MEMS component with thermally insulating covering

Abstract

A MEMS component with a substrate and a first covering, wherein an interior space is formed between the substrate and the first covering, wherein a MEMS element is arranged in the interior space, wherein the MEMS element is designed to interact with a fluid, wherein the first covering is fixedly connected to the substrate, wherein a thermally insulating second covering is provided between the MEMS element and the first covering, wherein the second covering is fastened to the first covering in a frictionally engaging and / or interlocking manner, wherein there is at least partially an air space between the first covering and the second covering.

Description

[0001] Description

[0002] title

[0003] MEMS component with thermally insulating cover

[0004] The invention relates to a MEMS component according to claim 1.

[0005] State of the art

[0006] From US 10793419 and US 11711641, MEMS devices are known in which a MEMS device has a support and a cover, wherein a layer element is applied to the inside of the cover. The layer element is in direct contact with the inside of the cover.

[0007] US patent 2022 / 0159360 A1 discloses a MEMS component that is covered by two covers. The two covers are spaced apart from each other and each is rigidly connected to the carrier. The sensor and an evaluation circuit are arranged on the carrier inside the inner cover.

[0008] Disclosure of the invention

[0009] The object of the invention is to provide an improved MEMS device.

[0010] The problem of the invention is solved by the independent patent claims. Further developments of the invention are described in the dependent claims.

[0011] A MEMS component is proposed comprising a carrier and a first cover, wherein an interior space is formed between the carrier and the first cover, wherein a MEMS element is arranged in the interior space, wherein the MEMS element is designed to interact with a fluid, wherein the first cover is firmly connected to the carrier, wherein a thermally insulating second cover is provided between the MEMS element and the first cover, wherein the second cover is attached to the first cover by force and / or form-fitting, and wherein an air space is formed at least partially between the first cover and the second cover.

[0012] The proposed MEMS device features a design that enables an improved signal-to-noise ratio through enhanced noise performance. Therefore, the MEMS device can be smaller for the same power output or more powerful for the same power output. This principle can be applied not only to acoustic MEMS devices but also to pressure sensing in pressure sensors. Furthermore, thermal noise components of the MEMS element's sensor signal can be reduced through non-adiabatic energy losses at the package surface.

[0013] In a further development, at least one spacer is provided between the first and second covers, defining the distance between them. This enables a more stable structure. Furthermore, the air space is protected from compression even under higher pressure differentials. The spacer can be designed as a local thickening of the cover material of the first and / or second cover, as a local indentation or protrusion of the cover material of the first and / or second cover, or as a separate element.

[0014] In a training course, the spacer is integrated as part of the first and / or second cover. This allows for a simpler assembly.

[0015] In a further development, a barrier element is provided between the airspace and the interior. This barrier element seals the airspace from the interior, specifically sealing it in such a way that only slow pressure equalization (within a frequency range <20 Hz) is possible between the airspace and the interior. This improves the insulating effect of the airspace. Air exchange can be achieved either by selecting a material for the second cover with suitable gas permeability, by the barrier element, and / or by targeted perforation of the second cover. Like the spacer, the barrier element can be designed as a local thickening of the cover material of the first and / or second cover, as a local indentation of the cover material of the first and / or second cover, and / or as a separate element.

[0016] In a further development, the sealing element is designed in the form of a fluid layer, whereby the fluid layer completely seals the airspace from the interior, bearing against the second cover and the first cover and / or the support. In this way, a simple seal of the airspace is achieved without mechanically connecting the second cover to the support.

[0017] In a further development, the locking element is designed as a mechanical sealing element, wherein the sealing element is formed as part of the first and / or second cover, and wherein the sealing element abuts the first and / or the second cover and / or the carrier in a sealing manner. In this way, sufficient sealing can be achieved with simple means. In addition, the mechanical stability of the second cover is improved. Furthermore, the mechanical sealing element can achieve a holding function of the second cover to the first cover, in particular through a snap-fit ​​connection and / or a clamping connection and / or an adhesive bond between the first and second covers.

[0018] In a further development, the first and second covers each have a trough-like shape with a base and four side surfaces, wherein the four side surfaces are arranged at an angle to a plane of the base, and wherein, in particular, the distance between the first and second covers is in the range of 1 pm to 20 pm, especially between 5 pm and 10 pm. The trough shape is easy to manufacture and enables reliable coverage of the interior. Furthermore, the two trough shapes allow for the formation of a relatively large air space with low heat capacity and high thermal insulation between the first and second covers.

[0019] In a further development, the second layer has a thickness ranging from 5 pm to 200 pm, particularly from 10 pm to 100 pm. This allows for sufficient thermal insulation while maintaining relatively high elasticity. Specifically, the second layer can be made thicker and more elastic than would be possible by simply coating the inner walls of the first layer.

[0020] In a further development, the second cover is made of a material with a lower heat capacity and lower specific thermal conductivity than the material of the first cover. The second cover can be made of a polymer material such as polypropylene, polycarbonate, parylene, polysiloxane, etc. This allows the second cover to provide high thermal insulation between the enclosed air and the first cover. Thus, the interior is relatively well protected against temperature fluctuations outside the transducer, and thermal fluctuations caused by non-adiabatic interactions with the cover walls are prevented. This protects the function of the MEMS element from temperature fluctuations, suppresses thermally induced noise through dissipative surface effects, and thereby improves its functionality.

[0021] In a further training course, the second cover is made of an elastic material, specifically with a modulus of elasticity within a specified range. This allows pressure changes in the interior to be compensated for, thereby reducing temperature changes.

[0022] In a further development, the first cover is electrically conductive and electrically connected to a ground terminal of the carrier, with the first cover in particular acting as a shield against electromagnetic radiation. Thus, the MEMS element is protected from electromagnetic radiation. In another embodiment, the second cover has no mechanically fixed connection to the carrier.

[0023] A method for manufacturing a MEMS component according to one of the preceding claims is proposed, comprising the following steps: - providing a carrier;

[0024] -Providing an initial covering that defines a space;

[0025] -Providing a second cover;

[0026] -Introducing the second cover into the space of the first cover and fixing the second cover to an inner wall of the first cover in the form of a force-fit and / or form-fit connection;

[0027] -Mounting a MEMS element on the carrier;

[0028] -Connecting the first cover to the carrier.

[0029] This provides a simple method for manufacturing the MEMS component.

[0030] In one embodiment, a barrier element is inserted between the airspace and the interior before the first cover is connected to the support. This barrier element seals the airspace from the interior, and in particular, it seals the airspace from the interior in such a way that only a slow pressure equalization between the airspace and the interior is possible. This provides a simple method for manufacturing a MEMS device with improved thermal insulation provided by the second cover.

[0031] In a further embodiment, at least one spacer is formed on the first and / or the second cover before the first cover is connected to the support, wherein the first and the second cover are connected to each other in such a way that the spacer defines a distance between the first and the second cover. This prevents changes to the air space, in particular a full contact between the second cover and the first cover.

[0032] The invention is explained in more detail below with reference to the figures. Figure 1 shows a schematic cross-section through a MEMS device of a first embodiment;

[0033] Figure 2 shows a schematic perspective representation of the two covers;

[0034] Figure 3 shows a cross-section through a schematic representation of another embodiment of the MEMS device; and

[0035] Figure 4 shows a schematic cross-section through another embodiment of the MEMS device.

[0036] Figure 1 shows a schematic cross-section through an embodiment of a MEMS device 1. The MEMS device 1 has a support 2, which is designed, for example, in the form of a flat plate and is realized, for example, in the form of a substrate; in particular, a printed circuit board substrate with at least two metallization layers.

[0037] A through-hole 3 is formed in the carrier 2, extending continuously from a lower surface 14 of the carrier 2 to the upper surface of the carrier 2. A MEMS element 4 is arranged on an upper surface 13 of the carrier 2. The MEMS element 4 can be configured, for example, as an actuator element or as a sensor element. In particular, the MEMS element 4 can be configured as a capacitive pressure sensor element, especially as a capacitive relative pressure sensor element. In another embodiment, the MEMS element 4 can, for example, be configured as a microforn.

[0038] Furthermore, an ASIC circuit 5 can be arranged on the top surface of the carrier 2, which processes the sensor signals from the MEMS element 4. For this purpose, the ASIC circuit 5 has electrical lines 6, 7, which connect the ASIC circuit 5 to the MEMS element 4 on one side and to the electrical lines 29 of the carrier 2 on the other. A first cover 8 is arranged on the top surface 13 of the carrier 2 and is connected to the carrier 2 via a first connection layer 9. The first cover 8 can have a trough-like shape with a base 10 and side surfaces 11. The side surfaces 11 extend from the base 10 towards the carrier 2. The side surfaces 11 are firmly connected to the top surface of the carrier 2 via the first connection layer 9.In particular, the first connecting layer 9 is hermetically sealed all around to both the top surface of the carrier 2 and to a bearing surface 12 of the side surfaces 11 of the first cover 8. The bearing surface 12 is frame-shaped and circumferential. The first cover 8, together with the top surface 13 of the carrier 2, defines an interior space 15. Furthermore, a second cover 18 is arranged at a predetermined distance 16 from an inner surface 17 of the first cover 8.

[0039] An air space 19 is formed, at least partially, between the first and second covers 8, 18. The distance 16 between the inner surface 17 of the first cover 8 and an outer surface 20 of the second cover 18 can, for example, be in a range of 1 pm to 10 pm. Spacers 21 can be provided between the first cover 8 and the second cover 18.

[0040] The second cover 18 can be in the form of a plate or a trough, analogous to the trough shape of the first cover 8. The second cover 18 can thus have a second base and second side surfaces 22, 23. The second base 22 can be arranged parallel to the base 10 of the first cover 8. The second side surfaces 23 can each be arranged parallel to the corresponding side surfaces 11 of the first cover 8. Depending on the chosen embodiment, the spacers 21 can be arranged between the base surfaces 10, 22 of the first and second covers and / or between the side surfaces 11, 23 of the first and second covers 8, 16. The spacers 21 can be designed as separate elements and / or be formed in one piece and uniformly, in particular made of the same material as the first cover 8 or the second cover 18.The fastening of the first cover 8 to the second cover 16 can be either positive-locking and / or force-locking. For example, an adhesive layer can be formed in the area of ​​the spacers 21 to connect the first and / or the second cover 8, 16 to the spacer 21.

[0041] Preferably, the spacers 21 occupy less than 50%, and in particular less than 10%, of the area of ​​the inner surface 17 of the first cover 8. Preferably, the second cover 18 covers at least 50%, and in particular at least 80%, and in particular at least 90% or more of the inner surface 17 of the first cover 8. Preferably, the shapes of the first and second covers are essentially mathematically similar, with the second cover 18 having smaller dimensions than the first cover, since the second cover 18 is arranged inside the first cover 8.

[0042] For example, the second cover 18 has a thickness along the y-axis in the region of the second base surface 22 and / or a thickness along the x-axis in the region of the second side surfaces 23 of 5–200 pm. The second cover is made of a material that has a thermal conductivity approximately 100 times lower (i.e., typically below 1 W / mK) than the material of the first cover.

[0043] In the illustrated embodiment, the airspace 19 is open around the second side surfaces 32 of the second cover 18 towards the interior 15. This allows for unimpeded pressure equalization and gas or air exchange between the interior 15 and the airspace 19. A frame-shaped slot is thus formed between the circumferential side surfaces of the first and second covers 8, 18, which opens into the interior 15.

[0044] For example, the second cover is made of an elastic material, in particular an elastic material with a modulus of elasticity below 10 GPa. The second cover can, for example, be made of a polymer material.

[0045] The spacers serve a spacing and / or holding function between the first and second covers. Alternatively, instead of the local thickening shown, the spacers could be formed by a corresponding bulge or indentation in the first and / or second cover material.

[0046] The first cover 8 can, for example, be made of or formed from an electrically conductive material, in particular metal. Thus, the first cover 8 can constitute an electromagnetic shield. Furthermore, the first cover 8 can be electrically connected to a ground connection 24 of the support 2 via an electrical conductor 25. The ground connection can, for example, be located on the top 13 or on the bottom 14 of the support 2.

[0047] The formation of the thin slot or slot opening connecting the air space 19 with the interior 15, the trough-shaped design of the air space 19, and the material and presence of the second cover 18, which provides thermal insulation, mitigate or reduce temperature fluctuations that can affect the interior 15 from the outside. For example, heat generated by the first cover 8 is better shielded from the air space 19 and the second cover 18 in the direction of the interior 15.

[0048] Figure 2 shows in schematic perspective views an embodiment for the first cover 8 in a tub shape and an embodiment for the second cover 18 also in a tub shape.

[0049] Figure 3 shows a schematic cross-section of another embodiment of a MEMS component, an embodiment that is essentially designed according to the embodiment of Figure 1, except that the spacers 21 are formed by protrusions in the second base surface 22 of the second cover 18. Furthermore, the second cover 18 is attached to the inner sides of the side surfaces 11 of the first cover 8 by means of retaining or locking elements 26 via a positive-locking connection using a snap-fit ​​or clamping connection. The retaining elements 26 can be designed as a circumferential frame and arranged in an end region 27 of the second side surfaces 23. In addition to the positive-locking retention of the second cover 18 on the inner side of the first cover 8, the circumferential frame-shaped retaining element 26 also seals the air space 19 from the interior 15.Thus, air or gas exchange between the airspace 19 and the interior 15 can be hindered or prevented.

[0050] This prevents air or gas that heats up in the air space 19 from flowing freely into the interior 15. Thus, the thermal insulation effect is improved by the second cover 18.

[0051] Figure 4 shows a schematic cross-sectional view of another embodiment of the MEMS component 1. The MEMS component 1 is essentially designed according to the embodiment of Figure 1, except that in this embodiment the air space 19 is sealed off from the interior 15 by a circumferential fluid layer 28. The fluid layer 28 can be arranged between the top surface 13 of the carrier 2 and an end region 27 of the second side surfaces 23 of the second cover 18, as shown in Figure 4. Depending on the chosen embodiment, the circumferential fluid layer 28 can also be arranged between the end region 27 of the second side surfaces 23 of the second cover 18 and the inner surface of the side surfaces 11 of the first cover 8.In both embodiments, the airspace 19 is sealed off from the interior space 15, thus preventing free, high-frequency gas or air exchange between the airspace 19 and the interior space 15. This also improves the insulating effect of the airspace 19.

[0052] The fluid layer 28 can be a gel layer. The fluid layer 28 does not form a rigid mechanical connection between the second cover 18 and the support 2, but is a flexible fluid layer that reduces, and in particular prevents, gas exchange between the air space and the interior. Depending on the chosen embodiment, the material of the fluid layer 28 can be designed such that gas or air exchange between the air space and the interior is permitted by allowing gas molecules to diffuse through the fluid material.

[0053] For example, this can achieve a quasi-static pressure equalization of the air space, which occurs particularly below a cutoff frequency of 20 Hz. For example, pressure equalization via the fluid layer and / or via the retaining elements 26 can occur over a period of 5 hours with a pressure change of 100 mbar.

[0054] The MEMS component shown in the figures can be, for example, a pressure sensor, a microphone, or a micro-speaker. The second cover 18 can be made of an electrically non-conductive material with a thermal conductivity below a predefined limit. The first cover 8 can be mechanically and sealingly connected to the carrier 2, for example, via a solder joint. Thus, the first connection layer 9 can, for example, consist of a circumferential solder layer.

[0055] Preferably, the second cover 18 rests directly against the inside of the first cover 8 with its outer surface in partial areas and / or in point contact areas, without, however, being mechanically firmly connected to the first cover 8.

[0056] The described MEMS component has the advantage, for example, that thermal noise generated by non-adiabatic energy losses on the inner surface 17 of the first cover 8 can be reduced or suppressed. Furthermore, the interior 15 is better protected against external EMC influences and, for example, their thermal effects. RF immunity can also be improved or achieved.

[0057] The proposed MEMS device has the advantage of suppressing thermal energy losses of the acoustic wave, thus achieving a higher signal-to-noise ratio, particularly in the frequency range from 300 Hz to 3 kHz. Furthermore, thermoacoustic interference signals, such as those caused by RF or thermal radiation absorbed in the first cover 8, can be reduced or suppressed.

[0058] Through the through-hole 3, a fluidic access point is provided from the external environment to the interior. This enables media and energy access into the interior of the MEMS component 1, through which acoustic energy can also be exchanged with the MEMS element, which, for example, represents an MEMS transducer.

[0059] The second cover 18 is formed, for example, from an electrically non-conductive material with preferably low thermal conductivity, such as polymer materials like polysiloxane, polypropylene, etc. In this way, the acoustic wave can exchange only a small amount of thermal energy with the second cover 18. The distance between the first and second covers creates an air gap, which acts as an additional thermal barrier against energy exchange. Furthermore, the second cover can exhibit a predetermined elastic flexibility (preferably a modulus of elasticity <10 GPa). This allows the air space 19, and thus the air gap, to deflect the second cover, thereby reducing the temperature change in the interior during a pressure wave in the medium, since some of the acoustic energy is reversibly converted into elastic energy instead of irreversible thermal energy.

[0060] The spacers allow the first cover 8 and the second cover 18 to be connected at a defined distance from each other. The arrangement of the spacers, preferably in the area of ​​the base surfaces 10, 22, enables a simple joining process with tight tolerances. The spacers can be designed as raised thickened areas and / or as protrusions on the first and / or the second cover 8, 18 and / or as separate elements.

[0061] The electrically conductive first cover 8 can be conductively connected to the carrier 2 via an electrically conductive bonding layer, in particular a solder connection. In this way, the first cover 8 can be connected to ground potential, thus achieving advantageous shielding against RF radiation from the environment.

[0062] The second cover 18 can preferably abut the inside of the first cover 8 and / or the carrier 2 at a substrate-side periphery, i.e., in the end region 27, without being mechanically rigidly connected to it or achieving a thermal seal of the air space 19. This has the advantage that a quasi-static pressure equalization of the air space below a certain limit with the internal volume, i.e., in the interior of the MEMS component 1, is possible. Thus, the size of the internal volume does not change with pressure changes in the external volume, and consequently, the sensor characteristics of the MEMS component 4, which is designed, for example, as a MEMS transducer, also remain essentially unchanged.

[0063] The fluid layer 28 can preferably enable diffuse gas exchange between the airspace and the interior. The surrounding fluid layer 28 can completely seal the airspace from the interior. A time constant for diffuse pressure equalization through the fluid layer can advantageously be selected such that it is greater than 50 ms in the infrasound range and, in particular, hardly or not at all impairs the audio quality of the MEMS element 4.

Claims

Claims 1. MEMS component (1) with a carrier (2) and a first cover (8), wherein an interior space (15) is formed between the carrier (2) and the first cover (8), wherein a MEMS element (4) is arranged in the interior space (15), wherein the MEMS element (4) is designed to interact with a fluid, wherein the first cover (8) is fixedly connected to the carrier (2), wherein a thermally insulating second cover (18) is provided between the MEMS element (4) and the first cover (8), wherein the second cover (18) is at least force-fit and / or form-fit attached to the first cover (8), wherein an air space (19) is formed at least partially between the first cover (8) and the second cover (18).

2. MEMS device according to claim 1, wherein at least one spacer is provided between the first and the second cover (8, 18) which determines the distance between the first and the second cover.

3. MEMS device according to claim 2, wherein the spacer (21) is designed as part of the first and / or the second cover (8, 18) or as a separate element.

4. MEMS component according to one of the preceding claims, wherein a barrier element (26, 28) is provided between the air space (19) and the interior space (15), wherein the barrier element (26, 28) seals the air space (19) against the interior space (15), wherein in particular the barrier element (26, 28) seals the air space (19) against the interior space (15) in such a way that only a slow pressure equalization between the air space (19) and the interior space (15) is possible.

5. MEMS device according to claim 4, wherein the barrier element is formed in the form of a fluid layer (28), wherein the fluid layer (28) circumferentially seals the air space (19) against the interior (15), wherein the fluid layer (28) is located on the second cover (18) and on the first cover (8) and / or on the support (2).

6. MEMS component according to one of claims 4 or 5, wherein the locking element is designed in the form of a mechanical sealing element (26), wherein the sealing element (26) is designed as part of the first and / or second cover (8, 18), wherein the sealing element (26) is in a sealing position against the first and / or the second cover and / or the carrier (2).

7. MEMS component according to one of the preceding claims, wherein the first and the second cover (8, 18) each have a trough-like shape with a base (10, 22) and four side surfaces (11, 23), wherein the four side surfaces (11, 23) are arranged at an angle to a plane of the base (10, 22), and wherein in particular a distance between the first and the second cover (8, 18) is in the range of 1 pm to 20 pm, in particular between 5 pm and 10 pm.

8. MEMS device according to one of the preceding claims, wherein the second cover (18) has a thickness in the range of 5 pm to 200 pm.

9. MEMS device according to one of the preceding claims, wherein the second cover (18) is formed from a material having a lower specific thermal conductivity than the material of the first cover (8), and wherein the second cover is in particular formed from a polymer material.

10. MEMS device according to one of the preceding claims, wherein the second cover (18) is made of an elastic material, in particular with a modulus of elasticity in a predetermined range of preferably below 10 GPa.

11. MEMS device according to one of the preceding claims, wherein the first cover (8) is electrically conductive and is electrically connected to a ground connection (24) of the carrier (2), and wherein in particular the first cover (8) constitutes an electromagnetic shield.

12. MEMS component according to one of the preceding claims, wherein the second cover (18) does not have a mechanically fixed connection with the carrier (2).

13. A method for manufacturing a MEMS component according to any of the preceding claims comprising the following steps: - providing a carrier; -Providing a first covering that encloses a space; -Providing a second covering; -Introducing the second cover into the space of the first cover and fixing the second cover to an inner wall of the first cover in the form of a force-fit and / or form-fit connection; -Mounting a MEMS element on the carrier; -Connecting the first cover to the carrier.

14. Method according to claim 13, wherein a barrier element is inserted between the airspace and the interior before connecting the first cover to the support, wherein the barrier element seals the airspace against the interior, wherein in particular the barrier element seals the airspace against the interior in such a way that only a slow pressure equalization between the airspace and the interior is possible.

15. Method according to one of claims 13 or 14, wherein at least one spacer is formed and / or introduced on the first and / or the second cover prior to connecting the first cover to the carrier, wherein the first and the second cover are connected to each other in such a way that the spacer establishes a distance between the first and the second cover.

Images