Abstract:
A method of preventing a mass flow controller from participating in crosstalk in an array of mass flow controllers is described. The method includes sensing and providing a signal indicative of a fluid pressure inside of a mass flow controller with a pressure sensor contained within the mass flow controller, determining a response of a control valve to a rapid pressure perturbation at the inlet of the mass flow controller using the signal indicative of the fluid pressure to avoid overcompensation for the rapid pressure perturbation, and adjusting a control valve contained within the mass flow controller downstream of the pressure sensor, based on the determined response, so that the mass flow controller avoids overcompensating for the rapid pressure perturbation. The pressure sensor is positioned such that the pressure sensor is sensitive to rapid pressure perturbations at the inlet of the mass flow controller.

Description:
RELATED APPLICATION 
     This application is a divisional of U.S. Application Ser. No. 10/758,968, filed Jan. 16, 2004, which claims the benefit of U.S. Provisional Application No. 60/440,928, filed Jan. 17, 2003. The contents of U.S. application Ser. No. 10/758,968 and U.S. Provisional Application No. 60/440,928 are incorporated here by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to process fluid control assemblies, and more particularly to shut-off valves for process fluid control assemblies. 
     BACKGROUND 
     Almost every process step during semiconductor wafer processing that adds, alters or removes material on silicon wafers utilizes one or more process fluids. These process fluids range from inert fluids, such as helium, to toxic and corrosive fluids, such as chlorine. Consequently, semiconductor wafer processing requires sophisticated fluid delivery systems that can delivery a variety of process fluids in precise amounts to a wafer processing chamber. 
     In a typical processing assembly, the process fluids are contained in individual pressurized cylinders that are under the control of a facility system external to the processing equipment. The fluids are then supplied to the equipment through tubing, and a fluid panel controls the flow of fluid from the point of connection to that tubing to the process chamber. The fluid panel is commonly divided into individual process fluid control assemblies, each of which is a complete assembly of components (such as valves, filters, fluid purifiers, pressure regulators, and transducers) for one fluid stream. 
       FIG. 1  shows a process fluid control assembly  101  configuration in a typical prior art fluid panel. The configuration shown is of the type commonly used for toxic fluids, such as chlorine. The process fluid control assembly comprises a manual diaphragm valve  103  that serves as a safety device by allowing the flow of fluid through the assembly to be manually turned off for maintenance and service. Fluid pressure is controlled by a pressure regulator  105  and a pressure transducer  107 . A filter  109  is provided to remove impurities from the fluid stream. First  111  and second  113  pneumatic valves operate to allow the flow of fluid to be remotely turned on and off by sending an electronic signal to both pneumatic valves and to the mass flow controller (MFC)  115 , the latter of which provides precision control of fluid flow through the process fluid control assembly. Third  117  and fourth  119  pneumatic valves are provided so that the mass flow controller can be purged for maintenance. (The third and fourth pneumatic valves are typically not present in process fluid control assemblies of this type which are designed for use with inert fluids.) A communication port  121  is provided on the mass flow controller to allow it to be accessed and controlled remotely. 
     While the process fluid control assembly configuration of  FIG. 1  allows the fluid panel to provide good control over fluid delivery to the wafer processing chamber, the number of components in this configuration causes the fluid panel to be exceedingly bulky and complex. This is especially so for wafer processing chambers that require several different process fluids. 
     There is thus a need in the art for process fluid control assembly and fluid panel configurations that are more compact and/or have fewer components, without sacrificing functionality, ease of serviceability and modularity of the configuration. These and other needs are met by the devices and methodologies disclosed herein. 
     SUMMARY 
     In one aspect, a device is provided which comprises an actuator and a handle. The actuator is adapted to move the device, in response to a pneumatic signal, from a first state (which may be a closed state) into a second state (which may be an open state), and the handle is adapted to move the device from the second state into the first state regardless of whether a pneumatic signal is present. The device may be, for example, a fluid control assembly equipped with a valve, wherein the valve is closed in the first state and is open in the second state, or it may be a pneumatically driven latch, wherein the latch is closed in the first state and is open in the second state. The handle is typically manually driven, as by rotating it about an axis, and the actuator is typically pneumatically driven. The device may comprise a diaphragm and a valve seat, and the actuator may be adapted to move the device, in response to a pneumatic signal, from a first state in which the diaphragm is pressed against the valve seat, to a second state in which the diaphragm is not pressed against the valve seat. The device may further comprise a valve chamber having a fluid inlet and a fluid outlet, wherein the diaphragm and the valve seat form a seal between the fluid inlet and the fluid outlet. In such embodiments, the fluid inlet and the fluid outlet will typically be in open communication with each other when the device is in the second state. 
     In another aspect, a combination manual/pneumatic valve for a process fluid control assembly is provided. The valve comprises (a) a housing, (b) a valve chamber disposed in the housing which has a fluid inlet and a fluid outlet and which may also contain a diaphragm and a valve seat, (c) a pneumatically driven actuator which is adapted to move the valve, in response to a pneumatic signal, from a first state in which the flow of fluid between the fluid inlet and the fluid outlet is stopped, into a second state in which flow of fluid between the fluid inlet and the fluid outlet is permitted; and (d) a handle adapted to move the valve from the second state into the first state, regardless of whether a pneumatic signal is present at the actuator. When the valve is in the first state, the diaphragm and the valve seat typically form a seal between the fluid inlet and the fluid outlet; conversely, when the valve is in the second state, the fluid inlet and the fluid outlet are typically in open communication with each other. The valve may further comprise an expansion chamber having a piston therein which is adapted to move the diaphragm from a position in which it is pressed against the valve seat to a different position in response to a signal, as, for example, by advancing along a longitudinal axis in a first direction, and the expansion chamber may be equipped with an inlet adapted to introduce pressurized air into the expansion chamber, and an outlet adapted to exhaust the expansion chamber. The valve may also comprise a spring adapted to maintain a compressive force on the diaphragm. 
     The handle of the valve may be equipped with a threaded cylinder that rotatingly engages a complementarily threaded aperture in the housing, thereby moving the valve into the first state. The handle of the valve may have a shaft that is equipped with a passageway defined by first and second apertures that are in open communication with each other, and wherein the first aperture is in open communication with the expansion chamber. The second aperture may be adjustable, by rotation of the handle, from a first position in which it is in open communication with the inlet, to a second position in which it is in open communication with the outlet. The valve seat may be an o-ring and may be disposed about the fluid inlet such that the actuator compresses the diaphragm against the o-ring when the valve is in the first state. 
     In some configurations, the valve is adapted such that a spring holds the diaphragm against the valve seat when the valve is in the first state and the pneumatic chamber and piston counteract the spring to allow the diaphragm to move so that the valve can enter the second state. The disconnection of the pneumatic chamber from the inlet and the connection of the pneumatic chamber to the outlet (accomplished by the single act of rotating the handle), places the valve in a closed position and disables the pneumatic control. Such a configuration may also include a mechanical linkage such that the rotation of the handle causes axial force to be applied to the diaphragm, holding it against the seat with a force in addition to that provided by the spring. 
     In still another aspect, a process fluid control assembly is provided herein which comprises first and second pneumatic valves, a mass flow controller, and a combination manual/pneumatic valve, wherein the first pneumatic valve is upstream from the mass flow controller, wherein the second pneumatic valve is downstream from the mass flow controller, and wherein the combination valve is upstream from the first pneumatic valve. 
     In yet another aspect, a fluid panel is provided herein which comprises a substrate, and a plurality of process fluid control assemblies disposed on said substrate. Each of the plurality of process fluid control assemblies comprises first and second pneumatic valves, a mass flow controller, and a combination manual/pneumatic valve. The first pneumatic valve is upstream from the mass flow controller, the second pneumatic valve is downstream from the mass flow controller, and the combination valve is upstream from said first pneumatic valve. 
     These and other aspects are described in greater detail below. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic illustration of a prior art process fluid control assembly. 
         FIG. 2  is a schematic illustration of a combination valve/manual handle (shown in a manually enabled, pneumatically closed position) in accordance with the teachings herein. 
         FIG. 3  is a schematic illustration of a combination valve/manual handle (shown in a manually enabled, pneumatically open position) in accordance with the teachings herein. 
         FIG. 4  is a schematic illustration of a combination valve/manual handle (shown in a manually disabled valve with a pneumatic signal to open the valve being provided, but with the valve closed) in accordance with the teachings herein. 
         FIG. 5  is a schematic illustration of a stem/handle interface in accordance with the teachings herein. 
         FIG. 6  is an illustration of the functionalities combined into a mass flow controller made in accordance with the teachings herein. 
         FIG. 7  is a functional illustration showing the fluid path of a conventional thermal-based mass flow controller. 
         FIG. 8  is a schematic illustration of the fluid path of a mass flow controller made in accordance with the teachings herein. 
         FIG. 9  is a graph illustrating crosstalk in a conventional fluid panel. 
         FIG. 10  is a graph illustrating the elimination of crosstalk through the use of a mass flow controller made in accordance with the teachings herein. 
         FIG. 11  is a schematic illustration of a process fluid control assembly configuration made in accordance with the teachings herein. 
         FIG. 12  is an illustration of a fluid pallet made in accordance with the teachings herein. 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION 
     As used herein, the term “fluid” is meant to include both liquids and gases. 
     It has now been found that the length of process fluid control assemblies, and hence the size of fluid panels, can be reduced by combining the functionalities of a manual valve and a pneumatic valve (such as the first pneumatic valve  111  of  FIG. 1 ) into a single valve. The resulting combination manual/pneumatic valve reduces the length of the process fluid control assembly and the size of the fluid panel without adversely affecting the serviceability of the fluid panel or process fluid control assembly and the modularity thereof. It has also been found that further reductions in the length of the process fluid control assembly and the size of the fluid panel can be obtained, again without adversely affecting the serviceability of the fluid panel or process fluid control assembly and the modularity thereof, by combining the functionalities of the pressure regulator, pressure transducer, and filter of a conventional process fluid control assembly such as that shown in  FIG. 1  into the mass flow controller. These and other aspects and features of the systems and devices disclosed herein are discussed in greater detail below. 
       FIGS. 2-4  illustrate one embodiment of a combination manual/pneumatic valve  11  made in accordance with the teachings herein. The combination valve has a housing  13  which is typically cylindrical and which contains a centrally disposed expansion chamber  15  and a centrally disposed valve chamber  17 . The expansion chamber and the valve chamber are typically coaxially aligned. The valve chamber has a process fluid inlet  19  and a process fluid outlet  21  defined therein, and is fitted with a diaphragm  23  and a valve seat  25  that cooperate to control the flow of fluid into and out of the valve chamber. Thus, when the diaphragm is spaced apart from the valve seat, the process fluid inlet and process fluid outlet are in open communication, and fluid is permitted to flow into and out of the valve chamber. However, when the diaphragm is compressed against the valve seat (that is, when the valve is if the “off” position), the process fluid inlet and process fluid outlet are isolated from each other, and the flow of fluid through the valve chamber is terminated. Typically, the valve seat will comprise an elastomeric material that has sufficient compliance to achieve a tight seal when a sufficient compressive force is applied to it, yet has sufficient resiliency to return to its original shape when the compressive force is removed. The valve seat will most typically comprise a fluoroelastomer which may be coated with a perfluoropolymer, given the chemical resistance of the latter to commonly used process fluids such as chlorine. 
     The expansion chamber  15  of the valve is typically cylindrical and has a coaxially aligned and longitudinally extending shaft  27  disposed therein. The shaft is connected on one end via a mandrel  28  to an actuator  29  which makes contact with the diaphragm  23 , and terminates on the other end in a handle  31 . The shaft is fitted with a spring-loaded piston  33  which is maintained under a minimum compressive force by means of a spring  35 . 
     The handle is fitted with a threaded male cylinder  37  that rotationally engages a complementary threaded female receptacle  39 . The handle is typically designed to be operated with an ergonomically reasonable amount of force. Consequently, as the handle is rotated in the (typically clockwise) disabling direction, the shaft  27  is advanced along the longitudinal axis such that the actuator compresses the diaphragm  23  against the valve seat  25 , thereby cutting off the flow of fluid between the process fluid inlet  19  and the process fluid outlet  21  and manually placing the valve in the disabled position. Conversely, when the handle is rotated in the (typically counterclockwise) enabling direction, the shaft is withdrawn along the longitudinal axis, and the valve is returned to a pneumatically controlled state. In this state, and in the absence of a pneumatic signal, the spring  35  continues to force the piston  33 , the shaft  27  coupled directly thereto, and the actuator  29  against the diaphragm  23 , thereby maintaining the valve in a closed position. Hence, the handle provides a mechanism whereby pneumatic control of the valve can be overridden solely for the purposes of disabling the valve (that is, to stop the flow of fluid). By contrast, the flow of fluid through the valve is enabled only when the handle is in a manually enabled position and a pneumatic opening signal is present. This aspect of the combination manual/pneumatic valve is significant from a safety aspect, since it does not allow manipulation of the valve to override the safety interlock circuits that function by disabling the pneumatic signal. 
     The housing  13  is also equipped with an air inlet  41  and an air exhaust  43  which can be alternatively brought into open communication with a central passageway  45  disposed in the shaft  27  by rotation of the handle  31 . The central passageway is in open communication with the portion of the expansion chamber disposed below the piston. When the handle  31  is in a manually enabled position as shown in FIG.  2 —that is, when the central passageway is in open communication with the air inlet, and when there is no air signal (i.e., air pressure sufficient to displace the piston against the spring is not applied) at the air inlet—the compressive force exerted by the spring  35  against the piston  33  causes the actuator to press against the diaphragm, hence maintaining the valve in a closed position. 
     When the handle  31  is in a manually enabled position as shown in FIG.  3 —that is, when the central passageway is in open communication with the air inlet  41 , and an air signal is present (i.e., sufficient air pressure is applied at the air inlet)—pneumatic pressure is applied to the spring loaded piston  33 , by way of the central passageway  45 . So long as the force exerted by this pneumatic pressure is greater than the expansive force exerted by the spring  35 , the spring will be compressed, the piston will be driven into abutment with a stop surface  47  on the shaft, and the actuator  29  will be withdrawn along its longitudinal axis. This, in turn, allows the diaphragm  23  to expand and bring the fluid inlet  19  and outlet  21  into open communication with each other, thereby permitting a flow of fluid through the valve chamber. 
     In valves of the type depicted, the diaphragm is typically driven upward by at least two forces. The first is that the pressure of the fluid in the inlet  19  or outlet  21  imposes an upward force on the diaphragm. The second is that the diaphragm&#39;s resting shape is usually concave downwards, so that it flexes unless it is being forced down against the valve seat  25 . With respect to this latter feature, it is to be noted that, in some embodiments, the actuator  29  is not connected to the piston  33  by a means that allows the piston  33  to pull the actuator  29 . In these embodiments, the upward motion of the piston  33  may simply allow the actuator  29  to be moved upward by the flexion of the diaphragm. 
     As shown in  FIG. 4 , when the handle  31  is in a manually disabled position—that is, when the handle is manually rotated such that the central passageway  45  is in open communication with the air exhaust  43 —the pressure in the expansion chamber is at ambient pressure even if a pneumatic signal is present at air inlet  41 . Moreover, the advancement of the shaft  27  along the longitudinal axis as the handle  31  is rotated into a disabled position drives the actuator  29  against the diaphragm  23 . Consequently, the valve is disabled by the longitudinal displacement of the shaft that precludes the piston being moved away from the diaphragm by the pneumatic signal. 
     The combination manual/pneumatic valve  11  may be lockable in the disabled position using a padlock, a cable, or other available locking devices (not shown). Hence, the valve may function as a Lock Out Tag Out (LOTO) device. Moreover, to ensure safety in case of failure in the fluid control components upstream of the manual valve, the valve may also be designed to withstand an inlet pressure of at least 3000 PSIA in the disabled position without allowing fluids to pass through the valve for 72 hours (irreversible damage to the valve is reasonable in this unlikely scenario). 
     It will be appreciated from the above description that the valve can be disabled manually or closed pneumatically, though manual disablement is independent of the pneumatic input state. Hence, the valve can be opened pneumatically to allow the flow of fluid, only if it is manually in the enabled position, and the valve can also be disabled manually to stop the flow of fluid, even if a pneumatic signal to open is present. This feature of the valve is highly advantageous from both an emergency shut-off and maintenance aspect. 
       FIG. 5  illustrates the shaft/handle interface  61  of the combination valve disclosed herein. This interface would typically be disposed inside the threaded male cylinder  37  in the combination manual/pneumatic valve depicted in  FIGS. 2-4 . The interface may be machined onto, or soldered onto, one end of the shaft  27  in the valve of  FIGS. 2-4 . The handle has a hollow cylindrical underbody which is adapted to mate with a complimentary shaped male member (shaft/handle interface  FIG. 5 ) that protrudes from the shaft  27  of the valve of  FIGS. 2-4 . The interface is also provided with an aperture  65  which is adapted to receive an Allen screw or other fastening device for securing a handle to the interface. 
     The shaft/handle interface  61  of  FIG. 5  is advantageous in that it can be provided on each component of the fluid panel that requires a handle, thus allowing the fluid panel to be readily standardized so that the same handle can be used to operate each component of the panel. This also allows each component fitted with the interface to be easily retrofitted and standardized as a LOTO device. The dimensions of the features on the shaft/handle interface  61  of  FIG. 5  can vary. 
     The combination manual/pneumatic valve described above in reference to  FIGS. 2-4  has several important safety advantages over many existing valves. One of these safety advantages relates to the use of the combination valve to provide Lockout/Tagout (AKA, LOTO, Hazardous Energy Isolation (HEI)). For example, reduction in fluid panel size could be obtained by placing a conventional lockable, manually-operated valve in the pneumatic control line to the valves, and this would permit the disabling of pneumatic control in a manner that would arguably meet the regulatory requirements for Lockout/Tagout devices. However, this approach is flawed in that the energy isolation could be subverted by connecting (deliberately or accidentally) another source of actuating pressure to the process fluid valve. For example, an accidental connection could be the result of an attempt to connect a control line to a different valve, or from the connection of the manually operated valve to a process chemical valve other than the one the person intended to isolate. 
     In addition, overriding the pneumatic control signal of a normally disabled valve leaves the valve in a state in which it relies on the spring force being greater than the force applied to the underside of the diaphragm by the fluid to keep the valve disabled. Valves can be made in accordance with the teachings herein that eliminate these flaws by disconnecting the pneumatic control within the valve assembly (preventing cross connection of control lines) and by providing a rigid mechanical linkage that applies closing force to the diaphragm (reducing the dependence on spring pressure to overcome the opening force applied by the gas). Notably, the opening force applied by a fluid of a given pressure at the valve outlet is approximately an order of magnitude greater than the opening force applied by a fluid of the same pressure on the fluid inlet. Consequently, the valves which rely on a spring to maintain closure are subject, when disabled, to reverse flow at much lower pressure than that at which they are subject to forward flow. 
     Another safety advantage is that the combination of the manual override and pneumatic actuation into a single valve renders moot the competition for first (closest to the point of connection to the fluid supply) position between pneumatic and manual valves. The manual valves, as described previously, are used to isolate the downstream fluid panel elements and the process chamber from the fluid supply. The safety advantage of placing the manual valve first is that it is then positioned to isolate all of the other elements of the fluid panel from the supply. This minimizes the chance of accidental release (either from component failure or human error) by minimizing the number of components that are still connected to the supply. 
     The pneumatic valves serve a different safety function. They may be used as the actuating elements of several interlock circuits that, in response to various conditions, disconnect the fluid supply from the elements of the fluid panel downstream of them and from the process chamber. Among the sensors in such interlock circuits are fluid detectors. If the detectors sense a leak and remove the actuating signal from a valve, control of the flow through the leak depends on whether the leak is upstream or downstream of the valve which is no longer being actuated. Therefore, it is advantageous in many applications to have the pneumatic valve that is the actuating element for such interlocks as far upstream in the assembly as possible. Consequently, the manual and pneumatic valves “compete” for the first position. As noted above, the combination valve described herein renders this matter moot, as the same valve is subject to control by both means. 
     The combination manual/pneumatic valve described above and illustrated in  FIGS. 2-4  enables significant reductions in process fluid control assembly length and fluid panel size by combining the functionalities of a pneumatic valve and manual shut-off valve into a single component. However, it has also been found that even further reductions in the length of the process fluid control assembly and in the size of the fluid panel can be obtained, without adversely affecting the serviceability of the fluid panel or process fluid control assembly and the modularity thereof, through modifications to the MFC. The resulting MFC is referred to herein as a “Pressure Insensitive MFC” (PIMFC). As seen in  FIG. 6 , the PIMFC  71  combines into a single unit the functionalities of a pressure regulator  73 , pressure transducer  75 , filter  77 , and MFC  79  as those elements are found in a conventional process fluid control assembly such as that shown in  FIG. 1 . The PIMFC is described in greater detail below.  FIG. 7  is a functional illustration of a conventional thermal-based MFC  81 . The MFC consists primarily of a control valve  83  and a thermal flow sensor  85 . The use of an MFC of this type necessitates the use of a pressure regulator to eliminate “crosstalk”, that is, pressure perturbations in the supply line supplying fluid to a first process fluid control assembly that can occur when a second process fluid control assembly operating from the same fluid source is brought online. Crosstalk commonly occurs when the second process fluid control assembly is supplying the fluid at a significantly higher pressure than the first fluid control assembly. Such pressure perturbations cause the MFC controlling the first process fluid control assembly to temporarily register an indicated fluid flow rate that is substantially different (typically much lower) than the actual flow rate. 
     The effect of crosstalk in a process fluid control assembly controlled by a conventional MFC (and without the aid of a regulator) is shown in the graph of  FIG. 9 . This graph was generated on a test station using a stimulus MFC to create a pressure perturbation of about 3 psi (20.7 MPa). The curve denoted “XDOR6” indicates pressure in the fluid line as a function of time as measured by a pressure transducer. The curve denoted “indicated flow” is the fluid flow through the process fluid control assembly as indicated by the MFC, while the curve denoted “ROR” is the Rate of Rise flow, a standard measurement of the actual fluid flow in the fluid control assembly. 
     After the initial perturbation of about 3 psi (20.7 MPa), the pressure perturbation relaxed to a pressure difference of about 2 psi (13.8 MPa). However, during the initial perturbation, the difference in indicated and actual fluid flow at the MFC was about 3 sccm. This demonstrates the tendency of the MFC, in the absence of a pressure regulator, to overcompensate for the initial pressure drop in the fluid supply at the process fluid control assembly inlet by ramping up the actual flow rate. The use of pressure regulators is thus necessitated with conventional MFCs of this type. The pressure regulator functions by controlling crosstalk by dampening out the pressure perturbations giving rise to crosstalk. This, in turn, allows the indicated flow rate to more closely track the actual flow rate. 
       FIG. 8  is a functional illustration of a PIMFC  91  made in accordance with the teachings herein. The specific details of the components of the PIMFC may vary significantly from one product to another, and have been omitted for purposes of clarity. However, these components are individually well understood in the art, and hence one skilled in the art will appreciate various specific implementations from the functional presentation of these components here. 
     As with the conventional MFC illustrated in  FIG. 7 , the PIMFC also contains a control valve  93  and a thermal flow sensor  95 . However, the PIMFC additionally contains a pressure sensor  97  and a filter  99 . The pressure sensor is upstream of the flow sensor and can be tied into the control loop operating the control valve. Consequently, the PIMFC can rapidly compensate for any changes in the inlet pressure through suitable manipulation of the valve. Since the PIMFC is thus adapted to deal with pressure perturbations in the fluid control assembly, the need for a separate regulator is eliminated. Moreover, since the filter  99  in a conventional process fluid control assembly exists primarily to filter out from the fluid stream debris created by the pressure regulator before the fluid stream enters the MFC, the need for a stand-alone filter is also eliminated. Consequently, the filter may be simplified and incorporated directly into the PIMFC  91  to protect the sensors and actuators from particulate accumulation generated elsewhere upstream. Also, since the PIMFC already contains a pressure sensor, there is no need for an external pressure transducer, and the display functionalities associated with the pressure transducer may be incorporated directly into the PIMFC (that is, the PIMFC may be provided with a display to indicate the pressure already being measured by the pressure sensor). 
       FIG. 10  illustrates the effectiveness of the PIMFC disclosed herein in eliminating crosstalk in a process fluid control assembly without the use of an external pressure regulator. As with the conventional MFC that was the subject of the graph in  FIG. 8 , the PIMFC was subjected to an initial pressure perturbation of about 3 psi (20.7 MPa), after which the pressure perturbation relaxed to a pressure difference of about 2 psi (13.8 MPa). However, unlike the conventional MFC, the PIMFC closely tracked the actual fluid flow rate through the process fluid control assembly during the entire perturbation. This demonstrates that the PIMFC, unlike a conventional MFC, will not overcompensate for pressure perturbations, and hence does not require the use of a separate pressure regulator. 
       FIG. 11  illustrates a process fluid control assembly  131  made in accordance with the teachings herein which is suitable for use with toxic fluids and which incorporates the combination manual/pneumatic valve and PIMFC described above. The process fluid control assembly comprises a combination manual/pneumatic valve  133  of the type illustrated in  FIGS. 2-4 , first  135  and second  137  pneumatic valves, and a PIMFC  139 . The first  135  and second  137  pneumatic valves allow the flow of fluid to be remotely turned on and off by sending an electronically controlled pneumatic signal (pressurized air) to both pneumatic valves. A communications port  141  is provided on the mass flow controller to allow it to be accessed and controlled remotely. This communications port, which may be adapted to accept wires, optical cables, and other such communications means, may be situated on various surfaces of the mass flow controller and may have various configurations. 
     In contrast to the conventional process fluid control assembly of  FIG. 1 , which requires a pressure regulator  105 , pressure transducer  107 , and filter  109 , in the process fluid control assembly  131  of  FIG. 11 , the pressure regulator has been eliminated and the functionalities of the remaining elements have been combined into the PIMFC  139  as described above. Consequently, pneumatic valve  113  of  FIG. 1  is no longer required, since the aforementioned elements can be isolated for purging or maintenance in the process fluid control assembly of  FIG. 11  via the first  135  and second  137  pneumatic valves. Furthermore, pneumatic valve  111  of  FIG. 1  has been combined into the manual/pneumatic valve  133  in the process fluid control assembly of  FIG. 11 , also as described above. Therefore, the process fluid control assembly of  FIG. 11  is sufficiently more compact than the conventional process fluid control assembly of  FIG. 1 . This compact design also simplifies pallet design for the fluid panel and reduces the cost thereof. Moreover, because the process fluid control assembly of  FIG. 11  has fewer components than conventional process fluid control assemblies such as that shown in  FIG. 1 , Mean Time Before Failure (MTBF) is higher for the entire system, and thus maintenance costs are reduced. 
     The process fluid control assembly  131  of  FIG. 11  is adapted for use with toxic fluids such as chlorine. However, one skilled in the art will appreciate that the principles herein may also be extended to process fluid control assemblies adapted for use with inert fluids. This may be accomplished, for example, by modifying the process fluid control assembly of  FIG. 11  through the elimination of pneumatic valves  135  and  137 . 
       FIG. 12  depicts one non-limiting example of a fluid panel  151  which incorporates a series of process fluid control assemblies  153  of the type depicted in  FIG. 11 . In a typical configuration, some of the process fluid control assemblies (typically the first six, going from left to right) control toxic, corrosive or flammable fluids, and the remainder of the process fluid control assemblies control the flow of inert fluids. These two types of process fluid control assemblies are referred to herein as toxic process fluid control assemblies and inert process fluid control assemblies, respectively. 
     Each of the process fluid control assemblies is supported on a common pallet  155  and comprises a combination manual/pneumatic valve  157  (of the type illustrated in  FIGS. 2-4 ), first  159  and second  161  pneumatic valves, and a PIMFC  163  equipped with a communication port  165 . The fluid panel further includes a main manifold  167  where various process fluids under the control of individual process fluid control assemblies can be mixed to form a fluid stream. The fluid stream exits the main manifold via the main manifold outlet  171 , from which it can be directed to a process chamber (not shown) or other end use device. 
     The main manifold is provided with a fluid inlet  173  and a fluid outlet  175  that allow it to be flushed with an inert fluid such as N 2  for maintenance purposes or to clear it of residual toxic fluids. The fluid flow through fluid inlet  173  and fluid outlet  175  may be controlled by purge valve  177 , in addition to one or more of the other valves on the main manifold. A fluid line  179  is provided through which the main manifold  167  and a purge manifold  160 , the latter of which is disposed under the set of first pneumatic valves  159 , can be brought into open communication, thus allowing the PIMFCs  163  to be isolated for maintenance or other purposes. 
     The main manifold  167  is provided with a first, second and third pair of valves that respectively consist of first  181 , second  185  and third  189  inlet valves and first  183 , second  187  and third  191  outlet valves. The first  183  and second  187  outlet valves are pneumatically coupled, with the first outlet valve operating to control the flow of inert fluids from the inert process fluid control assemblies into the main manifold, and the second outlet valve operating to control the flow of toxic fluids from the toxic process fluid control assemblies into the main manifold. Thus, for example, the first six process fluid control assemblies (from left to right) may be under control of the second outlet valve  187 , and the next six process fluid control assemblies may be under control of the first  183  outlet valve. Hence, when the first  183  and second  187  outlet valves are both enabled, the fluid streams from any enabled inert process fluid control assemblies will mix with the fluid streams from any enabled toxic process fluid control assemblies inside of the main manifold  167  and the resulting mixed fluid stream will exit the main manifold through the main manifold outlet  171 . 
     The fluid panel  151  is further provided with pass-through valves  181  and  185 . These pass-through valves, which are kept enabled during normal operation of the fluid panel, cooperate with the first  183  and second  187  outlet valves, respectively, to regulate the flow of fluid through the pump/purge manifold  186  and to allow for bidirectional pumping and purging of the fluid panel. 
     The third outlet valve  191  on the fluid panel regulates the flow of fluid through inlet  173  for purging and maintenance of the fluid panel. Similarly, the third inlet valve  189  regulates the flow of fluid into the pump/purge manifold  186  for purging and maintenance purposes. Thus, for example, if the third inlet valve  189  is disabled and the third outlet valve  191  is enabled, then fluid can be made to flow through fluid line  179  and subsequently through the purge manifold  160  under the set of first pneumatic valves  159  so that toxic fluids can be purged from the toxic process fluid control assemblies. 
     The principles disclosed herein have been described primarily with reference to combination manual/pneumatic valves and to the use of such valves in process fluid control assemblies. However, it will be appreciated that the manual/pneumatic actuators described herein have a number of applications that extend beyond process fluid control assemblies. For example, such actuators could be employed in various latching systems, such as those used in industrial and high security settings. In such applications, the manual/pneumatic actuators would maintain the latch in a closed position (and therefore maintain a door, hatch or other device under control of the latch in a closed position) unless a pneumatic signal is present. Moreover, even if a pneumatic signal is present, the manual/pneumatic actuator would allow for manual override of the pneumatic signal for safety, security, or maintenance purposes. 
     More generally, the principles disclosed herein may be applied to devices in which an energy input is provided to cause the movement of one or more movable components of the device. Such devices may be modified in accordance with the teachings herein to effect, as the result of a single manipulation of a manual control, the disconnection of the energy input and the engagement of a mechanical means of keeping the movable component (or components) from moving. Specific, non-limiting examples of such modified devices include valves in which the energy input is a control signal that allows a hazardous material to flow, and latches in which the energy input is a control signal which allows access to a hazardous area. The modified device could also be a manual valve that controls actuation air to a pneumatically powered device (e.g., a gate valve), and that includes a mechanism that, in the disabled state, engages a mechanical lock on the pneumatically powered device, precluding movement of one or more pneumatically driven components of the device. 
     It will also be appreciated that, while the principles disclosed herein have been frequently illustrated in reference to pneumatically actuated devices, these principles are also applicable to devices having various other energy inputs and actuating signals. Such energy inputs include, but are not limited to, electrical and fluid (e.g., hydraulic) signals. 
     A combination manual/pneumatic actuator has been described herein. A combination manual/pneumatic valve has also been described herein that utilizes such an actuator and that combines the functionalities of a manual valve and a pneumatic valve into a single valve. This combination valve allows for reductions in the length of process fluid control assemblies and of fluid panels incorporating these process fluid control assemblies, without any loss in functionality, ease of serviceability and modularity. Fluid panel configurations that make advantageous use of the shortened process fluid control assemblies have also been provided. 
     All the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps or any method or process so disclosed, may be combined in any combination, except combinations where at least some of the features and/or steps are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same equivalent or similar purpose, unless expressly stated otherwise. Thus unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features. Moreover, although a specific embodiment is specifically illustrated and described herein, it will be appreciated that modifications and variations of the invention are covered by the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.