JP2006083750A - Oil diffusion pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil diffusion pump capable of simply obtaining a high vacuum condition having high quality. <P>SOLUTION: This oil diffusion pump is provided with an electric motor 20 arranged by positioning a driving shaft 20a at a shaft axis of a casing 1 above a plurality of nozzles 8 and a rotary blade 21 composed of a plurality of blades 21a arranged in the peripheral direction of the driving shaft 20a of the electric motor 20 to push back oil vapor 5a scattering above the nozzles 8 in the casing 1 below the casing 1 by the rotary blade 21 rotated and driven by the electric motor 20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an oil diffusion pump that obtains a high vacuum, and more particularly, to an oil diffusion pump having a simple structure that effectively suppresses oil vapor ejected from a nozzle housed in a casing from entering an intake port.

  Conventionally, various vacuum pumps have been applied to obtain a high vacuum in processes such as a vacuum deposition apparatus, a semiconductor manufacturing apparatus, and a sputtering apparatus. Examples of this type of vacuum pump include a cryopump, a turbo molecular pump, an ion pump, and an oil diffusion pump. Among these vacuum pumps, the oil diffusion pump is a system in which oil vapor and gas molecules are ejected from a plurality of nozzles housed in a casing when a vapor of ultra-high speed oil (silicon oil or mineral oil) is ejected downward. , The gas molecules entering from the intake port above the casing are pushed downward, and the gas molecules are discharged from the exhaust port positioned below the casing to obtain a high vacuum.

The oil diffusion pump having such a structure has a simple structure compared to other vacuum pumps, and is preferably used at a low price. On the other hand, the oil vapor ejected from the nozzle is a suction port above the nozzle. Intrusion (backflow) to the side. For this reason, a baffle (trap) cooled to an extremely low temperature is provided on the intake port side above the nozzle so that oil vapor does not flow back to the intake port side (see, for example, Patent Document 1).
JP-A-5-296200

  However, in the oil diffusion pump described above, although a baffle (trap) is provided on the intake port side so that the oil vapor does not flow back to the intake port side, a part of the oil vapor passes through the baffle and is sucked. It cannot be denied that it flows backward to the mouth. For this reason, in a vacuum vapor deposition apparatus, a semiconductor manufacturing apparatus, a sputtering apparatus, or the like having a valve chamber communicating with the suction port, the back-flowed oil vapor adheres to the product. For this reason, there is a problem that the quality of products manufactured by these apparatuses deteriorates. Further, it is necessary to wipe off the oil adhering to the inner wall surfaces of the valve chamber and the vapor deposition chamber due to the backflow of the oil vapor periodically (for example, about once a week), and there is a problem that it takes time and effort for maintenance.

In addition, the oil diffusion pump needs to recover and clean the baffle by returning the oil vapor to a solid (liquid). For this purpose, for example, it is necessary to cool the baffle at an extremely low temperature (minus 196 ° C.) using liquid nitrogen, and there is a problem that a cooling facility must be provided.
The present invention has been made in view of such conventional circumstances, and an object of the present invention is to provide an oil diffusion pump that is simple and can obtain a high-quality high vacuum.

  The present invention was made to achieve the above-described object, and is an oil diffusion pump that is housed in a cylindrical casing and includes a plurality of nozzles that eject oil vapor below the casing. An electric motor having a drive shaft positioned at the axial center of the casing above the plurality of nozzles, and a rotary blade composed of a plurality of blades arranged in a circumferential direction of the drive shaft of the electric motor, The oil vapor scattered above the nozzles in the casing is pushed back below the casing by the rotating blades driven to rotate by an electric motor. In the oil diffusion pump described above, oil vapor (oil particles) about to enter a valve chamber or a vapor deposition chamber provided on the intake port side of the casing is struck by the blades forming the rotating blades and pushed back below the casing. The oil particles adhering to the rotating blades are blown off to the inner wall of the casing under the centrifugal force generated in the rotating blades rotating at high speed. And when it reaches the wall surface of the cooled casing, the oil vapor becomes liquid and is returned to the oil storage tank below the casing. On the other hand, the residual gas in the valve chamber or the vapor deposition chamber is sent to the oil diffusion pump side by a rotary blade that is driven to rotate.

Preferably, the rotary blade is configured to be driven by the electric motor at a rotational speed that obtains a flow rate that exceeds the mean free path of molecules at the gas pressure in the casing.
That is, the oil diffusion pump described above can obtain a flow rate of Mach 1 or 2 by rotating the rotary blade at a high speed, and can exceed the mean free path of gas at the pressure in the casing. Therefore, the oil that tries to enter the valve chamber or the vapor deposition chamber is pushed back below the casing.

  As described above, in the oil diffusion pump of the present invention, the rotating blades composed of a plurality of blades attached to the drive shaft of the electric motor are positioned above the plurality of nozzles, and the rotating blades are rotated at high speed. For this reason, the oil vapor (oil particles) that tends to flow back to the valve chamber or the vapor deposition chamber provided on the intake port side of the casing can be struck by the rotary blades and pushed back below the casing. Furthermore, it is possible to greatly reduce the work of periodically wiping off oil adhering to the inner wall surfaces of the valve chamber and the vapor deposition chamber.

  Also, the oil diffusion pump of the present invention blows off the oil particles adhering to the rotating blades to the inner wall of the casing by centrifugal force generated at the rotating blades rotating at high speed, cools them, changes them into liquid, and returns them to the oil storage tank below the casing. ing. For this reason, while preventing the oil vapor (oil particle) which tends to flow back to the valve chamber or vapor deposition chamber provided on the intake port side of the casing, this oil can be effectively recovered and recycled.

  Moreover, since the rotary blade is rotating at high speed, the mean free path of gas at the pressure in the casing can be exceeded. For this reason, it is possible to achieve an excellent effect such that it is possible to effectively push back the oil vapor (oil particles) to flow back into the valve chamber or the vapor deposition chamber.

  Hereinafter, an embodiment of an oil diffusion pump according to the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a main part including a diffusion pump showing an embodiment for implementing an oil diffusion pump according to the present invention. The lower side of FIG. 1 shows the lower side of the oil diffusion pump, and the upper side of FIG. 1 shows the upper side of the oil diffusion pump. FIG. 1 shows an embodiment of an oil diffusion pump according to the present invention, and the present invention is not limited by FIG.

  In FIG. 1, 1 is a casing that houses an oil diffusion pump. The casing 1 has a cylindrical shape, and the upper end portion of the casing 1 includes an open air inlet 1a. For example, a valve chamber 2 communicates with the intake port 1a. Headband-shaped flanges 2a and 1b are provided on the outer periphery of the communication portion between the valve chamber 2 and the casing 1, and are hermetically fastened by a plurality of bolts 3a and nuts 3b.

  The valve chamber 2 is configured such that a valve body 2b that seals the upper intake port side of the oil diffusion pump main body is movable up and down by a cylinder 2c positioned above the valve chamber 2. The valve chamber 2 communicates, for example, the vapor deposition chamber 30 of the vacuum vapor deposition apparatus and the intake port 1a of the oil diffusion pump. When the workpiece is taken in and out of the vapor deposition chamber 30 of the vacuum vapor deposition apparatus in an atmospheric pressure state. The cylinder 2c is driven and the valve body 2b is positioned at the lowermost part (on the intake port 1a of the oil diffusion pump), and the casing 1 of the oil diffusion pump is sealed to maintain a high vacuum in the casing 1. Bear.

  On the other hand, the lower side surface of the casing 1 is provided with an exhaust port 1c for discharging gas molecules flowing from the intake port 1a out of the casing 1. The exhaust port 1 c is provided with a vacuum pump 4 that discharges the gas in the casing 1 through the auxiliary valve 12. The vacuum pump 4 also serves to create a vacuum of about 10 [Pa] by discharging the gas in the vapor deposition chamber 30 and the valve chamber 2 prior to making the vapor deposition chamber 30 high vacuum by the oil diffusion pump. Yes. For this reason, a vacuum pump 4 is connected to the valve chamber 2 via a roughing valve 13.

Incidentally, the vacuum pump 4 is, for example, a rotary vacuum pump, and as described above, the roughing valve 13 is opened before the oil diffusion pump is started, and the inside of the vapor deposition chamber 30 and the valve chamber 2 is evacuated (roughened). At the same time, during the operation of the oil diffusion pump, the roughing valve 13 is closed and the auxiliary valve 12 is opened to discharge the residual gas in the casing 1.
The bottom of the casing 1 has an oil storage tank 6 for storing oil (silicon oil, mineral oil, etc.) 5. A plurality of chimneys 7 made of concentric cylinders are provided above the oil storage tank 6. Each chimney 7 has a tapered nozzle 8 at the tip thereof. Each nozzle 8 is directed downward in the casing 1. The oil storage tank 6 at the bottom of the casing 1 is provided with a heater 9 for heating the casing 1 from the bottom, and a power supply unit 10 for supplying electric power to the heater. The heater 9 heats the oil 5 (hydraulic oil) stored in the oil storage tank 6 to send the oil vapor 5a into the chimney 7, and from each nozzle 8 provided at the tip of the chimney 7, an ultra high-speed oil The steam 5a is spouted into the casing 1.

  A spiral circular tube 11 is provided on the side of the outer wall of the casing 1. Cooling water circulates inside the circular pipe 11 to cool the inner wall side surface of the casing 1. When the oil vapor 5a ejected from each of the plurality of nozzles 8 reaches the inner wall side surface, the oil vapor 5a is cooled and changed into a liquid, and returns to the oil storage tank 6 provided below the casing 1. Then, it is heated again by the heater 9 to become oil vapor 5a, and thereafter the circulation is repeated.

  In the oil diffusion pump configured as described above, the oil diffusion pump according to the present invention is characterized by the casing 1 between the intake port 1a and the valve chamber 2, specifically, the plurality of nozzles 8 above. The motor 20 is provided with an electric motor 20 having a drive shaft 20a positioned on the axis of the motor 20 and a rotary blade 21 composed of a plurality of blades 21a arranged in the circumferential direction of the drive shaft 20a of the electric motor 20. It is in the point which pushes back the oil vapor 5a scattered above the nozzle 8 in the casing 1 back to the lower side of the casing 1 by the rotary blade 21 that is driven to rotate. Incidentally, the rotary blade 21 includes a plurality of blades 21a having the same shape as shown in FIG. 2 and is arranged at predetermined angles (for example, 10 degrees) in the circumferential direction of the drive shaft 20a of the electric motor 20.

The operation of the oil diffusion pump of the present invention having such characteristics will be described. First, prior to operating the oil diffusion pump, the vacuum degree in the valve chamber 2, the vapor deposition chamber 30 and the casing 1 is evacuated to about 10 [Pa] in advance by the vacuum pump 4. Next, the valve body 2b of the valve chamber 2 is pulled upward by driving the cylinder 2c, and the electric motor 20 is rotated to give the rotary blade 21 a rotational driving force around the axis. For example, when the diameter of the rotary blade 21 is 660 mm, the rotational speed of the electric motor is 16000 revolutions per minute. At this time, the peripheral speed of the rotary blade 21 reaches 553 m / sec, and a flow rate of Mach 1 or 2 can be obtained.

  That is, the flow velocity provided by the rotary blade 21 exceeds the mean free path (mean free path) of gas molecules in the state of gas pressure in the casing 1. Then, the oil vapor 5 a ejected from the nozzle 8 is pushed back downward of the casing 1 so as to be struck by a plurality of blades 21 a constituting the rotary blade 21. Further, the oil adhering to each blade 21a of the rotary blade 21 is blown to the outer peripheral direction by the centrifugal force of the rotary blade 21 rotating at high speed, and is attached to the inner wall surface of the cooled casing 1 to become a liquid. 1 is returned to the oil storage tank 6. Residual gas molecules in the valve chamber 2 are sucked inwardly in the casing 1 by the rotating blades 21 rotating at high speed and discharged from the exhaust port 1c.

  Thus, according to the oil diffusion pump configured as described above, the motor 20 having the rotary blades 21 attached to the drive shaft 20a is rotated by positioning the drive shaft 20a at the axial center of the casing 1 above the plurality of nozzles 8. Since the blades 21 are rotated at a high speed, the oil vapor (oil particles) 5a that is about to enter the valve chamber 2 provided on the intake port 1a side of the casing 1 is struck by the rotary blades 21 and pushed back below the casing 1. Can do. For this reason, the oil adhering to the inner wall surface of the valve chamber 2 can be greatly reduced. Therefore, it is possible to reduce or omit the periodic cleaning work for wiping off this oil.

The oil particles adhering to the rotating blades 21 are subjected to centrifugal force generated at the rotating blades 21 rotating at a high speed and are blown off to the inner wall of the casing 1, and the oil particles reach the inner wall surface of the cooled casing 1. Since it becomes liquid, it can be returned to the oil storage tank 6 below the casing 1.
Further, since the rotary vane 21 rotates at a high speed, the flow velocity caused by the rotary vane 21 reaches Mach 1 to 2 and can exceed the mean free path of gas at the pressure in the casing 1. For this reason, the pumping speed of the rotary vane is added to the pumping speed of the oil diffusion pump, for example, the oil 5 about to enter the valve chamber 2 can be effectively pushed back down the casing. The effect which becomes.

Sectional drawing which shows the main structures of the oil diffusion pump which concerns on one Embodiment of this invention. The disassembled perspective view which shows a mode that the rotary blade applied to the oil diffusion pump shown in FIG. 1 is attached to a casing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Casing 2 Valve chamber 5a Oil vapor 8 Nozzle 20 Electric motor 20a Drive shaft 21 Rotating blade 21a Blade

Claims (2)

In an oil diffusion pump that is housed in a cylindrical casing and includes a plurality of nozzles that eject oil vapor below the casing,
An electric motor having a drive shaft positioned at the axial center of the casing above the plurality of nozzles, and a rotary blade composed of a plurality of blades arranged in a circumferential direction of the drive shaft of the motor, An oil diffusion pump, wherein the oil vapor scattered above the nozzles in the casing is pushed back below the casing by the rotating blades driven to rotate by an electric motor.   2. The oil diffusion pump according to claim 1, wherein the rotary blade is driven by the electric motor at a rotational speed that obtains a flow rate that exceeds a mean free path of molecules in a gas pressure in the casing.

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