MEMS sensor having a diaphragm and method for manufacturing a MEMS sensor

Abstract

The present invention relates to an EMS sensor having a diaphragm, wherein a base area of ​​the diaphragm is bounded by means of a surrounding wall structure, wherein the base area has at least two partial areas, wherein at least one of the partial areas can be arranged in an offset manner, wherein the at least two partial areas are separated from each other by means of at least one separating structure or are bounded by the separating structure, wherein the separating structure has at least one fluid channel for allowing a fluid to pass through.

Description

Technical Field

[0001] The invention relates to a MEMS sensor having a diaphragm.

[0002] The invention also relates to a method for producing a MEMS sensor.

[0003] Although the present invention is generally applicable to any MEMS sensor having a diaphragm, the present invention is described with reference to a MEMS pressure sensor having a diaphragm in a deflectable arrangement. Background Art

[0004] MEMS pressure sensors are used today in many areas, for example in automotive technology, where the pressure must be sensed quickly and accurately, for example in the area of ​​electronic stability control systems or in intake air management or the like of vehicles.

[0005] DE 10 2016 107 275 A1 discloses a method for carrying out a measurement using a MEMS device, wherein the MEMS device has different resonance frequencies. The method comprises applying an excitation signal to a first port of the MEMS device in such a way that each of a plurality of MEMS sensors is stimulated by the excitation signal. The method also comprises measuring a signal at a second port of the MEMS device and determining a measured value based on the measurement of the signal. The MEMS device comprises a plurality of pressure cells having a wall from a so-called "large surface" on which a pressure-sensitive rectangular diaphragm is arranged.

[0006] Furthermore, EP 2 994 733 B1 discloses a microelectromechanical pressure sensor structure comprising a housing structure and a diaphragm plate, wherein the housing structure comprises a planar base and side walls, wherein a first surface extends substantially along the planar base, wherein the side walls extend as a periphery away from the planar base, wherein the diaphragm plate extends along a second surface on the side walls, wherein the planar base, the side walls and the diaphragm plate are arranged one on top of the other in such a way that the first surface, the second surface and the inner surface of the side walls form a tightly closed gap at a reference pressure, wherein an upper edge of the inner surface of the side walls forms a periphery of the diaphragm having a length and a width in a direction toward the second surface, wherein the length extends in a direction of a longitudinal extension of the diaphragm and the width extends in a direction perpendicular to the length direction in a direction toward the second surface, wherein The pressure sensor structure comprises a fixed electrode on a first surface and a diaphragm electrode on a second surface so as to sense a change in capacitance across a gap, wherein the length of the diaphragm is at least three times the width of the diaphragm, and the pressure sensor structure comprises one or more recesses extending from the first surface into a planar substrate, wherein the recesses are arranged in one or more recessed areas on the first surface, wherein the position in the recessed area corresponds to the position in the second surface when a line connecting these positions is perpendicular to the plane of the first surface, wherein the diaphragm is designed such that the diaphragm has a maximum deflection corresponding to a maximum permissible extrusion of the diaphragm during operation, wherein the recessed area is arranged at a position where the deflection of the diaphragm at the corresponding position is less than two thirds of the maximum deflection. Summary of the invention

[0007] In an embodiment, the present invention provides a MEMS sensor having a diaphragm, wherein a base area of ​​the diaphragm is bounded by a surrounding wall structure, wherein the base area has at least two partial areas, wherein at least one of the partial areas can be arranged in an offset manner, wherein the at least two partial areas are separated from each other by at least one separating structure or are bounded by the separating structure, wherein the separating structure has at least one fluid channel for allowing a fluid to pass through.

[0008] In another embodiment, the present invention provides a method for manufacturing a MEMS sensor, the method comprising the following steps:

[0009] - providing a membrane on a base structure, wherein the membrane is spaced apart from the base structure by a wall structure,

[0010] - providing a base area of ​​the membrane having at least two partial regions, wherein at least one of the partial regions is arranged displaceably,

[0011] - the at least two partial regions are separated and / or delimited by means of at least one separating structure, and

[0012] - providing at least one fluid channel in the partition structure for the passage of a fluid.

[0013] In the following description, preferably in the specification, the term “fluid” is understood to mean in particular a liquid and / or a gas mixture, in particular a gas.

[0014] One of the advantages achieved thereby is that the flexibility in the production of different diaphragm shapes is significantly increased thereby. Another advantage is the simple and cost-effective production of different diaphragm shapes on a large, regularly shaped diaphragm surface that is simple to produce. Another advantage is that, in principle, a larger return volume, i.e. a tightly enclosed volume, can be used via the at least one fluid channel, which significantly improves the stability of the enclosed pressure, for example with respect to venting and the stability against temperature changes or the like.

[0015] Additional features, advantages and other embodiments of the invention are described below or may be disclosed thereby.

[0016] According to an advantageous embodiment, the at least two partial regions are arranged symmetrically to one another on the base surface and are in particular designed identically. This allows simple production and arrangement of the at least two partial regions.

[0017] According to a further advantageous embodiment, the partitioning structure comprises at least one column. By means of the at least one column, the partitioning structure can be produced in a simple manner while providing the fluid channel.

[0018] According to a further advantageous embodiment, the partitioning structure comprises a plurality of columns which are arranged at uniform spacings, in particular at the same spacings relative to one another. This also allows simple and cost-effective production while providing sufficient separation of the at least two partial regions.

[0019] According to a further advantageous embodiment, the at least one column is at least partially circular and / or angular in cross section, preferably trapezoidal, triangular, square and / or elliptical. The column can thus be produced in a flexible and at the same time simple manner.

[0020] According to a further advantageous embodiment, the at least one column has at least two sections which are designed differently. The column can thus also have different thicknesses and / or shapes, for example in the z-direction / vertical direction. The column can in particular have one or more steps or the like, or be designed to taper in the z-direction or the like.

[0021] According to a further advantageous embodiment, at least two of the columns have different diameters. This further improves the flexibility of the partitioning structure. Thus, for example, the columns can be designed to be thinner near the wall or wall structure, because the wall in this area serves as an additional support, while the wall in the middle area can be designed to be more stable, i.e. thicker. Furthermore, the properties can also be influenced to a certain extent by changing the columns, in particular in the case of a deflectable diaphragm, the vibration properties of the diaphragm.

[0022] According to a further advantageous embodiment, the at least two partial regions are of rectangular design, thereby making it possible to provide a plurality of partial membranes in a simple manner from a square base area.

[0023] According to a further advantageous embodiment, the wall structure and / or the partition structure are produced from two different materials. This enables a flexible adaptation to different criteria, such as stability or the like.

[0024] According to a further advantageous embodiment, the partitioning structure and / or the wall structure are produced from a membrane material and / or an insulating material and / or an electrically conductive material. As a result, the partitioning structure and the wall structure can be produced in a simple manner using MEMS production methods.

[0025] According to a further advantageous embodiment, a first electrode structure for forming a first capacitance and a second electrode structure for forming a second capacitance are arranged in at least one partial region, wherein the two electrode structures are spaced apart from one another by means of a separating structure. This makes it possible, for example, to provide a surrounding capacitance and an inner capacitance, which have different deflection characteristics, since the outer region of the diaphragm, which is connected to the wall structure or in particular the large surface, is usually less curved than the central region of the diaphragm. This makes it possible to provide a reference capacitance in a simple manner.

[0026] According to a further advantageous embodiment, at least one of the at least two sub-regions is designed as a reference capacitor. As a result, a reference capacitor can be provided in a simple manner via two different sub-regions.

[0027] Further important features and advantages of the invention emerge from the subsequent description, the drawings and the corresponding figure description with reference to the drawings.

[0028] Of course, the features mentioned above and those yet to be explained below can be used not only in the respectively specified combination but also in other combinations or alone without departing from the scope of the present invention.

[0029] Preferred embodiments and implementations of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals indicate identical or similar or functionally identical components or elements. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Here, it is shown schematically:

[0031] Figure 1 A cross section of a MEMS sensor according to an embodiment of the present invention;

[0032] Figure 2 A top view of a MEMS sensor according to an embodiment of the present invention;

[0033] Figure 3 A top view and cross section of a portion of a MEMS sensor according to an embodiment of the present invention;

[0034] Figure 4 a MEMS sensor according to an embodiment of the present invention; and

[0035] Figure 5 A method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] Figure 1 A MEMS sensor according to an embodiment of the invention is shown in cross section.

[0037] exist Figure 1Detailed description is given in the figure of the MEMS sensor 1, which is manufactured, for example, in the following manner: first, in a first step, an oxide layer 3 is applied to a silicon wafer 2. Here, the substrate 2 can be optionally doped in order to improve the electrical shielding effect. Then a layer 4, in particular a diaphragm layer, is deposited from a silicon-rich nitride (SiRiN), and then the layer is structured together with the oxide layer 3 so that a substrate contact can be realized. Then a lower electrode 5 is manufactured by depositing polysilicon, which is then structured. Here, the substrate contact is filled with conductive polysilicon. Then a first sacrificial layer below in the form of an oxide layer 6 is deposited and then structured, and in particular planarized by chemical mechanical polishing in addition. Then a second oxide layer 7 is deposited and structured in order to set a stop structure. Then polysilicon 8 is deposited and then structured in order to manufacture an upper electrode 8. Then a third oxide layer 9 is deposited and planarized. Then the support element for the rods, i.e. in the form of a column (Stelen) 22, and the structuring for the wall 23 are completed. Then, a membrane material 10 in the form of a silicon-rich nitride (SiRiN) is deposited. Then, a fourth oxide layer 11 is deposited and planarized by chemical mechanical polishing in order to complete the oxide filling in the rods or pillars 22 and the walls 23. Then, the final membrane material 12 is deposited and structured together with the upper electrode layer 8 in order to obtain one or more etching inlets leading to the sacrificial layers 6, 7, 9. Then, the sacrificial layers 6, 7, 9 are removed by gas phase etching or by means of a non-static wet release process (Stiction-free Nassrelease-Process) and the membranes 10, 12 are exposed. Advantageously, when the metal surface does not need to be loaded by the exposure process, as long as no gold pads or the like are used, undesirable effects such as film formation (Belagsbildung) on ​​the metal pads during gas phase etching or corrosion of the metal pads during the wet release process are avoided. Then, a stress-adapted SiN layer 13 is deposited at a correspondingly predetermined process pressure. This SiN layer is then structured for the contact pads. Optionally, a further thin polysilicon layer with a film thickness of approximately 100 nm can then be deposited and structured on the upper side of the SiN layer 13. This polysilicon layer can optionally provide electrical shielding similar to the substrate 2. A metal plane is then deposited and subsequently structured for producing the contact pads 14. The production of the MEMS sensor 1 with a deflectable membrane is thus essentially completed.

[0038] Here, the reference numeral 20 denotes a stop structure, the reference numerals 21a, 21b, 21c denote electrode pairs with a lower electrode and an upper electrode in the respective partial regions A, B, C, respectively, the reference numeral 22 denotes a corresponding connecting element or a pillar, and the reference numeral 23 denotes a wall of the cavity 30 produced by removing the sacrificial layer. The electrical contact is led out through the wall 23 at Figure 1Only the lower electrode 5 is shown to the right. In the region 24 to the right of the membranes 8 , 10 , contacting of the substrate 2 can be achieved via the contact pads 14 .

[0039] Overall, for example, the following division of partial regions and / or partial shapes of the base area 41 can be provided for a base area 41 of 350×350 μm for the membrane 40 . Other dimensions of the base area 41 are likewise possible.

[0040] 1. Large rectangular membranes 40 with side lengths up to 350 x 350 μm

[0041] 2. A plurality of square partial membranes with a side length of up to approximately 160 x 160 μm.

[0042] In this case, the area available for membrane 40 is reduced by approximately 30 μm relative to the square base area 41 , since the additional connection complexity and separation between the partial membranes reduces the area available for membrane 40 .

[0043] 3. Circular membrane 40 with a diameter of up to 350 μm

[0044] 4. Multiple circular segmental membranes with diameters up to approximately 160 μm

[0045] 5. A plurality of rectangular partial membranes having a side length of up to approximately 320 μm and a side length ratio of greater than 2:1.

[0046] Figure 2 A top view of a MEMS sensor according to an embodiment of the present invention is shown.

[0047] exist Figure 2 4 shows a MEMS sensor 1 with a diaphragm 40, which has a square base surface 41. In addition, four partial areas A, B, C, D of the diaphragm 40 are shown, which are respectively rectangular and can be offset. The rectangular areas A, B, C, D are arranged inside the square base surface 41 and are separated from each other by point-shaped, row-arranged columns 22 inside the base surface 41. The delimitation of the square base surface 41 is realized by an extended surrounding wall 23, which can also be composed of oxide-filled diaphragm material as the point-shaped columns 22. Here, the point-shaped columns 22 can be round, angular and / or square in cross section and are arranged parallel to the longitudinal sides of the rectangular areas A, B, C, D at a distance between 10 μm and 50 μm. With the help of the columns 22, openings or fluid channels 80 can be formed between the partial areas A, B, C, D, so that fluid connections between the spaces below the individual partial areas A, B, C, D can be realized. An electrode pair 21 is arranged inside each of the partial regions A, B, C, and D.

[0048] Figure 3 A top view and a cross section of a portion of a MEMS sensor according to an embodiment of the present invention are shown.

[0049] Specifically, in Figure 3 In the upper area, a top view of a partial area A of the diaphragm 40 is shown. Figure 3 The lower area of ​​​​shows a cross section. The diaphragm 40 is separated from the basic structure 2' by the wall structure 23. Here, the basic structure 2', the wall structure 23 and the diaphragm 40 surround a cavity 30. On the upper side of the basic structure 2' and on the lower side of the diaphragm 40, an electrode pair 21a for forming a first capacitor 50 is arranged. Here, the electrode pair 21a is basically arranged in the middle of the left and right parts of the wall structure 23. A vertical support structure is arranged between the first electrode pair 21a and the left or right part of the wall structure 23. Between the two support structures and the left or right part of the corresponding wall structure 23, a second electrode pair 21b is arranged on the upper side of the basic structure 2' and on the lower side of the diaphragm 40. Thus, a second capacitor 60 is formed, such as a reference capacitor. Here, the size 71, 72 of the partial area A is a length 72 of about 320 microns and a width 71 of about 70-80 microns.

[0050] Figure 4 A MEMS sensor according to an embodiment of the present invention is shown.

[0051] exist Figure 4 in Figure 4 In the middle of the figure, different MEMS sensors 1 are shown, each of which has a membrane 40 with a square base area 41, wherein each membrane 40 has four partial membrane areas A, B, C, D. In this case, electrode pairs are arranged on the bottom side of the membrane 40 and on the top side of the base structure 2 ', as shown in Figure 4 The four partial membrane areas A, B, C, D each have a size of 320 μm x 72 μm and the distance between the partial areas A, B, C, D is 10 μm. The electrodes 101, 102 as the upper electrodes and the electrodes 103, 104 as the lower electrodes are connected by the four partial membrane areas A, B, C, D according to the Figure 4 In particular, the lower electrodes 103, 104 in different partial regions A, B, C, D and / or the upper electrodes 101, 102 in different partial regions A, B, C, D can be connected to each other to form a capacitor and / or a reference capacitor. Figure 4 In the embodiment of , two reference capacitors and two variable capacitors are formed, wherein the two variable capacitors (respectively indicated by oblique arrows) are formed by two regions B and C in the middle of the diaphragm 40 .

[0052] It is also possible that the upper electrode regions 101, 102 and the lower electrode regions 103, 104 overlap only partially. Therefore, in this embodiment, these electrode regions can also be implemented geometrically asymmetrically relative to each other. In addition, one of the advantages of the connection shown in this way is the electrical symmetry of the pressure-sensitive measuring capacitor and the pressure-sensitive reference capacitor. In the case of an electrically asymmetrical design of the pressure-sensitive measuring capacitor and the pressure-sensitive reference capacitor, the pressure-sensitive measuring capacitor and the pressure-sensitive reference capacitor can be adapted to the evaluation circuit. In addition, geometric optimization in terms of electrical scattering fields or parasitic capacitances can also be achieved thereby.

[0053] Figure 5 A method according to an embodiment of the present invention is shown.

[0054] exist Figure 5 A method for manufacturing a MEMS sensor having Figure 1 's reference numerals.

[0055] In this case, in a first step S1 , a membrane 40 is provided on the base structure 2 , 3 , 4 , wherein the membrane 40 is spaced apart from the base structure 2 , 3 , 4 by the wall structure 23 .

[0056] In a second step S2 , a base surface 41 of a membrane sheet 40 is then provided, which base surface has at least two sub-regions A, B, C, D, wherein at least one of the sub-regions A, B, C, D is arranged so as to be displaceable.

[0057] In a third step S3a and / or S3b, the at least two partial regions are then separated and / or delimited by means of at least one separating structure.

[0058] Then, in a fourth step S4 , at least one fluid channel 80 is provided in the partition structure for the passage of a fluid.

[0059] In general, at least one embodiment of the present invention can achieve the following features and / or the following advantages:

[0060] The interconnection of the approximately rectangular individual diaphragms within the square diaphragm surface allows, in particular, an increase in the ratio of the basic capacitance ΔC / C0 in the capacitance component with a reduction in the basic capacitance C0, which is advantageous.

[0061] · The interconnection of polygonal individual membranes within a square base area.

[0062] The interconnection of approximately rectangular individual membranes within a square membrane surface, for example trapezoidal, polygonal, elliptical with an aspect ratio of edge length to width greater than or equal to 2:1

[0063] • The individual membranes are separated by oxide-filled walls in the membrane material.

[0064] The individual membranes are separated by oxide-filled, point-shaped pillars in the membrane material, which are, for example, circular, angular, triangular, polygonal or similar in shape.

[0065] Pressure sensitive reference capacitor through mechanical reinforcement of pillars in the inner electroactive area of ​​the diaphragm

[0066] Pressure-sensitive measuring capacitors through variable mechanical reinforcement of the column or wall.

[0067] • Variable mechanical support of the membrane by posts in circular, polygonal, square or triangular geometries.

[0068] • Variable mechanical support of the membrane by means of posts and walls with variable diameters from 2 μm to 20 μm.

[0069] • Surrounding capacitors with additional available capacitance internally and separated by support structures.

[0070] Although the invention has been described with reference to preferred embodiments, it is not restricted thereto but can be varied in many ways.

Claims

1. A MEMS sensor (1), comprising a diaphragm (40), wherein: The base area (41) of the membrane (40) is delimited by means of a surrounding wall structure (23), wherein: The base surface (41) has at least two partial regions (A, B, C, D), wherein at least one of the partial regions (A, B, C, D) is arranged so as to be displaceable, and The at least two partial regions (A, B, C, D) are separated from one another by means of at least one separating structure or are delimited by the separating structure, wherein the separating structure has at least one fluid channel (80) for passing a fluid, and a first electrode structure (21a) for forming a first capacitor (50) and a second electrode structure (21b) for forming a second capacitor (60) are arranged in at least one partial region (A, B, C, D), wherein the two electrode structures (21a, 21b) are spaced apart from each other by means of the separation structure, and At least one of the at least two sub-regions (A, B, C, D) is designed as a reference capacitor.

2. The MEMS sensor according to claim 1, wherein: The at least two partial regions (A, B, C, D) are arranged symmetrically to one another on the base surface (41).

3. The MEMS sensor according to any one of claims 1 to 2, wherein: The partition structure comprises at least one column (22).

4. The MEMS sensor according to claim 3, wherein: The partition structure includes a plurality of columns (22) arranged at uniform intervals.

5. The MEMS sensor according to claim 3, wherein: The at least one column (22) is designed at least partially circular and / or angular in cross section.

6. The MEMS sensor according to claim 3, wherein: The at least one column (22) has at least two sections which are configured differently.

7. The MEMS sensor according to claim 4, wherein: At least two of the columns (22) have different diameters.

8. The MEMS sensor according to any one of claims 1 to 2, wherein: The at least two partial regions (A, B, C, D) are of rectangular design.

9. The MEMS sensor according to any one of claims 1 to 2, wherein: The wall structure (23) and / or the partition structure are manufactured from two different materials.

10. The MEMS sensor according to claim 9, wherein: The partition structure and / or the wall structure (23) are made of a membrane material and / or an insulating material and / or a conductive material.

11. The MEMS sensor according to claim 2, wherein: The at least two partial regions (A, B, C, D) are designed identically.

12. The MEMS sensor according to claim 4, wherein: The plurality of columns are respectively arranged at the same distance from one another.

13. The MEMS sensor according to claim 5, wherein: The at least one column (22) is designed to be trapezoidal, triangular, square and / or elliptical in cross section.

14. A method for manufacturing a MEMS sensor (1), the method comprising the following steps: - providing (S1) a membrane (40) on a base structure (2, 3, 4), wherein the membrane (40) is spaced apart from the base structure (2, 3, 4) by a wall structure (23), - providing (S2) a base area (41) of the membrane (40) having at least two partial regions (A, B, C, D), wherein at least one of the partial regions (A, B, C, D) is arranged so as to be displaceable, - separating (S3a) and / or delimiting (S3b) the at least two partial regions by means of at least one separating structure, and - providing (S4) at least one fluid channel (80) in the partition structure for passing a fluid, wherein: - a first electrode structure (21a) for forming a first capacitor (50) and a second electrode structure (21b) for forming a second capacitor (60) are arranged in at least one partial region (A, B, C, D), wherein the two electrode structures (21a, 21b) are spaced apart from each other by means of the separation structure, and At least one of the at least two sub-regions (A, B, C, D) is designed as a reference capacitor.

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