DE102023122673A1 - Method for producing a plurality of sensor chips for determining a pressure of a medium - Google Patents

Abstract

The invention relates to a method for producing a plurality of sensor chips (1) for determining a pressure (p1) of a medium (2), wherein each sensor chip (1) has a sensor structure (3), wherein the method comprises at least the following method steps:
- providing an electrically conductive wafer (4) with a plurality of sensor structures (3) applied thereto, a carrier plate (5) and an insulation substrate (6),
- forming a wafer composite (7) from the wafer (4), the carrier plate (5) and the insulation substrate (6), wherein the carrier plate (5) is arranged between the wafer (4) and the insulation substrate (6) and is mechanically connected to both the wafer (4) and the insulation substrate (6),
- introducing at least one groove (8) into at least the insulation substrate (6), wherein the at least one groove (8) is arranged perpendicular to the wafer composite (7), wherein at least one section of the at least one groove (8) is arranged below a sensor structure (3),
- generating the plurality of sensor chips (1) by dividing the wafer assembly (7) along vertical axes, so that each sensor chip (1) has a sensor structure (3).

Description

The invention relates to a method for producing a plurality of sensor chips for determining a pressure of a medium, wherein each sensor chip has a sensor structure.

Absolute pressure, differential pressure and relative pressure sensors are known in pressure measurement technology. Absolute pressure sensors determine the prevailing pressure of a process medium absolutely, i.e. in relation to vacuum, while differential pressure sensors determine the difference between two different pressures of the process medium or media. With relative pressure sensors, the pressure of the process medium to be measured is determined in relation to a reference pressure, with the atmospheric pressure prevailing in the vicinity of the relative pressure sensor serving as the reference pressure.

Pressure sensors have a pressure-sensitive measuring element, the so-called pressure sensor, on the first and second surfaces of which a pressure is applied. In the case of relative or absolute pressure sensors, the pressure of the process medium to be determined acts on the first surface of the pressure sensor, while an absolute or reference pressure acts on the second surface. In the case of differential pressure sensors, a first pressure and a second pressure of a process medium are applied to both surfaces. The measuring element bends depending on the relative pressure present, which is formed from the difference between the pressures on the two surfaces. This bending is converted by an electronic unit into an electrical signal dependent on the relative pressure, which is then available for further processing or evaluation. A distinction is made between capacitive and piezoresistive pressure sensors, among others. A large number of such pressure sensors are manufactured and sold by companies in the Endress+Hauser Group.

Common pressure sensors, for example, have a silicon chip. For thermomechanical decoupling, this is usually bonded to a silicon substrate as a carrier plate. Due to the electrical conductivity of the silicon substrate, an electrically insulating substrate must also be connected to the silicon substrate. For example, the silicon substrate is glued or soldered to a ceramic base. The base is then glued or soldered to a current feedthrough. To produce a single sensor chip, a bonding step and at least one gluing or soldering step must be carried out.

The object of the present invention is therefore to provide a method which simplifies the production of a sensor chip.

• - Bereitstellen eines elektrisch leitfähigen Wafers mit einer Vielzahl von darauf aufgebrachten Sensorstrukturen, einer Trägerplatte und eines Isolationssubstrats,
• - Bilden eines Waferverbunds aus dem Wafer, der Trägerplatte und dem Isolationssubstrat, wobei die Trägerplatte zwischen dem Wafer und dem Isolationssubstrat angeordnet und sowohl mit dem Wafer als auch mit dem Isolationssubstrat mechanisch verbunden ist,
• - Einbringen mindestens einer Nut in zumindest das Isolationssubstrat, wobei die mindestens eine Nut senkrecht zum Waferverbund angeordnet ist, wobei mindestens ein Abschnitt der mindestens einen Nut jeweils unterhalb einer Sensorstruktur angeordnet ist,
• - Generieren der Vielzahl von Sensorchips durch Teilen des Waferverbunds entlang senkrechter Achsen, so dass jeder Sensorchip jeweils eine Sensorstruktur aufweist.

According to the invention, the object is achieved by a method for producing a plurality of sensor chips for determining a pressure of a medium, wherein each sensor chip has a sensor structure, wherein the method comprises at least the following method steps:

• - Providing an electrically conductive wafer with a plurality of sensor structures applied thereon, a carrier plate and an insulation substrate,
• - forming a wafer composite from the wafer, the carrier plate and the insulation substrate, wherein the carrier plate is arranged between the wafer and the insulation substrate and is mechanically connected to both the wafer and the insulation substrate,
• - introducing at least one groove into at least the insulation substrate, wherein the at least one groove is arranged perpendicular to the wafer composite, wherein at least one section of the at least one groove is arranged below a sensor structure,
• - Generating the plurality of sensor chips by dividing the wafer assembly along vertical axes so that each sensor chip has a sensor structure.

In the method according to the invention, a large number of sensor chips are produced in a simple manner by first forming a wafer composite, which is then divided. As the mechanical connection of the carrier plate to the wafer and the insulation substrate takes place within the wafer composite, the many individual soldering or gluing processes between the carrier plate and the insulation substrate are eliminated. In particular, the carrier plate is mechanically connected to the wafer and the insulation substrate over as much of its surface as possible. In addition, the method according to the invention enables better reproducibility in the production of the sensor chips.

After dividing the wafer assembly, each sensor chip comprises a stack of a sensor structure, a section of the carrier plate and a section of the insulation substrate, as well as at least one section of the at least one groove. The sensor structure is designed in particular to bend depending on a pressure difference. The pressure difference is applied in particular to the sensor structure. For example, the sensor structure has a measuring membrane, which in particular has a first surface and a second surface opposite the first surface. The The first surface and the second surface can each be subjected to the pressure of the medium and another pressure, e.g. an ambient pressure, an absolute pressure or another pressure of the medium.

The term “perpendicular” to the wafer composite or “perpendicular axes” refers to planes or axes that are arranged perpendicularly and thus not parallel to the layers of the wafer composite.

The at least one groove serves to decouple thermomechanical stresses of the subsequently generated sensor chip and is introduced in such a way that at least one section of the at least one groove is arranged within the wafer composite below a sensor structure, i.e. in a respective section of at least the insulation substrate, which is arranged vertically below the sensor structure.

In one embodiment, to form the wafer composite, the wafer is first mechanically connected to the carrier plate and then the carrier plate is mechanically connected to the insulation substrate.

In an alternative embodiment, to form the wafer composite, the carrier plate is first mechanically connected to the insulation substrate and then the carrier plate is mechanically connected to the wafer.

Preferably, the wafer is connected to the carrier plate by means of a bond connection. In particular, the plurality of sensor structures are bonded to the carrier plate.

Particularly preferably, the wafer, in particular the plurality of sensor structures, is connected to the carrier plate by means of a silicon direct bond connection. This is particularly the case when both the wafer and the carrier plate are made of silicon.

In one embodiment, the carrier plate is connected to the insulation substrate by means of anodic bonding. The anodic bonding leads to a chemical connection between the carrier plate and the insulation substrate under the influence of heat and the application of a voltage. Through anodic bonding, carrier plates and insulation substrates with a large surface area can be mechanically connected to one another, in particular over the entire surface.

In particular, silicon is used as the material for the wafer and/or the carrier plate. Glass, e.g. borosilicate glass, is used as the material for the insulation substrate.

In a further development, the at least one groove is introduced in such a way that the at least one groove extends over the entire width or depth of the insulation substrate. The width and depth of the insulation substrate are those dimensions of the insulation substrate which are arranged parallel to the wafer composite. Advantageously, a few grooves with a large length are introduced into the insulation substrate instead of many small grooves.

One embodiment provides that the at least one groove is introduced in such a way that a depth of the at least one groove extends over the entire height of the insulation substrate up to the carrier plate. The height of the insulation substrate refers to the extent of the insulation substrate perpendicular to the wafer composite. The depth of the at least one groove over the entire height of the insulation substrate achieves good decoupling of thermomechanical stresses of the sensor chips.

In a further embodiment, the at least one groove is introduced in such a way that the depth of the at least one groove extends through the insulation substrate into the carrier plate. The at least one groove is partially arranged in the carrier plate. This further improves the decoupling of thermomechanical stresses of the subsequently generated sensor chip.

In a further development, four grooves are each introduced below a sensor structure so that the four grooves form a grid on the underside of the insulation substrate. The underside of the insulation substrate is the surface of the insulation substrate that faces away from the carrier plate.

In one embodiment, the at least one groove is created using a saw. The saw has a saw blade for this purpose.

The wafer composite is advantageously divided by means of a wafer saw or a cutting grinder. The process of dividing the wafer composite is achieved by means of cutting grinding. In particular, the wafer saw or the cutting grinder has a saw blade for dividing the wafer composite.

• - Bereitstellen eines elektrisch leitfähigen Wafers mit einer Vielzahl von darauf aufgebrachten Sensorstrukturen, einer Trägerplatte und eines Isolationssubstrats, wobei die Trägerplatte eine Vielzahl von ersten Bohrungen und das Isolationssubstrat eine Vielzahl von zweiten Bohrungen aufweisen,
• - Ausrichten des Wafers, der Trägerplatte und des Isolationssubstrats derart, dass die Trägerplatte zwischen dem Wafer und dem Isolationssubstrat angeordnet ist und die ersten Bohrungen, die zweiten Bohrungen und die Sensorstrukturen übereinander liegen.

In one embodiment, the method comprises the following method step:

• - Providing an electrically conductive wafer with a plurality of sensor structures applied thereto, a carrier plate and an insulation substrate, wherein the carrier plate has a plurality of first holes and the insulation substrate has a plurality of second holes,
• - Aligning the wafer, the carrier plate and the insulation substrate such that the carrier plate is arranged between the wafer and the insulation substrate and the first holes, the second holes and the sensor structures lie one above the other.

As a rule, a first surface of the sensor structure is subjected to the (first) pressure of the medium. The hole in the pressure measuring device is then used to apply a further pressure to a second surface of the sensor structure. In the case of a relative pressure measuring device, the hole is designed to apply an ambient pressure to the second surface. In the case of a differential pressure measuring device, the hole is designed to apply a second pressure of the medium to the second surface. For example, the hole is filled with a pressure transmitter fluid. The wafer, carrier plate and insulation substrate can be aligned using a hole grid, for example. The first holes, the second holes and the sensor structures lie on top of one another after alignment, i.e. they overlap at least partially, in particular completely. The wafer, carrier plate and insulation substrate are aligned in particular before the wafer composite is formed.

• - Nach Generieren der Sensorchips, Verbinden der Sensorchips mit einer Stromdurchführung.

In a further embodiment, the method comprises the following step:

• - After generating the sensor chips, connect the sensor chips with a power feedthrough.

The sensor chips are connected to the power feedthrough in particular by means of gluing, soldering or glass soldering. The power feedthrough in the pressure measuring device is subsequently used, among other things, to electrically contact the sensor structure.

• 1: eine schematische Darstellung von Wafer, Trägerplatte und Isolationssubstrat.
• 2: eine schematische Darstellung des Waferverbunds nach seiner Bildung.
• 3: eine schematische Darstellung des Waferverbunds vor der Generierung der Sensorchips.
• 4: eine schematische Darstellung einer Untenansicht des Isolationssubstrats.
• 5a: eine schematische Darstellung einer Seitenansicht eines Sensorchips.
• 5b: eine schematische Darstellung einer perspektivischen Ansicht eines Sensorchips.
• 5c: eine schematische Darstellung eines Längsschnitts eines Sensorchips.
• 5d: eine schematische Darstellung einer Unteransicht eines Sensorchips.
• 6a, 6b: zwei weitere Ausgestaltungen eines Sensorchips.
• 7: eine schematische Seitenansicht eines Sensorchips, welcher auf eine Stromdurchführung aufgebracht ist.
• 8: eine schematische Aufsicht auf einen Sensorchip, welcher auf eine Stromdurchführung aufgebracht ist.

In the following, the present invention will be explained with reference to the figures 1-8 are explained in more detail. They show:

• 1 : a schematic representation of wafer, carrier plate and insulation substrate.
• 2 : a schematic representation of the wafer composite after its formation.
• 3 : a schematic representation of the wafer assembly before the generation of the sensor chips.
• 4 : a schematic representation of a bottom view of the insulation substrate.
• 5a : a schematic representation of a side view of a sensor chip.
• 5b : a schematic representation of a perspective view of a sensor chip.
• 5c : a schematic representation of a longitudinal section of a sensor chip.
• 5d : a schematic representation of a bottom view of a sensor chip.
• 6a , 6b : two further designs of a sensor chip.
• 7 : a schematic side view of a sensor chip applied to a current feedthrough.
• 8 : a schematic plan view of a sensor chip which is applied to a current feedthrough.

1 shows the first method step, namely the provision of the electrically conductive wafer 4, the carrier plate 5 and the insulation substrate 6. Preferably, the wafer 4, the carrier plate 5 and the insulation substrate 6 have surfaces of essentially the same size. Optionally, the carrier plate 5 and the insulation substrate 6 can have a plurality of first holes 10a and a plurality of second holes 10b. The first holes 10a and the second holes 10b are particularly relevant when using the subsequently generated sensor chips 1 in relative and differential pressure measuring devices. In the case that first holes 10a and second holes 10b are present, the wafer 4, the carrier plate 5 and the insulation substrate 6 are aligned with each other so that the carrier plate 5 is arranged between the wafer 4 and the insulation substrate 6 and the first holes 10a, the second holes 10b and the sensor structures 3 lie one above the other (see. 2 ). The first holes 10a and the second holes 10b can have the same or a different diameter. In particular, the first holes 10a and the second holes 10b are designed to transmit a second or further pressure to the sensor structure 3, in particular to the measuring membrane 17. The alignment can be carried out using a hole grid. The alignment takes place in particular before the formation of the wafer composite 7.

Subsequently, a wafer composite 7 is formed from the wafer 4, the carrier plate 5 and the insulation substrate 6 (see 2 ). The carrier plate 5 is arranged centrally. The carrier plate 5 can first be mechanically connected to the wafer 4 and then to the insulation substrate 6. Alternatively, the insulation substrate 6 can first be mechanically connected to the carrier plate 5 and then the carrier plate 5 can be mechanically connected to the wafer 4. The wafer has a plurality of sensor structures 3, which are shown in the figures 5b and 5c will be shown in more detail.

In 2 a saw 9 is also shown, by means of which at least one groove 8 can be introduced into at least the insulation substrate 6. The introduction of the at least one groove 8 can take place before or after the formation of the wafer composite 7. The introduction of the at least one groove 8 can take place in particular before the alignment of the wafer 4, the carrier plate 5 and the insulation substrate 6. However, the at least one groove 8 is particularly preferably introduced after the formation of the wafer composite 7. As a rule, the insulation substrate 6 is designed as a flat disk with a small disk height, so that the insulation substrate 6 can quickly break when the at least one groove 8 is introduced.

The at least one groove 8 is introduced in such a way that it is arranged perpendicular to the wafer composite 7 (which may be formed later). This also makes it possible, unlike in 2 shown to first provide the insulation substrate 6 with the at least one groove 8 and then to connect this to the carrier plate 5. However, if the at least one groove 8 is to protrude beyond the insulation substrate 6 into the carrier plate 5 or extend over the entire height H of the insulation substrate 6, the at least one groove 8 is preferably only introduced after the wafer composite 7 has been formed.

The at least one groove 8 serves as a decoupling structure, which is why at least one section of the at least one groove 8 is assigned to each sensor structure 3. For this purpose, the at least one groove 8 is introduced in such a way that at least one section of the at least one groove 8 is arranged below a sensor structure 3. This arrangement is, for example, in 3 and 5c The grooves 8 can be made in such a way that they extend over the entire width B or depth T of the insulation substrate 6. In this way, long grooves 8 are made in just a few steps, as shown in 4 shown.

After forming the wafer composite 7 and after the at least one groove 8 has been introduced, the wafer composite 7 is divided along vertical axes so that the plurality of sensor chips 1 is generated. The vertical axes are in 3 shown as dashed lines. The wafer assembly 7 can be divided using a wafer saw 13. In the example shown, the grooves 8 extend within the insulation substrate 6 without touching the carrier plate 5.

The wafer 4 including the sensor structures 3 applied thereto and/or the carrier plate 5 can be made of silicon. The wafer 4, in particular the sensor structures 3, are preferably connected to the carrier plate 5 by means of a bond connection, in particular a silicon direct bond connection (silicon direct bonding). The insulation substrate 6 can have glass as its material. The insulation substrate 6 is advantageously connected to the carrier plate 5 by means of anodic bonding.

The characters 5a -d show a sensor chip 1 obtained by dividing the wafer composite 7, which has a stack of a sensor structure 3, a section of the carrier plate 5 and a section of the insulation substrate 6. In addition, the sensor chip has grooves 8. In 5d It is shown by way of example that four grooves 8 were each introduced below a sensor structure 3, so that the four grooves 8 form a grid on an underside 12 of the insulation substrate 6.

The sensor structures 3 each have, for example, a measuring membrane 17 with a first surface 18 and a second surface 19, which can be subjected to a (first) pressure p1 of the medium 2 and a second pressure p2. The sensor structures 3 are particularly designed to bend depending on the relative pressure Δp formed by the first pressure p1 and the second pressure p2. The pressure-dependent bending of the measuring membrane 17 is converted by means of a pressure transducer into an electrical signal, which is guided by means of a current feedthrough 11 from the sensor chip 1 to an evaluation electronics.

For the introduction of the at least one groove 8, further embodiments are possible, which are shown in the figures 6a -b. So the at least one groove 8 in 6a such that the depth of the at least one groove 8 extends over the entire height H of the insulation substrate 6. In order to further improve the decoupling of thermomechanical stresses, it is possible, as in 6b shown to introduce the at least one groove 8 in such a way that the at least one groove 8 extends through the insulation substrate 6 into the carrier plate 5. The at least one groove 8 is then partially arranged in the carrier plate 5.

After generating the sensor chips 1, a current feedthrough 11 can be connected to the sensor chip 1, in particular the insulation substrate 6, as shown in 7 For example, the sensor chip 1 is applied to the current feedthrough 11 by means of an adhesive 14. The current feedthrough has optional pins 15. The pins 15 can be connected to the sensor structure 3 by means of bonding wires 16, as shown in 8 For example, the sensor structure 3 has one or more contact surfaces 20, which are designed in particular for the connection to the pins 15.

list of reference symbols

1

sensor chip

2

medium

3

sensor structure

4

wafer

5

carrier plate

6

insulation substrate

7

wafer assembly

8

grooves

9

saw

10a

first drilling

10b

second hole

11

power feedthrough

12

underside of the insulation substrate

13

wafer saw

14

bonding

15

pin

16

bonding wire

17

measuring membrane

18

first area

19

second surface

20

contact surface

B

width of the insulation substrate

T

depth of the insulation substrate

H

height of the insulation substrate

Claims (15)

Method for producing a plurality of sensor chips (1) for determining a pressure (p1) of a medium (2), each sensor chip (1) having a sensor structure (3), the method comprising at least the following method steps: - providing an electrically conductive wafer (4) with a plurality of sensor structures (3) applied thereto, a carrier plate (5) and an insulation substrate (6), - forming a wafer composite (7) from the wafer (4), the carrier plate (5) and the insulation substrate (6), the carrier plate (5) being arranged between the wafer (4) and the insulation substrate (6) and being mechanically connected to both the wafer (4) and the insulation substrate (6), - introducing at least one groove (8) into at least the insulation substrate (6), the at least one groove (8) being arranged perpendicular to the wafer composite (7), at least one section of the at least one groove (8) being below a sensor structure (3) is arranged, - generating the plurality of sensor chips (1) by dividing the wafer composite (7) along vertical axes, so that each sensor chip (1) has a sensor structure (3). procedure according to claim 1 , wherein for forming the wafer composite (7) first the wafer (4) is mechanically connected to the carrier plate (5) and then the carrier plate (5) is mechanically connected to the insulation substrate (6). procedure according to claim 1 , wherein for forming the wafer composite (7) first the carrier plate (5) is mechanically connected to the insulation substrate (6) and then the carrier plate (5) is mechanically connected to the wafer (4). Method according to one of the preceding claims, wherein the wafer (4) is connected to the carrier plate (5) by means of a bond connection. Method according to one of the preceding claims, wherein the wafer (4) is connected to the carrier plate (5) by means of a silicon direct bond. Method according to one of the preceding claims, wherein the carrier plate (5) is connected to the insulation substrate (6) by means of anodic bonding. Method according to one of the preceding claims, wherein silicon is used as material for the wafer (4) and/or the carrier plate (5). Method according to one of the preceding claims, wherein the at least one groove (8) is introduced such that the at least one groove (8) extends over the entire width (B) or depth (T) of the insulation substrate (6). Method according to one of the preceding claims, wherein the at least one groove (8) is introduced such that the depth of the at least one groove (8) extends over the entire height (H) of the insulation substrate (6) up to the carrier plate (5). Method according to one of the preceding claims, wherein the at least one groove (8) is introduced such that the depth of the at least one groove (8) extends through the insulation substrate (6) into the carrier plate (5). Method according to one of the preceding claims, wherein four grooves (8) are each introduced below a sensor structure (3), so that the four grooves (8) form a grid on an underside (12) of the insulation substrate (6). Method according to one of the preceding claims, wherein the at least one groove (8) is introduced by means of a saw (9). Method according to one of the preceding claims, wherein the division of the wafer composite (7) is carried out by means of a wafer saw (13) or a cutting grinder. Method according to one of the preceding claims, wherein the method comprises the following method step: - providing an electrically conductive wafer (4) with a plurality of sensor structures (3) applied thereto, a carrier plate (5) and an insulating substrate (6), wherein the carrier plate (5) has a plurality of first holes (10a) and the insulating substrate (6) has a plurality of second holes (10b), - aligning the wafer (4), the carrier plate (5) and the insulating substrate (6) such that the carrier plate (5) is arranged between the wafer (4) and the insulating substrate (6) and the first holes (10a), the second holes (10b) and the sensor structures (3) lie one above the other. Method according to one of the preceding claims, wherein the method comprises the following method step: - After generating the sensor chips (1), connecting the sensor chips (1) to a current feedthrough (11).

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