CN117088331A

CN117088331A - MEMS resonator structure and preparation method thereof

Info

Publication number: CN117088331A
Application number: CN202311210001.4A
Authority: CN
Inventors: 雷永庆; 谢国伟; 李明; 金怡; 朱彩伟; 林友玲
Original assignee: Mestar Microelectronics Shenzhen Co ltd
Current assignee: Mestar Microelectronics Shenzhen Co ltd
Priority date: 2023-09-19
Filing date: 2023-09-19
Publication date: 2023-11-21

Abstract

The application provides a MEMS resonator structure and a preparation method thereof, wherein the first substrate and a device wafer are electrically connected through a through silicon via structure, the device wafer and a second substrate are electrically connected through silicon bonding and eutectic bonding, and a vacuum resonant cavity is formed by sealing a first cavity and a second cavity; the silicon-silicon bonding between the first substrate and the device wafer avoids the problem of metal plastic deformation possibly generated by forming a metal bonding layer in the prior art, thereby greatly improving the reliability of the MEMS resonator, and the bonding process adopted in the MEMS resonator structure is mainly silicon bonding and eutectic bonding, thereby improving the structural consistency of the MEMS resonator and further improving the reliability of the formed device.

Description

MEMS resonator structure and preparation method thereof

Technical Field

The application relates to the technical field of micro-electromechanical systems, in particular to a MEMS resonator structure and a preparation method thereof.

Background

MEMS (Micro Electromechanical System, i.e., microelectromechanical systems) refers to microelectromechanical systems that integrate microsensors, actuators, and signal processing and control circuits, interface circuits, communications, and power, a high-tech frontend technology developed based on the latest efforts to integrate multiple micromachining technologies and employ modern information technology.

In particular resonators based on MEMS technology are playing an important role in modern electronics and sensors. The importance of MEMS resonators is mainly manifested in several aspects, such as: 1. the MEMS resonator can provide stable oscillation frequency, realizes high-precision clock and frequency control, and is a key for ensuring normal operation and data transmission of equipment in the fields of wireless communication, computers, consumer electronics and the like, so that the MEMS resonator becomes an ideal choice for realizing high-precision clock and frequency control; 2. the MEMS resonator can provide stable center frequency and narrow bandwidth, is used for frequency selection and filtering in a wireless communication system, realizes modulation, demodulation and filtering of signals, improves the performance and anti-interference capability of the wireless communication system, and can be also used for an oscillator and a filter in a radio frequency front-end module to realize high-performance radio frequency signal processing; 3. the MEMS resonator can realize high-precision measurement of environmental parameters (such as temperature, pressure, humidity and the like) through measuring frequency change, and can be widely applied to the field of sensors; 4. the MEMS resonator can be integrated with other electronic devices and systems on the same chip, so that highly integrated electronic equipment is realized, and the integrated mode can reduce the size of the equipment, reduce the power consumption of the equipment, improve the performance of the equipment and realize multi-function and multi-mode operation.

However, in the existing MEMS resonator structure, since the MEMS resonator needs to undergo frequent vibration and stress loading during the operation, the metal layer between the substrate and the device wafer often has problems such as plastic deformation, stress relaxation, and fatigue. The presence of the above problems can lead to deformation and damage of the metal layer, which affects both the performance and lifetime of the MEMS resonator and reduces the reliability of the MEMS resonator.

Based on the technical background, how to improve the reliability of the MEMS resonator without affecting the performance and the service life of the MEMS resonator becomes a problem to be solved currently.

Disclosure of Invention

In view of the above-mentioned drawbacks of the prior art, an object of the present application is to provide a MEMS resonator structure and a manufacturing method thereof, which are used for solving the problems of performance, reliability and lifetime degradation of the MEMS resonator caused by frequent vibration and deformation of a metal layer caused by stress loading during the operation of the MEMS resonator in the prior art.

To achieve the above and other related objects, the present application provides a method for manufacturing a MEMS resonator structure, comprising the steps of:

providing a first substrate, wherein the first substrate comprises a front surface and a back surface which are oppositely arranged, a patterned first barrier layer is formed on the front surface of the first substrate, and the first barrier layer is etched to form a plurality of island structures and first cavities;

providing a device wafer, wherein the device wafer comprises a first surface and a second surface which are oppositely arranged, the first surface of the device wafer is bonded with the front surface of the first substrate for the first time, and the second surface of the device wafer is etched to form a closed loop connecting part and a functional structure;

providing a second substrate, and etching the second substrate to form a second cavity;

bonding the second substrate and the second surface of the device wafer for the second time, so that the first cavity and the second cavity form a vacuum resonant cavity;

forming a patterned dielectric layer on the back of the first substrate, etching the dielectric layer to form an opening, exposing the first substrate to the opening, depositing metal in the opening, and performing patterned etching to form a metal lead layer, wherein the metal lead layer is electrically connected with the island structure.

Optionally, before forming the plurality of island structures and the first cavity, the method further comprises the steps of forming a plurality of deep trenches on the front surface of the first substrate, and forming an insulating ring by thermally and oxygen growing a dielectric material in the deep trenches.

Optionally, after etching to form the sealing ring connection portion and the functional structure, a step of thinning the back surface of the first substrate is further included, and after thinning, the insulating ring is exposed.

Optionally, after thinning the back surface of the first substrate, the method further includes a step of forming a first adhesive layer on the second surface of the device wafer.

Optionally, after forming the second cavity, a step of forming a metal layer on one side of the second substrate is further included, and bonding is performed between the metal layer and the first adhesive layer.

Optionally, after forming the second cavity, the method further comprises a step of depositing a getter in the second cavity to form a getter layer with a certain thickness.

Optionally, the method further comprises the step of locally etching two sides of the air suction layer so that the air suction layer is not connected with the side wall of the second cavity, wherein a certain gap is further formed between the air suction layer and the top of the second substrate, and the size of the gap is 1-10 μm.

Optionally, the functional structure at least includes a harmonic oscillator, a driving electrode and an induction electrode, wherein, the harmonic oscillator is located the driving electrode with the centre of induction electrode, and harmonic oscillator, driving electrode and induction electrode all with protruding island structure electricity is connected.

Optionally, the first bond is a silicon-silicon bond and the second bond is a eutectic bond.

The present application also provides a MEMS resonator structure comprising:

the semiconductor device comprises a first substrate, a second substrate, a first substrate and a second substrate, wherein the first substrate is provided with a front surface and a back surface which are oppositely arranged, a first blocking layer is arranged on the front surface of the first substrate, a plurality of deep grooves are formed in the front surface of the first substrate, dielectric materials are filled in the deep grooves to form insulating rings, a plurality of island structures and first cavities are also formed in the first substrate, and the island structures are positioned between the insulating rings;

the dielectric layer is positioned on the back surface of the first substrate and exposes the first substrate in the region corresponding to the island structure, and the metal lead layer is positioned on the dielectric layer and is electrically connected with the island structure through the first substrate;

the device wafer is provided with a first surface and a second surface which are oppositely arranged, the first surface of the device wafer is connected with the first substrate through silicon-silicon bonding, a closed loop connecting part and a functional structure are arranged in the device wafer, the closed loop connecting part is electrically connected with the first substrate, and the functional structure is electrically connected with the island structure;

and the second substrate is internally provided with a second cavity, and the second substrate is electrically connected with the second surface of the device wafer, so that the first cavity and the second cavity form a vacuum resonant cavity.

Optionally, a first adhesive layer is further disposed on the second surface of the device wafer, and the first adhesive layer is electrically connected to the device wafer.

Optionally, a metal layer is disposed on one side of the second substrate, and the metal layer is connected with the first bonding layer through eutectic bonding.

Optionally, an air-absorbing layer is further disposed in the second cavity, wherein the air-absorbing layer is not connected with the side wall of the second cavity.

Optionally, a certain gap exists between the getter layer and the top of the second substrate, and the size of the gap is 1-10 μm.

Optionally, the thickness of the insulating ring is 4 μm to 12 μm.

Optionally, the thickness of the dielectric layer is 2 μm to 4 μm.

Optionally, the thickness of the device wafer is 10 μm to 40 μm.

As described above, the MEMS resonator structure and the preparation method thereof have the following beneficial effects: the first substrate and the device wafer are electrically connected through the through silicon vias formed by the deep trenches and the convex island structures, so that the density of the MEMS resonator stacked in the three-dimensional direction is maximized, and compared with the traditional metal electrical connection, the interconnection lines between the wafer substrates are shortest and have the smallest outline dimension, thereby remarkably improving the transmission speed of electric signals and reducing the power consumption and the dimension of the MEMS resonator; the direct silicon bonding of the first substrate and the device wafer avoids the problem of metal plastic deformation possibly generated by forming a metal bonding layer in the prior art, thereby greatly improving the reliability of the MEMS resonator structure; and a gas absorbing layer is arranged in the second cavity, and a certain gap exists between the gas absorbing layer and the device wafer, so that no interaction force exists between the second substrate and the device wafer, and the internal stress of the MEMS resonator structure is smaller, thereby improving the performance of the device.

Drawings

Fig. 1 is a schematic flow chart of a method for manufacturing a MEMS resonator structure according to the present application.

Fig. 2 is a schematic cross-sectional view showing a first substrate of the MEMS resonator of the present application.

Fig. 3 is a schematic cross-sectional structure of the MEMS resonator according to the present application after forming a deep trench.

Fig. 4 is a schematic diagram showing a cross-sectional structure of the MEMS resonator according to the present application after a dielectric material is grown in the deep trench.

Fig. 5 is a schematic cross-sectional view of the MEMS resonator of the present application after the island structure and the first cavity are formed.

Fig. 6 is a schematic cross-sectional view of a MEMS resonator according to the present application after bonding a device wafer to a first substrate.

Fig. 7 is a schematic cross-sectional view showing the structure of the MEMS resonator of the present application after forming the closed loop connection and the functional structure.

Fig. 8 is a schematic cross-sectional view of a MEMS resonator according to the present application after a second cavity is formed in a second substrate.

Fig. 9 is a schematic cross-sectional view of a MEMS resonator according to the present application after a metal layer is formed on a second substrate.

Fig. 10 is a schematic cross-sectional view of the MEMS resonator of the present application after a gettering layer is formed in the second cavity.

Fig. 11 is a schematic cross-sectional view of a MEMS resonator according to the present application after bonding a metal layer to a device wafer.

Fig. 12 is a schematic cross-sectional view of a MEMS resonator according to the present application after a dielectric layer is formed.

Fig. 13 is a schematic cross-sectional view showing a structure after forming a metal wiring layer in the MEMS resonator of the present application.

Fig. 14 is a schematic top view of a device wafer in a MEMS resonator according to the present application.

Fig. 15 is a schematic cross-sectional view of a MEMS resonator according to a second embodiment of the present application.

Fig. 16 is a schematic cross-sectional view of a MEMS resonator according to a third embodiment of the present application.

Fig. 17 is a schematic cross-sectional view of a MEMS resonator according to a fourth embodiment of the present application.

Description of element reference numerals

101. A first substrate; 102. a first barrier layer; 103. deep trenches; 1031. an insulating ring; 104. a first cavity; 1041. a convex island structure; 105. a device wafer; 1051. a functional structure; 1052. a closed loop connection part; 1053. an induction electrode; 1054. a harmonic oscillator; 1055. a driving electrode; 106. a second substrate; 107. a second cavity; 108. a metal layer; 109. an air-absorbing layer; 110. a dielectric layer; 111. a metal lead layer; 112. a first adhesive layer; S1-S5, and the step.

Detailed Description

Other advantages and effects of the present application will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present application with reference to specific examples. The application may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present application.

As described in detail in the embodiments of the present application, the schematic drawings showing the structure of the apparatus are not partially enlarged to general scale, and the schematic drawings are merely examples, which should not limit the scope of the present application. In addition, the three-dimensional dimensions of length, width and depth should be included in actual fabrication.

For ease of description, spatially relative terms such as "under", "below", "beneath", "above", "upper" and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that these spatially relative terms are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the figures.

In the context of the present application, a structure described as a first feature being "on" a second feature may include embodiments where the first and second features are formed in direct contact, as well as embodiments where additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

Referring to fig. 1 to 17, it should be noted that the illustrations provided in the present embodiment are only schematic illustrations of the basic concept of the present application, and only the components related to the present application are shown in the illustrations, rather than being drawn according to the number, shape and size of the components in actual implementation, and the form, number and proportion of each component in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.

Embodiment one:

the embodiment provides a preparation method of a MEMS resonator structure, as shown in fig. 1, which is shown as a preparation process flow chart of the preparation method, and includes the following steps:

s1: providing a first substrate 101, wherein the first substrate 101 comprises a front surface and a back surface which are oppositely arranged, forming a patterned first barrier layer 102 on the front surface of the first substrate 101, and etching the first barrier layer 102 to form a plurality of island structures 1041 and first cavities 104;

s2: providing a device wafer 105, wherein the device wafer 105 comprises a first surface and a second surface which are oppositely arranged, the first surface of the device wafer 105 is bonded with the front surface of the first substrate 101 for the first time, and the second surface of the device wafer 105 is etched to form a closed loop connecting part 1052 and a functional structure 1051;

s3: providing a second substrate 106, and etching the second substrate 106 to form a second cavity 107;

s4: bonding the second substrate 106 to the second surface of the device wafer 105 a second time, such that the first cavity 104 and the second cavity 107 form a vacuum cavity;

s5: a patterned dielectric layer 110 is formed on the back surface of the first substrate 101, and an opening is etched on the dielectric layer 110, where the opening exposes the first substrate 101, a metal is deposited in the opening, and patterned etching is performed to form a metal lead layer 111, where the metal lead layer 111 is electrically connected with the island structure 1041.

The following describes a method for preparing the MEMS resonator structure with reference to the accompanying drawings, specifically as follows:

in step S1, referring to fig. 1 to 5, a first substrate 101 is provided, the first substrate 101 includes a front surface and a back surface that are disposed opposite to each other, a patterned first barrier layer 102 is formed on the front surface of the first substrate 101, and the first barrier layer 102 is etched to form a plurality of island structures 1041 and first cavities 104.

Specifically, as shown in fig. 2, a schematic cross-sectional structure of the first substrate 101 is shown, where the first substrate 101 has a front surface and a back surface opposite to each other, the material of the first substrate 101 may be a silicon-based material, and besides, the material of the first substrate 101 may also include other element semiconductors (such as germanium), or other compound semiconductors (such as silicon carbide, gallium arsenide, indium phosphide, etc.), and preferably, in this embodiment, the material of the first substrate 101 is monocrystalline silicon.

As an example, before forming the plurality of island structures 1041 and the first cavity 104, the method further includes forming a plurality of deep trenches 103 on the front surface of the first substrate 101, and forming an insulating ring 1031 by thermally and oxygen growing a dielectric material in the deep trenches 103.

Specifically, as shown in fig. 3, the patterned first barrier layer 102 is formed prior to the front surface of the first substrate 101, where the first barrier layer 102 may be a silicon oxide layer obtained by thermal oxygen growth, and the silicon oxide layer obtained by thermal oxygen growth has a higher density and is less prone to be corroded than a silicon oxide layer obtained by chemical vapor deposition (Chemical Vapor Deposition, CVD). The etching process is performed based on the patterned first barrier layer 102 to form a plurality of deep trenches 103 parallel to each other, the deep trenches 103 may or may not penetrate through the first substrate 101, and since the subsequent thinning process is further performed on the back surface of the first substrate 101, in order to save thinning of the deep trenches 103, the deep trenches 103 are selected to have a certain depth but not penetrate through the first substrate 101, as shown in fig. 4, dielectric materials with a certain thickness are grown in the deep trenches 103 by thermal oxidation to form insulating rings 1031, optionally, the dielectric materials may be insulating materials such as silicon oxide, and preferably, in order to make the deep trenches 103 have no cavity and reduce the difficulty of the subsequent flattening process on the insulating rings 1031, conductive metals and dielectric materials may be filled in the deep trenches 103 to fill the whole deep trenches 103, and flattening processes are performed on the insulating rings 1031 and the conductive metals in the deep trenches 103, so that the insulating rings 1031 and the conductive metals are flush with the front surface of the first substrate 101. The insulating rings 1031 and the conductive metal and the first sub-substrate between the insulating rings 1031 form a through-silicon via structure.

Specifically, as shown in fig. 5, the first blocking layer 102 is removed, then a patterned shielding layer (not shown in the drawing) is formed on the front surface of the first substrate 101, and the shielding layer and the first substrate 101 are etched again, so that a plurality of island structures 1041 and first cavities 104 are formed on the front surface of the first substrate 101, the island structures 1041 are located in the area of the first substrate 101 between the two insulating rings 1031, the first cavities 104 are located between the two island structures 1041 or between the island structures 1041 and the first substrate 101 that is not etched, the number of the island structures 1041 and the first cavities 104 is not limited, in this embodiment, the number of the island structures 1041 is 3, and of course, in other embodiments, the number of the island structures 1041 may be other.

In step S2, referring to fig. 1, 6 and 7, a device wafer 105 is provided, where the device wafer 105 includes a first surface and a second surface that are disposed opposite to each other, the first surface of the device wafer 105 is bonded to the front surface of the first substrate 101 for the first time, and the second surface of the device wafer 105 is etched to form a closed loop connection 1052 and a functional structure 1051.

Specifically, in this embodiment, as shown in fig. 6, a device wafer 105 is provided, where the device wafer 105 includes a first surface and a second surface opposite to each other, and the material of the device wafer 105 may be a silicon-based material, and in addition, the material of the device wafer 105 may also include other element semiconductors (such as germanium), or other compound semiconductors (such as silicon carbide, gallium arsenide, indium phosphide, etc.), and preferably, the material of the device wafer 105 is monocrystalline silicon. The first surface of the device wafer 105 and the front surface of the first substrate 101 are bonded, and since the device wafer 105 and the first substrate 101 are made of monocrystalline silicon, the bonding between the device wafer 105 and the first substrate 101 is silicon-silicon fusion bonding, so that problems caused by plastic deformation possibly generated by a metal intermediate adhesive layer are avoided, and the reliability of the device is greatly improved.

As an example, the step of thinning the back surface of the first substrate 101 is further included after etching to form the closed loop connection portion 1052 and the functional structure 1051, and the insulating ring 1031 is exposed after thinning.

Specifically, as shown in fig. 6, before etching the device wafer 105, the back surface of the first substrate 101 is thinned, and after thinning, the insulating ring 1031 is exposed, so that the conductive region in the through-silicon via structure is isolated by the insulating ring 1031.

Specifically, as shown in fig. 7, after the device wafer 105 is bonded to the first substrate 101, the second surface of the device wafer 105 is etched to form a closed loop connection portion 1052 and a functional structure 1051, where the connection between the closed loop connection portion 1052 and the front surface of the first substrate 101 is achieved by silicon-silicon eutectic bonding, as shown in fig. 14, in this embodiment, the functional structure 1051 is located in the middle of the closed loop connection portion 1052, the functional structure 1051 includes at least one resonator 1054, one driving electrode 1055 and one sensing electrode 1053, and the resonator 1054 is located in the middle of the driving electrode 1055 and the sensing electrode 1053, and the resonator 1054, the driving electrode 1055 and the sensing electrode 1053 are all electrically connected with the island structure 1041.

In step S3, referring to fig. 1 and 8, a second substrate 106 is provided, and the second substrate 106 is etched to form a second cavity 107.

Specifically, as shown in fig. 8, in the present embodiment, the second substrate 106 is provided, and the material of the second substrate 106 may be a silicon-based material, in addition to that, the material of the second substrate 106 may also include other element semiconductors (such as germanium), or other compound semiconductors (such as silicon carbide, gallium arsenide, indium phosphide, etc.), and preferably, in the present embodiment, the material of the second substrate 106 is monocrystalline silicon. The second substrate 106 is etched to form a second cavity 107, wherein the area of the second cavity 107 is larger than the area of the functional structure 1051.

In step S4, referring to fig. 1 and 11, the second substrate 106 is bonded to the second surface of the device wafer 105 for the second time, so that the first cavity 104 and the second cavity 107 form a vacuum resonator.

Specifically, as shown in fig. 11, the second substrate 106 is bonded to the second surface of the device wafer 105 for the second time, and since the second substrate 106 and the device wafer 105 are made of monocrystalline silicon materials, eutectic bonding is formed between the second substrate 106 and the device wafer 105, so that the problem caused by plastic deformation possibly generated by a metal adhesive layer is avoided, the reliability of the device is greatly improved, and the first cavity 104 and the second cavity 107 are formed by the eutectic bonding formed between the second substrate 106 and the device wafer 105, and the vacuum cavity can provide a stable working environment for the resonator 1054.

In some embodiments, after thinning the back surface of the first substrate 101, a step of forming a first adhesive layer 112 on the second surface of the device wafer 105 is further included. Specifically, as shown in fig. 9, a first adhesive layer 112 is formed on the second surface of the device wafer 105, and the first adhesive layer 112 is subjected to patterned etching, so that the first adhesive layer 112 is located at the closed loop connection portion 1052, so that the first adhesive layer 112 and the subsequent second substrate 106 can be bonded, the sealing degree of the device is improved, preferably, the material of the first adhesive layer 112 is polysilicon, and when the polysilicon is bonded with other metals, the requirement on the flatness of the bonding surface is low, so that the difficulty of the bonding process is low, and in addition, silicon bonding can be formed between the first adhesive layer 112 of polysilicon and the second substrate 106, so that the problem caused by plastic deformation possibly generated by the metal adhesive layer is avoided, and the reliability of the device is greatly improved.

In some embodiments, after forming the second cavity 107, a step of forming a metal layer 108 on one side of the second substrate 106 is further included. Specifically, as shown in fig. 9, the metal layer 108 is formed on one side of the second substrate 106, preferably, the metal layer 108 is made of gold, and when the metal layer 108 is bonded to the first adhesive layer 112, a gold-silicon bond is formed between the metal layer 108 and the first adhesive layer 112, so that the sealing strength can be improved, and the vacuum degree of the vacuum resonant cavity formed after the subsequent bonding of the device wafer 105 and the second substrate 106 can be more effectively maintained.

In some embodiments, the metal layer 108 may also be bonded to the first adhesive layer 112 on the second surface of the device wafer 105, so that the first cavity 104 and the second cavity 107 form a vacuum cavity, which can provide a stable working environment for the resonator 1054.

In some embodiments, after forming the second cavity 107, the method further includes a step of depositing a getter in the second cavity 107 to form a getter layer 109 with a certain thickness, and further includes a step of locally etching two sides of the getter layer 109 so that the getter layer 109 is not connected to the sidewall of the second cavity 107, wherein a certain gap is further present between the getter layer 109 and the top of the second substrate 106, and the size of the gap is 1 μm to 10 μm.

Specifically, as shown in fig. 10, in order to maintain the vacuum low-pressure environment in the vacuum resonant cavity, before the bonding process is performed on the second substrate 106 and the device wafer 105, a getter is deposited in the second cavity 107 to form a getter layer 109 with a certain thickness, and partial etching is performed on two sides of the getter layer 109 so that the getter layer 109 is not connected to the side wall of the second cavity 107, and a certain gap is preferably formed between the getter layer 109 and the top of the second substrate 106, and the size of the gap may be 1 μm to 10 μm, for example, 1 μm, 3 μm, 5 μm, 7 μm, 9 μm or 10 μm, and may be specifically set according to practical needs. Because of the gap between the getter layer 109 and the second substrate 106, no interaction force exists between the second substrate 106 and the device wafer 105, so that the internal stress of the MEMS resonator structure is small, and the structure and the function of the device are ensured.

In step S5, referring to fig. 1, 12 and 13, a patterned dielectric layer 110 is formed on the back surface of the first substrate 101, and an opening is etched on the dielectric layer 110, where the opening exposes the first substrate 101, metal is deposited in the opening, and patterned etching is performed to form a metal lead layer 111, and the metal lead layer 111 is electrically connected to the island structure 1041.

Specifically, as shown in fig. 12, a patterned dielectric layer 110 is formed on the back surface of the first substrate 101, and the patterned dielectric layer 110 is etched to form openings, where the first substrate 101 between the insulating rings 1031 is exposed, and optionally, the material of the dielectric layer 110 includes silicon oxide, silicon nitride or other suitable dielectric material, and as shown in fig. 13, a metal is deposited in the openings to form the metal lead layer 111. Optionally, the material of the metal lead layer 111 includes titanium, titanium nitride, silver, gold, copper, aluminum, tungsten, or other suitable conductive material.

According to the preparation method of the MEMS resonator structure, the first substrate 101 and the device wafer 105 are electrically connected through the through silicon via structure formed by the insulating ring 1031 and the first substrate 101, so that the density of the MEMS resonator stacked in the three-dimensional direction is maximum, and compared with the traditional metal electrical connection, the interconnection line between the wafers is shortest, and therefore the transmission speed of electric signals can be remarkably improved, and the power consumption and the size of the MEMS resonator are reduced; in addition, in the embodiment of the application, the first substrate 101 and the device wafer 105 are directly bonded through silicon, so that the problem of metal plastic deformation possibly generated by forming a metal bonding layer in the prior art is avoided, the reliability of the MEMS resonator is greatly improved, the bonding process adopted in the MEMS resonator structure is mainly silicon bonding and eutectic bonding, the consistency of the MEMS resonator structure is improved, the reliability of the formed device is further improved, and the getter layer 109 with a certain gap with the device wafer 105 is arranged in the second cavity 107, so that no interaction force exists between the second substrate 106 and the device wafer 105, and the internal stress of the MEMS resonator structure is smaller, thereby improving the performance of the device.

Embodiment two:

the present embodiment provides a MEMS resonator structure, as shown in fig. 15, which is a schematic cross-sectional structure of the MEMS resonator structure, and the MEMS resonator structure includes: the semiconductor device comprises a first substrate 101, wherein the first substrate 101 is provided with a front surface and a back surface which are oppositely arranged, a first barrier layer 102 is arranged on the front surface of the first substrate 101, a plurality of deep trenches 103 are formed on the front surface of the first substrate 101, dielectric materials are filled in the deep trenches 103 to form an insulating ring 1031, a plurality of island structures 1041 and first cavities 104 are also formed in the first substrate 101, and the island structures 1041 are positioned between the insulating rings 1031; a dielectric layer 110 and a metal lead layer 111, wherein the dielectric layer 110 is located on the back surface of the first substrate 101 and exposes the first substrate 101 in a region corresponding to the island structure 1041, and the metal lead layer 111 is located on the dielectric layer 110 and is electrically connected with the island structure 1041 through the first substrate 101; a device wafer 105, where the device wafer 105 has a first surface and a second surface that are disposed opposite to each other, the first surface of the device wafer 105 is connected to the first substrate 101 by silicon-silicon bonding, a closed loop connection portion 1052 and a functional structure 1051 are disposed in the device wafer 105, and the closed loop connection portion 1052 is electrically connected to the first substrate 101, and the functional structure 1051 is electrically connected to the island structure 1041; a second substrate 106, wherein a second cavity 107 is formed in the second substrate 106, and the second substrate 106 is electrically connected to the second surface of the device wafer 105, so that the first cavity 104 and the second cavity 107 form a vacuum resonant cavity.

Specifically, the materials of the first substrate 101, the device wafer 105 and the second substrate 106 may be silicon-based materials, and in addition, the materials of the first substrate 101, the device wafer 105 and the second substrate 106 may also include other element semiconductors (such as germanium), or other compound semiconductors (such as silicon carbide, gallium arsenide, indium phosphide, etc.), because the materials of the first substrate 101, the device wafer 105 and the second substrate 106 do not affect implementation of the technical solution, and the materials of the first substrate 101, the device wafer 105 and the second substrate 106 are not limited in the present application. Preferably, in some embodiments, the materials of the first substrate 101, the device wafer 105, and the second substrate 106 are monocrystalline silicon, so that the robustness of the device can be enhanced, and the Q value of the MEMS resonator structure can be further improved due to the low interface loss between the same materials.

Specifically, at least one dielectric layer 110 is further disposed on the back surface of the first substrate 101, and the dielectric layer 110 is used to locally isolate the electrical conduction between the metal lead layer 111 and the first substrate 101. The material of the dielectric layer 110 includes silicon oxide, silicon nitride, or other suitable dielectric material. The thickness of the dielectric layer 110 is 2 μm to 4 μm, for example, may be 2 μm, 3 μm or 4 μm, and in case of satisfying the performance of the MEMS resonator structure, the thickness of the dielectric layer 110 may be selected according to practical situations, and is not limited herein.

Specifically, the dielectric material includes silicon oxide, silicon nitride, or other suitable dielectric material, and the insulating ring 1031 formed by filling the dielectric material in the dielectric material is flush with the front surface of the first substrate 101. Alternatively, the shape of the insulating ring 1031 may be a circular, square, or a profiled geometry, without limitation. The thickness of the insulating ring 1031 is 4 μm to 12 μm, for example, may be 4 μm, 8 μm or 12 μm, and in the case of satisfying the performance of the MEMS resonator structure, the thickness of the insulating ring 1031 may be selected according to the actual situation, and is not limited herein.

Specifically, the device wafer 105 includes a closed loop connection portion 1052 and a functional structure 1051, the functional structure 1051 includes at least one resonator 1054, one driving electrode 1055 and one sensing electrode 1053, wherein the functional structure 1051 is located between the closed loop connection portion 1052, the resonator 1054 is located between the driving electrode 1055 and the sensing electrode 1053, and the resonator 1054, the driving electrode 1055 and the sensing electrode 1053 are all electrically connected with the island structure 1041 on the first substrate 101, so as to realize conduction of a circuit.

Specifically, the thickness of the device wafer 105 is 10 μm to 40 μm, for example, 10 μm, 20 μm, 30 μm or 40 μm, and in the case of satisfying the performance of the MEMS resonator structure, the thickness of the device wafer 105 may be selected according to the actual situation, and is not limited herein.

Specifically, the second substrate 106 has a second cavity 107 inside, where an area of the second cavity 107 is larger than an area of the functional structure 1051, and the second substrate 106 is electrically connected to the second surface of the device wafer 105, so that the first cavity 104 and the second cavity 107 form a vacuum resonant cavity, and the vacuum resonant cavity provides a stable working environment for the resonator 1054.

In this embodiment, the second cavity 107 is further provided with an air-absorbing layer 109, and the air-absorbing layer 109 is not connected to the sidewall of the second cavity 107, and has a certain gap with the top of the second substrate 106, where the size of the gap is 1 μm-10 μm.

Specifically, as shown in fig. 15, the second cavity 107 is provided with an air-absorbing layer 109, and the air-absorbing layer 109 is not connected to the sidewall of the second cavity 107, and a certain gap is formed between the air-absorbing layer and the top of the second substrate 106, preferably, the gap has a size of 1 μm to 10 μm, for example, 1 μm, 3 μm, 5 μm, 7 μm, 9 μm or 10 μm, and may be specifically set according to practical needs. The presence of the gettering layer 109 may maintain a vacuum low pressure environment within the vacuum cavity, and since a certain gap exists between the gettering layer 109 and the top of the second substrate 106, there is no interaction force between the second substrate 106 and the device wafer 105, so that the internal stress of the MEMS resonator structure is reduced, which is helpful for improving the performance of the device.

Example III

The present embodiment provides a MEMS resonator structure, as shown in fig. 16, which is a schematic cross-sectional structure of the MEMS resonator structure of the present embodiment, and the difference between the present embodiment and the second embodiment is that the second surface of the device wafer 105 is further provided with a first adhesive layer 112.

Specifically, as shown in fig. 16, the first adhesive layer 112 is located on the closed loop connection portion 1052, and the first adhesive layer 112 and the second substrate 106 can be directly bonded, so as to improve the sealing degree of the device, preferably, the material of the first adhesive layer 112 is polysilicon, so that the requirement on the flatness of the bonding surface is low when the polysilicon is bonded with other metals, and the bonding process difficulty is low.

Example IV

The present embodiment provides a MEMS resonator structure, as shown in fig. 17, which is a schematic cross-sectional structure of the MEMS resonator structure of the present embodiment, and the difference between the present embodiment and the third embodiment is that a metal layer 108 is further formed on one side of the second substrate 106.

Specifically, as shown in fig. 17, a metal layer 108 is formed on one side of the second substrate 106, and the metal layer 108 is fixedly connected to the first adhesive layer 112, preferably, the material of the metal layer 108 is gold, so that the device wafer 105 and the second substrate 106 are encapsulated by eutectic bonding.

Preferably, the metal layer 108 is made of gold, and when the metal layer 108 and the first adhesive layer 112 are bonded together, eutectic bonding is formed between the metal layer 108 and the first adhesive layer 112, and because the eutectic bonding only occurs between the closed loop connection portion 1052 and the second substrate 106 and does not occur in the areas of the resonator 1054, the driving electrode 1055 and the sensing electrode 1053, the problem of plastic deformation possibly caused by introduction of the metal adhesive layer is avoided, the reliability of the device is greatly improved, and in addition, the eutectic bonding between the closed loop connection portion 1052 and the second substrate 106 can improve the sealing strength, so that the vacuum degree of the vacuum resonant cavity can be more effectively maintained.

In summary, according to the MEMS resonator structure and the manufacturing method thereof, the first substrate and the device wafer are electrically connected through the through-silicon via structure formed by the insulating ring and the first substrate, so that the density of stacking the MEMS resonator in the three-dimensional direction is maximized, and compared with the conventional metal electrical connection, the interconnection line between the wafers in the embodiment of the application is shortest, thereby remarkably improving the transmission speed of the electrical signals and reducing the power consumption and the size of the MEMS resonator; in addition, the first substrate and the device wafer are directly bonded through silicon, the problem that metal plastic deformation possibly occurs when a metal bonding layer is formed in the prior art is avoided, and therefore reliability of the MEMS resonator is greatly improved. Therefore, the application effectively overcomes various defects in the prior art and has high industrial utilization value.

The above embodiments are merely illustrative of the principles of the present application and its effectiveness, and are not intended to limit the application. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the application. Accordingly, it is intended that all equivalent modifications and variations of the application be covered by the claims, which are within the ordinary skill of the art, be within the spirit and scope of the present disclosure.

Claims

1. A method of fabricating a MEMS resonator structure comprising the steps of:

2. The method of fabricating a MEMS resonator structure of claim 1, wherein: before forming the plurality of island structures and the first cavity, the method further comprises the steps of forming a plurality of deep trenches on the front surface of the first substrate, and forming an insulating ring by thermally and oxygen growing a dielectric material in the deep trenches.

3. The method of fabricating a MEMS resonator structure of claim 2, wherein: the step of thinning the back surface of the first substrate is further included after the sealing ring connecting part and the functional structure are formed by etching, and the insulating ring is exposed after the step of thinning.

4. A method of fabricating a MEMS resonator structure according to claim 3, wherein: after the back surface of the first substrate is thinned, the method further comprises the step of forming a first bonding layer on the second surface of the device wafer.

5. The method of fabricating a MEMS resonator structure of claim 4 wherein: after forming the second cavity, the method further comprises the step of forming a metal layer on one side of the second substrate, and bonding between the metal layer and the first adhesive layer.

6. The method of fabricating a MEMS resonator structure of claim 1, wherein: after the second cavity is formed, the method further comprises the step of depositing a getter in the second cavity to form a getter layer with a certain thickness.

7. The method of fabricating a MEMS resonator structure of claim 6 wherein: the method further comprises the step of carrying out partial etching on two sides of the air suction layer so that the air suction layer is not connected with the side wall of the second cavity, wherein a certain gap is formed between the air suction layer and the top of the second substrate, and the size of the gap is 1-10 mu m.

8. The method of fabricating a MEMS resonator structure of claim 1, wherein: the functional structure at least comprises a harmonic oscillator, a driving electrode and an induction electrode, wherein the harmonic oscillator is positioned between the driving electrode and the induction electrode, and the harmonic oscillator, the driving electrode and the induction electrode are electrically connected with the island structure.

9. A method of fabricating a MEMS resonator structure according to any one of claims 1-8, wherein: the first bonding is silicon-silicon bonding, and the second bonding is eutectic bonding.

10. A MEMS resonator structure, the resonator structure comprising: