CN115304020A - MEMS sensor structure and method of forming the same - Google Patents

Abstract

The application discloses MEMS sensor structure and forming method can reduce the cracked probability of the marginal zone of first wafer, reduces the probability of device inefficacy, includes: the first wafer is provided with a functional device on the surface and/or inside and comprises a first surface and a second surface which are oppositely arranged, the first surface is provided with a bonding pad, the bonding pad is positioned at the outer side of the area where the functional device is positioned and is electrically connected to the functional device and used for bonding and routing so as to electrically connect the functional device to the outside of the first wafer; the second wafer is supported by the first bonding assembly and is oppositely bonded to the second surface of the first wafer; the first key assembly includes: the main bonding piece is arranged around the functional device and is annular, and a first cavity is formed among the main bonding piece, the first wafer and the second wafer; and the auxiliary bonding part is bonded between the first wafer and the second wafer and arranged on the outer side of the main bonding part, and the distribution area of the auxiliary bonding part is opposite to the position of the bonding pad and supports the bonding pad of the first wafer.

Description

MEMS sensor structure and method of forming the same

Technical Field

The present application relates to the field of sensors, and more particularly, to MEMS sensor structures and methods of forming the same.

Background

With the development of the technology of the internet of things and the improvement of the life quality of people, the application prospect of the MEMS sensor structure is more and more extensive, the integrated packaging mainly integrates and packages the semiconductor chips such as the MEMS chip, the thermopile chip or the filter and the like with other functional devices or CMOS circuits, so that the finally formed sensor has the advantages of small size, light weight, no need of refrigeration, high sensitivity and the like, and is widely applied to the aspects of safety monitoring, medical treatment, life detection, consumer products and the like, and the development is rapid.

The yield of devices after the packaging of the thermopile chip is low, and a new structure or a new forming method is urgently needed to improve the yield of the devices.

Disclosure of Invention

In view of this, the present application provides an MEMS sensor structure and a method for forming the same, which can improve the yield of devices.

The application provides a MEMS sensor structure, includes: the MEMS sensor comprises a first wafer, wherein functional devices are formed on the surface and/or inside of the first wafer, the functional devices at least comprise MEMS sensors, the first wafer comprises a first surface and a second surface which are oppositely arranged, a bonding pad is formed on the first surface, the bonding pad is located on the outer side of the area where the functional devices are located, and the bonding pad is electrically connected to the functional devices and used for carrying out bonding and routing so as to electrically connect the functional devices to devices outside the first wafer; the second wafer is supported by the first bonding assembly and is oppositely bonded to the second surface of the first wafer; the first key assembly includes at least: the main bonding piece is bonded between the first wafer and the second wafer, is arranged around the functional device and is annular, and a first cavity is formed among the main bonding piece, the first wafer and the second wafer; and the auxiliary bonding part is bonded between the first wafer and the second wafer and arranged outside the main bonding part, and the distribution area of the auxiliary bonding part is opposite to the position of the bonding pad and used for supporting the bonding pad of the first wafer.

Optionally, the shape of the secondary bonding member is consistent with the shape of the distribution area of the bonding pads, and the projection of the bonding pads on the second surface of the first wafer is located in the projection of the secondary bonding member on the second surface of the first wafer

Optionally, an annular first groove is formed in a surface of one side, facing the first wafer, of the second wafer, the first groove surrounds the functional device, the main bonding member and the auxiliary bonding member are located in the first groove, and the main bonding member is arranged along the first groove.

Optionally, an annular second groove is formed on a surface of one side, facing the first wafer, of the third wafer, and a position of the annular second groove corresponds to a distribution area of the functional device; the second bonding assembly is bonded between the first wafer and the third wafer, is annular and surrounds the second groove.

Optionally, the secondary key is provided with an extension at a side facing the primary key for connection to the primary key.

Optionally, a length direction of the secondary bonding member is the same as a length direction of a distribution area of the bonding pad, and the extension portions are distributed at a head end and a tail end of the secondary bonding member in the length direction.

Optionally, the length direction of the secondary bonding member is the same as the length direction of the distribution area of the bonding pad, and the extending portions are distributed at the head end, the tail end and the middle section of the secondary bonding member in the length direction. .

The application also provides a method for forming the MEMS sensor structure, which at least comprises the following steps: providing a first wafer, forming a functional device on the surface and/or inside of the first wafer, wherein the functional device at least comprises a MEMS sensor, the first wafer comprises a first surface and a second surface which are oppositely arranged, the first surface is formed with a bonding pad, the bonding pad is positioned at the outer side of the area where the functional device is positioned, and the bonding pad is electrically connected to the functional device and used for bonding and routing, so that the functional device is electrically connected to a device outside the first wafer; providing a second wafer; bonding the first wafer and the second wafer by a first bonding assembly, the first bonding assembly at least comprising: the main bonding piece is bonded between the first wafer and the second wafer, is arranged around the functional device and is annular, and a first cavity is formed among the main bonding piece, the first wafer and the second wafer; and the auxiliary bonding part is bonded between the first wafer and the second wafer and is arranged on the outer side of the main bonding part, and the distribution area of the auxiliary bonding part is opposite to the position of the bonding pad and supports the bonding pad of the first wafer.

According to the MEMS sensor structure and the forming method thereof, the auxiliary bonding part is arranged below the bonding pad and can support the first wafer, stress action on the first wafer below the bonding pad in a metal bonding process is dispersed, the risk of cracking of the first wafer is reduced, the probability of failure of a product structure is reduced, and the productivity of the sensor is improved.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

Fig. 1 to 13 are schematic cross-sectional views corresponding to steps of manufacturing the MEMS sensor structure according to an embodiment of the present disclosure;

FIG. 14 is a schematic top view of the MEMS sensor structure in an embodiment of the present application.

FIG. 15 is a schematic diagram of a top view of the MEMS sensor structure in an embodiment of the present application.

FIG. 16 is a cross-sectional structure diagram of the MEMS sensor structure in an embodiment of the present application.

Fig. 17 is a flow chart illustrating steps of a method for forming the MEMS sensor structure according to an embodiment of the present disclosure.

Fig. 18 is a flowchart illustrating a step of forming a first metal bond in an embodiment of the present application.

Detailed Description

Research finds that, in the prior art, the important reason that the yield of the device is low is that double-sided wafer-level metal bonding vacuum packaging of the infrared thermopile array is required when packaging the first wafer, the second wafer and the third wafer of the thermopile chip, however, the first wafer provided with the functional device is easily broken in the packaging process, which results in low yield of the device. The important reason that the first wafer is easily broken is that a bonding pad for wire bonding is arranged in a partial region of the first wafer, the bonding pad is electrically connected with the functional device in the first wafer, and when the functional device in the first wafer needs to be electrically connected to other devices, the bonding pad needs to be wire bonded to realize the electrical connection between the functional device and other devices. During the process of bonding the first wafer to the third wafer, which is the bottom wafer, the first wafer itself may be subjected to a large stress, which may cause the first wafer to crack, and easily cause the finally formed device to fail, thereby affecting the yield of the device.

In order to solve the above problem, embodiments of the present application provide a MEMS sensor structure and a method for forming the same to solve the problem of edge chipping of the first wafer.

The MEMS sensor structure and the packaging method thereof according to the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and drawings, it being understood, however, that the concepts of the present invention may be embodied in many different forms and should not be construed as limited to the specific embodiments set forth herein. The drawings are in simplified form and are not to scale, but are provided for convenience and clarity in describing embodiments of the invention.

The terms "first," "second," and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the invention described herein are, for example, capable of operation in other sequences than described or illustrated herein. Similarly, if a method described herein comprises a series of steps, the order in which these steps are presented herein is not necessarily the only order in which these steps can be performed, and some of the described steps may be omitted and/or some other steps not described herein may be added to the method. Although elements in one drawing may be readily identified as such in other drawings, the present disclosure does not identify each element as being identical to each other in every drawing for clarity of description.

Referring to fig. 12 and 14, fig. 12 is a schematic structural diagram of a MEMS sensor structure according to an embodiment of the present disclosure, and fig. 14 is a schematic top structural diagram of the MEMS sensor structure according to an embodiment of the present disclosure.

In this embodiment, the MEMS sensor structure comprises: a first wafer 101, a surface and/or an interior of which a functional device is formed, the functional device including a MEMS sensor, the first wafer 101 including a first surface and a second surface which are opposite to each other, as shown in fig. 1, the first surface of the first wafer 101 having a pad 130, the pad 130 being located outside an area where the functional device is located and electrically connected to the functional device for performing a wire bonding process, so as to connect the functional device to a device outside the first wafer 101; a second wafer 106, as shown in fig. 10, supported by the first bonding assembly 202 and bonded to a second surface of the first wafer 101; the first key assembly 202 includes at least: a main bonding member 203 bonded between the first wafer 101 and the second wafer 106, wherein the main bonding member 203 is disposed around the functional device and has a ring shape, and a first cavity 40 is formed among the main bonding member 203, the first wafer 101 and the second wafer 106; and a secondary bonding member 205 bonded between the first wafer 101 and the second wafer 106 and disposed outside the primary bonding member 203, wherein the distribution region 205 of the secondary bonding member 205 is opposite to the bonding pad 130 and supports the bonding pad 130 of the first wafer 101.

In this embodiment, a sub-bonding element 205 is disposed below the bonding pad 130, and the sub-bonding element 205 can provide support for the first wafer 101 during the bonding and routing process, and disperse the stress effect on the first wafer 101 where the bonding pad 130 is located during the bonding and routing process, thereby reducing the risk of cracking of the first wafer 101, reducing the probability of product structure failure, and improving the productivity of the sensor.

In some embodiments, the first wafer 101 includes a substrate 101a, and the functional device is disposed on an upper surface of the substrate 101a or inside the substrate 101 a. In the embodiment shown in fig. 1, the functional device forms a functional sub-layer 101b.

In some embodiments, the material of the substrate 101a includes semiconductor materials, such as silicon (Si), germanium (Ge), silicon germanium (SiGe), silicon carbon (SiC), silicon germanium carbon (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP), or other III/V compound semiconductors, double Side Polished silicon Wafers (DSPs), ceramic substrates, quartz or glass substrates, such as aluminum oxide.

In some embodiments, the MEMS sensor may convert a target signal into an electrical signal, the functional device further includes an actuator coupled to the MEMS sensor for performing an action based on the electrical signal output by the MEMS sensor, and a micro-energy source coupled to the MEMS sensor and the actuator for providing energy to the sensor and the actuator.

In some embodiments, the MEMS sensor comprises an array of thermopile structures comprising a plurality of thermocouple pairs comprising two different materials in series, which may be stacked or juxtaposed, further, which may be polysilicon and aluminum, respectively; alternatively, the two materials may be polysilicon and copper, respectively; alternatively, the two materials may be polysilicon of two different doping levels. In other embodiments, the functional device as a sensing structure of the MEMS sensor structure may be a MEMS structure, a filter structure, etc., and the functional device may further include at least a portion of a thermistor or at least a portion of a photoresistor.

In the MEMS sensor structure, a first surface and a second surface of the first wafer 101 are respectively bonded with a third wafer 102 and the second wafer 106, the third wafer 102 and the second wafer 106 are respectively used as a cap wafer or a bottom wafer of the first wafer 101 to protect the first wafer 101, and the third wafer 102 is bonded to the surface of the first wafer 101 through a second bonding component 204.

In some embodiments, the materials of the second wafer 106 and the third wafer 102 include semiconductor materials, such as silicon (Si), germanium (Ge), silicon germanium (SiGe), silicon carbon (SiC), silicon germanium carbon (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP), or other III/V compound semiconductors, double Side Polished silicon Wafers (DSPs), ceramic substrates such as aluminum oxide, quartz or glass substrates, and the like.

In this embodiment, the material of the third wafer 102 is a semiconductor material, and infrared rays can be transmitted through the semiconductor material to perform infrared ray-related detection. In other embodiments, the material of the third wafer 102 may also be an optical material, such as glass, a filter, a lens, or the like, or a polymer material, such as a dry film, a molding compound, or the like.

In some embodiments, the shape of the secondary bonding member 205 is consistent with the shape of the distribution area of the bonding pads 130, and the projection of the bonding pads 130 on the second surface of the first wafer 101 is located in the projection of the secondary bonding member 205 on the second surface of the first wafer 101, so as to provide sufficient support for the bonding pads 130 and distribute the stress applied thereto during bonding.

In some embodiments, the projected area of the secondary bonding element 205 on the second surface of the first wafer 101 is 110% to 130% of the area of the bonding pad 130, so as to provide sufficient support for the first wafer 101, and have better stress dispersion effect, and prevent the silicon wafer from cracking near the bonding pad 130 for wire bonding.

In some embodiments, a side surface of the second wafer 106 facing the first wafer 101 is formed with an annular first groove 20, the first groove 20 is disposed around the functional device, the primary bonding member 203 and the secondary bonding member 205 are both located in the first groove 20, and the primary bonding member 203 is disposed along the first groove 20 (see fig. 10). In some embodiments, the first recess 20 may be used to limit the height of the MEMS sensor structure, preventing the height of the MEMS sensor from being too high, resulting in an increase in device volume.

The primary bonding member 203 is disposed around the distribution area of the functional devices of the first wafer 101, and may be used to support an edge portion of the distribution area of the functional devices of the first wafer 101.

In the embodiment shown in fig. 10, both the primary 203 and secondary 205 keys are distributed in the first groove 20. The first cavity 40 is formed between the first wafer 101 and the second wafer 106 based on the first recess 20.

Referring to fig. 14 and 15, fig. 15 is a schematic top view of a MEMS sensor structure according to an embodiment of the present disclosure.

In these embodiments, the bonding pads 130 are distributed on a side edge of the first wafer 101, and a projection of the bonding pads 130 on the first surface of the second wafer 106 is distributed along a side edge of the first groove 20.

The functional devices are distributed at the other end of the first wafer 101 in a centralized manner, and occupy most of the area of the first wafer 101.

In other embodiments, the bonding pads 130 may also be distributed along the periphery of the first wafer 101, and the secondary bonding members 205 are arranged along the periphery of the first wafer 101 to change along with the position change of the bonding pads 130.

In some embodiments, the projection of the primary bond 203 on the first surface of the first wafer 101 is annular. In some embodiments, the first groove 20 is in a rectangular ring shape, so that the main bonding member 203 is also in a rectangular ring shape and is disposed around the functional device, and the number of the pads 130 is a plurality and is uniformly distributed on one side of the rectangular ring-shaped main bonding member 203 and exposed on the first surface of the first wafer 101.

In the embodiment shown in fig. 14, the main bonding member 203 has a rectangular ring shape in a plan view, and is disposed around the distribution area of the functional device, at the edge of the distribution area of the functional device.

In some embodiments, the bonding pad 130 is rectangular, and in fact, the bonding pad 130 may be shaped as desired.

In some embodiments, the secondary bonding element 205 is provided with an extension portion on a side facing the primary bonding element 203 for connecting to the primary bonding element 203, so as to increase a force-bearing area of the secondary bonding element 205 under the bonding pad 130 when the bonding pad 130 is wire-bonded, further reduce the possibility of cracking of the first wafer 101 during wire bonding, and strengthen the connection between the primary bonding element 203 and the secondary bonding element 205. Since the extension 206 is located inside the gap between the bonding pad 130 and the distribution area of the functional devices, it does not extend out of the gap, which is beneficial to save on-board area used in manufacturing the MEMS sensor structure.

In the embodiment shown in fig. 14 and 15, the distribution area of the pads 130 is elongated, and the projection of the secondary bonding member 205 on the second surface of the first wafer 101 is elongated, and the length direction of the projection is the same as the length direction of the distribution area of the pads 130. The extension portions are distributed at least at the head end and/or the tail end of the secondary bonding member 205 in the length direction, so as to distribute the wire bonding stress in the length direction of the distribution area of the bonding pad 130.

In the embodiment shown in fig. 14, the length direction of the secondary bonding member 205 is the same as the length direction of the distribution area of the bonding pad 130, and the extension portions are distributed at the head end and the tail end of the secondary bonding member 205 in the length direction.

In the embodiment shown in fig. 15, the length direction of the secondary bonding member 205 is the same as the length direction of the distribution region of the bonding pad 130, and the extension portions are distributed at the head end, the tail end and the middle section of the secondary bonding member 205 in the length direction, so as to obtain a larger projection area.

In fact, the extension portions and the distribution area of the extension portions may also be provided as required.

The MEMS sensor structure is shown in fig. 16 from the perspective of the CD direction in fig. 15.

In the embodiment shown in fig. 16, one end of the first bonding assembly 202 is disposed in the first groove 20 of the second surface of the first wafer 101, and the other end is disposed in the second groove 30 (see fig. 2) of the second surface of the second wafer 106.

In some embodiments, the first bonding assembly 202 includes a plurality of metal key sets arranged in pairs, and the metal key sets include a first metal key 109 and a second metal key 107, wherein one end of the first metal key 109 is disposed on the second surface of the first wafer 101, and one end of the second metal key 107 is disposed on the second surface of the second wafer 106. The first metal keys 109 and the second metal keys 107 are arranged in a one-to-one correspondence and are positioned in a corresponding manner so as to be bonded in a one-to-one correspondence, and the first bonded assembly 202 is formed after bonding. The first metal key 109 and the second metal key 107 distributed in the corresponding area of the pad 130 are taken as the secondary bonding member 205, and the first metal key 109 and the second metal key 107 in the rest area are taken as the primary bonding member 203.

In some embodiments, the metal bond comprises at least one of a copper metal bond, a tin metal bond. These two metals are common metal bond preparation materials. The specific material of the metal bond may be set as desired.

In some embodiments, the shape of the first cavity 40 is designed, so that a cavity surrounding the functional device can be formed in the MEMS sensor structure, thereby achieving the requirements of thermal insulation and the like.

In some embodiments, the surface of the second wafer 106 is further formed with a gettering layer 111 to absorb moisture in air and keep the MEMS sensor structure dry.

In some embodiments, the MEMS sensor structure further comprises: the third wafer 102, as shown in fig. 1, is supported by the second bonding assembly 204 and bonded to the first surface of the first wafer 101, and a second cavity 10 is formed among the second bonding assembly, the first wafer 101 and the third wafer 102.

In some embodiments, the MEMS sensor structure comprises a thermopile sensor structure, and the functional devices comprise thermocouples distributed over a rectangular area on the first wafer 101. The positions of the first cavity 40 and the second cavity 10 correspond to the distribution areas of the functional devices, and the projections of the first cavity and the second cavity on the second surface of the first wafer 101 are rectangular, so that a certain heat insulation effect can be achieved, and the detection sensitivity of the thermopile sensor structure is enhanced.

In fact, the shape and distribution area of the first cavity 40 and the second cavity 10 can also be set according to the specific requirements of the MEMS sensor structure.

In some embodiments, the third wafer 102 forms an annular second groove 30 (see fig. 2) towards a side surface of the first wafer 101, the annular second groove being disposed around the second cavity; the second bonding assembly is bonded between the first wafer and the third wafer, is positioned in the second groove and is arranged along the second groove.

The second recess 30 may also serve as a temperature protection for the functional device, and may also serve to reduce the thickness of the MEMS sensor structure.

In some embodiments, the second Bonding assembly 204 is located in the second groove 30, and may be a Sealing ring (Sealing ring) or a Bonding ring (Bonding ring), etc., to seal the area surrounded by the second Bonding assembly 204.

In the embodiment shown in fig. 14, the second groove 30 is rectangular and annular, and the second key assembly 204 is located in the second groove 30 and also rectangular and annular. The areas surrounded by the main bonding element 203 and the second bonding element 204 correspond to the distribution areas of the functional devices of the first wafer 101, and correspond to the middle area of the first wafer 101.

In some embodiments, the second bonding assembly 204 includes a third metal key 105 disposed on a surface of the third wafer 102, and a fourth metal key 104 disposed on a surface of the first wafer 101. The third metal keys 105 and the fourth metal keys 104 are arranged in a one-to-one opposite manner, and bonding surfaces of the third metal keys 105 and the fourth metal keys 104 are large enough during bonding, so that stress can be effectively dispersed, and the probability of cracking of the first wafer 101 and/or the third wafer 102 caused by stress action during bonding is reduced.

In some preferred embodiments, at the edge positions of the first wafer 101 and the third wafer 102 and the second wafer 106, filling glue is used to prevent edge peeling (peeling) of the first wafer 101, the third wafer 102 and the second wafer 106 during bonding.

In some embodiments, the primary bonding element 203 and the secondary bonding element 204 are positioned relative to each other such that the secondary bonding element 204 distributes stress experienced by the first wafer 101 when bonding the first wafer 101 to the second wafer 106.

Referring now to fig. 14 and 15, the projection of the primary bonding element 203 onto the second surface of the first wafer 101 and the projection of the secondary bonding element 204 onto the second surface of the first wafer 101 are both disposed around the rectangular area where the functional device is disposed.

In some embodiments, the second bonding component 204 is at least partially coincident with a projection of the primary bonding element 203 onto the first surface of the first wafer 101. Due to the approximately same location of the bonding elements, when bonding the second wafer 106 and the first wafer 101, the stress on the first wafer 101 may also be dispersed by the second bonding element 204 between the first wafer 101 and the third wafer 102.

In the embodiment shown in fig. 8 to 15, the projected area of the second bonding element 204 on the second surface of the first wafer 101 is larger than the projected area of the main bonding element 203 of the first bonding element 202 on the second surface of the first wafer 101, so as to provide a sufficient contact area to distribute the stress when the first wafer 101 is subjected to the bonding force twice.

In some embodiments, the assembling step of the third wafer 102 occurs before the assembling step of the second wafer 106, and when packaging the second wafer 106, the second bonding element 204 between the third wafer 102 and the first wafer 101 needs to undergo two bonding force actions, including a bonding force action when the second bonding element 204 is bonded and a bonding force action when the first bonding element 202 is bonded. Therefore, the projected area of the second bonding element 204 on the second surface of the first wafer 101 is larger than the projected area of the main bonding element 203 of the first bonding element 202 on the second surface of the first wafer 101, so that the dispersion effect of the two bonding forces is enhanced, and the possibility of the first wafer 101 and the third wafer 102 being cracked is reduced.

In some embodiments, a side surface of the third wafer 102 away from the first wafer 101 is further provided with a Zero layer mark (Zero mark) for marking a Zero layer, an Alignment mark (Alignment mark) for Alignment, and the like.

In some embodiments, an anti-reflection film 108 is disposed on a surface of the third wafer 102 away from the first wafer 101. The antireflection film 108 layer may be used to reflect light in a desired wavelength band, such as infrared light. As shown in fig. 12. Fig. 12 is a sectional view from the perspective AB in fig. 14.

Referring to fig. 13, a dicing operation is performed to plan the morphology of the third wafer 102 such that the bonding pads 130 are directly exposed to the third wafer 102 for subsequent attachment. In fact, if the bonding pads 130 are disposed on the lower surface of the first wafer 101, the bonding pads 130 may also be exposed by planning the final shape of the second wafer 106.

In one embodiment, the bonding pads 130 may enable electrical connection of the sensor to other devices or chips. Other devices or chips include chips or devices that include CMOS circuitry, and the like.

The embodiment of the application also provides a packaging method of the MEMS sensor structure.

Fig. 17 is a schematic flowchart illustrating steps of the packaging method according to an embodiment.

In this embodiment, the packaging method comprises at least the following steps:

step S101: providing a first wafer 101, and forming functional devices on and/or in the first wafer 101, where the functional devices include MEMS sensors, and the first wafer 101 includes a first surface and a second surface that are oppositely disposed, as shown in fig. 1, the first surface of the first wafer 101 has pads 130, and the pads 130 are located outside an area where the functional devices are located, and are electrically connected to the functional devices for performing bonding wire bonding, so as to connect the functional devices to devices outside the first wafer 101.

Step S102: providing a second wafer 106;

step S103: bonding the first wafer 101 and the second wafer 106 by a first bonding assembly 202, the first bonding assembly 202 at least comprising: a main bonding member 203 bonded between the first wafer 101 and the second wafer 106, wherein the main bonding member 203 is disposed around the functional device and has a ring shape, and a first cavity 40 is formed among the main bonding member 203, the first wafer 101 and the second wafer 106; a secondary bonding element 205 located in the first groove 20, bonded between the first wafer 101 and the second wafer 106, and disposed outside the primary bonding element 203, wherein the distribution area 205 of the secondary bonding element 205 is opposite to the bonding pads 130, and supports the bonding pads 130 of the first wafer 101, as shown in fig. 11.

In this embodiment, a first bonding assembly 202 is formed between the first wafer 101 and the second wafer 106 to bond the second wafer 106 to the second surface of the first wafer 101, and the first bonding assembly 202 includes at least: the distribution area of the secondary bonding element 205 is opposite to the position of the bonding pad 130, so that the bonding pad 130 of the first wafer 101 can be sufficiently supported in the bonding and routing process, the stress effect on the first wafer 101 where the bonding pad 130 is located in the bonding and routing process is dispersed, the risk of the first wafer 101 breaking is reduced, the probability of product structure failure is reduced, and the productivity of the sensor is improved.

In this embodiment, the MEMS sensor may convert a target signal into an electrical signal, the functional device further includes an actuator connected to the MEMS sensor for performing an action based on the electrical signal output by the MEMS sensor, and a micro-energy source connected to the MEMS sensor and the actuator for providing energy to the sensor and the actuator.

After the first wafer 101 is bonded to the second wafer 106, the first cavity 40 is formed among the main bonding member 203, the first wafer 101 and the second wafer 106, and the first cavity 40 is disposed around the distribution area of the functional devices.

In some embodiments, the first bonding assembly 202 includes a first metal bond 109 disposed on a surface of the first wafer 101 and a second metal bond 107 disposed on a surface of the second wafer 106.

The first metal bond 109 and the second metal bond 107 are each made of metal. In some embodiments, when forming the first bonding assembly 202, the first metal bond 109 and the second metal bond 107, which are arranged in a one-to-one correspondence, are aligned, and the first metal bond 109 and the second metal bond 107 are melted to bond them in a one-to-one correspondence.

In some embodiments, a side surface of the second wafer 106 facing the first wafer 101 is formed with an annular first groove 20, the first groove 20 is disposed around the functional device, and the primary bonding member 203 is located in the first groove 20 and is disposed along the first groove 20.

Referring to fig. 18, a flowchart illustrating a step of forming a first metal key 109 on the second surface of the first wafer 101 according to an embodiment is shown.

In this embodiment, the bonding of the first wafer 101 and the second wafer 106 by the first bonding assembly 202 includes at least the following steps: step S201: forming a first metal key 109 on a second surface of the first wafer 101; step S202: forming second metal bonds 107 on the first surface of the second wafer 106, wherein the distribution positions of the second metal bonds 107 correspond to the distribution positions of the first metal bonds 109 one by one; step S203: aligning the first metal bond 109 with the second metal bond 107, and melting the contact surfaces of the first metal bond 109 and the second metal bond 107 to bond the first metal bond 109 and the second metal bond 107, thereby forming the first bonding assembly 202 to bond the second wafer 106 to the first wafer 101.

In this embodiment, the forming the first metal key 109 on the second surface of the first wafer 101 at least includes: forming a metal seed layer 110 on the second surface of the first wafer 101, as shown in fig. 6; growing a metal layer 50 based on the metal seed layer, as shown in fig. 7; the metal layer 50 is patterned, and the patterned metal layer is used as the first metal key 109, as shown in fig. 8.

In this embodiment, the material of the metal seed layer 110 may be selected as desired, generally consistent with the material of the first metal bond 109 to be ultimately produced. In some embodiments, the material of the first metal bond 109 is selected to be copper or tin, and thus the metal seed layer includes at least one of a copper layer or a tin layer.

In some embodiments, the metal seed layer is formed using physical vapor deposition. In fact, the metal seed layer can also be prepared by adopting methods such as chemical vapor deposition, atomic layer deposition and the like according to actual requirements.

In some embodiments, patterning the metal layer includes preparing a mask layer on the metal layer 50, and patterning the mask layer to expose a region to be etched on the surface of the metal layer and mask a region to be protected on the surface of the metal layer, and then etching the metal layer by at least one of dry etching and wet etching in a direction perpendicular to the upper surface of the metal layer and downward to form a metal bond required for the first metal bond 109.

In some embodiments, a first metal key 109 is formed on the second surface of the first wafer 101, and a portion of the first metal key 109 constitutes the secondary bonding element 205 for providing wire bonding support for the first wafer 101, and another portion thereof constitutes the primary bonding element 203, and the setting area corresponds to the distribution area of the functional devices of the first wafer 101 for providing a primary bonding effect.

The projection of the fourth metal key 104 on the second surface of the first wafer 101 may refer to fig. 14 or fig. 15. Third metal keys 105 corresponding to the fourth metal keys 104 are correspondingly formed on the second wafer 106, so that the projection of the third metal keys 105 on the second surface of the first wafer 101 can also refer to fig. 14 or fig. 15.

In some embodiments, the shape of the secondary bonding element 205 conforms to the shape of the distribution area of the bonding pads 130, and the projection of the bonding pads 130 on the second surface of the first wafer 101 is located within the projection of the secondary bonding element 205 on the second surface of the first wafer 101.

In some embodiments, the distribution region of the bonding pad 130 has an elongated shape, the secondary bonding member 205 has an elongated shape, and extensions 206 are formed at the head end and the tail end of the secondary bonding member 205 in the length direction, and the second metal bond 107 is connected to the primary bonding member 203 through the extensions 206. Reference is also made here to fig. 14 or fig. 15.

When the projected area of the second surface of the first wafer 101 needs to be further increased, the secondary bonding element 205 may adopt an extension 206 as shown in fig. 14 or fig. 15 to increase the projected area, and the extension only occupies a gap between the bonding pad 130 and the distribution area of the functional device, and does not extend outward, which is beneficial to saving the on-board area used in preparing the MEMS sensor structure.

In the embodiment shown in fig. 14, the two ends of the secondary key 205 are respectively provided with an extension 206, which is located between the primary key 203 and the secondary key 205, and is used for connecting the primary key 203 and the secondary key 205. In the embodiment shown in fig. 15, in order to obtain a larger projection area and thus a better supporting effect, an extension 206 is also provided at a middle position of the sub-key 205 to connect to the main key 203.

In the embodiment shown in fig. 14 and 15, the bonding pad 130 is disposed on one side edge of the first wafer 101, and therefore the sub-bonding element 205 is also disposed on one side edge of the first wafer 101, in fact, the bonding pad 130 may also be disposed along the periphery of the first wafer 101, and the sub-bonding element 205 may also be disposed along the periphery of the first wafer 101, and changes according to the position change of the bonding pad 130.

In some embodiments, the projected area of the secondary bond 205 on the second surface of the first wafer 101 is 110% to 130% of the area of the bond pad 130. It has been found that, at this size, the secondary bonding element 205 can provide better stress dispersion for the bonding pad 130, effectively reduce the possibility of the first wafer 101 cracking at the bonding pad 130, and also avoid using excessive metal material to prepare the first bonding element 202.

In some embodiments, further comprising the steps of: providing a third wafer 102; forming fourth metal keys 104 on the first surface of the first wafer 101, as shown in fig. 1, where the third metal keys 105 and the fourth metal keys 104 are arranged in a one-to-one correspondence; the third metal bonds 105 and the fourth metal bonds 104 are bonded in a one-to-one correspondence manner to form a second bonding element 204, as shown in fig. 3, and a second cavity 10 is formed among the second bonding element 204, the first wafer 101 and the third wafer 102.

In some embodiments, the third wafer 102 forms a second annular groove 30 (see fig. 2) towards a side surface of the first wafer 101, the second groove 30 is disposed around the second cavity 10, and the first surface of the third wafer 102 forms a third metal key 105, as shown in fig. 2.

The third metal keys 105 and the fourth metal keys 104 are arranged in a one-to-one correspondence manner, so that the projections of the third metal keys and the fourth metal keys on the second surface of the first wafer 101 are identical in shape to the second bonding assemblies 204 shown in fig. 14 or 15.

In some embodiments, in order to make the thickness of the first wafer 101 meet the requirement, in some embodiments, after the third metal keys 105 and the fourth metal keys 104 are bonded in a one-to-one correspondence, the method further includes the following steps: and thinning the second surface of the first wafer 101. Here as shown in figure 4.

After thinning, an Alignment mark 112 (Alignment mark) is formed on the second surface of the first wafer 101, as shown in fig. 5. Note that the alignment mark is not shown in the drawings after fig. 8.

In some embodiments, after the second wafer 106 is also disposed on the surface of the first wafer 101, in order to meet the requirement on the thickness of the MEMS sensor structure, the third wafer 102 and the second wafer 106 are thinned once.

The assembling step of the third wafer 102 occurs before the assembling step of the second wafer 106, so that when the second wafer 106 is packaged, the second bonding assembly 204 between the third wafer 102 and the first wafer 101 needs to undergo two bonding force actions, including a bonding force action when the second bonding assembly 204 is bonded and a bonding force action when the first bonding assembly 202 is bonded. Therefore, the size requirement of the second key assembly 204 is higher. In fig. 8 to 15, it can be seen that the projected area of the second bonding element 204 on the second surface of the first wafer 101 is larger than the projected area of the main bonding element 203 of the first bonding element 202 on the second surface of the first wafer 101, so as to provide a sufficient contact area for dispersing the stress when the first wafer 101 is subjected to the bonding force twice.

It should be noted that, in the present specification, all the embodiments are described in a related manner, and the same and similar parts among the embodiments are referred to each other, and each embodiment focuses on the differences from the other embodiments. In particular, for the structural embodiment, since it is substantially similar to the method embodiment, the description is relatively simple, and for the relevant points, reference may be made to the partial description of the method embodiment.

The above-mentioned embodiments are only examples of the present application, and not intended to limit the scope of the present application, and all equivalent structures or equivalent flow transformations made by the contents of the specification and the drawings, such as the combination of technical features between the embodiments and the direct or indirect application to other related technical fields, are also included in the scope of the present application.

Claims (17)

1. A MEMS sensor structure, comprising:

the MEMS sensor comprises a first wafer, wherein functional devices are formed on the surface and/or inside of the first wafer, the functional devices at least comprise MEMS sensors, the first wafer comprises a first surface and a second surface which are oppositely arranged, a bonding pad is formed on the first surface, the bonding pad is located on the outer side of the area where the functional devices are located, and the bonding pad is electrically connected to the functional devices and used for carrying out bonding and routing so as to electrically connect the functional devices to devices outside the first wafer;

the second wafer is supported by the first bonding assembly and is oppositely bonded to the second surface of the first wafer;

the first key assembly includes at least:

the main bonding piece is bonded between the first wafer and the second wafer, is arranged around the functional device and is annular, and a first cavity is formed among the main bonding piece, the first wafer and the second wafer;

and the auxiliary bonding part is bonded between the first wafer and the second wafer and arranged outside the main bonding part, and the distribution area of the auxiliary bonding part is opposite to the position of the bonding pad and used for supporting the bonding pad of the first wafer.

2. The MEMS sensor structure of claim 1, wherein the secondary bond has a shape that conforms to a shape of the distribution area of the bonding pads, and wherein a projection of the bonding pads on the first wafer second surface is within a projection of the secondary bond on the first wafer second surface.

3. The MEMS sensor structure of claim 1, wherein a projected area of the secondary bond on the second surface of the first wafer is 110% to 130% of an area of the bond pad.

4. The MEMS sensor structure of claim 1, wherein a side surface of the second wafer facing the first wafer is formed with an annular first groove, the first groove is disposed around the functional device, the primary bonding member and the secondary bonding member are both located in the first groove, and the primary bonding member is disposed along the first groove.

5. The MEMS sensor structure of claim 1, further comprising:

and the third wafer is supported by the second bonding assembly and is bonded to the first surface of the first wafer oppositely, and a second cavity is formed among the second bonding assembly, the first wafer and the third wafer.

6. The MEMS sensor structure of claim 5, wherein a side surface of the third wafer facing the first wafer is formed with an annular second groove disposed around the second cavity; the second bonding assembly is bonded between the first wafer and the third wafer, is positioned in the second groove and is arranged along the second groove.

7. The MEMS sensor structure of claim 5, wherein a projected area of the first bonding component on the second surface of the first wafer is smaller than a projected area of the second bonding component on the first surface of the first wafer.

8. The MEMS sensor structure of claim 4, wherein the first groove is rectangular and annular, the main bonding member is rectangular and annular, and the number of the bonding pads is multiple and is uniformly distributed on one side edge of the rectangular and annular main bonding member.

9. The MEMS sensor structure of claim 1, wherein the secondary bond is provided with an extension on a side facing the primary bond for connection to the primary bond.

10. The MEMS sensor structure of claim 9, wherein a length direction of the sub-bonding member is the same as a length direction of the distribution area of the bonding pads, and the extending portions are distributed at a head end and a tail end of the sub-bonding member in the length direction.

11. The MEMS sensor structure of claim 9, wherein the length direction of the secondary bonding member is the same as the length direction of the distribution area of the bonding pads, and the extensions are distributed at a head end, a tail end, and a middle section of the secondary bonding member in the length direction.

12. The MEMS sensor structure of claim 1, wherein the first bonding assembly comprises a plurality of metal bond groups arranged in pairs, the metal bond groups comprising a first metal bond and a second metal bond, wherein one end of the first metal bond is disposed on the first wafer surface, and one end of the second metal bond is disposed on the second wafer surface.

13. The MEMS sensor structure of claim 1, wherein the MEMS sensor structure comprises a thermopile sensor structure.

14. A method for forming a MEMS sensor structure, comprising at least the steps of:

providing a first wafer, forming a functional device on the surface and/or inside of the first wafer, wherein the functional device at least comprises a MEMS sensor, the first wafer comprises a first surface and a second surface which are oppositely arranged, the first surface is formed with a bonding pad, the bonding pad is positioned at the outer side of the area where the functional device is positioned, and the bonding pad is electrically connected to the functional device and used for bonding and routing, so that the functional device is electrically connected to a device outside the first wafer;

providing a second wafer;

bonding the first wafer and the second wafer by a first bonding assembly, the first bonding assembly comprising at least: the main bonding piece is bonded between the first wafer and the second wafer, the main bonding piece surrounds the functional device and is annular, and a first cavity is formed among the main bonding piece, the first wafer and the second wafer;

and the auxiliary bonding part is bonded between the first wafer and the second wafer and is arranged on the outer side of the main bonding part, and the distribution area of the auxiliary bonding part is opposite to the position of the bonding pad and supports the bonding pad of the first wafer.

15. The method of forming a MEMS sensor structure of claim 14, wherein the bonding the first and second wafers by the first bonding assembly includes at least the steps of:

forming a first metal key on the second surface of the first wafer;

forming second metal keys on the first surface of the second wafer, wherein the distribution positions of the second metal keys correspond to the distribution positions of the first metal keys one to one;

aligning the first metal bond and the second metal bond, melting the contact surfaces of the first metal bond and the second metal bond, bonding the first metal bond and the second metal bond, thereby forming the first bonding assembly, and bonding the second wafer to the first wafer.

16. The method of forming a MEMS sensor structure of claim 14, wherein a projected area of the secondary bond on the second surface of the first wafer is 110% to 130% of an area of the bonding pad.

17. The method of forming a MEMS sensor structure of claim 14, further comprising the steps of:

providing a third wafer;

forming a third metal key on the first surface of the third wafer;

forming fourth metal keys on the first surface of the first wafer, wherein the third metal keys and the fourth metal keys are arranged in a one-to-one correspondence manner;

and bonding the third metal keys and the fourth metal keys in a one-to-one correspondence manner to form a second bonding assembly, wherein a second cavity is formed among the second bonding assembly, the first wafer and the third wafer.

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