Sensor element and method for manufacturing the same

Abstract

A sensor element (100) for temperature measurement is described, comprising a carrier (2) and at least one functional layer (7) including a material with temperature-dependent electrical resistance, the functional layer (7) being disposed on an electrical insulating layer (3). The sensor element (100) further comprises at least two electrodes (4a, 4b) with electrode fingers (5) and at least two contact pads (10a, 10b) for electrical contact with the sensor element (100), each of the contact pads (10a, 10b) being disposed directly on a partial region of one of the electrodes (4a, 4b). The sensor element (100) is designed to be directly integrated into an electrical system as a discrete component. The sensor element (100) has narrow resistance tolerances, and the at least one functional layer (7) and / or at least one of the at least two electrodes (4a, 4b) are structured to adjust the resistance value. Furthermore, a method for manufacturing the sensor element (100) is described.

Description

[Technical Field]

[0001] The present invention relates to a sensor element, in particular a temperature sensor.The present invention further relates to a method for manufacturing at least one sensor element, preferably a temperature sensor. [Background technology]

[0002] To integrate passive components such as sensors, capacitors, protection components, and heaters into electrical systems, they must be adapted to modern packaging designs with dimensions in the micrometer and even nanometer range. To achieve such miniaturization, components are deposited as thin films on carrier structures with electrical connections, described as individual components. These new components can be integrated into MEMS (Micro Electro Mechanical Systems) and SESUB (Semiconductor Embedded in Substrate) structures, for example.

[0003] As the demand for accuracy in temperature measurement increases, narrow tolerances are required for the resistance variations of such sensor elements. However, as structures become smaller, the influence of manufacturing tolerances becomes increasingly greater, resulting in resistance variations exceeding the required tolerances. Process control can only reduce the resistance variations to a limited extent.

[0004] According to the prior art, temperatures for monitoring and control in various applications are mainly measured using ceramic thermistor elements (NTC), silicon temperature sensors (KTY), platinum temperature sensors (PRTD), or thermocouples (TC). NTC thermistors are the most widely used due to their low manufacturing costs. An additional advantage over metallic resistance elements such as thermocouples and platinum elements is their pronounced negative resistance-temperature characteristic.

[0005] For use in power modules, soldered SMD (surface mounted device) NTC temperature sensors are predominantly used, while lower power control modules use NTC chips attached to the underside using Ag sinter paste, soldering or adhesive, with the top side contacted via bonding wire.

[0006] For electrical contact of the NTC chip, metal electrodes have to be applied. According to the prior art, thick film electrodes based on silver or gold paste are applied by a screen printing process followed by firing.

[0007] For example, the integration of electronic components into MEMS or SESUB structures requires very small elements that must also be possible to integrate using suitable contact methods. Typical assembly techniques for SMD designs or NTC chips cannot be used for this.

[0008] German patent application DE 10 2020 122923 A1, the content of which is incorporated herein by reference, describes a sensor element for temperature measurement comprising a thin-film NTC thermistor.

[0009] Until now, thin film NTC temperature sensors could not be manufactured to the same tight tolerances as typical designs (SMD NTC or NTC chip). Summary of the Invention

[0010] The object of the present invention is to provide a sensor element and a method for manufacturing the sensor element that solves the above problems.

[0011] This problem is solved by a sensor element and a method for manufacturing a sensor element according to the independent claims.

[0012] According to one embodiment, a sensor element is described. The sensor element 1 is suitable for measuring temperature. The sensor element is a temperature sensor. Preferably, the sensor element is a thin-film NTC temperature sensor. The operating temperature of the sensor element is between -40°C and 125°C.

[0013] The sensor element has at least one carrier. Preferably, the sensor element has exactly one carrier. The carrier comprises a carrier material, preferably silicon, silicon carbide, GaN or glass (silicate or borosilicate glass). Alternatively, the carrier material can comprise Si3N4, AlN or Al2O3.

[0014] The carrier has a top surface and a bottom surface. The top surface is electrically insulating. Preferably, an insulating layer, such as Al2O3, AlN, SiO2, Si3N4, or a combination of layers of these materials, is formed directly on the top surface of the carrier. The insulating layer is formed directly on the top surface of the carrier and can be composed of one or more layers.

[0015] The sensor element further comprises at least one functional layer, which is arranged on the carrier, in particular on the electrically insulating upper surface of the carrier.

[0016] The carrier mechanically stabilizes the functional layer, which can be formed directly on the carrier, or other components of the sensor element, such as electrodes, can be formed between the carrier and the functional layer.

[0017] The resistance of the sensor element is influenced by the particular shape and / or structure of the functional layer, for example its size and width, which may vary or be varied.

[0018] The thickness of the functional layer is 50 nm to 1 μm, preferably 100 nm to 500 nm, and particularly preferably 250 nm to 400 nm. The functional layer contains a material (functional material) with special electrical properties. The functional layer contains a material with temperature-dependent electrical resistance. For example, the resistivity of the functional layer at an operating temperature of 25°C is ρ=3 Ωm.

[0019] Preferably, the functional layer is an NTC ceramic. Preferably, the functional layer is a thin film with NTC properties. Preferably, the NTC ceramic is based on an oxidizing material of the perovskite or spinel structure type. Alternatively, the functional layer can be based on a carbide or nitride material. Further options include thin films of vanadium oxide or SiC.

[0020] The sensor element further comprises at least two electrodes. The electrodes are preferably formed as thin-film electrodes. The electrodes are formed on the carrier at a distance from one another. Preferably, the electrodes do not protrude into the edge regions of the carrier. Particularly preferably, the electrodes are formed in the center or in the inner region of the carrier. Each electrode has a plurality of electrode fingers. The electrode fingers of the two electrodes are arranged alternately with one another. The electrodes thus form an interdigital structure.

[0021] The resistance of the sensor element is affected by the electrode structure, for example the length, number and / or distance between the electrode fingers (gap width).

[0022] The sensor element further has at least two contact pads for electrical contact of the sensor element. Preferably, the sensor element has exactly two contact pads. The contact pads are electrically and mechanically connected directly to the electrodes. One contact pad is respectively arranged directly on a partial region of one of the electrodes. The sensor element can also be attached using fine wire bonding via the contact pads.

[0023] The sensor element is designed to be very compact. In particular, the sensor element is configured for direct integration as a discrete component into an electrical or electronic system. For example, the maximum edge length of the sensor element is 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. The dimensions of the sensor element are particularly preferably 300 μm x 500 μm x 50 μm. The component is preferably configured for direct integration into MEMS and / or SESUB structures.

[0024] The sensor element also has a narrow resistance tolerance, which means that the sensor element has a very small range of deviation from the target resistance (nominal value of resistance).

[0025] The at least one functional layer and / or at least one of the at least two electrodes may be structured to adjust the resistance. The at least one functional layer and / or at least one of the at least two electrodes may be trimmable to adjust the resistance. In particular, at least a partial region of the at least one functional layer and / or at least a partial region of at least one of the at least two electrodes may be cut or severed to adjust the resistance.

[0026] If the resistance value of the component to be trimmed already corresponds to the target value, the structuring / trimmable area is not split.

[0027] By achieving a narrow resistance tolerance, the sensor element has a very high accuracy in temperature measurement. Preferably, the sensor element has a resistance tolerance comparable to the narrow resistance tolerance of classic designs such as SMD NTC or NTC chips.

[0028] The electrical characteristics of the sensor element are similar to a standard NTC chip: - R(25°C)=10kΩ or more and 100kΩ or less, - B(25 / 100) = 2000K or more and 4000K or less. For a nominal resistance value of R(25°C)<100 kΩ, the thickness of the functional layer is 300 nm in an optimized sensor element and the resistivity of the functional layer is ρ=3 Ωm.

[0029] According to an example embodiment, the functional layer only partially covers the carrier or the insulating layer on the carrier top surface, and further, the functional layer only partially covers the electrode fingers of the two electrodes.

[0030] The shape / arrangement of the functional layer is first selected so that it covers the carrier / insulating layer only in the region of the electrode finger structures. Alternatively, the functional layer can extend beyond or above the electrode finger structures. Preferably, the functional layer is formed only in the central region of the carrier. In particular, the functional layer does not extend into the edge regions of the carrier. Furthermore, the structure of the functional layer, for example its width, is selected so that a specific resistance value (target value) of the sensor element can be adjusted. In this way, the sensor element can be used particularly flexibly and with particularly high precision.

[0031] According to one embodiment, the functional layer comprises a plurality of strips, i.e., the functional layer is made up of individual or discrete elements. The strips are spaced apart from one another. The strips are arranged parallel to one another.

[0032] The design of the sensor element is based on the principle of parallel connection of individual resistors: the strips are designed perpendicular to the electrode fingers and make contact through them, resulting in multiple individual resistors connected in parallel between the electrode fingers.

[0033] The strip width can be the same for all strips of a functional layer. Alternatively, the strip width can be varied. For example, very thin, medium and wide strips can be combined. This results in a large variation in the resistance adjustment. In a parallel circuit, the individual resistances add up as reciprocal values, so trimming a large resistor results in a small change in the resistance of the entire sensor element. This makes it easier to fine-tune the target resistance.

[0034] Trimming can be done in two ways: either the functional layer or the electrode fingers can be cut, in particular at least one strip of the functional layer and / or at least one electrode finger is severed, preferably with a laser, in order to adjust the resistance of the sensor element (laser trimming).

[0035] According to one embodiment, the functional layer or at least a part of the functional layer is stepped, trapezoidal or triangular in shape, so that the functional layer does not have separate individual elements but is formed as a single piece, but only partially covers the electrodes, in particular the electrode fingers.

[0036] The special structure of the functional layer and the partial coverage of the electrode fingers results in different individual resistances connected in parallel between the electrode fingers. This facilitates trimming to a desired target resistance value. To adjust the resistance value, at least one electrode finger is cut, in particular with a laser (laser trimming). Another possible variation for adjusting the resistance value is to use a laser to cut the functional layer along (i.e. between) the electrode fingers.

[0037] According to one embodiment, at least one electrode finger is structured. In particular, at least one of the electrode fingers has a different shape from the other electrode fingers. Preferably, at least one of the electrode fingers is trapezoidally or triangularly shaped. In contrast, the other electrode fingers have a rectangular shape. In this way, a wider spread of the trimmable individual resistors between two adjacent electrode fingers allows for even finer resistance adjustment.

[0038] According to one example embodiment, the electrode fingers of at least one of the at least two electrodes are formed with different lengths, in other words at least one, and preferably exactly one, of the two electrodes has a different length.

[0039] In this way, the individual resistances of the electrode fingers are different and the electrode fingers are connected in parallel, which allows trimming to a desired target resistance.To adjust the resistance value, at least one of the electrode fingers of a different length is cut, particularly with a laser.

[0040] According to one embodiment, the distance between adjacent electrode fingers is varied, thereby making available additional areas with different distances for trimming and thus providing finer increments of resistance adjustment. To adjust the resistance value, at least one of the electrode fingers is cut, in particular using a laser.

[0041] According to one embodiment, at least one of the electrode fingers has a comb-shaped region with a plurality of teeth, the teeth pointing towards the subsequent electrode fingers, and the comb-shaped region is preferably formed on one of the outer electrode fingers.

[0042] The teeth of the comb region can be of different lengths and / or widths, resulting in a greater variation in resistance settings. In particular, this results in individual resistance values ​​that are different, allowing for trimming to a desired resistance value. To adjust the resistance of the sensor element, at least one tooth is cut.

[0043] According to one exemplary embodiment, the electrodes are formed directly on the upper surface of the functional layer. In other words, the functional layer is formed between the electrodes and the carrier. In this embodiment, the electrodes can be trimmed after the sensor element has been applied and tested. Furthermore, in this embodiment, the electrodes do not need to withstand the conditions of the sintering process of the functional layer. Alternatively, the electrodes can be disposed directly on the lower surface of the functional layer.

[0044] According to one embodiment, the sensor element has a protective layer. The protective layer can be made of oxide, nitride, ceramic, glass or plastic. The protective layer completely covers the upper side of the sensor element except for the contact pads. For this reason, the protective layer has voids at the locations of the contact pads. The thickness of the protective layer is <10 μm, preferably <5 μm, ideally <1 μm. The protective layer improves the long-term stability of the sensor element.

[0045] According to a further aspect, a method for manufacturing at least one sensor element, in particular a plurality of sensor elements, is described. It should be noted that this method preferably manufactures a number of sensor elements in parallel and finally separates them from each other. For simplicity, the following will essentially refer to one sensor element.

[0046] Preferably, the method produces the sensor element described above. All features disclosed in relation to the sensor element or the method are also disclosed in relation to each other aspect, and vice versa, even if the respective feature is not explicitly mentioned in the context of the respective aspect.

[0047] The method includes the following steps: A) Providing a carrier material to form a carrier. Preferably, the carrier material comprises Si, SiC, GaN, or glass. Alternatively, the carrier material may comprise Si3N4, AlN, or Al2O3. The carrier has an upper surface and a lower surface. An electrical insulating layer, preferably SiO2, may be further formed on the upper surface of the carrier material.

[0048] B) forming or depositing at least two electrodes on the carrier, the deposition being carried out by a PVD (physical vapor deposition) process, a CVD (chemical vapor deposition) process or by electroplating, or alternatively by an ALD (atomic layer deposition) process;

[0049] The electrodes are spaced apart from one another. In particular, the electrodes are spatially and electrically insulated from one another. The electrodes have electrode fingers. The electrodes are interdigitated in the form of an interdigital structure. Preferably, the electrodes are formed on the top surface of the carrier or directly on the insulating layer. Alternatively, the electrodes can be formed on the top surface of the functional layer. The electrodes are spaced apart from the edge regions of the carrier.

[0050] To adjust the resistance of the sensor element, the electrodes can be structured (see step E)).

[0051] C) Applying, preferably sputtering, a functional material onto a partial region of the electrode to form a functional layer. The functional material preferably comprises an NTC ceramic based on an oxidizing material of the perovskite or spinel structure type. Alternatively, the functional material can be based on a carbide or nitride material. Alternatively, the functional material can comprise or be a thin film of vanadium oxide or SiC.

[0052] The functional layer is formed as a thin film. It partially covers the carrier or electrode. In particular, the functional layer is formed so that it is spaced from the edge region of the carrier and forms on the region of the finger structure (interdigital structure) of the electrode. The functional layer can also protrude beyond the interdigital structure of the electrode or above the finger structure. The functional layer is deposited as a full-surface thin film and is structured in a further process, such as wet chemical etching or dry etching. After deposition, the NTC layer is not yet crystallized.

[0053] The functional layer can be structured to adjust the resistance of the sensor element (see step E).

[0054] D) Temperature treatment of the functional layer, which establishes the NTC properties of the functional material, can be carried out at temperatures up to 1000°C.

[0055] The functional layer is then measured, whereby an initial tolerance range for the resistance value is determined, which at this stage of the method is, for example, ±5% of the nominal resistance value.

[0056] E) Adjusting or setting the resistance of the sensor element. This is done by trimming at least one of the electrodes and / or the functional layer using a laser. The resistance is adjusted to a predetermined nominal value (target value). Due to the precise adjustment of the resistance, the finished sensor element has a very narrow resistance tolerance. The resistance tolerance of the finished sensor element is up to ±5%, preferably up to ±1%, and particularly preferably up to ±0.5% of the nominal value. The functional layer and / or at least one of the electrodes, e.g., at least one electrode finger, is structured for resistance adjustment. In other words, at least partial regions of the functional layer and / or electrode have structured regions. The initial resistance of the functional layer is selected to be within the tolerance range at low resistance values.

[0057] Trimming of the structured area is performed for final adjustment of the resistance value. In particular, at least one of the electrode fingers and / or at least a partial area of ​​the functional layer is cut using a laser. In other words, material is removed from at least one of the electrode fingers and / or at least a partial area of ​​the functional layer, which changes the resistance of the component and the overall resistance of the sensor element. The resistance of the sensor element is increased by trimming the structured area to a target value.

[0058] However, if the resistance of the sensor element already corresponds to the setpoint value, no further adjustment of the resistance is made.

[0059] According to an example embodiment, the method comprises the further steps of:

[0060] F) applying a protective layer to the upper surface of the sensor element, which completely covers the upper surface except for two partial areas, which are located on the flat end areas of the electrodes and to which contact pads can be applied in a later step; (a) by application to the entire surface and by subsequent processes such as wet chemical etching or dry etching or laser structuring to generate free partial areas, or (b) Direct structuring and application during the deposition process by using a mask.

[0061] G) Forming contact pads in the partial areas free of the protective layer for electrical contact of the sensor element. In each case, the contact pads are formed directly on one flat end area of ​​the electrode. The contact pads can protrude beyond the structured protective layer.

[0062] The contact pads can comprise Cu, Au, Ni, Cr, Ag, Ti, Ta, W, Pd, or Pt. If the sensor element is integrated into a SESUB structure, the contact pads preferably comprise Cu. Preferably, the contact pads have a thickness of 5 μm or greater. The contact pads are designed to protrude beyond the surface of the completed sensor element.

[0063] Instead of contact pads, bumps or thin electrodes can also be provided. All these possible contact elements contain at least one metal, for example Cu, Au or a solderable alloy.

[0064] H) Separating or individualizing the sensor elements. The individualizing is carried out in two steps. (1) Individualization in the x / y direction (length and width). This can be done, for example, by plasma etching or sawing. Here, the carrier is not cut, but only incised to a predetermined thickness. (2) Singulation in the Z direction (height direction): Grinding is carried out from the backside. A polishing process removes material from the underside of the carrier down to the desired final part thickness.

[0065] I) If a thick sensor element is desired, no thinning (grinding) of the carrier is necessary: ​​in this case, separation is performed solely by sawing or plasma etching.

[0066] J) Optionally plasma etching the polished lower surface of the carrier to reduce microcracks.

[0067] According to one embodiment, the functional material is applied in a structured manner. In other words, the functional layer is structured to adjust the resistance value. The functional layer can have multiple strips. Alternatively, parts of the functional layer can be formed in a stepped, trapezoidal or triangular shape. This results in different resistance values ​​connected in parallel between the electrode fingers, allowing trimming to the desired target resistance value.

[0068] According to an exemplary embodiment, the electrodes for adjusting the resistance are applied in a structured manner. At least one electrode finger of two electrodes can have different lengths. Alternatively or additionally, adjacent electrode fingers can have different distances between them. Alternatively or additionally, the electrode fingers can have different shapes. For example, at least one of the electrode fingers can have a trapezoidal shape, or at least one of the electrode fingers can have a comb-shaped region. The comb-shaped region can have a number of teeth, preferably pointing toward the subsequent electrode finger.

[0069] The structured formation of the electrodes and / or functional layers creates individual laser-trimmable regions, thus enabling adjustment of the resistance value. The corresponding trimming increases the resistance to the desired value. Individual trimmable / structured regions have a higher resistance value compared to unstructured regions. Since the individual resistance values ​​are reciprocally added in a parallel circuit, trimming a large resistor results in a smaller change in the resistance of the entire sensor element. This means that sensor elements with particularly narrow resistance tolerances can be provided.

[0070] The drawings described below should not be construed as being true to scale, rather individual dimensions may be enlarged, reduced or distorted for better visualization.

[0071] Elements that are identical or have the same function are given the same reference numerals. [Brief explanation of the drawings]

[0072] [Figure 1] 1 shows an exploded perspective view of a sensor element according to the prior art; [Figure 2] FIG. 2 shows a cross-sectional view of a sensor element according to FIG. 1 (prior art). [Figure 3a] 1 shows a partial area of ​​a sensor element according to a first embodiment example in a top view; FIG. [Figure 3b] 10 shows a partial region of a sensor element in a top view according to a further example embodiment; [Figure 4] 10 shows a partial region of a sensor element in a top view according to a further example embodiment; [Figure 5] 10 shows a partial region of a sensor element in a top view according to a further example embodiment; [Figure 6] 10 shows a partial region of a sensor element in a top view according to a further example embodiment; [Figure 7] 10 shows a partial region of a sensor element in a top view according to a further example embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0073] 1 and 2 show a sensor element 1 according to the prior art, which is intended to describe the basic structure of a sensor element 100 as described below. For the essential features of the sensor element 1 according to FIGS. 1 and 2, reference is made to German patent application DE 10 2020 122923 A1.

[0074] The sensor element 1 is an NTC thin-film temperature sensor and includes a carrier 2 having an upper surface 11 and a lower surface 12. The upper surface 11 of the carrier 2 includes an insulating layer 3, which may comprise, for example, SiO2. The sensor element 1 also includes at least two electrodes 4a, 4b. The two electrodes 4a, 4b are spaced apart from each other on the insulating layer 3 of the carrier 2 and include thin metal films.

[0075] The electrodes 4a and 4b are formed as interdigital thin film electrodes. In particular, the electrodes 4 a , 4 b each have a flat end region 6 and a region with electrode fingers 5 . The region with the electrode fingers 5 is formed in the central region of the carrier 2. The flat end region 6 and the region with the electrode fingers 5 transition into each other. The two electrodes 4a, 4b each interdigitate with each other in the region of the electrode fingers 5 in the central region of the carrier 2, forming an interdigitated structure there. The electrode fingers 5 of the electrodes 4a, 4b are arranged alternately.

[0076] The sensor element 1 also has a functional layer 7 with an upper surface 14 and a lower surface 15. The functional layer 7 is an NTC thin film. The functional layer 7 only partially covers the insulating layer 3 on the upper surface 11 of the carrier 2. Preferably, the functional layer 7 is applied at least partially on the electrodes 4a, 4b. As can be seen in FIGS. 1 and 2, the electrodes 4a, 4b are formed between the carrier 2 and the functional layer 7, in particular on the lower surface 15 of the functional layer 7. The functional layer 7 is directly above the area with the electrode fingers 5.

[0077] The sensor element 1 has at least two contact pads 10 a, 10 b for electrical contact of the sensor element 1 .

[0078] The sensor element 1 may also have a protective layer 8. The protective layer 8 completely covers the top surface of the sensor element 1 except for the contact pads 10a, 10b. The protective layer 8 has cavities 9 through which the contact pads 10a, 10b protrude for electrical contact of the sensor element 1.

[0079] Due to the compact design of the individual components of the sensor element 1, the sensor element 1 is particularly suitable for integration into MEMS or SESUB structures.

[0080] The basic design shown in Figures 1 and 2 is based on the principle of connecting individual resistors in parallel. However, the design of the sensor element 1 shown in Figures 1 and 2 does not allow for a component-specific or component-specific adjustment of the resistors, and therefore it is not possible to adjust the resistance variation within the required tolerance range.

[0081] 3a, 3b and 4 to 7 each show a partial region of the sensor element 100. The sensor element 100 has substantially the same components as the sensor element 1 according to FIGS. 1 and 2. The basic structure of the sensor element 100 corresponds, as mentioned above, to the structure of the sensor element 1 of FIGS. 1 and 2. Therefore, for component and functional details of the sensor element 100, please refer to the above description or to document DE 10 2020 122923 A1.

[0082] The sensor element 100 according to the present invention has an operating temperature of -40° C. to 125° C. The dimensions of the sensor element 100 are preferably 300 μm×500 μm×50 μm. The sensor element 100 has a resistance R, which is as follows: 10 kΩ≦R(25°C)≦100 kΩ.

[0083] In contrast to the sensor element 1, with the sensor element 100 shown in Figures 3 to 7 the resistance value can be adjusted to a specific component or component by component. This can be achieved by different variations of the layer structure of the sensor element 100, which will be described in more detail below. In particular, compared to the sensor element 1, the structure of the functional layer 7 and / or the electrodes 4a, 4b is adapted / changed.

[0084] The width and / or shape of the functional layer 7 and / or the length of the electrode fingers 5 and / or the distance (gap width) between the electrode fingers 5 and / or the number of electrode fingers 5 or the distance (gaps) between the electrode fingers 5 affect the resistance value of the sensor element 100.

[0085] The relationship between the resistance and the interdigital structure of the electrodes 4a, 4b is particularly shown in Table 1 below. Table 1: Relationship between electrode structure and resistance value [Table 1]

[0086] From this table, it can be seen that the resistance of the sensor element 100 at an operating temperature of 25°C decreases as the number of electrode fingers 5 / number of gaps between the electrode fingers 5 increases, the length of the electrode fingers 5 increases, and the distance between the electrode fingers 5 (gap width) decreases.

[0087] In variation B, where the electrode fingers 5 are long, there are many of them, and the distance between them is small, a resistance of R(25°C) = 12 kΩ can be expected. In variation A, where the electrode fingers 5 are short, there are few of them, and the distance between them is large, a resistance of R(25°C) = 50 kΩ can be expected.

[0088] The resistance value can therefore be influenced in particular by the intended structuring of the interdigitated structure of the electrodes 4a, 4b or of the functional layer 7. This will again be explained in more detail in connection with Figures 3A to 7.

[0089] By structuring the electrodes 4a, 4b and / or the functional layer 7, individual laser-trimmable regions are created, allowing the resistance to be adjusted. The initial resistance of the functional layer 7 is selected to be within the tolerance range for low resistance values. By corresponding trimming, the resistance is increased to the desired value.

[0090] The individual trimmable / structured areas have a larger resistance compared to the unstructured areas of the base structure (sensor element 1). In a parallel circuit where the individual resistance values ​​add as reciprocals, trimming a larger resistance value means that the resistance of the entire sensor element 100 changes slightly. The trimming is performed with a suitable laser.

[0091] In the embodiment example shown in Fig. 3a, the functional layer 7 is structured, in particular in such a way that, in contrast to the basic structure, the functional layer 7 is structured so that individual strips 7a are formed which are perpendicular to the electrode fingers 5 and make contact via them. This results in a number of individual resistors connected in parallel between the electrode fingers 5 .

[0092] The width b of the strips 7a may be the same for all strips 7a or may be different, e.g., by combining (very) narrow, medium, and wide strips 7a, a greater variation in resistance adjustment can be obtained. The strips 7a may only partially cover the electrode fingers 5, as shown in Figure 3a. Alternatively, the strips 7a may be formed on at least a part of the flat end region 6 of the electrodes 4a, 4b (not explicitly shown).

[0093] The trimming is carried out using a laser. Trimming can be done in two ways: Depending on the type of laser used, either the functional layer 7 (in particular individual strips 7a of the functional layer 7) or one or more electrode fingers 5 can be cut.

[0094] In this embodiment, the electrode fingers 5 can be cut both in the transition areas from the electrode fingers 5 to the flat end areas 6 of the electrodes 4a, 4b and in the areas between the individual strips 7a of the functional layer 7.

[0095] In the embodiment example according to Fig. 3b, the electrode fingers 5 of one of the electrodes 4a, 4b are also structured. In particular, in this embodiment example, the outer electrode finger 5 of the electrode 4a has a trapezoidal shape. Furthermore, several electrode fingers 5 can be formed structured, or alternatively or additionally, one of the inner electrode fingers 5 can also be structured (not explicitly shown). A special design of at least one electrode finger 5 results in a finer adjustment of the resistance due to a wider spread of the trimmable individual resistances between adjacent electrode fingers 5.

[0096] Here too, trimming can be performed (depending on the laser used) by cutting the individual strips 7a of the functional layer 7 or the electrode fingers 5. The cutting of the electrode fingers 5 can be done either in the transition region from the electrode fingers 5 to the flat ends 6 of the electrodes 4a, 4b or in the regions between the individual strips 7a of the functional layer 7.

[0097] In the embodiment shown in Fig. 4, the functional layer 7 is structured. In particular, it has a stepped structure. Alternatively, it can also be trapezoidally or triangularly shaped (not explicitly shown). In contrast to the embodiment shown in Figs. 3a and 3b, the functional layer does not have a plurality of separate elements but is formed as a single piece.

[0098] Despite the flat design, the functional layer 7 covers only partial areas, in particular partial areas of different sizes, of the individual electrode fingers 5. The functional layer 7 can also extend into the flat end regions 6 of the electrodes 4a, 4b (not explicitly shown), i.e. the overall width of the functional layer 7 can vary.

[0099] This results in different individual resistances connected in parallel between the electrode fingers 5, thus allowing trimming to a desired target resistance. The trimming is performed by trimming at least one electrode finger 5 using a laser.

[0100] In the example embodiment shown in Figure 5, one of the electrodes 4a, 4b is formed with a structure. In particular, the electrode 4a has electrode fingers 5 of different lengths, and a structure can alternatively or additionally also be formed on the electrode 4b.

[0101] The electrode finger illustrated at the bottom of FIG. 5 (the lower outer electrode finger 5) is the shortest electrode finger 5. The electrode finger illustrated at the top of FIG. 5 (the upper outer electrode finger 5) is the longest electrode finger 5. Of course, other electrode fingers 5, for example, the central electrode finger 5, can be shorter or longer than the other electrode fingers 5. In other words, the length of the electrode fingers 5 and the arrangement of electrode fingers 5 of different lengths can be freely selected depending on the desired resistance value.

[0102] In this example embodiment, the functional layer 7 is flat or rectangular, similar to the basic structure described in connection with Figures 1 and 2. However, the functional layer 7 may also extend into the flat end regions 6 of the electrodes 4a, 4b (not explicitly shown). In other words, the width of the functional layer 7, or the width of the region of the electrodes 4a, 4b covered by the functional layer 7, may vary. By varying the width, the resistance value can be influenced, as already mentioned.

[0103] Designing different lengths of the electrode fingers 5 results in different individual resistances which are connected in parallel between the electrode fingers 5 and can be trimmed to a desired target resistance.

[0104] Here too, trimming is performed by using a laser to separate at least one electrode finger 5. In contrast to the embodiment with a structured functional layer 7, the electrode finger 5 can only be cut in the transition region from the electrode finger 5 to the flat end region 6 of the electrodes 4a, 4b (the region of the electrode finger 5 that is not covered by the functional layer 7).

[0105] 6, the electrode fingers 5 are at different distances from one another. In particular, the particular design of the electrodes 4a, 4b can vary the distance A between adjacent electrode fingers 5. As noted above, the resistance of the sensor element 100 is affected by varying the distance A between the electrode fingers 5 (see Table 1).

[0106] For example, the electrode fingers 5 shown at the bottom of Figure 6 have a larger distance A between them than the other electrode fingers 5. This design is not limited to this particular embodiment, and the distance A between adjacent electrode fingers 5 can be increased or decreased arbitrarily depending on the resistance value desired. The distance A between only one pair of adjacent electrode fingers can be varied, or the distance A between multiple pairs of electrode fingers can be varied.

[0107] This special design allows for additional areas with different distances for trimming, resulting in even finer gradations of resistance adjustment.

[0108] 7, at least one electrode finger 5 is structured. In particular, one electrode finger 5 (in this example embodiment, the outer electrode finger 5 of electrode 4b) has an interdigitated region. However, corresponding interdigitated regions can also be provided on further or other outer electrode fingers 5 (not explicitly shown).

[0109] The comb-shaped region has a number of teeth 20, which point in the direction of the subsequent electrode fingers 5. The teeth 20 are designed with different lengths. Alternatively or additionally, the teeth 20 can also have different widths.

[0110] As can be seen in FIG. 7 , the functional layer 7 does not extend completely over the entire structured electrode fingers 5. Rather, the functional layer 7 only partially covers the structured electrode fingers 5. In this example embodiment, the functional layer can be wider, in particular extending up to and even partially over the flat end regions 6 of the electrodes 4 a, 4 b (see the dashed functional layer 22). As already mentioned above, the resistance value can be influenced by varying the width of the functional layer 7. The interdigitated structure of the electrode fingers 5 allows for a large variation in the adjustment of the resistance value. As a result, different individual resistances are obtained, allowing trimming to the desired target resistance value. Trimming is performed by separating the structured electrode fingers 5 using a laser (see the exemplary separation regions 21).

[0111] A method for manufacturing the sensor element 100 is described below. Preferably, the method is used to manufacture a plurality of sensor elements 100 according to one of the example embodiments described above (see Figures 3a, 3b and 4-7). Accordingly, all features described in relation to the sensor element 100 also apply to the method and vice versa.

[0112] In a first step A), a carrier material is provided to form the above-mentioned carrier 2. Preferably, the carrier material comprises Si, SiC, GaN, or glass. Alternatively, the carrier material may comprise Si3N4, AlN, or Al2O3. The carrier 2 has an upper surface 11 and a lower surface 12. Preferably, the carrier 2 has a maximum edge length L of less than 500 μm.

[0113] This is followed by the formation of an electrical insulating layer 3 on the upper surface 11 of the carrier 2. For example, the insulating layer 3 comprises SiO2. Ideally, an insulating layer 3 with a thickness of at most 1.5 μm is produced on the upper surface 11 of the carrier 2. In a next step B), at least two electrodes 4a, 4b are formed / deposited on the carrier 2. The deposition is carried out by a PVD process, a CVD process or by electroplating.

[0114] The electrodes 4a, 4b can be single-layer or multi-layer and include, for example, Cu, Au, Ni, Cr, Ag, Ti, Ta, W, Pd, or Pt. The electrodes 4a, 4b are formed as thin-film electrodes. Each of the electrodes 4a, 4b has a flat end region 6 and a plurality of electrode fingers 5.

[0115] The structuring of the electrodes 4a, 4b is carried out in a subsequent process, such as wet chemical etching, dry etching, laser structuring, etc. The electrode fingers 5 of at least one of the two electrodes 4a, 4b can have different lengths (FIG. 5). Alternatively or additionally, adjacent electrode fingers 5 can have a different distance A from each other (FIG. 6). Alternatively or additionally, the electrode fingers 5 can have different shapes (FIGS. 3b, 7). For example, at least one of the electrode fingers 5 can be trapezoidal or stepped, or at least one of the electrode fingers 5 can have a comb-shaped region with teeth 20. The resistance of the sensor element 100 is influenced by the structuring. The structuring forms laser-trimmable regions for adjusting the resistance of the sensor element 100. Additionally or alternatively, the functional layer 7 can also have a structuring (FIGS. 3a, 3b, 4). The resistance of the sensor element 100 is also influenced by the structuring of the functional layer 7. In a further step C), a functional material is applied to form the functional layer 7. This can be done, for example, by a sputtering or spin-coating process. The functional material is first applied to the entire surface and is structured in a further process (for example by wet chemical etching or dry etching or laser structuring). Preferably, the functional layer 7 has a thickness of between 250 nm and 400 nm.

[0116] Alternatively, step C) can be performed before step B), thus sputtering the functional material 7 directly onto the insulating layer 3 of the carrier 2, and then applying the electrodes 4a, 4b to the functional layer 7.

[0117] The functional material includes an NTC ceramic based on an oxidizing material of the perovskite or spinel structure type. Alternatively, the functional material can be based on a carbide or nitride material. As a further alternative, the functional material comprises or consists of a thin film of vanadium oxide or SiC.

[0118] The functional layer 7 only partially covers the upper surface of the carrier 2 and the electrodes 4a, 4b. The functional layer 7 can be structured to adjust the resistance of the sensor element 100. For example, the functional layer 7 can be formed in the shape of a strip (FIGS. 3a, 3b). Alternatively, the functional layer 7 can be formed in the shape of a step, trapezoid, or triangle (FIG. 4). Alternatively or additionally, the width of the functional layer can be varied. In this way, different individual resistors connected in parallel between the electrode fingers 5 are obtained, allowing trimming to the desired target resistance. The initial resistance of the functional layer 7 is selected to fall within an acceptable range for low resistance values.

[0119] In a further step D), the functional layer 7 is subjected to a heat treatment to build up its structure or properties.

[0120] The functional layer 7 is then measured, where an initial value of the resistance is determined so that in the next step the resistance can be adjusted to a target value.

[0121] In a next step E), the resistance is adjusted by using a laser to trim at least one of the electrodes 4a, 4b and / or the functional layer 7. Trimming is preferably performed in situ.

[0122] The resistance value is adjusted to a predetermined nominal value (target value). By precisely adjusting the resistance value, the finished sensor element 100 has a very narrow resistance tolerance. To adjust the resistance value, at least one of the electrode fingers 5 and / or at least partial regions of the functional layer 7 are cut off using a laser. In particular, the above-mentioned structured regions are cut off.

[0123] The next step F) involves the formation of a protective layer 8. The protective layer 8 comprises an oxide, nitride, ceramic, glass or polymer and is produced using a PVD or CVD process and structured using wet chemical or dry etching. The protective layer 8 has a thickness of <10 μm, preferably <5 μm, particularly preferably <1 μm. Ideally, the protective layer 8 has a thickness of less than 1.5 μm and completely covers the top surface of the sensor element 100 except for the contact pads 10 a, 10 b.

[0124] Thereafter, in step G), contact pads 10a, 10b are formed on at least partial regions of the electrodes 4a, 4b. The contact pads 10a, 10b are formed directly on the flat end regions 6 of the electrodes 4a, 4b, respectively. In one embodiment, the contact pads 10a, 10b comprise a metal such as Cu, Al or Au and have a thickness of more than 5 μm. In particular, the contact pads 10a, 10b protrude beyond the surface 13 of the sensor element 100 in the finished sensor element 100. Alternatively, bumps can be formed instead of contact pads.

[0125] In a further step H), the sensor elements 100 are separated, for example by plasma etching or sawing. The carrier 2 is not cut, but is only incised to a predetermined thickness.

[0126] An optional subsequent grinding (polishing process) from the backside removes material from the backside of the carrier 2 down to the predetermined final component thickness in a final step I), which leads to the actual singulation of the sensor elements 100. If a thicker design of the sensor elements 100 is desired, step I) can also be omitted. In this case, singulation of the sensor elements 100 is carried out solely by sawing or plasma etching. Assembly of the singulated sensor elements 100 can take place on the top side via fine wire bonding on the contact pads.

[0127] The description of the subject matter indicated herein is not limited to individual specific embodiments, but rather the features of the individual embodiments can be combined with one another as desired, to the extent that this makes technical sense. [Explanation of symbols]

[0128] 1,100 sensor elements 2. Career 3. Insulation layer 4a,4b electrode 5 electrode fingers 6 End area 7 Functional Layer 7a Strip 8 Protective layer 9 Vacant Space 10a, 10b Contact pads 11 Carrier top 12 Carrier bottom 13 Sensor element top surface 14 Top surface of functional layer 15 Lower surface of functional layer 20 teeth 21 Separation area 22 Functional Layer D Sensor element thickness L Carrier edge length A Distance between adjacent electrode fingers b Strip width

Claims

1. A sensor element for measuring temperature, comprising: at least one carrier (2) having an upper surface (11) and a lower surface (12), At least one carrier (2) having an electrical insulating layer (3) formed on the top surface (11) of the carrier (12); at least one functional layer (7) comprising a material with a temperature-dependent electrical resistance, a functional layer (7) disposed on the electrical insulating layer (3); at least two electrodes (4a, 4b) formed on said carrier (2) at a distance from each other, Each of said electrodes (4a, 4b) has a plurality of electrode fingers (5); two electrodes (4a, 4b) in which the electrode fingers (5) of the two electrodes (4a, 4b) are arranged alternately with one another; at least two contact pads (10a, 10b) for the electrical contact of said sensor element (100), at least two contact pads (10a, 10b), each of which is arranged directly on a partial region of one of the electrodes (4a, 4b); Equipped with The sensor element (100) is designed to be directly integrated into an electrical system as a discrete component; the sensor element (100) has a narrow resistance tolerance; the at least one functional layer (7) and / or at least one of the at least two electrodes (4a, 4b) is structured to adjust its resistance. Sensor element.

2. said functional layer (7) only partially covering the electrode fingers (5), The sensor element of claim 1 .

3. The width of the functional layer (7) varies; The sensor element according to claim 1 or 2.

4. The functional layer (7) has a plurality of strips (7a) arranged parallel to each other and spaced apart on the upper surface (11) of the carrier (2). A sensor element according to any one of claims 1 to 3.

5. The strips (7a) are formed perpendicular to the electrode fingers (5) and are contacted via the electrode fingers (5). The sensor element of claim 4.

6. the width (b) of said strips (7a) is the same for all strips (7a), or The width (b) of said strips (7a) varies; The sensor element according to claim 4 or 5.

7. In order to adjust the resistance of the sensor element (100), at least a partial area of ​​one strip (7a) and / or at least a partial area of ​​one electrode finger (5) is broken off. A sensor element according to any one of claims 4 to 6.

8. The functional layer (7) has a stepped, trapezoidal or triangular shape. A sensor element according to any one of claims 1 to 3.

9. At least one electrode finger (5) is split to adjust the resistance value; The sensor element of claim 8.

10. At least one of the electrode fingers (5) has a different shape from the other electrode fingers; the at least one electrode finger (5) is formed in a trapezoidal or triangular shape; A sensor element according to any one of claims 1 to 9.

11. the electrode fingers (5) of at least one of the at least two electrodes (4a, 4b) are formed with different lengths; A sensor element according to any one of claims 1 to 10.

12. At least one of the electrode fingers (5) of different lengths is cut to set the resistance value; The sensor element of claim 11.

13. The distance (A) between adjacent electrode fingers (5) varies. A sensor element according to any one of claims 1 to 3.

14. At least one of the electrode fingers (5) has a comb-shaped region; The comb-shaped region has a plurality of teeth (20) facing towards the subsequent electrode fingers (5), A sensor element according to any one of claims 1 to 13.

15. the comb-shaped region is formed on one of the outer electrode fingers (5); The sensor element of claim 14.

16. The teeth (20) are formed with different lengths and / or different widths. A sensor element according to claim 14 or 15.

17. In order to adjust the resistance of the sensor element (100), at least a partial region of the electrode finger (5) having the comb-shaped region is separated. A sensor element according to any one of claims 14 to 16.

18. Each of the electrodes (4a, 4b) is formed as a thin film electrode. A sensor element according to any one of claims 1 to 17.

19. The functional layer (7) is a thin film having NTC characteristics. A sensor element according to any one of claims 1 to 18.

20. The sensor element (100) is configured to be directly integrated into a MEMS structure and / or a SESUB structure; A sensor element according to any one of claims 1 to 19.

21. the carrier (2) comprises silicon, silicon carbide or glass, or The carrier (2) comprises Si3N4, AlN, GaN or Al2O3 as a carrier material; A sensor element according to any one of claims 1 to 20.

22. the functional layer (7) comprises an NTC ceramic based on an oxidizing material of perovskite or spinel structure type, or the functional layer (7) comprises an NTC ceramic based on a hydrocarbon-based material or a nitride-based material; A sensor element according to any one of claims 1 to 21.

23. The electrodes (4a, 4b) are formed in a single layer or in a multilayer and include at least one material or a combination of materials selected from the group consisting of Cu, Au, Ni, Cr, Ag, Ti, Ta, W, Pd and / or Pt. A sensor element according to any one of claims 1 to 22.

24. The contact pads (10a, 10b) are formed in a single layer or in a multi-layer and comprise at least one material or a combination of materials of Cu, Au, Ni, Cr, Ag, Ti, Ta, W, Pd and / or Pt; A sensor element according to any one of claims 1 to 23.

25. The electrical insulating layer (3) is formed as a single layer or multiple layers, and is made of Al ２ O ３ , AlN, SiO ２ or Si ３ N ４ or a combination of layers of these materials, A sensor element according to any one of claims 1 to 24.

26. Further provided with a protective layer (8), The protective layer (8) completely covers the top surface of the sensor element (100) except for the contact pads (10a, 10b). A sensor element according to any one of claims 1 to 25.

27. The protective layer (8) is formed as a single layer or a multilayer, and is made of Al ２ O ３ , AlN, SiO ２ or Si ３ N ４ or a combination of layers of these materials, 27. The sensor element of claim 26.

28. The protective layer (8) comprises an oxide, a nitride, a ceramic, a glass or a plastic as a material.

28. A sensor element according to claim 26 or 27.

29. A method for manufacturing a sensor element (100), comprising the steps of: A) providing a carrier material having an insulating layer (3) to form a carrier (2); B) forming at least two electrodes (4a, 4b) on said carrier (2), Each of the electrodes (4a, 4b) has a plurality of electrode fingers (5); the electrode fingers (5) of the two electrodes (4a, 4b) are arranged alternately with each other; C) applying a functional material onto partial areas of said electrodes (4a, 4b) to form a functional layer (7); D) a step of temperature treating said functional layer (7); E) adjusting the resistance by trimming at least partial areas of the electrodes (4a, 4b) and / or functional layer (7) using a laser. method.

30. the functional layer (7) and / or at least one of the electrodes (4a, 4b) is structured, The initial resistance of the functional layer (7) is selected so as to fall within an acceptable range at low resistance values, Trimming the structured area increases the resistance of the sensor element (100) to a target value.

30. The method of claim 29.

31. In step E), at least partial areas of the electrode fingers (5) and / or at least partial areas of the functional layer (7) are divided to adjust the resistance value.

31. The method of claim 29 or 30.

32. Before step E), measuring the functional layer (7), 32. The method of any one of claims 29 to 31.

33. F) applying a protective layer (8) on top of said sensor element (100), the protective layer (8) completely covers the top surface except for two partial areas; G) forming contact pads (10a, 10b) in the partial areas free of the protective layer for electrical contact of the sensor element (100); H) isolating said sensor element (100); 33. The method of any one of claims 29 to 32, further comprising:

34. I) optionally polishing said sensor element (100) from the underside, A grinding process removes material from the backside of the carrier (2) to a predetermined final part thickness, whereby the sensor element (100) is separated; J) optionally plasma etching the polished lower surface of the carrier (2) to reduce microcracks; 34. The method of any one of claims 29 to 33, further comprising:

35. the functional layer (7) comprises a plurality of strips (7a), or The functional layer (7) is formed in a stepped, trapezoidal or triangular shape.

35. The method of any one of claims 29 to 34.

36. The width of the functional layer (7) varies; 36. The method of any one of claims 29 to 35.

37. the electrode fingers (5) of at least one of the two electrodes (4a, 4b) have different lengths, and / or adjacent electrode fingers (5) have different distances (A) from each other, and / or the electrode fingers (5) have different shapes, 37. The method of any one of claims 29 to 36.

38. At least one of said electrode fingers (5) is trapezoidally or triangularly shaped, or At least one of the electrode fingers (5) has a comb-shaped region, the comb-shaped region has a plurality of teeth (20) pointing towards the subsequent electrode fingers (5); 38. The method of claim 37.

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