Method of manufacturing an integrated system comprising a capacitive pressure sensor and an inertial sensor and integrated system

Abstract

The present disclosure relates to a method of manufacturing an integrated system comprising a capacitive pressure sensor and an inertial sensor and to the integrated system. A method for manufacturing a microelectromechanical system, MEMS, integrating a first MEMS device and a second MEMS device. The first MEMS device is a capacitive pressure sensor and the second MEMS device is an inertial sensor. The steps of manufacturing the first MEMS device and the second MEMS device are at least partially shared with each other, resulting in a high integration on a single die, and allowing to implement the manufacturing process with high yield and controlled costs.

Description

Technical Field

[0001] This invention relates to a method for manufacturing microelectromechanical systems (MEMS), and to a MEMS comprising a first MEMS device and a second MEMS device. Specifically, the first MEMS device is a capacitive pressure sensor and the second MEMS device is an inertial sensor, or a combination of inertial sensors, such as, for example, an accelerometer and a gyroscope. Background Technology

[0002] The capacitive pressure sensor is provided with a suspended region or membrane that is movable relative to the rest of the structure. Specifically, this membrane represents a variable electrode, facing a fixed portion forming a fixed electrode, and separated from it by a partially or completely buried cavity. The inertial sensor and the pressure sensor are manufactured simultaneously using at least partially the same process.

[0003] As is well known, MEMS (Micro-Electro-Mechanical Systems) transducers include a movable, sensitive structure for converting environmental quantities (pressure, motion, sound waves, etc.) into electrical quantities (e.g., capacitance changes). Suitable readout electronics are used to perform processing operations on this electrical quantity (including amplification and filtering operations) in order to provide an electrical output signal (e.g., voltage) representing the sensed pressure value.

[0004] In capacitive sensing applications, microelectromechanical sensing structures typically include a movable electrode formed as a diaphragm or membrane, arranged facing a fixed electrode to provide a plate of sensing capacitor with variable capacitance. The movable electrode is anchored to the structural layer by its first portion (typically around the periphery of the structural layer), while its second portion (typically the central portion) is free to move or bend. The movable and fixed electrodes thus form a capacitor, and bending of the membrane forming the movable electrode results in a change in capacitance according to the quantity to be sensed.

[0005] Other types of transducers, such as those used to sense motion or vibration, are also known as accelerometers and gyroscopes, and their operation is similar to that described above. In this case, the sensing structure is not a membrane, but rather formed by one or more movable mass blocks coupled to a fixed support structure via springs. Also in this case, the conversion of motion signals can occur capacitively in a manner known per se.

[0006] These types of sensors, along with other MEMS sensors, are typically installed in multimedia electronic devices, such as smartphones, smartwatches, consumer electronics, or other specialized instruments. The integration of numerous MEMS systems / sensors in electronic devices requires the use of dedicated integrated circuit boards, thus significantly impacting space requirements.

[0007] Furthermore, according to existing technology, different sensors are typically housed in corresponding packages containing transducers and electronics for acquiring and preprocessing the electrical signals generated by the transducers, typically ASIC circuitry. In some solutions, the ASIC can be shared, as discussed, for example, in WO2013 / 061313.

[0008] However, there is a growing market demand for highly integrated solutions that allow for cost savings and, most importantly, reduced footprint. Summary of the Invention

[0009] The purpose of this disclosure is to provide a solution to the aforementioned needs.

[0010] According to this disclosure, a method for manufacturing a MEMS system and the MEMS system thereby provided are provided.

[0011] For example, in at least one embodiment of this disclosure, a method for manufacturing a microelectromechanical system (MEMS) including a first MEMS device and a second MEMS device includes the following steps: forming a first electrode of the first MEMS device on a substrate; forming a first sacrificial layer of material removable by an etching chemical solution on the first electrode; forming a protective layer impermeable to the etching chemical solution on the first sacrificial layer; selectively removing portions of the protective layer to expose corresponding sacrificial portions of the first sacrificial layer; forming a membrane of porous material permeable to the etching chemical solution on the sacrificial portions; using the etching chemical solution to remove the sacrificial portions through the membrane to form a cavity; forming a first structural layer, the first structural layer... A pore in the sealing film layer is formed and a suspension structure of the first MEMS device is formed therewith. The suspension structure is capacitively coupled to a second electrode of the first electrode via a cavity. A second sacrificial layer is formed above the first structural layer, which can be etched by a chemical solution. A second structural layer is formed above and in contact with the second sacrificial layer. The second structural layer is patterned to simultaneously form a movable structure of the second MEMS device and a bias structure for the first and second electrodes of the first MEMS device. Selective portions of the second sacrificial layer are removed by etching with a chemical solution, so that the movable structure of the second MEMS device and the suspension structure of the first MEMS device can move freely according to their respective degrees of freedom.

[0012] For example, in at least one embodiment of this disclosure, a microelectromechanical system (MEMS) includes a first MEMS device and a second MEMS device, and includes: a substrate; a first electrode belonging to the first MEMS device extending on the substrate; a first sacrificial layer of material on the first electrode that can be removed by an etching chemical solution; a protective layer on the first sacrificial layer that is impermeable to the etching chemical solution; a membrane layer of porous material on the sacrificial portion, the porous material being permeable to the etching chemical solution; a cavity extending below the membrane layer; a first structural layer that seals the pores of the membrane layer and forms with the membrane layer a suspension structure of the first MEMS device, the suspension structure being capacitively coupled to a second electrode of the first electrode through the cavity; and a second structural layer that is patterned to form a movable structure of the second MEMS device and a bias structure of the first and second electrodes of the first MEMS device, wherein the movable structure of the second MEMS device and the suspension structure of the first MEMS device are freely movable according to corresponding degrees of freedom. Attached Figure Description

[0013] To better understand this disclosure, preferred embodiments thereof will now be described by way of non-limiting example only with reference to the accompanying drawings, in which:

[0014] Figure 1 -19 shows the fabrication steps of an integrated microelectromechanical system (MEMS) according to an embodiment of the present disclosure in a cross-sectional view, the integrated microelectromechanical system specifically including a capacitive pressure sensor and an inertial sensor;

[0015] Figure 20 An integrated MEMS system according to another embodiment of the present disclosure is shown;

[0016] Figure 21 An integrated MEMS system according to another embodiment of the present disclosure is shown; and

[0017] Figure 22 -27 shows a cross-sectional view of an embodiment of the present disclosure for coupling to, such as Figure 19 The manufacturing steps of the cap for the integrated microelectromechanical system (MEMS) are shown. Detailed Implementation

[0018] Figure 1 -19 illustrates subsequent manufacturing steps of a microelectromechanical (MEMS) device or system 50 according to an embodiment of the present disclosure. In particular, the MEMS system 50 integrates one or more first MEMS structures 51 for converting environmental pressure signals into corresponding electrical signals, and one or more second MEMS structures 52 for converting motion signals (vibration, motion, etc.) into corresponding electrical signals.

[0019] In the following text, the first microelectromechanical structure 51 is also referred to as a pressure sensor; in particular, the conversion is performed based on changes in capacitance (capacitive pressure sensor).

[0020] In the following text, the second microelectromechanical structure 52 is also referred to as an inertial sensor. The second microelectromechanical structure 52 may be one of an accelerometer and a gyroscope, or a combination of both.

[0021] Figure 1 Figure 19 shows a cross-sectional view of the die in a triaxial reference system with mutually orthogonal axes X, Y, and Z. Die 1 is typically a portion of the wafer that is not fully shown up to the dicing or dicing step.

[0022] Figure 1 A bare die 1 is shown, having a front side 1a and a rear side 1b opposite each other along axis Z, and a substrate 2 comprising a semiconductor material (typically silicon).

[0023] refer to Figure 2 At the front side 1a, an insulating layer 3, for example silicon oxide (SiO2), is formed with a thickness between 0.2 and 2 μm, typically 0.5 μm. The insulating layer 3 is formed, for example, by thermal oxidation.

[0024] exist Figure 3 In this context, conductive materials such as N-type doped polycrystalline silicon (e.g., doping density including 1.10) are used. 19 and 2.10 20 A structural layer 4 (within the range of ions / cm3) is formed on the insulating layer 3. In one embodiment, the structural layer 4 is formed by depositing polycrystalline silicon using LPCVD technology; the structural layer 4 has a thickness, for example, between 0.2 and 0.6 μm.

[0025] Referring to a capacitive pressure sensor, structural layer 4 forms the bottom electrode of the pressure sensor (i.e., the base plate of the capacitor). Structural layer 4 is patterned (e.g., photolithographic) to define the desired and / or anticipated shape during the design steps of the bottom electrode of the pressure sensor.

[0026] Then, in Figure 4 In this process, a sacrificial layer 8, for example, of silicon oxide, is formed. The thickness of the sacrificial layer 8 at and above the structural layer 4 is between 0.4 and 2 μm. To compensate for the presence of a "step" between the insulating layer 3 and the structural layer 4, and to form a sacrificial layer 8 with a flat top surface, a planarization step (e.g., via CMP) is performed after the formation of the sacrificial layer 8.

[0027] Alternatively, the sacrificial layer 8 can be formed in two successive sub-steps, including:

[0028] A first sacrificial layer 8a is formed, which is silicon oxide (TEOS or silane-based oxide) deposited using PECVD technology, until it completely covers the structural layer 4 (the thickness of the first sacrificial layer 8a, measured along the Z axis transverse to the structural layer 4, is greater than the thickness of the structural layer 4).

[0029] For example, CMP technology is used to planarize the first sacrificial sublayer 8a to obtain a flat top surface; and

[0030] A second sacrificial layer 8b is formed on the first sacrificial layer 8a, here being silicon oxide (TEOS or silane-based oxide) deposited using PECVD technology; the thickness of the second sacrificial layer 8b, measured along axis Z from the top surface of the first sacrificial layer 8a, is between 300 nm and 2 μm; and

[0031] Optionally, a further flattening step can be performed on the second sacrificial sublayer 8b.

[0032] The first sacrificial sublayer 8a and the second sacrificial sublayer 8b together form the sacrificial layer 8. The thickness of the sacrificial layer 8 at the structural layer 4 includes, for example, between 500 nm and 2.3 μm.

[0033] Then Figure 5 Etching of the sacrificial layer 8 is performed to form a trench 10 that surrounds or internally defines a region 8′ of the sacrificial layer 8. The trench 10 extends along axis Z through the thickness of the sacrificial layer 8 above the structural layer 4 and exposes the corresponding region of the structural layer 4. In this way, region 8′ is separated from the remainder of the sacrificial layer 8 by the trench 10. The shape of region 8′ defined by the trench 10 corresponds to the desired shape of a cavity with two conductive plates having capacitors facing outwards to form the sensitive element of a pressure sensor, as will be better understood from the following description.

[0034] In the same manufacturing step, one or more additional portions of the sacrificial layer 8 extending above the structural layer 4 but outside the region 8′ defined by the trench 10 are also removed; thus an opening 11 is formed that reaches the structural layer 4 and through which a channel to the structural layer 4 is formed, through which, as better explained below, an electrical contact will be formed to bias the structural layer 4 (which is the bottom electrode of the capacitor of the pressure sensor).

[0035] Then continue with this method. Figure 6 An etch stop layer 5 is formed over the sacrificial layer 8 and the surface portion of the structural layer 4 exposed through the trench 10 and the opening 11. According to one embodiment of this disclosure, the etch stop layer 5 is aluminum oxide (Al2O3), also known as aluminum oxide. The etch stop layer 5 has a thickness of, for example, tens of nanometers, including, for example, between 20 and 60 nm, particularly 40 nm.

[0036] The etch stop layer 5 is formed using atomic layer deposition (ALD). Deposition of Al₂O₃ via ALD is known in the art and is typically performed using trimethylaluminum (TMA, Al(CH₃)₃) and water (H₂O) vapor as reactants. Ozone (O₃) can be used as an alternative to H₂O vapor. For example, TMA can be used as the aluminum source and H₂O as the oxidant for deposition. Possible methods for forming the etch stop layer 5 are described in the literature, including Steven M. George, Chem. Rev. 2010, 110, pp. 111–131, and Puurunen, RL, J. Appl. Phys. 2005, 97, pp. 121–301.

[0037] Patent document WO 2013 / 061313 also describes a method for forming an etch stop layer of Al2O3 that can be used in the context of this disclosure. Specifically, as described in WO 2013 / 061313, the etch stop layer 5 is formed using an ALD deposition process that provides two Al2O3 intermediate layers, both of which undergo crystallization. The following sequence: i) deposition of the first Al2O3 intermediate layer, ii) crystallization of the first intermediate layer, iii) deposition of the second Al2O3 intermediate layer, and iv) crystallization of the second intermediate layer, allows the formation of the Al2O3 etch stop layer 5, which is resistant to etching by solutions containing hydrofluoric acid (HF), and, most importantly, impermeable to such HF-based solutions.

[0038] In addition to being resistant to HF etching and impermeable to HF, the etch stop layer 5 exhibits optimal static tribological properties to the underlying silicon oxide layer 8 and polysilicon layer 4, exhibits optimal dielectric properties that do not change according to possible subsequent heat treatment, exhibits small (negligible) changes in the warpage radius of the die 1, and exhibits high compatibility with heat treatment at high temperatures (above 1000°C).

[0039] Then, Figure 7 The method involves forming or patterning the etch stop layer 5 (e.g., by mask etching using an etch mask 13) to selectively remove the etch stop layer 5 from the bottom of the opening 11 (to expose the structural layer 4 in the opening 11) and the peripheral region 12 of the die 1 at region 8′. Alignment marks to facilitate subsequent manufacturing steps, and / or anchors to provide structural robustness for the movable structure of the inertial sensor to be formed later, will be formed in region 12.

[0040] Specifically, it should be noted that the etch stop layer 5 is patterned by removing a selective portion of the etch stop layer 5 above region 8' until reaching the surface of region 8'. At least a portion of the surface of region 8' is thus exposed through an opening formed in the etch stop layer 5. The region of region 8' exposed in this process step more precisely and further defines the shape and spatial extent of the top plate of the capacitor forming the active element of the pressure sensor relative to the trench 10, as will be better seen from the following description.

[0041] Then, in Figure 8 In this process, a deposition step of structural layer 16 is performed above etch stop layer 15 and in cavity 15a, structural layer 16 covering the surface of region 8′. In one embodiment, structural layer 16 is a conductive material, such as doped polysilicon (e.g., doping includes 1.10...). 18 ions / cm 3 and 2.10 20 ions / cm 3 (between). Alternatively, structural layer 16 may be undoped polycrystalline silicon.

[0042] For example, structural layer 16 is deposited using LPCVD technology. Structural layer 16 has a thickness, for example, between 0.2 μm and 1 μm.

[0043] Structural layer 16 extends within opening 11 until it reaches and contacts structural layer 4, and extends within opening 12.

[0044] Subsequently, Figure 9 In this process, structural layer 16 is defined, for example by photolithography, to selectively remove it at the exposed surface of region 8′. Specifically, in one embodiment, structural layer 16 is not completely removed at the surface of region 8′ to leave space for subsequent layers to be deposited later. Figure 10 The region 16′ of the anchorage in layer 20) as described herein. Clearly, in other embodiments, the anchorage is believed not to require structural support. Figure 10 In the case of layer 20, region 16′ is not formed and structural layer 16 is completely removed at the surface of region 8′.

[0045] Then as Figure 10 As mentioned, the permeable layer 20 is formed over the structural layer 16, the anchoring region 16′ (if any), and the region 8′ exposed between the anchoring regions 16′.

[0046] In one embodiment of this disclosure, the permeable layer 20 is polycrystalline silicon, which is permeable to a chemical solution used for subsequent removal of region 8′. For example, in the described embodiment, region 8′ is silicon oxide, hydrofluoric acid (HF), or a solution containing HF, which can be used to selectively remove region 8′. In this case, the permeable layer 20 is provided with pores or openings to allow hydrofluoric acid to flow through the permeable layer 20, reach and remove region 8′, and form a burial cavity or chamber 22.

[0047] Specifically, the permeable layer 20 is polycrystalline silicon with pores (or pores) ranging in diameter from 1 to 50 nm. The thickness of the permeable layer 20 is in the range of 50 to 150 nm, for example, 100 nm. The permeable layer 20 is deposited, for example, by LPCVD technology. According to an exemplary, non-limiting embodiment, the deposition conditions are a deposition environment with a pressure of about 550 mTorr, using a silane source gas with a process window of about 600 °C, in a pull-to-compression transition region. Typically, the pore size of the permeable layer 20 is selected in such a way that the chemical etch solution (liquid or gas) used to remove region 8' can penetrate the pores until it reaches the permeable layer 20.

[0048] Typically, the permeable layer 20 can be porous polycrystalline silicon formed in a manner known in the literature, or polycrystalline silicon with pores (openings) that are actively formed after its deposition, used for selective removal of material by mechanical or physicochemical action.

[0049] refer to Figure 11 The etching step in region 8′ is performed using HF or a buffered HF mixture, or vapor etching using HF in vapor form. The material in region 8′ is completely removed and the buried cavity 22 is formed. As mentioned, the chemical reagent used for etching penetration passes through the openings or pores of the permeable layer 20 but not through the structural layer 16 and the etching stop layer 5.

[0050] Then, in Figure 12 In this process, other masks 14 are formed on the permeable layer 20, which are configured to protect the front side 1a of the bare die 1, except for the area overlapping with the opening 12. All layers exposed through the mask 14 are thus removed until the substrate 2 is reached. The opening 23 is thus formed.

[0051] Then, in Figure 13 In the process, after removing mask 14, a doped polysilicon layer 17 (e.g., N-type) is formed (e.g., epitaxially grown) above the permeable layer 20. This doped polysilicon layer is also grown in the opening 23 above the substrate 2. Figure 12The polysilicon layer 17 is exposed during the process. The thickness of the doped polysilicon layer 17 is, for example, in the range of 0.2 to 1.5 μm. An additional layer of polysilicon or other material with a corrugated surface may optionally be deposited to prevent possible static friction phenomena that may occur during the use of the inertial sensor. Alternatively, the surface of the polysilicon layer 17 may optionally be treated (mechanically or chemically) to provide the corrugated surface.

[0052] exist Figure 14 In this process, the doped polysilicon layer 17 is etched to remove selective portions of it to form a plurality of conductive regions 18. The conductive regions 18 include conductive strips or electrical interconnects at regions 1' where the die 1 in the inertial sensor will be formed; the conductive regions 18 also include the top electrode of the capacitor of the pressure sensor at regions 1" where the die 1 in the pressure sensor will be formed.

[0053] The etching of polysilicon layer 17 removes layers 17, 20 and 16, and stops at etch stop layer 5.

[0054] Then, in Figure 15 In this process, a sacrificial layer 25 (e.g., silicon oxide, particularly TEOS oxide) is formed. A polishing step (CMP) of the sacrificial layer 25 is then performed, at which point the sacrificial layer 25 has a thickness between 1.3 and 2 μm along the Z-axis. The sacrificial layer 25 also forms the conductive strip / electrical interconnect / top electrode (reference). Figure 14 (Limited) Extends within openings that are separated from each other.

[0055] The sacrificial layer 25 is also formed within the opening 23.

[0056] Then, in Figure 16 In this process, the sacrificial layer 25 is selectively etched to completely remove it from the interior of the opening 23 and from a selective region above the polysilicon layer 17, thereby forming the anchoring opening 27.

[0057] Then, in Figure 17 In this process, for example by growing epitaxial polysilicon, a structural layer 28 is formed over a sacrificial layer 25, in an opening 23, and in an additional anchoring opening 27. One or more contact pads 41a, 41b, 41c may be pre-formed on the structural layer 28. The plurality of contact pads 41a, 41b, 41c may include a first contact pad 41a, a second contact pad 41b, and a third contact pad 41c. In some embodiments, the first contact pad 41b and the second contact pad 41c may be contact pads of a first MEMS device 51, and the first contact pad 41a may be a contact pad of a second MEMS device 52.

[0058] The structural layer 28 can be processed as needed to form a structure with a desired shape.

[0059] exist Figure 18 In this process, structural layer 28 is selectively etched to form suspension structure 28a (e.g., stator and rotor) and electrical contact terminals 29, 30, which are configured to bias the top and bottom electrodes of the capacitor of the pressure sensor. In the same process step, portions of structural layer 28 extending on the membrane of the pressure sensor (at least partially on cavity 22) are removed.

[0060] However, it should be noted that during this manufacturing step, the suspension structure 28a remains constrained to the sacrificial layer 25 below and therefore cannot move freely. The sacrificial layer 25 also extends over the membrane of the top electrode of the capacitor forming the pressure sensor, which is too thick and at least partially restricts its movement.

[0061] Therefore, in Figure 19 In this process, a through-hole 31 is formed at the suspension structure 28a to allow the removal of the sacrificial layer 25, thereby partially suspending the suspension structure 28a.

[0062] For example, the etching step through the via 31 in HF allows a portion of the sacrificial layer 25 to be removed. Therefore, the suspension structure 28a can move or oscillate according to the degrees of freedom anticipated during the design steps. The shape and design details of the suspended movable structure 28a are known in the prior art and are not a technical solution of this disclosure.

[0063] In the same process step, a portion of the sacrificial layer 25 extending on the membrane of the pressure sensor is also removed.

[0064] Therefore, the formation of the first microelectromechanical structure 51 (in this paper, a capacitive pressure sensor) and the second microelectromechanical structure 52 (in this paper, an inertial sensor) of the MEMS system 50 is completed.

[0065] The manufacture of MEMS system 50 may include additional steps, such as forming and attaching cap 102 (see this disclosure). Figure 27 ) to form a semiconductor device or package 100 (see this disclosure) Figure 27 Cap 102 protects the first microelectromechanical structure 51 and the second microelectromechanical structure 52. Cap 102 includes a plurality of protrusions 120, which may be referred to as a plurality of mechanical coupling regions, provided with solder paste or tape or other coupling devices, configured to physically couple to corresponding regions of the bare die 1 to surround (in the top view) and protect the first microelectromechanical structure 51 and the second microelectromechanical structure 52. Through-hole 104 (see this disclosure) Figure 27 A pressure sensor is formed in the cap 102 to allow fluid channels toward the membrane (i.e., channels intended to be sensed / measured during use). Details of the formation of the cap 101 and the cap 101 itself will be described below with respect to this disclosure. Figure 22 -26 is discussed in more detail.

[0066] A getter layer of a known type may optionally be present to generate a predefined pressure (low pressure) at the inertial sensor 52.

[0067] As mentioned, in one embodiment, the pressure sensor 51 is capacitive, or more specifically, an absolute pressure sensor, configured to sense pressure changes outside the sensor relative to a pressure value present inside the buried cavity 22 (set during the manufacturing process). The first and second electrodes face each other through the buried cavity 22. According to different and further embodiments, the pressure sensor 51 is differential capacitive, configured to provide a signal identifying the difference between two ambient pressures experienced by the same sensor. The differential pressure sensor is manufactured according to the same steps described above for the pressure sensor 51, with the addition of another process step designed to connect the cavity 22 to the outside so that the pressure sensor can operate as a differential pressure sensor. For this purpose, the cavity 22 is fluidly connected to the outside of the pressure sensor, for example through a suitably provided channel that allows air (or other fluid in gaseous form) to flow out of and into the cavity 22. The final deformation of the membrane indicates the difference between the first ambient pressure P1 (outside the cavity 22) and the second ambient pressure P2 (inside the cavity 22), and the signal converted by the differential pressure sensor is a differential pressure signal. In use, pressures P1 and P2 are the pressures of environments separate from each other. Patent documents US7,763,487 and US8,008,738 describe packages that can be used in the context of this disclosure for encapsulating differential type pressure sensors.

[0068] exist Figure 20 In another embodiment, the pressure sensor 51 further includes another buried cavity or chamber 60 extending below the cavity 22 into the substrate 2. In this manner, another membrane is formed on a portion of the bare die 1 above the buried cavity 60, which can be deflected to release any residual stress from the manufacturing process or from residual stress generated during the use of the pressure sensor, thereby preventing any structural problems such as cracking, fissures, or deformation. The buried cavity 60 can be formed in a manner known per se, for example, according to the buried cavity formation processes described in US7,763,487 and US8,008,738.

[0069] According to another embodiment of this disclosure, such as Figure 21 As shown, cavity 22 further includes an anti-adhesion layer 65. The anti-adhesion layer 65 may completely or only partially cover the inner wall of cavity 22.

[0070] The anti-adhesion layer 65 is a material chosen in such a way that it limits or even prevents partial blockage of cavity 22 due to potential mutual static friction between the walls that define cavity 22 upwards and downwards. This undesirable effect would cause the membrane to malfunction and thus lead to failure of the pressure sensor 51.

[0071] The anti-adhesion layer 65 can be introduced into the cavity 22 through a suitable opening that communicates the cavity 22 with the environment in which the deposition of the anti-adhesion layer 65 occurs. This opening can then be closed in the case of an absolute pressure sensor, or it can be used as an opening to allow fluid communication between the cavity 22 and the external environment in the case of a differential pressure sensor.

[0072] The deposition of the anti-adhesion layer 65 can be achieved through a vapor phase process.

[0073] Materials that can be used in the anti-adhesion layer 65 include, but are not limited to, chlorosilanes, trichlorosilanes, dichlorosilanes, siloxanes, etc., such as:

[0074] DDMS – “Dimethyldichlorosilane”;

[0075] FOTS – “Perfluorooctyltrichlorosilane”;

[0076] PF10TAS – “Perfluorodecyltris(dimethylamino)silane”;

[0077] PFDA – “Perfluorodecanoic acid”.

[0078] Available materials and their deposition methods are known in the prior art, particularly from Ashurst, W. & Carraro, C. & Maboudian, Roya. (2004), “Vapor phase anti-stiction coatings for MEMS” Device and Materials Reliability, IEEE Transactions on. 3.173-178.10.1109 / TDMR.2003.821540.

[0079] A similar anti-adhesion layer may also be optionally formed in the burial cavity 60.

[0080] According to various embodiments, the above-described manufacturing methods and devices have many advantages.

[0081] Because the monolithic structure of the membrane has virtually no empty areas, the membrane is robust and therefore particularly well-suited for providing different types of MEMS structures, reducing the risk of breakage, deformation or damage that could impair its function.

[0082] This process is easy to implement because it does not have any particular execution criticality or difficulty, thus ensuring high yield and reduced final cost. It should also be noted that the method used to manufacture the transducer structures for MEMS sensors 51 and 52 requires the use of individual wafers of semiconductor material, thus being economically advantageous and having reduced criticality due to the absence of gluing or bonding steps between wafers.

[0083] Furthermore, this manufacturing method is particularly flexible because it allows for the simple provision of buried cavities and / or membranes of desired shape and size (regarding both area and thickness). Specifically, for applications as pressure sensors, high-thickness membranes can be obtained to increase the accuracy of the same sensor.

[0084] The use of porous silicon ensures that films with regular shapes are obtained and prevents the formation of undesirable formations that would damage or, in any case, reduce the electromechanical characteristics of the finished MEMS device.

[0085] The simultaneous presence of two crystalline aluminum oxide layers prevents short circuits between the top and bottom electrodes of the capacitor and allows the diameter of the film to be defined during the manufacturing process, independent of the etching time.

[0086] Furthermore, due to the use of a crystalline alumina layer, the size of the film can be precisely defined without the need for time-based etching. In fact, the crystalline alumina acts as a hard mask for subsequent HF etching, with the aim of removing the oxide layer beneath the film.

[0087] The use of an HF-permeable polysilicon layer enables the formation of porous gates that allow HF to permeate and etch oxides. The permeable polysilicon also serves as a support for the top layer.

[0088] As discussed in this disclosure, the simultaneous fabrication of inertial sensors allows for optimized integration of various sensors on the same die, simplifying the process and reducing costs.

[0089] Figure 22 -27 shows, in a cross-sectional view, the methods for forming the cap 102 and for coupling the cap 102 to, such as Figure 19 The bare wafer 1 shown is manufactured and formed as follows Figure 27 The manufacturing steps of the semiconductor device or package 100 shown.

[0090] like Figure 22 As shown, wafer 106 includes: a first surface 108, a second surface 110 opposite to the first surface 108, and a plurality of sidewalls 112 extending from the first surface 108 to the second surface 110. Wafer 106 may be made of semiconductor material, silicon material, or some other suitable material for wafer 106.

[0091] In such Figure 23In the first step shown, an oxide layer or insulating layer 114 is formed at a first surface 108, a second surface 110, and a plurality of sidewalls 112. For example, the oxide layer 114 can be formed by performing an oxidation process to oxidize the first surface 108 and the second surface 110 of the wafer 106. In some embodiments, the oxidation process can be a thermal oxidation process, wherein the silicon of the wafer 106 is converted into silicon oxide to form the oxide layer 114, which is made of silicon oxide.

[0092] Figure 24 The second step shown occurs during Figure 23 After the first step shown. In as... Figure 24 In the second step shown, the oxide layer 114 is patterned, resulting in the formation of a plurality of openings 116 extending through the oxide layer to the first surface 108 of the wafer 106, exposing corresponding areas or portions of the first surface 108 of the wafer 106 from the oxide layer 114. The plurality of openings 116 can be formed by first forming a hard mask layer on the oxide layer 114, removing portions of the hard mask layer to expose corresponding portions of the oxide layer 114 to be removed to form the plurality of openings 115, and removing the exposed corresponding portions of the oxide layer 114 to form the plurality of openings 116. After the plurality of openings 116 have been formed, the hard mask layer can be removed from the remainder of the oxide layer to form the plurality of openings 116, as shown. Figure 24 As shown in the image.

[0093] Figure 25 The third step shown occurs Figure 24 Following the second step shown. In as... Figure 25 In the third step shown, the corresponding portions and areas of wafer 106 exposed from oxide layer 114 are removed from wafer 106 through multiple openings 116, forming multiple recesses 118 and multiple protrusions 120 adjacent to some of the recesses 118. For example, an etching process can be performed to remove the corresponding portions and areas of wafer 106 exposed from oxide layer 114 through the multiple openings 116. This etching process can result in the removal of oxide layer 114 from wafer 106. Alternatively, oxide layer 114 can be removed by an additional process performed after the removal of the corresponding portions of wafer 106 that form the multiple recesses 118 and multiple protrusions 120, respectively. The multiple recesses 118 and multiple protrusions 120 are formed afterward. A getting layer 122 is formed on at least one corresponding surface of at least one of the plurality of recesses 118. The getting layer 122 may be referred to as a getter, getter layer, getter structure, dilute getter structure, or some other similar or analogous getting layer. Figure 25As shown, a getter layer 122 may be present to help provide a good vacuum within the cavity, which is at least partially defined by a corresponding recess among a plurality of recesses 118 in which the getter layer 122 is present.

[0094] Before or after the air-absorbing layer 122 is formed, an adhesive material or structure 124 (e.g., tape, solder paste, vitreous material, or some other suitable adhesive material or structure) is formed on one of the plurality of protrusions 120. Figure 25 In the illustrated embodiment, the adhesive material 124 is a vitreous material.

[0095] After the third step, the cover 102 is formed such that the cover 102 includes a recess 118 located between adjacent protrusions of the plurality of protrusions 120, and an adhesive material or structure 124 is present on each of the plurality of protrusions 120.

[0096] Figure 26 The fourth step shown occurs during Figure 25 Following the third step shown. In Figure 26 In the fourth step shown, the cap 102 can be flipped over, whereby the cap 102 is coupled to a corresponding area on the surface of the bare die 1 using adhesive material 124, as shown. Figure 19 As shown. Coupling the cap 102 to a corresponding region of the surface of the die 1 results in defining and delineating a plurality of cavities 126a, 126b, 126c. The plurality of cavities 126a, 126b, 126c includes a first cavity 126a, a second cavity 126b, and a third cavity 126c. The first cavity 126a and the second cavity 126b are in fluid communication with each other along a fluid path 128 located between one of the plurality of protrusions 120 of the cap 102 and the surface of the die 1.

[0097] Figure 27 The fifth step shown occurs during Figure 26 Following the fourth step shown. In as... Figure 27 In the fifth step shown, opening 130 is formed by a cap to expose the first contact pad 41a. Opening 130 can be formed to provide a passage to the first contact pad 41a. A plurality of vias 104 can be formed before or after opening 130, or can be formed simultaneously with opening 130. Vias 104 cause the membrane to be in fluid communication with the environment outside the third cavity 126c where the membrane is located. For example, the membrane can be the membrane of pressure sensor 51. After opening 130 is formed, a plurality of trenches 132 can be formed such that region 1' of the die is further defined between the plurality of trenches 132. Opening 130, vias 104 and trenches 132 can be formed by performing a series of etching steps or multiple techniques, which results in the removal of the cap 102 and corresponding portions of the die 1 to form opening 130, via 104 and trench 132, respectively.

[0098] In alternative embodiments of the methods for manufacturing cap 102 and coupling cap 102 to bare die 1, the various steps discussed above may be reorganized and performed in different orders to form a semiconductor device or package 100 or an alternative embodiment similar to a semiconductor device or package 100.

[0099] Finally, it is clear that modifications and variations may be made to the methods described and illustrated herein without departing from the scope of this disclosure as defined in the appended claims.

[0100] The teachings of this invention can be used to provide MEMS devices, semiconductor devices, or semiconductor packages of different types as described, such as accelerometers, gyroscopes, resonators, valves, etc., in which case the structure below and / or above the membrane is adapted according to the intended application.

[0101] Where it is desired to integrate electronic components (e.g., ASICs or other circuitry for processing or disposing of signals) in the same die 1, this can be done using the substrate 2 or an additional epitaxial layer formed between the substrate 2 and the structural layer 4.

[0102] A method for manufacturing a microelectromechanical system (MEMS) (50) including a first MEMS device (51) and a second MEMS device (52) can be summarized as including the following steps: forming a first electrode (3) of the first MEMS device (51) on a substrate (2); forming a first sacrificial layer (8, 8') of a material removable by an etching chemical solution on the first electrode (3); forming a protective layer (5) impermeable to the etching chemical solution on the first sacrificial layer (8, 8'); selectively removing portions of the protective layer (5) to expose corresponding sacrificial portions (8') of the first sacrificial layer (8, 8'); forming a porous film layer (20) permeable to the etching chemical solution on the sacrificial portions (8'); removing the sacrificial portions (8') through the film layer (20) using the etching chemical solution to form a cavity (22); forming a first structural layer (17) that seals the pores of the film layer (20) and is connected to the film. A suspension structure (17, 20) of the first MEMS device (51) is formed in a layer, the suspension structure (17, 20) being capacitively coupled to the second electrode of the first electrode (3) through a cavity (22); a second sacrificial layer (25) of material that can be etched by the etching chemical solution is formed on the first structural layer (17); a second structural layer (28) is formed on and in contact with the second sacrificial layer (25); the second structural layer (28) is patterned to simultaneously form the movable structure (28a) of the second MEMS device (52) and the bias structure (30) of the first electrode and the second electrode of the first MEMS device (51, 52); a selective portion of the second sacrificial layer (25) is removed by the etching chemical solution, so that the movable structure (28a) of the second MEMS device (52) and the suspension structure of the first MEMS device (51) can move freely according to their respective degrees of freedom.

[0103] The etching chemical solution may include hydrofluoric acid or HF, and the protective layer (5) may include crystalline aluminum oxide.

[0104] The film (20) can be porous silicon or silicon with multiple through holes or pores.

[0105] The first structural layer (17) can be conductive doped polysilicon.

[0106] Forming the second structural layer (28) may include: removing a selective portion of the second sacrificial layer (25) and forming a portion of the second structural layer (28) by passing through the removed portion of the second sacrificial layer (25) until reaching and electrically contacting the first structural layer (17).

[0107] The step of forming the second structural layer may include epitaxial growth of polycrystalline silicon.

[0108] The method may further include the step of forming a buried cavity (42) in the substrate (2), the buried cavity (42) being below the cavity (22) and at least partially aligned with the cavity (22).

[0109] The method may also include the step of connecting the cavity (22) to the external environment fluid through a through hole.

[0110] The method may further include the step of covering the cavity (22) internally with an anti-adhesion layer (65) that allows chemicals including chlorosilane, trichlorosilane, dichlorosilane, and siloxane to flow through the aforementioned through-hole.

[0111] The aforementioned movable structure (28a) of the second MEMS device (52) may include a movable mass block of a gyroscope and / or a movable mass block of an accelerometer.

[0112] The first MEMS device (51) may include a capacitive pressure sensor and the second MEMS device (52) may include an inertial sensor.

[0113] A microelectromechanical system (MEMS) (50) includes a first MEMS device (51) and a second MEMS device (52), and can be generally defined as including a substrate (2); a first electrode (3) belonging to the first MEMS device (51) extending on the substrate (2); a first sacrificial layer (8, 8') on the first electrode (3) of a material removable by an etching chemical solution; a protective layer (5) on the first sacrificial layer (8, 8') impermeable to the etching chemical solution; a film layer (20) on the sacrificial portion (8') made of a porous material permeable to the etching chemical solution; a cavity (22) extending below the diaphragm layer (20); a first A structural layer (17) that seals the holes of the film layer (20) and forms a suspension structure (17, 20) of the first MEMS device (51) with the film layer, the suspension structure (17, 20) being capacitively coupled to the second electrode of the first electrode (3) through a cavity (22); and a second structural layer (28) that is patterned to form a movable structure (28a) of the second MEMS device (52) and a bias structure (30) of the first electrode and the second electrode of the first MEMS device (51, 52), wherein the movable structure (28a) of the second MEMS device (52) and the suspension structure of the first MEMS device (51) are free to move according to their respective degrees of freedom.

[0114] The etching chemical solution may include hydrofluoric acid or HF, and the protective layer (5) may include crystalline aluminum oxide.

[0115] The film (20) can be porous silicon or silicon with multiple through holes or pores.

[0116] The first structural layer (17) can be conductive doped polysilicon.

[0117] The second structural layer can be epitaxial polycrystalline silicon.

[0118] The system may further include a buried cavity (42) in the substrate (2), which is below the cavity (22) and at least partially aligned with the cavity (22).

[0119] The system may further include a fluid connection path configured to connect the cavity (22) to the external environment of the aforementioned microelectromechanical system (50) via a through port.

[0120] The system may further include an anti-adhesion layer (65) that internally covers the cavity (22), the anti-adhesion layer comprising chlorosilane, trichlorosilane, dichlorosilane, or siloxane.

[0121] The aforementioned movable structure (28a) of the second MEMS device (52) may include a movable mass block of a gyroscope and / or a movable mass block of an accelerometer.

[0122] The first MEMS device (51) may include a capacitive pressure sensor, and the second MEMS device (52) may include an inertial sensor.

[0123] The various embodiments described above can be combined to provide other embodiments. If desired, aspects of the embodiments can be modified to incorporate concepts from various patents, applications, and publications to provide other embodiments.

[0124] Based on the detailed description above, these and other changes can be made to the embodiments. Generally, the terminology used in the following claims should not be construed 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 scope of the authorized equivalents of these claims. Therefore, the claims are not limited to this disclosure.

Claims

1. A method for manufacturing a microelectromechanical system (MEMS), the MEMS comprising a first MEMS device and a second MEMS device, the method comprising: The first electrode of the first MEMS device is formed on the substrate; A first sacrificial layer is formed on the first electrode; A protective layer impermeable to etching chemical solutions is formed on the first sacrificial layer; Selectively remove portions of the protective layer to expose corresponding sacrificial portions of the first sacrificial layer; A porous material membrane is formed on the sacrificial portion, the membrane being permeable to the etching chemical solution; A cavity is formed by removing the sacrificial portion through the film layer using the etching chemical solution; A first structural layer is formed, which seals the pores of the film layer and together with the film layer forms a suspension structure of the first MEMS device, the suspension structure being capacitively coupled to a second electrode of the first electrode through the cavity; A second sacrificial layer of material capable of being etched by the etching chemical solution is formed above the first structural layer; A second structural layer is formed, which is above and in contact with the second sacrificial layer; The second structural layer is patterned to simultaneously form a movable structure of the second MEMS device and a bias structure of the first electrode and the second electrode of the first MEMS device. The selective portion of the second sacrificial layer is removed by the etching chemical solution, allowing the movable structure of the second MEMS device and the suspended structure of the first MEMS device to move freely according to their respective degrees of freedom.

2. The method according to claim 1, wherein the etching chemical solution comprises hydrofluoric acid and HF, and the protective layer comprises crystalline alumina.

3. The method according to claim 1, wherein the film layer is porous silicon or silicon having multiple through holes or pores.

4. The method according to claim 1, wherein: The first structural layer is conductive doped polycrystalline silicon; as well as Forming the second structural layer includes: removing a selective portion of the second sacrificial layer, and forming a portion of the second structural layer by passing through the removed portion of the second sacrificial layer until reaching and electrically contacting the first structural layer.

5. The method of claim 1, wherein the step of forming the second structural layer comprises epitaxially growing polycrystalline silicon.

6. The method of claim 1, further comprising the step of forming a buried cavity in the substrate, the buried cavity being below the cavity and at least partially aligned with the cavity.

7. The method of claim 1, further comprising: The cavity is fluidly connected to the external environment of the microelectromechanical system through a through-hole; as well as The cavity is internally covered by an anti-adhesion layer, allowing chemicals including chlorosilanes, trichlorosilanes, dichlorosilanes, and siloxanes to pass through the through-hole.

8. The method of claim 1, wherein the movable structure of the second MEMS device comprises a movable mass block of a gyroscope and / or a movable mass block of an accelerometer.

9. The method of claim 1, wherein the first MEMS device comprises a capacitive pressure sensor, and the second MEMS device comprises an inertial sensor.

10. A device comprising: First MEMS device; Second MEMS device; Substrate; A first electrode is coupled to the first MEMS device extending on the substrate; The first layer on the first electrode; A protective layer on top of the first layer that is impermeable to etching chemical solutions; A porous membrane layer on the protective layer, the membrane layer being permeable to the etching chemical solution; The cavity overlapped by the membrane layers; A first structural layer, which seals the pores of the film layer and forms a suspension structure of the first MEMS device with the film layer, wherein the suspension structure is capacitively coupled to a second electrode of the first electrode through the cavity; as well as The second structural layer is on top of the first structural layer, and the second structural layer includes: The movable structure of the second MEMS device; as well as The bias structure of the first electrode and the second electrode of the first MEMS device.

11. The device of claim 10, wherein the etching chemical solution comprises hydrofluoric acid and HF, and the protective layer comprises crystalline alumina.

12. The device of claim 10, wherein the film layer is porous silicon or silicon having a plurality of through holes or pores.

13. The device of claim 10, wherein the first structural layer is conductive doped polysilicon.

14. The device of claim 10, wherein the second structural layer is epitaxial polysilicon.

15. The device of claim 10, further comprising a buried cavity in the substrate, the buried cavity being below the cavity and at least partially aligned with the cavity.

16. The device of claim 10, further comprising: A fluid connection path, configured to connect the cavity to the external environment of the microelectromechanical system via a through-port; as well as An anti-adhesion layer is internally covering the cavity, the anti-adhesion layer comprising chlorosilane, trichlorosilane, dichlorosilane, and siloxane.

17. The device of claim 10, wherein the movable structure of the second MEMS device comprises at least one of a movable mass block of a gyroscope and a movable mass block of an accelerometer.

18. The device of claim 10, wherein the first MEMS device comprises a capacitive pressure sensor, and the second MEMS device comprises an inertial sensor.

19. A device comprising: Including the substrate on the surface; A first electrode extending on the surface of the substrate; A plurality of layers on the surface of the substrate, the plurality of layers comprising: The first layer is located on the first electrode; A protective layer impermeable to etching chemical solutions is located on the first layer; and A porous material membrane layer is located on the protective layer, and the porous material of the membrane layer is permeable to the etching chemical solution; The cavity is defined by at least one lower surface of the film, at least one upper surface of the first electrode opposite to the at least one lower surface, and at least one sidewall of the protective layer perpendicular to the at least one lower surface of the film and the at least one upper surface of the first electrode; An anti-adhesion layer is located within the cavity and covers at least one lower surface of the film, at least one upper surface of the first electrode, and at least one sidewall of the protective layer; Structural layers on the plurality of layers; Multiple through holes, the multiple through holes extending into the structural layer and extending into the multiple layers; A first MEMS device, comprising a film of the plurality of layers and a structural layer overlapping the cavity, the first MEMS device having a suspension structure; A second MEMS device adjacent to the first MEMS device, the second MEMS device having a movable structure, wherein the movable structure and the suspension structure of the first MEMS device move freely according to corresponding degrees of freedom.

20. The device according to claim 19, wherein: The first MEMS device is a capacitive sensor; and The second MEMS device is an inertial sensor.

21. The device according to claim 20, wherein: The first MEMS device is a pressure sensor; and The second MEMS device is at least one of the following: a gyroscope, an accelerometer, or a combination of both the accelerometer and the gyroscope.

22. The device of claim 19, further comprising a fluid connection path configured to connect the cavity to the external environment of the microelectromechanical system via a through-port.

23. A device comprising: Substrate, including the surface; A first electrode extending on the surface of the substrate; A plurality of layers on the surface of the substrate, the plurality of layers comprising: The first layer is located on the first electrode; A protective layer impermeable to etching chemical solutions is located on the first layer; and A porous material membrane layer is located on the protective layer, and the porous material of the membrane layer is permeable to the etching chemical solution; The cavity is defined by at least one lower surface of the film, at least one upper surface of the first electrode, and at least one sidewall of the protective layer perpendicular to the at least one lower surface of the film and the at least one upper surface of the first electrode; An anti-adhesion layer is located within the cavity and covers at least one lower surface of the film, at least one upper surface of the first electrode, and at least one sidewall of the protective layer, and the anti-adhesion layer completely linerns the cavity; Structural layers, located on the plurality of layers; Multiple through holes extend into the structural layer and into the multiple layers; A first MEMS device includes a film composed of the plurality of layers and the structural layer overlapping the cavity; and The second MEMS device is adjacent to the first MEMS device.

24. The device of claim 23, wherein the porous material is porous silicon or silicon having a plurality of through-holes or pores.

25. The device of claim 23, further comprising a fluid connection path configured to connect the cavity to the external environment of the microelectromechanical system via a through-port.

26. The device of claim 23, wherein the first MEMS device is a capacitive sensor.

27. The device of claim 26, wherein the second MEMS device is an inertial sensor.

28. The device according to claim 27, wherein, The first MEMS device is a pressure sensor; and The second MEMS device is at least one of the following: a gyroscope, an accelerometer, or a combination of an accelerometer and a gyroscope.

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