WO2009083328A1 - Capteur de pression et son procédé d'étalonnage - Google Patents

Capteur de pression et son procédé d'étalonnage Download PDF

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Publication number
WO2009083328A1
WO2009083328A1 PCT/EP2008/065358 EP2008065358W WO2009083328A1 WO 2009083328 A1 WO2009083328 A1 WO 2009083328A1 EP 2008065358 W EP2008065358 W EP 2008065358W WO 2009083328 A1 WO2009083328 A1 WO 2009083328A1
Authority
WO
WIPO (PCT)
Prior art keywords
membrane
pressure sensor
deflection
electrostatic force
voltage
Prior art date
Application number
PCT/EP2008/065358
Other languages
German (de)
English (en)
Inventor
Ulrike Scholz
Marko Rocznik
Janpeter Wolff
Remigius Niekrawietz
Original Assignee
Robert Bosch Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Robert Bosch Gmbh filed Critical Robert Bosch Gmbh
Publication of WO2009083328A1 publication Critical patent/WO2009083328A1/fr

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L27/00—Testing or calibrating of apparatus for measuring fluid pressure
    • G01L27/002—Calibrating, i.e. establishing true relation between transducer output value and value to be measured, zeroing, linearising or span error determination

Definitions

  • the invention relates to a method for calibrating a pressure sensor and a pressure sensor, comprising a movable membrane, which extends over a cavity, at least one pair of electrodes, which can be acted upon by an electrical voltage, wherein the electrical voltage leads to a deflection of the membrane and means for Determination of the deflection of the membrane.
  • Such pressure sensors can be used to control various functions in motor vehicles, e.g. for engine control.
  • pressure ⁇ sensors of the type mentioned in pressure chambers to suspend different pressures and the distance between the Membrane and the underlying carrier substrate to measure. From these measurement signals Kalib ⁇ erkoefflzienten can be obtained, which can be stored in a memory integrated in the pressure sensor. During operation of the pressure sensor, the output signal is supplied with these stored calibration coefficients. As a result, a pressure value can be assigned directly to a measured capacitance value. To further improve the accuracy of measurement, it is known to record the pressure sensor map at different temperatures and to additionally carry out a temperature compensation of the output signal during operation of the pressure sensor.
  • the invention has for its object to provide a method for calibrating pressure sensors at your disposal, which manages without on ⁇ walligen use of a pressure chamber. Furthermore, the invention has for its object to provide a calibration method and a calibratable pressure sensor, which allows a self-calibration during the application of the pressure sensor and thus solves the problem of long-term drift.
  • the object is achieved according to the invention by a method for calibrating a pressure sensor, which has a movable membrane over a cavity, wherein for calibration, the membrane is deflected by an electrostatic force and this deflection is measured.
  • a pressure sensor comprising a movable membrane, which over a cavity extends, at least one electrode pair, which is acted upon by an electrical voltage, wherein the electrical voltage leads to a deflection of the membrane, means for determining the deflection of the membrane and a plurality of switching elements to each individual electrode of the electrode pair with a first electrical potential or to connect to a second electrical potential.
  • Pressure sensor comprising a movable membrane which extends over a cavity, at least one pair of electrodes, which is acted upon by an electrical voltage, wherein the electrical voltage leads to a deflection of the membrane, a charge amplifier for capacitive
  • the pressure sensor in the sense of the present invention has a membrane as a movable sensor element, which can be produced, for example, micromechanically or by precision engineering and is deflected by the action of an external gas or liquid pressure.
  • the movable sensor element has a restoring force, which brings the sensor element in the absence of an external force in the rest position. The deflection can be measured either capacitively or piezoresistively.
  • Erfmdungsgehold has been recognized that for the calibration of such a pressure sensor does not necessarily have to act caused by a pressure difference force on the membrane of the pressure sensor.
  • erfmdungsgebin proposed that the calibration can also be done by an electrostatic force, which is identical in magnitude and direction with the force generated by pressurization.
  • electrostatic force By varying the electrostatically generated force can be as well as in a pressure chamber determine the output signal of a pressure sensor in response to different measures. From this determined response function Kalib ⁇ er- koefflzienten can be obtained and stored, for example, in a memory integrated in the pressure sensor or in a connected to the pressure sensor control unit.
  • this is erfmdungsgeclar equipped with at least one electrode which is connectable to an AC voltage source.
  • the second terminal of the AC voltage source is connected to a counter electrode below the membrane.
  • the erfmdungsgebine method is based on the fact that the membrane with the underlying cavity and the counter electrode is a plate capacitor.
  • the capacitance of this capacitor is determined by the area of the membrane and the underlying counter electrode and their spacing.
  • the electrostatic force upon application of a voltage depends on the magnitude of the electrical voltage and the distance between the membrane and the underlying counter electrode. Since this distance can be greater than 10% in the manufacture of a variety of sensors, it must be determined by measurement before calibration. After the distance is determined, a defined force can be exerted on the membrane by applying a defined voltage. This then serves to determine the mechanical properties of the membrane, such as thickness and mechanical stress, which significantly influence the output signal of the pressure sensor.
  • the height of the cavity ie the distance between the membrane and the underlying counter electrode, determined by measuring the Grundkapazitat without a force acting on the membrane.
  • a membrane is referred to as being free from external forces when no electrostatic force acts on the membrane and preferably also no pressure difference occurs between the two sides of the membrane.
  • both sides can be connected to an identical reference pressure, for example the ambient pressure.
  • the influence of the normal ambient pressure may be so low that under normal environmental conditions the membrane can be considered as free of force for the purposes of the invention.
  • the intended determination of the height of the cavity is based on the fact that the capacitance of the sensor is determined by the area of the membrane and the underlying counterelectrode and their spacing. Since the surface of the membrane in the production of the pressure sensor with high accuracy is reproducible, a measurement of this area can remain ⁇ . For example, the fluctuating edge loss in the production of the membrane is only about 1/10 ⁇ m. With a diameter of the membrane of 1 mm ⁇ 2/10 microns, this results in an accuracy of the membrane surface of about 0.02%. Thus, a fluctuating basic capacity can be attributed mainly to the influence of a fluctuating height of Kavitat and the height of the Kavitat can be determined from the measured capacity with high accuracy.
  • the measurement of the deformation of the membrane takes place either capacitively over the height of the membrane or by piezoresistive elements which are shear-stiffly connected to the membrane and undergo a deformation upon deformation of the membrane, which leads to a change in resistance.
  • the electrostatic force is generated by an alternating voltage, in particular by an alternating voltage whose frequency is selected below the mechanical limit frequency of the membrane and above the bandwidth of the output signal of the pressure sensor.
  • the frequency is selected in a range of the mechanical transmission function, in which the drop is still negligible compared to the static deflection. Since the amount of voltage and thus the electrostatic force exerted on the membrane continuously changes with an alternating voltage, the entire measuring range is continuously passed through.
  • the electrostatic force for calibrating the sensor element is generated by an electrical alternating voltage with a constant frequency. Due to the constant frequency, a particularly simple separation of the calibration signal from the measurement signal can take place, for example by means of a narrow-band bandpass filter.
  • the electrostatic force can also be generated by a DC electrical voltage, which is modulated quasi-digitally by pulse width modulation or as a delta-sigma data stream.
  • a quasi-digital modulation is to be understood as meaning a signal which has a digital amplitude and an analog time behavior.
  • This signal together with the filtering transmission function of the sensor element, generates a force.
  • This in turn is digitally adjustable.
  • the sensor element is thus part of an electromechanical digital-to-analog converter.
  • the pressure sensor further comprises a device for detecting the output signal of the Divide pressure sensor into a dependent of the measured size part and a dependent on the electrostatic force part.
  • a splitting of the pressure sensor signal allows the continuous determination of a pressure while the sensitivity of the pressure sensor can be checked with the calibration method according to the invention.
  • the output signal of the pressure sensor is freed by a low-pass from those portions which are caused by the electrostatic force.
  • the output signal of the pressure sensor is released by a high pass from those portions which are caused by the pressure difference on both sides of the membrane. Both signal components can then be further processed in separate circuit parts.
  • Figure 1 shows a surface micromechanical pressure sensor according to the prior art.
  • FIG. 2 shows the surface micromechanical pressure sensor according to FIG. 1 with additional electrodes.
  • FIG. 3 shows a surface micromechanical pressure sensor with piezoresistive measuring devices for pressure measurement and the possibility of calibration according to the invention.
  • Figure 4 shows a surface micromechanical pressure sensor with piezoresistive measuring devices in the erfmdungsgewillen calibration on a chuck.
  • Figure 5 shows a block diagram of a system model for a self-test of a pressure sensor and FIG. 6 shows a possible realization of the self-test in analogue time-contingent circuit technology.
  • Figure 7 shows an exemplary embodiment of a erfmdungsgedorfen calibration device with quasi-digital generation of the test signal.
  • FIG. 1 shows a surface micromechham pressure sensor. This is constructed on a substrate 1. This is usually a silicon substrate. A membrane 2 with an underlying cavity is formed on the silicon substrate by a plurality of successive masking and etching steps. The membrane 2 has the thickness d and the diameter or the edge length D. It is either electrically conductive on its own or has a conductive coating on at least one surface. This conductive coating is connected via conductor tracks with a measuring electronics. Within the cavity and thus the membrane 2 opposite another electrode 3 is formed, for example by implantation or deposition of a conductive coating, for example of a metal or an alloy. Also, this electrode 3 is contacted by interconnects and connectable to an evaluation circuit. The evaluation circuit can also be designed monolithically integrated on the silicon substrate 1.
  • the membrane 2 or its conductive coating together with the electrode 3 forms a plate capacitor. Its capacity depends on the constant area of the membrane 2 and their distance from the counter electrode 3 from.
  • FIG. 2 shows the pressure sensor according to FIG. 1 with further components.
  • This pressure sensor further comprises additional electrodes 4.
  • an electrical voltage can be applied, which generates an electrostatic force between the membrane 2 and the counter electrode 3.
  • the applied electrical voltage is selected such that the same mechanical stress is induced in the membrane 2 as when a predefinable pressure is applied.
  • a capacitance can be determined via the capacitive distance measurement for a predefinable electrical voltage, which capacitance can be measured even when the corresponding pressure is present.
  • Capacitance value directly a mechanical tension of the diaphragm 2 and thus can be assigned to a prevailing pressure.
  • the coefficients of the calibration curve are finally stored in a memory, not shown in Figure 2 of the pressure sensor and are available for further operation at your disposal.
  • FIG. 3 shows a piezoresistive pressure sensor.
  • This also has a membrane 2, which extends over a Kavitat and upon application of a pressure difference between the cavity and the outer space enters a deformation of the membrane 2 a.
  • the membrane is at least one piezoresistive Element 5 shear stiff connected, so that the element 5 is also deformed upon deformation of the membrane. This deformation leads to a measurable change in the electrical resistance of the piezoelectric element 5.
  • a counter electrode 6 located in the cavity below the membrane 2 a counter electrode 6.
  • this counter electrode 6 is formed by a conductive doped wafer, which is bonded to the carrier substrate 1 by means of an intermediate oxide layer 7.
  • the oxide layer 7 serves for insulation if the membrane 12 strikes the electrode 6 at high deformation.
  • the voltage for generating the electrostatic force is applied between the electrode 6 and the likewise conductive membrane 2.
  • This electro ⁇ statically induced deformation acts in the same way as an applied during operation of the pressure sensor pressure.
  • the calibration can be performed without a pressure chamber.
  • the electrode 6 may also consist of another conductive material, for example a metal or an alloy.
  • the insulator 7 can also be formed by a polymer or a seal glass in a further embodiment. He may have a recess in the region of the cavity.
  • FIG. 4 shows a similar pressure sensor to FIG. 3 without the counterelectrode 6 used there.
  • the insulation 7 forms a gastight seal of the hollow space under the membrane 2.
  • the substrate 1 with the membrane 2 and the piezoresistive elements 5 can also be arranged in a differential pressure sensor can be used in which an unillustrated housing both sides of the membrane 2 are subjected to different pressures.
  • the counterelectrode necessary for the electrostatic calibration is formed by the chuck 8 of a wafer tester.
  • an electrostatic calibration according to the present invention or a functional test of the pressure sensors 5 immediately possible in the factory.
  • Figure 5 shows a block diagram of a erfmdungsgedorfen system model for self-test of a pressure sensor. From the result of the calibration procedure one obtains an adjustment curve, from which the coefficients for the sensor adjustment are obtained. After applying these coefficients in the Kalibriervor ⁇ chtung has the
  • an electrostatic force is applied to the membrane of the pressure sensor by means of an AC voltage source 9.
  • a measured variable for example an air pressure
  • the membrane is deflected by both forces, so that the measuring circuit of the sensor element detects a signal representing the sum of the electrostatic force and the force of the air pressure.
  • This sum is converted into a calibrated signal by means of a calibration device with the stored calibration coefficients.
  • This calibrated sum signal now also consists of the measured air pressure and the electrostatic force.
  • a high-pass filter is arranged in the second signal branch.
  • the cutoff frequency of this high pass filter is above the change frequency of the measurement signal below the
  • the response of the pressure sensor is compared to the electrostatic force with a desired value. Deviation from the target value indicates a defect in the pressure sensor. Such a defect can be, for example, soiling, icing or breakage of the membrane 2.
  • a detected error can either be issued to the user or trigger an automated recalibration.
  • FIG. 6 shows an embodiment of a circuit for calibration in analogue electronics.
  • a high-frequency carrier signal from an AC voltage source 9 is used. This carrier signal is transmitted via the capacitive pressure sensor to an evaluation circuit with an operational amplifier 10 fed.
  • the operational amplifier 10, R2 and C2 together form a capacitance-voltage converter (C / U converter).
  • the output voltage of the operational amplifier 10 after demodulation is a measure of the capacitance of the pressure sensor and thus the measured size.
  • This signal is fed to a drive and evaluation circuit 11.
  • Capacitor Cl thus forms a high-pass filter.
  • the voltage U ca i is varied over the desired voltage range and the capacitance value U c / u is detected.
  • the pressure is maintained at a constant reference value, for example the normal pressure.
  • the required calibration coefficients are determined in the drive circuit 11 and stored in a memory for later use.
  • a low-frequency test signal U ca i is fed in via the resistor Rl.
  • FIG. 7 shows an alternative embodiment in which the test signal is supplied by a digital circuit. This embodiment is particularly suitable for monolithic integration on the chip of the pressure sensor.
  • each side of a capacitive pressure sensor can optionally be connected to a reference potential, for example ground, or to an operating voltage V DD .
  • the output of the pressure sensor can via switch S5 to the input of an operational amplifier get connected.
  • the operational amplifier 10 in turn has a capacitance C2 in the negative feedback and forms a C / U converter for measuring the capacitance of the pressure sensor.
  • the output of the C / U converter is in turn connected to a drive circuit 11, which can occasionally control the switches Sl to S7.
  • the operating voltage V DD is applied as a delta-sigma data stream or via pulse width modulation via S3 and S4 to an electrode of the capacitive pressure sensor while S2 is closed and S1 is open.
  • the sensor element is connected to ground via S2 and S4 and thereby discharged.
  • the feedback capacitance C2 is discharged via S7 and S6.
  • Sl, S3 and S5 are open during this time. While the
  • Control voltage is applied to the pressure sensor to exert an electrostatic force on the sensor element, S5 remains open to preclude an action of the control voltage on the operational amplifier 10.

Abstract

La présente invention concerne un procédé d'étalonnage d'un capteur de pression présentant une membrane mobile au-dessus d'une cavité, la membrane étant déviée par une force électrostatique et cette déviation étant mesurée pour l'étalonnage. L'invention concerne également un capteur de pression présentant une membrane mobile s'étendant au-dessus d'une cavité, au moins une paire d'électrodes pouvant être sollicitée par une tension électrique, la tension électrique provoquant une déviation de la membrane, un moyen de détermination de la déviation de la membrane, ainsi qu'un dispositif de modulation de la tension électrique.
PCT/EP2008/065358 2007-12-27 2008-11-12 Capteur de pression et son procédé d'étalonnage WO2009083328A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102007062713A DE102007062713A1 (de) 2007-12-27 2007-12-27 Drucksensor und Verfahren zu dessen Kalibrierung
DE102007062713.2 2007-12-27

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WO2009083328A1 true WO2009083328A1 (fr) 2009-07-09

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Cited By (3)

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US9021887B2 (en) 2011-12-19 2015-05-05 Infineon Technologies Ag Micromechanical semiconductor sensing device
US9903779B2 (en) 2015-02-09 2018-02-27 Infineon Technologies Ag Sensor network supporting self-calibration of pressure sensors
CN108120552A (zh) * 2016-11-30 2018-06-05 德克萨斯仪器股份有限公司 用于校准微机电系统的方法和装置

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DE102010029903A1 (de) * 2010-06-10 2011-12-15 Robert Bosch Gmbh Sensoranordnung und Verfahren zur Online-Überwachung einer Sensoranordnung
DE102012200191A1 (de) 2012-01-09 2013-07-11 Ifm Electronic Gmbh Kapazitiver Drucksensor
US9210516B2 (en) 2012-04-23 2015-12-08 Infineon Technologies Ag Packaged MEMS device and method of calibrating a packaged MEMS device
DE102022200334A1 (de) 2022-01-13 2023-07-13 Robert Bosch Gesellschaft mit beschränkter Haftung Verfahren und Vorrichtung zum Kalibrieren einer MEMS-Vorrichtung, und MEMS-Vorrichtung
WO2023218260A1 (fr) * 2022-05-10 2023-11-16 Hossein Asli Ardebili Ali Capteur de pression différentielle basé sur l'impédance électrochimique de l'ouverture

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9021887B2 (en) 2011-12-19 2015-05-05 Infineon Technologies Ag Micromechanical semiconductor sensing device
US9567211B2 (en) 2011-12-19 2017-02-14 Infineon Technologies Ag Micromechanical semiconductor sensing device
US9790086B2 (en) 2011-12-19 2017-10-17 Infineon Technologies Ag Micromechanical semiconductor sensing device
US9903779B2 (en) 2015-02-09 2018-02-27 Infineon Technologies Ag Sensor network supporting self-calibration of pressure sensors
CN108120552A (zh) * 2016-11-30 2018-06-05 德克萨斯仪器股份有限公司 用于校准微机电系统的方法和装置

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