CN102169955B - For measuring the sensor element in magnetic field, magnetic field sensor and the method for the manufacture of sensor element - Google Patents

Abstract

A sensor element (42, 42') for measuring a magnetic field, having a wafer structure (12) with a semiconductor substrate (13), an insulating layer (14, 14') and a semiconductor layer (15 , 15'). The sensor element has a punch (16, 16') for punch-through contact through the insulating layer (14, 14'), the punch has a semiconductor substrate end face (17), a semiconductor layer end face (18) and a semiconductor substrate ( Pairs of parallel sides (19; 19') in 13), wherein the end faces (17, 18) and sides (19; 19') have sections (28, 29, 30) with high electrical conductivity , and said punch (16, 16') has a doping with low conductivity in the interior (27).

Description

Sensor element for measuring a magnetic field, magnetic field sensor and method for producing the sensor element

technical field

The invention relates to a sensor element for measuring a magnetic field.

Background technique

Magnetic sensors based on Hall elements can now be used in planar semiconductor processes. EP 1 462 770 thus describes a Hall sensor with a sensor element having contacts arranged in a mold on a semiconductor substrate. An excitation current flowing in the plane of the chip is introduced into the selected contacts and the Hall voltage is measured at the other contacts. By switching the contact part selection, deviation can be eliminated. By applying an excitation current and corresponding measurements in different directions, the magnetic field can be detected in the plane of the chip as well as perpendicular to the plane of the chip. With this sensor, magnetic field components perpendicular to the plane of the chip can be detected very well. For field components in the chip plane, only very low sensitivities can be achieved with a purely planar electrode arrangement.

Contents of the invention

In contrast, the sensor element according to the invention for measuring a magnetic field has the advantage that the Hall effect is also maximized for the direction of the magnetic field lying in the plane of the chip. In this way, the magnetic field vector can be determined with good accuracy in all three spatial directions. In particular, all magnetic field components can be detected simultaneously on one structure. They are thus subject to the same drift, for example due to temperature processes, stress influences. This can be ensured particularly well when the structures have similar lengths in all directions. The sensitivity of the Hall element is maximized by means of current conduction orthogonal to the direction of the magnetic field. Another advantage is that the Hall sensor can be structured in all three spatial directions by means of efficient production methods.

A sensor element for measuring a magnetic field has a wafer structure, wherein the wafer structure has a semiconductor substrate, an insulating layer and a semiconductor layer. This enables an efficient fabrication method of precise structures perpendicular to the plane of the chip. The sensor element has a punch through the punch-through contact, the punch having a semiconductor substrate end face, a semiconductor layer end face and pairs of parallel side faces in the semiconductor substrate, wherein the end face and the side faces There are sections with high conductivity, and the punch has internal dopants with lower conductivity between the sections with high conductivity. During operation, the excitation current can be guided successively in different directions through the punch, and the Hall voltage can be intercepted perpendicularly thereto in a section with high conductivity. The high electrical conductivity of this section enables good measurement due to the effective collection and separation of the charge carriers forming the Hall voltage at the end faces and sides of the punch.

In plan view, the punch preferably has the shape of a polyhedron. Advantageously, the punches have similar lengths in height and width. With the aid of a rectangular cross-section, simple, cube-shaped punches can be formed with symmetrical sensitivities and drifts in three dimensions. With the octahedral cross-section, measurements are possible by means of “spin currents” in the chip plane, wherein the excitation current is fed successively into the adjacent sides and the Hall voltage is measured on the side perpendicular thereto. The same applies for higher numbers of polyhedra, wherein in multiples of four the polyhedra each have pairs of sides perpendicular to one another.

The highly conductive sections of the end faces and sides are preferably spaced apart from one another. These sections are advantageously electrically conductively connected to the bonding pads on the surface of the sensor element. Both improve the interception of carriers forming the Hall voltage.

The side sections with high conductivity advantageously have a side doping which is higher than the inner doping of the inside of the punch. The conductive section of the upper face advantageously has a doping of the face that is higher than the doping of the interior. As a result, desired different conductivities can be produced.

In one refinement of the invention, the bonding surface, which is electrically conductively connected to the highly conductive portion of the side surface, is arranged on the punch substantially above the portion with high conductivity of the side surface.

In an alternative development of the invention, the side faces are situated in the trenches, and the highly conductive sections of the side faces are each connected to a conductive layer, which faces the substrate on its opposite side via the trenches. extension on the upper side. The bonding surface, which is electrically conductively connected to the side sections with high conductivity, is arranged on the semiconductor substrate next to the punch.

The sensor element preferably has an electrically conductive contact punch passing through the feedthrough, wherein the punch and the contact punch are electrically conductively connected to one another beneath the insulating layer. The contact punch is used to electrically connect the lower side of the punch to the bonding surface on the upper side of the sensor element. As a result, all bonding surfaces are located on the upper side of the sensor element. The electrical connection between the punch and the contact punch takes place via electrically conductive sections in the semiconductor layer below the insulating layer, or via conductors on the underside of the sensor.

A magnetic field sensor with a sensor element according to the invention for the multidimensional measurement of a magnetic field has a control unit for electrically actuating the sensor element and for measuring and evaluating the Hall voltage.

Preference is given to three-dimensional magnetic field measurements, but the invention can also be designed simply for two-dimensional measurements, for example with only one pair of sides configured as described above.

A method according to the invention for producing a sensor element for measuring a magnetic field will be described, in which all method steps do not have to be carried out in this order. The method comprises the following method steps:

a) production of the wafer structure with the semiconductor substrate, the insulating layer and the semiconductor layer, the upper side of the semiconductor substrate and thus the sensor elements being located on the back side of the wafer;

b) forming a punch through the through contact, the punch having a semiconductor substrate end face, a semiconductor layer end face and a pair of parallel side faces in the semiconductor substrate, the through contact being formed on the height of the semiconductor layer end face Conductive section;

c) doping the interior of the punch with low conductivity;

d) Formation of highly conductive segments on the end faces and side faces of the semiconductor substrate.

Preferably, the punch has a substantially polygonal cross-section, and the method has the following method steps:

e) Remove the corners (Ecken) of the adjacent sides of the punch. As a result, the highly conductive sections on the sides are separated from one another.

Advantageously, in another method step, carry out:

f) Forming a bonding surface on the upper side of the semiconductor substrate, which is electrically conductively connected to the highly conductive section.

For this purpose, in the first variant, the highly conductive sections on the sides are guided as far as the upper side of the semiconductor substrate, and the bonding surface is metallized there. In a second variant, the side sections with high conductivity are guided through the side walls of the trench to the upper side of the sensor element and outside the punch.

The electrical connection of the underside of the punch is advantageously carried out by means of the bonding surface on the upper side of the sensor element through the following method steps:

g) forming conductive contact punches through the feed-through contacts;

h) Forming the punch and the electrically conductive connections contacting the punch in the semiconductor layer.

Description of drawings

Embodiments of the invention will be illustrated with the aid of the accompanying drawings, in which:

Figure 1 shows a flow chart of the method according to the invention;

Figure 2 schematically shows the fabrication of sensor elements in a wafer according to the invention;

Fig. 3 shows schematically the machining of the punch of the sensor element according to the invention;

4 schematically shows the production of a sensor element with contacts in a wafer according to the invention;

FIG. 5 schematically shows the fabrication of a sensor element with another contact in a wafer according to the invention; and

FIG. 6 shows a top view of the backside of a wafer with sensor elements according to the invention.

Detailed ways

The method according to the invention for producing a sensor element for measuring a magnetic field is shown in a flowchart 10 in FIG. 1 , wherein all method steps described below do not have to be carried out in this order. The method steps of flowchart 10 are explained with the aid of and together with FIGS. 2 to 5 .

Referring firstly to FIG. 2A , in method step a) a wafer structure 12 is produced with a semiconductor substrate 13 , an insulating layer 14 and a semiconductor layer 15 ; from the semiconductor substrate 13 . An insulating layer 14 is deposited on a semiconductor substrate 13 , which is covered with a semiconductor layer 15 . The semiconductor layer 15 is electrically insulated from the semiconductor substrate 13 by means of the insulating layer 14 . In the case of silicon technology this results, for example, in silicon-on-insulator (SOI) wafers.

In a subsequent method step, b) with reference to FIG. 2B , forming a punch 16 through 14 for a feed-through contact, the punch has a semiconductor substrate end face 17 , a semiconductor layer end face 18 and a pair of parallel, on-semiconductor substrate 13 19 in the side. The punch 16 formed by means of trench etching is contacted via vias 20 . The sides 19 are in the channels 22 , 23 . Also visible in FIG. 2B is a contact punch 24 , which is contacted through vias 25 and is located between channels 23 and 26 . The via 20 covers the semiconductor layer end face 18 with a highly conductive section.

Method step c) of doping the interior 27 of the punch 16 with low electrical conductivity can be carried out, for example, after method step b) or already beforehand by selecting a predoped wafer.

Referring now to FIG. 2C , method step d) is carried out to form sections 28 , 29 , 30 with high conductivity on the end faces 17 and side faces 19 of the semiconductor substrate. This is done by covering the stamp 16 with a more highly doped semiconductor layer or preferably by diffusing in dopants. Emboss 16 and semiconductor substrate 13 , and optionally also insulating layer 14 , are partially protected against ingress by diffusion by means of mask 32 . Subsequently, the side or end face contacts can be covered electrically conductively, for example by means of dopant diffusion.

FIG. 3 ) now correspondingly shows method step e) removal of corners 33 of mutually adjoining sides 19 , 34 of punch 16 ; as punch 16 is restructured in order to achieve electrical separation of sides 19 , 34 . As a result, the highly conductive sections on the sides are separated from one another. If the completed sensor element is subsequently driven by means of an excitation current conducted via the end faces 17 , 18 , the Hall voltages Ux 35 and Uy 36 can be measured independently of one another.

FIG. 4 illustrates a further method step f) of forming bonding pads 37 , 38 on the upper side 39 of the semiconductor substrate 13 , which are connected to the highly conductive sections 28 , 29 , 30 . In a first variant, the highly conductive sections 28 , 29 on the sides are guided as far as the upper side 39 of the semiconductor substrate 13 and the bonding surfaces 37 and 38 are metallized there. The bonding surfaces 37 , 38 can be connected via bonding wires 40 to the evaluation electronics or to another chip.

FIGS. 4 and 2B also illustrate the advantageous electrical connection of the punch underside or end face 18 to the bonding surface 41 on the upper side of the sensor element 42 by the following method steps: g) Formation of an electrically conductive contact through 14 through-contact. The punch 24 ; h) forms the punch 16 and the electrically conductive connection 43 contacting the punch 24 under the insulating layer 14 .

The punch 16 shown in FIG. 4 and the electrically conductive connection 43 of the contact punch 24 are embodied as conductors 44 on the underside of the sensor element 42 on the semiconductor layer 15 . The punch 16 and the wafer sections 45 , 46 contacting the punch 24 are electrically separated from each other by a channel 47 .

FIG. 5 shows an embodiment which has alternative designs to FIG. 4 independently of each other. Elements similar to those in Figure 4 are provided with primed reference numerals. A first alternative design involves moving the bonding face of the punch 16 outwards. In this case, the now highly conductive sections of the side surfaces 19 ′ can also alternatively be guided as metal layers 48 , 49 via the side walls of the trench 50 onto the upper side 39 ′ of the sensor element 42 ′ in order to form side surfaces 19 ′. Wall contact portion 51 . Completely filled trenches are also possible. In this case, the bonding wire is directly connected to the sidewall contact 51 of the metal layers 48 , 49 . This design, which is spaced apart from each other, makes bonding easier.

A second alternative configuration involves the electrical connection of the punch underside or end face 18 to the bonding face 41 on the top side of the sensor element 42 . The punch 16' shown in FIG. 4 and the conductive connection 53 contacting the punch 24' are implemented as doped connections 54 in the semiconductor layer 15' below the insulating layer. The contact punch is surrounded by a channel 55 .

In Fig. 6 is shown the backside of the wafer with the sensor element 42' in Fig. 5 according to the invention, the upper side of the sensor element being located on the backside of the wafer. On the wafer structure 12', a punch 16' having a metal bonding surface 38' with a rectangular cross-section is surrounded by metal sidewall contacts 51,51. Next to it, the contact punch 24' is surrounded by a trench 55 as an underside contact, which likewise has a metallic bonding surface 41 .

The function of a magnetic field sensor with a sensor element according to the invention for multidimensional magnetic field measurement is explained with reference to the coordinate axes x, y in FIG. 6 , wherein the z-axis runs upward perpendicular to the image plane. The control unit for electrically actuating the sensor element and measuring and evaluating the Hall voltage passes a predetermined excitation current successively in the x, y and z directions respectively in the direction of the positive coordinate and in the direction of the negative coordinate through the contact pairs 38' and 41 ', 51 and 52 to boot.

The excitation current lz conducted via the contact pairs 38' and 41' flows through the punch 16' perpendicularly in the z direction, the magnetic field component in the chip plane also generating a Hall voltage in the chip plane perpendicular to the magnetic field component. The Hall voltage generated by the magnetic field component Bx in the x direction is measured on the contact pair 52 in the y direction, and the Hall voltage generated by the magnetic field component By in the y direction is measured on the contact pair 51 in the x direction .

The excitation current Ix conducted via the contact pair 51 flows horizontally through the punch 16' in the x direction, and the magnetic field components in the y and z directions also generate Hall voltages in the z and y directions perpendicular to the magnetic field components. The Hall voltage generated by the magnetic field component By in the y direction is measured on the contact pair 38 ′ and 41 ′ in the z direction, and the Hall voltage generated by the magnetic field component Bz in the z direction is measured on the contact pair 52 in the y direction. direction is measured.

The same applies for the excitation current Iy conducted via the contact pair 52 . The redundancy of the multiple measurements of the same magnetic field component (in particular added in each case in both current directions) is used to continuously determine deviations and drifts.

Claims (14)

1. A sensor element (42, 42') for measuring a magnetic field, having a wafer structure (12), characterized in that the wafer structure (12) has a semiconductor substrate (13), an insulating layer (14, 14' ) and the semiconductor layer (15, 15'), and the sensor element has a punch (16, 16') for through-contact through the insulating layer (14, 14'), the punch has a semiconductor substrate end face (17), A semiconductor layer end face (18) and a pair of parallel side faces (19; 19') in a semiconductor substrate (13), wherein the end faces (17, 18) and side faces (19; 19') have a height Conductive sections (28, 29, 30), and the punch (16, 16') has a doping with low conductivity in the interior (27), wherein the side (19; 19') has a high The electrically conductive sections ( 28 , 29 ) have a side doping that is higher than the doping in the interior ( 27 ). 2. The sensor element according to claim 1, characterized in that the punch (16, 16') has the shape of a polyhedron. 3. Sensor element according to claim 1 or 2, characterized in that the punches (16, 16') have equal or approximately equal lengths in height and width. 4. The sensor element according to claim 1 or 2, characterized in that the highly conductive sections (28, 29, 30) of the semiconductor substrate end face (17) and side faces (19; 19') spaced from each other. 5. The sensor element according to claim 1 or 2, characterized in that the highly conductive section (28, 29, 30) is bonded to a bonding surface on the surface (39; 39') of the sensor element (37, 38; 38', 51) conductive connection. 6 . The sensor element as claimed in claim 1 , characterized in that the electrically conductive section ( 30 ) of the semiconductor substrate face ( 17 ) has a face doping that is higher than the doping in the interior ( 27 ). 7. The sensor element as claimed in claim 1 or 2, characterized in that the side faces (19; 19') lie in channels (22, 23) and that sections of the sides with high conductivity ( 28 , 29 ) are each connected to a conductive layer ( 48 , 49 ), which extends on its opposite side towards the upper side ( 39 ′) of the substrate via a trench ( 50 ). 8 . The sensor element as claimed in claim 1 , characterized in that the sensor element ( 42 ; 42 ′) has an electrically conductive contact stud ( 24 ; 24 ′) which makes contact through the insulating layer ( 14 ; 14 ′). ), wherein the punch (16, 16') and the contact punch (24, 24') are electrically connected to each other under the insulating layer (14, 14'). 9. A magnetic field sensor with a control unit for electrically actuating sensor elements for multidimensionally measuring magnetic fields and measuring and evaluating Hall voltages, characterized in that it comprises a sensor according to one of the preceding claims element. 10. A method for producing a sensor element for measuring a magnetic field according to one of claims 1 to 8, wherein all method steps do not have to be carried out in this order, the method is based on the following method steps: a) fabrication of the wafer structure (12) with the semiconductor substrate (13), the insulating layer (14; 14') and the semiconductor layer (15, 15'), It is characterized in that, comprising further method steps: b) A punch (16, 16') forming a punch-through contact through the insulating layer (14; 14'), the punch has a semiconductor substrate end face (17), a semiconductor layer end face (18) and a pair of parallel, side (19; 19') in the semiconductor substrate (13); c) doping the interior (27) of the punch (16, 16') with low electrical conductivity; d) forming highly conductive segments (28, 29, 30) on the end faces (17) and side faces (19; 19') of the semiconductor substrate. 11. The method for producing a sensor element according to claim 10, characterized in that the punch (16, 16') has a polygonal cross-section and the method has the following method steps: e) The corners (33) of the adjacent sides (19; 19') of the punch (16, 16') are removed. 12. The method for producing a sensor element according to claim 10 or 11, comprising the further method steps of: f) Forming bonding surfaces (37, 38; 38', 51) on the upper side of the semiconductor substrate, which bonding surfaces are connected to the highly conductive sections (28, 29, 30). 13. The method for producing a sensor element according to claim 12, characterized in that the bonding surface (51) connected to the highly conductive section of the side face (19') is formed on the punch (16') outside. 14. The method for manufacturing a sensor element according to claim 10 or 11, characterized in that it comprises the further method steps: g) forming conductive contact punches (24, 24') for punch-through contacts through the insulating layer (14, 14'); h) Forming the conductive connection of the punch (16, 16') and contacting the punch (24, 24') under the insulating layer (14, 14').