Sensor element and method for producing a sensor element

Abstract

The invention relates to a sensor element (100) for measuring temperatures, comprising a substrate (2) and at least one functional layer (7), which has a material with a temperature-dependent resistance, the functional layer (7) being arranged on the substrate (2). The sensor element (100) also has at least two electrodes (4a, 4b) with electrode fingers (5) and at least two contact pads (10a, 10b) for electrically contacting the sensor element (100), wherein one contact pad (10a, 10b) is arranged directly on a sub-region of one of the electrodes (4a, 4b). The sensor element (100) is designed to be integrated as a discrete component into an electronic system. The sensor element (100) has a narrow resistance tolerance, wherein the at least one functional layer (7) and / or at least one of the at least two electrodes (4a, 4b) is structured for setting a resistance value. The invention further relates to a method for producing a sensor element (100).

Description

Technical Field

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

[0002] In order to integrate passive components, such as for example sensors, capacitors, protective devices or heaters, into an electronic system, the dimensions must be matched to modern packaging designs in the micrometer and even nanometer range. To achieve such a degree of miniaturization, the components are deposited as thin films on a carrier structure with electrical terminals and are described as discrete components. The novel components can in particular be integrated into MEMS (Mikro Elektro Mechanisches System, microelectromechanical system) or SESUB (Semiconductor Embedded in Substrate, semiconductor embedded in substrate) structures.

[0003] The demand for an increased accuracy of temperature measurement requires narrow tolerances with respect to the resistance dispersion of such sensor elements. However, as the structures become smaller, the manufacturing tolerances have an increasing influence and the resulting dispersion of the resistances exceeds the required tolerances. The resistance dispersion can only be reduced to a limited extent via process control.

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

[0005] For use in power modules, mainly soldered SMD ("surface mounted device" - surface mounted device) NTC temperature sensors are used. In control modules for low power, alternatively NTC chips are also used, which are mounted on the underside by means of Ag sintering paste, soldering or bonding and are contacted on the upper side via bonding wires.

[0006] In order to electrically contact the NTC chip, metal electrodes must be applied. According to the prior art, for this purpose thick-film electrodes mainly made of silver paste or gold paste are applied via a screen printing process and then burned through.

[0007] In order to integrate electronic components into, for example, MEMS or SESUB structures, very small components are required, which furthermore must be integrable with suitable contacting methods. For this purpose, traditional mounting techniques for SMD structures or NTC chips cannot be used.

[0008] German patent application DE 10 2020 122 923 A1 describes a sensor element for temperature measurement with a thin-film NTC thermistor, the content of which is incorporated herein by reference.

[0009] So far, thin-film NTC temperature sensors cannot be manufactured with tolerances as narrow as those of traditional structures (SMD NTC and NTC chips). SUMMARY OF THE INVENTION

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

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

[0012] A sensor element is described according to one aspect. 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, including the boundary values.

[0013] The sensor element has at least one carrier. Preferably, the sensor element has exactly one carrier. The carrier has a carrier material, preferably silicon, silicon carbide, GaN or glass (silicate or borosilicate glass). Alternatively, the carrier material can also have Si 3 N 4 、AlN or Al 2 O 3 .

[0014] The carrier has an upper side and a lower side. The upper side is configured electrically insulating. Preferably, an insulating layer, such as Al 2 O 3 、AlN, SiO 2 or Si 3 N 4 or a combination of layers of these materials is formed on the upper side of the carrier. The insulating layer is formed directly on the upper side of the carrier and can be constructed of one or more layers.

[0015] The sensor element also has at least one functional layer. The functional layer is arranged on the carrier. In particular, the functional layer is arranged on the electrically insulating upper side of the carrier.

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

[0017] The resistance of the sensor element is influenced by the structure of the functional layer, such as by the size or width and / or specific shape of the functional layer. The width of the functional layer can vary.

[0018] The thickness of the functional layer is between 50 nm and 1 μm, preferably between 100 nm and 500 nm, and particularly preferably between 250 nm and 400 nm. The functional layer has the following material (functional material) that has specific electrical properties. The functional layer has a material with a temperature-dependent resistance. For example, at an operating temperature of 25 °C, the specific resistance of the functional layer is ρ = 3 Ω·m.

[0019] Preferably, the functional layer has an NTC ceramic. Preferably, the functional layer is a thin film with NTC characteristics. Preferably, the NTC ceramic is based on an oxide material of the perovskite or spinel structure type. Alternatively, the functional layer can be constructed based on a carbide material or a nitride material. Another alternative is a thin layer made of vanadium oxide or SiC.

[0020] The sensor element also has at least two electrodes. The electrodes are preferably configured as thin-film electrodes. The electrodes are formed on the carrier spaced apart from each other. Preferably, the electrodes do not extend to the edge region of the carrier. In particular, the electrodes are preferably formed on the carrier in the middle region or the inner region. The corresponding electrodes have a plurality of electrode fingers. The electrode fingers of the two electrodes are arranged alternately with each other. Thus, the electrodes form a finger-combined structure.

[0021] The resistance of the sensor element is influenced by the structure of the electrodes, such as the length and / or number of the electrode fingers and / or by the spacing (gap width) between the electrode fingers.

[0022] The sensor element also has at least two contact pads for electrically contacting the sensor element. Preferably, the sensor element has exactly two contact pads. The contact pads are directly electrically and mechanically connected to the electrodes. One contact pad is directly arranged on a sub-region of one of the electrodes. The sensor element can also be mounted by means of wire bonding via the contact pads.

[0023] The sensor element is implemented very compactly. In particular, the sensor element is configured to be directly embedded as a discrete device into an electrical or electronic system. For example, the sensor element has a maximum side length of 1000 μm, preferably < 800 μm, particularly preferably < 500 μm. The thickness of the sensor element is < 100 μm, preferably < 80 μm, particularly preferably < 50 μm. Particularly preferably, the dimensions of the sensor element are 300 μm × 500 μm × 50 μm. Preferably, the device is configured for direct integration into a MEMS structure and / or a SESUB structure.

[0024] The sensor element also has a narrow resistance tolerance. That is, the sensor element has a very small deviation range from the desired resistance (the rated value of the resistance).

[0025] At least one functional layer and / or at least one of the at least two electrodes is structured to adjust the resistance value. At least one functional layer and / or at least one of the at least two electrodes is trimable to adjust the resistance value. In particular, at least one sub-region of at least one functional layer and / or at least one sub-region of at least one of the two electrodes is cut off for resistance adjustment.

[0026] As long as the resistance in the device to be trimmed already corresponds to the target value, the structured / trimmable region is not cut off.

[0027] By achieving a narrow resistance tolerance, the sensor element has a very high accuracy during temperature measurement. Preferably, the sensor element has a resistance tolerance that is similar to the narrow resistance tolerance of conventional construction forms, such as SMD NTC or NTC chips.

[0028] The electrical characteristics of the sensor element are similar to those in a standard NTC chip:

[0029] - R(25 °C) = 10 kΩ to 100 kΩ;

[0030] - B(25 / 100) = 2000 K to 4000 K,

[0031] where the boundary values are included respectively. When the rated resistance value R(25 °C) < 100 kΩ, in an optimal sensor element, the thickness of the functional layer is 300 nm and the specific resistance of the functional layer is ρ = 3 ΩΩm.

[0032] According to one embodiment, the functional layer only partially covers the carrier or the insulating layer on the upper side of the carrier. In addition, the functional layer only partially covers the electrode fingers of the two electrodes.

[0033] The geometry / arrangement of the functional layer is first selected such that the functional layer covers the carrier / insulating layer only in the region of the finger structures of the electrodes. However, alternatively thereto, the functional layer can also extend beyond the finger structures of the electrodes. Preferably, the functional layer is formed only in the middle region of the carrier. In particular, the functional layer does not extend to the edge region of the carrier. Furthermore, the structure of the functional layer, such as the width of the functional layer, is selected such that a specific resistance (desired value) of the sensor element can thereby be adjusted. Thus, the sensor element is particularly flexible to use and particularly precise.

[0034] According to one embodiment, the functional layer has a plurality of strips. In other words, the functional layer consists of discrete individual elements. The strips are arranged spaced apart from one another. The strips are arranged parallel to one another.

[0035] The construction of the sensor element is based on the principle of parallel connection of individual resistors. The strips are implemented perpendicular to the electrode fingers and are contacted via the electrode fingers. Thus, a plurality of individual resistors are obtained, which are connected in parallel between the electrode fingers.

[0036] The width of the strips can be the same for all strips of the functional layer. However, alternatively thereto, the width of the strips can also vary. For example, very narrow, medium, and wide strips can exist in a combined form. This results in a greater variation in resistance adjustment. In a parallel connection in which the individual resistances are added as reciprocals, this means that trimming a larger resistance causes a small resistance change at the entire sensor element. Thus, fine adjustment of the desired value of the resistance is feasible in a simple manner.

[0037] Trimming can be carried out in two ways. The functional layer or the electrode fingers can be cut. In particular, in order to adjust the resistance value of the sensor element, at least one strip of the functional layer and / or at least one electrode finger is cut, preferably by means of a laser (laser trimming).

[0038] According to one embodiment, the functional layer or at least one sub-region of the functional layer is formed stepwise, trapezoidally, or triangularly. Thus, the functional layer does not have discrete individual elements but is formed in one piece. The functional layer only partially covers the electrodes here, in particular the electrode fingers.

[0039] Different individual resistors are obtained through the specific structure of the functional layer and the partial coverage of the electrode fingers, which are connected in parallel between the electrode fingers. Thus, trimming to the desired target resistance (desired resistance) can be achieved in a simple manner and method. In order to adjust the resistance value, at least one electrode finger is cut, preferably by means of a laser (laser trimming). Another possible variant for adjusting the resistance value is to cut the functional layer along the electrode fingers (i.e., between the electrode fingers) by means of a laser.

[0040] 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 remaining electrode fingers. Preferably, at least one of the electrode fingers is configured trapezoidally or triangularly. In contrast, the remaining electrode fingers have a quadrilateral shape. Thus, a finer adjustment possibility of the resistance results from a wider spread of the trimmable individual resistances between two adjacent electrode fingers.

[0041] According to one embodiment, the electrode fingers of at least one of at least two electrodes are configured with different lengths. In other words, at least one of the two electrodes, preferably exactly one electrode, has electrode fingers of different lengths.

[0042] Thus, different individual resistances of the electrode fingers result, which are connected in parallel between the electrode fingers so that trimming to a desired target resistance can be achieved. To adjust the resistance value, at least one of the electrode fingers of different lengths is cut off, in particular by means of a laser.

[0043] According to one embodiment, the spacing between adjacent electrode fingers varies. Thus, additional regions with varying spacing can be provided for trimming, resulting in a finer gradation of the resistance adjustment. To adjust the resistance value, at least one of the electrode fingers is cut off, in particular by means of a laser.

[0044] According to one embodiment, at least one of the electrode fingers has a comb-shaped region. The comb-shaped region has a plurality of teeth. The teeth point in the direction of the following electrode finger. The comb-shaped region is preferably formed at one of the outer electrode fingers.

[0045] The teeth of the comb-shaped region can be configured with different lengths and / or different widths. This results in a greater variation in the resistance adjustment. In particular, different individual resistances result, by means of which trimming to a desired target resistance can be achieved. To adjust the resistance value of the sensor element, at least one of the teeth is cut off.

[0046] According to one embodiment, the electrodes are formed directly on the upper side of the functional layer. In other words, the functional layer is formed between the electrodes and the carrier. This embodiment allows the electrodes to be trimmed after the sensor element has been applied and tested. In addition, in this embodiment, the electrodes do not have to withstand the conditions of the sintering process of the functional layer. However, alternatively, the electrodes can also be arranged directly at the lower side of the functional layer.

[0047] According to one embodiment, the sensor element has a protective layer. As a material, the protective layer can have oxides, nitrides, ceramics, glass, and plastics. The protective layer completely covers the upper side of the sensor element except for the contact pads. For this purpose, the protective layer has a cutout at the location of the contact pads. The protective layer has a thickness of <10 μm, preferably <5 μm, ideally <1 μm. The long-term stability of the sensor element is improved by the protective layer.

[0048] According to another aspect, a method for manufacturing at least one sensor element, in particular a plurality of sensor elements, is described. It should be noted that preferably a plurality of sensor elements are produced in parallel by the method and finally the plurality of sensor elements are separated from each other. Hereinafter, for simplicity, the sensor element is basically referred to.

[0049] Preferably, the sensor element described above is manufactured by the method. All features disclosed with reference to the sensor element or the method also correspondingly refer to the corresponding other aspect and vice versa, even if the corresponding features are not exhaustively mentioned in the context of the corresponding aspect. The method has the following steps:

[0050] A) Providing a carrier material to form a carrier. Preferably, the carrier material has Si, SiC, GaN, or glass. Alternatively, the carrier material can have Si 3 N 4 、AlN or Al 2 O 3 。 The carrier has an upper side and a lower side. An electrically insulating layer, preferably SiO 2 can also be formed on the upper side of the carrier material.

[0051] B) Forming or depositing at least two electrodes on the carrier. The deposition is carried out by a PVD ("physical vapour deposition", physical vapour deposition) process, a CVD ("chemical vapour deposition", chemical vapour deposition) process, or electroplating. Alternatively, the deposition can also be carried out by an ALD (Atomic Layer Deposition, atomic layer deposition) method.

[0052] The electrodes are formed spaced apart from each other. In particular, the electrodes are spatially isolated and electrically insulated from each other. The electrodes have electrode fingers. The electrodes are interlaced with each other in the form of a finger-like combined structure. Preferably, the electrodes are formed directly on the upper side of the carrier or on the insulating layer. However, alternatively, the electrodes can also be formed on the upper side of the functional layer. The electrodes are configured such that they are spaced apart from the edge region of the carrier.

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

[0054] C) Apply, preferably sputter, the functional material onto a sub-region of the electrode to form a functional layer. The functional material preferably has an NTC ceramic of an oxide material based on a perovskite or spinel structure type. Alternatively, the functional material can also be based on a carbide material or a nitride material. Alternatively, the functional material can comprise or consist of a thin layer of vanadium oxide or SiC.

[0055] The functional layer is configured as a thin film. The functional layer only partially covers the carrier or the electrode. In particular, the functional layer is configured such that it is spaced apart from the edge region of the carrier and is formed on the region of the finger structure of the electrode (finger-combined structure). Here, the functional layer can also extend beyond the finger-combined structure of the electrode. The functional layer is deposited as a continuous thin layer and is only structured in another process step, for example by means of wet chemical etching or dry etching. After deposition, the NTC layer is not yet crystallized.

[0056] The functional layer can be configured in a structured manner to adjust the resistance of the sensor element (see step E)).

[0057] D) Perform a temperature treatment on the functional layer. This is used to form the NTC characteristics of the functional material and is carried out at a temperature up to 1000 °C.

[0058] Then measure the functional layer. Here, the initial tolerance range of the resistance value is determined. In this method stage, the initial tolerance range is, for example, ±5% around the rated value of the resistance.

[0059] E) Adjust the resistance value of the sensor element. This is done by means of laser trimming at least one of the electrodes and / or the functional layer in the electrode. The resistance value is hereby adjusted to a predetermined rated value (desired value). By precisely adjusting the resistance value, the manufactured sensor element has a very narrow resistance tolerance. The resistance tolerance of the rated value of the manufactured sensor element is at most ±5%, preferably at most ±1%, and particularly preferably at most ±0.5%. At least one of the functional layer and / or the electrodes, for example at least one electrode finger, is configured in a structured manner for resistance adjustment. In other words, at least one sub-region of the functional layer and / or the electrode has a structured region. The initial resistance of the functional layer is selected such that the initial resistance is within the tolerance window in the case of a low resistance value.

[0060] To finally adjust the resistance value, trimming of the structured region is carried out. In particular, at least one electrode finger of the electrode fingers and / or at least one sub-region of the functional layer is cut by means of a laser. In other words, the material of at least one electrode finger and / or at least one sub-region of the functional layer is removed, whereby the resistance of the component involved and thus the total resistance of the sensor element are changed. The resistance of the sensor element is increased by trimming the structured region to the desired value.

[0061] Conversely, once the resistance of the sensor element already corresponds to the desired value, the resistance value is no longer additionally adjusted.

[0062] According to one embodiment, the method has the following additional steps:

[0063] F) Apply a protective layer to the upper side of the sensor element. The protective layer completely covers the upper side except for two sub-regions. The sub-regions are arranged above the planar end regions of the electrodes, and contact pads can be applied to the planar end regions in subsequent process steps. The protective layer is structured

[0064] (a) Applied over the entire surface and the exposed sub-regions are produced by subsequent processes such as wet chemical etching, dry etching, or laser structuring, or

[0065] (b) Applied directly in a structured manner using a mask in a deposition process.

[0066] G) Form contact pads in the sub-regions without the protective layer for electrical contacting of the sensor element. One contact pad each is formed directly on the planar end region of one of the electrodes. The contact pads can protrude beyond the structured protective layer.

[0067] The contact pads can be made of 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 have Cu. Preferably, the contact pads then have a thickness of > 5 μm. The contact pads are configured such that they protrude beyond the surface of the fabricated sensor element.

[0068] As an alternative to the contact pads, bumps or thin electrodes can also be provided. All these possible contact elements have at least one metal, such as Cu, Au, or a weldable alloy.

[0069] H) Separate or divide the sensor element.

[0070] The division is carried out in two steps:

[0071] (1) Divide along the x-direction / y-direction (length & width). This can be carried out, for example, by plasma etching or sawing. The carrier is not sawn through but only sawn open to a defined thickness.

[0072] (2) Divide along the z-direction (height). Grinding is carried out from the back side. By means of a grinding process, material is removed from the lower side of the carrier until the defined final component thickness.

[0073] I) If a thicker design of the sensor element is desired, the carrier does not need to be thinned (ground). In this case, the separation is carried out only by sawing or plasma etching.

[0074] J) Optionally, the thinned lower side of the carrier is plasma-etched to reduce, for example, microcracks.

[0075] 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 may have a plurality of strips. Alternatively, sub-regions of the functional layer may be configured stepwise, trapezoidally, or triangularly. This results in different individual resistances, which are connected in parallel between the electrode fingers so that trimming to a desired target resistance can be achieved.

[0076] According to one embodiment, the electrodes are structured to adjust the resistance value. The electrode fingers of at least one of the two electrodes may have different lengths. Alternatively or additionally, adjacent electrode fingers may have different spacings from each other. Alternatively or additionally, the electrode fingers may have different shapes. For example, at least one of the electrode fingers is configured trapezoidally or at least one of the electrode fingers may have a comb-shaped region. The comb-shaped region may have a plurality of teeth, which preferably point to the following electrode fingers.

[0077] By structuring the electrodes and / or the functional layer, individual laser-trimmable regions are created, thereby providing the possibility for resistance adjustment. By corresponding trimming, the resistance is increased to the desired value. The individual trimable / structured regions have a higher resistance compared to the unstructured regions. In a parallel connection where the individual resistances are added as reciprocals, this means that trimming of the higher resistance causes a small resistance change at the entire sensor element. Therefore, a sensor element with a particularly narrow resistance tolerance can be provided. Description of the Drawings

[0078] The drawings described below should not be understood as being to scale. Rather, for better illustration, individual dimensions may be shown enlarged, reduced, or distorted.

[0079] Elements that are identical to each other or perform the same function are provided with the same reference numerals.

[0080] The drawings show:

[0081] FIG. 1 shows an exploded view of a sensor element according to the prior art;

[0082] FIG. 2 shows a sectional view of the sensor element according to FIG. 1 (prior art);

[0083] FIG. 3a shows a top view of a sub-region of a sensor element according to a first embodiment;

[0084] FIG. 3b shows a top view of a sub-region of a sensor element according to another embodiment;

[0085] Figure 4 Top view of a sub-region of a sensor element according to another embodiment;

[0086] Figure 5 Top view of a sub-region of a sensor element according to another embodiment;

[0087] Figure 6 Top view of a sub-region of a sensor element according to another embodiment;

[0088] Figure 7 Top view of a sub-region of a sensor element according to another embodiment. Detailed Description

[0089] Figures 1 and 2 show illustrations of a sensor element 1 according to the prior art. The sensor element 1 is used to illustrate the basic construction of the sensor element 100 described hereinafter. Reference is made to German patent application DE 10 2020 122923 A1 with regard to the basic features of the sensor element 1 according to Figures 1 and 2.

[0090] The sensor element 1 is an NTC thin-film temperature sensor and has a carrier 2 with an upper side 11 and a lower side 12. The upper side 11 of the carrier 2 has an insulating layer 3, which for example has SiO 2 . The sensor element 1 also has at least two electrodes 4a, 4b. The two electrodes 4a, 4b are formed on the insulating layer 3 of the carrier 2 spaced apart from each other and have thin metal films.

[0091] The electrodes 4a, 4b are configured as finger-combined thin-layer electrodes. In particular, the electrodes 4a, 4b each have a planar end region 5 and a region with electrode fingers 5. The regions with electrode fingers 5 are each formed in the middle region of the carrier 2. The planar end regions 6 and the regions with electrode fingers 5 transition into each other. The two electrodes 4a, 4b are each staggered in the middle region of the carrier 2 in the region of the electrode fingers 5 and form a finger-combined structure there. The electrode fingers 5 of the electrodes 4a, 4b are arranged alternately.

[0092] The sensor element 1 also has a functional layer 7 with an upper side 14 and a lower side 15. The functional layer 7 is an NTC thin film. The functional layer 7 only partially covers the insulating layer 3 on the upper side 11 of the carrier 2. Preferably, the functional layer 7 is at least partially applied on the electrodes 4a, 4b. As can be seen from Figures 1 and 2, the electrodes 4a, 4b are formed here between the carrier 2 and the functional layer 7, in particular at the lower side 15 of the functional layer 7. The functional layer 7 lies directly on the region with electrode fingers 5.

[0093] The sensor element 1 also has at least two contact pads 10a, 10b for electrically contacting the sensor element 1.

[0094] The sensor element 1 may also have a protective layer 8. The protective layer 8 completely covers the upper side of the sensor element 1 except for the contact pads 10a, 10b. The protective layer 8 has a cutout 9, from which the contact pads 10a, 10b project for electrical contact with the sensor element 1.

[0095] Due to the compact structural form of the individual components of the sensor element 1, the sensor element 1 is outstandingly suitable for integration into MEMS or SESUB structures.

[0096] The embodiment of the basic construction according to FIGS. 1 and 2 is based on the principle of the parallel connection of the individual resistors. However, in the construction of the sensor element 1 according to FIGS. 1 and 2, the resistors cannot be adjusted component-specifically. Therefore, the spread of the resistors cannot be adjusted within the required tolerances.

[0097] FIGS. 3a, 3b and Figures 4 to 7 each show a sub-region of the sensor element 100. The sensor element 100 basically has the same components as the sensor element 1 according to FIGS. 1 and 2. The basic construction of the sensor element 100 corresponds to the construction of the sensor element 1 according to FIGS. 1 and 2, as already mentioned in more detail above. Therefore, for details on the mode of operation and components of the sensor element 100, reference is made to the above description or to the document DE 10 2020 122 923 A1.

[0098] The sensor element 100 according to the invention has an operating temperature between -40 °C and 125 °C, including the boundary values. The dimensions of the sensor element 100 are preferably 300 μm × 500 μm × 50 μm. The sensor element 100 has a resistance value R, for which the following applies: 10 kΩ ≤ R(25 °C) ≤ 100 kΩ.

[0099] Different from the sensor element 1, in the sensor element 100 according to FIGS. 3 to Figure 7 the resistors can be adjusted component-specifically. This can be achieved by different variants of the layer construction of the sensor element 100, which are described in detail below. In particular, compared with the sensor element 1, the structure of the functional layer 7 and / or the electrodes 4a, 4b is adjusted / modified.

[0100] The width and / or shape of the functional layer 7 and / or the length of the electrode fingers 5 and / or the spacing (gap width) between the electrode fingers 5 and / or the number of electrode fingers 5 or the spacing (gap) between the electrode fingers 5 influences the resistance value of the sensor element 100 here.

[0101] The correlation between the resistance and the finger-shaped combined structure of the electrodes 4a, 4b is shown in particular in Table 1 below:

[0102] Variant form A Variant form B Length of electrode finger 5 (μm) 170 190 Width between electrode fingers 5 / gap width (μm) 10 5 Number of gaps 10 20 R(25°C) / kΩ 50 12

[0103] Table 1: Correlation between the structure of the electrodes and the resistance value

[0104] It can be seen from the table that at an operating temperature of 25 °C, as the number of electrode fingers 5 / the number of gaps between the electrode fingers 5 increases, the length of the electrode fingers 5 increases, and the spacing (gap width) between the electrode fingers 5 decreases, the resistance of the sensor element 100 decreases.

[0105] Therefore, in variant form B, in the case of a larger length and number of electrode fingers 5 and a smaller spacing between the electrode fingers 5, a resistance R(25 °C) = 12 kΩ is expected. In variant form A, in the case of a smaller length, number, and a larger spacing, there is a resistance R(25 °C) = 50 kΩ.

[0106] Therefore, by means of the finger-shaped combined structure of the electrodes 4a, 4b or the targeted structuring of the functional layer 7, the resistance value can be specifically influenced. This will be described more precisely again. Figures 3A to 7 Described more precisely again.

[0107] Through the structured configuration of the electrodes 4a, 4b and / or the functional layer 7, individual laser-trimmable regions are created, from which the possibility for resistance adjustment results. The initial resistance of the functional layer 7 is selected such that the resistance lies within the tolerance window in the case of a low resistance value. By means of a corresponding correction, the resistance is increased to the desired value.

[0108] Each trimable / structured region has a greater resistance compared to the unstructured region of the basic structure (sensor element 1). In a parallel connection in which the individual resistances are added as reciprocals, this means that trimming of a larger resistance causes a small resistance change at the entire sensor element 100. The trimming is carried out here by means of a suitable laser.

[0109] In the embodiment according to FIG. 3a, the functional layer 7 is structured. In particular, compared to the basic structure, the functional layer 7 is structured such that individual strips 7a are obtained, which are implemented perpendicular to the electrode fingers 5 and are in contact via the electrode fingers. Thus, a plurality of individual resistances are obtained, which are connected in parallel between the electrode fingers 5.

[0110] The width b of the strips 7a can be the same or variable for all strips 7a, such that for example (very) narrow, medium, and wide strips 7a are present in a combined form, thus obtaining a greater variation in resistance adjustment. The strips 7a can here only partially cover the electrode fingers 5, as shown in FIG. 3a. As an alternative to this, the strips 7a can also be formed in at least a part of the planar end region 6 of the electrodes 4a, 4b (not shown in detail).

[0111] Trimming is carried out by means of a laser. The trimming can be carried out in two ways. Depending on the type of laser used, the functional layer 7 (in particular the individual strips 7a of the functional layer 7) or one or more electrode fingers 5 can be cut off.

[0112] In the present design, it is feasible to cut off the electrode fingers 5 not only in the transition region of the electrode fingers 5 to the planar end region 6 of the electrodes 4a, 4b, but also in the region between the individual strips 7a of the functional layer 7.

[0113] In the embodiment according to FIG. 3b, additionally, the electrode fingers 5 of one of the electrodes 4a, 4b are structured. In particular, in this embodiment, the outer electrode fingers 5 of the electrode 4a are trapezoidally formed. In addition, a plurality of electrode fingers 5 can also be structured, or alternatively or additionally, one of the inner electrode fingers can be structured (not shown in detail).

[0114] Through a specific design of at least one electrode finger 5, a finer adjustment possibility of the resistance is obtained by a wider spread of the trimable individual resistances between adjacent electrode fingers.

[0115] Here, the trimming can be carried out (depending on the laser used) by cutting off the individual strips 7a of the functional layer 7 or the electrode fingers 5. It is feasible to cut off the electrode fingers 5 not only in the transition region of the electrode fingers 5 to the planar end region 6 of the electrodes 4a, 4b, but also in the region between the individual strips 7a of the functional layer 7.

[0116] In the embodiment according to Figure 4 the functional layer 7 is structured. In particular, the functional layer 7 has a stepped structure. Alternatively, the functional layer can also be trapezoidally or triangularly formed (not shown in detail). Different from the embodiments shown in FIGS. 3a and 3b, the functional layer is here formed in one piece and does not have a plurality of discrete individual elements.

[0117] Although it is a planar design, the functional layer 7 only covers sub-regions of the individual electrode fingers 5, in particular sub-regions of different sizes. Here, the functional layer 7 can also extend into the planar end region 6 of the electrodes 4a, 4b (not shown in detail), that is, the total width of the functional layer 7 can vary.

[0118] Thus, different individual resistances are obtained, which are connected in parallel between the electrode fingers 5 so that trimming to a desired target resistance can be achieved. The trimming is carried out by separating at least one electrode finger 5 by means of a laser.

[0119] In the embodiment according to Figure 5In an embodiment, one of the electrodes 4a, 4b is structured. In particular, the electrode 4a here has electrode fingers 5 of different lengths, where the structuring can alternatively or additionally also be formed in the electrode 4b.

[0120] Here, Figure 5 the electrode finger shown at the bottom in Figure 5 (the lower outer electrode finger 5) is the shortest electrode finger 5. In

[0121] the electrode finger 5 shown at the top in

[0122] (the upper outer electrode finger 5) is the longest electrode finger 5. It goes without saying that another electrode finger 5, for example, the middle electrode finger 5, can also be formed shorter or longer than the remaining electrode fingers 5. In other words, the length of the electrode fingers 5 and the arrangement of the electrode fingers 5 of different lengths - in relation to the desired resistance value - can be freely selected.

[0123] In this embodiment, the functional layer 7 is formed in a planar or rectangular shape similar to the basic structure described in connection with FIGS. 1 and 2. However, the functional layer 7 can also extend into the planar end regions 6 of the electrodes 4a, 4b (not shown in detail). 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 can vary. By varying the width, the resistance value can be influenced, as already mentioned above.

[0124] By designing the electrode fingers 5 with different lengths, different individual resistances are obtained, and these individual resistances are connected in parallel between the electrode fingers 5 so that trimming to the desired target resistance can be achieved. Figure 6

[0125] Figure 6 Here, trimming is also carried out by separating at least one electrode finger 5 by means of a laser. Different from the embodiment with a structured functional layer 7, the cutting of the electrode fingers 5 is only feasible in the transition region of the electrode fingers 5 to the planar end regions 6 of the electrodes 4a, 4b (the region of the electrode fingers 5 not covered by the functional layer 7).

[0126] An additional region with a varying pitch can be achieved by means of the specific design, enabling trimming. Thereby, options for a more refined grading of the resistance adjustment are obtained.

[0127] In an embodiment according to Figure 7 , at least one electrode finger 5 is structured. In particular, the electrode finger 5 (the electrode finger 5 outside the electrode 4b in this embodiment) has a comb-shaped region. However, a corresponding comb-shaped region can also be provided at another or other outer electrode fingers 5 (not shown in detail).

[0128] The comb-shaped region has a plurality of teeth 20. The teeth point in the direction of the following electrode finger 5. The teeth 20 are designed with different lengths. Alternatively or additionally, the teeth 20 can also be formed with different widths.

[0129] The functional layer 7 does not extend completely over the structured electrode finger 5, as can be seen from Figure 7 . Rather, the functional layer 7 only partially covers the structured electrode finger 5. In this embodiment, the functional layer can also be formed wider and in particular extend to the planar end region 6 and even partially over the planar end region 5 of the electrodes 4a, 4b (see the functional layer 22 indicated by the dashed line). As already mentioned above, the resistance value is affected by the variation in the width of the functional layer 7. A greater variation in the resistance adjustment is obtained through the comb-shaped structured region of the electrode finger 5. Thus, different individual resistances are obtained, which can thereby be trimmed to the desired target resistance. The trimming is carried out here by separating the structured electrode finger 5 by means of a laser (see the exemplary separation region 21).

[0130] Below, a method for manufacturing the sensor element 100 is described. Preferably, a plurality of sensor elements 100 according to one of the embodiments described above are manufactured by means of the method (see FIGS. 3a, 3b and Figures 4 to 7 ). Thus, all features described in connection with the sensor element 100 also apply to the method and vice versa.

[0131] In a first step A), a carrier material is provided for forming the carrier 2 described above. Preferably, the carrier material has Si, SiC, GaN or glass. As an alternative to this, the carrier material can have Si 3 N 4 , AlN or Al 2 O 3 . The carrier 2 has an upper side 11 and a lower side 12. Preferably, the carrier 2 has a maximum side length L of less than 500 μm.

[0132] Subsequently, an electrically insulating layer 3 is formed on the upper side 11 of the carrier 2. For example, the insulating layer 3 has SiO 2Ideally, an insulating layer 3 with a thickness up to 1.5 μm is produced on the upper side 11 of the carrier 2. In another step B), at least two electrodes 4a, 4b are formed / deposited on the carrier 2. The deposition is carried out by PVD or CVD process or electroplating.

[0133] The electrodes 4a, 4b can be formed in one layer or multiple layers and, for example, have Cu, Au, Ni, Cr, Ag, Ti, Ta, W, Pd or Pt. The electrodes 4a, 4b are formed as thin-film electrodes. The electrodes 4a, 4b each have a planar end region 6 and a plurality of electrode fingers 5.

[0134] The structuring of the electrodes 4a, 4b is carried out in a subsequent process, which can be, for example, wet chemical etching, dry etching or laser structuring. The electrode fingers 5 of at least one of the two electrodes 4a, 4b can have different lengths ( Figure 5 ). Alternatively or additionally, adjacent electrode fingers 5 can have different spacings A from each other ( Figure 6 ). Alternatively or additionally, the electrode fingers 5 can have different shapes (Fig. 3b, Figure 7 ). For example, at least one of the electrode fingers is formed trapezoidally or stepwise, or at least one of the electrode fingers can have a comb-shaped region with teeth 20. The resistance value of the sensor element 100 is affected by the structuring. Structuring produces a region that can be laser trimmed for adjusting the resistance value of the sensor element 100. Additionally or alternatively, the functional layer 7 can also have a structure (Fig. 3a, Fig. 3b, Figure 4 ). The resistance of the sensor element 100 is also affected by the structuring of the functional layer 7.

[0135] In another step C), a functional material is applied to form the functional layer 7. This is carried out, for example, by sputtering or spin coating process. The functional material is first applied over the entire surface and structured in another process (such as by wet chemical etching, dry etching or laser structuring). Preferably, the functional layer 7 has a thickness between 250 nm and 400 nm.

[0136] Alternatively, step C) can also be carried out before step B), such that the functional material 7 is directly sputtered on the insulating layer 3 of the carrier 2 and then the electrodes 4a, 4b are applied to the functional layer 7.

[0137] The functional material has an NTC ceramic of an oxide material based on the perovskite or spinel structure type. Alternatively, the functional material can also be based on carbide or nitride materials. In another alternative, the functional material includes a thin layer composed of vanadium oxide or SiC or is composed of them.

[0138] The functional layer 7 only partially covers the upper side of the carrier 2 or the electrodes 4a, 4b. The functional layer 7 can be structured to adjust the resistance value of the sensor element 100. The functional layer 7 can for example be formed in strips (Figs. 3a, 3b). Alternatively thereto, the functional layer 7 can be formed step-shaped, trapezoidally or triangularly( Figure 4 ). Alternatively or additionally, the width of the functional layer can vary. This results in different individual resistances which are connected in parallel between the electrode fingers 5 so that trimming to a desired target resistance can be achieved. The initial resistance of the functional layer 7 is selected here such that the initial resistance lies within the tolerance window in the case of a low resistance value.

[0139] In a further step D), the functional layer 7 is subjected to a heat treatment to form a structure or property.

[0140] Subsequently, the functional layer 7 is measured. Here, the initial value of the resistance value is determined such that the resistance can be adjusted to a desired value in the next step.

[0141] In the next step E), the resistance value is adjusted by trimming at least one of the functional layer 7 and / or the electrodes 4a, 4b by means of a laser. The trimming is preferably carried out in situ.

[0142] The resistance value is adjusted to a predetermined rated value (desired value). By precisely adjusting the resistance value, the fabricated 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 one sub-region of the functional layer 7 is cut by means of a laser. In particular, the structured regions described above are cut.

[0143] In the next step F), a protective layer 8 is formed. The protective layer 8 can have an oxide, nitride, ceramic, glass or polymer and is produced by means of a PVD or CVD process and structured by means of wet chemical etching 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 < 1.5 μm and completely covers the upper side of the sensor element 100 except for the contact pads 10a, 10b.

[0144] Subsequently, in step G), contact pads 10a, 10b are formed on at least one sub-region of the electrodes 4a, 4b. One contact pad 10a, 10b each is formed directly on the planar end region 6 of the electrodes 4a, 4b. In one embodiment, the contact pads 10a, 10b have a metal such as Cu, Al or Au and have a thickness of > 5 μm. In particular, the contact pads 10a, 10b protrude from the surface 13 of the fabricated sensor element 100. Alternatively thereto, bumps can be formed instead of the contact pads.

[0145] In a further step H), the sensor element 100 is segmented. This can be carried out, for example, by plasma etching or sawing. The carrier 2 is not sawn through here, but only sawn open up to a defined thickness.

[0146] By subsequently optionally grinding the back side (grinding process), in a final step I), material is removed from the back side of the carrier 2 up to a defined final component thickness. By means of said steps, the actual segmentation of the sensor element 100 occurs. If a thicker design of the sensor element 100 is desired, step I) can also be omitted. In this case, the segmentation of the sensor element 100 is carried out only by sawing or plasma etching. The mounting of the segmented sensor element 100 can be carried out on the upper side via wire bonding on the contact pads.

[0147] The description of the subject matter given here is not limited to the individual specific embodiments. Rather, the features of the individual embodiments can be combined with one another arbitrarily, provided that this is technically meaningful.

[0148] List of reference signs

[0149] 1, 100 Sensor element

[0150] 2 Carrier

[0151] 3 Insulating layer

[0152] 4a, b Electrodes

[0153] 5 Electrode fingers

[0154] 6 End region

[0155] 7 Functional layer

[0156] 7a Strip

[0157] 8 Protective layer

[0158] 9 Cutout

[0159] 10a, b Contact pads

[0160] 11 Upper side of the carrier

[0161] 12 Lower side of the carrier

[0162] 13 Surface of the sensor element

[0163] 14 Upper side of the functional layer

[0164] 15 Lower side of the functional layer

[0165] 20 Teeth

[0166] 21 Separation region

[0167] 22 Functional layer

[0168] Thickness of the D sensor element

[0169] Side length of the L carrier

[0170] Spacing between adjacent electrode fingers A

[0171] Width of the b strip

Claims

1. A sensor element (100) for measuring temperature, the sensor element having: - at least one carrier (2) with an upper side (11) and a lower side (12), wherein an electrically insulating layer (3) is formed on the upper side (11) of the carrier (12), - at least one functional layer (7), the functional layer having a material with a temperature-dependent resistance, wherein the functional layer (7) is arranged on the electrically insulating layer (3), - at least two electrodes (4a, 4b), the electrodes being formed on the carrier (2) spaced apart from each other, wherein each respective electrode (4a, 4b) has a plurality of electrode fingers (5), and wherein the electrode fingers (5) of the two electrodes (4a, 4b) are arranged alternately with each other, - at least two contact pads (10a, 10b) for electrically contacting the sensor element (100), wherein one contact pad (10a, 10b) each is arranged directly on a sub-region of one of the electrodes (4a, 4b), wherein the sensor element (100) is configured to be directly integrated as a discrete device into an electrical system, wherein the sensor element (100) has a narrow resistance tolerance, and wherein at least one of the at least one functional layer (7) and / or the at least two electrodes (4a, 4b) is structured to adjust the resistance value.

2. The sensor element (100) according to claim 1, wherein the functional layer (7) only partially covers the electrode fingers (5).

3. The sensor element (100) according to claim 1 or 2, wherein the width of the functional layer (7) varies.

4. The sensor element (100) according to any one of the preceding claims, wherein the functional layer (7) has a plurality of strips (7a), the plurality of strips being arranged spaced apart from each other and parallel to each other at the upper side (11) of the carrier (2).

5. The sensor element (100) according to claim 4, wherein the strips (7a) are formed perpendicular to the electrode fingers (5) and are contacted via the electrode fingers.

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

7. The sensor element according to any one of claims 4 to 6, wherein in order to adjust the resistance value of the sensor element (100), at least one sub-region of the strips (7a) and / or at least one sub-region of the electrode fingers (5) is cut off.

8. The sensor element (100) according to any one of claims 1 to 3, wherein the functional layer (7) is formed stepwise, trapezoidally or triangularly.

9. The sensor element (100) according to claim 8, wherein in order to adjust the resistance value, at least one electrode finger (5) is cut off.

10. The sensor element (100) according to any one of the preceding claims, At least one electrode finger (5) of the electrodes has a shape different from that of the remaining electrode fingers, and the at least one electrode finger (5) is formed trapezoidally or triangularly.

11. The sensor element (100) according to any one of the preceding claims, wherein the electrode fingers (5) of at least one of the at least two electrodes (4a, 4b) are formed with different lengths.

12. The sensor element (100) according to claim 11, wherein in order to adjust the resistance value, at least one of the electrode fingers (5) with different lengths is cut off.

13. The sensor element (100) according to any one of the preceding claims, wherein the spacing (A) between adjacent electrode fingers (5) varies.

14. The sensor element (100) according to any one of the preceding claims, wherein at least one of the electrode fingers (5) has a comb-shaped region, and the comb-shaped region has a plurality of teeth (20), and the teeth point in the direction of the following electrode finger (5).

15. The sensor element (100) according to claim 14, wherein the comb-shaped region is formed at one of the outer electrode fingers of the outer electrode fingers.

16. The sensor element (100) according to claim 14 or 15, wherein the teeth (20) are formed with different lengths and / or different widths.

17. The sensor element (100) according to any one of claims 14 to 16, wherein in order to adjust the resistance value of the sensor element (100), at least one sub-region of the electrode finger (5) having a comb-shaped region is cut off.

18. The sensor element (100) according to any one of the preceding claims, wherein the corresponding electrodes (4a, 4b) are formed as thin-film electrodes.

19. The sensor element (100) according to any one of the preceding claims, wherein the functional layer (7) is a thin film having NTC characteristics.

20. The sensor element (100) according to any one of the preceding claims, wherein the sensor element (100) is configured for direct integration into a MEM structure and / or a SESUB structure.

21. The sensor element (100) according to any one of the preceding claims, wherein the carrier (2) has silicon, silicon carbide or glass, or wherein the carrier (2) has Si as the carrier material 3 N 4 , AlN, GaN or Al 2 O 3 .

22. The sensor element (100) according to any one of the preceding claims, wherein the functional layer (7) has an NTC ceramic based on an oxide material of a perovskite or spinel structure type, or wherein the functional layer (7) has an NTC ceramic based on a carbide material or a nitride material.

23. The sensor element (100) according to any one of the preceding claims, wherein the electrodes (4a, 4b) are formed in one layer or multiple layers and have at least one material or material combination of Cu, Au, Ni, Cr, Ag, Ti, Ta, W, Pd, and / or Pt.

24. The sensor element (100) according to any one of the preceding claims, The contact pads (10a, 10b) are formed in one or more layers and have at least one material or material combination of Cu, Au, Ni, Cr, Ag, Ti, Ta, W, Pd, and / or Pt.

25. The sensor element (100) according to any one of the preceding claims, wherein the insulating layer (3) is formed in one or more layers and has Al 2 O 3 , AlN, SiO 2 or Si 3 N 4 or a combination of layers of these materials.

26. The sensor element (100) according to any one of the preceding claims, The sensor element further has a protective layer (8), wherein the protective layer (8) completely covers the upper side of the sensor element (100) except for the contact pads (10a, 10b).

27. The sensor element (100) according to claim 26, wherein the protective layer (8) is formed in one or more layers and has Al 2 O 3 , AlN, SiO 2 or Si 3 N 4 or a combination of layers of these materials.

28. The sensor element (100) according to claim 26 or 27, wherein the protective layer (8) has an oxide, nitride, ceramic, glass, or plastic as the material.

29. A method for manufacturing a sensor element (100), the method having the following steps: A) Providing a carrier material with an insulating layer (3) to form a carrier (2); B) Forming at least two electrodes (4a, 4b) on the carrier (2), wherein the respective electrodes (4a, 4b) have a plurality of electrode fingers (5), and the electrode fingers (5) of the two electrodes (4a, 4b) are arranged alternately with each other; C) Applying a functional material to a sub-region of the electrodes (4a, 4b) to form a functional layer (7); D) Performing a temperature treatment on the functional layer (7); E) Adjusting the resistance value by trimming at least one sub-region of the functional layer (7) and / or the electrodes (4a, 4b) by means of a laser.

30. The method according to claim 29, wherein at least one of the functional layer (7) and / or the electrodes (4a, 4b) is structured, and the initial resistance of the functional layer (7) is selected such that the initial resistance is within the tolerance window in the case of a low resistance value, and the resistance of the sensor element (100) is increased by trimming the structured region to the desired value.

31. The method according to claim 29 or 30, wherein in step E), at least one sub-region of the electrode fingers (5) and / or at least one sub-region of the functional layer (7) is cut off to adjust the resistance value.

32. The method according to any one of claims 29 to 31, wherein the functional layer (7) is measured before step E).

33. The method according to any one of claims 29 to 32, further having the following steps: F) Applying a protective layer (8) to the upper side of the sensor element (100), wherein the protective layer (8) completely covers the upper side except for two sub-regions; G) Forming contact pads (10a, 10b) in the sub-regions without the protective layer to electrically contact the sensor element (100); H) Separating the sensor element (100).

34. The method according to any one of claims 29 to 33, The method has additional steps: I) Optionally grind the sensor element (100) from the lower side, wherein material is removed from the back side of the carrier (2) by a grinding process until a defined final component thickness is reached, thereby separating the sensor element (100); J) Optionally plasma etch the thinned lower side of the carrier (2) to reduce microcracks.

35. The method according to any one of claims 29 to 34, wherein the functional layer (7) has a plurality of strips (7a), or wherein the functional layer (7) is configured stepwise, trapezoidally or triangularly.

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

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

38. The method according to claim 37, wherein at least one of the electrode fingers (5) is configured trapezoidally or triangularly, or wherein at least one of the electrode fingers (5) has a comb-shaped region, wherein the comb-shaped region has a plurality of teeth (20) that point in the direction of the following electrode finger (5).

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