Sensor element and method for producing a sensor element

Abstract

The invention relates to a sensor element (10) for measuring a temperature, comprising - at least one carrier (11) with an upper side (18) and a lower side (19), an insulating layer (12) being formed on the upper 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 arranged at least partially between the electrodes (13a, 13b), - at least two intermediate layers (14) comprising an insulating material, - at least two contact pads (16a, 16b) for electrically contacting the sensor element (10), wherein the sensor element (10) is designed to be integrated as a discrete component directly into an electrical system, and wherein the sensor element (10) has a small deviation range from a nominal resistance, wherein at least one of the at least two electrodes (13a, 13b) is structured for setting the resistance value. The invention also relates to a method for producing a sensor element (10).

Description

[0001] Description

[0002] Sensor element and method for producing a sensor element

[0003] The present invention relates to a sensor element, in particular a temperature sensor. The present invention further relates to a method for producing at least one sensor element, preferably a temperature sensor.

[0004] In order to integrate passive components such as sensors, capacitors, protective components or heaters into electrical systems, the dimensions for modern packaging

[0005] designs in the micrometer and even nanometer scale range. To achieve this level of miniaturization, the components are deposited as thin films on

[0006] Carrier structures with electrical connections were deposited and described as a discrete component. These novel

[0007] Components can be integrated into various printed circuit boards, MEMS (Micro Electro Mechanical System) or SESUB

[0008] ( Semiconductor Embedded in Substrate ) structures .

[0009] The increasing demands on the accuracy of temperature measurement require close tolerances in the resistance variation of such sensor elements. However, with ever smaller structures, the manufacturing tolerances have an ever greater influence, whereby the resulting

[0010] Resistance variation exceeds the required tolerances. Resistance variation can only be reduced to a limited extent through process control. According to the state of the art, temperatures for monitoring and control in a wide variety of applications are primarily measured using ceramic NTC thermistor elements.

[0011] (NTC), silicon temperature sensors (KTY), platinum temperature

[0012] Sensors (PRTD) or thermocouples (TC) are used. 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.

[0013] For use in power modules, SMD

[0014] (surface mounted device) NTC-

[0015] Temperature sensors are used which are soldered on.

[0016] Control modules for low power also use NTC chips, which are connected to the bottom by means of

[0017] Ag sintering paste, soldering or gluing and the top side is contacted via a bonding wire.

[0018] For electrical contact with the NTC ceramic, metallic electrodes must be applied. According to the current state of

[0019] In this technique, thick-film electrodes, predominantly made of silver or gold pastes, are applied using a screen printing process with subsequent firing.

[0020] For the integration of electronic components in, for example, MEMS or SESUB structures, very small elements are required, which, in addition, can be combined with suitable

[0021] Contacting procedures must be integrable. Classic

[0022] Assembly technologies for SMD packages or NTC chips cannot be used for this purpose. Document WO 2021 / 004957 A1, the content of which is incorporated by reference into this application, describes an NTC thin-film thermistor consisting of at least one first thin-film electrode, at least one NTC thin film, and at least one second thin-film electrode.

[0023] Until now, thin-film NTC temperature sensors could not be manufactured with tolerances as tight as classic designs (SMD NTC and NTC chips).

[0024] The object of the present invention is to describe a sensor element and a method for producing a sensor element which solve the above problems.

[0025] This object is achieved by a sensor element and a method for producing a sensor element according to the independent claims.

[0026] According to one aspect, a sensor element is described. The sensor element is suitable for measuring a temperature. The sensor element is a temperature sensor. The sensor element is a thin-film NTC temperature sensor.

[0027] The sensor element is very compact. In particular, the sensor element is designed as a discrete component to be embedded directly into an electrical system. The sensor element is preferably designed for direct integration into a MEMS structure and / or a SESUB structure. For this purpose, the sensor element must have very small dimensions and, moreover, be capable of integration using suitable contacting methods. For example, the sensor element has a maximum edge 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.

[0028] The sensor element has at least one carrier. Preferably, the sensor element has exactly one carrier. The

[0029] Carrier comprises a carrier material, preferably silicon,

[0030] Silicon carbide or glass (silica or borosilicate glass). Alternatively, the carrier can also be made of a ceramic material such as AlN, Si3N4, or Al2O3.

[0031] The support preferably has a rectangular base, but can also be square. In both cases, the maximum edge length of the support is 1000 gm, preferably < 800 gm, and ideally < 500 gm.

[0032] The carrier has a top and a bottom.

[0033] The upper side is electrically insulating. In particular, an insulating layer is formed on the upper side of the carrier. The insulating layer is directly on the

[0034] The insulating layer can be made up of one or more layers. The insulating layer can be, for example, Al2O3, AlN, SiO2 or

[0035] SiSNo or combinations of layers of these materials. The thickness of the insulating layer is < 1.5 gm.

[0036] The sensor element further comprises at least two electrodes. The sensor element can, of course, also comprise more than two

[0037] electrodes, for example four, six, or eight electrodes.

[0038] The electrodes are preferably designed as thin-film electrodes. The electrodes may also be referred to as electrode layers. This is intended to express that the electrodes represent individual layers of the sensor element. The terms "electrode" and "electrode layer" each refer to the same component of the sensor element.

[0039] The sensor element further comprises at least one functional layer. The sensor element can, of course, comprise more than one functional layer, for example, two, three, or four functional layers. In this case, the functional layers are arranged or stacked one above the other transversely to a main direction of extension of the sensor element.

[0040] The at least one functional layer is arranged on the carrier. The functional layer is at least partially formed on one of the at least two electrodes. In particular, the electrode (this can also be referred to below as "the bottom electrode") is formed directly on the insulating layer. The functional layer is at least partially formed directly on the bottom electrode. Another of the at least two electrodes is at least partially arranged directly on the functional layer. The at least one functional layer is therefore at least partially arranged between the electrodes (sandwich structure).

[0041] The thickness of the functional layer is between 50 nm and 1 pm, preferably between 100 nm and 500 nm, particularly preferably between 250 nm and 400 nm. The functional layer comprises a material (functional material) that has a specific electrical characteristic. The functional layer comprises a material with a temperature-dependent electrical resistance. The functional layer preferably comprises an NTC ceramic. The functional layer is preferably a thin film with NTC characteristics.

[0042] The NTC ceramic is preferably based on an oxide material with a perovskite or spinel structure. Alternatively, the functional layer can be based on a carbide or nitride material.

[0043] In particular, the following functional layers are possible:

[0044] - Oxidic: for example perovskite (based on solid solutions of the composition CaMnO3, in which Ca can be completely or partially replaced by, for example, Y, Cr, Al or La) or spinel (based on solid solutions of NiMn2O4, in which Ni and Mn can be completely or partially replaced by, for example, Fe, Co, Al); b) Carbide, for example (Si,Ti)C, hexagonal or cubic SiC; c) Nitridic, for example (Al,Ti)N, CrN.

[0045] Another alternative is thin films of vanadium oxide.

[0046] The sensor element further comprises at least two contact pads for electrically contacting the sensor element. Preferably, the sensor element comprises exactly two contact pads. The contact pads are directly electrically and mechanically connected to the electrodes.

[0047] 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. Each intermediate layer is designed to be insulating. In particular, each intermediate layer comprises an insulating material, for example, Al2O3, AlN, SiO2, or Si3N4.

[0048] The formation of intermediate layers can, for example, ensure electrical separation of electrodes of different polarity in the contacted sensor element. Furthermore, the intermediate layers serve to prevent the sensor element from taking on a stepped shape. In other words, the sensor element has (particularly due to the intermediate layers) a smooth surface, in particular smooth side surfaces, i.e., side surfaces that are as free of steps as possible. This effectively prevents electrical stray effects.

[0049] The corresponding sensor elements have a narrow resistance tolerance. This means that the respective sensor element exhibits a very small deviation range from a target resistance (nominal value of the resistance).

[0050] At least one of the at least two electrodes is structured to adjust the resistance value of the respective sensor element. The at least one electrode is trimmable to adjust the resistance value. In particular, at least a portion of this electrode is severed to adjust the resistance. However, if the resistance of the component to be trimmed already corresponds to the target value, the structured / trimmable regions are not severed.

[0051] By achieving a small deviation range from the target resistance, the sensor element exhibits very high temperature measurement accuracy. The corresponding sensor elements preferably have a resistance tolerance comparable to the narrow resistance tolerance of conventional designs such as SMD NTCs or NTC chips.

[0052] According to one embodiment, the sensor element has a top side and a bottom side. The top and bottom sides are arranged opposite one another and are connected to one another by side surfaces of the sensor element. The bottom side of the sensor element refers to the side that is closed off by the support. In particular, the bottom side of the sensor element is formed by the support.

[0053] The sensor element has a bottom and a top electrode. The top electrode is the electrode closest to the top side of the sensor element. The bottom electrode is the electrode closest to the bottom side of the sensor element. The bottom electrode is formed directly on the insulating layer. The bottom electrode does not have to completely cover the insulating layer. A portion of the insulating layer is preferably free of an electrically conductive material of the bottom electrode.

[0054] The electrode closest to the top side of the sensor element (i.e., the topmost electrode) is structured to adjust the resistance value. This results in trimmable regions on the topmost electrode. In particular, the topmost electrode has one or more trimmable regions. A trimmable region is preferably severed to adjust the resistance value of the sensor element, preferably by means of a laser (laser trimming). Several trimmable regions can also be severed. Separating trimmable regions results in a change in the total electrode area and thus the resistance. This allows the resistance tolerance of the final sensor elements to be optimized.

[0055] According to one embodiment, the respective intermediate layer is arranged such that, in the final contacted sensor element, electrical and mechanical contact between electrodes and contact pads of different polarity is prevented. In other words, the intermediate layer is designed and arranged as a separating layer or buffer between electrodes or contact pads of different polarity. A thickness (i.e., extent perpendicular to a main extension direction of the sensor element) of the respective intermediate layer can be greater than or equal to a thickness of the respective electrode.

[0056] Preferably, the respective intermediate layer is formed as an extension of the respective electrodes 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 a smooth side surface of the sensor element that is as free as possible from edges or steps. Scattering effects in the overlapping areas of the electrodes on the outer regions due to diagonal current paths with different path lengths are thus avoided.

[0057] Alternatively or additionally, the respective intermediate layer is arranged such that direct contact between the at least one functional layer and the contact pads is prevented. The intermediate layer can thus be designed and arranged as a separating layer or buffer between the at least one functional layer and the contact pads.

[0058] The electrodes have an overlap region. In the overlap region, the electrodes are formed one above the other. The at least one functional layer is formed in such a way that expansion of the functional layer beyond the overlap region is prevented. In other words, the functional layer is arranged only within the overlap region. The functional layer does not protrude beyond the overlap region. Rather, an intermediate layer is formed in a region between the functional layer and the contact pads.

[0059] This intermediate layer not only serves to mechanically / electrically separate the contact pads and the functional layer, but also ensures that the individual layers (electrodes, functional layer) have the same extension parallel to the substrate. The intermediate layers thus extend the functional layer and the electrodes, so that all layers have the same extension parallel to the substrate. This ensures that the side surface of the sensor element is as free as possible from edges or steps. Scattering effects are effectively avoided.

[0060] According to one embodiment, the respective intermediate layer is formed circumferentially around the at least one functional layer. The respective intermediate layer can furthermore be formed in a U-shape around the respective electrode. This allows the respective layer to be effectively protected from external influences. According to one embodiment, the sensor element further comprises insulation. The insulation protects the sensor element from external influences. The insulation is designed and arranged such that it completely encloses at least a partial region of the sensor element. Preferably, at least the at least one functional layer and the at least two intermediate layers are completely surrounded by the insulation. Furthermore, at least a partial region of the at least two electrodes is enclosed by the insulation. The electrodes are preferably completely enclosed by the insulation.The contact pads are designed in such a way that they protrude from the insulation on the upper side of the sensor element for electrical contact with the sensor element.

[0061] According to one embodiment, the sensor element has a first or upper partial region. The sensor element further has a second or lower partial region. The first partial region has a width B1. The second partial region has a width B2. In this context, width is understood to mean the extent of the respective partial region along the main direction of extent of the sensor element. In particular, width is understood to mean the extent parallel to the carrier.

[0062] The two subregions are arranged one above the other. The first subregion comprises, in particular, the functional layer, the electrodes, the intermediate layers, and the contact pads. The first subregion can also comprise the insulation. The second subregion comprises, in particular, the carrier and the insulating layer. One side surface, preferably all side surfaces of the first subregion and / or the second subregion are free of steps. In other words, the

[0063] The outer surfaces of each section are smooth.

[0064] The subregions are formed such that B1 < B2. In other words, the first subregion can be the same width as the second subregion. In this case, there is no step / edge at all on the side surface of the sensor element. Alternatively, the width of the first subregion can also be smaller than the width of the second subregion. In this case, a (single) step / edge is formed on the side surface of the sensor element at the transition between the first and second subregions.

[0065] According to a further aspect, a method for producing at least one sensor element is described. It should be noted that the method preferably involves producing a plurality of sensor elements, for example, 20,000 sensor elements, in parallel and then separating them from one another. For the sake of simplicity, reference will be made below primarily to one sensor element where appropriate.

[0066] Preferably, the above-described sensor element is produced by the method. The respective sensor element has only a small rejection range from a target resistance. The sensor elements produced by the method as a whole have a narrow resistance tolerance.

[0067] All properties disclosed with respect to the sensor element or the method are also disclosed correspondingly with respect to the respective other aspect, and vice versa, even if the respective property is not explicitly mentioned in the context of the respective aspect. The method comprises the following steps:

[0068] A) Providing a carrier material to form a support. The support 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.

[0069] B) Forming an insulating layer on a top side of the carrier. The insulating layer can comprise Al2O3AlN, SiO2 or Si3N4, or combinations of layers of these materials. Preferably, the insulating layer completely covers the top 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, depending on the material).

[0070] C) Applying a first electrode (bottom electrode) to the insulating layer / top surface of the substrate. The electrode material is deposited using a PVD process.

[0071] ("physical vapor deposition") process, a COVD ("chemical vapor deposition") process, or galvanically. Alternatively, deposition can also be carried out using an ALD (atomic layer deposition) process. Preferably, the electrode is deposited only on a partial area of ​​the insulating layer. In other words, a partial area of ​​the insulating layer / carrier remains free of the metallic material of the bottom electrode.

[0072] D) Applying at least one intermediate layer to the insulating layer. In particular, the intermediate layer is applied to the portion that remains free of the metallic material of the bottom electrode. The intermediate layer and bottom electrode can have the same thickness / height. In this case, the intermediate layer and bottom electrode form a single plane. Alternatively, the intermediate layer can also be made thicker.

[0073] E) Applying at least one functional layer to at least a portion of the bottom electrode. This is done, for example, by sputtering or a spin-coating process.

[0074] The functional layer can be formed on the plane formed by the intermediate layer and the bottom electrode. Alternatively, the functional layer can also be formed only on a portion of this plane. In this case, an additional intermediate layer is formed in a further step as a buffer between the functional layer and the contact pads described above.

[0075] F) Applying at least one additional electrode. The electrode is applied directly to at least a portion of the functional layer. In other words, a portion of the functional layer may remain free of the metallic material of the electrode.

[0076] G) Applying at least one further intermediate layer. The intermediate layer can be formed in the portion of the functional layer left free from the metallic material of the further electrode. Alternatively or additionally, an intermediate layer can be formed as a buffer between the functional layer and the contact pads described above. H) Structuring at least one of the electrodes to form at least one trimmable region for resistance adjustment. This can be done, for example, by wet-chemical etching, dry etching, or laser structuring. Preferably, the uppermost electrode is structured as described above.

[0077] I) Formation of contact pads for electrically contacting the sensor element. In the final contacted sensor element, the electrodes of the same polarity are connected vertically (i.e., in the stacking direction) with a metallic material. The contact pads preferably comprise metals such as Cu, Al, or Au.

[0078] The functional layer is then measured. This determines the initial tolerance range of the resistance value of the sensor elements, allowing the resistance of the respective sensor element to be adjusted to the desired value later.

[0079] J) Adjusting the resistance value by trimming at least one structured electrode. Trimming is preferably performed using a laser. The resistance value is adjusted to a predetermined nominal value (setpoint). By precisely adjusting the resistance value of the respective sensor element, the finished sensor elements as a whole exhibit a very tight resistance tolerance.

[0080] According to one embodiment, insulation is further formed on at least a partial area of ​​a surface of the sensor element. This protects the sensor element from external influences. This step can be performed before or after step J). If the insulation is formed before step J), the structured electrode remains free of insulation so that trimming can be performed subsequently.

[0081] The drawings described below are not to be considered true to scale. Rather, individual dimensions may be enlarged, reduced, or distorted for clarity.

[0082] Elements that are identical or that perform the same function are designated by the same reference symbols.

[0083] They show:

[0084] Figure 1 shows a sensor element according to the state of the

[0085] Technology,

[0086] Figure 2 shows a cross section of a sensor element according to a first embodiment,

[0087] Figure 3 shows a cross section of a sensor element according to a further embodiment,

[0088] Figure 4 shows a cross section of a sensor element according to a further embodiment,

[0089] Figures 5a to 5c show a plan view of individual components of the sensor element according to Figure 4,

[0090] Figure 6 shows a cross section of a sensor element according to a further embodiment, Figure 7 shows a plan view of the top side of the

[0091] Sensor element with the trimmable electrodes.

[0092] Figure 1 shows a representation of a sensor element 1 according to the prior art. The sensor element 1 is a multilayer NTC thin-film temperature sensor and has a carrier 4, first and second electrodes 3a, 3b, and functional layers 2.

[0093] The sensor element 1 serves to illustrate a basic structure of the sensor element 10 described below. With regard to the essential features of the sensor element 1 according to Figure 1, reference is made to the document WO 2021 / 004957 A1.

[0094] The design of sensor element 1 has several disadvantages. The stepped design complicates process control. In particular, the formation of electrodes 3a, 3b can result in insufficient edge coverage and thus poor contact. Furthermore, the stepped design leads to electrical scattering effects in the overlap areas at the outer regions due to diagonal current paths of different path lengths. For path lengths shorter than the distance from electrode 3a, 3b to functional layer 2, local hotspots occur due to increased voltage drop at the thin point. This makes it difficult to achieve low resistance scatter, and the scatter of the components is outside the usual scatter range. The disadvantages mentioned are reduced or eliminated in the exemplary embodiments of sensor element 10 described below.

[0095] Figure 2 shows a cross-section of a sensor element 10 according to a first embodiment. The sensor element 10 is a thin-film NTC temperature sensor. The sensor element 10 has a top side 10a and a bottom side 10b, as well as side surfaces 10c.

[0096] The sensor element 10 is designed for direct integration into a MEMS structure and / or into a SESUB structure. For this purpose, the sensor element 10 is designed to be very compact. A maximum edge length (i.e. the dimension along a main extension direction X) is 1000 pm, preferably < 800 pm, particularly preferably < 500 pm. A thickness or height of the sensor element 10 (i.e. the extension in a direction perpendicular to the main extension direction X) is < 100 pm, preferably < 80 pm, particularly preferably < 50 pm. Due to its small dimensions, the sensor element 10 is optimally suited to be embedded as a discrete component directly into a MEMS / SESUB structure.

[0097] The sensor element 10 has a carrier 11. The carrier 11 preferably comprises silicon, silicon carbide, or glass (silicate or borosilicate glass). Alternatively, the carrier 11 can also comprise AlN, Si3N4, or Al2O3. The carrier 11 can have a rectangular or square base area. As described above, a maximum edge length of the carrier 11 is 1000 pm in both cases, advantageously <800 pm, ideally <500 pm. The carrier 11 has a top side 18 and a bottom side 19. An insulating layer 12 is formed on the top side 18 and completely covers the top side 18 of the carrier. A thickness d of the insulating layer 12 (see also Figure 4) is < 1.5 gm. The insulating layer 12 can be constructed from one or more layers and can comprise, for example, Al2O3, AlN, SiO2 or Si3N4 or combinations of layers of these materials.

[0098] In this exemplary embodiment, the sensor element 10 further comprises three functional layers 15. The sensor element 10 can, of course, also comprise 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 realized. The functional layers 15 are arranged one above the other or stacked. The functional layers 15 are connected in parallel.

[0099] The thickness or height of the respective 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 layers 15 comprise a material with specific electrical characteristics. The respective functional layer 15 comprises an NTC ceramic. The respective functional layer 15 is preferably a thin film with NTC characteristics.

[0100] The functional layer 15 is preferably based on an oxide material in the perovskite or spinel structure type. Alternatively, the functional layer 15 can be constructed based on a carbide or nitride material. In particular, the following functional layers 15 are conceivable: - Oxide: for example, perovskite (based on mixed crystals of the composition CaMnO 3, in which Ca can be completely or partially replaced by, for example, Y, Cr, Al or La) or spinel (based on solid solutions of NiMn2O4, in which Ni and Mn can be completely or partially replaced by, for example, Fe, Co, Al); b) Carbide, for example (Si,Ti)C, hexagonal or cubic SiC; c) Nitridic, for example (Al,Ti)N, CrN.

[0101] Another alternative is thin films of vanadium oxide.

[0102] In this exemplary embodiment, the sensor element 10 further comprises a plurality of electrodes or electrode layers 13a, 13b, in particular four electrodes 13a, 13b. Of course, the sensor element 10 can also comprise 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 contacted). The electrodes 13a, 13b of opposite polarity can also be referred to as first electrodes 13a and second electrodes 13b. The electrodes 13a, 13b can be single-layered or multi-layered and comprise, for example, Cu, Au, Ni, Cr, Ag, Ti, Ta, W, Pd, or Pt. The electrodes 13a, 13b are designed as thin-film electrodes.

[0103] An electrode 13a, 13b (hereinafter the bottom electrode) is formed directly on the insulating layer 12. The bottom electrode does not completely cover the insulating layer 12, as can be seen from Figure 2. Rather, a strip-shaped region of the insulating layer 12 remains free of the electrically conductive material of the bottom electrode, as will be explained in more detail below.

[0104] A (lowest) functional layer 15 is formed directly on the lowest electrode 13a, 13b. The lowest electrode does not necessarily have to be completely covered by the functional layer 15. A further electrode 13a, 13b is arranged at least partially directly on the functional layer 15. This layered structure is continued. In particular, a functional layer 15 is always arranged at least partially between two electrodes 13a, 13b.

[0105] The respective electrodes 13a, 13b are vertically connected to one another at the side surfaces 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 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 this exemplary embodiment, the contact pads 16, 16b have direct contact with the functional layers 15. The contact pads can comprise Cu, Au, Ni, Cr, Ag, Ti, Ta, W, Pd, or Pt.

[0106] Furthermore, the sensor element 10 in this exemplary embodiment 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 explicitly shown), or the sensor element 10 can have more than four intermediate layers 14. The respective intermediate layer 14 comprises an insulating material. The respective intermediate layer 14 comprises, for example, Al2O3, AlN, SiO2, or Si3N4.

[0107] In this exemplary embodiment, a thickness or height (i.e., the extension perpendicular to the main extension direction X) of the respective intermediate layer 14 is as large as a thickness or height of the respective electrodes 13a, 13b. In other words, the electrodes 13a, 13b and the intermediate layers 14 are of equal height. However, the thickness / height of the intermediate layer 14 can also be greater than the thickness / height of the electrodes 13a, 13b (see Figures 3, 4, and 6). For example, the intermediate layer 14 can extend perpendicular to the main extension direction X across multiple layers of the sensor element 10, as will be explained in more detail below.

[0108] In the embodiment according to Figure 2, 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). For example, it can be seen from Figure 2 that the bottommost electrode does not completely cover the insulating layer 12. Rather, there is a region on the insulating layer 12 in the form of a strip that is not metallized, as already mentioned above.

[0109] This free space is filled with the insulating material of the intermediate layer 14. The intermediate layer 14 thus continues the bottom electrode. The bottom functional layer 15 is formed on these two layers (bottom electrode and intermediate layer 14) or the plane formed by these layers. A second electrode 13b is then formed on the bottom functional layer 15, which does not completely cover the functional layer 15 on the left side in Figure 2. This free space is again covered with an intermediate layer 14. Likewise, an intermediate layer 14 also continues or extends the other electrodes 13a, 13b in the X direction.

[0110] The insulating intermediate layers 14 fill the individual layers of the sensor element 10 (in this embodiment, the electrodes 13a, 13b). This reduces the stepped shape of the sensor element 10 compared to the prior art according to Figure 1, as explained in more detail below:

[0111] The sensor element 10 has a first partial area 23 and a second partial area 24 (see in particular Figure 6). The partial areas 23, 24 are arranged one above the other. The first partial area 23 has a width B1 and the second partial area 24 has a width B2. In this context, width is understood to mean the extent of the respective partial area 23, 24 along the main extension direction X (X direction). In this exemplary embodiment, B1 < B2. In principle, however, B1 = B2 is also possible (see, for example, Figures 3 and 6).

[0112] The first partial region 23 comprises, in particular, the functional layers 15, the electrodes 13a, 13b, the intermediate layers 14, and the contact pads 16a, 16b. The second partial region 24 comprises, in particular, the carrier 11 and the insulating layer 12. As can be seen from Figure 2, one side surface of the first partial region 23 is completely free of edges or steps. The same applies to the side surface of the second partial region 24. A step is only present in a transition region between the first partial region 23 and the second partial region 24. In other words, the outer surfaces of the respective partial regions 23, 24 are smooth. This is achieved in that all layers of the first partial region 23 have the same extent along the X-axis, since individual layers are filled with the intermediate layers 14.

[0113] The formation of the intermediate layers 14 and the resulting reduction in the stepped shape of the sensor element 10 effectively reduces electrical stray effects. Furthermore, the possibility of hot spots forming is reduced.

[0114] The entire sensor elements 10 exhibit a narrow resistance tolerance. This means that each sensor element 10 exhibits a very small deviation range from the nominal resistance.

[0115] To adjust the resistance value of the respective sensor element 10, one of the electrodes 13a, 13b is structured (see Figure 7). Preferably, the uppermost electrode, i.e., the one of the electrodes 13a, 13b closest to the top side 10a of the sensor element 10, is structured. The electrode thus has trimmable regions (see trimmable regions 17 in Figure 7). These regions can be severed with a laser, resulting in a change in the overall surface area of ​​the electrode and thus in the resistance. By achieving a narrow resistance tolerance of the sensor elements 10, the sensor elements 10 have very high temperature measurement accuracy. The sensor elements 10 preferably have a resistance tolerance comparable to the narrow resistance tolerance of conventional designs such as SMD NTCs or NTC chips.

[0116] In the embodiment described in connection with Figure 2, each functional layer 15 has an additional contact with the contact pads 16a, 16b, which can lead to scattering effects at the outer regions of the sensor element 10 due to diagonal current paths with different path lengths. To further eliminate scattering effects, in the embodiment according to Figure 3, the respective functional layer 15 is designed such that it is located only in one overlap region 21 formed by the two electrodes 13a, 13b.

[0117] As can be seen from Figure 3, the electrodes have the overlap region 21. In the overlap region 21, the electrodes 13a, 13b are layered one above the other. In contrast to the embodiment according to Figure 2, the functional layers 15 are now designed such that they do not extend beyond the overlap region 21. In other words, the width of the functional layers 15 is reduced compared to the functional layers according to Figure 2.

[0118] For this purpose, an intermediate layer 14 is formed in a region 22 between the respective functional layer 15 and the contact pads 16a, 16b. This intermediate layer 14 closes the gap that occurs because the functional layers 15 no longer extend beyond the overlap region 21. In this exemplary embodiment, the intermediate layers 14 therefore extend not only the electrodes 13a, 13b, but also the functional layers 15. This ensures that the side surface 10c of the sensor element 10 is as free as possible from edges or steps. Furthermore, a width of the individual layers of the first partial region 23 in this exemplary embodiment is selected such that a step between the first and second partial regions 23, 24 is eliminated (i.e., B1 = B2). Scattering effects are effectively avoided.

[0119] The thickness of the intermediate layer can be greater than the thickness of a single electrode 13a, 13b / electrode layer. In particular, the respective intermediate layer 14 extends perpendicular to the main extension direction X across multiple layers of the sensor element 10. Thus, the maximum thickness or height of the intermediate layer 14 can reach the total height of two functional layers 15 plus one electrode layer 13a, 13b, as can be seen from Figure 3. In other words, the intermediate layer 14 in the finally contacted sensor element 10 is filled at most by one electrode 13a, 13b of one polarity up to the electrode 13a, 13b of the same polarity following it in the stacking direction. The maximum thickness of the intermediate layer 14 therefore corresponds to the distance A between two electrodes 13a, 13b of the same polarity (see also Figure 4).

[0120] With regard to all further features of the sensor element 10, reference is made to the description in connection with Figure 2.

[0121] Figures 4 and 5a to 5c show a sensor element 10 and individual components thereof according to a further exemplary embodiment. In the two previously described embodiments according to Figures 2 and 3, two of four side surfaces of the individual layers are exposed and therefore not protected. To enable protection of these, the insulating intermediate layers 14 in the exemplary embodiment according to Figure 4 are each designed to run circumferentially around the functional layer 15 (see also Figure 5b). In other words, with the exception of a top side and a bottom side of the functional layer 15, all surfaces of the respective functional layer 15 are enveloped by the insulating material of the intermediate layer 14.

[0122] To avoid a stepped configuration of the sensor element 10, the intermediate layers 14 are deposited in a U-shape around each electrode 13a, 13b (Figures 5a and 5c). Thus, it can be seen from Figures 5a and 5c that, with the exception of a top side, a bottom side, and one side surface of the respective electrode 13a, 13b, the remaining side surfaces of the electrodes 13a, 13b are completely surrounded by the insulating material of the intermediate layer 14. In other words, three of the four side surfaces of the respective electrode 13a, 13b are encased in the intermediate layer 14.

[0123] With regard to all further features of the sensor element 10, reference is made to the description in connection with Figure 2.

[0124] Figure 6 shows a cross-section of the sensor element 10 according to a further exemplary embodiment. Here, the sensor element 10 is at least partially enclosed circumferentially by an insulation 20. In particular, at least the side surface 10c of the sensor element 10 (without the carrier 11) is preferably completely enclosed by the insulation 20. The insulation 20 encloses, in particular, the electrodes 13a, 13b (an exception to this may be the uppermost electrode, as described below), the functional layers 15 and the intermediate layers 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. Enclosing the insulating layer 12 and the carrier 11 is also possible in principle (not explicitly shown).

[0125] Since the top electrode has the trimmable areas 17 (see Figure 7), which can be cut depending on the desired resistance value, the top electrode must be freely accessible for laser trimming. Therefore, there are two possible designs for the insulation 20 in the area of ​​the top side 10a of the sensor element 10:

[0126] - The top electrode can remain completely free of the insulation 20 so that it is accessible at any time for resistance adjustment (not explicitly shown).

[0127] Alternatively, the insulation on the top side 10a of the sensor element 10 can also be formed after trimming. For example, after trimming, a polymer layer, an oxide, nitride, ceramic layer, a thin glass layer, or a combination of these layers can be formed as insulation 20 on the topmost / structured electrode.

[0128] As can be seen from Figure 6, the contact pads 16a, 16b protrude from the insulation 20 on the top side 10a of the sensor element in every possible embodiment to enable electrical contact with the sensor element 10. For this purpose, the contact pads 16a, 16b are constructed higher in this embodiment. In particular, an upper side of the contact pads 16a, 16b is not in the same plane as an upper side of the uppermost electrode.

[0129] With regard to all further features of the sensor element 10, reference is made to the description in connection with Figure 2.

[0130] A method for manufacturing the sensor element 10 is described below. In particular, the method produces a plurality of sensor elements 10 according to one of the exemplary embodiments described above (see Figures 2 to 7). For the sake of simplicity, reference is made below—where appropriate—to only one sensor element 10.

[0131] All features described in connection with the sensor element 10 also apply to the method and vice versa.

[0132] The procedure includes the following steps:

[0133] A) Providing a carrier material for forming the carrier 11. The carrier material preferably comprises Si, SiC, or glass. Alternatively, the carrier material can also comprise AlN, SiSn4, or Al2O3.

[0134] B) Forming the insulating layer 12 on the top side 18 of the carrier 11. The insulating layer 12 may comprise Al2O3, AlN, SiO2, or SiO2, or combinations of layers of these materials. Preferably, the insulating layer 12 is deposited such that it completely covers the top side 18 of the carrier 11.

[0135] The insulating layer 12 may be required as a flat base surface to form the additional layers (electrodes 13a, 13b, intermediate layers 14, functional layers 15) thereon. If the surface 18 of the carrier 11 is flat enough and / or the carrier 11 itself is formed from an insulating material, the formation of the insulating layer 12 according to step B) can also be omitted (optional step).

[0136] C) Application of a first electrode 13a, 13b (bottommost electrode). The electrode 13a, 13b is deposited using a DVD, ALD, or CVD process, or electroplating. Preferably, the electrode 13a, 13b is deposited only on a portion of the insulating layer 12. A strip-shaped region of the insulating layer 12 remains free of electrode material so that an intermediate layer 14 can subsequently be formed in this free region.

[0137] D) Applying at least one intermediate layer 14 to the insulating layer 12 to extend the electrode 13a, 13b. The intermediate layer 14 comprises an insulating material and is formed in the portion of the insulating layer 12 left free from the metallic material of the electrode 13a, 13b (free area). The intermediate layer 14 and the bottom electrode can form a plane, i.e., have the same height (Figure 2). Alternatively, the intermediate layer 14 can also be higher than the electrode 13a, 13b (Figures 3, 4, 6).

[0138] E) Applying at least one functional layer 15. This is done, for example, by sputtering or a spin-coating process, as well as at least one temperature process at T > 500°C during and / or after the deposition of the respective layer. The functional material comprises an NTC ceramic based on an oxide material in the perovskite or spinel structure type. Alternatively, the functional material can also be based on a carbide or nitride material. In a further alternative, the functional material comprises or consists of thin films of vanadium oxide.

[0139] The functional layer 15 is formed, for example, on the plane formed by the intermediate layer 14 and the bottommost electrode (see Figure 2). The functional layer 15 can either be deposited on the entire bottommost electrode 13a, 13b (Figure 2), or the functional layer 15 is not formed all the way to the edge of the bottommost electrode. This means that on the opposite side of the intermediate layer 14 (left in Figure 2), the bottommost electrode is not covered all the way to the edge. In this case, a further intermediate layer 14 is subsequently formed, which is formed on the area of ​​the bottommost electrode left free (by the functional layer 15) (Figures 3, 4, 6).

[0140] F) Applying at least one additional electrode 13a, 13b. The electrode 13a, 13b is deposited using a PVD, ALD, or CVD process, or galvanically. The additional electrode 13a, 13b is formed directly on the functional layer 5. The additional electrode 13a, 13b can, for example, be formed only on a partial area of ​​the functional layer 15 (see the exemplary embodiment according to Figure 2).

[0141] G) Applying at least one further intermediate layer 14.

[0142] The intermediate layer 14 comprises an insulating material and is formed, for example, in the portion of the functional layer 15 left free from the metallic material of the further electrode 13a, 13b. Alternatively or additionally, intermediate layers 14 can be formed in the region between the functional layer 15 and the contact pads 16a, 16b. This occurs following step I).

[0143] H) Structuring at least one of the electrodes 13a, 13b to form at least one trimmable region 17 for resistance adjustment. This can be done, for example, by wet-chemical etching, dry etching, or laser structuring. Preferably, the topmost electrode is structured as described above.

[0144] I) Forming contact pads 16a, 16b for electrically connecting the sensor element 10. In particular, in the fully contacted sensor element 10, the electrodes 13a, 13b of the same polarity are connected vertically (i.e., in the stacking direction) with a metallic material. The contact pads 16a, 16b preferably comprise metals such as Cu, Al, or Au.

[0145] The functional layer 15 is then measured. This determines the initial tolerance range of the resistance value of all the manufactured sensor elements 10, so that the resistance of each sensor element 10 can then be adjusted to the desired value.

[0146] J) Adjusting the resistance value by trimming the at least one structured electrode 13a, 13b. Trimming is preferably performed using a laser. The resistance value is set to a predetermined nominal value (setpoint). By precisely adjusting the resistance value, the finished sensor elements 10 exhibit a very narrow resistance tolerance. To adjust the resistance value, the previously described structured / trimmable regions 17 are at least partially severed.

[0147] K) Forming the insulation 20 on at least a partial area of ​​a surface of the sensor element 10.

[0148] Step K) can also be performed before step J). In this case, the top electrode remains free of insulation 20 so that trimming can be performed subsequently.

[0149] In addition to the above-mentioned process steps, the sensor element 10 can be subjected to a sintering process in a further process step.

[0150] The carrier material can then be thinned using a grinding or etching process.

[0151] 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 in any way—as long as technically feasible.

[0152] List of reference symbols

[0153] 1 sensor element

[0154] 2 functional layer

[0155] 3a First electrode

[0156] 3b Second electrode

[0157] 4 carriers

[0158] 10 Sensor element

[0159] 10a Top of the sensor element

[0160] 10b Bottom of the sensor element

[0161] 10c Side surface of the sensor element

[0162] 11 carriers

[0163] 12 Insulating layer

[0164] 13a Electrode / electrode layer

[0165] 13b Electrode / electrode layer

[0166] 14 Intermediate layer

[0167] 15 functional layer

[0168] 16a Contact pad

[0169] 16b Contact pad

[0170] 17 Trimmable area

[0171] 18 Top of the carrier

[0172] 19 Underside of the carrier

[0173] 20 Insulation

[0174] 21 Overlap area

[0175] 22 Area

[0176] 23 First section

[0177] 24 Second sub-area d Thickness of the insulating layer

[0178] Bl Width of the first subarea

[0179] B2 Width of the second sub-area

[0180] X Main direction of extension Distance

Claims

Patent claims 1. Sensor element (10) for measuring a temperature, 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 spaced apart from one another on the carrier (2), - at least one functional layer (15) comprising a material with a temperature-dependent electrical 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) comprising an insulating material, - at least two contact pads (16a, 16b) for electrically contacting the sensor element (10), wherein the sensor element (10) is designed to be integrated directly into an electrical system as a discrete component, and wherein 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 for adjusting the resistance value.

2. Sensor element (10) according to claim 1, comprising an upper side (10a) and a lower side (10b), wherein an electrode (13a, 13b) closest to the upper side (10a) of the sensor element (10) is structured for adjusting the resistance value.

3. Sensor element (10) according to claim 2, wherein the electrode (13a, 13b) closest to the top side (10a) of the sensor element (10) has trimmable regions (17).

4. Sensor element (10) according to one of the preceding claims, wherein the respective intermediate layer (14) is arranged such that direct contact between the at least one functional layer (15) and the contact pads (16a, 16b) is prevented.

5. Sensor element (10) according to one of the preceding claims, wherein the respective intermediate layer (14) is formed as an extension of the electrodes (13a, 13b) along a main extension direction (X) of the sensor element (10).

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

7. Sensor element (10) according to one of the preceding claims, wherein the electrodes (13a, 13b) have an overlap region (21) in which the electrodes (13a, 13b) are formed one above the other and wherein the at least one functional layer (15) is formed such that expansion of the functional layer (15) beyond the overlap region (21) is prevented.

8. Sensor element (10) according to one of the preceding claims, wherein the respective intermediate layer (14) is formed circumferentially around the at least one functional layer (15).

9. Sensor element (10) according to one of the preceding claims, wherein an intermediate layer (14) is U-shaped around the respective electrode (13a, 13b).

10. Sensor element (10) according to one of the preceding claims, wherein a thickness of the respective intermediate layer (14) is greater than or equal to a thickness of the respective electrode (13a, 13b).

11. Sensor element (10) according to one of the preceding claims, further comprising an insulation (20), wherein at least the at least one functional layer (15) and the intermediate layers (14) are completely surrounded by the insulation (20) and wherein at least a partial region of the electrodes (13a, 13b) is surrounded by the insulation (20).

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

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

14. Sensor element (10) according to one of the preceding claims, comprising a first partial region (23) with a width B1, which comprises the functional layer (15), the electrodes (13a, 13b), the intermediate layers (14) and the contact pads (16a, 16b) and a second partial region (24) with a width B2, which comprises the carrier (11) and the insulating layer (12), wherein B1 < B2.

15. Sensor element (10) according to claim 14, wherein a side surface of the first partial region (23) and / or the second partial region (24) is free of steps.

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

17. Sensor element (10) according to claim 16, wherein a portion of the insulating layer (12) is free of an electrically conductive material of the lowermost electrode.

18. Sensor element (10) according to claim 17, wherein one of the at least two intermediate layers (14) is formed in the free partial region.

19. Sensor element (10) according to one of the preceding claims, wherein the respective electrode (13a, 13b) is designed as a thin-film electrode.

20. Sensor element (10) according to one of the preceding claims, wherein the at least one functional layer (15) is a thin film with NTC properties.

21. Sensor element (10) according to one of the preceding claims, wherein the carrier (11) comprises silicon, silicon carbide or glass or wherein the carrier (11) comprises Si3N4AIN, GaN or Al2O3 as carrier material.

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

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

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

25. Sensor element (10) according to one of the preceding claims, wherein the insulating layer (12) is formed in a single layer or in multiple layers and AI2O3,AAIIA 22 OOLIN 33 , SiO2or Si3N4or combinations of layers of these materials.

26. Sensor element (10) according to one of claims 11 to 25, wherein the insulation (20) is formed in a single layer or in multiple layers and comprises Al2O3, AlN, SiO2 or Si3N4 or combinations of layers of these materials.

27. Sensor element (10) according to one of claims 11 to 26, wherein the insulation (20) comprises oxides, nitrides, ceramics, glasses or plastic as material.

28. Sensor element (10) according to one of the preceding claims, wherein 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 a temperature, comprising the following steps: A) providing a carrier material for forming a carrier (11); B) forming an insulating layer (12) on a top side (18) of the carrier (11); C) applying at least one electrode (13a, 13b) to a partial area of ​​the carrier (11) so that an area of ​​the carrier (11) remains free of electrode material; D) applying at least one intermediate layer (14) to the free portion of the carrier (11); E) applying at least one functional layer (15) to at least a partial area of ​​a plane formed by the electrode (13a, 13b) and the intermediate layer (14); F) Applying at least one further electrode (13a, 13b) to at least a partial area of ​​the functional layer G) applying at least one further intermediate layer (14) to a portion of the functional layer (15) free from the further electrode (13a, 13b); H) Structuring at least one of the electrodes (13a, 13b) to form at least one trimmable region (17) for resistance adjustment; I) Forming contact pads (16a, 16b) for electrically contacting the sensor element (10).

30. The method of claim 29, further comprising the step: J) Adjusting the resistance value by trimming the at least one structured electrode (13a, 13b).

31. The method according to any one of claims 29 or 30, further comprising the step: K) forming an insulation (20) on at least a partial area of ​​a surface of the sensor element (10).

32. The method according to any one of claims 29 to 31, further comprising the step: Forming at least one further intermediate layer (14) between the contact pads (16a, 16b) and the functional layer (15).

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