CN1541307A - Vacuum exhaust device and operation method of vacuum exhaust device - Google Patents

Abstract

Pairs of rotors (R1, R2, R3, R4, R5 and R6) driven rotationally by a motor (22) are disposed in the body (21) of a main pump (20) comprising a multistage Roots dry vacuum pump. A suction opening (23) communicating with the rotor chamber of the rotor R1 is provided in the upper wall portion at the left end of the body (21). A delivery section (24) communicating with the delivery side of the rotor chamber of rotor R6 on the final stage is coupled to an exhaust pipe (25) and is provided with a silencer (26) and further coupled to a check valve (28) through a pipe (27). The check valve (28) has its forward direction toward the atmospheric side. The delivery section (24), or a delivery section (24') at the side intermediate stage, is coupled to an auxiliary pump (30) having an exhaust capacity smaller than that of the main pump (20). When the motor (22) is driven, gas exhausted through rotation of the rotors (R1-R6) is carried sequentially to the downstream side from the rotor chambers and a vacuum processing chamber coupled to the suction opening (23) is exhausted. The delivery section (24) on the final stage is exhausted by driving the auxiliary pump (30), and the pressure is reduced. Consequently, the burden of the exhaust action on the rotor (R6) on the final stage or the rotor (R5) on the intermediate stage is lessened, and the power consumption of the motor (22) can be reduced significantly as compared with the prior art.

Description

Vacuum exhaust device and operation method of vacuum exhaust device

technical field

The present invention relates to, for example, a vacuum evacuator for semiconductor manufacturing equipment, and more particularly, to an energy-saving vacuum evacuator for reducing power consumption and an operating method of the vacuum evacuator.

Background technique

As vacuum pumps for early semiconductor manufacturing equipment, oil rotary vacuum pumps are often used. This pump is generally a vacuum pump with a structure that consumes less power and can easily obtain a lower attained pressure. When using it in a semiconductor manufacturing device, it is necessary to pay attention to the following points.

① Among the gases used in semiconductor manufacturing equipment, most of them are highly reactive gases. If such gases are exhausted, reaction products will be generated due to the reaction with vacuum pump oil. According to this, the pump may not be able to Rotation, or poor lubrication caused by pump oil deterioration.

② The vapor of the vacuum pump oil diffuses into the vacuum treatment chamber, causing pollution.

③Used vacuum pump oil often contains toxic substances such as arsenic compounds and phosphorus compounds, and it requires high processing costs for disposal as industrial waste. On the other hand, man-hours are also required for management .

For these reasons, in recent years, instead of oil rotary vacuum pumps, dry vacuum pumps that do not use vacuum pump oil are used. The dry vacuum pump described here can vacuum exhaust from atmospheric pressure, is a mechanical vacuum pump that does not have sealing oil (vacuum pump oil) in the suction chamber, and variable displacement Roots type and claw type (Cro-one type) are often used. ), spiral. These pumps have a double-shaft structure, and a pair of rotors rotate in opposite directions by maintaining a small gap between them to perform vacuum exhaust. Since there are no contact parts, the life is long, and it can also be sucked from semiconductor manufacturing equipment. Solid components contained in the gas are discharged, and corrosion resistance can be easily provided even against corrosive gases.

In this way, the vacuum pumps used in semiconductor manufacturing equipment are replaced with dry vacuum pumps that do not use vacuum pump oil. Compared with oil rotary vacuum pumps, dry vacuum pumps have a problem of greater power consumption. In particular, there is a desire to suppress the power consumption of dry vacuum pumps to 50% or less because of environmental concerns that require the reduction of energy consumption and the reduction of semiconductor manufacturing costs.

For example, the Roots-type dry vacuum pump is a rotating body with multiple rotors adjacent to the rotating shaft. The opposing rotors maintain a small gap between them and rotate in the opposite direction to suck and exhaust gas. The pump room is composed of 3 or 6 stages, and the pumping action is performed sequentially in the pump rooms of each level. In this pump, since the gas pressure increases as the exhausted gas moves from the front part to the rear part, the displacement of the rear part may be smaller than that of the front part. When multiple Roots-type rotors are installed on the same shaft, the respective rotors currently have the same outer shape for ease of processing and maintenance of synchronization between the rotors. Therefore, in order to gradually reduce the exhaust gas volume from the gas suction side to the discharge side, the thickness of the rotor is gradually reduced to cope.

Here, the compression of the exhausted gas in the Roots type dry vacuum pump is discharged into the space formed by the concave part on the surface of the rotor and the casing. Once the gas is enclosed, the space communicates with the discharge side space by the rotation of the rotor. At this moment, the gas passing through the discharge side flows back into the above-mentioned space. In the Roots-type dry vacuum pump, an arrival pressure of about 1 to 0Pa can be obtained, and from the arrival pressure to around 3kPa, it is used as a common pressure. The outlet pressure is constant at atmospheric pressure. Therefore, in order to maintain a vacuum on the suction side, it is necessary to push back the gas that has flowed back into the rotor chamber during the compression stroke, and in the final stage that blocks the backflow from the atmospheric pressure, the power required by the entire pump is used to push back the gas. About 70% to 80% of it.

In the above-mentioned multi-stage Roots-type dry vacuum pump, the job of the final stage is to push back as little gas as possible. Therefore, as described above, the thickness of the rotor is reduced to reduce the discharge volume of the pump's rear stage. In this way, the current situation is to reduce the power required in the normal pressure range of the pump by setting the discharge volume of the final stage to be relatively small for energy saving.

The claw type dry vacuum pump is different from the Roots type only in the shape of the rotor, and the exhaust principle is exactly the same. On the other hand, the screw type dry vacuum pump is the same as the Roots type in that the space formed by the screw grooves of two screws is moved in the axial direction, the gas is transported, and the gas in the discharge part flows into the space formed by the screw grooves to be compressed. . Since the screw grooves are continuous, it is possible to obtain a structure in which the exhaust volume to the rear stage is arbitrarily reduced and the pitch of the screw grooves is continuously reduced, as in the Roots type and claw type. However, since there is a limit to changing the pitch of the screw grooves, efforts have been made to combine rotors with different pitches into a block and reduce the exhaust volume of the final stage.

To further explain this, as shown in Fig. 18, if the rotors have the same size, as shown in Fig. 21, the discharge speed relative to the suction pressure changes as a Two are the same size, the middle stage is smaller than it, and the two rotors of the latter stage are the smallest, then the relationship between the suction pressure and the exhaust speed changes like b. In addition, as shown in FIG. 20 , if the rotor of the final stage is smaller, the exhaust velocity changes as shown in c in FIG. 21 . Fig. 22 shows the power consumption of the suction pressure with respect to those shown in Fig. 18, 19 and Fig. 20. As shown by c', b' and a', the power consumption is below 10 ² Pa which is a normal pressure for semiconductor manufacturing equipment. In this case, the power consumption is the smallest in the case of Fig. 20, followed by Fig. 19, and Fig. 18 is the largest.

The setting of the exhaust volume of the final stage differs depending on the application of the pump. For example, in a multi-stage Roots-type dry vacuum pump, setting the exhaust volume of the final stage to about 50% of that of the first stage is to generate more heat of compression in the usual pressure range. That is, in the decompression CVD apparatus or etching apparatus of the semiconductor manufacturing apparatus, the gas generated during the reaction process contains substances that precipitate as solids with a concentration exceeding the saturated vapor pressure in the vacuum evacuation apparatus. To exhaust these gases, it is necessary to keep the temperature of the dry vacuum pump at a high temperature of about 100 to 60° C. to prevent precipitation. For this purpose, an exhaust speed ratio of about 50% is adopted that enables the dry vacuum pump to be heated more efficiently due to the heat of compression.

In addition, in a sputtering device or a vapor deposition device, the exhausted gas is mainly an inert gas such as argon or helium, and since there is no need to increase the temperature of the dry vacuum pump, a dry vacuum pump with as little power consumption as possible is required. In this case, the exhaust volume of the final stage is set at about 20 to 5% of that of the first stage. With this setting, the power consumption at the time of reaching the pressure can be reduced by 30 to 60% compared to a dry vacuum pump in which the exhaust volume of the final stage is about 50% of that of the first stage.

However, in dry vacuum pumps that do not need to be used at high temperatures, further energy saving can be achieved by reducing the exhaust volume of the final stage to 20% or less of the exhaust volume of the first stage, but this poses a mechanical obstacle. For example, if the exhaust volume of the final stage is about 25% of that of the first stage, in a dry vacuum pump with a maximum exhaust velocity of 80m ³ /Hr, the rotor thickness of the first stage is about 30mm. There are many cases. In this case, the rotor thickness of the final stage is 7.5mm. Because the strength of the rotor itself is reduced, it is difficult to obtain the perpendicular angle between the rotor side and the axis during processing, and it is difficult to ensure the distance between the rotor side and the partition wall. The gap is from 0.1mm to 0.2mm in matter.

On the other hand, in Japanese Patent Laid-Open No. 6-129384, a vacuum exhaust device is disclosed, by combining a first vacuum pump with a large exhaust volume and a second vacuum pump with a small exhaust volume but sufficient low pressure. Link, to reduce the total power consumption, especially as shown in Figure 23, discloses a kind of vacuum exhaust device 2, connects the first exhaust hole 5 and the second exhaust hole 6 with exhaust pipe 7, in the way , the control valve 8 for opening and closing the exhaust pipe 7 is provided, and the control valve 8 is opened and closed by the intake side pressure of the first pump 3 to further reduce the total power consumption. The first exhaust hole 5 is in the above-mentioned The second exhaust hole 6 is formed on the exhaust side of the second pump 4 . In addition, in FIG. 23 , the first vacuum pump 3 is standardized by using a direct-acting vacuum pump, and 9 is an adsorption tower for treating the reaction gas contained in the exhaust gas.

The start-up of the vacuum exhaust device 2 is performed as follows. Fig. 23 shows the state after the start of exhaust, and the control valve 8 is opened. That is, when the first pump 3 and the second pump 4 are started, the suction pressure of the first pump 3 is at the same level as the atmospheric pressure, and the amount of discharged gas is large. When the pressure is not lower than the atmospheric pressure, the control valve 8 is opened, and the gas with a sufficiently high density is discharged through the first pump 3 and the second pump 4 .

Thereafter, if the discharge side of the first pump 3 is exhausted by the second pump 4 and reaches a predetermined pressure below atmospheric pressure, the control valve 8 is closed, and only the second exhaust hole formed on the exhaust side of the second pump 4 6 Connect to the exhaust side outside the pump. At this time, since the discharge side of the first pump 3 is maintained at a sufficiently low pressure by the second pump 4, the backflow gas to the first pump 3 can be greatly reduced, and the necessary power for pushing back to the backflow gas can be reliably reduced. Energy saving of the electric power consumption of the 1st pump 3 is aimed at.

However, according to this vacuum evacuation device 2, although the power consumption of the first pump 3 can be reliably reduced, it is not necessarily possible to achieve constant evacuation when the entire vacuum evacuation system including the second pump 4 is viewed. High efficiency and energy saving.

However, conventionally, a vacuum evacuation device connected to a vacuum processing chamber for manufacturing a semiconductor device is a piping diagram as shown in FIG. 24 . In Fig. 24, the vacuum exhaust device 10 is configured with a main valve 13 with a large diameter on the exhaust pipe 12. The exhaust pipe 12 communicates with the vacuum processing chamber 1 and the dry vacuum pump 20 with an exhaust speed of 1000 L/min, and is connected with the main valve. A small-diameter bypass valve 14 is installed in parallel with the valve 13 , and a pressure gauge 19 for measuring the pressure of the vacuum processing chamber 1 is installed on the exhaust pipe 12 .

Generally, in a semiconductor manufacturing apparatus, since the fine particles present in the vacuum processing chamber 1 fly and adhere to semiconductor wafers placed in the vacuum processing chamber 1, defective products may occur. When the processing chamber 1 is vacuum exhausted, the following start-up method is adopted. In the state where the main valve 13 and the bypass valve 14 are closed, the dry vacuum pump 20 is started, and the bypass valve 14 is opened for slow exhausting. The main valve 13 is opened after confirming that the vacuum processing chamber 1 has reached a predetermined pressure, or after confirming that a predetermined exhaust time has elapsed.

In the case of slow exhaust through the valve operation, that is, through the bypass valve 14 arranged on the main valve 13, in the case of slow exhaust, in addition to setting the bypass valve 14, it is necessary to make the main valve according to the pressure of the vacuum processing chamber 1. Control device for opening of valve 13.

As a method of slowly exhausting other than this, there is also a method of installing a butterfly valve capable of controlling the opening of the valve body instead of the main valve 13 and the bypass valve 14, and making the opening small at the initial stage of exhausting. As the pressure of the vacuum processing chamber 1 decreases, the degree of opening increases. In this case, the butterfly valve itself and the device for controlling the degree of opening of the valve body are expensive, resulting in an increase in cost.

In addition, in the vacuum evacuation device 2 of JP-A-6-129384 shown in FIG. 23 , when the evacuation is started, the first pump 3 and the second pump 4 are used to start the method of evacuation. In the case of the vacuum processing chamber 1, fine particles fly, and contamination of semiconductor wafers and the like is likely to occur.

It is an object of the present invention to provide a vacuum exhaust device that can achieve high energy-saving effects by simply adding a simple structure to a general-purpose dry vacuum pump.

Furthermore, the object of the present invention is to provide an operating method related to the operating method of the above-mentioned vacuum exhaust device, which can perform slow exhaust without installing an apparatus for slow exhaust.

Contents of the invention

In order to achieve the above objects, the vacuum exhaust device and its operating method of the present invention have the following configurations.

In the vacuum exhaust device of the present invention, the suction side of the auxiliary pump is connected to the discharge side of the pump chamber of the middle stage or the last stage of the main pump. It is preferable that the auxiliary pump has a smaller displacement than the main pump, and it is also preferable that at least one pump chamber of the rear stage of the main pump is smaller than that of the front stage. The discharge piping is connected to the discharge side of the pump chamber of the last stage of the main pump, and a check valve is connected to the discharge piping. The check valve only allows the gas to flow to the atmosphere side. It is preferable to connect the auxiliary pump and the check valve in parallel. . The check valve can also be connected in series, preferably with a spherical valve body that can float in the valve body. , if it is below its pressure, it will fall to the valve seat below due to its own weight and close the valve. In addition, it is preferable that the spherical valve body is composed of a hollow metal ball and the surface is covered with rubber. In addition, when connecting two check valves in series, it is preferable to connect the space where the two check valves are connected to the suction side of the auxiliary pump.

In addition, the vacuum exhaust device of the present invention has a main pump, a check valve, and an auxiliary pump. The check valve is connected to the discharge side of the main pump and only allows gas to flow from the main pump to the atmosphere side. The check valve is arranged side by side on the discharge side of the main pump, and the exhaust volume of the main pump is smaller than that of the main pump. Pump running at air speed. In this case, it is preferable that the main pump is a variable displacement dry vacuum pump or a composite pump in which multiple stages of the dry vacuum pump are connected in series. In addition, a plurality of main pumps may be arranged in parallel, and the suction side of the auxiliary pump may be connected to the discharge side of each main pump. In addition, the arrival pressure of the auxiliary pump is less than or equal to 20kPa, preferably a rotor type (Gade type), piston type, diaphragm type (membrane type) or scroll type vacuum pump.

In addition, the operating method of the present invention is to use a vacuum exhaust device to start the auxiliary pump when the vacuum processing chamber is exhausted from atmospheric pressure or its vicinity, and then start the main pump after the vacuum processing chamber reaches the specified pressure. Slow exhaust can be performed by setting up an instrument device for slow exhaust, the vacuum exhaust device has: a main pump connected to the vacuum processing chamber; connected to the discharge side of the main pump, only allowing gas from the main pump to the atmosphere A side flow check valve; an auxiliary pump that is arranged in parallel on the discharge side of the main pump with respect to the check valve and has a smaller displacement than the main pump. In addition, the operation method can also be to first start the auxiliary pump, and before the vacuum processing chamber reaches the specified pressure, start the main pump to rotate at a low speed with a small displacement, and gradually increase the number of revolutions according to the pressure of the vacuum processing chamber. .

Description of drawings

FIG. 1 is a diagram showing a vacuum evacuation device in an embodiment of the present invention, and is a schematic diagram of a case where a multi-stage Roots-type dry vacuum pump is used as a main pump.

2 is a diagram showing a modified example of the vacuum evacuation device in the embodiment of the present invention, and is a schematic diagram of a case where a multi-stage Roots-type dry vacuum pump is used as a main pump.

3 is a diagram showing a modified example of the vacuum evacuation device in the embodiment of the present invention, and is a schematic diagram of a case where a multi-stage Roots-type dry vacuum pump is used as a main pump.

4 is a diagram showing a modification example of the vacuum evacuation device in the embodiment of the present invention, and is a schematic diagram of a case where a multi-stage Roots-type dry vacuum pump is used as a main pump.

5 is a diagram showing a modification of the vacuum evacuation device according to the embodiment of the present invention, and is a schematic diagram of a case where a multi-stage Roots-type dry vacuum pump is used as a main pump.

6 is a cross-sectional view showing an example of a check valve used in the vacuum exhaust device of the present invention.

7 is a schematic piping configuration diagram showing a modified example of the vacuum evacuation device in the embodiment of the present invention.

8 is a cross-sectional view showing an example of a check valve used in the vacuum evacuation device shown in FIG. 7 of the present invention.

9 is a schematic piping configuration diagram showing a modified example of the vacuum evacuation device in the embodiment of the present invention.

Fig. 10 is a cross-sectional view showing an example of a check valve used in the vacuum evacuation device shown in Fig. 9 of the present invention.

Fig. 11 is a diagram showing a schematic piping configuration of the vacuum exhaust device in the embodiment of the present invention.

Fig. 12 is a diagram illustrating the operation of the vacuum exhaust device in the embodiment of the present invention, showing the relationship between the suction pressure of the main pump and the power consumption of the entire device.

13 is a diagram for explaining the operation of the vacuum exhaust device in the embodiment of the present invention, showing the relationship between the exhaust speed ratio of the auxiliary pump relative to the main pump and the power consumption ratio.

FIG. 14 is a graph showing the relationship between the discharge speed and power consumption of a typical auxiliary pump.

FIG. 15 is a graph showing power consumption characteristics of the vacuum evacuation device in the embodiment of the present invention.

Fig. 16 is a graph showing the relationship between the suction pressure and the exhaust velocity of the vacuum exhaust device in the embodiment of the present invention.

17 is a schematic piping configuration diagram showing a modified example of the vacuum evacuation device in the embodiment of the present invention.

Fig. 18 is a schematic view showing a multi-stage Roots-type dry vacuum pump, showing a case where the rotors of the multiple stages are equal in size.

Fig. 19 is a schematic view showing a multi-stage Roots-type dry vacuum pump, showing a case where the size of the rotor is changed by the front stage, the middle stage, and the rear stage.

FIG. 20 is a schematic diagram showing a multi-stage Roots-type dry vacuum pump, showing a case where the two rotors of the rear stage are made smaller than those in FIG. 19 .

FIG. 21 is a graph showing the relationship between the suction pressure and the exhaust velocity of the multi-stage Roots-type dry vacuum pump in the case of using the rotors of FIGS. 18 , 19 and 20 .

FIG. 22 is a graph showing the relationship between suction pressure and power consumption of a multistage Roots-type dry vacuum pump using the rotors shown in FIGS. 18 , 19 , and 20 .

Fig. 23 is a schematic diagram showing a conventional vacuum exhaust device capable of reducing power consumption.

Fig. 24 is a schematic piping configuration diagram of a conventional vacuum exhaust device.

Detailed ways

Embodiments of the vacuum evacuation device of the present invention will first be described with reference to FIGS. 1 to 5 by taking a case where a multistage Roots-type dry vacuum pump is used as an example as a main pump. In these figures, a multi-stage Roots-type dry vacuum pump is schematically shown.

That is, in the embodiment of the vacuum exhaust device 10 shown in FIG. 1 , in the main body 21 of the multi-stage Roots type dry vacuum pump 20 (main pump), a pair of rotors _R1 driven by the rotation of the motor 22 are respectively provided. , R ₂ , R ₃ , R ₄ , R ₅ and R ₆ . In addition, on the left end upper wall portion of the main body 21, a suction port 23 communicating with the rotor chamber of the rotor R1 is provided, and an exhaust pipe 25 having a silencer 26 is connected to the discharge side communicating with the rotor chamber of the last-stage rotor _R6 . The discharge part 24 is further connected to a check valve 28 through a pipe 27 . The positive direction of the check valve 28 is the direction to the atmosphere side. In addition, an auxiliary pump 30 having a displacement smaller than that of the main pump 20 is connected to the discharge unit 24 .

Next, its function will be described.

When the motor 22 is driven, the gas exhausted by the rotation of the rotors R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ is sequentially transferred from the respective rotor chambers to the downstream side and discharged to the suction port. 23 connected vacuum processing chamber (not shown). The pressure of the discharge part 24 at the last stage is the closest to the atmospheric pressure, and according to the present invention, decompression and exhaust can be performed by driving the auxiliary pump 30 . Therefore, the burden of the exhaust action by the rotor of the final stage can be greatly reduced. That is, the power consumption of the motor 22 can be significantly reduced compared with conventional ones.

FIG. 2 shows a modified example of the vacuum evacuation device 10 in the embodiment of the present invention, and parts corresponding to those in the embodiment in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

That is, according to the present embodiment, the discharge part 24 of the last stage of the main pump 20' is connected to the exhaust pipe 25 having the silencer 26 through the opening of the main body 21', and is further connected to the check valve 28 through the pipe 27. connected to the atmosphere. Further, an auxiliary pump 30 is connected through a pipe 31 parallel to the exhaust pipe 25 . The discharge port of the auxiliary pump 30 is connected to the atmosphere side of the check valve 28 through a pipe 32 . In this embodiment, not only can the same energy-saving effect as that of the embodiment shown in FIG. Even if the auxiliary pump 30 fails, the performance of the main pump 20' can be maintained by flowing through the exhaust pipe 25.

FIG. 3 shows a modification of the vacuum exhaust device 10 in the embodiment shown in FIG. 2. According to this embodiment, since the auxiliary pump 30 is connected in parallel with the check valve 28 through the pipes 31 and 32, it can be understood that The same effect as that of the embodiment shown in FIG. 2 can be achieved.

4 and 5 show modifications of the vacuum exhaust device 10 in the embodiment shown in FIGS. 1 and 2 . According to these embodiments, the intermediate stages of the main pumps 20A and 20B are provided with pumps different from the final stages. The discharge part 24' of the discharge part 24 connects the auxiliary pump 30' to the discharge part 24'. In this way, the pressure of the middle stage of the main pumps 20A, 20B is reduced, and by reducing the burden of the exhaust action by the rotor of the middle stage, the burden of the exhaust action by the rotor of the final stage is also reduced. burden. That is, the power consumption of the motor 22 is reduced compared with conventional ones.

In the above-mentioned embodiment, the paired rotors R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , and R ₆ all have the same size. Instead of these, as shown in FIGS. 19 and 20 , The size of the rotor is gradually reduced from the front stage to the rear stage. In this case, it can be seen that power consumption can be further reduced compared to the above-described embodiment.

In addition, the main pump 20 is not limited to a multi-stage Roots type dry vacuum pump, and the same effect can be obtained in a displacement type dry vacuum pump such as a screw type or a claw type.

Next, the configuration of the check valve 28 used in the embodiment of the present invention will be described with reference to FIG. 6 .

The check valve 28 has a housing 40 , a valve chamber 44 , an annular valve seat 45 , a spherical valve body 46 and a stopper 47 . The side cylindrical lower body 42 constitutes; the valve chamber 44 is formed between the upper body 41 and the lower body 42; the annular valve seat 45 is formed at the lower body 42 side end of the valve chamber 44; the spherical valve The body 46 can be seated or disengaged relative to the valve seat 45; the stopper 47 is used to limit the lifting action of the spherical valve body 46 formed on the upper body 41 side of the valve chamber 44 above a regulation.

An annular sealing ring 48 is installed on the joint surface of the upper body 41 and the lower body 42, and a plurality of bolt members 43 are used to combine the upper body 41 and the lower body 42 to make the two sealingly integrated. The spherical valve body 46 is made of, for example, a hollow stainless steel ball, and its surface is covered with a thin rubber film. In the present embodiment, the spherical valve body 46 has a self-weight of about 50 g, and when the pressure on the inlet side of the check valve 28 is about 700 Pa higher than the atmospheric pressure, it is lifted (raised) upward in FIG. 6 . As shown in the figure, the stopper 47 is composed of four claws protruding downward at intervals of 90° along the circumferential direction of the cylindrical lower end portion of the upper body 41 . Therefore, the spherical valve body 46 is lifted, and the gas flowing into the valve chamber 44 passes between the claws constituting the stopper 47 and flows out to the atmosphere side.

Since the check valve 28 having the above-mentioned structure has a small fluid resistance and can be opened by a slight pressure rise on the inlet side, it can also follow early pressure fluctuations. Generally, in the variable displacement type pump used as the main pump 20, the gas in the pump discharge part 24 repeatedly flows back into the rotor chamber or is pushed out from the rotor chamber, so the gas in the pump discharge part 24 pulsates. If the intake gas amount of the main pump 20 decreases, the valve body will repeatedly be seated and de-seated from the valve seat due to the influence of the pulsation here. In this case, if the followability of the valve body to the pulsation is poor, there will be no time for the valve body to be seated on the valve seat, and the suction side of the auxiliary pump 30 will remain open to the atmospheric pressure, and the discharge portion 24 of the main pump 20 will not be released. To decompress. Therefore, in this embodiment, the valve body of the check valve 28 is made into a spherical shape ( 46 ), and the check valve 28 can be opened and closed only by its own weight, thereby improving the followability to pulsation.

However, if the number of revolutions of the rotor of the main pump 20 increases, it may not be able to follow up. For example, in the case of a screw-type dry vacuum pump, before the rotation speed of the rotor reaches 3600rpm, it can completely follow. If it reaches 6000rpm, the spherical valve body 46 of the check valve 28 cannot follow the pulsation of the gas pressure of the discharge part 24. When the seat should be seated on the valve seat 45, the seat may not be seated at all. Therefore, although it is conceivable to use a spring with a small spring coefficient and good followability to press the spherical valve body 46 onto the valve seat 45, this method not only causes a large pressure loss on the exhaust pipeline due to the existence of the spring, but also The gas pressure required to open the check valve 28 by only floating the spherical valve body 46 is increased by an amount equivalent to the pressing force of the spring. In addition, although a method of increasing the displacement of the auxiliary pump 30 to reduce the gas pressure of the discharge part 24 of the main pump 20 early is also conceivable, but this method increases power consumption and reduces the energy-saving effect.

Therefore, in this case, as shown in the vacuum exhaust apparatus 10 of FIG. 7, two check valves 28a and 28b are connected in series. The number of check valves connected in series is not limited to two, but three or more are also possible. In addition, as shown in FIG. 8, the 1st check valve 28a and the 2nd check valve 28b are connected in series and have the same shape as the check valve 28 shown in FIG.

In this way, in the vacuum exhaust device 10 of FIG. 7, as the main pump 20, the rotor of the screw type dry vacuum pump is rotated at 6000 rpm to exhaust the vacuum processing chamber. The first check valve 28a and the second check valve The valve 28b operates accurately without being affected by the pressure pulsation at the discharge part of the screw type dry vacuum pump 20, and the power consumption can be reduced by about 70% compared with the case of simply using the screw type dry vacuum pump.

In addition, as a modified example of this embodiment, as shown in FIGS. 9 and 10 , the connecting portion of the first check valve 28 a and the second check valve 28 b may be connected to the suction port of the auxiliary pump 30 through a pipe 29 . side. Accordingly, more stable decompression can be performed.

In addition, FIG. 11 shows a schematic piping configuration of the vacuum evacuation device 10 according to the embodiment of the present invention. The main valve 13 and the pressure gauge 19 for measuring the degree of vacuum are installed on the exhaust pipe 12. The exhaust pipe 12 connects the vacuum processing chamber 1 and the main pump 20 composed of a single dry vacuum pump. A check valve 28 is connected to the pipe 25 , and an auxiliary pump 30 parallel to the check valve 28 is also connected. On the auxiliary pump 30, a dry pump whose exhaust speed is about 10% of that of the main pump 20 is used. On the check valve 28, a spherical valve body capable of floating in the valve chamber is used as shown in FIG. The check valve is a check valve that opens when the pressure is about 700 Pa higher than the atmospheric pressure, and closes when the lower valve seat is lowered by its own weight when the pressure is lower than that. The downstream side of the exhaust pipe 15 is connected to an exhaust treatment device (not shown). In addition, a pump for high vacuum exhaust such as a turbomolecular pump may be connected to the upstream side of the main pump 20 .

In this embodiment, the main pump 20 is composed of a displacement-type Roots-type dry vacuum pump. Of course, it is not limited to this, and other variable-displacement dry vacuum pumps of the so-called claw type or screw type can also be used. .

As the auxiliary pump 30, a pump having a low power consumption and an efficient structure is used. That is, as the pump structure, any structure can be used as long as the volume of the discharged gas can be reduced in the compression stroke of the pump. Specifically, it is suitable for rotor type (Gade type), piston type, diaphragm type (membrane type), and scroll type. Therefore, the exhaust rate of the auxiliary pump 30 is appropriately selected within a range of several percent to about 20% of the exhaust rate of the main pump 20 according to the expected capability of the vacuum exhaust device 10 .

Next, the present invention will be described in detail in conjunction with the action of the vacuum evacuation device 10 in the embodiment of the present invention configured as described above.

The vacuum processing chamber 1 is exhausted from atmospheric pressure to a predetermined vacuum degree by the main pump 20 . The auxiliary pump 30 is always in operation when the main pump 20 is in operation. Since the exhaust gas volume of the main pump 20 is large, even if the discharge side of the main pump 20 is exhausted by the auxiliary pump 30, the discharge side of the main pump 20 does not reach below the atmospheric pressure, the check valve 28 is opened, and the exhaust gas is discharged to the air. discharge in the direction indicated by the arrow a. On the other hand, if the exhaust action of the vacuum processing chamber 1 continues, the suction pressure of the main pump 20 decreases, and accordingly, the gas volume at the discharge port 24 of the main pump 20 also decreases.

When the discharge side of the main pump 20 becomes a gas flow rate below the atmospheric pressure due to the exhaust action of the auxiliary pump 30, the check valve 28 becomes a pulsating state in which it repeatedly opens and closes. In the present embodiment, as described above, since the check valve 28 has a structure that improves followability to pulsation, the vacuum exhaust device of the present invention can be operated while ensuring high reliability.

If the discharge side of the main pump 20 is below the atmospheric pressure, the check valve 28 is completely closed, after that, the flow of gas in the direction of arrow a in FIG. Exhaust in the direction of b. Accordingly, since the discharge pressure of the main pump 20 starts to decrease, the amount of backflow gas to the main pump 30 is reduced, so the power consumption of the main pump 20 is reduced.

In addition, before and after the check valve 28 is opened, the main pump 20 discharges a large amount of gas, and the auxiliary pump 30 basically does not function. The power consumption of the entire pneumatic device is larger than when the auxiliary pump 30 is not operated. However, for example, in semiconductor manufacturing equipment, the volume of the vacuum processing chamber is often below 100 liters, and the time for the auxiliary pump 30 to reach the effective pressure is several minutes, so it can be ignored from the point of view of energy saving.

Fig. 12 shows the characteristics of power consumption (main pump 20+auxiliary pump 30) with respect to the suction pressure of the main pump 20 of the vacuum exhaust device, which is a main pump at an exhaust rate of 150 m ³ /Hr On the subsequent stage (discharge side) of 20, an auxiliary pump 30 having an exhaust velocity of 1.8 m ³ /Hr is installed. As mentioned above, the main pump 20 is an energy-saving type pump in which the exhaust volume of the last stage is set to 25% of the exhaust volume of the first stage. In FIG. 12 , the dotted line indicates the case where the auxiliary pump 30 is not installed, and the solid line indicates the case where the auxiliary pump 30 and the check valve 28 are installed. In addition, the horizontal axis (suction pressure) is a logarithmic scale.

As shown in Figure 12, by installing the auxiliary pump 30, the power consumption drops sharply in the pressure range below 1kPa. If compared with the case where the auxiliary pump 30 is not installed, when the pressure is reached, the power consumption of 1.35kW is 0.32 kW, an energy saving rate (power consumption reduction rate) of about 76% was obtained. In addition, when the suction pressure of the main pump 20 is 400 Pa, the power consumption without the auxiliary pump is 1.4 kW, and the power consumption when the auxiliary pump 30 is installed is 0.67 kW, and the energy saving rate is about 52%.

In addition, when the exhaust speed of the auxiliary pump 30 increases, the pressure at which the power consumption of the main pump 20 starts to decrease moves from around 1 kPa in the figure to the right side in the figure, that is, to the side with a higher suction pressure, and becomes larger. Energy efficient pressure range. However, if the exhaust speed of the auxiliary pump 30 increases, the power consumption of the auxiliary pump increases, reducing the energy-saving effect. Generally, in a vacuum exhaust system used in semiconductor manufacturing equipment, a small amount of industrial waste gas flows into the vacuum processing chamber 1, and processing such as film formation is performed while maintaining a predetermined pressure. At this time, the suction pressure of the main pump 20 is about 1500 Pa even if it is high, so as long as the suction pressure range is below about 3000 Pa, if the energy saving effect can be obtained, the object of the present invention has been achieved.

Next, Fig. 13 shows the case where a dry vacuum pump as a main pump is used as a post-stage pump of a turbomolecular pump, and shows the exhaust speed ratio and power consumption when a main pump and an auxiliary pump having different exhaust speeds are combined. than the relationship. The suction pressure of the main pump is 400Pa.

Here, the exhaust speed ratio refers to the ratio of the exhaust speed of the auxiliary pump to the exhaust speed of the main pump, and the power consumption ratio refers to the ratio of the power consumption when the auxiliary pump is used to the power consumption when the auxiliary pump is not used, so , the power consumption ratio being 100% means that the energy saving effect does not exist at all. In addition, the power consumption when the auxiliary pump is used means the total power consumption of the main pump and the auxiliary pump, and the power consumption when the auxiliary pump is not used means the power consumption of the main pump.

As can be seen from FIG. 13, the larger the exhaust velocity ratio, the lower the power consumption, and therefore the higher the energy saving effect. In addition, when the exhaust speed ratio is around 3%, it is considered that the reduction rate of the power consumption ratio is small, and the reason for this will be described later. As can be seen from the above, when the suction pressure of the main pump is 400 Pa, energy saving can be efficiently achieved by using an auxiliary pump having a discharge speed of 3% or less of the discharge speed of the main pump.

In this embodiment, since the exhaust speed ratio of the main pump 20 and the auxiliary pump 30 is 1.2%, the above-mentioned condition is satisfied.

By increasing the exhaust speed ratio of the auxiliary pump relative to the main pump, the suction pressure that exhibits the energy-saving effect of the main pump moves to the high pressure side as described above. On the contrary, the power consumption of the auxiliary pump increases, combining the main pump and auxiliary pump. Electricity consumption is greater than that without the auxiliary pump. This will be described with reference to FIGS. 14 and 15 .

Here, FIG. 14 shows representative values of electric power consumption with respect to the discharge speed of a pump that can be used as an auxiliary pump. In addition, FIG. 15 is an example of a dry vacuum pump with an exhaust velocity of 150 m ³ /Hr as the main pump 20 in this embodiment, and the exhaust velocity shown in FIG. 14 is made relative to the main pump suction pressure 400 Pa The characteristics of the power consumption when the exhaust speed ratio of the auxiliary pump changes.

In Fig. 15, the single dotted line is only the power consumption of the main pump 20. By increasing the exhaust speed ratio of the auxiliary pump, the power consumption decreases sharply. 20 within the mechanical loss value. The dotted line shows the relationship between the electric power consumption of the auxiliary pump and the exhaust speed ratio of the characteristics shown in FIG. 14 . Thus, the solid line is the sum of these, which is the power consumption as a vacuum exhaust.

As can be seen from the results shown by the solid line in FIG. 15 , the electric power consumption is the lowest when the exhaust velocity ratio of the auxiliary pump 30 to the main pump 20 is about 3%. If the suction pressure of the main pump 20 is at 400Pa, and the energy-saving rate is 50% (refer to FIG. 12 ), then the above-mentioned exhaust velocity ratio can be either 1.2% or 9.4%, and the exhaust velocity ratio is 9.4% of the auxiliary pumps are larger than 1.2% of the auxiliary pumps (namely, the auxiliary pump 30 in the present embodiment), which poses a problem in comparison of installation space and energy for manufacturing the pumps. Therefore, it can be seen that if the auxiliary pump whose exhaust speed ratio is less than or equal to 3% is selected, a vacuum exhaust device with a high overall energy saving rate can be obtained. On the other hand, in the auxiliary pump whose exhaust speed ratio exceeds 3%, , but will eliminate the energy-saving effect.

On the other hand, as shown by the solid line in Fig. 12, in the suction pressure range below 10 Pa, the power consumption is substantially flat. In this state, when the discharge part pressure of the main pump 20 is lowered and the compression operation in the pump chamber is so small that the compression operation in the pump chamber is negligible, the power consumption here represents the mechanical loss (mechanical loss) of the main pump 20 . As the suction pressure of the main pump 20 gradually increases, the power consumption also gradually increases. This is a form showing that the compression work (here, the work of pushing back the counterflow gas) at the final stage of the main pump 20 becomes visible. Since the power consumption of the main pump 20 maintains a relationship proportional to the discharge pressure, in order to obtain the low power consumption shown in the solid line of FIG. ability to press.

Therefore, using various dry pumps with different exhaust speeds, setting the suction gas volume from the power consumption at the attained pressure to the power consumption increased by 10%, and investigating the pressure of the auxiliary pump at this time, it can be obtained Values from 6.5kPa to 20kPa. This means that unless a pump capable of exhausting to a pressure of 20 kPa or less is used as the auxiliary pump 30 , power consumption equivalent to the mechanical loss of the main pump 20 cannot be obtained when the pressure is reached.

Next, the solid line in FIG. 16 shows the comparison between the exhaust velocity characteristics of the vacuum exhaust device in this embodiment and the exhaust velocity characteristics without the auxiliary pump shown by the dotted line. In the suction pressure below 1kPa, the exhaust velocity is increased by about 10% compared with the case without the auxiliary pump. Also, the arrival pressure was raised from 2Pa to 1Pa. This is because the amount of counterflow gas decreases due to the decrease in discharge port pressure of the main pump 20, thereby increasing the effective volume ratio. Adding the auxiliary pump 30 not only reduces the power consumption, but also increases the exhaust speed and the attained pressure.

As described above, according to the present embodiment, since the power consumption of the main pump can be efficiently reduced by the auxiliary pump having a small exhaust capacity, effective energy saving can be achieved as a whole of the vacuum exhaust device.

The embodiments of the present invention have been described above. Of course, the present invention is not limited thereto, and various modifications can be made based on the technical idea of the present invention.

For example, in the above embodiment, a single dry vacuum pump was used as the main pump 20, but it is not limited thereto. The type pump is used as the above-mentioned main pump.

In addition, in the above embodiment, the configuration in which the auxiliary pump 30 is connected to the discharge side of the single main pump 20 has been described. For example, as shown in FIG. (Three in the drawing) The discharge side of the main pumps 20A to 20C is also applicable to the present invention. In the illustrated example, check valves 28A to 28C are provided corresponding to the main pumps 20A to 20C, respectively, and on-off valves 11A to 11C are provided between the auxiliary pump 30 . The respective main pumps 20A to 20C are connected to different vacuum processing chambers. In this case, the suction gas volume of the auxiliary pump 30 can be changed according to the operating number of the main pumps 20A to 20C, so it is desirable that the exhaust speed (number of revolutions) of the auxiliary pump can be changed according to the operating number of the main pumps 20A to 20C. .

In addition, the operation method of the vacuum evacuation device of the present invention will be specifically described with reference to the vacuum evacuation device 10 shown in FIG. 11 .

When the vacuum processing chamber 1 is evacuated from the atmospheric pressure by the evacuation device 10, the auxiliary pump 30 is first activated, and the main valve 13 is opened to start evacuation. Then, at the moment when it is confirmed that the vacuum degree of the vacuum processing chamber 1 reaches 10 ⁴ Pa by the pressure gauge 19, the main pump 20 is started to make the rotation speed of the rotor be, for example, 3600 rpm, and exhaust is carried out so that the vacuum degree of the vacuum processing chamber 1 reaches 1 Pa. . By employing such an activation method, it is possible to prevent flying of fine particles in the vacuum processing chamber 1 . That is, by activating only the auxiliary pump 30 when starting the exhaust from the atmospheric pressure, the exhaust can be slowly exhausted without providing the conventional small-diameter bypass valve 14 parallel to the main valve 13 . In addition, after the degree of vacuum reaches 1 Pa, then it enters normal operation, but because at this point, the exhaust volume is small, the check valve 28 is closed, and only the auxiliary pump 30 is exhausted, so the vacuum exhaust device 10 can be reduced. Power consumption can also be suppressed noise. In addition, in the exhaust pipe 15 of FIG. 11, a pipe with a nominal diameter of 40A is used, and since the exhaust volume of the auxiliary pump 30 and the exhaust gas of the main pump 20 connected thereto are small, it can be replaced by, for example, For pipes with a nominal diameter of 10A (diameter 10mm3/8 inch), since the pipes of this diameter can be bent, the construction cost of piping can be reduced.

Above, the operation method of the vacuum exhaust device of the present invention has been described through the embodiments. Of course, the present invention is not limited thereto, and various modifications can be made according to the technical idea of the present invention.

For example, in this embodiment, after the vacuum processing chamber reaches a specified vacuum degree through the exhaust of the auxiliary pump, when the main pump is started, the rotor is rotated at 3600 rpm, and the vacuum processing chamber can also reach the specified vacuum degree. Before switching to control the main pump, the number of rotations will gradually increase from a low number of rotations with a small displacement according to the vacuum degree of the vacuum processing chamber. Therefore, the drastic pressure change when the main pump is started can be avoided, and the main pump can be started. , without becoming a load on the auxiliary pump.

According to the vacuum evacuation device and the operation method of the vacuum evacuation device of the present invention, not only can achieve significant energy saving compared with conventional ones with a simple structure, but also can easily perform slow evacuation.

Claims (16)

1. A vacuum exhaust device, characterized in that the suction side of the auxiliary pump is connected to the discharge side of the pump chamber of the middle stage or the last stage of the main pump. 2. The vacuum evacuation apparatus according to claim 1, wherein the auxiliary pump has a smaller displacement than the main pump. 3. The vacuum exhaust device according to claim 1 or 2, characterized in that at least one pump chamber of the rear-stage part of the main pump is made smaller than the front-stage part, and the exhaust volume is smaller than that of the front-stage part. 4. The vacuum exhaust device according to any one of claims 1 to 3, wherein the exhaust pipe is connected to the discharge side of the last-stage pump chamber of the main pump, and the exhaust pipe is A non-return valve is connected to the top, which only allows the gas to flow to the atmosphere side. 5. The vacuum exhaust device according to claim 4, wherein the check valve is formed by connecting a plurality of check valves in series. 6. The vacuum exhaust device according to claim 5, wherein the check valve has a spherical valve body that can float in the valve body, and the first check valve is connected in series and is the same as the first check valve. The second check valve is a part of the second check valve. The first check valve is opened when the above-mentioned spherical valve body floats up due to the pressure of the exhaust gas of the above-mentioned main pump, and falls down due to its own weight when the above-mentioned pressure is lower than the above-mentioned pressure. Valve seat closes. 7. The vacuum exhaust device according to any one of claims 4 to 6, wherein the auxiliary pump is connected in parallel with the check valve. 8. The vacuum evacuation device according to claim 6, wherein a space connecting the first check valve and the second check valve is connected to a suction side of the auxiliary pump. 9. The vacuum exhaust device according to claim 6, wherein the spherical valve body is made of a hollow metal ball, and the surface is covered with rubber. 10. A vacuum exhaust device has a main pump, a check valve and an auxiliary pump, the check valve is connected to the discharge side of the main pump, and only allows gas to flow from the main pump to the atmosphere side, and the auxiliary pump is relatively The above-mentioned check valve is arranged in parallel on the discharge side of the above-mentioned main pump, and the displacement of the above-mentioned main pump is smaller than that of the above-mentioned main pump. Run the pump at an exhaust velocity that is 3% of the air velocity. 11 . The vacuum exhaust device according to claim 10 , wherein the main pump is a variable capacity dry vacuum pump, or a composite pump in which the dry vacuum pumps are connected in series in multiple stages. 12. The vacuum exhaust device according to claim 10, wherein a plurality of said main pumps are arranged in parallel, and the suction side of said auxiliary pump is connected to the discharge side of each of said main pumps. 13. The vacuum exhaust device according to claim 10, wherein the reaching pressure of the auxiliary pump is less than or equal to 20 kPa. 14. The vacuum evacuation device according to claim 13, wherein the auxiliary pump is a rotary vane type (Gade type), piston type, diaphragm type (diaphragm type) or scroll type vacuum pump. 15. A method of operating a vacuum exhaust device, characterized in that the vacuum exhaust device has a main pump connected to the above-mentioned vacuum processing chamber; it is connected to the discharge side of the main pump, and only gas is allowed to flow from the above-mentioned main pump to A check valve that flows on the atmospheric side; an auxiliary pump that is arranged in parallel on the discharge side of the above-mentioned main pump with respect to the above-mentioned check valve, and has a smaller displacement than the above-mentioned main pump; When exhausting at or near atmospheric pressure, the auxiliary pump is first activated, and the main pump is activated after the vacuum processing chamber reaches a predetermined pressure. 16. A method of operating a vacuum exhaust device, characterized in that the vacuum exhaust device has: a main pump connected to the vacuum processing chamber; connected to the discharge side of the main pump, only allowing gas to flow from the main pump to A check valve that flows on the atmospheric side; an auxiliary pump that is arranged in parallel on the discharge side of the main pump with respect to the check valve and has a smaller displacement than the main pump; When exhausting from atmospheric pressure or its vicinity, first start the above-mentioned auxiliary pump, start the above-mentioned main pump before the above-mentioned vacuum processing chamber reaches the specified pressure, and make it rotate at a small displacement at a low speed, and rotate according to the pressure of the above-mentioned vacuum processing chamber. The number gradually increased.

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