DE102018211280B4 - MEMS sensor and method for manufacturing a MEMS sensor - Google Patents

Abstract

MEMS sensor element (1b) with a deflectably arranged membrane (4), comprising a substrate (2), a support structure (9) for the deflectably arranged membrane (4), the support structure (9) with the substrate (2) at least in one Area (80) is connected and wherein the membrane (4) is partially connected to the support structure (9), and wherein a closed space (40) is formed between the support structure (9) and the membrane (4), and an electrode structure (6 ), which is arranged in the closed space (40) at a distance from the support structure (9) and membrane (4), the support structure (9) and substrate (2) being connected to one another via a spring structure (15).

Description

Technical area

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

The invention also relates to a MEMS sensor.

The invention further relates to a chip with at least one MEMS sensor element.

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

State of the art

Although the present invention is generally applicable to any sensors with sensor elements with a diaphragm arranged in a steerable manner, the present invention is described with reference to a MEMS sensor in the form of a capacitive pressure sensor.

Arrangements and methods for producing capacitive pressure sensors are known, a stationary electrode being arranged on a substrate. An insulating sacrificial layer is then applied and structured over the electrode. A first part of a membrane layer is applied to this and narrow access holes are arranged in the later membrane area. Through these holes, the sacrificial layer under the membrane is removed in partial areas using an etching process. The access holes are then closed with a deposit. With suitable methods it can be achieved that a low pressure is enclosed in the cavity under the membrane. Further layer deposits on the membrane enable the membrane to be sealed tightly.

From scripture DE 10 2013 213 065 A1 MEMS sensor element with a deflectably arranged membrane, comprising a substrate and a support structure for the deflectably arranged membrane, is known. The carrier structure is connected to the substrate at least in one area. The membrane is partially connected to the support structure via the layers. A closed space is formed between the support structure and the membrane. An electrode structure is spaced apart from the support structure and membrane in the enclosed space 34 arranged.

From scripture US 2006/0108652 A1 a method for producing a MEMS component is known in which structures are applied to a substrate by means of sacrificial layers.

The DE 10 2016 216 234 A1 shows a micromechanical component with a substrate and a cap wafer. The substrate is the support structure for a membrane and is partially connected to the membrane. An electrode structure is arranged over the membranes.

Further documents that describe the construction of MEMS components with the aid of sacrificial layer structures and carrier structures are from the documents DE 10 2013 213 071 B3 and DE 10 2014 200 512 A1 known.

Disclosure of the invention

In one embodiment, the invention provides a MEMS sensor element with a deflectably arranged membrane, comprising a substrate, a support structure for the deflectably arranged membrane, wherein the support structure is connected to the substrate at least in one area and wherein the membrane is partially connected to the support structure and wherein a closed space is formed between the support structure and the membrane, and an electrode structure which is arranged in the closed space at a distance from the support structure and the membrane, the support structure and substrate being connected to one another via a spring structure.

In a further embodiment, the invention provides a MEMS sensor with a first MEMS sensor element according to one of claims 1-9, and with a second MEMS sensor element which is designed as a reference sensor element for the first MEMS sensor element.

In a further embodiment, the invention provides a chip with at least one MEMS sensor element according to one of claims 1-9.

• - Bereitstellen eines Substrats,
• - Aufbringen einer ersten Opferschicht auf das Substrat, insbesondere wobei die erste Opferschicht nachfolgend strukturiert wird,
• - Aufbringen einer Membranschicht auf die erste Opferschicht, insbesondere wobei die Membranschicht nachfolgend strukturiert wird,
• - Aufbringen einer zweiten Opferschicht,
• - Bereitstellen zumindest einer Elektrodenstruktur auf der zweiten Opferschicht mittels Aufbringen zumindest einer Elektrodenschicht, welche anschließend strukturiert wird,
• - Aufbringen einer Isolationsschicht auf die Elektrodenstruktur, welche anschließend strukturiert wird,
• - Bereitstellen einer Trägerstruktur auf der Isolationsschicht mittels Aufbringen zumindest einer Trägerschicht, welche anschließend strukturiert wird,
• - Entfernen der Opferschichten mittels zumindest eines Zugangs zur jeweiligen Opferschicht, und
• - Verschließen des zumindest einen Zugangs.

In a further embodiment of the invention provides a method for producing a MEMS sensor element with a deflectably arranged membrane, comprising the steps

• - providing a substrate,
• Applying a first sacrificial layer to the substrate, in particular wherein the first sacrificial layer is subsequently structured,
• Applying a membrane layer to the first sacrificial layer, in particular wherein the membrane layer is subsequently structured,
• - applying a second sacrificial layer,
• - Providing at least one electrode structure on the second sacrificial layer by applying at least one electrode layer, which is then structured,
• - Application of an insulation layer on the electrode structure, which is then structured,
• - Provision of a carrier structure on the insulation layer by applying at least one carrier layer, which is then structured,
• Removing the sacrificial layers by means of at least one access to the respective sacrificial layer, and
• - Closing the at least one access.

One of the advantages achieved in this way is that stress and bending can be reduced considerably, since the membrane and support structure can be decoupled from the substrate. Another advantage is that the membrane is essentially directly connected to the carrier layer and the membrane span or the membrane diameter and thus the sensitivity of the MEMS sensor element is very well defined.

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

According to an advantageous development, the membrane is arranged at a distance from the support structure and substrate between them. One of the advantages achieved in this way is that the membrane is well protected by the arrangement between the carrier layer and the substrate.

The spring structure can be designed in such a way that the robustness of the carrier structure is increased without influencing the sensitivity of the MEMS sensor element, more precisely the bending properties of the membrane, too much. This can increase the robustness of the support structure.

According to a further advantageous development, the membrane is designed to be continuous and / or the membrane, support structure and electrode structure are made from the same material. If the membrane is made continuous, the membrane can be manufactured easily and the sensitivity of the MEMS sensor element is very well defined. If the membrane, the support structure and the electrode structure are made of the same material, such a structure has almost no intrinsic stress and, in particular, if polycrystalline silicon is used as the material for this, it also has very good temperature behavior.

According to a further advantageous development, the electrode structure is connected to the carrier structure via at least one insulating layer area, in particular wherein the insulating layer area is formed by a dielectric layer. In particular, the insulating layer region is designed to provide only punctiform connections between the carrier structure and the electrode structure. One of the advantages achieved in this way is that the carrier structure can be connected to the electrode structure in a reliable manner. Furthermore, a basic capacitance between the electrode structure and the carrier structure can be reduced, which enables a more precise evaluation of a change in capacitance.

According to a further advantageous development, the carrier structure and membrane are connected to one another via a circumferential connection, an opening being arranged in the region of at least one connection between the carrier structure and the substrate. The advantage of this is that, on the one hand, it enables the support structure and membrane to be reliably fixed to one another and, on the other hand, simple manufacture. Another advantage is that the electronic structure can thus be led electrically to the outside in a simple manner, that is to say contacted, and it is also optionally possible, for example, to lead an etching channel and / or a ventilation channel into the area of the membrane.

According to a further advantageous development, a distance between membrane and substrate is less than a fifth, preferably less than a tenth of the membrane diameter. This has the advantage that if water collects in the space between the membrane and the substrate and this freezes, the expansion of the water during freezing can be compensated for by moving the membrane and the support structure. In other words, only such a small amount of water is allowed in this area that the MEMS sensor element is not destroyed when the water freezes, but compensation takes place through movement of the membrane and support structure.

According to a further advantageous development, at least one overload stop is arranged for the membrane, preferably on the support structure. A short circuit between the membrane and the electrode structure in the event of an overload can thus be prevented in a reliable manner.

According to a further advantageous development, at least one through-contact for making electrical contact with the electrode structure is from arranged on the side of the substrate facing away from the support structure. In other words, in this way the electrical contacts can be routed over the back of the substrate, which enables a simpler construction on the front of the substrate.

According to an advantageous development of the MEMS sensor, the second MEMS sensor element has a membrane and an electrode structure, wherein the first MEMS sensor element in its starting position has a first distance between its membrane and its electrode structure in at least one partial area and wherein the second MEMS sensor element In its starting position, the sensor element has a second distance between its membrane and its electrode structure in at least one partial area, and the first distance and the second distance are different. One of the advantages achieved with this is that reference capacities can be defined in a simple manner. For example, with the same area of an electrode of the electrode structure, a reference capacitance can be provided which corresponds to that of a membrane that has already been deflected. Another advantage is that it is possible to set a desired distance between the membrane and the electrode structure in a particularly precise manner.

According to an advantageous development of the MEMS sensor, the second MEMS sensor element is designed according to one of claims 1-9 and the membrane of the second MEMS sensor element is more difficult to deflect by at least a factor of 2 compared to that of the first MEMS sensor element. The advantage of this is that the measuring range of the MEMS sensor can be increased overall, since the MEMS sensor elements are differently sensitive for different pressure ranges.

According to an advantageous development of the MEMS sensor, the first and second MEMS sensor elements have a common carrier structure, at least one of the two MEMS sensor elements being connected to the carrier structure in its deflectable area via a stiffening device. A reference capacitance can thus be made available in a particularly simple manner, which increases the accuracy of the MEMS sensor overall.

According to an advantageous development of the MEMS sensor, the first and second MEMS sensor elements are arranged on the same substrate and are of essentially identical geometrical design. This enables a second MEMS sensor element to be produced in a simple manner, which can be well matched to the first MEMS sensor element. The second MEMS sensor element can then be used, for example, as a reference element with a very well-defined capacitance in relation to the basic capacitance of the first MEMS sensor element, or as an element for expanding the measuring range of the MEMS sensor, the overlap of the two measuring areas being very precisely defined.

According to a further advantageous development of the method, a third sacrificial layer is applied and in particular structured before the insulation layer is applied. This enables a particularly simple application of the subsequent insulation layer. This means that the electrode structure can only be suspended from the support structure at individual points. This in turn makes it possible to reduce the amount of dielectric material in the area of the movable membrane and the electrode structure and the carrier layer. Harmful effects due, for example, to different expansion coefficients between the dielectric material and the conductive materials can thus be significantly reduced.

According to a further advantageous development of the method, at least one access is formed in the substrate and / or in at least the first sacrificial layer. In this way, the sacrificial layers can later be removed in a particularly simple manner and the membrane exposed.

Further important features and advantages of the invention emerge from the subclaims, from the drawings, and from the associated description of the figures on the basis of the drawings.

It goes without saying that 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.

Preferred designs and embodiments of the invention are shown in the drawings and are explained in more detail in the following description, with the same reference symbols referring to the same or similar or functionally identical components or elements.

Figure list

• 1 einen MEMS-Sensor gemäß einer Ausführungsform der vorliegenden Erfindung;
• 2 einen MEMS Sensor gemäß einer Ausführungsform der vorliegenden Erfindung;
• 3 einen MEMS-Sensor gemäß einer Ausführungsform der vorliegenden Erfindung;
• 4 einen Chip gemäß einer Ausführungsform der vorliegenden Erfindung;
• 5-14 Schritte eines Verfahrens gemäß einer Ausführungsform der vorliegenden Erfindung;
• 15 Schritte eines Verfahrens gemäß einer Ausführungsform der vorliegenden Erfindung; und
• 16 Schritte eines Verfahrens gemäß einer Ausführungsform der vorliegenden Erfindung.

Show in schematic form and in cross section

• 1 a MEMS sensor according to an embodiment of the present invention;
• 2 a MEMS sensor according to an embodiment of the present invention;
• 3 a MEMS sensor according to an embodiment of the present invention;
• 4th a chip according to an embodiment of the present invention;
• 5-14 Steps of a method according to an embodiment of the present invention;
• 15th Steps of a method according to an embodiment of the present invention; and
• 16 Steps of a method according to an embodiment of the present invention.

Embodiments of the invention

1 Figure 3 shows a MEMS sensor according to an embodiment of the present invention.

In 1 is a MEMS sensor with a MEMS sensor element 1b shown. The MEMS sensor element 1b has the following layer structure from bottom to top. On a substrate 2 is an insulating layer 3 arranged that is structured. On this structured insulating layer 3 is a membrane 4th arranged, which is formed movable in the vertical direction. On top of the membrane 4th and spaced therefrom is an electrode structure 6th arranged over punctual insulating layer connections 8th with one above the electrode structure 6th arranged support structure 9 connected is. The support structure 9 shows entrances 30th to the room 40 on that through the membrane 4th and the support structure 9 is formed. The entrances 30th are here on another layer 10 , on which a contact 11 is arranged, sealed pressure-tight. The space between the substrate 2 and membrane 4th has a - in 1 on the right - opening 16 on. In addition, there is a distance between the membrane 4th and substrate 2 less than 1/5, preferably less than 1/10 of the membrane diameter 60 . The membrane 4

In the electrode structure 6th as well as in the upper area of the substrate 2 below the deflection area of the membrane 4th are etching channels 20th , 21st arranged. In the area in the middle of the deflectable area of the membrane 4th is a stop 50 for the membrane 4th on the support structure 9 arranged. Polycrystalline silicon can be used here as the membrane material. The membrane 4th is not provided with access holes, thereby reaching the membrane 4th can only be made from one or a few materials. The membrane 4th is laterally - here by means of vertical connections 64a , 64b Made of electrode material on the left and right of the deflectable area of the membrane 4th - directly with the support structure 9 coupled. The left connection 64a has an opening 64 ' or an interruption of a circulating connection, for example 64a , 64b on, through which the electrode structure 6th is led out laterally to the left for electrical contacting. As described above is between membrane 4th and support structure 9 an electrode structure 6th provided that only via small isolation islands 8th punctually with the support structure 9 connected is. In the room 40 between membrane 4th and support structure 9 a reference pressure is included. The deflection of the membrane 4th at pressure is measured by measuring the change in capacitance between the membrane 4th and the electrode structure 6th certainly. The membrane 4th is in the 1 between the substrate 2 and the support structure 9 arranged, but can also be arranged in another way. The support structure 9 and the membrane 4th are essentially "floating" above the substrate 2 arranged. Like here in 1 the support structure is preferred 9 and the membrane 4th only in a partial area 80 , 80 ' each with the substrate 2 connected. The entrances are more precise on the left 30th in 1 in the area 80 ' the support structure 9 about the material of the electrode structure 6th , Material of the membrane 4th and the material of the insulating layer 3 with the substrate 2 connected. On the right in the area 80 , so to the right of the entrances 30th is the support structure 9 about the material of the electrode structure 6th , with the membrane 4th and this over material of the insulating layer 3 with the substrate 2 connected. The sub-area 80 ' is preferably on that of the opening 16 remote side of the membrane 4th arranged, the sub-area 80 preferably in the area of the definition of the electrode structure 6th Via membrane material and insulating material on the substrate 2 and / or on the side of the entrances 30th arranged which the area of the support structure 9 with the insulating layer connections 8th is turned away. It is also possible to have support structure 9 and membrane 4th in several sub-areas with the substrate 2 to connect, with at least a partial area 15th then has resilient properties, as shown in 4th is shown.

2 Figure 3 shows a MEMS sensor according to an embodiment of the present invention.

In 2 is essentially a MEMS sensor 1 according to 1 shown. In contrast to the MEMS sensor 1 according to 1 is at the MEMS sensor 1 according to 2 now instead of the stop 50 a stiffener 51 for the membrane 4th arranged. Essentially, that's the stop 50 of the 1 been designed as a stiffener by pulling this up to the membrane 4th has been extended in your resting position and connected to it. This can be done on the same substrate 2 not just a first MEMS sensor element 1b but also a second MEMS sensor element 1a in the form of a reference MEMS sensor element which, for example, has the same capacitance as the first MEMS sensor element 1b , and in particular to all external parameters, except for pressure, in the same way as the first MEMS sensor element 1b responds. With an evaluation circuit that measures the capacity of the first MEMS sensor element 1b with the capacitance of the reference MEMS sensor element 1a compares, drift effects that are not due to a change in pressure can be eliminated. Furthermore, in the reference MEMS sensor element 1a during its production, a smaller sacrificial layer thickness between the stiff membrane there 4th and the electrode structure 6th are provided. First MEMS sensor element 1b and its reference MEMS sensor element 1a are then essentially built geometrically similar. At a target working pressure that is higher than that in the first MEMS sensor element 1b included reference pressure, the capacity of the first MEMS sensor element can still 1b with the capacitance of the reference MEMS sensor element 1a match, so that a particularly precise and drift-free evaluation, in particular with the target working pressure, is made possible. The second or reference MEMS sensor element 1a points in 2 in its starting position in at least one sub-area 72 a second distance 70 between the common membrane 4th and the common electrode structure 6th on. The first MEMS sensor element has accordingly 1b in its starting position in at least one sub-area 73 a first distance 71 between the common membrane 4th and its electrode structure 6th on. In 2 are first distance 71 and second distance 70 different sizes, in particular the first distance 71 greater than the second distance 70 .

3 Figure 3 shows a MEMS sensor according to an embodiment of the present invention.

In 3 is essentially a MEMS sensor 1 according to 1 shown. In contrast to the MEMS sensor 1 according to 1 are at the MEMS sensor 1 according to 3 now instead of the entrances or access channels 30th in the support structure 9 corresponding accesses or channels 30 ' in the substrate 2 arranged. The contacting of the electrode structure 6th takes place by means of a via 12th in the substrate 2 . The entrances 30 ' are then using another layer 10 ' and a contact 11 ' for contacting the plated-through hole 12th locked.

4th Figure 3 shows a MEMS sensor according to an embodiment of the present invention.

In 4th is a chip 100 shown in ball grid array design. The structure of the chip 100 in 4th from bottom to top is as follows: on a ball grid array 101 , BGA for short, is an application-specific integrated circuit 102 , ASIC for short, 102 arranged by means of a bond wire connection 103 from the BGA 101 is contacted. On top of the ASIC 102 is a MEMS sensor 1 arranged, essentially according to 1 is trained. In contrast to the MEMS sensor 1 according to 1 are at the MEMS sensor 1 according to 4th now the entrances 30th not directly on the support structure 9 closed, but above the support structure 9 becomes a cap wafer 13 The accesses are bonded at a defined pressure and in the bonding process 30th through the cap wafer 13 hermetically sealed. The cap wafer 13 serves not only to close the entrances 30th , but also for mechanical protection of the support structure 9 and is in the area above the membrane 4th from the support structure 9 spaced. The support structure 9 is about contacting 11 with the cap wafer 13 connected. ASIC 102 and MEMS sensor 1 are by means of a bond wire connection 104 electrically connected and in a housing 105 Enclosed on the side. On top of the cap wafer 13 and the housing 105 is a windproof, waterproof, but water vapor permeable and therefore breathable membrane 14th arranged to avoid water getting into the MEMS sensor 1 penetrates. In addition, the support structure 9 via a spring structure 15th additionally on the substrate 2 anchored.

The 5-14 show steps of a method according to an embodiment of the present invention.

In 5 is a substrate 2 shown. On the substrate 2 are preferably etching channels 20th created. In particular, very narrow trenches are formed in the substrate 2 etched, which preferably open downwards, so that a cavity in a subsequent oxide deposition 20 ' arises. Alternatively, etching channels can be in a later sacrificial layer between the substrate 2 and a membrane layer are produced and / or these are produced in one of the subsequent steps before removal of the sacrificial layer, preferably a cavity is produced from the rear side of the substrate to the sacrificial layer.

In 6th is now the situation after the deposition of a sacrificial layer 3 and a membrane layer 4th shown. The sacrificial layer 3 is preferably made from an oxide compound. The sacrificial layer 3 can also be subsequently structured in order to produce substrate contacts, for example. Two or more sacrificial layers can also be deposited and structured. Furthermore, the sacrificial layer can be etched over one or more times 3 can be reduced in thickness in individual areas. This can be used, for example, to create stiffening grooves in the membrane layer 4th can be generated in individual areas. The membrane layer 4th is preferably made of polysilicon. The membrane layer 4th can subsequently also be structured, for example in areas outside the membrane 4th to be used as a conductor track.

7th shows the situation after applying and structuring a second sacrificial layer 5 .

Here is the second sacrificial layer 5 structured with cutouts 5a in order, for example, over a subsequently applied electrode structure 6th a connection between membrane 4th and a backing layer 9 to enable. Optionally, two or more sacrificial layers can also be deposited and structured. Recesses are only indicated 5a ' that are made outside of the drawing plane. It is also possible to etch the sacrificial layer over one or more time 5 to reduce their thickness in individual areas. This allows stops with a reduced distance 70 , 71 or reference capacitances with a reduced basic distance or areas with a larger distance 70 , 71 to reduce parasitic capacitances. Etching channels can optionally also be used in the sacrificial layer 5 be generated.

8th shows the situation after the deposition and structuring of recesses 6a in an electrode structure 6th .

A structuring is preferably used, such as that described in DE 10 2011 080 978 A1 and which is hereby incorporated by reference. This avoids topographies and creates cavities that can be used as etching channels. The structuring 5a , 5a ' , 6a are manufactured in such a way that the electrode structure 6th with the substrate 2 remains connected despite further manufacturing steps, at the same time a connection of a later carrier structure 9 with the substrate 2 is made possible without the electrode structure 6th with the later support structure 9 to connect to the substrate 2 to connect.

A third sacrificial layer is now optional 7th separated and structured with cutouts 7a , as in 9 shown. Recesses are only indicated 7a ' that are made outside of the drawing plane. These correspond to the recesses 7a ' established so that this then the left connection 64a with opening 64 ' for leading out the electrode structure 6th form like this in the further 11-14 is shown.

Then an insulation layer is applied 8th secluded and structured, as in 10 shown. A nitride layer or a silicon-rich nitride layer is preferably deposited.

This is followed by a backing layer 9 secluded and with accesses 30th to the sacrificial layers 3 , 5 , 7th structured as in 11 is shown. Is preferred as the carrier layer 9 deposited a polysilicon layer. The sum of the thickness of the carrier layer 9 and the electrode structure 6th is chosen to be at least twice as thick as the thickness of the membrane 4th . The entrances 30th are preferably in the area of the support structure 9 made by not making any insulating layer connections 8th are arranged, preferably directly adjacent to the area in which the insulating layer connections 8th Support structure 9 and electrode structure 6th connect and on the opposite side of the side opening 16 . This also increases the areas 80 , 80 ' formed as in the description for 1 described.

Subsequently, the sacrificial layers 3 , 5 , 7th etched the membrane 4th so optional, as in 12th is shown.

Then, as in 13 depicted a clasp 10 of the cavity 40 between membrane 4th and backing layer 9 by closing the entrances 30th , whereby a reference pressure is set. For this purpose, procedures as described above are used. It can be both the membrane 4th and the support structure 9 as well as the open, i.e. accessible oxides of the insulating layers 3 , 5 , 7th be covered with a thin protective layer. An oxide layer or a nitride layer or an aluminum oxide layer is preferably used for this purpose. For this purpose, an ALD deposition method, that is to say an atomic layer deposition method, is preferably used. The protective layer is preferably less than half as thick as the membrane 4th deposited.

Furthermore, a further protective structure can be placed over the carrier structure 9 be applied. Above the support structure 9 can be applied with a further sacrificial layer, preferably an oxide layer, a mechanical and electrical protective layer, preferably a polysilicon layer, and, if necessary, an aluminum layer as well. Optionally, a cap can be bonded on, with which the reference pressure is preferably set at the same time.

15th shows steps of a method according to an embodiment of the present invention.

In 15th steps of a manufacturing method for a MEMS sensor element are shown. This includes the following steps.

In a first step T1 becomes a substrate 2 etching channels are provided and preferably 20th created.

In a second step T2 becomes a sacrificial layer 3 secluded and especially structured.

In a third step T3 becomes a membrane layer 4th secluded and structured.

In a fourth step T4 becomes another layer of sacrifice 5 deposited.

In a fifth step T5 becomes an electrode layer 6th deposited and structured, wherein in particular etching channels are generated.

In a sixth step T6 becomes a sacrificial layer 7th secluded and structured.

In a seventh step T7 becomes an insulation layer 8th secluded and structured.

In an eighth step T8 becomes a carrier layer 9 secluded and structured.

In a ninth step T9 the sacrificial layers are etched and in a tenth step T10 there is a closure 10 of the between membrane 4th and backing layer 9 formed cavity.

16 shows steps of a method according to an embodiment of the present invention.

In 16 steps of a method for producing a MEMS sensor element with a deflectably arranged membrane are shown.

This is done in a first step S1 providing a substrate 2 .

In a second step S2 a first sacrificial layer is applied 3 onto the substrate, in particular wherein the first sacrificial layer 3 is structured below.

In a third step S3 a membrane layer is applied 4th on the first sacrificial layer 3 , in particular being the membrane layer 4th is structured below.

In a fourth step S4 a second sacrificial layer is applied 5 .

In a fifth step S5 at least one electrode structure is provided 6th , 6a on the second sacrificial layer 5 by applying at least one electrode layer 6th which is then structured.

In a sixth step S6 an insulation layer is applied 8th on the electrode structure 6th , 6a .

In a seventh step S7 a support structure is provided 9 , 30th on the insulation layer 8th by applying at least one carrier layer 9 which is then structured.

In an eighth step S8 the sacrificial layers are removed 3 , 5 by means of at least one access 30th to the respective sacrificial layer 3 , 5 .

In a ninth step S9 the at least one access is closed 30th .

• Eine dünne Membran 4 wird mit einem definierten Abstand über einem Substrat 2 angeordnet. Im Substrat 2 oder in einer Opferschicht 3 zwischen Substrat 2 und Membran 4 werden bevorzugt Ätzkanäle 20 angeordnet, damit die Membran 4 schnell und definiert unterätzt werden kann. Vorteilhaft ist ein Abstand zwischen Membran 4 und Substrat 2, der geringer ist als 1/10 des Membrandurchmessers. Sammelt sich Wasser in Raum zwischen Membran 4 und Substrat 2 und gefriert, so kann die Ausdehnung des Wassers beim Gefrieren durch die Bewegung der Membran 4 und einer Trägerstruktur 9 kompensiert werden.

In other words, the present invention provides the following features in identical or different embodiments:

• A thin membrane 4th is at a defined distance above a substrate 2 arranged. In the substrate 2 or in a sacrificial layer 3 between substrate 2 and membrane 4th etching channels are preferred 20th arranged so the membrane 4th can be undercut quickly and in a defined manner. A distance between the membrane is advantageous 4th and substrate 2 that is less than 1/10 of the diaphragm diameter. Water collects in the space between the membrane 4th and substrate 2 and freezes, so can the expansion of water when it freezes due to the movement of the membrane 4th and a support structure 9 be compensated.

Alternatively, access can also be made from the rear 30 ' through the substrate 2 to the membrane 4th etched, so that the protection of the membrane is omitted 4th , but it can also be a simple and defined etching of the sacrificial layer 3 respectively. This creates a print access from the back of the substrate 2 enables, which increases flexibility.

Above the membrane 4th is with a defined distance 70 , 71 an electrode structure 6th intended. This is done through a sacrificial layer 5 between membrane 4th and electrode structure 6th reached. Multiple sacrificial layers can also be used to provide different distances between electrode structures 6th and membrane 4th to realize. It can be advantageous, for example, in areas outside the electrode structure 6th or at the edge of the electrode structure 6th a greater distance 70 , 71 to adjust the basic capacitance of the MEMS sensor element 1b to be kept low relative to a change in capacitance. Furthermore, with smaller distances and additional electrode structures that are at membrane potential, defined stops 50 the membrane 4th against overload can be defined to short circuit the membrane 4th with the counter electrode in the form of the electrode structure 6th to prevent in case of overload. Reference capacitances can also be defined which are geometrically very similar to the actual sensor structure. This allows drift effects to be compensated. With a smaller sacrificial layer thickness, for example, with the same electrode area, the same basic capacitance can be made possible for the reference capacitance as that capacitance at the working pressure of an already deflected sensor membrane, as in FIG 2 is shown. The membrane can continue 4th the reference capacitance in the same way as the membrane 4th be released. The membrane 4th can have additional electrode structure elements 51 that are a link between membrane 4th and support structure 9 produce, be stiffened. It is favorable if these fasteners 51 in the same way and with similar geometry as the stop elements 50 the membrane 4th be arranged or formed.

The electrode structure 6th is further through a dielectric layer 8th on the support structure 9 "Hung up". It is advantageous between electrode structure 6th and support structure 9 additionally a sacrificial layer 7th to provide that allows the electrode structure 8th only at a few points on the support structure 9 hang up. Advantageously, the membrane 4th , the electrode structure 6th and the backing layer 9 made of the same material, so that no intrinsic stress is "built into" this layer structure. A particularly advantageous material is polycrystalline silicon. It is also advantageous in this context to use small suspensions 8th between electrode structure 6th and support structure 9 in order to reduce the amount of foreign material, i.e. material with different physical properties. In this way, for example, undesirable bimetal effects due to different expansion coefficients can be reduced.

The membrane 4th is advantageously circumferential with the support structure 9 connected. Only in one area 80 where the support structure 9 with the substrate 2 is connected, said connection is canceled in this, on the one hand to the electrode structure 6th to be able to lead electrically to the outside and to be able to optionally lead an etching channel and a ventilation channel into the membrane area.

The support structure 9 is preferably only at one point with the substrate in order to achieve good stress decoupling 2 connected. On a chip 100 can have multiple support structures 9 are provided. It can also be on a support structure 9 several membranes can be arranged. Will be a large support structure 9 provided, it can advantageously be fixed to the substrate at one point 2 get connected. The electrical feed to the electrode structure can then also be used at this fixed position 6th respectively. The support structure can be used in other places 9 about springs 15th additionally on the substrate 2 be anchored. The feathers 15th can be chosen so that they reduce the robustness of the support structure 9 but increase the stress sensitivity of the MEMS sensor element 1b do not influence the bending too much.

The reference pressure in the cavity 40 between membrane 4th and support structure 9 can in a simple case by etching accesses in the carrier structure 9 , a sacrificial layer etch through these etch accesses 30th and a subsequent closure 10 the etching accesses 30th can be achieved by, for example, oxide deposition.

However, it is particularly advantageous to use the etching access 30th and the containment area of the reference pressure over the suspension of the support structure 9 from the area of the movable membrane 4th divert and the clasp 10 in an area where the support structure 9 with the substrate 2 is connected to provide. To make this possible, either inside the electrode structure 6th , 21st and / or in the sacrificial layer 5 between membrane 4th and electrode structure 6th or in the sacrificial layer 7th between membrane 4th and backing layer 7th Etching channels are provided. Etching channels are understood to mean either cavities or materials, for example oxides, doped oxides or the like, which are etched faster than the dielectric material, for example nitride, silicon-rich nitride or the like between the electrode structure, can also be used 6th and backing layer 9 .

The closure 10 of the etching access 30th can be used to include the reference pressure. This can preferably be done by an oxide deposition (reference number 10 ), or by a deposition of polycrystalline silicon, by an epitaxial silicon deposition, by a metal deposition or a melting process, in particular a laser reseal process, in particular silicon, preferably under vacuum.

In a particularly advantageous embodiment, a cap wafer can also be used 13 onto a sensor wafer with the MEMS sensor 1 be bonded. A water-impermeable membrane can also be used 14th on this layer 13 applied to water in the MEMS sensor 1 to avoid. The bonding process also allows an etching access 30th be locked. At the same time, the cap wafer 13 to protect the support structure 9 be used. It can also create a step in the area of the pads 11 for wire bonding. In this variant, the component formed in this way can be molded into an inexpensive package, with the cap 13 with a pressure access protrudes from the mold housing and the sensitive wire bonds 103 , 104 through the molding compound 105 are protected. A water-impermeable membrane can also be used 14th applied to the housing to keep water in the sensor element 1 to avoid.

For electrical contacting, electrical contacts can be made via TSVs, vias 12th , be guided over the back of the substrate. In particular, the inclusion of the reference print and the sacrificial layer etching can be via the rear side of the substrate 2 together with the TSV manufacturing process. In this case in particular, it can be advantageous over the support structure 9 to arrange a further, preferably electrically conductive, layer over a sacrificial layer. This can be used as mechanical and electrical protection for the MEMS sensor 1 serve. A water-impermeable membrane can also be used 14th applied to, as described above, water in the MEMS sensor 1 to avoid.

• • Vollständige Entkopplung von Membran und Trägerstruktur vom Substrat.
• • Stress-Unabhängigkeit, insbesondere kein intrinsischer Stress.
• • Gutes Temperaturverhalten.
• • Kostengünstige Herstellung.
• • Einfache Herstellung.
• • Hohe Genauigkeit und Empfindlichkeit.
• • Schutz der Membran.

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

• • Complete decoupling of membrane and support structure from the substrate.
• • Stress independence, especially no intrinsic stress.
• • Good temperature behavior.
• • Inexpensive to manufacture.
• • Easy to manufacture.
• • High accuracy and sensitivity.
• • Protection of the membrane.

Although the present invention has been described on the basis of preferred exemplary embodiments, it is not restricted thereto, but rather can be modified in many ways.

Claims (16)

MEMS sensor element (1b) with a deflectably arranged membrane (4), comprising a substrate (2), a support structure (9) for the deflectably arranged membrane (4), the support structure (9) being connected to the substrate (2) at least in one region (80) and the membrane (4) being partially connected to the support structure (9) is, and wherein a closed space (40) is formed between the support structure (9) and the membrane (4), and an electrode structure (6) which is arranged in the closed space (40) at a distance from the support structure (9) and membrane (4), wherein the support structure (9) and substrate (2) are connected to one another via a spring structure (15). MEMS sensor element (1b) according to Claim 1 , wherein the membrane (4) is arranged at a distance from the support structure (9) and substrate (2) between them. MEMS sensor element (1b) according to one of the Claims 1 - 2 , wherein the membrane (4) is formed continuously and / or membrane (4), support structure (9) and electrode structure (6) are made of the same material. MEMS sensor element (1b) according to Claim 3 wherein the material comprises polycrystalline silicon. MEMS sensor element (1b) according to one of the Claims 1 - 4th wherein the electrode structure (6) is connected to the carrier structure (9) via at least one insulating layer region (8), in particular wherein the insulating layer region (8) is formed by a dielectric layer. MEMS sensor element (1b) according to one of the Claims 1 - 5 , wherein the support structure (9) and membrane (4) are connected to one another via a circumferential connection, an opening (16) being arranged in the region of at least one connection between the support structure (9) and the substrate (2). MEMS sensor element (1b) according to one of the Claims 1 - 6th , wherein a distance between membrane (4) and substrate (2) is less than 1/5, preferably less than 1/10 of the membrane diameter (60). MEMS sensor element (1b) according to one of the Claims 1 - 7th , wherein at least one overload stop (50) for the membrane (4), preferably on the support structure (9), is arranged. MEMS sensor element (1b) according to one of the Claims 1 - 8th wherein at least one through-contact (12) for electrical contacting of the electrode structure (6) is arranged on the side of the substrate (2) facing away from the carrier structure (9). MEMS sensor (1) with a first MEMS sensor element (1b) according to one of the Claims 1 - 9 , and with a second MEMS sensor element (1a), which is designed as a reference sensor element for the first MEMS sensor element (1b). MEMS sensor according to Claim 10 , wherein the second MEMS sensor element (1a) has a membrane (4) and an electrode structure (6), and wherein the first MEMS sensor element (1b) in its starting position in at least one partial area (73) has a first distance (71) between its Membrane (4) and its electrode structure (6) and wherein the second MEMS sensor element (1a) in its starting position in at least one partial area (72) has a second distance (70) between its membrane (4) and its electrode structure (6) and wherein the first distance (71) and the second distance (70) are different. MEMS sensor according to Claim 10 or 11 , wherein the second MEMS sensor element (1a) according to one of the Claims 1 - 9 and the membrane (4) of the second MEMS sensor element (1a) is more difficult to deflect by at least a factor of 2 compared to that of the first MEMS sensor element (1b). MEMS sensor according to one of Claims 10 - 12th , the first and second MEMS sensor elements (1a, 1b) having a common carrier structure (4), at least one of the MEMS sensor elements (1a, 1b) being connected to the carrier structure (9) in its deflectable area via a stiffening device (51) is. MEMS sensor according to one of Claims 10 - 13 , wherein the first and second MEMS sensor element (1a, 1b) are arranged on the same substrate (2) and are geometrically essentially identical. Chip (100) with at least one MEMS sensor element (1) according to one of the Claims 1 - 9 . Method for producing a MEMS sensor element (1b) with a deflectably arranged membrane (4), comprising the steps - providing (S1) a substrate (2), - Application (S2) of a first sacrificial layer (3) on the substrate, - Application (S3) of a membrane layer (4) on the first sacrificial layer (3), in particular wherein the membrane layer (4) is subsequently structured, - Application (S4) of a second sacrificial layer (5), - Providing (S5) at least one electrode structure (6, 6a) on the second sacrificial layer (5) by applying at least one electrode layer (6), which is then structured, - Application (S6) of an insulation layer (8) on the electrode structure (6, 6a), which is then structured, - providing (S7) a carrier structure (9, 30) on the insulation layer (8) by applying at least one carrier layer (9), which is then structured, - removing (S8) the sacrificial layers (3, 5) by means of at least one access (30) to the respective sacrificial layer (3, 5), and - Closing (S9) the at least one access (30), the carrier structure (9) and substrate (2) being connected to one another via a spring structure (15).

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