Micro-electro-mechanical structure

Abstract

A micro-electro-mechanical structure includes a first electrode, a second electrode, and a cantilevered arm. The cantilevered arm is fixed to the first electrode and over the second electrode with a gap between the first electrode and the second electrode. The cantilevered arm includes an arm structure and a lower protective dielectric layer disposed on a lower side of the arm structure.

Description

Technical Field

[0001] This disclosure relates to a microelectromechanical structure. Background Technology

[0002] The following content pertains to semiconductor devices and their manufacturing technologies, microelectromechanical (MEMS) technology, MEMS actuators and sensors and their manufacturing, MEMS comb drives and their manufacturing, and related technologies. Utility Model Content

[0003] Another embodiment of this disclosure reveals a microelectromechanical structure (MEMS) including a first electrode, a second electrode, and a cantilever arm. The cantilever arm is fixed to the first electrode and sits above the second electrode, with a gap between the first and second electrodes. The cantilever arm includes an arm structure and a lower protective dielectric layer disposed on the lower side of the arm structure.

[0004] Another embodiment of this disclosure reveals a microelectromechanical structure (MEMS) including a first electrode, a second electrode, and a cantilever arm. The cantilever arm is fixed to the first electrode and sits above the second electrode, with a gap between the first and second electrodes. The cantilever arm includes an arm structure and a lower protective dielectric layer disposed on the lower side of the arm structure, wherein the cantilever arm is capacitively coupled to the second electrode.

[0005] Another embodiment of this disclosure reveals a microelectromechanical structure (MEMS) including a first electrode, a second electrode, and a cantilever arm. The cantilever arm is fixed to the first electrode and sits above the second electrode, with a gap of 1 to 2 micrometers between the first and second electrodes. The cantilever arm includes an arm structure and a lower protective dielectric layer disposed on the lower side of the arm structure. Attached Figure Description

[0006] The state of this disclosure is in relation to the accompanying items. Figure 1 The best way to understand this text is by referring to the detailed description below. Note that, according to industry standards, the features are not drawn to scale. In practice, the dimensions of the features can be arbitrarily increased or decreased for clarity of explanation.

[0007] Figure 1 , Figure 2 , Figure 3 ,and Figure 4 The schematic diagram shows a cross-sectional view of a continuous intermediate structure used in the manufacturing process of a MEMS arm.

[0008] Figure 5 The illustration shows etching using a fluorine-based etchant. Figure 4 A cross-sectional view of the MEMS arm formed by the intermediate structure;

[0009] Figure 6Schematic diagrams include Figure 5 Capacitive MEMS sensors for MEMS arms;

[0010] Figure 7 Schematic diagrams include Figure 5 Capacitive MEMS actuator for MEMS arm;

[0011] Figure 8 , Figure 9 ,and Figure 10 The schematic diagram shows a cross-sectional view of an additional illustrative MEMS arm embodiment;

[0012] Figure 11 Schematic illustrations include using, for example Figure 5 and Figures 8 to 10 A cross-sectional view of a MEMS device with a properly fixed drive comb-like arm structure;

[0013] Figure 12 , Figure 13 , Figure 14 , Figure 15 , Figure 16 , Figure 17 ,and Figure 18 Schematic diagrams are used for manufacturing Figure 11 A cross-sectional view of the intermediate structure of an illustrative MEMS device manufacturing process.

[0014] [Symbol Explanation]

[0015] 10: First electrode

[0016] 12: Second electrode

[0017] 14: First electrode protective dielectric layer

[0018] 16: Second electrode protects the dielectric layer

[0019] 18: Spacers

[0020] 20: Release Structure

[0021] 22: Floor / First Floor

[0022] 24: Floor / Second Floor

[0023] 26: Opening

[0024] 28: Lower protective dielectric layer

[0025] 281: First lower protective dielectric layer

[0026] 282: Second lower protective dielectric layer

[0027] 30: Arm Structure

[0028] 301, 302: Floors

[0029] 32: Bending

[0030] 40, 50, 60, 70: Cantilever arm

[0031] 42: Fluorine atom

[0032] 44: Sensor readout circuit

[0033] 46: Actuator drive circuit

[0034] 100: Drive comb

[0035] 102: Comb-like structure

[0036] 104: Spring

[0037] 106: Middle Framework

[0038] 108: Metal Spring

[0039] 110: External Framework

[0040] 112: First wafer / Upper wafer

[0041] 114: Second wafer / lower wafer

[0042] 116: Cavity

[0043] 118: Legend

[0044] 120: Photoresist

[0045] 122: Passivation oxide layer

[0046] 123: Protecting oxides

[0047] 124: Photoresist

[0048] d: Spacing Detailed Implementation

[0049] The following disclosure provides numerous different embodiments or instances for implementing various features of the provided subject matter. Specific examples of components and configurations are described below to simplify this disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature above or on a second feature in the following description may include embodiments where the first and second features are formed in direct contact, and may also include embodiments where additional features may be formed between the first and second features such that the first and second features are not in direct contact. Furthermore, reference numerals and / or letters may be repeated in various instances of this disclosure. This repetition is for simplicity and clarity and does not, in itself, indicate any relationship between the various embodiments and / or configurations discussed.

[0050] Furthermore, for ease of description, spatial relative terms such as “below,” “under,” “lower,” “above,” “upper,” and the like are used herein to describe the relationship between one element or feature illustrated in the figures and another element(s). Spatial relative terms are intended to cover different orientations of the device during use or operation, other than those depicted in the figures. Devices may be oriented in other ways (rotated 90 degrees or otherwise), and the spatial relative descriptors used herein can be interpreted similarly accordingly.

[0051] Microelectromechanical (MEMS) devices typically include MEMS arm structures that can move in response to external stimuli or be actuated in response to electrical input. For example, a MEMS arm in the form of a cantilever, made of metal or other conductive material, can be configured with its anchored end connected to a first electrode and its free end positioned in proximate to a second electrode. In such a design, the first and second electrodes constitute a capacitive drive. The capacitance between the second electrode and the cantilever changes as the cantilever moves toward or away from the second electrode.

[0052] Such capacitive MEMS cantilever arms can be used as sensors, where the input to be measured (i.e., sensed) modifies the cantilever arm's positioning relative to a second electrode. For example, the input could be the acceleration of the moving cantilever arm. In other types of MEMS-based sensors, the input could be acoustic waves or magnetic signals. For instance, if the cantilever arm has a magnetic material at its free end, the arm can move in response to an external magnetic field.

[0053] Such capacitive MEMS cantilever arms can be used alternatively as MEMS actuators. In this case, the voltage or other electrical input between the first and second electrodes generates an electrostatic force on the cantilever arm, thereby producing motion.

[0054] In some designs, the cantilever arm can be a connector, with one component (such as a comb) attached to the free end of the cantilever connector arm. Such combs can provide stronger electrostatic interactions.

[0055] In some methods for forming MEMS arms, a sacrificial layer (also called a release layer) is formed, followed by the formation of an arm structure (e.g., a patterned metal layer) intended to be a cantilever arm. For example, the sacrificial layer may be made of silicon, while the arm structure is a patterned metal layer. The release layer is then removed by a fluorine-based etching process. Advantageously, fluorine-based etchants have higher selectivity for etching silicon than metals, thus the fluorine-based etching removes the release layer without removing the arm structure.

[0056] refer to Figures 1 to 5This describes the process for manufacturing MEMS arms that include cantilever arms. Figure 5 The diagram shows the final structure of the first electrode 10, the second electrode 12, and the cantilever arm 40. Figures 1 to 4 A cross-sectional view showing the sequential steps in its manufacturing process. Figure 1 The figure illustrates a basic structure on which a cantilever arm 40 is to be formed. An exemplary basic structure includes capacitive drive of a first electrode 10 and a second electrode 12. The first electrode 10 and the second electrode 12 are suitably formed of a conductive material. In some non-limiting illustrative embodiments, the first electrode 10 comprises a silicon material, such as, for example, silicon, polycrystalline silicon, amorphous silicon, or combinations thereof, although other materials besides silicon are also contemplated. The first electrode 10 is covered with a first electrode protection dielectric layer 14; similarly, in some non-limiting illustrative embodiments, the second electrode 12 comprises a silicon material, such as, for example, silicon, polycrystalline silicon, amorphous silicon, or combinations thereof, although other materials besides silicon are also contemplated. The second electrode 12 is covered with a second electrode protection dielectric layer 16. The first electrode protection dielectric layer 14 and the second electrode protection dielectric layer 16 comprise a dielectric material that is not removed by a fluorine-based etchant intended for removing the release layer. For example, as a non-limiting illustrative example, the first electrode protection dielectric layer 14 and the second electrode protection dielectric layer 16 may comprise silicon oxide (e.g., ideally sized silicon dioxide, SiO2, or non-ideally sized silicon oxide), silicon nitride (e.g., ideally sized Si3N4 or non-ideally sized silicon nitride), silicon carbide, silicon oxynitride, or glasses such as undoped silicon glass (USG), fluorosilicon glass (FSG), borosilicate glass (BPSG), or various combinations thereof, although other materials are also contemplated. As a non-limiting illustrative example, the thickness of the first electrode protection dielectric layer 14 and the second electrode protection dielectric layer 16 may be in the range of 0.1 to 0.3 micrometers, although thicknesses outside this range are also contemplated.

[0057] In other embodiments, the first electrode 10 and the second electrode 12 may comprise a type of conductive material that will not be strongly etched by a fluorine-based etchant intended to remove the release layer. For example, the first electrode 10 and the second electrode 12 may comprise metals such as aluminum (Al) or copper (Cu), metal alloys such as AlCu (optionally further including silicon, i.e., AlSiCu), metal nitrides such as titanium nitride (TiN) or tantalum nitride (TaN), or combinations thereof, but other materials are also contemplated. In these embodiments, the first electrode protective dielectric layer 14 and the second electrode protective dielectric layer 16 may optionally be omitted.

[0058] like Figure 1As further shown, in addition to the capacitive drive comprising the first electrode 10 and the second electrode 12, the basic structure further includes a spacer 18 inserted between the first electrode 10 and the second electrode 12. The illustrative spacer 18 is intended to be removed by a fluorine-based etchant used to remove the release layer. Therefore, the spacer 18 should be made of a material strongly etched by a fluorine-based etchant, such as a silicon material (e.g., silicon, polycrystalline silicon, amorphous silicon, or combinations thereof, although other materials are also contemplated).

[0059] In other embodiments, it is envisioned that the spacer between the first electrode 10 and the second electrode 12 is not removed by a fluorine-based etchant. In such alternative embodiments, the spacer should comprise an electrically insulating material, such that the first electrode 10 and the second electrode 12 in the final fabricated capacitive MEMS structure are electrically isolated from each other.

[0060] Figure 1 The basic structure can be manufactured in various ways. In one concept, a photolithographic patterning etching is performed on a substrate or layer containing silicon material intended to form the first electrode 10 and the second electrode 12 to form trenches in the substrate or layer. Next, layers of dielectric material for the first electrode protection dielectric layer 14 and the second electrode protection dielectric layer 16 are deposited, thereby covering the first electrode 10 and the second electrode 12 with the individual first electrode protection dielectric layers 14 and 16. Then, photolithographic controlled deposition is performed to fill the trenches with silicon material, thereby forming spacers 18. In an illustrative example, the first electrode 10 is intended to be an anchor for a cantilever arm, for which the first electrode 10 is higher than the second electrode 12, such as... Figure 1 As shown, this provides a step between the first electrode 10 and the second electrode 12. This can be accomplished in various ways, such as by photolithographic deposition of additional silicon material to increase the height of the first electrode 10 (before forming the first electrode protective dielectric layer 14), or by photolithographic etching of silicon material to decrease the height of the second electrode 12 (before forming the second electrode protective dielectric layer 16).

[0061] Now refer to Figure 2A release structure 20 is disposed on the basic structure. The release structure 20 is suitably formed of a silicon material, which is etched by a fluorine-based etchant to be used in a subsequent release step. For example, the release structure 20 may comprise a silicon material such as silicon, polycrystalline silicon, amorphous silicon, or combinations thereof, although other materials besides silicon are also contemplated. In an illustrative example, the release structure 20 is formed of two distinct first layers 22 and second layers 24 of different silicon materials. For example, in one embodiment, the first layer 22 comprises a silicon material forming a smooth interface with the underlying first electrode 10 and second electrode 12, which is formed as polycrystalline silicon using a deposition technique that provides small grains; while the second layer 24 comprises a silicon material that can be deposited at a faster deposition rate, such as polycrystalline silicon deposited with a larger average grain size. This is merely a non-limiting illustrative example. In a non-limiting illustrative embodiment, the total thickness of the release structure 20 is about 1 to 2 micrometers, although larger or smaller thicknesses are also contemplated. The thickness of the release structure 20 will determine the unbiased spacing between the second electrode 12 and the cantilever arm (which in turn will affect the unbiased capacitance), therefore the thickness of the release structure 20 is selected to provide a design-based unbiased spacing / capacitance. Figure 2 As shown, due to the height difference between the first electrode 10 and the second electrode 12, the illustrative release structure 20 includes a step located near the positioning of the spacer 18.

[0062] Now refer to Figure 3 The cantilever arm to be formed has one end anchored to an anchor. In the illustrative example, the anchor is the first electrode 10. Therefore, as... Figure 3 As shown, an opening 26 is formed in at least a portion of the release structure 20 disposed above the first electrode 10, for example, by photolithography etching of the release structure 20. In a suitable method, the opening 26 is etched using a fluorine-based etchant that etches the silicon material of the release structure 20 but not the first electrode protective dielectric layer 14, such that the first electrode protective dielectric layer 14 serves as an etch stop for etching the opening 26. The size of the opening 26 should be large enough to provide sufficient anchorage for the cantilever arm, thereby ensuring structural reliability under reliable expected forces that can be applied to the cantilever arm during use of the MEMS structure. In a non-limiting illustrative example, the opening 26 has a circular region with a diameter of approximately 2 to 3 micrometers, although larger or smaller opening sizes, as well as openings with non-circular regions, are conceivable.

[0063] Now refer to Figure 4 The lower protective dielectric layer 28 is deposited at least on the release structure 20, and in an exemplary embodiment, it is also deposited on the opening 26 (see Figure 3In the process, an arm structure 30 is then formed, positioned above the first electrode 10 and the second electrode 12, and above the spacer 18 between them. The arm structure 30 (and the lower protective dielectric layer 28) are planned to form a cantilever arm 40 (see...) after the release step. Figure 5 ), wherein the cantilever boom 40 is anchored to an anchor (in Figure 5 In this example, the anchor is one end of the first electrode 10. For Figures 1 to 5 In the illustrative example of the fabricated capacitive MEMS structure, a cantilever arm 40 is to be capacitively coupled to the second electrode 12. Therefore, the arm structure 30 (with the underlying lower protective dielectric layer 28) is also disposed above the second electrode 12. Figure 4 As shown. The purpose of the lower protective dielectric layer 28 is to protect the lower surface of the arm structure 30 during subsequent fluorine-based etching, as referenced. Figure 5 As described.

[0064] In some non-limiting illustrative embodiments, the lower protective dielectric layer 28 comprises silicon oxide (e.g., ideally saturated silicon dioxide, SiO2, or non-ideally saturated silicon oxide), silicon nitride (e.g., ideally saturated Si3N4 or non-ideally saturated silicon nitride), silicon carbide, silicon oxynitride, or glass such as USG, FSG, BPSG, or various combinations thereof. These materials are highly resistant to fluorine etching and thus provide protection for the lower surface of the arm structure 30 during etching. The thickness of the lower protective dielectric layer 28 is selected to provide sufficient protection for the underside of the arm structure 30 during subsequent fluorine etching, which in turn depends on various factors such as the type of materials constituting the lower protective dielectric layer 28 and the nature of the fluorine etching, such as the etching tool used, the etchant concentration, and the etching time. In some non-limiting illustrative examples, the lower protective dielectric layer 28 may have a thickness between 0.2 micrometers and 1 micrometer, although thicknesses outside this range are also conceivable.

[0065] The arm structure 30 is appropriately shaped into a layer disposed on the release structure 20 (with a lower protective dielectric layer 28 inserted therebetween, such as...). Figure 4 (As shown). The deposited arm structure 30 also covers the interior of the opening 26 to provide predetermined anchoring of the cantilever arm 40 to the first electrode 10, which serves as the anchor structure (see...). Figure 5In some non-limiting illustrative embodiments, the arm structure 30 comprises a metal (e.g., copper), a metal alloy (e.g., AlCu), AlSiCu, a metal nitride (e.g., TiN or TaN), or a combination thereof, although other materials are also contemplated. The material and thickness of the arm structure 30 are chosen to provide a cantilever arm with selected design-based properties, such as strength, flexibility, etc. In some non-limiting illustrative examples, the arm structure 30 may have a thickness between 0.2 micrometers and 1 micrometer, although thicknesses outside this range are also contemplated. The arm structure 30 (together with the underlying lower protective dielectric layer 28) coincides with the upper surface of the underlying release structure 20; therefore, in non-limiting illustrative examples, the arm structure 30 has Figure 4 The bend shown is 32.

[0066] refer to Figure 5 The release structure 20 is achieved by using a fluorine-based etchant (in... Figure 5 The fluorine atom 42 (illustrated in the diagram) is removed by etching. This causes the unanchored end of the arm structure 30 to be released, forming a cantilever arm 40. The cantilever arm 40 is also known as a microelectromechanical (MEMS) arm. In this embodiment, the cantilever arm 40 is fixed at one end to a first electrode 10, which serves as an anchor structure, and has a relative end that moves freely in response to an electrical input between the first electrode 10 and the second electrode 12, or in response to another type of stimulus such as sound waves, acceleration, etc. Figure 5 As shown, the cantilever arm 40 includes an arm structure 30 and a lower protective dielectric layer 28. Etching can be performed using various etching tools and processes, such as reactive ion etching (RIE), inductively coupled plasma etching (ICP), and distal plasma etching, as some non-limiting illustrative examples. Fluorine-based etchants include fluorine or fluorine compounds as active etchant species. For example, fluorine-based etchants may contain CF4 gas and / or SF6 gas, as two non-limiting illustrative examples. Fluorine is a highly reactive atom; therefore, the active fluorine or fluorine compounds in fluorine-based etchants effectively etch and release structure 20 (see...). Figure 4 As previously described, the release structure 20 is formed of a silicon material such as silicon, polycrystalline silicon, amorphous silicon, or combinations thereof. By comparison... Figure 4 and Figure 5 It can also be seen that spacer 18 (see Figure 4The spacer 18 is removed by a fluorine-based etchant. For this purpose, the spacer 18 is made of a material etched by a fluorine-based etchant, such as silicon (e.g., silicon, polycrystalline silicon, amorphous silicon, or combinations thereof, although other materials besides silicon are also conceivable). The removal of the spacer 18 results in the first electrode 10 and the second electrode 12 being spaced apart from each other by the width of the (now removed) spacer 18.

[0067] It should be understood that, in some embodiments, although the first electrode 10 and the second electrode 12 are suitably made of silicon material, they are protected from etching by fluorine-based etchants by individual first electrode protection dielectric layer 14 and second electrode protection dielectric layer 16, which are made of suitable resistive materials such as silicon oxide, silicon nitride, silicon carbide, silicon oxynitride, glass, or various combinations thereof.

[0068] As previously described, arm structure 30 comprises a metal or metal alloy, a metal nitride, or a combination thereof. Fluorine-based etchants typically exhibit higher selectivity for etching silicon than metals, metal alloys, and / or metal nitrides. In other words, fluorine-based etchants typically etch silicon very quickly, while they may not etch metals, metal alloys, and / or metal nitrides, or etch them at a much slower rate than silicon. Therefore, the fluorine-based etchant used in the release step selectively etches and removes the release structure 20 of silicon while leaving arm structure 30, thereby releasing arm structure 30 (except for its anchoring to the first electrode 10) to form cantilever arm 40. Therefore, the benefits provided by the lower protective dielectric layer 28 are not apparent due to the high selectivity of the fluorine-based etching.

[0069] However, this paper recognizes that fluorine-based etchants can erode the metal, metal alloy, or metal nitride material of arm structure 30, although at a much slower rate compared to the etching rate of the silicon material of release structure 20 (and the silicon material of spacer 18). For example, in the reference MEMS arm structure studied in this paper, scanning electron microscopy (SEM) revealed that the AlCu surface after etching with a fluorine-based etchant included protrusions or other non-planar features. Without being limited to any particular operational theory, these protrusions are considered to be generated by the fluorine etching of the AlCu surface during etching.

[0070] Based on the recognition that fluorine-based etching can produce protrusions or other non-planar features on AlCu surfaces, this paper discloses a lower protective dielectric layer 28 to protect the lower surface of the arm structure 30 during fluorine-based etching. As previously described, in some non-limiting illustrative embodiments, the lower protective dielectric layer 28 comprises silicon oxide, silicon nitride, silicon carbide, silicon oxynitride, glass, or various combinations thereof. These materials are impermeable to, or at least highly resistant to, etching by fluorine-based etchants. Therefore, the lower protective dielectric layer 28 disposed on the lower surface of the arm structure 30 protects the lower surface from fluorine-based etchants. Without the lower protective dielectric layer 28, fluorine etching would interact directly with the lower surface of the arm structure 30, which could result in the formation of protrusions or other non-planar features on the arm structure 30.

[0071] It is beneficial to protect the arm structure 30, especially its lower surface, from fluorine corrosion by the lower protective dielectric layer 28, because the erosion of the lower surface of the arm structure 30 by the fluorine-based etchant can alter the spacing between the lower surface of the cantilever arm 40 and the upper surface of the second electrode 12. Figure 5 The spacing d, as shown in the figure, is small and approximately equal to the thickness of the release structure 20 (e.g., Figure 4 As shown (before removal by fluorine-based etching). The spacing d can differ from the thickness of the release structure 20 due to various factors, such as sag under gravity and / or electrostatic attraction or repulsion caused by the accumulation of electrostatic charge on the second electrode 12 and / or the cantilever arm 40, which may attract the cantilever arm 40 toward the second electrode 12 or repel the cantilever arm 40 away from the second electrode 12, depending on the polarity of the electrostatic charge. As previously mentioned, in some non-limiting illustrative embodiments, the thickness of the release structure 20 is approximately 1 to 2 micrometers, although larger or smaller thicknesses are also conceivable. Therefore, in such embodiments, the spacing d is also approximately 1 to 2 micrometers, although larger or smaller spacing values ​​are also conceivable.

[0072] The spacing d has a strong influence on the operation of capacitive MEMS devices. The voltage difference ΔV between the first electrode 10 and the second electrode 12 manifests as the voltage difference ΔV between the cantilever arm 40 and the second electrode 12 (ignoring any voltage drop along the cantilever arm 40). The electric field exists in the gap d between the cantilever arm 40 and the second electrode 12. Quantity Therefore, by Give the value of the spacing d, and This inverse relationship with d means that a small change in spacing d caused by the corrosion of the lower surface of the cantilever arm by fluorine can significantly alter the strength of the electric field existing between the cantilever arm 40 and the second electrode 12. Furthermore, SEM analysis revealed that the erosion of the lower surface of the cantilever arm by fluorine was spatially non-uniform, resulting in surface roughness and / or protrusions. Without being limited to any particular operating theory, this is considered to constitute AlCu surface damage due to erosion by the fluorine-based etchant. Such roughness and / or protrusions can locally modify the electrostatic potential difference between the cantilever arm 40 and the second electrode 12, resulting in locally higher electric field regions at the protrusions, which can lead to performance degradation and / or failure mechanisms, such as coronal discharges at such protrusions. These problems are mitigated by including a lower protective dielectric layer 28 as disclosed herein, thereby making the cantilever arm 40 comprise the arm structure 30 and the lower protective dielectric layer 28.

[0073] refer to Figure 6 and Figure 7 , Figure 5 The illustrative capacitive MEMS device can be used in sensor applications. Figure 6 ) or used as an actuator ( Figure 7 ).exist Figure 6 In the sensor device, the sensor readout circuit 44 measures the capacitance (or related electrical parameters, such as voltage or current) between the first electrode 10 and the second electrode 12. If the cantilever arm 40 moves in response to a stimulus, this will be detected as a change in capacitance (or related electrical parameters) measured by the sensor readout circuit 44. The stimulus that causes the movement of the cantilever arm 40 may be, for example, acceleration (in this case, Figure 6 The sensing device is appropriately an accelerometer, or a sound wave, etc. Figure 7 In the actuator device, the actuator drive circuit 46 applies a voltage difference (or other driving electrical signal, such as current) to the first electrode 10 and the second electrode 12, thereby generating an electrostatic force (e.g., repulsion and / or attraction) between the second electrode 12 and the cantilever arm 40, causing the cantilever arm to actuate away from the second electrode 12 (repulsion) and / or toward the second electrode 12 (attraction). If an alternating voltage or current (i.e., an AC signal) is applied through the actuator drive circuit 46, an oscillating motion of the cantilever arm 40 can be generated. The resulting actuated motion can drive the movement of elements connected to the cantilever arm 40, or can generate sound waves, or perform another useful power function. In these non-limiting illustrative applications, the sensor readout circuit 44 or the actuator drive circuit 46 is suitably implemented as an electronic circuit including transistors, MOSFETs, etc.

[0074] refer to Figure 8 The image shows a cross-sectional view of another illustrative MEMS arm embodiment. Figure 8 The MEMS arm is similar to Figure 5The MEMS arm includes a first electrode 10 and a second electrode 12, a first electrode protective dielectric layer 14 and a second electrode protective dielectric layer 16, and a cantilever arm 50 including an arm structure 30 and a lower protective dielectric layer 28. Figure 8 In one embodiment, the arm structure 30 comprises a stack of at least two layers 301 and 302 of different materials, each layer comprising a metal, a metal alloy, a metal nitride, or a combination thereof. Figure 8 In one embodiment, the cantilever arm 50 includes a stacked arm structure 30 comprising layers 301 and 302 and a lower protective dielectric layer 28. Figure 8 The fabrication of the MEMS arm follows a previous reference. Figures 1 to 5 The difference in the order is that, in Figure 4 The stage depicted in the text shows two layers, 301 and 302, deposited consecutively.

[0075] exist Figure 8 In one hypothetical application of the embodiment, the two layers 301 and 302 may form a bimetallic thermometer. In such embodiments, the two layers 301 and 302 are made of different metals with different coefficients of thermal expansion. Therefore, when the temperature of the arm structure 30 changes, one metal expands (or contracts) faster than the other, causing the cantilever arm 50 to bend toward or away from the second electrode 12, thereby changing the capacitance. The change in capacitance (or another relevant electrical parameter) can be transmitted through... Figure 6 The sensor readout circuit 44 performs measurements to provide temperature sensing functionality.

[0076] refer to Figure 9 The image shows a cross-sectional view of another illustrative MEMS arm embodiment. Figure 9 The MEMS arm is similar to Figure 5 The MEMS arm includes a first electrode 10 and a second electrode 12, a first electrode protective dielectric layer 14 and a second electrode protective dielectric layer 16, and a cantilever arm 60 including an arm structure 30 and a lower protective dielectric layer 28. However, in Figure 9 In one embodiment, the lower protective dielectric layer 28 includes a dielectric layer stack, which includes a first lower protective dielectric layer 281 and a second lower protective dielectric layer 282. Figure 9 The fabrication of the MEMS arm follows a previous reference. Figures 1 to 5 The difference in the order is that, in Figure 4At the stages depicted, the deposition sequence includes depositing a first lower protective dielectric layer 281, followed by depositing a second lower protective dielectric layer 282, and then depositing or otherwise forming the arm structure 30. The first lower protective dielectric layer 281 and the second lower protective dielectric layer 282 are appropriately different fluorine-resistant etchant materials. For example, the first lower protective dielectric layer 281 may comprise silicon oxide (e.g., ideally sized silicon dioxide, SiO2, or non-ideally sized silicon oxide), silicon nitride (e.g., ideally sized Si3N4 or non-ideally sized silicon nitride), silicon carbide, silicon oxynitride, or glass such as USG, FSG, BPSG, or various combinations thereof; the second lower protective dielectric layer 282 may comprise silicon oxide (e.g., ideally sized silicon dioxide, SiO2, or non-ideally sized silicon oxide), silicon nitride (e.g., ideally sized Si3N4 or non-ideally sized silicon nitride), silicon carbide, silicon oxynitride, or glass such as USG, FSG, BPSG, or various combinations thereof; wherein the first lower protective dielectric layer 281 and the second lower protective dielectric layer 282 are different materials. These are also merely non-limiting illustrative examples. Figure 9 In the embodiment, the cantilever arm 60 therefore includes an arm structure 30 and a lower protective dielectric layer 28, wherein the latter includes a dielectric layer stack of a first lower protective dielectric layer 281 and a second lower protective dielectric layer 282. Although Figure 9 The illustration shows a variation of the lower protective dielectric layer 28, which is a stack of two constituent first and second lower protective dielectric layers 281 and 282. However, it should be understood that this can be extended to three, four, or more constituent dielectric layers.

[0077] refer to Figure 10 The image shows a cross-sectional view of another illustrative MEMS arm embodiment. Figure 10 The MEMS arm is formed by stacking dielectric layers, such as a first lower protective dielectric layer 281 and a second lower protective dielectric layer 282, through the lower protective dielectric layer 28. Figure 9 As shown), the arm structure 30 is also formed as a stack of two layers 301 and 302 made of different materials, effectively combining... Figure 8 and Figure 9 The embodiments thereby form a first lower protective dielectric layer 281 and a second lower protective dielectric layer 282 (as shown in the reference). Figure 9 As described above), and two layers 301 and 302 of different materials (as referenced). Figure 8 The cantilever arm 70 (described above).

[0078] Figures 1 to 10An illustrative example is a MEMS arm, wherein the MEMS arm is a cantilever arm 40 (or 50, or 60, or 70) anchored at one end to a first electrode 10, and its unanchored (i.e., free) end positioned near a second electrode 12 (e.g., having a...). Figures 5 to 7 The spacing d shown is used. This forms a capacitive MEMS device, in which the capacitance between the cantilever arm and the second electrode 12 can be used to perform sensing functionality (e.g., Figure 6 ), or can be operated as a capacitive actuator (e.g., Figure 7 Although not shown, the free end of the cantilever arm 40 may be connected to a component such as a comb, such that movement of the cantilever arm 40 causes movement of the comb (or other component) attached to the free end of the cantilever arm 40. It should be understood that other types of MEMS arms can be fabricated similarly. As another example, instead of a cantilever configuration, the MEMS arm may be anchored to (i.e., suspended from) the two ends of the arm, and the middle portion of the MEMS arm may flex in response to electrical input, sound waves, or other types of stimuli (while the two ends remain anchored). In another example, the MEMS arm may be a spring anchored to the two ends. These are merely further, non-limiting examples. In any such embodiment, the MEMS arm comprises a cantilever or suspended arm of metal, metal alloy, metal nitride, or a combination thereof, which is released by etching to remove the release layer using a fluorine-based etchant. For example, the methods disclosed herein are useful when fabricating MEMS spring structures comprising suspended arms of metal, metal alloy, metal nitride, or a combination thereof.

[0079] refer to Figure 11 The image shows a cross-sectional view of a MEMS device including a drive comb 100, which comprises a comb 102 fixed to a cantilever arm. The cantilever arm includes a cantilever arm 40 comprising an arm structure 30 and a lower protective dielectric layer 28. The comb 102 may, for example, comprise polysilicon (e.g.,...). Figure 11 (as shown), or silicon, amorphous silicon, or combinations thereof, and may be covered with a protective dielectric layer, such as an oxide, which is not removed by etching using a fluorine-based etchant, such as Figure 11 As further illustrated, comb actuation can be used, for example, in MEMS-based accelerometers, where acceleration is detected as a change in capacitance of the comb actuation structure. When used as a sensor, external conditions such as sound waves (or more generally, pressure waves), light, magnetic signals, or the like are converted into electrical signals such as voltage or current by the comb actuation. Conversely, when used as an actuator, the applied electrical signal (such as voltage or current) drives the movement of the comb, which can act as a converter to generate sound or other types of signals. Thus, sensing or actuation operation is similar to referencing an individual... Figure 6 or Figure 7The operation is as described, but the comb 102 is fixed to the cantilever arm 40 to provide a larger area for electrostatic interaction. Figure 11 The exemplary MEMS device further includes a spring 104, an intermediate frame 106, a metal spring 108, and an outer frame 110. All these components are fabricated in a first (e.g., upper) wafer 112, which is bonded to a second (e.g., lower) wafer 114 in which a cavity 116 is formed. Figure 118 indicates... Figure 11 Materials used in MEMS devices.

[0080] refer to Figures 12 to 18 It shows the materials used in manufacturing. Figure 11 A cross-sectional view of an intermediate structure illustrating the fabrication process of a MEMS device. Note that in... Figures 12 to 18 The same reference numbers are used in the sectional views of the continuous manufacturing steps, and the numbers related to the steps shown in the sectional view are discussed only with reference to the given sectional view. Figures 12 to 18 Each also includes Figure 118, and uses the same shading to indicate the various materials marked in Figure 118.

[0081] Figure 12 The diagram shows a cross-sectional view of the fabrication process at the stage where comb-like structures 102 have been formed in the silicon material of the upper wafer 112, and the lower wafer 114 has been processed to form cavities 116 and bonded to the upper wafer 112. Figure 12 The release structure 20, formed by two different layers 22 and 24 of different silicon materials, can also be seen, as previously referenced. Figure 2 As stated above.

[0082] Figure 13 A cross-sectional view showing the deposition of the underlying protective dielectric layer 28. (See image.) Figure 13 As shown, the lower protective dielectric layer 28 is deposited as a conformal blanket coating, which covers the entire upper surface.

[0083] Figure 14 This shows a cross-sectional view after photoresist 120 has been applied for etching of the underlying protective dielectric layer 28. The photoresist is deposited as a photoresist blanket layer, which is then patterned, as shown below. Figure 14 As shown, the patterned photoresist 120 is left to cover only the area corresponding to the driving comb 100.

[0084] Figure 15 This shows a cross-sectional view after etching of the lower protective dielectric layer 28 and stripping of the photoresist 120. The etching removed the blanket-covered lower protective dielectric layer 28, except for its composition... Figure 14 The area protected by the patterned photoresist 120 is shown; therefore, after etching, the remaining lower protective dielectric layer 28 only covers the area of ​​the driving comb 100, as shown. Figure 15 As shown.

[0085] Figure 16 This shows a cross-sectional view of the AlCu arm structure 30 after deposition and photolithography patterning etching. (See image below.) Figure 16 As shown, a deposited and patterned AlCu layer is disposed in the region of the drive comb 100, as well as in the regions of the spring 104 and the intermediate frame 106. Therefore, the spring 104 is made of the same material (such as AlCu) as the arm structure 30.

[0086] Figure 17 A cross-sectional view showing the deposition of a passivation oxide layer 122 on top of the arm structure 30. Figure 17 Also shown is a deposited and patterned protective oxide 123 disposed above the spring 104, the intermediate frame 106, the outer frame 110, and portions thereof that are intended to become the metal spring 108. Areas of the metal spring 108 not covered by the protective oxide 123 are suitably used as metal gaskets.

[0087] Figure 18 This shows a cross-sectional view after the lithography-controlled silicon etching step. Figure 18 The illustration shows some remaining photoresist 124 (e.g., in some embodiments, at least 4 micrometers thick).

[0088] return Figure 11 The image shows a cross-sectional view after releasing arm 30 using a fluorine-based etchant. Figure 18 The lithography-controlled etching creates openings for the entry of a fluorine-based etchant, which releases the arm structure 30 by removing the silicon material from the release structure 20 (which, in the illustrative example, comprises two layers 22 and 24 of different silicon materials). Since the fluorine-based etchant removes the silicon, the surface of the silicon region remaining after the fluorine-based etching is appropriately protected during etching by a protective oxide coating, such as the cavity 116 and other exposed surfaces of the lower wafer 114, which are covered with protective oxides. Figure 11 As shown.

[0089] Further embodiments are described below.

[0090] In a non-limiting illustrative embodiment, a method for fabricating a microelectromechanical (MEMS) structure is disclosed. The method includes: forming a release structure disposed on a base structure, wherein the base structure includes an anchor structure; depositing at least a lower protective dielectric layer on the release structure; forming an arm structure disposed on the lower protective dielectric layer and the anchor structure; and removing the release structure by etching with a fluorine-based etchant to form a MEMS arm fixed to the anchor structure, the MEMS arm including the arm structure and the lower protective dielectric layer.

[0091] In some embodiments, the release structure comprises silicon, polycrystalline silicon, amorphous silicon, or a combination thereof, and the arm structure comprises metal, metal alloy, metal nitride, or a combination thereof. In some embodiments, a lower protective dielectric layer is deposited at least on the release structure and the anchor structure. In some embodiments, the arm structure comprises a stack of at least two layers of different materials, each layer comprising metal, metal alloy, metal nitride, or a combination thereof. In some embodiments, the lower protective dielectric layer comprises a dielectric stack comprising at least two different dielectric layers. In some embodiments, the anchor structure of the basic structure comprises a first electrode, the basic structure further comprises a second electrode and a spacer inserted between the first electrode and the second electrode, and the release structure is disposed on the second electrode and the spacer. Etching with a fluorine-based etchant further removes the spacer, and the microelectromechanical structure manufactured by the method comprises a capacitive microelectromechanical structure, wherein the microelectromechanical arm is capacitively coupled to the second electrode. In some embodiments, the first electrode comprises silicon, polycrystalline silicon, amorphous silicon, or a combination thereof, covered with a first electrode protective dielectric layer, which is not removed by etching with a fluorine-based etchant. The second electrode comprises silicon, polycrystalline silicon, amorphous silicon, or a combination thereof, and is covered with a second electrode protective dielectric layer that is not removed by etching with a fluorine-based etchant. The spacer comprises silicon, polycrystalline silicon, amorphous silicon, or a combination thereof. In some embodiments, the method further comprises forming a comb-like structure fixed to the arm structure, the comb-like structure comprising silicon, polycrystalline silicon, amorphous silicon, or a combination thereof, the comb-like structure being covered with a comb-like structure protective dielectric layer that is not removed by etching with a fluorine-based etchant, wherein the capacitive microelectromechanical structure includes a comb-like drive.

[0092] In a non-limiting illustrative embodiment, a method for fabricating a MEMS structure is disclosed. The method includes: providing a capacitive drive including a first electrode and a second electrode; forming a release structure including silicon material disposed on the second electrode; depositing a lower protective dielectric layer at least on the release structure; forming an arm structure disposed on the lower protective dielectric layer and on the first electrode; and removing the release structure by etching with a fluorine-based etchant to form a cantilever arm fixed to the first electrode and capacitively coupled to the second electrode, the cantilever arm including the arm structure and the lower protective dielectric layer.

[0093] In some embodiments, the silicon material of the release structure comprises silicon, polycrystalline silicon, amorphous silicon, or a combination thereof. In some embodiments, the fluorine-based etchant comprises CF4, SF6, or a combination thereof. In some embodiments, a lower protective dielectric layer is deposited at least on the release structure and the first electrode. In some embodiments, the arm structure is formed of two layers of different materials. In some embodiments, the lower protective dielectric layer comprises a dielectric stack comprising at least two different dielectric layers.

[0094] In a non-limiting illustrative embodiment, the MEMS structure includes: a first electrode; a second electrode; and a cantilever arm fixed to the first electrode and above the second electrode, with a gap between the electrodes. The cantilever includes an arm structure and a lower protective dielectric layer disposed on the lower side of the arm structure.

[0095] In some embodiments, the microelectromechanical structure (MEMS) further includes a comb-like structure fixed to the cantilever arm, wherein the MEMS includes a capacitive MEMS with a comb-like actuation. In some embodiments, the MEMS further includes at least one spring made of the same material as the arm structure. In some embodiments, the MEMS further includes at least one spring disposed on one side of the comb-like structure. In some embodiments, the arm structure includes a metal, a metal alloy, a metal nitride, or a combination thereof. In some embodiments, the arm structure includes a bend. In some embodiments, the lower protective dielectric layer includes a dielectric stack comprising at least two different dielectric layers.

[0096] Another embodiment of this disclosure discloses a microelectromechanical structure (MEMS) including a first electrode, a second electrode, and a cantilever arm fixed to the first electrode and above the second electrode, with a gap between the first and second electrodes. The cantilever arm includes an arm structure and a lower protective dielectric layer disposed on the underside of the arm structure, wherein the cantilever arm is capacitively coupled to the second electrode. In some embodiments, the arm structure includes a bend. In some embodiments, the lower protective dielectric layer is deposited at least on the first electrode.

[0097] Another embodiment of this disclosure reveals a microelectromechanical structure (MEMS) including a first electrode, a second electrode, and a cantilever arm. The cantilever arm is fixed to the first electrode and sits above the second electrode, with a gap of 1 to 2 micrometers between the first and second electrodes. The cantilever arm includes an arm structure and a lower protective dielectric layer disposed on the lower side of the arm structure. In some embodiments, the cantilever arm is capacitively coupled to the second electrode. In some embodiments, the arm structure includes a bend.

[0098] The foregoing outlines the features of several embodiments to enable those skilled in the art to better understand the nature of this disclosure. Those skilled in the art will understand that this disclosure can be readily used as a basis for designing or modifying other processes and structures for implementing the embodiments introduced herein and / or achieving the same objectives and / or advantages. Those skilled in the art will also recognize that such equivalent constructions do not depart from the spirit and scope of this disclosure, and that such equivalent constructions can be modified, substituted, and replaced herein without departing from the spirit and scope of this disclosure.

Claims

1. A microelectromechanical structure, characterized in that, Include: A first electrode; A second electrode; and A cantilever arm is fixed to the first electrode and above the second electrode, with a gap between the first electrode and the second electrode. The cantilever arm includes an arm structure and a lower protective dielectric layer disposed on the lower side of the arm structure.

2. The microelectromechanical structure as described in claim 1, characterized in that, Further includes: A comb-like structure fixed to the cantilever arm, wherein the microelectromechanical system includes a capacitive microelectromechanical system, which includes a comb-like drive.

3. The microelectromechanical structure as described in claim 2, characterized in that, Further includes: At least one spring is provided on one side of the comb.

4. The microelectromechanical structure as described in claim 1, characterized in that, The lower protective dielectric layer includes a dielectric stack, which comprises at least two different dielectric layers.

5. A microelectromechanical structure, characterized in that, Include: A first electrode; A second electrode; and A cantilever arm is fixed to the first electrode and above the second electrode, with a gap between the first electrode and the second electrode. The cantilever arm includes an arm structure and a lower protective dielectric layer disposed on the lower side of the arm structure, wherein the cantilever arm is capacitively coupled to the second electrode.

6. The microelectromechanical structure as described in claim 5, characterized in that, The arm structure includes a bend.

7. The microelectromechanical structure as described in claim 5, characterized in that, The lower protective dielectric layer is deposited on at least the first electrode.

8. A microelectromechanical structure, characterized in that, Include: A first electrode; A second electrode; and A cantilever arm is fixed to the first electrode and above the second electrode, and there is a gap between the first electrode and the second electrode, the gap being 1 to 2 micrometers. The cantilever arm includes an arm structure and a lower protective dielectric layer disposed on the lower side of the arm structure.

9. The microelectromechanical structure as described in claim 8, characterized in that, The cantilever arm is coupled to the second electrode capacitor.

10. The microelectromechanical structure as described in claim 8, characterized in that, The arm structure includes a bend.

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