MEMS sensor structure and method of forming the same
By setting subbonded support pads in the MEMS sensor structure to disperse stress, the problem of first wafer breakage during packaging was solved, improving device yield and production capacity.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NINGBO SEMICON INT CORP
- Filing Date
- 2022-07-26
- Publication Date
- 2026-05-15
AI Technical Summary
In the prior art, the first wafer of a MEMS sensor structure is prone to breakage due to the stress caused by the electrical connection between the pads and functional devices during the packaging process, which affects the device yield.
A sub-bonded component is placed below the pad, and the main bond is arranged around the functional device. The sub-bonded component is located outside the main bond, supporting the pad, dispersing stress, and reducing the risk of the first wafer breaking.
This effectively reduces the risk of breakage of the first wafer during the bonding and wire bonding process, and improves the production capacity and yield of the sensor.
Smart Images
Figure CN115304020B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of sensors, specifically to MEMS sensor structures and their formation methods. Background Technology
[0002] With the development of IoT technology and the improvement of people's quality of life, the application prospects of MEMS sensor structures are becoming increasingly broad. Their integrated packaging mainly involves integrating semiconductor chips such as MEMS chips, thermopile chips or filters with other functional devices or CMOS circuits, so that the final sensor has the advantages of small size, light weight, no need for cooling, and high sensitivity. It has wide applications in security monitoring, medical treatment, life detection and consumer products, and is developing rapidly.
[0003] The yield of thermopile chips after packaging is low, and there is an urgent need to propose a new structure or formation method to improve the yield of the devices. Summary of the Invention
[0004] Therefore, this application provides a MEMS sensor structure and a method for forming the same, which can improve the yield of the device.
[0005] This application provides a MEMS sensor structure, comprising: a first wafer on which functional devices are formed on and / or inside, the functional devices including at least a MEMS sensor; the first wafer including a first surface and a second surface disposed opposite to each other, and the first surface having pads located outside the area where the functional devices are located, the pads being electrically connected to the functional devices for wire bonding, thereby electrically connecting the functional devices to devices outside the first wafer; a second wafer supported by a first bonding assembly and bonded to the second surface of the first wafer; the first bonding assembly including at least: a main bonding member bonded between the first wafer and the second wafer, the main bonding member being arranged around the functional devices in a ring shape, and a first cavity being formed between the main bonding member, the first wafer, and the second wafer; and a sub bonding member bonded between the first wafer and the second wafer, disposed outside the main bonding member, the distribution area of the sub bonding member being opposite to the position of the pads, supporting the pads of the first wafer.
[0006] Optionally, the shape of the sub-bonded component is consistent with the shape of the distribution area of the pads, and the projection of the pads on the second surface of the first wafer is located within the projection of the sub-bonded component on the second surface of the first wafer.
[0007] Optionally, an annular first groove is formed on the side surface of the second wafer facing the first wafer. The first groove surrounds the functional device, and the main bonding component and the sub-bonding component are both located in the first groove, with the main bonding component arranged along the first groove.
[0008] Optionally, the third wafer has an annular second groove formed on the side surface facing the first wafer, and the position of the annular second groove corresponds to the distribution area of the functional device; the second bonding assembly is bonded between the first wafer and the third wafer, and the second bonding assembly is annular and arranged around the second groove.
[0009] Optionally, the secondary bonding member has an extension on the side facing the primary bonding member for connecting to the primary bonding member.
[0010] Optionally, the length direction of the sub-bonded component is the same as the length direction of the distribution area of the pad, and the extension portion is distributed at the beginning and end of the sub-bonded component in the length direction.
[0011] Optionally, the length direction of the sub-bonded component is the same as the length direction of the distribution area of the solder pads, and the extension is distributed at the beginning, end, and middle sections of the sub-bonded component along its length.
[0012] This application also provides a method for forming a MEMS sensor structure, comprising at least the following steps: providing a first wafer on which functional devices are formed on and / or inside, the functional devices including at least a MEMS sensor, the first wafer including a first surface and a second surface disposed opposite to each other, and the first surface having a pad, the pad being located outside the area where the functional device is located, the pad being electrically connected to the functional device for wire bonding, thereby electrically connecting the functional device to a device outside the first wafer; providing a second wafer; bonding the first wafer and the second wafer together using a first bonding assembly, the first bonding assembly including at least: a main bonding member bonded between the first wafer and the second wafer, the main bonding member being disposed around the functional device in a ring shape, and a first cavity being formed between the main bonding member, the first wafer and the second wafer; and a sub bonding member bonded between the first wafer and the second wafer, disposed outside the main bonding member, the distribution area of the sub bonding member being opposite to the position of the pad, supporting the pad of the first wafer.
[0013] The MEMS sensor structure and its formation method described in this application include a sub-bonding component disposed below the bonding pad. This sub-bonding component can provide support for the first wafer, disperse the stress on the first wafer below the bonding pad during the metal bonding process, reduce the risk of the first wafer breaking, reduce the probability of product structure failure, and improve the production capacity of the sensor. Attached Figure Description
[0014] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0015] Figures 1 to 13 This is a schematic cross-sectional view of the steps involved in fabricating the MEMS sensor structure in one embodiment of this application.
[0016] Figure 14 This is a top view of the MEMS sensor structure in one embodiment of this application.
[0017] Figure 15 This is a top view of the MEMS sensor structure in one embodiment of this application.
[0018] Figure 16 This is a cross-sectional view of the MEMS sensor structure in one embodiment of this application.
[0019] Figure 17 This is a flowchart illustrating the steps of a method for forming a MEMS sensor structure according to one embodiment of this application.
[0020] Figure 18 This is a schematic flowchart illustrating the steps for forming a first metallic bond in one embodiment of this application. Detailed Implementation
[0021] Research has found that a significant reason for the low device yield in existing technologies is that the packaging of the first, second, and third wafers of the thermopile chip requires double-sided wafer-level metal bonding vacuum packaging of the infrared thermopile array. However, the first wafer, which houses the functional devices, is prone to breakage during the packaging process, leading to low device yield. A key reason for this breakage is that certain areas of the first wafer contain bonding pads for wire bonding. These pads are electrically connected to the functional devices within the first wafer. When connecting these functional devices to other devices, wire bonding is required on these pads to establish the connection. Furthermore, during the bonding process of the first wafer to the third wafer (which serves as the bottom wafer), the first wafer itself is subjected to significant stress, potentially causing it to break and leading to device failure, thus impacting overall device yield.
[0022] To address the aforementioned issues, embodiments of this application provide a MEMS sensor structure and its formation method to resolve the problem of edge fragmentation in the first wafer.
[0023] The MEMS sensor structure and its packaging method of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description and drawings; however, it should be noted that the concept of the technical solution of the present invention can be implemented in many different forms and is not limited to the specific embodiments described herein. The accompanying drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.
[0024] The terms “first,” “second,” etc., used in the specification and claims are used to distinguish between similar elements and are not necessarily used to describe a particular order or chronological sequence. It should be understood that these terms, used so in this way, may be replaced where appropriate, for example, to allow embodiments of the invention described herein to operate in a different order than that described or shown herein. Similarly, if the methods described herein comprise a series of steps, and the order of these steps presented herein is not necessarily the only possible order in which these steps can be performed, and some described steps may be omitted and / or some other steps not described herein may be added to the method. If a component in one figure is identical to a component in another figure, although these components are readily identifiable in all figures, this specification will not label all identical components in every figure for the sake of clarity.
[0025] Please see Figure 12 and Figure 14 ,in Figure 12 This is a schematic diagram of the MEMS sensor structure in one embodiment of this application. Figure 14This is a top view of the MEMS sensor structure in one embodiment of this application.
[0026] In this embodiment, the MEMS sensor structure includes: a first wafer 101, on which functional devices are formed, including a MEMS sensor, on its surface and / or internally; the first wafer 101 includes a first surface and a second surface disposed opposite to each other, such as... Figure 1 As shown, the first surface of the first wafer 101 has a pad 130, which is located outside the area where the functional device is located and is electrically connected to the functional device for wire bonding, thereby connecting the functional device to a device outside the first wafer 101; the second wafer 106, as shown... Figure 10 As shown, the device is supported by a first bonding assembly 202 and bonded to the second surface of the first wafer 101. The first bonding assembly 202 includes at least: a main bonding member 203, bonded between the first wafer 101 and the second wafer 106, and the main bonding member 203 is arranged around the functional device in a ring shape, and a first cavity 40 is formed between 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 main bonding member 203, the distribution area 205 of the secondary bonding member 205 being opposite to the pad 130, supporting the pad 130 of the first wafer 101.
[0027] In this embodiment, a sub-bonding component 205 is provided below the pad 130. The sub-bonding component 205 can provide support for the first wafer 101 during the bonding wire bonding process, disperse the stress on the first wafer 101 where the pad 130 is located during the bonding wire bonding process, reduce the risk of the first wafer 101 breaking, reduce the probability of product structure failure, and improve the production capacity of the sensor.
[0028] In some embodiments, the first wafer 101 includes a substrate 101a, and functional devices are disposed on the upper surface of the substrate 101a or inside the substrate 101a. Figure 1 In the embodiment shown, the functional device forms a functional sublayer 101b.
[0029] In some embodiments, the substrate 101a may be made of semiconductor materials such as silicon (Si), germanium (Ge), silicon germanium (SiGe), silicon carbide (SiC), silicon carbide (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP), or other III / V compound semiconductors. It may also be a double-side polished wafer (DSP), or a ceramic substrate such as alumina, a quartz substrate, or a glass substrate.
[0030] In some embodiments, the MEMS sensor can convert a target signal into an electrical signal. The functional device further includes an actuator and a micro-energy source. The actuator is connected to the MEMS sensor and is used to perform actions according to the electrical signal output by the MEMS sensor. The micro-energy source is connected to the MEMS sensor and the actuator and is used to provide energy to the sensor and the actuator.
[0031] In some embodiments, the MEMS sensor includes an array of thermopile structures, each thermopile comprising multiple thermocouple pairs. Each thermocouple pair comprises two different materials connected in series, which may be stacked or arranged side-by-side. Furthermore, the two materials may be polycrystalline silicon and aluminum; or polycrystalline silicon and copper; or two different doped polycrystalline silicon materials. In other embodiments, the functional device serves as the sensing structure of the MEMS sensor structure and may be a MEMS structure, a filter structure, etc. The functional device may also include at least a portion of a thermistor or at least a portion of a photoresistor.
[0032] In the MEMS sensor structure, a third wafer 102 and a second wafer 106 are bonded to the first surface and the second surface of the first wafer 101, respectively. The third wafer 102 and the second wafer 106 serve as capping wafers or base wafers of the first wafer 101 to protect the first wafer 101. The third wafer 102 is bonded to the surface of the first wafer 101 through a second bonding assembly 204.
[0033] 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 carbide (SiC), silicon carbide (SiGeC), indium arsenide (InAs), gallium arsenide (GaAs), indium phosphide (InP), or other III / V compound semiconductors. They may also be double-sided polished wafers (DSPs), or ceramic substrates such as alumina, quartz, or glass substrates.
[0034] In this embodiment, the material of the third wafer 102 is a semiconductor material, which can transmit infrared light and perform infrared-related detection. In other embodiments, the material of the third wafer 102 can also be an optical material, such as glass, a filter, a lens, etc., or a polymer material, such as a dry film, a molding compound, etc.
[0035] In some embodiments, the shape of the sub-bonding member 205 is consistent with the shape of the distribution area of the pad 130, and the projection of the pad 130 on the second surface of the first wafer 101 is located within the projection of the sub-bonding member 205 on the second surface of the first wafer 101, thereby providing sufficient support for the pad 130 and dispersing the stress at that location during bonding.
[0036] In some embodiments, the projected area of the subbonding member 205 on the second surface of the first wafer 101 is 110% to 130% of the area of the pad 130, thereby providing sufficient support for the first wafer 101 and having a better stress dispersion effect, preventing the silicon wafer from cracking near the bonding pad 130 for wire bonding.
[0037] In some embodiments, a first annular groove 20 is formed on the side surface of the second wafer 106 facing the first wafer 101. The first groove 20 surrounds the functional device, and the main bonding member 203 and the sub-bonding member 205 are both located within the first groove 20, with the main bonding member 203 disposed along the first groove 20 (see example...). Figure 10 In some embodiments, the first groove 20 can be used to limit the height of the MEMS sensor structure to prevent the MEMS sensor from becoming too tall, which would increase the size of the device.
[0038] The main bonding member 203 is disposed around the distribution area of the functional devices of the first wafer 101, and can be used to support the edge portion of the distribution area of the functional devices of the first wafer 101.
[0039] exist Figure 10 In the illustrated embodiment, both the primary bonding member 203 and the secondary bonding member 205 are distributed within the first groove 20. The first cavity 40 is formed between the first wafer 101 and the second wafer 106 based on the first groove 20.
[0040] Please see Figure 14 and Figure 15 ,in Figure 15 This is a top view of the MEMS sensor structure in one embodiment of this application.
[0041] In these embodiments, the pads 130 are distributed on one side edge of the first wafer 101, and the projection of the pads 130 on the first surface of the second wafer 106 is distributed along one side edge of the first groove 20.
[0042] The functional devices are concentrated at the other end of the first wafer 101 and occupy most of the area of the first wafer 101.
[0043] In other embodiments, the pads 130 may also be distributed around the perimeter of the first wafer 101, and the subbonding members 205 may be disposed around the perimeter of the first wafer 101, changing with the position of the pads 130.
[0044] In some embodiments, the projection of the main bonding member 203 onto the first surface of the first wafer 101 is annular. In some embodiments, the first groove 20 is rectangular annular, therefore the main bonding member 203 is also rectangular annular, arranged around the functional device, and the number of pads 130 is plurality of, evenly distributed on one side of the rectangular annular main bonding member 203, exposed on the first surface of the first wafer 101.
[0045] exist Figure 14 In the illustrated embodiment, the main bonding member 203 is a rectangular ring in the top view, surrounding the distribution area of the functional device and located at the edge of the distribution area of the functional device.
[0046] In some embodiments, the pad 130 is rectangular; in fact, the shape of the pad 130 can also be set as needed.
[0047] In some embodiments, the sub-bonded member 205 has an extension on the side facing the main bonded member 203 for connecting to the main bonded member 203. This increases the stress area of the sub-bonded member 205 below the pad 130 during wire bonding, further reducing the possibility of cracking of the first wafer 101 during wire bonding and strengthening the connection between the main bonded member 203 and the sub-bonded member 205. Since the extension 206 is located inside the gap between the pad 130 and the distribution area of the functional devices and does not extend outward from the gap, it helps to save the board area used in fabricating the MEMS sensor structure.
[0048] exist Figure 14 , Figure 15In the illustrated embodiment, the distribution area of the pads 130 is elongated, and the projection of the sub-bonding member 205 onto the second surface of the first wafer 101 is also elongated, with its length direction being the same as the length direction of the distribution area of the pads 130. The extension is distributed at least at the beginning and / or end of the sub-bonding member 205 in the length direction, thereby dispersing the stress of wire bonding in the length direction of the distribution area of the pads 130.
[0049] exist Figure 14 In the embodiment shown, the length direction of the sub-bonding member 205 is the same as the length direction of the distribution area of the pad 130, and the extension portion is distributed at the beginning and end of the sub-bonding member 205 in the length direction.
[0050] exist Figure 15 In the embodiment shown, the length direction of the sub-bonding member 205 is the same as the length direction of the distribution area of the pad 130, and the extension is distributed at the beginning, end and middle sections of the sub-bonding member 205 in the length direction to obtain a larger projected area.
[0051] In practice, the extension portion and the distribution area of the extension portion can also be set as needed.
[0052] from Figure 15 Viewed from the CD direction, the MEMS sensor structure is as follows: Figure 16 As shown.
[0053] exist Figure 16 In the illustrated embodiment, one end of the first bonding component 202 is disposed in a first groove 20 on the second surface of the first wafer 101, and the other end is disposed in a second groove 30 on the surface of the second wafer 106 (see [link]). Figure 2 )Inside.
[0054] In some embodiments, the first bonding assembly 202 includes a plurality of paired metal bond groups, each metal bond group including a first metal bond 109 and a second metal bond 107, wherein one end of the first metal bond 109 is disposed on the second surface of the first wafer 101, and one end of the second metal bond 107 is disposed on the surface of the second wafer 106. The first metal bond 109 and the second metal bond 107 are arranged in a one-to-one correspondence and are positioned accordingly, so as to bond in a one-to-one correspondence, and form the first bonding assembly 202 after bonding. The first metal bonds 109 and the second metal bonds 107 distributed in the corresponding areas of the pads 130 are used as secondary bonding members 205, and the first metal bonds 109 and the second metal bonds 107 in the remaining areas are used as primary bonding members 203.
[0055] In some embodiments, the metallic bond includes at least one of copper metallic bond and tin metallic bond. These two metals are common materials for preparing metallic bonds. In practice, the specific materials of the metallic bond can be set as needed.
[0056] In some embodiments, by planning the shape of the first cavity 40, a cavity can be formed around the functional device in the MEMS sensor structure to achieve requirements such as heat insulation.
[0057] In some embodiments, the surface of the second wafer 106 is further formed with an air-absorbing layer 111 for absorbing moisture in the air and keeping the MEMS sensor structure dry.
[0058] In some embodiments, the MEMS sensor structure further includes: a third wafer 102, such as Figure 1 As shown, the second bonding component 204 supports and bonds to the first surface of the first wafer 101, and a second cavity 10 is formed between the second bonding component, the first wafer 101 and the third wafer 102.
[0059] In some embodiments, the MEMS sensor structure includes a thermopile sensor structure, and the functional devices include a plurality of thermocouples distributed within a rectangular region on the first wafer 101. The positions of the first cavity 40 and the second cavity 10 correspond to the distribution area of the functional devices, and their projections on the second surface of the first wafer 101 are rectangular, which can provide a certain heat insulation effect, thereby enhancing the detection sensitivity of the thermopile sensor structure.
[0060] In fact, the shape and distribution area of the first cavity 40 and the second cavity 10 can be set according to the specific requirements of the MEMS sensor structure.
[0061] In some embodiments, the third wafer 102 has an annular second groove 30 formed on one side surface facing the first wafer 101 (see...). Figure 2 The annular second groove is disposed around the second cavity; the second bonding assembly is bonded between the first wafer and the third wafer and is located in the second groove, disposed along the second groove.
[0062] The second groove 30 can also protect the functional device from temperature and reduce the thickness of the MEMS sensor structure.
[0063] In some embodiments, the second bonding component 204 is located within the second groove 30 and can serve as a sealing ring or bonding ring, etc., to seal the area surrounded by the second bonding component 204.
[0064] exist Figure 14 In the illustrated embodiment, the second groove 30 is rectangular and annular, and the second bonding assembly 204, located within the second groove 30, is also rectangular and annular. The areas surrounded by the main bonding member 203 and the second bonding assembly 204 correspond to the distribution area of the functional devices on the first wafer 101, and to the central area of the first wafer 101.
[0065] In some embodiments, the second bonding assembly 204 includes a third metal bond 105 disposed on the surface of the third wafer 102 and a fourth metal bond 104 disposed on the surface of the first wafer 101. The third metal bond 105 and the fourth metal bond 104 are placed opposite each other, and the bonding surface of the third metal bond 105 and the fourth metal bond 104 is large enough during bonding to effectively disperse stress and reduce the probability of the first wafer 101 and / or the third wafer 102 cracking due to stress during bonding.
[0066] In some preferred embodiments, adhesive is filled at the edges of the first wafer 101, the third wafer 102, and the second wafer 106 to prevent peeling of the edges of the first wafer 101, the third wafer 102, and the second wafer 106 during the bonding process.
[0067] In some embodiments, the main bonding member 203 and the second bonding component 204 are positioned opposite each other, such that the second bonding component 204 can disperse the stress on the first wafer 101 when bonding the first wafer 101 and the second wafer 106.
[0068] This can be consulted. Figure 14 and Figure 15 The projection of the main bonding component 203 on the second surface of the first wafer 101 is almost identical to the projection of the second bonding component 204 on the second surface of the first wafer 101, and both are arranged around the rectangular area where the functional device is disposed.
[0069] In some embodiments, the projections of the second bonding component 204 and the main bonding component 203 on the first surface of the first wafer 101 at least partially overlap. Since the bonding components are approximately in the same position, the stress on the first wafer 101 can also be dispersed by the second bonding component 204 between the first wafer 101 and the third wafer 102 when bonding the second wafer 106 and the first wafer 101.
[0070] exist Figures 8 to 15In the embodiment shown, the projected area of the second bonding component 204 on the second surface of the first wafer 101 is larger than the projected area of the main bonding component 203 of the first bonding component 202 on the second surface of the first wafer 101, thereby providing sufficient contact area to disperse the stress of the first wafer 101 when it is subjected to the bonding force twice.
[0071] In some embodiments, the assembly step of the third wafer 102 occurs before the assembly step of the second wafer 106. During the packaging of the second wafer 106, the second bonding component 204 between the third wafer 102 and the first wafer 101 needs to undergo two bonding forces, including the bonding force during the bonding of the second bonding component 204 and the bonding force during the bonding of the first bonding component 202. Therefore, the projected area of the second bonding component 204 on the second surface of the first wafer 101 is larger than the projected area of the main bonding member 203 of the first bonding component 202 on the second surface of the first wafer 101, thereby enhancing the dispersion effect of the two bonding forces and reducing the possibility of the first wafer 101 and the third wafer 102 breaking.
[0072] In some embodiments, the surface of the third wafer 102 away from the first wafer 101 is further provided with a zero mark for marking the zero layer, an alignment mark for alignment, etc.
[0073] In some embodiments, an antireflection film 108 is disposed on the surface of the third wafer 102 away from the first wafer 101. The antireflection film 108 can be used to enhance the transmission of light in a desired wavelength range, such as infrared light. Figure 12 As shown. Figure 12 From Figure 14 A cross-sectional view taken from angle AB.
[0074] Please see Figure 13 A dicing operation was performed to plan the shape of the third wafer 102, allowing the pads 130 to be directly exposed on the third wafer 102 for subsequent connections. In fact, if the pads 130 are located on the lower surface of the first wafer 101, the pads 130 can also be exposed by planning the final shape of the second wafer 106.
[0075] In one embodiment, the pad 130 can enable electrical connection of the sensor to other devices or chips. Other devices or chips include chips or devices containing CMOS circuitry, etc.
[0076] The embodiments of this application also provide a packaging method for a MEMS sensor structure.
[0077] Please see Figure 17 This is a flowchart illustrating the steps of the encapsulation method in one embodiment.
[0078] In this embodiment, the encapsulation method includes at least the following steps:
[0079] Step S101: Provide a first wafer 101, on which functional devices are formed, including MEMS sensors. The first wafer 101 includes a first surface and a second surface disposed opposite to each other, such as... Figure 1 As shown, the first surface of the first wafer 101 has a pad 130, which is located outside the area where the functional device is located and is electrically connected to the functional device for wire bonding, thereby connecting the functional device to a device outside the first wafer 101.
[0080] Step S102: Provide a second wafer 106;
[0081] Step S103: The first wafer 101 and the second wafer 106 are bonded together by the first bonding assembly 202. The first bonding assembly 202 includes at least: a main bonding member 203, bonded between the first wafer 101 and the second wafer 106, the main bonding member 203 being arranged around the functional device in a ring shape, and a first cavity 40 being formed between the main bonding member 203, the first wafer 101, and the second wafer 106; and a sub-bonding member 205, located within the first groove 20, bonded between the first wafer 101 and the second wafer 106, and disposed outside the main bonding member 203, the distribution area 205 of the sub-bonding member 205 being opposite to the pad 130, supporting the pad 130 of the first wafer 101, such as... Figure 11 As shown.
[0082] 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. The first bonding assembly 202 includes at least a sub-bonding member 205, the distribution area of which is opposite to the position of the pad 130. Therefore, it can provide sufficient support for the pad 130 of the first wafer 101 during the bonding wire bonding process, disperse the stress on the first wafer 101 where the pad 130 is located during the bonding wire bonding process, reduce the risk of the first wafer 101 breaking, reduce the probability of product structural failure, and improve the production capacity of the sensor.
[0083] In this embodiment, the MEMS sensor can convert the target signal into an electrical signal. The functional device also includes an actuator and a micro-energy source. The actuator is connected to the MEMS sensor and is used to perform actions according to the electrical signal output by the MEMS sensor. The micro-energy source is connected to the MEMS sensor and the actuator and is used to provide energy to the sensor and the actuator.
[0084] After the first wafer 101 and the second wafer 106 are bonded, the first cavity 40 is formed between the main bonding member 203, the first wafer 101 and the second wafer 106, and the first cavity 40 is arranged around the distribution area of the functional device.
[0085] In some embodiments, the first bonding assembly 202 includes a first metal bond 109 disposed on the surface of the first wafer 101 and a second metal bond 107 disposed on the surface of the second wafer 106.
[0086] Both the first metal bond 109 and the second metal bond 107 are made of metal. In some embodiments, when forming the first bonding component 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 together in a one-to-one correspondence.
[0087] In some embodiments, the second wafer 106 has an annular first groove 20 formed on one side surface facing the first wafer 101. The first groove 20 surrounds the functional device, and the main bonding member 203 is located in the first groove 20 and is disposed along the first groove 20.
[0088] Please see Figure 18 This is a schematic flowchart of the steps for forming a first metal bond 109 on the second surface of the first wafer 101 in one embodiment.
[0089] In this embodiment, the bonding of the first wafer 101 and the second wafer 106 via the first bonding component 202 includes at least the following steps: Step S201: forming a first metal bond 109 on the second surface of the first wafer 101; Step S202: forming a second metal bond 107 on the first surface of the second wafer 106, wherein the distribution positions of the second metal bond 107 correspond one-to-one with the distribution positions of the first metal bond 109; Step S203: aligning the first metal bond 109 and 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 component 202 and bonding the second wafer 106 to the first wafer 101.
[0090] In this embodiment, forming the first metal bond 109 on the second surface of the first wafer 101 includes at least: forming a metal seed layer 110 on the second surface of the first wafer 101, such as... Figure 6 As shown; a metal layer 50 is grown based on the metal seed layer, as... Figure 7 As shown; the metal layer 50 is patterned, and the patterned metal layer is used as the first metal bond 109, as follows. Figure 8 As shown.
[0091] In this embodiment, the material used to prepare the metal seed layer 110 can be selected as needed, and is generally consistent with the material of the first metal bond 109 to be prepared. In some embodiments, the material of the first metal bond 109 is copper or tin, therefore the metal seed layer includes at least one of a copper layer or a tin layer.
[0092] In some embodiments, the metal seed layer is formed using physical vapor deposition. However, chemical vapor deposition, atomic layer deposition, or other methods can also be used to prepare the metal seed layer, depending on the specific requirements.
[0093] In some embodiments, patterning the metal layer includes preparing a mask layer on the metal layer 50 and patterning the mask layer to expose the area of the metal layer surface to be etched and to cover the area of the metal layer surface to be protected. Then, at least one of dry etching or wet etching is used to etch the metal layer in a direction perpendicular to the upper surface of the metal layer downward to form the metal bond required for the first metal bond 109.
[0094] In some embodiments, a first metal bond 109 is formed on the second surface of the first wafer 101, and a portion of the first metal bond 109 constitutes the sub-bonding member 205 for providing wire bonding support for the first wafer 101, and another portion constitutes the main bonding member 203, with the setting area corresponding to the distribution area of the functional devices of the first wafer 101 for providing the main bonding effect.
[0095] The projection of the fourth metallic bond 104 onto the second surface of the first wafer 101 can be referenced. Figure 14 or Figure 15 On the second wafer 106, third metal bonds 105 corresponding one-to-one with the fourth metal bonds 104 will be formed. Therefore, the projection of the third metal bonds 105 onto the second surface of the first wafer 101 can also be referenced. Figure 14 or Figure 15 .
[0096] In some embodiments, the shape of the sub-bonding member 205 is consistent with the shape of the distribution area of the pad 130, and the projection of the pad 130 on the second surface of the first wafer 101 is located within the projection of the sub-bonding member 205 on the second surface of the first wafer 101.
[0097] In some embodiments, the distribution area of the pad 130 is elongated, the sub-bonding member 205 is elongated, and extensions 206 are formed at the beginning and end of the sub-bonding member 205 along its length. The second metal bond 107 is connected to the main bonding member 203 through the extensions 206. See also [reference here]. Figure 14 or Figure 15 .
[0098] When the projected area of the sub-bonded component 205 on the second surface of the first wafer 101 needs to be further increased, it can be achieved by using methods such as... Figure 14 or Figure 15 The extension 206 shown increases the projected area. This extension only occupies the gap between the pad 130 and the distribution area of the functional devices and does not extend outward, which helps to save the board area used when fabricating the MEMS sensor structure.
[0099] exist Figure 14 In the illustrated embodiment, extensions 206 are respectively provided at both ends of the sub-bonded member 205. These extensions are located between the primary bonded member 203 and the sub-bonded member 205, and are used to connect the primary bonded member 203 and the sub-bonded member 205. Figure 15 In the embodiment shown, in order to obtain a larger projected area and thus a better support effect, an extension 206 is also provided at the middle position of the sub-bonding member 205 to connect to the main bonding member 203.
[0100] exist Figure 14 , Figure 15 In the illustrated embodiment, the pad 130 is disposed on one side edge of the first wafer 101, and therefore the sub-bonding member 205 is also disposed on one side edge of the first wafer 101. In fact, the pad 130 may also be disposed around the periphery of the first wafer 101, and the sub-bonding member 205 may also be disposed around the periphery of the first wafer 101, changing with the position of the pad 130.
[0101] In some embodiments, the projected area of the sub-bonding member 205 on the second surface of the first wafer 101 is 110% to 130% of the area of the pad 130. Studies have found that at this size, the sub-bonding member 205 can provide better stress dispersion for the pad 130, effectively reducing the possibility of the first wafer 101 breaking at the pad 130, and without using excessive metal material to fabricate the first bonding assembly 202.
[0102] In some embodiments, the method further includes the following steps: providing a third wafer 102; forming a fourth metallic bond 104 on a first surface of the first wafer 101, such as... Figure 1 As shown, the third metal bond 105 and the fourth metal bond 104 are configured in a one-to-one correspondence; the third metal bond 105 and the fourth metal bond 104 are bonded together to form the second bonding component 204, as shown. Figure 3 As shown, a second cavity 10 is formed between the second bonding component 204, the first wafer 101 and the third wafer 102.
[0103] In some embodiments, the third wafer 102 has an annular second groove 30 formed on one side surface facing the first wafer 101 (see...). Figure 2 The second groove 30 is disposed around the second cavity 10, and a third metal bond 105 is formed on the first surface of the third wafer 102, such as... Figure 2 As shown.
[0104] The third metal bond 105 and the fourth metal bond 104 are arranged in a one-to-one correspondence, so their projections on the second surface of the first wafer 101 are as follows: Figure 14 or Figure 15 The second bonding component 204 shown has the same shape.
[0105] In some embodiments, to ensure that the thickness of the first wafer 101 meets the requirements, after bonding the third metal bond 105 to the fourth metal bond 104 in a one-to-one correspondence, the method further includes the step of thinning the second surface of the first wafer 101. Here, as... Figure 4 As shown.
[0106] After thinning, an alignment mark 112 is formed on the second surface of the first wafer 101, such as... Figure 5 As shown. It should be noted that, in Figure 8 The alignment mark is not shown in the subsequent illustrations.
[0107] In some embodiments, after the second wafer 106 is also disposed on the surface of the first wafer 101, in order to meet the requirements for the thickness of the MEMS sensor structure, both the third wafer 102 and the second wafer 106 are thinned once.
[0108] The assembly step of the third wafer 102 occurs before the assembly step of the second wafer 106. Therefore, during the packaging of the second wafer 106, the second bonding assembly 204 between the third wafer 102 and the first wafer 101 needs to undergo two bonding force applications: the bonding force during the bonding of the second bonding assembly 204 and the bonding force during the bonding of the first bonding assembly 202. Therefore, the dimensional requirements for the second bonding assembly 204 are more stringent. Figures 8 to 15 As can be seen from the above, the projected area of the second bonding component 204 on the second surface of the first wafer 101 is larger than the projected area of the main bonding component 203 of the first bonding component 202 on the second surface of the first wafer 101, providing sufficient contact area to disperse the stress of the first wafer 101 when it is subjected to the bonding force twice.
[0109] It should be noted that the various embodiments in this specification are described in a related manner, and the same or similar parts between the various embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for structural embodiments, since they are basically similar to method embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method embodiments.
[0110] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, such as the combination of technical features between embodiments, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.
Claims
1. A MEMS sensor structure, characterized in that, include: A first wafer has functional devices formed on its surface and / or interior, the functional devices including at least a MEMS sensor. The first wafer includes a first surface and a second surface disposed opposite to each other, and the first surface has pads formed thereon. The pads are located outside the area where the functional devices are located and are electrically connected to the functional devices for wire bonding, thereby electrically connecting the functional devices to devices outside the first wafer. The second wafer is supported by the first bonding assembly and is bonded to the second surface of the first wafer. The first bonding component includes at least: A main bonding component is bonded between the first wafer and the second wafer, and the main bonding component is arranged around the functional device in a ring shape, and a first cavity is formed between the main bonding component, the first wafer and the second wafer; A sub-bonded component is bonded between the first wafer and the second wafer and is disposed outside the main bonded component. The distribution area of the sub-bonded component is opposite to the position of the pad and supports the pad of the first wafer. The sub-bonding member has an extension on the side facing the main bonding member for connecting to the main bonding member.
2. The MEMS sensor structure according to claim 1, characterized in that, The shape of the sub-bonded component is consistent with the shape of the distribution area of the pad, and the projection of the pad on the second surface of the first wafer is located within the projection of the sub-bonded component on the second surface of the first wafer.
3. The MEMS sensor structure according to claim 1, characterized in that, The projected area of the subbonded component on the second surface of the first wafer is 110% to 130% of the area of the pad.
4. The MEMS sensor structure according to claim 1, characterized in that, The second wafer has an annular first groove formed on the side surface facing the first wafer. The first groove surrounds the functional device. The main bonding component and the sub bonding component are both located in the first groove, and the main bonding component is arranged along the first groove.
5. The MEMS sensor structure according to claim 1, characterized in that, Also includes: The third wafer is supported by the second bonding assembly and bonded to the first surface of the first wafer, and a second cavity is formed between the second bonding assembly, the first wafer and the third wafer.
6. The MEMS sensor structure according to claim 5, characterized in that, The third wafer has an annular second groove formed on the side surface facing the first wafer, and the annular second groove is arranged around the second cavity; the second bonding assembly is bonded between the first wafer and the third wafer, located in the second groove, and arranged along the second groove.
7. The MEMS sensor structure according to claim 5, characterized in that, The projected area of the first bonding component on the second surface of the first wafer is smaller than the projected area of the second bonding component on the first surface of the first wafer.
8. The MEMS sensor structure according to claim 4, characterized in that, The first groove is in the shape of a rectangular ring, the main bonding component is in the shape of a rectangular ring, and there are multiple pads that are evenly distributed on one side of the rectangular ring-shaped main bonding component.
9. The MEMS sensor structure according to claim 1, characterized in that, The length direction of the subbonded component is the same as the length direction of the distribution area of the pads, and the extension portion is distributed at the beginning and end of the subbonded component in the length direction.
10. The MEMS sensor structure according to claim 1, characterized in that, The length direction of the subbonded component is the same as the length direction of the distribution area of the pads, and the extension is distributed at the beginning, end and middle sections of the subbonded component in the length direction.
11. The MEMS sensor structure according to claim 1, characterized in that, The first bonding assembly includes a plurality of paired metal bond groups, the metal bond groups including a first metal bond and a second metal bond, wherein one end of the first metal bond is disposed on the surface of the first wafer, and one end of the second metal bond is disposed on the surface of the second wafer.
12. The MEMS sensor structure according to claim 1, characterized in that, The MEMS sensor structure includes a thermopile sensor structure.