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

Abstract

The invention relates to a 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) coupled to a valve member (103) and 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) 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), which is designed to electrically control the actuator (101) in dependence on sensor signals of the sensor system.

Description

[0001] The invention relates to a mass flow control valve for supplying inert gas to a wafer container.

[0002] The proportional flow control valve VEMD is known from the applicant's product range. It 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 proportionally to a predetermined setpoint, and the flow control is carried out using an integrated thermal sensor.

[0003] The object of the invention is to provide a mass flow control valve for an inert gas supply to a wafer container.

[0004] 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 through which a fluid channel 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 in dependence on sensor signals from the sensor system.

[0005] 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 capable of ensuring an inert gas supply to a wafer container. Alternatively, the mass flow control valve can be designed as a functional module designed for integration into a group of other functional modules, in particular for connection to other 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 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.

[0006] Regardless of the design of the mass flow control valve as a single 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, 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.

[0007] A valve seat is formed in the fluid channel, which may, for example, be an annular, in particular circular, surface, which can be realized by a sudden change in the cross-section, in particular the diameter, of the fluid channel. This valve seat is designed to be closed or opened by a valve member, thereby selectively blocking or enabling a fluid flow through the fluid channel from the inert gas inlet to the inert gas outlet.

[0008] For this purpose, the valve member is coupled to an electrically controllable actuator, which is preferably completely accommodated in the valve housing and 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 effected. 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 against the valve seat, while a fluid flow can flow through the fluid channel when the valve member is arranged at a distance from the valve seat.

[0009] The actuator is electrically connected to a controller configured to provide electrical control signals to the actuator. For example, the controller comprises a microcontroller and an electrical power amplifier assembly. A computer program is executed in the microcontroller, which can be used to provide an enable signal to the power amplifier assembly, enabling it to allow electrical current to flow to the actuator. The controller provides this enable signal based on sensor signals from a sensor system that is electrically connected to the controller and configured to detect at least two physical variables from the group: mass flow, oxygen content, and moisture content.

[0010] By way of example, the sensor system comprises a mass flow sensor and an oxygen sensor, wherein the mass flow sensor is configured to detect an inert gas fluid flow, and wherein the oxygen sensor is configured to detect an oxygen content of a gas atmosphere 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, which is configured to detect a humidity content in the gas atmosphere present in the wafer container to be supplied by the mass flow control valve.

[0011] The sensors of the sensor system do not necessarily have to be arranged within the valve housing. For example, one or more of the sensors of the sensor system can be arranged on the wafer container and 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 in the group: mass flow sensor, oxygen sensor, humidity sensor, is designed to convert the respective physical quantity (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 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 to enable temperature compensation for the respective measured physical variable. 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 subclaims.

[0015] It is expedient if the mass flow sensor is designed to provide a sensor signal dependent on an inert gas mass flow in the fluid channel, and if the controller is designed to provide a regulated electrical control of the actuator dependent on 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, it 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 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 are provided to the controller, which then performs the conversion into the measured value. 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 specified inert gas mass flow must 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 potentially 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 the inert gas requirement for the wafer container, i.e., it can be variably adjusted within this inert gas mass flow interval. The closed-loop control loop required for this is contained in the computer program that runs in the controller and processes the measured value provided by the mass flow sensor. In practice, for example, the inert gas mass flow can be limited to 150 l / min.

[0016] It is advantageous if the mass flow sensor comprises a first pressure sensor arranged between the inert gas inlet and a throttle point in the fluid channel, and if the mass flow sensor comprises a second pressure sensor arranged between the throttle point in the fluid channel and the inert gas outlet, and if the controller is designed to determine the mass flow based on 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 differential pressure measurement performed by means of the first pressure sensor and the second pressure sensor can provide a reliable measurement result that can be used as the basis for determining the inert gas mass flow.For 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 located upstream of the throttle point and compared to a fluid channel section located downstream of the throttle point. Such a cross-sectional constriction can be realized 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 that are processed by the controller in order 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] Preferably, the controller is configured for electrically controlling the actuator as a function of a sensor signal from the second pressure sensor, such 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, at least approximately represents the inert gas pressure provided at the inert gas outlet. Since the inert gas pressure must be limited to a maximum pressure to prevent damage to or malfunctions of the wafer container, the controller is configured to control the actuator in such a way that this maximum value is not exceeded.

[0018] In a further development of the invention, it is provided that the controller is designed for the electrical control of the actuator such that the mass flow is minimal depending on an oxygen content in the wafer container determined by the oxygen sensor and / or depending on a 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 predetermined storage conditions for the wafers held in the wafer container. 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 such 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 control system is designed such that, if the oxygen threshold and / or the humidity threshold are undershot, the inert gas mass flow is reduced to a predetermined maintenance level, which ensures compliance with the oxygen threshold and / or the humidity threshold, at least for a certain period of time. This maintenance level can depend, for example, on the volume of the wafer container and / or the type of wafers accommodated in the wafer container and / or the 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.

[0019] In a further embodiment of the invention, the valve housing is penetrated by a measuring channel that 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 through the valve housing and, when the mass flow control valve is used as intended, serves to remove a gas mixture that exits at an outlet opening of the wafer container from the wafer container in an orderly manner. 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, only a fluid line between the inert gas outlet of the valve housing and an inert gas inlet of the wafer container, as well as 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 mounted locally on the wafer container, are not required.

[0020] It is advantageous if the actuator is designed as a piezoelectric bender, and if the valve element is made of a rubber-elastic material and is integrally connected to the actuator. Using an actuator designed as a piezoelectric bender enables precise movement of the actuator and the associated valve element, thus allowing precise control of the inert gas mass flow. Furthermore, a piezoelectric bender generates only minimal heat during operation, so that no undesirable temperature change occurs for the inert gas as it passes through the mass flow control valve. The valve element is preferably circular-disk-shaped and integrally attached to a largest surface of the strip-shaped piezoelectric bender.

[0021] 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 with reference to the accompanying drawings, in which: Fig. 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, Fig. 2 a perspective exploded view of central components of the mass flow controller according to the Fig. 1, Fig. 3 a planar sectional view of the mass flow controller according to the Fig. 1, Fig. 4 a schematic sectional view of a flow throttle designed as a turbulence throttle with an inlet plate, a throttle plate and an outlet plate, Fig. 5 a plan view of the entry plate according to the Fig. 1, Fig. 6 a plan view of the throttle plate according to the figure, and Fig. 7 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.

[0024] One in the Fig. The mass flow controller 1 shown in Figure 1 is intended as a standalone functional component for use in a fluid system configured as a wafer storage system 301. 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 store wafers received therein according to a predetermined storage specification.

[0025] 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. To ensure advantageous storage of the wafers, storage regulations usually stipulate a gas atmosphere in the space defined by the wafer container in which the oxygen content is below a predetermined oxygen threshold and / or in which the humidity content is below a predetermined humidity threshold. To permanently maintain this gas atmosphere, a continuous or discontinuous supply of inert gas to the wafer container is provided. The mass flow for the inert gas must be regulated so that the predetermined threshold values ​​for the gas atmosphere are maintained and as little inert gas as possible needs to be supplied.

[0026] 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.

[0027] 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 to an inlet connection 305 of the wafer container 302 via a fluid hose 315.

[0028] 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.

[0029] As the representation of the Fig. 1 can still be removed, 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).

[0030] 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.

[0031] 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.

[0032] The exploded view in the Fig. 2 focuses on the essential functional components of the Fig. 1. This includes: 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 Fig. 3 visible fluid channel 306. The fluid channel 306 comprises a supply channel 41 and a Fig. 3 visible working channel 42. Furthermore, the channel plate 11 has on an upper side 52 a in the perspective view of the Fig. 2 visible input connection 43, from which a Fig. 3 visible input channel 44 extends, which opens into the working channel 42, wherein the input connection 43 and the input channel 44 are also components of the fluid channel 206. Furthermore, the channel plate 11 is penetrated by a measuring channel 307, which is located between a according to the illustration of the Fig. 1 measuring inlet 308 designed as a hose coupling and a measuring outlet 309 designed as a hose coupling. As the Fig. 1 can be further removed, the measuring inlet 308 is fluidically connected to an outlet connection 311 of the wafer container 302 via a fluid hose 210.

[0033] 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, respectively.

[0034] On a left side surface 51 of the channel plate 11, which is preferably flat, two in the Fig. 3 visible sensor bores 57, 58 are provided, each of which opens into the working channel 42, and a further sensor bore 312 is provided, which opens into the measuring channel 307. Furthermore, further, invisible threaded bores 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) 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 from the pressure sensors 61, 62 and the combined oxygen and humidity sensor 313 to the electronic control circuit on the control board 75.

[0035] By way of example, it is assumed that the electronic control circuit on the control board 75 also includes 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 arranged in the valve module 2. Opposite the upper side 52 of the channel plate 11 is the valve module 2, which comprises a valve housing 71 and several 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 screw guide 80 and a right screw guide 81 attached to opposite narrow sides 78, 79 of the valve housing 71.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 only has a fraction, for example 20 percent, of the width 8. Starting from an underside 86 of the valve housing 71, in the direction of the height 84, five in the . Fig. 3 recognizable valve shafts 88.

[0036] 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 below in connection with the Fig. 3 and which can be inserted into the valve shaft 88 through an opening 90 of the respective valve shaft 88.

[0037] 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, instead of a valve arrangement 72, only a placeholder is arranged, unless all possible valve arrangements 72 are shown in the illustration of the Fig. 2 and Fig. 3 are required.

[0038] Opposite a top side 87 of the valve housing 71 is a circuit board holder 74, which is designed to accommodate the control board 75. The control board 75 is designed as a printed circuit board (PCB) and carries electrical and electronic components (not shown in detail) that form a control device for the mass flow controller 1. For 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 benders 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 benders 101 of the respective valve assembly 72. It is preferably provided that all piezo benders 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 portion 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 of the . Fig. 3, it may also be provided that some or all of the valve arrangements 72 are each equipped with only one piezo bender 101.

[0039] 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 double valve function is always provided.

[0040] Representation of the Fig. 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 board holder 74. Furthermore, the Fig. 3 that each of the valve assemblies 72 has a valve channel 102 which is arranged inside a valve chamber 104 shown in the illustrations of Fig. 2 and Fig. 3 visible cartridge housing 108 of the respective valve arrangement 72. The valve channels 102 of the valve arrangements 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 arrangements 72 are equally subjected to a uniform fluid pressure provided at the inert gas inlet 7.

[0041] As the representation of the Fig. 3, the two piezo benders 101 are arranged in the respective cartridge housing 108 in a mirror image of each other. 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, wherein an arrangement of these bearing edges is adapted to the strip-shaped piezo benders 101 such that the piezo benders 101 experience a change in curvature when a high electrical voltage is applied to the respectively assigned contact pins 105. As a result, sealing elements 103 attached to the ends of the piezo benders 101 of the respective valve arrangement 72 facing each other can be lifted off a respective oppositely arranged valve seat 314, as is particularly evident from the detailed illustration of the Fig. 3 can be seen.

[0042] 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.

[0043] Starting from the respective valve seat 314, an outlet channel (not shown in detail) extends in the cartridge housing 108, through which the respective portion of the fluid mass flow that has passed the valve seat 314 can exit the cartridge housing 108. A Fig. 2, which 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 the Fig. 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 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.

[0044] 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 symbolically shown in the working channel 42, which 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, thereby forming a section of the working channel 42 designed in the manner of a blind hole, which 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 into 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 mounted on the control board 12, projects.A second sensor bore 58 is also introduced into the working channel 42 transversely to the central axis 45, the second sensor bore 58 in the illustration of the . Fig. 3 is covered by the turbulence throttle 201 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 the Fig. 3 is represented by the dashed box.

[0045] In order to enable 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 is arranged between the inlet channel 44 and the inert gas outlet 8. The Fig. The turbulence throttle 201, shown in more detail in Figure 4, is designed as a standalone assembly that can be mounted independently of other components of the mass flow controller 1 and tested for its functionality. The turbulence throttle 201 comprises a tubular throttle sleeve 203 that is designed purely as an 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 as an example into three sections adjacent to 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 that essentially corresponds to an inner diameter of a first throttle section 49 in the working channel 42 that 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.

[0046] 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 a first annular channel 54 with the throttle section 49, in which a sealing ring 227 is arranged, which ensures a seal of the throttle sleeve 203 with respect to 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 projecting outward 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.

[0047] 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 designed to be slightly conical, starting from the holding section 210, and widen to an inflow opening 212 or an outflow opening 213, respectively. Several flow guide elements are arranged in the inflow section 209, with which the desired turbulence throttling function can be induced 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.

[0048] As the representation of the Fig. 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 are arranged purely by way of example 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 that 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 by a plastic injection molding process. Preferably, the inlet plate 214 and the outlet plate 216 are structurally identical.

[0049] 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 disc 221 as well as an upstream spacer ring 222 and a downstream spacer ring 223. The throttle disc 221 is circular in shape and has an outer diameter (not designated) that is slightly smaller than an inner diameter (also not designated) of the inflow section 209. The throttle disc 221 is provided with precisely one throttle bore 218 that is arranged coaxially to the outer diameter of the throttle disc 221. Purely as an example, the throttle bore 218 is circular in shape. As can be seen from the illustration of the Fig. 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. Circular spacer rings 222, 223 protrude from the throttle plate 221 at opposing axial end faces 224, 225, serving as axial spacers for the inlet plate 214 or the outlet plate 216. The spacer rings 222, 223 each have an inner diameter (not designated) 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.

[0050] 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 described in more detail below. The task of the holding section 210, which has a slightly smaller inner diameter than the subassembly consisting of the inlet plate 214, throttle plate 215 and outlet plate 216, is exclusively to provide axial support for this subassembly and also has no significant contribution to the throttling effect of the turbulence throttle 201 described in more detail below.

[0051] 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 fluidic communication between the outflow section 211 and the above-described second annular channel 55 and thus enables the second pressure sensor 62 to measure a fluid pressure prevailing in the outflow section 211 for the purpose of pressure determination.

[0052] As the representation of the Fig. 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 flow or a process gas flow flowing through the turbulence throttle 201, experiences multiple deflections of its flow direction. This creates the desired turbulent flow in the turbulence throttle 201. The advantage of such a turbulent flow is that the compactly designed turbulence throttle 201 enables a differential pressure measurement in which a pressure value upstream or upstream of the turbulence throttle 201, in particular in the region of the inlet opening 212, can be significantly differentiated from a pressure value downstream or downstream of the turbulence throttle 201, in particular 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.

[0053] In principle, the mass flow controller 1 can be used to provide a fluid mass flow to a fluid consumer. A preferred application for the mass flow controller 1 is the inert gas supply of a wafer container 302. In addition, the mass flow controller 1 can also be used as a pressure regulator. In the illustration of the Fig. 7, which shows a detail view of the channel plate 11 with the working channel 42 formed therein, is the only difference to the representation according to the Fig. 3, it is provided 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 carried out in the same way as in the representation of the Fig. 3 in the quiet zone 48. Deviating from the representation of the Fig. 7, the first tap 67 can also be arranged in the quiet zone 48.

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) coupled to a valve element (103) and configured for movement of the valve element (103) between a closed position sealing against the valve seat (314) and an open position spaced apart from the valve seat (314), and comprising a control unit (75) electrically connected to the actuator (101) and to a sensor system from the group consisting of: 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 configured to detect physical inert gas quantities and to provide sensor signals to the controller (75) and wherein the controller (75) is configured for electrical control of the actuator (101) depending on sensor signals from the sensor system. [2] Mass flow control valve (1) according to claim 1, characterized by , that the mass flow sensor (317) is designed to provide a sensor signal depending on an inert gas mass flow in the fluid channel (306) and that the control (75) is designed to perform a controlled electrical control of the actuator depending on 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 by, that the mass flow sensor (317) comprises a first pressure sensor (61) arranged between the inert gas inlet (7) and a throttling point (201) in the fluid channel (306), and that the mass flow sensor (317) comprises a second pressure sensor (62) arranged between the throttling point (201) in the fluid channel (306) and the inert gas outlet (8), and that the control (75) is designed for mass flow determination based on 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 by , that the control (75) is designed for the electrical control of the actuator (101) depending on a sensor signal of the second pressure sensor (62) such that a fluid pressure in the fluid channel (306) between the throttling 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 by , that the control (75) is designed for the electrical control of the actuator (101) such that the mass flow rate is minimal depending on an oxygen content in the wafer container (302) determined by the oxygen sensor and / or depending on 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 by , 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 any one of claims 1 to 6, characterized by , that the actuator (101) is designed as a piezo bender and that the valve element (103) is made of a rubber-elastic material and is materially bonded to the actuator (101). [8] Wafer storage system (301) comprising a wafer container (302) designed to hold a plurality of circular disk-shaped wafers and having a sealingly closable opening for inserting and removing wafers, wherein the wafer container (302) has at least one inlet port (305) for gas supply and at least one outlet port (311) for gas discharge, and comprising a mass flow control valve (1) according to one of the preceding claims, which is integrated into a fluid line (304, 315) running between an intermediate gas source (303) and the inlet port (305).

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