Sensor element and method for manufacturing the same

Abstract

A sensor element (10) for measuring temperature, comprising: at least one carrier (11) having an upper surface (18) and a lower surface (19), wherein an insulating layer (12) is formed on the upper surface (19) of the carrier (11); at least two electrodes (13a, 13b) arranged at a distance from one another on the carrier (11); at least one functional layer (15) comprising a material with a temperature-dependent electrical resistance, wherein at least one functional layer (14) is at least partially arranged between the electrodes (13a, 13b); The present invention relates to a method for manufacturing a sensor element (10), comprising at least two intermediate layers (14) containing an insulating material and at least two contact pads (16a, 16b) for electrical contact of the sensor element (10), the sensor element (10) being formed as an individual component directly integrated into an electrical system, the sensor element (10) having a small deviation range from a target resistance, and at least one of the at least two electrodes (13a, 13b) being structured for adjusting the resistance value.

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.

[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, narrower tolerances are required for the resistance dispersion of such sensor elements. However, as structures become smaller, the influence of manufacturing tolerances becomes greater, resulting in the resistance dispersion exceeding the required tolerance. Depending on the process control, the resistance dispersion can only be reduced 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. Alternatively, NTC chips are used in low-power control modules, where they are attached to the underside using Ag sinter paste, soldering, or adhesive, and the topside is contacted via a bonding wire.

[0006] For electrical contact of the NTC ceramic, 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, integrating electronic components into MEMS or SESUB structures requires very small elements that must be integrable using suitable contact methods: typical assembly techniques for SMD designs or NTC chips cannot be used for this.

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

[0009] Until now, thin film NTC temperature sensors could not be manufactured to the same tight tolerances as traditional designs (SMD NTC and NTC chips). 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 aspect, a sensor element is described. The sensor element is suitable for measuring temperature. The sensor element is a temperature sensor. The sensor element is a thin film NTC temperature sensor.

[0013] The sensor elements are designed to be very compact. In particular, they are designed to be embedded directly into electrical systems as individual components. They are designed to be directly integrated into MEMS and / or SESUB structures. For this purpose, the sensor elements must have very small dimensions and be able to be integrated using suitable contact methods. For example, the sensor elements have a maximum edge length of 1000 μm, preferably less than 800 μm, and particularly preferably less than 500 μm. The thickness of the sensor elements is less than 100 μm, preferably less than 80 μm, and particularly preferably less than 50 μm.

[0014] The sensor element has at least one carrier. Preferably, the sensor element has exactly one carrier. The carrier has a carrier material, preferably silicon, silicon carbide or glass (silicate glass or borosilicate glass). Alternatively, the carrier can consist of a ceramic material such as AlN, Si3N4 or Al2O3.

[0015] The carrier preferably has a rectangular base, but may also be square. In either case, the maximum edge length of the carrier is 1000 μm, advantageously <800 μm, ideally <500 μm.

[0016] The carrier has an upper surface and a lower surface. The upper surface is electrically insulating. In particular, an insulating layer is formed on the upper surface of the carrier. The insulating layer is disposed directly on the upper surface of the carrier. The insulating layer can be composed of one or more layers. The insulating layer can include, for example, Al2O3, AlN, SiO2, or Si3N4, or a combination of layers of these materials. The insulating layer has a thickness of 1.5 μm or less.

[0017] The sensor element further comprises at least two electrodes. Of course, the sensor element can also comprise more than two electrodes, for example four, six or eight electrodes.

[0018] The electrodes are preferably formed as thin-film electrodes. Hereinafter, the electrodes may also be referred to as electrode layers. This is intended to express that the electrodes represent individual layers of the sensor element. The terms electrode and electrode layer in each case refer to the same component of the sensor element.

[0019] The sensor element further comprises at least one functional layer. Of course, the sensor element may also comprise more than one functional layer, for example two, three or four functional layers, in which case the functional layers are arranged or stacked one above the other transversely to the main direction of extension of the sensor element.

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

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

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

[0023] In particular, the following functional layers are possible: a) oxides: for example perovskites (based on mixed crystals of the composition CaMnO3, in which Ca can be substituted in whole or in part by, for example, Y, Cr, Al or La) or spinels (based on mixed crystals of the composition NiMn2O4, in which Ni and Mn can be substituted in whole or in part by, for example, Fe, Co or Al); b) Carbides, such as (Si,Ti)C, hexagonal or cubic SiC; c) Nitrides, e.g. (Al,Ti)N, CrN.

[0024] A further alternative is a thin film of vanadium oxide.

[0025] The sensor element further comprises at least two contact pads for electrical contact of the sensor element, preferably exactly two contact pads, which are electrically and mechanically directly connected to the electrodes.

[0026] Furthermore, the sensor element has at least two intermediate layers. The sensor element can also have more than two intermediate layers, for example, four, five, or six intermediate layers. Each intermediate layer is formed to be insulating. In particular, each intermediate layer has an insulating material such as Al2O3, AlN, SiO2, or Si3N4.

[0027] By providing an intermediate layer, for example, electrical isolation of electrodes of different polarities in the contacted sensor element can be ensured. The intermediate layer also serves to prevent a stepped shape of the sensor element. In other words, the sensor element (especially due to the intermediate layer) has smooth surfaces, in particular smooth flanks, i.e. flanks that are as step-free as possible. This effectively prevents electrical scattering effects.

[0028] The corresponding sensor elements have a narrow resistance tolerance, which means that each sensor element has a very small range of deviation from the target resistance (nominal value of resistance).

[0029] At least one of the at least two electrodes is structured and trimmed to adjust the resistance of the respective sensor element. At least one electrode is trimmable to adjust the resistance. In particular, at least a portion of this electrode is cut to adjust the resistance. However, if the resistance of the component to be trimmed has already reached the target value, cutting of the structured / trimmable area is not performed.

[0030] Due to the small range of deviation from the target resistance, the sensor elements have very high accuracy in measuring temperature. The corresponding sensor elements preferably have resistance tolerances comparable to the narrow resistance tolerances of conventional designs such as SMD NTC or NTC chips.

[0031] According to one embodiment, the sensor element has an upper surface and a lower surface, which are arranged opposite each other and connected to each other by the side surfaces of the sensor element. Here, the lower surface of the sensor element refers to the surface closed by the carrier. In particular, the lower surface of the sensor element is formed by the carrier.

[0032] The sensor element has a bottom electrode and a top electrode. In this case, the top electrode is the electrode closest to the top surface of the sensor element. The bottom electrode is the electrode closest to the bottom surface of the sensor element. The bottom electrode is formed directly on an insulating layer. The bottom electrode does not need to completely cover the insulating layer. A portion of the insulating layer preferably does not include the conductive material of the bottom electrode.

[0033] The electrode closest to the upper surface of the sensor element (i.e., the top electrode) is structured to adjust the resistance. In this way, trimmable areas are created on the top electrode. In particular, the top electrode has one or more trimmable areas. The trimmable areas are advantageously cut using a laser (laser trimming) to adjust the resistance of the sensor element. Also, multiple trimmable areas may be cut.

[0034] By isolating the trimmable areas, the overall area of ​​the electrode changes, resulting in a change in resistance, allowing for optimization of the resistance tolerance of the final sensor element.

[0035] According to one embodiment, each intermediate layer is arranged in such a way that electrical and mechanical contact between contact pads and electrodes of opposite polarity is prevented in the sensor element that is ultimately contacted. In other words, the intermediate layer is formed and arranged as a separating layer or buffer between contact pads or electrodes of different polarity. The thickness of each intermediate layer (i.e., extension perpendicular to the main extension direction of the sensor element) may be equal to or greater than the thickness of the respective electrode.

[0036] Each intermediate layer is preferably formed as an extension of the respective electrode along the main extension direction of the sensor element. In other words, the intermediate layer extends the extent of the electrode parallel to the carrier or parallel to the functional layer. Therefore, each (electrode) layer has the same extent along the carrier. In this way, the side surface of the sensor element is smooth with as few edges or steps as possible. This avoids scattering effects in the overlapping regions of the electrodes in the outer regions due to diagonal current paths with different path lengths.

[0037] Alternatively or additionally, the respective intermediate layer is arranged such that direct contact between the at least one functional layer and the contact pads is prevented, and thus the intermediate layer can be formed and arranged as a separating layer or buffer between the at least one functional layer and the contact pads.

[0038] The electrodes have overlapping regions, where the electrodes are formed one above the other. At least one functional layer is designed to prevent the functional layer from extending beyond the overlapping region. That is, the functional layer is disposed only within the overlapping region. The functional layer does not protrude beyond the overlapping region. Rather, an intermediate layer is formed in the region between the functional layer and the contact pad.

[0039] This intermediate layer not only mechanically and electrically separates the contact pads and the functional layer, but also ensures that the individual layers (electrodes, functional layer) have the same extent parallel to the carrier. As a result, the intermediate layer extends the functional layers and electrodes, and all layers have the same extent parallel to the carrier. Therefore, the sides of the sensor elements can be kept as free of edges and steps as possible. Scattering effects are effectively avoided.

[0040] According to one embodiment, each intermediate layer is formed around at least one functional layer, and each intermediate layer may also be formed in a U-shape around each electrode, thereby effectively protecting each layer from external influences.

[0041] According to one embodiment, the sensor element further comprises an insulating portion. The insulating portion protects the sensor element from external influences. The insulating portion is formed and arranged to completely cover at least one partial region of the sensor element. The at least one functional layer and the at least two intermediate layers are preferably completely surrounded by the insulating portion. Furthermore, at least partial regions of the at least two electrodes are surrounded by the insulating portion. Preferably, the electrodes are completely surrounded by the insulating portion. Contact pads are formed on the upper surface of the sensor element so as to protrude from the insulating portion for electrical contact of the sensor element.

[0042] According to one embodiment, the sensor element has a first or upper partial region. The sensor element further has a second or lower partial region. The width of the first partial region is B1. The width of the second partial region is B2. Width in this context should be understood to mean the extension of the respective partial region along the main extension direction of the sensor element. In particular, width should be understood as the extension parallel to the carrier.

[0043] The two partial regions are arranged one above the other. The first partial region contains, in particular, the functional layer, the electrodes, the intermediate layer, and the contact pads. The first partial region may also contain an insulating part. The second partial region contains, in particular, the carrier and the insulating layer. One side, preferably all sides, of the first partial region and / or the second partial region are step-free. In other words, the outer surface of each partial region is smooth.

[0044] The partial regions are formed such that B1≦B2. In other words, the first partial region can be the same width as the second partial region. In this case, there are no steps / edges on the side surfaces of the sensor element. Alternatively, the width of the first partial region can be smaller than the width of the second partial region. In this case, a (single) step / edge is formed on the side surface of the sensor element at the transition between the first and second partial regions.

[0045] According to a further aspect, a method for manufacturing at least one sensor element is described. It should be noted that the method preferably involves manufacturing a plurality of sensor elements, for example 20,000 sensor elements, in parallel and finally separating them from one another. For the sake of brevity, in the following, reference will be made primarily to sensor elements where appropriate.

[0046] Advantageously, this method produces the above-mentioned sensor elements, each of which has only a small range of deviation from the target resistance, and the sensor elements produced by this method generally have a narrow resistance tolerance.

[0047] Even if a particular feature is not explicitly mentioned in the context of a particular aspect, a feature disclosed with respect to a sensor element or method is also disclosed with respect to each other aspect, and vice versa.

[0048] The method includes the following steps: A) Providing a carrier material for forming a carrier. The carrier is used to mechanically stabilize the sensor element. Preferably, the carrier material comprises Si, SiC or glass. Alternatively, the carrier material may comprise AlN or Al2O3.

[0049] B) forming an insulating layer on the top surface of the carrier; The insulating layer may comprise Al2O3, AlN, SiO2, or Si3N4, or a combination of layers of these materials. Preferably, the insulating layer completely covers the top surface of the carrier. If the carrier material is electrically insulating, the formation of the insulating layer according to step B) may also be omitted (optional step depending on the material).

[0050] C) Applying a first electrode (bottom electrode) on top of the carrier / insulating layer. The electrode material is deposited by a PVD (physical vapor deposition) process, a CVD (chemical vapor deposition) process, or electroplating. Alternatively, the deposition is performed by an ALD (atomic layer deposition) method. The electrode is preferably deposited only on a partial region of the insulating layer. In other words, a partial region of the insulating layer / carrier remains free from the metal material of the bottom electrode.

[0051] D) applying at least one intermediate layer over the insulating layer; In particular, the intermediate layer is applied over the area of ​​the bottom electrode that is left free of metal material. The intermediate layer and the bottom electrode can have the same thickness / height, in which case they form a plane. Alternatively, the intermediate layer can be made thicker.

[0052] E) Applying at least one functional layer to at least a portion of the area of ​​the bottom electrode. This is done, for example, by a sputtering or spin coating process.

[0053] The functional layer can be formed on the plane formed by the intermediate layer and the bottom electrode, or it can be formed only in a partial area of ​​this plane, in which case an additional intermediate layer is formed in a further step as a buffer between the functional layer and the above-mentioned contact pad.

[0054] F) Applying at least one further electrode. The electrode is applied directly onto at least some areas of the functional layer, in other words, partial areas of the functional layer can remain free of the metal material of the electrode.

[0055] G) Applying at least one further intermediate layer. The intermediate layer can be formed in partial areas of the functional layer that remain free of the metal material of the further electrode. Alternatively or additionally, the intermediate layer can be formed as a buffer between the functional layer and the above-mentioned contact pad.

[0056] H) Structuring at least one of the electrodes to form at least one trimmable area for adjusting the resistance. This can be done, for example, by wet chemical etching or dry etching or by laser structuring. Preferably, the top electrode is structured as described above.

[0057] I) forming contact pads for electrically contacting the sensor elements; In the final contacted sensor element, electrodes of the same polarity are connected perpendicularly to the metal material (i.e., in the stacking direction). Preferably, the contact pads comprise a metal such as Cu, Al, or Au.

[0058] The functional layer is then measured, in which case an initial tolerance for the resistance of the sensor elements is determined so that the resistance of each sensor element can later be adjusted to a target value.

[0059] J) Adjusting the resistance value by trimming at least one structured electrode. Trimming is preferably performed using a laser, and the resistance is adjusted to a predetermined nominal (target) value. By precisely adjusting the resistance of each sensor element, the completed sensor element as a whole has a very narrow resistance tolerance.

[0060] According to one embodiment, an additional formation of an insulating portion on at least a partial region of the surface of the sensor element is provided. In this way the sensor element is protected from external influences. This step can be carried out before or after step J). If the formation of the insulation takes place before step J), the structured electrode remains free of insulation and can therefore be trimmed subsequently.

[0061] 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.

[0062] The same reference signs are used for elements that are similar to one another or perform the same function. [Brief explanation of the drawings]

[0063] [Figure 1] FIG. 1 shows a sensor element according to the prior art. [Figure 2] FIG. 2 shows a cross-sectional view of a sensor element according to a first embodiment. [Figure 3] FIG. 3 shows a cross-sectional view of a sensor element according to a further embodiment. [Figure 4] FIG. 4 shows a cross-sectional view of a sensor element according to a further embodiment. [Figure 5a] 5a-5c show top views of the individual components of the sensor element of FIG. [Figure 5b] 5a-5c show top views of the individual components of the sensor element of FIG. [Figure 5c] 5a-5c show top views of the individual components of the sensor element of FIG. [Figure 6] FIG. 6 shows a cross-sectional view of a sensor element according to a further embodiment. [Figure 7] FIG. 7 shows a top view of a sensor element with trimmable electrodes. DETAILED DESCRIPTION OF THE INVENTION

[0064] 1 shows a prior art sensor element 1. The sensor element 1 is a multilayer NTC thin film temperature sensor having a carrier 4, first and second electrodes 3a, 3b and a functional layer 2.

[0065] The sensor element 1 is intended to illustrate the basic structure of the sensor element 10 described below. For the essential features of the sensor element 1 of Figure 1, please refer to WO 2021 / 004957 A1.

[0066] The design of the sensor element 1 has several drawbacks. The stepped design makes process control more difficult. In particular, when forming the electrodes 3a, 3b, insufficient edge coverage can result in poor contact. Furthermore, the stepped design creates electrical scattering effects in the overlapping areas of the outer regions due to the diagonal current paths with different path lengths. For path lengths shorter than the distance from the electrodes 3a, 3b to the functional layer 2, local hot spots occur due to increased voltage drops at thin locations. This makes it difficult to achieve low resistive scattering, and the scattering of the component exceeds the normal scattering range.

[0067] The above-mentioned drawbacks are mitigated or eliminated by the design of the sensor element 10 described below.

[0068] 2 shows a cross-sectional view of a sensor element 10 according to a first embodiment. The sensor element 10 is a thin-film NTC temperature sensor. The sensor element 10 has an upper surface 10a, a lower surface 10b, and a side surface 10c.

[0069] The sensor element 10 is configured to be directly integrated into a MEMS structure and / or a SESUB structure. For this purpose, the sensor element 10 is designed to be very compact. The maximum edge length (i.e., the dimension along the main extension direction X) is 1000 μm, preferably <800 μm, particularly preferably <500 μm. The thickness or height (i.e., the extension perpendicular to the main extension direction X) of the sensor element 10 is <100 μm, preferably <80 μm, particularly preferably <50 μm. Due to its small dimensions, the sensor element 10 is ideally suited as a separate component to be directly embedded in a MEMS / SESUB structure.

[0070] The sensor element 10 comprises a carrier 11, which preferably comprises silicon, silicon carbide or glass (silicate glass or borosilicate glass). Alternatively, the carrier 11 may comprise AlN, Si3N4 or Al2O3. The carrier 11 may have a rectangular or square base surface. As mentioned above, the maximum edge length of the carrier 11 is in each case 1000 μm, advantageously <800 μm, ideally <500 μm.

[0071] The carrier 11 has an upper surface 18 and a lower surface 19. An insulating layer 12 is formed on the upper surface 18, completely covering the upper surface 18 of the carrier. The insulating layer 12 (see also FIG. 4) has a thickness d of 1.5 μm or less. The insulating layer 12 may be composed of one or more layers and may, for example, comprise Al2O3, AlN, SiO2, or Si3N4, or a combination of layers of these materials.

[0072] In this embodiment, the sensor element 10 further includes three functional layers 15. Of course, the sensor element 10 may include only one functional layer 15 or three or more functional layers 15. Depending on the number of functional layers 15, different resistances of the sensor element 10 can be achieved. The functional layers 15 are arranged or stacked one above the other. The functional layers 15 are connected in parallel.

[0073] The thickness or height of each functional layer 15 is 50 nm to 1 μm, preferably 100 nm to 500 nm, and particularly preferably 250 nm to 400 nm. The functional layer 15 contains a material having specific electrical properties. Each functional layer 15 contains an NTC ceramic. Each functional layer 15 is preferably a thin film having NTC properties.

[0074] The functional layer 15 is preferably based on an oxide material having a perovskite or spinel structure. Alternatively, the functional layer 15 can be based on a carbide or nitride material. In particular, the following functional layers 15 are conceivable: a) oxides: for example perovskites (based on mixed crystals of the composition CaMnO3, where Ca can be completely or partially substituted, for example, by Y, Cr, Al, La, etc.) or spinels (based on mixed crystals of the composition NiMn2O4, where Ni and Mn can be completely or partially substituted, for example, by Fe, Co, Al); b) Carbides, such as (Si,Ti)C, hexagonal or cubic SiC. c) Nitrides, e.g. (Al,Ti)N, CrN. A thin film of vanadium oxide is also an alternative.

[0075] In this design, the sensor element 10 also has multiple electrodes or electrode layers 13a, 13b, in particular four electrodes 13a, 13b. Of course, the sensor element 10 can also have only two electrodes 13a, 13b or more than four electrodes 13a, 13b. The electrodes 13a, 13b have opposite polarities (as soon as the sensor element 10 finally contacts them). The electrodes 13a, 13b of opposite polarities can also be referred to as the first electrode 13a and the second electrode 13b. The electrodes 13a, 13b can be single-layer or multi-layer and include, for example, Cu, Au, Ni, Cr, Ag, Ti, Ta, W, Pd, or Pt. The electrodes 13a, 13b are configured as thin-film electrodes.

[0076] Electrodes 13a, 13b (hereafter referred to as the bottom electrodes) are formed directly on insulating layer 12. As can be seen in Figure 2, they do not completely cover insulating layer 12. Rather, strips of insulating layer 12 are left free of the conductive material of the bottom electrodes, as will be explained in more detail below.

[0077] The (bottom) functional layer 15 is formed directly on the bottom electrode 13a, 13b. The bottom electrode does not necessarily have to be completely covered by the functional layer 15. A further electrode 13a, 13b is at least partially arranged directly on top of the functional layer 15. This layered structure continues. In particular, the functional layer 15 is always at least partially arranged between the two electrodes 13a, 13b.

[0078] The electrodes 13a, 13b are connected to each other vertically on the side surface 10c of the sensor element 10. These connections serve as contact pads 16a, 16b for the sensor element 10 and can be contacted, for example, by wire bonding. This connects the functional layers 15 in parallel. The contact pads 16a, 16b are directly electrically and mechanically connected to the electrodes 13a, 13b. Furthermore, in this embodiment, the contact pads 16a, 16b are in direct contact with the functional layers 15. The contact pads may include Cu, Au, Ni, Cr, Ag, Ti, Ta, W, Pd, or Pt.

[0079] Furthermore, in this embodiment, the sensor element 10 has four intermediate layers 14. Alternatively, the sensor element 10 can have only two intermediate layers 14 (in which case the sensor element 10 has exactly one functional layer 15 and exactly two electrodes 13a, 13b; not explicitly shown), or the sensor element 10 can have more than four intermediate layers 14. Each intermediate layer 14 includes an insulating material. Each intermediate layer 14 includes, for example, Al2O3, AlN, SiO2, or Si3N4.

[0080] In this embodiment, the thickness or height (extension perpendicular to the main extension direction X) of each intermediate layer 14 is the same as the thickness or height of each electrode 13 a, 13 b. In other words, the electrodes 13 a, 13 b and the intermediate layer 14 have the same height. However, the thickness / height of the intermediate layer 14 may be greater than the thickness / height of the electrodes 13 a, 13 b (see FIGS. 3, 4, 6). For example, as will be explained in more detail below, the intermediate layer 14 may extend perpendicular to the main extension direction X beyond multiple layers of the sensor element 10.

[0081] In the embodiment shown in Figure 2, each intermediate layer 14 is formed as an extension of the respective electrode 13a, 13b along the main extension direction X of the sensor element 10 (or parallel to the top surface 18 of the carrier 11). For example, as can be seen in Figure 2, the bottom electrode does not completely cover the insulating layer 12. Rather, as already mentioned, there are strips on the insulating layer 12 that are not metallized.

[0082] This free space is filled with the insulating material of the intermediate layer 14, which then follows the bottom electrode. On top of these two layers (bottom electrode and intermediate layer 14) or on the plane formed by these layers, a bottom functional layer 15 is formed.

[0083] 2. A second electrode 13b is formed on the bottom functional layer 15, not completely covering the functional layer 15 on the left side of FIG. 2. This free area is again covered with an intermediate layer 14. Similarly, each intermediate layer 14 continues or extends the other electrodes 13a, 13b in the X direction.

[0084] An intermediate insulating layer 14 fills the individual layers (in this case, electrodes 13a, 13b) of the sensor element 10. As will be explained in more detail below, this reduces the step shape of the sensor element 10 compared to the prior art of FIG.

[0085] The sensor element 10 has a first partial region 23 and a second partial region 24 (see particularly FIG. 6). The partial regions 23, 24 are arranged one above the other. The width of the first partial region 23 is B1, and the width of the second partial region 24 is B2. Here, the width refers to the extent along the main extension direction X (X-direction) of the respective partial regions 23, 24. In this embodiment, B1 < B2. However, basically, it is also possible to set B1 = B2 (see, for example, FIGS. 3 and 6).

[0086] The first partial region 23 particularly includes a functional layer 15, electrodes 13a, 13b, an intermediate layer 14, and contact pads 16a, 16b. The second partial region 24 particularly includes a carrier 11 and an insulating layer 12.

[0087] As can be seen from FIG. 2, there are no edges or steps on the side surfaces of the first partial region 23. The same applies to the side surfaces of the second partial region 24. Steps exist only in the transition region between the first partial region 23 and the second partial region 24. In other words, the outer surfaces of the respective partial regions 23, 24 are smooth. This is achieved by the fact that the individual layers are filled with the intermediate layer 14, so that all the layers of the first partial region 23 have the same extent along the X-axis.

[0088] The formation of the intermediate layer 14 and the associated reduction in the stepped shape of the sensor element 10 effectively reduces the electrical scattering effect. Also, the possibility of forming hot spots is reduced.

[0089] The entire sensor element 10 has a narrow resistance tolerance. This means that each sensor element 10 has a very small deviation range from the target resistance.

[0090] To adjust the resistance of each sensor element 10, one of the electrodes 13a, 13b is structured (see FIG. 7). Preferably, the top electrode, i.e., the electrode 13a, 13b closest to the top surface 10a of the sensor element 10, is structured. The electrode therefore has trimmable areas (see trimmable areas 17 in FIG. 7). These areas are cut with a laser to change the total area of ​​the electrode and therefore its resistance.

[0091] The tight resistance tolerance of the sensor element 10 allows the sensor element 10 to have very high accuracy in temperature measurements. Preferably, the sensor element 10 has a resistance tolerance comparable to the tight resistance tolerance of typical designs such as SMD NTC or NTC chips.

[0092] 2, each functional layer 15 has additional contacts with contact pads 16a, 16b, which can result in scattering effects in outer regions of the sensor element 10 via diagonal current paths with different path lengths. In the embodiment of FIG. 3, to further eliminate scattering effects, each functional layer 15 is formed to lie only in the overlap region 21 formed by the two electrodes 13a, 13b.

[0093] As can be seen in Figure 3, the electrodes have an overlap region 21. The electrodes 13a, 13b are stacked one on top of the other in the overlap region 21. In contrast to the design of Figure 2, the functional layer 15 is formed so that it does not extend beyond the overlap region 21. In other words, the width of the functional layer 15 is narrower than that of the functional layer shown in Figure 2.

[0094] Therefore, in the region 22 between each functional layer 15 and the contact pads 16 a, 16 b, an intermediate layer 14 is formed between each functional layer 15 and the contact pads 16 a, 16 b, which closes the gaps that would otherwise be created if the functional layers 15 did not extend beyond the overlap region 21.

[0095] Therefore, in this embodiment, the intermediate layer 14 extends not only the electrodes 13a, 13b but also the functional layer 15. This makes it possible to minimize the presence of edges and steps on the side surface 10c of the sensor element 10. Furthermore, in this embodiment, the width of each layer of the first partial region 23 is selected so that there is no step between the first partial region 23 and the second partial regions 23, 24 (i.e., B1=B2). This effectively avoids scattering effects.

[0096] In this case, the thickness of the intermediate layer 14 may be greater than the thickness of the individual electrodes 13a, 13b / electrode layers. In particular, each intermediate layer 14 here extends across multiple layers of the sensor element 10 perpendicular to the main extension direction X. The maximum thickness or height of the intermediate layer 14 can therefore reach the combined height of two functional layers 15 and one electrode layer 13a, 13b, as can be seen in FIG. 3 . In other words, the intermediate layer 14 of the sensor element 10 that ultimately contacts the electrode 13a, 13b of one polarity extends in the stacking direction at most from the electrode 13a, 13b of one polarity to the next electrode 13a, 13b of the same polarity. The maximum thickness of the intermediate layer 14 therefore corresponds to the distance A between two electrodes 13a, 13b of the same polarity (see also FIG. 4 ).

[0097] For all other features of the sensor element 10, please refer to the description associated with FIG.

[0098] Figures 4 and 5a to 5c show a sensor element 10 and its individual components according to another embodiment.

[0099] In the two previously described embodiments, two of the four sides of the individual layers are exposed and therefore unprotected, as shown in Figures 2 and 3. To achieve this protection, the insulating intermediate layers 14 in the embodiment according to Figure 4 are each configured to surround the functional layers 15 (see also Figure 5b). In other words, all surfaces of each functional layer 15, except for the top and bottom surfaces of the functional layer 15, are enveloped by the insulating material of the intermediate layers 14.

[0100] To avoid a stepped configuration of the sensor element 10, the intermediate layer 14 is deposited in a U-shape around each electrode 13a, 13b (FIGS. 5a and 5c). Therefore, it can be seen from FIGS. 5a and 5c that, except for the top and bottom surfaces and one side surface of each electrode 13a, 13b, the remaining sides are completely surrounded by the insulating material of the intermediate layer 14. In other words, three of the four sides of each electrode 13a, 13b are surrounded by the intermediate layer 14.

[0101] For all other features of the sensor element 10, please refer to the description associated with FIG.

[0102] FIG. 6 shows a cross-sectional view of a sensor element 10 according to a further embodiment.

[0103] Here, the sensor element 10 is at least partially surrounded by an insulator 20. In particular, at least the side surface 10c of the sensor element 10 (excluding the carrier 11) is preferably completely enveloped by the insulator 20. The insulator 20 covers in particular the electrodes 13a, 13b (with the possible exception of the top electrode, described below), the functional layer 15, the intermediate layer 14, and parts of the contact pads 16a, 16b. In this way, these components of the sensor element 10 are protected from external influences. Covering the insulating layer 12 and the carrier 11 is also possible in principle (not explicitly shown).

[0104] Since the top electrode has a trimmable area 17 (see FIG. 7) where it can be (potentially) cut according to the desired resistance value, the top electrode must be freely accessible for laser trimming. Therefore, in the region of the top surface 10a of the sensor element 10, there are two possible embodiments for the insulating portion 20: the insulating portion 20 covers, in particular, the electrodes 13a, 13b (with the possible exception of the top electrode, which will be described later), the functional layer 15, the intermediate layer 14, and part of the contact pads 16a, 16b. In this way, these components of the sensor element 10 are protected from external influences. Covering the insulating layer 12 and the carrier 11 is also possible in principle (not explicitly shown).

[0105] Since the top electrode has a trimmable area 17 (see FIG. 7) that is (can be) cut depending on the target value of the resistance, the top electrode must be freely accessible for laser trimming. Therefore, in the region of the top surface 10a of the sensor element 10, there are two possible embodiments for the insulating part 20: The upper electrode can remain completely free of insulator 20, so that the insulator 20 is always accessible for adjusting the resistance (not explicitly shown). Alternatively, the insulation on the top surface 10a of the sensor element 10 may be formed only after trimming, for example after trimming a polymer layer, an oxide, a nitride, a ceramic layer, a thin glass layer or a combination of these layers may be formed as insulation 20 on the top / structured electrode.

[0106] 6, the contact pads 16a, 16b in all embodiments protrude from the insulating portion 20 of the upper surface 10a of the sensor element to allow electrical contact with the sensor element 10. For this purpose, in this exemplary embodiment, the contact pads 16a, 16b are configured higher. In particular, the upper surfaces of the contact pads 16a, 16b are not flush with the upper surface of the top electrode.

[0107] For all further features of the sensor element 10, please refer to the description associated with FIG.

[0108] In the following, a method for manufacturing a sensor element 10 is described. In particular, this method produces a plurality of sensor elements 10 according to any of the embodiments described above (see FIGS. 2-7). For the sake of brevity, the following will refer, where appropriate, to only one sensor element 10.

[0109] All features described in relation to the sensor element 10 also apply to the method and vice versa.

[0110] The method includes the following steps: A) Providing a carrier material to form a carrier 11. Preferably, the carrier material comprises Si, SiC or glass. Alternatively, the carrier material may comprise AlN, Si3N4 or Al2O3.

[0111] B) forming an insulating layer 12 on the top surface 18 of the carrier 11; The insulating layer 12 may comprise Al2O3, AlN, SiO2, or Si3N4, or a combination of layers of these materials. Preferably, the insulating layer 12 is deposited to completely cover the top surface 18 of the carrier 11.

[0112] The insulating layer 12 may be needed as a flat base on which to form further layers (electrodes 13a, 13b, intermediate layer 14, functional layer 15). If the surface 18 of the carrier 11 is sufficiently flat and / or the carrier 11 itself is made of an insulating material, the step of forming the insulating layer 12 according to step B) may be omitted (optional step).

[0113] C) Applying the first electrodes 13a, 13b (bottom electrodes). The electrodes 13a, 13b are deposited by PVD, ALD, or CVD processes or by electroplating. Advantageously, the electrodes 13a, 13b are deposited only on partial regions of the insulating layer 12. Strips of the insulating layer 12 remain free of electrode material, and the intermediate layer 14 can then be formed in these free regions.

[0114] D) Applying at least one intermediate layer 14 onto the insulating layer 12 to extend the electrodes 13a, 13b. The intermediate layer 14 contains an insulating material and is formed in a partial region (empty region) of the insulating layer 12 where the metal material of the electrodes 13a and 13b is not present. The intermediate layer 14 and the lower electrode can be flat, i.e., at the same height (Fig. 2). Alternatively, the intermediate layer 14 can be formed higher than the electrodes 13a and 13b (Figs. 3, 4, and 6).

[0115] E) Applying at least one functional layer 15. This is done, for example, by a sputtering or spin-coating process, as well as at least one temperature process at T > 500 °C during and / or after the deposition of each layer. The functional material comprises an NTC ceramic based on an oxide material of perovskite or spinel structure type. Alternatively, the functional material can be based on a carbide or nitride material. In a further alternative, the functional material comprises a thin film of vanadium oxide or consists of vanadium oxide.

[0116] The functional layer 15 is formed, for example, on the plane formed by the intermediate layer 14 and the bottom electrode (see FIG. 2). The functional layer 15 can either be deposited over the entire bottom electrode 13a, 13b (FIG. 2), or the functional layer 15 can be formed not up to the edge of the bottom electrode. This means that on the opposite side of the intermediate layer 14 (left side of FIG. 2), the bottom electrode is not covered up to its edge. In this case, a further intermediate layer 14 is subsequently formed on the area of ​​the bottom electrode exposed (by the functional layer 15) (FIGS. 3, 4, 6).

[0117] F) Applying at least one further electrode 13a, 13b. The deposition of the electrodes 13a, 13b is carried out by PVD, ALD or CVD processes or by electroplating. The further electrodes 13a, 13b are formed directly on the functional layer 15. The further electrodes 13a, 13b can, for example, be formed only on partial regions of the functional layer 15 (see variant in FIG. 2).

[0118] G) Applying at least one further intermediate layer 14. The intermediate layer 14 comprises an insulating material and is formed, for example, in partial areas of the functional layer 15 that are free from the metal material of the further electrodes 13a, 13b. Alternatively or additionally, the intermediate layer 14 may be formed in the areas between the functional layer 15 and the contact pads 16a, 16b. This is done after step I).

[0119] H) Structuring at least one of the electrodes 13a, 13b to form at least one trimmable area 17 for adjusting the resistance. This can be done, for example, by wet chemical etching or dry etching or by laser structuring. The top electrode is preferably structured as described above.

[0120] I) Forming contact pads 16a, 16b for electrical contact of the sensor element 10. In particular, in the completed contacted sensor element 10, the electrodes 13a, 13b of the same polarity are connected with one metal material in the vertical direction (i.e., stacking direction). Preferably, the contact pads 16a, 16b comprise a metal such as Cu, Al, or Au. The functional layer 15 is then measured. Here, an initial tolerance range for the resistance value of the entire manufactured sensor element 10 is determined, and the resistance of each sensor element 10 can then be adjusted to a target value.

[0121] J) Adjusting the resistance by trimming at least one structured electrode 13a, 13b. The trimming is preferably performed using a laser. The resistance value is set to a predetermined rating (target value). By precisely adjusting the resistance value, the finished sensor element 10 has a very narrow resistance tolerance. To adjust the resistance value, the aforementioned structured / trimmable area 17 is at least partially cut.

[0122] K) forming an insulating portion 10 on at least a partial area of ​​the surface of the sensor element 10;

[0123] Step K) can also be performed before step J), in which case the top electrode remains free of insulation 20 to allow for later trimming.

[0124] In addition to the process steps described above, the sensor element 10 may be subjected to a sintering process in a further process step.

[0125] A grinding or etching process can then be used to thin the carrier material.

[0126] The items described herein are not limited to each particular embodiment, but rather the features of each embodiment can be combined with each other in any way as long as it makes technical sense. [Explanation of symbols]

[0127] 1 Sensor element 2. Functional Layer 3a 1st electrode 3b 2nd electrode 4. Career 10 Sensor Elements 10a Top surface of sensor element 10b Underside of sensor element 10c Side of the sensor element 11. Career 12 Insulating layer 13a Electrode / electrode layer 13b Electrode / electrode layer 14 Middle Class 15 Functional Layers 16a contact pad 16b contact pad 17 Croppable area 18 Carrier top 19 Carrier bottom 20 Insulation section 21 Overlap Area 22 areas 23 1st subregion 24 Second subregion d thickness of insulating layer B1 Width of the first subregion B2 Width of the second subregion X main extension direction A. Distance

Claims

1. A sensor element (10) for measuring temperature, comprising: at least one carrier (11) having an upper surface (18) and a lower surface (19), a carrier (11) having an insulating layer (12) formed on an upper surface (19) of the carrier (11); at least two electrodes (13a, 13b) spaced apart from one another on said carrier (2); at least one functional layer (15) comprising a material with a temperature-dependent electrical resistance, at least one functional layer (14), the at least one functional layer being at least partially arranged between the electrodes (13a, 13b); at least two intermediate layers (14) comprising insulating material; - at least two contact pads (16a, 16b) for electrical contact of said sensor element (10), the sensor element (10) is formed as a separate component that is directly integrated into an electrical system, The sensor element (10) has a small deviation range from a target resistance; At least one of the at least two electrodes (13a, 13b) is structured to adjust the resistance value. Sensor element.

2. The sensor element has an upper surface (10a) and a lower surface (10b), The electrodes (13a, 13b) closest to the upper surface (10a) of the sensor element (10) are structured to adjust their resistance value; The sensor element of claim 1 .

3. The electrodes (13a, 13b) closest to the top surface (10a) of the sensor element (10) have a trimmable area (17). The sensor element of claim 2 .

4. each of said intermediate layers (14) is arranged so as to prevent direct contact between at least one functional layer (15) and a contact pad (16a, 16b); A sensor element according to any one of claims 1 to 3.

5. Each of the intermediate layers (14) is formed as an extension of an electrode (13a, 13b) along the main extension direction (X) of the sensor element (10). A sensor element according to any one of claims 1 to 4.

6. One intermediate layer (14) is formed in a region (22) between the functional layer (15) and each of the contact pads (16a, 16b). A sensor element according to any one of claims 1 to 5.

7. The electrodes (13a, 13b) have overlapping regions (21) where the electrodes (13a, 13b) are formed above and below each other, At least one functional layer (15) is formed so as to prevent the functional layer (15) from spreading beyond the overlap region (21). A sensor element according to any one of claims 1 to 6.

8. Each of the intermediate layers (14) is formed around the at least one functional layer (15). A sensor element according to any one of claims 1 to 7.

9. One of the intermediate layers (14) is formed in a U-shape around each electrode (13a, 13b). A sensor element according to any one of claims 1 to 8.

10. The thickness of each of the intermediate layers (14) is equal to or greater than the thickness of each of the electrodes (13a, 13b). A sensor element according to any one of claims 1 to 9.

11. Further provided with an insulating portion (20), The at least one functional layer (15) and the intermediate layer (14) are completely surrounded by the insulating portion (20); At least a part of the area of ​​the electrodes (13a, 13b) is surrounded by the insulating portion (20). A sensor element according to any one of claims 1 to 10.

12. The contact pads (16a, 16b) protrude from the insulating portion (20) on the upper surface (10a) of the sensor element (10). The sensor element of claim 11.

13. one of the at least two electrodes (13a, 13b) is formed under the at least one functional layer (14); The other of the at least two electrodes (13a, 13b) is formed on the at least one functional layer (14). A sensor element according to any one of claims 1 to 12.

14. a first partial region (23) having a width B1 and including the functional layer (15), the electrodes (13a, 13b), the intermediate layer (14) and the contact pads (16a, 16b); a second partial region (24) having a width B2 and including the carrier (11) and the insulating layer (12); B1≦B2; A sensor element according to any one of claims 1 to 13.

15. The side surfaces of the first partial region (23) and / or the second partial region (24) are free of steps. The sensor element of claim 14.

16. The lowermost electrode of the at least two electrodes (13a, 13b) is formed directly on the insulating layer (12). A sensor element according to any one of claims 1 to 15.

17. a partial region of the insulating layer (12) that is free from the conductive material of the bottom electrode; The sensor element of claim 16.

18. One of the at least two intermediate layers (14) is formed in the free area. The sensor element of claim 17.

19. Each of the electrodes (13a, 13b) is formed as a thin film electrode. A sensor element according to any one of claims 1 to 18.

20. The at least one functional layer (15) is a thin film having NTC properties. A sensor element according to any one of claims 1 to 19.

21. the carrier (11) comprises silicon, silicon carbide or glass, or The carrier (11) is made of Si as a carrier material. ３ N ４ , AlN, GaN or Al ２ O ３ Including, A sensor element according to any one of claims 1 to 20.

22. said functional layer (15) comprises an NTC ceramic based on an oxidizing material, of perovskite or spinel structure type, or the functional layer (15) comprises an NTC ceramic based on a carbide or nitride material; A sensor element according to any one of claims 1 to 21.

23. The electrodes (13a, 13b) are formed in a single layer or multiple layers and comprise at least one material or a combination of materials 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 (16a, 16b) are formed in a single layer or in a multilayer and comprise at least one material or combination of materials 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 23.

25. The insulating layer (12) 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 having a combination of layers of these materials, A sensor element according to any one of claims 1 to 24.

26. The insulating portion (20) is formed in a single layer or multiple layers, and is made of Al ２ O ３ , AlN, SiO ２ or Si ３ N ４ or having a combination of layers of these materials, A sensor element according to any one of claims 11 to 25.

27. The insulating portion (20) may be made of a material selected from the group consisting of oxide, nitride, ceramic, glass, and plastic. A sensor element according to any one of claims 11 to 26.

28. The sensor element (10) is configured to be directly integrated into a MEMS structure and / or a SESUB structure.

28. The sensor element of any one of claims 1 to 27.

29. A method for manufacturing a sensor element (10) for measuring temperature, comprising the steps of: A) providing a carrier material for forming a carrier (11); B) forming an insulating layer (12) on the upper surface (18) of said carrier (11); C) applying at least one electrode (13a, 13b) onto a partial area of ​​said carrier (11), leaving said partial area of ​​said carrier (11) free from electrode material; D) applying at least one intermediate layer (14) to the free part areas of said carrier (11); E) applying at least one functional layer (15) on at least a partial area of ​​the plane formed by said electrodes (13a, 13b) and said intermediate layer (14); F) applying at least one further electrode (13a, 13b) onto at least some areas of said functional layer (15); G) applying at least one further intermediate layer (14) onto partial areas of said functional layer (15) that are free of said further electrodes (13a, 13b); H) structuring at least one of said electrodes (13a, 13b) to form at least one trimmable area (17) for resistance adjustment; I) forming contact pads (16a, 16b) for electrical contact of said sensor element (10). method.

30. J) adjusting the resistance by trimming at least one of the structured electrodes (13a, 13b).

30. The method of claim 29.

31. K) forming an insulating portion (20) on at least one partial area of ​​the surface of the sensor element (10).

31. The method of claim 29 or 30.

32. forming at least one further intermediate layer (14) between said contact pads (16a, 16b) and said functional layer (15).

32. The method of any one of claims 29 to 31.

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