A method for preparing a micromechanical resonator

Abstract

The present invention provides a method for preparing a micromechanical resonator, which includes the following steps: obtaining a substrate structure, wherein the substrate structure is formed with a resonant portion and two electrode portions located on both sides of the resonant portion and spaced apart; growing a sacrificial layer on the substrate structure and patterning it, so as to partially expose the resonant portion and the two electrode portions; depositing a first polysilicon and patterning it, so as to form a resonant structure, an input electrode and an output electrode corresponding to the resonant portion and the two electrode portions, wherein a capacitance gap is formed between the input electrode and the output electrode and the resonant structure; releasing the sacrificial layer under the resonant structure to obtain a resonator wafer; preparing a package cover, vacuum bonding the package cover and the resonator wafer, and forming a MEMS resonator. The vacuum airtightness is ensured, and the overall process is simple and reliable, and high-precision, high-quality, large-scale and low-cost preparation can be achieved.

Description

Technical Field

[0001] The invention relates to the technical field of micro-electromechanical systems, and in particular to a method for preparing a micromechanical resonator. Background Art

[0002] High-precision resonator products are mainly aimed at high-performance, portable smart terminal markets such as 5G smart terminals, tablets, and wearable devices. With the development of advanced manufacturing technology, the size of electronic products continues to shrink, requiring electronic components to continue to develop towards miniaturization. Micromechanical resonators have the advantages of small size, high Q value, easy integration with IC circuits, low power consumption, and high reliability. They have adapted to the development needs of modern wireless communication technology and have moved from laboratories to actual production. They play an indispensable role in all aspects of the national economy, including communications, aerospace technology, transportation technology, biomedical fields, and the defense industry. Therefore, the demand for micromechanical resonators is growing.

[0003] However, to date, the manufacturing technology of micromechanical resonators cannot meet the large-scale manufacturing needs of the industrialization of high-end devices. Engineering problems such as manufacturing process consistency, yield, vacuum packaging methods and costs need to be broken through. It is urgent to develop a simple, highly reliable, high-yield, low-cost manufacturing method for MEMS resonators. In addition, vacuum airtight packaging is a necessary condition to ensure the normal operation of high-end resonators. In order to reduce manufacturing costs and noise interference, it is crucial to develop three-dimensional vacuum airtight packaging technology. Summary of the invention

[0004] The main purpose of the present invention is to provide a method for preparing a micromechanical resonator, aiming to solve the technical problem that the micromechanical resonator is difficult to manufacture.

[0005] To achieve the above object, the present invention provides a method for preparing a micromechanical resonator, which is characterized by comprising the following steps:

[0006] Acquire a substrate structure, wherein the substrate structure is formed with a resonant portion and two electrode portions located on both sides of the resonant portion and spaced apart from each other;

[0007] Growing a sacrificial layer on the substrate structure and patterning it so as to partially expose the resonant portion and the two electrode portions;

[0008] Depositing a first polysilicon and patterning it, forming a resonant structure, an input electrode and an output electrode corresponding to the resonant portion and the two electrode portions, wherein a capacitance gap is formed between the input electrode and the output electrode and the resonant structure;

[0009] releasing the sacrificial layer under the resonant structure to obtain a resonator wafer;

[0010] A packaging cover sheet is prepared, and the packaging cover sheet and the resonator wafer are vacuum bonded to form a MEMS resonator.

[0011] Optionally, the step of obtaining a substrate structure, wherein the substrate structure is formed with a resonant portion and two electrode portions located on both sides of the resonant portion and spaced apart from each other, comprises:

[0012] Obtain a silicon substrate substrate, grow a dielectric layer on the surface of the silicon substrate substrate and pattern it as a signal isolation layer;

[0013] A second polysilicon is deposited and patterned to form the resonance portion and the two electrode portions as a signal transmission layer, wherein the signal transmission layer and the signal isolation layer together form the substrate structure.

[0014] Optionally, the material of the dielectric layer includes any one of silicon oxide and silicon nitride.

[0015] Optionally, a packaging ring is formed by depositing the first polysilicon and patterning it, and the input electrode, the resonant structure and the output electrode are all located in the packaging ring;

[0016] Before releasing the sacrificial layer under the resonant structure and obtaining the resonator wafer, the step further includes:

[0017] A metal layer is deposited and patterned, two electrode pads are formed corresponding to the input electrode and the output electrode, and a packaging ring pad is formed corresponding to the packaging ring.

[0018] Optionally, the material of the electrode pad and the packaging ring pad includes any one of Si, Au, Sn, In, Al and glass paste.

[0019] Optionally, the step of preparing the package cover sheet includes:

[0020] Obtain a silicon substrate, and arrange two conductive silicon pillars on the silicon substrate corresponding to the input electrode and the output electrode, and arrange two insulating structures corresponding to the two conductive silicon pillars;

[0021] The silicon substrate comprises a packaging surface and an exposed surface which are arranged opposite to each other, and a packaging cavity is formed on the packaging surface, wherein the two conductive silicon pillars are located in the packaging cavity, and the ends thereof are arranged to protrude from the bottom wall of the packaging cavity;

[0022] A surface metal layer is prepared on the exposed surface, and a welding structure is prepared on one side of the packaging surface, wherein the surface metal layer is arranged corresponding to the conductive silicon column to form the packaging cover sheet.

[0023] Optionally, a packaging ring is formed by depositing the first polysilicon and patterning it, and the input electrode, the resonant structure and the output electrode are all located in the packaging ring;

[0024] The welding structure includes a packaging pad arranged corresponding to the packaging ring and an electrical pad arranged corresponding to the end surfaces of the two conductive silicon columns.

[0025] Optionally, the step of obtaining a silicon substrate, providing two conductive silicon pillars on the silicon substrate corresponding to the input electrode and the output electrode, and providing two insulating structures corresponding to the two conductive silicon pillars further includes:

[0026] Obtain a silicon substrate, and etch two annular grooves on the silicon substrate corresponding to the input electrode and the output electrode to form the two conductive silicon pillars;

[0027] Filling insulating material in the two annular grooves to form the insulating structure;

[0028] The silicon substrate is ground to expose the conductive silicon pillar and the insulating structure on both side end surfaces of the silicon substrate.

[0029] Optionally, the insulating material includes any one of SiO2, glass and silicon nitride.

[0030] Optionally, the material of the sacrificial layer includes any one of SiO2 and PSG.

[0031] In the technical solution provided by the present invention, a resonant structure, an input electrode and an output electrode are formed by depositing a first polysilicon and patterning it. The active resonant chip of the sacrificial layer under the resonant structure is released, and the sealing of the resonator is achieved through a packaging cover to ensure vacuum airtightness. The overall process is simple and reliable, and can achieve high-precision, high-quality, large-scale and low-cost production. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the overall cross-sectional structure of the MEMS resonator provided by the present invention;

[0033] Figure 2 A schematic cross-sectional view of a substrate structure provided by the present invention;

[0034] Figure 3 for Figure 2 A schematic cross-sectional structure diagram of depositing a first polysilicon;

[0035] Figure 4 for Figure 3 A schematic cross-sectional structure diagram of releasing the sacrificial layer;

[0036] Figure 5A schematic diagram of the cross-sectional structure of a growth medium layer of a silicon substrate provided by the present invention;

[0037] Figure 6 for Figure 5 A schematic cross-sectional structure diagram of depositing a second polysilicon;

[0038] Figure 7 for Figure 4 A schematic diagram of the cross-sectional structure of a deposited metal layer;

[0039] Figure 8 A schematic cross-sectional structural diagram of a silicon substrate provided by the present invention;

[0040] Fig. 9 for Figure 8 A schematic diagram of a cross-sectional structure of a packaging cavity prepared in FIG.

[0041] Fig.10 for Fig. 9 Schematic diagram of the cross-sectional structure of the prepared surface metal layer and the welding structure;

[0042] Fig.11 This is a schematic diagram of the cross-sectional structure of the silicon substrate provided by the present invention.

[0043] Description of Figure Numbers:

[0044] Label name Label name 1 Resonant structure 10 Surface metal layer 2 Input electrode 11 Dielectric layer 3 Output electrode 12 Second polysilicon 4 Capacitor gap 13 Sacrificial layer 5 Package cavity 14 The first polysilicon 6 Packaging ring 15 Electrode pad 7 Package Ring Pad 16 Electrical pads 8 Package pad 17 Annular groove 9 Conductive silicon pillar DETAILED DESCRIPTION

[0045] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0046] It should be noted that if a directional indication is involved in the embodiment of the present invention, the directional indication is only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture. If the specific posture changes, the directional indication will also change accordingly.

[0047] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0048] See also Figure 1The present application provides a MEMS resonator, which includes a resonant structure 1, an input electrode 2, an output electrode 3, and a capacitive gap 4.

[0049] The input electrode 2 and the output electrode 3 are located on the side of the resonant structure 1 and have a small gap. The small gap between the input electrode 2 and the resonant structure 1 forms a capacitive driving force, and when an AC signal is added during operation, the resonant structure 1 can be driven to vibrate in the plane. The small gap between the resonant structure 1 and the output electrode 3 can realize the capacitance change, and a stable resonant frequency signal is induced at the output electrode.

[0050] See also Figures 2 to 4 The present application also provides a method for preparing a micromechanical resonator, comprising the following steps:

[0051] S10, obtaining a substrate structure, wherein the substrate structure is formed with a resonant portion and two electrode portions located on both sides of the resonant portion and spaced apart from each other;

[0052] S20, growing a sacrificial layer 13 on the substrate structure and patterning it so as to partially expose the resonant portion and the two electrode portions;

[0053] S30, depositing a first polysilicon 14 and patterning it, forming a resonance structure 1, an input electrode 2 and an output electrode 3 corresponding to the resonance part and the two electrode parts, wherein a capacitance gap 4 is formed between the input electrode 2 and the output electrode 3 and the resonance structure 1;

[0054] S40, releasing the sacrificial layer 13 under the resonant structure 1 to obtain a resonator wafer;

[0055] S50, preparing a packaging cover sheet, and vacuum bonding the packaging cover sheet and the resonator wafer to form a MEMS resonator.

[0056] In the technical solution provided by the present invention, a resonant structure, an input electrode and an output electrode are formed by depositing a first polysilicon and patterning it. The active resonant chip of the sacrificial layer under the resonant structure is released, and the sealing of the resonator is achieved through a packaging cover to ensure vacuum airtightness. The overall process is simple and reliable, and can achieve high-precision, high-quality, large-scale and low-cost production.

[0057] It should be noted that the resonant structure 1 is arranged in a beam shape, wherein its top cross section is arranged in a disk, a square plate, a circular ring or a square ring, and no specific limitation is made here.

[0058] In addition, in order to facilitate the release of the sacrificial layer 13 under the resonant structure 1, a release hole is provided on the resonant structure 1, and the shape of the release hole includes any one of a circular and a square shape. The release hole can be provided in plurality, and the plurality of release holes are arranged in different arrays according to the shape of the resonant structure.

[0059] For further information, see Figures 5 and 6 , step S10 comprises:

[0060] S11, obtaining a silicon substrate substrate, growing a dielectric layer 11 on the surface of the silicon substrate substrate and patterning it as a signal isolation layer;

[0061] S12, depositing a second polysilicon 12 and patterning it to form the resonance portion and the two electrode portions as a signal transmission layer, wherein the signal transmission layer and the signal isolation layer together form the substrate structure.

[0062] It should be noted that the material of the dielectric layer 11 includes any one of silicon oxide and silicon nitride.

[0063] On the other hand, for ease of encapsulation, see Figure 7 , depositing a first polysilicon 14 and patterning it to form a packaging ring 6, wherein the input electrode 2, the resonant structure 1 and the output electrode 3 are all located in the packaging ring 6; before step S40, the following steps are further included:

[0064] S401 , depositing a metal layer and patterning it, forming two electrode pads 15 corresponding to the input electrode and the output electrode, and forming a packaging ring pad 7 corresponding to the packaging ring 6 .

[0065] In this embodiment, the material of the electrode pad and the packaging ring pad 7 includes any one of Si, Au, Sn, In, Al and glass paste.

[0066] On the other hand, see Figures 8 to 10 The steps of preparing the package cover sheet include:

[0067] S51, obtaining a silicon substrate, and arranging two conductive silicon pillars 9 on the silicon substrate corresponding to the input electrode and the output electrode, and arranging two insulating structures corresponding to the two conductive silicon pillars 9;

[0068] S52, the silicon substrate comprises a packaging surface and an exposed surface which are arranged opposite to each other, and a packaging cavity 5 is formed on the packaging surface, wherein the two conductive silicon pillars 9 are located in the packaging cavity 5, and the ends of the two conductive silicon pillars are arranged to protrude from the bottom wall of the packaging cavity 5;

[0069] S53, preparing a surface metal layer 10 on the exposed surface, and preparing a welding structure on the packaging surface side, wherein the surface metal layer 10 is arranged corresponding to the conductive silicon pillar 9 to form the packaging cover sheet.

[0070] It should be noted that the method for preparing and forming the packaging cavity 5 includes any one of wet etching or dry etching, and can be anisotropic etching or isotropic etching.

[0071] Specifically, a first polysilicon 14 is deposited and patterned to form a packaging ring 6, and the input electrode 2, the resonant structure 1 and the output electrode 3 are all located in the packaging ring 6;

[0072] The welding structure includes a packaging pad 8 arranged corresponding to the packaging ring 6 and an electrical pad 16 arranged corresponding to the end surfaces of the two conductive silicon pillars 9 .

[0073] Further, please participate Fig.11 , step S51 further includes:

[0074] S511, obtaining a silicon substrate, and etching two annular grooves 17 on the silicon substrate corresponding to the input electrode 2 and the output electrode 3 to form two conductive silicon pillars 9;

[0075] S512, filling the two annular grooves with insulating material to form the insulating structure;

[0076] S513, grinding the silicon substrate to expose the conductive silicon pillars 9 and the insulating structure on both side end surfaces of the silicon substrate.

[0077] It should be noted that the insulating material includes any one of SiO2, glass and silicon nitride.

[0078] On the other hand, the material of the sacrificial layer includes any one of SiO2 and PSG.

[0079] It should be noted that the vacuum bonding method of the package cover sheet and the resonator wafer includes any one of anodic bonding, eutectic bonding and intermediate layer bonding, which is not specifically limited here.

[0080] In order to make the method steps described in the present invention clearer and more understandable, a specific example of preparation is provided below:

[0081] 1. Growing a dielectric layer 11 on the surface of a silicon substrate and patterning it as a signal isolation layer;

[0082] 2. Deposit and pattern the second polysilicon 12 as a signal transmission layer to define electrodes and electrode leads;

[0083] 3. Growing and patterning a sacrificial layer 13 to isolate the electrode and the resonant structure;

[0084] 4. Deposit the first polysilicon 14 and pattern it to make the resonant structure 1, the input electrode 2, the output electrode 3, the capacitor gap 4, and the packaging ring 6;

[0085] 5. Deposit a metal layer and pattern it, prepare an electrode pad 15 and a packaging ring pad 7, and obtain a resonator wafer;

[0086] 6. Remove the sacrificial layer 13 under the resonant structure through the release hole to release the resonant structure 1;

[0087] 7. Etching the silicon substrate to form an annular groove 17;

[0088] 8. Fill the annular groove 17 with insulating material to achieve electrical insulation;

[0089] 9. Double-sided grinding and thinning of the silicon substrate to expose the conductive silicon pillar 9 and the insulating structure at the same time;

[0090] 10. Etching on any side of the thinned silicon cover substrate to form a packaging cavity 5 for accommodating the resonant structure;

[0091] 11. A packaging pad 8 and an electrical pad 16 are fabricated on one side of the silicon substrate containing the packaging cavity 5, and a surface metal layer 10 is fabricated on the other side as a planar electrical lead to obtain a packaging cover sheet;

[0092] 12. Bond the resonator wafer and the package cover sheet in a vacuum-tight manner, and simultaneously realize electrical pad connection and package ring bonding.

[0093] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a micromechanical resonator, characterized in that: The following steps are involved: Acquire a substrate structure, wherein the substrate structure is formed with a resonant portion and two electrode portions located on both sides of the resonant portion and spaced apart from each other; Growing a sacrificial layer on the substrate structure and patterning it so as to partially expose the resonant portion and the two electrode portions; Depositing a first polysilicon and patterning it, forming a resonant structure, an input electrode and an output electrode corresponding to the resonant portion and the two electrode portions, wherein a capacitance gap is formed between the input electrode and the output electrode and the resonant structure; releasing the sacrificial layer under the resonant structure to obtain a resonator wafer; A packaging cover sheet is prepared, and the packaging cover sheet and the resonator wafer are vacuum bonded to form a MEMS resonator; wherein the step of obtaining a substrate structure, wherein the substrate structure is formed with a resonating portion and two electrode portions located on both sides of the resonating portion and spaced apart from each other, comprises: Obtain a silicon substrate substrate, grow a dielectric layer on the surface of the silicon substrate substrate and pattern it as a signal isolation layer; Depositing a second polysilicon and patterning it to form the resonance portion and the two electrode portions as a signal transmission layer, wherein the signal transmission layer and the signal isolation layer together form the substrate structure; The steps of preparing the package cover sheet include: Obtain a silicon substrate, and arrange two conductive silicon pillars on the silicon substrate corresponding to the input electrode and the output electrode, and arrange two insulating structures corresponding to the two conductive silicon pillars; The silicon substrate comprises a packaging surface and an exposed surface which are arranged opposite to each other, and a packaging cavity is formed on the packaging surface, wherein the two conductive silicon pillars are located in the packaging cavity, and the ends thereof are arranged to protrude from the bottom wall of the packaging cavity; A surface metal layer is prepared on the exposed surface, and a welding structure is prepared on the packaging surface side, wherein the surface metal layer is arranged corresponding to the conductive silicon pillar to form the packaging cover sheet; The step of obtaining a silicon substrate, providing two conductive silicon pillars on the silicon substrate corresponding to the input electrode and the output electrode, and providing two insulating structures corresponding to the two conductive silicon pillars also includes: Obtain a silicon substrate, and etch two annular grooves on the silicon substrate corresponding to the input electrode and the output electrode to form the two conductive silicon pillars; Filling insulating material in the two annular grooves to form the insulating structure; The silicon substrate is ground to expose the conductive silicon pillar and the insulating structure on both side end surfaces of the silicon substrate.

2. The method for preparing a micromechanical resonator according to claim 1, characterized in that: The material of the dielectric layer includes any one of silicon oxide and silicon nitride.

3. The method for preparing a micromechanical resonator according to claim 1, characterized in that: Depositing a first polysilicon and patterning it to form a packaging ring, wherein the input electrode, the resonant structure and the output electrode are all located in the packaging ring; Before releasing the sacrificial layer under the resonant structure and obtaining the resonator wafer, the step further includes: A metal layer is deposited and patterned, two electrode pads are formed corresponding to the input electrode and the output electrode, and a packaging ring pad is formed corresponding to the packaging ring.

4. The method for preparing a micromechanical resonator according to claim 3, characterized in that: The material of the electrode pad and the packaging ring pad includes any one of Si, Au, Sn, In, Al and glass paste.

5. The method for preparing a micromechanical resonator according to claim 1, characterized in that: Depositing a first polysilicon and patterning it to form a packaging ring, wherein the input electrode, the resonant structure and the output electrode are all located in the packaging ring; The welding structure includes a packaging pad arranged corresponding to the packaging ring and an electrical pad arranged on the end surfaces of the two conductive silicon columns.

6. The method for preparing a micromechanical resonator according to claim 1, characterized in that: The insulating material includes any one of SiO2, glass and silicon nitride.

7. The method for preparing a micromechanical resonator according to claim 1, characterized in that: The material of the sacrificial layer includes any one of SiO2 and PSG.

Images