Multiple vacuum chamber exhaust system and method for evacuating multiple vacuum chambers

Abstract

A vacuum exhaust system and a method for evacuating a plurality of chambers (10) are disclosed. The vacuum exhaust system is located in a clean room and includes: a plurality of branch process gas channels (14), each branch process gas channel being configured to be connected to a corresponding chamber (10); and a shared process channel (16), the shared process channel being formed by the confluence of the branch channels and being configured to provide a shared fluid communication path for process gas from each of the chambers to flow from the clean room to a process channel outside the clean room. There are also a plurality of branch exhaust channels (30), each branch exhaust channel being configured to be connected to a corresponding chamber (10) and a shared exhaust channel (32), the shared exhaust channel being formed by the confluence of the branch exhaust channels and being configured to provide a fluid communication path for fluid to flow from the clean room to the exhaust channel outside the clean room during exhaustion of at least one of the vacuum chambers (10).

Description

Technical Field

[0001] The present invention relates to vacuum exhaust manifolds and methods and systems for pumping gases from multiple chambers, such as process chambers used in semiconductor manufacturing. Background Art

[0002] Semiconductor manufacturing facilities have multiple vacuum chambers located within cleanrooms to reduce the chance of contamination. They need to maintain a low, stable pressure within each chamber. This is typically accomplished using a vacuum exhaust system consisting of a turbomolecular pump attached to the vacuum chamber and a booster and backing pump attached to the turbomolecular pump's exhaust. Backing and booster pumps can be located outside the cleanroom in subfabs to reduce contamination and vibration within the cleanroom.

[0003] The semiconductor process within each chamber is asynchronous, cyclical, and intermittent, where the type and amount of gas being evacuated varies over time. Gases generated by reactions with the process gas (reaction product gases) and residual process gases are exhausted to the outside of the chamber through a vacuum exhaust system, where they can be fed to the abatement system.

[0004] Therefore, the exhaust system for such a chamber should be able to evacuate different gases and varying amounts, and generate and maintain a stable high vacuum.

[0005] A typical setup for etch systems in production today uses a dedicated backing pump for each process chamber.

[0006] It is desirable to share pumps across multiple semiconductor processing chambers to reduce the overhead associated with multiple pumps while still providing a stable high vacuum within each chamber. Summary of the Invention

[0007] A first aspect provides a vacuum exhaust system for evacuating multiple chambers in a clean room, the vacuum exhaust system comprising:

[0008] a plurality of branch process gas channels, each of which is configured to be connected to a corresponding chamber; a shared process channel, formed by the confluence of the branch channels, and configured to provide a shared fluid communication path for process gas from each of the chambers to flow from the clean room to a process channel outside the clean room during processing; and a plurality of branch exhaust channels, each of which is configured to be connected to a corresponding chamber; a shared exhaust channel, formed by the confluence of the branch exhaust channels, and configured to provide a fluid communication path for fluid to flow from the clean room to an exhaust channel outside the clean room during exhaust of at least one of the vacuum chambers.

[0009] In semiconductor processing applications such as wafer etching, it is desirable to match the vacuum chambers in a vacuum system so that the wafers processed in each chamber are substantially identical. To achieve this, each chamber should provide a substantially identical vacuum environment at the same stage of the process. This requirement is conventionally addressed by providing each chamber with identical piping arrangements, which feed similar pumps. The inventors recognized that one way to "automatically" achieve this matching is to use one or more shared pumps and shared piping / channels within the tool / cleanroom. This arrangement would automatically match the vacuum piping and pumps and also provide significant savings in piping and pumping. While there are advantages associated with sharing pumps within a system, there are also potential disadvantages. In particular, the shared piping connecting the vacuum chambers to the remote pumps provides a path between chambers, so that pressure peaks in one chamber are transmitted to the shared piping and potentially affect the pressure in other chambers. In semiconductor processing systems, different vacuum chambers typically perform different processing steps at different times, and therefore, the pressures within different chambers will vary at different times. Furthermore, they are periodically vented and need to be pumped back to the operating high vacuum. Thus, where one chamber experiences a pressure spike, perhaps due to venting and subsequent pump down, this will affect the vacuum in the shared conduit and therefore the vacuum felt in the other chambers.

[0010] The inventors of the present invention recognized the advantages of sharing a pump and realized that the disadvantages could be alleviated by providing separate pumping channels for pumping during pumping and for pumping during processing. As a result, pressure peaks from the pumping of one chamber are isolated from the process gas shared channel and therefore do not affect the pressure in other chambers. The cost in terms of hardware or space of providing additional pumping channels is not as great as expected because the pumping channels can have a relatively small cross-section because the pumped gas is at a relatively high pressure. In addition, these channels do not need to be heated because they do not conduct process gas. Both the pumping and process gas channels are shared channels, one of which is for the process gas to leave the clean room and one is for the gas pumped during pumping. It should be noted that the process gas transported by the process channel includes the process gas fed to the chamber and the gaseous products of the reaction in the chamber.

[0011] In some embodiments, the vacuum exhaust system further includes a plurality of vacuum pumps for evacuating the plurality of chambers, the plurality of vacuum pumps being configured to be connected to the corresponding plurality of vacuum chambers, and the plurality of branch process gas channels being connected to corresponding exhaust devices of the plurality of vacuum pumps.

[0012] In some embodiments, the vacuum pump comprises a high vacuum pump configured to operate in a molecular flow region of the evacuated gas.

[0013] Vacuum chambers may have high vacuum pumps, such as turbomolecular pumps, attached to them where the chamber requires a high vacuum, such as during an etching process. Where the pump is a turbomolecular pump, it is particularly important to maintain a steady-state pressure in the shared process gas channel as changes in pressure at the exhaust of the turbomolecular pump affect its pumping speed and therefore the vacuum it produces.

[0014] In some embodiments, the vacuum exhaust system further includes a process lower vacuum pump configured to operate in the viscous flow region of the gas, the process lower vacuum pump being connected to the process channel outside the clean room; and an exhaust vacuum pump configured to operate in the viscous flow region of the gas, the exhaust vacuum pump being connected to the exhaust gas channel outside the clean room.

[0015] The use of a shared process gas channel and a shared exhaust gas channel allows a single process vacuum pump and a single exhaust vacuum pump to be located outside the cleanroom. These pumps can be backing pumps for a high vacuum pump, or in the case of a chamber used for deposition, for example, they can be the pumps used to evacuate the chamber. In any case, they are typically dry pumps and are located outside the cleanroom in the cleanroom to isolate the chamber from vibrations from such pumps. Space within a cleanroom is limited, so being able to provide multiple vacuum chambers with a single vacuum pump for pumping process gases and a single pump for exhaust significantly reduces the amount of space occupied by the pumps in the cleanroom and can be very advantageous.

[0016] In some embodiments, the plurality of branch process gas channels are configured such that the effective conductance of each branch channel is substantially the same, with the effective conductance varying by less than 20%, preferably less than 10%, between each of the branch channels.

[0017] As previously noted, it is advantageous if the chambers are matched and therefore the vacuum system of each chamber should be substantially identical. In the case where they use a shared pump, the pump will be identical for each chamber, and to provide effective chamber matching, it is advantageous if the tubing is also identical, or more specifically, if the effective conductivities of the branch channels that are not shared channels are substantially identical or at least vary by less than 20%. That is, the branch channel with the highest effective conductivities has an effective conductivities that are less than 20% greater than the branch channel with the lowest effective conductivities.

[0018] In some embodiments, the vacuum exhaust system further includes a control module, the control module including a pressure control circuit configured to generate a control signal for controlling the pressure in the shared process channel.

[0019] As previously noted, it is desirable to reduce any fluctuations in pressure within the shared process channels. Having separate extraction channels and extraction pumps helps reduce fluctuations, but further reductions can be achieved by using a pressure control system that generates control signals to control the pressure within the shared process channels. This control can be performed to reduce pressure fluctuations that are determined by the control circuit based on received measurements or predicted based on other received signals.

[0020] In some embodiments, the vacuum exhaust system further comprises: a pressure sensor for monitoring the pressure in the shared process channel;

[0021] The pressure control circuit is configured to receive signals from the pressure sensors and generate at least one of the control signals in response to at least one of the received signals to reduce fluctuations in the monitored pressure.

[0022] One way in which pressure may be controlled is to associate a pressure sensor with the shared line, and in response to a measurement indicating a change in pressure, a varying control signal may be generated.

[0023] Alternatively and / or additionally, in some embodiments, the pressure control circuit is configured to receive a signal indicating activity within at least one of the chambers, and the pressure control circuit is configured to generate at least one of the control signals in response to at least one of the received signals indicating the activity.

[0024] The pressure control circuitry can receive signals indicative of activity within the chamber. These signals can come from sensors within the chamber, or they can come from control circuitry controlling processing within the chamber. Receiving signals indicative of activity within the chamber allows the control circuitry to generate a pressure control signal that can alter the pressure in the shared channel to account for pressure changes that would otherwise be caused by activity within the chamber.

[0025] In some embodiments, the pressure control circuit is configured to receive a signal indicative of future activity within at least one of the chambers, the pressure control circuit being configured to generate at least one of the control signals in response to the received signal indicative of the future activity.

[0026] The signals may not only indicate current activity, they may also indicate future activity in the chamber, which may be activity predicted from detected previous and / or current activity, or it may be an indication of future activity from the semiconductor control circuitry. Where the signals indicate future activity, then the control signals may be proactive and may be generated to change the pressure in the shared channel before any pressure change is sensed, thereby allowing pressure fluctuations to be reduced still further.

[0027] In some embodiments, at least one of the control signals generated by the pressure control circuit is a control signal for controlling a pumping speed of at least one of the high vacuum pump or the process lower vacuum pump.

[0028] One way in which the pressure in the system, and in particular the pressure in the shared pumping channels, can be controlled is by controlling the speed of one or more of the pumps within the system.

[0029] In some embodiments, the vacuum exhaust system further comprises: a purge gas inlet for providing a controlled purge gas flow to the shared process channel; and at least one of the control signals generated by the pressure control circuit is a control signal for controlling the purge gas flow.

[0030] Alternatively and / or additionally, the system may comprise a controllable purge gas supply for controlling the amount of purge gas supplied to the shared process channel, and thereby controlling the pressure in the shared process gas channel.

[0031] In some embodiments, at least one of the process channels includes at least one variable flow restrictor.

[0032] Alternatively and / or additionally, in some embodiments, variable restrictors in one or more of the process channels may be used to control pressure.

[0033] At least one of the control signals generated by the pressure control circuit is a control signal for controlling the at least one variable restrictor.

[0034] In some embodiments, the vacuum exhaust system includes multiple valves, including: multiple process valves for isolating the multiple chambers from the corresponding multiple branch process channels or connecting them to the corresponding multiple branch process channels; and multiple exhaust valves for isolating the multiple chambers from the corresponding multiple branch exhaust channels or connecting them to the corresponding multiple branch exhaust channels.

[0035] The vacuum exhaust system may include valves to allow process lines or pump lines to be connected to each vacuum chamber.

[0036] In some embodiments, at least one of the control signals generated by the control module is a control signal for controlling at least one of the plurality of valves.

[0037] The control module can also control valves that interconnect the pumping channels and process gas channels to different chambers. Having a central control module to control the pressure in the shared process channels and control the valves during pumping allows for the prediction and mitigation of pressure fluctuations that will be caused by the different connections.

[0038] In some embodiments, the control module further includes a pump monitoring circuit for monitoring a signal received from a sensor associated with the pump, wherein the signal received from the sensor includes at least one of an indication of current supplied to a motor for driving the pump and a signal from a vibration sensor indicating vibration generated by the pump.

[0039] The control module can also receive signals from sensors associated with the pumps, allowing it to monitor and control the pumps' operation. The signals received from the pumps can indicate their operating condition and can be used to determine when a pump should be serviced. The control module can then control the valves and operation of any spare pumps, isolating the pump requiring service from the system and, in some cases, replacing it with a spare pump.

[0040] In some embodiments, the system further comprises a process vacuum pump configured to operate in a viscous flow region of the gas, the process vacuum pump being connected to the process channel outside the clean room, the system further comprising an abatement module configured to receive a gas flow from the process vacuum pump, the control module being configured to transmit a signal to the abatement module indicating an amount of abatement gas to be supplied to the abatement module.

[0041] Having a central control module that receives signals from the processing chambers and / or signals indicating the pressure within the shared process lines and the currently supplied purge gas allows the control module to know the amount of process gas and reaction product gas currently being exhausted by the vacuum system and that needs to be reduced. The control module can use this information to control the abatement system to supply the required amount of gas to the abatement system, thereby allowing the abatement system to be adjusted for current operating conditions.

[0042] A second aspect provides a vacuum system comprising a plurality of chambers connected to the vacuum exhaust system of the first aspect.

[0043] A third aspect provides a method for evacuating multiple vacuum chambers in a clean room, the method comprising: connecting a process gas exhaust manifold to multiple vacuum chambers so that multiple process gas branch channels connect the multiple vacuum chambers to a shared process gas channel in the clean room; connecting a pumping gas exhaust manifold to multiple vacuum chambers so that multiple pumping branch channels connect the multiple vacuum chambers to a shared pumping channel in the clean room; evacuating the multiple vacuum chambers through the process gas channels using a vacuum pump, the vacuum pump being located outside the clean room and connected to the shared process gas channel; monitoring the pressure in the shared process channel; and generating a control signal for controlling the pressure in the shared process channel to reduce fluctuations in the monitored pressure.

[0044] In some embodiments, the method further comprises: receiving signals indicative of activity within at least one of the vacuum chambers; and generating, in response to at least one of the received signals, at least one control signal for controlling the pressure in the shared process channel so as to reduce fluctuations in the monitored pressure due to the activity.

[0045] In some embodiments, the method further comprises receiving a signal indicative of future activity within at least one of the chambers; and generating, in response to at least one of the received signals, at least one control signal for controlling the pressure in the shared process channel so as to reduce fluctuations in the monitored pressure that are predicted to occur due to the future activity.

[0046] In some embodiments, the control signal includes a signal for controlling the flow of a purge gas into the shared process line; and the method includes controlling the flow of the purge gas in response to the control signal.

[0047] Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of the dependent claims may be combined with features of the independent claims as appropriate, and in combinations other than those explicitly set out in the claims.

[0048] Where an apparatus feature is described as being operable to provide a function, it will be appreciated that this includes apparatus features that provide that function or that are adapted or configured to provide that function. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Embodiments of the present invention will now be further described with reference to the accompanying drawings, in which:

[0050] Figure 1 shows a vacuum system according to one embodiment;

[0051] Figure 2 shows a vacuum system and an abatement system according to another embodiment; and

[0052] Figure 3 A flow chart illustrating steps in a method for evacuating a plurality of vacuum chambers is shown. DETAILED DESCRIPTION

[0053] Before discussing the embodiments in more detail, an overview will first be provided.

[0054] Embodiments provide shared pumping of multiple chambers while maintaining a stable vacuum environment through pressure control management of a common foreline manifold, and are applied within an etching system. Embodiments also integrate the entire vacuum system, including the chamber pumps, into a common control system. This may be driven from an OEM (original equipment manufacturer) perspective and may offer several performance advantages over an end-user-driven approach.

[0055] Embodiments provide designs for vacuum layouts of multi-chamber etching systems, which may include:

[0056] • Symmetrical or nearly symmetrical process vacuum line design within a multi-chamber system, connected via a process vacuum manifold to a single process vacuum exit point from the etch system;

[0057] • A single foreline pump (with emergency backup) connected to the etching system vacuum outlet to provide vacuum for the entire system;

[0058] • Vacuum control module, which monitors and controls the pressure management system of the chamber TMP, backing pump, and process vacuum manifold.

[0059] Embodiments provide a vacuum exhaust system for multiple vacuum chambers used for semiconductor processing, such as wafer etching or wafer deposition. Within such a processing system, it is desirable for the vacuum chamber to present identical conditions to each wafer, resulting in uniform wafers in each chamber. Such systems also have space limitations, particularly in cleanrooms below cleanrooms, where foreline pumps or dry pumps are typically located. The amount of space available for such pumps is limited. Furthermore, multiple pumps can be expensive and may also have difficulty providing uniform pumping. Embodiments provide for a shared pump between chambers, with a single process gas line exiting the cleanroom and entering the cleanroom.

[0060] Embodiments provide a single extraction pump with a single extraction line exiting the cleanroom, so that when the chamber is evacuated from atmosphere during maintenance, for example, a pump different from the process gas pump is used, and pressure spikes that may be generated by the process gas line and pump during the extraction are avoided or at least reduced. In some cases, although only a single process gas pump is in operation at any one time, there may be two process gas pumps within the cleanroom, one of which is a backup pump to provide pumping operation while, for example, the other pump is undergoing maintenance.

[0061] Although the only vacuum pumps used in the system can be those in the cleanroom, in the case of deposition or some other process step that does not require high vacuum, in some embodiments, there are high vacuum pumps, such as turbo pumps, attached to each of the chambers, and the exhausts of these pumps are connected to the process gas line via branching process gas pipes, which are then each connected to a shared process gas line that exits the cleanroom and brings the process gas to the pump in the cleanroom. In embodiments, the process gas lines or channels are designed to be symmetrical so that each chamber sees the same effective conductance, or at least very similar effective conductances. In this regard, the design is such that the effective conductances provided by the pipes from each chamber are within 20% of each other, and preferably within 10% of each other. That is, the maximum conductance seen by any chamber is at most 20% higher than the minimum conductance seen by any other chamber, and preferably within 10% of that value.

[0062] Embodiments also provide a central control module configured for pressure control within a shared process gas line, thereby reducing pressure variations within the line and, therefore, providing more uniform conditions within each chamber. In this regard, embodiments provide pressure control circuitry that may include a pressure sensor and a controllable purge gas supply for supplying purge gas to the shared process gas line. The purge gas supply is increased to compensate for a decrease in airflow from the chamber, and decreased to compensate for an increase in airflow from the chamber. In this regard, the pressure control system can reactively respond to these changes by sensing pressure changes within the shared line and altering the purge gas flow in response to these detected changes. Alternatively, and / or additionally, the control circuitry can be proactive and predict pressure changes within the shared line and adjust the purge gas flow before such changes are detected. In this regard, the central control module can receive signals from the system controlling the chamber. In this case, the signals can indicate when a change in processing within the chamber will occur, or the circuitry can predict which activity will occur next based on a signal indicating a current activity. In response, the circuitry can generate appropriate control signals to compensate for any changes in airflow output from the chamber. In this way, by having a central control system, a reduction in pressure fluctuations in the shared process gas channels can be achieved.

[0063] In some cases, the central control system can also be used to monitor the operating status of the pump by monitoring, for example, the airflow supplied to the pump and / or the vibrations generated by the pump. Based on these signals, the control circuit can determine when such a pump may need maintenance. The central control module can also be used to control the abatement system downstream of the pump within the clean room. In this regard, the amount of abatement gas required depends on the amount of process and reaction product gases output from the multiple chambers. If the control module has access to signals from the chamber control system, it will have at least some visibility into the processing steps being performed and will be able to provide signals to the abatement system that control the amount of abatement gas currently required based on the amount of process gas output. This can have a significant impact on reducing the amount of abatement gas used in the abatement process.

[0064] Figure 1 A vacuum system according to a first embodiment is shown. In this embodiment, the vacuum system has ten chambers 10, each with its own turbomolecular pump 12 connected to the chamber. Chamber valves, not shown, in the form of poppet valves, are present, which can isolate or connect the turbomolecular pumps 12 to the chambers. Branch pipes or channels 14 lead from each of the turbomolecular pump exhausts to a shared pipe 16, which draws process gas from all chambers and exits the cleanroom via an outlet in the cleanroom floor 45, conducting the process gas to a backing pump 20 in the cleanroom. In this embodiment, a backup backing pump 22 is also present.

[0065] In addition to the process gas branch lines 14 and the shared line 16, there are also extraction channels from each chamber for use during the extraction of the chambers after they have been vented. These are shown as branch extraction lines 30 and shared extraction lines 32. As for the process gas lines, they exit the cleanroom at a single point and connect to an extraction dry pump 40 within the cleanroom. Because the extraction pump 40 is used to extract the chambers that have already been vented to atmosphere, these lines 30, 32 can be significantly smaller than the process gas lines 14, 16 operating at a higher vacuum. Furthermore, since they do not carry process gas, they do not require heating, which may be required to prevent material deposition in the process gas channels. Therefore, while providing a separate exhaust system for extraction has some overhead, it is not as significant as providing a separate process gas exhaust system, and it does have the advantage of isolating the many pressure peaks that occur during extraction from the shared process channel 16.

[0066] To control the evacuation of the various chambers, valves are located on both the pump lines 30 and 32 and the process gas lines 14 and 16. Downstream of each turbomolecular pump's exhaust is a valve 18 that isolates both the turbomolecular pump 12 and the chamber from the process gas vacuum line 14. This can be used when the chamber and turbomolecular pump require maintenance. Each branch channel 30 of the pump line also has a valve 38 that isolates the pump chamber from the pump line when it is not being evacuated. In some embodiments, a line runs between the pump branch channel 30 and the process gas branch channel 14, and this connecting channel has its own valve 37. This valve allows the chamber and turbomolecular pump to be evacuated together, even if the turbomolecular pump has already been vented due to maintenance. Furthermore, a chamber valve is located between the chamber and the turbomolecular pump for use when the chamber is to be vented. Venting the chamber is a more common occurrence than venting the turbomolecular pump.

[0067] In this embodiment, there is a vacuum control module 50 that is used to provide central control of the vacuum system. The vacuum control module 50 provides pressure control for maintaining a uniform pressure within the shared process gas line 16 and reducing any pressure fluctuations.

[0068] To provide pressure control, the control module 50 can control a purge gas supply 54 that provides a controlled flow of purge gas into the shared channel 16. The control module 50 can also be configured to control various pumps and valves within the system. In some cases, there can be controllable restrictions within at least some of the conduits to control the conductance of the conduits, and these can also be controlled by the central control module 50.

[0069] In some embodiments, the control module 50 receives signals from the chamber, providing visibility into activity within the chamber. These signals may come from sensors associated with the chamber, or from control circuitry used to control processes within the chamber. In some embodiments, the central control module 50 may include control circuitry for controlling processes within the chamber and control circuitry for controlling the vacuum exhaust system. The central control module 50 may also be configured to control dry pumps 20, 40 within the cleanroom.

[0070] In some embodiments, the vacuum control module 50 provides pressure control within the shared channel 16 by monitoring the pressure within the shared channel using a pressure sensor 52. In response to detected changes in the monitored pressure, the control module 50 sends a control signal to the purge gas supply 54 to change the amount of purge gas supplied to the shared channel to compensate for any detected pressure changes. Alternatively and / or additionally, the vacuum control module 50 can have a more proactive, predictive role and can determine different processes being performed based on signals received from the chamber and control the purge gas supply 54 based on, and in advance of or in synchronization with, these predicted gas flow changes. The control module 50 can also control valves and the pumps themselves in response to these received signals, such that pumping speeds can be varied depending on the process step being performed, and valves can be opened or closed when the chamber requires maintenance or venting.

[0071] In some embodiments, the vacuum control module 50 may also receive signals from sensors associated with the pump that provide an indication of the pump's operating condition, such as the airflow used to drive the turbomolecular pump 12 or the vibrations generated by the pump in the cleanroom. For example, if there is a significant change in the airflow required to drive the turbomolecular pump, this indicates that the pump requires maintenance. Similarly, vibration sensors associated with the dry pumps 40, 20 may indicate that they also require maintenance. In the case of a dry pump 20 with a backup pump 22, a valve (not shown) may be used to disconnect the pump 20 from the system, and the backup pump may serve as the system's pump.

[0072] Figure 2 An alternative embodiment is shown, similar to Figure 1 , but this embodiment additionally has abatement systems 60, 62 attached to the process pumps for abatement of process and reaction product gases output from the vacuum system. The abatement system 60 can also be controlled by the vacuum control module 50, and the amount of abatement gas sent to the abatement system can vary depending on the amount and type of gas currently output from the vacuum system. This can be determined by the central control module, which receives signals from the chambers indicating their current and / or future activity. In this way, a more efficient and environmentally friendly system for abatement is provided. The abatement system 60 can have a backup abatement system 62 for use, for example, when the system 60 is being repaired.

[0073] Figure 3A flow chart illustrating steps S10 to S110 in a method for evacuating a plurality of vacuum chambers according to an embodiment is shown. In step S10, a process gas exhaust manifold including a plurality of branch channels leading to a shared channel is connected to the corresponding plurality of vacuum chambers. In step S20, an exhaust manifold including a plurality of branch channels leading to the shared channel is also connected to the corresponding plurality of vacuum chambers. Then, in step S30, at least some of the chambers are evacuated through the process gas channel, and the pumped gas leaves the clean room via the shared process gas channel and passes through a shared pump operating in a viscous flow region located in the clean room. In some embodiments, each chamber has a turbomolecular pump between the process branch channel and the vacuum chamber.

[0074] In step S40, a controlled amount of purge gas is supplied to the shared process gas line to maintain a substantially constant pressure within the line. In step S50, the pressure in the shared process line is monitored using a pressure sensor, and if a change is detected in step S60, the amount of purge gas supplied is varied in step S70 to offset the detected change. In the event that no change is detected, or after step S70, step S80 is performed, in which a determination is made as to whether a signal has been received indicating a change in activity within one or more of the chambers. Such changes in activity may indicate a change in the amount and / or type of gas being exhausted from the chambers, and accordingly, if this is determined to be the case in step S90, a control signal is generated in step S100 to vary the amount of purge gas to offset any change in gas flow from the chambers and to substantially stabilize the pressure within the shared process gas line.

[0075] Furthermore, such signals may be used to control the abatement system in step S110 such that where the amount and perhaps type of gas exhausted from the chamber as signalled in step S90 changes, the amount of abatement gas required will also change, and therefore these signals may be used to control the abatement system in step S110, and in particular to control the amount of gas used in the abatement system, and thereby make it more efficient.

[0076] In summary, embodiments provide vacuum chambers in which chambers are matched, and wafers in different chambers see substantially the same vacuum environment. Embodiments are fully integrated with symmetrical piping, i.e., piping having the same effective conductance. Matching occurs to a degree automatically by providing shared process lines and shared pumps, and pressure fluctuations that may arise from different processes in different chambers are mitigated by providing a pressure control system and separate backup lines.

[0077] Using a central control system to control the vacuum system, the treatment system and also the abatement system allows the abatement system to be adjusted to current conditions and means that it does not always have to be adjusted up to maximum, which adjustment results in a more efficient system.

[0078] The central control module can receive signals from the chambers, and this allows changes in airflow to be predicted, rather than simply detected, so that they can be responded to before pressure changes occur in the shared lines. This in turn allows for more effective pressure control and reduced pressure fluctuations.

[0079] In some embodiments, there is also a communication and control link between the abatement system and the vacuum control module, enabling integration of the exhaust management control system into the general process control system.

[0080] Although illustrative embodiments of the present invention have been disclosed herein in detail with reference to the accompanying drawings, it should be understood that the invention is not limited to the precise embodiments and that various changes and modifications may be made therein by those skilled in the art without departing from the scope of the invention as defined by the appended claims and their equivalents.

[0081] Reference Symbols

[0082] 10 Vacuum chamber

[0083] 12 Turbomolecular pump

[0084] 14 Process gas branch channel

[0085] 16 shared process gas channels

[0086] 18, 37, 38 valves

[0087] 20 Dry Pump

[0088] 22 spare dry pump

[0089] 30 branch exhaust channels

[0090] 32 shared exhaust channels

[0091] 40 Vacuum pump

[0092] 45 Clean room floor

[0093] 50 control module

[0094] 52 Purge gas supply

[0095] 54 pressure sensor

[0096] 60 Reduction Module

[0097] 62 Spare abatement modules.

Claims

1. A vacuum exhaust system for evacuating a plurality of chambers in a clean room, the vacuum exhaust system comprising: a plurality of branch process gas channels, each branch process gas channel being configured to be connected to a corresponding chamber; a shared process channel formed by the confluence of the branch process gas channels and configured to provide a shared fluid communication path for process gas from each of the chambers to flow from the clean room to a process channel external to the clean room; and a plurality of branched exhaust channels, each branched exhaust channel being configured to be connected to a corresponding chamber; a shared extraction channel formed by the confluence of the branch extraction channels and configured to provide a fluid communication path for fluid to flow from the clean room to an extraction channel outside the clean room during extraction of at least one of the chambers; a control module comprising a pressure control circuit configured to generate control signals for controlling pressure in the shared process channel, the pressure control circuit configured to receive a signal indicative of future activity within at least one of the chambers, the pressure control circuit configured to generate at least one of the control signals in response to the received signal indicative of the future activity; a purge gas inlet for providing a controlled flow of purge gas to the shared process channel; At least one of the control signals generated by the pressure control circuit is a control signal for controlling the purge gas flow.

2. The vacuum exhaust system according to claim 1 further comprises a plurality of vacuum pumps for evacuating the plurality of chambers, the plurality of vacuum pumps being configured to be connected to the corresponding plurality of chambers, and the plurality of branch process gas channels being connected to corresponding exhaust devices of the plurality of vacuum pumps.

3. The vacuum exhaust system according to claim 2, wherein: The plurality of vacuum pumps includes a plurality of high vacuum pumps configured to operate in a molecular flow region of the evacuated gas.

4. The vacuum exhaust system according to any one of the preceding claims 1 to 3, further comprising a lower vacuum pump configured to operate in a viscous flow region of the gas, the lower vacuum pump being connected to the process channel located outside the clean room; and An exhaust vacuum pump configured to operate in a viscous flow region of the gas is connected to the exhaust passage outside the clean room.

5. The vacuum exhaust system according to any one of claims 1 to 3, wherein: The plurality of branch process gas channels are configured such that effective conductance of each branch process gas channel is substantially the same, with effective conductance varying by less than 20% between each of the branch process gas channels. 6 . The vacuum exhaust system of claim 5 , wherein effective conductance varies by less than 10% between each of the branch process gas channels.

7. The vacuum exhaust system according to claim 1 , further comprising: a pressure sensor for monitoring the pressure in the shared process channel; The pressure control circuit is configured to receive signals from the pressure sensor and generate at least one of the control signals in response to at least one of the received signals to reduce fluctuations in the monitored pressure.

8. The vacuum exhaust system of claim 7 , wherein the pressure control circuit is configured to receive signals indicative of activity within at least one of the chambers, the pressure control circuit being configured to generate at least one of the control signals in response to at least one of the received signals indicative of the activity.

9. The vacuum exhaust system according to any one of claims 7 to 8, further comprising at least one of the following: a plurality of vacuum pumps for evacuating the plurality of chambers, the plurality of vacuum pumps being configured to be connected to the corresponding plurality of vacuum chambers, the plurality of branch process gas channels being connected to corresponding exhaust devices of the plurality of vacuum pumps; and a process lower vacuum pump configured to operate in a viscous flow region of the gas, the process lower vacuum pump being connected to the process channel located outside the clean room; At least one of the control signals generated by the pressure control circuit is a control signal for controlling a pumping speed of at least one of the vacuum pumps.

10. The vacuum exhaust system according to any one of claims 1 to 3, comprising a plurality of valves, wherein the plurality of valves comprises: a plurality of process valves for isolating the plurality of chambers from the corresponding plurality of branch process gas channels or connecting them to the corresponding plurality of branch process gas channels; and A plurality of air extraction valves are used to isolate the plurality of chambers from the corresponding plurality of branch air extraction channels or to connect the plurality of chambers to the corresponding plurality of branch air extraction channels.

11. The vacuum exhaust system according to claim 10, wherein: At least one of the control signals generated by the pressure control circuit is a control signal for controlling at least one of the plurality of valves.

12. The vacuum exhaust system according to any one of claims 7 to 8, wherein: The control module also includes a pump monitoring circuit for monitoring a signal received from a sensor associated with the pump, wherein the signal received from the sensor includes at least one of an indication of current supplied to a motor for driving the pump and a signal from a vibration sensor indicative of vibration generated by the pump.

13. The vacuum exhaust system according to any one of claims 7 to 8, wherein: The system also includes a process vacuum pump configured to operate in a viscous flow region of the gas, the process vacuum pump connected to the process channel located outside the clean room, and an abatement module configured to receive a gas flow from the process vacuum pump, the control module being configured to transmit a signal to the abatement module indicating an amount of abatement gas to be supplied to the abatement module.

14. A vacuum system comprising a plurality of chambers connected to a vacuum exhaust system according to any preceding claim.

15. A method for evacuating a plurality of vacuum chambers in a clean room, the method comprising: connecting a process gas exhaust manifold to the plurality of vacuum chambers such that a plurality of process gas branch channels connect the plurality of vacuum chambers to a shared process gas channel within the clean room; connecting an evacuation gas exhaust manifold to a plurality of vacuum chambers so that a plurality of evacuation branch channels connect the plurality of vacuum chambers to a shared evacuation channel within the clean room; evacuating the plurality of vacuum chambers through the process gas channel using a vacuum pump, the vacuum pump being located outside the clean room and connected to the shared process gas channel; monitoring the pressure in the shared process gas channel; and generating a control signal for controlling the pressure in the shared process gas channel to reduce fluctuations in the monitored pressure; receiving a signal indicative of future activity within at least one of the chambers; and In response to at least one of the received signals, at least one control signal is generated for controlling the pressure in the shared process gas channel to reduce fluctuations in the monitored pressure predicted to occur due to the future activity, wherein the control signal includes a signal for controlling the flow of purge gas into the shared process gas channel; and the method includes controlling the purge gas flow in response to the control signal.

16. The method according to claim 15, further comprising: receiving a signal indicative of activity within at least one of the vacuum chambers; and In response to at least one of the received signals, at least one control signal is generated for controlling the pressure in the shared process gas channel to reduce fluctuations in the monitored pressure due to the activity.

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