Mass flow control valve for supplying inert gas to a wafer container

Abstract

The invention relates to a mass flow control valve (1) for supplying inert gas to a wafer container (302), the valve comprising: a valve housing (316) through which a fluid channel (306) extends, the fluid channel extending between an inert-gas inlet (7) and an inert-gas outlet (8), wherein a valve seat (314) is formed in the fluid channel (306); an electrically controllable actuator (101) which is coupled to a valve element (103) and which is designed to move the valve element (103) between a closed position, in which the valve element is sealingly in contact with the valve seat (314), and an open position, in which the valve element is spaced apart from the valve seat (314); and a controller (75) which is electrically connected to the actuator (101) and to a sensor system from the following group: mass flow sensor (317) and oxygen sensor; mass flow sensor (317) and moisture sensor; mass flow sensor (317) and oxygen sensor and moisture sensor, wherein the sensor system is designed to detect physical inert-gas variables and to provide sensor signals to the controller (75) which is designed to electrically control the actuator (101) according to sensor signals from the sensor system.

Description

[0001] Mass flow control valve for inert gas supply to a wafer container

[0002] The invention relates to a mass flow control valve for supplying inert gas to a wafer container.

[0003] The proportional flow control valve VEMD is known from the applicant's product range. This valve is designed as a mass flow controller with an integrated piezo actuator and can be used to control the flow of air or an inert gas in proportion to a predetermined setpoint, and the flow control is carried out using an integrated thermal sensor.

[0004] The object of the invention is to provide a mass flow control valve for an inert gas supply to a wafer container.

[0005] This object is achieved for a mass flow control valve of the type mentioned at the outset in that the mass flow control valve has a valve housing which is penetrated by a fluid channel which extends between an inert gas inlet and an inert gas outlet, wherein a valve seat is formed in the fluid channel, and has an electrically controllable actuator which is coupled to a valve member and which is designed to move the valve member between a closed position sealingly adjacent to the valve seat and an open position arranged at a distance from the valve seat, and has a control which is electrically connected to the actuator and to a sensor system from the group: mass flow sensor and oxygen sensor, mass flow sensor and humidity sensor, mass flow sensor and oxygen sensor and humidity sensor,wherein the sensor system is designed to detect physical inert gas variables and to provide sensor signals to the controller, and wherein the controller is designed to electrically control the actuator as a function of sensor signals from the sensor system.

[0006] The mass flow control valve can be designed as a single component which, after connection to an inert gas source, in particular a nitrogen source, and to an electrical supply, is able to ensure an inert gas supply to a wafer container. Alternatively, the mass flow control valve can be designed as a functional module which is designed for integration into a group of further functional modules, in particular for being arranged in series with further functional modules. In this case, it can be provided that all of the functional modules are connected to a common base plate via electrical plug connections and that an electrical connection can be established via the base plate to a central controller which is designed to control the functional modules.Furthermore, it can be provided that at least the mass flow control valve is connected to an inert gas source, in particular a nitrogen source, in order to ensure an inert gas supply to a wafer container.

[0007] Regardless of the design of the mass flow control valve as an individual component or as a functional module, the valve housing of the mass flow control valve has an inert gas inlet and an inert gas outlet on an outer surface, which can each be provided with a hose coupling, for example, in order to be able to connect a fluid hose. For example, the inert gas inlet can be connected to an inert gas source via a fluid hose. Furthermore, the inert gas outlet can be connected to a wafer container via another fluid hose. The objective of using the mass flow control valve is to supply the wafer container with inert gas, in particular nitrogen, in order to protect the contents of the wafer container from oxidation by oxygen.The contents of this container can be, for example, wafers, i.e. preferably circular disk-shaped silicon plates, which are formed into semiconductor components, for example microprocessors or memory chips, using a large number of processing steps.

[0008] A valve seat is formed in the fluid channel, which may, for example, be an annular, in particular circular, surface, which may be realized by a sudden change in the cross-section, in particular a change in the diameter, of the fluid channel. This valve seat is intended to be closed or opened by a valve member, whereby a fluid flow through the fluid channel from the inert gas inlet to the inert gas outlet is selectively blocked or enabled.

[0009] For this purpose, the valve member is coupled to an electrically controllable actuator, which is preferably completely accommodated in the valve housing and which is designed to convert an electrical control signal into a movement of the valve member. For example, the actuator is a solenoid drive or a piezoelectric drive, with which a translational relative movement of the valve member with respect to the valve seat can be brought about. The valve member is adapted to the valve seat in such a way that a sealing effect can be achieved when a surface of the valve member rests on the valve seat, while when the valve member is arranged at a distance from the valve seat, a fluid flow can flow through the fluid channel.

[0010] The actuator is electrically connected to a controller which is designed to provide electrical control signals to the actuator. For example, the controller comprises a microcontroller and an electrical output stage arrangement, wherein a computer program is processed in the microcontroller with which an enable signal can be provided to the output stage arrangement so that it releases an electrical current flow to the actuator. The controller provides this enable signal as a function of sensor signals from a sensor system which is electrically connected to the controller and which is designed to detect at least two physical variables from the group: mass flow, oxygen content, moisture content.

[0011] By way of example, the sensor system has a mass flow sensor and an oxygen sensor, wherein the mass flow sensor is designed to detect an inert gas fluid flow and wherein the oxygen sensor is designed to detect an oxygen proportion of a gas atmosphere that is present in the wafer container to be supplied by the mass flow control valve. In addition to or as an alternative to the oxygen sensor, a humidity sensor is provided that is designed to detect a humidity proportion in the gas atmosphere that is present in the wafer container to be supplied by the mass flow control valve. The sensors of the sensor system do not necessarily have to be arranged inside the valve housing. By way of example, it can be provided that one or more of the sensors of the sensor system are arranged on the wafer container and are electrically connected to the controller via one or more sensor lines.However, it is preferably provided that the sensors of the sensor system are arranged in the valve housing.

[0012] Each of the sensors from the group: mass flow sensor, oxygen sensor, humidity sensor, is designed to convert the respective physical variable (mass flow, oxygen content, humidity content) into an electrical sensor signal, which is provided via a respective electrical sensor line. The controller, in turn, is designed to process the incoming electrical sensor signals and to generate the release signals for the actuator from them.

[0013] Preferably, at least one of the sensors from the group consisting of mass flow sensor, oxygen sensor, and humidity sensor is provided with a temperature sensor in order to be able to perform temperature compensation for the respective physical variable being detected. Additionally or alternatively, the oxygen sensor and the humidity sensor can be implemented in a common sensor arrangement.

[0014] Advantageous further developments of the invention are the subject of the dependent claims.

[0015] It is expedient if the mass flow sensor is designed to provide a sensor signal as a function of an inert gas mass flow in the fluid channel, and if the controller is designed to carry out a regulated electrical control of the actuator as a function of the sensor signal from the mass flow sensor in order to limit the inert gas mass flow in the fluid channel to a predetermined mass flow value. Depending on the measuring principle of the mass flow sensor, this is either arranged directly in the fluid channel, surrounds the fluid channel, or is arranged adjacent to the fluid channel. This ensures that the mass flow sensor can determine the actual inert gas mass flow flowing through the fluid channel. The mass flow sensor can comprise one or more sensors, each sensor providing a sensor signal that is dependent on the inert gas mass flow.The sensor signal or signals are either converted directly in the mass flow sensor into a measured value that represents the inert gas mass flow, or they are provided to the controller, where the conversion into the measured value is then carried out. As soon as the measured value is made available to the controller, this measured value can be processed there in order to enable controlled activation of the actuator, which must move the valve element into a position relative to the valve seat in which the specified inert gas mass flow can flow through the fluid channel.The predetermined inert gas mass flow is to be limited to a maximum value depending on the properties of the wafer container, in particular the volume and / or the structural design, in order to avoid an excessive inert gas mass flow into the wafer container, which could possibly lead to damage to the wafer container and / or the wafers contained therein. Furthermore, it is provided that the inert gas mass flow can be adjusted within an inert gas mass flow interval, which extends, for example, between zero and the maximum value, depending on an inert gas requirement for the wafer container, i.e. can be variably adjusted within this inert gas mass flow interval. The control loop (closed loop) required for this is contained in the computer program that runs in the controller and in which the measured value provided by the mass flow sensor is processed.In practice, for example, the inert gas mass flow may be limited to 150 1 / min.

[0016] It is advantageous if the mass flow sensor comprises a first pressure sensor which is arranged between the inert gas inlet and a throttle point in the fluid channel, and that the mass flow sensor comprises a second pressure sensor which is arranged between the throttle point in the fluid channel and the inert gas outlet, and that the control is designed to determine the mass flow on the basis of a pressure difference between the first pressure sensor and the second pressure sensor. The throttle point is intended to ensure a significant pressure difference within the fluid channel with which a reliable measurement result can be provided by means of a differential pressure measurement carried out by means of the first pressure sensor and the second pressure sensor, which measurement result can be used as the basis for determining the inert gas mass flow.By way of example, the throttle point is designed as a local cross-sectional constriction for the fluid channel, in which a cross-section of the fluid channel is narrowed by at least 30 percent compared to a fluid channel section upstream of the throttle point and compared to a fluid channel section downstream of the throttle point. Such a cross-sectional constriction can be implemented by a throttle element built into the fluid channel, for example a throttle sleeve, or by an arrangement of one or more orifices in the fluid channel. The first pressure sensor and the second pressure sensor each provide pressure signals which are processed by the controller in order to be able to determine a pressure difference across the throttle point and, based on this pressure difference, the inert gas mass flow in the fluid channel.

[0017] It is preferably provided that the controller is designed for the electrical control of the actuator as a function of a sensor signal from the second pressure sensor in such a way that a fluid pressure in the fluid channel between the throttle point and the inert gas outlet is limited to a predetermined maximum pressure. The sensor signal from the second pressure sensor, which is arranged downstream of the throttle point in the fluid channel, represents at least approximately the inert gas pressure provided at the inert gas outlet. Since the inert gas pressure must be limited to a maximum pressure to avoid damage to or malfunctions of the wafer container, the controller is designed to control the actuator in such a way that this maximum value is not exceeded.

[0018] In a further development of the invention, the controller is designed for the electrical control of the actuator in such a way that the mass flow is minimal depending on the oxygen content in the wafer container determined by the oxygen sensor and / or the moisture content in the wafer container determined by the humidity sensor. This is intended to ensure that only as much inert gas is supplied to the wafer container as is necessary to maintain the specified storage conditions for the wafers contained in the wafer container.

[0019] The controller therefore has the task of keeping the inert gas mass flow within the inert gas mass flow interval and further controlling the actuator in such a way that the oxygen content in the wafer container is below a predetermined oxygen threshold value and / or that the moisture content in the wafer container is below a predetermined moisture threshold value. In particular, the controller is designed in such a way that if the oxygen threshold value and / or the moisture threshold value is undershot, the inert gas mass flow is reduced to a predetermined maintenance level, which ensures compliance with the oxygen threshold value and / or the moisture threshold value at least over a certain period of time. This maintenance level can depend, for example, on the volume of the wafer container and / or on the type of wafers accommodated in the wafer container and / or on an aging state of the wafer container.For example, it can be provided that the maintenance level, which corresponds to a minimum inert gas mass flow, can be preset and is maintained even if the oxygen threshold and / or the humidity threshold are significantly undershot.

[0020] In a further embodiment of the invention, the valve housing is penetrated by a measuring channel which extends between a measuring inlet and a measuring outlet, and at least one sensor of the sensor system is assigned to the measuring channel. The measuring channel runs independently of the fluid channel in the valve housing and, when the mass flow control valve is used as intended, serves to remove a gas mixture which escapes from an outlet opening of the wafer container in an orderly manner from the wafer container. Such an exit of the gas mixture at the outlet opening occurs in particular when inert gas is supplied to the wafer container at the inert gas outlet of the mass flow control valve. The gas mixture thus flows through the measuring channel and passes the oxygen sensor and / or the humidity sensor, so that an oxygen content and / or a moisture content in the gas mixture can be determined.By arranging the oxygen sensor and / or the humidity sensor in the measuring channel, it is no longer necessary to arrange the oxygen sensor and / or the humidity sensor on the wafer container in order to determine the oxygen content and / or the moisture content in the gas mixture present in the wafer container. Rather, when the mass flow control valve is used as intended for the inert gas supply to the wafer container, only a fluid line between the inert gas outlet of the valve housing and an inert gas inlet of the wafer container and a fluid line between the outlet opening of the wafer container and an inlet connection of the measuring channel on the valve housing are required. Electrical connections between the mass flow control valve and the wafer container, as would be required for sensors attached locally to the wafer container, are not required.

[0021] It is expedient if the actuator is designed as a piezo bender and that the valve member is made from a rubber-elastic material and is materially connected to the actuator. By using an actuator designed as a piezo bender, precise movement of the actuator and the valve member connected to it and thus precise influencing of the inert gas mass flow can be achieved. Furthermore, a piezo bender only develops a small amount of heat during operation, so that no undesirable temperature change occurs for the inert gas when it passes through the mass flow control valve. The valve member is preferably designed in the shape of a circular disk and is materially attached to a largest surface of the strip-shaped piezo bender.The object of the invention is achieved according to a second aspect of the invention for a storage system for wafers in that the storage system has a wafer container for receiving a plurality of circular disk-shaped wafers, which has a sealingly closable opening for inserting and removing wafers, wherein the container has at least one inlet connection for a gas supply and at least one outlet connection for a gas discharge, and in that the wafer container is assigned a mass flow control valve according to the invention, which is integrated into a fluid line that runs between an inert gas source and the inlet connection.

[0022] It is particularly preferred that the mass flow control valve is penetrated by a measuring channel to which an oxygen sensor and / or a humidity sensor are assigned, and that the outlet connection of the wafer container is connected via a fluid line to an inlet connection of the measuring channel on the valve housing.

[0023] The invention is explained in more detail below using the attached drawing, which shows:

[0024] Figure 1 is a strictly schematic, partially perspective view of a wafer storage system with a mass flow controller, an inert gas source and a wafer container,

[0025] Figure 2 is a perspective exploded view of central components of the mass flow controller according to Figure 1,

[0026] Figure 3 is a planar sectional view of the mass flow controller according to Figure 1, Figure 4 is a schematic sectional view of a flow throttle designed as a turbulence throttle with an inlet plate, a throttle plate and an outlet plate,

[0027] Figure 5 is a plan view of the entry plate according to Figure 1,

[0028] Figure 6 is a plan view of the throttle plate according to the figure, and

[0029] Figure 7 is a detail view of a working channel of the mass flow controller, to which an absolute pressure sensor and a differential pressure sensor are assigned.

[0030] A mass flow controller 1 shown in Figure 1 is provided as an independent functional component for use in a fluid system designed as a storage system 301 for wafers. Purely by way of example, the mass flow controller 1 is used to supply a predetermined mass flow of an inert gas, for example nitrogen, into a wafer container 302 in order to be able to store wafers received therein according to a predetermined storage specification.

[0031] The wafer container 302 is also referred to as a FOUP (Front Opening Universal Pod) and is used particularly in the production of semiconductor components for the transport and storage of wafers between individual manufacturing steps. In order to ensure advantageous storage of the wafers, the storage regulations usually provide for a gas atmosphere in the volume delimited by the wafer container in which the oxygen content is below a predetermined oxygen threshold and / or in which the moisture content is below a predetermined moisture content. In order to be able to maintain this gas atmosphere permanently, a continuous or discontinuous supply of inert gas to the wafer container is provided. The mass flow for the inert gas is to be regulated such that the predetermined threshold values ​​for the gas atmosphere are maintained and as little inert gas as possible needs to be supplied.

[0032] For this purpose, the mass flow controller 1 is connected to an inert gas source 303 and to the wafer container 302. Furthermore, the mass flow controller 1 requires electrical energy and, if necessary, control or communication signals regarding the inert gas mass flow to be delivered by the mass flow controller 1 to the wafer container 302.

[0033] For connecting the mass flow controller 1 to the inert gas source 303, a hose coupling designated as inert gas inlet 7 is provided on a front side 21 of the mass flow controller 1, to which a fluid hose 304 connected to the inert gas source 303 is connected. Furthermore, for connecting the mass flow controller 1 to the wafer container, another hose coupling designated as inert gas outlet 8 is arranged on a rear side 22 of the mass flow controller 1 opposite the front side 21, which is connected via a fluid hose 315 to an inlet connection 305 of the wafer container 302.

[0034] As described in more detail below, a fluid mass flow, which can be provided by the inert gas source 303, is passed through the mass flow controller 1 to the wafer container 302 8. It is provided that the fluid mass flow is influenced in the mass flow controller 1 in order to be able to provide a fluid mass flow at the wafer container 302 according to a predetermined setpoint.

[0035] As can also be seen from the illustration in Figure 1, the mass flow controller 1 has an electrical interface 4 on a top side 23, designed purely as an example as a 9-pin D-Sub connector. Electrical energy can be supplied to the mass flow controller 1 via the interface 4. Furthermore, the electrical interface 4 can be used for communication purposes between the mass flow controller 1 and a higher-level control system (not shown).

[0036] On the upper side 23, in addition to the electrical interface 4, a first status display 5 and a second status display 6 are arranged purely by way of example, which can be used for optical output of status information about a state of the mass flow controller 1 and are designed, for example, as light-emitting diodes.

[0037] On a right side surface 26 of the mass flow controller 1, a selector switch arrangement 10 is provided, which is designed purely as an example as a DIP switch arrangement and enables a configuration of the mass flow controller 1 by a user by selecting different switch positions.

[0038] The exploded view in Figure 2 focuses on the essential functional components of the mass flow controller 1 shown in Figure 1. These include: the valve module 2 and a measuring arrangement 3, which comprises a channel plate 11 and a sensor board 12. The valve module 2 and the channel plate 11 form a valve housing 316, in which the fluidic functions of the mass flow controller 1 are implemented. The channel plate 11 is made purely by way of example from a metallic material, in particular aluminum, or from a plastic, and contains a fluid channel 306, visible in Figure 3. The fluid channel 306 comprises a supply channel 41 and a working channel 42, also visible in Figure 3.Furthermore, the channel plate 11 has on an upper side 52 an inlet connection 43 which can be seen in the perspective view in Figure 2 and from which an inlet channel 44 which is visible in Figure 3 extends and opens into the working channel 42, the inlet connection 43 and the inlet channel 44 likewise being components of the fluid channel 206. Furthermore, the channel plate 11 is penetrated by a measuring channel 307 which extends between a measuring inlet 308 which is designed as a hose coupling according to the illustration in Figure 1 and a measuring outlet 309 which is designed as a hose coupling. As can also be seen from Figure 1, the measuring inlet 308 is connected to an outlet connection via a fluid hose 210.

[0039] 311 of the wafer container 302 f fluidly communicating.

[0040] By way of example, the channel plate 11 is cuboid-shaped, wherein the inert gas inlet 7 and the inert gas outlet 8 as well as the measuring inlet 308 and the measuring outlet 309 are each arranged on opposite end faces, which are part of the front side 21 and the rear side 22 of the mass flow controller 1.

[0041] On a left side surface 51 of the channel plate 11, which is preferably flat, two sensor holes 57, 58 visible in Figure 3 are provided, each of which opens into the working channel 42 and also has a sensor hole

[0042] 312 is provided, which opens into the measuring channel 307. Furthermore, further, invisible threaded holes are provided on the left side surface 51, which enable a sealing attachment of pressure sensors 61, 62 and a combined oxygen and humidity sensor 313 to the channel plate 11. It is provided that the pressure sensors 61, 62, which form a pressure sensor arrangement, as well as the combined oxygen and humidity sensor 313 are arranged on an upper side of the sensor board 12 opposite the left side surface 51 and can be attached to the left side surface 51 of the channel plate 11 with fastening screws 63, which penetrate the sensor board 12. Purely by way of example, it is provided that the sensor board 12 comprises an electronic circuit (not shown in detail) which is designed to process sensor signals from the pressure sensors 61, 62 and the combined oxygen and humidity sensor 313.Furthermore, it is provided that the sensor board 12 is electrically connected to the control board 75 in a manner not shown, for example via a cable connection or a flexible conductor arrangement, in order to be able to provide the sensor signals of the pressure sensors 61, 62 and the combined oxygen and humidity sensor 313 to the electronic control circuit on the control board 75.

[0043] By way of example, it is assumed that the electronic control circuit on the control board 75 also contains the controller which, based on the sensor signals from the pressure sensors 61, 62 and the combined oxygen and humidity sensor 313, controls valve assemblies 72 which are arranged in the valve module 2. The valve module 2 is arranged opposite the upper side 52 of the channel plate 11 and comprises a valve housing 71 and a plurality of valve assemblies 72 accommodated in the valve housing 71, a collecting plate 73, a circuit board holder 74, a control board 75, an upper sealing element 76 and a lower sealing element 77. The valve housing 71 has a cuboid shape, with a left-hand screw guide 80 and a left-hand screw guide 81 on opposite narrow sides 78, 79 of the valve housing 71. a right screw guide 81 is attached.Each of the two screw guides 80, 81 is penetrated by a fastening screw 82 which is provided for fixing the valve housing 71 and the collecting plate 73 to the channel plate 11. The two sealing elements 76, 77 serve to seal between the valve housing 71, the collecting plate 73 and the channel plate 11. Purely by way of example, it is provided that the valve housing 71 has a width 83 and a height 84 essentially corresponding to the width 83, while a depth 85 of the valve housing 71 has only a fraction, for example 20 percent, of the width 8. Starting from an underside 86 of the valve housing 71, five valve shafts 88 which can be seen purely by way of example in Figure 3 extend in the direction of the height 84.

[0044] By way of example, it is provided that in each of the valve shafts 88, which are also part of the fluid channel 306, a cartridge-like valve arrangement 72 is accommodated, which is described in more detail below in connection with Figure 3 and which can be inserted into the valve shaft 88 through an opening 90 of the respective valve shaft 88.

[0045] In an embodiment of the mass flow controller 1 not shown, it can be provided that in one or more of the valve shafts 88 only a placeholder is arranged instead of a valve arrangement 72, unless all possible valve arrangements 72 according to the illustration in Figures 2 and 3 are required.

[0046] Opposite an upper side 87 of the valve housing 71 is a circuit board holder 74 which is designed to receive the control board 75. The control board 75 is designed as a printed circuit board (circuit board) and carries electrical and electronic components (not shown in detail) which form a control device for the mass flow controller 1. By way of example, in addition to passive electrical components (not shown) such as resistors and capacitors, one or more microcontrollers or microprocessors are also arranged on the control board 75, with the aid of which the control of the fluid mass flow described in more detail below can be carried out.Since each of the valve assemblies 72 has, purely by way of example, two piezo bender 101 described in more detail below, the control board 75 is further equipped with high-voltage components (not shown) which are designed for the individual high-voltage supply, in particular with a direct voltage in the range from 250 volts to 500 volts, of each of the piezo bender 101 of the respective valve assembly 72. It is preferably provided that all piezo bender 101 of all valve assemblies 72 are controlled by the control device on the control board 75 in such a way that an at least substantially identical proportion of the fluid mass flow to be provided at the inert gas outlet 8 flows through each of the valve assemblies 72. Deviating from the illustration in Figure 3, it can also be provided that some or all of the valve assemblies 72 are only equipped with one piezo bender 101 each.

[0047] In a minimal configuration of the mass flow controller 1 (not shown), either one valve arrangement with two piezo benders or two valve arrangements, each with one piezo bender, are provided, so that at least a dual valve function is always provided. As can be seen from the illustration in Figure 3, the piezo benders 101 of the valve arrangements 72 are electrically connected to the control board 75 via contact pins 105, which each pass through the circuit board holder 74. Furthermore, it can be seen from Figure 3 that each of the valve arrangements 72 has a valve channel 102, which is formed inside a cartridge housing 108 of the respective valve arrangement 72, visible in the illustrations in Figures 2 and 3.The valve channels 102 of the valve assemblies 72 are in fluid communication with a feed channel 89 of the valve housing 71, which in turn is fluidly connected to the supply channel 41 via a branch channel 53 in the channel plate 11, and are also components of the fluid channel 306. Thus, all valve channels 102 of the valve assemblies 72 are equally subjected to a uniform fluid pressure provided at the inert gas inlet 7.

[0048] As can be seen from the illustration in Figure 3, the two piezo benders 101 are arranged in a mirror image of one another in the respective cartridge housing 108. Furthermore, it is provided that the piezo benders 101 are pressed against bearing edges (not shown in detail) in the valve channel 102 by leaf springs 106, which are also accommodated in the valve channel 102. An arrangement of these bearing edges is adapted to the strip-shaped piezo benders 101 in such a way that the piezo benders 101 experience a change in curvature when a high electrical voltage is provided to the respectively associated contact pins 105. As a result, sealing elements 103 attached to the ends of mutually facing surfaces of the piezo benders 101 of the respective valve arrangement 72 can be lifted off from a valve seat 314 arranged opposite one another, as can be seen in particular from the detailed illustration in Figure 3.It should be noted that due to the sectional view, only a sealing element 103 of the right piezo bender 101 can be seen; the same applies to the valve seat 314, which is also only shown for the right piezo bender 101.

[0049] Extending from the respective valve seat 314 in the cartridge housing 108 is an outlet channel (not shown in detail), through which the respective portion of the fluid mass flow that has passed through the valve seat 314 can exit the cartridge housing 108. An outlet nozzle 111, visible in Figure 2, projects into this outlet channel and extends from an upper side 112 of the collecting plate 73, which is essentially designed as a plane-parallel plate, in the direction of the respective valve arrangement 72, and is sealingly connected to the outlet channel. As can be seen from the sectional view of Figure 3, the collecting plate 73 is provided on a bottom side 114 with a cuboid-shaped recess 113, which forms a collecting space for the proportional fluid mass flows that are provided by the respective valve arrangements 72 via the outlet channels and the associated outlet nozzles 111.The channel sections between the valve seat 314 and the recess 113 also form components of the fluid channel 306.

[0050] Starting from this recess 113, which can also be referred to as the outlet connection of the valve module 2, the fluid mass flow can flow into the inlet connection 43 of the channel plate 11 and from there is guided into the inlet channel 44. The inlet channel 44 has an inlet channel axis 46 which is aligned transversely to a central axis 45 of the working channel 42 and thus enters the inlet channel 44 in a radial direction. Since the working channel 42 extends in a straight line along the central axis 45 to the inert gas outlet 8, the fluid mass flow is deflected at a right angle parallel to the central axis 45 of the working channel 42 upon exiting the inlet channel 44 and can flow from there to the inert gas outlet 8. This determines a main flow direction which is symbolically shown in the working channel 42 and is aligned parallel to the central axis 45.By way of example, it is provided that the working channel 42 extends counter to the main flow direction 47 over the inlet channel 44 along the central axis 45, whereby a section of the working channel 42 designed in the manner of a blind hole is formed, which section is referred to as the rest zone 48. Due to the above-described deflection of the fluid mass flow starting from the inlet connection 43 in the main flow direction 47 in the working channel 42, a fluid pressure can be determined in the rest zone 48, in which the fluid pressure has only small or even negligible dynamic components and predominantly or even entirely only static components. Accordingly, in the rest zone 48, a first sensor bore 57 is introduced into the working channel 42 transversely to the central axis 45, into which the first pressure sensor 61, which is attached to the control board 12, projects.A second sensor bore 58 is also introduced into the working channel 42 transversely to the central axis 45. In the illustration in Figure 3, the second sensor bore 58 is concealed by the turbulence throttle 201, which is described in more detail below, and is therefore only shown in dashed lines. A second pressure sensor 62, which is also mounted on the control board 12, projects into the second sensor bore 58. The two pressure sensors 61 and 62, together with the turbulence throttle 201, form a mass flow sensor 317, as shown in Figure 3 by the dashed box. In order to enable a reliable and precise differential pressure measurement in the working channel 42, the working channel 42 is provided with a flow throttle designed purely as an example as a turbulence throttle 201, which extends completely over the cross section of the working channel 42 and which is arranged between the inlet channel 44 and the inert gas outlet 8.The turbulence throttle 201 shown in more detail in Figure 4 is designed as an independent assembly which can be mounted independently of other components of the mass flow controller 1 and whose functionality can be tested. The turbulence throttle 201 comprises a tubular throttle sleeve 203 which is designed purely by way of example to be rotationally symmetrical to a central axis 202 and extends along the central axis 202. An outer surface 204 of the throttle sleeve 203 is divided purely by way of example into three sections which adjoin one another along the central axis 202, namely a first guide section 205, a sealing section 206 and a second guide section 207. The first guide section 205 has a first outer diameter 231 which essentially corresponds to an inner diameter of a first throttle section 49 in the working channel 42 which serves to accommodate the first guide section 205.For example, it can be provided that the first guide section 205 and the first throttle section 49 are provided with mutually corresponding external and internal threads, so that the turbulence throttle 201 can be screwed into the working channel 42.

[0051] The sealing section 206 arranged between the first guide section 205 and the second guide section 207 has a smaller outer diameter 233 than the two guide sections 205, 207 and, when the turbulence throttle 201 is mounted in the throttle section 49 of the working channel 42, forms with the throttle section 49 a first annular channel 54 in which a sealing ring 227 is arranged, which ensures that the throttle sleeve 203 is sealed against the throttle section 49. Furthermore, it is provided that the second guide section 207 has a similar or identical outer diameter 232 to that of the first guide section 205.Since the working channel 42 has a second throttle section 50 with a larger inner diameter adjacent to the throttle section 49 in the direction of the main flow direction 47, a second annular channel 55 is formed by the turbulence throttle 201 with the working channel 42, which is delimited by an annular collar 228 formed at the end of the throttle sleeve 203 and protruding outwards in the radial direction. The second pressure sensor 62 is arranged in this second annular channel 55, which, similar to the quiet zone 48 20, is arranged fluidically away from the main flow of the fluid mass flow.

[0052] A recess 208 of the throttle sleeve 203, which is designed purely as an example to be rotationally symmetrical to the central axis 202, can be divided into an inflow section 209, a holding section 210 and an outflow section 211. The inflow section 209 and the outflow section 211 have a larger diameter than the holding section 210. Purely as an example, it is provided that both the inflow section 209 and the outflow section 211 are each designed to be slightly conical, starting from the holding section 210, and widen to an inflow opening 212 or to an outflow opening 213. A plurality of flow guide elements are arranged in the inflow section 209, with which the desired turbulence throttling function can be brought about when a gaseous fluid flows through the turbulence throttle 201.Starting from the inlet opening 212, an inlet plate 214, a throttle plate 215 directly adjacent thereto in the axial direction along the central axis 202 and an outlet plate 216 directly adjacent the throttle plate 215 in the axial direction along the central axis 202 are provided in the inlet section 209.

[0053] As can be seen from the illustration in Figure 5, the inlet plate 214 is circular disk-shaped and designed as a plane-parallel plate and has a plurality of inlet bores 217 which, purely by way of example, are arranged on a common pitch circle 220 at a constant angular pitch to one another. For example, the inlet plate 214 can be made from a metal sheet which is provided with the inlet bores 217 by a laser cutting process or an etching process. Alternatively, the inlet plate can also be made from a plastic material, in particular using a plastic injection molding process. It is preferably provided that the inlet plate 214 and the exit plate 216 are of identical construction.

[0054] The throttle plate 215 has a considerably greater axial extent along the central axis 202 compared to the inlet plate 214 and the outlet plate 216. Functionally, the throttle plate 215 can be divided into a throttle disk 221 and an upstream spacer ring 222 and a downstream spacer ring 223. The throttle disk 221 is circular in shape and has an outer diameter (not designated) that is slightly smaller than an inner diameter (likewise not designated) of the inflow section 209. The throttle disk 221 is provided with precisely one throttle bore 218 that is arranged coaxially to the outer diameter of the throttle disk 221. Purely as an example, the throttle bore 218 is circular in shape.As can be seen from the illustration in Figure 4, the throttle plate 221 has an axial extension along the central axis 202 which corresponds approximately to seven times the axial extension of the inlet plate 214 or the outlet plate 216. On opposite axial end faces 224, 225, circular spacer rings 222, 223 protrude from the throttle plate 221 and serve as axial spacers for the inlet plate 214 or the outlet plate 216. The spacer rings 222 , 223 each have an unspecified inner diameter which is selected such that the inlet bores 217 of the inlet plate 214 and the outlet bores 219 of the outlet plate 216 are not covered .

[0055] Rather, the spacer rings 222, 223 are provided exclusively for the spaced arrangement of the inlet plate 214 and the outlet plate 216 and have no significant contribution to the throttling effect of the turbulence throttle 201, which is described in more detail below. The task of the holding section 210, which has a slightly smaller inner diameter than the subassembly comprising the inlet plate 214, throttle plate 215, and outlet plate 216, is solely to provide axial support for this subassembly and likewise has no significant contribution to the throttling effect of the turbulence throttle 201, which is described in more detail below.

[0056] The outflow section 211 has a substantially identical axial extension along the central axis as the inflow section 209 and serves to calm the fluid flow after passing through the above-described flow guide elements (inlet plate 214, throttle plate 215, outlet plate 216). Furthermore, a radial bore 226 is formed in the outflow section 211, which ensures fluid communication between the outflow section 211 and the above-described second annular channel 55 and thus enables the second pressure sensor 62 to sense a fluid pressure prevailing in the outflow section 211 for the purpose of pressure determination.

[0057] As can be seen from the illustration in Figure 5, a projection 227 of the throttle bore 218 onto the inlet plate 214 has no overlaps with the inlet bores 217. This ensures that a fluid, in particular a compressed air stream or a process gas stream flowing through the turbulence throttle 201, experiences multiple deflections of its flow direction. This causes the desired turbulent flow in the turbulence throttle 201.The advantage of such a turbulent flow is that the compact design of the turbulence throttle 201 enables a differential pressure measurement in which a pressure value upstream or in front of the turbulence throttle 201, particularly in the region of the inlet opening 212, can be significantly differentiated from a pressure value downstream or after the turbulence throttle 201, particularly at the radial bore 226, thereby enabling a precise differential pressure measurement. From this differential pressure measurement, the fluid mass flow through the turbulence throttle 201 can then be determined with high accuracy.

[0058] In principle, the mass flow controller 1 can be used to provide a fluid mass flow to a fluid consumer. A preferred area of ​​application for the mass flow controller 1 is the inert gas supply to a wafer container 302. In addition, the mass flow controller 1 can also be used as a pressure regulator. In the illustration in Figure 7, which shows a detail of the channel plate 11 with the working channel 42 formed therein, the only difference from the illustration in Figure 3 is that instead of the second absolute pressure sensor 62, a differential pressure sensor 66 is used, which is designed to determine the pressure difference across the turbulence throttle 201. For this purpose, the differential pressure sensor 66 has a first tap 67, which is provided for pressure determination immediately upstream of the turbulence throttle 201.Furthermore, the differential pressure sensor 66 has a second tap 68, which is designed to determine the pressure in the second 55. The tap for the first absolute pressure sensor 61 is made in the same way as in the illustration in Figure 3 in the rest zone 48. Deviating from the illustration in Figure 7, the first tap 67 can also be arranged in the rest zone 48.

Claims

Claims 1. Mass flow control valve (1) for supplying inert gas to a wafer container (302), comprising a valve housing (316) through which a fluid channel (306) extends between an inert gas inlet (7) and an inert gas outlet (8), wherein a valve seat (314) is formed in the fluid channel (306), and comprising an electrically controllable actuator (101) which is coupled to a valve member (103) and which is designed to move the valve member (103) between a closed position sealingly adjacent to the valve seat (314) and an open position arranged at a distance from the valve seat (314), and comprising a controller (75) which is electrically connected to the actuator (101) and to a sensor system from the group: mass flow sensor (317) and oxygen sensor, mass flow sensor (317) and humidity sensor, mass flow sensor (317) and oxygen sensor and humidity sensor,wherein the sensor system is designed to detect physical inert gas variables and to provide sensor signals to the controller (75), and wherein the controller (75) is designed to electrically control the actuator (101) in dependence on sensor signals of the sensor system.

2. Mass flow control valve (1) according to claim 1, characterized in that the mass flow sensor (317) is designed to provide a sensor signal as a function of an inert gas mass flow in the fluid channel (306) and that the controller (75) is designed to carry out a controlled electrical control of the actuator as a function of the sensor signal of the mass flow sensor (317) in order to limit the inert gas mass flow in the fluid channel (306) to a predetermined mass flow value.

3. Mass flow control valve (1) according to claim 2, characterized in that the mass flow sensor (317) comprises a first pressure sensor (61) which is arranged between the inert gas inlet (7) and a throttle point (201) in the fluid channel (306), and in that the mass flow sensor (317) comprises a second pressure sensor (62) which is arranged between the throttle point (201) in the fluid channel (306) and the inert gas outlet (8), and in that the controller (75) is designed to determine the mass flow on the basis of a pressure difference between the first pressure sensor (61) and the second pressure sensor (62).

4. Mass flow control valve (1) according to claim 3, characterized in that the controller (75) is designed for the electrical control of the actuator (101) in dependence on a sensor signal of the second pressure sensor (62) such that a fluid pressure in the fluid channel (306) between the throttle point (201) and the inert gas outlet (8) is limited to a predetermined maximum pressure.

5. Mass flow control valve (1) according to claim 2, 3 or 4, characterized in that the controller (75) is designed for the electrical control of the actuator (101) such that the mass flow is minimal as a function of an oxygen content in the wafer container (302) determined by the oxygen sensor and / or as a function of a moisture content in the wafer container (302) determined by the humidity sensor.

6. Mass flow control valve (1) according to one of the preceding claims, characterized in that the valve housing (316) is penetrated by a measuring channel (307) which extends between a measuring input (308) and a measuring output (309), and that at least one sensor (313) of the sensor system is assigned to the measuring channel (307).

7. Mass flow control valve (1) according to one of claims 1 to 6, characterized in that the actuator (101) is designed as a piezo bender and that the valve member (103) is made of a rubber-elastic material and is materially connected to the actuator (101).

8. A storage system (301) for wafers, comprising a wafer container (302) which is designed to accommodate a plurality of circular disk-shaped wafers and which has a sealingly closable opening for inserting and removing wafers, wherein the wafer container (302) has at least one inlet connection (305) for a gas supply and at least one outlet connection (311) for a gas discharge, and with a mass flow control valve (1) according to one of the preceding claims, which is integrated into a fluid line (304, 315) which runs between an inert gas source (303) and the inlet connection (305).

Images