JP2004218648A - Vacuum device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vacuum device having a small power consumption and a small occupation area of the device, free of the risk that impurity gases go around into vacuum vessels from the exhaust system, and capable of allowing a large rate of gas to flow. <P>SOLUTION: The vacuum device is equipped with a plurality of vacuum vessels furnished with a gas lead-in hole and an exhaust hole, a gas supply system for introducing the desired gas from the gas lead-in hole into the vacuum vessels, and an exhaust system for keeping the vacuum vessels in the decompressed condition, wherein the exhaust system has a plurality of vacuum pumps connected in series at stages, and among the vacuum pumps, ones with a lower degree of vacuum is located the nearest to the vacuum vessels, and a plurality of low vacuum pumps are connected through common piping to the final stage vacuum pumps. The exhaust hole pressure of each final stage vacuum pump is approximately the atmospheric, and the final stage vacuum pumps are arranged so that each of them exhausts the gas from a plurality of pre-stage vacuum pumps. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a vacuum device, and more particularly to a small vacuum device that consumes less power in a vacuum pump.

  Vacuum devices are used in many industrial fields, including the semiconductor and liquid crystal display manufacturing fields. In particular, in the field of manufacturing semiconductors and liquid crystal displays, most processes such as film formation, etching, and ashing are performed under reduced pressure in a vacuum apparatus. In a vacuum device, a vacuum pump is used to keep the inside of a vacuum vessel for performing processes, measurements, and the like in a vacuum or reduced pressure state.

  There are various types of vacuum pumps, but they can be roughly classified into pumps, which are pump-type pumps that exhaust gas from the pump's intake port through the exhaust port, and plug-in type pumps that store the gas that is sucked from the pump's intake port inside. Classified as pump. Although a built-in pump can generally be evacuated to a high vacuum region by itself, the amount of gas that can be evacuated is naturally limited. For this reason, for a process which is performed under a reduced pressure while constantly flowing a gas, a built-in pump is not suitable and a pump of a scraping type is used.

In general, a pump of a scraping type tends to have a higher exhaust speed and a lower allowable back pressure as the ultimate vacuum degree is higher. Vacuum pumps operating in a molecular flow region of 1.33 × 10 ⁻⁴ Pa (10 ⁻⁶ Torr) or more with a high ultimate vacuum degree include a turbo molecular pump, a screw groove pump, an oil diffusion pump, and the like. These pumps have a high pumping speed even with small pumps, but have an extremely low allowable back pressure of 133 Pa (1 Torr) or less. There are many types of pumps having a low ultimate vacuum and operating at a back pressure of about the atmospheric pressure, such as a roots pump, a screw pump, a rotary pump, and a diaphragm pump. As a pump having a middle degree of ultimate vacuum classified in between these, there are booster pumps such as a mechanical booster pump and an executor pump.

  For the vacuum device, an optimal vacuum pump must be used according to the required gas pressure, gas cleanliness, gas flow rate, gas type, vacuum vessel volume, and the like. In general, when the gas pressure is relatively high (about 40 Pa (300 mTorr) or more), a pump that operates at a back pressure of about atmospheric pressure is used alone. On the other hand, when the gas pressure is low, an exhaust system is used in which a pump operating in the molecular flow region and a pump operating at a back pressure of about atmospheric pressure are connected in series. When the gas flow rate is large, a booster pump may be inserted between these pumps, and three pumps may be connected in series to perform exhaust.

  In semiconductor and liquid crystal display mass production plants where most processes are performed under reduced pressure, several vacuum vessels to be processed can be integrated in one device, and substrates can be transferred between vacuum vessels in a vacuum. A plurality of such cluster tools are arranged adjacent to each other. That is, a large number of vacuum vessels are generally arranged adjacent to each other. In the conventional apparatus, even when a plurality of vacuum vessels are arranged adjacent to each other, an independent exhaust system is provided for each vacuum vessel. That is, there is a one-to-one correspondence between a vacuum vessel and a vacuum pump for exhausting the vacuum vessel, and each vacuum pump is configured to exhaust only one vacuum vessel.

  A vacuum pump that operates at a back pressure of about the atmospheric pressure requires a larger power to rotate the rotor and the like than a pump with the same pumping speed that operates at a low back pressure, and consumes much more power. In addition, the size is large and the weight is heavy. In a conventional apparatus, such a large-sized vacuum pump having large power consumption is required as many as the number of vacuum vessels. For this reason, the installation of the pump increases the power consumption of the device and the area occupied by the device, and as a result, it has been difficult to reduce the manufacturing cost of the product.

  Further, a vacuum pump operating at a back pressure of about the atmospheric pressure has a problem that since the ultimate vacuum degree on the suction side is low, the impurity gas flows from the exhaust system into the vacuum vessel. If the impurity gas adheres to the surface of the wafer or the inner surface of the vacuum vessel, the process performance is significantly reduced. In addition, since the pump is large in size, it is often difficult to install the pump near the vacuum vessel, so that the pump must be connected via a long pipe. For this reason, the gas conductance of the pipe is small, and in a process in which a large amount of gas needs to flow, this has been a major factor in reducing the process speed and process performance.

Further, there is a case where a deposition component is contained in an exhaust gas from a vacuum vessel applied to a semiconductor manufacturing process or the like. When such precipitated exhaust gas causes solid components to adhere to the inside of the pipe, it causes a reduction in the exhaust conductance of the vacuum apparatus.
SUMMARY OF THE INVENTION It is a main object of the present invention to provide a vacuum apparatus which has a small power consumption and a small area occupied by the apparatus, does not allow an impurity gas to flow into a vacuum vessel from an exhaust system, and can flow a large amount of gas. Further, with this main purpose, the impurity gas does not flow into the vacuum vessel, and the cross-sectional area of the piping is narrowed and the exhaust conductance is reduced even when used in a manufacturing process in which a precipitating exhaust gas is generated. It is also an object of the present invention to provide a vacuum device that does not need to be used.

The present invention solves the above problem as described in claim 1.
A plurality of vacuum vessels having a gas inlet and an exhaust port, a gas supply system for introducing a desired gas from the gas inlet into the vacuum vessel, and an exhaust system for keeping the inside of the vacuum vessel at reduced pressure. In the provided vacuum device,
The exhaust system has a plurality of vacuum pumps connected in series in multiple stages,
Among the plurality of vacuum pumps, a low vacuum pump is installed in the immediate vicinity of the vacuum vessel, and the low vacuum pump is connected to a final stage vacuum pump by a common pipe from the plurality of low vacuum pumps,
The exhaust pressure of the final stage vacuum pump is approximately atmospheric pressure,
The last-stage vacuum pump is a vacuum device characterized by being configured to exhaust gas from a plurality of front-stage vacuum pumps per unit.
Also, as described in claim 2,
The vacuum apparatus according to claim 1, wherein the low vacuum pump is a booster pump.
Also, as described in claim 3,
The solution is solved by the vacuum apparatus according to claim 1 or 2, wherein the last-stage vacuum pump is a roots pump.

  In the vacuum apparatus of the present invention, a back pressure of the preceding vacuum pump is kept low by newly adding a common auxiliary pump for simultaneously exhausting a plurality of vacuum apparatuses to the atmosphere side. Compared with the conventional configuration in which the back pressure is the atmospheric pressure, the operation power of the vacuum pump is reduced, and the power consumption and size of the vacuum pump are significantly reduced. As a result, the power consumption of the entire apparatus is reduced, the area occupied by the apparatus is reduced, and low-cost production becomes possible.

  Further, the ultimate vacuum degree of the preceding vacuum pump is improved, and it is possible to completely suppress the impurity gas from flowing into the vacuum vessel. Furthermore, the size of the vacuum pump in the former stage has been greatly reduced, so that this pump can be installed near the vacuum vessel. As a result, it becomes possible to flow a large amount of gas even at a low pressure, and the process speed and process performance are greatly improved.

  Further, by providing a means for effectively removing solid products from the precipitating exhaust gas contained in the exhaust gas, a vacuum device capable of maintaining the exhaust conductance in a favorable state for a long period of time can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, the power consumption of an apparatus and the area occupied by the apparatus are small, and a vacuum apparatus capable of flowing a large amount of gas without an impurity gas flowing from an exhaust system into a vacuum vessel can be realized.

  Further, by providing a means for effectively removing the precipitable by-products contained in the exhaust gas, a vacuum device capable of maintaining the exhaust conductance in a favorable state for a long period of time can be provided.

  Hereinafter, the vacuum apparatus of the present invention will be described with reference to the drawings, but it goes without saying that the present invention is not limited to these examples.

  FIG. 1 shows an embodiment in which the vacuum apparatus of the present invention is applied to a semiconductor processing apparatus.

  101 is a vacuum container, and 102 and 103 are a gas inlet and a gas outlet provided in the vacuum container 101, respectively. Reference numeral 104 denotes a cluster tool in which three vacuum vessels are integrated on one platform. Reference numeral 105 denotes a pressure control valve for controlling the gas pressure in the vacuum vessel 101 by changing the gas conductance. Reference numeral 106 denotes a high vacuum pump, and in this embodiment, a thread groove type molecular pump is used. Reference numeral 107 denotes a low vacuum pump for keeping the back pressure of the high vacuum pump 106 at a low pressure. In this embodiment, a mechanical booster pump is used. Reference numeral 108 denotes an auxiliary pump for keeping the back pressure of the low vacuum pump 107 at a low pressure. In this embodiment, a roots pump is used. Reference numerals 109 and 110 denote valves, and in this embodiment, electromagnetic valves are used. 111, 112, and 113 are pipes for flowing gas. The inside of the pipe 113 is almost at atmospheric pressure. The gas discharged from the auxiliary pump 108 is led to a gas processing device through a pipe 113. The present vacuum apparatus has a configuration in which 33 cluster tools and 99 vacuum vessels are connected by a pipe 112, but FIG. 1 shows only two cluster tools for simplification. . In this embodiment, the vacuum container is used for etching or resist ashing of a silicon substrate having a diameter of 200 mm.

In high-speed and high-performance etching of a substrate having a diameter of 200 mm, a gas of a maximum of 1 atm · L / min (1 L / min calculated in atmospheric pressure, the same applies hereinafter) is flowed at a pressure of about 4.00 Pa (30 mTorr). The gas species are Ar, CO, C ₂ H ₆ , O ₂ , and the majority is Ar. In the high-speed ashing process, a gas of a maximum of 1 atm.L / min is flowed at a pressure of 6.67 Pa (50 mTorr). Gas species is _{O 2.} It is necessary to construct an exhaust system that can satisfy these conditions.

First, regarding the high vacuum pump 106, in order to reduce the intake port pressure to 4.00 Pa (30 mTorr) or less when a gas of 1 atm · L / min flows, a screw groove type molecular pump having an exhaust speed of 1800 L / sec or more. In this embodiment, a thread groove type molecular pump having a pumping speed of 2000 L / sec was adopted. When the back pressure exceeds 53.33 Pa (0.4 Torr), the compression ratio of the 2000 L / sec class thread groove type molecular pump is greatly reduced, and the pump does not operate. For this reason, with respect to the low vacuum pump 107, when the gas of 1 atm · L / min flows, the intake port pressure falls below 53.33 Pa (0.4 Torr). As a result, a pumping speed of 2000 L / min was required. In this embodiment, a mechanical booster pump having a pumping speed of 2000 L / min was employed. Next, regarding the auxiliary pump 108, a gas of a maximum of 1 atm · L / min × 99 = 99 atm · L / min flows into this pump, assuming that the process was performed simultaneously in all the vacuum vessels. The allowable back pressure of the mechanical booster pump is 6.67 × 10 ³ (50 Torr). For this reason, the pumping speed of the auxiliary pump 108 is required to be 1500 L / min or more. In this embodiment, a roots pump of 2000 L / min is adopted in consideration of the gas conductance of the pipe 112.

  Here, the power consumption and size of the vacuum pump will be compared with the conventional example. As for the high vacuum pump, the power consumption is 680 W per unit, and the power consumption is 68 kW for 99 units.

With respect to the low vacuum pump, a pump such as a Roots pump that operates at a back pressure of about atmospheric pressure has conventionally been used, whereas a mechanical booster pump that operates at 1/10 atm or less is used in this embodiment. I have. A comparison will be made between a roots pump having a pumping speed of 2000 L / min and a mechanical booster pump. The power consumption of the roots pump is 3.7 kW and that of the mechanical booster pump is 0.4 kW, and the power consumption of the roots pump is nine times larger than that of the same pumping speed. This is because a higher back pressure of the pump requires more power to rotate the rotor. The volume of the pump, Roots pump ^{0.95 × 0.42 × 0.55m 3 = 0.22m} 3, a mechanical booster pump is a ^{0.48 × 0.21 × 0.18m 3 = 0.018m} 3, The roots pump is 12 times larger. The mass of the roots pump is 223 kg and that of the mechanical booster pump is 22 kg, and the mass of the roots pump is 10 times larger. That is, the mechanical booster pump that operates at a low back pressure is orders of magnitude smaller and consumes less power. Further, the mechanical booster pump has a simple structure and is inexpensive.

  FIG. 2 shows the exhaust characteristics of the mechanical booster pump and the roots pump. 201 is a characteristic of a mechanical booster pump having an exhaust speed of 2000 L / min, 202 is a characteristic of a roots pump of 2000 L / min, and 203 is a characteristic of a roots pump of 2400 L / min. It can be seen that the mechanical booster pump operates in the low pressure region by one digit or more than the roots pump. As a back pump of the molecular pump, a pump having a large pumping speed at a pressure of 133.32 Pa (1 Torr) or less is required. In the mechanical booster pump, the pumping speed is maintained up to a low pressure region of about 4.00 Pa (30 mTorr), whereas in the Roots pump, the pumping speed is considerably deteriorated in a pressure region of 133.32 Pa (1 Torr) or less. Therefore, in order to obtain a required pumping speed with a roots pump, it is necessary to select a larger pump. For example, in order to obtain a pumping speed of 2000 L / min at 53.33 Pa (0.4 Torr), which is an allowable back pressure of the thread groove type molecular pump, it is understood from FIG. 2 that a roots pump of 2400 L / min is required. A comparison between a 2000 L / min mechanical booster pump and a 2400 L / min roots pump shows that the roots pump consumes 11 times, consumes 14 times, and has 12 times greater mass. The power consumption for 99 low vacuum pumps is 440 kW for the roots pump and 40 kW for the mechanical booster pump.

  In the present embodiment, this power consumption is added because a new auxiliary pump is provided, but since a large number of vacuum vessels are simultaneously evacuated, only a slight increase is seen as a whole. As a result, the total power consumption of all the vacuum pumps is 68 + 440 = 508 kW in the conventional example, and 68 + 40 + 3.7 = 111.7 kW in the present embodiment, and it can be seen that the power consumption can be suppressed to 22%.

Next, let us estimate the amount of impurity gas flowing into the vacuum vessel from the exhaust system when gas is not flowing through the vacuum vessel. FIG. 2 shows that the ultimate pressure of the pump is 6.00 Pa (45 mTorr) for the roots pump and 0.53 Pa (4 mTorr) for the mechanical booster pump. The compression ratio of the thread groove type molecular pump is 3000 times (relative to He gas), and considering only the sneaking from the exhaust system, the impurities in the vacuum vessel when the roots pump and the mechanical booster pump are used as the back pump. The gas partial pressures are 2.00 × 10 ⁻³ Pa (1.5 × 10 ⁻⁵ Torr) and about 1.73 × 10 ⁻⁴ (1.3 × 10 ⁻⁶ Torr), respectively. Therefore, it can be seen that the amount of impurity gas flowing into the vacuum vessel from the exhaust system can be reduced by about one digit compared to the conventional example.

  In the conventional apparatus, it is often difficult to install the low vacuum pump near the vacuum vessel due to its large size, and it has been necessary to connect the high vacuum pump with a long pipe. For this reason, when flowing a large flow gas, the back pressure of the high vacuum pump increases due to the influence of the gas conductance of the piping. For example, when a gas of 1 atm · L / min was flown, the pressure was 53.33 Pa (0.4 Torr) without a pipe, but when the gas was passed through a cylindrical pipe having an inner diameter of 40 mm and a length of 10 m, the flow was 111.99 Pa (0 Torr). .84 Torr). In order to reduce the back pressure of the high vacuum pump to 53.33 Pa (0.4 Torr) or less with this pipe connected, the gas flow rate must be restricted to 0.25 atm · L / min or less, which is １ ／. As a result, in processes such as etching and plasma CVD which require a large flow of gas, this has been a major factor in lowering the process speed and process performance. On the other hand, in this embodiment, the low vacuum pump is very small, so that it can be installed in the immediate vicinity of the vacuum vessel. Absent.

  For the pipe 111, a stainless flexible tube having an inner diameter of 36 mm and a length of about 0.55 m was used. As described above, the gas conductance of this pipe is sufficiently large and can be ignored. As the pipe 112, a stainless steel straight pipe having an inner diameter of 40 mm and a length of 42 m was used. Although a pipe having a large diameter is not particularly used, even when a gas having a maximum gas flow rate of 99 atm · L / min is supplied, the pressure difference between both ends of the pipe 112 is at most 386.63 Pa (2.9 Torr). Yes, at a negligible level. As described above, it is not necessary to use a large-diameter pipe as compared with the conventional apparatus, and the installation cost of the pipe does not increase.

  The auxiliary pump 108 and the pipe 113 were set in a clean area of the semiconductor manufacturing plant, and the other parts were set in the clean area.

  FIG. 3 shows a second embodiment in which the vacuum apparatus of the present invention is applied to a semiconductor processing apparatus.

  Reference numeral 301 denotes a vacuum vessel, and 302 and 303 denote gas inlets and gas exhaust ports provided in the vacuum vessel 301, respectively. Reference numeral 304 denotes a cluster tool in which three vacuum vessels are integrated on one platform. Reference numeral 305 denotes a pressure control valve for controlling the gas pressure in the vacuum vessel 301 by changing the gas conductance. Reference numeral 306 denotes a high vacuum pump. In this embodiment, a thread groove type molecular pump is used. Reference numeral 307 denotes a low vacuum pump for keeping the back pressure of the high vacuum pump 306 at a low pressure. In this embodiment, a mechanical booster pump is used. An auxiliary pump 308 uses a roots pump in this embodiment. Numerals 309 and 310 are valves, and in this embodiment, electromagnetic valves are used. 311, 312, and 313 are pipes for flowing gas.

The difference from the first embodiment is that one low vacuum pump 307 simultaneously exhausts three vacuum containers in the cluster tool. When the low-vacuum pump 307 is used in this way, the number of low-vacuum pumps 307 is reduced to 1/3, and the power consumption and the device installation area are further reduced as compared with the case of the first embodiment, so that the cost can be reduced.
In the present embodiment, three vacuum vessels are simultaneously evacuated by one low vacuum pump, but the invention is not limited to three.

  FIG. 4 shows a third embodiment in which the vacuum apparatus of the present invention is applied to a semiconductor processing apparatus.

  Reference numerals 401a, 401b, and 401c denote vacuum vessels, and 402 and 403 denote gas introduction ports and gas exhaust ports provided in the vacuum vessel 401, respectively. Reference numeral 404 denotes a cluster tool in which three vacuum vessels are integrated on one platform. Reference numeral 405 denotes a pressure control valve for controlling the gas pressure in the vacuum vessel 401 by changing the gas conductance. Reference numeral 406 denotes a high vacuum pump. In this embodiment, a thread groove type molecular pump is used. Reference numeral 407 denotes a low vacuum pump. In this embodiment, a mechanical booster pump is used. An auxiliary pump 408 uses a roots pump in this embodiment. Reference numerals 409 and 410 denote valves, and in this embodiment, electromagnetic valves are used. 411, 412, 413, and 414 are pipes for flowing gas.

  The vacuum vessels 401a and 401b are plasma CVD apparatuses of polysilicon, and the process is performed at a relatively high pressure of 53.33 Pa (400 mTorr) or more. Reference numeral 401c denotes a polysilicon etching apparatus which performs a process at a low pressure of 4.00 Pa (30 mTorr). The difference from the first embodiment is that a high vacuum pump is not connected to the two vacuum vessels 401a and 401b in the cluster tool, and the vacuum is directly exhausted by a low vacuum pump. This is because the process is performed at a relatively high pressure of 53.33 Pa (400 mTorr) or more, so that no exhaust capability in a low vacuum region is required. As described above, when the process is performed at a relatively high pressure, the power consumption and the installation area of the apparatus are further reduced as compared with the case of the first embodiment, and the cost can be reduced by not installing the high vacuum pump.

  FIG. 5 shows a fourth embodiment in which the vacuum apparatus of the present invention is applied to a semiconductor processing apparatus.

  FIG. 5 shows only changes from the first embodiment. Reference numeral 501 denotes an auxiliary pump. In this embodiment, two Roots pumps of 2000 L / min are connected in parallel as in the first embodiment. Reference numerals 502, 503, and 504 denote valves. In this embodiment, 502 is an electric valve, and 503 and 504 are manual valves. 505 and 506 are pipes for flowing gas. The inside of the pipe 506 is almost at atmospheric pressure.

  In the first to third embodiments, since a single auxiliary pump exhausts a large number of vacuum containers, there is a problem that if the auxiliary pump breaks down, a large number of vacuum containers become unusable at the same time. In this embodiment, normally, the valves 503 and 504 are always open, and the two auxiliary pumps simultaneously exhaust air. If one of the auxiliary pumps 501 fails, the valves 503 and 504 before and after the auxiliary pump 501 are closed, and the pump is replaced or repaired. During this time, exhaust is performed only by the other auxiliary pump. That is, even if one of the auxiliary pumps fails, the apparatus can be used without any trouble.

  FIG. 6 shows a fifth embodiment in which the vacuum apparatus of the present invention is applied to a semiconductor processing apparatus. This is obtained by adding a rough evacuation system used to evacuate the vacuum vessel from atmospheric pressure to reduced pressure to the apparatus of the second embodiment. Here, only the differences from the second embodiment will be described.

  Reference numeral 601 denotes a roughing pump. In this embodiment, a 360 L / min scroll pump was used. The power consumption of this pump is as small as 0.45 kW, and is very small. The ultimate vacuum degree is 1.33 Pa (10 mTorr). Reference numerals 602 and 603 denote valves, and in this embodiment, electric valves are used. Reference numeral 604 denotes a pipe. In this embodiment, a stainless steel pipe having a diameter of 9.525 mm (3/8 inch) is used. Reference numeral 605 denotes a pipe, the inside of which is substantially at atmospheric pressure.

  When performing maintenance or the like inside the vacuum vessel, it is necessary to release the inside of the vacuum vessel to the atmosphere. If a large amount of air flows into the exhaust system when the inside of the vacuum vessel is evacuated again, the back pressure of the low vacuum pump may increase and affect other vacuum vessels. In this embodiment, this problem is solved by newly adding a rough exhaust system.

  In a state where the vacuum vessel is open to the atmosphere, the corresponding high vacuum pump is stopped, and the corresponding valves 602 and 603 are closed. When the inside of the vacuum container is evacuated, the valve 602 is opened with the valve 603 closed, and the atmosphere is exhausted by the roughing pump 601 through the pipe 604. Thereafter, when the pressure inside the vacuum vessel decreases to about 2666 to 7999 Pa (several tens of Torr), the valve 602 is closed and the valve 603 is opened. After that, the high vacuum pump is started to return to the normal operation state.

  In this embodiment, if the process is not performed in two or more vacuum vessels at the same time in the cluster tool, the valve 603 of the vacuum vessel that is not performing the process is closed and the roughing pump 601 is switched to the high vacuum pump. By using this as a back pump, it is possible to completely prevent the gas from flowing around and improve the cleanliness as compared with the apparatus shown in the second embodiment.

  In this embodiment, a rough exhaust system is added to the apparatus of the second embodiment, but the same effect can be obtained by adding the rough exhaust system to the apparatuses of the first to fourth embodiments. Further, in the present embodiment, the pipe 604 is connected to the exhaust side of the high vacuum pump, but may be directly connected to the vacuum vessel or may be connected to the exhaust side of the low vacuum pump.

  FIG. 7 shows a sixth embodiment in which the vacuum apparatus of the present invention is applied to a semiconductor processing apparatus. This is obtained by adding a rough evacuation path used when the inside of the vacuum vessel is evacuated from the atmospheric pressure to a reduced pressure, to the apparatus of the second embodiment. Here, only the differences from the second embodiment will be described.

  Numerals 701 and 702 denote valves. In this embodiment, electric valves are used. Reference numeral 703 denotes a pipe. In this embodiment, a stainless steel pipe having a diameter of 3.175 mm (1/8 inch) is used.

  In a state where the vacuum vessel is open to the atmosphere, the corresponding high vacuum pump is stopped, and the corresponding valves 701 and 702 are closed. When the inside of the vacuum container is evacuated, the valve 701 is opened with the valve 702 closed, and the atmosphere is exhausted through a pipe 703 by a low vacuum pump. At this time, since the inside diameter of the pipe 703 is small and the gas conductance is small, the flow rate of the gas flowing into the low vacuum pump is suppressed, and the rise of the back pressure of the low vacuum pump is suppressed. Thereafter, when the pressure inside the vacuum vessel decreases to about 2666 to 7999 Pa (several tens of Torr), the valve 701 is closed and the valve 702 is opened. After that, the high vacuum pump is started to return to the normal operation state.

  In the present embodiment, the rough evacuation path is added to the apparatus of the second embodiment, but the same effect can be obtained by adding the rough exhaust path to the apparatus of the first to fourth embodiments.

  FIG. 8 shows a seventh embodiment in which the vacuum apparatus of the present invention is applied to a semiconductor processing apparatus. In the seventh embodiment, the apparatus of the second embodiment is provided with a means for removing a part of the gas and a means for heating the pipe between the vacuum vessel and the pipe to 90 ° C. or more.

  In FIG. 8, reference numerals 801 and 802 denote valves with a heater, and reference numerals 803 and 804 denote pipes with a heater. These pipes 803 and 804 are covered with a rubber heater 809, so that the temperature is always kept at 90 ° C. or higher when a vacuum device is used. In addition, 805 and 806 are ordinary pipes. 807 is a water-cooled trap. Reference numeral 808 denotes an auxiliary pump corresponding to the auxiliary pump 308 shown in FIG.

  In a plasma CVD apparatus or a plasma etching apparatus, exhaust gas generated after processing in a vacuum vessel contains a large amount of precipitated by-products and the like. These substances are contained in the gas phase component and the exhaust gas in the vacuum vessel, but may be cooled while passing through the pipe, change to a solid phase component, and adhere to the inside of the pipe. Such deposits cause a reduction in the evacuation performance of the vacuum pump and a failure of the apparatus itself. Such deposits reduce the cross-sectional area of the pipe, and thus include the problem of reducing the conductance of the exhaust gas. It is therefore desirable to take measures to prevent the deposits.

  In the present embodiment, a water-cooled trap 807 is provided as a means for removing gaseous components that cause the adhesion. Furthermore, by heating the pipes up to the water-cooled trap 807 to a temperature at which no deposits are generated, it is possible to prevent the pipes up to the water-cooled trap 807 from being adhered.

  In the present embodiment, the water-cooled trap 807 is used as a means for removing the precipitated components in the exhaust gas. However, it is needless to say that the present invention is not limited to this. Also, the heating means may be any means that can heat a portion in contact with the exhaust gas in the exhaust path to at least 90 ° C. or more, and is not limited to the rubber heater of the embodiment, such as using a ceramic heater. is there.

  Although the present embodiment has been described as being added to the device of the second embodiment, the same effect can be obtained by adding the device to the above-described other embodiment.

  As described above, according to the present invention, it is possible to realize a vacuum apparatus that has a small power consumption and a small area occupied by the apparatus, allows the impurity gas to flow from the exhaust system into the vacuum vessel, and allows a large flow rate of gas to flow.

  Further, by providing a means for effectively removing the precipitable by-products contained in the exhaust gas, a vacuum device capable of maintaining the exhaust conductance in a favorable state for a long period of time can be provided.

FIG. 1 is a schematic diagram of an apparatus according to the first embodiment. FIG. 2 is a graph comparing the exhaust characteristics of the mechanical booster pump and the roots pump according to the first embodiment. FIG. 3 is a schematic diagram of an apparatus according to the second embodiment. FIG. 4 is a schematic diagram of an apparatus according to the third embodiment. FIG. 5 is a schematic diagram of an apparatus according to the fourth embodiment. FIG. 6 is a schematic diagram of an apparatus according to the fifth embodiment. FIG. 7 is a schematic diagram of an apparatus according to the sixth embodiment. FIG. 8 is a schematic diagram of an apparatus according to the seventh embodiment.

Claims (3)

A plurality of vacuum vessels having a gas inlet and an exhaust port, a gas supply system for introducing a desired gas from the gas inlet into the vacuum vessel, and an exhaust system for keeping the inside of the vacuum vessel at reduced pressure. In the provided vacuum device,
The exhaust system has a plurality of vacuum pumps connected in series in multiple stages,
Among the plurality of vacuum pumps, a low vacuum pump is installed in the immediate vicinity of the vacuum vessel, and the low vacuum pump is connected to a final stage vacuum pump by a common pipe from the plurality of low vacuum pumps,
The exhaust pressure of the final stage vacuum pump is approximately atmospheric pressure,
The vacuum apparatus, wherein the last-stage vacuum pump is configured to exhaust gas from a plurality of previous-stage vacuum pumps per unit.   The vacuum apparatus according to claim 1, wherein the low vacuum pump is a booster pump.   The vacuum apparatus according to claim 1, wherein the last-stage vacuum pump is a roots pump.

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