Sensor element and method for producing a sensor element

Abstract

In an embodiment a sensor element includes at least one carrier layer having a top side and an underside and at least one functional layer, wherein the functional layer is arranged at the top side of the carrier layer and includes a material having a temperature-dependent electrical resistance, wherein the sensor element is configured to be integrated as a discrete component directly into an electrical system, and wherein the sensor element is configured to measure a temperature.

Claims

1. A sensor element comprising: at least one carrier layer having a top side and an underside; at least one functional layer arranged at the top side of the carrier layer and comprising a material having a temperature-dependent electrical resistance; and at least one protective layer, wherein the protective layer is arranged at a top side of the sensor element and at at least one side surface of the sensor element, wherein the protective layer completely covers the top side of the sensor element, wherein the sensor element is configured to be integrated as a discrete component directly into an electrical system, and wherein the sensor element is configured to measure a temperature.

2. The sensor element according to claim 1, wherein the carrier layer comprises silicon, silicon carbide or glass.

3. The sensor element according to claim 1, wherein the functional layer comprises a thin-film negative temperature coefficient (NTC) layer.

4. The sensor element according to claim 1, wherein the functional layer comprises a semiconducting material based on silicon carbide in a hexagonal, wurtzite-like structure or a cubic phase in a zinc blende structure type, or wherein the functional layer comprises a metal nitride in the wurtzite structure type.

5. The sensor element according to claim 1, wherein the protective layer comprises SiO.sub.2.

6. The sensor element according to claim 1, further comprising at least one feedthrough, wherein the feedthrough completely penetrates through the carrier layer, and wherein at least one contact element for electrically contacting the sensor element is arranged at the underside of the carrier layer.

7. The sensor element according to claim 6, wherein the sensor element comprises at least two feedthroughs, wherein two contact elements are arranged at the underside of the carrier layer.

8. The sensor element according to claim 1, further comprising at least one top electrode, wherein the top electrode is configured for electrically contacting the functional layer from a top side of the functional layer.

9. The sensor element according to claim 8, wherein the top electrode is arranged directly on the functional layer.

10. The sensor element according to claim 8, wherein the top electrode comprises at least one sputtered layer.

11. The sensor element according to claim 8, further comprising at least two top electrodes, wherein the top electrodes are arranged next to one another, and wherein the top electrodes are spatially separated and electrically isolated from one another by at least one cutout.

12. The sensor element according to claim 1, wherein the sensor element is configured for direct integration into a MEMS structure and/or into a semiconductor embedded in substrate (SESUB) structure.

13. A method for producing the sensor element according to claim 1, the method comprising: providing a carrier material for forming the carrier layer; forming at least one feedthrough, wherein the feedthrough completely penetrates through the carrier material; filling the at least one feedthrough with a metallic material; coating the carrier material with a sensor material for forming the functional layer; and singulating for forming the sensor element.

14. The method according to claim 13, further comprising depositing at least one top electrode onto a top side of the sensor material before singulating the sensor element.

15. The method according to claim 13, wherein the sensor material comprises a negative temperature coefficient (NTC) material.

16. The method according to claim 13, further comprising heating after coating the carrier material with the sensor material.

17. The method according to claim 13, wherein coating the carrier material with the sensor material is performed before forming the at least one feedthrough.

18. A sensor element comprising: at least one carrier layer having a top side and an underside; at least one functional layer, wherein the functional layer is arranged at the top side of the carrier layer and comprises a material having a temperature-dependent electrical resistance; and at least one protective layer arranged at a top side of the sensor element and at least one side surface of the sensor element, wherein the protective layer completely covers the top side of the sensor element, wherein the sensor element is configured to be integrated as a discrete component directly into an electrical system, wherein the sensor element is configured for direct integration into a MEMS structure and/or into a semiconductor embedded in substrate (SESUB) structure, and wherein the sensor element is configured to measure a temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The drawings described below should not be regarded as true to scale. Rather, individual dimensions may be illustrated in an enlarged, reduced or even distorted way for the sake of better illustration.

(2) Elements which are identical to one another or which perform the same function are designated by identical reference signs.

(3) In the figures:

(4) FIG. 1 shows a sensor element in a first embodiment;

(5) FIG. 2 shows a sensor element in a second embodiment;

(6) FIG. 3 shows a sensor element in a third embodiment;

(7) FIG. 4 shows a sensor element in a fourth embodiment;

(8) FIG. 5 shows a sensor element in a fifth embodiment; and

(9) FIGS. 6-10 show a method for producing a sensor element.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(10) FIG. 1 shows a sensor element 1 in accordance with a first embodiment. The sensor element 1 is preferably configured for measuring a temperature. The sensor element 1 comprises at least one carrier layer 2 or wafer 2. The carrier layer 2 has a top side 2a and an underside 2b. The carrier layer 2 comprises a carrier material, preferably silicon (Si), silicon carbide (SiC) or glass. The carrier layer 2 serves for mechanically stabilizing the sensor element 1.

(11) The sensor element 1 furthermore comprises at least one functional layer 5 or sensor layer 5. In this exemplary embodiment, the sensor element 1 comprises exactly one functional layer 5. However, a plurality of functional layers 5 is also conceivable, for example two, three or four functional layers 5, which can be arranged next to one another or one above another, for example.

(12) In this exemplary embodiment, the functional layer 5 is arranged at the top side 2a of the carrier layer 2. The functional layer 5 preferably completely covers the top side 2a of the carrier layer 2. The functional layer 5 is arranged in a positively locking and cohesive manner on the carrier layer 2. As an alternative thereto, the functional layer 5 is produced directly in the carrier material locally or as a layer.

(13) The functional layer 5 comprises a material having a temperature-dependent electrical resistance, preferably a material having an NTC R/T characteristic. Preferably, the functional layer 5 is formed as a thin-film NTC layer on the carrier layer 2. The functional layer 5 has a very small thickness of less than or equal to 1 ?m.

(14) By way of example, the functional layer 5 comprises a semiconducting material based on SiC in the hexagonal, wurtzite-like structure or the cubic phase in the zinc blende structure type. In this case, the silicon carbide can be present in a pure form, in doped fashion (for example with Ti, Cr, N, Be, B, Al, Ga) or as a mixed crystal (for example (SiC).sub.x(AlN).sub.1?x), or can contain intermetallic phases such as, for example, Al.sub.4SiC.sub.4, Ti.sub.3SiC.sub.2 or Y.sub.3Si.sub.2C.sub.2.

(15) As an alternative thereto, the functional layer 5 can also be based on metal nitrides in the Wurtzit structure type, such as AlN or GaN. AlN can be present in a pure form, as a mixed crystal (for example (Al.sub.xTi.sub.1?x)(N.sub.yO.sub.1?y) or Al.sub.xGa.sub.1?xN, where 0?x, y?1) or in doped fashion (for example with Si, Mg, C, Ge, Se or Zn).

(16) In this exemplary embodiment, the carrier layer 2 furthermore has two feedthroughs 3. As an alternative thereto, the sensor element 1 can also have only one feedthrough 3 (in this respect, see FIG. 3) or no feedthrough 3 at all (in this respect, see FIG. 4). Furthermore, more than two feedthroughs 3, for example three or four feedthroughs, are also conceivable (not explicitly illustrated).

(17) The respective feedthrough 3 completely penetrates through the carrier layer 2. In other words, the feedthrough 3 projects from the top side 2a as far as the underside 2b of the carrier layer 2. The feedthrough 3 comprises a metallic material, for example copper or gold.

(18) The sensor element 1 shown in FIG. 1 furthermore comprises two contact elements 4. The contact elements 4 are arranged at the underside 2b of the carrier layer 2. The contact elements 4 are formed in a direct way or directly at the feedthroughs 3. The contact elements 4 are in electrical and mechanical contact with the feedthroughs 3. The contact elements 4 serve for electrically contacting the sensor element 1. Furthermore, the sensor element 1 can be stacked onto other components of an electrical system, for example, by way of the contact elements 4.

(19) The contact elements 4 can be embodied for example as bumps or as a thin electrode. The contact elements 4 comprise a metal, for example copper, gold, or solderable alloys. The feedthroughs 3 serve to connect the functional layer 5 at the top side 2a of the carrier layer 2 to the contact elements 4 at the underside 2b of the carrier layer 2 and thus to electrically contact the functional layer 5. A robust and reliable sensor element 1 is thus provided.

(20) In a further exemplary embodiment (not explicitly illustrated), a protective layer 7 is furthermore arranged at a top side is of the sensor element 1. In this case, the protective layer 7 is formed directly on the functional layer 5. The protective layer 7 completely covers a top side 5a of the functional layer 5. The protective layer 7 preferably comprises SiO.sub.2. The protective layer 7 serves to protect the functional layer 5 and the sensor element 1 against external influences (in this respect, also see FIG. 2).

(21) The sensor element 1, by virtue of its specific contacting (feedthroughs 3, contact elements 4) and the specific layer construction (thin-film NTC layer), is designed such that it can be integrated as a complete component in an Si chip or on a printed circuit board. In particular, the sensor element 1 is configured to be integrated as a discrete component in MEMS or SESUB structures.

(22) Overall, the sensor element 1 is embodied very compactly. The sensor element 1 has a very small dimensioning. The sensor element 1 has a width of preferably less than or equal to 500 ?m, for example 50 ?m, 100 ?m, 250 ?m, 300 ?m, 400 ?m or 450 ?m. The sensor element 1 has a length of preferably less than or equal to 500 ?m, for example, 50 ?m, 100 ?m, 250 ?m, 300 ?m, 400 ?m or 450 ?m. Preferably, the sensor element 1 has a rectangular basic shape. The sensor element 1 has a height (extent in the stacking direction) of preferably less than or equal to 100 ?m, for example 10 ?m, 50 ?m or 80 ?m.

(23) By virtue of the compact design and the contacting by means of the feedthroughs 3 and the contact elements 4, the sensor element is outstandingly suitable for integration in MEMS or SESUB structures.

(24) FIG. 2 shows a sensor element 1 in a second embodiment. In contrast to the sensor element 1 described in association in FIG. 1, the sensor element 1 in accordance with FIG. 2 additionally comprises a top electrode 6. The top electrode 6 is arranged on the top side 5a of the functional layer 5. In particular, the top electrode 6 is applied directly on the functional layer 5. In this exemplary embodiment, the top electrode 6 completely covers the top side 5a of the functional layer 5. The functional layer 5 can be contacted from the top side by means of the top electrode 6. The contacting on the underside is affected by way of the feedthroughs 3 and contact elements 4.

(25) The top electrode 6 comprises a metallic material, preferably Au, Ni, Cr, Ag, W, Ti or Pt. Preferably, the top electrode 6 is deposited on the functional layer 5, for example by means of a PVD or CVD process or electrolytically. Preferably, the top electrode 6 is sputtered on the functional layer 5. The top electrode 6 is a thin-film electrode. In other words, the top electrode 6 preferably comprises a thin metal film. The top electrode 6 has a thickness d or height of ?100 nm and ?1 ?m, for example 500 nm.

(26) In this exemplary embodiment, the sensor element 1 furthermore comprises the protective layer 7 already described in association with FIG. 1. Therefore, in the case shown, the top electrode 6 is arranged between functional layer 5 and protective layer 7. To put it another way, in this exemplary embodiment, the protective layer 7 is formed directly on the top electrode 6.

(27) In an alternative exemplary embodiment (not explicitly illustrated), however, the protective layer 7 can also be omitted. In this case, the top electrode 6 forms the top side of the sensor element 1. In this exemplary embodiment, there is the possibility of realizing additional contacting, for example by wire bonding on the top electrode 6 (not explicitly illustrated).

(28) With regard to all further features of the sensor element 1 in accordance with FIG. 2, reference is made to the description concerning FIG. 1.

(29) FIG. 3 shows a sensor element 1 in a third embodiment. In this exemplary embodiment, the sensor element 1 comprises only one feedthrough 3 and one contact element 4, whereby the functional layer 5 is contacted from the underside. The contact element 4 can be embodied as a bump or as a thin electrode, as already described.

(30) In this exemplary embodiment, the sensor element 1 furthermore comprises the top electrode 6 already described in association with FIG. 2. Unlike in FIG. 2, in this exemplary embodiment, the top electrode 6 is absolutely necessary for the (top-side) contacting of the functional layer 5.

(31) With regard to all further features of the sensor element 1 in accordance with FIG. 3, reference is made to the description concerning FIG. 1 and concerning FIG. 2.

(32) FIG. 4 shows a sensor element 1 in a fourth embodiment. In this exemplary embodiment, the sensor element 1 comprises no feedthroughs 3 and also no contact elements 4 at the underside 2b of the carrier layer 2. Rather, the functional layer 5 here is contacted exclusively from the top side. In particular, the sensor element 1 comprises two top electrodes 6a, 6b for the electrical connection of the sensor element 1. The top electrodes 6a, 6b are formed, preferably deposited, directly on the functional layer 5, as has already been explained in association with FIG. 2. The top electrodes 6a, 6b are arranged next to one another on the functional layer 5.

(33) The respective top electrode 6a, 6b can be formed as a single layer or in a multilayered fashion. The respective top electrode 6a, 6b is preferably a thin-film electrode. The respective top electrode 6a, 6b preferably comprises at least one sputtered metal layer. By way of example, the respective top electrode 6a, 6b comprises Au, Ni, Cr, Ag, W, Ti or Pt. Preferably, the respective top electrode 6a, 6b has a thickness or height of between 100 ?m and 1 ?m.

(34) In this exemplary embodiment, the top electrodes 6a, 6b form the top side of the sensor element 1. As an alternative thereto (not explicitly illustrated), however, a protective layer 7 can also be provided, which is arranged on the top electrodes 6a, 6b.

(35) The top electrodes 6a, 6b are electrically isolated from one another. For this purpose, at least one cutout or gap 8 is formed between the top electrodes 6a, 6b, as is illustrated in FIG. 4. Said cutout 8 spatially separates and electrically isolates the top electrodes 6a, 6b. The resistance of the sensor element 1 can be set by way of the size (horizontal extent, that is to say extent perpendicular the stacking direction) of the cutout 8. If the cutout 8 is reduced in size, then the resistance decreases. As a result, however, a variation of the resistance is also increased. In order to avoid this or in order to enlarge the area between the top electrodes 6a, 6b and thus to reduce the resistance, a comb structure can also be provided between the top electrodes 6 (not explicitly illustrated). In this case, the top electrodes 6 are arranged next to one another in an intermeshing manner.

(36) FIG. 5 shows a sensor element 1 in a fifth embodiment. In this exemplary embodiment, the sensor element 1 comprises two feedthroughs 3, two contact elements 4, and two top electrodes 6.

(37) In comparison with the exemplary embodiment shown in FIG. 1, in this exemplary embodiment the feedthroughs 3 completely penetrate through not only the carrier layer 2 but also the functional layer 5. In particular, the respective metallic feedthrough 3 projects into the functional layer 5 and is enclosed by the latter. The respective feedthrough thus extends from the underside 2b of the carrier layer 2 through the carrier layer 2 and the functional layer 5 as far as the top side 5a of the functional layer 5.

(38) A respective top electrode 6 is formed at the top side of the respective feedthrough 3. In this exemplary embodiment, the respective top electrode 6 is also embedded at least partly into the functional layer 5. The top electrodes 6 thus at least partly form the top side 5a of the functional layer 5.

(39) The protective layer 7 is formed directly on the functional layer 5. In this case, the protective layer 7 covers the top side 5a of the functional layer 5 which is at least partly formed by the top electrodes 6.

(40) The contacting on the underside is affected by way of feedthroughs 3 and contact elements 4, for example bumps. In this case, it is also possible for more than the feedthroughs illustrated in FIG. 5 to be provided, for example four feedthroughs. Furthermore, in this exemplary embodiment, a protective layer 7 is situated at the top side is of the sensor element 1.

(41) FIGS. 6 to 10 show a method for producing a sensor element 1. Preferably, the sensor element 1 in accordance with any of the exemplary embodiments described above is produced by the method. Therefore, all features that have been described in association with the sensor element 1 also find application for the method, and vice versa.

(42) In a first step A), a carrier material 10 for forming the carrier layer 2 described above is provided (see top of FIG. 6). The carrier material 10 preferably comprises Si, SiC or glass.

(43) In a next step B), the feedthroughs 3 described above are produced. For this purpose, vias/perforations 12 are produced in the carrier material 10 for example by photolithography and subsequent plasma etching (dry etching) (see middle and bottom of FIG. 6). Alternatively, the vias 12 can also be produced by a laser (laser drilling).

(44) In a step C), the vias/perforations 12 are filled with a metallic material 13 (for example copper), for example electrolytically (in this respect, see FIG. 7). The photoresist 11 (see FIG. 6) used during the photolithography is subsequently washed away.

(45) In a further step D), the carrier material 10 is coated with a sensor material 14 for forming the functional layer 5 (in this respect, see FIG. 8). The sensor material 14 comprises an NTC ceramic, for example. The coating is preferably affected by means of a PVD or CVD process. In this case, a thin sensor film is produced on the carrier material 10 (thin-film NTC). Optionally, a heat treatment step can be affected after step D).

(46) In an alternative exemplary embodiment, method step D) can also be affected before producing the vias/perforations 12 (step B)). In this case, the metallic material 13 projects into the functional layer 5 and is enclosed by the latter (in this respect, also see the exemplary embodiment described in association with FIG. 5).

(47) In a further step, depositing electrode material 15 for forming the at least one top electrode 6 is affected (in this respect, see FIG. 9 in association with FIGS. 2 to 5). The electrode material 15 preferably comprises Au, Ni, Cr, Ag, W, Ti or Pt. The depositing is affected by means of a PVD or CVD process of electrolytically. A single-layer or multilayered thin top electrode 6 (thin-film electrode) is produced in this case. In particular, the top electrode 6 is deposited as a thin electrode film on the sensor material 14 in this method step. If two top electrodes 6 are deposited, then provision is made of a cutout (see FIG. 4) or a comblike structure for electrically isolating the top electrodes 6a, 6b.

(48) An optional step can furthermore involve forming the protective layer 7 by applying the corresponding material (preferably SiO.sub.2) either to the sensor material 14 (exemplary embodiment in accordance with FIG. 1) or to the electrode material 15 (exemplary embodiments in accordance with FIGS. 2 to 5).

(49) In a final step E), the sensor elements 1 are singulated (in this respect, see FIG. 10). This is affected by application of photoresist 11 and subsequent plasma etching or sawing of the functional layer 5 and that part of the carrier material 10 which determines the height or thickness of the later carrier layer 2 (notching).

(50) As an alternative thereto, thinning the carrier material 10 on the underside can be affected in two steps, wherein in a first step the carrier material 10 is two-dimensionally etched away or ground away, and in a second step the singulation is affected by areal etching and the contact elements 4 are uncovered, without the metal being oxidized in the process.

(51) The description of the subjects specified here is not restricted to the individual specific embodiments. Rather, the features of the individual embodiments can be combined with one another in any desired wayinsofar as is technically practical.