Gas separation – With separating media bypass or system gas pressure relief
Reexamination Certificate
2000-02-14
2002-04-09
Hopkins, Robert A. (Department: 1724)
Gas separation
With separating media bypass or system gas pressure relief
C055S440000
Reexamination Certificate
active
06368371
ABSTRACT:
TECHNICAL FIELD
A conventional evacuating system will be described below with reference to FIG.
11
. In
FIG. 11
, a vacuum chamber
10
comprises a process chamber for use in a semiconductor fabrication process such as an etching apparatus or a chemical vapor deposition (CVD) apparatus, and is connected to a vacuum pump
12
through a discharge pipe
14
. The vacuum pump
12
serves to increase the pressure of gases discharged from the process to the atmospheric pressure. The vacuum pump
12
has heretofore been composed of an oil rotary pump, but mainly comprises a dry pump at present. If the level of vacuum required by the vacuum chamber
10
is higher than the level of vacuum that can be produced by the vacuum pump
12
, an ultra-high vacuum pump such as a turbo-molecular pump may be disposed upstream of the dry pump.
The gases discharged from the process cannot directly be discharged into the atmosphere because they may be toxic or explosive depending on the type of the process. Therefore, a discharge processing apparatus
20
is disposed downstream of the vacuum pump
12
. Of the gases discharged from the process, whose pressure has been increased to the atmospheric pressure, those gases that cannot directly be discharged into the atmosphere are treated by a process such as adsorption, decomposition, absorption by the discharge processing apparatus
20
, from which only harmless gases are discharged into the atmosphere. Necessary valves are provided at appropriate locations of the pipe
14
.
The conventional evacuating system is disadvantageous in that if a substance having a high sublimation temperature is contained in the reaction by-products, then since the gas of the substance is discharged by the vacuum pump, the gas is solidified while its pressure is being increased, and deposited in the vacuum pump, thus tending to cause a failure of the vacuum pump.
For example, if BCl
3
or Cl
2
which is a typical process gas for aluminum etching is used, then 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 in 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, and it is deposited, solidified, and attached to the inner pump wall, resulting in a failure of the vacuum pump. The same problem occurs with reaction by-products of (NH
4
)
2
SiF
6
and NH
4
Cl that are produced from a CVD apparatus for depositing films of SiN.
It has heretofore been attempted to heat the vacuum pump in its entirety to pass the reaction by-products in a 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, but has been problematic in that a solid substance is deposited in the discharge processing apparatus disposed downstream of the vacuum pump, thereby clogging a filled layer in the discharge processing apparatus.
One solution is to install a trap apparatus upstream or downstream of the pump for trapping products for removal of components which will generate solid substances for thereby protecting various devices provided at the discharge pipe. It is conceivable that as shown in
FIGS. 12 and 13
, such trap apparatus
100
has a hermetically sealed container
102
disposed in a discharge pipe and forming part thereof, with plate-like baffles
104
(a trap unit) housed therein. When a certain amount of deposited material is attached to the baffles
104
, the discharge passage is switched to another discharge passage, and the trap unit is cleaned or replaced for continuous processing.
However, the conventional trap apparatuses are poor in trapping efficiency, and most components of discharged gases flow without being attached to the trap unit and are attached to downstream pipes and devices. This is because the baffles
104
comprise parallel plates and the trap unit is not brought into sufficient contact with the discharged gases.
If the baffle plates are of a complex shape, then they trap components of discharged gases partly, the conductance is extremely lowered, the baffle plates cause clogs which make the flow of discharged gases unstable, the trap unit cannot smoothly be replaced or switched over, and the trap apparatus is structurally so complex that its manufacturing and maintenance costs will be increased.
DISCLOSURE OF INVENTION
The present invention has been made in view of the above drawbacks. It is an object of the present invention to provide a trap apparatus which is capable of increasing the trapping efficiency while fulfilling a conductance allowed by a vacuum chamber in a film depositing process or the like, for thereby increasing the service life of a vacuum pump and protecting a toxic substance removing device for increased operation reliability, and reducing equipment and running costs.
Since a trapped solid substance is accumulated in a trap unit of a trap apparatus, it is necessary to replace the trap unit or remove the solid substance according to a predetermined process for regenerating the trap unit after elapse of a certain time. The replacement of the trap unit needs to prepare many trap units, and cannot easily be automatized.
One solution would be to provide a regenerating passage disposed adjacent to the discharge pipe
14
for the passage of a warm water heated to a predetermined temperature, for example, and to shift the trap unit between the discharge passage and the regenerating passage for alternately performing a trapping action and a regenerating action for automatic operation.
However, such a trap apparatus would be required to have a heating means such as a heater and ancillary equipment for generating the warm water for cleaning the trap unit, resulting in an increase in the equipment cost such as due to the occupation of a floor of a clean room. Furthermore, if the warm water were continuously circulated, the warm water (cleaning liquid) would be contaminated and the cleaning efficiency would be lowered. Therefore, a new water would be needed to be heated and used, and hence the consumption of electric energy would be increased, and the running cost for maintenance or the like would also be increased.
Therefore, a second object of the present invention is to provide a trap system capable of regenerating a trap unit while suppressing an equipment cost and a running cost.
According to the invention defined in claim 1, there is provided a trap apparatus disposed in a discharge passage for discharging therethrough a gas from a vacuum chamber with a vacuum pump and having a trap unit for trapping and removing a product in a discharged gas, characterized in that: the trap unit has trap passages comprising an upstream passage portion spreading outwardly from the center and a downstream passage portion directed inwardly toward the center.
In as much as the gas flows outwardly in the upstream passage portion, and then changes its direction and flows inwardly in the downstream passage portion, the gas has a greater chance of contacting the walls of the trap passages, and the trapping efficiency is increased. Because the passages are not excessively complex, the manufacturing cost and the maintenance cost are not increased, and the influence on the discharge system is small as the conductance is not excessively reduced.
According to the invention defined in claim 2, the trap passages are formed by curved surfaces. Since the passages change their direction sequentially, their trapping efficiency is higher than with straight passages.
The trap passages may be arranged in a multi-layered configuration. Guide surfaces for guiding the flow of the gas may be disposed at an inlet of the trap passages.
According to the invention defined in claim 3, a downstream portion of any one of the trap passages is partly divided into at least two passages. Therefore, the gas is kept stagnant for an increased time in the downs
Noji Nobuharu
Nomura Norihiko
Armstrong Westerman & Hattori, LLP
Ebara Corporation
Hopkins Robert A.
LandOfFree
Trap device and trap system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Trap device and trap system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Trap device and trap system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2879555