Micro-electro-mechanical sensor device with wafer level integration and corresponding manufacturing method

Abstract

The embodiment of the invention relates to a micro-electro-mechanical sensor device with wafer level integration and a corresponding manufacturing method. Described herein is a microelectromechanical sensor device comprising a stack of a first die integrated with a pressure detection structure and a second die integrated with an inertia detection structure, the first die constituting a cap for the inertia detection structure and bonded to the second die thereby defining a sealed cavity. The first die has a first substrate having a front surface and a back surface, the back surface being bonded to the second die, the buried cavity being buried and completely contained in the first substrate and arranged in a position corresponding to the front surface, the buried cavity being separated from the front surface by a film. In particular, the aforementioned buried cavity is distinct from and separate from the sealed cavity.

Description

Technical Field

[0001] The present disclosure relates to a wafer-level integrated micro-electromechanical sensor device with a pressure sensing structure and an inertia sensing structure. The present disclosure also relates to a corresponding manufacturing method. Background Art

[0002] As is known, current micromachining techniques make it possible to manufacture microelectromechanical systems (MEMS) starting from layers of semiconductor material that have been deposited (e.g. layers of polysilicon) or grown on sacrificial layers (e.g. epitaxial layers) and then removed via chemical etching. Inertial sensors obtained with this technique, such as accelerometers, resonators or gyroscopes, are achieving increasing success in fields such as the automotive sector, inertial navigation, or portable devices for consumer electronics (so-called consumer applications).

[0003] Pressure sensors manufactured using MEMS technology are also known, and generally include a membrane made in a die of semiconductor material, suspended above a cavity so as to deform in response to an incident pressure wave. A sensing element (e.g., a piezoresistor) formed at the membrane provides an electrical detection signal indicative of the value of the pressure acting on the sensor.

[0004] In particular, solutions are known which envisage integrating inertial sensing structures (eg accelerometers or gyroscopes) and pressure sensing structures in the same package to provide complex sensing units for several applications ranging, for example, from the automotive field to consumer electronics.

[0005] For example, MEMS accelerometers and pressure sensors have been integrated at the package level to obtain tire pressure monitoring systems (TPMS) for motor vehicles. Furthermore, motion sensing units are known, which enclose an inertial sensing structure and a pressure sensing structure in the same package to obtain an inertial measurement unit (IMU) with several degrees of freedom.

[0006] However, integrating several MEMS sensing structures (especially pressure sensing structures and inertial sensing structures) in the same package brings some problems, especially with regard to the size and space occupation of the resulting device and with regard to the compatibility of manufacturing technologies.

[0007] In this regard, different sensors (especially inertial sensors and pressure sensors) may have different operating principles and technical requirements. For this reason, different front-end manufacturing technologies are usually used to manufacture these devices (where "front-end" refers to the step of processing the semiconductor material wafer of the sensor to produce the corresponding detection structure).

[0008] Using different technologies has the advantage of removing the constraints imposed by the integration of processes of different devices and providing greater flexibility for each technology in producing the sensor and achieving the final performance.

[0009] For the reasons stated above, the detection structures are typically integrated at the package level, after being made in the corresponding die, with back-end technology ("back-end" refers to the last steps of packaging of the already processed die, in which the corresponding detection structures are already provided, for example, these steps include mechanically coupling the same die to the lead frame of the package, electrically coupling through wire bonding, and applying a coating or some other type of packaging covering).

[0010] Within the same package, another die with an integrated electronic ASIC (application-specific integrated circuit) may also be enclosed, which is electrically coupled to various sensors (e.g., pressure sensors and inertial sensors) for performing appropriate processing operations (e.g., filtering, amplification, comparison with thresholds, etc.) on the detection signals provided by the corresponding detection structures and for supplying output signals to external electronic systems.

[0011] This integration at the package level generally follows two approaches.

[0012] The first approach envisages positioning the MEMS dies integrating the various sensing structures side by side, thereby increasing the space occupied in the horizontal plane of the final package.

[0013] The second approach envisages stacking in the vertical direction of the MEMS die, thereby increasing the thickness of the final package.

[0014] In the latter case, since the inertial sensing structure requires a sealed package, the stack usually consists of at least three substrates: a first substrate, in which the inertial sensing structure is provided; a second substrate, which operates as a cover for the same inertial sensing structure; and a third substrate, in which the pressure sensing structure is provided.

[0015] In general, there is a need to provide an improved solution for integrating different MEMS sensors (particularly pressure sensing structures and inertial sensing structures) in the same package, so that the size of the resulting package can be reduced and at the same time there are no restrictions on the implementation of the same sensing structures. Summary of the invention

[0016] It is an object of the present disclosure to at least partially address the problems previously highlighted and meet the above-mentioned needs.

[0017] According to the present disclosure, a wafer-level integrated micro-electromechanical sensor device having a pressure sensing structure and an inertia sensing structure and a method for manufacturing the same are therefore provided.

[0018] For example, at least one embodiment of the microelectromechanical sensor device of the present disclosure is summarized as including: a stack of a first die and a second die, the first die being integrated with a pressure detection structure, the second die being integrated with an inertial detection structure, the first die constituting a cover for the inertial detection structure and being bonded to the second die to define a sealed cavity, wherein the first die includes a first substrate, the first substrate having a front surface and a rear surface, the rear surface being bonded to the second die, a buried cavity being buried and completely contained in the first substrate and being arranged at the front surface, the buried cavity being separated from the front surface by a membrane, and wherein the buried cavity is different from and separated from the sealed cavity. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to better understand the present disclosure, preferred embodiments thereof will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which:

[0020] Figure 1 is a schematic cross-sectional view of a stack formed by a pressure sensing structure and an inertial sensing structure according to aspects of the present disclosure;

[0021] Figure 2 yes Figure 1 A schematic cross-sectional view of a stack of microelectromechanical sensor devices in a corresponding package;

[0022] FIG. 3A to FIG. 3I yes Figure 1 schematic cross-sectional views of a stack of in successive steps of a manufacturing method; and

[0023] Figure 4 is a schematic cross-sectional view of an alternative step of a manufacturing method. DETAILED DESCRIPTION

[0024] As will be described in detail below, aspects of the present disclosure contemplate wafer-level integration of different MEMS sensors (particularly pressure sensors and inertial sensors) prior to dicing corresponding wafers of semiconductor material for forming corresponding die and prior to back-end manufacturing steps (i.e., for packaging within corresponding packages).

[0025] In particular, a first wafer of semiconductor material (in which the sensing structure of the pressure sensor has been previously formed) is stacked (via appropriate bonding) to a second wafer of semiconductor material (in which the sensing structure of the inertial sensor has been previously formed).

[0026] After possible further specific bonding steps, which will be described below, the two stacked wafers subsequently undergo dicing.

[0027] like Figure 1As schematically illustrated in the figure, the aforementioned cutting results in the formation of a stack 1 consisting of a first tube die 2, the first tube die 2 integrating a pressure detection structure 4, the pressure detection structure 4 is bonded (due to the previous bonding between the wafers) to a second semiconductor material tube die 6, and the second semiconductor material tube die 6 integrates an inertial detection structure 8, the inertial detection structure 8, for example, implements an accelerometer, a gyroscope, a resonator, or a suitable combination of these sensors (for example, a combination of a three-axis accelerometer and a three-axis gyroscope).

[0028] According to aspects of the present disclosure, in the aforementioned stack 1 , the first die 2 is a cover for the underlying inertial detection structure 8 so as to define a sealed environment required for the operation of the same inertial detection structure 8 .

[0029] like Figure 2 As schematically illustrated in the figure, the back-end manufacturing steps can subsequently lead to the manufacture of a package 10 of the resulting micro-electromechanical sensor device 100, wherein the aforementioned stack 1 is attached to a third die 12, for example by die attachment, and the third die 12 integrates an electronic ASIC circuit, which is electrically coupled to the first die 2 (and the corresponding pressure detection structure 4) and to the second die 6 (and the corresponding inertial detection structure 8) by corresponding electrical connection lines using wire bonding technology.

[0030] In particular, the first electrical connection line 14a connects the first solder pad 13a carried by the top surface 12a of the third tube core 12 to the corresponding solder pad 13a′ carried by the first tube core 2 (and electrically connected to the pressure detection structure 4), and the second electrical connection line 14b connects the second solder pad 13b carried by the top surface 12a of the third tube core 12 to the corresponding solder pad 13b′ carried by the second tube core 4 (and electrically connected to the inertial detection structure 8).

[0031] The resulting arrangement of the stack 1 can be arranged in a cavity-type package 15, which includes an access hole 16 at the top surface to transmit pressure to the pressure sensing structure 4 in the first tube core 2 (in particular, to the corresponding sensing membrane). As an alternative, the resulting arrangement of the stack 1 can be covered with a coating (acting as a packaging material in this case), for example made of epoxy resin, which can coat the top of the third tube core 12 and laterally coat the stack 1 formed by the first tube core 2 and the second tube core 6, and can also coat the top of the aforementioned first tube core 2. In this case as well, the front surface 10a of the package 10 defined by the aforementioned coating has an access hole to enable the pressure wave to enter toward the pressure sensing structure 4.

[0032] In at least one embodiment, cavity-type package 15 is a lid.

[0033] The rear surface 10b of the same package 10 can be defined by the rear surface 12b of the aforementioned third tube core 12, or, as illustrated here, by a different substrate 17 having the function of a base of the package 10, and appropriate electrical connection elements 18 (in the form of conductive pads or bumps) can be formed on the rear surface 10b for electrical connection to an external system (for example, to an electronic device using the microelectromechanical sensor device 100 for pressure and one or more inertial quantities (such as acceleration or angular velocity)).

[0034] The through-vias 19 connected to the aforementioned stack 1 by corresponding electrical connection lines 19 ′ are advantageously made through the third die 12 or, as illustrated here, through the aforementioned different substrate 17 for connection to the aforementioned electrical connection elements 18 .

[0035] In more detail, the first die 2 comprises a substrate 20 of semiconductor material, in particular silicon, having a front surface 20a and a rear surface 20b extending in a horizontal plane xy and separated from each other along a vertical axis z, perpendicular to the horizontal plane xy.

[0036] The pressure sensing structure 4 comprises a buried cavity 22 which is buried and completely contained in the substrate 20 and is arranged at the front surface 20a, the buried cavity 22 being separated from the front surface 20a by a membrane 24 having a small thickness along the vertical axis z. For example, the thickness of the membrane 24 may have a value (along the aforementioned vertical axis z) comprised between 2 and 10 μm, while the buried cavity 22 has a depth comprised between 2 and 5 μm.

[0037] In particular, the film 24 constituting the surface portion of the substrate 20 has at the front surface 20 a a first main surface 24 a forming part of the same front surface 20 a and a second main surface 24 b facing the buried cavity 22 .

[0038] Thus, the buried cavity 22 is separated and isolated from the front surface 20a of the first die 2 by the aforementioned film 24, and is separated and isolated from the back surface 20b by a monolithic body 25 consisting of the lower portion of the substrate 20, i.e., a compact and uniform area of ​​material, such as single crystal silicon. Thus, the aforementioned buried cavity 22 forms a buried environment, which is completely contained and isolated within the first die 2, and cannot be accessed from the outside of the same first die 2.

[0039] In a possible embodiment, the pressure detection structure 4 further comprises a piezoresistance element 26 , for example formed by a doped diffusion region and arranged in the membrane 24 at a corresponding first surface 24 a , in a peripheral position relative to the same membrane 24 .

[0040] In a manner not described in detail, the piezoresistor elements 26 may be electrically connected, for example in a Wheatstone bridge configuration, to output an electrical signal indicative of deformation of the membrane 24 due to an incident pressure wave (and thus indicative of a pressure value).

[0041] As an alternative, the pressure sensing structure 4 may be of a capacitive type, in which case a displacement of the membrane 24 causes a change in the capacitive coupling between an associated arrangement of mobile sensing electrodes coupled to the membrane 24 (or constituted by the membrane, or constituted by parts of the same membrane) and a corresponding arrangement of fixed sensing electrodes.

[0042] The pressure detection structure 4 includes one or more output pads (the aforementioned pads 13a′), which are electrically connected to the output of the aforementioned Wheatstone bridge or the aforementioned detection electrode, for example, and are arranged on the front surface 20a, in the dielectric layer 27, whether a single layer or a composite layer, the dielectric layer 27 coats and electrically insulates the same front surface 20a.

[0043] In this embodiment, below the buried cavity 22 (relative to the vertical axis z) and at the rear surface 20b, the first tube core 2 also has a facing cavity 28, which constitutes a recess of the aforementioned rear surface 20b and faces the lower layer second tube core 6 in the aforementioned stack 1.

[0044] At the same rear surface 20b, laterally with respect to the facing cavity 28, the first die 2 has a bonding portion 29 of the substrate 20 designed for bonding to the aforementioned second die 6 by means of a bonding area 29' of, for example, glass frit or other suitable material.

[0045] In detail, the second die 6 comprises a respective substrate 30 of semiconductor material, in particular silicon, having a respective front surface 30a and a respective back surface 30b extending in a horizontal plane xy and separated from each other along a vertical axis z.

[0046] The inertial detection structure 8 includes a suspension structure 32 , which is arranged on the front surface 30 a and is separated from the substrate 30 by a separation cavity 34 .

[0047] The suspension structure 32 is made in a structural layer 33 (e.g., made of polysilicon), which is formed on the substrate 30 and is defined to provide a suspension element (e.g., one or more suspended masses, detection electrodes, and elastic elements), which is suspended above the separation cavity 34 and is configured to allow movement through inertial effects.

[0048] The inertial detection structure 8 also includes: appropriate conductive leads or paths 35 on the substrate 30 (and / or formed in a surface portion of the substrate 30 itself at the front surface 30a), insulated by a surface dielectric layer 36 arranged on the same front surface 30a; and one or more electrical connection pads (the aforementioned pads 13b′), which are coupled to the conductive leads or paths 35 and are formed on the structural layer 33, laterally relative to the suspension structure 32, in particular in a position not covered by the first tube core 2 in the aforementioned stack 1.

[0049] The structure described for the wafer-level integration of the pressure sensing structure 4 and the inertial sensing structure 8 allows a reduction in the number of substrates in the microelectromechanical sensor device 100 (equal to two), and therefore a reduction in the thickness of the stack 1 in the direction of the vertical axis z and the resulting thickness of the package 10.

[0050] Furthermore, the pressure detection structure 4 and the inertial detection structure 8 can be manufactured independently and do not affect each other in the manufacturing method, so they can be optimized separately and independently for the corresponding performance.

[0051] Likewise, advantageously, the third die 12 can be independently manufactured using specific manufacturing steps of the ASIC.

[0052] Furthermore, the disclosed subject matter described achieves complete independence between the buried cavity 22 associated with pressure detection and the sealed cavity associated with inertial detection (formed together by the separate cavity 34 and by the connected facing cavity 28); in this way, the pressure in the buried cavity 22 is independent of the operational requirements of the sealed cavity.

[0053] Furthermore, the depth (along the vertical axis z) of the sealed cavity associated with inertial sensing is independent of the thickness of the substrate 20 of the first die 2 .

[0054] Furthermore, the structure described is robust from a mechanical point of view both during its manufacture and during its operation, since the cover used to protect the inertial sensor consists of a thick silicon layer (represented by the aforementioned substrate 20 of the first die 2 ).

[0055] A more detailed description of some specific steps of the manufacturing method is now presented, in particular regarding the bonding of wafers of semiconductor material in which the pressure sensing structure 4 and the inertial sensing structure 8 are provided and the subsequent formation of the aforementioned stack 1 by dicing the stacked wafers.

[0056] in this regard, Figure 3A A first wafer 40 of semiconductor material (particularly silicon) is shown, in which a plurality of the aforementioned first pressure sensing structures 4 (by way of example, in FIG. 4 ) has been provided using known process steps. Figure 3A Two of them are shown in the figure).

[0057] These pressure sensing structures 4 are separated from each other by corresponding scribe lines SL, and the wafer dicing operation is to be performed along the scribe lines SL.

[0058] Each pressure detection structure 4 can be obtained, for example, using the process described in EP 1 324 382 B1 filed in the name of the present applicant.

[0059] In short, the process envisages defining, by means of a suitable mask, an etched area corresponding to the area to be occupied by the buried cavity 22 and having an extension corresponding to the extension of the membrane 24 to be formed on the buried cavity 22. The etch mask comprises a plurality of mask portions (for example, hexagonal) defining a lattice (for example, a honeycomb lattice).

[0060] Using an etching mask, anisotropic chemical etching is performed on the substrate 20, and then trenches are formed, which are connected to each other and define a plurality of pillars. The trenches form an open area with a complex shape (corresponding to the grid of the etching mask), and the pillars (having a shape corresponding to the mask portion) extend in the open area.

[0061] Next, the etching mask is removed and epitaxial growth is performed in a deoxidized environment (generally, in an atmosphere with a high concentration of hydrogen, preferably in an atmosphere with trichlorosilane-SiHCl3). Thus, an epitaxial layer grows on the pillars and closes the aforementioned open area formed by the trench at the top.

[0062] A thermal annealing step is then carried out, for example at a temperature of 1190° C. for a duration of 30 minutes, preferably in a reducing atmosphere (generally a hydrogen atmosphere). The annealing step causes the migration of silicon atoms, which tend to move to lower energy positions. Thus, also due to the short distances between the pillars, the silicon atoms migrate entirely from the portion of the pillars present in the aforementioned open area formed by the trenches, and the buried area is formed starting from this open area.

[0063] In particular, the buried region defines the aforementioned buried cavity 22, within which an environment with a controlled atmosphere is created, as a result of the described process steps, containing residual gases (eg hydrogen and silane) at a desired pressure.

[0064] A layer of single-crystal silicon remains on the buried region, the layer being composed partly of epitaxially grown silicon atoms and partly of migrated silicon atoms, which forms the aforementioned film 24 .

[0065] like Figure 3B As illustrated in , the bonding process subsequently envisages etching the dielectric layer 27 in the region of the scribe line SL for defining an access opening 41 , which exposes the front surface 20 a of the substrate 20 .

[0066] Then, a sacrificial layer 42 ( 42 ) of a protective coating material, for example, composed of a polyamide tape, is formed on the dielectric layer 27 and in the aforementioned access opening 41. Figure 3C ).

[0067] Then, the wafer 40 is subjected to ( Figure 3D ) a thinning process from the back side (eg via grinding), which results in a thickness reduction in a direction perpendicular to the axis z, for example from approximately 700 μm to between 300 and 400 μm.

[0068] like Figure 3E As illustrated in , the resulting rear surface 20b of the substrate 20 is chemically etched for forming the aforementioned facing cavity 28 which, for each pressure sensing structure 4, extends in the substrate 20 by an amount, for example, between 10 and 100 μm along the vertical axis z.

[0069] The same backside etch results in defining the aforementioned bonding portion 29 of the substrate 20 , which is to be bonded to the second die 6 and is separated by a respective further cavity 43 along a respective scribe line SL.

[0070] Therefore, the sacrificial layer 42 is removed from the top surface of the wafer 40 ( Figure 3F ).

[0071] after, Figure 3G The bonding area 29' is formed, for example, using a technique of printing and curing a material such as glass frit (or some other suitable material).

[0072] Then, the process envisions ( Figure 3H ) A semiconductor material (in particular silicon) is bonded between a first wafer 40 and a second wafer 45 via the aforementioned bonding area 29', wherein a plurality of the aforementioned inertial detection structures 8 have been provided using known process steps. A flexible layer (not shown here) may be temporarily arranged on the first wafer 40 to prevent any surface damage during the aforementioned bonding step.

[0073] In short, using the so-called ThELMA (Thick Epitaxial Layers for Microactuators and Accelerometers) process, the inertial sensing structure 8 can be formed using surface micromachining.

[0074] The process envisages depositing a conductive layer on a substrate 30. This conductive layer is then patterned by a photolithographic process to define horizontal electrical interconnections, providing the aforementioned conductive leads or paths 35.

[0075] Next, a sacrificial layer of silicon oxide is deposited and patterned on the aforementioned conductive layer. Next, an epitaxial growth of a structural layer 33, for example made of polysilicon, is performed, which will form the suspended structures 32 and the corresponding anchoring elements (which extend through the openings previously defined in the sacrificial layer until they contact the conductive layer).

[0076] The structural layer 33 is then defined by trench etching to form trenches defining what will be the suspended elements of the aforementioned suspension structure 32 (eg, one or more suspended masses, capacitively coupled sensing electrodes, elastic suspension elements).

[0077] The oxide of the sacrificial layer is then removed by chemical etching performed through the trenches for releasing the suspended elements and defining the separation cavities 34. The unremoved portions of the same sacrificial layer also form the aforementioned surface dielectric layer 36 provided on the front surface 30a of the substrate 30.

[0078] At this point, the coupling process may envisage a step of thinning the back side of the second wafer 45 , for example by grinding, so as to achieve a resulting substrate 30 thickness of, for example, between 300 and 900 μm.

[0079] Then( Fig. 3I ), using an appropriate mask (not shown) on the first wafer 40, a dry chemical etching step is performed through the entire thickness of the first wafer 40, thereby opening an access window 48 towards the underlying second wafer 45 in the area corresponding to the pad 13b' of the corresponding inertial detection structure 8.

[0080] Furthermore, this etching is performed through the structural layer 33 in order to electrically insulate from each other the pads 13 b ′ belonging to the different inertial detection structures 8 formed in the aforementioned second wafer 45 (and to enable appropriate procedures for electrical testing of the operation of the inertial detection structures 8 at wafer level).

[0081] The process then continues with dicing the stack formed by the aforementioned first wafer 40 and the second wafer 45, thereby defining a stack 1 of micro-electromechanical sensor devices 100, and then packaging the same stack 1 in a corresponding package 10 (e.g., bonded to a third die 12 integrating an electronic ASIC, as described above and as described above). Figure 1 and Figure 2 ).

[0082] like Figure 4 As shown in , an alternative to the aforementioned step of performing dry chemical etching through the entire thickness of the first wafer 40 can be envisaged, in which case the pads 13 b ′ belonging to the different inertial detection structures 8 have already been separated and isolated in the second wafer 45, by opening the aforementioned access window 48 by a sawing operation from the front side of the first wafer 40 using a suitable blade, which is schematically illustrated and designated by 49.

[0083] The advantages of the proposed disclosure are clearly apparent from the foregoing description.

[0084] Regardless, it is emphasized that the present disclosure enables the dimensions of the package 10 of the micro-electromechanical sensor device 100 to be reduced, in particular with regard to the thickness of the corresponding stack 1 in the direction perpendicular to the axis z.

[0085] Furthermore, the described disclosure advantageously keeps the manufacturing processes of the pressure sensing structure 4 and the inertial sensing structure 8 , as well as the manufacturing processes of the associated ASICs, separate, thereby ensuring the desired flexibility and independence in defining the corresponding mechanical and electrical characteristics.

[0086] Finally, it is evident that modifications and variations may be made to what has been described and illustrated herein without thereby departing from the scope of the present disclosure as defined in the appended claims.

[0087] In particular, it is emphasized again that the described disclosure enables wafer-level integration of different MEMS sensors with different implementation technologies within the same package, which sensors may also differ in number and type from the pressure sensors and inertial sensors that have been mentioned previously in particular detail.

[0088] The micro-electromechanical sensor device (100) comprises: a stack (1) of a first die (2) and a second die (6), the first die (2) being integrated with a pressure sensing structure (4), the second die (6) being integrated with an inertial sensing structure (8), the first die (2) constituting a cover for the inertial sensing structure (8) and being bonded to the second die (6) to define a sealed cavity (28, 34), wherein the first die (2) comprises a first substrate (20), the first substrate having a front surface (20a) and a rear surface (20b), the rear surface (20b) being bonded to the second die (6), a buried cavity (22) being buried and completely contained in the first substrate (20) and being arranged at the front surface (20a), the buried cavity (22) being separated from the front surface (20a) by a membrane (24); and wherein the buried cavity (22) is distinct from and separate from the sealed cavity (28, 34).

[0089] The inertial detection structure (8) comprises a second substrate (30) and a suspension structure (32), wherein the second substrate (30) has a front surface (30a) and a rear surface (30b), the suspension structure (32) is arranged above the front surface (30a), and the suspension structure is separated from the second substrate (30) by a separation cavity (34); and the first tube core (2) has a facing cavity (28) at the rear surface (20b) of the first substrate, the facing cavity constituting a recess of the aforementioned rear surface (20b) and facing the second tube core (6) in the stack (1); the facing cavity (28) and the separation cavity (34) jointly define the sealed cavity.

[0090] The facing cavity (28) is separated from the buried cavity (22) by a monolithic portion (25) of the first substrate (20).

[0091] The first die (2) has a bonding portion (29) laterally relative to the facing cavity (28) and at the rear surface (20b), which is bonded to the second die (6) through an area made of a bonding material (29').

[0092] The second tube core (6) includes a structural layer (33) which is arranged above the corresponding front surface (30a) of the second substrate (30), and the suspension structure (32) is defined in the structural layer (33); the bonding portion (29) of the first tube core (2) is bonded to the structural layer (33) laterally and externally relative to the suspension structure (32).

[0093] The device also includes a package (10) which accommodates the stack (1); wherein the stack (1) is attached to a third tube die (12), the third tube die (12) is integrated with an electronic circuit, and the electronic circuit is electrically coupled to the first tube die (2) and the corresponding pressure detection structure (4) through corresponding electrical connection lines (14a, 14b) and is electrically coupled to the second tube die (6) and the corresponding inertia detection structure (8).

[0094] The package (10) further comprises a coating (15); wherein a front surface (10a) of the package (10) defined by the coating (15) has an entry hole (16) for allowing pressure waves to enter toward the pressure detection structure (4) in the first tube core (2).

[0095] The inertial sensing structure (8) provides one or more of the following MEMS sensors: an accelerometer; a gyroscope; a resonator; or a suitable combination of the MEMS sensors.

[0096] A method for manufacturing a micro-electromechanical sensor device (100) comprises: forming a pressure detection structure (4) in a first wafer (40) of semiconductor material; forming an inertia detection structure (8) in a second wafer (45) of semiconductor material; coupling the first wafer (40), wherein the first wafer (40) is stacked on the second wafer (45); cutting the first wafer (40) and the second wafer (45) to obtain a stack (1) of a first die (2) and a second die (6), wherein the first die (2) is integrated with the pressure detection structure (4), the second die (6) is integrated with the inertia detection structure (8), and the first die (2) constitutes a sensor for the inertia detection. The pressure sensing structure (8) is covered by a cover and is bonded to the second die (6) to define a sealed cavity (28, 34), wherein forming the pressure sensing structure (4) includes: defining a first substrate (20) in the first wafer (40) and forming a buried cavity (22), the first substrate (20) having a front surface (20a) and a rear surface (20b), the buried cavity (22) being buried and completely contained in the first substrate (20), and being arranged at the front surface (20a), the front surface (20a) being separated from the front surface (20a) by a membrane (24), so that in the stack (1), the buried cavity (22) is different from and separated from the sealed cavity (28, 34).

[0097] Forming the pressure detection structure (4) includes: after forming the buried cavity (22), etching from the back side of the substrate (20) to form a facing cavity (28) at the rear surface (20b), wherein the facing cavity (28) constitutes a recess of the aforementioned rear surface (20b) and faces the second tube core (6) in the stack (1), and promotes the definition of the sealed cavity.

[0098] Forming the inertial detection structure (8) includes: defining a second substrate (30) in the second wafer (45), the second substrate having a corresponding front surface (30a) and a corresponding rear surface (30b); forming a structural layer (33), the structural layer (33) being arranged above the corresponding front surface (30a) of the second substrate (30); and defining the structural layer (33) to form a suspended structure (32), the suspended structure being separated from the corresponding front surface (30a) by a separation cavity (34); wherein in the stack (1), the separation cavity (34) and the facing cavity (28) jointly define the sealed cavity.

[0099] The method further comprises: after bonding between the first wafer (40) and the second wafer (45), opening an access window (48) toward the underlying second wafer (45) at an area corresponding to the contact pad (13b') of the inertial detection structure (8), the access window (48) passing through the first wafer (40).

[0100] Forming the access window (48) comprises one of the following steps: performing a dry chemical etching of the first wafer (40) through the entire thickness of the first wafer (40), the etching further being performed through the structural layer (33) of the second wafer (45), thereby electrically insulating the contact pads (13b') from each other; or opening the access window (48) by a sawing operation from the front side of the first wafer (40).

[0101] The method also includes: mechanically coupling a third tube die (12) to the stack (1), the third tube die (12) integrating an electronic circuit; and electrically coupling the electronic circuit to the first tube die (2) and the corresponding pressure detection structure (4) and to the second tube die (6) and the corresponding inertia detection structure (8) through corresponding electrical connection lines (14a, 14b).

[0102] The method further comprises: forming a package (10), the package (10) accommodating the stack (1); wherein forming the package (10) comprises: forming a coating (15); wherein a front surface (10a) of the package (10) defined by the coating (15) has an entry hole (16) to enable a pressure wave to enter toward a pressure detection structure (4) in the first die (2).

[0103] The various embodiments described above can be combined to provide other embodiments. If necessary, aspects of the embodiments can be modified to employ concepts of various patents, applications, and publications to provide more embodiments.

[0104] These and other changes can be made to the embodiments in light of the above detailed description. In general, in the appended claims, the terms used should not be interpreted as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be interpreted to include all possible embodiments and the full range of equivalents to which these claims are entitled. Therefore, the claims are not limited by this disclosure.

Claims

1. A micro-electromechanical sensor device, comprising: a stack of a first die having a pressure sensing structure integrated therein and a second die having an inertia sensing structure integrated therein, the first die constituting a cover for the inertia sensing structure and being bonded to the second die to define a sealed cavity, wherein the first die comprises a first substrate having a front surface and a back surface, the back surface being bonded to the second die, a buried cavity being buried and completely contained in the first substrate and arranged at the front surface, the buried cavity being separated from the front surface by a film, and The buried cavity is distinct and separate from the sealed cavity.

2. The device according to claim 1, wherein the inertial detection structure comprises a second substrate and a suspension structure, the second substrate having a front surface and a rear surface, the suspension structure being arranged above the front surface, and the suspension structure being separated from the second substrate by a separation cavity; and wherein the first die has a facing cavity at the rear surface of the first substrate, the facing cavity constituting a recess of the rear surface and facing the second die in the stack; The facing chamber and the separation chamber jointly define the sealed chamber. 3 . The apparatus of claim 2 , wherein the facing cavity is separated from the buried cavity by a monolithic portion of the first substrate. 4 . The device of claim 2 , wherein the first die has a bonding portion laterally relative to the facing cavity and at the rear surface, the bonding portion being bonded to the second die through an area made of a bonding material.

5. The device according to claim 4, wherein the second tube core includes a structural layer, which is arranged above the corresponding front surface of the second substrate, and the suspension structure is defined in the structural layer; the bonding portion of the first tube core is bonded to the structural layer laterally and externally relative to the suspension structure.

6. The device according to claim 1 further includes a package that accommodates the stack; wherein the stack is attached to a third tube core, the third tube core integrating an electronic circuit, and the electronic circuit is electrically coupled to the first tube core and the corresponding pressure detection structure through corresponding electrical connection lines and is electrically coupled to the second tube core and the corresponding inertial detection structure.

7. The device of claim 6, wherein the package further comprises a coating; wherein a front surface of the package defined by the coating has an entry hole to enable pressure waves to enter toward the pressure sensing structure in the first die.

8. The apparatus of claim 1, wherein the inertial sensing structure provides one or more of the following MEMS sensors: an accelerometer; a gyroscope; a resonator; or a suitable combination of the MEMS sensors.

9. A method for manufacturing a micro-electromechanical sensor device, comprising: forming a pressure sensing structure in a first wafer of semiconductor material; forming an inertial sensing structure in a second wafer of semiconductor material; coupling the first wafer, the first wafer being stacked on the second wafer; performing dicing of the first wafer and the second wafer to obtain a stack of a first die and a second die, the first die being integrated with the pressure detection structure, the second die being integrated with the inertia detection structure, the first die constituting a cover for the inertia detection structure and being bonded to the second die to define a sealed cavity, The formation of the pressure detection structure includes: defining a first substrate in the first wafer and forming a buried cavity, the first substrate having a front surface and a rear surface, the buried cavity being buried and completely contained in the first substrate, and being arranged at the front surface, the buried cavity being separated from the front surface by a membrane, so that in the stack, the buried cavity is different and separated from the sealed cavity.

10. The method of claim 9, wherein forming the pressure detection structure comprises: After formation of the buried cavity, etching is performed from the back side of the substrate to form a facing cavity at the rear surface, the facing cavity constituting a recess of the rear surface and facing the second die in the stack and facilitating the definition of the sealed cavity.

11. The method of claim 10, wherein forming the inertial sensing structure comprises: defining a second substrate in the second wafer, the second substrate having a corresponding front surface and a corresponding back surface; forming a structural layer disposed over the corresponding front surface of the second substrate; and defining the structural layer to form a suspended structure, the suspended structure being separated from the corresponding front surface by a separation cavity; wherein, in the stack, the separation cavity and the facing cavity jointly define the sealed cavity.

12. The method according to claim 11, further comprising: After bonding between the first wafer and the second wafer, an access window is opened toward the underlying second wafer at a region corresponding to the contact pad of the inertial detection structure, the access window penetrating through the first wafer.

13. The method of claim 12 , wherein forming the access window comprises one of the following steps: performing a dry chemical etch of the first wafer through the entire thickness of the first wafer, the etching further being performed through the structural layer of the second wafer, thereby electrically insulating the contact pads from each other; or opening the access window by a sawing operation from the front side of the first wafer.

14. The method according to claim 9, further comprising: mechanically coupling a third die to the stack, the third die having integrated electronic circuitry; And the electronic circuit is electrically coupled to the first die and the corresponding pressure detection structure and to the second die and the corresponding inertia detection structure through corresponding electrical connection lines.

15. The method according to claim 14, further comprising: forming a package, the package housing the stack; Wherein forming the package comprises: forming a coating; The front surface of the package defined by the coating has an entry hole to allow pressure waves to enter toward the pressure detection structure in the first tube die.

16. A device comprising: A first tube core, wherein the first tube core comprises: First side; a second side, the second side being opposite to the first side; a first dielectric layer on the first side; a first buried cavity, the first buried cavity being within the first die; a second die coupled to the second side of the first die, the second die comprising: a substrate having a first surface and a second surface, the second surface being opposite to the first surface; a second dielectric layer, the second dielectric layer being on the first surface of the substrate; a conductive layer on the second dielectric layer; and a structural layer, the structural layer being on the second dielectric layer, the structural layer comprising a suspension structure, the suspension structure being suspended, the structural layer being at the second side and coupled to the second side of the first die; an electrical connection structure laterally spaced from the structural layer, the electrical connection structure extending through the second dielectric layer to the conductive layer, and the electrical connection structure extending outwardly from the second dielectric layer; A sealed cavity, the sealed cavity is defined by the first tube core and the second tube core, the sealed cavity contains the suspension structure, and the sealed cavity includes: a separation cavity defined by the conductive layer, the second dielectric layer, and the structural layer, and extending from the suspended structure to the conductive layer; and A facing cavity is defined by the first side and the structural layer, and the facing cavity extends from the second side to the structural layer. 17 . The apparatus of claim 16 , wherein the first buried cavity is closer to the first side than to the second side.

18. The device of claim 16, wherein the first die comprises at least one piezoresistor element, the at least one piezoresistor element is at the first side, and the at least one piezoresistor element is covered by the first dielectric layer.

19. The apparatus of claim 16, further comprising a third die coupled to the second surface of the substrate.

20. The apparatus of claim 19, further comprising: a base substrate coupled to the third die, the base substrate being spaced apart from the substrate by the third die; a cover coupled to the base substrate, the cover comprising an access hole extending through the cover; A cavity is defined by the cover and the base substrate, the cavity containing the first die, the second die, and the third die.

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