A vertical resonant MEMS electric field sensor based on GIS-SOI-GOS

Abstract

The application provides a vertical resonant MEMS electric field sensor based on GIS-SOI-GOS, which is composed of GIS layer, SOI layer and GOS layer. The GIS layer comprises an upper driving electrode, an insulating ring, conductive silicon, a plurality of through holes and a groove on a glass layer, and the upper driving electrode is insulated from the conductive silicon through the insulating ring. The SOI layer is composed of a device layer, a buried oxygen layer and a substrate layer, the device layer is provided with a lower driving electrode, a shielding electrode, an induction electrode, an elastic beam and an anchor point, and the buried oxygen layer and the substrate layer are etched to have a hollow window, which together with the groove on the glass layer below the GIS provides a vertical vibration space for a movable structure. The GOS layer comprises an electric field induction cover plate and a glass layer provided with a window, and is used to establish an electric field induction channel. The application realizes integrated wafer-level preparation of a sensitive structure and vacuum packaging of the vertical resonant MEMS electric field sensor, and has the characteristics of high electric field induction efficiency, high quality factor, low driving voltage and the like.

Description

Technical Field

[0001] This invention belongs to the field of sensor technology and microelectromechanical systems (MEMS), specifically relating to a vertical resonant MEMS electric field sensor based on GIS-SOI-GOS. Background Technology

[0002] Electric field sensors are widely used in meteorological detection, aerospace, petrochemicals, power systems, and other fields. Miniature electric field sensors based on MEMS (Micro-Electro-Mechanical System) technology, with their advantages of small size, low cost, and mass production capability, have become an important development direction for electric field sensors.

[0003] To improve the environmental adaptability of MEMS electric field sensors, the sensitive structure needs to be packaged. Existing MEMS electric field sensors typically involve fabricating the sensitive chip first, and then packaging each chip individually. This process is costly and not conducive to mass production. Wafer-level vacuum packaging not only allows for simultaneous vacuum packaging of the sensitive structure on the entire wafer, reducing the cost of mass production and improving packaging efficiency, but also significantly reduces the impact of damping on the vibration of the resonant structure. This improves the sensor's quality factor, reduces the driving voltage of the sensitive structure, and minimizes crosstalk noise to the output signal.

[0004] Currently, mainstream MEMS electric field sensors are mainly of two types: horizontal resonant and vertical resonant. There are currently no reports of wafer-level vacuum packaging for vertical resonant MEMS electric field sensors. Unlike horizontal resonant MEMS electric field sensors, the vertical vibration characteristics of vertical resonant MEMS electric field sensors dictate the uniqueness of their driving structure. The driving structure needs to be a two-layer structure at a different height from the resonator, making the lead wires for the driving signal a challenge, and the driving signal is prone to crosstalk to the output signal. Therefore, the design of the driving structure is a major difficulty in wafer-level vacuum packaging of vertical resonant MEMS electric field sensors. Summary of the Invention

[0005] In view of the above problems, this invention proposes a vertical resonant MEMS electric field sensor based on GIS-SOI-GOS, which is expected to have higher electric field modulation efficiency than the sensing structure of the horizontal resonant MEMS electric field sensor, thereby achieving higher electric field sensing performance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] An embodiment of the present invention provides a vertical resonant MEMS electric field sensor based on GIS-SOI-GOS. The structure mainly includes: a GIS (Glassin Silicon) layer, which consists of an upper driving electrode, an insulating ring, an outer conductive silicon layer, multiple through holes, and a glass layer with grooves etched underneath; an SOI (Silicon on Insulator) layer, which consists of a device layer, a buried oxide layer, and a substrate layer, wherein the device layer is etched with some sensitive structures, and the buried oxide layer and the substrate layer are etched with cutout windows; and a GOS (Glasson Silicon) layer, which consists of an electric field sensing cover plate and a glass layer with windows.

[0008] According to an embodiment of the present invention, the upper driving electrode is made of conductive silicon and is electrically insulated from the outer conductive silicon by an insulating ring;

[0009] According to an embodiment of the present invention, the sensitive structure includes an upper driving electrode, a lower driving electrode, a shielding electrode, a sensing electrode, an elastic beam, and an anchor point;

[0010] According to an embodiment of the present invention, the shielding electrode is connected to the lower driving electrode, the lower driving electrode is connected to the device layer through an elastic beam, and the sensing electrode is fixed to the buried oxide layer through anchor points;

[0011] According to an embodiment of the present invention, the hollowed-out window etched on the buried oxide layer and the substrate layer, together with the groove on the lower glass of the GIS layer, provides a vertical vibration space for the lower driving electrode, the shielding electrode and the elastic beam;

[0012] According to an embodiment of the present invention, an electric field induction channel is established through the electric field induction cover plate;

[0013] According to an embodiment of the present invention, the via penetrates the GIS layer to bring out electrical signals from the device layer and the substrate layer.

[0014] The above-described technical solutions employed in the embodiments of the present invention can achieve the following beneficial effects:

[0015] (1) The structure provided by the present invention can realize the integrated wafer-level fabrication of the sensing structure and vacuum packaging of the vertical resonant MEMS electric field sensor, thereby improving the quality factor of the sensor, reducing the driving voltage of the sensing structure and its crosstalk noise to the output signal;

[0016] (2) The structure provided by the present invention can realize the vibration of the shielding electrode in the plane direction perpendicular to the GIS layer, and has high modulation efficiency for the electric field distributed on the lower surface and side wall of the sensing electrode.

[0017] (3) The structure provided by the present invention can reduce the coupling noise of the driving voltage to the output signal. The silicon grounding of the peripheral conductor in the GIS layer can effectively reduce the crosstalk noise coupled from the side wall of the upper driving electrode to the sensing electrode.

[0018] (4) The structure provided by the present invention can realize the mass production of vertical resonant MEMS electric field sensors with wafer-level vacuum packaging, which is beneficial to reducing production costs. Attached Figure Description

[0019] To gain a more complete understanding of the invention and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, wherein:

[0020] Figure 1 This schematic diagram illustrates the front structure of a vertical resonant MEMS electric field sensor based on GIS-SOI-GOS provided in an embodiment of the present invention.

[0021] Figure 2 This schematic diagram illustrates the back structure of a vertical resonant MEMS electric field sensor based on GIS-SOI-GOS provided in an embodiment of the present invention.

[0022] Figure 3 This schematic diagram illustrates a three-dimensional cross-sectional structure of a vertical resonant MEMS electric field sensor based on GIS-SOI-GOS provided in an embodiment of the present invention.

[0023] in:

[0024] 100-GIS layer; 200-SOI layer; 300-GOS layer;

[0025] 101 - Upper driving electrode; 102 - Insulating ring; 103 - Peripheral conductor silicon; 104 - Through hole; 105 - Groove;

[0026] 201 - Lower driving electrode; 202 - Shielding electrode; 203 - Sensing electrode; 204 - Elastic beam; 205 - Anchor point; 206 - Hollowed-out window;

[0027] 301 - Electric field induction cover plate; 302 - Glass layer with window. Detailed Implementation

[0028] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0029] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0030] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0031] See Figure 1 , Figure 2 and Figure 3 This invention provides a vertical resonant MEMS electric field sensor based on GIS-SOI-GOS, which consists of a three-layer structure, including: a GIS layer 100, an SOI layer 200, and a GOS layer 300. The SOI layer 200 is located between the GIS layer 100 and the GOS layer 300.

[0032] The GIS layer 100 comprises an upper driving electrode 101, an insulating ring 102, a peripheral conductive silicon 103, multiple vias 104, and a glass layer with grooves 105 etched beneath it. The upper driving electrode 101 is located at the center of the GIS layer 100 and is electrically insulated from the peripheral conductive silicon 103 by the insulating ring 102. The vias 104 are located around the peripheral conductive silicon 103, penetrating the entire GIS layer 100, and are used to introduce and extract electrical signals from the SOI layer 200. The grooves 105 are located below the glass layer below the upper driving electrode 101, providing vertical vibration space for the movable sensitive structures of the device layer in the SOI layer 200.

[0033] The SOI layer 200 consists of a three-layer structure: a device layer, a buried oxide layer, and a substrate layer. The device layer is etched with sensitive structures, including a lower driving electrode 201, a shielding electrode 202, a sensing electrode 203, an elastic beam 204, and anchor points 205. The shielding electrode 202 is connected to the lower driving electrode 201, which is connected to the device layer via the elastic beam 204. The sensing electrode 203 is fixed to the buried oxide layer via the anchor points 205. Hollow windows 206 are etched on both the buried oxide layer and the substrate layer.

[0034] The GOS layer 300 consists of an electric field sensing cover plate 301 and a glass layer 302 with a window. The glass layer 302 with the window is connected to the substrate of the SOI layer 200, and the electric field sensing cover plate 301 is located outside the glass layer 302 with the window to sense the external electric field.

[0035] The GIS layer 100 is fabricated using multiple techniques, including DRIE (Deep Reactive Ion Etching), silicon-glass anodic bonding, glass reflow, and CMP (Chemical Mechanical Polishing).

[0036] The working principle of the vertical resonant MEMS electric field sensor based on GIS-SOI-GOS proposed in this invention is as follows: A voltage is applied between the upper driving electrode 101 and the lower driving electrode 201. The lower driving electrode 201 is electrostatically excited and vibrates in a direction perpendicular to the plane of the GIS layer 100, thereby driving the shielding electrode 202 to vibrate up and down, periodically modulating the electric field from the inside of the electric field sensing cover plate 301 to the surface of the sensing electrode 203, causing the amount of induced charge on the surface of the sensing electrode 203 to change periodically, generating an induced current at the anchor point 205 connected to the sensing electrode 203. The electrical signal is led out to the external signal processing circuit through the through hole 104 corresponding to the anchor point 205 in the vertical direction. The magnitude of the external electric field strength to be measured can be demodulated based on the current signal.

[0037] The following describes in detail, with reference to embodiments, various parts of a vertical resonant MEMS electric field sensor based on GIS-SOI-GOS according to the present invention.

[0038] Example

[0039] An embodiment of the vertical resonant MEMS electric field sensor based on GIS-SOI-GOS of the present invention is as follows.

[0040] See Figure 1 , Figure 2 and Figure 3 The structure consists of three layers: GIS layer 100, SOI layer 200, and GOS layer 300.

[0041] The GIS layer 100 is fabricated using multiple techniques including DRIE, silicon-glass anodic bonding, glass reflow, and CMP. The GIS layer consists of an upper driving electrode 101, an insulating ring 102, a peripheral conductive silicon 103, multiple vias 104, and a glass layer with grooves 105 etched beneath. The upper driving electrode 101 is electrically insulated from the peripheral conductive silicon 103 by the insulating ring 102. The insulating ring 102 is made of glass and is connected to the glass layer beneath the GIS layer 100. Two upper driving electrodes 101 are used. In actual operation, equal and opposite AC / DC voltages are applied to the two upper driving electrodes 101. The driving voltages inevitably cause crosstalk noise to the sensing electrode 203. However, because the crosstalk signals from the two upper driving electrodes 101 to the sensing electrode 203 are equal in magnitude and opposite in sign, This greatly reduces the crosstalk of the driving voltage to the output signal; the grounded outer conductor silicon 103 can not only shield the electric field generated by the side wall of the upper driving electrode 101 from the influence of the sensing electrode 203, but also shield the influence of the external electromagnetic environment on the sensitive structure; the through holes 104 penetrate the GIS layer 100 and are used to introduce and lead out electrical signals at different locations. A total of 6 through holes are provided. Among them, 2 through holes are directly opposite the anchor point 205, 2 through holes are directly opposite the device layer of the SOI layer 200, and the remaining 2 through holes are directly opposite the substrate layer of the SOI layer 200.

[0042] The SOI layer 200 consists of a three-layer structure: a device layer, a buried oxide layer, and a substrate layer. The device layer contains a lower driving electrode 201, a shielding electrode 202, a sensing electrode 203, elastic beams 204, and anchor points 205. The lower driving electrode 201 is located directly below the upper driving electrode 101 and is connected to the device layer via the elastic beams 204. The shielding electrode 202 is rigidly connected to the lower driving electrode 201, and the sensing electrode 203 is fixed to the buried oxide layer via the anchor points 205. There is at least one set of both the shielding electrode 202 and the sensing electrode 203, and they are arranged in a staggered manner. The specific number and size of the shielding electrode 202 and the sensing electrode 203 are not limited in this invention. In this embodiment, there are four elastic beams 204, used to support the lower driving electrode 201 suspended in the middle and the shielding electrode 202 connected to it. Two anchor points 205 are provided, and an isolation groove is provided between the anchor points 205 and the surrounding device layers, achieving electrical insulation between the anchor points 205 and the surrounding device layers through the isolation groove. Hollow windows 206 are etched on the buried oxide layer and the substrate layer.

[0043] The GOS layer 300 consists of two layers: an electric field sensing cover plate 301 and a glass layer 302 with perforated windows. The electric field sensing cover plate 301, made of wafer-grade conductive silicon, is used to introduce an external electric field into the vacuum cavity inside the structure. The perforated windows on the glass layer 302 allow the electric field lines introduced from the electric field sensing cover plate 301 into the internal vacuum cavity to reach the device layer of the SOI layer 200 without obstruction, forming a sensitive structure. The electric field sensing cover plate 301 and the glass layer 302 with perforated windows are connected by anodic bonding.

[0044] The GIS layer 100, SOI layer 200, and GOS layer 300 are connected by anodic bonding.

[0045] The groove 105 of the glass layer below the GIS layer 100, together with the hollow window 206 etched on the buried oxide layer and substrate layer in the SOI layer 200, provides a vibration space perpendicular to the plane of the GIS layer for the lower driving electrode 201, the shielding electrode 202 and the elastic beam 204.

[0046] In summary, this invention provides a vertical resonant MEMS electric field sensor based on GIS-SOI-GOS. By bonding the GIS, SOI, and GOS three-layer structure together, the sensor's sensing structure and vacuum packaging are integrated into a wafer-level fabrication, improving the sensor's quality factor and reducing the driving voltage and its crosstalk to the sensitive structure's output signal. Furthermore, this sensing structure exhibits high modulation efficiency for electric fields distributed on the lower surface and sidewalls of the sensing electrode, demonstrating high electric field sensing efficiency.

[0047] Those skilled in the art will understand that the features described in the various embodiments and / or claims of the present invention can be combined and / or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments and / or claims of the present invention can be combined and / or combined in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or combinations fall within the scope of the present invention.

[0048] Although the invention has been shown and described with reference to specific exemplary embodiments thereof, those skilled in the art will understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents. Therefore, the scope of the invention should not be limited to the above embodiments, but should be determined not only by the appended claims but also by their equivalents.

Claims

1. A vertical resonant MEMS electric field sensor based on GIS-SOI-GOS, characterized in that, include: The GIS layer is fabricated with an upper driving electrode, an insulating ring, an outer conductor silicon, multiple through holes, and a groove on the underlying glass layer. The SOI layer consists of three layers: a device layer, a buried oxide layer, and a substrate layer. The device layer is etched with some sensitive structures, and the buried oxide layer and the substrate layer are etched with cutout windows. The sensitive structures include an upper driving electrode, a lower driving electrode, a shielding electrode, a sensing electrode, an elastic beam, and an anchor point. The shielding electrode is rigidly connected to the lower driving electrode and is movable. The sensing electrode is fixed to the buried oxide layer by the anchor point. The GOS layer consists of an electric field induction cover and a glass layer with windows. The GIS layer, SOI layer, and GOS layer are bonded together to form an integrated wafer-level vacuum encapsulation structure.

2. The vertical resonant MEMS electric field sensor based on GIS-SOI-GOS according to claim 1, characterized in that, The upper driving electrode is made of conductive silicon and is electrically insulated from the outer conductive silicon by an insulating ring.

3. The vertical resonant MEMS electric field sensor based on GIS-SOI-GOS according to claim 1, characterized in that, The via extends through the entire GIS layer to introduce and extract electrical signals from the SOI layer.

4. A vertical resonant MEMS electric field sensor based on GIS-SOI-GOS according to claim 1, characterized in that, The etched perforated windows on the buried oxide layer and substrate layer, together with the grooves on the glass layer below the GIS layer, provide a vibration space perpendicular to the plane of the GIS layer for the lower drive electrode, shielding electrode, and elastic beam.

5. A vertical resonant MEMS electric field sensor based on GIS-SOI-GOS according to claim 1, characterized in that, An electric field induction channel is established through the electric field induction cover plate.

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