JP3695865B2 - Vacuum exhaust device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a vacuum exhaust apparatus suitable for use in a vacuum system for circulating and reusing gas.
[0002]
[Prior art]
In a conventional semiconductor manufacturing apparatus, for example, an etching apparatus or a chemical vapor deposition apparatus (CVD), as shown in FIG. 2, semiconductor manufacturing is performed toward a wafer 2 disposed inside a vacuum chamber 1. Necessary gas is ejected from the shower head 3 to process the wafer 2. Here, all the processed gas in the vacuum chamber 1 is exhausted from the vacuum chamber 1 through a gate valve 4 by a high vacuum pump 5 such as a turbo molecular pump or a composite molecular pump, and then coarsely discharged from a foreline valve 6. It was discharged to the atmosphere via the pulling pump 7.
[0003]
[Problems to be solved by the invention]
However, in recent years, semiconductor manufacturing apparatuses tend to use a large amount of gas in order to increase the diameter of wafers and improve the quality of film formation. A part of the gas introduced into the vacuum chamber of the semiconductor manufacturing apparatus only contributes to the reaction, and most of the remaining gas is discharged unreacted. Therefore, in the future, as shown in FIG. 3, in order to effectively use the gas, a part of the gas exhausted from the vacuum chamber 1 by the high vacuum pump 5 such as a turbo molecular pump is again put in the vacuum chamber 1. The necessity to devise and raise the utilization efficiency of unreacted gas becomes high.
[0004]
That is, as shown in the figure, a gas circulation pipe 8 that branches from between the high vacuum pump 5 and the foreline valve 6 and returns to the inlet of the vacuum chamber 1 is provided, and a shutoff valve 9 is provided inside the gas circulation pipe 8. And a flow rate adjusting valve 10 is interposed between the foreline valve 6 and the roughing pump 7, and the gas circulating pipe 8 is inserted through the flow rate adjusting valve 10 and the cutoff valve 9. It is conceivable to circulate the gas having the flow rate Q2 to introduce the gas having the flow rate Q1 + Q2 into the vacuum chamber 1 and to release the gas having the flow rate Q1 to the atmosphere.
[0005]
Here, when the gas is introduced into the vacuum chamber, a gas ejection device, usually referred to as a shower head, is used as described above in order to uniformly distribute the gas to the wafer. The gas to be circulated must also be returned to the vacuum chamber via a gas blowing device such as this shower head. However, since this shower head is provided with dozens of minute holes having a diameter of 1 mm or less and gas is ejected from these holes, the conductance is very small. For example, the conductance of a shower head provided with 50 holes with a diameter of 0.8 mm is approximately 1 × 10 ⁻² l / s. Therefore, when returning 1000 sccm of the circulating gas into the vacuum chamber through this shower head, it must be compressed to about 20 Torr.
[0006]
However, turbo molecular pumps and composite molecular pumps that are conventionally used generally cannot be used as the high vacuum pump 5 shown in FIG. In addition, even if sufficient compression performance is provided to circulate the gas, the pump has a large bore to exhaust a large amount of gas, and the number of blade stages is increased to improve the compression performance. Since the axial length of the rotor has to be increased, the pump has an increased outer diameter and height.
[0007]
This is not preferable considering the demand for a compact exhaust system for semiconductor manufacturing equipment.
Further, depending on the amount of gas, it is conceivable that the screw groove rotor cannot be sufficiently compressed and the gas cannot be circulated.
[0008]
The present invention provides a vacuum evacuation apparatus that solves these problems and is used in an exhaust system that circulates gas for reuse. The gas can be reliably circulated in a compact configuration. It is intended to do.
[0009]
[Means for Solving the Problems]
The invention according to claim 1 is used in a vacuum system in which a gas is introduced into a vacuum chamber, the gas is exhausted from the vacuum chamber, and a part of the exhausted gas is returned to the vacuum chamber again. A vacuum evacuation device having a first vacuum pump having a sufficient pumping speed to keep the inside of the vacuum chamber at a predetermined pressure, and a capability of compressing the gas to a pressure necessary for returning the gas back into the vacuum chamber. A second vacuum pump having an exhaust port of the first vacuum pump and an intake port of the second vacuum pump, the first vacuum pump being used for both the drive system and the exhaust system. It is an oil-free pump that does not use lubricating oil, the second vacuum pump is a dry pump that does not use lubricating oil in at least the exhaust system, and the first vacuum pump has a low compression ratio and its height. Reduce the second vacuum pump Provides low pumping speed by reducing the outer diameter, a vacuum exhaust device being characterized in that to reduce the volume as a whole.
[0010]
In other words, the first vacuum pump has a pumping speed performance necessary for keeping the inside of the vacuum chamber at a predetermined process pressure with respect to a predetermined amount of gas introduced, and the gas exhausted by the first vacuum pump is supplied to the vacuum chamber. The second vacuum pump has the ability to compress to the pressure required to return it inside.
[0011]
In this way, the first vacuum pump is divided into the first vacuum pump and the second vacuum pump, and by sharing the role in exhausting the gas, the first vacuum pump has a large outer diameter to achieve the exhaust speed. However, since the compression capacity may be small, the height is small, and the second vacuum pump achieves a large compression capacity, but the height is large, but the exhaust speed may be small, so the outer diameter can be small. If this is achieved with a single pump, both the outer diameter and the height of the pump become large, and the present invention can achieve a compact evacuation apparatus as a whole.
[0012]
For example, if the first vacuum pump requires a pumping speed of 3000 l / s, the outer diameter of the first vacuum pump is about 400 mm, but the compression ratio may be about 10-50, so the height of the pump Can be 300 mm or less. And since the 2nd vacuum pump exhausts the gas compressed with the 1st vacuum pump, the exhaust speed may be about 60-300l / s, and the outer diameter dimension of a pump will be 100-170mm. Therefore, the diameter of the second vacuum pump can be significantly reduced as compared with the first vacuum pump. If the height of the second vacuum pump is, for example, 500 mm from the necessary compression conditions, the total volume occupied by the first and second vacuum pumps is 42 to 49 l. On the other hand, if the gas is circulated by a single vacuum pump, the vacuum pump occupies a volume of 100 l. According to the present invention, the volume of the vacuum exhaust device can be reduced by 50 to 60%. It becomes possible.
[0013]
In the present invention, since the first vacuum pump and the second vacuum pump are separately provided, if the amount of gas is too large and the turbo molecular pump or the complex molecular pump cannot be compressed to a predetermined pressure, The second vacuum pump can be compressed to a required pressure by adopting an exhaust principle pump capable of increasing the compression capacity.
[0015]
Here, the oil-free pump is a Roots type pump, a scroll type pump, a screw type pump, a turbo molecular pump, a turbo molecular pump (composite molecular pump) in which a thread groove is formed on the downstream side in the axial direction of the rotor, a molecular drag pump, or This is a dry pump (pump that does not use lubricating oil in the exhaust system) such as a vacuum pump having a vortex rotor, and further uses a magnetic bearing or the like as a drive system and does not use any oil.
[0016]
Another embodiment of the present invention, both before Symbol first vacuum pump and the second vacuum pump, characterized in that an oil-free pump using a magnetic bearing.
[0017]
Another embodiment of the invention features in that a device for removing certain gas component in the path back to the evacuated part again vacuum chamber of the gas.
[0018]
This has the following meaning. The gas component introduced into the vacuum chamber for the purpose of reacting with the material in the vacuum chamber changes the gas component due to the reaction. If a component that inhibits the reaction is mixed in the changed gas component, if all the gas components are circulated as they are, the reaction in the vacuum chamber may not be performed correctly. . Therefore, by installing a device for removing a specific component contained in the circulating gas on the intake port side or the exhaust port side of the second vacuum pump, components that adversely affect the reaction in the vacuum chamber are installed. Since it can be removed before returning to the vacuum chamber, the intended reaction of the vacuum system can be performed correctly.
[0019]
The vacuum exhaust apparatus of the present invention is mainly used for a vacuum system including a process of reacting a gas introduced into a vacuum chamber with a material in the vacuum chamber, and further includes the following aspects: Can be used.
[0020]
The volume occupied by the vacuum evacuation device can be minimized by directly connecting the first vacuum pump and the second vacuum pump, or by incorporating them into an integral casing.
On the other hand, by connecting the first vacuum pump and the second vacuum pump via a vacuum pipe, a space for directly connecting the first vacuum pump and the second vacuum pump or accommodating an integrated object When there is no, a 2nd vacuum pump can be installed in an appropriate place via vacuum piping.
[0021]
In another aspect of the present invention, the first vacuum pump has a second exhaust port in addition to the exhaust port connected to the second vacuum pump. Thereby, the gas which does not return to a vacuum chamber can be discharged | emitted from the 2nd exhaust port of a 1st vacuum pump. Furthermore, by making the vacuum pipe connecting the first vacuum pump and the second vacuum pump have a branch pipe, the gas that does not return to the vacuum chamber can be discharged from the branch pipe.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIG.
As shown in the figure, a gas necessary for manufacturing a semiconductor is blown from a shower head 3 toward a wafer 2 disposed inside a vacuum chamber 1 to perform processing on the wafer 2. The processed gas in the chamber 1 is exhausted from the vacuum chamber 1 by the vacuum exhaust device 20 through the gate valve 4.
[0023]
The vacuum exhaust device 20 compresses the first vacuum pump 21 having a sufficient exhaust speed to keep the inside of the vacuum chamber 1 at a predetermined pressure and a pressure necessary for returning the gas back into the vacuum chamber 1. The second vacuum pump 22 having performance is provided, and the discharge port 21 a of the first vacuum pump 21 and the suction port 22 a of the second vacuum pump 22 are connected by a vacuum pipe 23.
[0024]
A foreline valve 6 and a flow rate control valve 10 are sequentially interposed in a branch pipe 24 branched from the middle of the vacuum pipe 23 and connected to the roughing pump 7. On the other hand, a gas circulation pipe 8 returning to the inlet of the vacuum chamber 1 is connected to the exhaust port of the second vacuum pump 22 of the vacuum exhaust device 20, and a shutoff valve 9 is interposed in the gas circulation pipe 8. Yes.
[0025]
Accordingly, as the first pump 21 and the second pump 22 are driven, the gas at the flow rate Q2 circulates in the gas circulation pipe 8 through the flow rate adjusting valve 10 and the shutoff valve 9, and the vacuum chamber 1 is circulated. A gas having a flow rate Q1 + Q2 is introduced into the gas, and a gas having a flow rate Q1 is released into the atmosphere.
[0026]
Here, the first vacuum pump 21 is, for example, a turbo molecular pump that achieves oil-free by using a magnetic bearing, or an oil-free turbo molecular pump (composite that includes a thread groove type rotor on the downstream side of the rotor. In order to achieve the pumping speed, the first pump 21 has a pumping speed performance necessary to keep the inside of the vacuum chamber 1 at a predetermined process pressure with respect to a predetermined gas introduction amount. Although the outer diameter is increased, the compression capacity may be small, so that the height can be reduced.
[0027]
The second vacuum pump 22 is a so-called dry-type roots-type vacuum pump or screw-type vacuum pump that employs a structure in which, for example, oil vapor used for lubricating bearings and gears does not leak to the vacuum side. By providing the second vacuum pump 22 with the ability to compress the gas exhausted by the first vacuum pump 21 to the pressure required to return it into the vacuum chamber 1, a large compression capacity is achieved. Therefore, although the height increases, the outer diameter can be reduced because the exhaust speed may be small.
[0028]
As described above, the vacuum exhaust device 20 can be made compact as a whole by configuring the vacuum exhaust device 20 with the first pump 21 and the second pump 22 that share the role.
[0029]
Further, as described above, an oil-free turbo molecular pump or a complex molecular pump is used for the first vacuum pump 21, and a dry roots type vacuum pump or a screw type vacuum pump is used for the second vacuum pump 22. Thus, it is possible to prevent oil molecules that adversely affect the reaction in the vacuum chamber 1 from being substantially mixed into the gas circulating in the gas circulation pipe 8.
[0030]
As the second vacuum pump 22, a molecular drag pump, a roots type vacuum pump, a screw type vacuum pump or the like that has achieved oil-free by using a magnetic bearing can be used. In addition, by using a vacuum pump that achieves oil-free by adopting magnetic bearings for both of the second vacuum pumps 21 and 22, the reaction in the vacuum chamber 1 is caused by the gas circulating in the gas circulation pipe 8. It is possible to completely prevent oil molecules that affect the oil from being mixed.
[0031]
Although not shown, in a semiconductor manufacturing apparatus that performs aluminum etching, it is desirable to provide a low temperature trap on the suction side of the second vacuum pump 22.
[0032]
That is, in such a semiconductor manufacturing apparatus, the reaction in the vacuum chamber 1 produces aluminum chloride having a low vapor pressure and a tendency to solidify (solidifies at about 80 degrees or less at 0.1 Torr), which circulates. It will be contained in the gas. For this reason, in general, in an apparatus for etching aluminum, the temperature of gas passages and piping in the pump is raised to prevent the aluminum chloride from solidifying and adhering in the pump.
[0033]
Thus, the first vacuum pump 21 is provided with such a temperature raising means, and a trap having a low temperature surface is provided in front of the intake port of the second vacuum pump 22 so that the low temperature surface of the trap is chlorinated. Aluminum can be attached, and thereby, aluminum chloride, which is an unnecessary component, can be removed from the circulating gas.
[0034]
Further, when the vapor pressure of the unnecessary component is higher than the vapor pressure of the component to be circulated, the unnecessary component cannot be removed by the low temperature trap, but the unnecessary component is generated by the reaction in the vacuum chamber 1. In the case of powder, by providing an electrostatic dust collector on the intake side or exhaust side of the second vacuum pump 22, unnecessary fine powder can be removed by this electrostatic dust collector.
[0035]
In the illustrated example, an example in which the first vacuum pump 21 and the second vacuum pump 22 are connected by a vacuum pipe 23 is shown. By configuring in this way, Although the arrangement of the second vacuum pump 22 can be arbitrarily selected, the first vacuum pump 21 and the second vacuum pump 22 can be directly connected, and thus the direct connection is possible. By doing so, the pressure loss of the connecting portion can be minimized, the back pressure of the first vacuum pump 21 can be kept low, and this load can be minimized.
[0036]
【The invention's effect】
As described above, according to the present invention, in a vacuum system in which a gas is introduced into a vacuum chamber, the gas is exhausted from the vacuum chamber, and then a part of the exhausted gas is returned to the vacuum chamber. A vacuum exhaust device for circulating gas can be realized in a compact manner. Further, it is possible to provide a vacuum exhaust device that can be reliably circulated even if the amount of gas to be circulated is large. Furthermore, by removing unnecessary components from the circulated gas, the reaction in the vacuum chamber can be performed correctly.
[Brief description of the drawings]
FIG. 1 is a system diagram of a vacuum system showing an embodiment of the present invention.
FIG. 2 is a system diagram of a vacuum system showing a conventional example.
FIG. 3 is a system diagram showing a virtual vacuum system.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Vacuum chamber 3 Shower head 7 Roughing pump 8 Gas circulation piping 20 Vacuum exhaust apparatus 21 First vacuum pump 21a Same exhaust port 22 Second vacuum pump 22a Same intake port 23 Vacuum piping 24 Branch pipe

Claims (3)

A vacuum exhaust apparatus used in a vacuum system that introduces a gas into a vacuum chamber, exhausts the gas from the vacuum chamber, and then returns a part of the exhausted gas back into the vacuum chamber.
A first vacuum pump having a pumping speed sufficient to keep the inside of the vacuum chamber at a predetermined pressure, and a second vacuum pump having a capability of compressing the gas to a pressure necessary for returning the gas back into the vacuum chamber. And connecting the exhaust port of the first vacuum pump and the intake port of the second vacuum pump,
The first vacuum pump is an oil-free pump that does not use lubricating oil for both the drive system and the exhaust system, and the second vacuum pump is a dry pump that does not use lubricating oil for at least the exhaust system, The first vacuum pump has a reduced compression ratio to reduce its height, and the second vacuum pump has a lower exhaust speed to reduce its outer diameter and reduce its overall volume. A vacuum exhaust device that is characterized. The vacuum exhaust apparatus according to claim 1, wherein both the first vacuum pump and the second vacuum pump are oil-free pumps using magnetic bearings. 3. The vacuum exhaust apparatus according to claim 1, wherein a device for removing a specific gas component is provided in a path for returning a part of the exhausted gas back into the vacuum chamber.

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