparatus or a chemical vapor deposition (CVD) apparatus. The hermetically sealed chamber
201
is connected to a vacuum pump
203
through a discharge path
202
. The vacuum pump
203
serves to increase the pressure of gases discharged from the process in the hermetically sealed chamber
201
to the atmospheric pressure. An oil-sealed rotary vacuum pump has heretofore been used as the vacuum pump
203
. A dry pump is mainly used as the vacuum pump
203
at present.
If the degree of vacuum required by the hermetically sealed chamber
201
is higher than the ultimate vacuum of the vacuum pump
203
, then an ultra-high vacuum pump such as a turbo-molecular pump is additionally disposed upstream of the vacuum pump
203
. A discharged gas processing apparatus
204
is disposed downstream of the vacuum pump
203
. In the discharged gas processing apparatus
204
, gas components that cannot directly be discharged into the atmosphere because of their toxicity or explosive properties depending on the type of the process are treated by a process such as adsorption, decomposition, or absorption. Only harmless gases are discharged from the discharged gas processing apparatus
204
into the atmosphere. Necessary valves are provided at appropriate locations of the discharge path
202
.
The conventional evacuating system has the following disadvantages.
In the conventional evacuating system, if reaction by-products contain a substance having a high sublimation temperature, then the gas of the substance is solidified while its pressure is being increased, and deposited in the vacuum pump. This tends to cause a failure of the vacuum pump.
For example, when BCl
3
or Cl
2
which is a typical process gas for aluminum etching is used, the process chamber discharges the remainder of the process gas of BCl
3
or Cl
2
and a reaction by-product of AlCl
3
via the vacuum pump. AlCl
3
is not deposited at the suction side of the vacuum pump because its partial pressure is low. However, while AlCl
3
is being discharged under pressure, its partial pressure rises to cause AlCl
3
to be deposited and attached to the inner wall of the vacuum pump, resulting in a failure of the vacuum pump. The same problem occurs with reaction by-products such as (NH
4
)
2
SiF
6
and NH
4
Cl that are produced in a CVD apparatus for depositing films of SiN.
It has heretofore been attempted to heat the vacuum pump to pass the reaction by-products in gaseous state through the vacuum pump so that no solid substance is deposited in the vacuum pump. The attempt has been effective to prevent a solid substance from being deposited in the vacuum pump. However, it has been problematic in that a solid substance is deposited in the discharged gas processing apparatus disposed downstream of the vacuum pump, thereby clogging a filled layer in the discharged gas processing apparatus.
One solution is to install a trap apparatus upstream or downstream of the pump. The trap apparatus attaches products to a trap unit disposed in the trap apparatus, and hence previously removes portions (components) which will generate solid substances, for thereby protecting various devices provided at the discharge path. In general, however, the conventional trap apparatus has a poor trapping efficiency, and about 60% of the components of discharged gases flow through the trap apparatus without being attached to the trap unit and are attached to downstream pipes and devices. This is mainly because the discharged gases flow through a portion having a poor trapping efficiency between the inner wall of a container and the trap unit in the trap apparatus, and pass through the trap apparatus without being trapped.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above drawbacks. It is therefore an object of the present invention to provide a trap apparatus which, in a film deposition process or the like, can increase the trapping efficiency while the necessary conductance on the hermetically sealed chamber side is being maintained, and increase the service life of the vacuum pump, protect a toxic substance removing device, and, in addition, can reduce the equipment cost and the running cost.
According to a first aspect of the present invention, there is provided a trap apparatus comprising: a discharge path for evacuating a hermetically sealed chamber through a vacuum pump; a hermetically sealed trap container extended across the discharge path and a regeneration path disposed adjacent to the discharge path; a trap unit disposed in the trap container for attaching a product in a discharged gas thereon and removing the product from the discharged gas, the trap unit being selectively located at the discharge path or the regeneration path; a valve element disposed on both sides of the trap unit and being movable integrally with the trap unit; and a sealing material mounted on an outer circumferential surface of the valve element so as to slide over an inner circumferential surface of the trap container when the trap unit is moved.
With the above arrangement, since the outer diameter of the trap unit can be designed to a near value to the inner diameter of the trap container, the contact efficiency of the discharged gas introduced into the trap container with the trap unit can be increased. Therefore, the trapping efficiency of products in the discharged gas can be increased while the conductance of the discharged gas and a predetermined exhaust capacity are being maintained without affecting the performance of the process in the hermetically sealed chamber or the vacuum pump. Further, since the trap unit is selectively located at the discharge path or the regeneration path, the regeneration of the trap to be carried out in an in-line manner, and hence the trap regeneration work can be simplified.
The hermetically sealed chamber may comprise a process chamber for a semiconductor fabrication device or the like. If necessary, a discharged gas processing apparatus for removing a toxic substance from a process gas is provided. The vacuum pump preferably comprises a dry pump which uses no lubricating oil in the discharge path in order to prevent contamination of the chamber caused by the back-diffusion of oil.
According to a second aspect of the present invention, there is provided a trap apparatus, wherein at least two trap units are disposed in the trap container to perform a trapping operation in the discharge path and a regenerating operation in the regeneration path simultaneously.
With the above arrangement, since it is not necessary to stop the device for the regeneration of the trap unit and to prepare a trap unit for replacement even in the case of operation for a long period of time, a continuous stable operation can be achieved in the hermetically sealed chamber. Further, it is easy to fully automate the system by using a suitable means for controlling timing of the switching.
When the trap unit is used as a temperature trap unit, a heat medium may be externally introduced into the trap unit. Heat of gasification of liquefied gas (for example, liquid nitrogen), cooling water, or a coolant is used as the heat medium. In another method, a thermoelectric element (a Peltier element), a pulse tube refrigerator, or the like is used to generate low temperature at the trap unit without the flow of any heat medium per se.
In the regeneration section as in the case of the trap unit, a heat medium may be used, or alternatively a heater, a thermoelectric element, spontaneous temperature rising or the like may be used. In the regeneration operation, a heat medium f
Armstrong Westerman & Hattori, LLP
Ebara Corporation
Pham Minh-Chau T.
Simmons David A.
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