DE102017212318A1 - Micromechanical sensor device and corresponding manufacturing method - Google Patents

Abstract

The invention provides a micromechanical sensor device and a corresponding manufacturing method. The micromechanical sensor device is equipped with a sensor substrate (1) with a front side (VS) and a rear side (RS); a sensor area (4) provided on the front side (VS), which can be brought into contact with an environmental medium; wherein the sensor region (4) is elastically suspended in the sensor substrate (1) via a spring device (7). In the sensor substrate (1) below the sensor region (4), a cavity (6) is provided, which extends to the back (RS); and a grid layer (11) applied on the back side (RS) spans the cavity (6).

Description

The invention relates to a micromechanical sensor device and a corresponding manufacturing method.

State of the art

Although any micromechanical components are applicable, the present invention and the problems underlying it are explained with reference to micromechanical pressure sensor devices.

The US 2015/0001651 A1 discloses a micromechanical pressure sensor device.

6 is a schematic cross-sectional view for explaining the of US 2015/0001651 A1 known micromechanical pressure sensor device.

In 6 denotes reference numeral 1 a sensor substrate, for example a silicon sensor substrate, in which over a cavern 2 a thin membrane 3 is formed. In the membrane 3 is a sensor area 4 provided, which has, for example piezoresistive resistors for pressure measurement. When an external pressure is applied to the membrane 3 this is bent, whereupon the piezoresistive resistors change their resistance values, so that it can be concluded by measuring the resistance values on the applied external pressure.

For decoupling the known micromechanical pressure sensor device from external forces is in the sensor substrate 1 below the membrane 3 a cavity 6 provided, and in addition is the sensor area 4 laterally via a spring device 7 from the sensor substrate 1 mechanically elastic decoupled. From the back is on the sensor substrate 1 a back cap wafer 11 bonded on. On the front of the sensor substrate 1 is a front cap wafer 9 Bonded, which a pressure access 10 for the sensor area 4 having.

The back cap wafer 11 For example, it can also be designed as an evaluation ASIC. The composite of the cap wafers 9 . 11 and the sensor substrate 1 is on a carrier substrate 8th glued and at the same time with a molding compound 5a packed up. Thus, external forces acting on the housing 5 total abut, if possible from the sensor area 4 be decoupled.

Thus, the known micromechanical pressure sensor device requires two cap wafers and the associated bonding processes, which makes the manufacturing process expensive, and moreover, the known micromechanical pressure sensor device has a relatively large construction height.

Disclosure of the invention

The invention provides a micromechanical sensor device according to claim 1 and a corresponding manufacturing method according to claim 7.

Preferred developments are the subject of the respective subclaims.

Advantages of the invention

The inventive micromechanical sensor device according to claim 1 or the corresponding manufacturing method according to claim 7 make it possible to provide a stress-decoupled micromechanical sensor device which can be produced cost-effectively and has a low overall height.

The idea underlying the present invention is that a grid layer is provided on the backside of the sensor wafer, wherein the etching process for the cavity located below the sensor area is performed through this grid layer. At the front, the sensor area is suspended by springs formed in the sensor substrate. The backside grid layer can either be closed after the etching process via a layer deposition or used as media access. In the latter case, it is advantageous to provide an evaluation ASIC for capping the front side instead of the cap wafer.

According to a preferred development, a cap substrate is bonded to the front side, which has a media access to the sensor area, and wherein the grid layer is closed by a sealing layer in a media-tight manner. This allows a thin back closure.

According to a further preferred development, the sensor region is arranged on a stamp of the sensor substrate, which extends to the rear side. This additionally increases the stability and protects against vibrations.

According to another preferred embodiment
4. The micromechanical sensor device according to claim 2, wherein one or more stabilizing webs of the sensor substrate are arranged in the cavity on the grid layer, which are separated from the sensor area. This makes it possible to produce a thin stabilized grid layer.

According to a further preferred development, the front side is bonded to an ASIC substrate, wherein a lateral media access to the sensor area to the sensor area is formed in a gap between the sensor substrate and the ASIC substrate, and wherein the grid layer is closed media-tight by a precluding layer. This saves a front cap wafer and further increases its compactness.

According to a further preferred development, the front side of the sensor substrate is bonded to an ASIC substrate in a media-tight manner, wherein the grid layer is designed as a media access. Thus, a front cap wafer can be saved and the mesh layer functionally useful.

list of figures

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

• 1 eine schematische Querschnittsdarstellung zur Erläuterung einer mikromechanischen Sensorvorrichtung gemäß einer ersten Ausführungsform der vorliegenden Erfindung;
• 2 eine schematische Querschnittsdarstellung zur Erläuterung einer mikromechanischen Sensorvorrichtung gemäß einer zweiten Ausführungsform der vorliegenden Erfindung;
• 3a),b) schematische Querschnittsdarstellungen zur Erläuterung einer mikromechanischen Sensorvorrichtung gemäß einer dritten Ausführungsform der vorliegenden Erfindung, wobei 3b) eine Ausschnittsvergrößerung des Ausschnitts A von 3a) ist;
• 4 eine schematische Querschnittsdarstellung zur Erläuterung einer mikromechanischen Sensorvorrichtung gemäß einer vierten Ausführungsform der vorliegenden Erfindung;
• 5 eine schematische Querschnittsdarstellung zur Erläuterung einer mikromechanischen Sensorvorrichtung gemäß einer fünften Ausführungsform der vorliegenden Erfindung; und
• 6 eine schematische Querschnittsdarstellung zur Erläuterung einer bekannten mikromechanischen Sensorvorrichtung.

Show it:

• 1 a schematic cross-sectional view for explaining a micromechanical sensor device according to a first embodiment of the present invention;
• 2 a schematic cross-sectional view for explaining a micromechanical sensor device according to a second embodiment of the present invention;
• 3a) , b) schematic cross-sectional views for explaining a micromechanical sensor device according to a third embodiment of the present invention, wherein 3b) a detail enlargement of the clipping A from 3a) is;
• 4 a schematic cross-sectional view for explaining a micromechanical sensor device according to a fourth embodiment of the present invention;
• 5 a schematic cross-sectional view for explaining a micromechanical sensor device according to a fifth embodiment of the present invention; and
• 6 a schematic cross-sectional view for explaining a known micromechanical sensor device.

Embodiments of the invention

In the figures, like reference numerals designate the same or functionally identical elements.

1 is a schematic cross-sectional view for explaining a micromechanical sensor device according to a first embodiment of the present invention.

In 1 denotes reference numeral 1 a silicon sensor substrate with a front side VS and a back RS , On the front side VS is a sensor area 4 provided, which, for example, a cavern 2 , a membrane 3 and in the membrane 3 having integrated piezoresistors (not shown).

The sensor area 4 is via a laterally arranged spring device 7 elastic in the sensor substrate 1 suspended. In the sensor substrate 1 below the sensor area 4 is a cavity 6 provided, extending to the back RS extends. On the back side RS is a grid layer 11 provided, which is made for example of a metal, in particular aluminum, or of an oxide layer and which in the region of the cavity 6 has small grid openings of the order of typically 1 to 10 microns. The grid layer 11 is through a sealing layer 12 , For example, a silicon nitride or silicon oxide layer, media-tightly closed.

On the front side VS an insulating layer I, for example a silicon oxide layer is provided, into which a printed conductor arrangement LB integrated, which is an electrical connection 13 of the sensor area with an electrical connection 14 for an external connection connects. On the insulation layer I is a cap wafer 9 via a bond connection B Bonded, which a media access 10 to the sensor area.

The mode of operation of the micromechanical sensor device constructed in this way corresponds to that which has already been described with reference to the known micromechanical sensor device according to claim 6. Due to the thin grid layer the construction height is significantly reduced, whereby the stress decoupling is just as effective. Although not shown, a housing package in an analogous manner to the known micromechanical sensor device according to 6 respectively.

For producing the micromechanical sensor device according to 1 In the present embodiment, first, the sensor substrate becomes 1 from the front VS processed to the sensor area 4 and the spring device 7 manufacture. Then the insulation layer I and the conductor track device embedded therein LB as well as the electrical contacts 13 . 14 produced. Finally, the cap wafer 9 over the bond area B bonded on.

In a subsequent process step, if necessary, the sensor substrate 1 at the back RS be first ground back to the desired target thickness. This is followed by the application of the grid layer 11 on the back RS ,

As an etching process for perforating the grid layer 11 in the area of the cavity to be freed 6 a trench process is preferably used. In such a trench process, the lateral undercutting is preferably selected such that the webs of the grid layer 11 all completely undercut. The closure of the grid layer 11 is then preferably carried out with a LPCVD deposition (Low Pressure Chemical Vapor Deposition), wherein as a sealing layer 11 Silizumnitrid or silica or combinations of such layers are preferred. In a preferred embodiment, a nitride / oxide layer stack is used, which is chosen in total such that the grid layer 11 in combination with all the sealing layers result in a layer which is easily under tensile stress and thus a bulging of the layer can be avoided.

After the back RS closed and protected, then in a further process step the media access 10 in the cap wafer 9 be created.

2 FIG. 12 is a schematic cross-sectional view for explaining a micromechanical sensor device according to a second embodiment of the present invention. FIG.

In 2 the sensor substrate bears reference numbers 1' , Unlike the sensor substrate 1 According to the first embodiment, the sensor substrate 1' according to 2 a central stamp 15 under the sensor area 4 on. In other words, the sensor area 4 on a stamp 15 of the sensor substrate 1' arranged, which is up to the back RS extends, being in the area of the punch 15 the grid layer 11 closed is. Through the stamp, the sensor area 4 especially for high vibration applications. The spring device 7 may be made softer in this embodiment, if necessary, as in the first embodiment.

Otherwise, the function and structure of the second embodiment are the same as in the first embodiment.

3a) , b) are schematic cross-sectional views for explaining a micromechanical sensor device according to a third embodiment of the present invention, wherein 3b) a detail enlargement of the clipping A from 3a) is.

In the third embodiment, the sensor substrate carries reference numerals 1" , wherein the grid layer 11 in strip-shaped areas with bars 16 of the sensor substrate 1" closed is. The bridges 16 serve to the grid layer 11 to stabilize. For the production of the webs 16 with the overlying cavity 6 between sensor area 4 and the jetties 16 a two-stage etching process is used. The first stage of the etching process is performed as an anisotropic trench etching process such that the grating structures in the area 18 be underestimated. The second stage of the etching process is in an isotropic etching step in the range 18 executed such that the webs 16 be etched.

4 FIG. 12 is a schematic cross-sectional view for explaining a micromechanical sensor device according to a fourth embodiment of the present invention. FIG.

In the fourth embodiment, the sensor substrate carries reference numerals 1"' and is analogous to the sensor substrate 1 constructed according to the first embodiment described above. In contrast to the first embodiment, however, no cap wafer is provided, but the sensor substrate 1"' is over a bond area B to an evaluation ASIC 19 bonded. In this case, a bonding process is used which also involves an electrical contact 20 between the sensor substrate 1 and the evaluation ASIC 19 allows. In this embodiment, the media access is 21 lateral to the sensor area 4 in a space between the sensor substrate 1"' and the ASIC substrate 19 educated.

5 FIG. 12 is a schematic cross-sectional view for explaining a micromechanical sensor device according to a fifth embodiment of the present invention. FIG.

In the fifth embodiment, the sensor substrate carries reference numerals 1"" and differs from the sensor substrate 1 according to the first embodiment, that no sealing layer on the grid layer 11 is provided.

The front VS of the sensor substrate 1"" In this fifth embodiment, it is media-tight on an ASIC substrate 19a bonded, with the grid layer 11 as media access 25 is trained. Such an arrangement is called a bare-die element 22 designated.

As in the fourth embodiment, there is a bonding region and an electrical contact realized via the bonding connection 20 between the sensor substrate 1 and the ASIC substrate 19a , About vias 23 the ASIC signal is applied to the sensor substrate 1"" opposite side of the ASIC substrate 19a passed and is over solder regions 24 towards the outside on a corresponding carrier substrate electrically connected.

The as media access 25 functioning grid layer 11 is either not closed at all, in which case the grid area acts as particle protection. In addition, the grid area 11 For example, be provided with a water-repellent layer (not shown), which may additionally act as a protective layer against a liquid medium.

On the other hand, if only a point access and no area access as media access 25 is desired, can also be a media access 25 in the grid layer 11 which is larger than the normal lattice constant, which is not closed in the closing process, but the smaller lattice passages with the sealing layer 12 be closed.

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.

Particularly preferred further applications for the micromechanical sensor device according to the invention are, for example, chemical gas sensors, such as metal oxide gas sensors, thermal conductivity sensors, Pirani elements, mass flow sensors, such as air mass meters, lambda probes on a micromechanical membrane, infrared sensor devices, etc.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2015/0001651 A1 [0003, 0004]

Claims (12)

Micromechanical sensor device with: a sensor substrate (1; 1 '; 1 "; 1"; 1 "") having a front side (VS) and a back side (RS); a sensor area (4) provided on the front side (VS), which can be brought into contact with an environmental medium; wherein the sensor region (4) is elastically suspended in the sensor substrate (1; 1 '; 1 "; 1"; 1 "") by means of a spring device (7); wherein in the sensor substrate (1; 1 '; 1 "; 1"; 1 "") below the sensor region (4) a cavity (6) is provided which extends to the rear side (RS); and a grid layer (11) applied on the rear side (RS), which spans the cavity (6). Micromechanical sensor device according to Claim 1 , wherein on the front side (VS) a cap substrate (9) is bonded, which has a media access (10) to the sensor area (4), and wherein the grid layer (11) is sealed media-tight by a precoat layer (12). Micromechanical sensor device according to Claim 2 , wherein the sensor area (4) is arranged on a punch (15) of the sensor substrate (1 ') which extends to the rear side (RS). Micromechanical sensor device according to Claim 2 in which one or more stabilizing webs (16) of the sensor substrate (1 ") are arranged in the cavity (6) on the grid layer (11), which are separated from the sensor area (4). Micromechanical sensor device according to Claim 1 wherein the front side (VS) is bonded to an ASIC substrate (19), wherein a lateral media access (21) to the sensor area (4) to the sensor area (4) in a space between the sensor substrate (1 "') and the ASIC Substrate (19) is formed, and wherein the grid layer (11) by a precursor layer (12) is sealed media-tight. Micromechanical sensor device according to Claim 1 , wherein the front side (VS) of the sensor substrate (1 "") is media-tightly bonded to an ASIC substrate (19a) and wherein the grid layer (11) is designed as a media access (25). Method for producing a micromechanical sensor device with the steps: Providing a sensor substrate (1; 1 '; 1 "; 1"; 1 "") having a front side (VS) and a rear side (RS), Forming a sensor area (4) provided on the front side (VS) which can be brought into contact with an environmental medium; Forming a spring device (7) via which the sensor region (4) is suspended in the sensor substrate (1; 1 '; 1 "; 1"; 1 ""); Forming a grid layer (11) on the back side (RS); Forming a cavity in the sensor substrate (1; 1 '; 1 "; 1"; 1 "") below the sensor region (4) which extends to the rear side (RS) by an etching process in which an etching medium is conveyed through the mesh layer (11 ) is guided into the sensor substrate (1; 1 '; 1 "; 1"; 1 ""), whereby the spring device (7) is released so that the sensor region (4) in the sensor substrate (1; 1'; 1 "; 1" ") is suspended elastically. Method according to Claim 7 , wherein on the front side (VS) a cap substrate (9) is bonded, which has a media access (10) to the sensor area (4), and wherein the grid layer (11) by a precoat layer (12) is sealed media-tight. Method according to Claim 8 in that, during the formation of the cavity (6), a stamp (15) of the sensor substrate (1'9) is formed, which extends to the rear side (RS), so that the sensor region (4) on a plunger (15) of the sensor substrate (FIG. 1 ') is arranged. Method according to Claim 8 in which one or more stabilizing webs (16) of the sensor substrate (1) are formed in the cavity (6) on the grid layer (11) in a two-stage etching process which are separate from the sensor region (4), the etching process including a first anisotropic etching step and an etching process second isotropic etching step. Method according to Claim 7 wherein the front side (VS) is bonded to an ASIC substrate (19), wherein a lateral media access (21) to the sensor area (4) to the sensor area (4) in a space between the sensor substrate (1 "') and the ASIC Substrate (19) is formed, and wherein the grid layer (11) by a precursor layer (12) is sealed media-tight. Method according to Claim 7 wherein the front side (VS) of the sensor substrate (1 "") is bonded to an ASIC substrate (19a) in a media-tight manner and wherein the grid layer (11) is designed as a media access (25).

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