DE102018210063A1 - MEMS sensor and method for manufacturing a MEMS sensor - Google Patents

Abstract

The invention relates to a MEMS sensor having a deflectably arranged membrane, wherein the deflectable membrane forms at least partially a boundary for a cavity and wherein at least one element as a support element for spacing the membrane of a boundary of the cavity and / or as a limiting element for limiting the cavity is arranged, wherein the element is at least partially made of membrane material.

Description

Technical area

The invention relates to a MEMS sensor with a deflectably arranged membrane.

The invention further relates to a method for producing a MEMS sensor with a deflectably arranged membrane.

Although the present invention is generally applicable to any MEMS sensors having a deflectable diaphragm, the present invention will be described in terms of MEMS pressure sensors.

State of the art

MEMS pressure sensors are now used in a variety of fields, such as automotive, where pressures must be rapidly and accurately sensed, such as in electronic stability control or in vehicle intake air management or the like.

From the DE 10 2016 107 275 A1 For example, a method of performing a measurement using a MEMS device that includes a plurality of MEMS sensors having different resonant frequencies has become known. The method includes applying an excitation signal to a first port of the MEMS device such that each of the plurality of MEMS sensors is paced by the excitation signal. The method further includes measuring a signal at a second port of the MEMS device and determining a measured value based on measuring the signal. The MEMS device comprises a plurality of pressure cells with walls from the so-called "mainland" above which pressure-sensitive rectangular membranes are arranged.

Disclosure of the invention

In one embodiment, the invention provides a MEMS sensor having a deflectably disposed membrane, the deflectable diaphragm at least partially defining a cavity and at least one element as a support member for spacing the diaphragm from a cavity boundary and / or as a limiting element for limiting the cavity is arranged, wherein the element is at least partially made of membrane material.

• - Bereitstellen einer auslenkbar angeordneten Membran,
• - Bereitstellen eines Hohlraums, wobei der Hohlraum durch die auslenkbar angeordnete Membran zumindest teilweise begrenzt wird,
• - Anordnen eines Elements als Stützelement zur Beabstandung der Membran von einer Begrenzung des Hohlraums und/oder als ein Begrenzungselement zur Begrenzung des Hohlraums, wobei das Element zumindest teilweise aus Membranmaterial hergestellt wird.

In a further embodiment, the invention provides a method of fabricating a MEMS sensor having a deflectable membrane comprising the steps

• Providing a deflectable membrane,
• Providing a cavity, wherein the cavity is at least partially bounded by the deflectably arranged membrane,
• Arranging an element as a support element for spacing the membrane from a boundary of the cavity and / or as a limiting element for defining the cavity, wherein the element is made at least partially of membrane material.

One of the advantages achieved with this is that the design of the membrane can essentially be chosen freely. For example, not only quadrangular but also octagonal and / or asymmetrical membranes can be realized. In addition, the membrane size is more freely selectable. Overall, thus, the flexibility of the MEMS sensor is increased.

Further features, advantages and further embodiments of the invention are described below or will become apparent.

According to an advantageous development, the element is at least partially made of an insulating layer material, in particular wherein the insulating layer material is predominantly surrounded by membrane material. One of the advantages achieved with this is that an insulating side wall can thus be produced, so that, for example, two electrode layers can be electrically separated from one another. Another advantage is increased design flexibility: By using an element made of insulating layer material, which is in particular at least partially encased or surrounded by membrane material, substantially larger elements can be manufactured with a freer shape, and thus the MEMS sensor, for example, in terms of performance, Breaking strength or the like can be optimized in a more flexible manner.

According to a further advantageous development, the membrane material has tensile-stressable material. By means of such material, which can be provided with a slight tensile stress, a particularly high accuracy or sensitivity of the MEMS sensor can be made possible. Another advantage of tensioned membrane material is its lower tendency to form undulations under pressure. In other words, a flat membrane can be provided even under pressure stress.

According to a further advantageous development, the membrane material has a compound of nitride. This allows a particularly simple application of the membrane material. On Another advantage of a nitride compound in the membrane material is its diffusion-reducing property. Diffusion of moisture, for example into a cavern of the MEMS sensor, can thus be prevented.

According to a further advantageous development, the membrane material has silicon-rich nitride and / or silicon carbonitride. Thus, for example, side walls or general boundaries of the cavity can be realized, which automatically serve as etch stops in a corresponding membrane release process. Silicon-rich nitride Si _x N _y with x> = 3 has a higher proportion of silicon than stoichiometrically deposited nitride, Si ₃ N ₄ . Silicon carbonitride has the empirical formula SiCN.

According to a further advantageous development, the element is U-shaped from membrane material and filled with a second material. This can be produced in a particularly simple manner stable support elements.

According to a further advantageous embodiment, at least one electrode is arranged in the cavity, which has at least one contact, which is led out of the cavity and which is at least partially surrounded by insulating material outside the cavity. This makes it possible to realize in a particularly simple manner insulated contact paths for an electrode, which can be led out of the cavity.

According to a further advantageous development, the material of the electrode comprises polycrystalline silicon. This allows a simple production of the electrode.

According to a further advantageous embodiment of the method, the diaphragm material is arranged zugverspannt to provide the deflectable arranged membrane, in particular with a train between 25 MPa and 150 MPa. This makes it possible to easily achieve a tensile film tension of the membrane material.

According to a further advantageous development, the provision of the deflectably arranged membrane comprises a deposition of membrane material by means of an LPCVD and / or PECVD process. This makes it easy to deposit or apply membrane material. Here, LPCVD is a chemical vapor deposition at low pressure and PECVD is a plasma enhanced chemical vapor deposition.

Further important features and advantages of the invention will become apparent from the subclaims, from the drawings, and from associated figure description with reference to the drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Preferred embodiments and embodiments of the invention are illustrated in the drawings and will be described in more detail in the following description, wherein like reference numerals refer to the same or similar or functionally identical components or elements.

list of figures

• 1-16 Schritte eines Verfahrens zur Herstellung eines MEMS-Sensors, dargestellt im Querschnitt, mit einer auslenkbar angeordneten Membran gemäß einer Ausführungsform der vorliegenden Erfindung; und
• 17 Schritte eines Verfahrens zur Herstellung eines MEMS-Sensors, dargestellt im Querschnitt, mit einer auslenkbar angeordneten Membran gemäß einer Ausführungsform der vorliegenden Erfindung

This show in a schematic form

• 1-16 Steps of a method for manufacturing a MEMS sensor, shown in cross-section, with a deflectable membrane according to an embodiment of the present invention; and
• 17 Steps of a method for manufacturing a MEMS sensor, shown in cross-section, with a deflectably arranged membrane according to an embodiment of the present invention

Embodiments of the invention

The 1-16 show steps of a method for manufacturing a MEMS sensor with a deflectably arranged membrane.

In detail is in 1 a silicon wafer 2 shown on the first step in an oxide layer 3 was applied. Optionally, while the substrate 2 be doped to improve the electrical shielding effect.

Subsequently, in an optional second step according to 2 a layer 4 , in particular membrane layer, of silicon-rich nitride - SiRiN - deposited and then together with the oxide layer 3 structured so that a substrate contact 4a is possible.

Subsequently, in a third step according to 3 a lower electrode 5 produced by deposition of polycrystalline silicon, which is subsequently patterned. The substrate contact 4a is filled with the conductive polycrystalline silicon.

Subsequently, in a fourth step according to 4 a lower, first sacrificial layer in form an oxide layer 6 deposited and then structured and in particular additionally planarized by chemical-mechanical polishing.

Subsequently, in an optional fifth step according to 5 a second oxide layer 7 deposited and structured to create stop structures.

Subsequently, in a sixth step according to 6 polycrystalline silicon 8th deposited and then patterned to an upper electrode 8th manufacture.

Subsequently, in a seventh step according to 7 a third oxide layer 9 deposited and planarized.

Subsequently, an eighth step according to 8th a structuring 9a for posts, so supporting elements 22 and for walls 23 created.

Subsequently, in a ninth step according to 9 membrane material 10 in the form of silicon-rich nitride - SiRiN - deposited.

Subsequently, in a tenth step according to 10 a fourth oxide layer 11 deposited and planarized by chemical-mechanical polishing to form an oxide filling in the posts 22 and the walls 23 to create.

Subsequently, in an eleventh step according to 11 final membrane material 12 deposited and structured together with the upper electrode layer 8th to provide one or more etch accesses to the sacrificial layers 6 . 7 . 9 to obtain.

Subsequently, in a twelfth step according to 12 the sacrificial layers 6 . 7 . 9 cleared by gas phase etching or by a stiction-free wet-release process and the membrane 10 . 12 optional. It is advantageous if the release process does not require the application of metal surfaces, so that unwanted effects, for example deposit formation on metal pads during gas phase etching or etching of metal pads in the wet release process, if no gold pads are used or the like, are avoided.

Subsequently, in a thirteenth step according to 13 a stress-matched SiN layer 13 deposited at a correspondingly predetermined process pressure. This is then structured for contact pads. Optionally, then another thin polysilicon layer, with about 100 nm film thickness on top of the SiN layer 13 be deposited and structured. This can optionally have an electrical shield similar to the substrate 2 provide.

Subsequently, in a fourteenth step according to 14 deposited a metal level and then for the production of contact pads 14 structured. This is essentially the production of the MEMS sensor 1 completed with a deflectable membrane. Here are with reference numerals 20 Stop structures, with reference numerals 21 the two electrodes, with reference numerals 22 corresponding connecting elements or posts, and with reference numerals 23 Walls of the cavity 30 designated. Leading the electrical contact through the walls 30 is in 14 only for the lower electrode 5 shown to the right. In the area 24 right of the membrane 8th . 10 is via the contact pads 14 a contacting of the substrate 2 allows.

Subsequently, in a fifteenth step according to 15 the sealing layer 13 be structured, provided the membrane 10 . 12 only partially closure material 13 to get over the Ätzzugängen.

Subsequently, in a sixteenth step according to 16 a reference capacity by stiffening the pressure-sensitive membrane 10 . 12 be provided by unstructured sealing layer and / or by means of a thick sealing layer.

In other words, by means of the method of 1-16 a thin-film MEMS pressure sensor 1 manufactured. Here, the membrane 10 . 12 made of SiCN and / or SiRiN. The connecting side walls 23 and columns 22 between the membranes 10 . 12 or the substrate 2 are made of SiCN / SiRiN filled with oxide. The movable membrane 10 . 12 is through walls 23 connected to a mainland. These walls 23 are the same as the posts 22 realized, enclose the membrane 10 . 12 however completely. Furthermore, the electrical contacts in one plane are realized by having polycrystalline silicon tracks through the outer walls 23 be passed and enclosed or superimposed by the membrane material.

The SiCN / SiRiN deposits can be carried out as PECVD or LPCVD processes. Advantageous here is a slight tensile film tension of the membrane material, for example 25 MPa.

The oxide deposits may also vary in the deposition process. In particular, for the oxides, which has a capacitor gap of two microphone capacities of a microphone, So determine an acoustic MEMS sensor, advantageously a sufficiently controllable LPCVD process is used.

The structuring of the SiCN / SiRiN layer can be carried out in particular with an SF ₆ -based plasma etching process.

The structuring of the oxide layers can likewise be carried out with plasma or wet-chemical etching processes, depending on the design tolerances intended for the design.

Depending on requirements, topography reductions can be achieved by planarizing oxide layers using chemical mechanical polishing techniques.

Optionally, the top SiN layer 13 be structured (reference numerals 50 ), if the mechanical influence of the SiN sealing layer is too high in rigidity, as shown in FIG 15 is shown.

Also optional is the formation of a reference capacity in which the upper membrane is stiffened and thus can not be deflected by pressure. This stiffening is done by way of example by a targeted deposition of a comparatively thick sealing layer 13 of SiN, shown in 16 ,

17 shows steps of a method for manufacturing a MEMS sensor, shown in cross-section, with a deflectable membrane according to an embodiment of the present invention.

In 17 For example, there is shown a method of making a MEMS sensor having a deflectable diaphragm.

This includes in a first step S1 providing a deflectably arranged membrane in a second step S2 providing a cavity, wherein the cavity is at least partially limited by the deflectably arranged membrane, and in a third step S3 arranging an element as a support element for spacing the membrane from a boundary of the cavity and / or as a limiting element for defining the cavity, wherein the element is made at least partially of membrane material.

• - Geringe Herstellungsprozesskomplexität mit ca. 10 Maskenebenen.
• - Bereitstellen einer planarisierten Membran 10, 12.
• - topographiefreier Prozess, der hochauflösende Lithographie bis in die obersten Ebenen oder Schichten ermöglicht.
• - Trennung der elektrischen und mechanischen Anforderungen an untere Membran und obere Membran beziehungsweise der Gegenelektrode aus polykristallinem Silizium und SiRiN, was eine signifikante Reduktion der Parasitar-Kapazitäten ermöglicht.
• - Bei Nutzung eines Laser-Reseal-Prozesses zum Verschluss der oberen Membran 10, 12 sind variable Innendrücke im Hohlraum 30 in verschiedenen Membranbereichen realisierbar. Dies kann zum Beispiel für einen Referenzdruckbereich in der Membran genutzt werden.
• - Realisierung einer Wand 23 und/oder Post 22 als Membranunterstützung oder Membranaufhängungsstruktur.
• - Realisierung einer Wand 23 und/oder Posts 22 zur Abgrenzung einzelner Membranbereiche. Dies ermöglicht zum Beispiel unterschiedliche kleine

In summary, at least one of the embodiments of the invention provides at least one of the following advantages:

• - Low manufacturing process complexity with approx. 10 Mask layers.
• - Providing a planarized membrane 10 . 12 ,
• - Topography-free process that enables high-resolution lithography down to the highest levels or layers.
• - Separation of the electrical and mechanical requirements of the lower membrane and upper membrane or the counter electrode of polycrystalline silicon and SiRiN, which allows a significant reduction of parasitic capacitances.
• - When using a laser reseal process to close the upper membrane 10 . 12 are variable internal pressures in the cavity 30 feasible in different membrane areas. This can be used, for example, for a reference pressure range in the membrane.
• - Realization of a wall 23 and / or post 22 as membrane support or membrane suspension structure.
• - Realization of a wall 23 and / or posts 22 for the delimitation of individual membrane areas. This allows, for example, different small

Sub-membrane areas, or unbalanced membrane areas within a spanning membrane.

• - Eine Realisierung eines MEMS Drucksensors 1 mit dünnen Nitridschichten als strukturelles Element. Diese können aus SiCN oder auch SiRiN hergestellt werden oder auch aus einem anderen nichtleitenden Material, das selektiv zu HF geätzt werden kann
• - Vorteilhafterweise wird tensiles Material als Membranmaterial verwendet.
• - Verschluss der SiCN/SiRiN-Membran mit einem stressadaptierten Nitrid bei Niederdruck beziehungsweise durch einen Laser-Reseal-Prozess. Es können auch andere nichtleitende Materialien verwendet werden, zum Beispiel SiO₂, Polyimide oder dergleichen.
• - Nutzung von polykristallinem Silizium oder eines anderen leitenden Materials, insbesondere eines Metalls oder eines Halbmetalls, vorzugsweise Germanium, in einem SiCN/SiRiN basierten Drucksensor zur elektrischen Kontaktierung und/oder zur Ausbildung der kapazitiven Messstrukturen.
• - Realisierung der verbindenden Stelen - „Posts“ - zwischen Nitridschichtvorderseite und -rückseite mittels einer u-förmigen Nitridwanne, welche mit Oxid aufgefüllt wird.
• - Nutzung eines Gasphasenätzschrittes oder Stiction-free Nassrelease-Prozesses zur Freistellung der Membran. Insbesondere ein Gasphasenätzschritt ermöglicht Ätzöffnungen mit einer Dimension unterhalb von 0,5 µm.
• - Realisierung von Seitenwänden 23 aus SiCN und/oder SiRiN mit Oxidverfüllung/Oxidkern. Diese Wände 23 bilden insbesondere bei Verwendung von SiRiN/SiCN als Wandmaterial automatisch Ätzstopps des Membranfreistellungsprozesses.
• - Druckdichte Seitenwände 23 zum Einschluss von Vakuum, wobei insbesondere der Innendruck variabel ist, beginnend bei minimal circa 1 mbar im Inneren des Sensors.
• - Umschließen von Kontaktbahnen aus polykristallinem Silizium durch die Seitenwände 23 - sogenannte „Runner“ - durch Oxidabscheidungen. Hierdurch wird ein Herausführen der elektrischen Signale aus dem Hohlraum 30, insbesondere einer evakuierten Kaverne ermöglicht.
• - Ausbildung von Anschlagstrukturen zwischen Kondensatorelektroden, hergestellt aus SiCN/SiRiN oder alternativ durch leitfähiges Membran-Material aus polykristallinem Silizium.

At least one embodiment of the invention provides or enables:

• - A realization of a MEMS pressure sensor 1 with thin nitride layers as a structural element. These can be made of SiCN or SiRiN or of another nonconducting material that can be selectively etched to HF
• Advantageously, tensile material is used as membrane material.
• - Closure of the SiCN / SiRiN membrane with a stress-adapted nitride at low pressure or by a laser reseal process. Other non-conductive materials may also be used, for example SiO ₂ , polyimides or the like.
• Use of polycrystalline silicon or another conductive material, in particular a metal or a semimetal, preferably germanium, in a SiCN / SiRiN-based pressure sensor for electrical contacting and / or for forming the capacitive measuring structures.
• - Realization of the connecting steles - "posts" - between nitride layer front and back by means of a U-shaped nitride trough, which is filled up with oxide.
• Use of a gas phase etch step or stiction-free wet release process to release the membrane. In particular, a gas phase etching step allows etching openings with a dimension below 0.5 microns.
• - Realization of side walls 23 SiCN and / or SiRiN with oxide filling / oxide core. These walls 23 especially when using SiRiN / SiCN as wall material automatically etch stops the diaphragm exemption process.
• - Print-proof sidewalls 23 to include vacuum, wherein in particular the internal pressure is variable, starting at a minimum of about 1 mbar inside the sensor.
• - Enclosing contact paths of polycrystalline silicon through the side walls 23 - so-called "Runner" - by oxide deposits. This results in a lead out of the electrical signals from the cavity 30 , in particular an evacuated cavern allows.
• - Formation of stop structures between capacitor electrodes, made of SiCN / SiRiN or alternatively by conductive membrane material made of polycrystalline silicon.

Although the present invention has been described in terms of preferred embodiments, it is not limited thereto, but modifiable in a variety of ways.

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

• DE 102016107275 A1 [0005]

Claims (11)

MEMS sensor (1) with a deflectable membrane (10, 12), wherein the deflectable membrane (10, 12) at least partially forms a boundary for a cavity (30) and wherein at least one element (22, 23) as a support element (22) for spacing the membrane (10, 12) from a boundary of the cavity (30) and / or as a limiting element (23) for limiting the cavity (30) is arranged, wherein the element (22, 23) at least partially Membrane material is made. MEMS sensor according to Claim 1 wherein the element (22, 23) is at least partially made of an insulating layer material, in particular wherein the insulating layer material is predominantly surrounded by membrane material. MEMS sensor according to one of Claims 1 - 2 , wherein the membrane material comprises zugverspannbares material. MEMS sensor according to one of Claims 1 - 3 wherein the membrane material comprises a compound of nitride. MEMS sensor according to one of Claims 1 - 4 wherein the membrane material comprises silicon rich nitride and / or silicon carbonitride. MEMS sensor according to one of Claims 1 - 5 , wherein the element (22, 23) is U-shaped from membrane material and filled with a second material. MEMS sensor according to one of Claims 1 - 6 in which at least one electrode (5, 8) is arranged in the cavity (30), which has at least one contact, which is led out of the cavity (30) and which is at least partially surrounded by insulating material outside the cavity (30). MEMS sensor according to one of Claims 1 - 7 wherein the material of the electrode (5, 8) comprises polycrystalline silicon. A method of making a MEMS sensor (1) having a deflectable diaphragm (10, 12) comprising the steps Providing (S1) a deflectably arranged membrane (10, 12), Providing (S2) a cavity (30), wherein the cavity (30) is at least partially delimited by the deflectably arranged membrane (10, 12), - arranging (S3) an element (22, 23) as a support element for spacing the membrane (10, 12) from a boundary of the cavity (30) and / or as a limiting element for defining the cavity (30), the element at least partially made of membrane material. Method according to Claim 9 , wherein for providing the deflectable arranged membrane (10, 12), the membrane material is arranged zugverspannt, in particular with a train between 25 MPa and 150 MPa. Method according to one of Claims 9 - 10 wherein providing the deflectably disposed membrane (10, 12) comprises depositing membrane material by means of an LPCVD and / or PECVD process.

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