Pumps – Combined
Reexamination Certificate
2001-07-26
2003-10-07
Walberg, Teresa (Department: 3742)
Pumps
Combined
Reexamination Certificate
active
06629824
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vacuum pump that may avoid precipitate of gas molecular composition by heating a discharge path of gas effectively with a small amount of electrical power and is superior in handling property and safety aspect in low cost.
2. Description of the Related Art
Conventionally, a vacuum pump such as a turbo molecular pump or a screw groove type pump is well known. Such a vacuum pump has been extensively used for analysis and measurement utilizing electronic rays or in the case where a vacuum process such as a dry etching process or a CVD through a semiconductor manufacturing apparatus or a liquid crystal manufacturing process is performed by discharging process gas within the chamber.
In such a vacuum pump, a stator portion and a rotor portion are received in an outer sleeve portion having a hollow portion, and a flow path of gas is formed by means of the stator portion and the rotor portion. Then, the rotor portion is rotated by means of a motor to thereby move the gas of the flow path so as to suck the gas from the outside through an intake port.
Such a vacuum pump is a turbo molecular pump in which a plurality of spacers are arranged coaxially with the rotor portion, stator blades projecting toward the rotor portion are arranged between the spacers and rotor blades projecting between the stator blades are arranged in the rotor portion. In this turbo molecular pump, gas molecular is struck to be transferred by the rotation of the rotor blades.
In another example, a screw groove is formed in one of circumferential surfaces, facing each other, of the rotor portion and the stator portion, and a screw groove type vacuum pump for transferring the gas utilizing viscosity of the gas by the rotation of the rotor is used in combination with the turbo molecular pump. This is usually used in a semiconductor manufacturing apparatus or the like.
By the way, in the above-described vacuum pump, a pressure is low on the intake port side upon the suction of gas and a pressure is kept high on the discharge port side. Also, in order to prevent the excessive heating due to the provision of electronic equipments such as motors arranged in the central portion, the interior of the vacuum pump is kept at a temperature not higher than a predetermined temperature by means of a cooling means for recirculating water.
For this reason, in the case where reactive gas such as AlCl3 or the like being process gas is to be sucked in an etching process in the case where the pump is used in the semiconductor manufacturing apparatus, in some cases, the gas is precipitated by the sublimation of gas to be transferred in the vicinity of the discharge port to stick to the surface of the flow path.
Then, due to this deposition, there is a possibility that the flow of gas is prevented, the transfer efficiency of gas by the vacuum pump becomes low, or in the worst case, the depositions adhered to the rotor portion and the stator portion are brought into contact with each other to cause the damage of the members.
In the vacuum pump, as a technology for avoiding the precipitation due to the sublimation of the reactive gas by heating the flow path of gas, there is a conventional technology for arranging a heater using a nichrome line around the lower portion of the vacuum pump.
FIG. 9
is a schematic view representing an overview structure of the vacuum pump adopting such a technology.
The conventional vacuum pump shown in
FIG. 9
is a composite pump. A stator portion
118
and a rotor portion
114
are received in an outer sleeve portion
116
having a hollow portion. The outer sleeve portion
116
and the stator portion
118
are fixed and supported onto a base
119
. The rotor portion
114
is supported rotatably coaxially to the stator portion
118
on the base
119
. Rotor blades
1141
projecting in a radial direction of rotation at one end in an axial direction are provided in a plurality of stages in the axial direction of rotation. The stator portion
118
is provided with a plurality of stator blades
1181
projecting from an outer side of the rotor portion
114
between the rotor blades
1141
, and is provided with groove provided spacers
1180
surrounding the outer circumferential surface of the rotor portion
114
in the vicinity thereof at the other end of the axial direction.
Also, a temperature sensor
151
for detecting the temperature in the vicinity of the flow path of the gas is provided in the vicinity of the base
119
. Also, a water-cooling pipe
171
is in contact with the bottom surface of the base
119
. The water-cooling pipe
171
is adapted to be opened and closed by means of an electromagnetic valve
172
. Furthermore, a nichrome heater
160
is wound around the outer circumferential surface of the base
119
.
Then, the rotor portion
114
is rotated relative to the stator portion
118
by a motor disposed in the substantially center of the vacuum pump. The gas molecular is stuck down by means of the rotor blades
1141
and the stator blades
1181
on the side of the above-described end. On the other end side, the viscous flow of the gas molecular stuck down is formed in the groove provided spacers
1180
to transfer the gas molecular to the discharge port by the viscosity. Thus, the gas from the opening portion (suction port) on one end side of the outer sleeve portion
116
is discharged from the discharge port formed in the base
119
through the flow path of gas formed between the rotor portion
114
and the stator portion
118
.
In this vacuum pump, as shown in
FIG. 10
, a decision is made as to whether a heater
160
and an electromagnetic valve
172
is turned on or off on a judgement device
185
on the basis of a set temperature Td set in advance and a temperature Tr detected from the temperature sensor
151
by means of a controller
180
on the basis of the output from a temperature sensor
151
. Namely, if Tr<Td, the heater
160
is turned on to heat the gas flow path, and the electromagnetic valve
172
is turned off to thereby stop the flow of water through the water-cooling pipe
171
. Also, in the case where Tr≧Td, the electromagnetic valve
172
is turned on so that the flow of water through the water-cooling pipe
171
is recirculated. The heater
160
is turned off so that the gas flow path is cooled down. Then, the flow path of gas is kept in the predetermined temperature range by means of the elevation of temperature by the heater
160
and the cooling-effect by the flow of water through the water-cooling pipe
171
. Thus, the precipitation due to the sublimation of the reactive gas is controlled.
Also, as a technology for avoiding the precipitation of the gas composition in the vicinity of the discharge port, there is a proposal of the technology to heat the flow path of gas by providing an alternative current to a coil using magnetic material as a core (Japanese Utility Model Registration No. 2570575).
According to the technology, the flow path of gas is heated by means of the heat generation of the magnetic hysteresis and the heat generation within the core due to the eddy current by embedding a coil using the magnetic material as a core into the base supporting the outer sleeve and having the discharge port to feed alternating current to the coil.
However, in the vacuum pump using the heater shown in
FIG. 9
, the heating of the vicinity of the discharge port is performed only by means of the nichrome line heater
160
. Accordingly, it is necessary to use a large capacity heater
160
at about 300 W. For this reason, there is a problem that a large load is applied to the controller power source, it is difficult to handle the vacuum pump since it is necessary to use a cable having a greater diameter, or the manufacturing cost and the running cost are high.
Also, in order to provide the heater
160
on the surface of the vacuum pump and heat the flow path of gas from the outside, the heat is likely to escape to the outside and it is impossible to give Joule's heat effective
Adams & Wilks
Patel Vinod D.
Seiko Instruments Inc.
Walberg Teresa
LandOfFree
Vacuum pump 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 pump, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vacuum pump will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3119548