How the Pressure Sensor Group Works

Abstract

1. A method (100) for operating a pressure sensor group, the group comprising at least a first pressure sensor having a first pressure measurement range and a second pressure sensor having a second pressure measurement range, the first pressure sensor and the second pressure sensor being configured to be able to measure pressure in a common measurement volume, the first pressure measurement range and the second pressure measurement range overlapping within an overlapping pressure measurement range, the method comprising: aa) substantially simultaneously reading out 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 overlapping pressure measurement range; bb) defining the read-out first measurement signal as a calibration point for the second pressure sensor; and cc) determining at least one calibration parameter, in particular a gas-dependent calibration parameter, of the second pressure sensor as a function of the first measurement signal, as a function of the calibration point for the second pressure sensor defined in step bb), and as a function of the second measurement signal. The invention also relates to a method for operating a vacuum process plant, an apparatus for carrying out the method, and a computer program product.

Description

[Technical field]

[0001] The present invention relates to a method for operating a pressure sensor group.Furthermore, the present invention relates to a method for operating a vacuum processing system, an apparatus for carrying out the method, and a computer program product. [Background technology]

[0002] In the prior art, various types of pressure sensors are known. These include pressure sensors whose measurement principle is based on the deformation of a diaphragm due to a pressure difference between the two sides of the diaphragm, such as the so-called capacitance diaphragm gauge (abbreviation: CDG). The so-called thermal conduction gauges determine the pressure via pressure-dependent thermal conduction of the gas, for example in the case of the Pirani gauge or Pirani sensor, via the determination of the heat power given by a current-carrying wire to the surrounding gas. Another type of pressure sensor, the ionization gauge, measures the pressure indirectly by a gas-type-dependent determination of the gas density. By ionizing the gas molecules by electrons, the gas density is determined based on the neutralization speed of the ions on the collecting electrode, which is determined by current measurement.

[0003] Different types of pressure sensors have different measurement ranges. For example, there are pressure sensors that provide a meaningful reading at atmospheric pressure, but can no longer detect differences at very low pressures, such as precision or high vacuum. Other vacuum pressure sensors require pressures in the millibar (mbar) range to operate and can resolve very low pressures. In the prior art, it is known to use a pressure sensor group, for example consisting of two pressure sensors with overlapping measurement ranges, to cover a pressure measurement range larger than a single pressure sensor type. For example, the PCG550 product family from INFICON AG combines a Pirani sensor and a ceramic capacitance diaphragm gauge in one measurement device, where the measurement ranges of the Pirani sensor and the ceramic capacitance diaphragm gauge overlap.

[0004] A method for evaluating the output signals of two pressure sensors is known from EP 0 658 755 A1. In this publication, in particular for the combination of a cold cathode ionization sensor with a Pirani sensor, a weighting technique in the transition region of the respective sensor measuring ranges is proposed in order to obtain a well-defined measuring range which is substantially extended compared to the measuring ranges of the respective sensor types, whereby the sensor characteristics are continuously transferred one-to-one to one another. Summary of the Invention [Problem to be solved by the invention]

[0005] It was an object of the present invention to provide an alternative method of operation, in particular one which increases the accuracy of pressure measurements over the entire pressure measurement range. [Means for solving the problem]

[0006] This object is solved by a method according to claim 1. The method according to the invention is a method for operating a pressure sensor group. The pressure sensor group comprises at least one first pressure sensor having a first pressure measurement range and at least one second pressure sensor having a second pressure measurement range. The first pressure sensor and the second pressure sensor are configured to measure pressure in a common measurement volume. The first pressure measurement range and the second pressure measurement range overlap in an overlapping pressure measurement range. The method comprises: aa) substantially simultaneously reading a first measurement signal from a first pressure sensor and a second measurement signal from a second pressure sensor while the pressure in the common measurement volume is within an overlapping pressure measurement range; bb) defining the read first measurement signal as a calibration point for the second pressure sensor; cc) determining at least one calibration parameter of the second pressure sensor as a function of the first measurement signal, as a function of the adjustment points defined in step bb) and as a function of the second measurement signal.

[0007] The inventors have recognized that as a result of this method, an accurate determination of pressure is possible. In particular, where at least one of the pressure sensors is of a type that provides a measurement signal that is independent of gas composition, a surprisingly simple method of achieving a large degree of independence of the read pressure from gas type or gas composition can be achieved.

[0008] One or more pressure sensors in the pressure sensor group may be a vacuum pressure sensor, i.e., a pressure sensor capable of sensing, for example, low vacuum (i.e., pressure range of about 1 mbar to 1013 mbar, i.e., atmospheric pressure), precision vacuum (i.e., 10 -3 mbar to 1 mbar pressure range), high vacuum (i.e., 10 -8 mbar~10 -3 The pressure sensor may be used to measure pressures in the vacuum pressure range (pressure ranges from 100 to 2000 mbar), or a combination of two or three of the above vacuum pressure ranges. The principles of the invention also work for pressure sensors or overpressure sensors for measuring pressures close to atmospheric pressure.

[0009] The at least one calibration parameter may in particular be a gas type dependent calibration parameter. Step aa) is carried out at least once. Step aa) can also be carried out several times, in particular at different pressures, in order to collect measurement data that can be the basis for adjusting several calibration parameters in step cc). For example, the offset and the slope can be determined based on two measurements according to step aa) carried out at different pressures. This is advantageous, for example, in the case of gaseous water vapor, where the slope of the Pirani range deviates from the normal slope, so that the curve "indicated pressure" versus "effective pressure" is not described sufficiently accurately by the offset or coefficient alone.

[0010] As a specific example, a pressure sensor group may include a 13 mm CDG as the first pressure sensor and a Pirani sensor as the second pressure sensor. In this case, the adjustment point may be selected within a 100 mTorr pressure range, i.e., about 10 times above the lower end of the measurement range of the first pressure sensor designed for 10 Torr full scale. In this example, the gas type dependent calibration parameter of the second pressure sensor may be the factor by which the measurement signal of the Pirani sensor at a pressure defined by the gas to be calibrated and the adjustment point deviates from the measurement signal obtained with nitrogen at the pressure according to the adjustment point.

[0011] In particular, step cc) can be performed with a known gas type in the measurement volume or with a number of gases differing in gas type (e.g. air, nitrogen, oxygen, hydrogen, helium, argon, etc.) or concentration ratio (e.g. 20% helium, 80% nitrogen) in the measurement volume in succession.

[0012] The calibration parameters can then be stored, for example, in the form of a table for a number of different gas types. In this way, the combination of the second measurement signal and the information about the gas type present in the measurement volume can be determined with increased accuracy. The information about the gas type present in the measurement volume can be provided, for example, by a control unit that controls the process in the vacuum chamber. The information can be, for example, that an inlet valve for an inert gas, for example helium or argon, is opened.

[0013] One possible calibration parameter that can be adjusted in step cc) is the factor by which the pressure of the selected gas type deviates from the pressure corresponding to the pressure of a reference gas, for example nitrogen, if the measurement signal is the same.

[0014] Thus, on the one hand, the gas-type-dependent pressure measurement signal of the second pressure sensor can be adjusted by this coefficient, such that even in the range where only the second pressure sensor measures, the pressure measurement value is corrected accordingly and the gas-type dependence is minimized, and on the other hand, the coefficient provides information about the gas composition relative to the reference gas.

[0015] Small size and compact capacitance diaphragm gauges are available, for example, as the product from INFICON under the name "Porter™ CDG 020 D", which reach a full scale of pressure indication of about 10...1000 Torr and can measure pressures up to 10 mTorr (10 Torr at full scale). The method according to the invention is suitable for the operation of a combination of two or more of the above mentioned pressure sensors capable of measuring in a common measurement volume.

[0016] For example, the BCG450 Triple-Gauge™ covers the range from atmospheric pressure to ultra-high vacuum through three sensors. The INFICON BCG450 combination gauge (Triple-Gauge™) provides a 5×10 -10 ~1500mbar(3.75×10 -10 The BCG450 combines the advantages of three different technologies in a single compact and economical device for measuring process and base pressures in the range of 1000 torr (~1125 Torr). The BCG450 is designed to replace three individual sensors (hot ion, Pirani and a small CDG with a diameter of 11 mm). This reduces the cost and the space required for the equipment. This combined device can be operated, for example, by the method according to the invention.

[0017] However, the method according to the invention is also suitable for devices in which several different pressure sensors are attached to the same vacuum chamber, thus forming a pressure sensor group with a common measurement volume.

[0018] Embodiments of the method result from the features of dependent claims 2 to 16. In one variation of this method, the adjustment point of the second pressure sensor is 10 -2 mbar~10 0 mbar, in particular in the pressure range of 0.1 to 0.4 mbar.

[0019] For example, in a combination of a CDG and a Pirani sensor, the overlap pressure range of the two pressure sensors can be advantageously arranged by sizing the CDG in a pressure range where the gas type dependence of the Pirani sensor is characterized by a log-log diagram with a linear and substantially parallel shifted curve for each gas type, i.e. avoiding the range of higher pressures where non-linear diverging gas type characteristics occur. This further increases the accuracy. This variant of the method is particularly suitable for the operation of a pressure sensor group formed by the combination of two CDGs and a Pirani sensor dimensioned for different pressure measurement ranges, the first CDG with a lower pressure measurement range providing an overlap range with the linear range of the Pirani sensor and the second CDG with a higher pressure measurement range extending the effective measurement range of the pressure sensor group towards higher pressures.

[0020] A variation of this method is dd) substantially simultaneously reading out 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 within the overlap pressure measurement range, the pressure in the common measurement volume differing from the pressure of step aa), in particular the pressure in the common measurement volume differing from the pressure of step aa) by a factor of 2, 10 or more; ee) defining the retrieved further first measurement signal as a further calibration adjustment point for the second pressure sensor; ff) determining a further calibration parameter (K2), in particular a further gas-dependent calibration parameter, of the second pressure sensor as a function of the further first measurement signal, as a function of a further adjustment point of the second pressure sensor defined in step ee) and as a function of the further second measurement signal.

[0021] This variant can be extended to the recording of more than two measurement points and the determination of further calibration parameters, the number of calibration parameters corresponding at most to the number of measurement points. In particular, more measurement points can be recorded than the calibration parameters are determined. In this case, a compensation algorithm can be used to determine the set of calibration parameters that best matches the measurement points. The calibration parameters are therefore less dependent on the measurement noise.

[0022] In one variant of the method, a current pressure measurement in the measurement volume is determined as a function of the current second measurement signal and at least one previously determined calibration parameter or a previously determined calibration parameter.

[0023] This variation of the method includes the actual step of determining the current pressure value using a previous calibration of the second pressure sensor, which calibration is based on information obtained in the overlapping pressure measurement range and can now be applied to the entire second measurement range.

[0024] In one variation, the method comprises: gg) determining whether the gas composition present in the common measurement volume deviates from a target specification taking into account the deviation of the current pressure measurement relative to the pressure measurement derived from the first measurement signal, wherein the reading of the first measurement signal is performed substantially simultaneously with the reading of the current second measurement signal and while the pressure in the common measurement volume is within the overlapping pressure measurement range.

[0025] Step gg) corresponds to a check step of the gas composition. By specifying a tolerance range of acceptable deviations from the target specification, a yes / no decision can be made, for example, as to whether the next process step should be performed or not. The inventors have now realized that the functionality typically required for a residual gas analyzer can be obtained in a very simple way.

[0026] This variation can be used, for example, to detect gas composition fluctuations in a PVD process.

[0027] In a variant of the method, the further calibration parameter determined in step ff) is the slope of a log-log diagram of the second measurement signal as a function of the first measurement signal or the slope of the log-log 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). hh) determining the deviation of this gradient from the gradient expected for a reference gas, for example gaseous nitrogen; ii) comparing the deviation determined in step hh) with a predetermined tolerance threshold of deviation; jj) triggering an alarm for the presence of water vapor in the common measurement volume if a tolerance threshold is exceeded.

[0028] The inventors have recognised the fact that in the case of water vapour, the above slope differs from the slopes observed for virtually all relevant residual gases, and as a result, the presence of water vapour can be detected based on this property, which is clearly evident for the Pirani sensor.

[0029] In one variant of the method, the first pressure sensor is a pressure sensor of a pressure sensor type that is independent of the gas composition in the measurement volume. Furthermore, the second pressure sensor is a pressure sensor of a pressure sensor type that is dependent on the gas composition in the measurement volume, in particular the second pressure sensor is Thermal conductivity gauges, in particular Pirani or with thermocouple sensors, or a cold cathode ionization gauge, in particular a Penning ionization gauge, or a non-reversed or reversed magnetron, or Ionization gauges with hot cathodes, in particular Bayard-Alpert gauges, extractor or triode gauges, or It may be a rotating rotor gauge sensor.

[0030] Pressure sensors can be divided into two classes of pressure sensor types: those that directly sense force per area, and those that use the indirect effect of pressure on another physical quantity, such as the thermal conductivity of the gas under the pressure being measured, to determine the pressure. The latter type of pressure sensor is usually dependent on the type of gas. The inventors have recognized that a pressure sensor group comprising a first pressure sensor of a first type and a second pressure sensor of a second type particularly benefits from the method of operation according to the invention.

[0031] Depending on the desired measurement range, i.e. the pressure range within which a high measurement accuracy is achieved, the combination of pressure sensors can be selected. Thermal conduction vacuum gauges according to Pirani have a measurement range of about 100...0.1 Pa, ionization vacuum gauges with cold cathodes according to Penning have a measurement range of about 10 0 ...10 -9 The Bayard-Alpert hot cathode ionization gauge has a measuring range of Pa and is approximately 1...10 -8 The ionization gauge with a measuring range of Pa and equipped with an extractor measuring system is -1 ...10 -10 An ionization vacuum gauge with a measurement range of Pa or with a triode is 10 3 ...10 -10 The Pirani thermal conductivity vacuum gauge has a measurement range of 10 Pa. 5 It can be used up to Pa, but the accuracy is greatly reduced.

[0032] In one variant of the method, the first pressure sensor is a diaphragm gauge, in particular a capacitance diaphragm gauge, in particular a ceramic capacitance diaphragm gauge, or an optical diaphragm gauge.

[0033] Diaphragm gauges respond directly to force per area and are therefore gas type independent. In one variant of the method, the second pressure sensor is a thermal conductivity gauge, in particular a Pirani or thermocouple.

[0034] Thermal conductivity gauges have a well-defined gas type dependence and therefore benefit from calibration by the method of the present invention.

[0035] In one variant of this method, steps aa), bb) and cc) are repeated at regular intervals, in particular once a day or once a week.

[0036] The time intervals can in particular be adapted to the timing of further process steps. Depending on the circumstances, it may also be useful in advance to carry out step a), i.e. to reduce 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 in each case at regular time intervals. The sequence of steps aa), bb) and cc) can also be repeated as a function of the process, for example when strong temperature cycles are operated in a vacuum process plant.

[0037] In one variation of the method, the method is a method for operating a vacuum processing system comprising a pressure sensor group, wherein steps aa), bb) and cc) are repeated once per process cycle of the vacuum processing system.

[0038] Such a process cycle may, for example, include aeration, introduction of the substrate, reducing the pressure to the high vacuum range, allowing the inflow of the process gas, extraction of the process gas, aeration and removal of the substrate. Steps aa) to cc) of the method may each be carried out in conjunction with reducing the pressure to the high vacuum range. This variant may, for example, be combined with an automatic pressure measurement quality check, in which several pressure values ​​are determined at short time intervals related to the duration of the process steps and it is checked whether these pressure values ​​are within a defined value range. In this way, it may be excluded that pressure changes are too fast to record good quality data.

[0039] For example, the method may be automatically triggered whenever an operating pressure range is reached or crossed. For example, as described above, the overlapping pressure measurement range may be the operating pressure range for determining the calibration parameters of the Pirani sensor.

[0040] In a variation of this method, the second pressure measurement range includes a low pressure range in which the pressure is lower than the lower limit of the first pressure measurement range. kk) the additional step of checking whether a low pressure range has been reached by a second measurement signal from a second pressure sensor; ll) the additional step of reading out a first measurement signal of the first pressure sensor while the pressure in the common measurement volume is within a low pressure range; mm) defining the read-out first measurement signal as a zero-point signal of the first pressure sensor.

[0041] For example, a capacitance diaphragm gauge allows to determine which value of the output signal corresponds to zero pressure (or to a pressure at the lower end of the measurement range). This value may drift slowly, making the measurement signal difficult to interpret. In a variant of the method, this zero point can be determined and updated repeatedly as necessary, while ensuring that there is a sufficiently low pressure in the common measurement volume of the two pressure sensors so that this zero point can be determined. For example, in the case of the above-mentioned PCG550 product family, a Pirani sensor can be used as a second pressure sensor to establish the zero point of the CDG, which in this case has the role of the first pressure sensor in the method according to the invention. The combination of the determination of the calibration parameters and pre-zeroing according to this variant of the method significantly increases the accuracy of the pressure measurement over the entire pressure measurement range.

[0042] A variation of this method is nn) increasing the pressure in the common measurement volume to a first pressure measurement range; oo) reading out a current first measurement signal of the first pressure sensor; pp) determining a current pressure measurement as a function of the current first measurement signal and the zero point signal determined in step mm), in particular as a function of the difference between the current first measurement signal and the zero point signal.

[0043] This way the current pressure reading is the current pressure reading with the correct 0. In one variant of the method, the low pressure range includes only pressures that are at least 10 times, in particular at least 100 times, lower than the lower limit of the first pressure measurement range.

[0044] The inventors have realized that this variant allows the zero point of the first sensor to be determined particularly accurately.

[0045] In one variation of this method, the low pressure range is 10 -3 mbar~10 -4 Includes the mbar range.

[0046] This variant can be implemented, for example, in combination with the variant described above, in which the second pressure sensor is a Pirani thermal conductivity gauge. Ceramic capacitance gauges in the role of the first pressure sensor particularly benefit from the periodic determination of the zero point according to this variant of the method.

[0047] In one variant of the method, the pressure sensor group comprises at least three pressure sensors, steps according to the method of the invention are applied to a first pair of pressure sensors of the pressure sensor group and steps according to the method of the invention are also applied to a second pair of pressure sensors of the pressure sensor group, in which case one of the pressure sensors of the first pair is also a pressure sensor of the second pair.

[0048] According to this variant, the method according to the invention can be extended in a cascaded manner to a pressure sensor group having more than two pressure sensors, where in a first pair of pressure sensors one has the role of the first pressure sensor and the other has the role of the second pressure sensor. In another pair of pressure sensors the second pressure sensor can have the role of the first pressure sensor according to the method, and so on. A prerequisite for the cascaded extension of the total pressure measurement range of a group is in each case that the measurement ranges of two adjacent pressure sensors overlap with respect to their measurement ranges.

[0049] For example, in a pressure sensor group including a capacitance diaphragm gauge, a Pirani sensor, and an ionization gauge, a cascaded chain of measurement ranges of different pressure sensors is possible. For example, the adjustment point of the capacitance diaphragm gauge as the first pressure sensor of the first pair and the Pirani sensor as the second pressure sensor of the first pair can be set to about 1 mbar. Furthermore, the adjustment point of the Pirani sensor as the first pressure sensor of the second pair and the ionization gauge as the second pressure sensor of the second pair can be set to about 10 -3 The calibration can be cascaded according to this variant. For example, the ionization manometer can be a Bayard-Alpert type manometer or another ionization manometer as mentioned above. For example, the pressure sensor group can involve a fourth pressure sensor in the form of a capacitance diaphragm gauge that is fully deflected at atmospheric pressure. In combination, it can therefore be set to 10 mbar from atmospheric pressure. -10 Such a "quadruple" pressure sensor with a total measurement range up to mbar pressure can be obtained, which by operation according to the invention achieves high accuracy or considerable independence from the gas type over the entire measurement range.

[0050] Furthermore, the invention also relates to an apparatus according to claim 17, which is an apparatus for carrying out the method according to the invention.

[0051] This device is A pressure sensor group, a pressure sensor group, the group comprising at least a first pressure sensor having a first pressure measurement range and a second pressure sensor having a second pressure measurement range, the first pressure sensor and the second pressure sensor being configured to measure pressure in a common measurement volume, the first pressure measurement range and the second pressure measurement range overlapping within an overlapping pressure measurement range; and a control unit operatively connected to the first signal output of the first vacuum pressure sensor and the second signal output of the second vacuum pressure sensor for processing the measurement signals of the vacuum pressure sensors.

[0052] The device can in particular be realised as a unit (pressure sensor unit, "pressure gauge") comprising all described elements in a common housing. For example, the housing can have a standard vacuum flange for connection to a vacuum system. For example, the unit can have a data interface providing a single processed pressure signal to the outside, which is obtained by taking into account all available pressure sensors of all calibrations and groups. In particular, the unit can include a computer program product, for example in the form of firmware, which has not yet been described.

[0053] In one embodiment of the device, the first pressure sensor is a diaphragm gauge. An overlapping pressure measurement range where the first pressure measurement range and the second pressure measurement range overlap includes a pressure of 0.1 mbar. The pressure sensor group includes a third pressure sensor having a third pressure measurement range, where the third pressure measurement range extends the first pressure measurement range to higher pressures.

[0054] This embodiment of the device can be realized, for example, by the following combination of pressure sensors: a capacitance diaphragm gauge as the first pressure sensor, a Pirani sensor as the second pressure sensor, and again a capacitance diaphragm gauge as the third sensor. The first pressure sensor can have, for example, a measurement range that includes a pressure of 0.1 mbar and covers 30 times. The Pirani sensor in this example has a measurement range that also includes a pressure of 0.1 mbar. The third pressure sensor can have a third pressure measurement range with a full scale at atmospheric pressure, extending the pressure range of the entire pressure sensor group to high pressures. The third pressure measurement range may overlap with the first pressure measurement range and / or the second pressure measurement range. All three pressure sensors of the group may be installed in a common housing.

[0055] In one embodiment, the apparatus comprises at least one means for varying the pressure in the common measurement volume, the at least one means for varying the pressure operably connected to the pressure control unit to initiate a reduction or increase in the pressure in the common measurement volume.

[0056] The pressure control unit may be a control unit for processing measurement signals from the vacuum pressure sensor or may be operatively connected to the vacuum pressure sensor, for example to transmit the status of a valve or pump, or to receive control commands such as changing the pressure in preparation for adjustment.

[0057] The means for varying the pressure may include, for example, a pump or a valve. Furthermore, the invention relates to a computer program product as claimed in claim 20.

[0058] A computer program product according to the invention comprises instructions which, when executed by a control unit of an apparatus of the invention, cause the control unit to carry out the steps of the method of the invention.

[0059] For example, the computer program product may include firmware in a pressure sensor arrangement or may consist of firmware in a pressure sensor arrangement.

[0060] Exemplary embodiments of the invention are explained in more detail below with reference to the figures. [Brief description of the drawings]

[0061] [Figure 1] FIG. 2 is a flow diagram of a method according to the present invention. [Diagram 2] 1 is a flow chart of one embodiment of the method. [Diagram 3] 1 is a flow chart of one embodiment of the method. [Figure 4] FIG. 2 is a flow diagram of a further embodiment of the method. [Diagram 5] 1 is a flow chart of an embodiment of a method that includes zeroing a first pressure sensor. [Figure 6] 3 is a schematic diagram of possible relative positions of a first pressure measurement range and a second pressure measurement range; FIG. [Figure 7] FIG. 1 is a schematic diagram of an apparatus for carrying out the method. [Figure 8] FIG. 13 is a schematic diagram of pressure time series for a variant of the method. [Figure 9] FIG. 2 is a log-log diagram showing the dependence of the pressure determined by the Pirani sensor on the type of gas. [Figure 10] A log-log diagram of the indicated pressure as a function of the effective pressure shows 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 according to the invention using one or more calibration factors, so that the pressure measurement value is corrected and the gas-type dependency is eliminated even within the range measured only by the second gas-type-dependent pressure sensor. [Figure 11]A log-log diagram of the indicated pressure as a function of the effective pressure shows 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 according to the invention using one or more calibration factors, so that the pressure measurement value is corrected and the gas-type dependency is eliminated even within the range measured only by the second gas-type-dependent pressure sensor. [Figure 12] A log-log diagram of the indicated pressure as a function of the effective pressure shows 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 according to the invention using one or more calibration factors, so that the pressure measurement value is corrected and the gas-type dependency is eliminated even within the range measured only by the second gas-type-dependent pressure sensor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0062] FIG. 1 shows a flow chart of a method 100 according to the present invention, which comprises: aa) step 101 of substantially simultaneously reading out a first measurement signal of a first pressure sensor and a second measurement signal of a second pressure sensor while the pressure in the common measurement volume is within an overlapping pressure measurement range; bb) step 102 of defining the read first measurement signal as a calibration point for the second pressure sensor; cc) determining 103 at least one calibration parameter K1, K2, in particular a gas-dependent calibration parameter, of the second pressure sensor as a function of the first measurement signal, as a function of the adjustment point of the second pressure sensor determined in step bb) and as a function of the second measurement signal.

[0063] Steps 101, 102, and 103 are performed in sequence. In Fig. 2, a flow chart of an embodiment 120 of the method is shown. First, all steps of the method 100 according to the invention are executed. Following this, dd) a step 104 of substantially simultaneously reading out 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 within an overlapping pressure measurement range, the pressure in the common measurement volume being different from the pressure of step aa); ee) a step 105 of defining the read-out further first measurement signal as a further adjustment point of the second pressure sensor; ff) a step 106 of determining a further calibration parameter K2 of the second pressure sensor, in particular a further gas-dependent calibration parameter, 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 is carried out.

[0064] 3 shows a flow chart of an embodiment 130 of the method. First, all steps of the method 100 according to the invention are performed. This is followed by a step 107 of determining whether the gas composition present in the common measurement volume 2 deviates from a target specification, taking into account the deviation of the current pressure measurement value from the pressure measurement value derived from the first measurement signal, the reading of the first measurement signal being made substantially simultaneously with the reading of the current second measurement signal and while the pressure in the common measurement volume is within the overlapping pressure measurement range 6.

[0065] Figure 4 shows a flow diagram of a further embodiment 140 of the method. First, the steps of variant 120 (see Figure 2) or variant 130 (see Figure 3) are alternatively performed. This is followed by: hh) a step 108 of determining the deviation of this gradient from the gradient expected for a reference gas, in this case gaseous nitrogen; ii) a step 109 of comparing the deviation determined in step hh) with a predetermined tolerance threshold of deviation; jj) A step 110 is executed of triggering an alarm about the presence of water vapour in the common measurement volume 2 if a tolerance threshold is exceeded.

[0066] Fig. 5 shows a flow chart of an embodiment 150 of the method. This is a combination in which a sequence of steps 111, 112, 113 for zeroing the first pressure sensor is performed before the steps of the embodiment continue, alternatively according to any of Figs. 100, 120, 130 or 140. Shown in dashed lines is a further sequence of steps 114, 115 and 116, the addition of which results in a further embodiment. The blocks separated by arrows in Fig. 5 can be performed far apart in time. The steps combined in the blocks are preferably performed immediately one after the other.

[0067] FIG. 6 shows diagrammatically the relative position of the first pressure measurement range 4' and the second pressure measurement range 4'' of the first pressure sensor 1' or the second pressure sensor 1'' of the pressure sensor group on the pressure axis p. The pressure axis p should be understood here diagrammatically and may be, for example, a linear or logarithmic axis. High pressures are drawn further up on the axis than low pressures. There is an overlapping pressure measurement range 6 in which the first pressure measurement range 4' and the second pressure measurement range 4'' overlap. The readout of the first and second measurement signals in step aa) of the method is performed while the pressure in the common measurement volume is within this overlapping pressure measurement range 6.

[0068] In the illustrated example, a variation of the method is further shown in which the second pressure measurement range 4'' includes a low pressure range 5 in which the pressure is lower than the lower limit of the first pressure measurement range 4'. While the pressure is in this low pressure range, the pressure sensor having the higher pressure measurement range (4') can be zeroed. See the procedure shown in FIG. 8.

[0069] FIG. 7 shows diagrammatically an exemplary device 10 for carrying out the method. The device comprises a pressure sensor group 1 with at least one first pressure sensor 1′ and one second pressure sensor 1″ capable of measuring the pressure in a common measurement volume 2. The measurement volume 2 may in particular be a partial volume of a vacuum chamber, as diagrammatically indicated by the area enclosed by a dashed and dotted line. The first pressure sensor 1′ is set up to transfer a first measurement signal 3′ to a control unit 12. The second pressure sensor 1″ is set up to transfer a second measurement signal 3″ to the control unit 12. In the illustrated example, the control unit has an operational connection 13 for controlling a pump 11′ and an operational connection 14 for controlling an inlet valve 11″. The pump 11′ and the inlet valve 11″ are means for varying the pressure in the chambers to which they are connected, and thus in particular also means for varying the pressure in the common measurement volume 2 including the partial volume of the chamber. The measurement signal and operational connections depicted in dashed lines can be implemented, for example, by wires. They may also be implemented, for example, by radio signals (such as Bluetooth) or optical signal transmission.

[0070] Parts of the illustrated device or the entire device can be installed in a common housing. In particular, the pressure sensor group and the control unit can be combined in a common housing to form a pressure sensor unit. In the illustrated configuration, the control unit 12 designed to process the measurement signals also performs the control of the means for varying the pressure. The latter function can also be performed by a separate pressure control unit.

[0071] FIG. 8 shows a schematic time-pressure diagram of the pressure in a variant of the method. The time t is shown horizontally, the pressure axis p runs vertically, and the same pressure ranges as in FIG. 6 are shown. The pressure curve over time is shown in bold. The dotted rectangles mark the time positions of the individual method steps. If necessary, this is preceded by a step of lowering the pressure from above the low pressure range 5 to the low pressure range. Steps 111 of checking the zero point signal, 112 of reading out, and 113 of determining are all performed at a pressure in the low pressure range 5. Now, using the zero point signal determined in step 113, the current first measurement signal can be converted into an accurate pressure measurement value that is independent of any zero point drift of the first pressure sensor. Then, in the illustrated example, the pressure is increased into the overlap pressure measurement range 6. Steps 101, 102 and 103 of the basic sequence of the method according to the invention are carried out in this overlap pressure measurement range 6. This is followed by further steps in which zeroing and calibration parameters are used to increase measurement accuracy over the measurement range of the pressure sensor group.

[0072] FIG. 9 shows the dependence of the pressure determined by the Pirani sensor on a particular gas species in logarithmic representation. In the horizontal direction, the “effective” pressure p eff is shown, which is determined using a gas type independent sensor, for example a CDG pressure sensor, which may have the role of the first pressure sensor in the method according to the invention. In the vertical direction, the pressure p (mbar) read on the Pirani sensor corresponds to the effective pressure p of the different gas types, each with a separate curve. eff The pressures are plotted as a function of pressure (mbar). See the labels for each curve in the upper right region of the graph. The pressure range shown is 10 -3 mbar~10 2 mbar, i.e. over 5 orders of magnitude. In this case, the Pirani sensor measures the pressure p eff In the pressure range below about 1 mbar, the effect of the gas species is peff This can be explained by the coefficient between the pressure p of the gas species and the pressure p measured by the Pirani sensor. eff Nonlinear deviations from the characteristics occur. Effective pressure p eff A can be measured when determining the first pressure measurement, and a pressure p can be determined in the step of determining the second pressure measurement. A stored curve of the type shown in FIG. 9 can be used to compare p and p to determine whether the gas composition present in the measurement volume matches an expected gas composition, or whether the effective gas composition deviates from a target specification. eff (step gg), see 107). As a result of, for example, the presence of hydrogen (H2) throughout the indicated pressure range, the pressure values ​​read at the Pirani sensor are significantly higher than would be expected for, for example, the gas type nitrogen (N2). One possible application of this evaluation is leak measurement. A determination of the external gas and an estimation of its concentration are possible. The degree of deviation from the target value can be used, for example, as a basis for a decision to proceed / avoid further process steps.

[0073] FIG. 10 shows in double logarithmic representation the two possible basic situations described in FIG. 11 and FIG. 12, i.e. how the gas type-dependent pressure measurement signal of the second gas type-dependent pressure sensor can be adjusted by the method according to the invention with one or more calibration coefficients, so that the pressure measurement value is corrected accordingly and the gas type dependence is eliminated even in the range where only the second gas type-dependent pressure sensor measures. The illustration is similar to FIG. 9, the thin dashed line indicates the desired optimal output signal 90, and applies effective pressure (horizontal axis)=indicated pressure (vertical axis). Furthermore, a signal 91 from the first pressure sensor (in this case the same for all gases), a signal 92 from the second pressure sensor in H2, a signal 93 from the second pressure sensor in water vapor and a signal 94 from the second pressure sensor in xenon are shown. 10 -3 mbar~10 +3 Pressures over six orders of magnitude of mbar are shown in the figures.

[0074] 10 shows the output signal 91 of a gas type independent sensor 1, in this case a capacitive diaphragm sensor with a full scale of 10 mbar and a working range of 25 times, and the output signals 92, 93, 94 of a gas type dependent Pirani sensor for various gases. This results in a 5×10 -2 An overlapping pressure measurement range in the range of 500 psi to about 5 mbar is obtained, and the upper end of the measurement range of the Pirani sensor at 5 mbar for H2 is applied as the test gas. -2 It should be emphasized here that the overlapping pressure measurement range of interest, from 0.4 mbar to approximately 0.4 mbar, is such that most of the gas characteristics in Figure 9, as in Figure 10, are linear in a double logarithmic representation.

[0075] If the calibration parameter K of the Pirani characteristic is determined for xenon in this overlapping pressure measurement range by simultaneous reading, as in FIG. 11.a), then the Pirani characteristic can be adjusted by adjusting the curve by a calibration factor, as shown in FIG. 11.b), so that a correct measurement signal is output also in the low pressure range 5, where the pressure can only be read by Pirani. The effect of the adjustment 95 of the signal of the second pressure sensor is shown by the thick arrow. For example, the curve of the adjusted indication signal 97 in xenon is read in a method step at the effective pressure 96, resulting in an indication signal 97, as shown by the dashed line. In the case shown in FIG. 11, a pressure of 0.1 to 1 mbar, more precisely about 0.2 mbar, is determined as the adjustment point 102.

[0076] In Fig. 12.a) and Fig. 12.b) it is shown that the adjustment method can be improved if several pressure points are used in the method. Simultaneous reading at different pressure points p1 and p2 results in different calibration parameters depending on the read pressure points of the gas type independent sensor 1, in this case K1 and K2, see Fig. 12.a). By suitable correction methods, such as a pressure-dependent linear calibration factor in pressure, it is now possible to correct the characteristic curve, which has a slope of the log-log representation different from the slope of the other gases, as in the case of water vapor, so that a correct measurement signal is output even in the low pressure range 5, where the pressure can only be read by Pirani. The effect of the adjustment 95 of the signal of the second pressure sensor is shown by the thick arrow. For example, the curve of the adjusted indication signal 98 in water vapor is read in a method step at the effective pressure 96, resulting in an indication signal 98, as shown by the dashed line. The pressures p1 and p2, which serve as adjustment points, are slightly less than ten times apart. Specifically shown here is p1 about 0.5 mbar and p2 about 0.07 mbar.

[0077] Therefore, in summary, the present invention and the above-mentioned embodiments of the present invention can achieve the following effects:

[0078] a) Increases pressure measurement accuracy over the entire pressure measurement range. b) Minimizing the gas type dependency even in the measurement range of pressure sensors having a gas type dependent pressure measurement principle.

[0079] d) Provides the ability to determine gas composition beyond pressure measurement within certain limits. e) Alerting the user to changes in gas composition, or at least changes in gas type dependent pressure measurements, so as to alert the user to unintended system modifications.

[0080] f) Facilitates zeroing of pressure sensors as a quadratic function. [Explanation of symbols]

[0081] List of reference symbols 1 Pressure Sensor Group 1' First pressure sensor in group 1'' Group of 2nd Pressure Sensor Common measurement volume of two pressure sensors 3' First measurement signal 3'' Second measurement signal 4' First pressure measurement range 4'' Secondary Pressure Measurement Range 5. Low Pressure Range 6 Overlapping pressure measurement ranges 10 Apparatus for carrying out the method 11' Pump 11'' Inlet Valve 12 Control unit 13 Operating connection (for controlling the pump) 14 Operating connection (for controlling the inlet valve) 90 Optimal output signal (effective pressure = indicated pressure) 91 First pressure sensor signal (for all gases) 92 Signal of the second pressure sensor during H2 93 Signal of the second pressure sensor in water vapor 94 Signal of the second pressure sensor in xenon 95 Conditioning the signal of the second pressure sensor 96 Effective pressure in method step 1xx 97 Adjusted display signal in xenon 98 Adjusted display signal in water vapor 100 Method according to the present invention 101 Step aa) Reading out the first measurement signal and the second measurement signal 102 Step bb) Define adjustment points 103 Step cc) Determine at least one calibration parameter 104 Step dd) Further reading out the first measurement signal and the second measurement signal 105 Further adjustment steps ee) 106 Step ff) Determine further calibration parameters 107 Step gg) Determine the current pressure reading 108 Step hh) Determine the deviation from the expected slope 109 Step ii) Compare the deviation to the tolerance threshold 110 Step jj) Triggering the water vapor alarm 111 Step kk) Check whether low pressure range has been reached 112 Step II) Read out the first measurement signal (in the low pressure range) 113 Steps (mm) Specify the zero point signal 114 Step nn) Increase pressure 115 Step oo) Current reading of the first measurement signal 116 Step PP) Determine the current pressure measurement (taking into account the zero point signal) 120, 130, 140, 150 Method embodiments K, K1, K2 calibration parameters P Pressure p1 Measurement point 1 (pressure) p2 Measurement point 2 (pressure) t time Start Start of method (in a flowchart) End End of method (in the flowchart)

Claims

1. A method (100) for operating a pressure sensor group (1), comprising: 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''), the first pressure sensor and the second pressure sensor being configured to be able to measure a pressure in a common measurement volume (2), the first pressure measurement range (4') and the second pressure measurement range (4'') overlapping in an overlapping pressure measurement range (6), the method comprising: aa) substantially simultaneously reading out (101) a first measurement signal of the first pressure sensor and a second measurement signal of the second pressure sensor while the pressure in the common measurement volume is within the overlapping pressure measurement range; bb) defining (102) the read first measurement signal as a calibration point for the second pressure sensor; cc) determining (103) at least one gas-dependent calibration parameter (K1, K2) of the second pressure sensor as a function of the first measurement signal, as a function of the adjustment points defined in step bb) and as a function of the second measurement signal, A current pressure measurement in the measurement volume is determined as a function of a current second measurement signal and at least one previously determined calibration parameter (K1) or previously determined calibration parameters (K1, K2), the method comprising: gg) determining (107) whether the gas composition present in the common measurement volume (2) deviates from a target specification taking into account the deviation of the current pressure measurement relative to a pressure measurement derived from the first measurement signal, wherein the reading of the first measurement signal is performed substantially simultaneously with the reading of the current second measurement signal and while the pressure in the common measurement volume is within the overlapping pressure measurement range (6).

2. The adjustment point of the second pressure sensor is 10 －２ mbar~10 ０ The method (100) of claim 1, wherein the pressure is in the range of 1000 to 10 ...

3. dd) reading (104) a further substantially simultaneously 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 within the overlapping pressure measurement range, the pressure in the common measurement volume being different from the pressure of step aa); ee) defining (105) the read-out further first measurement signal as a further calibration adjustment point for the second pressure sensor; ff) determining (106) a further gas-dependent calibration parameter (K2) of the second pressure sensor as a function of the further first measurement signal, as a function of the further adjustment point defined in step ee) and as a function of the further second measurement signal.

4. The further calibration parameter determined in step ff) is the slope of a log-log diagram of the second measurement signal as a function of the first measurement signal or the slope of the log-log 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 method comprising the steps of: hh) determining the deviation of this gradient from the gradient expected for a reference gas, for example gaseous nitrogen (108); ii) comparing (109) the deviation determined in step hh) with a predetermined tolerance threshold of the deviation; jj) triggering (110) an alarm for the presence of water vapor in said common measurement volume (2) if said tolerance threshold is exceeded.

5. The first pressure sensor (1') is a pressure sensor of a pressure sensor type independent of the gas composition in the measurement volume, and the second pressure sensor (1'') is a pressure sensor of a pressure sensor type dependent on the gas composition in the measurement volume, the second pressure sensor (1'') being Thermal conductivity gauge, or Cold cathode ionization vacuum gauge, or non-reversed magnetron or reversed magnetron, or an ionization gauge with a hot cathode, or The method (100, 120, 130, 140) of any one of claims 1 to 4, which is a rotating rotor gauge sensor.

6. The method (100, 120, 130, 140) according to any one of claims 1 to 5, wherein the first pressure sensor (1') is a diaphragm gauge.

7. The method (100, 120, 130, 140) according to any one of claims 1 to 6, wherein the second pressure sensor (1'') is a Pirani or thermocouple based thermal conductivity gauge.

8. The method (100, 120, 130, 140) of any one of claims 1 to 7, wherein steps aa), bb) and cc) are repeated at regular time intervals.

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

10. The second pressure measurement range includes a low pressure range (5) in which the pressure is lower than a lower limit of the first pressure measurement range, and the method further comprises: kk) checking (111) whether the low pressure range has been reached by a second measurement signal (3'') from the second pressure sensor; ll) reading (112) a first measurement signal (3') of the first pressure sensor while the pressure in the common measurement volume is within the low pressure range; mm) defining the read-out first measurement signal as a zero-point signal of the first pressure sensor.

11. nn) increasing (114) the pressure in the common measurement volume to the first pressure measurement range (4'); oo) a step (115) of reading out a current first measurement signal (3') of said 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).

12. 12. The method (150) of claim 10 or 11, wherein the low pressure range (5) includes only pressures at least 10 times lower than the lower limit of the first pressure measurement range.

13. The low pressure range (5) is 10 －３ mbar~10 －４ The method (150) of any one of claims 10 to 12, comprising the range of mbar.

14. 14. The method according to claim 1, wherein the pressure sensor group includes at least three pressure sensors, the steps of claim 1 are applied to a first pair of pressure sensors from the pressure sensor group, and the steps of claim 1 are applied to a second pair of pressure sensors from the pressure sensor group, and 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 the method according to any one of claims 1 to 14, comprising: A pressure sensor group (1), a pressure sensor group (1), said group comprising 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''), said first pressure sensor and said second pressure sensor being configured to measure pressure in a common measurement volume (2), said first pressure measurement range (4') and said second pressure measurement range (4'') overlapping in an overlapping pressure measurement range (6); and a control unit (12) 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, the control unit (12) being adapted to perform the method according to any one of claims 1 to 14.

16. 16. The apparatus (10) of claim 15, wherein the first pressure sensor (1') is a diaphragm gauge, the overlapping pressure measurement range (6) where the first pressure measurement range (4') and the second pressure measurement range (4'') overlap includes a pressure of 0.1 mbar, and the pressure sensor group (1) includes a third pressure sensor having a third pressure measurement range, the third pressure measurement range extending the first pressure measurement range to higher pressures.

17. 17. The apparatus (10) of claim 15 or 16, further comprising at least one means for varying the pressure in the common measurement volume, the at least one means for varying the pressure being operatively connected to a pressure control unit (12) for initiating a reduction or increase of the pressure in the common measurement volume.

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

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