Patent Application
20230375424
The present invention relates to a sensor device and a production method for a sensor device. The present invention also relates to a method for detecting the internal pressure and/or a change in the internal pressure in a gas-tight internal volume of a housing component and a pressure measurement method.
The prior art pressure sensor shown schematically in
The housing component 12 of the conventional pressure sensor shown schematically in
The present invention provides a sensor device, a method for producing a sensor device, a method for detecting the internal pressure and/or a change in the internal pressure in a gas-tight internal volume of a housing component, and a pressure measurement method.
The present invention provides advantageous options for detecting and/or determining the internal pressure and/or a change in the internal pressure in a gas-tight internal volume of a housing component. Detecting/determining the internal pressure or the change in the internal pressure is often necessary, because it is temperature-dependent and therefore a temperature-dependent counterforce can be applied, e.g., to a membrane inner side, based on the respective internal pressure. The temperature-dependent counterforce can affect a deflection of the membrane and can distort the measurement of an external pressure at the membrane outer side or a change in the external pressure. The greater the internal pressure in the internal volume sealed off by the membrane, the greater the temperature-dependent effect on the internal pressure on the measurement result. Outgassing of a gas from the housing component, for example hydrogen, or aging effects on the gas-tight seals of the housing component often have a significant effect on the internal pressure in the gas-tight internal volume and thus on the measurement accuracy. Due to the progressive miniaturization of devices and micromechanical components, the dimensions of housing components are decreasing more and more, which is why the respective gas-tight internal volume configured therein is becoming smaller and smaller and outgassing effects and aging effects can lead to significantly larger deviations in the internal pressure in the internal volume. The present invention, however, makes it possible to reliably ascertain the internal pressure in the respective internal volume and/or its change and use it to correct the measured external pressure.
In one advantageous embodiment of the sensor device of the present invention, the housing component comprises a deformable membrane with a membrane inner side which adjoins the internal volume and the sensor device comprises a measuring electrode which is suspended on the membrane inner side and at least one measuring counter electrode which is fixedly disposed on and/or in the housing component, wherein the electronic device is additionally designed and/or programmed to detect or determine the external pressure at a membrane outer side of the membrane facing away from the membrane inner side and/or a change in the external pressure while taking into account at least one measurement signal, which is dependent on an electrical voltage or capacitance between the suspended measuring electrode and the single measuring counter electrode or at least one of the measuring counter electrodes, and the determined internal pressure and/or the determined change in the internal pressure. The here-described embodiment of the sensor device can thus advantageously be used as a pressure sensor for measuring an external pressure/ambient pressure or a change to said pressure. The here-described embodiment of the sensor device makes it possible to determine/measure the external pressure more accurately and with less errors in the long term based on the accurate and reliable knowledge of the internal pressure and/or the change in the internal pressure relative to the time at which an electronic adjustment of the pressure sensor took place.
According to an example embodiment of the present invention, as the at least one counter electrode, the sensor device preferably comprises a respective first counter electrode disposed on a side of the at least one adjustable and/or bendable electrode structure facing away from the membrane adjacent to the at least one electrode structure and a respective second counter electrode disposed on a side of the at least one electrode structure facing the membrane adjacent to the at least one electrode structure, and wherein the electronic device is designed and/or programmed to form a difference signal from a first sensor signal, which is dependent on a first electrical voltage or capacitance between the at least one electrode structure and the first counter electrode, and a second sensor signal, which is dependent on a second electrical voltage or capacitance between the at least one electrode structure and the second counter electrode. An evaluation of the difference signal obtained in this manner enables a more accurate and reliable determination of the internal pressure in the internal volume and/or the change in the internal pressure.
According to an example embodiment of the present invention, as the at least one measuring counter electrode, the sensor device can alternatively or additionally comprise a first measuring counter electrode disposed on a side of the suspended measuring electrode facing away from the membrane adjacent to the suspended measuring electrode and a second measuring counter electrode disposed on a side of the suspended measuring electrode facing the membrane adjacent to the suspended measuring electrode, wherein the electronic device is designed and/or programmed to form a difference measurement signal from a first measurement signal, which is dependent on an electrical voltage or capacitance between the suspended measuring electrode and the first measuring counter electrode, and a second measurement signal, which is dependent on an electrical voltage or capacitance between the suspended measuring electrode and the second measuring counter electrode. Forming the difference measurement signal in the above-described manner likewise makes it possible to improve the measurement sensitivity and/or measurement accuracy when determining the external pressure. The measurement sensitivity and/or the measurement accuracy of the measured external pressure can be improved by using the measured internal pressure and/or the measured change in the internal pressure and also the currently prevailing ambient temperature to adjust/correct the ascertained external pressure.
According to an example embodiment of the present invention, the housing component preferably comprises a substrate, wherein the at least one first counter electrode and the first measuring counter electrode are structured out of a first semiconductor and/or metal layer deposited on a substrate surface of the substrate and/or at least one intermediate layer which at least partially covers the substrate surface, the at least one adjustable and/or bendable electrode structure and the suspended measuring electrode are structured out of a second semiconductor and/or metal layer deposited on the first semiconductor and/or metal layer and/or at least one first sacrificial layer which at least partially covers the first semiconductor and/or metal layer, the at least one second counter electrode and the second measuring counter electrode are structured out of a third semiconductor and/or metal layer deposited on the second semiconductor and/or metal layer and/or at least one second sacrificial layer which at least partially covers the second semiconductor and/or metal layer and the membrane is formed from a fourth semiconductor and/or metal layer deposited on the third semiconductor and/or metal layer and/or at least one third sacrificial layer which at least partially covers the third semiconductor and/or metal layer. The here-described embodiment of the sensor device is cost-efficient and can be produced by carrying out easily-implementable method steps while at the same time maintaining an advantageous level of accuracy.
In a further advantageous embodiment of the sensor device of the present invention, in an acceleration and/or rotation rate measurement mode, the electronic device is designed and/or programmed to determine at least one sensor variable relating to the acceleration and/or the rotation rate of the sensor device during an acceleration and/or rotation of the sensor device taking into account the at least one sensor signal. The here-described embodiment of the sensor device can thus also be used as an acceleration sensor and/or as a rotation rate sensor, wherein the multifunctionality of its at least one electrode structure makes it easy to miniaturize the sensor device, despite its versatility.
The above-described advantages can also be realized by carrying out a corresponding production method for a sensor device. Carrying out a corresponding method for measuring an internal pressure in a gas-tight internal volume of a housing component likewise provides the above-described advantages. The above-described advantages are furthermore also ensured when a corresponding pressure measurement method is carried out. It is expressly noted that the methods listed here can be further developed in accordance with the embodiments of the sensor device discussed above.
Further features and advantages of the present invention are explained in the following with reference to the figures.
The sensor device shown schematically in
By evaluating a measuring capacitance km of at least one measuring capacitor formed by the measuring electrode 56 and the at least one measuring counter electrode 58, the external pressure pa can thus be detected and/or determined/measured relative to or with reference to the enclosed internal pressure pi in the internal volume 52. A change in the external pressure pa relative to a predetermined external pressure value can correspondingly be detected and/or determined/measured by means of the evaluation of the measuring capacitance km as well. A detected or determined change in the internal pressure pi relative to a predetermined internal pressure value can also be used to detect and/or determine/measure the external pressure pa and/or the change in the external pressure pa.
To accurately and reliably detect and/or determine/measure the internal pressure pi in the gas-tight internal volume 52 and/or the change in the internal pressure pi (relative to the predetermined internal pressure value), the sensor device also comprises at least one electrode structure 60 which is disposed in the internal volume 52 in an adjustable and/or bendable manner. The sensor device moreover also comprises at least one counter electrode 62 which is fixedly disposed on and/or in the housing component 50. This is intended to be understood to mean that the at least one counter electrode 62 is not/barely adjustable or bendable (without damaging the sensor device). The sensor device additionally comprises an electronic device 64 which is designed and/or programmed to apply at least one electrical excitation voltage signal Ua between the at least one adjustable or bendable electrode structure 60 and the single counter electrode or at least one of the counter electrodes 62 such that the at least one electrode structure 60 is set in an oscillating motion (shown with the dashed lines 66) relative to the housing component 50. The oscillating motion of the at least one electrode structure 60 can be understood to be both a bending oscillating motion and an adjusting oscillating motion. The electronic device 64 is furthermore also designed and/or programmed to detect and/or determine the internal pressure pi in the internal volume 52 and/or the change thereof while taking into account at least one sensor signal S which is dependent on an electrical voltage or capacitance between the at least one electrode structure 60 and the single counter electrode or at least one of the counter electrodes 62. The at least one sensor signal S can be a sensor capacitance of a sensor capacitor formed from the at least one electrode structure 60 and the at least one counter electrodes 62, for example.
The here-described sensor device thus utilizes the at least one electrode structure 60 as an oscillatable structure within the internal volume 52 for detecting the internal pressure pi and/or the change in the internal pressure pi (relative to the predetermined internal pressure value) in the internal volume 52. Since an oscillatable structure often already exists or is structurally easy to implement in the internal volume 52, the advantageous additional function of the sensor device described in the preceding paragraph can easily be implemented with a minor structural modification and/or by programming the electronic device 64. The electronic device 64 can advantageously utilize the knowledge of the internal pressure pi and/or the change in the internal pressure pi to reliably detect and/or more accurately determine the external pressure pa and/or the change in the external pressure pa. For this purpose, the electronic device 64 in the example of
To detect/determine the internal pressure pi and/or the change in the internal pressure pi in the internal volume 52, at least one parameter x representing the oscillating motion of the at least one electrode structure 60, for example, can be established first while taking into account the at least one sensor signal S. The at least one parameter x can, for example, be a quality of the oscillating motion, a resonance frequency of the oscillating motion, a damping of the oscillating motion, a signal rise time of the at least one sensor signal S and/or a signal fall time of the at least one sensor signal S. The internal pressure pi in the internal volume 52 and/or the change thereof can then be determined/measured taking into account the at least one parameter x.
As can also be seen from the coordinate system of
By measuring the internal pressure pi in the internal volume 52, the sensor device can promptly detect a non-reversible change in the internal pressure pi in the internal volume 52 relative to the time of the first adjustment of the sensor device. This monitoring of the internal pressure pi in the internal volume 52 makes it possible to correct a measured value determined as the external pressure pa if a deviation of the internal pressure pi from a predefined “normal value” is observed. If the sensor device also comprises a temperature sensor or a device for measuring temperature, a deviation of the internal pressure pi from the predetermined “normal value” can be precisely determined. The “normal value” can be understood here as a value in a parameter field ascertained during an adjustment of the sensor device, e.g. a pressure sensor.
It is thus possible to determine whether the deviation of the internal pressure pi correlates to a change in the external pressure pa, for example, or whether, because of outgassing and/or aging effects, an adjustment of the measured value describing the external pressure pa should be considered. Another significant advantage of the here-described sensor device is that, since the internal pressure pi and/or the change in the internal pressure pi in the internal volume 52 can be determined repeatedly even over a long service life of the sensor device and used to adjust/correct the ascertained value for the external pressure pa, precise measurements of the external pressure pa by means of the sensor device are possible in the long term as well.
Since the internal pressure pi does not have to be measured continuously, the at least one electrode structure 60 can also be used for other purposes. For example, shocks to the sensor device/its housing component 50 can be detected/identified by means of the at least one electrode structure 60 and its at least one counter electrode 62. The electronic device 64 can alternatively or additionally also be designed and/or programmed to determine at least one sensor variable relating to the acceleration and/or the rotation rate of the sensor device during an acceleration and/or rotation of the sensor device taking into account the at least one sensor signal, or to measure at least one corresponding measured value. This, too, can be accomplished by evaluating the at least one sensor signal S. Appropriate design of the at least one electrode structure 60 and its at least one counter electrode 62 makes it possible to ensure that shocks to the sensor device, linear accelerations of the sensor device and/or rotational accelerations of the sensor device cause the at least one electrode structure 60 to carry out movements which can extend or are oriented perpendicular to the membrane inner side 54a and/or the membrane outer side 54b and/or parallel to the membrane inner side 54a and/or the membrane outer side 54b and are detected using the at least one counter electrode 62.
To minimize the risk of a measurement error resulting from shocks to the sensor device, linear accelerations of the sensor device or rotational accelerations of the sensor device when determining/measuring the internal pressure pi and/or the change in the internal pressure pi, the determination/measurement of the internal pressure pi and/or the change in the internal pressure pi is preferably carried out at a point in time at which the at least one electrode structure 60 is in a state in which it is not excited from the outside.
As an optional further development, the sensor device of
The sensor device shown schematically in
The further semiconductor and/or metal layer 84 is moreover covered at least partially (directly) with at least one insulating layer 88, such as a silicon dioxide layer, which is used to close the internal volume 52 in a gas-tight manner and to enclose the defined internal pressure pi in the internal volume 52 and on which a metallization 90 is deposited to form a contact region 92. The metallization 90 can in particular be aluminum copper. The metallization 90 can additionally be covered with a passivation 94, such as in particular silicon nitride.
As can also be seen from a comparison of
Of the sensor device of
With regard to further properties and features of the sensor device of
As a further development with respect to the sensor device of
With regard to further properties and features of the sensor device of
The only difference of the sensor device of
With regard to further properties and features of the sensor device of
As can be seen when comparing
With regard to further properties and features of the sensor device of
As the at least one counter electrode 62a and 62b, the sensor device of
As the at least one measuring counter electrode 58a and 58b, the sensor device of
In the sensor device of
The above-described differential capacitances/differential capacitance structures also eliminate the need for a conventionally often necessary “large area” arrangement of reference capacitor structures that can, for instance, be used for an external pressure measurement using a Wheatstone bridge circuit. The insertion of the third semiconductor and/or metal layer 98 and the configuration of differential capacitances thus facilitate miniaturization of the sensor device of
In the differential measuring capacitor structure shown in
It is also advantageous to reduce a distance between the third semiconductor and/or metal layer 98 and the second semiconductor and/or metal layer 82 in the region of the later second measuring counter electrode 58b in order to ensure equally large capacitance values for the capacitance cmess1 between the suspended measuring electrode 56 and the first measuring counter electrode 58a and the capacitance cmess2 between the suspended measuring electrode 56 and the second measuring counter electrode 58b at the time of the electrical adjustment of the sensor device. Since the internal pressure pi in the internal volume 52 is generally significantly lower than the external pressure pa, the pressure difference between the external pressure pa and the internal pressure pr leads to a deformation of the membrane 54 and an increase of cmess1 relative to cmess2 To ensure that there is no offset in the measurement of the electrical bridge voltage at the time of the adjustment of the sensor device with an existing external pressure pa and a corresponding deformation of the membrane 54 (the bridge voltage is equal to zero), the distance between the suspended measuring electrode 56 and the first measuring counter electrode 58a can be adjusted accordingly by at least locally adjusting the layer thickness of the second sacrificial layer 96 as described above.
With regard to further properties and features of the sensor device of
The sensor device of
With regard to further properties and features of the sensor device of
In the sensor device of
With regard to further properties and features of the sensor device of
In a method step St1, at least one electrode structure of the later sensor device is formed, which is disposed in an adjustable and/or bendable manner in an internal volume of a housing component of the later sensor device. Also in method step St1, at least one counter electrode of the later sensor device is formed, which is fixedly disposed on and/or in the housing component. In a further method step St2, the internal volume is closed off in a gas-tight manner.
In a method step St3, the sensor device is electrically connected to an electronic device of the later sensor device, which is designed and/or programmed to apply at least one electrical excitation voltage signal between the at least one adjustable or bendable electrode structure and the single counter electrode or at least one of the counter electrodes such that the at least one electrode structure is set in an oscillating motion relative to the housing component. The electronic device is also designed and/or programmed to detect and/or determine the internal pressure in the internal volume and/or a change in the internal pressure while taking into account at least one sensor signal which is dependent on an electrical voltage or capacitance between the at least one electrode structure and the single counter electrode or at least one of the counter electrodes. The advantages of the sensor device produced by means of at least the method steps St1 to St3 have already been discussed above.
Preferably, in method step St1, a deformable membrane with a membrane inner side which adjoins the internal volume is formed as part of the housing component, wherein (at least) one measuring electrode which is suspended on the membrane inner side and at least one measuring counter electrode which is fixedly disposed on and/or in the housing component are formed as well. In this case, the electronic device can also be designed and/or programmed in method step St3 to detect and/or determine the external pressure at a membrane outer side of the membrane facing away from the membrane inner side and/or a change in the external pressure while taking into account at least one measurement signal, which is dependent on an electrical voltage or capacitance between the suspended measuring electrode and the single measuring counter electrode or at least one of the measuring counter electrodes, and the internal pressure and/or the change in the internal pressure.
As already discussed above, a first semiconductor and/or metal layer can be deposited onto a substrate surface of a substrate as part of the housing component and/or at least one intermediate layer which at least partially covers the substrate surface, and at least one first counter electrode and a first measuring counter electrode can be structured out of the first semiconductor and/or metal layer. Likewise, a second semiconductor and/or metal layer can be deposited on the first semiconductor and/or metal layer and/or at least one first sacrificial layer which at least partially covers the first semiconductor and/or metal layer, so that the at least one electrode structure and the suspended measuring electrode can be structured out of the second semiconductor and/or metal layer. A third semiconductor and/or metal layer can furthermore be deposited on the second semiconductor and/or metal layer and/or at least one second sacrificial layer which at least partially covers the second semiconductor and/or metal layer and at least one second counter electrode and a second measuring counter electrode can be structured out of the third semiconductor and/or metal layer. If desired, a fourth semiconductor and/or metal layer can be deposited on the third semiconductor and/or metal layer and/or at least one third sacrificial layer which at least partially covers the third semiconductor and/or metal layer and the membrane can be formed from the fourth semiconductor and/or metal layer.
The method steps St1 to St3 can be carried out in any order, overlapping in time or simultaneously.
When carrying out the here-described method, as method step St10, at least one electrical excitation voltage signal is applied between at least one electrode structure which is disposed in the internal volume in an adjustable and/or bendable manner and at least one counter electrode which is fixedly disposed on and/or in the housing component, such that the at least one electrode structure is set in an oscillating motion relative to the housing component.
Subsequently, as method step St11, the internal pressure in the internal volume and/or a change in the internal pressure are detected and/or determined while taking into account at least one sensor signal which is dependent on an electrical voltage or capacitance between the at least one adjustable or bendable electrode structure and the single counter electrode or at least one of the counter electrodes. As already explained above, the internal pressure in the internal volume can be reliably determined using method steps St10 and St11.
Method steps St10 and St11 can in particular be used to measure the internal pressure and/or a change in the internal pressure in a gas-tight internal volume of a housing component comprising a deformable membrane, the membrane inner side of which adjoins the internal volume with a measuring electrode which is suspended on the membrane inner side. As an optional method step St12, the external pressure at a membrane outer side of the membrane facing away from the membrane inner side and/or a change in the external pressure can be detected and/or determined/measured while taking into account at least one measurement signal, which is dependent on an electrical voltage or capacitance between the suspended measuring electrode and at least one measuring counter electrode which is fixedly disposed on and/or in the housing component, and the internal pressure and/or the change in the internal pressure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102020214757.4 | Nov 2020 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2021/081693 | 11/15/2021 | WO |
