Sensor unit and method for manufacturing a sensor unit

Abstract

Sensor unit (1) comprising a first semiconductor device (10) and a second semiconductor device (20), wherein the first semiconductor device (10) has a first substrate (11) and a sensor structure (12), wherein the second semiconductor device (20) has a second substrate (21), wherein the first and second semiconductor devices (10, 20) are connected to each other via a wafer connection (40), characterized in that the sensor unit (1) has a decoupling structure (50) configured such that the sensor structure (12) is thermomechanically and / or mechanically decoupled from the second semiconductor device (20), wherein the decoupling structure comprises at least one membrane element (55) spanning a cavity (56) in the layer structure of the first semiconductor device (10) and formed in the region above the wafer connection (40).

Description

State of the art

[0001] The invention relates to a sensor unit according to the preamble of claim 1.

[0002] Such sensor units are well known. For example, it is known to combine two semiconductor devices formed from different wafers into a sensor unit using a wafer bonding process. For instance, one semiconductor device might contain a sensor structure, and the other an integrated circuit. However, with such known sensor units, detection is comparatively strongly affected by external disturbances.

[0003] Further sensor units are disclosed, for example, in the patent applications US 2008 / 0236292A1 and WO 2012 / 037536A2. Disclosure of the invention

[0004] It is an object of the present invention to propose a sensor unit in which the influence of external disturbances - for example thermomechanical and / or mechanical stresses - on a sensor structure of the sensor unit is reduced.

[0005] The sensor unit according to the invention and the inventive method for manufacturing a sensor unit according to the dependent claims have the advantage over the prior art that a sensor unit is provided in which the transmission of thermomechanical and / or mechanical stresses from the second semiconductor device to the sensor structure is reduced in such a way that the detection properties of the sensor unit are improved. In particular, the sensor structure is decoupled from the second semiconductor device with respect to thermomechanical and / or mechanical stresses. In particular, the disturbances transmitted via the wafer connection produced by the wafer bonding process between the two semiconductor devices are reduced. According to the invention, the decoupling structure is configured such that the sensor structure is thermomechanically and / or mechanically decoupled from the second semiconductor device.Decoupling means, in particular, that mechanical and / or thermomechanical stresses—for example, due to temperature changes or deformations of the second semiconductor device—are not transferred to the sensor structure or are transferred only in a negligible manner—i.e., with regard to detection by the sensor unit. Preferably, the sensor unit comprises a third semiconductor device, for example, a printed circuit board, connected to the first or second semiconductor device via a component interconnect, wherein the decoupling structure is configured such that the sensor structure is also thermally and / or mechanically decoupled from the third semiconductor device.

[0006] In particular, the sensor unit is integrated into a wafer-level chip-scale package (WLCSP) – i.e., a packaging for semiconductor components, especially sensors – i.e., in a chip package on the order of the size of a semiconductor chip (die) separated from a wafer – for example, by sawing or breaking. Advantageously, the stress sensitivity – i.e., the sensitivity of the sensor unit to external disturbances such as thermal and / or mechanical stresses – is reduced in the WLCSP according to the invention.

[0007] In particular, the sensor unit is an inertial sensor unit and / or a pressure sensor unit. For example, the sensor unit is a barometer, altimeter, accelerometer, gyroscope, or a combination thereof for use in mobile telecommunications devices, smartphones, and tablet PCs.

[0008] Advantageous embodiments and further developments of the invention can be found in the dependent claims and the description with reference to the drawings.

[0009] According to a preferred embodiment, the decoupling structure is provided to have a trench structure, wherein the trench structure extends into the first substrate along a normal direction perpendicular to the main extension plane of the first substrate - i.e., in particular, not completely through it - or completely through the first substrate.

[0010] This makes it advantageously possible to achieve decoupling in a particularly efficient manner by selectively adjusting the stiffness of the first substrate through a trench height and / or trench depth, in order to decouple the sensor structure from the second and / or third semiconductor device with regard to external disturbances. The decoupling structure preferably has a trench structure which contains one or more trenches surrounding the sensor structure in the first substrate. Preferably, the sensor unit comprises a microelectromechanical system (MEMS); in particular, the sensor structure is a MEMS sensor structure with a MEMS sensor element (MEMS core). The resulting thinner regions—i.e.,Areas of smaller extent of the first substrate (MEMS substrate) along the normal direction can accommodate or absorb the deformation of the second semiconductor device—which, for example, comprises an integrated circuit (ASIC)—and / or the third semiconductor device—which, for example, comprises an application circuit board—while the sensor element of the sensor structure remains virtually undeformed due to its comparatively large thickness and high stiffness. This significantly improves the stability of offset, sensitivity, and other (MEMS) sensor parameters compared to the prior art.

[0011] According to a further preferred embodiment, the decoupling structure is provided to have coupling elements for coupling the sensor structure to a land-based structure of the first substrate.

[0012] This makes it advantageously possible to connect the sensor structure to the mainland structure - especially exclusively indirectly - via coupling elements, so that decoupling is achieved.

[0013] According to a further preferred embodiment, the trench structure extends mainly parallel to the main extension plane of the first substrate, wherein the trench structure surrounds the sensor structure, wherein in particular the trench structure is meandering or frame-shaped, especially ring-shaped.

[0014] This advantageously enables efficient decoupling of the sensor structure. In particular, the decoupling structure additionally features a further trench structure. Specifically, this further trench structure, or according to an alternative embodiment, the trench structure – with respect to a projection direction parallel to the normal direction – encloses a contact area of ​​the wafer connection and / or a further contact area of ​​the component connection. In particular, the further trench structure is meandering. The contact areas are, in particular, solder bumps or bond pads.

[0015] As already mentioned, the decoupling structure of the sensor unit according to the invention is configured such that the sensor structure is thermomechanically and / or mechanically decoupled from the second semiconductor device. Such decoupling proves advantageous not only for the micromechanical sensor function of the first semiconductor device, but also for the function of the second semiconductor device, particularly if it is an ASIC device.

[0016] The wafer connection between the semiconductor components of a sensor unit of the type under discussion is preferably produced by silicon direct bonding or eutectic bonding. In these bonding processes, the two wafers to be joined are pressed together at elevated temperature. Wafer bows and surface roughness are compensated for by a relatively high contact pressure. Since this contact pressure is only transferred to the components to be joined via the bond contact points, the bonding process leads to an uneven pressure load on the individual chip areas. This proves particularly problematic for an ASIC component. During ASIC processing, the material of the dielectric insulating layers of the ASIC layer structure is optimized with regard to the lowest possible dielectric constant in order to minimize RC delays in the conductor tracks of the wiring layers.Since the dielectric constant decreases with increasing porosity of the dielectric material, mechanically fragile materials are increasingly being used for the insulating layers of ASIC layer structures. Therefore, there is a risk that the functional elements of the ASIC device will be damaged during the bonding process due to the low mechanical stability of the individual layers.

[0017] According to the invention, the decoupling structure therefore comprises at least one membrane element that spans a cavity in the layer structure of the first semiconductor device and is formed in the region above the wafer interconnect. The cavity under the membrane element can be closed, but it can also be connected to the environment via pressure equalization openings.

[0018] By using such a membrane element over a cavity in the layer structure of the MEMS semiconductor device, the high contact pressure required for bonding processes can be locally limited to the bonding frame, i.e., the connection area, without damaging the sensitive circuit elements of an ASIC device. The deflection or deformation of the membrane element during the bonding process prevents the contact pressure from being transmitted to the surrounding area of ​​the bonding frame. In this way, the membrane element and the cavity contribute to the mechanical decoupling of the connection area from adjacent chip areas of the sensor unit according to the invention.

[0019] The membrane elements in the connection area also enable an even distribution of the contact pressure during the bonding process and ensure topography compensation, thus avoiding the occurrence of local force increases.

[0020] According to a further preferred embodiment, the sensor structure comprises a structural element encompassed by the first substrate and a sensor element encompassed by a functional layer of the first semiconductor device, wherein the sensor element is connected to the first substrate exclusively indirectly via the coupling elements, wherein in particular the coupling elements are formed from the first substrate and / or from the functional layer.

[0021] According to a further preferred embodiment, the sensor unit has a cavity and / or a separate further cavity, wherein the cavity and / or further cavity is arranged between the first and second semiconductor device, wherein the wafer connection has a bond frame structure enclosing the cavity and / or further cavity, which is configured such that the cavity and / or the separate further cavity can be hermetically sealed or are sealed, wherein in particular a ventilation channel extends through the first substrate into the cavity or further cavity.

[0022] This makes it advantageously possible to decouple a sensor structure with a sensor element arranged in a cavity from external disturbances. In particular, it is also possible to implement two decoupled sensor structures in the sensor unit in a particularly efficient manner, with each sensor structure being assigned to a cavity.

[0023] According to a further preferred embodiment, the sensor structure is a pressure sensor structure, wherein a pressure sensor channel is arranged in the first substrate, the pressure sensor channel extending into the sensor unit up to a membrane of the pressure sensor structure.

[0024] This makes it advantageously possible to provide a pressure sensor in which the sensor structure of the pressure sensor is decoupled from mechanical and / or thermomechanical stresses of the second and / or third semiconductor component.

[0025] According to a further preferred embodiment, the sensor unit has a through-hole connection, in particular a silicon through-hole connection, formed in the first substrate for electrical contacting the sensor element of the sensor structure.

[0026] This makes it advantageously possible to provide a comparatively compact sensor unit, in which the influence of thermal and / or mechanical stresses on the detection is still comparatively low.

[0027] According to a further preferred embodiment, the decoupling structure is a trench structure filled with a backfill material, wherein the backfill material is in particular a polymer material, wherein the backfill material has a shear modulus that is at least one order of magnitude smaller than a substrate material, in particular silicon material, of the first substrate.

[0028] This makes it advantageously possible to protect the sensor structure from contamination.

[0029] According to a preferred embodiment of the inventive method, it is provided that in the third manufacturing step -- the decoupling structure and / or -- a pressure sensor channel and / or -- a through-hole and / or -- a ventilation duct and / or -- an isolation structure is structured in the first semiconductor device, in particular the first substrate, by time-controlled etching, in particular by reactive ion deep etching, and / or by means of a laser beam.

[0030] This makes it advantageously possible to form the decoupling structure and / or the pressure sensor channel and / or the via hole and / or the ventilation channel and / or the insulation structure in the first substrate in a comparatively simple way.

[0031] According to a further preferred embodiment of the inventive method, it is provided that in the third manufacturing step in the first semiconductor device, in particular the first substrate, -- the decoupling structure and / or -- the pressure sensor channel and / or -- the via hole and / or -- the ventilation duct and / or -- the isolation structure is formed simultaneously.

[0032] This makes it advantageously possible to manufacture the sensor unit with a decoupled sensor structure with comparatively little additional effort. By simultaneously forming different structures for the various arrangements, an improvement in stress sensitivity is achieved with virtually no additional process costs.

[0033] According to one embodiment of the invention, the sensor unit is configured for pressure measurement, wherein the sensor structure is a pressure sensor structure and the second semiconductor device comprises an evaluation structure, in particular designed as an integrated circuit (ASIC). Specifically, the first semiconductor device (sensor chip) is mounted on the second semiconductor device (evaluation ASIC) using flip-chip (FC) technology. Specifically, the second semiconductor device, connected to the first semiconductor device, is mounted on the third semiconductor device (circuit board) using FC technology. Preferably, the decoupling structure comprises a trench structure with one or more trenches, which are, for example, slots for voltage decoupling. Additionally, the decoupling structure comprises, in particular, double-bridge elements and / or membrane elements, especially PorSi membrane elements.In particular, the membrane elements are arranged along a projection direction parallel to the normal direction of the first substrate under the contact areas.

[0034] Exemplary embodiments of the present invention are shown in the drawings and explained in more detail in the following description. Brief description of the drawings

[0035] They show Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11, Fig. 12, Fig. 13, Fig. 14, Fig. 15, Fig. 16, Fig. 17, Fig. 18, Fig. 19, Fig. 20, Fig. 21 to Fig. 22 sensor units according to various embodiments of the present invention.

[0036] In Fig. Figure 1 shows a sensor unit 1 configured as a pressure sensor, wherein the sensor unit 1 comprises a first semiconductor component 10, which is mounted on a second semiconductor component 20 using flip-chip technology. Here, the first semiconductor component 10 has a sensor structure 12, and the second semiconductor component 20 has an evaluation structure 22, in particular an integrated circuit (ASIC). Here, the first and second semiconductor components 10, 20 are mechanically and electrically connected to each other via a contact area 41. Here, the evaluation structure 22 has a via 23, which is also referred to as a through-hole or silicon through-hole. In particular, the via 23 is configured such that an output signal from the sensor structure 12 is routed to a rear side (in the drawing, the underside) of the sensor unit 1.Via a further contact area 41', the second semiconductor component 20 connected to the first semiconductor component 10 can be connected to a third semiconductor component 30 (for example, to a printed circuit board of a circuit as in . Fig. 3 shown) are soldered.

[0037] In Fig. Figure 2 shows a sensor unit 1 according to an embodiment of the present invention. The embodiment shown here corresponds in particular essentially to that described in Figure 2. Fig. 1. In the embodiment shown, the first semiconductor device 10 additionally has a decoupling structure 50 according to the invention for voltage decoupling. Here, the decoupling structure 50 has a groove structure 51 – in particular, a slot. Here, the groove structure 51 surrounds the sensor structure 12 in a plane that is parallel to the main extension plane 100 of a first substrate 11 of the first semiconductor device 10. A first direction 101 parallel to the main extension plane 100 is here referred to as the X-direction, and a second direction 102 parallel to the main extension plane 100 and perpendicular to the X-direction is here referred to as the Y-direction. In particular, the decoupling structure 50 is configured here such that thermomechanical and / or mechanical surface stresses – which, for example, are transmitted via the further contact areas 41' from the third semiconductor device 30 (see Figure 1) – are prevented from occurring. Fig. 3) to the second semiconductor device 20 and / or via the contact areas 41 from the second semiconductor device 20 to the first semiconductor device 10 – not directly to the sensor structure 12. This means that the sensor structure 12 is largely decoupled from the second and / or third semiconductor devices 20, 30 with respect to thermomechanical and / or mechanical stresses. Optionally, the grooves of the trench structure 51 extend along the normal direction 103 into the first semiconductor device 10 – i.e., not completely through it – or completely through the first substrate 11 and / or a functional layer 13 of the first semiconductor device 10.

[0038] In Fig. Figure 3 shows a sensor unit 1 according to an embodiment of the present invention, wherein the second semiconductor device 20 is mounted on the third semiconductor device 30, in particular a printed circuit board 30. In particular, the printed circuit board 30 has a coefficient of thermal expansion that is greater—especially by one or more orders of magnitude—than the coefficient of thermal expansion of silicon. Temperature changes can, for example, generate shear forces (see arrows 200) at the further contact areas 41'—here bond pads—which lead to mechanical stresses in the first and / or second semiconductor device 10, 20. A trench of the trench structure 51, which is also referred to in particular as a stress decoupling trench 51, extends through the entire first semiconductor device 10. Fig. 5 and Fig. Figure 6 shows exemplary embodiments of this sensor unit 1 in a top view.

[0039] In Fig. 4 shows a sensor unit 1 according to an embodiment of the present invention, which essentially comprises the Fig. 2 and Fig. The embodiments shown in Figure 3 correspond to the decoupling structure 50 of the sensor unit 1, wherein the decoupling structure 50 comprises additional membrane elements 55, in particular membranes made of porous silicon (PorSi). Specifically, the membrane elements 55 overlap—partially or completely—along a projection direction parallel to the normal direction 103 with the contact areas 41 and / or further contact areas 41', so that the thermally and / or mechanically induced stresses can relax outside the sensor structure 12, in particular outside a pressure sensor membrane 123 of the sensor structure 12. Specifically, the membrane elements 55 project beyond the contact areas 41 along a first direction 101 parallel to the main extension plane 100 of the first substrate 11.

[0040] In Fig. Figure 5 shows a sensor unit 1 according to an embodiment of the present invention in a schematic top view, which essentially comprises the Fig. 2, Fig. 3 to Fig. The embodiment 51 corresponds to the embodiments shown in Figure 4, where the trench structure 51 extends around the sensor structure 12. Here, the sensor structure 12 is a pressure sensor structure 12 with a pressure sensor membrane 18 and a piezoelectric resistor 19. Here, the trench structure 51 has a meandering shape and, in particular, does not extend along a closed path around the sensor structure 12. Furthermore, the sensor unit 1 has a conductor track structure 17', which is provided for electrical contacting the sensor structure 12. In particular, conductor tracks of the conductor track structure 17' extend between the grooves or trenches of the trench structure 51. The pressure sensor membrane 18 is, in particular, spring-elastically suspended from a base structure 11' of the first semiconductor device 10.This advantageously makes it possible to decouple the sensor structure 12 from externally imposed mechanical stresses, so that no or almost no mechanical stresses are transferred to the sensor structure 12. The trench structure 12 particularly preferably extends parallel to the main extension plane 100 along the entire first substrate 11.

[0041] In Fig. 6 shows a sensor unit 1 according to an embodiment of the present invention in a schematic top view, which essentially comprises the Fig. 2, Fig. 3, Fig. 4 to Fig. This corresponds to the embodiments shown in Figure 5, wherein the sensor structure 12 is not attached centrally, but at offset points to the main substrate structure 11'. In this way, effective retaining springs are created in the first substrate 11, on which the conductor tracks 17' are led out and which suppress the assembly stress.

[0042] In Fig. 7 shows a sensor unit 1 according to an embodiment of the present invention in a schematic top view, which essentially comprises the Fig. 2, Fig. 3, Fig. 4 to Fig. This corresponds to the embodiments shown in Figure 5, where the trench structure 51 surrounds the contact areas 41. In the area of ​​the contact areas 41, this creates a spring-elastic connection between the first and second semiconductor components 10, 20, thus decoupling the sensor structure 12.

[0043] In Fig. Figure 8 shows a sensor unit 1 according to an embodiment of the present invention in a schematic side view. The sensor unit 1 comprises a first semiconductor device 10 and a second semiconductor device 20. The first semiconductor device 10 comprises a first substrate 11 and a functional layer 13 – in particular, a polycrystalline silicon functional layer. The functional layer 13 comprises a sensor element 123, in particular a microelectromechanical sensor element 123 (MEMS sensor element or MEMS chip). The sensor element 123 is connected to the first substrate 11 – in particular, exclusively indirectly – via a suspension element 121. Furthermore, in particular, a further layer 13' with an electrode structure 122 is arranged between the first substrate 11 and the functional layer 13. This electrode structure is configured, for example, for the capacitive detection of a deflection of a movable structure of the sensor element 123.The second semiconductor device 20 comprises a second substrate 21. The first and second semiconductor devices 10, 20 are connected to each other via a wafer connection 40. The wafer connection 40 comprises a contact area 41 and a bonding frame structure 42. Furthermore, the second semiconductor device 20 is connected to a third semiconductor device 30 – for example, a printed circuit board – via further contact areas 41', in particular electrically conductively. In particular, the second semiconductor device 20 has an evaluation structure 22 – in particular, an integrated electronic circuit. Preferably, vias 23 extend through the second substrate 21 of the second semiconductor device for the electrically conductive contacting of the evaluation structure 22 – here via the further contact areas 41' and a contact element 23'.

[0044] The first substrate 11 is, in particular, a silicon substrate and here comprises an oxide layer structure 13' and, in particular, an electrode structure 122 arranged in a conductor plane. A sensor element 123 with a movable MEMS structure – for example, for acceleration, angular rate, or magnetic sensors – is formed from the functional layer 13. The first semiconductor device 10, in particular, comprises further silicon functional layers and oxide insulating layers, which are applied, for example, by wafer bonding and subsequent re-grinding (not shown).

[0045] The second semiconductor device 20 comprises, in particular, a complementary metal-oxide semiconductor (CMOS), which includes the second substrate 21 with doped semiconductor layers 24 for realizing the electrical circuits and a metal-oxide stack with the evaluation structure 22, in particular for wiring and for realizing capacitances. The first and second semiconductor devices 10, 20 are connected to each other, for example, via a metallic wafer bonding process, in particular by eutectic bonding of aluminum with germanium. For example, an uppermost aluminum wiring layer on the evaluation structure 22 is used as the bonding surface, and germanium is deposited as the uppermost layer on the first semiconductor device 10. The two wafers are then pressed together at temperatures above 430°C under sufficient pressure so that a eutectic liquid phase is formed.The wafer interconnect 40 then comprises an aluminum-germanium compound, which, by means of a circumferential bonding frame structure 42, ensures a hermetic encapsulation of the sensor element 123 and, in particular, forms an electrically conductive contact area 41 between the first and second semiconductor components 10, 20. Other metallic bonding methods, such as copper-tin bonding or thermocompressive methods, can be implemented analogously.

[0046] In Fig. Figure 9 shows a sensor unit 1, which does not have a decoupling structure 50, distorted to illustrate a bending or deformation of the sensor unit 1 that can occur, for example, when the first and second semiconductor components 10, 20 are pressed together to connect with the third semiconductor component 30. Here, the sensor unit 1 is deformed differently in the area of ​​a cantilevered MEMS element of the sensor element 123 than in an area of ​​the electrode structure 122. With capacitive evaluation, the distance between a movable MEMS element and the electrode structure 122 thus changes. The decoupling structure according to the invention advantageously prevents drift resulting from bending—e.g., of sensitivity, offset, and other detection parameters—by decoupling the sensor structure 12 (see Figure 9). Fig. 10) largely avoided.

[0047] In Fig. 10 shows a sensor unit 1 according to an embodiment of the present invention in a schematic top view, which essentially comprises the Fig. 8 to Fig. This corresponds to the embodiments shown in Figure 9. Here, the first substrate 11 has a decoupling structure 50, wherein the decoupling structure 50 comprises a trench structure 51. The trench structure 51 extends completely through the first substrate 11 along a projection direction parallel to a normal direction 103. In particular, the trench structure extends mainly along a plane parallel to the main extension plane 100. Here, the trench structure 51 has the form of a circumferential rectangle or ring (see, for example, the one in Figure 9). Fig. (see top view shown in Figure 11). In particular, the first semiconductor device 10 in the functional layer 13 comprises coupling elements 52 for connecting the sensor structure 12 to a land-based structure 11' of the first substrate 11. Preferably, the bending stiffness of the first substrate 11 in the region of the coupling elements 52 is reduced compared to the bending stiffness of the first substrate 11 in the region of the land-based structure 11'. The decoupling structure 50 is configured in particular such that an externally imposed bending or deformation of the sensor unit 1 is largely absorbed and a structural element 120 of the sensor structure 12 enclosed by the trench structure 51 is essentially not bent – ​​i.e., is decoupled. Fig. Figure 12 shows an example of such a bending. In particular, this significantly reduces the influence of mechanical and / or thermomechanical stresses on both the structural element and the sensor element 123 – and thus on the entire sensor structure 12 including the suspension element 121 and the electrode structure 122 arranged in the conductor track plane – to such an extent that detection by the sensor unit 1 is not disturbed by external disturbances, or at least is disturbed to a much lesser degree than in the prior art. Depending on the trench width of a circumferential trench of the trench structure 51 and the width and / or height of the coupling elements 52, the stiffness of the decoupling structure can be specifically adapted or adjusted.

[0048] In Fig. Figure 11 is a sensor unit 1 according to an embodiment of the present invention, shown in a schematic top view. The first substrate 11 here has a trench structure 51 surrounding the sensor structure 12 in a plane parallel to the main extension plane 100. Here, the trench structure is arranged within the bond frame structure 42. In particular, the bond frame structure 42 comprises a eutectic material. In particular, according to the embodiment shown here, the trench structure 51 overlaps with one or more further contact areas 41' of the component connection 40'.

[0049] In Fig. 13 shows a sensor unit 1 according to an embodiment of the present invention. In the Fig. In the embodiment shown in Figure 13, the trench structure 51 extends into the first substrate 11 of the first semiconductor device 10 along a projection direction parallel to the normal direction 103, but particularly not through the first substrate 11. Preferably, the trench depth of the trench structure 51 extending parallel to the normal direction 103 is between 60% and 100%, particularly preferably between 70% and 90%, and most preferably approximately 80%, of the substrate thickness of the first substrate 11 extending parallel to the normal direction 103. In this case, the coupling elements 52 extend exclusively within the first substrate 11—i.e., additional coupling elements in a functional layer—as, for example, in Figure 13. Fig. 10 shown - are not provided in the embodiment shown here.

[0050] In Fig. 14, Fig. 15, Fig. 16, Fig. 17, Fig. 18, Fig. 19 to Fig. Figure 20 shows sensor units 1 according to various embodiments of the present invention. Fig. Figure 14 shows a sensor unit 1, wherein the first semiconductor device 10 here has a sensor structure 12 and a separate further sensor structure 12', wherein the decoupling structure 50 here comprises a substructure 50' and a further substructure 50'', wherein the substructure 50' is configured such that the sensor structure 12 is thermomechanically and / or mechanically decoupled from the second semiconductor device 20, wherein the further substructure 50'' is configured such that the further sensor structure 12' is thermomechanically and / or mechanically decoupled from the second semiconductor device 20.

[0051] Furthermore, the additional sensor structure 12' here includes, in particular, another sensor element 123'. The sensor element 123 of the sensor structure 12 and the additional sensor element 123' of the additional sensor structure 12' are arranged here in two hermetically separated caverns 60, 60', wherein the sensor structure 12 is assigned to one cavern 60 and the additional sensor structure 12' to another cavern 60' of the two caverns 60, 60'. For example, the sensor structure 12 is configured for the detection of accelerations and the additional sensor structure 12' is configured for the detection of rotation rates. The hermetic separation of the two caverns 60, 60' is achieved here by means of a bond bridge 42' of the bond frame structure 42 ( Fig. 15).

[0052] In particular, the two caverns 60, 60' have different internal pressures, with the internal pressure of the further cavern 60' being set by means of a resealing process. For this purpose, the further cavern 60' has a ventilation hole 16 extending parallel to the normal direction 103 through the first substrate 11, which is sealed by a closure 162 in a completed sensor unit. In particular, a metal film 161 is arranged on the closure 162. Furthermore, the sensor unit has a first and second passage area 61, 62. Fig. 15 is the one in Fig. 14. The embodiment is shown in a top view.

[0053] In Fig. 16 shows a sensor unit 1 according to an embodiment of the present invention, which is essentially the same as the one described in Fig. The embodiment shown in Figure 10 corresponds to the sensor unit 1. Here, the sensor unit 1 is designed as a pressure sensor unit and has a pressure sensor channel 14. The pressure sensor channel 14 extends along a projection direction parallel to the normal direction 103 through the first substrate 11 to a membrane 18 of the sensor structure 12.

[0054] In Fig. 17 shows a sensor unit 1 according to an embodiment of the present invention, which is essentially the same as the one described in Fig. This corresponds to the embodiment shown in Figure 10. Here, the first semiconductor device 10 has the further contact area 41' for connection with a third semiconductor device 30. The further contact area 41' is connected to the first substrate 11. Here, the evaluation structure 22 is electrically conductive – in particular via contact elements 23' arranged in a layer 23'', a via 15 arranged in a via hole 15', and a contact area 41 – connected to the further contact area 41'. Here, the via hole 15' extends through the first substrate 11. Fig. 18 is sensor unit 1 according to Fig. Figure 17 shows the sensor unit 1 comprising the first, second, and third semiconductor components 10, 20, and 30. Here, the first semiconductor component 10 is electrically connected to the third semiconductor component 30 via the additional contact areas 41'.

[0055] In Fig. Figure 19 shows a sensor unit 1 according to an embodiment of the present invention. The embodiment shown here corresponds essentially to the other embodiments, wherein the second semiconductor component 20 is designed as a cap or housing of the sensor unit 1.

[0056] In Fig. Figure 20 shows a sensor unit 1 according to an embodiment of the present invention. The embodiment shown here corresponds essentially to the other embodiments, wherein the trench structure 51 of the decoupling structure 50 comprises a filling material, wherein the filling material 54 is in particular a polymer material, and wherein the filling material 54 has a modulus of elasticity that is at least one order of magnitude smaller – i.e., softer – than a substrate material, in particular silicon material, of the first substrate 11.

[0057] In Fig. Figure 21 shows a sensor unit 1 according to a further embodiment of the present invention in a schematic side view. The sensor unit 1 comprises a MEMS device 10 with a sensor structure and an ASIC device 20 with an evaluation circuit 22 for the sensor function of the MEMS device 10.

[0058] In the functional layer 13 above the substrate 11 of the MEMS device 10, a deflectable sensor element 123 is formed, which is connected to the MEMS substrate 11 via a suspension element 121. The deflections of the sensor element 123 are capacitively detected by means of an electrode structure 122, which is formed in a further layer 13' between the MEMS substrate 11 and the functional layer 13.

[0059] The MEMS device 10 and the ASIC device 20 are connected to each other via a wafer connection 40. The wafer connection 40 comprises a contact area 41 for electrical contacting the MEMS sensor function and a bond frame structure 42.

[0060] The electrical signals of the ASIC evaluation circuit 22 are routed via vias 23 in the ASIC substrate 21 to the back of the ASIC component 20, where it is connected to a circuit board 30 via solder balls 41'.

[0061] The wafer connection 40 between the MEMS device 10 and the ASIC device 20, for example, is a eutectic bond between aluminum and germanium. For this purpose, the top aluminum wiring layer of the ASIC device 20 can be used as the bonding surface, and a germanium layer can be deposited on the MEMS device 10. The two wafers are then pressed together at temperatures above 430°C with relatively high pressure, resulting in a eutectic liquid phase. In this way, a hermetically sealed aluminum-germanium bond is created in the area of ​​the surrounding bonding frame structure 42, thus hermetically encapsulating the sensor element 123. Other metallic bonding methods, such as copper-tin bonding or thermocompressive methods, can be implemented analogously.

[0062] According to the invention, the decoupling structure of the Fig. The sensor unit shown in Figure 21 includes a membrane element 55 that spans a cavity 56 in the layer structure of the MEMS device 10 and is formed in the area above the wafer connection 40, specifically above the bonding frame 42. This cavity 56 was created in the MEMS substrate 11 prior to the actual MEMS processing. To define the position, shape, and extent of the cavity 56, the MEMS substrate 11 was first doped with a 57, which serves as a boundary for an APSM process. This process then created the cavity 56 and exposed the membrane element 55. Finally, the layer structure with the micromechanical sensor structure was produced on the pre-processed MEMS substrate 11.

[0063] With the aid of the membrane element 55 or the buried cavity 56, the contact pressure required for the wafer bonding process can be locally limited to the area of ​​the bonding frame 42 in order to protect the sensitive circuit elements of the ASIC component 20. This is achieved by deflecting the membrane 55 under the contact pressure during the bonding process until the restoring force corresponds to the applied external force. This also ensures a very good distribution of the contact pressure over the entire bonding area.

[0064] It should be noted that the position and extent of the membrane element 55 or the cavern 56 can also be selected such that the cavern 56 opens laterally during the singulation process, thus creating an even more flexible overhang. However, the opening of the cavern 56 can also occur during the structuring of the MEMS component 10, for example, in a trenching process.

[0065] Fig. Figure 22 shows an alternative realization possibility for a membrane element 55, which spans a cavern 56 in the layer structure of the MEMS device 10 and is formed in the area above the wafer connection 40, specifically above the bonding frame 42.

[0066] Cavern 56 is located here between the MEMS substrate 11 and the functional layer 13. It was created in a sacrificial layer etching process in the layer build-up on the MEMS substrate 11 and subsequently opened in a trenching process, in which pressure equalization openings 58 were created in the functional layer 13.

[0067] In the various figures, identical parts are always marked with the same reference symbols and are therefore usually only named or mentioned once.

Claims

[1] Sensor unit (1) comprising a first semiconductor device (10) and a second semiconductor device (20), wherein the first semiconductor device (10) comprises a first substrate (11) and a sensor structure (12), wherein the second semiconductor device (20) comprises a second substrate (21), wherein the first and second semiconductor devices (10, 20) are connected to each other via a wafer connection (40), characterized by , that the sensor unit (1) has a decoupling structure (50) configured such that the sensor structure (12) is thermomechanically and / or mechanically decoupled from the second semiconductor device (20), wherein the decoupling structure comprises at least one membrane element (55) spanning a cavity (56) in the layer structure of the first semiconductor device (10) and formed in the area above the wafer connection (40). [2] Sensor unit (1) according to claim 1, characterized by, that the decoupling structure (50) has a trench structure (51), wherein the trench structure (51) extends into or completely through the first substrate (11) along a normal direction (103) perpendicular to the main extension plane (100) of the first substrate (11). [3] Sensor unit (1) according to one of the preceding claims, characterized by , that the decoupling structure (50) has coupling elements (52) for coupling the sensor structure (12) to a mainland structure (11') of the first substrate (11). [4] Sensor unit (1) according to claim 2, characterized by , that the trench structure (51) surrounds the sensor structure (12), wherein in particular the trench structure (51) is meandering or frame-shaped, especially ring-shaped. [5] Sensor unit (1) according to claim 1, characterized bythat the cavern (56) is closed off under the at least one membrane element (55) or has at least one pressure equalization opening (58). [6] Sensor unit (1) according to claim 3, characterized by , that the sensor structure (12) comprises a structural element (120) encompassed by the first substrate (11) and a sensor element (123) encompassed by a functional layer (13) of the first semiconductor device (10), wherein the sensor element (123) is connected to the first substrate (11) exclusively indirectly via the coupling elements (52), wherein in particular the coupling elements (52) are formed from the first substrate (11) and / or from the functional layer (13). [7] Sensor unit (1) according to one of the preceding claims, characterized by, that the sensor unit (1) has a cavity (60) and / or a separate further cavity (60'), wherein the cavity (60) and / or further cavity (60') is arranged between the first and second semiconductor device (10, 20), wherein the wafer interconnection (40) has a bond frame structure (42) enclosing the cavity (60) and / or further cavity (60'), which is configured such that the cavity (60) and / or the separate further cavity (60') are hermetically sealable or sealed, wherein in particular a ventilation channel (16) extends through the first substrate (11) into the cavity (60) or further cavity (60'). [8] Sensor unit (1) according to one of the preceding claims, characterized by , that the sensor structure (12) is a pressure sensor structure, wherein a pressure sensor channel (14) is arranged in the first substrate (11), the pressure sensor channel (14) extending into the sensor unit (1) up to a membrane (18) of the pressure sensor structure. [9] Sensor unit (1) according to any one of the preceding claims, characterized by , that the sensor unit (1) has a via (15), in particular a silicon via, formed in the first substrate (11) for electrical contacting the sensor element (123) of the sensor structure (12). [10] Sensor unit (1) according to any one of the preceding claims, characterized by , that the decoupling structure (50) is a trench structure (51) filled with a backfill material (54), wherein the backfill material (54) is in particular a polymer material, wherein the backfill material (54) has an elastic modulus that is at least one order of magnitude smaller than a substrate material, in particular silicon material, of the first substrate (11). [11] Method for manufacturing a sensor unit (1) according to any one of the preceding claims, characterized by, that in a first manufacturing step a first semiconductor device (10) with a first substrate (11) and a sensor structure (12) is provided, wherein a second semiconductor device (20) with a second substrate (21) is provided, wherein in a second manufacturing step the first and second semiconductor devices (10, 20) are connected to each other via a wafer connection (40) to form the sensor unit (1), wherein in a third manufacturing step a decoupling structure (50) is formed for thermomechanical and / or mechanical decoupling of the sensor structure (12) from the second semiconductor device (20), wherein the decoupling structure comprises at least one membrane element (55) that spans a cavity (56) in the layer structure of the first semiconductor device (10) and is formed in the region above the wafer connection (40). [12] Method according to claim 11, characterized by that in the third manufacturing step -- the decoupling structure (50) and / or -- a pressure sensor channel (14) and / or -- a through-hole (15') and / or -- a ventilation duct (16) and / or -- an insulation structure is structured in the first semiconductor device (10), in particular the first substrate (11), by time-controlled etching, in particular by reactive ion deep etching, and / or by means of a laser beam. [13] Method according to claim 11 or 12, characterized by , that in the third manufacturing step in the first semiconductor device (10), in particular the first substrate (11), -- the decoupling structure (50) and / or -- the pressure sensor channel (14) and / or -- the via hole (15') and / or -- the ventilation duct (16) and / or -- the isolation structure is formed simultaneously.

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