CN117088330A

CN117088330A - MEMS device packaging method and MEMS device

Info

Publication number: CN117088330A
Application number: CN202311295364.2A
Authority: CN
Inventors: 张兆林
Original assignee: Semiconductor Manufacturing Electronics Shaoxing Corp SMEC
Current assignee: Semiconductor Manufacturing Electronics Shaoxing Corp SMEC
Priority date: 2023-10-09
Filing date: 2023-10-09
Publication date: 2023-11-21

Abstract

The embodiment of the application relates to a packaging method of an MEMS device and the MEMS device, which comprises the steps of providing a sealing cover substrate with a sacrificial layer embedded inside; forming a first groove on the first surface of the cover substrate, wherein the first groove exposes a part of the sacrificial layer at a first position; providing a device substrate, wherein a first MEMS structure is formed on the device substrate; bonding the cover substrate and the device substrate, wherein the first MEMS structure is opposite to the first groove, so that the first groove is formed into a first cavity; forming an air suction groove on the second surface of the sealing cover substrate, wherein the air suction groove exposes a part of the sacrificial layer, which is positioned at the second position; removing at least part of the sacrificial layer via the air extraction groove to form an air extraction channel which is communicated with the air extraction groove and the first cavity in the direction perpendicular to the thickness of the cover substrate; pumping the first cavity through the pumping groove and the pumping channel; forming a cover layer which at least seals the opening of the air suction channel facing the air suction groove; thus, the problem of difficult hole sealing is solved.

Description

MEMS device packaging method and MEMS device

Technical Field

The present application relates to the field of semiconductor technologies, and in particular, to a method for packaging an MEMS device and an MEMS device.

Background

MEMS devices such as inertial sensors fabricated based on MEMS (Micro Electro Mechanical System, microelectromechanical systems) processing technology have been widely used, and have received attention because of their simple structure, good compatibility with microelectronic fabrication processes, mass production, small footprint, and ease of use.

Like integrated circuits, MEMS devices are also evolving towards high performance, miniaturization, and low cost and integration. To achieve complete motion detection, it is often necessary to integrate multiple MEMS devices onto a single integrated chip. At present, when the vacuum degree reaches the requirement, two kinds of device integrated wafers are subjected to a laser hole sealing process, and special machine tables are used for hole sealing one by one, but the process has high cost, high process requirement and low efficiency, and cannot be applied to a sealing process with a larger size.

Disclosure of Invention

In view of the above, embodiments of the present application provide a packaging method of a MEMS device and the MEMS device for solving at least one of the problems in the background art.

In a first aspect, an embodiment of the present application provides a method for packaging a MEMS device, where the method includes:

providing a cover substrate, wherein a sacrificial layer is buried in the cover substrate; the sacrificial layer extends from at least a first location to a second location in a direction perpendicular to a thickness of the cover substrate;

Forming a first groove on a first surface of the cover substrate, the first groove exposing a portion of the sacrificial layer at the first location;

providing a device substrate, wherein a first MEMS structure is formed on the device substrate;

bonding the cover substrate and the device substrate, wherein the first MEMS structure is opposite to the first groove, so that the first groove is formed into a first cavity for providing a movable space for the first MEMS structure;

forming an air extraction groove on the second surface of the cover substrate, wherein the air extraction groove exposes a part of the sacrificial layer, which is positioned at the second position;

removing at least part of the sacrificial layer via the air extraction groove to form an air extraction channel communicating the air extraction groove and the first cavity in a direction perpendicular to the thickness of the cover substrate;

pumping the first cavity through the pumping groove and the pumping channel;

and forming a cover layer, wherein the cover layer at least seals the opening of the air suction channel facing the air suction groove.

With reference to the first aspect of the present application, in an optional embodiment, the providing a capping substrate includes:

providing a first substrate;

forming a receiving groove on a first surface of the first substrate;

Forming a sacrificial layer filling the accommodating groove;

providing a second substrate;

and bonding the first substrate and the second substrate by taking the first surface as a bonding surface.

With reference to the first aspect of the present application, in an alternative embodiment, the sacrificial layer includes a plurality of branches to form a plurality of air extraction channels communicating the air extraction grooves and the first cavity in a direction perpendicular to a thickness of the cover substrate after at least a portion of the sacrificial layer is removed via the air extraction grooves.

With reference to the first aspect of the present application, in an alternative embodiment, the sacrificial layer includes a plurality of branches, and gaps exist between the branches;

forming a first groove on a first surface of the cover substrate, including: executing an etching process on the first surface of the cover substrate; at the position where the sacrifice layer is buried, etching is stopped on the sacrifice layer; etching is continued downwards at the gap position to form a concave part;

the method further comprises the steps of: and forming a gas absorption layer in the first groove, wherein the gas absorption layer at least covers the bottom wall and the side wall of the concave part.

In an alternative embodiment, in combination with the first aspect of the present application, the device substrate further has a second MEMS structure formed thereon, and the method further includes:

Forming a second groove on the first surface of the cover substrate;

in the step of bonding the cap substrate to the device substrate, the second MEMS structure is opposite the second recess such that the second recess is formed as a second cavity providing a movable space for the second MEMS structure;

and bonding the cover substrate and the device substrate under the condition of meeting the vacuum degree requirement of the second MEMS structure.

forming a second groove on the first surface of the cover substrate; the sacrificial layer is further buried in the forming position of the second groove and serves as an etching stop layer for forming the second groove;

in the step of bonding the cap substrate to the device substrate, the second MEMS structure is facing the second recess such that the second recess is formed as a second cavity providing a movable space for the second MEMS structure.

In combination with the first aspect of the present application, in an alternative embodiment, forming a suction groove on the second surface of the cover substrate includes:

Forming an air suction groove with the upper opening size larger than the lower opening size.

With reference to the first aspect of the present application, in an alternative embodiment, the material at the second surface of the cover substrate comprises silicon; and forming an air suction groove on the second surface of the sealing cover substrate, wherein the air suction groove is implemented by adopting an etchant comprising tetramethyl amino hydroxide TMAH.

With reference to the first aspect of the present application, in an optional embodiment, the forming a cover layer includes:

and forming the covering layer by adopting a physical vapor deposition or evaporation process under the condition of meeting the vacuum degree requirement of the first MEMS structure.

In a second aspect, an embodiment of the present application provides a MEMS device, which is manufactured by using the packaging method of the MEMS device according to any one of the first aspect.

According to the MEMS device packaging method and the MEMS device, the cover substrate is provided, and the sacrificial layer is buried in the cover substrate; the sacrificial layer extends from at least a first position to a second position along a direction perpendicular to the thickness of the cover substrate; forming a first groove on the first surface of the cover substrate, wherein the first groove exposes a part of the sacrificial layer at a first position; providing a device substrate, wherein a first MEMS structure is formed on the device substrate; bonding the cover substrate and the device substrate, wherein the first MEMS structure faces the first groove, so that the first groove forms a first cavity for providing a movable space for the first MEMS structure; forming an air suction groove on the second surface of the sealing cover substrate, wherein the air suction groove exposes a part of the sacrificial layer, which is positioned at the second position; removing at least part of the sacrificial layer via the air extraction groove to form an air extraction channel which is communicated with the air extraction groove and the first cavity in the direction perpendicular to the thickness of the cover substrate; pumping the first cavity through the pumping groove and the pumping channel; forming a cover layer which at least seals the opening of the air suction channel facing the air suction groove; in this way, compared with the air extraction holes extending along the vertical direction, the air extraction channel which is communicated with the air extraction groove and the first cavity along the direction perpendicular to the thickness of the cover substrate in the embodiment of the application can be easily sealed by forming the sealing layer, the sealing effect is good, the special machine is not required to be used for executing the laser hole sealing process, the problem that hole sealing is required one by one is avoided, the sealing layer can realize the sealing of a plurality of air extraction channels, the sealing layer can be applied to the sealing process with larger size, the forming method of the air extraction channel is simple, and the cost of the whole process is reduced.

Additional aspects and advantages of the application will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the application.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the application and do not constitute a limitation on the application. In the drawings:

FIGS. 1 to 2 are schematic cross-sectional views of a MEMS device during packaging;

FIG. 3 is a schematic flow chart of a packaging method of a MEMS device according to an embodiment of the present application;

fig. 4 to 14 are schematic cross-sectional views of a MEMS device according to an embodiment of the present application during a packaging process;

FIG. 15 is a schematic plan view of a MEMS device according to an embodiment of the present application;

fig. 16 and 17 are schematic diagrams illustrating another cross-sectional structure of a MEMS device in a packaging process according to an embodiment of the present application.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the application are shown in the drawings, it should be understood that the application may be embodied in various forms and should not be limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present application. It will be apparent, however, to one skilled in the art that the application may be practiced without one or more of these details. In other instances, well-known features have not been described in detail so as not to obscure the application; that is, not all features of an actual implementation are described in detail herein, and well-known functions and constructions are not described in detail.

In the drawings, the size of layers, regions, elements and their relative sizes may be exaggerated for clarity. Like numbers refer to like elements throughout.

It will be understood that when an element or layer is referred to as being "on" … …, "" adjacent to "… …," "connected to" or "coupled to" another element or layer, it can be directly on, adjacent to, connected to or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on" … …, "" directly adjacent to "… …," "directly connected to" or "directly coupled to" another element or layer, there are no intervening elements or layers present. It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present application. When a second element, component, region, layer or section is discussed, it does not necessarily mean that the first element, component, region, layer or section is present.

Spatially relative terms, such as "under … …," "under … …," "below," "under … …," "above … …," "above," and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use and operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements or features described as "under" or "beneath" other elements would then be oriented "on" the other elements or features. Thus, the exemplary terms "under … …" and "under … …" may include both an upper and a lower orientation. The device may be otherwise oriented (rotated 90 degrees or other orientations) and the spatially relative descriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term "and/or" includes any and all combinations of the associated listed items.

In order to provide a thorough understanding of the present application, detailed steps and detailed structures will be presented in the following description in order to explain the technical solution of the present application. Preferred embodiments of the present application are described in detail below, however, the present application may have other embodiments in addition to these detailed descriptions.

Motion sensors often use MEMS accelerometers (simply accelerometers) in combination with MEMS gyroscopes (simply gyroscopes). The accelerometer detects acceleration and the gyroscope detects angular velocity. To meet the need for low cost, small volume accelerometers and gyroscopes may be integrated on the same substrate.

Taking a single-axis gyroscope as an example, the working principle is as follows: the two moving mass blocks continuously move in opposite directions, and as long as an angular velocity parallel to a movement plane is applied, ke Liao force (Coriolis force for short) perpendicular to the movement direction of the mass blocks is generated, so that the mass blocks are displaced, and the displacement is proportional to the applied angular velocity. This displacement will cause a change in capacitance between the comb electrodes and the fixed electrodes of the mass, and therefore the angular rate applied by the input part of the gyroscope is converted into an electrical parameter that can be detected by a dedicated circuit. The working principle of the accelerometer is similar to that of a gyroscope, and the acceleration is detected according to capacitance change generated by displacement of a mass block.

The ideal vacuum level varies for different types of MEMS devices. For example, the main performance index of gyroscopes includes a quality factor (QualityFactor) for measuring the sensitivity of gyroscopes, and the main influencing factor is the vacuum level in the cavity. The gyroscope is in resonance motion in the cavity when not in operation, and in order to improve sensitivity, the cavity needs to have higher vacuum degree. The main performance indexes of the accelerometer comprise damping factors, wherein the damping factors generally have two modes, and the first mode is structural damping generated by friction between structural layers; the second is air viscous damping, which is produced by atmospheric pressure, which is much more powerful than the structural damping. The accelerometer mass block needs to be restored to the original position after deformation, and in order to avoid adsorption between comb teeth, relatively large air viscous damping is needed. That is, a gyroscope requires a higher vacuum level in order to ensure high sensitivity and low power consumption, while an accelerometer requires a lower vacuum level in order to maintain high performance and reliability.

In order to enable different MEMS devices on the same substrate to have different vacuum degrees, as shown in FIG. 1, a sealing cover substrate 100 and a device substrate 200 are subjected to wafer-level sealing bonding, an air suction hole H is etched in the sealing cover substrate 100, and air is sucked through the air suction hole H to improve the vacuum degree of a cavity communicated with the air suction hole H; after the vacuum degree reaches the requirement, as shown in fig. 2, a laser hole sealing process is adopted, and a special machine is used for sealing each die one by one. The process has high cost because of the need of using a special machine, and the expensive special machine and the high requirement of machine transformation. In addition, the laser hole sealing process only can seal holes one by one, and has low efficiency; moreover, the process is feasible for the pumping holes with extremely small size, and cannot be applied to the sealing process of larger holes; and thus cannot be applied to a sealing process of a large size.

In view of this, an embodiment of the present application provides a method for packaging a MEMS device, as shown in fig. 3, the method includes:

step S01, providing a cover substrate, wherein a sacrificial layer is buried in the cover substrate; the sacrificial layer extends from at least a first position to a second position along a direction perpendicular to the thickness of the cover substrate;

step S02, forming a first groove on the first surface of the cover substrate, wherein the first groove exposes a part of the sacrificial layer at a first position;

step S03, providing a device substrate, wherein a first MEMS structure is formed on the device substrate;

step S04, bonding the cover substrate and the device substrate, wherein the first MEMS structure faces the first groove, so that the first groove forms a first cavity providing a movable space for the first MEMS structure;

s05, forming an air extraction groove on the second surface of the sealing cover substrate, wherein the air extraction groove exposes a part of the sacrificial layer, which is positioned at a second position;

step S06, removing at least part of the sacrificial layer through the air suction groove to form an air suction channel which is communicated with the air suction groove and the first cavity in the direction perpendicular to the thickness of the cover substrate;

step S07, pumping the first cavity through a pumping groove and a pumping channel;

in step S08, a cover layer is formed, and the cover layer at least seals the opening of the air extraction channel facing the air extraction groove.

As can be appreciated, compared with the air extraction hole H extending in the vertical direction and etched in the capping substrate 100, the air extraction channel in the embodiment of the application, which communicates the air extraction groove and the first cavity in the direction perpendicular to the thickness of the capping substrate, can be easily sealed by forming a sealing layer, so that the sealing effect is good, the laser hole sealing process is not required to be performed by using a special machine, and the problem that hole sealing is required one by one is avoided; in addition, the sealing layer can realize the sealing of a plurality of air extraction channels, so that the efficiency is high, and the possibility of arranging small-size and large-number air extraction channels for the same first cavity is provided, so that the sealing layer can be applied to a sealing process with a larger size. The formation method of the air extraction channel is simple, and the cost of the whole process is reduced.

Next, a method for packaging a MEMS device and the MEMS device according to embodiments of the present application will be described in further detail with reference to fig. 4 to 17.

First, please refer to fig. 7. Step S01 is performed to provide a capping substrate 100, wherein the sacrificial layer 120 is buried inside the capping substrate 100; the sacrificial layer 120 extends from at least a first location to a second location in a direction perpendicular to the thickness of the capping substrate 100.

As shown in the figure, the third direction in the drawing is the thickness direction of the capping substrate 100, and the thickness direction of the capping substrate 100 is also the stacking direction of the material layers deposited during the device manufacturing process, or the height direction of the device. The cover substrate 100 includes two surfaces opposite to each other perpendicular to the thickness direction, and the surfaces on which the two surfaces of the cover substrate 100 are located, or strictly speaking, the center surface in the thickness direction of the cover substrate 100, that is, the cover substrate plane; the direction parallel to the plane of the cover substrate is the direction along the plane of the cover substrate. In a direction perpendicular to the thickness of the capping substrate 100, i.e., in the capping substrate plane direction. In the figure, two first directions and two second directions which are intersected with each other are defined in the plane direction of the cover substrate; the sacrificial layer 120 extends in particular in a first direction at least from a first position to a second position. Further, the first direction and the second direction are, for example, two directions perpendicular to each other.

As an alternative embodiment, the forming process of the capping substrate 100 includes:

first, a first substrate 110 is provided (see fig. 4). The material of the first substrate 110 is, for example, silicon; the first substrate 110 may also be referred to as a first silicon wafer. The present application is not limited thereto, and the material of the first substrate 110 may include at least one of: si, ge, siGe, siC, siGeC, inAs, gaAs, inP, inGaAs or other III/V compound semiconductors may also include multilayer structures of these semiconductors, etc., or silicon-on-insulator (SOI), germanium-on-insulator (GeOI), etc.

Next, a receiving groove is formed in the first surface of the first substrate 110; a sacrificial layer 120 filling the accommodating groove is formed (refer to fig. 5).

Forming a receiving groove on the first surface of the first substrate 110 may specifically include: forming a mask layer, such as a patterned photoresist layer, on a first surface of the first substrate 110, the openings of the photoresist layer corresponding to locations where the accommodating grooves are to be formed; next, the first substrate 110 is etched using the patterned mask layer as a mask, forming a receiving groove extending from the first surface of the first substrate 110 to the inside thereof.

The pattern of the accommodating groove, or the pattern of the photoresist layer, is the pattern of the sacrificial layer 120 formed later.

Forming the sacrificial layer 120 filling the accommodating groove may specifically include: the accommodating groove is filled with a sacrificial layer material, and the sacrificial layer material is annealed to form the sacrificial layer 120. Since the sacrificial layer 120 will be exposed in the first cavity and/or the second cavity in the subsequent process, by annealing the sacrificial layer material, impurities in the sacrificial layer material can be removed, and impurities are prevented from entering the first cavity and/or the second cavity, thereby affecting the air tightness. In addition, by annealing, it can also act to release stress.

In an actual process, a layer of sacrificial layer material may be deposited on the first substrate 110, where the sacrificial layer material not only fills the accommodating groove, but also is deposited on the first surface of the first substrate 110; the upper surface of the sacrificial layer 120 is then made coplanar with the first surface of the first substrate 110 by a planarization process (specifically, for example, CMP).

As an alternative embodiment, the sacrificial layer 120 includes a plurality of branches with gaps between the branches. Fig. 15 shows a planar structure of the MEMS device in a specific example, and since the distribution positions of the branches of the sacrificial layer 120 are related to the preset formation positions of the first grooves 131, patterns related to the sacrificial layer 120 will be described below.

Next, please refer to fig. 6. Providing a second substrate 130; the first substrate 110 is bonded to the second substrate 130 with the first surface as a bonding surface.

The material of the second substrate 130 may also be silicon; the second substrate 130 may also be referred to as a second silicon wafer. Of course, other suitable materials for the second substrate 130 may be selected.

After bonding the first substrate 110 and the second substrate 130, a thinning step may be further included. Specifically, the surface of the second substrate 130 on the side far from the first substrate 110 may be thinned on one side; the first substrate 110 and the second substrate 130 may be thinned, which is not particularly limited in the present application. After the thinning, the total thickness of the bonding structure formed by the first substrate 110 and the second substrate 130 can meet the process design requirement.

It should be understood that while the figures illustrate the capping substrate 100 having the sacrificial layer 120 embedded therein formed by bonding the two sides Si together by direct bonding, it is apparent that the present application does not preclude the capping substrate 100 from being formed by other means.

Next, please refer to fig. 7. Forming a first bond ring structure 140.

The material of the first bonding ring structure 140 includes metal materials such as germanium, aluminum, copper, nickel, gold, etc. In some embodiments, a bond metal material may be deposited on a surface of the second substrate 130 on a side remote from the first substrate 110; then, a patterned mask layer is formed by a photolithography process, and the bonding metal material is etched by using the mask layer as a mask, so as to form the first bonding ring structure 140.

Next, please refer to fig. 8. Step S02 is performed in which a first groove 131 is formed in the first surface of the capping substrate 100, the first groove 131 exposing a portion of the sacrificial layer 120 located at the first position.

The first groove 131 corresponds to a position of the first MEMS structure on the subsequent device substrate, so that after the cap substrate 100 is bonded with the device substrate, the first groove 131 is formed as a first cavity providing a movable space for the first MEMS structure.

In addition, a second groove 132 may be formed on the first surface of the cover substrate 100; the second groove 132 corresponds to the location of the second MEMS structure on the subsequent device substrate, such that after the cap substrate 100 is bonded to the device substrate, the second groove 132 forms a second cavity providing a movable space for the second MEMS structure.

According to the device requirement, the vacuum degree of the first cavity is different from that of the second cavity. One of the first and second MEMS structures, for example, comprises a comb structure of an accelerometer, and the other of the first and second MEMS structures, for example, comprises a comb structure of a gyroscope. Illustratively, the first MEMS structure comprises a comb structure of a gyroscope, thereby correspondingly forming the gyroscope in the region thereof; the second MEMS structure comprises a comb structure of the accelerometer, thereby correspondingly forming the accelerometer in the area where it is located.

One of the two MEMS structures forms a cavity of a desired vacuum level during bonding of the cover substrate 100 to the device substrate; taking this embodiment as an example, the bonding process is performed under the vacuum requirement of the second cavity; and the other forms a cavity with required vacuum degree through the air extraction groove and the air extraction channel provided by the embodiment of the application.

It should be appreciated that while the improved concepts of the present application are developed in the context of solving the problem of integrating multiple MEMS devices having different vacuum requirements, the present application is not limited to application on integrated wafers of at least two devices. The vacuum pumping of a single MEMS device can obviously also be achieved by the encapsulation method provided by the application, if there is a corresponding need.

In a specific process, a patterned mask layer can be formed through a photoetching process, and the mask layer exposes the position of a cavity structure necessary for a device; next, the capping substrate 100 is etched using the mask layer as a mask, specifically, for example, the second substrate 130 is etched to form the first groove 131. Similarly, the mask layer may also leave the location of the second cavity, thereby also forming a second recess 132 after etching.

Referring to fig. 15, the sacrificial layer 120 includes a plurality of branches corresponding to the first grooves 131; gaps exist between the branches.

Each branch extends from a certain first position located in the first groove 131 to a certain second position located outside the first groove 131. It will be appreciated that the first position may be different between the branches, and that the second position may be different for the branches accordingly; the first position and the second position are only used to indicate the position exposed through the first groove 131 and the position exposed through the pumping groove in the subsequent process, and not a certain exact position of the feature; thus, it is intended herein to illustrate boundary lines between the branches respectively extending across the planar pattern of the first groove 131.

The first recess 131 includes a plurality of sidewalls, one of which is adjacent to the second recess 132. In the third direction, the inter-branch projections of the sacrificial layer 120 intersect with the other sidewalls of the first recess 131 except the sidewalls immediately adjacent to the second recess 132. Taking the planar pattern (or opening shape) of the first groove 131 as an example, the first groove 131 includes four sidewalls, wherein the right sidewall as shown in the drawing is adjacent to the second groove 132, and the forming positions of the branches are respectively located at the other three sidewalls and respectively penetrate through the corresponding sidewalls. In this way, in the subsequent process, the air extraction channels can be formed at the multiple side walls of the first groove 131, so that the air extraction difficulty is reduced, and the air extraction effect is improved; and no branches are provided immediately adjacent to the sidewalls of the second recess 132 to prevent an increase in the area of the integrated chip.

At least some of the plurality of branches extend from one end to the other end of the bottom of the first groove 131; thus, the length of the gaps between the branches is increased, which is beneficial to depositing more gas absorbing layers. Illustratively, as shown in fig. 15, the sacrificial layer 120 includes a plurality of branches intersecting the left sidewall of the first groove 131, at least a portion of the branches extending from the left sidewall to the right sidewall of the first groove 131, to adjacent to the right sidewall, or through the right sidewall, which are hereinafter referred to as "long branches". The long branches may be parallel to each other. In addition, a plurality of short branches may be further included, and each short branch may have a smaller extension length in the first groove 131 than the long branch. The short branches are for example distributed between the long branches. Each long branch increases the length of the gap between branches; each short branch increases the number of bleed passages.

Outside the first recess 131, the branches may be connected, thereby ensuring that the branches are released when the sacrificial layer is removed via the pumping grooves in a subsequent process.

In performing step S02, an etching process is performed on the first surface of the capping substrate 100, and etching is stopped on the sacrificial layer 120 at the position where the sacrificial layer 120 is buried; at the gap position between the branches of the sacrificial layer 120, etching proceeds downward to form a recess (see fig. 16).

After step S02, the method may further include: a gas absorbing layer 150 is formed in the first groove 131, the gas absorbing layer 150 covering at least the bottom wall and the side walls of the recess (see fig. 17).

It can be appreciated that fig. 16 and 17 are schematic diagrams illustrating another cross-sectional structure of the MEMS device during the packaging process according to the embodiment of the present application; referring to fig. 15, fig. 4 to 14 correspond specifically to the cross section along AA in fig. 15, and fig. 16 and 17 correspond specifically to the cross section along BB in fig. 15. It should be noted that each drawing is only a schematic drawing, and the dimensional relationship, the pitch, the number of branches, and the like of each structure in the drawing may not be very accurate.

The gas absorbing layer 150 serves to absorb gas, thereby further increasing the vacuum degree of the first cavity. Since the sacrificial layer 120 does not cover the entire bottom surface of the first recess 131 but includes a plurality of branches with gaps therebetween, etching proceeds downward at the gap positions to form recesses, and the gas absorbing layer 150 may cover the bottom wall and the sidewalls of the recesses, so that more gas absorbing material may be deposited.

The material of the gas absorbing layer 150 may be a metal, including but not limited to Ti in particular. Illustratively, a photoresist layer exposing the first grooves 131 may be formed using a thick photoresist process, and the gas absorbing layer 150 is deposited at the bottom of the first grooves 131.

In one embodiment, the device substrate is further formed with a second MEMS structure, and the first surface of the cover substrate 100 is formed with a second recess 132; the sacrificial layer 120 is also buried in the formation position of the second recess 132, and the sacrificial layer 120 serves as an etching stop layer for forming the second recess 132.

In the second MEMS structure, the height of the second cavity (i.e., the depth of the second recess 132) has an impact on device performance. In conventional processes, the etch depth is often controlled by the etch time alone, whereas the etch rate of the etch process is often different in the middle of the recess and at the boundaries of the recess, which results in a non-uniform height of the second cavity, affecting the device performance. By providing an etch stop layer, the etch can be stopped at the surface of the sacrificial layer 120, thereby obtaining a second cavity that is highly compliant with design requirements. Because the sacrificial layer 120 is required to be pre-buried in the cover substrate 100, the pre-buried process can be utilized, so that not only is the sacrificial layer buried at the position of the first groove 131 to form an air extraction channel, but also the sacrificial layer is buried at the preset forming position of the second groove 132 synchronously to serve as an etching stop layer; therefore, the precise control of the height of the second cavity can be realized without adding additional working procedures.

Next, please refer to fig. 9. Step S03 is performed to provide a device substrate 200, and a first MEMS structure is formed on the device substrate 200.

In addition, as previously described, a second MEMS structure may also be formed on the device substrate 200.

The device substrate 200 may include a semiconductor substrate, a dielectric layer, a lower electrode layer, an interconnect structure, etc.; the device substrate 200 may be fabricated using processes conventional in the art, and the steps of the metal routing, dielectric layer planarization process, etc. are not discussed herein. In addition, a structural layer 210 on the semiconductor substrate is included; the structural layer 210 is formed, for example, by an epitaxial process. Comb-tooth structures in the first and second MEMS structures are formed by etching the structural layer 210. The type and number of MEMS structures on the device substrate 200 may be set according to actual requirements.

The comb structures may also be referred to as masses, and when the MEMS device is moved, the capacitance between the comb structures and between the comb and the semiconductor substrate changes, thereby converting the motion parameters into electrical parameters.

The second bonding ring structure 240 may be formed on the first surface of the structural layer 210 before bonding the cap substrate 100 to the device substrate 200.

Optionally, forming the second bond ring structure 240 includes the steps of: depositing a metal material layer; forming a mask layer, such as a photoresist layer, on the metal material layer; etching the metal material layer with the mask layer as a mask to form a second bonding ring structure 240; and then removing the mask layer.

In some embodiments, the material of the second bond ring structure 240 includes a metallic material such as germanium, aluminum, copper, nickel, gold, and the like. In some embodiments, a sputtering or evaporation process may be used to deposit the metal material layer. The metal material layer is etched to form the second bonding ring structure 240 may be selected from a dry etching, a Reactive Ion Etching (RIE), an ion beam etching, a plasma etching, and the like.

Next, please refer to fig. 10. Step S04 is performed to bond the cap substrate 100 and the device substrate 200, and the first MEMS structure faces the first recess 131, so that the first recess 131 forms a first cavity providing a movable space for the first MEMS structure.

Further, in some embodiments, the second MEMS structure is facing the second recess 132 such that the second recess 132 is formed as a second cavity providing a movable space for the second MEMS structure.

The cover substrate 100 is bonded to the device substrate 200, specifically, the first bonding ring structure 140 on the cover substrate 100 is bonded to the second bonding ring structure 240 on the device substrate 200.

Optionally, bonding the capping substrate 100 to the device substrate 200 is performed under conditions that meet the vacuum requirements of the second MEMS structure.

It can be appreciated that when metal bonding is performed, the vacuum pressure control process can save the vacuum pumping process according to the processing of devices without designing pumping grooves and pumping channels.

After bonding, the cover substrate 100 may be thinned to a certain thickness.

Next, please refer to fig. 11 and 12. Step S05 is performed, in which an air extraction groove 111 is formed on the second surface of the capping substrate 100, and the air extraction groove 111 exposes a portion of the sacrificial layer 120 at the second position.

Specifically, forming the suction groove 111 may include:

first, a patterned first mask layer 160 is formed (see fig. 11). In an actual process, the first mask layer 160 may be a silicon dioxide layer, and the patterned first mask layer 160 may be formed by etching using the patterned photoresist layer as a mask.

Next, the cover substrate 100, specifically, the first substrate 110 in the cover substrate 100 is etched with the patterned first mask layer 160 as a mask until stopping on the sacrificial layer 120, so as to form the pumping grooves 111 (please refer to fig. 12).

In some embodiments, and in conjunction with fig. 15, the pumping channel 111 may be semi-looped around the first recess 131 so as to communicate with the respective branches of the sacrificial layer 120.

Optionally, a suction groove 111 having an upper opening size larger than a lower opening size is formed. Thus, the side wall of the air extraction groove 111 is more beneficial to sealing the air extraction channel in the subsequent process, and the cover layer covers the air extraction groove 111 better.

In some embodiments, the material at the second surface of the cover substrate 100 comprises silicon; an air suction groove 111 is formed in the second surface of the cover substrate 100, and is performed using an etchant including TMAH (tetramethylamino hydroxide). By using TMAH as the etchant, etching silicon at a specific angle can be achieved, thereby forming the pumping channel 111 having an upper opening size larger than a lower opening size. As shown in fig. 12, the cross section of the air extraction groove 111 has an inverted trapezoid shape.

Next, please refer to fig. 13. Step S06 is performed to remove at least part of the sacrificial layer 120 via the air extraction groove 111 to form an air extraction channel 121 communicating the air extraction groove 111 and the first cavity in a direction perpendicular to the thickness of the capping substrate 100.

The sacrificial layer 120 may be etched by a VHF process, thereby connecting the first cavity to the outside.

In some embodiments, the sacrificial layer 120 includes a plurality of branches to form a plurality of pumping channels 121 communicating the pumping grooves 111 and the first cavity in a direction perpendicular to a thickness of the capping substrate 111 after removing at least a portion of the sacrificial layer 120 via the pumping grooves 111. As can be appreciated, the plurality of air extraction channels 121 can better control the vacuum degree in the first cavity, so that the vacuum degree meeting the preset requirement can be realized even if the size of the first cavity is large; in addition, by setting the number of the suction passages 121 to be plural, the opening area of each suction passage 121 can be set smaller in the case where the total opening area of the suction passages for the same first cavity is satisfied without being reduced, thereby reducing the difficulty of sealing the suction passages 121.

Next, please refer to fig. 14. Step S07 is performed to pump the first cavity through the pumping groove 111 and the pumping channel 121; step S08 is performed to form the cover layer 170, and the cover layer 170 seals at least the opening of the pumping channel 121 toward the pumping channel 111.

In a practical process, the first chamber may be evacuated first, and then the process of forming the cover layer 170 may be performed in the same vacuum chamber, so that the first cavity maintains a high vacuum level after forming the cover layer 170.

Specifically, the capping layer 170 may be formed using a Physical Vapor Deposition (PVD) or evaporation process under conditions that meet the vacuum requirements of the first MEMS structure. The capping layer 170 deposited using a physical vapor deposition or evaporation process is, for example, a metal layer. Since the main device structure fabrication is already completed and the cap substrate 100 is already bonded to the device substrate 200 prior to the step of forming the cap layer 170, the process temperature for forming the cap layer 170 should not be too high to damage the existing structure, and the temperature of the physical vapor deposition or evaporation process may be sufficient.

Since the pumping channel 121 extends in the horizontal direction, the opening of the pumping channel 121 can be easily sealed by depositing the cover layer 170, thereby achieving the purpose of vacuum sealing.

Thereafter, a step of selectively removing the cover layer material at the remaining locations may also be included.

In this step, since the first cavity is communicated with the outside through the air suction channel 121 and the air suction groove 111, the gas in the first cavity can be extracted during the process of vacuumizing, and the vacuum degree of the first cavity is improved; the second cavity is not communicated with the outside, so that the vacuumizing step does not influence the vacuum degree of the second cavity. Thus, the first MEMS structure and the second MEMS structure formed on the same substrate can be made to have different vacuum degrees.

The embodiments of the application solve the problem of hole sealing of products with different vacuum requirements integrated in an inertial device. The first groove with the preset pattern is processed through the special surface layout, the sacrificial layer is filled in the first groove, and a transverse air suction channel is formed after the sacrificial layer is released, so that the problem that the sealing material is difficult to fill in the vertical air suction hole is solved, and a good sealing effect can be achieved; after the sacrificial layer material is deposited, carrying out surface annealing to remove impurities in the sacrificial layer material, so as to avoid affecting the air tightness of the cavity; meanwhile, through the design of the layout, the sacrificial layer comprises a plurality of branches, gaps exist among the branches, so that when the first groove is etched, a concave part is etched at the gaps, and more gas absorption layer materials are deposited; processing an air exhaust groove with the upper opening size being larger than the lower opening size through the known selective silicon etching process such as TMAH and the like, facilitating the deposition of a subsequent covering layer, stopping etching on the sacrificial layer, and having simple and controllable process; through reasonable arrangement of the air suction channel, the problem that the air suction hole with a larger size is difficult to fill and seal is solved; according to the embodiment of the application, metal is deposited by PVD/evaporation equipment capable of achieving extreme vacuum (gyroscope vacuum degree), and the positions of the thinner sacrificial layers are filled, so that hole sealing and sealing are carried out. Provides a solution for sealing holes in the semiconductor back-end process without adopting an integral high-temperature process.

On the basis, the embodiment of the application also provides an MEMS device which is manufactured by adopting the packaging method of the MEMS device.

The MEMS device is specifically, for example, an inertial device. The MEMS device may include a first MEMS structure and a second MEMS structure having different vacuum requirements.

With continued reference to fig. 14, the mems device includes: the device comprises a cover substrate 100 and a device substrate 200 bonded with each other, wherein the device substrate 200 is provided with a first MEMS structure, the cover substrate 100 is provided with a first groove 131, and the first MEMS structure faces the first groove 131, so that the first groove 131 is formed into a first cavity for providing a movable space for the first MEMS structure; the inside of the cap substrate 100 is buried with a pumping channel 121 extending in a direction perpendicular to the thickness of the cap substrate 100; the cover substrate 100 has an air suction groove 111 on a side thereof remote from the device substrate 200; the air extraction channel 121 is communicated with the air extraction groove 111 and the first cavity, and the air extraction channel 121 and the air extraction groove 111 are used for extracting air from the first cavity; further comprises: the cover layer 170 seals at least the opening of the pumping channel 121 toward the pumping channel 111.

It should be noted that, the embodiment of the MEMS device provided by the present application and the embodiment of the packaging method of the MEMS device belong to the same concept; the features of the embodiments described in the present application may be combined arbitrarily without any conflict.

It should be understood that the above examples are illustrative and are not intended to encompass all possible implementations encompassed by the claims. Various modifications and changes may be made in the above embodiments without departing from the scope of the disclosure. Likewise, the individual features of the above embodiments can also be combined arbitrarily to form further embodiments of the application which may not be explicitly described. Therefore, the above examples merely represent several embodiments of the present application and do not limit the scope of protection of the patent of the present application.

Claims

1. A method of packaging a MEMS device, the method comprising:

pumping the first cavity through the pumping groove and the pumping channel;

2. The method of packaging a MEMS device of claim 1, wherein the providing a capping substrate comprises:

providing a first substrate;

forming a receiving groove on a first surface of the first substrate;

forming a sacrificial layer filling the accommodating groove;

providing a second substrate;

3. The method of claim 1, wherein the sacrificial layer comprises a plurality of branches to form a plurality of pumping channels that communicate the pumping channel and the first cavity in a direction perpendicular to a thickness of the capping substrate after removing at least a portion of the sacrificial layer via the pumping channel.

4. The method of packaging a MEMS device of claim 1, wherein the sacrificial layer comprises a plurality of branches, a gap being present between each branch;

5. The method of packaging a MEMS device of claim 1, wherein the device substrate further has a second MEMS structure formed thereon, the method further comprising:

forming a second groove on the first surface of the cover substrate;

6. The method of packaging a MEMS device of claim 1, wherein the device substrate further has a second MEMS structure formed thereon, the method further comprising:

7. The method of packaging a MEMS device of claim 1, wherein forming an air extraction trench in the second surface of the capping substrate comprises:

8. The method of packaging a MEMS device of claim 7, wherein the material at the second surface of the cap substrate comprises silicon; and forming an air suction groove on the second surface of the sealing cover substrate, wherein the air suction groove is implemented by adopting an etchant comprising tetramethyl amino hydroxide TMAH.

9. The method of packaging a MEMS device of claim 1, wherein the forming a cap layer comprises:

10. A MEMS device manufactured by the method of packaging a MEMS device according to any one of claims 1 to 9.