阅读说明：本技术 一种mems器件的晶圆级封装方法和封装结构 (Wafer-level packaging method and packaging structure of MEMS device ) 是由 倪正春 盛荆浩 江舟 于 2020-07-15 设计创作，主要内容包括：本发明提供了一种MEMS器件的晶圆级封装方法和封装结构,封装方法包括：提供基板,所述基板一侧具有MEMS器件和与MEMS器件电连接的焊盘；在焊盘表面形成与焊盘电连接的连接线；提供盖板,所述盖板的一侧具有凹槽和分离槽；将盖板具有凹槽的一侧与基板具有MEMS器件的一侧键合,连接线容纳于分离槽内,MEMS器件密封于盖板具有凹槽的区域与基板构成的空腔内；去除焊盘上的盖板,以暴露出焊盘和连接线。与现有的纵向TSV技术相比,本发明中的MEMS器件的晶圆级封装方法工艺简单,使得MEMS器件的晶圆级封装结构的制作难度较小、成本较低。(The invention provides a wafer level packaging method and a packaging structure of an MEMS device, wherein the packaging method comprises the following steps: providing a substrate, wherein one side of the substrate is provided with a MEMS device and a bonding pad electrically connected with the MEMS device; forming a connecting wire electrically connected with the bonding pad on the surface of the bonding pad; providing a cover plate, wherein one side of the cover plate is provided with a groove and a separation groove; bonding one side of the cover plate with the groove with one side of the substrate with the MEMS device, wherein the connecting wire is accommodated in the separation groove, and the MEMS device is sealed in a cavity formed by the area of the cover plate with the groove and the substrate; and removing the cover plate on the bonding pad to expose the bonding pad and the connecting wire. Compared with the existing longitudinal TSV technology, the wafer level packaging method of the MEMS device is simple in process, so that the wafer level packaging structure of the MEMS device is low in manufacturing difficulty and low in cost.)

1. A wafer level packaging method of a MEMS device is characterized by comprising the following steps:

providing a substrate, wherein one side of the substrate is provided with a MEMS device and a bonding pad electrically connected with the MEMS device;

forming a connecting wire electrically connected with the bonding pad on the surface of the bonding pad, wherein the height of the connecting wire is greater than that of the MEMS device;

providing a cover plate, wherein one side of the cover plate is provided with a groove and a separation groove, and the depth of the separation groove is greater than that of the groove;

bonding one side of the cover plate with the groove and one side of the substrate with the MEMS device, wherein the connecting wire is accommodated in the separating groove, and the MEMS device is sealed in a cavity formed by the area of the cover plate with the groove and the substrate;

and reserving a cover plate on the MEMS device, and removing the cover plate on the bonding pad to expose the bonding pad and the connecting wire.

2. The method of claim 1, wherein the depth of the separation groove is 3 to 5um greater than the height of the connection line.

3. The method of claim 1, wherein retaining the cover plate on the MEMS device and removing the cover plate on the bonding pad comprises:

and etching the cover plate by adopting a wet etching process to remove the cover plate on the bonding pad and reserve the cover plate on the MEMS device.

4. The method of claim 1, wherein retaining the cover plate on the MEMS device and removing the cover plate on the bonding pad comprises:

grinding one side of the cover plate, which is far away from the substrate, by adopting a mechanical grinding process to thin the cover plate;

and etching the thinned cover plate by adopting a wet etching process so as to remove the cover plate on the bonding pad and reserve the cover plate on the MEMS device.

5. The method of claim 4, wherein the thinnest area of the thinned cover plate has a thickness in the range of 5um to 10 um.

6. The method of claim 1, wherein after exposing the bonding pads and the connecting wires, the connecting wires have a height exceeding a height of the cover plate;

and, the height of connecting wire surpasss the scope of the height of apron is 15um ~ 30 um.

7. The method of claim 1, further comprising:

and forming a passivation layer on the surface of the cover plate.

8. A wafer-level packaging structure of a MEMS device, which is manufactured by the method of any one of claims 1 to 7, the wafer-level packaging structure of the MEMS device comprises:

the MEMS device comprises a substrate, wherein one side of the substrate is provided with an MEMS device and a bonding pad electrically connected with the MEMS device;

the connecting wire is positioned on the surface of the bonding pad and electrically connected with the bonding pad;

the cover plate is located above the MEMS device and exposes the bonding pad and the connecting line, and the MEMS device is sealed in a cavity formed by bonding the cover plate and the substrate.

9. The package structure according to claim 8, wherein the connecting wires have a height exceeding a height of the cover plate;

and, the height of connecting wire surpasss the scope of the height of apron is 15um ~ 30 um.

10. The package structure of claim 8, wherein the cover plate surface further has a passivation layer.

Technical Field

The invention relates to the technical field of MEMS devices, in particular to a wafer-level packaging method and a packaging structure of an MEMS device.

Background

A Micro Electro Mechanical System (MEMS) is a Micro System in which a Micro Mechanical element, a Micro sensor, a Micro actuator, a signal processing and control circuit, and the like are integrated. With the integration of MEMS devices with microelectronics, photovoltaics, and emerging nanotechnology, MEMS devices have become widely used in more and more fields. However, since there is no standardized packaging method due to the wide variety of MEMS devices, there is an urgent need for a packaging method for MEMS devices suitable for mass production in various fields.

The wafer level packaging technology is an advanced packaging technology widely applied to MEMS devices, and is to complete all or most of packaging and testing procedures on a whole wafer and then perform slicing and dividing. The conventional wafer level packaging technology includes a vertical TSV (through hole) technology, and referring to fig. 1, in the technology, after a cover plate 10 and a wafer 11 are bonded, a through hole 12 is directly formed in the cover plate 10, and then a conductive metal is filled in the through hole 12 to be electrically connected to a pad 13 in the wafer 11.

Disclosure of Invention

In view of this, the present invention provides a wafer level packaging method and a packaging structure of a MEMS device, so as to reduce the packaging cost and the packaging difficulty of the MEMS device.

In order to achieve the purpose, the invention provides the following technical scheme:

a wafer level packaging method of a MEMS device comprises the following steps:

providing a substrate, wherein one side of the substrate is provided with a MEMS device and a bonding pad electrically connected with the MEMS device;

forming a connecting wire electrically connected with the bonding pad on the surface of the bonding pad, wherein the height of the connecting wire is greater than that of the MEMS device;

providing a cover plate, wherein one side of the cover plate is provided with a groove and a separation groove, and the depth of the separation groove is greater than that of the groove;

bonding one side of the cover plate with the groove and one side of the substrate with the MEMS device, wherein the connecting wire is accommodated in the separating groove, and the MEMS device is sealed in a cavity formed by the area of the cover plate with the groove and the substrate;

and reserving a cover plate on the MEMS device, and removing the cover plate on the bonding pad to expose the bonding pad and the connecting wire.

Optionally, the depth of the separation groove is 3um to 5um greater than the height of the connecting line.

Optionally, the retaining the cover plate on the MEMS device and the removing the cover plate on the bonding pad include:

and etching the cover plate by adopting a wet etching process to remove the cover plate on the bonding pad and reserve the cover plate on the MEMS device.

Optionally, the retaining the cover plate on the MEMS device and the removing the cover plate on the bonding pad include:

grinding one side of the cover plate, which is far away from the substrate, by adopting a mechanical grinding process to thin the cover plate;

and etching the thinned cover plate by adopting a wet etching process so as to remove the cover plate on the bonding pad and reserve the cover plate on the MEMS device.

Optionally, in the thinned cover plate, the thickness of the thinnest area ranges from 5um to 10 um.

Optionally, after the bonding pad and the connecting wire are exposed, the height of the connecting wire exceeds the height of the cover plate;

and, the height of connecting wire surpasss the scope of the height of apron is 15um ~ 30 um.

Optionally, the method further comprises:

and forming a passivation layer on the surface of the cover plate.

A wafer level packaging structure of a MEMS device manufactured by the method of any one of the above claims, the wafer level packaging structure of the MEMS device comprising:

the MEMS device comprises a substrate, wherein one side of the substrate is provided with an MEMS device and a bonding pad electrically connected with the MEMS device;

the connecting wire is positioned on the surface of the bonding pad and electrically connected with the bonding pad;

the cover plate is located above the MEMS device and exposes the bonding pad and the connecting line, and the MEMS device is sealed in a cavity formed by bonding the cover plate and the substrate.

Optionally, the height of the connecting line exceeds the height of the cover plate;

and, the height of connecting wire surpasss the scope of the height of apron is 15um ~ 30 um.

Optionally, the surface of the cover plate is further provided with a passivation layer.

Compared with the prior art, the technical scheme provided by the invention has the following advantages:

according to the wafer-level packaging method and the packaging structure of the MEMS device, the connecting line is formed on the surface of the bonding pad, the cover plate is bonded with the substrate, the MEMS device is sealed in the cavity formed by the area, provided with the groove, of the cover plate and the substrate, then the cover plate is etched, the cover plate on the bonding pad is removed, the bonding pad and the connecting line are exposed, and therefore the sealed MEMS device is electrically connected with other devices through the connecting line. Compared with the existing longitudinal TSV technology, the wafer level packaging method of the MEMS device is simple in process, so that the wafer level packaging structure of the MEMS device is low in manufacturing difficulty and low in cost.

In addition, in the invention, because the cover plate at the top of the separation groove is thinner and the cover plate at the top of the groove is thicker, when the cover plate is etched, and when the cover plate at the top of the connecting line, namely the cover plate at the top of the separation groove is completely etched, the cover plate at the top of the groove, namely the cover plate at the top of the MEMS device, still has a certain thickness, so that photoresist does not need to be formed on the surface of the cover plate and then the cover plate is etched, and the manufacturing cost is greatly reduced.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.

FIG. 1 is a schematic diagram of a wafer level package structure of a MEMS device fabricated using conventional vertical TSV techniques;

FIG. 2 is a flow chart of a wafer level packaging method for a MEMS device according to one embodiment of the present invention;

FIG. 3 is a schematic cross-sectional view of a substrate with a MEMS device and a bonding pad according to an embodiment of the present invention;

FIG. 4 is a schematic cross-sectional view of a substrate with MEMS devices, bonding pads and connecting wires according to an embodiment of the present invention;

FIG. 5 is a schematic cross-sectional view of a cover plate having a groove and a separation groove according to an embodiment of the present invention;

FIG. 6 is a schematic cross-sectional view of a bonded structure of a substrate and a cover plate according to an embodiment of the present invention;

FIG. 7 is a cross-sectional view of a wafer level package structure of a MEMS device according to an embodiment of the present invention;

FIG. 8 is a schematic cross-sectional view of a thinned cover plate and a thinned substrate according to an embodiment of the present invention;

fig. 9 is a schematic cross-sectional view of a wafer level package structure of a MEMS device according to another embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, so that the above is the core idea of the present invention, and the above objects, features and advantages of the present invention can be more clearly understood. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

An embodiment of the present invention provides a wafer-level packaging method for an MEMS device, as shown in fig. 2, including:

s101: providing a substrate, wherein one side of the substrate is provided with a MEMS device and a bonding pad electrically connected with the MEMS device;

referring to fig. 3, a MEMS device 21 and a pad 22 electrically connected to the MEMS device 21 are fabricated in advance on one side of a substrate 20. The substrate 20 may be a wafer, and the material of the wafer may be silicon, silicon germanium, or the like. Of course, the present invention is not limited thereto, and in other embodiments, the substrate 20 may be a sapphire substrate. Moreover, the MEMS device 21 is formed on the surface of the substrate 20, and the pad 22 may be located on the surface of the substrate 20, for example, a metal film is directly formed on the surface of the substrate 20, or may be located in a groove of the substrate 20, for example, a groove is first etched on the surface of the substrate 20, and then the pad 22 is formed by filling a metal material into the groove.

S102: forming a connecting wire electrically connected with the bonding pad on the surface of the bonding pad, wherein the height of the connecting wire is greater than that of the MEMS device;

referring to fig. 4, after providing the substrate 20 having the MEMS device 21 and the pad 22, a connection line 23 of a predetermined height is formed on the surface of the pad 22 by using a plating process or the like, and the connection line 23 is electrically connected to the pad 22. Wherein, the connecting wire 23 is only located on the surface of the pad 22, i.e. the connecting wire 23 is only electrically connected with the pad 22. Optionally, the material of the connection line 23 includes one or more of copper, gold, palladium, aluminum, nickel, tin, silver, and the like. Preferably, the material of the connection line 23 is copper.

It should be noted that the height of the connection line 23 needs to be predetermined, and the height of the connection line 23 is greater than the height of the MEMS device 21, so that the finally formed package structure can expose the connection line 23, and facilitate the electrical connection between the connection line 23 and other devices.

S103: providing a cover plate, wherein one side of the cover plate is provided with a groove and a separation groove, and the depth of the separation groove is greater than that of the groove;

referring to fig. 5, one side of the cap plate 30 has a groove 31 and a separation groove 32, wherein the groove 31 and the separation groove 32 may be formed on one side of the cap plate 30 using a dry etching process or the like. Optionally, the depth of the recess 31 is determined by the height of the MEMS device 21, so that the MEMS device 21 can be accommodated in the recess 31 after the substrate 20 is bonded to the cover plate 30. The depth of the separation groove 32 is determined by the height of the connection wire 23 so that the connection wire 23 is received in the separation groove 32 after the base plate 20 is bonded to the cover plate 30. Since the height of the connection line 23 is greater than the height of the MEMS device 21, the depth of the separation groove 32 is greater than the depth of the groove 21.

Optionally, the depth of the separation groove 32 is greater than the height of the connection line 23, so that after the cover plate 30 is bonded to the substrate 20, the connection line 23 can be accommodated in the separation groove 32, and the thickness of the cover plate 30 in the region corresponding to the separation groove 32 is relatively thin, which facilitates subsequent etching. Further optionally, the depth of the separation groove 32 is 3um to 5um greater than the height of the connection line 23.

In the embodiment of the present invention, the material of the cover plate 30 may be the same as or different from the material of the substrate 20. Alternatively, the material of the cover plate 30 may be silicon, glass, metal, or ceramic material, etc.

S104: bonding one side of the cover plate with the groove with one side of the substrate with the MEMS device, wherein the connecting wire is accommodated in the separation groove, and the MEMS device is sealed in a cavity formed by the area of the cover plate with the groove and the substrate;

after providing the cover plate 30, referring to fig. 6, the cover plate 30 and the substrate 20 are bonded using a bonding process, and optionally, the cover plate 30 and the substrate 20 may be bonded by an adhesive 33. During bonding, it is necessary to ensure that the side of the cover plate 30 having the groove 31 is bonded to the side of the substrate 20 having the MEMS device 21, and after bonding, it is necessary to ensure that the connecting wire 23 is accommodated in the separating groove 32 and the MEMS device 21 is accommodated in the groove 31, that is, the MEMS device 21 is sealed in the cavity formed by the substrate 20 and the area of the cover plate 30 having the groove 31.

S105: and reserving a cover plate on the MEMS device, and removing the cover plate on the bonding pad to expose the bonding pad and the connecting wire.

After bonding the cover plate 30 and the substrate 20, in an embodiment of the present invention, the cover plate 30 may be directly etched by a wet etching process to retain the cover plate 30 on the MEMS device 21, remove the cover plate 30 on the bonding pad 22, and expose the bonding pad 22 and the connection line 23, so as to form the structure shown in fig. 7.

That is, the steps of retaining the cap plate 30 on the MEMS device 21 and removing the cap plate 30 on the bonding pad 22 include: the cover plate 30 is etched using a wet etching process to remove the cover plate 30 over the bonding pads 22 and leave the cover plate 30 over the MEMS device 21.

Of course, the invention is not limited thereto, and in another embodiment of the invention, in order to improve the etching uniformity, after the cover plate 30 and the substrate 20 are bonded, a mechanical grinding process may be first used to grind and thin the side of the cover plate 30 away from the substrate 20 to form the structure shown in fig. 8, and then a wet etching process may be used to etch the thinned cover plate 30 to form the structure shown in fig. 7. That is, the steps of retaining the cap plate 30 on the MEMS device 21 and removing the cap plate 30 on the bonding pad 22 include:

grinding one side of the cover plate 30, which is far away from the substrate 20, by adopting a mechanical grinding process to thin the cover plate 30;

and etching the thinned cover plate 30 by using a wet etching process to remove the cover plate 30 on the bonding pad 22 and reserve the cover plate 30 on the MEMS device 21.

It should be noted that, when the cover plate 30 is thinned, the cover plate 30 is not worn through, so as to reduce the grinding difficulty, and solve the problems of large grinding and thinning difficulty and dust deposition in the groove after grinding caused by only adopting the grinding process. Alternatively, the thickness d1 of the cover plate 30 at the top of the separation groove 32, which is the thinnest region of the thinned cover plate 30, ranges from 5um to 10 um. Alternatively, the thickness of the thinned cover plate 30 is preferably 30 um.

In the embodiment of the present invention, the cover plate 30 may be wet etched by using a KOH (potassium hydroxide)/TMAH (tetramethylammonium hydroxide) etching solution, but the present invention is not limited thereto, and in other embodiments, the cover plate 30 may also be etched by using other etching processes, such as dry etching.

It should be noted that, in the present invention, since the thickness of the cover plate 30 at the top of the separation groove 32 is thinner and the thickness of the cover plate 30 at the top of the groove 31 is thicker, when the cover plate 30 is etched, and when the top of the connection line 23, that is, the cover plate 30 at the top of the separation groove 32 is completely etched, the top of the groove 31, that is, the top of the MEMS device 21 still has a certain thickness of the cover plate 30, so that a photoresist does not need to be formed on the surface of the cover plate 30, and the manufacturing cost is greatly reduced.

As shown in fig. 7, after the cover plate 30 is etched to expose the pads 22 and the connection lines 23, the height of the connection lines 23 exceeds the height of the cover plate 30. Optionally, the height of the connection line 23 exceeds the height of the cover plate 30 by 15um to 30um, so as to facilitate the electrical connection of the connection line 23 with other devices.

It should be noted that if the thickness of the cover plate 30 to be finally formed is too thin, referring to fig. 9, a passivation layer 34 may be formed on the surface of the cover plate 30 to enhance the mechanical strength and reliability of the cover plate 30. That is, the packaging method provided in the embodiment of the present invention further includes, after the cover plate 30 is etched to expose the pads 22 and the connection lines 23: a passivation layer 34 is formed on the surface of the cap plate 30. The material of the passivation layer 34 may be aluminum nitride or silicon nitride. Of course, the invention is not limited thereto, and in other embodiments, the passivation layer 34 may be a passivation layer exposing the connection line 23, or a protection layer exposing only the connection line 23 may be formed on the top of the cover plate 30, which will not be described herein again.

Compared with the existing longitudinal TSV technology, the wafer level packaging method of the MEMS device provided by the embodiment of the invention has the advantages of low manufacturing cost, simple process and the like. In addition, after the substrate 20 and the cover plate 30 are bonded, the substrate does not need to enter a vacuum etching cavity for etching, and the risk of vacuum cavity fragments and the like does not exist.

In addition, the cover plate 30 is etched by adopting a wet etching process or a grinding and wet etching process, compared with the mode of cutting the cover plate in the prior art, the problems of device failure and equipment damage caused by cutting and scratching the bonding pad are solved, and the total process cost can be reduced by firstly mechanically grinding and then etching by adopting a wet method.

Secondly, compared with the mode of bonding the etching cover plate and then electroplating to form the connecting line, the mode of firstly electroplating to form the connecting line 23 and then bonding the etching cover plate solves the problems of high cost of the photoetching process and difficult electroplating and photoetching process caused by larger grooves between the etched MEMS device and the MEMS device.

In the invention, the cover plate at the top of the separation groove is thinner, and the cover plate at the top of the groove is thicker, so that when the cover plate is etched, and when the cover plate at the top of the connecting line, namely the cover plate at the top of the separation groove is completely etched, the cover plate at the top of the groove, namely the cover plate at the top of the MEMS device still has a certain thickness, photoresist does not need to be formed on the surface of the cover plate and then the cover plate is etched, and the manufacturing cost is greatly reduced.

An embodiment of the present invention further provides a wafer level package structure of an MEMS device, which is manufactured by applying the method provided in any of the above embodiments, and referring to fig. 7, the wafer level package structure of the MEMS device includes:

a substrate 20, one side of the substrate 20 is provided with a MEMS device 21 and a bonding pad 22 electrically connected with the MEMS device 21;

a connecting line 23 located on the surface of the bonding pad 22 and electrically connected with the bonding pad 22;

and the cover plate 30 is positioned above the MEMS device 21, the bonding pads 22 and the connecting lines 23 are exposed, and the MEMS device 21 is sealed in a cavity formed by bonding the cover plate 30 and the substrate 20.

In the embodiment of the present invention, referring to fig. 7, the height of the connection line 23 exceeds the height of the cover plate 30, and the range of the height of the connection line 23 exceeding the height of the cover plate 30 is 15um to 30um, so that the connection line 23 is electrically connected to other electronic devices.

In another embodiment of the present invention, if the thickness of the cover plate 30 is too thin, as shown in fig. 9, the surface of the cover plate 30 is further provided with a passivation layer 34 to enhance the mechanical strength and reliability of the cover plate 30.

Of course, the invention is not limited thereto, and in other embodiments, the passivation layer 34 may be a passivation layer exposing the connection line 23, or a protection layer exposing only the connection line 23 may be formed on the top of the cover plate 30, which will not be described herein again.

The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.