Membrane-based microelectromechanical system (MEMS) devices and methods of making

Abstract

The embodiment of the present application provides a MEMS device and a preparation method thereof, wherein the MEMS device comprises: a substrate; a first electrode layer formed based on the substrate; a second electrode layer located on the first electrode layer, wherein the second electrode layer comprises a beam and an anchor point; the beam is suspended on the first electrode, the beam extends along a first direction and has two oppositely arranged ends, the beam has two oppositely arranged sides along a second direction, the first direction and the second direction are both perpendicular to the thickness direction of the substrate, and the first direction is perpendicular to the second direction; at least one end of the beam is provided with the anchor point, each anchor point comprises two anchor parts, the two anchor parts are fixed on the two sides of the beam respectively, and each anchor part is in electrical contact with the first electrode layer. The MEMS device and the preparation method thereof provided by the embodiment of the present application have the advantages that the beam bending is avoided, and the performance of the MEMS device is improved.

Description

Technical Field

[0001] This application relates to the field of electronic technology, specifically to a MEMS device and its fabrication method. Background Technology

[0002] MEMS (Micro-Electro-Mechanical Systems) is an industrial technology that integrates microelectronics and mechanical engineering. MEMS devices are mechanically movable structures fabricated using MEMS technology. As a type of MEMS device, MEMS resonators achieve frequency-selective filtering of electrical signals through electromechanical coupling. MEMS resonators have the following advantages: small size, low power consumption, shock resistance, compatibility with microelectronic integrated circuit processes, ease of system integration, stable performance, high reliability, and operating frequencies concentrated in the radio frequency band, reaching up to the GHz level, with a high quality factor.

[0003] For electrostatic capacitive MEMS resonators, there are currently two main fabrication processes. One is a bulk silicon deep etching process using an SOI substrate, with the top silicon layer as the structural layer of the resonator. Its advantages are no film layer stress and no frequency drift in the resonant structure, but the device fabrication cost is relatively high. The other is a planar process using multiple thin film deposition and etching, with the deposited polycrystalline silicon thin film as the structural layer. The advantages of this approach are compatibility with CMOS processes and relatively low cost. However, because the stress of the polycrystalline silicon thin film itself is difficult to control, the device resonant frequency will drift when the process repeatability is poor. More importantly, the internal stress of the resonant structure will also change with the change of the external ambient temperature, thus causing frequency drift. Summary of the Invention

[0004] To address the issue of significant variations in internal stress within the resonant structure due to changes in ambient temperature, this application provides a MEMS device and its fabrication method.

[0005] According to a first aspect of the embodiments of this application, a MEMS device is provided, comprising: a substrate; a first electrode layer formed on the substrate; a second electrode layer located on the first electrode layer, the second electrode layer including a crossbeam and an anchor point; the crossbeam is suspended on the first electrode, the crossbeam extends along a first direction and has two oppositely disposed ends, the crossbeam has two oppositely disposed sides along a second direction, the first direction and the second direction are both perpendicular to the substrate thickness direction, and the first direction is perpendicular to the second direction;

[0006] At least one end of the crossbeam is provided with the anchor point, each anchor point includes two anchoring parts, the two anchoring parts are respectively fixed to both sides of the crossbeam, and each anchoring part is in electrical contact with the first electrode layer.

[0007] In one possible implementation, the anchoring portion includes a connecting section and a fixing section, the connecting section being connected to one side of the crossbeam and extending along a second direction, and the fixing section being connected to the connecting section and extending along a first direction.

[0008] In one possible implementation, the fixed segment has two opposing ends along the first direction, with at least one end extending beyond the connecting segment.

[0009] In one possible implementation, the crossbeam includes a main body segment and an extension segment; the main body segment is elongated and extends along a first direction; the extension segment is disposed at one or both ends of the main body segment along the first direction, and both ends of the extension segment along the second direction extend beyond the main body segment; the anchoring portion is connected to the extension segment.

[0010] In one possible implementation, the extension has two opposing sides along the second direction; the anchoring portion is connected to the sides of the extension and extends along the first direction, and at least one of the ends of the anchoring portion along the first direction extends beyond the extension.

[0011] In one possible implementation, the anchoring portion comprises two parts; the extension has two oppositely disposed end faces along the first direction; each end face is connected to a portion of the anchoring portion.

[0012] In one possible implementation, the first electrode layer has a top surface facing the second electrode layer, and a groove is formed on the top surface; the anchoring portion is in electrical contact with the top surface of the first electrode layer, and the crossbeam is suspended on the groove.

[0013] In one possible implementation, the first electrode layer has a top surface facing the second electrode layer, and a groove is formed on the top surface; at least a portion of the anchoring portion is located within the groove, and the crossbeam is suspended on the groove.

[0014] In one possible implementation, the second electrode layer has a bottom surface facing the first electrode layer, and a groove is formed on the bottom surface corresponding to the crossbeam so that the crossbeam can be suspended on the first electrode layer, and the bottom surface corresponding to the anchoring part is in electrical contact with the first electrode layer.

[0015] In one possible implementation, the MEMS device includes a MEMS resonator.

[0016] According to a second aspect of the present application, a method for fabricating a MEMS device is provided, comprising: forming a first conductive layer on a substrate; patterning the first conductive layer to form a first electrode layer; forming a sacrificial layer on the first electrode layer; partially etching the sacrificial layer to expose a portion of the first electrode layer; forming a second conductive layer on the first electrode layer and the sacrificial layer; patterning the second conductive layer to expose the sacrificial layer, wherein the patterned second conductive layer includes a crossbeam and an anchor point to form a second electrode layer; the crossbeam is spaced apart from the first electrode layer by the sacrificial layer; the crossbeam extends along a first direction and has two oppositely disposed ends; the crossbeam has a first side and a second side oppositely disposed along a second direction; both the first direction and the second direction are perpendicular to the substrate thickness direction, and the first direction is perpendicular to the second direction; at least one end of the crossbeam is connected to the anchor point; each anchor point includes two anchoring portions, the two anchoring portions being respectively fixed to the first side and the second side of the crossbeam, and each anchoring portion being in electrical contact with the first electrode layer; and removing the sacrificial layer to suspend the crossbeam on the first electrode layer.

[0017] In one possible implementation, the MEMS device includes a MEMS resonator.

[0018] The MEMS device and its fabrication method provided in this application embodiment, wherein the stacked first electrode and second electrode, the upper second electrode includes a crossbeam and an anchor point, wherein the crossbeam is suspended on the first electrode and there is a preset distance between them; the anchor point is in contact with and electrically connected to the first electrode, and the two anchoring parts of the anchor point are separated by the crossbeam and respectively disposed on both sides of the crossbeam. Through the above-described anchor point structure, the bending of the crossbeam can be effectively avoided, which is beneficial to improving the performance of the MEMS device.

[0019] In particular, by dividing each anchorage into two parts and placing them at both ends of the beam extension, the defect of large variations in internal stress of the beam structure with changes in ambient temperature can be further improved. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0021] Figure 1 This is a top view of the upper electrode layer of a MEMS resonator in related technologies;

[0022] Figure 2 for Figure 1 The diagram shows the upper electrode before and after changes in external temperature.

[0023] Figure 3 A top view of a MEMS device provided in an embodiment of this application;

[0024] Figure 4 A top view of another MEMS device provided in the embodiments of this application;

[0025] Figure 5 A top view of yet another MEMS device provided in an embodiment of this application;

[0026] Figure 6 A top view of yet another MEMS device provided in an embodiment of this application;

[0027] Figure 7 A cross-sectional view of a MEMS device provided in an embodiment of this application;

[0028] Figure 8 A cross-sectional view of another MEMS device provided in an embodiment of this application;

[0029] Figure 9 A cross-sectional view of yet another MEMS device provided in an embodiment of this application;

[0030] Figure 10 A cross-sectional view of yet another MEMS device provided in an embodiment of this application;

[0031] Figures 11A-11K for Figure 10 A cross-sectional view showing the manufacturing process of a MEMS device.

[0032] Key reference numerals:

[0033] 100-substrate;

[0034] 200 - Grounding layer;

[0035] 300 - Insulation layer; 310 - Silicon nitride layer; 320 - Silicon oxide layer;

[0036] 400 - First electrode layer; 410 - Groove; 411 - Small cross-section groove; 412 - Large cross-section groove;

[0037] 500-Sacrificial Layer;

[0038] 600 - Second electrode layer; 610 - Crossbeam; 611 - Main body section; 612 - Extension section; 621 - First anchoring part; 6211 - First connecting section; 6212 - First fixing section; 6213 - First joint section; 622 - Second anchoring part; 6221 - Second connecting section; 6222 - Second fixing section; 6223 - Second joint section;

[0039] 710 - Upper electrode; 711 - Anchor point; 712 - Crossbeam; 720 - Lower electrode. Detailed Implementation

[0040] The following uses a MEMS resonant beam device as an example to illustrate the specific implementation of the present invention. Figure 1 This is a top view of the upper electrode layer of a MEMS resonator in related technologies. Figure 2 for Figure 1 The diagram shows the upper electrode before and after changes in external temperature. (Reference) Figure 1 and Figure 2 In related technologies, a MEMS resonator includes an upper electrode 710 and a lower electrode 720 stacked together. The upper electrode 710 may include an anchor point 711 and a crossbeam 712. The anchor point 711 is fixed to one end of the crossbeam 712 and connected to the lower electrode 720, leaving the other end of the crossbeam 712 suspended above the lower electrode 720. In other words, the end of the crossbeam 712 away from the anchor point 711 is a free end. Furthermore, the width of the anchor point 711 is the same as the width of the crossbeam 712.

[0041] refer to Figure 2 At the initial temperature, the crossbeam portion 712a of the upper electrode 710 remains essentially parallel to the lower electrode 720. As the temperature rises, the crossbeam portion 712a deforms and bends towards the lower electrode 720. Figure 2 The crossbeam portion 712b is longer than the crossbeam portion 712a by a certain dimension, denoted as ΔD1. Furthermore, the gap between the free end of the crossbeam portion 712 and the lower electrode 720 has changed significantly, thereby affecting the resonant frequency and causing temperature drift.

[0042] To address the aforementioned issues, the inventors of this application, through experiments and multiple simulations, believe the cause is likely due to internal stress generated at the anchor point caused by thermal expansion and contraction during temperature changes. The magnitude of this stress is related to the shape and location of the anchor point. In particular, simulation results show that when the anchor point is positioned on the side wall near the end of the crossbeam, the amplitude of temperature change at the free end of the crossbeam decreases, suggesting that this arrangement likely reduces the internal stress.

[0043] In view of this, the MEMS device provided in this application provides two anchor points respectively on both sides of the crossbeam, so that the connection between the anchor points and the crossbeam is located on the side of the crossbeam, thereby reducing internal stress and effectively preventing the crossbeam from bending due to temperature changes.

[0044] To make the technical solutions and advantages of the embodiments of this application clearer, the exemplary embodiments of this application will be described in further detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other.

[0045] The technical solutions of the embodiments of this application will be explained below using MEMS resonators as an example. Figures 3-6 Top view of different implementations of the MEMS device provided in the embodiments of this application. Figures 7-10 Cross-sectional views of different embodiments of the MEMS device provided in this application. (Refer to...) Figures 3-10 The MEMS device provided in this application embodiment may include a substrate 100, a first electrode layer 400, and a second electrode layer 600 including a crossbeam and anchor points.

[0046] The substrate 100 can be a semiconductor substrate, a semiconductor compound substrate, or an SOI (Semiconductor Over Insulator) substrate. Specifically, the semiconductor substrate can be a silicon substrate. The semiconductor compound substrate can specifically be a silicon carbide substrate, a germanium silicide substrate, a gallium arsenide substrate, etc.

[0047] refer to Figures 7-10 A first electrode layer 400 may be formed on the substrate 100. For ease of explanation, the surface of the first electrode layer 400 facing the substrate 100 is referred to as the bottom surface, and the surface of the first electrode layer 400 away from the substrate 100 is referred to as the top surface. The first electrode layer 400 may have a groove 410, and the groove 410 may have an upward-facing (along the Z direction in the figure) slot. A second electrode layer 600 may be formed on the side of the first electrode layer 400 away from the substrate 100, that is, the second electrode layer 600 is located on the top surface of the first electrode layer 400, and the second electrode layer 600 may include a crossbeam 610.

[0048] refer to Figures 3-6 The crossbeam 610 can extend along a first direction X (as shown in the figure, the X direction and the opposite direction of the X direction), and the crossbeam 610 can have a first end and a second end that are arranged opposite to each other along the first direction X. (Reference) Figures 7-10 The crossbeam 610 is suspended relative to the first electrode layer 400, and there is a certain distance between the crossbeam 610 and the bottom of the groove 410.

[0049] To achieve electrical connection between the crossbeam 610 and the first electrode layer 400, the second electrode layer 600 also includes anchor points. (See reference...) Figures 3-10The crossbeam may have a first side and a second side arranged opposite to each other along the second direction Y (as shown in the figure, the Y direction and the opposite direction of the Y direction). The second direction Y is perpendicular to the first direction X, and both the first direction X and the second direction Y are perpendicular to the Z direction in the figure. Each anchor point includes two anchoring parts, which are referred to as the first anchoring part 621 and the second anchoring part 622 respectively in the embodiments of this application for ease of explanation. Figures 3-6 The shaded area in the image represents the anchoring part. Figures 7-10 The dotted line in the middle can be used to distinguish the crossbeam 610 from the anchorage.

[0050] Among them, the crossbeam 610 can be Figures 3-5 The cantilever beam shown has an anchor point at only one end of the crossbeam 610. Alternatively, the crossbeam 610 can also be... Figure 6 The double-ended fixed beam shown, namely the crossbeam 610, has anchor points connected to both its first and second ends.

[0051] For example, refer to Figures 3-5 When the crossbeam 610 is a cantilever beam, the first anchoring part 621 and the second anchoring part 622 can both be connected to the first end of the crossbeam 610 or the second end of the crossbeam 610. Figures 3-5 An example is shown where both the first anchoring part 621 and the second anchoring part 622 are connected to the first end of the crossbeam 610.

[0052] The shape of the crossbeam 610 can be as follows: Figure 3 The elongated shape shown, the crossbeam 610, can also be... Figure 4 and Figure 5 The T-shape shown.

[0053] For example, refer to Figure 3 When the crossbeam 610 is elongated, it may have a first side and a second side disposed opposite to each other along the second direction Y. A first anchoring part 621 may be disposed on the first side of the crossbeam 610, and the side of the first anchoring part 621 may be connected to the first side of the crossbeam 610. A second anchoring part 622 may be disposed on the second side of the crossbeam 610, and the side of the second anchoring part 622 may be connected to the second side of the crossbeam 610. Thus, the first anchoring part 621 and the second anchoring part 622 have a certain distance in the second direction Y, so that the two connection points between the second electrode layer 600 and the first electrode layer 400 are located at opposite ends of the second electrode layer 600 in the second direction Y. This reduces the internal stress of the crossbeam 610 caused by temperature changes, prevents the crossbeam 610 from undergoing large-scale bending deformation, and thus helps improve the performance of the MEMS device.

[0054] refer to Figures 7-10The third direction Z (which can be considered as the substrate thickness direction, referring to the Z direction and the opposite direction of the Z direction in the figure) can be perpendicular to the plane formed by the first direction X and the second direction Y. The first anchoring part 621 can have a top surface and a bottom surface disposed opposite each other in the third direction Z. The bottom surface of the first anchoring part 621 can contact and be electrically connected to the top surface of the first electrode layer 400. In order to improve the connection strength between the first anchoring part 621 and the first electrode layer 400, optionally, it can be combined with Figure 3 The first anchoring portion 621 may include a first connecting segment 6211 and a first fixing segment 6212. The first connecting segment 6211 may be connected to a first side surface of the crossbeam 610 and may extend along the second direction Y. The first fixing segment 6212 may be connected to the first connecting segment 6211 and may extend along the first direction X. This increases the connection strength by increasing the contact area between the first anchoring portion 621 and the first electrode layer 400.

[0055] Furthermore, the first fixed segment 6212 may have a first end and a second end disposed opposite to each other along the first direction X. At least one end of the first fixed segment 6212 extends beyond the first connecting segment 6211. In other words, there are three possibilities: Case 1, only the first end of the first fixed segment 6212 extends beyond the first connecting segment 6211; Case 2, only the second end of the first fixed segment 6212 extends beyond the first connecting segment 6211; Case 3, as... Figure 3 As shown, the first end of the first fixed segment 6212 extends beyond the first connecting segment 6211, and the second end of the first fixed segment 6212 extends beyond the first connecting segment 6211.

[0056] Similarly, optionally, the second anchoring portion 622 may include a second connecting segment 6221 and a second fixing segment 6222. The second connecting segment 6221 may be connected to a first side of the crossbeam 610 and may extend along a second direction Y. The second fixing segment 6222 may be connected to the second connecting segment 6221 and may extend along a first direction X. In this way, the connection strength is improved by increasing the contact and connection area between the second anchoring portion 622 and the first electrode layer 400.

[0057] Furthermore, the second fixing segment 6222 may have a first end and a second end disposed opposite to each other along the first direction X. The first end of the second fixing segment 6222 may extend beyond the second connecting segment 6221; or, the second end of the second fixing segment 6222 may extend beyond the second connecting segment 6221; or, both the first and second ends of the second fixing segment 6222 and the second connecting segment 6221 may extend beyond the second connecting segment 6221. For example... Figure 3 In the structure shown, both ends of the second fixed segment 6222 extend beyond the second connecting segment 6221 along the first direction X.

[0058] Another example, refer to Figure 4 and Figure 5 The crossbeam 610 may include a main body segment 611 and an extension segment 612. The main body segment 611 may be elongated. The extension segment 612 may be located at one end of the main body segment 611 along a first direction X, and both ends of the extension segment 612 along a second direction Y may extend beyond the main body segment 611. For example, the crossbeam 610 may be T-shaped overall.

[0059] The first anchoring part 621 and the second anchoring part 622 can be implemented in the following possible ways:

[0060] In one possible implementation, such as Figure 4 As shown, the extension segment 612 may have two oppositely arranged sides along the second direction Y. A first anchoring portion 621 may be disposed on one side of the extension segment 612, and the side of the first anchoring portion 621 may be connected to one of the sides of the extension segment 612. Optionally, to improve the connection strength between the first anchoring portion 621 and the first electrode layer 400, the first anchoring portion 621 may extend along the first direction X, and both ends of the first anchoring portion 621 along the first direction X may extend beyond the extension segment 612.

[0061] Similarly, the second anchoring portion 622 can be disposed on the other side of the extension segment 612, and the side of the second anchoring portion 622 can be connected to the other side of the extension segment 612. In order to improve the connection strength between the second anchoring portion 622 and the first electrode layer 400, optionally, the second anchoring portion 622 can extend along the first direction X, and both ends of the second anchoring portion 622 along the first direction X can extend beyond the extension segment 612.

[0062] When the first anchoring part 621 and the second anchoring part 622 adopt the above method, the distance between the first anchoring part 621 and the second anchoring part 622 in the second direction Y can be further increased, so that the distance between the two connection points of the second electrode layer 600 and the first electrode layer 400 is larger, thereby reducing the internal stress of the crossbeam 610 caused by temperature changes, avoiding bending of the crossbeam 610, and improving the performance of the MEMS device.

[0063] In another possible implementation, the epitaxial segment 612 may have two oppositely arranged end faces along the first direction X. A first anchoring portion 621 may be connected to one end of the end face of the epitaxial segment 612 along the second direction Y, and a second anchoring portion 622 may be connected to the other end of the end face of the epitaxial segment 612 along the second direction Y. In this way, the two connection points of the second electrode layer 600 and the first electrode layer 400 are spaced far apart, and a greater connection force between the two electrode layers can be achieved, preventing the beam 610 from bending and improving the performance of the MEMS device.

[0064] Optionally, refer to Figure 5To improve the stability of the extension segment 612 during vibration, the first anchoring portion 621 may include two parts, each referred to as a first joint segment 6213. These two first joint segments 6213 may be arranged opposite to each other and may be connected to two opposite end faces of the extension segment 612 along the first direction X, respectively. Similarly, the second anchoring portion 622 may include two second joint segments 6223. These two second joint segments 6223 may be arranged opposite to each other and may be connected to two opposite end faces of the extension segment 612 along the first direction X, respectively.

[0065] refer to Figure 6 When the crossbeam 610 is a double-ended fixed beam, the crossbeam 610 may have a first end and a second end arranged opposite to each other along the first direction X. Each end is connected to an anchor point, and each anchor point includes a first anchoring part 621 and a second anchoring part 622. The method by which the first anchoring part 621 and the second anchoring part 622 are connected to the two ends of the crossbeam 610 can be referred to the above description. Figure 6 This example only illustrates the shape of the crossbeam 610 as a long strip, and does not impose any specific limitations.

[0066] It should be noted that for a capacitive MEMS resonator, its main structure is an electrostatic capacitor. One of the electrode plates of this electrostatic capacitor is a movable electrode plate, which includes the first electrode layer and the second electrode layer mentioned above. The other electrode plate of the electrostatic capacitor can adopt a conventional structure, which is not the focus of this application and will not be described in detail. Of course, for a capacitive MEMS resonator, in addition to the substrate and electrodes mentioned above, it also includes other structures such as a ground layer, which can also adopt a conventional structure and will not be described in detail here either.

[0067] The following is for reference. Figures 7-10 The longitudinal structure of the first anchoring part 621 and the second anchoring part 622 of the MEMS device provided in the embodiments of this application is described. This structure is applicable to both cantilever beams and double-ended fixed beams.

[0068] For example, refer to Figure 7 and Figure 8 The first electrode layer 400 may have a top surface and a bottom surface disposed opposite each other along a third direction Z, wherein the top surface faces the second electrode layer 600 and the bottom surface faces the substrate 100; a groove 410 recessed towards the bottom surface is provided on the top surface of the first electrode layer 400; of course, the depth of the groove 410 is less than the thickness of the first electrode layer 400. Both the first anchoring part 621 and the second anchoring part 622 can be formed on the top surface of the first electrode layer 400 and are in electrical contact with the top surface of the first electrode layer 400. The crossbeam 610 is suspended relative to the bottom of the groove 410, and the crossbeam 610 can be... Figure 7 As shown, it is formed on the outside of the groove 410, or the crossbeam 610 can be as follows: Figure 8 It is formed in the inner cavity of the groove 410 as shown.

[0069] Another example, refer to Figure 9 and Figure 10 At least a portion of the first anchoring portion 621 and at least a portion of the second anchoring portion 622 may be formed in the groove 410 of the first electrode layer 400.

[0070] In one of the ways, refer to Figure 9 The groove 410 may include an inner bottom wall and an inner side wall connected to the inner bottom wall. The bottom surfaces of the first anchoring portion 621 and the second anchoring portion 622 may both contact and connect with the inner bottom wall of the groove 410. Further, the sides of the first anchoring portion 621 and the second anchoring portion 622 facing away from each other may both connect with the inner side wall of the groove 410, so as to increase the contact area between the first anchoring portion 621 and the first electrode layer 400 and the second anchoring portion 622 and the first electrode layer 400, thereby enhancing the connection strength.

[0071] In another way, refer to Figure 10 The groove 410 can be a stepped groove, which may include a connected small-section groove 411 and a large-section groove 412, with the large-section groove 412 being relatively further away from the substrate 100. A portion of the first anchoring portion 621 and a portion of the second anchoring portion 622 may be formed in the large-section groove 412, and a portion of the first anchoring portion 621 and a portion of the second anchoring portion 622 may be formed on the top surface of the first electrode layer 400. In this way, the connection strength is improved by increasing the contact area. Furthermore, a portion of the first anchoring portion 621 and a portion of the second anchoring portion 622 may also be formed in the small-section groove 411.

[0072] It should be noted that the above description of the connection between the side of the crossbeam 610 and the side of the two anchoring parts is only used to introduce the specific connection and positional relationship between the three. In fact, the crossbeam and the anchoring parts are made of the same material, are an integrated structure, and can be formed in the same process step.

[0073] Figures 11A-11K for Figure 10 A cross-sectional view showing the manufacturing process of a MEMS device. (Reference) Figures 11A-11K The manufacturing process for MEMS devices can be as follows:

[0074] S101, Reference Figure 11A Substrate 100 is provided.

[0075] S102, Reference Figure 11B A ground layer 200 is obtained by heavily doping a substrate 100 with concentrated boron. The sheet resistance of the ground layer 200 is, for example, less than 3 Ω / □.

[0076] S103, Reference Figure 11C and Figure 11DAn isolation layer 300 is formed on the ground layer 200. The isolation layer 300 can be a single-layer structure, such as a single-layer silicon oxide layer or a single-layer silicon nitride layer. Figure 11C In the structure shown, the isolation layer 300 is a single-layer silicon nitride layer 310. The isolation layer 300 can also be a multi-layer structure, for example... Figure 11D In the structure shown, the isolation layer 300 includes a silicon nitride layer 310 and a silicon oxide layer 320 stacked together. The following explanation of the MEMS device fabrication process will continue with an example of a multi-layered isolation layer. Furthermore, the isolation layer 300 can be formed using PECVD (Plasma Enhanced Chemical Vapor Deposition) or LPCVD (Low Pressure Chemical Vapor Deposition).

[0077] S104, Reference Figure 11E A first conductive layer 400' is formed on the side of the isolation layer 300 away from the ground layer 200. Specifically, the first conductive layer 400' can be made of doped polysilicon. Furthermore, the first conductive layer 400' can be formed by LPCVD.

[0078] S105, Reference Figure 11F and Figure 11G The first conductive layer 400' is patterned to form the first electrode layer 400. For example, refer to... Figure 11F Photoresist can be coated onto the first conductive layer 400', and then the photoresist can be patterned (e.g., exposed and developed) to form an etching window, exposing the first conductive layer 400' to be etched; the first conductive layer 400' can be initially etched through the etching window, and a [formation] can be formed in the first conductive layer 400'. Figure 11F The large cross-section trench 412 shown in the figure has a depth less than the thickness of the first conductive layer 400′. Subsequently, photoresist is coated on the first conductive layer 400′ after preliminary etching, and the photoresist is patterned to expose part of the bottom of the large cross-section trench 412 to be etched, so as to form an etching window at the bottom of the large cross-section trench 412. The first conductive layer 400′ is then etched again through the etching window to form... Figure 11G The small cross-section groove 411 is shown in the figure. Thus, a first electrode layer 400 is formed, which includes a groove 410 having an upward-facing opening, and the groove 410 is a stepped groove.

[0079] S106, Reference Figure 11HA sacrificial layer 500 is formed on the side of the first electrode layer 400 away from the isolation layer 300. Exemplarily, the sacrificial layer 500 is formed within the small cross-section groove 411, the large cross-section groove 412, and on the top surface of the first electrode layer 400. Of course, in practice, a portion of the top surface of the isolation layer 300 is also exposed during the formation of the first electrode layer 400, so the sacrificial layer 500 also covers this portion of the isolation layer 300.

[0080] The sacrificial layer 500 can be made of silicon oxide or phosphosilicate glass (PSG) and obtained through processes such as PECVD or LPCVD, which will not be elaborated here.

[0081] S107, Reference Figure 11I The sacrificial layer 500 is etched. Exemplarily, photoresist can be coated on the sacrificial layer 500, and then patterned to form an etching window, exposing the sacrificial layer 500 to be etched. The sacrificial layer 500 is etched through the etching window to remove the sacrificial layer 500 formed in the large cross-section trench 412 and on the first electrode layer 400 and the isolation layer 300, retaining only the sacrificial layer formed in the small cross-section trench 411. Of course, Figure 11I In the structure shown, the top surface of the etched remaining sacrificial layer 500 is almost flush with the opening of the small cross-section groove 411 (or the bottom of the large cross-section groove 412). In other implementations, the top surface of the remaining sacrificial layer 500 may be slightly lower than or higher than the opening of the small cross-section groove 411.

[0082] S108, Reference Figure 11J A second conductive layer 600' is formed on the sacrificial layer 500 and the first electrode layer 400. Exemplarily, the second conductive layer 600' fills the large cross-section trench 412 and covers the first electrode layer 400 and the sacrificial layer 500. The material of the second conductive layer 600' can also be doped polycrystalline silicon. Furthermore, the second conductive layer 600' can be formed by LPCVD.

[0083] refer to Figure 11K S109. The second conductive layer 600' is patterned to obtain the second electrode layer 600. For example, photoresist can be coated on the surface of the second conductive layer 600' and patterned to form an etching window, exposing the second conductive layer 600' to be etched; the second conductive layer 600' is etched through the etching window to remove at least a portion of the second electrode layer 600 formed on the top surface of the first electrode layer 400.

[0084] S110, Reference Figure 10The sacrificial layer 500 is removed to release the crossbeam 610. For example, multiple through holes can be simultaneously etched into the crossbeam 610 during the etching process to form the second electrode layer 600, and then the sacrificial layer 500 is removed using an etching material such as VHF (Vapor Hydrogen Fluoride).

[0085] The above combination Figures 11A-11K Explained Figure 10 The manufacturing process of the MEMS device is shown. For Figures 7-9 The manufacturing process of the MEMS device shown can be used as a reference by those skilled in the art. Figures 11A-11K The results were derived through simple deduction and related textual explanations. Further details will not be elaborated upon here.

[0086] It should be noted that, Figures 7 to 10 In the structures of the MEMS devices shown, a first electrode layer with grooves is first formed. Then, a crossbeam in the second electrode layer is suspended based on a sacrificial layer. The shape of the crossbeam is basically determined by the shape of the sacrificial layer, and the construction of the anchor points depends on the shape of the grooves and the thickness and patterning of the sacrificial layer. In other embodiments, grooves may not be formed in the first electrode layer. Instead, the sacrificial layer is patterned to expose part of the first electrode layer, facilitating electrical contact with the subsequently formed second electrode layer (this contacted part later forms the anchor points). The sacrificial layer corresponding to the crossbeam portion is made higher than the top surface of the first electrode layer. Thus, the subsequently formed second electrode layer forms a groove due to its shape. The bottom of the groove faces away from the first electrode layer, and the groove opening faces the first electrode layer. After removing the sacrificial layer, the crossbeam portion of the second electrode layer can be suspended on the first electrode layer.

[0087] The technical solution of this application embodiment is explained above using a MEMS resonant beam device as an example. In other embodiments, all MEMS devices with cantilever beams or double-ended fixed beams and other anchor-fixed ends can adopt the above structure.

[0088] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0089] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0090] Although preferred embodiments of this application have been described above, those skilled in the art may make other modifications and variations beyond these embodiments without departing from the spirit of this application and / or beyond the scope of the claims of this application. Such modifications and variations shall fall within the scope of the claims of this application and their equivalents.

Claims

1. A MEMS device, characterized in that, include: Substrate; A first electrode layer is formed based on the substrate; A second electrode layer located on the first electrode layer, the second electrode layer including a crossbeam and an anchor point; The crossbeam is suspended on the first electrode. The crossbeam extends along a first direction and has two oppositely arranged ends. The crossbeam has two oppositely arranged sides along a second direction. Both the first direction and the second direction are perpendicular to the substrate thickness direction, and the first direction is perpendicular to the second direction. At least one end of the crossbeam is provided with the anchor point, each anchor point includes two anchoring parts, the two anchoring parts are respectively fixed to both sides of the crossbeam, and each anchoring part is in electrical contact with the first electrode layer; the crossbeam includes a main body segment and an extension segment; the main body segment is elongated and extends along a first direction; the extension segment is provided at one or both ends of the main body segment along the first direction, and both ends of the extension segment along the second direction extend beyond the main body segment; the anchoring parts are connected to the extension segment; The first electrode layer has a top surface facing the second electrode layer, and a groove is formed on the top surface; the crossbeam is suspended on the groove.

2. The MEMS device according to claim 1, characterized in that, The anchoring part includes a connecting section and a fixing section. The connecting section is connected to one side of the crossbeam and extends along a second direction, and the fixing section is connected to the connecting section and extends along a first direction.

3. The MEMS device according to claim 2, characterized in that, The fixed segment has two opposing ends along the first direction, wherein at least one end extends beyond the connecting segment.

4. The MEMS device according to claim 1, characterized in that, The extension has two opposing sides along the second direction; the anchoring portion is connected to the side of the extension and extends along the first direction, and at least one of the two ends of the anchoring portion along the first direction extends beyond the extension.

5. The MEMS device according to claim 1, characterized in that, The anchoring part comprises two parts; The extension segment has two oppositely arranged end faces along the first direction; each end face is connected to a portion of the anchoring part.

6. The MEMS device according to any one of claims 2-4, characterized in that, The anchoring part is in electrical contact with the top surface of the first electrode layer.

7. The MEMS device according to any one of claims 2-4, characterized in that, At least a portion of the anchoring portion is located within the groove.

8. The MEMS device according to any one of claims 2-4, characterized in that, The second electrode layer has a bottom surface facing the first electrode layer, and a groove is formed on the bottom surface corresponding to the crossbeam so that the crossbeam can be suspended on the first electrode layer, and the bottom surface corresponding to the anchoring part is in electrical contact with the first electrode layer.

9. The MEMS device according to any one of claims 1-5, characterized in that, The MEMS device includes a MEMS resonator.

10. The MEMS device according to claim 6, characterized in that, The MEMS device includes a MEMS resonator.

11. The MEMS device according to claim 7, characterized in that, The MEMS device includes a MEMS resonator.

12. The MEMS device according to claim 8, characterized in that, The MEMS device includes a MEMS resonator.

13. A method for fabricating a MEMS device, characterized in that, include: A first conductive layer is formed on a substrate, and the first conductive layer is patterned to form a first electrode layer; A sacrificial layer is formed on the first electrode layer, and the sacrificial layer is partially etched to expose a portion of the first electrode layer; A second conductive layer is formed on a first electrode layer and a sacrificial layer. The second conductive layer is patterned to expose the sacrificial layer. The patterned second conductive layer includes a beam and anchor points to form the second electrode layer. The beam is spaced apart from the first electrode layer by the sacrificial layer. The beam extends along a first direction and has two oppositely arranged ends. The beam has a first side and a second side oppositely arranged along a second direction. Both the first and second directions are perpendicular to the substrate thickness direction, and the first direction is perpendicular to the second direction. Each end of the beam is connected to an anchor point. The crossbeam includes two anchoring parts, which are respectively fixed to a first side and a second side of the crossbeam, and each anchoring part is in electrical contact with a first electrode layer. The first electrode layer has a top surface facing the second electrode layer, and a groove is formed on the top surface. The crossbeam is suspended on the groove. The crossbeam includes a main body segment and an extension segment. The main body segment is elongated and extends along a first direction. The extension segment is disposed at one or both ends of the main body segment along the first direction, and both ends of the extension segment along the second direction extend beyond the main body segment. The anchoring parts are connected to the extension segment. Remove the sacrificial layer so that the beam is suspended on the first electrode layer.

14. The preparation method according to claim 13, characterized in that, The MEMS device includes a MEMS resonator.

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