Radio frequency switch, preparation method thereof and electronic equipment

Abstract

The invention provides a radio frequency switch. The radio frequency switch comprises a substrate, a first reference electrode, a second reference electrode, a driving electrode, an interlayer insulating layer and a film bridge structure. A first gap is arranged between the driving electrode and the first reference electrode, and a second gap is arranged between the driving electrode and the second reference electrode. The first gap defines a first groove portion. The second gap defines a second groove portion. The interlayer insulating layer is arranged on the side, away from the substrate, of the driving electrode, and the surface of the side, away from the substrate, of the interlayer insulating layer located within the orthographic projection limiting range of the driving electrode on the substrate is a first surface. The film bridge structure is arranged on the side, away from the substrate, of the interlayer insulating layer. The driving electrode is located in a space defined by the film bridge and the substrate. The first groove part and the second groove part are filled with filling structures; the maximum distance from the surface, deviating from the substrate, of the filling structure to the substrate is a first distance, and the maximum distance from the first surface to the substrate is a second distance; the difference between the second distance and the first distance is not more than 200 nm.

Description

Technical Field

[0001] This disclosure belongs to the field of radio frequency technology, specifically relating to a radio frequency switch and its fabrication method, and electronic equipment. Background Technology

[0002] Compared to traditional silicon-based MEMS RF switches, glass-based devices offer lower insertion loss and higher isolation. While glass wafers can still be planarized using CMP (Chemical Motion Processing) in silicon-based processes, the significantly increased cost of glass wafers and their associated processes limits the commercialization of glass-based MEMS RF switches. Utilizing large-size glass substrates (such as G2.5 and G5.5 glass substrates) from semiconductor display technology for MEMS RF switch fabrication has become an important direction for reducing the cost of glass-based devices. However, there is currently no CMP process for large-size glass substrates, and it is unlikely that non-wafer CMP processes will be implemented in the foreseeable future. Therefore, achieving planarization through non-CMP processes has become a key technology for manufacturing MEMS RF devices on large-size glass substrates. Summary of the Invention

[0003] This invention aims to at least solve one of the technical problems existing in the prior art, and provides a radio frequency switch, comprising:

[0004] Substrate;

[0005] A first reference electrode and a second reference electrode are disposed on the substrate, and a driving electrode is disposed between the first reference electrode and the second reference electrode; the driving electrode has a first gap with the first reference electrode, and the driving electrode has a second gap with the second reference electrode;

[0006] An interlayer insulating layer at least covers the surface of the driving electrode facing away from the substrate; the surface of the interlayer insulating layer facing away from the substrate within a defined range of the orthographic projection of the driving electrode onto the substrate is a first surface;

[0007] A membrane bridge structure is disposed on the side of the interlayer insulating layer facing away from the substrate; the membrane bridge structure includes a bridge surface and a bridge arm connected to the bridge surface; the bridge arm is connected to the first reference electrode, one end of the bridge surface is connected to the bridge arm, and the other end at least partially overlaps with the orthographic projection of the second reference electrode on the substrate; the driving electrode is located within the space defined by the bridge surface and the substrate.

[0008] The radio frequency switch further includes a first groove defined by the first gap and a second groove defined by the second gap; the first groove and the second groove are filled with a filling structure; the maximum distance between the filling structure and the surface of the substrate and the substrate is a first distance, and the maximum distance between the first surface and the substrate is a second distance; the difference between the second distance and the first distance is not greater than 200nm.

[0009] In some embodiments, the first reference electrode, the second reference electrode, and the driving electrode are disposed in the same layer, and the interlayer insulating layer is disposed on the side of the layer containing the first reference electrode, the second reference electrode, and the driving electrode that is away from the substrate.

[0010] The bridge arm is connected to the first reference electrode through a first via penetrating the interlayer insulation layer.

[0011] In some embodiments, the bridge surface includes a main body and a protrusion connected to the main body; one end of the main body is connected to the bridge arm, and the other end is connected to the protrusion, and the protrusion is disposed on the side of the main body close to the substrate.

[0012] The radio frequency switch further includes a contact structure corresponding to the protrusion; the contact structure is disposed on the side of the interlayer insulating layer away from the substrate, and is connected to the second reference electrode through a second via penetrating the interlayer insulating layer; the orthogonal projection of the contact structure on the substrate covers the orthogonal projection of the protrusion on the substrate, and the contact structure and the protrusion have a third distance in the thickness direction of the substrate.

[0013] In some embodiments, the radio frequency switch further includes a connection electrode disposed on the side of the interlayer insulating layer away from the substrate; the connection electrode is connected to the second reference electrode through a third via penetrating the interlayer insulating layer, and the connection electrode is disposed on the side of the contact structure away from the driving electrode.

[0014] In some embodiments, the bridge surface includes a first window extending through its thickness direction; the first window at least partially overlaps with the orthographic projection of the driving electrode onto the substrate.

[0015] This disclosure also provides a method for fabricating a radio frequency switch, comprising:

[0016] Provide a substrate;

[0017] A first reference electrode, a second reference electrode, and a driving electrode disposed between the first reference electrode and the second reference electrode are formed on the substrate; a first gap is formed between the driving electrode and the first reference electrode, and a second gap is formed between the driving electrode and the second reference electrode; the first gap defines a first groove, and the second gap defines a second groove.

[0018] An interlayer insulating layer is formed on the side of the layer containing the driving electrode that is away from the substrate; the interlayer insulating layer at least covers the surface of the driving electrode on the side away from the substrate; the surface of the interlayer insulating layer on the side away from the substrate within the defined range of the orthographic projection of the driving electrode onto the substrate is a first surface;

[0019] A filling structure is formed in the first groove and the second groove;

[0020] A membrane bridge structure is formed on the side of the interlayer insulating layer opposite to the substrate; the membrane bridge structure includes a bridge surface and a bridge arm connected to the bridge surface; the bridge arm is connected to the first reference electrode, one end of the bridge surface is connected to the bridge arm, and the other end at least partially overlaps with the orthographic projection of the second reference electrode on the substrate; the driving electrode is located within the space defined by the bridge surface and the substrate.

[0021] Wherein, the maximum distance between the surface of the filling structure away from the substrate and the substrate is the first distance, and the maximum distance between the first surface and the substrate is the second distance; the difference between the second distance and the first distance is not greater than 200nm.

[0022] In some embodiments, the filling structure includes at least two stacked sub-filling portions; the step of forming the sub-filling portions includes:

[0023] A photoresist layer is formed in the first and second trenches, and then exposed, developed, and etched to form a pattern including the sub-filled portion.

[0024] In some embodiments, the mask used to form the sub-fill portion exposure includes a first pattern portion and a second pattern portion; the orthographic projection of the first pattern portion on the substrate covers the orthographic projection of the first groove portion on the substrate, and the orthographic projection of the second pattern portion on the substrate covers the orthographic projection of the second groove portion on the substrate.

[0025] The width ratio of the first patterned portion to the width ratio of the first grooved portion is 1.1-1.2; the width ratio of the second patterned portion to the width ratio of the second grooved portion is 1.1-1.2.

[0026] In some embodiments, the step of forming a film bridge structure on the side of the interlayer insulating layer opposite to the substrate includes:

[0027] A pattern including the bridge arm is formed on the side of the interlayer insulating layer away from the substrate by a patterning process;

[0028] A sacrificial layer is formed on the side of the bridge arm away from the substrate, and a fourth via is formed that penetrates along the thickness direction of the sacrificial layer; the orthographic projection of the fourth via on the substrate covers the orthographic projection of the bridge arm on the substrate.

[0029] A pattern including the bridge is formed on the side of the sacrificial layer away from the substrate by a patterning process;

[0030] Remove the sacrificial layer.

[0031] This disclosure also provides an electronic device, including the radio frequency switch described in the above embodiments. Attached Figure Description

[0032] Figures 1a-1b This is a schematic diagram of the structure of a metal membrane bridge in the prior art;

[0033] Figure 2 This is a schematic diagram of the structure of a radio frequency switch provided in an embodiment of the present disclosure;

[0034] Figure 3 This is a schematic diagram of the structure of a radio frequency switch provided in an embodiment of the present disclosure;

[0035] Figure 4 This is a schematic diagram of the membrane bridge structure provided in an embodiment of the present disclosure;

[0036] Figure 5 for Figure 2 Top view of the RF switch;

[0037] Figure 6 This is a schematic diagram of an intermediate product in step S1 of the method for fabricating a radio frequency switch provided in this disclosure;

[0038] Figure 7 This is a schematic diagram of an intermediate product in step S2 of the method for fabricating a radio frequency switch provided in this disclosure;

[0039] Figure 8 A schematic diagram of an intermediate product in step S3 of the method for fabricating a radio frequency switch provided in this disclosure;

[0040] Figure 9 This is a schematic diagram of an intermediate product in step S401 of the method for fabricating a radio frequency switch provided in this disclosure;

[0041] Figure 10This is a schematic diagram of an intermediate product in step S402 of the method for fabricating a radio frequency switch provided in this disclosure;

[0042] Figure 11 This is a schematic diagram of an intermediate product in step S403 of the method for fabricating a radio frequency switch provided in this disclosure;

[0043] Figure 12 This is a schematic diagram of an intermediate product in step S404 of the method for fabricating a radio frequency switch provided in this disclosure;

[0044] Figure 13 This is a schematic diagram of an intermediate product in step S405 of the method for fabricating a radio frequency switch provided in this disclosure;

[0045] Figure 14 This is a schematic diagram of an intermediate product in step S406 of the method for fabricating a radio frequency switch provided in this disclosure;

[0046] Figure 15 This is a schematic diagram of an intermediate product in step S501 of the method for fabricating a radio frequency switch provided in this disclosure;

[0047] Figure 16 This is a schematic diagram of an intermediate product in step S502 of the method for fabricating a radio frequency switch provided in this disclosure;

[0048] Figure 17 This is a schematic diagram of an intermediate product in step S503 of the method for fabricating a radio frequency switch provided in this disclosure;

[0049] Figure 18 This is a schematic diagram of an intermediate product in step S504 of the method for fabricating a radio frequency switch provided in this disclosure;

[0050] Figure 19 A schematic diagram of an intermediate product according to a specific embodiment of the radio frequency switch fabrication method provided in this disclosure;

[0051] Figure 20 A schematic diagram of an intermediate product according to a specific embodiment of the radio frequency switch fabrication method provided in this disclosure;

[0052] Figure 21 This is a partial schematic diagram of a product using a specific embodiment of the radio frequency switch fabrication method provided in this disclosure. Detailed Implementation

[0053] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0054] Unless otherwise defined, the technical or scientific terms used in this application shall have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms “a,” “an,” “an,” “the,” and similar words used in this application do not indicate quantity limitation and may indicate singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that includes a series of steps or modules (units) is not limited to the listed steps or units, but may also include steps or units not listed, or may include other steps or units inherent to these processes, methods, products, or devices. The terms “connected,” “linked,” “coupled,” and similar words used in this application are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. “Multiple” used in this application refers to two or more. “And / or” describes the relationship between related objects, indicating that three relationships may exist; for example, “A and / or B” can represent: A alone, A and B simultaneously, and B alone. The character " / " generally indicates that the preceding and following objects are in an "or" relationship. The terms "first," "second," and "third" used in this application are merely to distinguish similar objects and do not represent a specific ordering of objects. "Above," "below," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0055] As used herein, “parallel” and “perpendicular” include the described situation and situations that are similar to the described situation, within an acceptable range of deviation, which is determined by those skilled in the art taking into account the measurement under discussion and the error associated with the measurement of a particular quantity (i.e., the limitations of the measurement system). For example, “parallel” includes absolute parallelism and approximate parallelism, where an acceptable range of deviation for approximate parallelism may be, for example, within 5°; “perpendicular” includes absolute perpendicularity and approximate perpendicularity, where an acceptable range of deviation for approximate perpendicularity may also be, for example, within 5°.

[0056] With the rapid development of the information age, wireless terminals with high integration, miniaturization, multifunctionality, and low cost are gradually becoming the development trend of communication technology. Radio frequency (RF) MEMS switches are one of the key devices used in wireless communication to control electromagnetic wave transmission, featuring low loss, small size, low cost, and high reliability. MEMS RF switches can be combined with MEMS antennas, MEMS filters, MEMS phase shifters, etc., to form tunable RF MEMS devices, enabling multifunctional applications. In related technologies, the fabrication of MEMS RF devices involves multiple thin film deposition and etching steps, each inevitably resulting in grooves. Failure to planarize these grooves will affect subsequent film processing, leading to reduced device performance or even failure. Figures 1a-1b This is a schematic diagram of a metal membrane bridge fabricated on an uneven groove. (Example) Figure 1a and Figure 1b As indicated by the black box, the metal membrane bridge bent at the groove, causing its working condition to deviate significantly from the design value.

[0057] Based on this, this disclosure provides a radio frequency switch, with reference to Figures 2-3The radio frequency switch includes: a substrate 1, a first reference electrode 21, a second reference electrode 22 disposed on the substrate 1, a driving electrode 23 located between the first reference electrode 21 and the second reference electrode 22, an interlayer insulating layer 3, and a membrane bridge structure 5. A first gap AG1 is formed between the driving electrode 23 and the first reference electrode 21, and a second gap AG2 is formed between the driving electrode 23 and the second reference electrode 22. The widths of the first gap AG1 and the second gap AG2 may be equal or unequal. The first gap AG1 defines a first groove LG1, and the second gap AG2 defines a second groove LG2. The interlayer insulating layer 3 is disposed on the side of the driving electrode 23 facing away from the substrate 1, and at least covers the surface of the driving electrode 23 facing away from the substrate 1. The surface of the interlayer insulating layer 3 facing away from the substrate 1 within the range defined by the orthographic projection of the driving electrode 23 onto the substrate 1 is a first surface W1. The membrane bridge structure 5 is disposed on the side of the interlayer insulating layer 3 facing away from the substrate 1, and the membrane bridge structure 5 is isolated from the driving electrode 23 by the interlayer insulating layer 3. Specifically, the membrane bridge structure 5 includes a bridge surface 52 and a bridge arm 51 connected to the bridge surface 52. The bridge arm 51 is electrically connected to the first reference electrode 21. The bridge surface 52 has a first end and a second end disposed opposite to each other. The first end is connected to the first reference electrode 21 through the bridge arm 51. The orthographic projection of the second end on the substrate 1 overlaps with the orthographic projection of the second reference electrode 22 on the substrate 1. That is, the orthographic projection of the bridge surface 52 on the substrate 1 covers at least a portion of the orthographic projection of the driving electrode 23 on the substrate 1, at least a portion of the orthographic projection of the first reference electrode 21 on the substrate 1, and at least a portion of the orthographic projection of the second reference electrode 22 on the substrate 1. The driving electrode 23 is located within the space defined by the bridge surface 52, the substrate 1, the first reference electrode 21, and the second reference electrode 22. By applying a voltage to the driving electrode 23, an electrostatic force is generated between the driving electrode 23 and the membrane bridge structure 5, controlling the second end of the bridge surface 52 to move towards the second reference electrode 22 until the second end of the bridge surface 52 contacts the second reference electrode 22 to achieve electrical connection. At this time, the RF switch is in the off state, and signal conduction can be realized. In particular, in the embodiments of this disclosure, a filling structure 4 is provided in both the first groove LG1 defined by the first gap AG1 and the second groove LG2 defined by the second gap AG2. The maximum distance between the filling structure 4 and the substrate 1 is a first distance d1, and the maximum distance between the first surface W1 and the substrate 1 is a second distance d2. The difference between the second distance d2 and the first distance d1 is not greater than 200nm. That is to say, the step height formed at the connection between the filling structure 4 and the driving electrode 23 is not greater than 200nm. This setting can make the device surface more flat, reduce the impact of the step on the subsequent fabrication of the membrane bridge structure 5, thereby improving the device flatness and product yield.The filling structure 4 is made of insulating material. The filling structure 4 can also increase the tolerance of the RF switch to the driving voltage, prevent voltage breakdown between the electrodes, and extend the device life.

[0058] It should be noted that, Figure 2 and Figure 3 The structures of the radio frequency switches in the two are exactly the same, the only difference being the different reference numerals in the accompanying drawings. Figure 2 The various vias mentioned in this specification are labeled. Figure 3 The various distances mentioned in this instruction manual are marked.

[0059] In some examples, refer to Figure 2 The first reference electrode 21, the second reference electrode 22, and the driving electrode 23 are disposed in the same layer and are formed by a single patterning process, so their thicknesses are basically the same. The interlayer insulating layer 3 is disposed on the side of the layer containing the first reference electrode 21, the second reference electrode 22, and the driving electrode 23 that is away from the substrate 1, and the orthographic projection of the interlayer insulating layer 3 on the substrate 1 covers at least a portion of the orthographic projection of the driving electrode 23 on the substrate 1, at least a portion of the orthographic projection of the first reference electrode 21 on the substrate 1, and at least a portion of the orthographic projection of the second reference electrode 22 on the substrate 1.

[0060] In one example, the orthographic projection of the interlayer insulating layer 3 onto the substrate 1 completely coincides with the orthographic projection of the driving electrode 23 onto the substrate 1. In this case, neither the first trench LG1 nor the second trench LG2 contains the interlayer insulating layer 3. In this example, the interlayer insulating layer 3 does not obstruct the first reference electrode 21 and the second reference electrode 22. Therefore, when connecting the two reference electrodes to other circuit elements, it is not necessary to fabricate the connection electrode 7, which simplifies the process.

[0061] In another example, the orthographic projection of the interlayer insulating layer 3 onto the substrate 1 not only covers the orthographic projection of the driving electrode 23 onto the substrate 1, but also covers the orthographic projections of the first reference electrode 21 and the second reference electrode 22 onto the substrate 1. In this case, the bottom and sidewalls of both the first trench LG1 and the second trench LG2 are provided with the interlayer insulating layer 3, such as... Figure 2 As shown. In this example, the interlayer insulating layer 3 covers the entire substrate 1, which can improve the isolation between the membrane bridge structure 5 and the driving electrode 23. At the same time, the interlayer insulating layer 3 can serve as a protective layer to protect the first reference electrode 21 and the second reference electrode 22 from water and oxygen erosion.

[0062] For ease of description and explanation, the following text will only use the term "foreign language". Figure 2 The radio frequency switch of this disclosure will be described using an embodiment in which the interlayer insulating layer 3 covers the entire surface of the substrate 1 as an example.

[0063] Continue to refer to Figure 2 In the membrane bridge structure 5, the bridge arm 51 is connected to the first reference electrode 21 through a first via VIA1 penetrating the interlayer insulating layer 3. Referring to Figure 1, the bridge arm 51 is a frustum structure, which may specifically include a truncated pyramid or a frustum of a cone. The frustum structure has an upper surface and a lower surface that are arranged opposite to each other. The area of ​​the upper surface is larger than the area of ​​the lower surface, and the orthographic projection of the upper surface on the substrate 1 covers the orthographic projection of the lower surface on the substrate 1. This arrangement can increase the stability of the bridge structure.

[0064] In some examples, refer to Figure 4 The bridge surface 52 includes a main body 521 and a protrusion 522 connected to the main body 521. The main body 521 defines the space for the driving electrode 23 and generates electrostatic induction with the driving electrode 23 when the driving electrode 23 is energized. The protrusion 522 is used to contact the second reference electrode 22. Referring to FIG1, the main body 521 extends along the direction from the first reference electrode 21 to the second reference electrode 22. The main body 521 has a first end and a second end disposed opposite to each other. The first end is connected to the bridge arm 51, and the second end is connected to the protrusion 522. The protrusion 522 is disposed on the side of the main body 521 near the substrate 1. The protrusion 522 can reduce the distance between the bridge surface 52 and the second reference electrode 22, thereby improving the response rate, and can also reduce the resistivity of the RF switch, thereby improving the signal transmission quality.

[0065] Accordingly, refer to Figures 2-3 The RF switch also includes a contact structure 6 corresponding to the protrusion 522. The protrusion 522 and the contact structure 6 have a third distance d3 in the thickness direction of the substrate 1. The contact structure 6 is disposed on the side of the interlayer insulating layer 3 away from the substrate 1 and is electrically connected to the second reference electrode 22 through a second via VIA2 penetrating the interlayer insulating layer 3. When no power is applied, the protrusion 522 and the contact structure 6 are disconnected. After a voltage is applied to the driving electrode 23, an electrostatic force is generated between the main body 521 and the driving electrode 23, causing the main body 521 to bend toward the side closer to the second reference electrode 22, while simultaneously driving the protrusion 522 to move toward the direction closer to the contact structure 6 until the protrusion 522 contacts the contact structure 6 to achieve electrical connection. To ensure accurate contact and connection between the protrusion 522 and the contact structure 6 when the RF switch is closed, the orthogonal projection of the contact structure 6 on the substrate 1 is arranged to cover the orthogonal projection of the protrusion 522 on the substrate 1.

[0066] In some examples, refer to Figure 2The RF switch also includes a connection electrode 7 disposed on the side of the interlayer insulating layer 3 facing away from the substrate 1. The connection electrode 7 is electrically connected to the second reference electrode 22 through a third via VIA3 penetrating the interlayer insulating layer 3, and the connection electrode 7 is disposed on the side of the contact structure 6 facing away from the driving electrode 23. The connection electrode 7 is used to connect the RF switch to other circuit components. For example, the second reference electrode 22 of the RF switch is connected to a power source through the connection electrode 7. When a voltage is applied to the driving electrode 23, the RF switch closes, and the electrical signal generated by the power source is transmitted sequentially through the connection electrode 7, the second reference electrode 22, the contact structure 6, and the membrane bridge structure 5 to the first reference electrode 21, thereby realizing signal transmission. It is understood that the connection electrode 7 can also be disposed on the side of the first reference electrode 21, and the electrical signal can be transmitted to other circuit components through the connection electrode 7.

[0067] In some examples, refer to Figure 5 The bridge surface 52 also includes a first window ON that extends through its thickness direction. The first window ON can reduce the weight of the bridge surface 5 and improve the sensitivity of the RF switch. On the other hand, it can facilitate the removal of the sacrificial layer located below the bridge surface 5 and avoid the residual sacrificial layer from affecting the device response speed.

[0068] In some examples, the radio frequency switch of this disclosure embodiment further includes a reverse stress layer 8 disposed between the layer containing the driving electrode 23 and the substrate 1, such as... Figures 2-3 As shown. The reverse stress layer 8 can effectively prevent stress warping, and the material of the reverse stress layer 8 includes silicon nitride, etc.

[0069] This disclosure also provides a method for fabricating a radio frequency switch, which can be used to fabricate the radio frequency switch described in the above embodiments. The fabrication method includes the following steps:

[0070] S1. Provide a substrate 1, such as Figure 6 As shown.

[0071] In some examples, the substrate 1 can be made of glass, or silicon, etc. Step S1 may specifically include:

[0072] S101. Clean the substrate 1 using a standard cleaning process. The cleaning methods for the substrate 1 may include: alkaline cleaning, in which the substrate 1 is immersed in a solution containing sodium hydroxide or ammonium hydroxide, with a commonly used solution concentration of 5%–10%, which can remove organic matter and metal ions from the surface of the substrate 1; acidic cleaning, in which the substrate 1 is immersed in a solution containing hydrofluoric acid or hydrochloric acid, with a commonly used solution concentration of 10%–30%, which can remove oxides and silica gel impurities from the surface of the substrate 1; oxidative cleaning, in which the substrate 1 is immersed in a solution containing potassium hydroxide or hydrogen peroxide, with a commonly used solution concentration of 5%–10%, which can remove carbon and metal elements from the surface of the substrate 1; and ultrapure water cleaning, in which the substrate 1 is immersed in or sprayed with ultrapure water, which can remove minute particles from the surface of the substrate 1.

[0073] In some examples, step S1 may also include:

[0074] S102. A reverse stress layer 8 is formed on the substrate 1. The reverse stress layer 8 may include inorganic materials such as silicon oxide (SiOx), silicon nitride (SiNx), and / or silicon oxynitride (SiON), and may be formed as a multilayer or a single layer.

[0075] S2. A first reference electrode 21, a second reference electrode 22, and a driving electrode 23 disposed between the first reference electrode 21 and the second reference electrode 22 are formed on the side of the reverse stress layer 8 away from the substrate 1; a first gap AG1 is formed between the driving electrode 23 and the first reference electrode 21, and a second gap AG2 is formed between the driving electrode 23 and the second reference electrode 22.

[0076] Figure 7 This is a schematic diagram of the intermediate product formed in step S2. For example... Figure 7 As shown, step S2 can be performed using a patterning process to form the first reference electrode 21, the second reference electrode 22, and the driving electrode 23. The first gap AG1 between the driving electrode 23 and the first reference electrode 21 defines the first groove LG1, and the second gap AG2 between the driving electrode 23 and the second reference electrode 22 defines the second groove LG2.

[0077] In some examples, the materials of the first reference electrode 21, the second reference electrode 22, and the driving electrode 23 may include gold (Au), gold alloys, silver (Ag), silver alloys, aluminum (Al), aluminum alloys, aluminum nitride (AlNx), tungsten (W), tungsten nitride (WNx), copper (Cu), copper alloys, nickel (Ni), chromium (Cr), chromium nitride (CrNx), molybdenum (Mo), molybdenum alloys, titanium (Ti), titanium nitride (TiNx), platinum (Pt), tantalum (Ta), tantalum nitride (TaNx), neodymium (Nd), scandium (Sc), strontium ruthenium oxide (SRO), zinc oxide (ZnOx), tin oxide (SnOx), indium oxide (InOx), gallium oxide (GaOx), indium tin oxide (ITO), indium zinc oxide (IZO), etc.

[0078] S3. An interlayer insulating layer 3 is formed on the side of the layer containing the first reference electrode 21, the second reference electrode 22, and the driving electrode 23 that is away from the substrate 1. The interlayer insulating layer 3 covers the orthogonal projections of the first reference electrode 21, the second reference electrode 22, and the driving electrode 23 onto the substrate 1. The surface of the interlayer insulating layer 3 on the side away from the substrate 1 within the range defined by the orthogonal projection of the driving electrode 23 onto the substrate 1 is the first surface W1.

[0079] Figure 8 This is a schematic diagram of the intermediate product formed in step S3. For example... Figure 8 As shown, the reason for forming the interlayer insulating layer 3 on the side of the driving electrode 23 facing away from the substrate 1 is to prevent a short circuit between the driving electrode 23 and the subsequently formed film bridge structure 5. (Continuing to refer to...) Figure 8 Part of the interlayer insulating layer 3 covers the bottom and side surfaces of the first trench LG1 and the second trench LG2, which can increase the isolation between the membrane bridge device and the driving electrode 23 and improve the reliability of the device.

[0080] In some examples, the interlayer insulating layer 3 may include silicon oxynitride (SiON), silicon oxide (SiOx), silicon oxycarbide (SiOxCy), silicon carbide nitride (SiCxNy), aluminum oxide (AlOx), tantalum oxide (TaOx), hafnium oxide (HfOx), zirconium oxide (ZrOx), titanium oxide (TiOx), etc. The interlayer insulating layer 3 may be formed as a single layer or multiple layers.

[0081] In some examples, step S3 further includes etching the interlayer insulating layer 3 to form a first via VIA1, a second via VIA2, and a third via VIA3 that extend through its thickness direction, such as... Figure 8As shown. The orthographic projection of the first via VIA1 on the substrate 1 is within the range defined by the orthographic projection of the first reference electrode 21 on the substrate 1, and the orthographic projections of the second via VIA2 and the third via VIA3 on the substrate 1 are within the range defined by the orthographic projection of the second reference electrode 22 on the substrate 1.

[0082] S4. A filling structure 4 is formed in the first groove LG1 and the second groove LG2.

[0083] In some examples, the filling structure 4 includes at least two stacked sub-filling layers, with the multiple sub-filling layers formed sequentially. Taking a filling structure 4 comprising two sub-filling layers as an example, that is, the filling structure 4 includes a first sub-filling layer 41 and a second sub-filling layer 42, and the first sub-filling layer 41 is closer to the substrate 1 than the second sub-filling layer 42. In this case, the steps for forming the filling structure 4 may include:

[0084] S401. A layer of photoresist is spin-coated onto the side of the interlayer insulating layer 3 facing away from the substrate 1, followed by pre-baking to obtain a photoresist film, such as... Figure 9 As shown. In some examples, the photoresist may include materials with good leveling properties, such as polyimide.

[0085] The spin coating process can be divided into pre-spin coating and main spin coating. Pre-spin coating is to make the photoresist film form more uniformly on the inner walls of the first groove LG1 and the second groove LG2. The photoresist film formed by main spin coating plays the main planarization function.

[0086] S402. Using a photomask to block the first trench LG1 and the second trench LG2, the photoresist film not blocked by the photomask is removed through exposure, development, and etching processes, followed by post-baking. Figure 10 As shown.

[0087] In some examples, the mask includes a first patterned portion MASK1 and a second patterned portion MASK2. The orthographic projection of the first patterned portion MASK1 onto the substrate 1 overlaps the orthographic projection of the first groove portion LG1 onto the substrate 1, and the orthographic projection of the second patterned portion MASK2 onto the substrate 1 overlaps the orthographic projection of the second groove portion LG2 onto the substrate 1. The width of the first patterned portion MASK1 is greater than the width of the first groove portion LG1, and the ratio between the two is 1.1-1.2. Similarly, the width ratio of the second patterned portion MASK2 to the width of the second groove portion LG2 is also 1.1-1.2. This arrangement helps to avoid over-etching during the etching process.

[0088] S403. Place the substrate 1, after completing step S402, into an oven for thermal curing to allow the photoresist film to undergo a cross-linking reaction, thus avoiding the influence of other solvents in subsequent processes, such as... Figure 11 As shown.

[0089] At this point, the first sub-filling part 41 has been prepared. Next, the second sub-filling part 42 will be prepared. The preparation process is exactly the same as that for the first sub-filling part 41. The steps for preparing the second sub-filling part 42 are as described in S404-S406.

[0090] S404. A layer of photoresist is spin-coated onto the side of the first sub-filling portion 41 facing away from the substrate 1, followed by pre-baking to obtain a photoresist film, such as... Figure 12 As shown.

[0091] S405. Using a photomask to block the first groove LG1 and the second groove LG2, the photoresist film not blocked by the photomask is removed through exposure, development, and etching processes, followed by post-baking. Figure 13 As shown.

[0092] S406. The substrate 1, after completing step S405, is placed in an oven for thermosetting to form the second sub-filling portion 42, as shown below. Figure 14 As shown.

[0093] This completes the preparation of the first sub-filling part 41 and the second sub-filling part 42. Figure 16 The product image is prepared after the first sub-filling part 41 and the second sub-filling part 42 are prepared through the above steps S401 to S406. According to the measurement, the distance from the surface of the second sub-filling part 42 away from the substrate 1 to the substrate 1 is less than 200nm from the distance from the first surface W1 to the substrate 1, which has good flatness.

[0094] It should be noted that during the above preparation process, the thicknesses of the first sub-filling portion 41 and the second sub-filling portion 42 can be the same or different. Preferably, the first sub-filling portion 42 and the second sub-filling portion 42 with the same thickness can be prepared using the exact same process to fill the first groove portion LG1 and the second groove portion LG2. It should also be noted that the filling structure 4 in the embodiments of this disclosure may further include more layers of sub-filling portions, such as three or four layers. The filling structure 4 prepared by multiple spin coatings and photolithography can flatly fill the first groove portion LG1 and the second groove portion LG2, thereby increasing the surface flatness of the device and improving the product yield.

[0095] Specifically, the spin-coating process parameters and the corresponding photoresist film thickness are shown in Table 1. Taking the first row of data as an example, the steps for preparing the 620nm sub-filler include: spreading a layer of photoresist solution on substrate 1, followed by pre-spin-coating and main spin-coating. The pre-spin-coating parameters are: spin-coating for 3 seconds, ramping up to 500 rpm and holding for 10 seconds; the main spin-coating parameters are: spin-coating for 10 seconds, ramping up to 3000 rpm and holding for 10 seconds. Then, substrate 1 is pre-baked at 120 degrees Celsius for 30 seconds to obtain a 620nm thick photoresist film. Next, a mask is used to remove the unmasked portions through exposure, development, and etching processes. Then, a post-baking at 120 degrees Celsius is performed for 120 seconds. Finally, substrate 1 is placed in a 230 degrees Celsius oven for 1 hour for thermal curing to fully cross-link the photoresist, resulting in a 620nm thick sub-filler.

[0096] Table 1

[0097]

[0098] S5. A membrane bridge structure 5 is formed on the side of the interlayer insulating layer 3 facing away from the substrate 1.

[0099] The membrane bridge structure 5 includes a bridge surface 52 and a bridge arm 51 connected to the bridge surface 52. The bridge surface 52 includes a main body 521 and a protrusion 522 connected to the main body 521. In some examples, the RF switch also includes a contact structure 6 and a connection electrode 7 disposed on the same layer as the bridge arm 51. The orthographic projection of the contact structure 6 on the substrate 1 overlaps the orthographic projection of the protrusion 522 on the substrate 1. The connection electrode 7 is disposed on the side of the contact structure 6 opposite to the drive electrode 23.

[0100] At this point, step S5 includes:

[0101] S501. A metal film is deposited on the side of the interlayer insulating layer 3 facing away from the substrate 1, and a pattern including a bridge arm 51, a contact structure 6, and a connecting electrode 7 is formed by a patterning process. The bridge arm 51 is located in the first via VIA1, the contact structure 6 is located in the second via VIA2, and the connecting electrode 7 is located in the third via VIA3, as shown. Figure 15 As shown.

[0102] In some examples, the metal film may include gold (Au), gold alloys, silver (Ag), silver alloys, aluminum (Al), aluminum alloys, aluminum nitride (AlNx), tungsten (W), tungsten nitride (WNx), copper (Cu), copper alloys, nickel (Ni), chromium (Cr), chromium nitride (CrNx), molybdenum (Mo), molybdenum alloys, titanium (Ti), titanium nitride (TiNx), platinum (Pt), tantalum (Ta), tantalum nitride (TaNx), neodymium (Nd), scandium (Sc), strontium ruthenium oxide (SRO), zinc oxide (ZnOx), tin oxide (SnOx), indium oxide (InOx), gallium oxide (GaOx), indium tin oxide (ITO), indium zinc oxide (IZO), etc. The metal film may be a single layer or multiple layers.

[0103] S502. A sacrificial layer 9 is formed on the side of the layer containing the bridge arm 51, contact structure 6, and connecting electrode 7 that faces away from the substrate 1. A fourth via VIA4 and a first blind via BlindVIA, penetrating along the thickness direction of the sacrificial layer 9, are formed by etching. Figure 16 As shown.

[0104] Among them, the orthographic projection of the fourth via VIA4 on the substrate 1 covers the orthographic projection of the bridge arm 51 on the substrate 1, and the orthographic projection of the first blind via VIA on the substrate 1 is within the defined range of the orthographic projection of the contact structure 6 on the substrate 1.

[0105] S503. A metal film layer is deposited on the side of the sacrificial layer 9 opposite to the substrate 1, and a pattern including a main body portion 521 and a protrusion portion 522 is formed by a patterning process. The main body portion 521 at least fills the fourth via VIA4 and is electrically connected to the bridge arm 51. The protrusion portion 522 is located within the first blind via VIA, as shown below. Figure 17 As shown.

[0106] In some examples, step S503 also includes forming a first window ON through the thickness direction of the sacrificial layer 9 by a patterning process. The setting of the first window ON can reduce the difficulty of removing the sacrificial layer 9.

[0107] S504. Remove sacrificial layer 9, thus forming an RF switch, as shown below. Figure 18 As shown.

[0108] This disclosure also provides a specific embodiment of a radio frequency switch prepared using the above steps S1 to S5. In step S1, the substrate 1 is made of glass and has dimensions of 370mm x 470mm. The reverse stress layer 8 is made of silicon nitride and has a thickness of 150nm.

[0109] In step S2, the thickness of the first reference electrode 21, the second reference electrode 22 and the driving electrode 23 is 1 μm, and the width of the first gap AG1 and the second gap AG2 can be 5-20 μm. In the experiment, the width of the first gap AG1 and the second gap AG2 is 8 μm.

[0110] In step S3, the interlayer insulating layer 3 covers the entire substrate 1, namely the first reference electrode 21, the second reference electrode 22, and the driving electrode 23. The interlayer insulating layer 3 is made of silicon nitride and has a thickness of 200 μm.

[0111] In step S4, the filling structure 4 includes a stacked first sub-filling portion 41 and a second sub-filling portion 42. The thickness of both the first sub-filling portion 41 and the second sub-filling portion 42 is 550 nm. The parameters for preparing the first sub-filling portion 41 and the second sub-filling portion 42 are as follows: pre-spin coating parameters are spin coating for 3 seconds, ramping up to 300 rpm and holding for 10 seconds; main spin coating parameters are spin coating for 10 seconds, ramping up to 5000 rpm and holding for 30 seconds; pre-baking at 120 degrees Celsius for 30 seconds; exposure for 2.5 seconds, development for 30 seconds; post-baking at 120 degrees Celsius for 120 seconds; and thermal curing at 230 degrees Celsius for 1 hour. Furthermore, the dimensions of the first patterned portion and the second patterned portion in the mask used are both 9 μm * 50 μm.

[0112] Figure 19 The image shows a cross-sectional view after the first sub-filling portion 41 is prepared in step S4. According to the measurement, the distance between the surface of the first sub-filling portion 41 away from the substrate 1 and the first surface W1 in the thickness direction of the substrate 1 is 500 nm. Figure 20 The image shows a cross-sectional view after the second sub-filling portion 42 is prepared in step S4. Measurements show that the distance between the surface of the first sub-filling portion 41 away from the substrate 1 and the first surface W1 in the thickness direction of the substrate 1 is less than 200 nm, indicating a significant planarization effect.

[0113] In step S5, the layers containing bridge arm 51, contact structure 6, and connecting electrode 7 adopt a Mo / Al / Mo multilayer structure with a thickness of 300 nm. The sacrificial layer 9 is made of silicon oxide with a thickness of 1 μm. The layer containing bridge surface 52 adopts a Mo / Al / Mo multilayer structure with a thickness of 2-3 μm.

[0114] Figure 21 This diagram illustrates the contact position between the driving electrode 23 and the filling structure 4 of the RF switch fabricated using the above method. As can be seen from the diagram, the RF switch device fabricated using the method provided in this disclosure exhibits good surface flatness and planarization effect. Therefore, the fabrication method provided in this disclosure can improve product yield, making it possible to fabricate large-area glass-based RF devices for application in various scenarios.

[0115] This disclosure also provides an electronic device that includes the radio frequency switch described in the above embodiments. In some embodiments, the electronic device may include a television set, a computer, an electronic measuring instrument, a robot, a camera, a mobile phone, etc.

[0116] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A radio frequency switch, comprising: Substrate; A first reference electrode and a second reference electrode are disposed on the substrate, and a driving electrode is disposed between the first reference electrode and the second reference electrode; There is a first gap between the driving electrode and the first reference electrode, and there is a second gap between the driving electrode and the second reference electrode; An interlayer insulating layer covers at least the surface of the driving electrode on the side opposite to the substrate. The surface of the interlayer insulating layer on the side facing away from the substrate, located within the defined range of the orthogonal projection of the driving electrode on the substrate, is the first surface; A membrane bridge structure is disposed on the side of the interlayer insulating layer opposite to the substrate; the membrane bridge structure includes a bridge surface and a bridge arm connected to the bridge surface; The bridge arm is connected to the first reference electrode, one end of the bridge surface is connected to the bridge arm, and the other end at least partially overlaps with the orthographic projection of the second reference electrode on the substrate. The driving electrode is located within the space defined by the bridge surface and the substrate. The radio frequency switch further includes a first groove defined by the first gap and a second groove defined by the second gap; the first groove and the second groove are filled with a filling structure; the maximum distance between the filling structure and the surface of the substrate away from the substrate is a first distance, and the maximum distance between the first surface and the substrate is a second distance; The difference between the second distance and the first distance is no greater than 200nm.

2. The radio frequency switch according to claim 1, wherein, The first reference electrode, the second reference electrode, and the driving electrode are disposed in the same layer, and the interlayer insulating layer is disposed on the side of the layer containing the first reference electrode, the second reference electrode, and the driving electrode that is away from the substrate. The bridge arm is connected to the first reference electrode through a first via penetrating the interlayer insulation layer.

3. The radio frequency switch according to claim 2, wherein, The bridge surface includes a main body and a protrusion connected to the main body; one end of the main body is connected to the bridge arm, and the other end is connected to the protrusion, and the protrusion is disposed on the side of the main body close to the substrate. The radio frequency switch further includes a contact structure corresponding to the protrusion; the contact structure is disposed on the side of the interlayer insulating layer away from the substrate, and is connected to the second reference electrode through a second via penetrating the interlayer insulating layer; The orthographic projection of the contact structure on the substrate covers the orthographic projection of the protrusion on the substrate, and the contact structure and the protrusion have a third distance in the thickness direction of the substrate.

4. The radio frequency switch according to claim 3, wherein, The radio frequency switch further includes a connection electrode disposed on the side of the interlayer insulating layer away from the substrate; the connection electrode is connected to the second reference electrode through a third via penetrating the interlayer insulating layer, and the connection electrode is disposed on the side of the contact structure away from the driving electrode.

5. The radio frequency switch according to claim 1, wherein, The bridge deck includes a first window extending through it along its thickness direction.

6. A method for fabricating a radio frequency switch, comprising: Provide a substrate; A first reference electrode, a second reference electrode, and a driving electrode disposed between the first reference electrode and the second reference electrode are formed on the substrate. There is a first gap between the driving electrode and the first reference electrode, and there is a second gap between the driving electrode and the second reference electrode; The first gap defines a first groove, and the second gap defines a second groove; An interlayer insulating layer is formed on the side of the layer containing the driving electrode that is away from the substrate. The interlayer insulating layer at least covers the surface of the driving electrode on the side opposite to the substrate. The surface of the interlayer insulating layer on the side facing away from the substrate, located within the defined range of the orthogonal projection of the driving electrode on the substrate, is the first surface; A filling structure is formed in the first groove and the second groove; A membrane bridge structure is formed on the side of the interlayer insulating layer opposite to the substrate. The membrane bridge structure includes a bridge deck and bridge arms connected to the bridge deck; The bridge arm is connected to the first reference electrode, one end of the bridge surface is connected to the bridge arm, and the other end at least partially overlaps with the orthographic projection of the second reference electrode on the substrate. The driving electrode is located within the space defined by the bridge surface and the substrate. Wherein, the maximum distance from the surface of the filling structure away from the substrate to the substrate is a first distance, and the maximum distance from the first surface to the substrate is a second distance; The difference between the second distance and the first distance is no greater than 200nm.

7. The preparation method according to claim 6, wherein, The filling structure includes at least two stacked sub-filling sections; The step of forming the sub-fill portion includes: A photoresist layer is formed in the first and second trenches, and then exposed, developed, and etched to form a pattern including the sub-filled portion.

8. The preparation method according to claim 7, wherein, The mask used to form the sub-fill portion exposure includes a first pattern portion and a second pattern portion; the orthographic projection of the first pattern portion on the substrate covers the orthographic projection of the first groove portion on the substrate, and the orthographic projection of the second pattern portion on the substrate covers the orthographic projection of the second groove portion on the substrate. The width ratio of the first patterned portion to the width ratio of the first grooved portion is 1.1-1.2; the width ratio of the second patterned portion to the width ratio of the second grooved portion is 1.1-1.

2.

9. The preparation method according to claim 6, wherein, The step of forming a film bridge structure on the side of the interlayer insulating layer opposite to the substrate includes: A pattern including the bridge arm is formed on the side of the interlayer insulating layer away from the substrate by a patterning process; A sacrificial layer is formed on the side of the bridge arm away from the substrate, and a fourth via is formed that penetrates along the thickness direction of the sacrificial layer; the orthographic projection of the fourth via on the substrate covers the orthographic projection of the bridge arm on the substrate. A pattern including the bridge is formed on the side of the sacrificial layer away from the substrate by a patterning process; Remove the sacrificial layer.

10. An electronic device comprising a radio frequency switch as claimed in any one of claims 1-5.

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