Patent Publication Number: US-9418857-B2

Title: Sensor component for a gas and/or liquid sensor, production method for a sensor component for a gas and/or liquid sensor, and method for detecting at least one material in a gaseous and/or liquid medium

Description:
FIELD OF THE INVENTION 
     The present invention relates to a sensor component for a gas and/or liquid sensor, and to a gas and/or liquid sensor. The present invention also relates to a production method for a sensor component for a gas and/or liquid sensor, and to a production method for a gas and/or liquid sensor. In addition, the present invention relates to a method for detecting at least one material in a gaseous and/or liquid medium. 
     BACKGROUND INFORMATION 
     In German Published Patent Appln. No. 44 45 359, a sensor is described for detecting combustible gases. The sensor includes a substrate having two printed conductors having comb-type interlacing at their head ends. In the area of the interlaced ends, a sensitive semiconducting metal oxide layer is applied over the printed conductors. The sensitive semiconducting metal oxide layer can have a spongelike structure, or can be fashioned as a composite of grains sintered together. 
     SUMMARY 
     The present invention creates a sensor component for a gas and/or liquid sensor, a gas and/or liquid sensor, a production method for a sensor component for a gas and/or liquid sensor, a production method for a gas and/or liquid sensor, and a method for detecting at least one material in a gaseous and/or liquid medium. 
     The subject matters of the present invention have increased sensitivity for at least one detectable material. As explained below in more detail, using the present invention smaller quantities of the at least one material can already be detected in a gaseous and/or liquid medium. In particular, using the present invention lower concentrations of a material can already be reliably measured. The present invention thus contributes to the more reliable detection of the at least one material and/or the more precise determination of its concentration. 
     Moreover, using the present invention even a comparatively small volume of the medium can be reliably examined for the occurrence of the at least one material or the concentration thereof. Due to the possibility of carrying out such investigations using only a relatively small quantity of the medium, the present invention can advantageously be used for various purposes, for example in fine trace analysis and/or molecular biology. It is also advantageous that due to the small volume a small access channel to the sensor is sufficient for the medium, and a particularly short response time is achieved because the ratio of the volume surrounding the sensor to the channel volume can be made very advantageous. The present invention can however also be used to examine exhaust gases, in medicine, in environmental protection, in consumer protection, and for a large number of further uses. The present invention thus has many possible applications. 
     Moreover, the present invention realizes gas and/or liquid sensors that need to be equipped only with a comparatively small quantity of the at least one sensitive semiconductor material. Thus, even given the use of a comparatively expensive material as the at least one sensitive semiconductor material, it is still ensured that the gas and/or liquid sensor equipped with a sufficient quantity thereof can be produced at relatively low cost. The present invention thus reduces the costs for a gas and/or liquid sensor and increases the number of materials that can be used therein as the at least one sensitive semiconductor material. 
     In addition, the present invention offers a possibility for realizing a comparatively small gas and/or liquid sensor. Due to the small constructive space requirement of such a gas and/or liquid sensor, it can be used in many different ways. 
     Preferably, the two inner side surfaces, parallel to the side of the substrate, contacted by the first contact segment of the first printed conductor and by the first contact segment of the second printed conductor are situated at a distance from one another that is equal to a diameter of the individual particle, grain, or crystal of the at least one sensitive semiconductor material filled into the respective trench, or are larger by at most a factor of 3 than an average diameter of the particles, grains, and/or crystals of the at least one sensitive semiconductor material filled into the at least one trench. In particular, the distance between the two inner side surfaces parallel to the side of the substrate can be greater by at most a factor of 2.5, advantageously at most a factor of 2, preferably at most by a factor of 1.5, than the average diameter of the particles, grains, and/or crystals of the at least one sensitive semiconductor material filled into the at least one trench. As explained in more detail below, such a realization of the sensor component can advantageously increase its sensitivity. 
     For example, at most a number of ten particles, grains, and/or crystals per trench can be filled into the at least one trench. Here, in particular a trench segment can be designated that results from the multiplication of the trench cross surface by a length of the trench segment, which preferably corresponds approximately to the diameter of the crystals or particles filled in—in particular to the diameter of from approximately 50% to 85% of the filled particles. Specifically, an average number of from one to five particles, grains, and/or crystals, in particular an average number of two to three particles, grains, and/or crystals, can be filled into the at least one trench or into a trench segment as just stated. In this case, even small changes in a concentration of the at least one material can be reliably recognized. 
     Preferably, at least one surface-active glued and/or adhesive bond is fashioned between a roughened surface of the first contact segment of the first printed conductor and at least one particle, grain, or crystal, contacted thereby, of the at least one sensitive semiconductor material, and/or between a roughened surface of the first contact segment of the second printed conductor and at least one particle, grain, or crystal, contacted thereby, of the at least one sensitive semiconductor material. The adhesive bond can also advantageously result from a bond, achieved in the production process, of the crystals and tilting thereof in the trench structure with elements of the surface roughnesses of the trench structure. In this way, an advantageous hold of the at least one particle, grain, and/or crystal in the respective trench is ensured, as is also a reliable contact between the at least one contact segment and the contacted particle, grain, and/or crystal. 
     In an advantageous specific embodiment, the at least one sensitive semiconductor material includes tin oxide, zinc oxide, titanium oxide, indium oxide, and/or tungsten oxide. Thus, materials that are easy to sinter can also be used. 
     Advantageously, the at least one sensitive semiconductor material is doped with tantalum and/or niobium. This ensures a reliably recognizable change in resistance of the at least one sensitive semiconductor material as a response to the contact with the at least one material. 
     Preferably, the at least one sensitive semiconductor material is doped with at least one alkaline earth metal and/or at least one rare earth metal. In this way, an undesired growth of the particles, grains, and/or crystals of the at least one sensitive semiconductor material can be reliably prevented. In this way, the particles, grains, and/or crystals of the at least one sensitive semiconductor material can be fashioned with a comparatively small average diameter, enabling a good sensitivity of the sensor component. 
     Moreover, the at least one particle, the at least one grain, and/or the at least one crystal of the at least one sensitive semiconductor material can be coated at least partly with gold, silver, platinum, palladium, rhodium, and/or ruthenium. This ensures in particular a good sensitivity of the sensor component fashioned in this way to particular gases. Likewise, the metal that coats the crystals can be present, in addition to on the surface, also in the interior thereof, e.g. in clusters of from 0.5 to 150 nm, preferably from 1 to 50 nm, and can also be distributed uniformly in the interior, so that according to the present invention no cluster of the outer surface can easily wander into defective places in the interior of the crystal. 
     In a further advantageous specific embodiment, the at least one trench parallel to the side of the substrate has a U-shaped cross-section, the inner side surfaces with the first contact segment of the first printed conductor and the first contact segment of the second printed conductor being situated on a first limb of the U-shaped cross-section, and a second contact segment of the first printed conductor and a second contact segment of the second printed conductor being fashioned on two further inner side surfaces, situated at a distance from one another, of the at least one trench wall that are situated on a second limb of the U-shaped cross-section. A sensor component fashioned in this way can be fashioned in a relatively simple manner even when there is a comparatively small spacing of the respective inner side surfaces having the associated contact segments. 
     The advantages enumerated above are also ensured in a gas and/or liquid sensor having such a sensor component. 
     The advantages can also be realized by carrying out a corresponding production method for a sensor component for a gas and/or liquid sensor. The production method can be developed according to the above-described specific embodiments. 
     In an advantageous development, after the filling of the at least one particle, the at least one grain, and/or the at least one crystal of the at least one sensitive semiconductor material respectively into the at least one trench, the sensor component is heated to a temperature between 400° C. and 700° C. This ensures the at least one advantageous surface-active glued and/or adhesive bond. 
     A carrying out of the corresponding production method for a gas and/or liquid sensor also realizes the above-described advantages. 
     In addition, the above-described advantages can be realized by carrying out the corresponding method for detecting at least one material in a gaseous and/or liquid medium. The method can also be developed in a manner corresponding to the above-described specific embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic representation of a first specific embodiment of the sensor component. 
         FIG. 2  shows a schematic representation of a second specific embodiment of the sensor component. 
         FIGS. 3 a  and 3 b    show a top view and a cross-section of a third specific embodiment of the sensor component,  FIG. 3 b    showing a cross-section along the line A-A′ of  FIG. 3   a.    
         FIG. 4  shows a schematic representation of a fourth specific embodiment of the sensor component. 
         FIGS. 5 a  through 5 c    show schematic representations of a fifth specific embodiment of the sensor component. 
         FIG. 6  shows a flow diagram explaining a specific embodiment of the production method for a sensor component for a gas and/or liquid sensor. 
         FIG. 7  shows a flow diagram explaining a specific embodiment of the method for detecting at least one material in a gaseous and/or liquid medium. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a schematic representation of a first specific embodiment of the sensor component. 
     The sensor component shown schematically in  FIG. 1  can be used in/on a gas and/or liquid sensor. The sensor component includes a substrate  10  having at least one trench  14  fashioned on a side  12  of substrate  10 . The at least one trench  14  is fashioned having at least one trench wall  16  and at least one trench floor  18 , each made of at least one electrically insulating material. Moreover, substrate  10  has at least one first printed conductor  20  and one second printed conductor  22 . First printed conductor  20  and second printed conductor  22  are fashioned such that a voltage U can be applied between first printed conductor  20  and second printed conductor  22 . For example, voltage U can be applied by an operating device, external to the sensor component, of the gas and/or liquid sensor. Likewise, however, a circuit (not shown) fashioned on substrate  10  can also be used to apply voltage U. 
     A first contact segment  20   a  of first printed conductor  20  and a first contact segment  22   a  of second printed conductor  22  are situated on two inner side surfaces, at a distance from one another, of the at least one trench wall  16  (of the same trench  14 ). Thus, voltage U can also be applied between contact segments  20   a  and  22   a  in the interior of the respective trench  14 . At least one sensitive semiconductor material in the form of at least one particle, grain, and/or crystal  24  is filled into the at least one trench  14 , at least between the at least one first contact segment  20   a  of first printed conductor  20  and first contact segment  22   a  of second printed conductor  22 . Examples for the at least one sensitive semiconductor material are named below. 
     The above-described embodiment of the sensor component ensures an advantageous sensitivity in the detection of at least one material in a gaseous and/or liquid medium present in the at least one trench  14 . The detection of the at least one material can be understood as a detection of the at least one material, a measurement of its concentration in the gaseous and/or liquid medium, and/or a determination of at least one chemical and/or physical property of the gaseous and/or liquid medium. In all cases, a good degree of sensitivity is possible in the use of the sensor component. This is explained in the following, and as an example it is assumed that via voltage U first contact region  20   a  of first printed conductor  20  is used as anode, and first contact region  22   a  of second printed conductor  22  is used as cathode. The valence electrons of the at least one sensitive semiconductor material are in this case drawn from first contact region  20   a  of first printed conductor  20 . In the at least one particle, grain, and/or crystal  24 , in the at least one trench  14  there is thus formed a first zone  24   a  that is enriched with electrons. At a distance from first zone  24   a  there is also formed in each case a second zone  24   b  in the respective particle, grain, or crystal  24 , which has a lower electron density than an intermediate zone  24   c  situated between first zone  24   a  and associated second zone  24   b.  While first zone  24   a  is situated closer to first contact region  20   a  of first printed conductor  20 , second zone  24   b  is oriented to first contact region  22   a  of second printed conductor  22 . 
     Thus, due to their surface charges under the influence of contact regions  20   a  and  22   a  with applied voltage U, Schottky barriers thus occur on the at least one particle, grain, and/or crystal  24  of the sensitive semiconductor material. Moreover, the Schottky barriers can be tuned by reinforcing the depletion thickness of the surface of the particle, grain, and/or crystal  24 . In this way, a zone having fewer charge barriers is also possible. 
     This results in a highly sensitive region close to the surface of the respective particle, grain, or crystal  24 , in which even low concentrations of particular molecules can contribute to a significant change in a resistance present between contact regions  20   a  and  22   a  of printed conductors  20  and  22 . Oxidative materials, such as for example NO 2  or ozone, attract electrons and therefore contribute to an increase in the resistance present between contact regions  20   a  and  22   a.  In contrast, other materials, in particular combustion gases, have the opposite effect, and therefore reduce the resistance present between contact regions  20   a  and  22   a.    
     In general, the resistance present between contact regions  20   a  and  22   a  of printed conductors  20  and  22  is significantly lower than in the case of a conventional sensor structure having a complete sensitive semiconducting layer between two contacts. In particular, the resistance of an individual particle, grain, and/or crystal  24  of the at least one sensitive semiconductor material is significantly lower than that of a complete sensitive semiconducting layer. In comparison to a conventional sensor structure, in the sensor component small quantities of a particular material in contact with the at least one particle, grain, and/or crystal  24  captured between contact regions  20   a  and  22   a  therefore already cause a significant change in resistance. Thus, the sensor component ensures a sensitivity in the detection of the at least one material that is significantly increased in comparison to conventional sensor components. 
     Voltage U applied between contact regions  20   a  and  22   a  for the operation of the sensor component can for example be between 0.1 V and 5 V. Voltage U can optionally be applied as a direct voltage or as an alternating voltage. For example, for voltage U an alternating voltage can be used having a frequency in the range from 0.1 Hz to 50 Hz, preferably between 1 Hz and 20 Hz. In this way, migration processes of metal atoms from printed conductors  20  and  22  into the regions in the crystal having Schottky barriers  24   a  and  24   b  and into the depletion zones themselves are preventable even when there is a comparatively strong electrical field between contact regions  20   a  and  20   b.  The sensor component can thus still be operated reliably even at a comparatively high temperature, for example between 200 and 400° C., although the metal atoms can easily exit at such a temperature; in particular the metal atoms can pass over into the semiconducting sensitive crystal through electromigration. This can be prevented by reversing the polarity of the operating voltage. In addition to the method with the alternating voltage, this can also take place with direct voltages whose polarity has been reversed, e.g. by a circuit that reverses the polarity of the sensor or the voltage, so that for a time T+ a positive voltage is present at sensor electrode e.g.  20 , and during a time T− a negative voltage is present at sensor electrode  20 . The times T+ and T− can be equally long or can have different lengths, in order to make the migration of the metal atoms into the sensitive crystal reversible for the intended purpose. 
     Preferably, the two inner side surfaces parallel to side  12  of substrate  10 , contacted by first contact segment  20   a  of first printed conductor  20  and by first contact segment  22   a  of second printed conductor  22 , are at a distance from one another that is equal to a diameter of the single particle, grain, or crystal  24  of the at least one sensitive semiconductor material filled into the respective trench, or is larger by at most a factor of three than an average diameter of the particles, grains, and/or crystals  24  of the at least one sensitive semiconductor material filled into the at least one trench  14 . For example, the distance between the inner side surfaces is greater by at most a factor of 2.5, preferably at most a factor of 2, preferably at most a factor of 1.5, than the average diameter of the particles, grains, and/or crystals  24  filled into the at least one trench  14 . This can be realized for example in that the at least one trench  14  is fashioned with an (almost) round cross-section parallel to side  12  of the substrate, a trench diameter being equal to the diameter of the single particle, grain, or crystal  24  filled into the respective trench  14 , or being a larger by at most a factor of 3, preferably at most a factor of 2.5, in particular at most a factor of 2, preferably at most by a factor of 1.5, than the average diameter of the particles, grains, and/or crystals  24  filled into the at least one trench  14 . The at least one trench  14  can have a corresponding width and a depth of e.g. 1 μm. The depth of the at least one trench  14  is however relatively freely determinable. As explained below in more detail, the realization of the at least one trench  14  is also not limited to a round cross-section parallel to side  12  of substrate  10 . 
     Thus, at most ten particles, grains, and/or crystals  24  per trench  14  can be filled into the at least one trench. For example, an (average) number of from one to five particles, grains, and/or crystals  24 , in particular an (average) number of two to three particles, grains, and/or crystals  24 , per trench  14  can be filled into the at least one trench  14 . This ensures an advantageously increased sensitivity of the sensor component in comparison with conventional sensor components. Here, the smallest volume unit of the trench for which this enumeration is applied is a segment of this trench in which the cross-sectional surface of the trench is multiplied by the diameter of approximately 50-85% of the filled particles. 
     At least one surface-active glued and/or adhesive bond can be formed between a roughened surface of first contact segment  20   a  of first printed conductor  20  and at least one particle, grain, and/or crystal  24 , contacted thereby, of the at least one sensitive semiconductor material, and/or between a roughened surface of first contact segment  22   a  of second printed conductor  22  and at least one particle, grain, and/or crystal  24 , contacted thereby, of the at least one sensitive semiconductor material. 
     This ensures an advantageous hold of the respective particle, grain, and/or crystal  24  in the at least one trench  14  and a good contact between the respective contact segment  20   a  and  22   a  and the at least one particle, grain, and/or crystal  24  contacted thereby. The at least one sensitive semiconductor material can also be present in the form of sol-gel particles that are thermally treated and have few or no edges. 
     An average diameter of the at least one particle, grain, and/or crystal  24  can be between 10 nm and 5 μm. It is to be noted that the average diameter of the at least one particle, grain, and/or crystal  24  can be selected relatively freely. Preferably, particles are used in the 0.2 to 0.8 μm range. 
     The at least one sensitive semiconductor material is preferably at least one n-type semiconductor material. For example, the at least one sensitive semiconductor material can include tin oxide, zinc oxide, titanium oxide, indium oxide, and/or tungsten oxide. In order to ensure an advantageous sensitivity, the at least one sensitive semiconductor material is advantageously doped. Preferably, the doping has one valence electron more than the base material. For example, the at least one sensitive semiconductor material can be doped with tantalum and/or niobium. A concentration of the doping can be from 0.0001 mol % to 0.1 mol %, specifically from 0.0025 mol % to 0.01 mol %. 
     Moreover, the at least one sensitive semiconductor material can be doped with at least one alkaline earth metal and/or at least one rare earth metal. The doping with the at least one alkaline earth metal and/or the at least one rare earth metal can be present in a concentration from 0.1 to 3 mol %. Such an (additional) doping can prevent undesired crystal growth. For example, in this way crystals  24  can be grown whose average diameter is from 10 nm to 500 nm. 
     In order to ensure a good sensitivity to the at least one particular material, the at least one particle, the at least one grain, and/or the at least one crystal  24  of the at least one sensitive semiconductor material can also be at least partly coated with gold, silver, platinum, palladium, rhodium, and/or ruthenium. However, the materials for the coating listed here are to be understood only as examples. For example, in the detection method described here at least one receptor molecule can also be bound additionally to at least one particle, grain, and/or crystal  24 . 
     For substrate  10 , many materials, such as silicon, silicon carbide, and/or silicon nitride, can be used whose coefficient of expansion is lower than that of the at least one sensitive semiconductor material. In this way as well, an advantageous pressing of at least one particle, grain, and/or crystal  24  of the at least one sensitive semiconductor material against the at least one trench wall  16  of the at least one trench  14  can be ensured in particular when the sensor component is heated. In this way as well, a contact between printed conductors  20  and  22  and the at least one sensitive semiconductor material, as well as a good hold of the at least one particle, grain, and/or crystal  24  in the at least one trench  14 , can be ensured. The at least one particle, the at least one grain, and/or the at least one crystal  24  can also be held in the at least one trench  14  by an electrical or Van der Waals force of attraction. 
     In the specific embodiment shown in  FIG. 1 , the advantageous electrically insulating realization of the at least one trench wall  16  and of the at least one trench floor  18  of the at least one trench  14  is ensured in that, after a structuring of openings in substrate  10 , the at least one trench wall  16  is formed from a first insulating layer  26  and the at least one trench floor  18  is formed from a second insulating layer  28 . In this way, an advantageous insulation of printed conductors  20  and  22  relative to substrate  10  is also ensured even if substrate  10  includes at least one conductive material. 
     Insulating layers  26  and  28  can include for example silicon nitride, silicon oxide, in particular thermal silicon oxide, and/or some other electrically insulating substance. Printed conductors  20  and  22  can be made of gold, platinum, and/or some other noble metal. Moreover, printed conductors  20  and  22  can also be impregnated with titanium, tantalum, niobium, tungsten, and/or some other metal that has a good adhesion between the covered insulating material and the metal of the printed conductors  20  and  22  applied thereon. 
       FIG. 2  shows a schematic representation of a second specific embodiment of the sensor component. 
     The sensor component shown schematically in  FIG. 2  can be regarded as a development of the above specific embodiment. The sensor component has at least three trenches  14 , each of which are, corresponding to the above specific embodiment, filled with at least one particle, grain, and/or crystal  24 . The resistances realized by trenches  14  are connected in series. For this purpose, at least a third printed conductor  30  and a fourth printed conductor  32  are additionally fashioned on substrate  10 . At least second printed conductor  22  and third printed conductor  30  extend over separating hills  34  fashioned between each two adjacent trenches  14 . Printed conductors  22  and  30  extending over separating hills  34  each have two contact segments  22   a,    22   b,    30   a,  and  30   b,  each of which contacts at least one particle, grain, and/or crystal  24  in a trench  14  of the two adjacent trenches  14 . Thus, via the two external printed conductors  20  and  32  having only one contact region  20   a  and  32   a,  a series circuit is realized. It can easily be seen that instead of only three trenches  14  a larger number of trenches  14  can also be connected in series in this way. 
       FIGS. 3 a  and 3 b    show a top view and a cross-section of a third specific embodiment of the sensor component;  FIG. 3 b    shows a cross-section along the line A-A′ of  FIG. 3   a.    
     In the specific embodiment of  FIGS. 3 a    and  3   b,  the at least one trench  14  parallel to side  12  of substrate  10  has a U-shaped cross-section. The inner side surfaces having first contact segment  20   a  of first printed conductor  20  and first contact segment  22   a  of second printed conductor  22  are situated on a first limb of the U-shaped cross-section. A second contact segment  20   b  of first printed conductor  20  and a second contact segment  22   b  of second printed conductor  22  are fashioned on two further inner side surfaces, at a distance from one another, of the at least one trench wall  16  that are situated on a second limb of the U-shaped cross-section. At least one particle, grain, and/or crystal  24  is also placed between second contact segment  20   b  of first printed conductor  20  and second contact segment  22   b  of second printed conductor  22 . Preferably, contact segments  22   a  and  22   b  of second printed conductor  22  are situated on a separating hill  34  that runs centrically between the two limbs of the U-shaped cross-section. This permits a comparatively simple contacting of contact segments  20   a,    20   b,    22   a,  and  22   b  using only the two printed conductors  20  and  22 . For this purpose, first printed conductor  20  can have a fork that surrounds trench  14  at least partly. In contrast, second printed conductor  22  extends at least partly on separating hill  34 . In this way, a parallel circuit of two trenches is realized that here significantly reduces the electrical resistance of the configuration by a factor of two. 
     As can be seen on the basis of the cross-section shown in  FIG. 3   b,  the at least one trench  14  can also be covered by a porous protective layer  36  (not shown in FIG.  3   a ). The at least one porous protective layer  36  is preferably made of an electrically insulating material such as aluminum oxide. The material of the at least one porous protective layer  36  can also extend into the at least one trench  14  over a height h. The at least one porous protective layer  36  can prevent an undesired contamination of the at least one trench  14 . Moreover, the at least one porous protective layer  36  also ensures a reliable hold of at least one particle, grain, and/or crystal  24  under it. The protective layer can also contain a catalyst that for example oxidizes a disturbing gas component (e.g. hydrogen, carbon monoxide) that is a disturbing factor in the detection of a second gas component such as nitrogen dioxide. Likewise, the catalyst, which is made of platinum or rhodium or one or more other noble metals or an alloy thereof, can for example oxidize nitrogen monoxide to nitrogen dioxide, which is then easier to detect. 
     In the cross-section shown in  FIG. 3   b,  heating lines  42  embedded in at least one insulating layer  38  and  40  can also be seen, which are preferably fashioned on a rear side  44  of substrate  10  oriented away from side  12 . 
     As an alternative to the fashioning of the at least one trench  14  with the U-shaped cross-section, it is also possible for only the limbs to be fashioned (as in each case a trench  14 ). The structuring of the connecting part can be omitted. 
       FIG. 4  shows a schematic representation of a fourth specific embodiment of the sensor component. 
     The specific embodiment of  FIG. 4  can be regarded as a development of  FIG. 3 . Bearer structures  46  and membrane structures  48  of the at least one material of substrate  10 , or at least one further material, are additionally fashioned on side  12  of substrate  10 . Membrane structures  48  can for example also be made of a silicon carbide or oxygen nitride. For example, a rear-side etching can be carried out to form structures  46  and  48 . Via the at least one membrane structure  48 , an undesired heat transport in a direction from the at least one trench  14  to the outer regions of substrate  10  can be reliably prevented. At the same time, membrane structures  48  protect functionalized regions, situated thereunder, of the substrate from contamination. Bearer structures  46  can additionally ensure a stable hold of the substrate material region  50  surrounding the at least one trench  14 . 
     It is to be noted that the represented realization of bearer structures  46  is to be interpreted only as an example. For example, bearer structures  46  can also have more than two arms. In a development, substrate  10  can also have at least one opening through which an air stream or liquid stream can flow. Substrate  10  can therefore be developed with a high degree of design freedom. 
       FIGS. 5 a  through 5 c    show schematic representations of a fifth specific embodiment of the sensor component. 
     In the specific embodiment of  FIGS. 5 a    through  5   c,  two heat plates  52  are fashioned that surround the two trenches  14 . A circuit  54  can also be fashioned on side  12  of substrate  10 . 
     Moreover,  FIGS. 5 b  and 5 c    show possible examples of the heating lines  42  that can be fashioned on rear side  44  of substrate  10 . For example, heating lines  42  can be fashioned as a double U structure in which an outer U-shaped segment surrounds an inner U-shaped segment ( FIG. 5 b   ). Equally, heating lines  42  can cover a surface of rear side  44  of substrate  10  in meander-shaped fashion ( FIG. 5 c   ). Heating lines  42  can for example have a width and/or height from 1 μm to 3 μm. In particular, bent segments of heating lines  42  can be made wider than straight segments of heating lines  42  in order to reinforce the heating effect in a targeted manner at particular surfaces. 
     The advantages of the above-indicated sensor components are also ensured in a gas and/or liquid sensor having such a sensor component. Such a gas and/or liquid sensor can be used for environmental protection, to monitor the atmosphere of a living space, and/or to monitor an exhaust gas/combustion gas. Due to its comparatively low energy consumption, such a gas and/or liquid sensor can also be used in a mobile device such as a mobile telephone or a tablet, or in a computer. A use of such a gas and/or liquid sensor in a vehicle is also advantageous because, due to the small extension of the sensor components, only comparatively little energy is required for its heating, so that the energy that can be provided by the vehicle battery is adequate for the operation of the gas and/or liquid sensor. 
       FIG. 6  shows a flow diagram illustrating a specific embodiment of the production method for a sensor component for a gas and/or liquid sensor. 
     The production method described below can be used for example to produce the above-indicated sensor components. However, the realization of the production method is limited to the production of such sensor components. 
     In a method step S 1 , at least one first printed conductor and a second conductor are fashioned on a substrate for the application of a voltage between the first printed conductor and the second printed conductor during (later) operation of the gas and/or liquid sensor. For this purpose, at least one trench is fashioned going through a side of the substrate, having at least one trench wall and at least one trench floor, each made of at least one electrically insulating material. A contact segment of the first printed conductor and a contact segment of the second printed conductor are fashioned on two inner side surfaces, at a distance from one another, of the at least one trench wall (of the same trench). 
     For the advantageous electrically insulating realization of the at least one trench wall and of the at least one trench floor, after a structuring of openings in the substrate, first a first insulating layer made of a first insulating material can be deposited on the whole surface on the side of the substrate on which the at least two printed conductors are formed. Subsequently, sub-areas of the first insulating layer can be removed from the floor surfaces of the openings, along with undesired excess parts of the printed conductors. For this purpose, the same etching mask can be used as is used in the formation of the openings. Subsequently, the at least one trench floor is formed by depositing a second insulating layer. 
     However, as an alternative to this an electrically insulating substrate can also be used to produce the sensor component. In this case it is not necessary to form the at least one trench floor and the at least one trench wall from additional insulating layers. Instead, the execution of a simple etching step is already sufficient to form the at least one trench having the at least one electrically insulating trench wall and the at least one electrically insulating trench floor. For example, an undoped and highly pure silicon substrate, a quartz substrate, and/or an electrically insulating ceramic substrate can be used for this purpose as the substrate. 
     To form the printed conductors, a comparatively thin coating of at least one metal and/or at least one doped semiconductor material can be deposited. 
     In a further method step S 2 , at least one sensitive semiconductor material, in the form of at least one particle, grain, and/or crystal, can be filled at least between the contact segment of the first printed conductor and the contact segment of the second printed conductor. The production of the at least one particle, grain, and/or crystal can take place in a separate chemical process, for example a crystal growth process, separately from the substrate. Thus, temperatures above 900°, which would cause damage to the substrate or to the at least one trench, can also be used during the chemical process. At least one particle, grain, and/or crystal can also be sintered. Subsequently, a coating method can be used to place at least one particle, grain, and/or crystal into the at least one trench. 
     In an optional method step S 3 , the sensor component (after the filling of the at least one particle, the at least one grain, and/or the at least one crystal made of the at least one sensitive semiconductor material into the at least one trench) can be heated to a temperature between 400° C. and 700° C. In order to further improve the hold of the at least one particle, grain, and/or crystal in the at least one trench, a sol-gel solution and/or some other conductive glue can also be deposited, for example in a spraying, sputtering, or vaporization step. 
     In a development, bearer structures and/or membrane structures can also be formed by etching, starting from a rear side of the substrate. A silicon nitride membrane left on the substrate can be used as an etching mask. Subsequently, the side of the bearer structure having the at least one trench can be formed. The printed conductors can then for example be laid over the silicon nitride membrane. 
       FIG. 7  shows a flow diagram illustrating a specific embodiment of the method for detecting at least one material in a gaseous and/or liquid medium. 
     The method for detecting at least one material in a gaseous and/or liquid medium can for example be carried out using the above-described sensor components. However, the realization of the method for detecting at least one material in a gaseous and/or liquid medium is not limited to the use of such sensor components. 
     In a method step S 10 , the medium is conducted into at least one trench going through a side of a substrate. The trench is fashioned with at least one trench wall and at least one trench floor, each made of at least one electrically insulating material. In the trench there are present, at two inner side surfaces at a distance from one another of the at least one trench wall, a contact segment of a first printed conductor and a contact segment of a second printed conductor, at least one sensitive semiconductor material, in the form of at least one particle, grain, and/or crystal, being filled into the at least one trench at least between the contact segment of the first printed conductor and the contact segment of the second printed conductor. With regard to the shapes and materials of the at least one trench and of the at least one particle, grain, and/or crystal, reference is made to the above statements. 
     An application of a voltage between the first printed conductor and the second printed conductor takes place in a method step S 11 . At the same time, in a method step S 12  a quantity is determined relating to a change in resistance that occurs between the contact segment of the first printed conductor and the contact segment of the second printed conductor. 
     In a method step S 13 , taking into account the determined quantity, a detectability is determined of the at least one material in the gaseous and/or liquid medium, a concentration is determined of the at least one material in the gaseous and/or liquid medium, and/or at least one chemical and/or physical property of the gaseous and/or liquid medium is determined.