GB2439948A

GB2439948A - A vacuum pumping system

Info

Publication number: GB2439948A
Application number: GB0613788A
Authority: GB
Inventors: David Paul Manson; Clive Reginald Steer
Original assignee: BOC Group Ltd; Edwards Ltd
Current assignee: Edwards Ltd
Priority date: 2006-07-12
Filing date: 2006-07-12
Publication date: 2008-01-16
Anticipated expiration: 2026-07-12
Also published as: GB2439948B; GB0613788D0

Abstract

A vacuum pumping arrangement 38 comprises a controller 50 for controlling a vacuum pump. A purge gas supply apparatus is provided for supplying purge gas to the pumping arrangement. The gas supply apparatus comprises a manifold 12 having a gas inlet (14, fig 1) for receiving pressurised purge gas and a plurality of gas outlets (16, fig 1) each for supplying purge gas to a respective port of the pumping arrangement. The supply of purge gas to the gas outlets is controlled by a plurality of solenoid valves 28. A valve controller 60 is mounted on the manifold for receiving data from the pump controller of the pumping arrangement and for controlling the solenoid valves dependent on the received data.

Description

GAS SUPPLY APPARATUS

This invention relates to apparatus for supplying a purge gas to a vacuum pumping arrangement, and to a method of controlling the supply of purge gas to a vacuum pumping arrangement.

Vacuum pumping arrangements used to pump fluid from semiconductor tools typically employ, as a backing pump, a multi-stage positive displacement pump employing inter-meshing rotors. The rotors may have the same type of profile in io each stage or the profile may change from stage to stage.

During semiconductor processes such as chemical vapour deposition processing, deposition gases are supplied to a process chamber to form a deposition layer on the surface of a substrate. As the residence time in the chamber of the deposition is gas is relatively short, only a small proportion of the gas supplied to the chamber is:. . consumed during the deposition process. Consequently, unconsumed gas.**:*.

molecules pumped from the chamber by a vacuum pump can pass through the pump in a highly reactive state. As a result, pump components can be subjected to damage due to corrosion and degradation resulting from the pumping of aggressive, unconsumed gas molecules. Furthermore, if the unconsumed process gas or by-product is condensable, sublimation on lower temperature surfaces can result in the accumulation of powder or dust within the pump, which can effectively fill the vacant running clearance between the rotor and stator elements of the pump. Other processes use gases that can result in potentially flammable mixtures forming in the pump.

To dilute these gases as they pass through the pump, an inert purge gas, such as nitrogen, can be supplied to the pump. As this gas can also serve to increase the longevity and effectiveness of dynamic shaft seals of the pump, and can ensure that certain sensors within the pumping arrangement are maintained in a clean and functional state, it is typically supplied through a plurality of purge ports provided at various locations about the pumping arrangement.

Figure 1 illustrates a known apparatus for supplying purge gas to a number of purge ports. The apparatus 10 comprises a manifold 12 having an inlet 14 and a plurality of outlets 16. The inlet 14 is connected to a source 18 of pressurised purge gas, such as nitrogen or argon, via a conduit 20, which includes a check valve 22. As the pressure of the purge gas at the source 18 may be variable, for example, within the range from 20 to 100 psi, the conduit 20 also includes a pressure regulator 24 for adjusting the pressure of the stream of purge gas conveyed to the inlet 14.

Within the manifold 12, the received stream of purge gas passes through a mass flow transducer 26 before being split into a plurality of streams for conveyance to the outlets 16. As the flow requirement at each outlet 16 may be different, depending on the purpose for which the purge gas is being supplied to a particular purge port of the pumping arrangement, the manifold 16 contains solenoid valves is 28 for selectively opening and closing the supply of purge gas to each of the:. . outlets 16, together with fixed flow restrictors 30 and variable flow restrictors, for:: example needle valves, 32 for fixing the flow rate of each stream of purge gas supplied to an outlet 16. With reference also to Figure 2, the outlets 16 are * connected by conduits 34 to purge ports 36 of the vacuum pumping arrangement 38. Pressure transducers 40 may also be provided for monitoring the gas flow rate and/or gas pressure within one or more of the conduits 34. :;:; The operation of the solenoid valves 28 of the apparatus 10 is controlled by the pump controller that controls operation of the pumping arrangement 38. As illustrated in Figure 3, the pump controller 50 is connected by wires 52 to each of the mass flow transducer 26, solenoid valves 28 and pressure transducers 40.

The pump controller 50 interprets signals received from the transducers 26, 40 and issues actuating signals to the solenoid valves 28 to open or close the valves in whatever sequence is appropriate for the current operational state of the pumping arrangement 38. The pump controller 50 may also manage the power supply to the solenoid valves 28 in order to reduce power consumption when the valves are maintained in an actuated position for prolonged periods.

The pump controller 50 is normally located remote from the manifold 12 and pressure transducers 40, and so relatively long lengths of wire are required to connect the pump controller 50 to the solenoid valves 28 and the transducers 26, 40. This can also impair EMC performance, as power management and sequencing is performed remote from the apparatus 10. Due to the number of connections required between the pump controller 50 and the various components of the apparatus 10, a relatively complex communications interface is required for the pump controller 50. Furthermore, if the performance of the apparatus 10 is to be upgraded, or new gas handling technologies are to be introduced to the apparatus 10, then the design of the pump controller 50 may require modification, which may disrupt the use of the pumping arrangement 38.

It is an aim of at least the preferred embodiment of the present invention to seek to solve these and other problems. * . * S *

In a first aspect, the present invention provides apparatus for supplying a purge gas to a vacuum pumping arrangement, the apparatus comprising: a manifold having a gas inlet for receiving pressurised gas from a source thereof, a plurality of gas outlets each for supplying gas to a respective port of the ***.

pumping arrangement, and a plurality of solenoid valves for controlling the supply of gas to the gas outlets; and: a valve controller mounted on the manifold for receiving data from a pump controller of the pumping arrangement and for controlling the solenoid valves dependent on the received data.

By providing the apparatus with such a valve controller, the apparatus can be afforded a level of software and electronic intelligence that can enable the apparatus to take control of the actuation, sequencing and power consumption of the solenoid valves. This can provide the following advantages: * Improved EMC performance, as the power management and sequencing can be carried out in close proximity to the solenoid valves; * A simplified communications interface between the apparatus and the pump controller, such as a Modbus data communication protocol; * A significant reduction in the number of wires or other connectors between the apparatus and the pump controller; and * The ability to upgrade performance of the gas supply apparatus, or to introduce new gas handling technologies, with minimal disruption to the design of the pump controller.

The valve controller is preferably configured to supply to the solenoid valves actuating signals having a voltage of varying duty cycle, the duty cycle having an initial value sufficient to cause an armature of a solenoid valve to move to an actuated position and a subsequent lower value sufficient to hold the armature in the actuated position. The actuating signals are preferably supplied sequentially to the solenoid valves so that at any given time not all of the valves have a voltage of the initial duty cycle being supplied thereto. By staggering the supply of the actuating signals to the valves in this manner so that at not all of the valves, preferably no more than two of the valves, and more preferably no more than one of the valves, have the voltage of the initial duty cycle being supplied thereto at any given time, the maximum total power consumption of the valves at any given time will be lower than if all of the valves were actuated simultaneously.

The valve controller may be configured to control the solenoid valves dependent on received data indicative of the state of the pumping arrangement. Alternatively, or additionally, the valve controller may be configured to control the solenoid valves dependent on a received bit pattern, wherein each bit of the bit pattern indicates the required state of a respective solenoid valve.

The valve controller may be configured to perform other functions in response to received data. For example, the valve controller may perform a reset procedure upon receipt of an appropriate command from the pump controller. As another example, the valve controller may update firmware or code stored in the valve controller upon receipt of appropriate data from the pump controller.

The valve controller may be configured to output various items of information to the pump controller, either periodically or in response to a command received from the pump controller. For example, the valve controller may supply to the pump controller data indicative of: * the current state of each of the solenoid valves; * the identity of the gas supply apparatus, for example type and part/serial io numbers; and/or * the results of a self-test performed by the valve controller Furthermore, the apparatus may comprise at least one sensor for monitoring a parameter associated with the supply of purge gas from at least one of the gas outlets. This monitored parameter may be one of purge gas flow rate and purge gas pressure. The valve controller may be configured to receive and interpret the data received from the sensor(s), and output data indicative of the monitored S. parameter to the pump controller. For example, the valve controller may return to the pump controller data indicative of the current gas flow rate, total flow rate or measured pressures. Removing the requirement for the pump controller to interpret signals received from sensors can reduce the burden on the pump controller.

In a second aspect, the present invention provides a vacuum pumping arrangement comprising a vacuum pump, a manifold having a gas inlet for receiving pressurised purge gas from a source thereof, a plurality of gas outlets each for supplying purge gas to a respective port of the pumping arrangement, and a plurality of solenoid valves for controlling the supply of purge gas to the gas outlets, a pump controller for controlling the vacuum pump, and a valve controller mounted on the manifold for receiving signals from the pump controller and for controlling the solenoid valves dependent on the received data.

In a third aspect, the present invention provides a method of controlling the supply of a purge gas to a vacuum pumping arrangement from a manifold having a gas inlet for receiving pressurised purge gas from a source thereof, a plurality of gas outlets each for supplying purge gas to a respective port of the pumping arrangement, and a plurality of solenoid valves for controlling the supply of purge gas to the gas outlets, the method comprising the steps, at a valve controller mounted on the manifold, of receiving data from a pump controller, and controlling the state of the solenoid valves dependent on the received data.

io Features described above in relation to the first aspect are equally applicable to any of the second and third aspects, and vice versa.

Preferred features of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 15.. * **

Figure 1 illustrates a known apparatus for supplying purge gas to a pumping arrangement;

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Figure 2 illustrates a pumping arrangement having ports connected to the apparatus of Figure 1; ***** S... *... * S I

Figure 3 illustrates a known control system for controlling the apparatus of Figure 1;and Figure 4 illustrates a control system for controlling the apparatus of Figure 1 according to an embodiment of the invention.

With reference to Figure 4, apparatus for supplying purge gas to a vacuum pumping arrangement 38 includes the known apparatus illustrated in Figure 1 for supplying purge gas to the purge ports of the pumping arrangement 38. A valve controller 60 is mounted on the manifold 12, and is connected to each of the solenoid valves 28 of the manifold 12, the mass flow transducer 26 and to each of -7--the pressure transducers 40. In this embodiment, the valve controfler 60 comprises a printed circuit board 62 upon which a processor chip 64 is mounted.

The valve controller 50 is linked to the pump controller 50 by signal line 66, which may be a connecting wire or a wireless link.

In this embodiment, a Modbus data communication protocol is established between the pump controller 50 and the valve controller 60, although other alternative communication protocols may be used. The signals transmitted between the pump controller 50 and the valve controller 60 may therefore adopt a to Modbus message structure, having the four basic elements of: * device address; * function code; * data bytes; and * error check.

i5 The pump controller 50 assumes the role of a Modbus master and the valve controller 60 assumes the role of a Modbus slave. Consequently, when the pump * ,* : controller 50 sends a message addressed to the valve controller 60, the valve controller 60 takes action and, depending on the contents of the message, outputs: a message addressed to the pump controller 60. **.

4U * * The function code defines the message type, and therefore the action that is to be taken by the valve controller 60 in response to the message. One action that may be taken by the valve controller 60 is to control the state of the solenoid valves 28 of the manifold 12 by supplying actuating signals to the solenoid valves 28. As is known, solenoid valves generally comprise an armature which is moveable against the force of a return spring by a magnetic field generated in a coil. Each valve may be normally closed, with the armature moving to an actuated, open position when the actuating signal is supplied to the coil of the valve. Alternatively, the valve may be normally open, with the armature moving to an actuated, closed position when the actuating signal is supplied to the coil of the valve. In this embodiment, the valves are normally closed, and so in the event that one or more of the valves are to be opened, the valve controller 60 generates actuating signals for supply to the valves as required. In the event that one or more of the valves are to be closed, the valve controller 60 simply stops the supply of the actuating signals to those valves, so that the armatures of those valves move to the closed position.

The valve controller 60 may determine which of the solenoid valves are to be opened (actuated) or closed (non-actuated) from data included in the data field of the message received from the pump controller 50. For example, the data field may include a bit pattern, wherein each bit of the bit pattern indicates the required state of a respective solenoid valve. The valve controller 60 can interpret the received bits, for example a 1" may indicate that the valve is to be in an actuated position, and a may indicate that the valve is to be in a non-actuated position, and either issue or terminate actuating signals as required to place the solenoid valves 28 in the required states. * *.

Alternatively, the data field may include data which is indicative of the current state of the pumping arrangement. The valve controller 60 may store, for each state of the pumping arrangement, data which indicates the required state (actuated/non-actuated) of each solenoid valve. The valve controller can look up the required state of the solenoid valves 28 for the current state of the pumping arrangement **** 38, and either issue or terminate actuating signals as required to place the solenoid valves 28 in the required states.

Each actuating signal generated by the valve controller 60 has a voltage Va of varying duty cycle. The duty cycle initially has a value sufficient to cause an armature of the valve to move to an actuated position. In this example, the initial value of the duty cycle is 100%. The duration, t1, of the initial duty cycle is sufficient to cause the armature to be moved to the actuated position, and, depending on the design of the valve, may be between 0.1 and 5 seconds. The duty cycle of the signal voltage is then reduced to a value sufficient to hold the armature in the actuated position. In this example, the reduced value of the duty cycle is 50%. The voltage of the actuating signal is maintained with this reduced duty cycle until the valve is to be closed, at which point the supply of the actuating signal to the valve is stopped.

The valve controller 60 may select the sequence in which the valves are to be opened and at time t=0 an actuating signal is supplied to a first one of the valves 28. At time t1, the duty cycle of the voltage of the actuating signal reduces from 100% to 50%, and a second actuating signal is supplied to a second one of the valves 28. At time 2t1, the duty cycle of the voltage of the second actuating signal reduces from 100% to 50%, and a third actuating signal is supplied to a third one of the valves 28. This supply of actuating signal to the valves with a period of t1 continues until all of the valves that are to be actuated in accordance with the data received from the pump controller 50 have been actuated.

The power consumption of a valve when the voltage of 100% duty value is Is supplied thereto iS Pa, and so the power consumption of a valve when the voltage of 50% duty value is supplied thereto IS %Pa. By staggering the supply of the actuating signals to the valves in this manner, the voltage of initial duty value is supplied to no more than one of the valves at any given time. Therefore, the maximum power consumption of n actuated valves is S * S...

pp((n_I)F;J when the initial duty valve is 100% and the reduced duty value is 50%. This can enable the capacity of a power supply for supplying power to the valve controller to be reduced.

The valve controller 60 may perform other actions dependent on the value of the function code within the message received from the pump controller 50.

For example, the valve controller 60 may return to the pump controller 50 a message indicating the current state of the valves. This message may contain a bit pattern similar to the bit pattern contained in the message received from the pump controller 50 to indicate the current state of each valve. This message may be issued once the state of the valves has been set in response to a command from the pump controller 50, or alternatively in response to a separate message from the pump controller 50. In order to generate this message, the valve controller 60 may determine which of the valves are currently receiving actuating signals, and therefore are in an actuated (open) position, or the valve controller 60 may simply return the most recently received bit pattern to the pump controller 50.

As another example, the valve controller 60 may perform a self-test and/or self-initialisation upon power-up, and so in response to an appropriate command from the pump controller 50 the valve controller 60 may generate a message reporting the results for the self-test and output that message to the pump controller 50.

The valve controller 60 may perform a reset procedure upon receipt of an appropriate command from the pump controller 50. Firmware or code stored in the valve controller 60 may be updated using data contained in the messages from the pump controller 50.

One or more identifiers for the gas supply apparatus may be stored in the memory of the chip 64 of the valve controller 60. These identifiers may include the type of manifold 12, and part or serial numbers for the manifold 12. In response to an appropriate command from the pump controller 50, the valve controller 60 may generate a message containing these identifiers, and output the message to the pump controller 50.

As mentioned above, the valve controller 60 is connected to the mass flow transducer 26 and to the pressure transducers 40. The valve controller 60 is preferably configured to receive and interpret the data received from these transducers 26, 40. In reply to a command from the pump controller 50, the valve controller 60 may generate one or more messages containing data indicative of the parameters monitored by one or more of these transducers 26, 40, and send the message(s) to the pump controller 50. For example, the valve controller may -11 -return to the pump controiler data indicative of the current gas flow rate, total flow rate or measured pressures. * S. ** Se * .. * .

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S *S S (. S S... *..i * S* cc.

Claims

CLJMS

1. Apparatus for supplying a purge gas to a vacuum pumping arrangement, the apparatus comprising: a manifold having a gas inlet for receiving pressurised gas from a source thereof, a plurality of gas outlets each for supplying gas to a respective port of the pumping arrangement, and a plurality of solenoid valves for controlling the supply of gas to the gas outlets; and a valve controller mounted on the manifold for receiving data from a pump controller of the pumping arrangement and for controlling the solenoid valves dependent on the received data.

2. Apparatus according to Claim 1, wherein the valve controller is configured to control the power consumption of the solenoid valves. * * * * **

3. Apparatus according to Claim 1 or Claim 2, wherein the valve controller is configured to supply to the solenoid valves actuating signals having a voltage of varying duty cycle, the duty cycle having an initial value sufficient to cause an armature of a solenoid valve to move to an actuated position and a subsequent lower value sufficient **** to hold the armature in the actuated position. *:::: 4. Apparatus according to Claim 3, wherein the valve controller is configured to supply actuating signals sequentially to the solenoid valves so that at any given time not all of the valves have a voltage of the initial duty cycle being supplied thereto.

5. Apparatus according any preceding claim, wherein the valve controller is configured to output to the pump controller data indicative of the state of each of the solenoid valves.

6. Apparatus according to any preceding claim, comprising at least one sensor for monitoring a parameter associated with the supply of purge gas from at least one of the gas outlets, and wherein the valve controller is configured to receive data from said at least one sensor and to output data indicative of the monitored parameter to the pump controller.

7. Apparatus according to Claim 6, wherein the monitored parameter is one of purge gas flow rate and purge gas pressure.

8. Apparatus according to any preceding claim, wherein the valve controller is configured to control the solenoid valves dependent on received data indicative of the state of the pumping arrangement.

9. Apparatus according to any preceding claim, wherein the valve controller is configured to control the solenoid valves dependent on a received bit pattern, wherein each bit of the bit pattern indicates the *.

required state of a respective solenoid valve. "S

10. A vacuum pumping arrangement comprising: a vacuum pump; a manifold having a gas inlet for receiving pressurised purge gas from a source thereof, a plurality of gas outlets each for supplying purge gas to a respective port of the pumping arrangement, and a plurality of solenoid valves for controlling the supply of purge gas to the gas outlets; a pump controller for controlling the vacuum pump; and a valve controller mounted on the manifold for receiving signals from the pump controller and for controlling the solenoid valves dependent on the received data.

-14 - 11. A method of controlling the supply of a purge gas to a vacuum pumping arrangement from a manifold having a gas inlet for receiving pressurised purge gas from a source thereof, a plurality of gas outlets each for supplying purge gas to a respective port of the pumping arrangement, and a plurality of solenoid valves for controlling the supply of purge gas to the gas outlets, the method comprising the steps, at a valve controller mounted on the manifold, of: receiving data from a pump controller; and io controlling the state of the solenoid valves dependent on the received data.

12. A method according to Claim 11, wherein the power consumption of the solenoid valves is controlled by the valve controller.

13. A method according to Claim 11 or Claim 12, wherein actuating signals having a voltage of varying duty cycle are supplied to the solenoid valves by the valve controller, the duty cycle having an initial.:: value sufficient to cause an armature of a solenoid valve to move to an actuated position and a subsequent lower value sufficient to hold the armature in the actuated position.

S S...

14. A method according to Claim 13, wherein the actuating signals are supplied sequentially to the solenoid valves so that at any given time not all of the valves have a voltage of the initial duty cycle being supplied thereto.

15. A method according to any of Claims 11 to 14, wherein data indicative of the state of each of the solenoid valves is output from the valve controller to the pump controller.

16. A method according to any of Claims 11 to 15, wherein a parameter associated with the supply of purge gas from at least one of the gas outlets is supplied to the valve controller from at least one sensor, and data indicative of the monitored parameter is output from the valve controller to the pump controller.

17. A method according to Claim 16, wherein the monitored parameter is one of purge gas flow rate and purge gas pressure.

18. A method according to any of Claims 11 to 17, wherein the state of the solenoid valves is controlled dependent on data indicative of the state of the pumping arrangement.

19. A method according to any of Claims 11 to 18, wherein the state of the solenoid valves is controlled dependent on a bit pattern received from the pump controller, wherein each bit of the bit pattern indicates the required state of a respective solenoid valve. * * * * *

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S * . S. S... * S * S S *s.