Sensor element and method for producing a sensor element

Abstract

The invention relates to a sensor element (10) for measuring temperatures, comprising at least one carrier (11) having an upper side (18) and an underside (19), an insulating layer (12) being formed on the upper side (19) of the carrier (11), at least two electrodes (13a, 13b) being formed on the carrier (11) at a distance from one another, at least one functional layer (15) having a material having a temperature-dependent resistance, wherein the at least one functional layer (14) is arranged at least partially between the electrodes (13a, 13b),-at least two intermediate layers (14) having an insulating material,-at least two contact discs (16a, 16b) for electrically contacting the sensor element (10), the sensor element (10) being designed for direct integration as a discrete component into an electrical system, the sensor element (10) has a small deviation range from a desired resistance, and at least one of the at least two electrodes (13a, 13b) is structured to set a resistance value. The invention further relates to a method for producing a sensor element (10).

Description

Technical Field

[0001] The invention relates to a sensor element, in particular a temperature sensor. The invention also relates to a method for producing at least one sensor element, preferably a temperature sensor. Background Art

[0002] In order to integrate passive components such as sensors, capacitors, protective devices or heaters into electrical systems, the dimensions must be adapted to modern packaging designs in the micrometer and even nanometer range. In order to achieve this degree of miniaturization, the components are deposited as thin films on carrier structures with electrical interfaces and are described as discrete components. These novel components can be integrated in particular into different circuit boards, MEMS (Mikro Elektro Mechanisches System) or SESUB (Semiconductor Embedded in Substrate) structures.

[0003] The increasing demands on temperature measurement accuracy require tight tolerances on the resistance dispersion of such sensor elements. However, as these structures become smaller and smaller, manufacturing tolerances have an increasing influence, resulting in a dispersion of the resistance that exceeds the required tolerance. The resistance dispersion can only be reduced to a limited extent via process control.

[0004] According to the prior art, the temperature for monitoring and regulation in various applications is mainly measured by means of ceramic thermal conductor thermistor elements (NTC), silicon temperature sensors (KTY), platinum temperature sensors (PRTD) or thermocouples (TC). Here, NTC thermistors are the most widely used due to their low manufacturing costs. Another advantage compared to thermocouples and metal resistance elements, such as Pt elements, is the obvious negative resistance-temperature characteristic.

[0005] For use in power modules, soldered SMD ("surface mounted device") NTC temperature sensors are mainly used. In control modules for low power, NTC chips are also used as an alternative to this, which are mounted on the bottom side by means of Ag sintering paste, soldering or gluing and contacted to the top side via bonding wires.

[0006] In order to make electrical contact with the NTC ceramic, metal electrodes must be applied. According to the prior art, for this purpose, thick-layer electrodes, mainly made of silver paste or gold paste, are applied via a screen printing process and then sintered.

[0007] In order to integrate electronics into, for example, MEMS or SESUB structures, very small components are required, which must also be integrated by means of suitable contact methods. Conventional mounting techniques for SMD structures or NTC chips cannot be used for this purpose.

[0008] Document WO 2021 / 004957 A1, the content of which is incorporated by reference in its entirety into the present application, describes an NTC thin-film thermistor which consists of at least one first thin-film electrode, at least one NTC thin film and at least one second thin-film electrode.

[0009] Until now, thin-film NTC temperature sensors could not be manufactured with similarly tight tolerances as conventional designs (SMD NTC and NTC chips). Summary of the invention

[0010] The object of the present invention is to describe a sensor element and a method for producing a sensor element which solve the above-mentioned problems.

[0011] This object is achieved by a sensor element and a method for producing a sensor element according to the independent claims.

[0012] According to one aspect a sensor element is described. The sensor element is suitable for measuring temperature. The sensor element is a temperature sensor. The sensor element is a thin film NTC temperature sensor.

[0013] The sensor element is designed to be very compact. In particular, the sensor element is designed to be directly embedded in an electrical system as a discrete component. Preferably, the sensor element is designed to be directly integrated into a MEMS structure and / or directly into a SESUB structure. For this purpose, the sensor element must have very small dimensions and can also be integrated by means of suitable contact methods. For example, the sensor element has a maximum side length of 1000 μm, preferably <800 μm, particularly preferably <500 μm. The thickness of the sensor element is <100 μm, preferably <80 μm, particularly preferably <50 μm.

[0014] 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 nitride or glass (silicate or borosilicate glass). Alternatively, the carrier can also consist of a ceramic material such as AlN, Si3N4 or Al2O3.

[0015] The carrier preferably has a rectangular base, but can also be designed in a square shape. In both cases, the maximum side length of the carrier is 1000 μm, advantageously <800 μm, ideally <500 μm.

[0016] The carrier has an upper side and an underside. The upper side is electrically insulating. In particular, the insulating layer is formed on the upper side of the carrier. The insulating layer is arranged directly on the upper side of the carrier. The insulating layer can be constructed from one or more layers. The insulating layer can, for example, include Al2O3, AlN, SiO2 or Si3N4, or a combination of layers of these materials. The thickness of the insulating layer is ≤1.5 μm.

[0017] The sensor element also has at least two electrodes. The sensor element can of course also have more than two electrodes, for example four, six or eight electrodes.

[0018] The electrodes are preferably designed as thin-film electrodes. Furthermore, the electrodes can also be referred to as electrode layers. This should be expressed in such a way that the electrodes are individual layers of the sensor element. Here, the terms electrode and electrode layer refer to the same component of the sensor element.

[0019] The sensor element also has at least one functional layer. The sensor element can of course have more than one functional layer, for example two, three or four functional layers. In this case, the functional layers are arranged or stacked one on top of the other transversely to the main extension direction of the sensor element.

[0020] At least one functional layer is arranged on a carrier. The functional layer is at least partially formed on one of the at least two electrodes. In particular, the electrode (which may also be referred to as the "lowermost electrode" hereinafter) is formed directly on the insulating layer. The functional layer is at least partially formed directly on the lowermost electrode. The other electrode of the at least two electrodes is at least partially arranged directly on the functional layer. Thus, at least one functional layer is at least partially arranged between the electrodes (sandwich structure).

[0021] The thickness of the functional layer is between 50 nm and 1 μm, preferably between 100 nm and 500 nm, particularly preferably between 250 nm and 400 nm. The functional layer comprises a material with special electrical properties (functional material). The functional layer comprises a material with temperature-dependent electrical resistance. Preferably, the functional layer comprises an NTC ceramic. Preferably, the functional layer is a film with NTC properties.

[0022] Preferably, the NTC ceramic is based on an oxide material of the perovskite or spinel structure type. Alternatively, the functional layer can be formed on the basis of a carbide material or a nitride material.

[0023] In particular, the following functional layers are possible:

[0024] - Oxidized: for example perovskites (mixed crystals based on the composition CaMnO3, in which Ca can be completely or partially replaced by, for example, Y, Cr, Al or La) or spinels (mixed crystals based on NiMn2O4, in which Ni and Mn can be completely or partially replaced by, for example, Fe, Co, Al);

[0025] b) Carbonized, such as (Si, Ti) C, hexagonal or cubic SiC;

[0026] c) Nitrided, such as (Al, Ti) N, CrN.

[0027] Another alternative is a thin layer of vanadium oxide.

[0028] The sensor element also has at least two contact pads for electrically contacting the sensor element. Preferably, the sensor element has exactly two contact pads. The contact pads are directly electrically and mechanically connected to the electrodes.

[0029] Furthermore, the sensor element has at least two intermediate layers. The sensor element can also have more than two intermediate layers, for example four, five or six intermediate layers. The respective intermediate layers are designed to be insulating. In particular, the respective intermediate layers have an insulating material, for example Al2O3, AlN, SiO2 or Si3N4.

[0030] By forming the intermediate layer, for example, it is possible to ensure electrical separation of electrodes of different polarities in the contacted sensor element. In addition, the intermediate layer serves to prevent the sensor element from having a stepped shape. In other words, the sensor element (especially due to the intermediate layer) has a smooth surface, especially a smooth side surface, i.e. a side surface that is as free of steps as possible. This effectively avoids electrical scattering effects.

[0031] The corresponding sensor element has a tight resistance tolerance, which means that the corresponding sensor element has a very small deviation range from the expected resistance (nominal value of the resistance).

[0032] At least one of the at least two electrodes is structured for setting the resistance value of the corresponding sensor element. At least one electrode is adjustable for setting the resistance value. In particular, at least one sub-region of the electrode is cut off for setting the resistance. In contrast, if the resistance in the device to be adjusted already corresponds to the target value, the structured / adjustable region is not cut off.

[0033] By achieving a small deviation range from the expected resistance, the sensor element has a very high accuracy in temperature measurement. Preferably, the corresponding sensor element has a resistance tolerance that is similar to the strict resistance tolerances of conventional construction types such as SMD NTC or NTC chips.

[0034] According to one embodiment, the sensor element has an upper side and an underside. The upper side and the underside are arranged opposite to each other and are connected to each other via the side surfaces of the sensor element. The underside of the sensor element here refers to the side closed by the carrier. In particular, the underside of the sensor element is formed by the carrier.

[0035] The sensor element has a bottommost and a topmost electrode. The topmost electrode is the electrode closest to the top side of the sensor element. The bottommost electrode is the electrode closest to the bottom side of the sensor element. The bottommost electrode is formed directly on the insulating layer. In this case, the bottommost electrode does not have to completely cover the insulating layer. A subregion of the insulating layer preferably does not have the conductive material of the bottommost electrode.

[0036] The electrode closest to the upper side of the sensor element, i.e. the uppermost electrode, is structured for setting the resistance value. Thus, an adjustable region is obtained on the uppermost electrode. In particular, the uppermost electrode has one or more adjustable regions. The adjustable region is cut out, preferably by means of a laser (laser adjustment), preferably for setting the resistance value of the sensor element. A plurality of adjustable regions can also be cut out.

[0037] The separation of the adjustable regions results in a change in the total electrode surface and thus in the resistance. The resistance tolerance of the resulting sensor element can thereby be optimized.

[0038] According to one embodiment, the respective intermediate layer is arranged such that in the sensor element that is ultimately contacted, electrical and mechanical contact between electrodes and contact pads of different polarity is prevented. In other words, the intermediate layer is formed and arranged as a separation layer or buffer between electrodes or contact pads of different polarity. The thickness of the respective intermediate layer (i.e. the extension perpendicular to the main extension direction of the sensor element) can be greater than or equal to the thickness of the respective electrode.

[0039] Preferably, the respective intermediate layer is designed as an extension of the respective electrode along the main extension direction of the sensor element. In other words, the intermediate layer extends the extension of the electrode parallel to the carrier or parallel to the functional layer. This ensures that each (electrode) layer has the same extension along the carrier. This results in smooth side surfaces of the sensor element that are as free of edges or steps as possible. In this way, scattering effects caused by diagonal current paths of different lengths in the outer region in the overlapping region of the electrodes are avoided.

[0040] Alternatively or additionally, the corresponding intermediate layer is arranged such that direct contact between the at least one functional layer and the contact pad is prevented. Thus, the intermediate layer can be formed and arranged as a separating layer or buffer zone between the at least one functional layer and the contact pad.

[0041] The electrodes have an overlapping region. In the overlapping region, the electrodes are arranged in a superimposed manner. At least one functional layer is designed so as to prevent the functional layer from extending beyond the overlapping region. In other words, the functional layer is arranged only within the overlapping region. The functional layer does not extend out of the overlapping region. More precisely, an intermediate layer is implemented in the region between the functional layer and the contact disk.

[0042] The intermediate layer not only serves to mechanically / electrically separate the contact pad and the functional layer, but also ensures that the individual layers (electrodes, functional layers) have the same extent parallel to the carrier. The intermediate layer thus extends the functional layer and the electrodes so that all layers have the same extent parallel to the carrier. This ensures that the side surfaces of the sensor component are as free of edges or steps as possible. Scattering effects are effectively avoided.

[0043] According to one embodiment, the corresponding intermediate layer is formed in a circumferential manner around at least one functional layer. The corresponding intermediate layer can also be formed in a U-shaped manner around the corresponding electrode. In this way, the corresponding layer can be effectively protected from external influences.

[0044] According to one embodiment, the sensor element further comprises an insulating portion. The sensor element is protected from external influences by the insulating portion. The insulating portion is designed and arranged such that it completely encloses at least one sub-region of the sensor element. Preferably, at least at least one functional layer and at least two intermediate layers are completely surrounded by the insulating portion. Furthermore, at least one sub-region of at least two electrodes is enclosed by the insulating portion. Preferably, the electrodes are completely enclosed by the insulating portion. The contact pad is designed such that it protrudes from the insulating portion at the upper side of the sensor element for electrically contacting the sensor element.

[0045] According to one embodiment, the sensor element has a first or upper sub-region. The sensor element also has a second or lower sub-region. The first sub-region has a width B1. The second sub-region has a width B2. In this context, the width is understood to be the extension of the respective sub-region along the main extension direction of the sensor element. In particular, the width is understood to be the extension parallel to the carrier.

[0046] The two sub-regions are arranged in an overlapping manner. The first sub-region includes in particular the functional layer, the electrode, the intermediate layer and the contact plate. The first sub-region may also include the insulating portion. The second sub-region includes in particular the carrier and the insulating layer. The side surfaces of the first sub-region and / or the second sub-region, preferably all side surfaces, have no steps. In other words, the outer surface of the corresponding sub-region is smooth.

[0047] The sub-regions are designed such that B1≤B2. In other words, the first sub-region can be as wide as the second sub-region. In this case, there are no steps / edges at all on the side of the sensor element. Alternatively, the width of the first sub-region can also be smaller than the width of the second sub-region. In this case, a (single) step / edge is formed on the side of the sensor element at the transition between the first and second sub-regions.

[0048] According to another aspect, a method for producing at least one sensor element is described. It should be noted that the method preferably produces a plurality of sensor elements, for example 20,000 sensor elements, in parallel and finally separates the sensor elements from one another. For reasons of simplicity, reference is made below essentially to the sensor element where it seems appropriate.

[0049] Preferably, the sensor element described above is produced by the method. A corresponding sensor element has only a small deviation range from the desired resistance. The sensor element produced by the method has a tight resistance tolerance in its entirety.

[0050] All characteristics disclosed with respect to the sensor element or the method are correspondingly also disclosed with respect to the respective other aspect, and vice versa, even if the corresponding features are not mentioned in detail in the context of the respective aspect. The method has the following steps:

[0051] A) Providing a carrier material for forming a carrier. The carrier serves to mechanically stabilize the sensor element. Preferably, the carrier material comprises Si, SiC or glass. Alternatively, the carrier material can also comprise AlN or Al2O3.

[0052] B) Forming an insulating layer on the upper side of the carrier. The insulating layer can comprise Al2O3, AlN, SiO2 or Si3N4 or a combination of layers of these materials. Preferably, the insulating layer completely covers the upper side of the carrier. If the carrier material is electrically insulating, the formation of the insulating layer according to step B) can also be omitted (optional step, material-dependent).

[0053] C) Applying the first electrode (the lowermost electrode) to the upper side of the insulating layer / carrier. The electrode material is deposited by a PVD (“physical vapour deposition”) process, a CVD (“chemical vapour deposition”) process or electroplating. As an alternative to this, the deposition can also be carried out by an ALD (Atomic Layer Deposition) method. Preferably, the electrode is deposited only onto a subregion of the insulating layer. In other words, the subregion of the insulating layer / carrier remains free of the metallic material of the lowermost electrode.

[0054] D) At least one intermediate layer is applied to the insulating layer. In particular, the intermediate layer is applied to a sub-region which remains free of the metallic material of the lowermost electrode. The intermediate layer and the lowermost electrode can have the same thickness / height. In this case, the intermediate layer and the lowermost electrode form a plane. Alternatively, the intermediate layer can also be thicker.

[0055] E) Applying at least one functional layer to at least a subregion of the lowermost electrode. This is done, for example, by a sputtering or spin coating process.

[0056] The functional layer can be formed on a plane formed by the intermediate layer and the lowermost electrode. Alternatively, the functional layer can also be formed only on a sub-region of the plane. In this case, an additional intermediate layer is formed in a further step as a buffer between the functional layer and the contact pad described in detail above.

[0057] F) Applying at least one further electrode. The electrode is applied directly to at least one sub-region of the functional layer. In other words, the sub-region of the functional layer can remain free of the metallic material of the electrode.

[0058] G) Applying at least one further intermediate layer. The intermediate layer can be formed in a sub-region of the functional layer that remains free of metallic material of further electrodes. Alternatively or additionally, the intermediate layer can be formed as a buffer between the functional layer and the contact pad described in more detail above.

[0059] H) Structuring at least one of the electrodes to form at least one adjustable region for setting the resistance. This can be done, for example, by wet chemical etching or dry etching or laser structuring. Preferably, the uppermost electrode is structured as described above.

[0060] I) forming a contact pad for electrically contacting the sensor element. In the final contacted sensor element, electrodes of the same polarity are connected vertically (ie in the stacking direction) to the metal material. Preferably, the contact pad has a metal such as Cu, Al or Au.

[0061] The functional layer is then measured. In this process, an initial tolerance range for the resistance value of the sensor element is determined, so that the resistance of the respective sensor element can then be set to a desired value.

[0062] J) Setting the resistance value by adjusting at least one structured electrode. The adjustment is preferably performed by means of a laser. The resistance value is set to a predetermined nominal value (desired value). By accurately setting the resistance value of the corresponding sensor element, the sensor element produced has a very tight resistance tolerance in its entirety.

[0063] According to one embodiment, an insulation is also formed on at least a sub-region of the surface of the sensor element. The sensor element is thereby protected from external influences. The steps can be carried out before or after step J). If the formation of the insulation is carried out before step J), the structured electrode remains free of insulation so that adjustments can be carried out later.

[0064] The drawings described below are not to be understood as being true to scale. Rather, individual dimensions may be shown exaggerated, reduced or even distorted for the sake of a better illustration. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Elements which are identical to one another or which perform the same function are provided with the same reference numerals.

[0066] The accompanying drawings show:

[0067] FIG1 shows a sensor element according to the prior art;

[0068] Figure 2 shows a cross section of a sensor element according to a first embodiment;

[0069] Figure 3 shows a cross section of a sensor element according to another embodiment;

[0070] Figure 4 shows a cross section of a sensor element according to another embodiment;

[0071] 5a to 5c show the Figure 4 A top view of the various components of the sensor element;

[0072] Figure 6 shows a cross section of a sensor element according to another embodiment;

[0073] Figure 7 A top view of the upper side of a sensor element with adjustable electrodes is shown. DETAILED DESCRIPTION

[0074] 1 shows a schematic representation of a sensor element 1 according to the prior art. The sensor element 1 is a multilayer NTC thin-film temperature sensor and comprises a carrier 4 , first and second electrodes 3 a , 3 b and a functional layer 2 .

[0075] The sensor element 1 serves to illustrate the basic construction of the sensor element 10 described in more detail below. With regard to the essential features of the sensor element 1 according to FIG. 1 , reference is made to document WO 2021 / 004957 A1.

[0076] The design of the sensor element 1 brings some disadvantages. The step-shaped implementation makes process control difficult. In particular, when forming the electrodes 3a, 3b, insufficient edge coverage will result, resulting in poor contact. In addition, the step-shaped implementation electrically causes scattering effects in the overlapping area in the outer area due to diagonal current paths of different path lengths. In the case where the path length is shorter than the distance between the electrodes 3a, 3b and the functional layer 2, hot spots are locally caused by increased voltage drops at weak points. Small resistance dispersion (Widerstandsstreuung) is thus difficult and the dispersion (Streuung) of the component is located outside the remaining discrete area.

[0077] The aforementioned disadvantages are reduced or eliminated in the exemplary embodiments of sensor element 10 described below.

[0078] Figure 2 A cross section of a sensor element 10 according to a first embodiment is shown. The sensor element 10 is a thin-film NTC temperature sensor. The sensor element 10 has an upper side 10a and an underside 10b as well as a side surface 10c.

[0079] The sensor element 10 is designed for direct integration into a MEMS structure and / or a SESUB structure. For this purpose, the sensor element 10 is designed to be very compact. The maximum edge length (i.e. the dimension along the main extension direction X) is 1000 μm, preferably <800 μm, particularly preferably <500 μm. The thickness or height of the sensor element 10 (i.e. the extension in a direction perpendicular to the main extension direction X) is <100 μm, preferably <80 μm, particularly preferably <50 μm. Due to the small size, the sensor element 10 is optimally suitable for direct embedding in a MEMS / SESUB structure as a discrete component.

[0080] The sensor element 10 has a carrier 11. The carrier 11 preferably has silicon, silicon carbide or glass (silicate or borosilicate glass). Alternatively, the carrier 11 can also have AlN, Si3N4 or Al2O3. The carrier 11 can have a rectangular or square bottom surface. As described above, the maximum edge length of the carrier 11 is 1000 μm in both cases, advantageously <800 μm, and ideally <500 μm.

[0081] The carrier 11 has a top side 18 and a bottom side 19. An insulation layer 12 is formed on the top side 18, which completely covers the top side 18 of the carrier. The thickness d of the insulation layer 12 (see also Figure 4 ) is ≤1.5 μm. The insulating layer 12 can be constructed from one or more layers and include, for example, Al 2 O 3 , AlN, SiO 2 or Si 3 N 4 , or a combination of layers of these materials.

[0082] In the present exemplary embodiment, the sensor element 10 also has three functional layers 15. The sensor element 10 can of course also have only one functional layer 15 or more than three functional layers 15. Depending on the number of functional layers 15, different resistances of the sensor element 10 can be achieved. The functional layers 15 are arranged one above the other or stacked. The functional layers 15 are connected in parallel.

[0083] The thickness or height of the corresponding functional layer 15 is between 50 nm and 1 μm, preferably between 100 nm and 500 nm, particularly preferably between 250 nm and 400 nm. The functional layer 15 comprises a material with special electrical properties. The corresponding functional layer 15 comprises an NTC ceramic. Preferably, the corresponding functional layer 15 is a thin film with NTC properties.

[0084] Preferably, the functional layer 15 is based on an oxide material of the perovskite or spinel structure type. Alternatively, the functional layer 15 can be formed on the basis of a carbide material or a nitride material. In particular, the following functional layers 15 are conceivable:

[0085] - oxidized: for example perovskite (mixed crystals based on the composition CaMnO3, in which Ca can be completely or partially replaced by, for example, Y, Cr, Al or La) or spinel (mixed crystals based on NiMn2O4, in which Ni and Mn can be completely or partially replaced by, for example, Fe, Co, Al); b) carbonized, for example (Si, Ti) C, hexagonal or cubic SiC;

[0086] c) Nitrided, such as (Al, Ti) N, CrN.

[0087] Another alternative is a thin layer of vanadium oxide.

[0088] In the present exemplary embodiment, the sensor element 10 also has a plurality of electrodes or electrode layers 13a, 13b, in particular four electrodes 13a, 13b. Of course, the sensor element 10 can also have only two electrodes 13a, 13b or more than four electrodes 13a, 13b. The electrodes 13a, 13b have opposite polarity (once the sensor element 10 is finally in contact). The electrodes 13a, 13b of opposite polarity can also be referred to as first electrode 13a and second electrode 13b. The electrodes 13a, 13b can be formed in one layer or in multiple layers and have, for example, Cu, Au, Ni, Cr, Ag, Ti, Ta, W, Pd or Pt. The electrodes 13a, 13b are formed as thin-layer electrodes.

[0089] The electrodes 13a, 13b (the lowermost electrode below) are formed directly on the insulating layer 12. Here, the lowermost electrode does not completely cover the insulating layer 12, as can be seen from Figure 2Rather, a strip-shaped region of the insulating layer 12 remains free of the conductive material of the lowermost electrode, as will be explained in greater detail below.

[0090] The (lowest) functional layer 15 is formed directly on the lowest electrode 13a, 13b. In this case, the lowest electrode does not necessarily have to be completely covered by the functional layer 15. Further electrodes 13a, 13b are arranged at least partially directly on the functional layer 15. This layer-by-layer construction continues. In particular, the functional layer 15 is always arranged at least partially between two electrodes 13a, 13b.

[0091] The corresponding electrodes 13a, 13b are connected to one another vertically at the side surface 10c of the sensor element 10. These connections serve as contact pads 16a, 16b for the sensor element 10, which can be contacted, for example, by means of wire bonding. This results in a parallel connection of the individual functional layers 15. The contact pads 16a, 16b are directly electrically and mechanically connected to the electrodes 13a, 13b. Furthermore, in the present exemplary embodiment, the contact pads 16, 16b have direct contact with the functional layer 15. The contact pads can comprise Cu, Au, Ni, Cr, Ag, Ti, Ta, W, Pd or Pt.

[0092] Furthermore, in the present exemplary embodiment, the sensor element 10 has four intermediate layers 14. The sensor element 10 can also have only two intermediate layers 14 (in this case, the sensor element 10 has exactly one functional layer 15 and exactly two electrodes 13a, 13b; not shown in detail), or the sensor element 10 can have more than four intermediate layers 14. The respective intermediate layers 14 have an insulating material. The respective intermediate layers 14 have, for example, Al2O3, AlN, SiO2 or Si3N4.

[0093] In the present embodiment, the thickness or height of the respective intermediate layer 14 (i.e. the extension perpendicular to the main extension direction X) is the same as the thickness or height of the respective electrode 13a, 13b. In other words, the electrodes 13a, 13b and the intermediate layer 14 are of the same height. However, the thickness / height of the intermediate layer 14 can also be greater than the thickness / height of the electrodes 13a, 13b (see Figure 3 , Figure 4 and Figure 6 ). For example, the intermediate layer 14 can extend perpendicularly to the main extension direction X over a plurality of layers of the sensor element 10 , as will be explained in more detail below.

[0094] In accordance with Figure 2 In the embodiment of the present invention, the respective intermediate layer 14 is formed as an extension of the respective electrode 13a, 13b along the main extension direction X of the sensor element 10 (or parallel to the upper side 18 of the carrier 11). Figure 2For example, it can be seen in FIG. 1 that the lowermost electrode does not completely cover the insulating layer 12 . Rather, there are regions in the form of unmetallized strips on the insulating layer 12 , as already mentioned above.

[0095] This free area is filled with the insulating material of the intermediate layer 14. The intermediate layer 14 thus continues the lowermost electrode. The lowermost functional layer 15 is formed on these two layers (lowermost electrode and intermediate layer 14) or on the plane formed by these layers.

[0096] A second electrode 13 b is then formed on the lowermost functional layer 15 , which is Figure 2 The functional layer 15 is not covered over the entire surface on the left side in FIG. This free area is then covered by the intermediate layer 14. Similarly, each intermediate layer 14 also continues or extends the other electrodes 13a, 13b in the X direction.

[0097] The individual layers of the sensor element 10 (in the present exemplary embodiment, the electrodes 13a, 13b) are filled by an insulating intermediate layer 14. As a result, the stepped shape of the sensor element 10 is reduced compared to the prior art according to FIG. 1 , as will be explained in more detail below:

[0098] The sensor element 10 has a first sub-region 23 and a second sub-region 24 (see in particular Figure 6 ). The sub-regions 23, 24 are arranged one above the other. The first sub-region 23 has a width B1 and the second sub-region 24 has a width B2. In this context, the width is understood to be the extent of the respective sub-region 23, 24 along the main extension direction X (X direction). In the present embodiment, B1<B2. However, in principle, B1=B2 is also possible (see, for example Figure 3 and Figure 6 ).

[0099] The first subregion 23 comprises in particular the functional layer 15 , the electrodes 13 a , 13 b , the intermediate layer 14 and the contact pads 16 a , 16 b . The second subregion 24 comprises in particular the carrier 11 and the insulation layer 12 .

[0100] As from Figure 2 As can be seen in the figure, the side surfaces of the first sub-region 23 are completely free of edges or steps. The same applies to the side surfaces of the second sub-region 24. Steps are present only in the transition region between the first sub-region 23 and the second sub-region 24. In other words, the outer surfaces of the respective sub-regions 23, 24 are smooth. This is achieved in that all layers of the first sub-region 23 have the same extension along the X axis, since the individual layers are filled with the intermediate layer 14.

[0101] Electrical scattering effects are effectively reduced by forming the intermediate layer 14 and thereby reducing the stepped shape of the sensor element 10. In addition, the possibility of hot spot formation is reduced.

[0102] The sensor element 10 has a strict resistance tolerance as a whole, that is, the corresponding sensor element 10 has a very small deviation range from the expected resistance.

[0103] In order to set the resistance value of the respective sensor element 10, one of the electrodes 13a, 13b is structured (see Figure 7 ). Preferably, the uppermost electrode, ie the electrode of the electrodes 13a, 13b which is closest to the upper side of the sensor element 10, is structured. As a result, the electrode has an adjustable area (see Figure 7 Adjustable regions 17 in the electrode are formed. These regions can be cut out with the aid of a laser, resulting in a change in the total area of ​​the electrode and thus in the resistance.

[0104] By achieving a tight resistance tolerance of the sensor element 10 , the sensor element 10 has a very high accuracy in measuring temperature. Preferably, the sensor element 10 has a resistance tolerance that is similar to the tight resistance tolerance of conventional structures such as SMD NTC or NTC chips.

[0105] In combination Figure 2 In the described embodiment, each functional layer 15 has additional contacts with contact pads 16a, 16b, which also results in scattering effects at the outer regions of the sensor element 10 due to diagonal current paths of different lengths. Figure 3 In the specific embodiment of FIG. 1 , the respective functional layer 15 is designed in such a way that it is located only in the overlapping region 21 formed by the two electrodes 13 a , 13 b .

[0106] As from Figure 3 It can be seen from FIG. 2 that the electrodes have an overlapping region 21. In the overlapping region 21, the electrodes 13a, 13b are layered one on top of the other. From now on, the functional layer 15 is connected to the electrode according to Figure 2 In contrast to the embodiment of the present invention, the functional layer is configured so that it does not extend beyond the overlapping region 21. In other words, the width of the functional layer 15 is equal to the width of the functional layer 15 according to Figure 2 The functional layer is smaller than that of the

[0107] In the region 22 between the respective functional layer 15 and the contact pads 16a, 16b, an intermediate layer 14 is formed for this purpose. The intermediate layer 14 closes the gap which is produced by the functional layer 15 no longer extending beyond the overlap region 21.

[0108] Therefore, in the present embodiment, the intermediate layer 14 not only extends the electrodes 13a, 13b, but also extends the functional layer 15. This ensures that the side surface 10c of the sensor element 10 is as free of edges or steps as possible. In addition, in the present embodiment, the width of each layer of the first sub-region 23 is selected so that the step between the first and second sub-regions 23, 24 is eliminated (i.e., B1=B2). The scattering effect is effectively avoided.

[0109] The thickness of the intermediate layer can be greater than the thickness of the individual electrodes 13a, 13b / electrode layers. In particular, the respective intermediate layer 14 extends perpendicularly to the main extension direction X over a plurality of layers of the sensor element 10. Thus, the maximum thickness or height of the intermediate layer 14 can reach the total height of the two functional layers 15 plus the electrode layers 13a, 13b, as shown in FIG. Figure 3 In other words, the intermediate layer 14 is filled in the sensor element 10 that is finally contacted with at most one electrode 13a, 13b of one polarity up to the electrode 13a, 13b of the same polarity that follows it in the stacking direction. Therefore, the maximum thickness of the intermediate layer 14 corresponds to the spacing A between the two electrodes 13a, 13b of the same polarity (see also Figure 4 ).

[0110] For all other features of the sensor element 10, reference is made to Figure 2 Description.

[0111] Figure 4 5a to 5c show a sensor element 10 and its individual components according to another embodiment.

[0112] Based on the two previously described Figure 2 and Figure 3 In the embodiment of the present invention, two of the four sides of each layer are exposed and thus unprotected. In order to achieve protection of these layers, the insulating intermediate layer 14 is arranged according to Figure 4 In the exemplary embodiments of the present invention, the functional layer 15 is respectively embodied around the functional layer 15 (see also FIG. 5 b for this). In other words, all surfaces of the respective functional layer 15 are surrounded by the insulating material of the intermediate layer 14 except for the upper side and the lower side of the functional layer 15 .

[0113] In order to avoid the stepped configuration of the sensor element 10, the intermediate layer 14 is also deposited in a U-shaped manner around each electrode 13a, 13b (FIG. 5a and FIG. 5c). Thus, as can be seen from FIG. 5a and FIG. 5c, except for the upper side, the lower side and the side of the corresponding electrode 13a, 13b, the remaining side of the electrode 13a, 13b is completely surrounded by the insulating material of the intermediate layer 14. In other words, three of the four side surfaces of the corresponding electrode 13a, 13b are encapsulated by the intermediate layer 14.

[0114] For all other features of the sensor element 10, reference is made to Figure 2 Description.

[0115] Figure 6 A cross section through a sensor element 10 according to a further exemplary embodiment is shown.

[0116] In this case, the sensor element 10 is at least partially surrounded by an insulation 20. Particularly preferably, at least the side surface 10c of the sensor element 10 (without the carrier 11) is completely enclosed by the insulation 20. The insulation 20 in particular encloses the electrodes 13a, 13b (with one exception, which may be the uppermost electrode, as described below), the functional layer 15 and the intermediate layer 14 as well as parts of the contact pads 16a, 16b. In this way, these components of the sensor element 10 are protected from external influences. In principle, an encapsulation of the insulation layer 12 and the carrier 11 is also possible (not shown in detail).

[0117] Since the uppermost electrode has an adjustable area 17 (see Figure 7 ), which region can be cut off depending on the desired value of the resistance, and the uppermost electrode must be freely accessible for laser adjustment. Therefore, there are two possible embodiments for the insulation 20 in the region of the upper side 10a of the sensor element 10:

[0118] The uppermost electrode can remain completely free of insulation 20 , so that it is accessible at any time for setting the resistance (not shown in detail).

[0119] Alternatively, the insulation can also be formed after conditioning on top side 10a of sensor element 10. For example, after conditioning, a polymer layer, an oxidic, nitrided, ceramic layer, a thin glass layer or a combination of these layers can be formed as insulation 20 on the uppermost / structured electrode.

[0120] As from Figure 6 As can be seen in FIG. 1 , contact pads 16a, 16b protrude from insulation 20 at top side 10a of sensor element in each possible embodiment in order to enable electrical contacting of sensor element 10. For this purpose, in the present exemplary embodiment, contact pads 16a, 16b are designed to be higher. In particular, the top side of contact pads 16a, 16b is not located in the plane with the top side of the uppermost electrode.

[0121] For all other features of the sensor element 10, reference is made to Figure 2 Description.

[0122] Next, a method for manufacturing the sensor element 10 is described. In particular, a plurality of sensors according to the above-described embodiments (see Figures 2 to 7) of one of the sensor elements 10. For the sake of simplicity, in the following - wherever applicable - reference is made to only one sensor element 10.

[0123] All features described in conjunction with sensor element 10 also apply to the method, and vice versa.

[0124] The method comprises the following steps:

[0125] A) Providing a carrier material for forming the carrier 11. Preferably, the carrier material comprises Si, SiC or glass. Alternatively, the carrier material can also comprise AlN, Si3N4 or Al2O3.

[0126] B) An insulating layer 12 is formed on the upper side 18 of the carrier 11. The insulating layer 12 can include Al2O3, AlN, SiO2 or Si3N4 or a combination of layers of these materials. Preferably, the insulating layer 12 is deposited such that it completely covers the upper side 18 of the carrier 11.

[0127] The insulating layer 12 may be required as a flat bottom surface in order to form other layers thereon (electrodes 13a, 13b, intermediate layer 14, functional layer 15). If the surface 18 of the carrier 11 is sufficiently flat and / or the carrier 11 itself is composed of an insulating material, the formation of the insulating layer 12 according to step B) may also be omitted.

[0128] C) Applying the first electrode 13a, 13b (the lowermost electrode). The electrodes 13a, 13b are deposited by PVD, ALD or CVD processes or electroplating. Preferably, the electrodes 13a, 13b are deposited only on a sub-region of the insulating layer 12. Strip-shaped regions of the insulating layer 12 remain free of electrode material so that the intermediate layer 14 can then be formed in the free regions.

[0129] D) At least one intermediate layer 14 is applied to the insulating layer 12 for extending the electrodes 13a, 13b. The intermediate layer 14 comprises an insulating material and is formed in a sub-region (recessed region) of the insulating layer 12 which remains free of metallic material of the electrodes 13a, 13b. The intermediate layer 14 and the lowermost electrode can form a plane, i.e. have the same height ( Figure 2 However, as an alternative to this, the intermediate layer 14 can also be formed higher than the electrodes 13a, 13b ( Figure 3 , Figure 4 , Figure 6 ).

[0130] E) Applying at least one functional layer 15. This is done, for example, during and / or after the deposition of the corresponding layer by a sputtering or spin coating process and at least one temperature process at T>500° C. The functional material has an NTC ceramic based on an oxide material of the perovskite or spinel structure type. Alternatively, the functional material can also be based on a carbide material or a nitride material. In another alternative, the functional material comprises or consists of a thin layer consisting of vanadium oxide.

[0131] The functional layer 15 is formed, for example, on a plane formed by the intermediate layer 14 and the lowermost electrode (see Figure 2 The functional layer 15 may be deposited on the entire bottom electrodes 13a, 13b ( Figure 2 ), or does not form a functional layer 15 up to the edge of the lowest electrode. That is, on the opposite side of the intermediate layer 14 (on Figure 2 The lowermost electrode (left in the middle) is not covered up to the edge. In this case, a further intermediate layer 14 is then formed, which is formed on the exposed region of the lowermost electrode (where no functional layer 15 is formed) ( Figure 3 , Figure 4 , Figure 6 ).

[0132] F) applying at least one further electrode 13a, 13b. The electrodes 13a, 13b are deposited by a PVD, ALD or CVD process or electroplating. The further electrodes 13a, 13b are formed directly on the functional layer 5. The further electrodes 13a, 13b can, for example, be formed only on a sub-region of the functional layer 15 (see Figure 2 of the embodiment of the invention).

[0133] G) Applying at least one further intermediate layer 14. The intermediate layer 14 comprises an insulating material and is formed, for example, in a subregion of the functional layer 15 which remains free of metallic material of the further electrodes 13a, 13b. Alternatively or additionally, the intermediate layer 14 can be formed in the region between the functional layer 15 and the contact pads 16a, 16b. This takes place after step I).

[0134] H) Structuring at least one of the electrodes 13a, 13b to form at least one adjustable region 17 for setting the resistance. This can be done, for example, by wet chemical etching or dry etching or laser structuring. Preferably, the uppermost electrode is structured as described above.

[0135] I) forming contact pads 16a, 16b for electrically contacting the sensor element 10. In particular, in the contacted sensor element 10, electrodes 13a, 13b of the same polarity are connected vertically (i.e. in the stacking direction) to the metal material. Preferably, the contact pads 16a, 16b have a metal such as Cu, Al or Au. Then the functional layer 15 is measured. Here, an initial tolerance range of the overall resistance value of the manufactured sensor element 10 is determined so that the resistance of the corresponding sensor element 10 can be set to a desired value below.

[0136] J) Setting the resistance value by adjusting at least one structured electrode 13a, 13b. The adjustment is preferably performed by means of a laser. The resistance value is set to a predetermined nominal value (desired value). By accurately setting the resistance value, the sensor element 10 is manufactured to have a very tight resistance tolerance. In order to set the resistance value, the structured / adjustable area 17 described above is at least partially cut off.

[0137] K) Insulation 20 is formed on at least a partial region of the surface of sensor element 10 .

[0138] Step K) can also be carried out before step J). In this case, the uppermost electrode remains free of insulation 20 so that adjustment can be carried out later.

[0139] Following the aforementioned method steps, sensor element 10 may be subjected to a sintering process in a further method step.

[0140] The carrier material can then be thinned by means of a grinding or etching process.

[0141] The description of the subject matter described here is not limited to a single specific embodiment. Rather, the features of the individual embodiments can be combined with one another as desired—as long as this is technically sensible.

[0142] Reference numerals list

[0143] 1 Sensor element

[0144] 2 Functional layer

[0145] 3a First electrode

[0146] 3b Second electrode

[0147] 4 Carrier

[0148] 10 Sensor element

[0149] 10a Upper side of the sensor element

[0150] 10b Underside of sensor element

[0151] 10c Side view of sensor element

[0152] 11 Carrier

[0153] 12 Insulation layer

[0154] 13a Electrode / electrode layer

[0155] 13b Electrode / electrode layer

[0156] 14 Middle Layer

[0157] 15 Functional Layer

[0158] 16a Contact plate

[0159] 16b Contact plate

[0160] 17 Adjustable Area

[0161] 18 Upper side of carrier

[0162] 19 Underside of carrier

[0163] 20 Insulation

[0164] 21 Overlapping Area

[0165] 22 Regions

[0166] 23 First sub-area

[0167] 24 Second sub-area

[0168] d Thickness of the insulation layer

[0169] B1 The width of the first sub-area

[0170] B2 The width of the second sub-area

[0171] X main extension direction

[0172] A Spacing

Claims

1. A sensor element (10) for measuring temperature, the sensor element comprising: at least one carrier (11) having a top side (18) and a bottom side (19), wherein an insulating layer (12) is formed on the top side (19) of the carrier (11), at least two electrodes (13a, 13b), which are formed on the carrier (2) at a distance from one another, at least one functional layer (15) comprising a material with a temperature-dependent electrical resistance, wherein the at least one functional layer (14) is at least partially arranged between the electrodes (13a, 13b), - at least two intermediate layers (14) comprising insulating material, - at least two contact pads (16a, 16b) for electrically contacting the sensor element (10), The sensor element (10) is designed to be directly integrated into an electrical system as a discrete device, and The sensor element (10) has a small deviation range from a desired resistance, wherein at least one of the at least two electrodes (13a, 13b) is structured in order to set the resistance value.

2. The sensor element (10) according to claim 1, The sensor element has a top side (10a) and a bottom side (10b), wherein the electrodes (13a, 13b) closest to the top side (10a) of the sensor element (10) are structured to set the resistance value.

3. The sensor element (10) according to claim 2, The electrodes (13a, 13b) closest to the upper side (10a) of the sensor element (10) have an adjustable region (17).

4. The sensor element (10) according to any one of the preceding claims, The intermediate layer (14) is arranged in each case in such a way that direct contact between the at least one functional layer (15) and the contact pads (16a, 16b) is prevented.

5. The sensor element (10) according to any one of the preceding claims, The respective intermediate layer (14) is designed as an extension of the electrode (13a, 13b) along a main extension direction (X) of the sensor element (10).

6. The sensor element (10) according to any one of the preceding claims, The intermediate layer (14) is formed in the region (22) between the functional layer (15) and the respective contact pad (16a, 16b).

7. The sensor element (10) according to any one of the preceding claims, The electrodes (13a, 13b) have an overlapping region (21) in which the electrodes (13a, 13b) are arranged one on top of the other, and the at least one functional layer (15) is designed such that an extension of the functional layer (15) beyond the overlapping region (21) is prevented.

8. The sensor element (10) according to any one of the preceding claims, The respective intermediate layer (14) is designed so as to surround the at least one functional layer (15).

9. The sensor element (10) according to any one of the preceding claims, The intermediate layer (14) is designed in a U-shape around the respective electrode (13a, 13b).

10. The sensor element (10) according to any one of the preceding claims, The thickness of the corresponding intermediate layer (14) is greater than or equal to the thickness of the corresponding electrode (13a, 13b).

11. The sensor element (10) according to any one of the preceding claims, The sensor element further comprises an insulation (20), wherein at least the at least one functional layer (15) and the intermediate layer (14) are completely surrounded by the insulation (20), and wherein at least a subregion of the electrode (13a, 13b) is surrounded by the insulation (20).

12. The sensor element (10) according to claim 11, The contact pads (16a, 16b) protrude from the insulation (20) at the upper side (10a) of the sensor element (10).

13. The sensor element (10) according to any one of the preceding claims, One of the at least two electrodes (13a, 13b) is formed below the at least one functional layer (14), and the other of the at least two electrodes (13a, 13b) is formed above the at least one functional layer (14).

14. The sensor element (10) according to any one of the preceding claims, The sensor element comprises a first sub-region (23) with a width B1, wherein the first sub-region comprises the functional layer (15), the electrodes (13a, 13b), the intermediate layer (14) and the contact pads (16a, 16b), and a second sub-region (24) with a width B2, wherein B1≤B2.

15. The sensor element (10) according to claim 14, The side surfaces of the first sub-region (23) and / or the second sub-region (24) have no steps.

16. The sensor element (10) according to any one of the preceding claims, The lowermost electrode of the at least two electrodes (13a, 13b) is formed directly on the insulating layer (12).

17. The sensor element (10) according to claim 16, The sub-region of the insulating layer (12) is free of the conductive material of the lowermost electrode.

18. The sensor element (10) according to claim 17, In this case, one of the at least two intermediate layers (14) is formed in the freed-up subregion.

19. The sensor element (10) according to any one of the preceding claims, The respective electrodes (13a, 13b) are designed as thin-film electrodes.

20. The sensor element (10) according to any one of the preceding claims, The at least one functional layer (15) is a thin film having NTC properties.

21. The sensor element (10) according to any one of the preceding claims, The carrier (11) comprises silicon, silicon carbide or glass, or the carrier (11) comprises Si3N4, AlN, GaN or Al2O3 as carrier material.

22. The sensor element (10) according to any one of the preceding claims, The functional layer (15) comprises an NTC ceramic based on an oxide material of the perovskite or spinel structure type, or the functional layer (15) comprises an NTC ceramic based on a carbide material or a nitride material.

23. The sensor element (10) according to any one of the preceding claims, The electrodes (13a, 13b) are formed in one layer or in multiple layers and comprise at least one material and / or a material combination of Cu, Au, Ni, Cr, Ag, Ti, Ta, W, Pd and / or Pt.

24. The sensor element (10) according to any one of the preceding claims, The contact plates (16a, 16b) are formed in one layer or in multiple layers and comprise at least one material and / or a material combination of Cu, Au, Ni, Cr, Ag, Ti, Ta, W, Pd and / or Pt.

25. The sensor element (10) according to any one of the preceding claims, The insulating layer (12) is formed in one or more layers and comprises Al2O3, AlN, SiO2 or Si3N4 or a combination of layers of these materials.

26. The sensor element (10) according to any one of claims 11 to 25, The insulation (20) is designed in a single or multi-layered manner and comprises Al2O3, AlN, SiO2 or Si3N4 or a combination of layers of these materials.

27. The sensor element (10) according to any one of claims 11 to 26, The insulating part (20) comprises oxide, nitride, ceramic, glass or plastic as material.

28. The sensor element (10) according to any one of the preceding claims, The sensor element (10) is designed for direct integration into a MEMS structure and / or into a SESUB structure.

29. A method for producing a sensor element (10) for measuring temperature, the method comprising the following steps: A) providing a carrier material for forming a carrier (11); B) forming an insulating layer (12) on the upper side (18) of the carrier (11); C) applying at least one electrode (13a, 13b) to a subregion of the carrier (11) such that the region of the carrier (11) remains free of electrode material; D) applying at least one intermediate layer (14) to the freed-up sub-region of the carrier (11); E) applying at least one functional layer (15) to at least a sub-region of the plane formed by the electrodes (13a, 13b) and the intermediate layer (14); F) applying at least one further electrode (13a, 13b) to at least one subregion of the functional layer (15); G) applying at least one further intermediate layer (14) to the subregion of the functional layer (15) which is free of the further electrode (13a, 13b); H) structuring at least one of the electrodes (13a, 13b) to form at least one adjustable region (17) for setting the resistance; I) forming contact pads (16a, 16b) for electrically contacting the sensor element (10).

30. The method according to claim 29, The method further comprises the following steps: J) Setting the resistance value by adjusting the at least one structured electrode (13a, 13b).

31. The method according to any one of claims 29 or 30, The method further comprises the following steps: K) An insulation (20) is formed on at least a subregion of the surface of the sensor element (10).

32. The method according to any one of claims 29 to 31, The method further comprises the following steps: At least one further intermediate layer (14) is formed between the contact pads (16a, 16b) and the functional layer (15).

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