WO2017102160A1

WO2017102160A1 - Production method for a micromechanical sensor device and corresponding micromechanical sensor device

Info

Publication number: WO2017102160A1
Application number: PCT/EP2016/076105
Authority: WO
Inventors: David Gross; Fabian Utermoehlen
Original assignee: Robert Bosch Gmbh
Priority date: 2015-12-15
Filing date: 2016-10-28
Publication date: 2017-06-22
Also published as: DE102015225184A1

Abstract

The invention relates to a production method for a micromechanical sensor device and a corresponding micromechanical sensor device. The method comprises the following steps: providing a wafer with a first electrode and a second electrode; applying and structuring a first photoresist onto the front side, wherein the first electrode is completely covered by the first photoresist and at least some sections of the second electrode are free of the first photoresist; applying and structuring a second photoresist onto the front side, wherein the first photoresist is completely covered by the second photoresist and a first recess is formed in the second photoresist to the second electrode; depositing an electrically conductive material into the first recess and on a side of the second photoresist which faces away from the front side; structuring the electrically conductive material, wherein a region which overlaps at least in some regions with the first photoresist is formed in the electrically conductive material, and removing the second photoresist from the region which overlaps at least in some regions, wherein a second recess is formed and the first photoresist is removed by means of the second recess.

Description

Description title

Manufacturing method for a micromechanical sensor device and corresponding micromechanical sensor device

The present invention relates to a manufacturing method for a

Micromechanical sensor device and a corresponding

micromechanical sensor device.

State of the art

Capacitive pressure sensors with hermetically sealed caverns are based on sacrificial layer etching of porous silicon. For producing these capacitive pressure sensors is a complex, complex and

costly manufacturing process used. Based on this

Manufacturing method using porous silicon, these pressure sensors can not be integrated by a back-end CMOS integration at the wafer level or substrate level. The capacitive pressure sensors and the associated electronics are thus manufactured on separate substrates and then connected to one another by means of a wafer bonding process. As a result, complex Waferdurchkontakte be required, with a corresponding single-wafer process or the separation of the wafer made tedious and costly.

EP 0 515 416 B1 describes a method for producing a

integrable, capacitive pressure sensor.

Disclosure of the invention

The present invention provides a manufacturing method for a

Micromechanical sensor device according to claim 1 and a corresponding micromechanical sensor device according to claim 8. Preferred developments are the subject of the respective subclaims.

Advantages of the invention

The idea underlying the present invention is to provide a cost-effective and simple method for producing the

micromechanical sensor device and a corresponding

To provide micromechanical sensor device, in particular the second photoresist is used as a functional and carrier layer or acts.

Thus, the corresponding micromechanical sensor device

In particular, very cost-effective in the CMOS wafer (Complementary Metal-Oxide-Semiconductor, complementary metal-oxide-semiconductor) are integrated at wafer level, with a read-out by means of the described here

micromechanical sensor device can be carried out in particular capacitive.

According to one aspect of the present invention, in step A of the

Manufacturing method of the wafer provided, wherein at least in certain areas on the front side of the wafer at a distance having a first electrode and a second electrode are arranged. Advantageously, the wafer may comprise evaluation electronics (CMOS). The first electrode and the second electrode are flush with the front of the wafer. In other words, the first electrode and the second electrode are free of a material of the wafer.

In step B, the first photoresist is applied to the front side of the wafer and patterned. In this case, in particular only the first electrode is completely covered by the first photoresist and the second electrode is at least partially freed from the first photoresist. In particular, the second electrode can be completely free from the first photoresist by structuring the first photoresist.

In a subsequent step C, the second photoresist is applied to the front side and patterned. In this case, the first photoresist is covered by the second photoresist and, by structuring, a first recess is formed in the first photoresist to form the second electrode. That means that the first recess exposes the second electrode at least partially, so that the second electrode is accessible via the first recess.

In step D, an electrically conductive material is deposited in the first recess and on the side facing away from the front side of the second photoresist.

The electrically conductive material deposited on the side of the second photoresist facing away from the front side can in particular completely cover the opposite side of the second photoresist. The electrically conductive material of the first recess connects the second electrode to the electrically conductive material deposited on the side of the second photoresist facing away from the front side.

In step E, the electrically conductive material is patterned, wherein in the electrically conductive material with the first photoresist at least

partially overlapping area is formed. The one with the first

Photoresist at least partially overlapping area can thus be free of the electrically conductive material.

In step F, the second photoresist is removed in the at least partially overlapping region. Here, the second recess is formed and removed by means of the second recess of the first photoresist. In other words, the first electrode is completely exposed by means of the second recess. In this case, a cavern is formed in a region in which the first photoresist was located. The cavern has at least partially a

Geometry like the first photoresist patterned in step B on the first

Electrode on.

According to a preferred embodiment, the second recess is closed by a high-viscosity paint. Thus, in a simple manner, due to the capacitive structures formed here, a pressure can be measured which can be exerted on the micromechanical sensor device. The highly viscous lacquer is applied in particular by a spraying process and can in particular subsequently be structured such that regions of the electrically conductive material are largely free of the highly viscous lacquer and only the second recess is closed by the highly viscous lacquer. According to a further preferred refinement, an evaluation circuit is integrated in the wafer. Thus, a micromechanical sensor device with evaluation circuit at wafer level can be provided in a simple manner. In other words, to a wafer bonding method for

Arranging an evaluation circuit can be dispensed with. This makes it easy to implement a backend CMOS integration. Integration at the wafer level of the evaluation circuit-for example, CMOS-by back-end CMOS integration is possible, in particular, because in the manufacturing method described here, no high process temperatures are used which can damage the evaluation circuit.

According to a further preferred development, the first photoresist is developed positively. In particular, the first photoresist is easy to put into one

Transform sacrificial layer. By the positive development of the first

Photoresist this can be easily removed by conventional paint etchant, such as DMSO (dimethyl sulfoxide) or acetone.

According to a further preferred development, the second photoresist is developed negatively. Thus, the second photoresist can be stabilized in a simple manner against conventional paint etchants. The second photoresist thus remains largely unaffected when using conventional paint etchants.

According to a further preferred development, an SU-8 is used for the second photoresist. This material is preferably suitable for use of the method described here. In particular, SU-8 is particularly resistant to conventional paint etchants. Furthermore, structures with high edge steepness can be produced in SU-8 materials. The photoresists described here can in particular be spin-coated or sprayed on. A

Structuring can be carried out in particular by means of photolithography. In particular, after the post-exposure bake, SU-8 is insensitive to most conventional paint etchants, so that, accordingly, free-standing structures of the first photoresist can be easily removed.

According to a further preferred refinement, the second photoresist is crosslinked by an annealing step before the first electrode is exposed. So In addition, the second photoresist can additionally be stabilized against etching attacks by conventional paint etchants before the first photoresist is removed.

According to a further preferred development, the second comprises

Recess a cavern and the cavern is at least partially parallel to the front of the CMOS wafer and spaced the first electrode to the second photoresist.

By the method described here, a corresponding

micromechanical sensor device are produced. The for the

Manufacturing characteristics disclosed also apply to the

Micromechanical sensor device and vice versa.

Brief description of the drawings

Further features and advantages of the present invention will be explained below with reference to embodiments with reference to the figures.

Show it:

1a-1e are schematic vertical cross-sectional views for explaining a manufacturing method for a micromechanical sensor device according to a first embodiment of the present invention; and

Fig. 2 is a schematic vertical cross-sectional view of

Explain a micromechanical sensor device according to a second embodiment of the present invention.

Embodiments of the invention

In the figures, like reference numerals designate the same or functionally identical elements. 1a-1j are schematic vertical cross-sectional views for explaining a manufacturing method of a micromechanical sensor device according to a first embodiment of the present invention.

In Fig. La, reference numeral 1 denotes a wafer having a front side VI. On the front side VI, a distance 2 comprising a first electrode El and a second electrode E2 are arranged at least in regions relative to one another.

In Fig. Lb, a first photoresist 10 is applied to the front side VI of the wafer 1. Here, the first electrode El and the second electrode E2 is completely covered by the first photoresist 10.

In Fig. Lc, the first photoresist 10 is patterned. In this case, the first electrode El remains completely covered by the first photoresist 10 and the second electrode E 2 is freed from the first photoresist 10.

In Fig. Ld, a second photoresist 20 is applied to the front side VI.

Here, the first photoresist 10 and the front side VI of the wafer 1 are completely covered by the second photoresist 20.

In FIG. 1e, the second photoresist 20 is patterned from a side facing away from the front side VI such that a first photoresist 20 is formed in the second photoresist 20

Recess AI is formed to the second electrode E2. As shown in Fig. Le, by forming the first recess AI, the second

E2 electrode at least partially exposed.

In Fig. Lf an electrically conductive material 30 is deposited in the first recess AI, wherein on a side facing away from the front VI 12 of the second photoresist 20 also the electrically conductive material 30 is deposited. In particular, the electrically conductive material 30 homogeneously covers the opposite side 12 of the second photoresist 20. As shown in FIG. 1 f, the electrically conductive material 30 connects the second electrode E 2 to the electrically conductive material 30 formed on the opposite side 12.

In Fig. Lg, the electrically conductive material 30 is at least partially structured. Here, in the electrically conductive material 30 with a first photoresist 10 formed at least partially overlapping area Bl.

In Fig. Lh the second photoresist 20 is removed from the at least partially overlapping region Bl. In this case, a second recess A2 is formed, wherein at least one side surface Sl of the second recess A2 comes into contact with the first photoresist 10. That is, the first photoresist 10 is accessible via the second recess A2.

In Fig. Ii, the first photoresist 10 is removed by means of the second recess A2. In this case, traces of a chemical erosion CA1 are formed at least partially on side surfaces S1 of the second recess A2 of the second photoresist 20. As shown in Fig. Ii, a cavity Kl is formed by the removal of the first photoresist 10 via the second recess A2.

In Fig. Lj, the second recess A2 is closed by a high-viscosity paint 40. With the micromechanical sensor device shown in FIG. 1j, by forming capacitive structures, a pressure which is exerted in particular on the electrically conductive material can be measured.

FIG. 2 is a schematic vertical cross-sectional view for explaining a micromechanical sensor device according to a second embodiment of the present invention. FIG.

In Fig. 2, reference numerals 100 'and 100 designate a micromechanical sensor device. The sensor device shown in FIG. 2 is based on the micromechanical sensor devices shown in FIGS. 1i and 1j, with the difference that these sensor devices 100; 100 'by means of a CMOS wafer 1', 1, Cl are interconnected or interconnected. If the micromechanical sensor device 100 'does not have a high-viscosity lacquer 40 in the second recess A2 and is thus not closed, in particular a temperature can be determined (see right micromechanical sensor device in FIG. 2). If, in contrast, the second recess A2 is closed by a high-viscosity paint 40, a pressure p can be detected by means of this micromechanical sensor device 100. So the highly viscous lacquer 40 promotes homogeneous bending, in particular of the electrically conductive material 30.

The micromechanical sensor device 100; 100 'comprises the CMOS wafer 1', Cl with the front side VI. The front side VI comprises the first electrode El and the second electrode E2. The first electrode E1 and the second electrode E2 are flush with the front side VI of the wafer 1. Furthermore, the micromechanical sensor device 100 comprises; 100 ', the first recess AI, wherein by means of the first recess AI, an electrical connection between the second electrode E2 and the electrically conductive material 30 can be formed. Furthermore, the micromechanical sensor device 100 comprises; 100 ', the second recess A2, wherein by means of the second recess A2, the first electrode El is freely accessible. Here, the first electrode is El and the second

Electrode E2 connected by means of the electrically conductive material 30 such that a capacitive change is measurable, wherein between the first electrode El and the second electrode E2 at least partially, the second photoresist 20 is formed. The second photoresist 20 has at least partially on side surfaces Sl of the second recess A2 traces of chemical erosion CA1.

As shown in FIG. 2, the second recess A2 comprises a cavern K1 and the cavern K1 extends at least in regions parallel to the front side VI of the CMOS wafer 1 and spaces the first electrode E1 from the second photoresist 20.

In particular, a pressure of about 1000 millibars can be measured with the micromechanical sensor device described here. This pressure range is particularly interesting for customer applications.

Although the present invention has been described in terms of preferred embodiments, it is not limited thereto. In particular, the materials and topologies mentioned are only examples and not limited to the illustrated examples.

Claims

claims

1. A manufacturing method for a micromechanical sensor device (100) with the steps:

A) providing a wafer (1), wherein a distance (2) having a first electrode (El) and a second electrode (E2) are arranged at least partially to one another at a front side (VI);

B) applying and structuring a first photoresist (10) on the

Front side (Vl), wherein the first electrode (El) is completely covered by the first photoresist (10) and the second electrode (E2) is at least partially freed from the first photoresist (10);

C) applying and patterning a second photoresist (20) on the front side (VI), wherein the first photoresist (10) is completely covered by the second photoresist (20) and in the second photoresist (20) to a first recess (AI) the second electrode (E2) is formed;

D) depositing an electrically conductive material (30) in the first

Recess (AI) and on a side facing away from the front side (VI) (12) of the second photoresist (20);

E) structuring the electrically conductive material (30), wherein in the electrically conductive material (30) with the first photoresist (10) at least

partially overlapping area (Bl) is formed, and

F) removing the second photoresist (20) from the at least partially overlapping region (Bl), wherein a second recess (A2) is formed and by means of the second recess (A2) of the first photoresist (10) is removed.

2. A manufacturing method according to claim 1, wherein the second recess (A2) is closed by a high-viscosity paint (40).

3. A manufacturing method according to claim 1, wherein in the wafer (1) a

Evaluation circuit (Cl) is integrated.

4. The manufacturing method according to claim 1, wherein the first photoresist (10) is developed positively.

5. The manufacturing method according to claim 1, wherein the second photoresist (20) is negatively developed.

6. The manufacturing method according to claim 5, wherein an SU-8 is used for the second photoresist (20).

7. Production method according to one of the preceding claims, wherein prior to the exposure of the first electrode (El), the second photoresist (20) is crosslinked by an annealing step.

A micromechanical sensor device (100, 100 ') comprising: a CMOS wafer (12) having a front side (VI), said front side (VI) including a first electrode (El) and a second electrode (E2); a first recess (AI), wherein by means of the first recess (AI) an electrical connection between the second electrode (E2) and an electrically conductive material (30) can be formed; a second recess (A2), wherein by means of the second recess (A2), the first electrode (El) is freely accessible; wherein the first electrode (El) and the second electrode (E2) are connected by means of the electrically conductive material (30) such that a capacitive change is measurable; in which between the first electrode (El) and the second electrode (E2) at least in regions a second photoresist (20) is formed; and the second photoresist (20) at least in regions on side surfaces (Sl) of the second recess (A2) traces of chemical erosion (CA1).

9. A micromechanical sensor device (100, 100 ') according to claim 8; wherein in the second recess (A2) a highly viscous lacquer (40) is arranged.

10. Micromechanical sensor device (100, 100 ') according to claim 8, wherein the second recess (A2) comprises a cavern (Kl) and the cavern (Kl) at least partially parallel to the front side (VI) of the CMOS wafer (1) and the first electrode (El) spaced from the second photoresist (20).