Electric resistance heating devices – Heating devices – Continuous flow type fluid heater
Reexamination Certificate
1998-12-17
2001-06-26
Walberg, Teresa (Department: 3742)
Electric resistance heating devices
Heating devices
Continuous flow type fluid heater
C417S292000, C415S090000
Reexamination Certificate
active
06253029
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vacuum processing apparatus with a vacuum pump, in which products of reaction in exhaust gas can be prevented from adhering to the inside of the vacuum pump so that the maintenance operation is easier, although the conductance of an exhaust pipe system is lowered so that a trap unit and the vacuum pump can be reduced in size.
2. Information of the Related Art
In manufacturing processes for semiconductor devices, a semiconductor wafer (hereinafter referred to as “wafer”) is subjected to various processes, such as CVD, etching, ashing, etc., using process gases in a vacuum. In these vacuum processes, exhaust gas that contains products of reaction and unaffected process gases, based on reactions of the process gases, is discharged through an exhaust pipe system in a process chamber. If unwanted by-products, such as the reaction products, unaffected gases, etc., adhere to the inside of the exhaust pipe system, however, exhaust pipes, valves, and vacuum pump must be cleaned. The cleaning of the exhaust pipe system involves troublesome operations, including removal of the exhaust pipes, valves, and vacuum pump and cleaning of the pump. If the reaction products are corrosive, moreover, the exhaust pipes or the like may possibly be corroded, so that adhesion of the reaction products to the exhaust pipe system must be minimized.
Conventionally, a vacuum processing apparatus is constructed in the manner shown in
FIG. 4
, in order to prevent the reaction products and other unwanted by-products from adhering to the exhaust system. In
FIG. 4
, numeral
1
denotes an airtight process chamber, which contains a wafer stage
11
, having a heater therein, and a process gas inlet portion
12
. The process chamber
1
is connected with an exhaust pipe
15
, which is provided with a drag pump
13
and a dry pump
14
. Thus, the exhaust pipe system is arranged so that after the process chamber
1
is first evacuated through a branch line
16
to a predetermined degree of vacuum by means of the dry pump
14
, it can be further evacuated to a higher degree of vacuum by means of the drag pump
13
.
A trap
17
is provided on the upstream side of the drag pump
13
, and heating means, e.g., a tape heater, is wound around that portion of the exhaust pipe system between the exhaust port of the process chamber
1
and the trap
17
. According to this arrangement, the exhaust pipe
15
can be heated to prevent the adhesion of the reaction products, and the reaction products can be cooled to a temperature lower than their sublimating points and compulsorily separated in the trap
17
. Thus, the reaction products can be prevented from adhering to the exhaust pipe system on the downstream side. In
FIG. 4
, symbols Va, Vb and Vc designate valves.
Since the trap
17
is located on the upstream side of the drag pump
13
, however, the apparatus with the above-described construction involves the following problems.
Since the trap
17
is subject to a substantial exhaust loss, the conductance of the exhaust pipe
15
must be increased, and the diameter of the pipe
15
is adjusted to about 4 to 8 inches, for example. Accordingly, the trap
17
and the drag pump
13
are expected to be large-sized. If the trap
17
, which should be cleaned periodically, is located on the upstream side of the drag pump
13
, water remaining in the cleaned trap
17
may possibly flow into the process chamber
1
, thereby corroding the elements in the chamber
1
or exerting a bad influence on the process of a wafer W.
Accordingly, the inventors hereof intend to solve the above problems by locating the trap
17
on the exhaust side (downstream side) of the drag pump
13
. To attain this, an arrangement is proposed such that a tape heater, for example, is wound around the drag pump
13
, as well as the exhaust pipe, and products of reaction are passed in a gaseous phase through the pump
13
.
In the drag pump
13
, a rotor unit is located in a casing, which is provided with a water cooling jacket, and a distributor is located on the casing side so as to surround the rotor unit. The process chamber
1
is evacuated as the rotor unit is rotated. Even though the tape heater is wound around the casing, therefore, heat is absorbed by the water cooling jacket and the distributor, so that it cannot be easily transferred to the rotor unit. Thus, it is difficult to heat the rotor unit to a temperature of, for example, about 120!n, which is higher than the separation temperature of the reaction products.
It is hard for a conventional tape heater to heat the casing to a temperature such that the rotor unit temperature is increased to the aforesaid level. Accordingly, a special resistance heating element must be used to attain this, entailing substantially increased power consumption. If the casing is heated to too high a temperature, moreover, a sealing member of the drag pump will inevitably be degraded. In consequence, the casing temperature should not be increased excessively.
Even though the interior of the exhaust pipe and the inner wall of the casing are heated to a temperature high enough to prevent the adhesion of the products of reaction, therefore, the rotor unit cannot be heated to this temperature level, so that the reaction products adhere to the rotor unit, thus requiring frequent maintenance operation for the drag pump.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a vacuum processing apparatus with a vacuum pump, in which products of reaction and the like can be prevented from adhering to the inside of the vacuum pump so that the maintenance operation is easier, although the conductance of an exhaust pipe system is lowered so that a trap unit and the vacuum pump can be reduced in size.
In order to achieve the above object, a first vacuum processing apparatus according to the present invention, which is adapted to subject an object of process to a predetermined process in a substantially vacuum state, comprises: an airtight process chamber for subjecting the object to a vacuum process in a vacuum formed as a process gas is introduced into the chamber; a vacuum pump connected to the process chamber by means of an exhaust pipe and used to rotate a rotor unit in a casing, thereby evacuating exhaust gas from the process chamber; and first heating means in the vacuum pump for heating the rotor unit and the rotor-side surface of the casing to a temperature higher than the temperature at which unwanted by-products in the exhaust gas discharged from the process chamber are separated.
A second vacuum processing apparatus according to the invention, which is adapted to subject an object of process to a predetermined process in a substantially vacuum state, comprises: an airtight process chamber for subjecting the object to a vacuum process in a vacuum formed as a process gas is introduced into the chamber; a vacuum pump connected to the process chamber by means of an exhaust pipe and used to rotate a rotor unit in a casing, thereby evacuating exhaust gas from the process chamber; first heating means in the vacuum pump for heating the rotor unit and the rotor-side surface of the casing to a temperature higher than the temperature at which unwanted by-products in the exhaust gas discharged from the process chamber are separated; a trap unit on the exhaust side of the vacuum pump for capturing the unwanted by-products in the exhaust gas from the process chamber; and second heating means for heating the inner surface of the exhaust pipe, which extends from the process chamber to the vacuum pump and from the vacuum pump to the trap unit, to a temperature higher than the temperature at which the unwanted by-products in the exhaust gas are separated.
Thus, the inside of the vacuum pump is heated by means of the first heating means to a temperature higher than the temperature at which products of reaction discharged from the process chamber are separated, and the inner surface of the exhaust pipe is heated to a temperature h
Hayashi Kazuichi
Iwata Teruo
Campbell Thor
Smith , Gambrell & Russell, LLP
Tokyo Electron Limited
Walberg Teresa
LandOfFree
Vacuum processing apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Vacuum processing apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vacuum processing apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2492661