Radio frequency MEMS switch and method of manufacturing the same

Abstract

The application provides a radio frequency MEMS switch and a manufacturing method thereof. A sacrificial layer is formed on a substrate, the sacrificial layer comprising a first part sacrificial layer and a second part sacrificial layer connected with the first part sacrificial layer, the first part sacrificial layer being aligned with a switch contact, and the surface of the first part sacrificial layer being lower than or flush with the surface of the second part sacrificial layer. Thus, after a metal layer is formed on the sacrificial layer and the sacrificial layer is released, the metal layer can be in good contact with the switch contact in the radio frequency MEMS switch, and the yield and reliability of the radio frequency MEMS switch are improved.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a radio frequency MEMS switch and its manufacturing method. Background Technology

[0002] Radio frequency (RF) MEMS (Micro-Electro-Mechanical Systems) switches are RF switches fabricated using MEMS technology. They control the conduction and disconnection of RF signals through the movement of micromechanical structures. RF MEMS switches are one of the core components of microwave and RF transceiver systems, with wide applications in satellite communications, radar, and missile control. Compared to traditional PIN (diode) and FET (field-effect transistor) microwave switches, RF MEMS switches not only possess superior microwave performance, including high isolation, low loss, low insertion loss, and high linearity, but also offer advantages such as mass production capabilities, small size, and easy integration with advanced microwave and RF circuits. They are a key technology for achieving miniaturized, low-cost, and high-performance microwave transceiver front-end systems.

[0003] Existing RF MEMS switches often suffer from contact abnormalities, resulting in low yield and reliability. Summary of the Invention

[0004] The purpose of this invention is to provide a radio frequency MEMS switch and its manufacturing method to solve the problem of contact abnormalities that often exist in existing radio frequency MEMS switches.

[0005] To address the aforementioned technical problems, this invention provides a method for manufacturing an RF MEMS switch, the method comprising:

[0006] A substrate is provided on which switching contacts are formed;

[0007] A sacrificial layer is formed on the substrate. The sacrificial layer includes a first part sacrificial layer and a second part sacrificial layer connected to the first part sacrificial layer. The first part sacrificial layer is aligned with the switch contact. The surface of the first part sacrificial layer is lower than or flush with the surface of the second part sacrificial layer.

[0008] A metal layer is formed on the sacrificial layer; and,

[0009] The sacrificial layer is released to form an RF MEMS switch.

[0010] Optionally, in the method for manufacturing the radio frequency MEMS switch, forming a sacrificial layer on the substrate includes:

[0011] A first sacrificial layer is formed on the substrate, the first sacrificial layer covering the substrate and the switch contact;

[0012] An opening is formed in the first sacrificial layer, the opening exposing the switch contact; and,

[0013] A second sacrificial layer is formed, which fills the opening and covers the first sacrificial layer, wherein the first portion of the sacrificial layer includes the second sacrificial layer located in the opening, and the second portion of the sacrificial layer includes the first sacrificial layer and the second sacrificial layer located on the first sacrificial layer.

[0014] Optionally, in the method for manufacturing the radio frequency MEMS switch, forming the second sacrificial layer includes:

[0015] A sacrificial material layer is spin-coated onto the surface of the first sacrificial layer and into the opening; and

[0016] The sacrificial material layer is cured to form the second sacrificial layer.

[0017] Optionally, in the manufacturing method of the radio frequency MEMS switch, the material of the first sacrificial layer and the material of the second sacrificial layer are the same.

[0018] Optionally, in the method for manufacturing the radio frequency MEMS switch, the switch contact is located in the central region of the opening.

[0019] Optionally, in the manufacturing method of the radio frequency MEMS switch, the cross-sectional width of the opening is 1.2 to 5 times the cross-sectional width of the switch contact; and the height of the opening is 1.1 to 2 times the height of the switch contact.

[0020] Optionally, in the method for manufacturing the radio frequency MEMS switch, the metal layer includes a first part metal layer and a second part metal layer connected to the first part metal layer, wherein the first part metal layer covers the first part sacrificial layer, the second part metal layer covers the second part sacrificial layer, and the lower surface of the first part metal layer is closer to the substrate than the lower surface of the second part metal layer.

[0021] Optionally, in the manufacturing method of the radio frequency MEMS switch, the thickness of the first portion of the metal layer is thicker than the thickness of the second portion of the metal layer.

[0022] Optionally, in the manufacturing method of the radio frequency MEMS switch, the material of the metal layer is the same as the material of the switch contacts.

[0023] The present invention also provides an RF MEMS switch, the RF MEMS switch comprising:

[0024] A substrate, wherein switching contacts are formed on the substrate; and,

[0025] A metal layer located on the substrate, the metal layer comprising a first portion metal layer and a second portion metal layer connected to the first portion metal layer, the first portion metal layer being aligned with the switch contact, wherein the lower surface of the first portion metal layer is closer to the substrate than the lower surface of the second portion metal layer.

[0026] In the radio frequency MEMS switch and its manufacturing method provided by the present invention, a sacrificial layer is formed on a substrate. The sacrificial layer includes a first part of the sacrificial layer and a second part of the sacrificial layer connected to the first part of the sacrificial layer. The first part of the sacrificial layer is aligned with the switch contacts. The surface of the first part of the sacrificial layer is lower than or flush with the surface of the second part of the sacrificial layer. Thus, after a metal layer is formed on the sacrificial layer and the sacrificial layer is released, the metal layer in the formed radio frequency MEMS switch can make good contact with the switch contacts, thereby improving the yield and reliability of the radio frequency MEMS switch. Attached Figure Description

[0027] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0028] Figure 1 This is a schematic flowchart of the manufacturing method of the radio frequency MEMS switch according to an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the structure after the formation of the first sacrificial layer in an embodiment of the present invention.

[0030] Figure 3 This is a schematic diagram of the structure after the opening is formed according to an embodiment of the present invention.

[0031] Figure 4 This is a schematic diagram of the structure after the formation of the second sacrificial layer in an embodiment of the present invention.

[0032] Figure 5 This is a schematic diagram of the structure after the metal layer is formed according to an embodiment of the present invention.

[0033] Figure 6 This is a schematic diagram of the structure after the sacrificial layer is released to form a radio frequency MEMS switch according to an embodiment of the present invention.

[0034] Figure 7 This is a schematic diagram of the state when the radio frequency MEMS switch is connected according to an embodiment of the present invention.

[0035] Figure 8This is a schematic diagram of the structure of a radio frequency MEMS switch.

[0036] Figure 9 yes Figure 8 The diagram shows the state when the RF MEMS switch is connected.

[0037] Figure 10 This is a schematic diagram of the structure during the formation process of a radio frequency MEMS switch.

[0038] The reference numerals in the attached figures are explained as follows:

[0039] 100 - Substrate; 110 - Metal layer; 120 - Switch contact; 130 - Sacrificial layer.

[0040] 200 - Substrate; 210 - Switch contact; 220 - Sacrificial layer; 220A - First part of sacrificial layer; 220B - Second part of sacrificial layer; 221 - First sacrificial layer; 222 - Opening; 223 - Second sacrificial layer; 230 - Metal layer; 230A - First part of metal layer; 230B - Second part of metal layer; 2 - RF MEMS switch.

[0041] W1, W2 - Cross-sectional width; H1, H2 - Height. Detailed Implementation

[0042] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, further illustrates the radio frequency MEMS switch and its manufacturing method proposed in this invention. The advantages and features of this invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of this invention.

[0043] The terminology used in this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. Unless otherwise defined in this application, the technical or scientific terms used in this invention should be understood in their ordinary sense by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, "a" or "one," and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. "A plurality" or "several" indicates two or more. Unless otherwise stated, terms such as "front," "rear," "lower," and / or "upper" are for ease of description only and are not limited to a location or spatial orientation. Terms such as "comprising" or "including" indicate that the element or object preceding "comprising" encompasses the element or object listed following "comprising" or its equivalents, and do not exclude other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections and can include electrical connections, whether direct or indirect. The singular forms “a,” “the,” and “the” used in this specification and appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0044] Existing RF MEMS switches often suffer from contact abnormalities. The inventors conducted in-depth research on this issue and discovered that the cause lies in, for example... Figure 8 and Figure 9 As shown, the portion of the metal layer 110 aligned with the switch contact 120 has an upward bulge, which results in poor contact between the metal layer 110 and the switch contact 120 when the RF MEMS switch is turned on. This leads to poor conduction of the RF MEMS switch, thus reducing the yield and reliability of the RF MEMS switch.

[0045] Further investigation revealed that the upward bulge of the portion of the metal layer 110 aligned with the switch contact 120 is due to, for example... Figure 10As shown, the sacrificial layer 130 covers the switch contact 120 and the substrate 110. The portion of the sacrificial layer 130 aligned with the switch contact 120 has an upward bulge, causing the metal layer 110 formed on the sacrificial layer 130 to suffer from the same problem. After releasing the sacrificial layer 130 to form an RF MEMS switch, poor contact exists between the metal layer 110 and the switch contact 120. The difficulty in solving this problem lies in the fact that planarizing the sacrificial layer 130 is challenging, resulting in poor planarization. Furthermore, a specialized chemical mechanical polishing (CMP) platform is typically required, significantly increasing manufacturing costs. Additionally, planarization reduces the adhesion of the sacrificial layer 130, often leading to poor formation quality of the subsequent metal layer 110 and increasing the risk of splitting. This greatly increases the difficulty of resolving the problem of poor conduction in RF MEMS switches.

[0046] Therefore, after in-depth research, the inventors proposed a method for manufacturing radio frequency MEMS switches, such as... Figure 1 As shown in the embodiments of this application, the manufacturing method of the radio frequency MEMS switch includes:

[0047] Step S10: Provide a substrate on which switch contacts are formed;

[0048] Step S20: A sacrificial layer is formed on the substrate. The sacrificial layer includes a first part sacrificial layer and a second part sacrificial layer connected to the first part sacrificial layer. The first part sacrificial layer is aligned with the switch contact, and the surface of the first part sacrificial layer is lower or flush with the surface of the second part sacrificial layer.

[0049] Step S30: Form a metal layer on the sacrificial layer; and,

[0050] Step S40: Release the sacrificial layer to form an RF MEMS switch.

[0051] In this embodiment, a sacrificial layer is formed on a substrate. The sacrificial layer includes a first part of the sacrificial layer and a second part of the sacrificial layer connected to the first part of the sacrificial layer. The first part of the sacrificial layer is aligned with the switch contacts. The surface of the first part of the sacrificial layer is lower than or flush with the surface of the second part of the sacrificial layer. Thus, after a metal layer is formed on the sacrificial layer and the sacrificial layer is released, the metal layer in the formed RF MEMS switch can make good contact with the switch contacts, thereby improving the yield and reliability of the RF MEMS switch.

[0052] Please refer to Figures 2 to 7 This is a schematic diagram of the structure formed by performing the manufacturing method of the radio frequency MEMS switch according to the embodiments of this application.

[0053] like Figure 2As shown, a substrate 200 is provided, wherein the substrate 200 may be a silicon substrate, a germanium substrate, a germanium-silicon substrate, a silicon carbide substrate, a silicon-on-insulator substrate, etc. In some embodiments of this application, the substrate 200 may include multiple functional regions (not shown in the figure) to form different functional structures in different functional regions.

[0054] In this embodiment, a switch contact 210 is formed on the substrate 200. The switch contact 210 is made of metal, such as copper or aluminum. The shape of the switch contact 210 can be, for example, cuboid or cylindrical.

[0055] In this embodiment, multiple sacrificial layers are formed to adjust the surface morphology of the formed sacrificial layers. Please continue to refer to... Figure 2 Next, a first sacrificial layer 221 is formed on the substrate 200, covering the substrate 200 and the switch contact 210. The first sacrificial layer 221 may be made of polyimide (PI), and in some embodiments of this application, it can be formed by a deposition process. For example... Figure 2 The portion of the first sacrificial layer 221 aligned with the switch contact 210 has an upward convexity.

[0056] Please refer to Figure 3 In this embodiment, an opening 222 is then formed in the first sacrificial layer 221, exposing the switch contact 210. In some embodiments of this application, the opening 222 can be formed by an etching process. Here, the opening 222 exposes the switch contact 210 and a portion of the substrate 200. In some embodiments of this application, the cross-sectional width W1 of the opening 222 is 1.2 to 5 times the cross-sectional width W2 of the switch contact 210. This allows for better control of the surface morphology of the final sacrificial layer. In some embodiments of this application, the switch contact 210 is located in the central region of the opening 222. The height H1 of the opening 222 is 1.1 to 2 times the height H2 of the switch contact 210. This facilitates control of the surface morphology of the final sacrificial layer and also allows for better control of the physical and electrical properties of the final RF MEMS switch.

[0057] like Figure 4As shown, a second sacrificial layer 223 is then formed, which fills the opening 222 and covers the first sacrificial layer 221. Due to the presence of the opening 222, when the second sacrificial layer 223 is formed, it will form a recess at the opening 222 relative to the portion located on the first sacrificial layer 221, thereby facilitating contact between the subsequently formed metal layer and the switch contact 210.

[0058] In some embodiments of this application, the second sacrificial layer 223 can be made of a fluid resin material, such as polyimide (PI). Polyimide has excellent fluidity, and the limiting effect of the opening 222 allows the surface of the second sacrificial layer 223 in the opening 222 to be relatively flat. That is, the second sacrificial layer 223 in the opening 222 is recessed relative to the second sacrificial layer 223 on the first sacrificial layer 221, and the surface of the second sacrificial layer 223 in the opening 222 is flat, which greatly facilitates the contact between the subsequently formed metal layer and the switch contact 210. In some embodiments of this application, forming the second sacrificial layer 223 may include: spin-coating a sacrificial material layer on the surface of the first sacrificial layer 221 and in the opening 222; then, the sacrificial material layer can be cured at high temperature to form the second sacrificial layer 223, wherein the curing temperature can be between 300°C and 600°C.

[0059] In this embodiment, the material of the second sacrificial layer 223 is the same as that of the first sacrificial layer 221, thereby improving the film quality of the second sacrificial layer 223 and the adhesion between the second sacrificial layer 223 and the first sacrificial layer 221, and improving the quality of the formed sacrificial layer 220.

[0060] In this embodiment, a sacrificial layer 220 is formed, comprising a first sacrificial layer 221 having an opening 222, and a second sacrificial layer 223 filling the opening 222 and covering the first sacrificial layer 221. The surface of the second sacrificial layer 223 located in the opening 222 is lower than or flush with the surface of the second sacrificial layer 223 located on the first sacrificial layer 221.

[0061] That is, the sacrificial layer 220 includes a first sacrificial layer 220A and a second sacrificial layer 220B connected to the first sacrificial layer 220A. The first sacrificial layer 220A is aligned with the switch contact 210, and the surface of the first sacrificial layer 220A is lower than or flush with the surface of the second sacrificial layer 220B; that is, the portion of the sacrificial layer 220 aligned with the switch contact 210 is concave. In this embodiment, the first sacrificial layer 220A includes a second sacrificial layer 223 located in the opening 222, and the second sacrificial layer 220B includes the first sacrificial layer 221 and the second sacrificial layer 223 located on the first sacrificial layer 221. The surface of the first sacrificial layer 220A is lower than the surface of the second sacrificial layer 220B.

[0062] Next, as Figure 5 As shown, a metal layer 230 is formed on the sacrificial layer 220. The metal layer 230 is made of the same material as the switch contact 210 to improve the contact performance between them, thereby improving the electrical performance of the formed radio frequency MEMS switch.

[0063] In this embodiment, the metal layer 230 is formed conformally on the surface of the sacrificial layer 220, and the metal layer 230 can be formed by a deposition process. In this embodiment, the portion of the sacrificial layer 220 aligned with the switch contact 210 is concave, and thus the portion of the metal layer 230 aligned with the switch contact 210 is convex. This improves the contact reliability between the metal layer 230 and the switch contact 210 when the RF MEMS switch is formed and turned on.

[0064] like Figure 5 As shown in this embodiment, the metal layer 230 includes a first metal layer 230A and a second metal layer 230B connected to the first metal layer 230A. The first metal layer 230A covers the first sacrificial layer 220A, and the second metal layer 230B covers the second sacrificial layer 220B. The lower surface of the first metal layer 230A is closer to the substrate 200 than the lower surface of the second metal layer 230B. That is, the first metal layer 230A has a downward convexity, which facilitates contact with the switch contact 210 when the RF MEMS switch is formed and turned on. In this embodiment, the thickness of the first metal layer 230A is greater than the thickness of the second metal layer 230B.

[0065] Next, as Figure 6As shown, the sacrificial layer 220 is released to form the radio frequency MEMS switch 2. In some embodiments of this application, the sacrificial layer 220 can be removed by an etching process, i.e., the sacrificial layer 220 is released, so that the metal layer 230 is suspended above the switch contact 210. The sacrificial layer 220 can be released by a dry etching process or a wet etching process.

[0066] Accordingly, this application also provides a radio frequency MEMS switch 2, such as... Figure 6 As shown, the radio frequency MEMS switch 2 includes:

[0067] Substrate 200, wherein switch contacts 210 are formed on substrate 200; and,

[0068] A metal layer 230 is located on the substrate 200. The metal layer 230 includes a first metal layer 230A and a second metal layer 230B connected to the first metal layer 230A. The first metal layer 230A is aligned with the switch contact 210, wherein the lower surface of the first metal layer 230A is closer to the substrate 200 than the lower surface of the second metal layer 230B. That is, the first metal layer 230A has a downward convexity, thereby facilitating contact between the RF MEMS switch 2 and the switch contact 210 when the switch is turned on. Figure 7 As shown, this improves the yield and reliability of the RF MEMS switch 2.

[0069] Please compare and refer to the above. Figure 7 and Figure 9 In existing RF MEMS switches, the portion of the metal layer 110 aligned with the switch contact 120 has an upward bulge, resulting in poor contact between the metal layer 110 and the switch contact 120 when the RF MEMS switch is turned on. However, in the RF MEMS switch 2 of this application embodiment, the portion of the metal layer 230 aligned with the switch contact 210 has a downward bulge, which allows the metal layer 230 to make good contact with the switch contact 210 when the RF MEMS switch 2 is turned on, thereby improving the yield and reliability of the RF MEMS switch 2.

[0070] In this embodiment, the surface morphology of the sacrificial layer 220 is adjusted by modifying the formation process of the sacrificial layer 220, thereby adjusting the morphology of the metal layer 230 thereon. This achieves good contact between the metal layer 230 and the switch contact 210, improving the yield and reliability of the RF MEMS switch 2. This avoids the use of an additional specialized chemical mechanical polishing machine, reducing manufacturing costs. Simultaneously, it preserves the good adhesion of the sacrificial layer 220 surface, avoiding problems such as film splitting, resulting in a low-cost, high-quality RF MEMS switch 2.

[0071] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the protection scope of the claims.

Claims

1. A method for manufacturing a radio frequency MEMS switch, characterized in that, The method for manufacturing the radio frequency MEMS switch includes: A substrate is provided on which switching contacts are formed; A sacrificial layer is formed on the substrate. The sacrificial layer includes a first sacrificial layer and a second sacrificial layer connected to the first sacrificial layer. The first sacrificial layer is aligned with the switch contact. The surface of the first sacrificial layer is lower than or flush with the surface of the second sacrificial layer. A metal layer is formed on the sacrificial layer; and, The sacrificial layer is released to form an RF MEMS switch.

2. The method for manufacturing an RF MEMS switch as described in claim 1, characterized in that, Forming a sacrificial layer on the substrate includes: A first sacrificial layer is formed on the substrate, the first sacrificial layer covering the substrate and the switch contact; An opening is formed in the first sacrificial layer, the opening exposing the switch contact; and, A second sacrificial layer is formed, which fills the opening and covers the first sacrificial layer, wherein the first portion of the sacrificial layer includes the second sacrificial layer located in the opening, and the second portion of the sacrificial layer includes the first sacrificial layer and the second sacrificial layer located on the first sacrificial layer.

3. The method for manufacturing an RF MEMS switch as described in claim 2, characterized in that, The formation of the second sacrificial layer includes: A sacrificial material layer is spin-coated onto the surface of the first sacrificial layer and into the opening; and The sacrificial material layer is cured to form the second sacrificial layer.

4. The method for manufacturing an RF MEMS switch as described in claim 2, characterized in that, The material of the first sacrificial layer is the same as that of the second sacrificial layer.

5. The method for manufacturing an RF MEMS switch as described in claim 2, characterized in that, The switch contact is located in the central region of the opening.

6. The method for manufacturing an RF MEMS switch as described in any one of claims 2 to 5, characterized in that, The cross-sectional width of the opening is 1.2 to 5 times the cross-sectional width of the switch contact; the height of the opening is 1.1 to 2 times the height of the switch contact.

7. The method for manufacturing an RF MEMS switch as described in claim 1, characterized in that, The metal layer includes a first portion metal layer and a second portion metal layer connected to the first portion metal layer, wherein the first portion metal layer covers the first portion sacrificial layer, the second portion metal layer covers the second portion sacrificial layer, and the lower surface of the first portion metal layer is closer to the substrate than the lower surface of the second portion metal layer.

8. The method for manufacturing an RF MEMS switch as described in claim 7, characterized in that, The thickness of the first part of the metal layer is greater than the thickness of the second part of the metal layer.

9. The method for manufacturing an RF MEMS switch as described in claim 1, characterized in that, The metal layer is made of the same material as the switch contacts.

10. A radio frequency MEMS switch, characterized in that, The radio frequency MEMS switch includes: A substrate, wherein switching contacts are formed on the substrate; and, A metal layer located on the substrate, the metal layer comprising a first portion metal layer and a second portion metal layer connected to the first portion metal layer, the first portion metal layer being aligned with the switch contact, wherein the lower surface of the first portion metal layer is closer to the substrate than the lower surface of the second portion metal layer.

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