Method for producing at least one membrane arrangement, membrane arrangement and component for a micromechanical sensor

Abstract

The invention discloses a method for producing a diaphragm arrangement of at least one micromechanical sensor for calorimetric detection of gases, wherein: a wafer-shaped substrate is provided; at least one reference volume is introduced into the wafer-shaped substrate from the front side by a surface or volume micromechanical process while forming a reference diaphragm which at least partially covers the reference volume; at least one measuring volume adjacent to the at least one reference volume is introduced into the substrate from the back side or the front side of the wafer-shaped substrate while forming a measuring diaphragm; a wafer-shaped cover substrate is applied to the front side of the wafer-shaped substrate. In addition, a diaphragm arrangement and a component are disclosed.

Description

Technical Field

[0001] The invention relates to a method for producing at least one diaphragm arrangement for a micromechanical sensor for the calorimetric detection of a gas, as well as to a diaphragm arrangement and a component having such a diaphragm arrangement. Background Art

[0002] For the detection of hydrogen, sensors based on the calorimetric principle can be used. Such sensors usually consist of a membrane on which a heating element is arranged. Such a heating element can be operated with a constant current / voltage or with a constant power by the control electronics. This results in a temperature that is too high compared to the ambient temperature. The functional principle of such sensors is based on the thermal conductivity of hydrogen, which is higher at 1810 μW / cmK than the thermal conductivity of air, which is 260 μW / cmK.

[0003] If hydrogen is present in the environment of the heating element, the temperature of the heating element drops due to the higher thermal conductivity of hydrogen and the associated greater heat dissipation. The resistance of the heating element is reduced in this way. This change in resistance leads to additional heating power, which must be applied by the control electronics in order to keep the heating element at a constant temperature. The additional heating power is proportional to the concentration of hydrogen.

[0004] Since the thermal conductivity is dependent on the ambient temperature, the ambient temperature can be measured in an adjacent region of the membrane by means of a further temperature sensor, for example using a further platinum resistor.

[0005] The air humidity in the environment of the membrane is likewise important when considering the thermal conductivity of the air and must be taken into account by means of additional sensors or more complex evaluation of the measured data.

[0006] The large number of factors to be taken into account makes the design of the control electronics difficult, since large measuring ranges and a large number of variables have to be taken into account. However, in parallel therewith a high resolution and precision are required in the hydrogen detection.

[0007] In addition to using a Wheatstone bridge to filter out environmental effects, the operating voltage can also be varied in order to be able to differentiate between hydrogen and air moisture. This differentiation is necessary in particular when, for example, hydrogen should be detected in the exhaust gas of a fuel cell stack, but this is not necessary, for fuel cell vehicles. There, high air humidity is present. Summary of the invention

[0008] The object on which the invention is based can be seen as providing a production method and an improved membrane arrangement which reduce external influences on the concentration measurement.

[0009] This object is achieved according to the invention by means of the respective content of the independent claims. Advantageous embodiments and developments of the invention are the subject matter of the respective dependent claims and are evident from the description.

[0010] According to one aspect of the present invention, a method is provided for producing at least one membrane arrangement for a micromechanical sensor for the calorimetric detection of a gas.

[0011] In a method step of the solution according to the invention, a wafer-shaped substrate is provided. The wafer-shaped substrate can preferably be a doped or undoped semiconductor. Preferably, a thermally and electrically insulating coating composed of, for example, oxides, nitrides, nitrogen monoxide (Oxid-Nitrit) or nitrogen dioxide (Oxid-Nitrit-Oxid) or the like can be applied to the wafer-shaped substrate. The thermally and electrically insulating layer ideally forms an etching stop layer hereinafter. The material is advantageously selected in such a way that air moisture cannot accumulate in the layer or diffuse through the layer.

[0012] The wafer-shaped substrate preferably already includes an electrically conductive structure for forming a thermal element, for example composed of platinum, aluminum, molybdenum, tungsten, copper, gold, silver, doped silicon or the like, with or without an adhesion promoter layer (Haftvermittlerschichten), which is composed of aluminum, titanium, tantalum or its oxide or nitride and the like. This structure can be equipped, sprayed or evaporated, for example, and a combination of these steps is also possible. In addition, the wafer-shaped substrate has another electrical isolation portion, which is composed of oxide or nitride or the like by metallization. Another function of the isolation layer is to protect or separate from environmental influences, such as dust and moisture.

[0013] In the method according to the invention, at least one reference volume is introduced into the wafer-shaped substrate from its front side by means of a surface micromechanical or volumetric micromechanical process, forming a reference membrane which at least partially covers the reference volume.

[0014] This can be achieved, for example, by wet etching or sacrificial layer etching.

[0015] Alternatively or additionally to this method step, at least one reference volume can be introduced into the wafer-shaped substrate from the front side by a PorSi process with the formation of a reference membrane which at least partially covers the reference volume, with or without subsequent removal of the porous silicon by, for example, a dry etching step or cloud trenching.

[0016] Alternatively, only one process or a combination of individual processes may be used.

[0017] The reference volume can be used as a reference for the gas measurement, for example when using a Wheatstone measuring bridge in the metal layer.

[0018] The reference volume can be configured to be open or closed in the direction of the two surfaces of the wafer-shaped substrate, and in the open embodiment, an exchange with the gas and / or gas mixture in the environment can be achieved. In the closed variant, a certain gas and / or gas mixture can be enclosed in the reference volume.

[0019] In a further method step, at least one measuring volume adjacent to the at least one reference volume is introduced into the wafer-shaped substrate from the rear side or the front side of the wafer-shaped substrate, forming a measuring membrane.

[0020] The measurement volume can also be introduced into the wafer-shaped substrate by means of suitable surface micromechanical processes, just like the reference volume. In addition, volumetric micromechanical processes consisting of anisotropic and isotropic etching methods and / or a combination of anisotropic and isotropic etching methods can also be used. This can be carried out, for example, by sacrificial layer etching and / or wet etching.

[0021] Alternatively or additionally thereto, at least one reference volume can be introduced into the wafer-shaped substrate from the front side by forming a measuring membrane which at least partially covers the measuring volume and by means of a PorSi process, with or without subsequent removal of the porous silicon.

[0022] Another possible process control is a surface micromechanical process and / or a volume micromechanical process and a PorSi process acting from the front side of a wafer-shaped substrate in order to simultaneously generate a reference volume and a measurement volume. This method has the advantage of a shortened process control, and a volume micromechanical process acting from the back side can be considered for opening the measurement volume in a gas-conducting manner. In this embodiment, a wafer-shaped cover substrate (Kappensubstrat) can be omitted as a whole, which is further defined in more detail below. This is possible, for example, in a wet etching process and leads to a very advantageous production form of the wafer arrangement, since the material costs and production time of the sensor can be further reduced.

[0023] In the production of the reference volume or measuring volume or reference or measuring cavity, a diaphragm which delimits the volume can be formed at the same time. The embodiment as a diaphragm, for example a reference diaphragm and / or a measuring diaphragm has the advantage that an overtemperature relative to the environment can be controlled with minimal power consumption.

[0024] Due to the diaphragm arrangement and the electrical design as a Wheatstone bridge, the sensor signal can hardly be influenced by changing ambient conditions, such as temperature and air humidity, as well as aging of the chip and the accompanying drift of the sensor.

[0025] In a further method step, a wafer-shaped cover substrate is applied to the front side of the wafer-shaped substrate. The advantage of applying a wafer-shaped cover substrate to the front side of the wafer-shaped substrate is that the mechanical stability and mechanical load-bearing capacity are increased. The wafer-shaped cover substrate achieves fixed thermal boundary conditions, so that the adjustability and reproducibility of the system are increased. In a closed embodiment of the wafer-shaped cover substrate, a further cavity can be realized above the diaphragm, which cavity can be filled, for example, with a gas of different thermal conductivity. In particular, in the case of gases with poor thermal conductivity or vacuum, the sensitivity of the proposed measuring device is increased.

[0026] Based on the described method steps, a simplified production method for a micromechanical sensor, in particular for a double-diaphragm chip with an included reference volume for detecting gases, in particular hydrogen, can be achieved, in particular using the principles of thermal conductivity, convection or radiation in gases and / or gas mixtures.

[0027] In a further embodiment according to the invention, a channel structure can be provided in the wafer-shaped cover substrate for the targeted supply of measuring and reference gases.

[0028] The wafer can then be separated into a plurality of wafer segments, and the corresponding wafer segments can be used for the production of sensors.

[0029] According to one embodiment of the method, a wafer-shaped cover substrate is applied to the wafer-shaped substrate after the reference volume has been introduced. The measurement volume can thus be introduced into the wafer-shaped substrate similarly to the reference volume by surface micromechanical processes and volume micromechanical processes or PorSi processes acting from the front side of the wafer-shaped substrate. Subsequently, the wafer-shaped cover substrate can be arranged on the processed wafer-shaped substrate.

[0030] This particularly advantageous and simplified processability of the method according to the invention makes it possible, for example, to implement face-down processing for production and / or opening of the measuring volume for gas conduction by means of trench technology. Direct contact of the front side of the wafer with the fixture—hereinafter referred to as chuck, which is referred to as face-down processing—can lead to damage to the reference diaphragm and / or breakage of the diaphragm during processing due to unevenness and particles on the fixture.

[0031] According to a further embodiment of the invention, a wafer-shaped cover substrate is applied to the wafer-shaped substrate after the at least one measurement volume has been introduced.

[0032] This has the advantage that the seams and the wafer-shaped cover substrate are not damaged, for example, in wet etching methods.

[0033] According to another embodiment of the method, at least one measurement volume is introduced into the wafer-shaped substrate by dry etching. The advantage of the dry etching method is that previously designed sacrificial structures can be removed in a defined manner. Thus, undercuts can be produced, which can bring fluid dynamic advantages, for example, when introducing the gas to be measured.

[0034] Alternatively and / or additionally, at least one measuring volume is introduced into the wafer-shaped substrate by means of a trench process. The advantage of the manufacturing process using trenches is that any geometric structures can be introduced. Thus, small chips can be realized.

[0035] Alternatively and / or additionally, at least one measuring volume is introduced into the wafer-shaped substrate by a wet chemical etching method. In this case, the wafer-shaped substrate is not located on a chuck and this step can therefore already be carried out before the cover is applied. If further mechanical protection or increased stability of the wafer-shaped substrate is not necessary, the cover can be omitted.

[0036] Another advantage of wet-chemical etching methods is that the front side and the back side of a wafer-shaped substrate can be processed in a simultaneous working step, thus making it very cost-effective to process with a high degree of process uniformity.

[0037] Thus, at least one measurement volume can be introduced flexibly into the wafer-shaped substrate by removal of material via a plurality of different production methods.

[0038] According to another embodiment of the method, the wafer-shaped cover substrate is applied to the front side of the wafer-shaped substrate by gluing, soldering, wafer bonding or welding, wherein "wafer bonding" is understood to mean glass frit bonding, eutectic bonding or anodic bonding. Different bonding methods allow further process control, in particular with regard to the existing boundary layers of the wafer-shaped substrate and the wafer-shaped cover substrate. In addition, the different bonding methods have different medium resistances in conjunction with the achievable structural width.

[0039] Alternatively, the bonding step can also be carried out after soldering, joining or welding of the wafer-shaped cover substrate. This can be used for additional fixing of the wafer-shaped cover substrate or for encapsulation of the diaphragm arrangement.

[0040] The wafer-shaped cover substrate can thus be arranged flexibly on the wafer-shaped substrate by different methods.

[0041] According to another embodiment of the method according to the invention, when applying a wafer-shaped cover substrate to a wafer-shaped substrate, at least one reference volume is formed between at least one reference diaphragm and the wafer-shaped cover substrate and / or between at least one measuring diaphragm and the wafer-shaped cover substrate, which is open or closed in the direction of the front side of the wafer-shaped cover substrate. For this purpose, the wafer-shaped cover substrate can have grooves introduced in the region of at least one reference diaphragm and / or in the region of at least one measuring diaphragm in a preparation phase. These grooves can extend through the thickness of the wafer-shaped cover substrate and thus form gas channels through the wafer-shaped cover substrate.

[0042] Alternatively or additionally, the wafer-shaped cover substrate can form an additional volume above the membrane, which can be filled with a reference gas, for example.

[0043] According to another embodiment of the method according to the invention, at least one measuring volume introduced into the wafer-shaped substrate from the front side of the wafer-shaped substrate while forming a measuring diaphragm is opened from the back side of the wafer-shaped substrate in a gas-conducting manner. In this case, the measuring volume can be introduced into the wafer-shaped substrate open on the back side or it can be designed so that the gas is guided through an opening additionally introduced into the wafer-shaped substrate.

[0044] The advantage of introducing the reference volume from the front side and the measuring volume from the back side is that different gases can be supplied from the front side and the back side. For example, it is possible to supply air from the front side and hydrogen from the back side.

[0045] For example, the channels and openings can be introduced into the rear wall of the at least one measuring volume by means of a groove process. The openings are dimensioned in such a way that a gaseous medium can enter the at least one measuring volume. In this case, particles and aerosols cannot enter the at least one measuring volume through the connection due to their particle size.

[0046] Alternatively, the at least one measuring volume can be opened very cost-effectively by a wet-chemical process.

[0047] By means of the process-controlled manner in which the reference volume is produced from the front side of the wafer-shaped substrate according to the invention, sealing of the reference volume in the direction of the back side of the wafer-shaped substrate can be omitted, since a closed reference volume is produced which does not need to be additionally closed by, for example, a separate base wafer (sockelwafer).

[0048] According to another embodiment of the method according to the invention, at least one measuring volume is opened on the back side by a gas-conducting etching process applied to the back side of the wafer-shaped substrate. The etching process can be a trench process, a dry etching process, a wet etching process and / or a combination of steps or the like. At least one measuring volume and / or a reference volume introduced into the wafer-shaped substrate can be modified by gas-conducting in the direction of the back side of the wafer-shaped substrate by porous semiconductor technology, for example PorSi technology.

[0049] The reference volume can be opened here in the same way as the measuring volume only from the front side of the device. This has the advantage that the Wheatstone bridge can be more easily coordinated with the measuring volume due to the higher symmetry.

[0050] The advantage of a porous semiconductor structure in at least one measuring volume is that the semiconductor structure has a large surface and an adjustable pore size and can therefore take on a filter function for other gases and / or particles. The porous structure is configured in such a way that particles, aerosols or luminescent moisture cannot enter the at least one measuring volume due to the particle size. The porous semiconductor structure is set up in the process control with PorSi and the porosity can be adjusted by the process control.

[0051] According to another embodiment of the method according to the invention, a sealing device is arranged on the back side of the wafer-shaped substrate. The cross section of the back side of the wafer-shaped substrate to be sealed can be reduced by the gas-conducting supply to the measurement volume, so that by means of a wide sealing ring, which, for example, serves for media resistance, sealing against moisture and other environmental influences can be achieved in a technically simpler manner in the region of at least one measurement volume.

[0052] The advantage of the installed sealing device is that the gas located below the measuring volume, for example a hydrogen-humidity mixture, can be separated in the exhaust pipe from a second gas located above the wafer-shaped substrate, for example the ambient air. A particular advantage is that the bonding pads and bonding wires can thereby be separated from gases or other components of the air (humidity) that damage them. The sealing device is located in particular on the back side, because the dielectric layer present there is particularly moisture-stable. It is also conceivable to arrange the sealing device on the front side if other sealing functions are involved, such as dust.

[0053] According to another embodiment of the method according to the invention, at least one resistor and at least one electrically conductive connection are arranged on at least one reference diaphragm and at least one measuring diaphragm, wherein the wafer-shaped substrate connected to the wafer-shaped cover substrate is separated into at least two diaphragm arrangements. In particular, a Wheatstone bridge circuit can thus be applied to the diaphragm arrangement before the separation step. As a result, a plurality of diaphragm arrangements can be processed or produced simultaneously in a technically simple manner.

[0054] The realization of the bridge circuit can take place on a single chip in the embodiment of at least one double diaphragm or on a chip with a diaphragm, wherein the cover provides the measurement and reference volume and separates them from one another. The sensor signal of such a sensor cannot change due to changing environmental conditions or aging of the chip or applied metal and the accompanying drift of the resistance, because all the resistances of the bridge circuit are subject to the same fluctuations and the bridge voltage does not change as a result.

[0055] Furthermore, manufacturing technology fluctuations in the resistors applied to the membrane arrangement can influence the performance of the sensor, since the resistors of the bridge circuit are arranged in direct proximity to one another and are therefore subject to these fluctuations to the same extent. If all resistors in a bridge circuit experience the same fluctuations, this has little effect on the resulting bridge voltage.

[0056] According to a further embodiment of the method according to the invention, at least one reference volume is introduced into a wafer-shaped substrate from the front side by a PorSi process with or without subsequent removal of the porous silicon, while forming a reference membrane which at least partially covers the reference volume.

[0057] Furthermore, according to one embodiment of the method according to the invention, at least one reference volume is introduced from the front side into a wafer-shaped substrate by means of a PorSi process with or without subsequent removal of the porous silicon, while forming a reference diaphragm which at least partially covers the reference volume, and in the case of forming a measuring diaphragm which at least partially covers the measuring volume, the initially closed measuring volume is introduced from the front side into the wafer-shaped substrate by means of a PorSi process with or without subsequent removal of the porous silicon.

[0058] In the process control with PorSi, the reference volume and the measurement volume can be introduced simultaneously or individually. It is then possible to open the cavity to the top side and / or the back side, depending on the desired subsequent application.

[0059] In the case of process control using PorSi, a wafer-shaped cover substrate can be omitted, which further simplifies the process sequence. In addition, the stability of the reference and / or measuring diaphragms can be increased by supporting the stability with a porous structure, thereby enabling measurements to be performed at higher pressures in the reference and / or measuring volumes.

[0060] The advantage of process control using the PorSi process is that a filter function is purposefully implemented in at least one reference volume and / or measurement volume by porous silicon. The porous semiconductor structure has a large surface and a pore size that can be adjusted by process control and can therefore assume a filter function with respect to undesired particles, aerosols and / or luminescent moisture. Undesired components cannot enter the at least one reference volume and / or measurement volume due to the particle size. This can be particularly advantageous if the gas and / or gas mixture to be measured is contaminated.

[0061] According to a further aspect of the invention, a diaphragm arrangement of a sensor for calorimetrically detecting gases is provided, which is produced according to the method according to the invention. The diaphragm arrangement comprises: a cover substrate segment connected to the substrate segment; and at least one reference volume, which is introduced into the substrate segment and is bounded at least on one side by a reference diaphragm in the direction of the cover substrate segment. In addition, the diaphragm arrangement comprises at least one measuring volume, which is introduced into the substrate segment and is bounded by a one-sided measuring diaphragm in the direction of the cover substrate segment, wherein the reference diaphragm is preferably at least partially open in a fluid-conducting manner in the direction of the front side of the cover substrate segment. The measuring volume is configured in a fluid-conducting manner in the direction of the back side of the substrate segment.

[0062] The diaphragm arrangement of a sensor for calorimetrically detecting gases produced according to the method comprises: at least one measuring vessel, which comprises a gas inlet from the rear side of a wafer-shaped substrate, and at least one reference volume, which is closed in the direction of the rear side of the wafer-shaped substrate. The closed reference volume can be used as a reference for gas measurements, for example in the use of a Wheatstone measuring bridge in a metal layer.

[0063] The membrane arrangement can be used, for example, for a configuration as a double membrane chip, in which a cavity or measuring volume is open, for example, from the rear side of a wafer-shaped substrate and thus has a gas inlet, wherein an adjacent reference volume is sealed off from this inlet side (see PA 13).

[0064] The spatial separation of the reference membrane from the measuring membrane has proven to be particularly advantageous since, in conjunction with the electrically conductive structure, it can form a reference resistor in order to decouple possible changes, for example humidity and temperature in the environment and / or the like, from the measurement signal.

[0065] A further advantage of a reference volume is that a defined gas and / or gas mixture can be enclosed and measurements can therefore be performed relative to the reference volume.

[0066] According to a further aspect of the invention, a component, in particular a sensor, is provided, which comprises a membrane arrangement according to the invention.

[0067] The diaphragm arrangement can preferably be a section of a wafer arrangement which is processed according to the method of the invention and subsequently separated into a plurality of sections. By means of openings for the measurement volume and the reference volume which are introduced in opposite directions, the gas flow can be technically simply conducted into the respective volumes. In particular, a sealed shielding of the reference volume can be achieved by means of the cover substrate section. The sealed shielding can also be achieved by opening the reference volume without conducting gas or by closing it again after filling with the reference gas. This can reduce external influences on the measurement, for example the hydrogen concentration, so that the control electronics for operating the sensor based on the diaphragm arrangement can be designed to be technically simpler and more cost-effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] A preferred embodiment of the content of the present invention is further explained below based on an extremely simplified schematic diagram. In which:

[0069] Figure 1 A schematic cross-sectional view showing a membrane device according to a first embodiment of the present invention;

[0070] Figure 2 A schematic cross-sectional view showing a membrane device according to a second embodiment of the present invention;

[0071] Figure 3 A schematic diagram shows a method for producing a membrane arrangement according to a first exemplary embodiment.

[0072] In the figures, identically constructed elements are each provided with the same reference symbols. DETAILED DESCRIPTION

[0073] Figure 1 A schematic cross-sectional view of a membrane arrangement 1 according to a first specific embodiment of the invention is shown. The membrane arrangement 1 is a section from a wafer having a plurality of membrane arrangements 1 which are separated from one another by a separation process.

[0074] The diaphragm device 1 is designed as a device for a double diaphragm chip and can be used for the layers of the diaphragm, for example an ONO diaphragm (oxide-nitride-oxide) - which includes at least one conductor track contained therein, for example composed of metals such as platinum, gold, silver, copper, molybdenum, tungsten - or a non-metallic conductive layer such as polysilicon or similar materials. Alternatively, the diaphragm can consist of only oxide, only nitride or a mixture of the two. The device 1 has a reference diaphragm 2, which is produced in a wafer-shaped substrate 4 by a surface micromechanical process or a volume micromechanical process or a PorSi process, the latter optionally combined with a dry etching step for removing porous silicon structures. At the same time, a reference volume 6 is generated, which is delimited by the reference diaphragm 2 in the direction of the front side V of the wafer-shaped substrate 4. The reference diaphragm 2 is open at least in places here, so that gas exchange with the reference volume 6 can take place.

[0075] The device 1 has a wafer-shaped cover substrate 8, which is applied to the wafer-shaped substrate 4 after the reference diaphragm 2 is produced. The wafer-shaped cover substrate 8 has a recess 7 extending through the wafer-shaped cover substrate 8 in the regions 2, 10 of the diaphragm. The regions 2 and 10 can also be connected to each other. According to this embodiment, the recess 7 has oblique side edges, which can be caused by a wet etching process. However, the recess 7 can also be introduced into the wafer-shaped cover substrate 8 using other material removal methods, such as, for example, trenches.

[0076] The wafer-shaped cover substrate 8 is arranged on the wafer-shaped substrate 4 by means of wafer bonding with glass frit. The device 1 acquires additional stability by means of the wafer-shaped cover substrate 8 .

[0077] Furthermore, the device 1 has a measuring diaphragm 10 adjacent to the reference diaphragm 2. The measuring diaphragm 10 is produced in a wafer-shaped substrate 4 in a further processing with a so-called "face-down" orientation of the device 1. In this case, an etching method is applied from the back side R of the wafer-shaped substrate to produce a measuring volume 14. The measuring volume 14 is designed to be open in the direction of the back side R and thus enables an unimpeded flow of gas to the measuring diaphragm 10, but not through it. In other types of etching processes, which do not require face-down processing, such as wet etching or fixing the device 1 on an edge, the wafer-shaped cover substrate 8 can also be omitted if necessary.

[0078] In the region of the measurement volume 14 , a seal 15 in the form of a sealing ring 15 is arranged on the back side R of the wafer-shaped substrate 4 .

[0079] exist Figure 2 A schematic cross-sectional view of a diaphragm device 1 according to a second embodiment of the present invention is shown in . Unlike the diaphragm device 1 according to the first embodiment, here the measuring volume 14 is also introduced into the wafer-shaped substrate 4 from the front side V of the wafer-shaped substrate 4 by a surface micromechanical process or a volume micromechanical process or a PorSi process. So-called cloud grooves can also be used here. Ideally, a coating with an ONO diaphragm and an embedded metal structure composed of platinum is then implemented. The measuring volume 14 is thus closed to the front side and back side R of the wafer-shaped substrate 4 and is opened to the back side R for gas guidance by subsequent steps, for example by a groove process or other etching process. The measuring volume 14 thus has an opening 16 arranged on the back side, which preferably prevents particles and moisture from entering the measuring volume 14.

[0080] Figure 3 A schematic diagram of a method 18 for producing a membrane arrangement 1 according to a first exemplary embodiment is shown.

[0081] In a first method step 20 , a wafer-shaped substrate 4 is provided.

[0082] The wafer-shaped substrate 4 can then be equipped or provided with a resistor or an electrically conductive connection in the form of one or more coatings and their structuring by lithography, and the electrically conductive layer can be surrounded by an insulating layer 21. The electrically conductive connection preferably forms a heating resistor.

[0083] Subsequently, at least one reference volume 6 is introduced 22 into the wafer-shaped substrate 4 from the front side V by means of a surface micromachining process, a volume micromachining process or a PorSi process in combination with a dry etching step, while forming a reference membrane 2 which at least partially covers the reference volume 6 .

[0084] Alternatively or additionally, electrical lines and surrounding electrical and thermal insulation layers can be applied to the wafer-shaped substrate 4 according to method step 21 also after the reference volume 6 and / or the measurement volume 14 have been formed 22 .

[0085] In a further step 23 , a wafer-shaped cover substrate 8 is applied to the wafer-shaped substrate 4 and the wafer arrangement is turned 24 , so that processing of the back side R can be carried out. Alternatively, this step can be omitted.

[0086] In this case, in step 25, at least one measuring volume 14 adjacent to at least one reference volume 6 is introduced into the wafer-shaped substrate 4 from the rear side R of the wafer-shaped substrate 4 while forming the measuring membrane 10. If the measuring volume 14 has already been produced, an air inlet or a fluid-conducting connection to the measuring volume 14 can be introduced from the rear side R of the wafer-shaped substrate 4 in step 25.

[0087] In a final step 26 , the wafer-shaped substrate 4 connected to the wafer-shaped cover substrate 8 is always separated into at least two membrane arrangements 1 .

Claims

1. A method for producing at least one membrane arrangement (1) for a micromechanical sensor for calorimetrically detecting gases, wherein: - providing a wafer-shaped substrate (4); - introducing at least one reference volume (6) into the wafer-shaped substrate (4) from the front side (V) by means of surface or volume micromachining technology, while forming a reference membrane (2) which at least partially covers the reference volume (6); - introducing at least one measuring volume (14) from the back side (R) or the front side (V) of the wafer-shaped substrate (4) into the wafer-shaped substrate (4) while forming a measuring membrane (10), the at least one measuring volume being adjacent to the at least one reference volume (6); - applying a wafer-shaped cover substrate (8) to the front side (V) of the wafer-shaped substrate (4); - the at least one measuring volume (14) is opened on the back side in a gas-conducting manner via a porous opening (16) introduced on the back side (R) of the wafer-shaped substrate (4), wherein the porous opening (16) is set up in a process control using PorSi and is introduced into the back side wall of the at least one measuring volume (14) by a trench process and / or a dry etching process and / or a wet etching process.

2. The method according to claim 1, wherein: The opening (16) is dimensioned such that a gaseous medium can enter the at least one measuring volume (14), while particles and aerosols cannot enter the at least one measuring volume (14) through the opening (16) due to their particle size.

3. The method according to claim 1, wherein: After the reference volume (6) has been introduced, the wafer-shaped cover substrate (8) is applied to the wafer-shaped substrate (4).

4. The method according to claim 1, wherein: After the at least one measuring volume (14) has been introduced, the wafer-shaped cover substrate (8) is applied to the wafer-shaped substrate.

5. The method according to any one of claims 1 to 4, wherein: The at least one measuring volume (14) is introduced into the wafer-shaped substrate (4) by dry etching, a trench process or a wet etching process.

6. The method according to any one of claims 1 to 4, wherein: The wafer-shaped cover substrate (8) is applied to the front side (V) of the wafer-shaped substrate (4) by anodic or eutectic bonding, bonding by means of glass frit, adhesive bonding, soldering or welding.

7. The method according to any one of claims 1 to 4, wherein: When the wafer-shaped cover substrate (8) is applied to the wafer-shaped substrate (4), at least one reference volume (6) is formed between the at least one reference diaphragm (2) and the wafer-shaped cover substrate (8) and / or between the at least one measuring diaphragm (10) and the wafer-shaped cover substrate (8): the reference volume is open or closed in the direction of the front side (V) of the wafer-shaped cover substrate (8).

8. The method according to any one of claims 1 to 4, wherein: A sealing device (15) is arranged on the rear side (R) of the wafer-shaped substrate (4).

9. The method according to any one of claims 1 to 4, wherein: At least one resistor and at least one electrically conductive connection are arranged on the at least one reference diaphragm (2) and the at least one measuring diaphragm (10), wherein the wafer-shaped substrate (4) connected to the wafer-shaped cover substrate (8) is separated into at least two diaphragm arrangements (1).

10. The method according to any one of claims 1 to 4, wherein: At least one reference volume (6) is introduced into the wafer-shaped substrate (4) from the front side (V) by means of a PorSi process with or without subsequent removal of the porous silicon, while forming a reference membrane (2) which at least partially covers the reference volume (6).

11. The method according to any one of claims 1 to 4, wherein: In forming a reference diaphragm (2) at least partially covering the reference volume (6), at least one reference volume (6) is introduced into the wafer-shaped substrate (4) from the front side (V) by means of a PorSi process with or without subsequent removal of the porous silicon, while in forming a measuring diaphragm (10) at least partially covering the measuring volume, a first closed measuring volume (14) is introduced into the wafer-shaped substrate (4) from the front side (V) by means of a PorSi process with or without subsequent removal of the porous silicon.

12. A diaphragm device (1), which is a sensor for calorimetrically detecting a gas and which is produced according to the method according to any one of claims 1 to 11, comprising: - a cover substrate (8), which is connected to the substrate (4); at least one reference volume (6) which is introduced into the substrate (4) and is delimited on one side by a reference membrane (2) in the direction of the cover substrate (8); at least one measuring volume (14) which is introduced into the substrate (4) and is delimited on one side by a measuring membrane (10) in the direction of the cover substrate (8); The reference membrane (2) is designed at least in regions to conduct fluid in the direction of the front side (V) of the cover substrate (8), while the measurement volume (14) is designed to conduct fluid in the direction of the rear side (R) of the substrate (4).

13. A component comprising a membrane arrangement (1) according to claim 12.

14. The component according to claim 13, wherein The component is a sensor.

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