JPH11210655A - Vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mount a high vacuum part on a basic unit in common with a vacuum pump having various exhaust characteristics by constituting a first pump part by a pair of first rotors and a housing, and constituting a second pump part by a pair of second rotors and a housing coaxially with the first pump part. SOLUTION: Lower rotors 10, 11 are fastened to rotary shafts 1, 2 by bolts 50a, 50b, and lower spacers 27a, 27b are fastened to the lower rotors 10, 11 by bolts 51a, 51b. The lower spacers 27a, 27b and upper rotors 8, 9 are fastened to each other by bolts 52a, 52b. When base common unit is assembled, the lower rotors 10, 11 are fastened to the rotary shafts 1, 2 while regulating a positioning relation between contact preventing gears 24, 25 and lower screw grooves 12, 13. The lower spacers 27a, 27b having each installing screw hole formed while taking a phase relation between upper screw grooves 14, 15 in consideration are mounted on upper end surfaces of the lower rotors 10, 11. It is thus possible to simplify a phase matching work of the upper screw grooves 14, 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum pump used for semiconductor manufacturing equipment and the like.

[0002]

2. Description of the Related Art A vacuum pump for creating a vacuum environment is indispensable for a CVD apparatus, a dry etching apparatus, a sputtering apparatus and the like in a semiconductor manufacturing process. The demand for vacuum pumps has been increasing in recent years in order to respond to the high integration and miniaturization of semiconductor processes. The main contents are that high vacuum ultimate pressures can be obtained and cleanliness is required. , Maintenance is easy, small and compact.

An evacuation system mainly including a roughing pump is configured to evacuate a film forming chamber and a load lock chamber in a semiconductor facility. For example, in the case of a film forming chamber of a CVD device,
It is necessary to ensure the stability of the degree of vacuum during the reaction.
For example, the pressure condition at the time of film formation in the case of plasma CVD is 2 to 100 mmtorr, and the case of LP-CVD is 50 to 200 mm.
torr, and the fluctuation range of the set pressure at this time is ± 5 mmtorr
It must be held below. Normally, a pressure regulating valve is used to maintain this set pressure, but CVD with a large amount of reactive gas
In such a process, the evacuation capacity is insufficient with only the roughing pump, and it is difficult to settle the pressure. Therefore, an exhaust system is provided in which an auxiliary pump having a high evacuation speed in the middle vacuum region or lower is provided upstream of the roughing pump.

[0004] An auxiliary pump is also used for evacuation of the load lock chamber in order to increase the production tact time or to reduce the background vacuum pressure. In the latter case, under the same tact condition, for example, if the background pressure of the preliminary chamber is changed from 100 mmtorr to 10 mmtorr, the generation of impurities (moisture and the like) can be suppressed low. As described above, in order to supplement the performance of the roughing pump and to create a high vacuum in the semiconductor equipment, a vacuum evacuation system comprising a combination of a roughing pump (a positive displacement vacuum pump) and an auxiliary pump (a high vacuum pump) is usually configured. I have.

[0005] The following describes the prior art and its problems [1]
In the case of a general exhaust system, [2] the case of a wide-area vacuum pump proposed by the present inventors will be described.

[1] In the case of a general exhaust system In a conventional general exhaust system, either a turbo molecular pump or a mechanical booster is used as an auxiliary pump depending on a process to be applied. Hereinafter, the structures of a roughing pump and a mechanical booster widely used as an auxiliary pump thereof will be described.

(1) Structure of roughing pump FIG. 9 shows a screw groove type (a kind of screw type) dry vacuum pump which is a kind of a conventional roughing pump. In the figure, 101 is a housing, 102, 10
3 is a rotating shaft, 104 and 105 are rotating shafts 102, respectively.
A cylindrical rotor fastened to 103. On the outer periphery of each rotor 104 and 105, thread grooves 106 and 107 are provided.
Are formed. When the rotors 104 and 105 rotate, the closed space formed by the screw groove and the housing moves from the suction side to the discharge side with the rotation, and performs the suction action and the discharge action. Further, in the screw groove type vacuum pump shown in the figure, the synchronous operation of the two rotors 104 and 105 is performed by the operation of the timing gears 110a and 110b. That is, the rotation of the motor 108
9a to the intermediate gear 109b,
The transmission is transmitted to one of the timing gears 110b provided on the shafts 4 and 105 and meshing with each other. Both rotors 10
The phases of the rotation angles of the gears 4 and 105 are adjusted by the engagement of the two timing gears 110a and 110b. An oil pump 111 is provided at an end of the driving gear 109b.
Is incorporated. Oil 112 for lubrication is sucked by the oil pump from an oil pan 113 at the lowermost part of the pump, and is supplied to the bearing and the gear via an oil filter.

(2) Structure of Mechanical Booster FIGS. 10A and 10B show a mechanical booster used as an auxiliary pump of the above-described roughing pump. 200 is a motor rotor, 201 is a motor stator, 202 and 203
Hamayu-shaped rotor, 204 is a suction port, 205 is a discharge port, 2
06 is a rotating shaft, 207, 208, 209 are ball bearings that support the rotating shaft, 210 is a timing gear, and 211 is a rotor casing. In the mechanical booster with the above configuration, a set of timing gears provided at the shaft end
The two cocoon rotors rotate in opposite directions without contacting each other and maintaining a phase of 90 degrees. The gas is transported from the suction port to the discharge port by the movement of the closed space formed by the rotor and the casing.

However, with the recent incorporation of semiconductor processes, a so-called multi-chamber system, in which a plurality of vacuum chambers are independently evacuated and evacuated, has become the mainstream of semiconductor thin film processing equipment. To cope with the multi-chamber system, a vacuum pumping system comprising a combination of a roughing pump and an auxiliary pump (high vacuum pump) is required for each chamber. If it is configured for the chamber, there is a problem that the entire vacuum evacuation device becomes large and complicated.

[2] In the case of a wide-area vacuum pump As an alternative to the above-described vacuum evacuation system, the present inventors, on the same axis as the rotor constituting the positive displacement roughing pump,
A wide-area pump in which a pump portion for transporting a low-pressure gas in a middle vacuum (intermediate flow) region or below is constituted by a positive displacement type has already been proposed (Japanese Patent Application Laid-Open No. Hei 5-72478).

The wide-area vacuum pump shown in FIG. 11 has a first rotating shaft 302 and a second rotating shaft 30 in a housing 301.
3 are housed vertically and rotatably. Cylindrical rotors 304 and 305 are fitted at the upper ends of the two rotating shafts. On the outer peripheral surface of the rotor, screw grooves (a type of screw groove) having different pitches and groove depths are formed at an upper portion (position B) and a lower portion (position A) so as to mesh with each other.

Reference numerals 304 and 305 denote lower screw grooves and a first pump part, and reference numerals 308 and 309 denote upper screw grooves and constitute a second pump part. The closed space formed by these screw grooves and the housing 301 moves from the intake port 310 side to the discharge port 311 side with the rotation of both rotating shafts, and the movement of this space causes the suction / exhaust as a positive displacement pump. Action is obtained. The volume of the sealed space formed by the upper screw grooves 308 and 309 and the housing is equal to that of the lower screw groove 30.
6, 307 and much larger than the volume of the enclosed space formed by the housing. That is, the lower thread groove (A
Part) covers the function as a roughing pump that transports gas at the pressure in the viscous flow area, and the upper thread groove (part B) functions as a mechanical booster that transports gas at a pressure below the intermediate flow area and the intermediate flow area. ing.

On the upstream side (part C) of the rotor 305 coaxially and away from the upper thread groove 309, a momentum transfer type ultra-high vacuum pump (third pump part) is formed.
The gas molecules in the minute gaps between the rotating members 312 and 313 and the fixed members 314 and 315 are given a rotational momentum by the high-speed rotation of the rotating members, and the positive displacement type vacuum pump parts (part B → part A) ) To be transported.

The first rotating shaft 302 and the second rotating shaft 303
AC servo motors 316 and 3 provided for each axis
17, the motor rotates synchronously at a high speed of tens of thousands of rpm. The rotation signals of both shafts are detected by rotary encoders 318 and 319 provided at the lower ends of the respective rotation shafts on the side opposite to the intake port side.

With the above configuration, the intermediate flow region (1 to 10 ^-3)
Since it is possible to greatly improve the exhaust performance of the gas below the torr) and the intermediate flow region, a mechanical booster can be omitted, and the vacuum exhaust system can be significantly reduced in size and simplified.

[0016]

In a semiconductor factory, vacuum pumps having various displacements are used in accordance with a target to be applied. Usually, 200 to 300 vacuum pumps are used per line. .

In the case of a dry roughing pump, for example, five or more pumps having different displacements are used. As an example of a dry pump widely used at present, 700 to 5000 liters / min is covered by product series. Of these, up to 2500 liters / min are handled by roughing pumps with different rotor shapes,
For 3000 liter / min or more, a dry pump is constructed by combining a mechanical pump with a roughing pump.

In the meantime, troubles in vacuum equipment during mass production of a semiconductor factory often cause fatal business losses in some cases. For this reason, great care has been taken to minimize any damage. In the case of a vacuum pump, in principle, periodic maintenance such as replacing the pump body or consumable parts with a spare after a certain period of time before a trouble occurs will be performed. While the vacuum pump is overhauled during this regular maintenance, a spare pump that has already been prepared is used in place to prevent production from stopping.

As described above, in a semiconductor factory where pumps of various displacements are used, spare pumps and parts must be prepared according to each model. It was extremely large.

[0020]

In order to solve the above problems, a vacuum pump according to the present invention comprises: a plurality of shafts housed in a housing; a bearing for supporting rotation of these shafts; A rotor fastened to each of the plurality of shafts, a means for rotating and driving the plurality of shafts while performing a synchronous operation, a suction port and a discharge port for fluid formed in the housing, and the rotor and the housing. A positive-displacement first pump portion for transporting gas in a viscous flow region provided on the discharge port side by utilizing the movement of the enclosed space from the suction port side to the discharge port side, and the suction port In a vacuum pump provided with a positive displacement second pump portion that transports gas at a pressure below the intermediate flow region and the intermediate flow region provided on the side, the first pump portion has a pair of first rotor and the House The second pump portion is coaxially formed of a pair of second rotors and the housing, and the second rotor formed of a separate component from the first rotor is the The vacuum pump is configured to be detachable from the shaft.

[0021]

The first pump portion (corresponding to a roughing pump) and a portion composed of a motor drive portion are used as a basic unit common to pumps, and a second pump portion (corresponding to a mechanical booster) ) Is configured to be detachable. In steady state operation, the second pump is
It is used under low pressure conditions of ^-1 to 10 ^-3 Torr or less. Therefore, unlike the roughing pump in which the size of the exhaust volume has a large effect on the power consumption, the effect of the second pump portion on the motor load is small. In other words, the common basic unit only needs to incorporate a motor with no excess or deficiency for only the roughing pump. By utilizing this point, a vacuum pump that can select a wide range of exhaust performance can be realized by preparing various types of removable rotor and cylinder as the second pump part for one model of the common basic unit it can.

In summary, by fully equipping the first and second pump parts, it can be used as a wide area pump having both functions as a roughing pump and a mechanical booster.

If the second pump section is separated from the common basic unit, only the first pump section can be used as a roughing pump.

By changing the blade shape (groove depth, pitch, etc.) of the second pump portion in a detachable manner, exhaust performance (evacuation speed, vacuum ultimate pressure) can be selected according to the application of the pump. .

The present invention is more effective if an electronic control system in which the two rotating shafts are driven by independent motors and operated synchronously is applied. By adopting the electronic synchronous control, the timing gear accompanying a large torque transmission can be omitted, so that the rotor can be rotated at a high speed of, for example, 10,000 or more. As a result, the performance of the first pump, which is a roughing pump, as well as the performance of the second pump as a high vacuum pump can be dramatically improved. As a result, the second pump can be configured with a sufficiently small exhaust volume (small rotor diameter and length). In other words, the effect of the present invention, in which the pumping performance in the high vacuum region can be changed by variously transferring the second pump based on the common basic unit, is extremely effectively combined with this electronically controlled synchronous operation. realizable.

[0026]

1 and 3 show an embodiment of a vacuum pump according to the present invention. FIG. 1 shows a wide area type and FIG. 3 shows a rough type. First, the wide-area vacuum pump of FIG. 1 will be described.

The first rotating shaft 1 and the second rotating shaft 2 are arranged in an upper housing 3 (first housing), a lower housing 4 (second housing) and a motor case 5 which are composed of upper, middle and lower stages. The bearings 6a, 6b, 7a, 7b support and are housed in the vertical direction. Above each rotating shaft, a pair of cylindrical upper rotors 8, 9 (second rotor) are disposed on the lower side by bolts 52a, 52b via spacers. ), And the lower rotor is fastened to the flanged rotary shaft by bolts 50a and 50b. On the outer peripheral surface of each of the rotors, screw grooves (a type of screw groove) having different pitches and groove depths are formed so as to mesh with each other.

Numerals 12 and 13 are lower thread grooves and a first pump portion, and numerals 14 and 15 are upper thread grooves and constitute a second pump portion. The closed space formed by these screw grooves and the upper and lower housings 3 and 4 moves from the intake port 16 side to the discharge port 17 side (indicated by a dashed line) with the rotation of both rotating shafts. Thus, a suction / exhaust action as a positive displacement pump can be obtained.

Upper screw grooves 14, 15 and upper housing 3
The volume of the closed space formed by
And the volume of the sealed space formed by the lower housing 4. In other words, the lower screw groove (part A) is a roughing pump that transports gas at a pressure in the viscous flow region, and the upper screw groove (part B) is a mechanical pump that transports gas at a pressure below the intermediate flow region and the intermediate flow region. Covers the function as a booster.

Reference numeral 18 denotes an upper cover having a suction port, and 19 denotes a lower case. Rotational position sensors 20 and 21 are provided at the lower ends of the respective rotation shafts, and are accommodated in the lower case which also serves as an oil tank.

Reference numerals 22a and 22b denote motor rotors on the rotating side of the AC servomotor, and reference numerals 23a and 23b denote motor stators on the fixed side. The first rotary shaft 1 and the second rotary shaft 2 are rotated at a high speed of 10,000 rpm or more in the embodiment by the AC servomotor. The rotation signals of both axes are output from rotation position sensors 20 and 2.
1 is detected.

Now, the two rotating shafts 1 and 2 in this embodiment are described.
The following method was used for the synchronization control. That is, the output pulses from the rotational position sensors 20 and 21 are compared with a set command pulse (target value) set assuming a virtual rotating rotor. The deviation between the target value and the output value (rotation speed, rotation angle) from each of the sensors 20 and 21 is processed by a phase difference counter, and the rotation of the servo motor of each axis is corrected so as to eliminate this deviation. Controlled.

In the vacuum pump of the embodiment, each rotor 1
Contact prevention gears 24 and 25 for preventing the rotors from contacting each other are provided in a form directly connected to the lower ends of 0 and 11.

The vacuum pump according to the present invention has the following features. By fully equipping the first and second pump parts, it can be used as a wide area pump (FIG. 1) having both functions as a roughing pump and a mechanical booster.

If the second pump part is separated from the pump body, only the first pump part will roughly pump (FIG. 3)
Can be used as

The blade shape of the second pump part (groove depth,
By changing the pitch or the like, the exhaust performance can be selected according to the application of the pump.

The above can be realized by constructing the pump as described in the embodiment of FIG. In the embodiment, the whole pump is configured such that the transfer from the above to the above or vice versa is as easy as possible. That is, as shown in FIG. 2, the first pump portion (A
The second pump part (part B) is configured to be detachable from the common basic unit, with the part composed of the part) and the motor drive part as the basic unit (Z part) common to the pumps. However, in order for the integration by the combination of the upper and lower rotors to function as a wide-area vacuum pump, the phase relationship between the screw groove of the upper rotor, the screw groove of the lower rotor, and the contact prevention gear is accurately adjusted. It is assumed that

In the embodiment, the following configuration is adopted by the following configuration.
The phase relationship of point parts can be set accurately and easily. That is, the lower rotors 10, 11 are connected to the bolts 50a, 50
b to the rotating shafts 1 and 2 and the lower spacer 27
a, 27b were fastened to the lower rotor by bolts 51a, 51b. The lower spacers 27a, 27b and the upper rotors 8, 9 were fastened by bolts 52a, 52b.

The assembling procedure is as follows. When assembling the basic common unit, the contact prevention gear 2
The lower rotors 10 and 11 are fastened to the rotating shafts 1 and 2 while adjusting the phase relationship between the lower screw grooves 4 and 25 and the lower screw grooves 12 and 13. At this time, upper screw grooves 14 and 15 when the upper rotors 8 and 9 are fastened are formed on the upper end surfaces of the lower rotors 10 and 11.
The lower spacers 27a and 27b having the mounting screw holes formed in consideration of the phase relationship are mounted. By such a method, the upper thread grooves 14, 1 which usually require a great deal of labor
5 can simplify the phase matching operation.

The case of shifting from the wide area pump to the roughing pump is as follows. Upper rotors 8, 9 mounted on lower rotors 10, 11 via upper spacers 26a, 26b and lower spacers 27a, 27b;
The upper cover 18 is removed from the basic common unit. Thereafter, when only the upper cover 18 is mounted on the lower housing 4 again, the roughing pump shown in FIG. 3 is obtained.

The upper spacers 26a, 26b are provided with seal members 28a, 28b for sealing between the upper rotors 8, 9 and the upper spacer. This seal member can prevent high-pressure gas from entering the suction side 16 from the space 54 in which the bearing and the motor are housed and the space 55 between the first and second pumps. As a result, in the embodiment of the wide area vacuum pump, a clean high vacuum of 10 ⁻⁵ torr or less could be realized.

Although the configuration for exactly matching the phase relationship between the upper and lower rotors has been described by way of example, the following method may be used. That is, before mounting the rotating member on the rotating shaft, the upper rotor and the lower rotor are first fastened. At this time, the phase matching relationship between the thread grooves of the upper and lower rotors has already been set. Thereafter, the integrated upper and lower rotors are fastened to the rotating shaft.

FIG. 4A is an exhaust characteristic (exhaust speed with respect to intake pressure) as a wide-area pump when both the first and second pumps are provided, and FIG. 1 shows an example of the exhaust characteristics.

In the vacuum pump of the embodiment, a thread groove type which is a kind of a screw type having a thread groove on an outer peripheral portion of the rotor is employed for both the first pump portion and the second pump portion.
In the embodiment, the respective thread grooves of the first pump portion and the second pump portion are formed at the same pitch, but the pitch (or groove depth) of these thread grooves is continuous toward the discharge side. The shape may be such that it gradually increases.

The upper and lower housings may have an integral structure. However, if the upper and lower housings are divided according to the upper and lower rotors as in the present embodiment, the range of selection of the exhaust characteristics of the second pump can be expanded, and when the roughing pump is used. Thus, downsizing can be achieved.

If a momentum transfer type pump of, for example, a screw groove type is provided on one axis of the second pump, an ultra-wide area vacuum pump capable of covering up to an ultra-high vacuum area can be obtained. In this case, a momentum transfer type screw groove may be formed on one upper part of the second rotor, and a second housing adapted to the shape may be provided. Alternatively, the third threaded rotor and the housing may be configured to be detachable from the second component.

The rotors 500 of the first and second pumps to which the present invention can be applied include roots type (FIG. 5), gear type (FIG. 6), single-lobe type (FIG. 7 (a)), It may be a double-lobe type (FIG. 7B), a screw type (FIG. 8), or a screw type (not shown) composed of a pair of male and female rotors. Regardless of the type of pump, the method and configuration for adjusting the phases of the first and second rotors may be the same as those of the thread groove type of the embodiment.

[0048]

According to the present invention, if the rotor and the cylinder of the high vacuum pump are prepared in various pairs, a vacuum pump having various exhaust characteristics required for the film forming chamber and the load lock chamber can be used in common. It can be realized simply by mounting the pair of high vacuum components on the unit.

Further, by utilizing the fact that the rotor can be downsized by applying the electronically controlled high-speed synchronous operation, and a dynamically stable wide-area dry pump can be constructed even with a cantilevered support structure, the attachment and detachment of a high vacuum pump can be realized. Becomes easier.

The vacuum pump according to the present invention can be widely applied to a film forming chamber, a load lock chamber, a spare chamber, and the like. Usually, in a semiconductor factory, more than 1,000 pumps having various exhaust characteristics are used, and a considerable portion thereof can be covered by a model in which the pump of the present invention is as small as possible. As a result, the pump and its maintenance parts can be easily shared in common, and the management effect is extremely large.

[Brief description of the drawings]

FIG. 1 is a sectional view of a vacuum pump according to an embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between components in the embodiment.

FIG. 3 is a sectional view of the roughing pump.

FIG. 4 is an exhaust characteristic diagram of a wide area pump and a roughing pump according to an embodiment of the present invention.

FIG. 5 is a configuration diagram of a pump to which the present invention can be applied.

FIG. 6 is the same configuration diagram

FIG. 7 is the same configuration diagram

FIG. 8 is the same configuration diagram

FIG. 9 is a sectional view of a conventional roughing pump.

FIG. 10 is a sectional view of a conventional mechanical booster pump.

FIG. 11 is a sectional view of a wide-area vacuum pump already proposed by the present inventors.

[Explanation of symbols]

 3, 4 Housing 10, 11 Shaft 8, 9 Second rotor 10, 11 First rotor 16 Inlet 17 Outlet

Claims (9)

[Claims] A plurality of shafts housed in a housing;
A bearing for supporting the rotation of these shafts, a rotor fastened to each of the plurality of shafts, a means for rotating and driving the plurality of shafts synchronously, and a suction of a fluid formed in the housing The gas is transported in the viscous flow region provided on the discharge port side by utilizing the movement of the closed space formed by the port and the discharge port and the rotor and the housing from the suction port side to the discharge port side. A vacuum pump provided with a positive displacement first pump portion and a positive displacement second pump portion for transporting gas at a pressure lower than the intermediate flow region and the intermediate flow region provided on the suction port side, One pump portion is constituted by a pair of first rotors and the housing, and on the same axis, the second pump portion is constituted by a pair of second rotors and the housing, and the first rotor is Separate part Vacuum pump said second rotor in configured is characterized in that detachable from the shaft 2. The vacuum pump according to claim 1, further comprising a plurality of motors for independently rotating and driving the plurality of shafts, and means for synchronously controlling the plurality of motors. 3. The position of a fastening member for fixing the second rotor to the shaft is determined so that the phase relationship between the second rotor and the first rotor is accurately set. Item 7. The vacuum pump according to Item 1. 4. The vacuum pump according to claim 1, wherein the first and second rotors, whose phase relations are set, can be fastened to a shaft in a fastened state. 5. The vacuum pump according to claim 1, wherein the second rotor is fastened to the first pump portion or the shaft via a spacer. 6. A housing, comprising: a first housing having substantially the same height as the first rotor; and a second housing having substantially the same height as the second rotor. Item 7. The vacuum pump according to Item 1. 7. The vacuum pump according to claim 1, wherein the first pump portion is of a thread groove type or a screw type. 8. The vacuum pump according to claim 1, wherein the second pump portion is of a thread groove type or a screw type. 9. The vacuum pump according to claim 1, wherein sealing means is provided between the second rotor and the rotating shaft or the first rotor.