Micro-electro-mechanical system and method of manufacturing the same

Abstract

The present disclosure relates to a microelectromechanical system and a method of manufacturing a microelectromechanical system, the microelectromechanical system comprising an ASIC layer, a mediator layer, a MEMS layer with movable structures and a cover layer stacked on top of each other in the listed order. The mediator layer and the cover layer form one isolated enclosure and the ASIC layer and the cover layer form another isolated enclosure, wherein the pressure in the isolated enclosures is different. The arrangement of the present disclosure has the advantage that it allows to reliably set different pressures in the isolated enclosures without the need for additional processing steps.

Description

Technical Field

[0001] This disclosure relates to a microelectromechanical system (MEMS), and more particularly to a system having an isolated enclosure with different internal pressures. This disclosure also relates to a method of manufacturing the MEMS. Background Technology

[0002] Microelectromechanical (MEMS) devices, such as those used to measure acceleration, rotational speed, magnetic fields, pressure, and / or combinations thereof, typically consist of a MEMS wafer and an ASIC wafer. A movable transducer structure resides within the MEMS wafer, while the ASIC wafer is designed to evaluate the measurement signals from the MEMS wafer. To minimize the design space of the MEMS device, the ASIC wafer can be vertically integrated with the MEMS wafer structure.

[0003] Typically, MEMS structures comprise two moving structures with different functions, thus requiring different ambient pressures for proper operation. For example, a MEMS system might combine a gyroscope and an accelerometer; the gyroscope requires low pressure for its operation, while the accelerometer can operate at ambient pressure. US20120326248A1 discloses a MEMS structure with two housings having different internal gas pressures, and a method for manufacturing such a structure. However, in US20120326248A1, additional design space and complex manufacturing process steps are required to set different pressures within the housings, unnecessarily complicating the process and potentially leading to undesirable pressure irregularities. Therefore, a MEMS structure that allows for reliably and efficiently setting different pressures within the housings is desired. Summary of the Invention

[0004] The purpose of this disclosure is to provide a MEMS system that addresses the aforementioned problems.

[0005] The purpose of this disclosure is achieved by a MEMS system characterized by the features set forth in the first aspect of this disclosure. Some implementation methods are also disclosed in this disclosure.

[0006] According to a first aspect of this disclosure, a microelectromechanical system (MEMS) is provided, comprising: - an ASIC layer, wherein the ASIC layer includes control circuitry; - an interposer layer, the interposer layer including a first side and a second side, wherein the ASIC layer is attached to the first side of the interposer layer; - a MEMS layer, the MEMS layer including a first side and a second side, wherein the second side of the interposer layer is attached to the first side of the MEMS layer; - a capping layer, the capping layer being attached to the second side of the MEMS layer; wherein - the interposer layer and the capping layer form a first isolation housing, wherein the MEMS layer is located within the first isolation housing; and the ASIC layer and the capping layer form a second isolation housing, wherein the MEMS layer is located within the second isolation housing; wherein the pressure in the first isolation housing is different from the pressure in the second isolation housing; and wherein the MEMS layer includes a first movable structure and a second movable structure, wherein the first movable structure is located within the first isolation housing, and the second movable structure is located within the second isolation housing.

[0007] This disclosure is based on a concept of a MEMS system comprising an ASIC layer, an interposer layer, a MEMS layer, and a capping layer attached to each other. The MEMS system also includes two isolation housings formed between the ASIC layer and the capping layer, wherein each isolation housing includes a movable structure formed in the MEMS layer, and wherein the two isolation housings have different internal pressures.

[0008] The advantage of this arrangement is that it allows for the reliable setting of different pressures within the isolation enclosure. Attached Figure Description

[0009] In the following, the present disclosure will be described in more detail with reference to the accompanying drawings, in which:

[0010] Figure 1 The MEMS structure of this disclosure is shown;

[0011] Figure 2a An example of a MEMS system including a first measuring electrode is shown;

[0012] Figure 2b An example of a movable MEMS system including a first measuring electrode, a second measuring electrode, and a first movable structure is shown.

[0013] Figure 3a This illustrates an example of how the ASIC layer connects to the outside world through an intermediary layer, a device layer, and a capping layer.

[0014] Figure 3b This illustrates an example of how to connect an ASIC layer to the outside using wire bonding;

[0015] Figure 4 The manufacturing process of the MEMS system disclosed herein is illustrated. Detailed Implementation

[0016] This disclosure relates to a microelectromechanical system (MEMS) comprising: an ASIC layer, wherein the ASIC layer includes control circuitry; an interposer layer including a first side and a second side, wherein the ASIC layer is attached to the first side of the interposer layer; a MEMS layer including a first side and a second side, wherein the second side of the interposer layer is attached to the first side of the MEMS layer; and a capping layer attached to the second side of the MEMS layer, wherein the interposer layer and the capping layer form a first isolation housing, wherein the MEMS layer is inside the first isolation housing, and the ASIC layer and the capping layer form a second isolation housing, wherein the MEMS layer is inside the second isolation housing, wherein the pressure in the first isolation housing is different from the pressure in the second isolation housing, and wherein the MEMS layer includes a first movable structure and a second movable structure, wherein the first movable structure is in the first isolation housing and the second movable structure is in the second isolation housing.

[0017] The microelectromechanical (MEMS) system 100 disclosed herein is in Figure 1 As shown in the diagram, the MEMS system 100 includes an ASIC layer 101. The ASIC layer includes control circuitry 102. The ASIC layer 101 may include a first layer and a second layer attached to one another. The first layer may be an ASIC substrate 103. The second layer may be the control circuitry 102. The ASIC layer 101 may include a first side 1011 and a second side 1012. The first side 1011 may correspond to the ASIC substrate 103. The second side 1012 may correspond to the control circuitry 102. The ASIC layer 101 may include ASIC conductive elements at the second side, such as... Figure 2a 205 as shown.

[0018] The MEMS system 100 also includes an interposer layer 104. The interposer layer 104 includes a first side 1041 and a second side 1042 opposite to each other. The second side of the ASIC layer 101 can be attached to the first side 1041 of the interposer layer 104. Specifically, the control circuitry 102 of the ASIC layer 101 can be attached to the first side 1041 of the interposer layer 104. The ASIC layer 101 can be attached to the first side 1041 of the interposer layer 104 by means of bonding. Specifically, the ASIC layer 101 can be attached to the first side 1041 of the interposer layer 104 by means of metal bonding.

[0019] like Figure 2a and Figure 2b As shown, the interposer 104 may include a first insulating layer 201. The first insulating layer 201 may be attached to the underlying MEMS layer (disclosed below). The interposer 104 may also include a first conductive layer 202 above the first insulating layer 201. The interposer 104 may include a second insulating layer 203 above the first conductive layer 202. The interposer 104 may include further alternating insulating and conductive layers. The insulating layer may be made of silicon oxide. The conductive layer may be made of polysilicon. The conductive layer may be made of metal. The layered structure of the interposer allows for the addition of multiple routing paths for connecting the ASIC layer to the rest of the MEMS system.

[0020] Intermediate layer 104 may include an intermediate conductive element at the first side, for example Figure 2a As shown in the diagram, 204 and 214. Some interposer conductive elements (such as 204) can be used to bond the interposer to the ASIC layer. Other interposer conductive elements (such as 214) can be used to route signals from the interposer to the ASIC layer.

[0021] A microelectromechanical system, wherein the interposer layer includes a first measuring electrode on the second side, wherein the first measuring electrode is adjacent to the first movable structure in the first isolation housing.

[0022] Intermediate layer 104 may include first measuring electrode 105 at second side 1042, such as Figure 2a As shown in the diagram. The material of the first measurement electrode 105 can be polycrystalline silicon. The first measurement electrode 105 may not be patterned. Alternatively, the first measurement electrode 105 may be pre-patterned, for example, by providing notches, slots, holes, grooves, trenches, or through-holes. The structure of the MEMS system 100 allows the first measurement electrode 105 to be located at the interposer layer 104 within the MEMS system 100, which does not require any modification to the ASIC layer 101 and simplifies the manufacturing process.

[0023] Intermediate layer 104 may include an upper detection gap 211 formed by recessing the second side 1042.

[0024] MEMS system 100 also includes a MEMS layer 106. MEMS layer 106 includes a first side 1061 and a second side 1062. A second side of an interposer layer 104 is attached to the first side 1061 of MEMS layer 106. Interposer layer 104 can be attached to MEMS layer 109 by means of bonding. Alternatively, interposer layer 104 can be deposited on MEMS layer 106. In this case, interposer layer 104 can be partially released from MEMS layer 106 after deposition, allowing the movable structure of MEMS layer 106 to move.

[0025] MEMS layer 106 may define a device plane. The device plane may also be referred to as a horizontal plane or an xy-plane. A direction perpendicular to the device plane may be referred to as a vertical direction or a z-direction. Terms such as “horizontal,” “vertical,” “bottom,” “top,” “above,” and “below” in this disclosure do not refer to the orientation of the device relative to the Earth's gravitational field when the device is manufactured or used. Rather, the word “horizontal” simply defines a plane, while “vertical” defines a direction perpendicular to that plane. Other terms then refer to relative positions within that “vertical” direction.

[0026] MEMS layer 106 includes a first movable structure 107 and a second movable structure 108. MEMS layer 106 may include moving components in addition to the first movable structure 107 and the second movable structure 108. Furthermore, MEMS layer 106 may include static components (not shown). The static components remain stationary relative to surrounding components of the MEMS system 100. The first and second movable structures may be attached to the static components using flexible springs, which allow the movable structures to move relative to the static structures. The flexible springs may also be referred to as hangers. The static components of the MEMS layer may define a device plane. Alternatively, moving components in a non-actuated state may define a device plane.

[0027] The first movable structure 107 and the second movable structure 108 can be configured to move independently of each other.

[0028] MEMS layer 106 can be formed from a silicon wafer. The silicon can be doped, and MEMS layer 106 can actually be conductive.

[0029] MEMS layer 106 may include a lower detection gap 212 formed by recessing a second side 1062. The recess of 1062 can be performed using many different etching methods. In some applications, performing the recess in a localized oxidation of silicon (LOCOS) process is particularly advantageous. This allows for very precise control of the height of the lower gap. The height of the upper detection gap 211 in the z-direction can be approximately equal to the height of the lower detection gap 212 in the z-direction.

[0030] The heights of the upper detection gap 211 and the lower detection gap 212 in the z-direction can be from 0.9 μm to 3.0 μm. The heights of the upper detection gap 211 and the lower detection gap 212 in the z-direction can be from 1.4 μm to 2.4 μm. For both the upper detection gap 211 and the lower detection gap 212, the gap height tolerance can be less than + / - 40 nm.

[0031] MEMS layer 106 may include vias (not shown). A via is a set of relatively small holes extending through MEMS layer 106 in the z-direction. The vias facilitate easier access to the first insulating layer 201 through MEMS layer 106 when the first insulating layer 201 is removed during the manufacturing process. The vias may be etched into movable structures 107 or 108 (measuring areas) in MEMS layer 106, but they may alternatively be located elsewhere. The optimal location and size of the vias depend on the geometry of the device, the thickness of the first insulating layer 201, and the etching process used to remove the first insulating layer 201. MEMS system 100 also includes a capping layer 109. Capping layer 109 is attached to a second side 1062 of MEMS layer 106. Capping layer 109 may include a first side 1091 that can be attached to MEMS layer 106. Capping layer 109 may be attached to MEMS layer 106 by means of bonding. Capping layer 109 may be attached to MEMS layer 106 by means of anodic bonding. The cover layer 109 may include a second side 1092 opposite to the first side 1091.

[0032] The cover layer 109 may include a cover recess 214 in the first surface, such as Figure 2a As shown in the diagram. Specifically, the cover recess 214 can be located within the second isolation housing 111. The depth of the cover recess in the z-direction can be between 10 μm and 30 μm. Specifically, the depth of the cover recess in the z-direction can be greater than 10 μm or less than 30 μm. The recess 214 is particularly useful when the second movable structure 108 is part of the accelerometer structure, to provide more space for out-of-plane movement (discussed in detail later).

[0033] The ASIC layer 101, the interposer layer 104, the MEMS layer 106, and the capping layer 109 can be attached to each other in the vertical direction in the order described.

[0034] Intermediate layer 104 and capping layer 109 form a first isolation housing 110, wherein MEMS layer 106 is located inside the first isolation housing 110. ASIC layer 101 and capping layer 109 form a second isolation housing 111, wherein MEMS layer 106 is located inside the second isolation housing 111. In other words, a portion of MEMS layer 106 may be located within the first isolation housing 110, while another portion of the MEMS layer may be located within the second isolation housing 111. The term "isolation" may mean that the housing is hermetically sealed from the external environment, and, if more than one housing exists, hermetically sealed to another housing.

[0035] The pressure in the first isolation housing 110 differs from the pressure in the second isolation housing 111. The pressure in the first isolation housing 110 can be lower than the pressure in the second isolation housing 111. The manufacturing process of the MEMS system (described below) allows for different pressures in the first and second isolation housings, which is crucial for the proper operation of movable structures within the isolation housings. The pressure setting is reliable and efficient in the manufacturing process because it does not require any additional structural modifications to the MEMS system. The pressure is set when bonding the ASIC layer to the interposer layer (e.g., via metal bonding) and when bonding the capping layer to the MEMS layer (e.g., via anodic bonding).

[0036] Specifically, the pressure in the first isolation enclosure 110 can be a vacuum. The pressure in the first isolation enclosure 110 can be from 0.4 mbar to 1.1 mbar. The pressure in the second isolation enclosure 111 can be from 1250 mbar to 2000 mbar. The gas in the first isolation enclosure 110 and the second isolation enclosure 111 can be pure argon. Other rare gases, such as neon and helium, can also be used. Nitrogen (N2) can also be used.

[0037] The first movable structure 107 can be located within the first isolation housing 110. The second movable structure 108 can be located within the second isolation housing 111. The first measuring electrode 105 can be located within the first isolation housing 110. The first measuring electrode 105 can be adjacent to the first movable structure 107 in the z-direction. The first measuring electrode 105 can be located via a first measuring through-hole (e.g., ...). Figure 2a (206 shown) is connected to the intermediate layer conductive element 214 in the intermediate layer 104. The first measuring electrode 105 can be configured to measure the out-of-plane displacement of the first movable structure 107. Specifically, the out-of-plane displacement of the first movable structure 107 can be measured using the capacitance change in the first measuring electrode 105. The first movable structure 107 can be used as one of the electrodes of a capacitor, and the first measuring electrode 105 can be the first pair of electrodes of a capacitor.

[0038] The first movable structure 107 and the second movable structure 108 can be configured to move out of the device plane, such as... Figure 2b As shown. In Figure 2b In this configuration, the first movable structure 107 rotates out of the device plane, while the second movable structure 108 remains in the device plane (without rotation). Specifically, the first movable structure 107 and / or the second movable structure 108 can be configured to rotate about a first axis of rotation. The first axis of rotation can be located in the device plane. The first axis of rotation can be along the x-direction and pass through point 209, as shown below. Figure 2bAs shown in the figure. Alternatively, the first movable structure 107 and / or the second movable structure 108 can be configured to perform a linear translation in the z-direction (not shown).

[0039] The advantage of having an interposer layer 104 between the ASIC layer 101 and the MEMS layer 106 is that it provides design freedom for the arrangement of movable structures 107 and 108 and the first measurement electrode 105 with excellent electrical performance. The interposer layer 104 provides low parasitic capacitance and a built-in bias environment for sensitive signal detection. Without the interposer layer 104, out-of-plane detection would need to be performed against the second surface of the ASIC layer 101, which is difficult and expensive because it requires accommodating a large and electrically undisturbed detection electrode on the second surface of the ASIC layer 101.

[0040] According to the microelectromechanical system of this disclosure, the cover layer includes a first side attached to the MEMS layer, and the cover layer also includes a second measurement electrode at the first side, wherein the second measurement electrode is adjacent to the first movable structure in the first isolation housing.

[0041] According to the microelectromechanical system of this disclosure, the first measuring electrode is polycrystalline silicon.

[0042] According to the microelectromechanical system of this disclosure, the first measuring electrode and / or the second measuring electrode are metals.

[0043] like Figure 1 As shown, the cover layer 109 may include a second measuring electrode 207 at its first side 1091. The second measuring electrode 207 may be in the first insulating housing 110. The second measuring electrode 207 may be adjacent to the first movable structure 107 in the z-direction. The second measuring electrode 207 may be provided by means of a second measuring through-hole (e.g., Figure 2a (208) is connected to ASIC layer 101.

[0044] The second measuring electrode 207 can be configured to measure the out-of-plane displacement of the first movable structure 107. In other words, both the first measuring electrode 105 and the second measuring electrode 207 can be configured to measure the out-of-plane displacement of the first movable structure 107 within the first isolation housing 110. Specifically, the out-of-plane displacement of the first movable structure 107 can be measured using the capacitance change in the first measuring electrode 105 and the second measuring electrode 207. Specifically, the first movable structure may include a first measuring region facing the first measuring electrode 105 and a second measuring region facing the second measuring electrode 207. The first measuring region and the second measuring region may be aligned one over the other along the z-direction. The first measuring region of the first movable structure 107 (e.g., made of monocrystalline silicon) can serve as the first electrode of a capacitor, and the first measuring electrode 105 can be the first pair of electrodes of the capacitor. The second measuring region of the first movable structure 107 can serve as the second electrode of a capacitor, and the second measuring electrode 207 can be the second pair of electrodes of the capacitor.

[0045] The advantage of using the same first movable structure 107 to align the first and second measurement regions is that it facilitates differential measurement. The capacitance measured across the first measurement gap to the first measurement electrode 105 can be labeled C1, and the capacitance measured across the second measurement gap to the second measurement electrode 207 can be labeled C2. When the first and second measurement regions are aligned one on top of the other, movement of the first movable structure 107 in the positive z-direction (upward in the figure) decreases C1 and increases C2, while movement in the negative z-direction (downward) increases C1 and decreases C2. The differential capacitance DC = C1 - C2 will generally exhibit a stronger linear dependence on the mass displacement compared to either of the two capacitances alone.

[0046] Primarily, the measuring gap and measuring electrodes can be used for out-of-plane displacement detection as discussed above. However, the measuring gap and measuring electrodes can also be used to actuate movable structures.

[0047] The first measuring electrode 105 can be made of polycrystalline silicon. The first measuring electrode 105 and the second measuring electrode 207 can be made of metal. Specifically, the second measuring electrode 207 can be made of aluminum. The thickness of the aluminum second measuring electrode 207 can be 80 nm. The aluminum second measuring electrode 207 may also include a 50 nm insulating diamond-like carbon (DLC) layer thereon.

[0048] According to the microelectromechanical system of this disclosure, the ASIC layer is electrically connected to the capping layer via the interposer layer and the ASIC via in the MEMS layer, and signals from the ASIC layer are routed from the capping layer to the outside of the MEMS system.

[0049] Figure 3a An example of how signals from a MEMS system 100 can be routed to the outside is shown. In this example, the ASIC layer 101 can be routed via ASIC vias (such as, for example, ASIC TSVs). Figure 3a The ASIC via 301 is schematically shown as being electrically connected to the capping layer 109. The ASIC via 301 can be arranged to pass through the interposer layer 104 and the MEMS layer 106 to reach the capping layer 109.

[0050] The capping layer 109 may be made of silicon, and it may be doped to make it conductive. The capping layer 109 may include a first vertical contact (not shown) extending from a first side 1091 to a second side 1092. The first vertical contact may be electrically isolated from the rest of the capping layer by an insulating cap region. The first vertical contact may be connected to an output contact pad, such as 302.

[0051] The ASIC via 301 may terminate at an output contact pad 302 on a second side of the capping layer 109. The output contact pad 302 may be electrically connected to the outside of the MEMS system 100. For example, the capping layer 109 may include conductive solder balls 303 on a second side 1092, which may be connected to an external printed circuit board (PCB, not shown). The MEMS system 100 may include a number of arrangements including ASIC vias (e.g., 301), output contact pads (e.g., 302), and conductive solder balls (e.g., 303).

[0052] The advantage of this arrangement is that it reduces the lateral space in MEMS system design because all electrical connections are arranged vertically.

[0053] According to the microelectromechanical system disclosed herein, signals from the ASIC layer to the outside of the MEMS system are configured to be routed directly from the ASIC layer.

[0054] According to the microelectromechanical system of this disclosure, the signals from the ASIC layer to the outside of the MEMS system are configured to be routed via a guide connected to the ASIC layer.

[0055] Alternatively, signals can be routed directly from ASIC layer 101 to the outside of MEMS system 100, such as... Figure 3b As shown in the diagram. Specifically, the ASIC layer 101 may include an output electrode 304 at the second side 1012. The output electrode 304 may be electrically connected to an external electronic device 306 by means of, for example, wire bonding 305. In this arrangement, the capping layer 109 may be passive and does not include conductive elements. Alternatively, the capping layer 109 may include conductive elements ( Figure 3b(not shown in the diagram), the conductive elements are electrically connected to the MEMS layer 106, the interposer layer 104 and / or the ASIC layer 101, but are not directly electrically connected to the outside of the MEMS system 100.

[0056] The advantage of this arrangement is that it simplifies the manufacturing process of MEMS systems because fewer vias are needed for internal signal routing. Another advantage of routing signals directly from the ASIC layer via wire bonding is that less mechanical stress is generated on the MEMS structure due to the lack of solder ball assemblies on the external printed circuit board.

[0057] The first movable structure can be a gyroscope.

[0058] A gyroscope is a device used to detect and measure changes in the angular velocity and orientation of an object. Traditional MEMS gyroscopes contain a moving sensing mass, such as... Figure 1 The first movable structure 107 typically comprises a portion of a silicon wafer. A movable detection mass is suspended from a fixed element, which is typically a fixed portion of the same wafer. The detection mass is connected to a force sensor, which drives the detection mass to oscillate. As the gyroscope undergoes angular rotation, the Coriolis effect modulates the oscillation of the movable detection mass. This modulation of the oscillation is proportional to the angular rate of the gyroscope, and the magnitude of the angular rotation rate can be determined.

[0059] When the first movable structure is a gyroscope, the first and second measuring electrodes can be used for orthogonal signal compensation by applying corresponding voltages to adjust the unwanted movement direction of the movable structure.

[0060] The second movable structure can be an accelerometer.

[0061] An accelerometer is a device used to detect and measure the magnitude of acceleration of an object. In traditional MEMS accelerometers, such as... Figure 1 The mass element of the second movable structure 108 is suspended from the fixed structure by a flexible suspension spring. When an external force is applied to the accelerometer to accelerate it, the mass element displaces from its rest position. The magnitude of the acceleration can be determined by measuring the magnitude of this displacement using a force sensor. Ideally, the accelerometer should not generate any output signal during steady-state motion.

[0062] The pressure in the first isolation housing 110 where the gyroscope is located can be lower than the pressure in the second isolation housing 111 where the accelerometer is located. Specifically, the pressure in the first isolation housing 110 can be a vacuum.

[0063] The second isolation housing 111 may include a first protrusion 210, such as Figure 2bAs shown in the diagram. A first bump 210 may be located on a first side 1091 of the capping layer 109. The purpose of the first bump 210 may be to mechanically stop the movement of the second movable structure 108 in the second isolation housing 111 before the capacitor is electrically short-circuited. The first bump 210 would be particularly useful if the second isolation housing 111 includes an accelerometer. Another purpose of the first bump 210 is to prevent the MEMS layer 106 from bonding to the capping layer 109 structure during anodic bonding. During the anodic bonding of the capping layer 109 and the MEMS layer 106, the capping layer 109, which may be alkaline glass, is biased to a high voltage, while the silicon of the MEMS layer 106 remains at ground potential. This potential difference causes a strong electrostatic field to pull all movable structures of the MEMS layer 106 toward the capping layer 109. The first bump 210 at the capping layer 109 may be made of silicon dioxide covered with DLC, which can prevent the MEMS layer 106 structure from permanently bonding to the capping layer 109. The ultimate purpose of the first bump 210 may be for electrical testing. The second movable structure 108 can undergo a pull-in test (against the stop protrusion) during the final detection, enabling the characterization of various functional characteristics of the MEMS gyroscope and / or MEMS accelerometer.

[0064] Intermediate layer 104 may include a second bump 213 on side 1042, such as Figure 2b As shown in the diagram. The second bump serves the same purpose as described above with respect to the first bump 210, except to prevent static friction, since it can be bonded to the ASIC layer side on the interposer layer via non-biased metal bonding.

[0065] The material of the second bump on the interposer 104 can be polysilicon. The second bump can be fabricated during the formation of the first measuring electrode 105.

[0066] Manufacturing method

[0067] A method for manufacturing a microelectromechanical system according to the present disclosure includes the following steps: a) forming an interposer layer on a first wafer; b) forming a MEMS layer from the first wafer, the MEMS layer including a first movable structure and a second movable structure; c) attaching a capping layer to the MEMS layer such that a first isolation shell is formed between the capping layer and the interposer layer, and applying pressure in the first isolation shell; d) removing a portion of the interposer layer on the second movable structure; e) attaching an ASIC layer to the interposer layer such that a second isolation shell is formed between the ASIC layer and the capping layer, and applying pressure in the second isolation shell.

[0068] According to Figure 4 The following processes are shown to manufacture MEMS systems:

[0069] - Step a:

[0070] ○ Take silicon wafer 401 and expose it to thermal oxidation to obtain a first oxide layer of a certain thickness. Use photolithography and dry etching to form recesses in / through the first oxide layer.

[0071] ○ A first conductive layer (e.g., polysilicon) is deposited on top of the first oxide layer. A first conductive pattern is obtained in the first conductive layer using photolithography and dry etching.

[0072] A second oxide layer is formed on the first conductive pattern and the exposed first oxide layer. The first oxide layer, the first conductive layer, and the second oxide layer form the interposer layer 104 of the MEMS system.

[0073] Optionally, a thick third oxide layer may be deposited on the second oxide layer.

[0074] - Step b:

[0075] ○ The temporary silicon carrier wafer 402 is attached to the third oxide layer by means of, for example, fusion bonding.

[0076] The structure of MEMS layer 106 is formed in silicon wafer 401 by using, for example, a first local silicon oxidation (LOCOS) process to define a MEMS layer recess (detection gap 212) and a second photolithography and HF etching process to define a first movable structure 107 and a second movable structure 108.

[0077] - Step c:

[0078] ○ The capping layer 109 is attached to the MEMS layer by means of, for example, anodic bonding. Other attachment methods are also possible. Pressure is set in the first isolation housing 110 at this step. The pressure can be set by performing bonding under the desired pressure.

[0079] ○ Remove the temporary silicon carrier wafer 402 and form a conductive via, for example 206, through the third oxide layer (optional) and the second oxide layer.

[0080] ○ A metal layer, such as titanium and germanium, is deposited on the third oxide layer and patterned using photolithography and wet etching to form metal contacts 204.

[0081] - Step d:

[0082] ○ Remove the first oxide layer, second oxide layer, third oxide layer and first conductive layer on part 403 of the MEMS layer.

[0083] - Step e:

[0084] ○ The ASIC layer 101 is attached to the metal contact 204 by means of, for example, metal bonding. Pressure is set in the second isolation housing 111 at this step. The pressure can be set by performing bonding under the desired pressure.

[0085] ○ Optionally, electrical contacts for external connections are provided in the cover layer.

[0086] The disclosed manufacturing method relates to the fabrication of MEMS systems, wherein multiple systems are simultaneously fabricated from stacked wafers through wafer-level processing. After the fabrication steps are completed, the wafers are diced to produce individual MEMS systems.

Claims

1. A microelectromechanical system, comprising: - ASIC layer, wherein the ASIC layer includes control circuitry. - An intermediary layer, the intermediary layer including a first side and a second side, wherein the ASIC layer is attached to the first side of the intermediary layer, and - A MEMS layer, comprising a first side and a second side, wherein the second side of the interposer layer is attached to the first side of the MEMS layer. - A capping layer, which is attached to a second side of the MEMS layer. in The intermediate layer and the capping layer form a first isolation shell, wherein the MEMS layer is inside the first isolation shell, and the ASIC layer and the capping layer form a second isolation shell, wherein the MEMS layer is inside the second isolation shell, wherein the pressure in the first isolation shell is different from the pressure in the second isolation shell. - And wherein the MEMS layer includes a first movable structure and a second movable structure, and wherein the first movable structure is in the first isolation housing, and the second movable structure is in the second isolation housing.

2. The microelectromechanical system according to claim 1, wherein, The intermediate layer includes a first measuring electrode on the second side, wherein the first measuring electrode is adjacent to the first movable structure in the first insulating housing.

3. The microelectromechanical system according to claim 1 or 2, wherein, The cover layer includes a first side attached to the MEMS layer, and the cover layer includes a second measurement electrode at the first side, wherein the second measurement electrode is adjacent to the first movable structure in the first isolation housing.

4. The microelectromechanical system according to any one of the preceding claims, wherein, The first measuring electrode is polycrystalline silicon.

5. The microelectromechanical system according to any one of claims 1 to 3, wherein, The first measuring electrode and / or the second measuring electrode are metals.

6. The microelectromechanical system according to any one of the preceding claims, wherein, The ASIC layer is electrically connected to the capping layer via ASIC vias in the interposer layer and the MEMS layer, and signals from the ASIC layer are routed from the capping layer to the outside of the microelectromechanical system.

7. The microelectromechanical system according to any one of claims 1 to 5, wherein, Signals from the ASIC layer to the outside of the microelectromechanical system are configured to be routed directly from the ASIC layer.

8. The microelectromechanical system according to claim 7, wherein, The signals from the ASIC layer to the outside of the microelectromechanical system are configured to be routed via wires connected to the ASIC layer.

9. The microelectromechanical system according to any one of the preceding claims, wherein, The first movable structure is a gyroscope, and the second movable structure is an accelerometer.

10. A method for manufacturing a microelectromechanical system according to any one of the preceding claims, comprising the following steps: a) Forming an intermediary layer on top of the first wafer b) Forming a MEMS layer from the first wafer, the MEMS layer comprising a first movable structure and a second movable structure. c) Attaching a capping layer to the MEMS layer to form a first isolation shell between the capping layer and the interposer layer, and setting pressure within the first isolation shell. d) Remove the portion of the intermediary layer on the second movable structure. e) Attach the ASIC layer to the interlayer such that a second isolation housing is formed between the ASIC layer and the capping layer, and set pressure in the second isolation housing.

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