Sensor element

Abstract

The invention relates to a sensor element (100) for contactlessly measuring a temperature, the sensor element comprising - at least one carrier (2), - at least one first functional layer (7a) for contactlessly measuring the temperature of an object, and at least one second functional layer (7b) for contact-based measurement of an ambient temperature, - at least one upper electrode (50), wherein a first contact region (c1) is formed between the upper electrode (50) and one of the two functional layers (7a, 7b), - at least one lower electrode (40), wherein a second contact region (c2) is formed between the lower electrode (40) and the functional layer (7a, 7b) that is in contact with the upper electrode (50), wherein said functional layer (7a, 7b), the at least one upper electrode (50), and the at least one lower electrode (40) are designed and positioned such that a specific electrical resistance of the sensor element (100) is achieved. The invention also relates to the use of the sensor element (100).

Description

[0001] Description

[0002] SENSOR ELEMENT

[0003] The present invention relates to a sensor element, in particular a temperature sensor for contactless temperature measurement.

[0004] To integrate passive components such as sensors, capacitors, protective devices, or heaters into electrical systems, the dimensions must be adapted to modern packaging designs, which are in the micrometer and even nanometer scale range. To achieve this level of miniaturization, the components are deposited as thin films on carrier structures with electrical connections and described as discrete components. These novel components can be integrated, for example, into MEMS (Micro Electro Mechanical System) structures.

[0005] According to the state of the art, temperatures for monitoring and control in a wide variety of applications are mainly measured using ceramic thermistor elements

[0006] (NTC), silicon temperature sensors (KTY), platinum temperature sensors (PRTD), or thermocouples (TC). NTC thermistors are the most widely used due to their low manufacturing costs. A further advantage over thermocouples and metallic resistance elements, such as Pt elements, is their pronounced negative resistance-temperature characteristic.

[0007] For non-contact temperature measurement of an object's temperature using an infrared sensor, it is necessary to measure the ambient temperature of the functional element (e.g., thermopile, bolometer, etc.) within the sensor. Inaccurate temperature measurement of the ambient temperature at the functional element leads to errors in interpreting the measured value. A separate element for measuring the ambient temperature is required in addition to the functional element.

[0008] The current state-of-the-art solution for ambient temperature measurement in contactless temperature sensors, such as thermopiles, is an NTC chip. This separate NTC chip must be installed in an additional process step and is therefore located at some / greater distance from the functional element.

[0009] The object of the present invention is to describe an improved sensor element.

[0010] This object is achieved by a sensor element according to the independent claim.

[0011] According to one aspect, a sensor element is described. The sensor element is suitable for contactless temperature measurement. The sensor element is an IR (infrared) temperature sensor. In particular, the sensor element is a TF (thin film) IR-NTC temperature sensor.

[0012] The sensor element has at least one carrier. Preferably, the sensor element has exactly one carrier. The carrier has a carrier material, preferably silicon, silicon carbide or glass (silica or borosilicate glass). Alternatively, the carrier material can also comprise AlN or Al2O3. The carrier has a top side and a bottom side. The top side is electrically insulating. Preferably, an insulating layer, for example SiO2 or SiAn4, is formed on the top side of the carrier.

[0013] The insulating layer is formed directly on top of the carrier and can be constructed from one or more layers.

[0014] The sensor element further comprises at least one first functional layer. The first functional layer is designed and arranged for contactless temperature measurement. In particular, the first functional layer is used to measure the temperature of an object contactlessly based on its emitted radiation.

[0015] The first functional layer is formed on the carrier, in particular on the insulating layer. The carrier mechanically stabilizes the first functional layer. The first functional layer is arranged in a first region / IR region of the carrier or the sensor element. The first region / IR region is also referred to below as the IR sensor.

[0016] The sensor element further comprises at least one second functional layer. The second functional layer is designed to measure, in particular for contact-based measurement, an ambient temperature. In particular, the second functional layer is designed and arranged to measure the temperature of the carrier.

[0017] The second functional layer is formed on the carrier, in particular on the insulating layer. The carrier mechanically stabilizes the second functional layer. The second functional layer is arranged in a second region / reference region of the carrier or the sensor element. The second region / reference region is also referred to below as the reference sensor.

[0018] The first and second functional layers are thin films (TF). The thickness of each functional layer is between 50 nm and 1 pm, preferably between 100 nm and 500 nm, particularly preferably between 250 nm and 400 nm.

[0019] The respective functional layer comprises a material (functional material) that has a specific electrical characteristic. The respective functional layer comprises a material with a temperature-dependent electrical resistance. The respective functional layer preferably comprises an NTC ceramic.

[0020] The NTC ceramic is preferably based on an oxide material with a perovskite or spinel structure. Alternatively, the respective functional layer can be based on a carbide or nitride material. Thin films of vanadium oxide or SiC represent another alternative.

[0021] The two functional layers are arranged spatially separated from one another on a single carrier. The carrier thus has two sensitive areas. In other words, the invention combines two sensors (IR sensor and reference sensor) in a very small space on a single chip.

[0022] There is no direct contact between the two functional layers. The two functional layers / sensors can, for example, be formed next to each other on the carrier. Alternatively, the second functional layer can surround the first functional layer. In other words, the reference sensor can be formed around the IR sensor.

[0023] By combining two sensitive areas on a single chip, the ambient temperature in the immediate vicinity of the IR sensor can be measured. This provides a particularly precise and compact sensor element.

[0024] The sensor element further comprises at least one upper electrode, for example, exactly one upper electrode. The upper electrode can be formed in the first region (IR region) or in the second region (reference region) of the sensor element.

[0025] The upper electrode is arranged at least partially directly above the functional layer of the respective region (i.e., above the first or second functional layer). The upper electrode is arranged at least partially on an upper side of the respective functional layer. A contact region (first or upper contact region) is formed between the upper electrode and the respective functional layer.

[0026] Ideally, the sensor element has at least two upper electrodes, in particular at least one first upper electrode (upper electrode of the IR sensor / in the first region) and at least one second upper electrode (upper electrode of the reference sensor / in the second region).

[0027] Of course, the sensor element can also comprise more than two upper electrodes, e.g., three, four, or more upper electrodes. The plurality of upper electrodes can be formed either all in one region (IR region or reference region) or in both regions of the sensor element. The (respective) upper electrode can comprise one or more layers of thin-film metals, wherein the materials include, for example, Cu, Au, Ni, Cr, Ag, Ti, W, Pd, or Pt.

[0028] If there are at least two upper electrodes, the respective upper electrode is arranged directly above the respective functional layer. In particular, the at least one first upper electrode is arranged above the first functional layer. The at least one second upper electrode is arranged above the second functional layer.

[0029] A contact region (i.e., the first contact region) is formed between the respective upper electrode and the respective functional layer. In other words, there is direct electrical and mechanical contact between the respective upper electrode and the respective functional layer.

[0030] The sensor element further comprises at least one lower electrode, for example, precisely one lower electrode. The lower electrode can be formed in the first region (IR region) or in the second region (reference region) of the sensor element. If precisely one lower electrode and one upper electrode are present, the lower electrode is arranged in the same region (IR region or reference region) as the one upper electrode.

[0031] The lower electrode is arranged at least partially beneath the functional layer in the respective region (first or second region). The lower electrode is arranged at least partially on an underside of the functional layer. This means that the upper and lower electrodes are formed on different sides of the respective functional layer (top and bottom of the functional layer). A contact region (second or lower contact region) is formed between the lower electrode and the respective functional layer.

[0032] Ideally, the sensor element has at least two lower electrodes. The sensor element then has, in particular, at least one first lower electrode (lower electrode of the IR sensor / in the first region) and at least one second lower electrode (lower electrode of the reference sensor / in the second region).

[0033] Of course, the sensor element can also comprise more than two lower electrodes, e.g., three, four, or more lower electrodes. The plurality of lower electrodes can be formed either all in one region (IR region or reference region) or in both regions of the sensor element.

[0034] The respective lower electrode may comprise single or multiple layers of thin-film metals, wherein the materials include, for example, Cu, Au, Ni, Cr, Ag, Ti, W, Pd, or Pt. The respective lower electrode may be arranged directly on top of the carrier or on the insulating layer.

[0035] The (respective) lower electrode is arranged at least partially directly or immediately beneath the respective functional layer. If there are at least two lower electrodes, the at least one first lower electrode is arranged at least partially beneath the first functional layer. The at least one second lower electrode is arranged at least partially beneath the second functional layer. A contact region (i.e. the second contact region) is formed between the respective lower electrode and the respective functional layer. In other words, there is a region with direct electrical and mechanical contact between the respective lower electrode and the respective functional layer.

[0036] The respective functional layer in question is arranged at least partially between the respective lower electrode and the respective upper electrode (sandwich structure or stacked structure). In particular, the first region and / or the second region of the sensor element have an electrode(s)-NTC-electrode(s)-stacked structure.

[0037] The sensor element has a specific nominal electrical resistance. More precisely, the sensor element has two nominal resistances (one for the IR sensor / IR range and one for the reference sensor / reference range), although these should ideally be equal. "Nominal resistance" refers to the nominal resistance of the respective range (IR sensor / first range or reference sensor / second range).

[0038] The first / second functional layer, the at least one upper electrode, and the at least one lower electrode are configured and / or arranged and / or connected such that a specific electrical nominal resistance can be achieved. In other words, the respective functional layer, the lower electrode, and / or the upper electrode comprise a specific material, a specific contact area, and / or a specific position relative to one another in order to control the resistance of the sensor element or the respective area. In this way, a very precise sensor element is provided.

[0039] Overall, the sensor element is also very compact, i.e., it has a miniaturized design, allowing it to be embedded directly into an electrical system as a discrete component. The term "discrete" in this context means that the sensor element can be integrated into electrical structures as a compact and self-contained system.

[0040] For example, the sensor element has a maximum edge length (length or width) of 2000 pm, preferably < 1500 pm. The thickness of the sensor element (extension in a stacking direction) is < 1000 pm, preferably < 700 pm, particularly preferably < 300 pm. For example, the component is designed for direct integration into a MEMS structure.

[0041] The two sensors combined in one sensor element (IR sensor and reference sensor) make it possible to determine the ambient temperature in the immediate vicinity of the IR sensor. This eliminates the need for an additional NTC chip, which would have to be assembled in an additional process step. This provides a very compact, cost-effective, sustainable, and precise sensor element.

[0042] According to one embodiment, the sensor element has at least one upper and at least one lower electrode, which are formed either in the IR range or in the reference range. In addition, the sensor element can have at least two interdigital electrodes in the other region of the sensor element for electrically contacting the functional layer that is free of contact with the upper electrode and the lower electrode. The two interdigital electrodes are formed at least partially beneath the relevant functional layer. Alternatively, the interdigital electrodes can also be formed on the relevant functional layer.

[0043] Furthermore, in this case, the sensor element can have two contact elements, each of which is arranged directly on at least a partial area of ​​one of the interdigital electrodes. The contact elements serve to electrically contact the sensor element.

[0044] Each interdigital electrode is designed as a thin-film electrode. Each interdigital electrode has a flat end region, with at least one contact element arranged on the flat end region of at least one of the electrodes. Each interdigital electrode also has a plurality of electrode fingers that form an interdigital structure with the electrode fingers of the other interdigital electrode.

[0045] According to one embodiment, the sensor element has a cavity in the carrier. In other words, a hollow space is formed in the carrier. In one embodiment, the cavity penetrates the carrier completely. In an alternative embodiment, an underside of the carrier is free of a cavity. Consequently, the underside of the carrier in this embodiment has a smooth profile. In other words, the cavity does not penetrate the carrier completely. The cavity is formed directly beneath the insulating layer. The insulating layer covers the cavity upwards (membrane structure). The cavity is formed in the first region / IR region of the carrier or of the sensor element. The cavity is located in the region of the first functional layer. In particular, the cavity is located at least partially beneath the first functional layer.

[0046] The cavity may have a smaller area than the area of ​​the first functional layer. In this context, "area" refers to an extension perpendicular to a stacking direction / thickness of the sensor element. Preferably, the cavity and the first functional layer occupy the same area. Ideally, the area of ​​the cavity is larger than the area of ​​the first functional layer.

[0047] The cavity is designed and arranged to thermally decouple the first functional layer (and all other components of the sensor element formed on the first functional layer) from the carrier. This reduces thermal losses to the carrier and enables a maximized temperature change at the first functional layer. This also maximizes the resistance change.

[0048] However, a complete decoupling of the first functional layer and the environment is not possible. This means that there is always a loss of heat to the environment. The temperature of the first functional layer will therefore differ from that of the object being measured. The greater the temperature difference between the first functional layer and the environment, the greater the thermal losses. This means that a reference sensor (second area) is necessary to measure the ambient temperature. In addition, heat transport via solids is significantly faster than via gases, which means that the main heat loss occurs via the carrier. Consequently, the influence of the carrier is dominant compared to the rest of the environment. It is therefore of particular interest to determine the temperature of the carrier (and thus of the environment) in order to be able to make a correction for the thermal losses.This is done via the reference sensor / the second functional layer in close proximity to the IR sensor.

[0049] According to one embodiment, a region of the carrier below the second functional layer is free of a cavity. In other words, no cavity is formed in the second region / reference region. In other words, the reference sensor has no cavity (in the carrier).

[0050] A cavity decouples the functional layer from the carrier. This delays the reaction time of the functional layer to changes in the carrier and makes it more easily affected by other influences. Without a cavity, the thermal interaction between the second functional layer and the carrier is consequently improved, and the temperature response time and stability are optimized. The thin-film structure of the functional layer has a significantly lower heat capacity than that of the carrier. This means that the carrier has a negligible influence on the carrier temperature. This also enables very precise measurement of the carrier temperature.

[0051] Overall, the cavity-free design of the reference sensor allows for fast, accurate, and stable ambient temperature determination. At the same time, mechanical stability is improved and design options are minimally restricted. For example, the first and second functional layers (IR sensor and reference sensor) can be positioned closer together compared to the state of the art, there is no weight limit for the membrane on the reference sensor, and so on. For example, the reference sensor can also surround the IR sensor for more uniform ambient temperature determination.

[0052] According to one embodiment, the sensor element further comprises at least one insulating layer. The sensor element may also comprise two, three, four, or a plurality of insulating layers. Alternatively, the sensor element may also be free of an insulating layer.

[0053] The insulating layer comprises an insulating material. The at least one insulating layer comprises a thin, non-conductive material, e.g., oxides, nitrides, ceramics, glasses, and polymers. The insulating layer can comprise SiO2, for example.

[0054] There are the following options where an insulating layer can be applied:

[0055] 1. Between the carrier and the respective lower electrode; In other words, the above-mentioned insulating layer on the carrier constitutes an insulating layer, and / or

[0056] 2. Between the lower electrode and the respective (first or second) functional layer and / or

[0057] 3. Between the respective functional layer and the upper electrode and / or

[0058] 4. Between the upper electrode and a contact pad connected to the upper electrode.

[0059] Accordingly, there can be between zero and four insulating layers. In other words, the insulating layer can at least partially cover a top surface of the sensor element. Additionally or alternatively, the insulating layer can at least partially cover a top surface of the respective lower electrode. Additionally or alternatively, the insulating layer can at least partially cover the top surface of the carrier (= insulating layer or insulating layer on the top surface of the carrier). The insulating layer can improve the long-term stability of the sensor element.

[0060] The insulating layer may comprise at least one window. The insulating layer may comprise more than one window, e.g., two or more windows. The at least one window forms a recess in the insulating layer. The window is designed and arranged such that electrical contact is possible between the (respective) upper electrode / the (respective) lower electrode and the respective functional layer. According to one embodiment, the sensor element further comprises at least one, preferably precisely one, absorber layer. The absorber layer is formed in the first region / IR region. The second region (reference region) is free of an absorber layer.

[0061] The absorber layer is formed above the first functional layer, as viewed in a stacking direction of the sensor element. The absorber layer is formed on the insulating layer, in particular directly on the insulating layer.

[0062] The absorber layer is preferably formed congruently with the first functional layer. This means that the surface area of ​​the absorber layer is as large as the surface area of ​​the first functional layer. Alternatively, the absorber layer can also partially extend beyond the first functional layer (on one side or both sides) or be smaller than it.

[0063] The absorber layer comprises a material that absorbs infrared radiation. The absorber layer is preferably made of an IR-absorbing material. Examples of materials suitable for the absorber layer include thin metal layers, dielectric materials (e.g., silicon oxide, silicon nitride, aluminum nitride, etc.), nanoporous metals, or polymers (e.g., polyimide resins, polymers with dispersed carbon particles, etc.).

[0064] The first functional layer / IR sensor measures the temperature of an object contactlessly based on its emitted radiation. The radiation is absorbed by the absorber layer, causing its temperature to change. The absorber layer is in thermal contact with the first functional layer. This changes the temperature of the first functional layer. This is expressed as a change in the material's resistance.

[0065] According to one embodiment, the sensor element further comprises at least one, preferably exactly one, reflector layer. The reflector layer is formed in the second region / reference region. The first region (IR region) is free of a reflector layer.

[0066] The reflector layer is formed above the second functional layer, viewed in a stacking direction of the sensor element. The reflector layer is formed on the insulating layer. In particular, the reflector layer is formed directly on the insulating layer. The reflector layer can be formed congruently with the second functional layer. This means that an area of ​​the reflector layer is as large as an area of ​​the second functional layer. Alternatively, the reflector layer can also partially project beyond the second functional layer (on one side or both sides) or be smaller than it.

[0067] The reflector layer comprises a material that reflects infrared radiation. The reflector layer preferably consists of a material that reflects IR radiation. The reflector layer preferably comprises metallic materials with a sufficient thickness. For example, the same material used for the upper electrode can also be used for the reflector layer. For example, the reflector layer comprises Au.

[0068] The reflector layer minimizes the influence of IR radiation on the reference sensor. Because the reflector layer reflects IR radiation, the temperature of the second functional layer changes little or not at all due to IR radiation incident on the reflector layer. This results in little or no change in the resistance of the material of the second functional layer due to the incident IR radiation. Consequently, the reflector layer ensures reliable operation of the reference sensor / second functional layer. This results in a very precise sensor element.

[0069] According to one embodiment, one of the upper electrodes functions as a reflector layer. In particular, an upper electrode formed above the second functional layer (i.e., in the second region / reference region) is designed such that it simultaneously assumes the function of a contact pad and the function of the reflector layer. An additional reflector layer is thus omitted. This allows the number of process steps for manufacturing the sensor element to be reduced. Thus, a particularly cost-effective sensor element with a simplified structure is provided.

[0070] According to one embodiment, the sensor element comprises at least two contact pads, for example three, four, or more contact pads. These can be arranged either in the first region or in the second region, or distributed across the two regions of the sensor element. Preferably, the sensor element has at least two first contact pads (upper electrodes) and at least two second contact pads (lower electrodes). The contact pads facilitate the electrical connection of the sensor element to the outside world.

[0071] The respective upper electrode can serve as a contact pad (i.e., as the first contact pad) of the sensor element for electrically contacting the sensor element. In this case, an additional / separate contact pad connected to the respective upper electrode is unnecessary. The respective upper electrode and the contact pad can form a single component of the sensor element.

[0072] Alternatively, the sensor element may also have separate contact pads that are electrically connected to the respective upper electrode. In this case, the respective upper electrode and the respective contact pad represent different material layers of the sensor element.

[0073] The respective lower electrode can also serve as a contact pad (i.e., a second contact pad) of the sensor element. In this case, an additional / separate contact pad connected to the respective lower electrode is unnecessary. The respective lower electrode and the contact pad can form a single component of the sensor element. This case is particularly suitable for wire bonding. If an insulating layer is present on top of the lower electrode, the lower electrode can be connected to a wire via a window in the insulating layer.

[0074] Alternatively, the sensor element comprises an additional / separate contact pad that is electrically connected to the respective lower electrode. If an insulating layer is present on top of the lower electrode, the respective (second) contact pad is connected to the respective lower electrode via a window in the insulating layer.

[0075] According to one embodiment, the resistance of the sensor element is determined / controlled by the size of the contact area between the respective upper electrode and the respective (ie first / second) functional layer, ie by the size of the respective first contact area.

[0076] For this purpose, the contact area between the respective lower electrode and the respective functional layer (second contact area) must be at least the same size as the contact area between the respective upper electrode and the respective functional layer (first contact area). Preferably, the second contact area is larger than the first contact area.

[0077] The larger contact area should be at least as large as the smaller one. Ideally, the larger contact area should have an additional width / extension equal to 8 times the thickness of the respective functional layer. Ideally, the size / width of the second contact area is greater than or equal to the size / width of the first contact area plus 3 times the thickness of the respective functional layer.

[0078] The size of the first contact area can be controlled by the size of a window arranged in the insulating layer on top of the sensor element.

[0079] According to one embodiment, a resistance of the sensor element is controlled by an area of ​​the respective upper electrode. This can be achieved, for example, by making the window size in the insulating layer larger than the area of ​​the respective upper electrode or by not having an insulating layer between the respective upper electrode and the respective functional layer.

[0080] According to one embodiment, a resistance of the sensor element is determined / controlled by the size of the contact area between the respective lower electrode and the respective functional layer (i.e., the second contact area). In this case, the second contact area is smaller than the first contact area.

[0081] Ideally, the size / width of the first contact area is greater than or equal to the size of the second contact area plus three times the thickness of the respective functional layer.

[0082] The size of the second contact region can be controlled by a manufacturing process of the lower electrode, i.e., during the manufacture of the sensor element. Additionally or alternatively, the size of the second contact region can be controlled by the size of a window arranged in an insulating layer that is at least partially applied between the respective lower electrode and the respective functional layer.

[0083] According to one embodiment, a resistance of the sensor element is jointly controlled / determined by the respective upper electrode and the respective lower electrode. The resistance can be limited by the size of the respective upper electrode and the size of the respective lower electrode.

[0084] In particular, the resistance is determined by the size of the first contact area and, at the same time, by the size of the second contact area. Additionally or alternatively, the resistance of the sensor element can be controlled / determined by a position of the respective upper electrode and the respective lower electrode relative to one another, in particular by an overlap area between the respective upper electrode and the respective lower electrode, more precisely by an overlap area between the first contact area and the second contact area.

[0085] According to one embodiment, the sensor element has at least two lower electrodes and at least four upper electrodes. These can be arranged either in the first region or in the second region, or distributed across the two regions of the sensor element. The resistance of the sensor element can be determined / controlled by the size of the first contact regions.

[0086] Alternatively or additionally, the resistance of the sensor element can be determined / controlled by a size of the second contact areas. Alternatively or additionally, the resistance of the sensor element can be determined / controlled by a relative position of the upper electrodes and the lower electrodes, and in particular by a size of the overlap areas between the upper electrodes and the lower electrodes, more precisely by the size of the overlap areas between the first contact areas and the second contact areas.

[0087] According to one embodiment, the sensor element comprises a plurality of upper electrodes, for example a plurality of first upper electrodes (upper electrodes of the IR sensor) and a plurality of second upper electrodes (upper electrodes of the reference sensor). In addition, the sensor element comprises a plurality of lower electrodes, for example a plurality of first lower electrodes (lower electrodes of the IR sensor) and a plurality of second lower electrodes (lower electrodes of the reference sensor). The upper electrodes and the lower electrodes are connected in series. This results in the current flowing multiple times through the respective functional layer, as if several smaller resistors were connected in series, which leads to a larger overall resistance of the sensor element.

[0088] The final resistance of the sensor element (nominal resistance) can be determined by the size of the first contact areas and / or by the size of the second contact areas. Additionally or alternatively, the resistance of the sensor element can be determined / controlled by a relative position of the upper electrodes and the lower electrodes, and in particular by the size of the overlap areas between the upper electrodes and the lower electrodes, more precisely by a size of the overlap areas between the first contact areas and the second contact areas.

[0089] Additionally or alternatively, the resistance of the sensor element can be determined / controlled by a number of resistors connected in series. This means that the resistance is controlled by controlling the number of current flows through the respective functional layer.

[0090] According to one embodiment, the sensor element has a narrow resistance tolerance, i.e., a small deviation range from the nominal resistance. To achieve the narrow resistance tolerance, the sensor element comprises at least one additional contact pad.

[0091] The additional contact pad is connected to at least one of the upper electrodes to further adjust the final resistance of the sensor element. In particular, the additional contact pad enables an additional / intermediate connection of at least one of the series-connected upper electrodes. An undesirable / excessively frequent current flow through the functional layer, which would increase the overall resistance of the sensor element, can thus be avoided.

[0092] Preferably, the additional contact pad extends beyond a surface of the respective functional layer. In particular, the additional contact pad is not arranged directly above the respective functional layer, but can be offset laterally.

[0093] According to one embodiment, the sensor element has a narrow resistance tolerance, i.e., a small deviation range from the nominal resistance. To achieve the narrow resistance tolerance, the sensor element also includes trimming electrodes. The trimming electrodes are additional electrodes that enable additional electrical connections to the upper electrodes.

[0094] The trimming electrodes are connected to the upper electrodes (specifically, only to certain upper electrodes). The trimming electrodes connect certain series-connected upper electrodes and leave other upper electrodes unconnected. This prevents unwanted / excessively frequent current flow through the functional layer, which would increase the overall resistance of the sensor element.

[0095] Preferably, the trimming electrodes are not arranged directly above the respective functional layer, but offset laterally.

[0096] According to one embodiment, at least one of the trimming electrodes is trimmed, i.e., the electrode material is at least partially removed, e.g., by laser cutting, sawing, or grinding, to fine-tune the resistance of the final sensor element. This geometry change allows the resistance to be modified to better match the nominal resistance.

[0097] According to one embodiment, the sensor element has a plurality of upper electrodes (for example, a plurality of first upper electrodes and a plurality of second upper electrodes) and at least two lower electrodes (first lower electrode / lower electrode of the IR sensor and second lower electrode / lower electrode of the reference sensor). The upper electrodes are connected in parallel. Alternatively, the sensor element can also comprise at least two upper electrodes (for example, first upper electrode and second upper electrode) and a plurality of lower electrodes. The lower electrodes are connected in parallel.

[0098] Alternatively, the sensor element may comprise a plurality of upper electrodes and a plurality of lower electrodes. These may be arranged either in the first region or in the second region, or distributed between the two regions of the sensor element. The upper electrodes and the lower electrodes are connected in parallel.

[0099] The resistance of the sensor element can be determined / controlled by the size of the respective first contact areas and / or by the size of the respective second contact areas. Additionally or alternatively, the resistance of the sensor element can be determined / controlled by a number of upper electrodes and lower electrodes connected in parallel.

[0100] According to one embodiment, the sensor element has a narrow resistance tolerance. This means that the sensor element has a very small deviation range from the nominal resistance. To achieve the narrow resistance tolerance, the sensor element further comprises trimming electrodes.

[0101] The trimming electrodes are connected to the upper electrodes (in particular, to all upper electrodes) in a row, a circle, or a spiral. The trimming electrodes can also be connected to any upper electrodes. Preferably, the trimming electrodes are not arranged directly above the respective functional layer, but rather offset laterally. At least one of the trimming electrodes can be further trimmed, e.g., with a laser, to fine-tune the resistance of the final sensor element, thereby eliminating certain resistances.

[0102] According to one embodiment, the respective upper electrode can be transparent. In particular, the upper electrode in the first region / the upper electrode of the IR sensor can be transparent. For example, the upper electrode of the IR sensor comprises ITO (indium tin oxide). This can reduce the reflection of IR radiation and increase the sensitivity of the IR sensor.

[0103] According to one exemplary embodiment, the electrodes formed in the first region (upper and lower electrodes) have a specific structure for thermal decoupling. In other words, the at least one lower electrode and at least one upper electrode of the IR sensor are designed and arranged such that heat transfer between the carrier and the first functional layer is minimized. Consequently, the electrodes in the first region can have a different structure than the electrodes in the second region, despite an analogous layer structure (electrode-NTC-electrode structure).

[0104] Preferably, the upper electrode is designed to be as narrow or thin as possible in a connection region between a bonding region (coupling region between the upper electrode / sensor element and an external application) and a connection region (coupling region between the upper electrode and the first functional layer). Alternatively or additionally, the upper electrode can be designed to be as long as possible in the connection region. For example, the upper and / or lower electrode of the IR sensor can be partially meander-shaped to achieve optimal thermal decoupling.

[0105] According to a further aspect, a use of a sensor element is described. The sensor element is in particular the IR sensor element described above. All features described in connection with the sensor element also apply to the use of the sensor element. The sensor element is used for temperature monitoring and / or temperature control, e.g. in the automotive sector or in so-called smart wearables (electronic objects that can be worn directly on the body, for example fitness trackers, data glasses, headphones, smartwatches, etc.). Since the sensor element has a certain nominal electrical resistance and a narrow resistance tolerance, very precise monitoring and / or control is possible.

[0106] The drawings described below are not to be considered to scale. Rather, individual dimensions may be enlarged, reduced, or distorted for clarity.

[0107] Elements that are identical or that perform the same function are designated by the same reference symbols.

[0108] It shows :

[0109] Figure 1 is a sectional view of the sensor element according to the invention,

[0110] Figure 2 shows a sectional view of the sensor element according to the invention according to a further embodiment, Figure 3 shows a sectional view of the sensor element according to the invention according to a further embodiment,

[0111] Figure 4 is a schematic plan view of a sensor element according to the invention according to a further embodiment.

[0112] Figure 5 is a perspective view of a portion of a sensor element according to the invention,

[0113] Figure 6 is a sectional view of the section from Figure 5,

[0114] Figure 7 is a sectional view of a portion of a sensor element according to the invention according to a further embodiment,

[0115] Figure 8 is a sectional view of a portion of a sensor element according to the invention according to a further embodiment,

[0116] Figure 9 is a sectional view of a portion of a sensor element according to the invention according to a further embodiment,

[0117] Figure 10 is a sectional view of a portion of a sensor element according to the invention according to a further embodiment,

[0118] Figure 11 is a sectional view of a portion of a sensor element according to the invention according to a further embodiment,

[0119] Figure 12 is a sectional view of a portion of a sensor element according to the invention according to a further embodiment,

[0120] Figure 13 is a sectional view of a portion of a sensor element according to the invention according to a further embodiment,

[0121] Figure 14 is a sectional view of a portion of a sensor element according to the invention according to a further embodiment,

[0122] Figure 15 is a sectional view of a portion of a sensor element according to the invention according to a further embodiment,

[0123] Figure 16 is a sectional view of a partial area of ​​a sensor element according to the invention according to a further embodiment, Figure 17 is a sectional view of a partial area of ​​a sensor element according to the invention according to a further embodiment,

[0124] Figure 18 is a sectional view of a portion of a sensor element according to the invention according to a further embodiment,

[0125] Figure 19 is a schematic plan view of the

[0126] Partial area according to Figures 17 , 18 ,

[0127] Figure 20 is a schematic plan view of a

[0128] Partial region of a sensor element according to the invention according to a further embodiment,

[0129] Figure 21 is a schematic plan view of a

[0130] Partial region of a sensor element according to the invention according to a further embodiment,

[0131] Figure 22 is a sectional view of a portion of a sensor element according to the invention according to a further embodiment,

[0132] Figure 23 is a sectional view of a partial area of ​​a sensor element according to the invention according to a further embodiment, Figure 24 is a schematic plan view of the

[0133] Partial area according to Figures 22 , 23 ,

[0134] Figure 25 is a schematic plan view of a sensor element according to the invention according to a further embodiment,

[0135] Figure 26 is a sectional view of the sensor element according to the invention according to a further embodiment,

[0136] Figure 27 is a perspective view of a

[0137] Partial area of ​​the sensor element according to Figure 26 .

[0138] Figures 1 to 27 show exemplary embodiments of a sensor element 100 according to the invention. The sensor element 100 is an NTC thin-film temperature sensor. The sensor element 100 is designed for contactless temperature measurement of an object and has a narrow resistance tolerance. The sensor element 100 is a TF IR-NTC temperature sensor with a specific nominal resistance.

[0139] The sensor element 100 has a top side 1a and a bottom side 1b. The sensor element 100 further has a carrier 2 with a top side 11 and a bottom side 12. The top side 11 of the carrier 2 has an insulating layer 8, for example comprising SiO2. A thickness of the insulating layer 8 can be between 50 nm and 1 pm, preferably between 250 nm and 600 nm. Ideally, the thickness is 500 nm. The carrier 2 is preferably a rectangle and can be square. A thickness T (extension in a stacking direction S) of the sensor element 100 is <1000 pm, preferably <700 pm, particularly preferably <300 pm (see Figures 1 and 6). For example, the sensor element 100 is designed for direct integration into a MEMS structure.

[0140] The sensor element 100, and thus also the carrier 2, have a first region B1 and a second region B2 (see, for example, Figures 1 and 4). The first region B1 is IR-sensitive (IR sensor 101) and the second region B2 is ambient temperature-sensitive (reference sensor 102). The sensor element 100 thus combines two sensitive regions on a single chip. An additional NTC chip for determining a reference temperature is therefore superfluous.

[0141] In the exemplary embodiments according to Figures 1 to 3, the two regions B1 and B2 are located at a spatial distance from one another on the carrier 2. A region lying between the regions B1, B2 is free of functional elements of the sensor element 100. In particular, the region lying between B1 and B2 is free of functional material.

[0142] In an alternative embodiment (Figure 4), the second region B2 can also surround the first region B1. In other words, the reference sensor 102 then surrounds the IR sensor 101. In this embodiment, too, an area lying between the regions B1, B2 is free of functional elements of the sensor element 100.

[0143] The IR sensor 101 measures the temperature of an object contactlessly based on its emitted radiation. The IR sensor 101 has a functional material (first functional layer 7a), which, in the embodiments shown in Figures 1 to 14, is formed directly on at least a portion of a lower electrode 40 (first lower electrode 40). The first functional layer 7a is an NTC thin film.

[0144] A contact region c2 (second or lower contact region c2) is formed between the first functional layer 7a and the first lower electrode 40. In this region, there is immediate / direct electrical and mechanical contact between the lower electrode 40 and the first functional layer 7a. The lower electrode 40 can itself function as a contact pad 40a or be connected to a separate contact pad 40a, as will be described in more detail later.

[0145] In the embodiments shown in Figures 1 to 14, the IR sensor 101 further comprises an upper electrode (first upper electrode 50). This is directly connected to the first functional layer 7a via a contact region (first or upper contact region c1). Consequently, in this region, there is immediate / direct electrical and mechanical contact between the first upper electrode 50 and the first functional layer 7a. The first upper electrode 50 can function as a contact pad 50a or be connected to a separate contact pad 50a, as will be described in more detail later.

[0146] The sensor element 100 has an insulating layer 8, already mentioned above. The insulating layer 8 can have multiple regions / sections, as will be explained later. An (IR) absorber layer 21 is located on the insulating layer. In this exemplary embodiment, the absorber layer 21 is congruent with the first functional layer 7a. This means that the absorber layer 21 and the first functional layer 7a have the same area (same extent in the xy direction, i.e., extent perpendicular to the stacking direction S of the sensor element 100 / perpendicular to the z direction).

[0147] However, the absorber layer 21 can also be larger than the first functional layer 7a and partially protrude beyond it (not explicitly shown). Alternatively, the absorber layer 21 can also be smaller than the first functional layer 7a (not explicitly shown).

[0148] The absorber layer 21 is thermally coupled to the first functional layer 7a and comprises an IR radiation-absorbing material. For example, the absorber layer 21 comprises a thin metal layer, a dielectric material (e.g., silicon oxide, silicon nitride, or aluminum nitride), a nanoporous metal, or a polymer (e.g., a polyimide resin or a polymer with dispersed carbon particles).

[0149] The absorber layer 21 is located exclusively in the first region B1, i.e., in the region of the IR sensor 101. This means that in the second region B2, no IR radiation-absorbing material is formed on the insulating layer 8.

[0150] The IR radiation impinging on the absorber layer 21 is absorbed by the absorber layer 21, resulting in a temperature change of the absorber layer 21. Due to the thermal coupling with the first functional layer 7a, this leads to a resistance change at the first functional layer 7a.

[0151] The IR sensor 101 further has a cavity 20 in the carrier 2. The cavity 20 is formed only in the first region B1. It extends neither into the second region B2 nor into the region between B1 and B2. In particular, the second region B2 (reference sensor 102) is completely free of a cavity in the carrier 2.

[0152] In the embodiment shown, the cavity 20 completely penetrates the carrier 2. In the embodiments shown in Figures 1 to 3, the cavity 20 is formed directly beneath the insulating layer / insulating layer 8.

[0153] Alternatively, the cavity 20 can also be formed such that it only partially penetrates the carrier 2 (not explicitly shown). In this case, the cavity does not extend from the top side 11 to the bottom side 12 of the carrier 2. The cavity 2 is formed starting from the bottom side 12 of the carrier 2. Thus, should the cavity 20 not completely penetrate the carrier 2, some carrier material is still in direct contact with the insulating layer 8.

[0154] Viewed in the stacking direction S, the cavity 20 is located below the first functional layer 7a. In the illustrated embodiment, an area (extension perpendicular to the stacking direction, i.e., in the xy direction) of the cavity 20 is approximately as large as an area of ​​the first functional layer 7a. However, the area of ​​the cavity 20 can also be smaller or larger than the area of ​​the first functional layer 7a (not explicitly shown).

[0155] The cavity 20 ensures that the first functional layer 7a is thermally decoupled from the carrier 2. This results in fewer thermal losses to the carrier 2 and enables a maximized temperature change at the first functional layer 7a. Thus, the resistance change of the first functional layer 7a is also maximized.

[0156] The second functional layer 7b is formed on the carrier 2 in close proximity to the first functional layer 7a. This layer is part of the reference sensor 102. The second functional layer 7b is an NTC thin film. The reference sensor 102 is designed to measure an ambient temperature and, in particular, a temperature of the carrier 2. The reference sensor 102 functions as a contact-type sensor.

[0157] The reference sensor 102 measures the temperature in the immediate vicinity of the IR sensor 101. Since complete decoupling of the IR sensor 101 (and in particular the first functional layer 7a) from the environment is not possible, there is always heat loss to the environment. Therefore, the temperature of the first functional layer 7a will differ from that of the object to be measured. The greater the temperature difference between the first functional layer 7a and the environment, the greater the thermal losses.

[0158] Therefore, a reference sensor 102 is necessary to measure the ambient temperature. Furthermore, heat transfer via solids is significantly faster than via gases, meaning that the main heat loss occurs via the carrier 2. Thus, the influence of the carrier 2 is dominant compared to the rest of the environment. Therefore, it is of particular interest to determine the temperature of the carrier 2 (and thus of the environment) in order to be able to make a correction for the thermal losses.

[0159] The reference sensor 102 has a functional material (second

[0160] Functional layer 7b) which, in the embodiments shown in Figures 1 to 14, is formed directly on at least a partial region of a lower electrode 40 (second lower electrode). A contact region c2 (second or lower contact region c2) is formed between the second functional layer 7b and the second lower electrode. In this region there is immediate / direct electrical and mechanical contact between the lower electrode 40 and the second functional layer 7b. The second lower electrode 40 can function as a contact pad 40a or be connected to a separate contact pad 40a, as will be described in more detail later.

[0161] In the embodiments shown in Figures 1 to 4, the reference sensor 102 has an upper electrode (second upper electrode 50). This is directly connected to the second functional layer 7b via a contact region (first or upper contact region c1). In this region, there is immediate / direct electrical and mechanical contact between the upper electrode 50 and the second functional layer 7b. The second upper electrode 50 can function as a contact pad 50a or be connected to a separate contact pad 50a, as will be described in more detail later.

[0162] In addition, a reflector layer 22 is also formed on the insulating layer 8. In this exemplary embodiment, the reflector layer 22 is congruent with the second functional layer 7b. This means that the reflector layer and the second functional layer 7b have an equally large area (same extent in the xy direction, i.e. extent perpendicular to the stacking direction S of the sensor element 100). However, the reflector layer 22 can also be larger than the second functional layer 7b and partially project beyond it (not explicitly shown). Alternatively, the reflector layer 22 can also be smaller than the second functional layer 7b (not explicitly shown).

[0163] The reflector layer 22 comprises a material that reflects IR radiation. For example, the reflector layer 22 comprises a Au layer with a sufficient thickness to reflect IR radiation.

[0164] The reflector layer 22 is located exclusively in the second region B2, i.e., in the region of the reference sensor 102. It does not extend into the region between B1 and B2. In particular, the first region B1 (IR sensor 101) is free of any component that reflects IR radiation.

[0165] The layer structure of the sensor element 100, and in particular the electrode structure and the insulating layer(s) 8, are illustrated in more detail below in conjunction with Figures 5 to 24. For the sake of simplicity, the figures essentially show only a partial region of the sensor element 100, i.e., only the first region B1 (IR sensor 101) or the second region B2 (reference sensor 102), which is intended to be clarified by the use of the reference symbols 7a / 7b (i.e., first or second functional layer 7a, 7b).

[0166] However, the structure described in connection with Figures 5 to 24 is present in both areas (IR sensor 101 / first area B1 and reference sensor 102 / second area B2) of the sensor element 100. Ideally, in the embodiments shown in Figures 1 to 24, the electrode structure of the two areas B1 and B2 is constructed analogously in order to design the IR sensor 101 and the reference sensor 102 as similarly as possible.

[0167] In an alternative embodiment (see Figures 26 and 27), the IR sensor 101 and the reference sensor 102 can also have different electrode structures. For example, the IR sensor 101 could have the electrode structure described below, and the reference sensor 102 could have two lower electrodes in the form of an interdigital structure (interdigital electrodes 4) and two contact elements 10, or vice versa, as will be described later in connection with Figures 26 and 27, respectively.

[0168] As already mentioned, the sensor element 100 according to Figures 1 to 3 has exactly two upper electrodes 50 (first and second upper electrodes 50) and exactly two lower electrodes 40 (first and second lower electrodes 40). In particular, each region B1, B2 of the sensor element 100 has a lower electrode 40 and an upper electrode 50.

[0169] Of course, the sensor element 100 can also comprise more upper electrodes 50 / lower electrodes 40, as described in the embodiments in connection with Figures 17 to 24.

[0170] The respective upper electrode 50 / lower electrode 40 may comprise single or multiple layers of thin-film metals, wherein the materials may be Cu, Au, Ni, Cr, Ag, Ti, W, Pd or Pt.

[0171] The respective lower electrode 40 is arranged directly / immediately on the upper side 11 of the carrier 2 (Figures 5 and 6) or on the insulating layer 8 arranged on the upper side 11 of the carrier 2 (see Figure 7). The respective lower electrode 40 is arranged between the carrier 2 and the respective functional layer 7a, 7b. The respective lower electrode 40 is arranged directly beneath the respective functional layer 7a, 7b. In other words, the respective lower electrode 40 is at least partially in direct electrical and mechanical contact with the respective functional layer 7a, 7b.

[0172] The contact region c2 (second or lower contact region c2) is formed between the respective lower electrode 40 and the respective functional layer 7a, 7b. The second contact region c2 is the region in which the respective functional layer 7a, 7b rests directly on the respective lower electrode 40.

[0173] The respective upper electrode 50 is arranged on top of the respective functional layer 7a, 7b, i.e., above the functional layer 7a, 7b. In other words, the respective functional layer 7a, 7b is embedded between the upper electrode 50 and the lower electrode 40.

[0174] The respective upper electrode 50 is at least partially in direct electrical and mechanical contact with the respective functional layer 7a, 7b. The contact region cl (first or upper contact region cl) is formed between the respective upper electrode 50 and the functional layer 7a, 7b. The first contact region cl is the region in which the upper electrode 5 rests directly on the functional layer 7a, 7b. As already mentioned, there can be several insulating layers 8. In the embodiment according to Figures 5 to 7, the sensor element 100 further comprises an insulating layer 8, which is arranged on an upper side 1a of the sensor element 1. This insulating layer 8 covers the upper side 1a at least partially, as can be seen, for example, from Figure 6. An insulating layer 8 further covers an upper surface of the respective lower electrode 40 with the exception of the contact region c2 between the lower electrode 40 and the respective functional layer 7a, 7b.An insulating layer 8 also covers an upper surface of the respective functional layer 7a, 7b with the exception of the contact region cl between the upper electrode 50 and the functional layer 7a, 7b.

[0175] The respective insulating layer 8 contains windows or cutouts 70. Since there can be several insulating layers 8, there can also be several windows 70. Between the lower electrode 40 and the functional layer 7a, 7b there is a window 70 (Figure 7). Between the lower electrode 40 and the contact pad 40a there can be another window (see Figure 3). Between the upper electrode 50 and the functional layer 7a, 7b there can be another window 70. Between the upper electrode 50 and the contact pad 50a there can also be a window 70 (see Figures 1 and 2). And theoretically the windows 70 can all be present at the same time. Just because one insulating layer 8 has a window 70 does not mean that another insulating layer 8 cannot also have one or more windows 70.

[0176] These windows 70 are designed and arranged so that they allow direct contact between the upper electrode 50 and the functional layer 7a, 7b and / or between the lower electrode 40 and the functional layer 7a, 7b and / or between the lower electrode 40 and the contact pad 40a, etc. In particular, in Figures 5 to 7, a

[0177] Window 70 is arranged directly below the upper electrode 50 to enable electrical contact between the upper electrode 50 and the functional layer 7a, 7b in the first contact region c1. Another window 70 is arranged directly above the lower electrode 40 to enable electrical contact between the lower electrode 40 and a contact pad 40a.

[0178] The respective insulating layer 8 can improve the long-term stability of the sensor element 100, particularly when the insulating layer 8 is arranged on an outer surface of the sensor element 100. An insulating layer thickness is between 50 nm and 1 pm, preferably between 200 nm and 600 nm, and ideally between 400 nm and 500 nm.

[0179] The respective insulating layer 8 comprises a thin, non-conductive material, for example comprising oxides, nitrides, ceramics, glasses and / or polymers.

[0180] As already mentioned, an insulating layer 8 covers the upper side 1a of the sensor element 100 with the exception of the contact pads 40a, 50a. The contact pads 40a, 50a facilitate the electrical contacting of the sensor element 100 and have a thickness of > 100 nm, preferably > 1 pm and ideally > 5 pm. The contact pads 40a, 50a comprise single- or multi-layer thin-film metals with materials such as Cu, Au, Ni, Cr, Ag, Ti, W, Pd or Pt.

[0181] The contact pads 40a, 50a are directly connected to the electrodes 40, 50. In the embodiment according to Figures 5 to 7, the contact pad 40a is directly connected to the lower electrode 40 via the window / recess 70. Furthermore, in this embodiment, the upper electrode 50 functions directly as the contact pad 50a. In other words, there is no additional first contact pad 50a connected to the upper electrode 50, as can be seen in Figures 5 to 7.

[0182] In an alternative embodiment (not explicitly shown), the lower electrode 40 can also function directly as a contact pad 40a. In other words, in this case, there is no additional second contact pad 40a connected to the lower electrode 40.

[0183] In an alternative embodiment (see Figure 8), a special electrode material can be used to contact the functional layer 7a, 7b and the upper electrode 50 to improve adhesion. In other words, in the embodiment according to Figure 8, a separate first contact pad 50a is provided, which electrically and mechanically contacts the upper electrode 50. The materials of the upper electrode 50 and the first contact pad 50a can be different.

[0184] In any case (Figures 5 to 8), the upper electrode 50 is connected directly via the window 70 in the insulating layer 8 to the upper side of the functional layer 7a or 7b in order to produce the contact region cl.

[0185] As can be seen from Figures 6 to 8, the current flow F occurs from the second contact pad 40a to the lower electrode 4 and further to the functional layer 7a, 7b and via the functional layer 7a, 7b to the upper electrode 50, 50a. The sensor element 100 has a specific resistance (nominal resistance). In the embodiment according to Figures 4 to 8, the resistance is determined and in particular limited by a size of the first contact area c1, i.e. the contact area between the upper electrode 50 and the functional layer 7a or 7b.

[0186] In order to limit the resistance through the first contact region cl, the second contact region c2 must have at least the same size as the first contact region cl. Preferably, the second contact region c2 is larger than the first contact region cl, as shown in Figures 4 to 8. In particular, a width of the second contact region c2 (extension of the second contact region c2 perpendicular to the stacking direction S) is equal to or larger than a width of the first contact region cl plus three times the thickness t of the respective functional layer 7a or 7b: c2 > cl + 3t.

[0187] The size / width of the first contact area cl is determined by the size of the window 70, which is arranged in the insulating layer 8 directly below the upper electrode 50. The larger the window 70, the larger the first contact area cl. The larger the first contact area cl, the lower the resistance of the sensor element 100.

[0188] If the window size is larger than the size of the area of ​​the first contact pad 50a and / or if an insulating layer 8 is missing (not explicitly shown), the resistance of the sensor element 100 can also be controlled via the area of ​​the upper electrode 50, wherein in the embodiment according to Figures 4 to 6 the resistance is also controlled via an area of ​​the upper electrode 50, since the upper electrode 50 functions as the first contact pad 50a. Figures 9 and 10 show a sectional view of a partial area of ​​the sensor element 100 according to a further embodiment. In this embodiment, the electrical resistance is controlled with the aid of the respective lower electrode 40. In particular, the resistance is determined by the size or width of the second contact area c2. The larger the contact area c2, the smaller the resistance of the sensor element 100.

[0189] To determine / control the resistance by the second contact region c2, the first contact region cl must have at least the same size as the second contact region c2. Preferably, the first contact region cl is larger than the second contact region c2 (see Figures 9 and 10). In particular, a width of the first contact region cl (extension of the first contact region cl perpendicular to the stacking direction S) is equal to or larger than a width of the second contact region c2 plus three times the thickness t of the respective functional layer 7a or 7b: cl 1 c2 + 3t.

[0190] In this embodiment, the size of the second contact area c2 is controlled by the manufacture of the sensor element 100, in particular during the manufacture of the lower electrode 40.

[0191] As can be seen from the embodiment in Figure 10, the lower electrode 40 is deposited starting from the carrier 2. The contact region c2 can now be defined either by the structure of the lower electrode 40 or, as in the figure, by a window 70 in an insulating layer 8. To create this window 70, a SiCl layer is deposited and, for example, a hole is etched into the SiCl. The functional layer 7a or 7b is then deposited over the hole. The lower electrode 40 is therefore a flat layer and the functional layer 7a or 7b fills the window 70. Subsequently, a further SiCt layer / insulating layer 8 is deposited and a further window 70 is created for the upper electrode / contact pad 50, 50a.

[0192] It should be noted that the images shown are a very rough description of the layer structure and that the windows actually result in a gradation in the layers above, with the layer thickness remaining the same regardless of the position.

[0193] Figures 11 and 12 show a sectional view of a partial region of the sensor element 100 according to a further embodiment. In this embodiment, the resistance is controlled by both the respective upper electrode 50 and the respective lower electrode 40. More precisely, the resistance is controlled by a size of the (respective) first contact region c1 between the upper electrode 50 and the functional layer 7a or 7b and by the size of the (respective) second contact region c2 between the lower electrode 40 and the functional layer 7a or 7b.

[0194] The resistance is controlled here analogously to the embodiments according to Figures 4 to 10, i.e. via the size of the contact regions c1, c2. In addition, the resistance can be controlled by the position of the first contact region c1 and the second contact region c2 relative to one another, in particular by an overlap region o perpendicular to the stacking direction S between the first and second contact regions c1, c2, as shown in Figures 11 and 12. The larger the overlap region o, the lower the resistance. Here too, as already described in connection with Figures 4 to 6, there are several insulating layers 8 and windows 70. As already described above, the insulating layer 8 can be present between the respective lower electrode 40 and the respective functional layer 7a, 7b in order to control the size of the second contact region c2 via a window 70 in the insulating layer 8.

[0195] By controlling the size of the contact areas cl, c2 and / or the position of the contact areas cl, c2 relative to one another, the nominal resistance of the sensor element 100 can be precisely controlled.

[0196] In this embodiment, the upper electrode 50 can also function as the first contact pad 50a, as shown in Figures 11 and 12. Alternatively, the upper electrode 50 and the first contact pad 50a can also consist of separate material layers, as shown in Figure 8.

[0197] Figures 13 to 16 show a sectional view of a partial region of the sensor element 100 according to a further embodiment. In this embodiment, the functional layer 7a or 7b is embedded between two upper electrodes 50 and a lower electrode 40, i.e., two upper electrodes 50 are formed in the first region B1 and in the second region B2.

[0198] This causes the current to flow through the NTC several times (see current flow F). The current flows through the left upper electrode 50 (left in Figure 13) through the functional layer 7a or 7b to the lower electrode 40. From the lower electrode 40, the electrical current flows along the lower electrode 40 to below the second upper electrode 50 (right in Figure 13). There, the current flows through the functional layer 7a or 7b to the upper electrode 50.

[0199] The resistance of the sensor element 100 can be controlled in the same way as in the embodiments described above, either by changing / controlling the first contact area c1, the second contact area c2, or by varying the position and size of the contact areas c1, c2. Here, too, the upper electrode 50 can be an additional layer (see Figures 15, 16) or be integral with the first contact pad 50a, i.e., the upper electrode 50 functions as the first contact pad 50a, as shown in Figures 11, 12.

[0200] Figures 17 and 18 show a sectional view of a partial region of the sensor element 100 according to a further embodiment. In this embodiment, a plurality of upper electrodes 50 and a plurality of lower electrodes 40 are used per region B1 / B2 and are connected in series. Thus, a plurality of upper electrodes 50 and lower electrodes 40 are present for the IR sensor 101 and for the reference sensor 102, and thus a plurality of first contact regions c1 and second contact regions c2, which may also be of different sizes.

[0201] The specific structure results in the current flowing multiple times through the respective functional layer 7a, 7b, as if several smaller resistors were connected in series, which leads to a larger total resistance (see current flow F in Figures 17, 18).

[0202] In this embodiment, two factors influence the final resistance of the sensor element 100: First, the first and second contact areas c1, c2, as mentioned in the embodiments described above. For example, the resistance can be controlled via the size of the first contact areas c1, by the design of the upper electrodes 50 or the size of the window 70 in the insulating layer 8, or by the second contact areas c2, or by the size and position of both the first and second contact areas c1, c2 simultaneously, as described above. The upper electrodes 50 can in turn either be an additional layer (not explicitly shown) or simultaneously function as the first contact pads 50a.

[0203] The other factor controlling resistance is the number of resistors connected in series. By limiting the number of resistors connected in series, the total resistance of the sensor element 100 can be determined.

[0204] This also allows for fine-tuning of the resistance after production. This fine-tuning ensures that the finished sensor element 100 exhibits a very small deviation range from the nominal resistance.

[0205] There are two options for fine-tuning:

[0206] One possibility is to provide trimming electrodes 80, as shown in Figure 19. The trimming electrodes 80 are separate / additional electrodes that are connected to specific upper electrodes 50 arranged in a row. Alternatively, the trimming electrodes 80 can also be connected to specific upper electrodes arranged in a circle or spiral, or to any upper electrodes (not explicitly shown). The trimming electrodes 80 are also connected to a contact pad 50a, as can be seen in Figure 19. The trimming electrodes 80 act like short-circuit electrodes. They connect specific / some upper electrodes 50 and omit other upper electrodes 50 that are arranged between the connected upper electrodes 50.

[0207] The more frequently the current flows through the respective functional layer 7a, 7b (current flow F, Figure 18), the higher the final resistance of the sensor element 100. By introducing the trimming electrodes 80, the current can be prevented from flowing through the functional layer 7a or 7b more frequently than intended. Specifically, for the embodiment shown in Figure 19, this means that in the upper row of the upper electrodes 50, it is possible to jump further to the right with the aid of the trimming electrodes 80, so that a current flow F through the functional layer 7a or 7b and the upper electrodes 50 arranged between them can be avoided. In this case, the overall resistance can be reduced.

[0208] For further fine-tuning and depending on the measured resistance, the trimming electrodes 80 connected to the upper electrode 50 can also be separated, e.g., with a laser. This means that the electrode material of the trimming electrodes 80 is at least partially removed, e.g., by laser cutting, sawing, or grinding, to fine-tune the resistance of the finished sensor element 100.

[0209] In Figure 19, for example, cutting the leftmost terminal would increase the resistance by the smallest increment, and each additional cut terminal would further increase the resistance. This allows for very good fine-tuning to the nominal resistance of the sensor element 100. Ideally, the trimming electrodes 80 are not arranged directly above the respective functional layer 7a, 7b, but rather laterally, as shown in Figure 19. In other words, the trimming electrodes 80 are not arranged directly above the top side of the functional layer 7a or 7b.

[0210] The embodiment in Figure 19 also shows that all upper electrodes 50 contact the lower electrode 40 via the respective functional layer 7a, 7b. However, this is not required, and only a portion of the upper electrodes 50 can be arranged on the respective functional layer 7a, 7b and touch the lower electrode 40, as shown, for example, in Figure 20. This would be particularly interesting for trimming electrodes by laser cutting, as it allows for even smaller steps in fine-tuning the resistance.

[0211] The second way to fine-tune the resistance of the sensor element 100 is to provide additional contact pads 90 that are connected to the upper electrodes 50 at other locations. This is shown in Figure 21. The additional contact pads 90 are another way to directly contact (certain) upper electrodes 50 without having to introduce trimming electrodes 80.

[0212] Depending on which additional contact pads 90 are used for the second connection, the resistance can be fine-tuned to achieve the target / nominal resistances. In the embodiment shown, the first contact pad 50a would be the left electrode and the second contact pad would be either the upper left contact pad 90 (lowest resistance), the upper right contact pad 90 (slightly higher resistance), or the right contact pad 90 (highest resistance) for fine-tuning to the target resistances. Ideally, the contact pads 50a, 90, which are intended for electrically contacting the sensor element 100 with an external source, are not located completely above the respective functional layer 7a, 7b, but protrude beyond the functional layer 7a, 7b, as shown in Figure 21.

[0213] Figures 22 and 23 show a sectional view of a partial region of the sensor element 100 according to another embodiment. In this embodiment, several upper electrodes 50 and one lower electrode 40 are provided per region B1 / B2 and are connected in parallel. This allows the current to flow through the respective functional layer 7a, 7b at several points simultaneously, as shown in Figures 22, 23 (see current flow F).

[0214] Here too, two factors influence the total resistance of the sensor element 100 :

[0215] First, as described in the previous embodiments, the size and relative position of the contact areas c1, c2. The second factor is the number of electrodes 40, 50 connected in parallel. In this embodiment, it is also possible to trim the electrodes and fine-tune the resistance after the sensor element 100 has been manufactured. An example of fine-tuning is shown in Figure 24.

[0216] The sensor element 100 shown in Figure 24 has a lower electrode 40 and a plurality of upper electrodes 50 per area B1 / B2. This embodiment also features trimming electrodes 80 which are connected in series to all upper electrodes 50 of an area B1 / B2. The trimming electrodes 80 can be trimmed by laser cutting in order to adjust the final resistance of the sensor element 100 and thus obtain a sensor element 100 with a small deviation range from the nominal resistance. By laser cutting the trimming electrodes 80, individual resistors can be removed, thereby increasing the overall resistance of the sensor element 100. The adjustment is preferably carried out in an area which is not directly above the respective functional layer 7a, 7b.

[0217] The lower electrode 40 can also be divided into several electrodes for each region B1 / B2, while maintaining the parallel connection. Alternatively, the structure can also be implemented in a mirror image with several lower electrodes 40 and one large upper electrode 50 per region B1 / B2 (not explicitly shown). In this case, the upper electrode 50 can also be divided into several electrodes while maintaining the parallel connection.

[0218] In the embodiment shown in Figure 1, the sensor element 100 has a separate reflector layer 22 as described above. In particular, the reference sensor 102 has a reflector layer 22 in addition to the contact pads 40a, 50a of the reference sensor 102.

[0219] Alternatively, as shown in Figure 2, one of the contact pads (here contact pad 50a) of the reference sensor 102 can also take on the function of the reflector layer 22. In other words, one of the contact pads of the reference sensor 102 can be designed such that it reflects IR radiation (IR radiation-reflecting contact pad 50a, 22 in Figure 2). A separate reflector layer 22 is omitted in this case. For this purpose, one of the contact pads of the reference sensor 102, i.e. a contact pad in the second region B2, is designed such that it extends at least partially over the insulating layer 8. Unlike the other contact pads 40a, 50a, the contact pad functioning as a reflector layer is therefore located at least partially on the insulating layer 8.

[0220] The contact pad acting as a reflector layer is designed such that its area approximately corresponds to the area of ​​the second functional layer 7b and is preferably larger than the area of ​​the second functional layer 7b. The thickness of the reflected contact pad can also be adjusted, in particular increased, compared to the other contact pads of the sensor element 100. In contrast to the other contact pads, the contact pad acting as a reflector layer has IR radiation-reflecting properties.

[0221] In one exemplary embodiment, one of the contact pads 40a, 50a of the IR sensor 101 and one of the contact pads 40a, 50a of the reference sensor 102 can also be combined to form a single contact pad (combined contact pad 103, Figure 3). Thus, the sensor element 100 according to Figure 3 has a total of two lower electrodes 40 and three contact pads 40a, 50a, 103. In this case, the combined contact pad 103 is electrically and mechanically connected to the two lower electrodes 40.

[0222] Combining the two upper electrodes 50 (upper electrode 50 of IR sensor 101 and upper electrode 50 of reference sensor 102) into a single combined electrode is also possible (not explicitly shown). In one exemplary embodiment, the upper electrode 50 / upper contact pad 50a of IR sensor 101 is transparent. For example, the upper electrode / contact pad 50a can comprise ITO. This can reduce the reflection of IR radiation and increase the sensitivity of IR sensor 101.

[0223] In the exemplary embodiment according to Figure 25, the electrodes 40, 50 of the first region B1 (IR sensor 101) also have a specific structure that serves to provide thermal decoupling between the carrier 2 and the first functional layer 7a. In other words, the structure of the respective upper electrode 50 / lower electrode 40 can be different depending on their position on the carrier 2 (first region B1 or second region B2), although both regions B1 and B2 have an electrode-NTC layer structure.

[0224] In the IR sensor area (first area Bl), the goal is to achieve the maximum possible temperature difference through the incident light. Since the sandwich structure (lower electrode 40 - functional layer 7a - upper electrode 50) results in large areas with metal contacts that exhibit good thermal conductivity, it is desirable to provide thermal decoupling.

[0225] The heat conduction between the carrier 2 and the first functional layer 7a can be reduced as much as possible by the upper electrode 50 having a narrow (preferably < 5 pm, ideally < 1 pm) electrical connection region 105 between a bonding region 104 (i.e. a coupling region between the upper electrode 50, 50a / sensor element 100 and an external application) and the first functional layer 7a. In other words, in a connection region 105 between the bonding region 104 and a connection region 106 to the first functional layer 7a, the upper electrode 50 is long and narrow (width < 5 pm, ideally < 1 μm). The upper electrode 50 can also be wound in the connection region 105. For example, the upper electrode 50 has a meandering structure in the connection region 105.

[0226] Thus, the upper electrode 50 of the IR sensor 101 is structured differently and in particular has several areas:

[0227] - At least one flat area (bonding area 104): large area, for example square;

[0228] - At least one long and narrow, for example also winding / meandering area (connecting area 105 ): small area, preferably winding;

[0229] - a connection region 106 in which the upper electrode 50 is directly connected to the first functional layer 7a: the size of the area lies between the area of ​​the bonding region 104 and the connection region 105, for example square shape.

[0230] The regions 104, 105, 106 of the upper electrode 50 merge directly into one another. The connecting region 105 is formed between the bonding region 104 and the connection region 106.

[0231] Likewise, the lower electrode 40 of the IR sensor 101 / of the first region B1 can also be structured to achieve good thermal decoupling. As can be seen from Figure 25, the lower electrode 40 can also have a long, narrow, for example, twisted (meander-shaped) region (connection region 107), which directly adjoins a large-area region of the lower electrode 40. This allows the influence of the carrier 2 on the IR sensor region / first functional layer 7a to be further minimized.

[0232] Figure 26 shows a sectional view of the sensor element 100 according to another exemplary embodiment. In the reference region B2, the sensor element 100 has the above-described structure with an upper electrode 50 and a lower electrode 40 (sandwich or stacked structure). An alternative electrode structure is formed in the IR region B1.

[0233] In particular, the sensor element 100 has two interdigital electrodes 4 in the first region B1 (IR sensor 101), as can be seen from Figure 27. The two interdigital electrodes 4 are formed spaced apart from one another on the insulating layer 8 of the carrier 2 and have thin metal films.

[0234] The interdigital electrodes 4 are designed as interdigital thin-film electrodes. They each have a flat end region 6 and a region with electrode fingers 5. The region with the electrode fingers 5 is formed in a central region of the carrier 2 and in particular of the first region B1. The flat end region 6 and the region with the electrode fingers 5 merge into one another. The two interdigital electrodes 4 each engage with one another in the region of the electrode fingers 5 in the central region of the carrier 2 and form an interdigital structure there. The IR sensor 101 furthermore has two contact elements 10. The interdigital electrodes 4 are contacted via windows 70 in the insulating layer 8 by means of the contact elements 10.As an alternative to the embodiment shown, the IR sensor 101 can also have the stack structure described in connection with Figures 1 to 25, comprising lower electrode 40 - first functional layer 7a - upper electrode 50, and the reference sensor 102 can have contact via interdigital electrodes 4 and contact elements 10 according to Figures 26, 27 (not explicitly shown).

[0235] The IR sensor element 100 described in connection with Figures 1 to 27 can be used for contactless temperature measurement. The sensor element 100 is used for temperature monitoring and / or temperature control, e.g., in the automotive sector or in so-called smart wearables (electronic items worn directly on the body, such as fitness trackers, data glasses, headphones, smartwatches, etc.). Since the sensor element 100 has a specific electrical nominal resistance and a narrow resistance tolerance, very precise monitoring and / or control of the temperature is possible.

[0236] The description of the objects specified here is not limited to the individual specific embodiments. Rather, the features of the individual embodiments can be combined with one another as desired—provided technically feasible.

[0237] Reference symbol list

[0238] 100 Sensor element la Top of the sensor element lb Bottom of the sensor element

[0239] 2 carriers

[0240] 4 Interdigital electrode

[0241] 5 electrode fingers

[0242] 6 End area

[0243] 7a First functional layer

[0244] 7b Second functional layer

[0245] 8 I insulating layer

[0246] 10 Contact element

[0247] 11 Top of the carrier

[0248] 12 Underside of the carrier

[0249] 20 cavities

[0250] 21 Absorber layer

[0251] 22 Reflector layer

[0252] 40 Lower electrode

[0253] 40a Second contact pad

[0254] 50 Upper electrode

[0255] 50a First contact pad

[0256] 70 windows

[0257] 80 trimming electrode

[0258] 90 Additional contact pad

[0259] 101 IR sensor

[0260] 102 Reference sensor

[0261] 103 Combined contact pad

[0262] 104 Bond area

[0263] 105 Connection area

[0264] 106 connection area

[0265] 107 Connection area

[0266] S Stacking direction Bl First area / IR area of ​​the carrier / sensor element

[0267] B2 Second area / reference area of ​​the wearer / the

[0268] Sensor elements T Thickness of the sensor element t Thickness of the functional layer o Overlap area between upper electrode and lower electrode cl Contact area between upper electrode and functional layer / first or upper contact area c2 Contact area between lower electrode and functional layer / second or lower contact area

[0269] F Current flow

Claims

Claims 1. Sensor element (100) for contactless measurement of a temperature comprising - at least one carrier (2) with a top side (11) and a bottom side (12), - at least one first functional layer (7a) for contactless temperature measurement of an object and at least one second functional layer (7b) for contact-based measurement of an ambient temperature, wherein the respective functional layer (7a, 7b) comprises a material with a temperature-dependent electrical resistance and wherein the functional layers (7a, 7b) are arranged separately from one another on the carrier (2), - at least one upper electrode (50), wherein a first contact region (cl) is formed between the upper electrode (50) and one of the two functional layers (7a, 7b), - at least one lower electrode (40), wherein a second contact region (c2) is formed between the lower electrode (40) and that functional layer (7a, 7b) which is in contact with the upper electrode (50), wherein the respective functional layer (7a, 7b), the at least one upper electrode (50) and the at least one lower electrode (40) are designed and arranged such that a specific electrical resistance of the sensor element (100) is achieved.

2. Sensor element (100) according to claim 1, further comprising: - at least two interdigital electrodes (4) for electrically contacting the functional layer (7a, 7b) which is free from contact with the upper electrode (50) and the lower electrode (40), - at least two contact elements (10) for electrically contacting the sensor element (100), wherein in each case one contact element (10) is arranged directly on at least a partial area of ​​one of the interdigital electrodes (4).

3. Sensor element (100) according to claim 1, comprising - at least two upper electrodes (50), wherein a first contact region (cl) is formed between one of the upper electrodes (50) and a functional layer (7a, 7b), and - at least two lower electrodes (40), wherein in each case a second contact region (c2) is formed between one of the lower electrodes (40) and a functional layer (7a, 7b), wherein the respective functional layer (7a, 7b) is arranged at least partially between at least one of the at least two lower electrodes (40) and at least one of the at least two upper electrodes (50).

4. Sensor element (100) according to one of the preceding claims, wherein the first functional layer (7a) is formed in a first region (B1) of the carrier (2) and wherein the second functional layer (7b) is formed in a second region (B2) of the carrier (2).

5. Sensor element (100) according to one of the preceding claims, wherein the second functional layer (7b) is designed and arranged to measure a temperature of the carrier (2).

6. Sensor element (100) according to one of the preceding claims, further comprising an insulating layer (8) on the top side (11) of the carrier (2) and a cavity (20) in the carrier (2), wherein the cavity (20) is located below the insulating layer (8) and wherein the cavity (20) is in a first region (Bl) of the sensor element (100) and at least partially below the first functional layer (7a).

7. Sensor element (100) according to one of the preceding claims, wherein a region of the carrier (2) below the second functional layer (7b) is free of a cavity.

8. Sensor element (100) according to one of the preceding claims, further comprising an insulating layer (8), wherein the insulating layer (8) at least partially covers an upper side (1a) of the sensor element (100) and / or at least partially covers an upper side of the respective lower electrode (4) and / or at least partially covers an upper side (11) of the carrier (2).

9. Sensor element (100) according to one of the preceding claims, further comprising at least one absorber layer (21), wherein the absorber layer (21) is formed above the first functional layer (7a) as seen in a stacking direction (S) of the sensor element (100).

10. Sensor element (100) according to claim 8 and claim 9, wherein the absorber layer (21) is formed on the insulating layer (8).

11. Sensor element (100) according to claim 9 or 10, wherein the absorber layer (21) is in thermal contact with the first functional layer (7a).

12. Sensor element (100) according to one of claims 9 to 11, wherein the absorber layer (21) comprises a material which absorbs infrared radiation.

13. Sensor element (100) according to one of the preceding claims, further comprising at least one reflector layer (22), wherein the reflector layer (22) is formed above the second functional layer (7b) as seen in a stacking direction (S) of the sensor element (100).

14. Sensor element (100) according to claim 13 and claim 8, wherein the reflector layer (22) is formed on the insulating layer (8).

15. Sensor element (100) according to claim 13 or 14, wherein the reflector layer (22) comprises a material which reflects infrared radiation.

16. Sensor element (100) according to one of claims 13 to 15, wherein one of the upper electrodes (50) functions as a reflector layer (22).

17. Sensor element (100) according to one of claims 8 to 16, comprising at least one window (70), wherein the at least one window (70) represents a recess in the at least one insulating layer (8), wherein the at least one window (70) is designed and arranged to form an electrical connection between the respective lower electrode (40) and the respective functional layer (7a, 7b) and / or between the respective upper electrode (50) and the respective functional layer (7a, 7b).

18. Sensor element (100) according to one of the preceding claims, wherein the upper electrode (50) is designed as a first contact pad (50a) of the sensor element (100) functions to electrically contact the sensor element (1) and / or wherein the sensor element (100) has at least one first contact pad (50a) which is electrically connected to the upper electrode (50).

19. Sensor element (100) according to one of the preceding claims, wherein the lower electrode (40) functions as a second contact pad (40a) of the sensor element (100) and / or wherein the sensor element (100) has at least one second contact pad (40a) which is electrically connected to the lower electrode (40).

20. Sensor element (100) according to claim 18, wherein a resistance of the sensor element (100) is determined by an area of ​​the first contact pad (50a).

21. Sensor element (100) according to one of the preceding claims, wherein a resistance of the sensor element (100) is determined by a size of the first contact region (cl) formed between the respective upper electrode (50) and the respective functional layer (7a, 7b).

22. Sensor element (100) according to claim 21, wherein the second contact area (c2) has at least the same size as the first contact area (cl).

23. Sensor element (100) according to claim 21 or 22, wherein a width of the second contact region (c2) is equal to or greater than a width of the first contact region (cl) plus three times a functional layer thickness (t): c2 > cl + 3t.

24. Sensor element (100) according to one of claims 21 to 23, wherein the size of the first contact region (cl) is determined by a size of a window (70) arranged in an insulating layer (8) on an upper side (1a) of the sensor element (100).

25. Sensor element (100) according to one of claims 1 to 19, wherein a resistance of the sensor element (100) is determined by a size of the second contact area (c2) and wherein the second contact area (c2) is smaller than the first contact area (c1).

26. Sensor element (100) according to claim 25, wherein a width of the first contact region (cl) is equal to or greater than a width of the second contact region (c2) plus three times a functional layer thickness (t): cl 1 c2 + 3t.

27. Sensor element (100) according to claim 25 or 26, wherein the size of the second contact region (c2) is determined by a manufacturing process of the lower electrode (40) and / or by a size of a window (70) arranged in an insulating layer (8) arranged at least partially on the upper side of the lower electrode (40).

28. Sensor element (100) according to one of claims 1 to 19, wherein a resistance of the sensor element (100) is determined by a size of the first contact region (cl) and by a size of the second contact region (c2) and / or by a position of the first contact region (cl) and the second contact region (c2) relative to one another.

29. Sensor element (100) according to claim 28, wherein the resistance of the sensor element (100) is determined by a size of an overlap area (o) between the first contact area (c1) and the second contact area (c2).

30. Sensor element (100) according to one of claims 1 to 19, comprising at least two upper electrodes (50), wherein a resistance of the sensor element (100) is controlled by a size of the respective first contact area (cl) and / or by a size of the respective second contact area (c2) and / or by a relative position of the respective first contact area (cl) and the respective second contact area (c2) and / or by a size of overlap areas (o) between the respective first contact area (cl) and the respective second contact area (c2).

31. Sensor element (100) according to one of claims 1 to 19, comprising a plurality of upper electrodes (50) and a plurality of lower electrodes (40) connected in series, wherein a resistance is determined - by a size of the respective first contact area (cl) and / or - by a size of the respective second contact area (c2) and / or - by a relative position of first contact areas (cl) and second contact areas (c2) and / or - by a size of overlap areas (o) between first contact areas (cl) and second contact areas (c2) and / or - by a number of resistors connected in series.

32. Sensor element (100) according to claim 31, having a narrow resistance tolerance, wherein the sensor element (100) further comprises at least one additional contact pad (90) connected to at least one of the upper electrodes (50) for fine-tuning the resistance of the sensor element (100), wherein the additional contact pad (90) extends beyond a surface of the respective functional layer (7a, 7b).

33. The sensor element (100) of claim 31, having a tight resistance tolerance, wherein the sensor element (100) further comprises trimming electrodes (80) connected to certain upper electrodes (50), wherein at least one of the trimming electrodes (80) is cut with a laser to fine-tune the resistance of the final sensor element (100).

34. Sensor element (100) according to one of claims 1 to 19, comprising a plurality of parallel-connected upper electrodes (50) and at least two lower electrodes (40) or comprising at least two upper electrodes (50) and a plurality of parallel-connected lower electrodes (40) or comprising a plurality of parallel-connected upper electrodes (50) and a plurality of parallel-connected lower electrodes (40), wherein a resistance of the sensor element (100) is determined - by a size of the first contact areas (cl) and / or - by a size of the second contact areas (c2) and / or - by a number of upper electrodes (50) and lower electrodes (40) connected in parallel.

35. The sensor element (100) of claim 34, having a tight resistance tolerance, wherein the sensor element (100) further comprises trimming electrodes (80) connected in series to the upper electrodes (50), and wherein at least one of the trimming electrodes (80) is cut by a laser to fine-tune the resistance of the final sensor element (100).

36. Sensor element (100) according to one of claims 4 to 35, wherein the first region (B1) represents an IR sensor (101) and the second region (B2) represents a reference sensor (102), and wherein the second region (B2) surrounds the first region (B1).

37. Sensor element (100) according to one of claims 4 to 36, wherein the first region (B1) has an electrode-NTC-electrode stack structure and / or wherein the second region (B2) has an electrode-NTC-electrode stack structure.

38. Sensor element (100) according to one of claims 4 to 37, wherein the at least one lower electrode (40) and / or at least one upper electrode (50) formed in the first region (B1) has a specific structure for thermal decoupling.

39. Sensor element (100) according to one of claims 4 to 38, wherein the at least one upper electrode (50) formed in the first region (B1) is transparent.

40. Use of a sensor element (100) according to one of the preceding claims for temperature monitoring and / or temperature control.

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