KR200372323Y1 - Improvements in pumping efficiency - Google Patents

Abstract

The vacuum pumping system includes a plurality of vacuum pumps P1 to P8 for pumping fluid from each load lock chamber C1 to C8, respectively. In order to reduce the fluid pressure at the pump outlet and thus reduce the power consumption of the pump, the fluid exhausted from the pump is transferred to an additional pump (P _exhaust ) which pumps all the exhaust fluid. In order to prevent overloading of the additional pump when multiple chambers are evacuated simultaneously, the blowoff valve 60 selectively diverts some of the exhaust fluid away from the additional pump.

Description

Vacuum pumping system {IMPROVEMENTS IN PUMPING EFFICIENCY}

The present invention relates to the improvement of pumping efficiency, and more particularly to the reduction of power consumption of a vacuum pumping system having a plurality of pumps.

Vacuum treatment is commonly used to deposit thin films on substrates in the manufacture of semiconductor devices. Typically, the treatment chamber is evacuated to a very low pressure (which can be as low as 10 ^-6 mbar, depending on the type of treatment) using a vacuum pump and the feed gas is introduced into the evacuated chamber so that the desired material is located in the chamber. Attached on one or more substrates. Upon completion of the attachment, the substrate is removed from the chamber and another substrate is inserted to repeat the attachment process.

Significant vacuum pumping time is required to evacuate the processing chamber to the required pressure. Thus, a transfer chamber and a load lock chamber are typically used to maintain the pressure in the chamber at or near the required level when replacing the substrate. The loadlock chamber is connected to the transfer chamber by a first window or passageway, which may be selectively opened to insert or remove the substrate into the transfer chamber. The capacity of the loadlock chamber can range from just a few liters to thousands of liters for some large flat panel display tools. The loadlock chamber also has a second window, which may be selectively opened to the atmosphere to insert or remove the substrate into or from the loadlock chamber. In use, the process chamber is maintained at the desired vacuum by the process chamber vacuum pump. With the first window closed, the second window opens to the atmosphere to allow the substrate to be inserted into the loadlock chamber. Next, the second window is closed and the load lock chamber is evacuated until the load lock chamber is at substantially the same pressure as the conveying chamber using a load lock vacuum pump. Next, the first window is opened to allow the substrate to be transferred to the transfer chamber. Thereafter, the transfer chamber is evacuated to a pressure substantially the same as that of the processing chamber, and then the substrate is transferred to the processing chamber.

When the vacuum treatment is completed, the processed substrate is returned to the load lock chamber again. By introducing a non-reactive gas such as air or nitrogen into the load lock chamber with the first window closed to maintain the vacuum in the processing chamber, the pressure in the load lock chamber is brought to atmospheric pressure. When the pressure in the loadlock chamber is at or near atmospheric, the second window opens to allow the processed substrate to be removed. Thus, for the loadlock chamber, a repeating cycle of exhaust from atmospheric pressure to low vacuum or intermediate vacuum is required.

Loadlock pumps typically do not have oil in their vacuum chamber because any lubricant present in the vacuum chamber may cause contamination in the clean environment in which the vacuum treatment is performed. Such "dry" vacuum pumps are usually multi-stage positive displacement pumps using inter-meshing rotors. The rotor can have the same type of profile in each stage, or the profile can change between stages. An example of such a pump suitable for use as a loadlock vacuum pump is one of the "iL" series of BOC Edwards dry vacuum pumps.

Factors that contribute to the power used by the vacuum pump include power to overcome parasitic losses, power to compress the fluid to be pumped, and power losses due to motor inefficiency. In order to reduce the power required to compress the pumping fluid, it is known to reduce the pump exhaust pressure. For example, the Ulvac Eco-Shock attachment provides an additional pump for pumping gas exhaust from the vacuum pump.

In a semiconductor processing plant, vacuum processing can be performed simultaneously in multiple reaction chambers, each with a separate load lock. In order to provide such accessories for each loadlock, the vacuum pump must increase the cost considerably and increase the number of power supplies required for the pumping system and the overall foot-print of the pumping system. In at least its preferred embodiment, the present invention is directed to solving these or other problems.

The present invention provides a plurality of vacuum pumps each pumping fluid from each chamber, means for transferring the fluid discharged from the vacuum pump to an additional pump for pumping the exhaust fluid, and in fluid communication with the transfer means, Provided is a vacuum pumping system comprising means for selectively diverting away from an additional pump.

By connecting two or more vacuum pumps to a common exhaust port carrying the exhausted fluid from the vacuum pump up to an additional pump that pumps the exhaust fluid, the fluid pressure at the pump outlet can be from about 1000 mbar (atmospheric pressure), for example 10 mbar. It can be reduced to a pressure in the range of from 100 mbar. By reducing the pressure difference between the pump inlet and the pump outlet by a factor of 10 or more, the power required to compress the pumped fluid from the chamber is greatly reduced, thereby greatly increasing the power consumption at each vacuum pump. Decrease.

If the vacuum pump comprises a loadlock pump that exhausts a plurality of loadlock chambers, the mass flow rate of the exhaust fluid from the pump outlet is, for example, the loadlock currently being evacuated from a relatively high pressure after the substrate has been inserted into the chamber. It depends on the number of chambers. As a result, the mass flow rate of the exhaust fluid from the vacuum pump, and thus the pressure at the inlet to the further pump, typically varies greatly with time. If the throughput of the loadlock pump exceeds the throughput of the additional pump, for example, if four or more loadlock chambers are evacuated simultaneously from relatively high pressure, the "excess" exhaust fluid is diverted away from the pump and added The fluid pressure upstream from the pump is prevented from exceeding the fluid pressure downstream of the further pump, thereby preventing overloading the inlet stage of the further pump and the exhaust stage of the loadlock pump.

Thus, a single relatively low capacity and low power pump can be used as the pump for the exhaust fluid from all vacuum pumps. As a result, the cost of providing and operating such an additional pump can be further compensated by the annual cost saved by reducing the power consumption of the vacuum pump.

Advantageously, said transfer means comprises a plurality of first conduits for respectively transferring exhaust fluid from each vacuum pump to a second conduit, said second conduit receiving exhaust fluid from each first conduit, The exhaust fluid is directed towards the further pump.

Preferably the diverting means comprises a valve. The valve allows the exhaust fluid to flow from the valve inlet to the valve outlet when the pressure difference between the valve inlet containing the exhaust fluid and the valve outlet and the valve inlet and valve outlet exceeds a predetermined value, for example about 50 mbar. Means may be included. Conveniently, the valve may be in the form of a ball valve, and includes a ball seated relative to the valve seat to block passage of fluid from the valve outlet to the valve inlet, the ball being displaceable from the valve seat in use. By pressurizing the exhaust fluid at the valve inlet end, passage of the exhaust fluid from the valve inlet to the valve outlet is allowed. Preferably, the further pump has an outlet in fluid communication with the valve outlet, such that the valve outlet and the pump outlet have the same pressure.

Preferably, the conveying means comprises means for separating the fluid exhausted from the vacuum pump upstream of the further pump into a first stream flowing towards the further pump and a second stream flowing towards the diverting means. .

In one embodiment, the separating means may comprise a branching point that separates the flow of exhaust fluid from the vacuum pump into two flows. In another embodiment, said separating means also comprises a three-way valve, said three-way valve comprising: a valve inlet for receiving fluid exhausted from the pump, a first valve outlet for discharging the received exhaust fluid towards the further pump; And a second valve outlet for discharging the received exhaust fluid away from the further pump. Means may be provided for selectively discharging the received exhaust fluid only at the first valve outlet or for selectively controlling the three-way valve to discharge the exhaust fluid at both the first valve outlet and the second valve outlet. For example, a sensor may be provided that senses the pressure of the exhaust fluid at the valve inlet, the control means being arranged to control the three-way valve based on the output from the sensor. This allows the second valve outlet to open when the pressure at the valve inlet exceeds a predetermined level, for example when four or more chambers are evacuated from relatively high pressure. The blowdown valve located downstream from the second valve outlet may provide a safety feature that closes the second valve outlet if the pressure drops below a predetermined level in the event of a three-way valve failure.

Alternatively, or in addition, a means for monitoring the power consumption of the vacuum pump may be provided, said control means being arranged to control the further valve based on the output from said monitoring means. This allows the second valve outlet to open when the pump's power consumption rises above a certain level, which is transferred to the current displacement by the pump from a plurality of chambers at relatively high pressures, and thus to additional pumps. It may also be indicated by the current or expected increase in the flow rate of the exhaust gas. Alternatively, the monitoring means may monitor the opening and closing of the valve located between the chamber and the pump.

The system preferably comprises an additional chamber in fluid communication with the transfer means and pumped using an additional pump. By providing such a chamber, it is possible to reduce the pressure increase at the inlet to the additional pump when one or more loadlock chambers are evacuated from relatively high pressure, which can help to prevent the overload of the further pump.

The minimum pressure of the exhaust fluid can be controlled by the amount of purge gas pumped continuously by the vacuum pump. However, if no purge gas is used, the exhaust fluid may be pumped as low as the extreme vacuum of the additional pump (which may be less than 1 mbar, depending on the nature of the additional pump). Since pumping the exhaust fluid below, for example, 5 mbar, may reduce the overall efficiency of the pumping system, the system preferably includes means for controlling the power consumption of the further pump. Thus, the power consumption can be reduced when and when necessary, so that the exhaust pump can be prevented from aspirating to a vacuum of less than 5 mbar, for example.

Hereinafter, preferred features of the present invention are described with reference to the accompanying drawings by way of example only.

1 shows a vacuum pumping system,

2 shows the change in power consumption with exhaust pressure for a BOC Edwards iL600 pump.

Explanation of symbols for main parts of the drawings

10: vacuum pumping system 20, 32, 34: conduit

60: blowoff valve 70: additional chamber

C1 to C8: Load lock chamber P1 to P8: Vacuum pump

N5: branch point V1 to V8: load lock valve

Referring to FIG. 1, one embodiment of the vacuum pumping system 10 is a plurality (8 shown in FIG. 1, respectively) connected to each of the chambers C1 to C8 via respective valves V1 to V8. A suitable number of pumps may be provided). In this embodiment, each chamber C1-C8 is a loadlock chamber of a semiconductor processing system and each vacuum pump is a loadlock pump. Examples of suitable pumps for use as load lock pumps include BOC Edwards iL70 and iL600 dry pumps.

The outlet of each loadlock pump P1-P8 is connected to each conduit 20. Conduit 20 delivers fluid exhausted from the loadlock pump to a common exhaust port 30, which includes conduits 32, 34. The branch point N5 has an inlet 40 for receiving all the fluid exhausted from the load lock pump, a first outlet 42 for discharging the exhaust fluid toward the inlet 50 of the exhaust pump (P _exhaust ), and a blowout ( blow-off) with a second outlet 44 for discharging the exhaust fluid towards the inlet 62 of the valve 60. The exhaust pump may also be in the form of a dry pump, such as a BOC Edwards iL70 pump. The exhaust pump has an outlet 52 which is connected to the outlet 64 of the blowoff valve 60 via conduits 54 and 56.

In use, the loadlock chambers C1 to C8 are maintained at low pressure, typically in the range of 10 ⁻² mbar to 10 ⁻³ mbar, by the load lock pumps P1 to P8. The fluid exhausted from the loadlock pump is transferred to the exhaust pump, which then exhausts the fluid into the atmosphere. As shown in FIG. 1, a light purge gas, such as nitrogen, can be supplied to each loadlock pump, for example at 4 slm, so that in the presence of such purge gas, it is exhausted from the loadlock pump and continues. The amount of fluid delivered to the exhaust pump will therefore be at least 32slpm. At this flow rate, the exhaust pump can reduce the fluid pressure at the outlet of the loadlock pump to less than 100 mbar, typically up to about 12 mbar. Referring to Fig. 2, by reducing the exhaust pressure of the loadlock pump from 1000 mbar (atmospheric pressure) to about 12 mbar, the power consumption of the pump can be significantly reduced. For example, the average power savings for a single BOC Edwards iL600N pump operating at 60 Hz with an exhaust pressure of about 5 mbar is expected to be about 0.6 kW, which can provide a cost savings of about $ 300 per year. For an eight pump system as shown in FIG. 1, including for example five iL70 pumps and three iL600 pumps, annual cost savings are expected to exceed $ 1000.

In use, each loadlock chamber C1 to C8 will be periodically pressurized to atmospheric pressure using a source of non-reactive gas such as, for example, air or nitrogen. Considering this pressurization, for example against the load lock chamber C1, the valve V1 is first closed to isolate the load lock pump P1 from the chamber C1. Next, gas is supplied to chamber C1 to bring the chamber back to atmospheric pressure so that the treated substrate can be removed from the chamber and a new substrate can be inserted for the next treatment. Thereafter, the valve V1 is opened to allow the chamber C1 to be exhausted by the load lock pump P1.

During the evacuation of the chamber, the mass flow rate of the fluid exhausted from the pump P1 increases, increasing the pressure of the exhaust fluid at the inlet 50 of the exhaust pump P _exhaust . If the pressure at the inlet 50 of the exhaust pump does not exceed the pressure at the outlet 52 of the exhaust pump, the exhaust pump can pump the exhaust fluid efficiently. However, depending on the length of the process performed in each processing chamber (not shown) linked to the loadlock chamber, two or more loadlock chambers may be evacuated simultaneously. By providing a blowoff valve 60 in fluid communication with the inlet 50 of the exhaust pump, it is possible to avoid a state in which the flow rate of the fluid from the loadlock pumps P1 to P8 is large enough to overload the exhaust pump. For example, if the pressure difference between the inlet 62 and the outlet 64 of the blowoff valve 60 is greater than 50 mbar, for example, the pressurized exhaust fluid may cause the ball of the valve 60 to exit from the valve seat 68. By moving away, the exhaust fluid can bypass the exhaust pump 50 and be discharged to the atmosphere. Once the pressure differential drops back below 50 mbar, the valve 60 is closed and all exhaust fluid is once again exhausted through the exhaust pump.

The minimum pressure of the exhaust fluid is controlled by the amount of purge gas pumped continuously by the vacuum pump. However, if no purge gas is used, the exhaust fluid may be pumped as low as the extreme vacuum (which may be less than 1 mbar) of the exhaust pump. As pumping exhaust fluid below 5 mbar, for example, can reduce the overall efficiency of the pumping system, a control system can be provided to control the power consumption of the exhaust pump. Thus, the power consumption can be reduced when and when necessary, so that the exhaust pump can be prevented from aspirating to a vacuum of less than 5 mbar, for example.

As shown in FIG. 1, an additional chamber 70 for pumping using an exhaust pump can be provided downstream from the load lock pumps P1-P8. By providing such a chamber 70, it is possible to reduce the pressure increase at the inlet to the exhaust pump when one or more of the loadlock chambers C1 to C8 is exhausted, so that the inlet stage and the loadlock pump of the exhaust pump are reduced. Can help prevent overload of the exhaust stage.

It should be understood that what has been described above represents one embodiment of the present invention, and that other embodiments can be made by those skilled in the art without departing from the true scope of the present invention as defined by the appended utility model claims. Do.

For example, instead of or in addition to the blowoff valve 60, a three-way valve may be provided at the branch point N5. Such a valve can be controlled to direct exhaust fluid towards and / or away from the exhaust pump as needed, thereby preventing overload of the exhaust pump. For example, a sensor may be provided for sensing the pressure of the exhaust fluid at the inlet 40. Depending on the output from the sensor, if the pressure at the inlet 40 exceeds a predetermined level, for example if four or more loadlock chambers are evacuated simultaneously, through the outlet 44, ie the exhaust pump It can be controlled to direct the fluid away from it. Alternatively, or in addition, the power consumption of the loadlock pump can be monitored and the three-way valve can be controlled to open the second outlet 44 when the power consumption of the pump increases above a certain level, The power consumption may be expressed in terms of the current displacement by the pump from the plurality of chambers at relatively high pressures, and thus the current or expected increase in the flow rate of the exhaust gas delivered to the exhaust pump. Alternatively, the three-way valve may be controlled by monitoring the state of the valves V1-V8. The blowoff valve 60 located downstream from the outlet 44 provides a safety feature that closes the second outlet 44 if the fluid pressure at the inlet 40 drops below a predetermined level in the event of a three-way valve failure. can do.

In summary, the vacuum pumping system includes a plurality of vacuum pumps for respectively pumping fluid from each loadlock chamber. In order to reduce the fluid pressure at the pump outlet and thus reduce the power consumption of the pump, the fluid exhausted from the pump is transferred to an additional pump which pumps all the exhaust fluid. In order to prevent overloading of the additional pump when multiple chambers are evacuated simultaneously, the blowoff valve selectively diverts some of the exhaust fluid away from the additional pump.

According to the present invention, it is possible to greatly reduce the power required to compress the fluid pumped from the chamber, thereby greatly reducing the power consumption in each vacuum pump.

Claims (14)

In a vacuum pumping system, A plurality of vacuum pumps each pumping fluid from each chamber, Means for transferring the fluid discharged from said vacuum pump to an additional pump for pumping exhaust fluid; Means in fluid communication with the conveying means and selectively diverting exhaust fluid away from the further pump Vacuum pumping system. The method of claim 1, The conveying means comprises a plurality of first conduits for respectively conveying the exhaust fluid from each vacuum pump to the second conduit, the second conduit receiving the exhaust fluid from each of the first conduits, thereby receiving the exhaust fluid. To the additional pump Vacuum pumping system. The method of claim 1, The diverting means comprises a valve Vacuum pumping system. The method of claim 3, wherein The valve includes a valve inlet containing the exhaust fluid and means for causing the exhaust fluid to flow from the valve inlet to the valve outlet when the pressure difference between the valve inlet and the valve outlet exceeds a predetermined value. Vacuum pumping system. The method of claim 4, wherein The valve includes a ball seated against the valve seat and arranged to block the passage of fluid from the valve outlet to the valve inlet, the ball being displaceable from the valve seat in use to pressurize the exhaust fluid at the valve inlet end. To allow the passage of exhaust fluid from the valve inlet to the valve outlet. Vacuum pumping system. The method of claim 4, wherein The further pump has an outlet in fluid communication with the valve outlet. Vacuum pumping system. The method of claim 1, The conveying means comprises upstream of the further pump means for separating the fluid exhausted from the vacuum pump into a first stream flowing towards the further pump and a second flow flowing towards the diverting means. Vacuum pumping system. The method of claim 7, wherein The separating means comprises a three-way valve, the three-way valve comprising a valve inlet for receiving fluid exhausted from the pump, a first valve outlet for discharging the received exhaust fluid towards the further pump, and an additional pump for the received exhaust fluid A second valve outlet that discharges away from the Vacuum pumping system. The method of claim 8, Means for selectively discharging the received exhaust fluid only at the first valve outlet or selectively controlling the three-way valve to discharge the exhaust fluid at both the first valve outlet and the second valve outlet. Vacuum pumping system. The method of claim 9, A sensor for sensing the pressure of the exhaust fluid at the valve inlet, wherein the control means is arranged to control the three-way valve based on the output from the sensor Vacuum pumping system. The method of claim 9, Means for monitoring the power consumption of the vacuum pump, said control means being arranged to control a three-way valve based on an output from said monitoring means; Vacuum pumping system. The method of claim 1, An additional chamber in fluid communication with said conveying means and pumped using an additional pump; Vacuum pumping system. The method of claim 1, Means for controlling the power consumption of the further pump; Vacuum pumping system. The method of claim 1, The vacuum pump includes a plurality of load lock vacuum pumps, each exhausting a respective load lock chamber. Vacuum pumping system.