OPERATING PROCEDURES FOR GROUP OF PRESSURE SENSORS

Description

[0001] The present invention relates to a method for operating a group of pressure sensors according to the attached claim 1, a device for carrying out the method according to the attached claim 15, and a computer program product according to the attached claim 18.

[0002] Various types of pressure sensors are known in the art. These include pressure sensors whose measuring principle is based on the deformation of a diaphragm due to a pressure difference between the two sides of the diaphragm, such as capacitance diaphragm gauges (CDGs). Thermal conductivity vacuum gauges determine the pressure via the pressure-dependent thermal conductivity of a gas, for example, in the case of a Pirani vacuum gauge or Pirani sensor, by determining the heat output transferred from a current-carrying wire to the surrounding gas. Ionization manometers, another type of pressure sensor, indirectly measure pressure by determining the gas-specific density. The gas density is determined by ionizing the gas molecules with electrons based on the neutralization rate of the ions on a collector electrode, which is determined by measuring the current.

[0003] Different types of pressure sensors have different measuring ranges. For example, some pressure sensors provide meaningful readings at atmospheric pressure but cannot detect differences at very low pressures, such as in fine vacuum or high vacuum. Other pressure sensors require a pressure in the millibar (mbar) range to operate and can resolve very low pressures. It is known in the art to use a group of pressure sensors, for example, consisting of two pressure sensors with overlapping measuring ranges, to cover a larger pressure measuring range than a single pressure sensor type can. For example, the PCG550 product family from INFICON AG combines a Pirani sensor and a ceramic capacitance diaphragm manometer in a measuring device, with the measuring ranges of the Pirani sensor and the ceramic capacitance diaphragm manometer overlapping.

[0004] DE 198 60 500 A1 relates to a device for pressure measurement comprising a first pressure sensor for detecting a pressure in a first pressure range, a second pressure sensor for detecting a pressure in a second pressure range, wherein the first and second pressure ranges overlap, and a calibration device for calibrating the second pressure sensor using the first pressure sensor by correcting the output of the second pressure sensor based on the outputs of the first and second pressure sensors within the overlap range of the first and second pressure ranges, such that the calibrated output of the second pressure sensor in the overlap range is substantially equal to the output of the first pressure sensor.This allows for a simple yet accurate calibration of the second pressure sensor, which is particularly advantageous when pressure measurements need to be carried out in the vacuum range, where the first pressure sensor is an absolute pressure sensor, and the second pressure sensor is, for example, a thermal conductivity pressure sensor or an ionization pressure sensor, etc., which depends on the type of gas.

[0005] DE 10 2005 029 114 A1 concerns the measurement of pressure over a wide range, particularly absolute pressure from atmospheric pressure up to ultra-high vacuum. Since no single measurement principle is known to cover the entire range, different principles are usually combined. To save costs and reduce space requirements, sensor arrangements have been developed that integrate several measurement principles. For these combined pressure sensors, methods for value alignment in the overlap region of two different sensors are necessary to obtain a clear output signal even in this transition region. A method is described in which a suitable value alignment range is automatically determined by observing the signals of the involved sensors, even outside the overlap region, thereby reducing the error in the output signal.Another method, which uses the same observation technique, aims to automatically readjust one of the pressure sensors in a state where its "sensor signal" is not included in the "output signal". Furthermore, arrangements of pressure sensors suitable for this method are described.

[0006] US 2020 / 0103323 A1 relates to a system for comparative pressure measurement comprising a measuring chamber filled with a gas mixture exhibiting a gas pressure. A first sensor is arranged in the measuring chamber. The first sensor is designed to measure the gas pressure regardless of the type of gas mixture. A second sensor is arranged in the measuring chamber. The second sensor is designed to measure the gas pressure based on a known dependence on a specific type of gas mixture. An evaluation unit determines the state of the gas mixture based on the gas pressure values ​​measured simultaneously by the first and second pressure sensors.

[0007] EP 0 379 841 A2 presents a method for measuring pressure, preferably vacuum. The measurement signals from a thermal conductivity manometer and measurement signals from a gas friction manometer are, for example, linearly superimposed, added, or processed into a common measurement signal by multiplication. Preferably, a Pirani manometer is used as the thermal conductivity manometer and a tuning fork quartz manometer as the gas friction manometer.

[0008] From publication EP 0 658 755 A1, a method for evaluating the output signal of two pressure sensors is known. In this publication, a weighting technique in the transition region of the respective sensor measurement ranges is proposed, particularly for the combination of cold cathode ionization sensors and Pirani sensors, to obtain a significantly extended, unambiguous measurement range compared to the measurement ranges of the respective sensor types. This technique involves continuously and unambiguously converting the sensor characteristics into one another.

[0009] The object of the present invention was to provide an alternative operating method. In particular, the object was to provide an operating method that increases the accuracy of the pressure measurement over the entire pressure measuring range.

[0010] This problem is solved by the method according to claim 1. The method according to the invention is a method for operating a group of pressure sensors. The group of pressure sensors comprises at least one first pressure sensor with a first pressure measuring range and at least one second pressure sensor with a second pressure measuring range. The first and the second pressure sensors are arranged such that they can measure the pressure in a common measuring volume. The first and second pressure measuring ranges overlap in an overlap pressure measuring range. The method comprises the steps: (aa) essentially simultaneous reading of a first measurement signal from the first pressure sensor and a second measurement signal from the second pressure sensor while the pressure in the common measurement volume is within the overlap pressure measurement range; (bb) defining the read-out first measurement signal as the adjustment point for the second pressure sensor;(cc) Determining at least one gas-dependent calibration parameter for the second pressure sensor as a function of the first measurement signal, as a function of the adjustment point determined in step (bb), and as a function of the second measurement signal, wherein a current pressure measurement in the measurement volume is determined as a function of a current second measurement signal and the previously determined at least one calibration parameter or parameters, and the procedure further comprising the step: (gg) Deciding whether a gas composition present in the common measurement volume deviates from a target value, taking into account any deviation of the current pressure measurement from a pressure measurement derived from the first measurement signal, wherein the reading of the first measurement signal is carried out substantially simultaneously with the reading of the current second measurement signal and while the pressure in the common measurement volume is within the overlap pressure measurement range.

[0011] The inventors recognized that this method enables an accurate determination of pressure. In particular, a surprisingly simple way can be achieved to a large extent that the read pressure is independent of the type or composition of the gas, provided that at least one of the pressure sensors is a type that delivers a measurement signal independent of the gas composition.

[0012] One or more of the pressure sensors in the group of pressure sensors can be a vacuum pressure sensor, i.e., a pressure sensor which is used, for example, to measure the pressure in a rough vacuum (i.e., in the pressure range of approximately 1 mbar to 1013 mbar). dh up to atmospheric pressure), in a fine vacuum (i.e. in Pressure range from 10⁻³ mbar to 1 mbar), in high vacuum (i.e.The device is designed for pressure ranges from 10⁻⁸ < mbar to 10⁻³ < mbar or a combination of two or three of the aforementioned vacuum pressure ranges. The principle of the present invention also works for pressure sensors for measuring pressures close to atmospheric pressure or for overpressure sensors.

[0013] The at least one calibration parameter can, in particular, be a gas-type-dependent calibration parameter.

[0014] Step aa) is performed at least once. Step aa) can also be performed multiple times, particularly at different pressures, to collect measurement data on which a number of calibration parameters can be adjusted in step cc). For example, based on two measurements according to step aa), performed at different pressures, an offset and a slope can be determined. This is advantageous, for instance, for the gas water vapor, where the slope in the Pirani region deviates from the normal slope, meaning that the curve "indicated pressure" versus "effective pressure" would not be described with sufficient accuracy by an offset or factor alone.

[0015] As a concrete example, the group of pressure sensors could include a 13 mm CDG as the first pressure sensor and a Pirani sensor as the second. In this case, the calibration point can be selected in the 100 mTorr pressure range, i.e., approximately one decade above the lower end of the measuring range of the first pressure sensor, which is designed for 10 Torr full-scale deflection. The gas-type-dependent calibration parameter of the second pressure sensor could, in this example, be the factor by which the measurement signal of the Pirani sensor, for the gas being calibrated and at the pressure defined by the calibration point, deviates from the measurement signal obtained with nitrogen at the pressure defined by the calibration point.

[0016] Step cc) can be carried out in particular with a known type of gas in the measuring volume or successively with a plurality of gases different from each other in type of gas (for example, air, nitrogen, oxygen, hydrogen, helium, argon, etc.) or concentration ratios (for example, 20% helium, 80% nitrogen) in the measuring volume.

[0017] Calibration parameters can then be stored, for example, in tabular form for different gas types. In this way, the combination of the second measurement signal with information about the type of gas present in the measurement volume allows for a more precise determination. This information can be provided, for example, by a control unit that manages a process in a vacuum chamber. The information could, for instance, consist of the fact that an inlet valve for a protective gas, such as helium or argon, has been opened.

[0018] One possible calibration parameter that can be adjusted in step cc) is a factor by which the pressure for the selected gas type deviates from a pressure which, with the same measurement signal, would correspond to the pressure of a reference gas, for example nitrogen.

[0019] This allows, for example, the gas-type-dependent pressure measurement signal of the second pressure sensor to be adjusted by this factor, so that the pressure measurement is corrected accordingly even in the range where only the second pressure sensor is measuring, and the gas-type dependency is minimized. Furthermore, the factor provides information about the gas composition with respect to the reference gas.

[0020] Compact capacitive diaphragm pressure gauges with a small form factor are available, for example, from INFICON under the name "Porter™< CDG020D". They reach full scale deflection of their pressure gauge at approximately 10 to 1000 Torr and can measure pressures down to 10 mTorr (at full scale deflection of 10 Torr). The method according to the invention is suitable for operating a combination of two or more of the aforementioned pressure sensors, which can measure in a common measuring volume.

[0021] For example, the BCG450 Triple-Gauge™< covers the range from atmospheric pressure to ultra-high vacuum using three sensors. The INFICON BCG450 combination gauge (Triple-Gauge™<) combines the advantages of three different technologies in a single, compact, and economical device for measuring process and base pressure in the range of 5×10⁻¹⁰ to 1500 mbar (3.75×10⁻¹⁰ to 1125 Torr). The BCG450 was developed to replace three individual sensors (Hot Ion, Pirani, and a small 11 mm diameter CDG). This reduces costs and the space required on the system. This combination device can, for example, be operated using the method according to the invention.

[0022] The inventive method is also suitable for devices in which different pressure sensors are attached to the same vacuum chamber and thus form a group of pressure sensors which have a common measuring volume.

[0023] Embodiments of the method are derived from the features of dependent claims 2 to 16.

[0024] In one variant of the procedure, the adjustment point for the second pressure sensor lies in the pressure range 10 -2< mbar to 10 0< mbar, in particular in the pressure range 0.1 to 0.4 mbar.

[0025] For example, in a combination of CDG and Pirani sensor, an overlapping pressure range of the two pressure sensors can be advantageously placed in a pressure range by dimensioning the CDG in which the gas-type dependence of the Pirani sensor is characterized in a double-logarithmic diagram by linear and essentially parallel shifted curves for each gas type. dhThis avoids the higher pressure range where non-linear, diverging gas characteristics occur, further increasing accuracy. This variant of the method is particularly suitable for operating a group of pressure sensors formed by combining two CDGs dimensioned for different pressure measuring ranges and a Pirani sensor. A first CDG with a lower pressure measuring range covers the overlap with the linear range of the Pirani sensor, while a second CDG with a higher pressure measuring range extends the effective measuring range of the pressure sensor group to higher pressures.

[0026] One variant of the procedure further comprises the following steps: dd) essentially simultaneous reading of another first measurement signal from the first pressure sensor and another second measurement signal from the second pressure sensor while the pressure in the common measurement volume is within the overlap pressure measurement range and wherein the pressure in the common measurement volume differs from the pressure in step aa), in particular wherein the pressure in the common measurement volume differs from the pressure in step aa) by a factor of two, by a decade or more; ee) defining the further read-out first measurement signal as a further adjustment point for the second pressure sensor;ff) Determining a further calibration parameter (K2), in particular a further gas-dependent calibration parameter, for the second pressure sensor as a function of the further first measurement signal, as a function of the further adjustment point for the second pressure sensor determined in step ee) and as a function of the further second measurement signal.;

[0027] This variant can be extended to include the acquisition of three or more measurement points and the determination of additional calibration parameters, where the number of calibration parameters is limited to the number of measurement points. In particular, more measurement points can be acquired than the number of calibration parameters to be determined. In this case, a balancing algorithm can be used to determine a set of calibration parameters that optimally matches the measurement points. This makes the calibration parameters less dependent on measurement noise.

[0028] As already mentioned, a current pressure measurement value in the measuring volume is determined as a function of a current second measurement signal and the previously determined at least one calibration parameter or calibration parameters.

[0029] This includes the actual step of determining current pressure values, using the prior calibration of the second pressure sensor. This calibration is based on the information obtained in the overlap pressure measurement range and can now be applied to the entire second measurement range.

[0030] As already mentioned, the procedure further includes the step: gg) Deciding whether a gas composition present in the common measuring volume deviates from a target specification, taking into account a deviation from the current pressure measurement value compared to a pressure measurement value derived from the first measurement signal, whereby the reading of the first measurement signal takes place essentially simultaneously with the reading of the current second measurement signal and while the pressure in the common measuring volume is in the overlap pressure measurement range.

[0031] Step gg) corresponds to a verification step for the gas composition. By specifying a tolerance range for acceptable deviations from the target value, a yes / no decision can be made, e.g., as to whether a next process step should be carried out. The inventors recognized that this provides a functionality in a very simple way that would normally require a residual gas analyzer.

[0032] This can be used, for example, to detect gas composition fluctuations in PVD processes.

[0033] In one variant of the procedure, the additional calibration parameter determined in step ff) is a slope in a double-logarithmic function diagram of the second measurement signal as a function of the first measurement signal, or a slope in a double-logarithmic function diagram of the second measurement signal as a function of the first measurement signal is calculated from the calibration parameter determined in step cc) and the calibration parameter determined in step ff). The procedure further comprises the following steps: hh) Determining a deviation of this slope from a slope expected for a reference gas, for example nitrogen; ii) Comparing the deviation determined in step hh) with a predetermined tolerance threshold for the deviation; jj) If the tolerance threshold is exceeded, triggering an alarm for the presence of water vapor in the common measuring volume.

[0034] The inventors recognized that the fact that the slope in the presence of water vapor differs from that observed in virtually all relevant residual gases allows for the detection of water vapor. This property is particularly pronounced in Pirani sensors.

[0035] In one variant of the method, the first pressure sensor is a pressure sensor of a type that is independent of the gas composition in the measuring volume. Furthermore, the second pressure sensor is a pressure sensor of a type that is dependent on the gas composition in the measuring volume. In particular, the second pressure sensor can be a thermal conductivity vacuum gauge, especially according to Pirani or with a thermocouple sensor, or an ionization vacuum gauge with a cold cathode, especially an ionization vacuum gauge according to Penning, or a non-inverted magnetron or an inverted magnetron, or an ionization vacuum gauge with a hot cathode, especially an ionization vacuum gauge according to Bayard-Alpert, an ionization vacuum gauge with extractor or with triode, or a spinning rotor gauge sensor.

[0036] Pressure sensors can be divided into two classes of pressure sensor types: those that are directly sensitive to a force per unit area, and those that detect an indirect effect of pressure on another physical quantity, such as... e.g.The thermal conductivity of the gas under the pressure to be measured is used to determine the pressure. This latter type of pressure sensor is generally dependent on the type of gas. The inventors have recognized that a group of pressure sensors comprising a first pressure sensor of the first type and a second pressure sensor of the second type particularly benefits from the operating method according to the invention.

[0037] Depending on the desired measuring range, i.e., the pressure range in which high measuring accuracy is achieved, a combination of pressure sensors can be selected. Pirani thermal conductivity vacuum gauges have a measuring range of approximately 100 to 0.1 Pa, Penning cold cathode ionization vacuum gauges have a measuring range of approximately 10⁰ to 10⁻⁹ Pa, and Bayard-Alpert hot cathode ionization vacuum gauges have a measuring range of approximately 1 to 10⁻⁸ Pa, or 10⁻¹ to 10⁻¹ Pa for extractor systems, or 10³ to 10⁻¹ Pa for triodes. Pirani thermal conductivity vacuum gauges can be used down to atmospheric pressures of 10⁵ Pa, but with significantly reduced accuracy.

[0038] In one variant of the method, the first pressure sensor is a diaphragm manometer, in particular a capacitance diaphragm manometer, in particular a ceramic capacitance diaphragm manometer, or an optical diaphragm manometer.

[0039] Membrane manometers react directly to the force per unit area and are therefore independent of the type of gas.

[0040] In one variant of the method, the second pressure sensor is a thermal conductivity vacuum gauge, in particular according to Pirani, or a thermocouple.

[0041] Thermal conductivity vacuum gauges have a significant gas type dependency and therefore benefit from calibration according to the inventive method.

[0042] In one variant of the procedure, steps aa), bb) and cc) are repeated at regular intervals, in particular once daily or once weekly.

[0043] The time intervals can be adapted to the timing of further process steps. Depending on the context, it may also be useful to perform step a) beforehand, namely reducing the pressure in the common measuring volume to the low-pressure range, so that the entire sequence of steps aa), bb), and cc) is repeated at regular intervals. The sequence of steps aa), bb), and cc) can also be repeated depending on the process, for example, if strong temperature cycles are carried out in a vacuum processing plant.

[0044] In one variant of the procedure, the method is a procedure for operating a vacuum processing plant which includes the group of pressure sensors. Steps aa), bb), and cc) are repeated once per process cycle of the vacuum processing plant.

[0045] Such a process cycle can, for example, include aeration, substrate insertion, pressure reduction to the high-vacuum range, introduction of a process gas, extraction of the process gas, aeration, and substrate removal. Steps aa) to cc) of the procedure can each be performed in conjunction with the pressure reduction to the high-vacuum range. This variant can, for example, be combined with an automated pressure measurement quality check, whereby several pressure values ​​are determined at short intervals relative to the duration of a process step, and it is verified whether these pressure values ​​lie within a defined range. This prevents pressure changes from occurring too rapidly to capture high-quality data.

[0046] For example, the procedure can be automatically triggered whenever an activation pressure range is reached or exceeded. For instance, the overlap pressure measurement range, as mentioned above, can be the activation pressure range for determining a calibration parameter of a Pirani sensor.

[0047] In one variant of the method, the second pressure measurement range includes a low-pressure range in which the pressure is lower than a lower limit of the first pressure measurement range. The method includes the following additional steps: kk) Check whether the low-pressure range has been reached using a second measurement signal from the second pressure sensor; ll) Read out a first measurement signal from the first pressure sensor while the pressure in the common measuring volume is in the low-pressure range; and mm) Set the read-out first measurement signal as the zero-point signal for the first pressure sensor.

[0048] For example, with capacitance diaphragm pressure gauges, it is possible to determine the value of an output signal that corresponds to zero pressure (or a pressure at the lower end of the measuring range). This value drifts slowly and can complicate the interpretation of the measurement signal. With this variant of the method, this zero point can be repeatedly determined and updated as needed, ensuring that a sufficiently low pressure prevails in the common measuring volume of the two pressure sensors to establish the zero point. For example, for the aforementioned PCG550 product family, the Pirani sensor can be used as a second pressure sensor to establish the zero point of the CDG, which in this case acts as the first pressure sensor, according to the inventive method.A combination of determining a calibration parameter and prior zeroing according to this variant of the procedure significantly increases the accuracy of the pressure measurement across the entire pressure measurement range.

[0049] One variant of the procedure further includes the following steps: nn) Increasing the pressure in the common measuring volume into the first pressure measuring range; oo) Reading a current first measurement signal from the first pressure sensor; pp) Determining a current pressure measurement value as a function of the current first measurement signal and the zero-point signal determined in step mm), in particular as a function of a difference between the current first measurement signal and the zero-point signal.

[0050] In this way, the current pressure reading is a current pressure reading with a correct zero point.

[0051] In one variant of the method, the low-pressure range includes only pressures that are at least ten times smaller, and in particular at least one hundred times smaller, than the lower limit of the first pressure measurement range.

[0052] The inventors realized that this variant allows the zero point for the first sensor to be determined particularly accurately.

[0053] In one variant of the procedure, the low-pressure range covers the range 10 -3< mbar to 10 -4< mbar.

[0054] This variant can, for example, be implemented in combination with the variant mentioned above, in which the second pressure sensor is a Pirani thermal conductivity vacuum gauge. Ceramic capacitance manometers acting as the first pressure sensor particularly benefit from regular zero-point determination using this variant of the method.

[0055] In one variant of the method, the group of pressure sensors comprises at least three pressure sensors. The steps according to the inventive method are applied to a first pair of pressure sensors from the group of pressure sensors, and the steps according to the inventive method are also applied to a second pair of pressure sensors from the group of pressure sensors. One of the pressure sensors of the first pair is also a pressure sensor of the second pair.

[0056] According to this variant, the inventive method can be cascaded to a group of pressure sensors with more than two pressure sensors, wherein in a first pair of pressure sensors, one sensor acts as the first and the other as the second. The second pressure sensor can then act as the first pressure sensor in a further pair of pressure sensors, and so on. A prerequisite for such a cascaded extension of the total pressure measurement range of the group is that there are overlapping measurement ranges of any two pressure sensors that are adjacent with respect to their measurement range.

[0057] For example, such a cascade-like chaining of measuring ranges from different pressure sensors is possible in a group of pressure sensors comprising a capacitive diaphragm manometer, a Pirani sensor, and an ionization manometer. For instance, an adjustment point for the capacitive diaphragm manometer (the first pressure sensor of the first pair) and the Pirani sensor (the second pressure sensor of the first pair) can be set at approximately 1 mbar. Furthermore, an adjustment point for the Pirani sensor (the first pressure sensor of the second pair) and for the ionization manometer (the second pressure sensor of the second pair) can be set at approximately 10⁻³ mbar. The calibrations are then cascaded according to this configuration. For example, the ionization manometer could be a Bayard-Alpert type or one of the other ionization manometers mentioned above.For example, the group of pressure sensors can include a fourth pressure sensor in the form of a capacitive diaphragm manometer with full deflection at atmospheric pressure. In combination, a "quadruple" pressure sensor with a total measuring range from atmospheric pressure down to a pressure of 10⁻¹⁰ mbar can be obtained, which, through operation according to the present invention, achieves high accuracy and a high degree of independence from the type of gas over the entire measuring range.

[0058] Furthermore, the invention also relates to a device according to claim 15. This is a device for carrying out the method according to the invention.

[0059] The device includes: a group of pressure sensors, wherein the group comprises at least a first pressure sensor with a first pressure measuring range and a second pressure sensor with a second pressure measuring range, wherein the first and the second pressure sensors are arranged such that they can measure the pressure in a common measuring volume and wherein the first and second pressure measuring ranges overlap in an overlap pressure measuring range; and a control unit which is operatively connected to a first signal output of the first pressure sensor and to a second signal output of the second pressure sensor for processing measurement signals from the pressure sensors, wherein the control unit is designed to perform the method described above.

[0060] This device can be implemented, in particular, as a unit (pressure sensor unit, "pressure gauge") that incorporates all the aforementioned elements in a common housing. For example, this housing can have a standard vacuum flange for connection to a vacuum system. This device can also have a data interface that provides a single, processed pressure signal to the outside, this processed pressure signal being generated taking into account all calibrations and all available pressure sensors in the group. This unit can, in particular, include a computer program product, for example, in the form of firmware, which will be discussed later.

[0061] In one embodiment of the device, the first pressure sensor is a diaphragm manometer. The overlap pressure measuring range, in which the first and second pressure measuring ranges overlap, covers a pressure of 0.1 mbar. The group of pressure sensors includes a third pressure sensor with a third pressure measuring range, wherein the third pressure measuring range extends the first pressure measuring range to higher pressures.

[0062] This embodiment of the device can be implemented, for example, by the following combination of pressure sensors: A capacitive diaphragm manometer as the first pressure sensor, a Pirani sensor as the second, and another capacitive diaphragm manometer as the third. The first pressure sensor can, for example, have a measuring range that includes a pressure of 0.1 mbar and spans three decades. In this example, the Pirani sensor also has a measuring range that includes a pressure of 0.1 mbar. The third pressure sensor can have a third pressure measuring range that exhibits full deflection at atmospheric pressure, thus extending the pressure range of the entire group of pressure sensors to higher pressures. The third pressure measuring range can overlap with the first and / or the second pressure measuring range. All three pressure sensors in the group can be installed in a common housing.

[0063] In one embodiment, the device comprises at least one means for changing the pressure in the common measuring volume, wherein the at least one means for changing the pressure is operatively connected to a pressure control unit for triggering a reduction or an increase of the pressure in the common measuring volume.

[0064] The pressure control unit can be the control unit for processing measurement signals from the pressure sensors, or it can be functionally connected to it, for example to transmit the status of valves or pumps, or to receive control commands, such as changing the pressure in preparation for an adjustment.

[0065] The means of changing the pressure can include, for example, a pump or valves.

[0066] The invention further relates to a computer program product according to claim 18.

[0067] The computer program product according to the invention comprises instructions which, when executed by a control unit of a device according to the invention, cause the control unit to carry out the steps of the method according to the invention.

[0068] The computer program product may, for example, include firmware in a pressure sensor assembly, or it may consist of firmware in a pressure sensor assembly.

[0069] Exemplary embodiments of the present invention are explained in more detail below with reference to the figures. These show Fig. 1 a flowchart of a known process; Fig. 2 a flowchart of an embodiment of the method; Fig. 3 a flowchart of the inventive process; Fig. 4 a flowchart of another embodiment of the method; Fig. 5a flowchart of an embodiment of the method which includes zeroing the first pressure sensor; Fig. 6 schematically possible relative positions of the first and second pressure measuring ranges; Fig. 7 schematically a device for carrying out the procedure; Fig. 8 schematically depicts the temporal sequence of the pressure in one variant of the process; Fig. 9 The graph shows, in a double-logarithmic representation, the dependence of a pressure determined by a Pirani sensor on the type of gas; Figs. 10 to 12Using double-logarithmic diagrams of the displayed pressure as a function of the effective pressure, they show two ways in which the gas-type-dependent pressure measurement signal of the second, gas-type-dependent pressure sensor can be adjusted by the method with one or more calibration factors, so that the pressure measurement is corrected accordingly and the gas-type dependency is eliminated even in the area where only the second gas-type-dependent pressure sensor measures.

[0070] In Figure 1 A flowchart of a known method 100 is shown. The method comprises the steps aa) essentially simultaneous reading 101 of a first measurement signal from the first pressure sensor and a second measurement signal from the second pressure sensor while the pressure in the common measurement volume is in the overlap pressure measurement range; bb) Determine 102 the read-out first measurement signal as the adjustment point for the second pressure sensor; cc) Determine 103 at least one gas-dependent calibration parameter K1, K2 for the second pressure sensor as a function of the first measurement signal, as a function of the adjustment point for the second pressure sensor determined in step bb) and as a function of the second measurement signal.

[0071] Steps 101, 102 and 103 are performed sequentially.

[0072] In Figure 2A flowchart of an embodiment 120 of the method is shown. First, all steps of the method 100 are carried out. Then, steps dd) are performed again essentially simultaneously, reading out 104 another first measurement signal from the first pressure sensor and another second measurement signal from the second pressure sensor while the pressure in the common measurement volume is in the overlap pressure measurement range and wherein the pressure in the common measurement volume is different from the pressure in step aa); ee) Determine 105 the further read-out first measurement signal as a further adjustment point for the second pressure sensor; ff) Determine 106 a further calibration parameter K2, in particular a further gas-dependent calibration parameter, for the second pressure sensor as a function of the further first measurement signal, as a function of the further adjustment point determined in step ee) and as a function of the further second measurement signal.

[0073] In Figure 3 A flowchart of the inventive method 130 is shown. First, all steps of method 100 are carried out. Then, step gg) 107, deciding whether a gas composition present in the common measuring volume 2 deviates from a target value, is performed, taking into account a deviation from the current pressure measurement value compared to a pressure measurement value derived from the first measurement signal, whereby the reading of the first measurement signal takes place essentially simultaneously with the reading of the current second measurement signal and while the pressure in the common measuring volume is within the overlap pressure measurement range 6.

[0074] In Figure 4 A flowchart of embodiment 140 of the method is shown. First, the steps of variant 120 are shown as an alternative (see Fig. 2 ) or the variant according to the invention 130 (see Fig. 3 ). The following steps are then carried out. hh) Determine 108 a deviation of this slope from a slope expected for a reference gas, in this case nitrogen; ii) Compare 109 the deviation determined in step hh) with a predetermined tolerance threshold for the deviation; jj) if the tolerance threshold is exceeded, trigger 110 an alarm for the presence of water vapor in the common measuring volume 2.

[0075] In Figure 5 A flowchart of embodiment 150 of the method is shown. This is a combination in which the sequence of steps 111, 112, 113 for zeroing the first pressure sensor is performed beforehand, before the steps of one of the embodiments follow, alternatively according to one of diagrams 100, 120, 130, or 140. A further sequence of steps 114, 115, and 116 is shown with a dashed outline; the addition of these steps creates another embodiment. The blocks separated by arrows in Fig. 5Steps can be performed at widely separated times. Steps grouped together in one block are preferably performed consecutively.

[0076] Figure 6 Figure 1 schematically shows the relative position of the first 4' and second 4'' pressure measurement ranges of the first 1' and second 1'' pressure sensors of the group of pressure sensors on a pressure axis p. The pressure axis p is to be understood schematically here; it could, for example, be a linear or a logarithmic axis. Higher pressures are shown higher up on the axis than lower pressures. An overlap pressure measurement range 6 exists in which the first 4' and the second 4'' pressure measurement ranges overlap. The reading of the first and second measurement signals in step aa) of the procedure takes place while the pressure in the common measurement volume lies within this overlap pressure measurement range 6.

[0077] The example shown here further illustrates the case where the second pressure measuring range 4'' includes a low-pressure range 5, in which the pressure is lower than a lower limit of the first pressure measuring range 4'. While the pressure is in this low-pressure range, the pressure sensor can be zeroed using the higher pressure measuring range (4'), as shown in the Fig. 8 shown sequence.

[0078] In Figure 7An exemplary device 10 for carrying out the method is shown schematically. The device comprises a group 1 of pressure sensors, with at least one first pressure sensor 1' and a second pressure sensor 1'', which can measure pressures in a common measuring volume 2. The measuring volume 2 can, in particular, be a partial volume of a vacuum chamber, as schematically indicated by the dashed-dotted outline. The first pressure sensor 1' is configured to transmit a first measurement signal 3' to a control unit 12. The second pressure sensor 1'' is configured to transmit a second measurement signal 3'' to the control unit 12. In the example shown, the control unit has an operative connection 13 for controlling a pump 11' and an operative connection 14 for controlling an inlet valve 11''.Pump 11' and inlet valve 11'' are means of changing the pressure in the chamber to which they are connected, and thus also, in particular, means of changing the pressure in the common measuring volume 2, which comprises a partial volume of the chamber. The measuring signal and functional connection, indicated by dashed lines, can be implemented, for example, via wired connections, radio signals (Bluetooth, etc.), or optical signal transmission.

[0079] The components of the device shown, or the complete device, can be installed in a common housing. In particular, the group of pressure sensors and the control unit can be combined in a common housing to form a pressure sensor unit. In the arrangement shown, the control unit 12, which is designed to process the measurement signals, also controls the means for changing the pressure. This latter function can also be performed by a separate pressure control unit.

[0080] Figure 8 The diagram schematically shows a time-pressure curve illustrating the pressure over time in one variant of the process. Time t is represented horizontally, and the pressure axis p runs vertically, with the same pressure ranges shown as in [reference to diagram]. Figure 6The pressure profile over time is shown by the thick line. Rectangles with dashed borders mark the timing of the individual process steps. If necessary, this is preceded by a step of reducing the pressure from a level above the low-pressure range 5 into the low-pressure range. Steps 111 (Check), 112 (Read), and 113 (Set Zero Point Signal) are all performed at a pressure within the low-pressure range 5. The zero-point signal determined in step 113 can now be used to translate the current first measurement signal into an accurate pressure reading, independent of any zero-point drift of the first pressure sensor. In the example shown, the pressure is then increased into the overlap pressure measurement range 6. Steps 101, 102, and 103 of the basic procedure are performed within this overlap pressure measurement range 6.This is followed by further steps that use zeroing and calibration parameters to increase the measurement accuracy across the entire measuring range of the group of pressure sensors.

[0081] Figure 9This double-logarithmic graph shows the dependence of a pressure determined by a Pirani sensor on a specific gas type. The horizontal axis represents the "effective" pressure peff, determined by a gas-independent sensor, such as a CDG pressure sensor, which can serve as the primary pressure sensor in this process. The vertical axis shows the pressure p (mbar) read from a Pirani sensor as a function of the effective pressure peff (mbar) for different gas types, each represented by a separate curve. See the labels for each curve in the upper right of the graph. The pressure range shown extends from 10-3 mbar to 102 mbar on both axes, spanning five orders of magnitude. In this case, the Pirani sensor is calibrated to display the pressure peff for air; therefore, the pressure curve for air is a straight line on the diagonal of the double-logarithmic plot.In a pressure range below approximately 1 mbar, the effect of the gas type can be described by a factor between peff and the pressure p measured by the Pirani sensor. At higher pressures, a non-linear deviation from the pressure peff, characteristic of the gas type, occurs. When determining a first pressure measurement, the effective pressure peff can be measured, and in the step of determining a second pressure measurement, the pressure p can be determined. Using stored curves of the data in... Figure 9In the manner shown, the deviation between p and peff allows a statement to be made as to whether the gas composition present in the measuring volume corresponds to an expected gas composition, or whether the effective gas composition deviates from a target value (see step gg), 107). For example, the presence of hydrogen (H₂) across the entire pressure range shown leads to a significantly higher pressure reading on the Pirani sensor than would be expected for nitrogen (N₂), for example. One possible application of this evaluation is leak detection. Determining the presence of a foreign gas, as well as estimating its concentration, is possible. The extent of the deviation from a target value can, for example, be used as a basis for a go / no-go decision for further process steps.

[0082] Fig. 10 shows the basic situation for the in a double-logarithmic representation. Fig. 11 and12 They explained two ways in which the gas-type-dependent pressure measurement signal of the second, gas-type-dependent pressure sensor can be adjusted using one or more calibration factors, so that the pressure measurement is corrected accordingly and the gas-type dependency is eliminated even in the range where only the second gas-type-dependent pressure sensor is measuring. The illustration is as in Fig. 9 The thin dashed line shows the desired optimal output signal 90, for which the following applies: effective pressure (horizontal axis) = displayed pressure (vertical axis). Also shown are signal 91 from the first pressure sensor (identical for all gases in this case), signal 92 from the second pressure sensor in H₂, signal 93 from the second pressure sensor in water vapor, and signal 94 from the second pressure sensor in xenon. Pressures over six orders of magnitude, from 10⁻³ < mbar to 10⁺³ < mbar, are represented in the diagram.

[0083] In Fig. 10The output signals 91 of a gas-independent sensor 1, here a capacitive membrane sensor with a full-scale deflection of 10 mbar and a working range of 2.5 decades, as well as the output signals 92, 93, 94 of a gas-dependent Pirani sensor for various gases are shown. This results in an overlap pressure measurement range from 5 × 10⁻² < mbar to approximately 5 mbar for all gases, with the upper end of the Pirani sensor's measurement range at 5 mbar for H₂ as the test gas. Of particular note is the interesting overlap pressure measurement range from 5 × 10⁻² < mbar to approximately 0.4 mbar, within which the vast majority of gas characteristics are covered. Fig. 9 How Fig. 10 linear in double-logarithmic representation.

[0084] Will it now be like in Fig. 11.a ) for xenon in this overlapping pressure measurement range, a calibration parameter K for the Pirani characteristic curve is determined by simultaneous reading, so, as in Fig. 11.bAs shown, the Pirani characteristic curve can be adjusted by adjusting the curve using the calibration factor so that a correct measurement signal is output even in the low-pressure range 5, in which the pressure can only be read by the Pirani. The effect of adjusting 95 of the signal from the second pressure sensor is illustrated by bold arrows. The curve of the adjusted display signal 97 in Xenon is read, for example, in one process step at the effective pressure 96 and leads to the display signal 97, as shown by the dashed line. In the case as shown in Fig. 11 As shown, a pressure between 0.1 and 1 mbar is determined as the adjustment point 102, more precisely approx. 0.2 mbar.

[0085] In Fig. 12.aIn paragraphs 1 and 12(b), it is shown that the adjustment method can be improved by using multiple pressure points in the procedure. By simultaneously reading the data at different pressure points p1 and p2, one different calibration parameter is obtained depending on the pressure point read from the gas-independent sensor; in this case, K1 and K2 are obtained (see paragraphs 1 and 12(b)). Fig. 12.aBy using suitable correction methods, such as a pressure-dependent first-order calibration factor, characteristic curves that, as with water vapor, have a different slope compared to other gases in a double-logarithmic representation, can now also be corrected so that, again in the low-pressure range 5, where the pressure can only be read by the Pirani, the correct measurement signal is output. The effect of the adjustment 95 of the signal from the second pressure sensor is illustrated by bold arrows. The curve of the adjusted display signal 98 in water vapor is read, for example, in one process step at the effective pressure 96 and leads to the display signal 98, as shown by the dashed line. The pressures p1 and p2, which serve as adjustment points, are slightly less than a decade apart. Specifically, p1 is shown here as approximately 0.5 mbar and p2 as approximately 0.07 mbar.

[0086] In summary, the following effects can be achieved with the described method: a) increase the accuracy of pressure measurement across the entire pressure measurement range, b) minimize the gas type dependency even in the measurement range of pressure sensors with gas-type-dependent pressure measurement principles, d) offer the possibility of determining the gas composition beyond pressure measurement to a certain extent, e) alert the user to a change in gas composition or at least to a change in a gas-type-dependent pressure measurement in order to draw attention to unintended system changes, and f) facilitate the zeroing of pressure sensors as a secondary function.

[0087] The present invention makes it possible to achieve, in particular, the effects listed under points d) & e). Reference symbol list

[0088] 1 Group of pressure sensors 1' First pressure sensor of the group 1" Second pressure sensor of the group 2 Common measuring volume of the pressure sensors 3' First measuring signal 3" Second measuring signal 4' First pressure measuring range 4" Second pressure measuring range 5 Low-pressure range 6 Overlap pressure measuring range 10 Device for carrying out the method 11' Pump 11'' Inlet valve 12 Control unit 13 Functional connection (for controlling a pump) 14 Functional connection (for controlling an inlet valve) 90 Optimal output signal (effective pressure = displayed pressure) 91 Signal of the first pressure sensor (for all gases) 92 Signal of the second pressure sensor in H2 93 Signal of the second pressure sensor in water vapor 94 Signal of the second pressure sensor in xenon 95 Adjustment of the signal of the second pressure sensor 96 Effective pressure in process step 1xx 97 Adjusted display signal in xenon 98 Adjusted display signal in Water vapor 100 inventive method 101 Step aa) Reading the first and secondMeasurement signal 102 Step bb) Set adjustment point 103 Step cc) Determine at least one calibration parameter 104 Step dd) Read out the first and second measurement signals 105 Step ee) Determine another adjustment point 106 Step ff) Determine another calibration parameter 107 Step gg) Determine current pressure reading 108 Step hh) Determine deviation from an expected slope 109 Step ii) Compare the deviation with the tolerance threshold 110 Step jj) Trigger water vapor alarm 111 Step kk) Check if low-pressure range reached 112 Step ll) Read out a first measurement signal (while pressure is in the low-pressure range) 113 Step mm) Set zero-point signal 114 Step nn) Increase the pressure 115 Step oo) Read out a current first measurement signal 116 Step PP) Determine a current pressure reading (Zero-point signal taken into account) 120, 130, 140, 150 Models of the method K, K1, K2 Calibration parameters p Pressurep1 Measuring point 1 (pressure) p2 Measuring point 2 (pressure) t Time START Beginning of a process (in a flowchart) END End of a process (in a flowchart)

Claims

1. Method (100) for operating a group (1) of pressure sensors, wherein the group comprises at least a first pressure sensor (1') having a first pressure measurement range (4') and a second pressure sensor (1") having a second pressure measurement range (4"), wherein the first and second pressure sensors are arranged in such a manner that they can measure the pressure in a common measurement volume (2), wherein the first (4') and second (4") pressure measurement ranges overlap in an overlap pressure measurement range (6), and wherein the method comprises the steps of: aa) reading out (101) a first measurement signal of the first pressure sensor and a second measurement signal of the second pressure sensor substantially at the same time while the pressure in the common measurement volume is in the overlap pressure measurement range; bb) stipulating (102) the first measurement signal which has been read out as the adjustment point for the second pressure sensor; cc) determining (103) at least one gas-dependent calibration parameter (Kl, K2) for the second pressure sensor as a function of the first measurement signal, as a function of the adjustment point as stipulated in step bb) and as a function of the second measurement signal, characterized in that a current pressure measurement value in the measurement volume is determined as a function of a current second measurement signal and the previously determined at least one calibration parameter (K1) or the previously determined calibration parameters (K1, K2), and in that the method further comprises the step of: gg) deciding (107) whether a gas composition present in the common measurement volume (2) deviates from a target specification, taking into account a deviation of the current pressure measurement value with respect to a pressure measurement value derived from the first measurement signal, wherein the reading out of the first measurement signal is performed substantially simultaneously with the reading out of the current second measurement signal and while the pressure in the common measurement volume is in the overlap pressure measurement range (6).

2. Method (100) according to claim 1, wherein the adjustment point for the second pressure sensor is in the pressure range 10-2 mbar to 100 mbar, in particular in the pressure range 0.1 to 0.4 mbar.

3. Method (120) according to claim 1 or 2, wherein the method further comprises the steps of: dd) a further substantially simultaneous reading out (104) of a further first measurement signal of the first pressure sensor and a further second measurement signal of the second pressure sensor while the pressure in the common measurement volume is in the overlap pressure measurement range and wherein the pressure in the common measurement volume is different from the pressure in step aa), in particular wherein the pressure in the common measurement volume differs by a factor of two, by a decade or more from the pressure in step aa); ee) stipulating (105) the further first measurement signal which has been read out as a further adjustment point for the second pressure sensor; ff) determining (106) a further calibration parameter (K2), in particular a further gas-dependent calibration parameter, for the second pressure sensor as a function of the further first measurement signal, as a function of the further adjustment point stipulated in step ee) and as a function of the further second measurement signal.

4. Method (140) according to claim 3, wherein the further calibration parameter determined in step ff) is a slope in a double-logarithmic function diagram of the second measurement signal as a function of the first measurement signal, or wherein a slope in a double-logarithmic function diagram of the second measurement signal as a function of the first measurement signal is calculated from the calibration parameter determined in step cc) and the calibration parameter determined in step ff), and wherein the method further comprises the steps of: hh) determining (108) a deviation of this slope from a slope expected for a reference gas, for example the gas nitrogen; ii) comparing (109) the deviation determined in step hh) with a predetermined tolerance threshold for the deviation; jj) triggering (110) an alarm for the presence of water vapor in the common measurement volume (2) if the tolerance threshold is exceeded.

5. Method (100, 120, 130, 140) according to one of claims 1 to 4, wherein the first pressure sensor (1') is a pressure sensor of a pressure sensor type independent of a gas composition in the measurement volume, and wherein the second pressure sensor (1'') is a pressure sensor of a pressure sensor type dependent on the gas composition in the measurement volume, in particular wherein the second pressure sensor (1'') is - a heat conduction vacuum meter, especially according to Pirani or with thermocouple sensor, or - a cold cathode ionization vacuum meter, in particular a Penning ionization vacuum meter, or a non-inverted magnetron or an inverted magnetron, or - an ionization vacuum meter with hot cathode, in particular an ionization vacuum meter according to Bayard-Alpert, an ionization vacuum meter with extractor or with triode, or - a spinning rotor gauge sensor.

6. Method (100, 120, 130, 140) according to one of claims 1 to 5, wherein the first pressure sensor (1') is a diaphragm gauge, in particular a capacitance diaphragm gauge, in particular a ceramic capacitance diaphragm gauge, or an optical diaphragm gauge.

7. Method (100, 120, 130, 140) according to one of claims 1 to 6, wherein the second pressure sensor (1'') is a heat conduction vacuum meter, in particular according to Pirani or a thermocouple.

8. Method (100, 120, 130, 140) according to one of claims 1 to 7, wherein steps aa), bb) and cc) are repeated at regular time intervals, in particular once daily or once weekly.

9. Method (100, 120, 130, 140) according to one of claims 1 to 8 for operating a vacuum process system, comprising the group (1) of pressure sensors, wherein steps aa), bb) and cc) are repeated once per process cycle of the vacuum process system.

10. Method (150) according to one of claims 1 to 9, wherein the second pressure measurement range comprises a low-pressure range (5) in which the pressure is lower than a lower limit of the first pressure measurement range, wherein the method comprises the steps of: kk) checking (111) whether the low-pressure range has been reached by means of a second measurement signal (3'') from the second pressure sensor; ll) reading out (112) a first measurement signal (3') of the first pressure sensor while the pressure in the common measurement volume is in the low-pressure range; and mm) stipulating (113) the first measurement signal which has been read out as a zero point signal for the first pressure sensor.

11. Method (150) according to claim 10, wherein the method further comprises the steps of: nn) increasing (114) the pressure in the common measurement volume to the first pressure measurement range (4'); oo) reading out (115) a current first measurement signal (3') of the first pressure sensor; pp) determining (116) a current pressure measurement value as a function of the current first measurement signal and the zero point signal determined in step mm), in particular as a function of a difference of the current first measurement signal and the zero point signal.

12. Method (150) according to one of claims 10 or 11, wherein the low-pressure range (5) comprises only pressures that are lower than the lower limit of the first pressure measurement range by at least a factor of ten, in particular by at least a factor of one hundred.

13. Method (150) according to one of the claims 10 to 12, wherein the low-pressure range (5) comprises the range of 10-3 mbar up to 10-4 mbar.

14. Method according to one of claims 1 to 13, wherein the group of pressure sensors comprises at least three pressure sensors, and wherein the steps according to claim 1 are applied to a first pair of pressure sensors from the group of pressure sensors, and wherein the steps according to claim 1 are applied to a second pair of pressure sensors from the group of pressure sensors, wherein one of the pressure sensors of the first pair is also a pressure sensor of the second pair.

15. An apparatus (10) for carrying out a method according to one of claims 1 to 14, wherein the apparatus comprises: - a group (1) of pressure sensors, wherein the group comprises at least a first pressure sensor (1') having a first pressure measurement range (4') and a second pressure sensor (1'') having a second pressure measurement range (4''), wherein the first and second pressure sensors are arranged to measure pressure in a common measurement volume (2), and wherein the first (4') and second (4'') pressure measurement ranges overlap in an overlap pressure measurement range (6); and - a control unit (12), which is operatively connected to a first signal output of the first pressure sensor and to a second signal output of the second pressure sensor, for processing measurement signals (3', 3'') of the pressure sensors, wherein the control unit (12) is adapted to carry out the method according to one of claims 1 to 14.

16. Apparatus (10) according to claim 15, wherein the first pressure sensor (1') is a diaphragm gauge, wherein the overlap pressure measurement range (6) in which the first (4') and second (4'') pressure measurement ranges overlap comprises the pressure 0.1 mbar, and wherein the group (1) of pressure sensors comprises a third pressure sensor having a third pressure measurement range, wherein the third pressure measurement range extends the first pressure measurement range to greater pressures.

17. Apparatus (10) according to one of claims 15 or 16, further comprising at least one means for changing the pressure in the common measurement volume, wherein the at least one means for changing the pressure is operatively connected to a pressure control unit (12) for initiating a lowering or an increasing of the pressure in the common measurement volume.

18. Computer program product comprising instructions which, when the instructions are executed by a control unit (12) of an apparatus (10) according to one of claims 15 to 17, cause the control unit to perform the steps of a method (100, 120, 130, 140, 150) according to one of claims 1 to 14.