Method for operating a group of pressure sensors, device for carrying out the method, and computer program product

Abstract

A method 100 for operating a group of pressure sensors, wherein the group includes at least a first pressure sensor having a first pressure measurement range and a second pressure sensor having a second pressure measurement range, wherein the first and second pressure sensors are configured to measure pressure in a common measurement volume, wherein the first and second pressure measurement ranges overlap in overlapping pressure measurement ranges, and wherein the method includes the steps of: aa) substantially simultaneously reading 101 a first measurement signal from the first pressure sensor and a second measurement signal from the second pressure sensor, wherein the pressure in the common measurement volume is within the overlapping pressure measurement ranges; bb) defining 102 the read first measurement signal as an adjustment point for the second pressure sensor; cc) determining 103 at least one calibration parameter, particularly a gas-dependent calibration parameter, 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 defined in step bb), and as a function of the second measurement signal. The invention also relates to a method for operating a vacuum processing plant, apparatus for performing this method, and computer program products.

Description

[Technical Field]

[0001] This invention relates to a method for operating a group of pressure sensors. The invention further relates to a method for operating a vacuum processing system, an apparatus for performing this method, and a computer program product. [Previous Technology]

[0002] In the prior art, many types of pressure sensors are known. These include pressure sensors whose measurement principle is based on the deformation of a diaphragm caused by a pressure difference between two sides of the diaphragm, such as the so-called capacitance diaphragm gauge (CDG). So-called thermally conductive vacuum gauges determine pressure through the pressure-dependent thermal conduction of a gas, for example, in the case of a Pirani vacuum gauge or Pirani sensor, by determining the heat output emitted through a current-carrying wire to the surrounding gas. Depending on the type of gas, another type of pressure sensor, the ionization barometer, measures pressure indirectly by determining the gas density. This gas density is determined by the ionization of gas molecules by electrons, based on the ion neutralization rate on a collector 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 meaningful measurements at atmospheric pressure, but cannot detect differences at very low pressures, such as medium or high vacuum. Other vacuum pressure sensors require pressures in the millibar (mbar) range to operate fully and can handle very low pressures. In the prior art, it is known to use groups of pressure sensors, such as two pressure sensors with overlapping measurement ranges, to cover a larger pressure measurement range than a single pressure sensor type can cover. For example, INFICON AG's PCG550 product series combines a Pirani sensor and a ceramic capacitive diaphragm meter in a single measuring device, where the measurement ranges of the Pirani sensor and the ceramic capacitive diaphragm meter overlap.

[0004] A method for evaluating the output signals of two pressure sensors is known from disclosure EP 0 658 755 A1. In this disclosure, particularly for a combination of a cold cathode ionization sensor and a Pirani sensor, a weighting technique is proposed in the transition region of the measurement range of each sensor to compare with the measurement range of the respective sensor type, thereby obtaining a substantially extended and defined measurement range, by which sensor characteristics are continuously transmitted to each other in a defined, one-to-one manner. [Summary of the Invention]

[0005] The object of the present invention is to provide an alternative method of operation. In particular, this object is to provide a method of operation that improves the accuracy of pressure measurement throughout the entire pressure measurement range.

[0006] This objective is achieved by the method as claimed in claim 1. The method according to the invention is a method for operating a group of pressure sensors. The group of pressure sensors includes 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 and second pressure sensors are configured to measure pressure in a common measurement volume. The first and second pressure measurement ranges overlap in overlapping pressure measurement ranges.

[0007] This method includes the following steps: aa) substantially simultaneously reading a first measurement signal from a first pressure sensor and a second measurement signal from a second pressure sensor, wherein the pressure in the common measurement volume is within an overlapping pressure measurement range; bb) defining the read first measurement signal as an adjustment point for the second pressure sensor; cc) determining at least one 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.

[0008] The inventors have recognized that pressure can be accurately determined by this method. In particular, if at least one pressure sensor is a type of pressure sensor that provides a measurement signal independent of gas composition, a surprisingly simple method can be achieved that reads pressure with a high degree of independence from gas type or gas composition.

[0009] One or more pressure sensors in this group of pressure sensors may be vacuum pressure sensors, that is, pressure sensors used for measuring, for example, low vacuum (i.e., pressure range from about 1 mbar to 10¹³ mbar, i.e., to atmospheric pressure), medium vacuum (i.e., pressure range from 10⁻³ mbar to 1 mbar), high vacuum (i.e., pressure range from 10⁻⁸ mbar to 10⁻³ mbar), or combinations of two or three of the above vacuum pressure ranges. The principles of the present invention are also applicable to pressure sensors or overpressure sensors that measure pressures close to atmospheric pressure.

[0010] At least one calibration parameter may be a calibration parameter related to the gas type.

[0011] Step aa) is performed at least once. Step aa) may also be performed several times, especially at different pressures, to collect measurement data, on which basis multiple calibration parameters can be adjusted in step c). For example, based on two measurements performed at different pressures according to step aa), the offset and slope can be determined. This is advantageous, for example, for gas types such as water vapor, where the slope in the Pirani range deviates from the normal slope, so that the curve of "indicated pressure" versus "effective pressure" cannot be adequately and accurately described by offset or factor alone.

[0012] As a specific example, this group of pressure sensors may include a 13mm CDG as the first pressure sensor and a Pirani sensor as the second pressure sensor. In this case, the calibration point can be selected within a 100 mTorr pressure range, that is, approximately one decimal place higher than the lower edge of the measurement range of the first pressure sensor designed for a 10 Torr full scale. In this example, the gas type-related calibration parameter for the second pressure sensor may be a factor by which the measurement signal of the Pirani sensor at the gas to be calibrated and at the pressure defined by the calibration point deviates from the measurement signal obtained with nitrogen at the pressure of the calibration point.

[0013] Step cc) can be performed in the measuring volume using a known type of gas, or by continuously using a plurality of gases in the measuring volume, wherein the types of these gases are the same (e.g., air, nitrogen, oxygen, hydrogen, helium, argon, etc.) or the concentration ratios are different (e.g., 20% helium, 80% nitrogen).

[0014] Then, the calibration parameters can be stored, for example, in tabular form for different gas types. In this way, the combination of the second measurement signal and information about the type of gas present in the measurement volume results in improved accuracy. For example, information about the type of gas present in the measurement volume can be provided by a control unit that controls the process in the vacuum chamber. For example, this information may include, for example, the fact that the inlet valve for an inert gas, such as helium or argon, is open.

[0015] The possible calibration parameters that can be adjusted in step cc) are the factors of the pressure deviation between the selected gas type and the pressure of a reference gas, such as nitrogen, under the same measurement signal.

[0016] Therefore, on the one hand, the gas-type dependent pressure measurement signal of the second pressure sensor can be adjusted by this factor, thereby correcting the pressure measurement and minimizing gas-type dependence even within the range measured by only the second pressure sensor. On the other hand, this factor provides information about the gas composition relative to a reference gas.

[0017] Small capacitive diaphragm gauges with small dimensions, such as those from INFICON under the designation "Porter™ CDG020D," reach full scale for their pressure indication at approximately 10...1000 Torr and can measure pressures as low as 10 mTorr (at full scale of 10 Torr). The method according to the invention is applicable to the operation of combinations of two or more of the aforementioned pressure sensors, which can measure in a common measuring volume.

[0018] For example, the BCG450 Triple-Gauge™ measuring device covers a range from atmospheric pressure to ultra-high vacuum with three sensors. The INFICON BCG450 Triple-Gauge™ combines the advantages of three different technologies into a single, small, and economical device for measuring process and base pressures in the range of 5 × 10⁻¹⁰ to 1500 mbar (3.75 × 10⁻¹⁰ to 1125 Torr). The BCG450 is designed to replace three separate sensors (thermal ionization, Pirani, and a small CDG with a diameter of 11 mm). This reduces costs and the space required on the system. For example, this combined device can be operated using the method according to the invention.

[0019] However, the method according to the invention is also applicable to devices that attach different pressure sensors to the same vacuum chamber, thereby forming a group of pressure sensors with a common measuring volume.

[0020] Embodiments of this method are derived from the features of appendix claims 2 to 16.

[0021] In a variation of this method, the adjustment point of the second pressure sensor is in the pressure range of 10-2 mbar to 100 mbar, especially in the pressure range of 0.1 to 0.4 mbar.

[0022] For example, in a combination of a CDG and a Pirani sensor, the overlapping pressure range of the two pressure sensors can be advantageously placed within a single pressure range by designing the size of the CDG, where the gas type dependence of the Pirani sensor is characterized in a double logarithmic plot by linear and substantially parallel shift curves for each gas type, i.e., avoiding nonlinear divergent gas type characteristics in higher pressure ranges. This further improves accuracy. This variation of the method is particularly suitable for the operation of a pressure sensor group formed by a combination of two CDGs and Pirani sensors designed with different pressure measurement ranges, wherein the first CDG with a lower pressure measurement range provides an overlap with the linear range of the Pirani sensor, and the second CDG with a higher pressure measurement range extends the effective measurement range of the pressure sensor group toward higher pressures.

[0023] A variation of this method further includes the following steps: dd) Additionally, substantially simultaneously reading out another first measurement signal of the first pressure sensor and another second measurement signal of the second pressure sensor, wherein the pressure in the common measurement volume is within an overlapping pressure measurement range, and wherein the pressure in this common measurement volume is different from the pressure in step aa), particularly wherein the pressure in this common measurement volume differs from the pressure in step aa) by more than 2 times or 10 times; ee) Defining the additionally read first measurement signal as an additional adjustment point for the second pressure sensor; ff) Determining additional calibration parameters (K2) for the second pressure sensor, particularly additional gas-dependent calibration parameters, as a function of the first measurement signal, as a function of the additional adjustment point for the second pressure sensor determined in step ee), and as a function of the additional second measurement signal.

[0024] This variation can be extended to recording more than three measurement points and determining additional calibration parameters, where the number of calibration parameters corresponds at most to the number of measurement points. In particular, more measurement points can be recorded than the calibration parameters to be determined. In this case, a fitting algorithm can be used to determine a set of calibration parameters that best match the measurement points. Therefore, the calibration parameters are less dependent on measurement noise.

[0025] In a variation of this method, the current pressure measurement in the measuring volume is determined as a function of the current second measurement signal and at least one or more previously determined calibration parameters.

[0026] This variation of the method includes the practical step of determining the current pressure value using prior calibration of the second pressure sensor. This calibration is based on information obtained over the overlapping pressure measurement range and can now be applied to the entire second measurement range.

[0027] In a variation, the method further includes the following steps: gg) determining whether the gas composition present in the common measurement volume deviates from the target specification, taking into account the deviation of the current pressure measurement value from the pressure measurement value obtained from the first measurement signal, wherein the reading of the first measurement signal is substantially simultaneous with the reading of the current second measurement signal, and the pressure in the common measurement volume is within the overlapping pressure measurement range.

[0028] Step gg) corresponds to the gas composition inspection step. By specifying a tolerance range for acceptable deviation from the target specification, a yes / no determination can be made, for example, whether the next process step should be performed. The inventors have recognized that functionality can be obtained in a very simple way here, for which a residual gas analyzer would typically be required.

[0029] For example, this variation can be used to detect changes in gas composition during the PVD process.

[0030] In a variation of this method, the additional calibration parameter determined in step ff) is the slope of the second measurement signal as a function of the first measurement signal in the double logarithmic function graph of the second measurement signal, or the slope of the second measurement signal as a function of the first measurement signal in the double logarithmic function graph is calculated by the calibration parameters determined in step cc) and the calibration parameters determined in step ff). This method further includes the following steps: hh) determining the deviation of this slope from the slope expected for a reference gas, such as nitrogen; ii) comparing the deviation determined in step hh) with a predetermined tolerance threshold for this deviation; jj) if the tolerance threshold is exceeded, triggering an alarm for the presence of water vapor in the co-measurement volume.

[0031] The inventors have recognized that, in the case of water vapor, the slope mentioned differs from that observed in almost all related residual gases, such that the presence of water vapor can be detected due to this characteristic. This characteristic of the Pirani sensor is very evident.

[0032] In one variation of this method, the first pressure sensor is a pressure sensor of the type that is independent of the gas composition in the measurement volume. Furthermore, the second pressure sensor is a pressure sensor of the type that is related to the gas composition in the measurement volume, and in particular, the second pressure sensor may be: - a thermally conductive vacuum gauge, especially according to the Pirani gauge or with a thermocouple sensor, or - a cold cathode ionization vacuum gauge, especially a Penning ionization vacuum gauge, or a non-inverted magnetron or an inverted magnetron, or - an ionization vacuum gauge with a hot cathode, especially according to the Bayard-Alpert ionization vacuum gauge, an ionization vacuum gauge with an extractor or a triode, or - a spintronic sensor.

[0033] Pressure sensors can be divided into two types: pressure sensors that are directly sensitive to force per unit area; and pressure sensors that utilize the indirect effect of pressure on another physical quantity, such as the thermal conductivity of a gas under the pressure to be measured, to determine the pressure. The latter type of pressure sensor is usually related to the type of gas. The inventors have recognized that pressure sensor groups comprising a first pressure sensor of the first type and a second pressure sensor of the second type are particularly beneficial to the operating method according to the invention.

[0034] The combination of pressure sensors can be selected depending on the desired measurement range, i.e., the pressure range required to achieve high measurement accuracy. According to Pirani's thermal conductivity vacuum gauge, it has a measurement range of approximately 100...0.1 Pa; according to Penning's ionization vacuum gauge with a cold cathode, it has a measurement range of approximately 100...10⁻⁹ Pa; and according to Baya-Eppert's ionization vacuum gauge with a hot cathode, it has a measurement range of approximately 1...10⁻⁸ Pa. For extractor measurement systems, these ranges are 10⁻¹...10⁻¹⁰ Pa, and for triodes, they are 10³...10⁻¹⁰ Pa. Pirani's thermal conductivity vacuum gauge can be used up to atmospheric pressure of 10⁵ Pa, but the accuracy is significantly reduced.

[0035] In a variation of this method, the first pressure sensor is a diaphragm pressure gauge, particularly a capacitive diaphragm gauge, especially a ceramic capacitive diaphragm gauge, or an optical diaphragm pressure gauge.

[0036] Diaphragm pressure gauges respond directly to the force per unit area and are therefore independent of the type of gas.

[0037] In a variation of this method, the second pressure sensor is a thermally conductive vacuum gauge, particularly based on a Pirani or thermocouple.

[0038] Thermally conductive vacuum gauges have a significant gas type dependence and therefore benefit from calibration according to the method of the present invention.

[0039] In a variation of this method, steps aa), bb) and cc) are repeated at regular intervals, especially once a day or once a week.

[0040] The time interval can be particularly adapted to the timing sequence of other process steps. Depending on the context, it is also useful to perform step a) in advance, that is, to reduce the pressure in the common measurement volume to a low pressure range, so that in each case, the entire sequence of steps aa), bb), and cc) is repeated 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 running a high-temperature cycle in a vacuum processing plant.

[0041] In one variation of this method, the method is used to operate a vacuum processing system containing this group of pressure sensors. Steps aa), bb), and cc) are repeated once in each process cycle of the vacuum processing system.

[0042] This process cycle may include, for example, gas filling, substrate introduction, reducing pressure to a high vacuum range, allowing process gas inflow, extracting process gas, gas filling, and substrate removal. Each of process steps aa) to cc) may be performed concurrently with reducing pressure to a high vacuum range. This variation may be combined, for example, with an automated pressure measurement quality check, wherein several pressure values ​​related to the duration of the process step are determined at short time intervals, and wherein it checks whether these pressure values ​​are within a defined range. In this way, situations where pressure changes are too rapid to obtain high-quality data can be eliminated.

[0043] For example, this method can be automatically triggered whenever the start-up pressure range is reached or exceeded. For example, as described above, the overlapping pressure measurement range can be the start-up pressure range used to determine the calibration parameters of the Pirani sensor.

[0044] In a variation of this method, the second pressure measurement range includes a low pressure range, wherein this pressure is lower than the lower limit of the first pressure measurement range. The method includes the following additional steps: kk) checking whether the low pressure range has been reached using a second measurement signal from the second pressure sensor; ll) reading out a first measurement signal from the first pressure sensor when the pressure in the common measurement volume is in the low pressure range; and mm) setting the read first measurement signal as the zero-point signal for the first pressure sensor.

[0045] For example, for a capacitive diaphragm gauge, it may be necessary to determine which value of the output signal corresponds to zero pressure (or the pressure at the lower end of the measurement range). This value drifts slowly and can make the interpretation of the measurement signal difficult. With this variation of the method, this zero point can be determined and repeatedly updated as needed, while ensuring sufficiently low pressure in the common measurement volume of the two pressure sensors to allow for zero point determination. For example, for the aforementioned PCG550 product series, in the method according to the invention, the Pirani sensor can be used as a second pressure sensor to establish the zero point of the CDG, in which case it functions as the first pressure sensor. According to this variation of the method, the combination of determining the calibration parameters and prior zeroing significantly increases the accuracy of pressure measurements across the entire pressure measurement range.

[0046] A variation of this method further includes the following steps: nn) increasing the pressure in the common measurement volume to a first pressure measurement range; oo) reading the current first measurement signal of the first pressure sensor; pp) determining the 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 the difference between the current first measurement signal and the zero-point signal.

[0047] In this way, the current pressure reading is the current pressure reading with the correct zero point.

[0048] In a variation of this method, the low pressure range includes only pressures that are at least 10 times lower, and especially at least 100 times lower, than the lower limit of the first pressure measurement range.

[0049] The inventors have realized that, through this variation, the zero point for the first sensor can be determined with particular accuracy.

[0050] In a variation of this method, the low pressure range includes the range of 10⁻³ mbar to 10⁻⁴ mbar.

[0051] This variation can be implemented, for example, in conjunction with the above-described variation, wherein the second pressure sensor is a Pirani thermal conductivity vacuum gauge. The ceramic capacitive pressure gauge, which acts as the first pressure sensor, particularly benefits from the periodic determination of the zero point according to this variation of the method.

[0052] In a variation of this method, the group of pressure sensors comprises at least three pressure sensors. The steps of the method according to the invention apply to the first pair of pressure sensors in this group of pressure sensors, and the steps of the method according to the invention also apply to the second pair of pressure sensors in this group of pressure sensors. In this case, one of the pressure sensors in the first pair is also a pressure sensor in the second pair.

[0053] According to this variation, the method according to the invention can be cascaded to a group of pressure sensors having two or more pressure sensors, wherein in a first pair of pressure sensors, one pressure sensor functions as a first pressure sensor and the other pressure sensor functions as a second pressure sensor. In another pair of pressure sensors, according to this method, the second pressure sensor may function as a first pressure sensor, and so on. A prerequisite for this cascaded expansion of the total pressure measurement range of this group is that in each case, there are overlapping measurement ranges of two pressure sensors that are adjacent to each other with respect to their measurement ranges.

[0054] For example, in a group of pressure sensors including a capacitive diaphragm gauge, a Pirani sensor, and an ionization barometer, this cascaded linkage of the measurement ranges of different pressure sensors is possible. For example, the adjustment point for the capacitive diaphragm gauge, which is the first pair of pressure sensors, and the Pirani sensor, which is the second pair of pressure sensors, can be set to approximately 1 mbar. Furthermore, the adjustment point for the Pirani sensor, which is the first pair of pressure sensors, and the ionization barometer, which is the second pair of pressure sensors, can be set to approximately 10⁻³ mbar. According to this variation, the calibration system is cascaded.

[0055] For example, the ionization pressure gauge may be a Bayer-Eppert type pressure gauge or another ionization pressure gauge described above. For example, this group of pressure sensors may be a fourth pressure sensor in the form of a capacitive diaphragm gauge with full deflection at atmospheric pressure. Combined, a "quadruple" pressure sensor with a total measurement range from atmospheric pressure up to 10-10 mbar can be obtained, which achieves high accuracy throughout the measurement range by operation according to the invention, and has broad independence from gas type.

[0056] Furthermore, the present invention also relates to an apparatus as claimed in claim 17, which is an apparatus for performing the method according to the present invention.

[0057] This device includes: - a group of pressure sensors; wherein the group includes at least a first pressure sensor having a first pressure measurement range and a second pressure sensor having a second pressure measurement range, wherein the first and second pressure sensors are configured to measure pressure in a common measurement volume, and wherein the first and second pressure measurement ranges overlap in overlapping pressure measurement ranges; and - a control unit operatively connected to a first signal output of the first vacuum pressure sensor and a second signal output of the second vacuum pressure sensor for processing measurement signals from the vacuum pressure sensors.

[0058] This device can be implemented as a single unit (pressure sensor unit, "pressure gauge"), which includes all the components mentioned in the common housing. For example, the housing may have a standard vacuum flange for connection to a vacuum system. For example, the unit may have a data interface that provides a single processed pressure signal to the outside, wherein the processed pressure signal is obtained by taking into account all calibrations and all available pressure sensors in this group. In particular, the unit may include a computer program product, for example in the form of firmware, which will be discussed below.

[0059] In one embodiment of this device, the first pressure sensor is a diaphragm pressure gauge. The overlapping pressure measurement range of the first and second pressure measurement ranges includes a pressure of 0.1 mbar. The group of pressure sensors includes a third pressure sensor having a third pressure measurement range, wherein this third pressure measurement range extends the first pressure measurement range to a greater pressure.

[0060] For example, this embodiment of the device can be implemented by a combination of the following pressure sensors: a capacitive diaphragm gauge as a first pressure sensor, a Pirani sensor as a second pressure sensor, and a capacitive diaphragm gauge as a third sensor. For example, the first pressure sensor may have a measurement range including a pressure of 0.1 mbar and covering three decimal numbers. The Pirani sensor in this example also has a measurement range including a pressure of 0.1 mbar. The third pressure sensor may have a third pressure measurement range with full scale at atmospheric pressure, extending the pressure range of the entire group of pressure sensors to high pressures. The third pressure measurement range may overlap with the first and / or second pressure measurement ranges. All three pressure sensors in this group can be mounted in a common housing.

[0061] In one embodiment, the device includes 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 for initiating a decrease or increase in the pressure in the common measurement volume.

[0062] The pressure control unit may be a control unit for processing measurement signals from a vacuum pressure sensor, or operatively connected to them, 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.

[0063] Means for changing pressure may include, for example, pumps or valves.

[0064] Furthermore, the present invention relates to a computer program product according to claim 20.

[0065] The computer program product according to the present invention includes commands that, when executed by the control unit of the device according to the present invention, cause the control unit to perform the steps of the method according to the present invention.

[0066] For example, a computer program product may include firmware in a pressure sensor device, or firmware that may be included in a pressure sensor device.

Implementation Method

[0068] Figure 1 shows a flowchart of a method 100 according to the present invention. This method includes the following steps: aa) substantially simultaneously reading out a first measurement signal of a first pressure sensor and a second measurement signal of a second pressure sensor, wherein the pressure in the common measurement volume is within an overlapping pressure measurement range; bb) defining the readout first measurement signal 102 as an adjustment point for the second pressure sensor; cc) determining 103 at least one calibration parameter K1, K2, particularly a gas-dependent calibration parameter, 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 defined in step bb), and as a function of the second measurement signal.

[0069] Steps 101, 102 and 103 are performed in sequence.

[0070] Figure 2 shows a flowchart of embodiment 120 of this method. First, all steps of method 100 according to the invention are performed. Next are the following steps: dd) Additionally, substantially simultaneously, another first measurement signal of the first pressure sensor and another second measurement signal of the second pressure sensor are read out, where the pressure in the common measurement volume is within the overlapping pressure measurement range, and wherein the pressure in the common measurement volume is different from the pressure in step aa); ee) Define the additionally read first measurement signal 105 as an additional adjustment point for the second pressure sensor; ff) Determine 106 additional calibration parameters K2 for the second pressure sensor, in particular additional gas-dependent calibration parameters, as a function of the additional first measurement signal, as a function of the additional adjustment point defined in step ee), and as a function of the additional second measurement signal.

[0071] Figure 3 shows a flowchart of embodiment 130 of this method. First, all steps of method 100 according to the invention are performed. Next are the following steps: gg) Determine whether the gas composition present in the common measurement volume 2 deviates from the target specification, wherein the deviation between the current pressure measurement value and the pressure measurement value obtained from the first measurement signal is taken into consideration, wherein the reading of the first measurement signal is performed substantially simultaneously with the reading of the current second measurement signal, and the pressure in the common measurement volume is within the overlapping pressure measurement range 6.

[0072] Figure 4 shows a flowchart of embodiment 140 of this method. First, the steps of variation 120 (see Figure 2) or variation 130 (see Figure 3) are performed alternately. The following steps are then performed: hh) determining 108 the deviation of this slope from the slope expected to be used for the reference gas, which in this case is nitrogen; ii) comparing the deviation determined in step hh) with a predetermined tolerance threshold for this deviation; jj) if this tolerance threshold is exceeded, triggering 110 an alarm for the presence of water vapor in the co-measurement volume 2.

[0073] Figure 5 shows a flowchart of one embodiment 150 of this method. This is a combination in which the order of steps 111, 112, and 113 for zeroing the first pressure sensor is alternately performed before a step in a subsequent embodiment, according to one of Figures 100, 120, 130, or 140. The dashed lines indicate an additional order of steps 114, 115, and 116, which, together with these steps, lead to another embodiment. The blocks separated by the arrows in Figure 5 can be performed at long intervals in time. The steps combined within the blocks are preferably performed consecutively.

[0074] Figure 6 schematically shows the relative positions of the first and second pressure measurement ranges 4' and 4" of the first and second pressure sensors 1' and 1" of the pressure sensor group on the pressure axis p. This pressure axis p is schematically understood here as, for example, a linear axis or a logarithmic axis. Higher pressures are drawn further away on the axis than lower pressures. There are overlapping pressure measurement ranges 6, where the first and second pressure measurement ranges 4' and 4" overlap. The readout of the first and second measurement signals in step aa) of this method occurs, and the pressure in the common measurement volume is within this overlapping pressure measurement range 6.

[0075] In the example shown here, a further example is shown where the second pressure measurement range 4" includes a low pressure range 5, where this pressure is below the lower limit of the first pressure measurement range 4'. When the pressure is in this low pressure range, the pressure sensor can be zeroed using a higher pressure measurement range (4'), as shown in the sequence in Figure 8.

[0076] Figure 7 schematically shows an exemplary apparatus 10 for performing this method. This apparatus includes a group 1 of pressure sensors, having at least one first pressure sensor 1' and one second pressure sensor 1" which can measure the pressure in a common measuring volume 2. The measuring volume 2 may be a portion of the volume of a vacuum chamber, as schematically indicated by the area outlined by the dashed line. 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 exemplary example, the control unit has a movable connection 13 for controlling the pump 11' and a movable connection 14 for controlling the inlet valve 11" Pump 11' and inlet valve 11" are means for changing the pressure in the chambers to which they are connected, and therefore especially for changing the pressure in the common measuring volume 2, which includes a portion of the chamber's volume. The measurement signals and active connections, indicated by dashed lines, can be implemented, for example, in a wired manner, but they can also be implemented, for example, via radio signals (Bluetooth, etc.) or optical signal transmission.

[0077] The components or the entire device shown can be mounted 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 illustrated configuration, the control unit 12, designed to process the measurement signal, also performs control over the means of changing the pressure. The latter function can also be performed by a separate pressure control unit.

[0078] Figure 8 shows a schematic time-pressure graph of the pressure in a variation of this method. Time t is displayed in the horizontal direction, and the pressure axis p extends in the vertical direction, having the same pressure range as shown in Figure 6. The pressure curve changing over time is indicated by thick lines. Dashed rectangles mark the time positions of individual method steps. If necessary, there is a step prior to this to reduce the pressure from above the low pressure range 5 to the low pressure range. The steps of checking the zero-point signal 111, reading 112, and defining 113 all occur at pressures within the low pressure range 5. The zero-point signal determined in step 113 can now be used to convert the current first measurement signal into an accurate pressure measurement value, which is independent of any zero-point drift of the first pressure sensor. Thereafter, in the exemplary example, the pressure increases into the overlapping pressure measurement range 6. Steps 101, 102, and 103 of the basic sequence of the method according to the invention are performed within this overlapping pressure measurement range 6. The next step involves zeroing and calibration parameters used to improve measurement accuracy across the entire measurement range of this group of pressure sensors.

[0079] Figure 9 shows the dependence of pressure determined by a Pirani sensor on a certain gas type in a double logarithmic graph. In the horizontal direction, the "effective" pressure peff is shown, which is determined by a gas-independent sensor, such as a CDG pressure sensor, which can act as the first pressure sensor in the method according to the invention. In the vertical direction, the pressure p (mbar) read at the Pirani sensor is plotted as a function of the effective pressure peff (mbar) for different gas types, with a separate curve for each gas type; see the label for each curve in the upper right area of ​​the graph. The pressure range shown extends from 10⁻³ mbar to 10² mbar on both axes, i.e., more than five orders of magnitude. In this case, the Pirani pressure sensor is calibrated in the manner that it displays the pressure peff for the gas type air, i.e., the pressure curve for air is a straight line on the diagonal of the double logarithmic plot. In the pressure range below approximately 1 mbar, the effect of gas type can be described by the factor between peff, measured by a Pirani sensor, and pressure p. At higher pressures, a non-linear deviation from pressure peff occurs, which is characteristic of gas type. The effective pressure peff can be measured when determining the first pressure measurement, and pressure p can be determined in the step of determining the second pressure measurement. Using a storage curve of the type shown in Figure 9, a statement can be derived from the deviation between p and peff, indicating whether the gas composition present in the measurement volume matches the expected gas composition, or whether the effective gas composition deviates from the target specification (see step gg, 107). For example, in the entire pressure range shown, the presence of hydrogen (H2) causes the pressure value read at the Pirani sensor to be, for example, significantly higher than that expected for the gas type nitrogen (N2). One possible application of this assessment is leak measurement. The determination of foreign gases and the estimation of their concentration are possible. For example, the degree of deviation from the target value can be used as a basis for the decision to remove or not remove in other methodological steps.

[0080] Figure 10 shows, as a double logarithmic graph, the basic scenarios for the two possibilities explained in Figures 11 and 12, namely, how the gas-dependent pressure measurement signal of the second gas-dependent pressure sensor can be adjusted by more than one calibration factor using the method according to the invention, so as to correct the pressure measurement and also eliminate gas dependence in the range where only the second gas-dependent pressure sensor is measured. The illustration is as shown in Figure 9, where the thin dashed line shows the desired optimal output signal 90, for which the following applies: effective pressure (horizontal axis) = indicated pressure (vertical axis). Further shown are the signal 91 from the first pressure sensor (which is the same for all gases in this case), the signal 92 from the second pressure sensor in H2, the signal 93 from the second pressure sensor in water vapor, and the signal 94 from the second pressure sensor in xenon. The schematic diagram shows six orders of magnitude pressure from 10⁻³ mbar to 10⁺³ mbar.

[0081] Figure 10 shows the output signal 91 of a gas-independent sensor 1, in this case a capacitive diaphragm sensor with a full-scale of 10 mbar and an operating range of 25 years, and the output signals 92, 93, and 94 of a gas-type dependent Pirani sensor for a variety of gases. This results in an overlapping pressure measurement range from 5 × 10⁻² mbar to approximately 5 mbar for all gases, while for H₂ as the test gas, the upper limit of the measurement range of the Pirani sensor is 5 mbar. It should be emphasized here that the overlapping pressure measurement range of interest is from 5 × 10⁻² mbar to approximately 0.4 mbar, where, as in Figure 10, the gas characteristics of most gases in Figure 9 are linear in the double logarithmic representation.

[0082] As shown in Figure 11.a), if the calibration curve K used for the Pirani feature is determined by the synchronous reading of xenon within this overlapping pressure measurement range, then, as shown in Figure 11.b), the Pirani feature can be adjusted in a manner also within the low pressure range 5 by means of the calibration factor adjustment curve, where the correct measurement signal can be output by reading the pressure from the Pirani feature alone. The effect of adjusting the signal 95 of the second pressure sensor is illustrated by the thick arrow. For example, in the method step, the adjusted display signal 97 is read as a curve in xenon at the effective pressure 96, resulting in the display signal 97 as indicated by the dashed line. In the case shown in Figure 11, the pressure between 0.1 and 1 mbar is determined as the adjustment point 102, more precisely, approximately 0.2 mbar.

[0083] In Figures 12.a) and 12.b), it shows that this adjustment method can be improved if several pressure points are used in this method. By reading out simultaneously at different pressure points p1 and p2, it depends on the readout pressure points of sensor 1 independent of the gas type get different calibration parameters, in this case K1 and K2, see Figure 12.a). By a suitable method of calibration, as in the first-order correction factor of the dependent pressure in this pressure, it may now, as in the case of water vapor, correct those features that have a different slope than other gases in the logarithmic representation plot, so that again the correct measurement signal is output in the low pressure range 5 where the pressure can only be read out by Pirani. The effect of adjustment 95 of the signal of the second pressure sensor is illustrated with a thick arrow. For example, in a method step, the curve of the adjusted display signal 98 in water vapor is read at an effective pressure 96 and results in a display signal 98 as shown with a dashed line. The pressures p1 and p2 of characters with adjustment points differ by slightly less than decimals. Specifically displayed here is that p1 is approximately 0.5 mbar, and p2 is approximately 0.07 mbar.

[0084] Thus, in short, the invention and the foregoing embodiments of the invention may achieve the following effects: a) improve the accuracy of pressure measurements over the entire range of pressure measurements, b) minimize gas type dependence even in the measurement range of a pressure sensor having a pressure measurement principle dependent on the gas type, and d) provide the ability to determine gas composition beyond the pressure measurement within a certain limit value; e) alerting the user to changes in the gas composition, or at least changes in pressure measurements dependent on the type of gas, in order to alert the user to unplanned system changes, and f) to facilitate zeroing of the pressure sensor as an auxiliary function. [Brief explanation of the diagram]

[0067] The exemplary embodiments of the present invention will be explained in further detail below with reference to the figures, in which: Figure 1 shows a flowchart of the method according to the present invention; Figure 2 shows a flowchart of an embodiment of the method; Figure 3 shows a flowchart of an embodiment of the method; Figure 4 shows a flowchart of another embodiment of the method; Figure 5 shows a flowchart of an embodiment of the method, which includes zeroing a first pressure sensor; Figure 6 schematically shows the possible relative positions of the first and second pressure measurement ranges; Figure 7 schematically shows the apparatus for performing the method; Figure 8 schematically shows the order in which pressures are recorded in a variation of the method in chronological order; Figure 9 shows the dependence of pressure determined by the Pirani sensor on gas type in a double logarithmic graph; Figures 10 to 12 show two ways in which the pressure measurement signal of a second gas type dependent pressure sensor can be adjusted by more than one calibration factor by the method according to the present invention, so that the pressure measurement is also corrected in the range measured only by the second gas type dependent pressure sensor, and this gas type dependence is eliminated.

Claims

1. A method (140) 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 configured to measure pressure in a common measurement volume (2), wherein the first and second pressure measurement ranges (4') and (4") overlap in an overlapping pressure measurement range (6), and wherein the method comprises the step of: aa) substantially simultaneously reading (101) a first measurement signal from the first pressure sensor and a second measurement signal from the second pressure sensor. The pressure in the common measurement volume is within the overlapping pressure measurement range; bb) the read first measurement signal is defined (102) as an adjustment point for the second pressure sensor; cc) a gas-dependent calibration parameter (K1) is determined (103) for the second pressure sensor as a function of the first measurement signal, as a function of the adjustment point defined in step bb), and as a function of the second measurement signal; dd) additionally, substantially simultaneously (104) another first measurement signal of the first pressure sensor and another second measurement signal of the second pressure sensor are read (104) the pressure in the common measurement volume is within the overlapping pressure measurement range, and wherein The pressure in the common measurement volume is different from the pressure in step aa); ee) defines the additionally read first measurement signal (105) as an additional adjustment point for the second pressure sensor; ff) determines (106) additional gas-dependent calibration parameters (K2) for the second pressure sensor, as a function of the first measurement signal, as a function of the additional adjustment point defined in step ee), and as a function of the additional second measurement signal, wherein the current pressure measurement value in the measurement volume is determined as a function of the current second measurement signal and / or the previously determined calibration parameters (K1, K2), wherein the additional calibration parameters determined in step ff) are the first The slope of the second measurement signal as a function of the first measurement signal in a double logarithmic function graph, or the slope of the second measurement signal as a function of the first measurement signal in a double logarithmic function graph, is calculated by the calibration parameters determined in step cc) and step ff), and the method further includes the following steps: hh) determining (108) the deviation of this slope from the slope expected for the reference gas; ii) comparing the deviation determined in step hh) with a predetermined tolerance threshold for the deviation (109); jj) if the tolerance threshold is exceeded, triggering (110) an alarm for the presence of water vapor in the common measurement volume (2).

2. The method (140) of claim 1, wherein the adjustment point for the second pressure sensor is in the pressure range of 10-2 mbar to 100 mbar.

3. The method (120) of request item 1 or 2, wherein in step (dd), the pressure in the commonly measured volume is more than 2 times or 10 times different from the pressure in step aa).

4. The method (140) of claim 1, wherein the method further comprises the following steps: gg) determining (107) whether the gas composition present in the common measurement volume (2) deviates from the expected specification, wherein the deviation of the current pressure measurement value from the pressure measurement value derived from the first measurement signal is taken into consideration, wherein the reading of the first measurement signal is substantially simultaneous with the reading of the current second measurement signal, and the pressure in the common measurement volume is within the overlapping pressure measurement range (6).

5. The method (140) of request item 1, wherein the reference gas is nitrogen.

6. The method (140) of claim 1, wherein the first pressure sensor (1') is a pressure sensor of a type independent of the gas composition in the measuring volume, and wherein the second pressure sensor (1") is a pressure sensor of a type dependent on the gas composition in the measuring volume, wherein the second pressure sensor (1") is - a thermally conductive vacuum gauge, or - a cold cathode ionization vacuum gauge or a non-inverted magnetron or an inverted magnetron, or - an ionization vacuum gauge with a hot cathode, or - a spintronic sensor.

7. The method (140) of claim 1, wherein the first pressure sensor (1') is a diaphragm gauge.

8. The method (140) of claim 1, wherein the second pressure sensor (1") is a thermal conductivity vacuum gauge.

9. The method (140) of request item 1, wherein steps aa), bb) and cc) are repeated at regular time intervals.

10. The method (140) of claim 1 for operating a vacuum processing system comprising a group (1) of pressure sensors, wherein steps aa), bb) and cc) are repeated once in each process cycle of the vacuum processing system.

11. The method (150) of claim 1, wherein the second pressure measurement range includes a low pressure range (5) with pressure below the lower limit of the first pressure measurement range, wherein the method includes the following steps: kk) checking (111) whether the low pressure range has been reached based on a second measurement signal (3") from the second pressure sensor; ll) reading (112) the first measurement signal (3') of the first pressure sensor when the pressure in the common measurement volume is in the low pressure range; and mm) setting (113) the read first measurement signal as a zero signal for the first pressure sensor.

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

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

14. The method (150) of claim 11, wherein the low pressure range (5) includes a range of 10⁻³ mbar to 10⁻⁴ mbar.

15. The method of claim 1, wherein the group of pressure sensors comprises at least three pressure sensors, and wherein the step of claim 1 is applied to a first pair of pressure sensors from the group of pressure sensors, and wherein the step of claim 1 is applied to a second pair of pressure sensors from the group of pressure sensors, wherein one of the first pair of pressure sensors is also a pressure sensor of the second pair.

16. An apparatus (10) for performing the method of any one of claims 1 to 15, 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 configured to measure pressure in a common measurement volume (2), and wherein the first and second pressure measurement ranges (4') and (4") overlap 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 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 perform the method of any one of claims 1 to 15.

17. The apparatus (10) of claim 16, wherein the first pressure sensor (1') is a diaphragm pressure gauge, wherein the overlapping pressure measurement range (6) of the first and second pressure measurement ranges (4') and (4") contains a pressure of 0.1 mbar, and wherein the group (1) of pressure sensors includes a third pressure sensor having a third pressure measurement range, wherein the third pressure measurement range extends the first pressure measurement range to a greater pressure.

18. The apparatus (10) of any one of claims 16 or 17 further 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 the pressure control unit (12) for initiating a decrease or increase in the pressure in the common measuring volume.

19. A computer program product comprising commands that, when executed by a control unit (12) of a device (10) as described in any of claims 16 to 18, cause the control unit to perform the steps of the method (140, 150) as described in any of claims 1 to 15.

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