JP4718302B2 - Vacuum exhaust device - Google Patents

Description

  The present invention relates to a vacuum exhaust apparatus including a main pump connected to a vacuum processing chamber and an auxiliary pump that exhausts the discharge side of the main pump.

  2. Description of the Related Art Conventionally, some evacuation apparatuses that evacuate a vacuum processing chamber include an auxiliary pump on the discharge side of a main pump in order to obtain a higher evacuation speed (see, for example, Patent Document 1 below). FIG. 8 shows a schematic configuration of this type of conventional evacuation apparatus. 1 is a vacuum processing chamber, 2 is a main pump, 3 is an auxiliary pump, and 4 is a main valve.

  The main pump 2 is a booster pump, and for example, a single-stage roots pump is used. The auxiliary pump 3 is also referred to as a fore pump, and a rotary pump, a multistage roots type pump, or a screw type pump is used.

  For example, in a Roots-type pump, rotating bodies including a plurality of rotors are provided adjacent to each other along a rotation axis, and the rotors rotate in opposite directions with a slight gap therebetween to perform gas intake and exhaust. Therefore, by exhausting the discharge side of the main pump 2 with the auxiliary pump 3 and keeping the back pressure of the main pump 2 at a low pressure, the exhaust efficiency of the main pump 2 is increased and the vacuum processing chamber 1 can be exhausted at a higher exhaust speed. become.

  The evacuation apparatus is started to operate with the main valve 4 closed. Then, the main valve 4 is opened and the gas in the vacuum processing chamber 1 starts to be exhausted. At this time, particularly in the case of a large evacuation apparatus, a gas that greatly exceeds the evacuation capacity of the auxiliary pump 3 is discharged from the main pump 2 in the initial state. Since this state is an overload state for the motor of the main pump 2, the operation of the motor is stopped or the operation speed of the motor is decelerated to such an extent as not to be overloaded.

  However, the atmospheric pressure gas corresponding to the displacement (displacement amount) of the pump is sucked into the main pump 2 until the countermeasure is taken. The displacement of the main pump 2 is usually about 5 to 10 times that of the auxiliary pump 3. Therefore, when the main valve 4 is opened and the atmospheric pressure gas is exhausted from the state where the intake side of the exhaust device is closed, in the initial process, the pressure inside the connecting pipe of the main pump 2 and the auxiliary pump 3 is several atmospheric pressures. To reach.

  The pressure increase becomes larger as the exhaust device has a larger displacement ratio between the main pump 2 and the auxiliary pump 3. When the pressure inside the connecting pipe between the main pump 2 and the auxiliary pump 3 becomes abnormally high, an excessive force is applied to the rotor of the main pump 2 in the direction opposite to the rotor rotation. As a result, problems such as a bearing failure that supports the rotor shaft and a rotor timing shift due to a timing gear disengagement occur.

  In order to prevent such problems, conventionally, as shown in FIG. 9A, a bypass pipe 5 for returning a gas having a predetermined pressure or higher from the discharge side of the main pump 2 to the suction side of the main pump 2 is installed. As shown in FIG. 9B, a bypass pipe 7 for sending a gas having a predetermined pressure or higher from the suction side of the auxiliary pump 3 to the discharge side of the auxiliary pump 3 is installed. These bypass pipes 5 and 7 are provided with check valves 6 and 8 for preventing a back flow of gas in a steady state, respectively.

JP 2003-139080 A

  However, in the configuration shown in FIGS. 9A and 9B, a space for arranging the bypass pipes 5 and 7 and the check valves 6 and 8 is required. Thereby, there exists a problem that a vacuum exhaust apparatus enlarges and the cost corresponding to it increases. Further, if a malfunction occurs in the operation of the check valves 6 and 8, the exhaust performance is affected, so that there is a problem that reliability is impaired.

  On the other hand, it is possible to avoid an excessive pressure increase on the discharge side of the main pump 2 by selecting a pump having a sufficient displacement speed for the auxiliary pump 3. This will lead to an increase in the overall size, and an increase in cost cannot be suppressed.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a vacuum exhaust apparatus that can suppress an increase in size of the apparatus and can ensure an appropriate exhaust operation of the main pump.

  In order to solve the above-described problems, the vacuum exhaust apparatus of the present invention includes a buffer unit that relaxes the discharge gas pressure from the main pump between the main pump and the auxiliary pump.

  With this configuration, it is possible to prevent an abrupt pressure increase that occurs on the discharge side of the main pump at the beginning of operation, and to ensure an appropriate exhaust operation of the main pump, thereby improving reliability. Further, even if a buffer unit is added, a smaller auxiliary pump can be employed, so that the size of the apparatus can be suppressed.

  The buffer unit is not particularly limited as long as it can increase the volume of the connection pipe that connects the main pump and the auxiliary pump. For example, a buffer tank is suitable. In this case, the buffer tank may be arranged in series between the main pump and the auxiliary pump, or may be arranged in parallel. Further, the capacity may be variable according to the pressure on the discharge side of the main pump.

  In the vacuum exhaust apparatus according to the present invention, preferably, the main pump, the auxiliary pump, and the buffer unit are accommodated in a common casing. Since a buffer part can be arrange | positioned in arbitrary areas in a casing, the enlargement of a casing can be suppressed.

  According to the vacuum exhaust apparatus of the present invention, it is possible to ensure an appropriate exhaust operation of the main pump while suppressing an increase in size of the entire apparatus. As a result, it is possible to improve the operation reliability and suppress an increase in manufacturing cost due to an increase in the size of the apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the following embodiments, and various modifications can be made based on the technical idea of the present invention.

[First Embodiment]
FIG. 1 is a schematic configuration diagram of an evacuation apparatus 10 according to a first embodiment of the present invention.

  Reference numeral 1 denotes a vacuum processing chamber, which constitutes a processing chamber of various vacuum processing apparatuses such as a film forming apparatus, a heat treatment apparatus, and an etching apparatus. A main pump 2 is connected to the exhaust port of the vacuum processing chamber 1 via a main valve 4. For example, a roots type vacuum pump is used as the main pump 2. An auxiliary pump 3 is connected to the discharge side of the main pump 2 via a buffer tank 11. As the auxiliary pump 3, various vacuum pumps such as a rotary type, a root type, and a screw type are used.

  In the vacuum exhaust apparatus 10 of the present embodiment, a buffer tank 11 is disposed between the main pump 2 and the auxiliary pump 3. The buffer tank 2 is configured as a “buffer unit” that relieves the pressure of gas discharged from the main pump 2.

  By disposing the buffer tank 11, the internal volume of the pipe line connecting the main pump 2 and the auxiliary pump 3 can be partially expanded, and a sudden pressure on the discharge side of the main pump 2 (the suction side of the auxiliary pump 3). The rise can be suppressed. Accordingly, a rapid pressure rise between the main pump 2 and the auxiliary pump 3 can be suppressed at the initial stage of the exhaust operation of the vacuum processing chamber 1, and therefore, in the main pump 2 constituted by a roots type pump or the like, the rotor shaft is It is possible to avoid problems such as a bearing failure to be supported and a rotor timing shift, and an appropriate exhaust operation of the main pump 2 is ensured. Thereby, the operation reliability of the vacuum exhaust apparatus 10 can be improved.

  Further, it is possible to employ a pump having a smaller capacity as the auxiliary pump 3, and it is possible to reduce the apparatus cost. Thereby, even if the displacement ratio between the main pump 2 and the auxiliary pump 3 is large, the operational reliability of the vacuum exhaust device can be maintained.

  The pressure relaxation action is higher as the capacity (volume) of the buffer tank 11 is larger. However, if the capacity of the buffer tank 11 becomes too large, the ratio occupied by the buffer tank 11 in the total volume of the vacuum evacuation device 10 increases, and the overall size of the device increases.

  As an example, consider a case where a main pump having a pumping speed of 40,000 L / min. Is operated by an auxiliary pump having a pumping speed of 3000 L / min. In the evacuation apparatus having this configuration, the maximum pressure at the connection between the main pump and the auxiliary pump when starting to exhaust gas at atmospheric pressure reaches 4 to 5 atmospheres. In this example, the main pump and the auxiliary pump are connected by a single pipe, and the internal volume of the pipe is about 1 to 2L.

  Therefore, FIG. 2 shows a calculation result when the buffer tank according to the present invention is arranged between the main pump and the auxiliary pump and the volume of the connection portion is increased. In FIG. 2, the horizontal axis represents the volume (volume) of the connecting portion including the buffer tank, and the vertical axis represents the maximum pressure at the connecting portion when starting to discharge the atmospheric pressure gas. It can be seen that the maximum pressure is drastically decreased by increasing the volume of the connecting portion to about 10 L. It can be seen that if the volume of the connecting portion is 20 L or more, the maximum pressure can be suppressed to approximately 2 atmospheres or less. Therefore, in the above example, the volume of the buffer tank can be at least 10L, preferably 20L-30L.

  FIG. 3A shows a vacuum exhaust apparatus having a conventional structure in which the main pump 2 and the auxiliary pump 3 are accommodated in a common casing 12. On the other hand, FIG. 3B shows the vacuum exhaust apparatus 10 in which the main pump 2, the auxiliary pump 3, and the buffer tank 11 are accommodated in a common casing 12. In the figure, reference numeral 13 denotes a suction port of the vacuum exhaust device, and 14 denotes a discharge port thereof.

  In the vacuum evacuation device 10 of the present embodiment, the height L2 of the entire unit is set to the conventional height L1 simply considering the additional arrangement of the buffer tank 11 having a constant capacity in the casing 12. Compared to larger. However, since the shape of the buffer tank 11 is not limited to a fixed shape, L2 can be suppressed to the same level as L1 if the empty space in the casing 12 can be used effectively.

  Furthermore, since the auxiliary pump 3 can be reduced in size by installing the buffer tank 11, the reduced space occupied by the auxiliary pump 3 can be diverted to the installation space of the buffer tank 11. Depending on the design, the unit height can be increased. It is also possible to make the length L2 lower than the conventional structure (L2 <L1).

  As described above, according to the present embodiment, the overall size of the apparatus can be suppressed, and accordingly, the increase in the installation space of the exhaust system of the vacuum processing apparatus including the vacuum processing chamber 1 can be suppressed. it can.

  When the buffer tank 11 is arranged in series between the main pump 2 and the auxiliary pump 3, as shown in FIG. 4, the discharge port 15 of the main pump 2 and the suction port 16 of the auxiliary pump 3 are connected to each other. They can be connected to the buffer tank 11 so as not to face each other. Thereby, the relaxation effect of the discharge gas pressure from the main pump 2 can be exhibited effectively.

[Second Embodiment]
FIG. 5 is a schematic configuration diagram of an evacuation apparatus 20 according to the second embodiment of the present invention. In the figure, portions corresponding to those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  The vacuum exhaust apparatus 20 of the present embodiment is common to the above-described first embodiment in that the main pump 2, the auxiliary pump 3, and the buffer tank 11 are accommodated in a common casing 12. However, it differs from the first embodiment in that the buffer tank 11 is disposed in parallel between the main pump 2 and the auxiliary pump 3. In this example, the buffer tank 11 is connected to a connection pipe 17 that connects between the main pump 2 and the auxiliary pump 3 via a branch pipe 18.

  Of course, the present embodiment can provide the same effects as those of the first embodiment described above. In particular, according to the present embodiment, as shown in FIG. 5, the unit height L3 of the vacuum evacuation device 20 is set to a conventional unit by arranging the buffer tank 11 on the side of the main pump 2 and the auxiliary pump 3. The height L1 (FIG. 3A) can be suppressed to approximately the same.

[Third Embodiment]
FIG. 6 is a schematic configuration diagram of an evacuation apparatus 30 according to the third embodiment of the present invention. In the figure, portions corresponding to those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  The vacuum exhaust apparatus 30 of the present embodiment includes a variable capacity buffer tank 31 between the main pump 2 and the auxiliary pump 3. The buffer tank 31 is configured such that at least a part of the side periphery thereof can be expanded and contracted in a bellows shape, and its volume is variable within a certain range in response to a change in internal pressure.

  By arranging the buffer tank 31 configured as described above as a “buffer unit” according to the present invention, a sudden pressure increase on the discharge side of the main pump 2 at the beginning of the operation of the vacuum evacuation device 30 can be prevented. 31 can be mitigated by the volume increasing action, thereby ensuring proper operation of the main pump 2. In addition, since the inside of the buffer tank 31 becomes a negative pressure at the steady state, the volume of the buffer tank 31 is reduced to the initial volume or a smaller volume.

  The variable volume buffer tank 31 according to the present embodiment is not limited to the above-described configuration example, and part or all of the tank is made of an elastic body, and the tank can be elastically deformed by changing the internal pressure, or can be expanded by increasing the internal pressure. The buffer tank 31 may be made of any material.

  Further, the example shown in FIG. 6 shows a configuration example in which the buffer tank 31 is arranged in series between the main pump 2 and the auxiliary pump 3, but of course the present invention is not limited thereto, and the buffer tank 31 is arranged in the main pump 2. And the auxiliary pump 3 may be arranged in parallel.

[Fourth Embodiment]
FIG. 7 is a schematic configuration diagram of an evacuation apparatus 40 according to the fourth embodiment of the present invention. In the figure, portions corresponding to those of the first embodiment described above are denoted by the same reference numerals, and detailed description thereof is omitted.

  The vacuum evacuation device 40 according to the present embodiment has the above-described configuration in which the structure of the buffer portion disposed between the main pump 2 and the auxiliary pump 3 is configured by connection pipes 41 bent at a plurality of locations. This is different from the embodiment. By configuring the buffer portion with such a connection pipe 41, the length of the pipe line between the discharge port of the main pump 2 and the suction port of the auxiliary pump 3 can be increased, thereby increasing the volume in the pipe line, The rapid pressure rise at the discharge port of the main pump 2 is alleviated.

  Also according to the present embodiment, the same effects as those of the above-described embodiments can be obtained. In particular, according to the present embodiment, since the connection pipe 41 extends while being bent in the gap from the discharge port of the main pump 2 to the suction port of the auxiliary pump 3, the conventional straight connection pipe is used. The pipe length can be increased within the same height dimension. Thereby, the unit height L4 of the vacuum evacuation device 40 can be suppressed to be substantially equal to or less than the unit height L1 of the conventional vacuum evacuation device shown in FIG. 3A.

  The connection pipe 41 may be composed of a combination of a curved pipe and a straight pipe, but by adopting a flexible pipe structure, in addition to improving the mounting property, the gap between the main pump 2 and the auxiliary pump 3 Can be shortened. Further, by configuring a part or all of the connection pipe 41 with a stretchable part such as a bellows, the pipe length may be increased as the internal pressure increases.

1 is a schematic configuration diagram of a vacuum exhaust apparatus 10 according to a first embodiment of the present invention. It is a figure which shows an example of the relationship between the volume of the buffer tank which concerns on this invention, and the ultimate pressure. It is a schematic block diagram of the vacuum exhaust apparatus of the form which accommodated the main pump 2 and the auxiliary pump 3 in the common casing, A is a prior art example, B has shown one Embodiment of this invention, respectively. FIG. 3 is an enlarged view of a main part for explaining connection forms of a main pump 2, a buffer tank 11, and an auxiliary pump 3. It is a schematic block diagram of the vacuum exhaust apparatus 20 by the 2nd Embodiment of this invention. It is a schematic block diagram of the vacuum exhaust apparatus 30 by the 3rd Embodiment of this invention. It is a schematic block diagram of the vacuum exhaust apparatus 40 by the 4th Embodiment of this invention. It is a schematic block diagram of the conventional vacuum exhaust apparatus. It is a figure which shows the other structural example of the conventional vacuum exhaust apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Vacuum processing chamber 2 Main pump 3 Auxiliary pump 10 Vacuum exhaust apparatus 11 Buffer tank (buffer part)
12 Casing 20 Vacuum exhaust device 30 Vacuum exhaust device 31 Buffer tank (buffer part)
40 Vacuum exhaust system 41 Connection piping (buffer part)

Claims (7)

A main pump connected to a vacuum processing chamber and composed of a booster pump or a roots pump;
An auxiliary pump for evacuating the discharge side of the main pump,
A buffer unit that is disposed between the main pump and the auxiliary pump and relieves discharge gas pressure from the main pump ;
An evacuation apparatus having a relationship of V ≧ 0.015 × S, where V [L] is a capacity of the buffer section and S [L / s] is an exhaust speed of the main pump .   The vacuum exhaust apparatus according to claim 1, wherein the buffer unit is a buffer tank.   The vacuum exhaust apparatus according to claim 2, wherein the buffer tank is disposed in series between the main pump and the auxiliary pump.   The vacuum exhaust apparatus according to claim 3, wherein the discharge port of the main pump and the suction port of the auxiliary pump are provided at positions that do not face each other.   The evacuation apparatus according to claim 2, wherein the buffer tank is disposed in parallel between the main pump and the auxiliary pump.   The vacuum evacuation device according to claim 1, wherein a capacity of the buffer unit changes according to a pressure on a discharge side of the main pump.   The evacuation apparatus according to claim 1, wherein the main pump, the auxiliary pump, and the buffer unit are accommodated in a common casing.

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