JPH02153294A - Variable capacity type vacuum pump - Google Patents

Abstract

PURPOSE:To enable control of capacity of a vacuum pump by a method wherein, in a device in which a screw groove forming a flow passage for gas molecules is formed at least in the one of a stator and a rotor, at least the one of the stator and the rotor is movable in the direction an axis. CONSTITUTION:A rotor 101 in the side of which a plurality of lines of screw grooves are formed is concentrically and rotatably arranged facing the inner surface of a stator 102 secured to a housing 100, and the screw groove is formed such that the depth of the groove is gradually decreased from the upper part toward the lower part of the stator 101. The inner surface of the stator 102 forms a slope inclined at a given angle with the direction of the rotary axis of the rotor 101, and the side of the rotor 101 also forms a slope inclined based on the direction of a rotary axis. The rotor 101 is supported in a levitating state by using two sets of upper and lower radial magnetic bearings 103a and 103b and one set of thrust magnetic bearings 104, and a volume is controlled through control of a levitating amount in the direction of thrust.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a vacuum pump that is applied when gas is mainly in the molecular flow to intermediate flow region, and particularly relates to a vacuum pump with variable capacity. be.

[Conventional technology]

Turbomolecular pumps and groove-type vacuum pumps have been known as typical vacuum pumps. These vacuum pumps are used, for example, in exhaust systems of semiconductor manufacturing equipment. In this case, in the 11-conductor manufacturing apparatus, a supply gas flow rate control valve is provided in the semiconductor gas introduction pipe, and a vacuum container internal pressure control valve is provided between the vacuum container and the vacuum pump. (In the Jt gas supply flow rate control valve, the gas flow rate in the semiconductor gas introduction pipe is measured using a hot wire flow meter, etc., and the valve opening degree is highly precisely feedback controlled based on this measurement, and the pressure inside the vacuum vessel is In the control valve, the valve opening degree is subjected to feedbank control based on the pressure signal obtained from a high-precision diaphragm vacuum gauge attached to the vacuum vessel.This allows the flow rate of the semiconductor gas and the pressure inside the vacuum vessel to be controlled. It is possible to maintain each of these at desired values and form a uniform thin film in this state.

[Problems to be Solved by the Invention] However, in the exhaust system of this semiconductor manufacturing equipment, in order to accurately set the degree of vacuum in the vacuum container to a desired value, a stepping motor or the like is installed in the vacuum container pressure control valve. Expensive variable pressure regulating valves with high resolution were required.

The present invention has been made in view of the above points, and its purpose is to provide a vacuum pump whose capacity can be controlled, for example, by applying the vacuum pump of the present invention to the exhaust system of semiconductor manufacturing equipment. In some cases, the vacuum pump itself controls the pressure within the vacuum container, thereby eliminating the need for the variable pressure control valve and simplifying and reducing the cost of the exhaust system of semiconductor manufacturing equipment.

[Means to solve the problem]

In order to achieve the above object, a variable displacement vacuum pump according to the present invention includes a rotor that faces the inner surface of a stator having a circle M and is arranged concentrically with the stator in parentheses, and has the following features: A vacuum pump in which a threaded groove is formed at least in the - direction, the threaded groove serves as a flow path for gas molecules, and the gas molecules are moved in the direction of the rotational axis of the rotor by rotation of the rotor, the inner surface of the stator. and a side surface of the rotor has an inclined surface inclined with respect to the direction of the rotation axis, and in order to control a gap between the rotor and the stator, at least one side of the stator and the rotor is rotated. The vacuum pump is movable in the axial direction and includes a control means for controlling the amount of movement, thereby controlling the capacity of the vacuum pump.

[Effect]

According to the above configuration, since the inner surface of the stator and the side surface of the rotor have an inclined surface that is inclined with respect to the rotational axis direction of the rotor, the relative position between the stator and the rotor can be controlled. If you change it, the gap between the stator and rotor will also change. Here, in the present invention, at least one of the stator and the rotor is movable in the direction of the rotation axis of the rotor, and the amount of this movement can be controlled. As a result, the gap between the stator and the rotor can be controlled, so the flow rate of gas molecules flowing through the thread grooves, that is, the capacity of the vacuum pump can be controlled.

〔Example〕

A first embodiment of the present invention will be described below based on the drawings. In this embodiment, a thread groove type vacuum pump is used as the vacuum pump.

In FIG. 1, a stator 102 is fixed to a housing 100 of a cylindrical thread groove type vacuum pump, and a rotor 101 is installed concentrically and rotatably opposite the inner surface of the stator 102. The inner surface of the stator 102 has a 1/1 slope (tapered surface) that is inclined at a predetermined angle with respect to the rotational axis direction of the rotor 101 (arrow Y direction in the figure).
Accordingly, the side surface of the rotor 101 also has an inclined surface inclined with respect to the rotation axis direction. Several thread grooves are formed on the side surface of the rotor 101, as shown in FIG. Note that this thread groove is formed so that the groove depth gradually becomes shallower from the top to the bottom of the jetter 101 in FIG.

In addition, in the illustrated embodiment, the bearing ≠ the upper and lower 2 as members.
A set of radial magnetic bearings 103a and 103b and a set of thrust magnetic bearings 104 are used, and a general squirrel cage three-phase induction motor 105 is used as a rotating means. With this configuration, the rotor 101 is completely floating at each magnetic bearing, and the stator 102 and each upper and lower auxiliary bearing
No contact with 06, 107, etc., enabling high speed rotation.

Further, in the figure, 108 and 109 are non-contact displacement sensors that constantly measure the behavior of the rotor 101, and 110 is a rotation speed sensor that measures the rotation speed of the rotor 101 in a non-contact manner. When the rotor 101 is rotating in a floating state, each magnetic bearing 103a is controlled by the output from the non-contact displacement sensors 108 and 109.

The voltage and current applied to 103b and ]04 are PID controlled. At the same time, the voltage applied to the three-phase induction morph 105 is controlled by the output from the rotational speed sensor 110.

Next, before explaining the operation of the vacuum pump configured as described above, FIG. 3 shows an example of a vacuum device in a semiconductor manufacturing apparatus.

(2) is a vacuum container in which a semiconductor substrate is housed; (2) and (3) are flow rate control valves attached to gas introduction pipes, respectively, (2a, (3a))
4 is a flow rate detector, and 4 is a pressure detector such as a tire flam type vacuum gauge for detecting the pressure inside the vacuum container 1. 5 is the screw vortex type vacuum pump of this embodiment, 6 is the screw vortex type ↓" is the empty pump 5
This control device controls the signals supplied to the thrust magnetic bearing 104 of the rotor 101. The flying height of the rotor 101 in the rotational axis direction (thrust I direction) is controlled by control signals from the control device 6. This control device 6 receives a pressure signal from the pressure detector 4, a non-contact displacement sensor 109 that detects the flying height of the rotor 01 in the thrust direction, and a semiconductor gas supplied to the vacuum vessel 1. Flow rate detector 2a showing a meteor of
, 3a, the control signal is given to the thrust magnetic bearing #-104. Note that 7 is an oil rotary pump, 8, 9, and 10 are pneumatic operation valves, and 11 is an exhaust pipe.

Here, the pump operations of the screw vortex type vacuum pump 5 and the oil rotary pump 7 shown in FIG. 1 will be explained in relation to the internal pressure control of the vacuum container 1. A vacuum container 1 for semiconductor manufacturing uses a screw vortex vacuum pump 5 to draw the inside of the vacuum container to a high vacuum once to exhaust gas such as water vapor contained in the atmosphere. At the same time, the reaction gas, etc. continues to flow at a constant flow rate into the vacuum container I, and the screw vortex vacuum pump 5
In order to draw from the vacuum container 1 the amount of gas necessary to keep the pressure inside the vacuum container 1 constant, the reactor gas flow rate and the pressure inside the vacuum container 1 are operated to be kept constant. Ru. In this state, a thin film is formed on the wafer etc. carried into the vacuum container. The operation using the screw vortex vacuum pump 5 is performed every time a thin film is formed on a wafer or the like. In connection with the above operation, the spiral vortex vacuum pump 5 provided on the side of the vacuum container 1 and the oil rotary pump 7 provided at the next stage are used as follows. In the screw vortex vacuum pump 5,
Due to the groove depth provided in several stages and the long stroke, the intake port side pressure is about 10-'Torr or less, and the number is -042/s.
It has an evacuation speed of ec to several 1001/sec, and exhausts the gas in the vacuum container 1 before semiconductor production. In addition, the spiral vortex vacuum pump 5 has an inlet side pressure of 10-4 to 10°To
It exhibits performance even at temperatures as low as RR, has an exhaust flow rate of several 1105 CCCM to several 1000 SCCM, and performs the exhaust function of reaction gases, etc. during semiconductor manufacturing. In addition, the oil rotary pump 7 is
It is a roughing pump that pulls the vacuum container 1 to a low vacuum to a pressure at which the groove type vacuum pump 5 etc. can exert an evacuation effect,
Demonstrates performance at temperatures below about 2°Torr. Therefore, the vacuum container 1 is first roughly pumped to a low vacuum state of about 10° Torr by the oil rotary pump 7, and then, as described above, is first brought to a high vacuum state by the screw vortex type vacuum pump 5 for exhausting gas before semiconductor manufacturing. The internal pressure is then adjusted to the set pressure for semiconductor manufacturing. However, in controlling the pressure inside the vacuum container 1 to the set pressure in -)2, the rotor 10 of the spiral vortex vacuum pump 5 is
The flying height in the first thrust direction is controlled.

Next, the control device 6 that controls the flying height of the rotor 101 in the thrust direction will be explained based on FIG. In FIG. 3, the control device 6 is composed of a control calculation circuit 201, a thrust magnetic bearing drive circuit 202, and a thrust position detection circuit 203. The control calculation circuit 201 includes a pressure detector 4.
and the output signal of the non-contact displacement sensor 109 in the thrust position detection circuit 203. A signal indicating the amount of slush detected based on the flow rate control valves 2 and 3 and a signal indicating the gas flow rate from the flow rate detectors 2a and 3a of the flow rate regulating valves 2 and 3 are respectively input manually. Control circuit 2
01 is a target value for the flying height of the rotor 101 in the thrust direction (thrust target value) based on these input signals.
204 is calculated and output to the thrust magnetic bearing drive circuit 202.

The relationship between the amount of movement of the rotor 101 in the thrust I direction and the pressure change within the vacuum vessel 1 will now be explained based on FIGS. 4, 5, and 6.

In FIG. 4, the rotor 101 floats in the thrust direction.
The amount is controlled by the control device 6 within the range shown in the figure.

For this range of flying height, the rotor 101 and the stator 1
The amount of change Δδ in the gap δ between the rotor 101 and the rotor 101 is α.

Δδ−hsinα(,°δ−δ.+△δ) ・・・・・・
・It can be expressed as (1).

Here, the relationship between the gap δ between the rotor 101 and the stator 102 and the exhaust flow rate of the vacuum pump 5 is shown in FIG. It can be seen from FIG. 5 that the air flow rate of the molecular pump 5 can be controlled by the gap δ between the rotor 101 and the stake 102. However, if the gap δ is too large, the pumping action will no longer be achieved, so care must be taken.

In addition, since the equation of state of an ideal gas is considered to hold within the vacuum vessel 1, the equation of state within the vacuum vessel 1 is as follows: (2) P: Pressure inside the vacuum vessel ■o: Inside the vacuum vessel Volume Q,; gas suction volumetric flow rate Qo = gas exhaust volumetric flow rate Rg: gas constant T: vacuum vessel internal temperature. Furthermore, there is a relationship shown in FIG. 6 between the exhaust flow rate of the threaded slot vacuum pump 5 and the intake port pressure. According to Fig. 6, the exhaust flow rate is approximately 10” Torr to 1Q Torr.
It is almost constant for the inlet pressure of r, and in this range, as shown in FIG. Therefore, Qo=+ δ−+−K z
−・−・−(3) K+, 2: Can be set as a constant. Substituting equation (3) into equation (2), O = 3-, δ...
...(4) K3. 4: A constant relationship holds true. Also, by substituting equation (1) into equation (4), P = 3- to 4 (δo+hsinα) = 5- to 6
h...(5) K, , , , : A constant is obtained.

As explained above, by controlling the levitation 1h of the rotor 101 in the thrust direction, the exhaust flow rate of the vacuum pump 5 and the pressure P in the vacuum vessel 1 can be controlled.

Here, as an example of the effect when the slotted hole vacuum pump of this embodiment is applied to semiconductor manufacturing equipment, the time required for the pressure inside the vacuum container to reach a steady state is significantly longer than in conventional semiconductor manufacturing equipment. can be shortened to The reason for this will be explained below.

In the manufacturing process of conventional semiconductor manufacturing equipment, after loading a wafer etc. into a vacuum container, the inside of the vacuum container is first brought into a vacuum state with a high degree of 0-' Torr by using a turbo molecular pump, etc. By flowing semiconductor gas from a vacuum state as a steady meteor, and controlling the pressure inside the vacuum container with a variable pressure control valve,
The pressure inside the vacuum container is maintained at about 10 Torr.

However, in the conventional example, the pressure at the initial stage of operation (10-
'~10Torr) and steady-state pressure (IO-'T
orr), and since the gas flow rate control valve only controls a constant flow rate, it takes a long time to maintain the pressure inside the vacuum container at a constant level.

On the other hand, in the semiconductor manufacturing equipment to which the groove-type vacuum pump of this embodiment is applied, the pressure inside the vacuum chamber is changed from a high vacuum state (10-' to 10-6 Torr) to a steady state (10-6 Torr).
0'-'Torr), the internal volume of the vacuum vessel 1 and the exhaust characteristics of the vacuum pump 5 are determined by the thrust direction of the rotor 101 as a target based on the large gas flow rate, target pressure, etc. : ih is calculated, and the control device 6 immediately controls the levitation lh of the rotor 101. A floating Jib whose target is the flying height of the rotor 101 in the thrust direction.
Since the time required to perform the control is very short, the time required to shift to a steady state can be significantly shortened compared to the conventional example. FIG. 7 shows an example of the convergence state of the pressure inside the vacuum container when the groove-type vacuum pump 5 of the wooden embodiment is applied to a semiconductor manufacturing apparatus. Note that in FIG. 7, the time when the semiconductor gas is introduced is set to 0 minutes.

FIG. 8 shows a second embodiment of the present invention. In the second embodiment, the inclinations of the inclined surfaces of the rotor 101a and the stator 102a in the thrust direction are reversed from those in the first embodiment.

In this second embodiment as well, the same effects as in the first embodiment can be obtained, except that the moving direction of the rotor 101a is reversed.

In the third embodiment shown in FIG. 9, strays 1 to A are provided in parts of the rotor 101b and the stator 102b. In the third embodiment, by providing this stoshi-1 section A, the floating height 11 of the rotor 101d in the thrust direction changes greatly, which may cause the lubricating oil etc. of the oil rotary pump 7 to flow backward. This can be prevented by moving the exhaust flow rate to the rear and back portions, where the exhaust flow rate does not change even when the exhaust gas is in use.

The fourth embodiment shown in FIG. 10 is a wide-area turbomolecular pump in which a rotor blade 101d is arranged in the second part of a rotor 101c, and a stator blade 113 is provided in the upper part of a stator 102c. gear 1
12 etc. so that it can move in the thrust direction. Such a configuration is particularly effective in a wide-area turbomolecular pump in which the gap between the rotor blade 101 (i) and the stator blade 113 is small and the levitation 1h of the rotor 101c in the thrust I direction cannot be changed much. The fourth embodiment is also effective in a groove type vacuum pump or a wide area turbo molecular pump using a ball bearing or the like as a bearing.

The fifth embodiment shown in FIG. 11 has a plurality of rotors 20Ia, 2
01b and stators 202a and 202b constitute a vacuum pump. In FIG. 11, the rotor 201 is moved as described above by the signal from the non-contact displacement sensor 204.
The flying heights of a and 201b in the thrust direction are controlled.

In addition, in FIG. 11, 203 is a thrust magnetic bearing;
05 is a rotational drive mechanism for the rotors 201a and 201b, 20
6° 207 is a radial bearing, 208 is an intake port, 209 is an exhaust port, and J is shown.

Further, the present invention is also effective for a pump having a shape in which a thread groove is not formed on the side surface of the rotating rotor 101d but is formed on the inner surface of the stator 102d, as in the sixth embodiment shown in FIG. Furthermore, it is also effective in a pump in which spiral grooves are formed in opposite directions on the side surface of the rotor 101e and the inner surface of the stator 1.degree. 2e in order to improve the exhaust characteristics, as in the seventh embodiment shown in FIG. be.

Further, in the variable displacement vacuum pump of the present invention, by making at least one of the rotor and the stake movable in the thrust direction, the gap between the rotor and the stator is changed, and the exhaust performance of the threaded groove portion is changed. Any shape may be used as long as the gap between the rotor and the stator can be changed when at least one of the rotor and the stake is moved in the thrust direction. Other examples of these shapes are shown in FIGS. 14 to 17.

In the eighth embodiment shown in FIG.
So that the angle of the slope of f increases as it goes downward,
The inclined surface is curved with a smooth curved surface. 1st
In the ninth embodiment shown in FIG. 5, contrary to the example shown in FIG. 14, the angle of the slope of the stake 102g becomes smaller as it goes downward. In the tenth embodiment shown in FIG. 16, the slope of the inclined surface in the direction of the rotation axis of the stator 102h is formed to be opposite to the example shown in FIG. 15. In the eleventh embodiment shown in FIG.
The longest diameter is near the center in the axial direction of 021, and the diameter becomes smaller toward the top and bottom in the figure. In this example, grooves with different exhaust performance are formed in the half and lower part of the rotor 1011, and the rotor 101j
The pump on the F side may be operated when the value is at the binary level, and the pump on the lower side may be operated when the value is at the lower level.

〔Effect of the invention〕

As described above, according to the present invention, the inner surface of the stator and the side surface of the rotor are provided at an angle with respect to the rotation axis of the rotor,
Since at least one of the stator and rotor is movable in the direction of the rotor's rotation axis, the capacity of the vacuum pump including the stator and rotor can be made variable.

Furthermore, when the vacuum pump of the present invention is used in the exhaust system of micro-conductor manufacturing equipment, the conventionally required variable pressure regulating valve is no longer necessary, and the exhaust system of semiconductor manufacturing equipment is simplified and reduced in cost. can.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of a thread groove vacuum pump according to a first embodiment of the present invention, FIG. 2 is a front view of the rotor of the thread groove vacuum pump shown in FIG. 1, and FIG. 4th block diagram of the case where the thread groove 2 vacuum pump of the embodiment is applied to semiconductor manufacturing equipment
Figure 5 is an enlarged cross-sectional view of the main parts of a groove-type vacuum pump to explain the amount of change in the gap between the rotor and stator with respect to the floating I-amount of the rotor in the thrust direction 1. A characteristic diagram showing the relationship between the gap between the rotor and the stake and the exhaust flow rate, Figure 6 is a characteristic diagram showing the relationship between the suction port pressure and the exhaust flow rate of a thread groove vacuum pump, and Figure 7 is a characteristic diagram showing the relationship between the vacuum vessel internal pressure. Characteristic diagrams showing changes, FIGS. 8 to 17 are the second characteristics of the present invention.
- It is a sectional view showing the structure of the 11th example. 101.101a-1011...1:1-Evening, 102
゜102a-1021...Stator, ]03a, 10
3b...Radial magnetic bearing 1104...Slus l-
Magnetic bearing, I05...Three-phase induction motor, 106,10
7...Auxiliary bearing, 108.109...Non-contact displacement sensor"2110...Rotational speed center.

Claims (1)

[Scope of Claims] A rotor is provided which faces an inner surface of a cylindrical stator and is arranged concentrically with the stator, and a thread groove is formed in at least one of the stator and the rotor, and the thread groove is formed in at least one of the stator and the rotor. is a flow path for gas molecules, and in a vacuum pump in which the gas molecules are moved in the direction of the rotation axis of the rotor by rotation of the rotor, the inner surface of the stator and the side surface of the rotor are inclined with respect to the direction of the rotation axis. the stator and the rotor, at least one of the stator and the rotor is movable in the direction of the rotation axis in order to control a gap between the rotor and the stator, and a control means is provided for controlling the amount of movement. A variable capacity vacuum pump characterized in that the capacity of the vacuum pump is controlled by: