A radio frequency switch and a method for manufacturing the same

Abstract

The present invention provides a radio frequency switch and a method for manufacturing the same, comprising: a substrate having a plurality of deep trenches therein; an epitaxial layer covering the inner walls of the deep trenches and extending over the substrate; a trench isolation structure located within the deep trenches and covering at least the openings thereof, thereby forming a first air gap within the deep trenches; and a gate structure located on the epitaxial layer and between adjacent deep trenches. Because the first air gaps have a very low dielectric constant, the first air gaps and the trench isolation structure effectively isolate the substrate from the epitaxial layer, preventing signals from being transmitted on the substrate when the radio frequency switch is in the off state. This provides the radio frequency switch with improved isolation and enhances its performance.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing, and in particular to a radio frequency switch and a preparation method thereof. Background Art

[0002] RF switches are very important components in many wireless communication systems. They have the advantages of simple structure, wide application range, low cost, low power consumption, easy installation and high reliability. They are widely used in carrier telephone switching, cable TV signal switching, cable TV signal switching and other fields.

[0003] A typical RF switch consists of a series of transistor structures connected in series. When the RF switch is operating, some areas are in the on state and some areas are in the off state. However, in actual applications, it is found that signals are still transmitted on the substrate of the RF switch in the off state, which deteriorates the isolation of the RF switch, causes signal loss, and reduces the sensitivity of the device. Summary of the Invention

[0004] The object of the present invention is to provide a radio frequency switch and a preparation method thereof, so as to avoid signal transmission on a substrate when the radio frequency switch is in an off state and improve the isolation of the device.

[0005] In order to achieve the above object, the present invention provides a radio frequency switch, comprising:

[0006] a substrate having a plurality of deep trenches therein;

[0007] an epitaxial layer covering an inner wall of the deep trench and extending to cover the substrate;

[0008] a trench isolation structure located in the deep trench and covering at least an opening of the deep trench, so as to form a first air gap in the deep trench;

[0009] The gate structure is located on the epitaxial layer and between adjacent deep trenches.

[0010] Optionally, the trench isolation structure further extends to fill a portion of the depth of the deep trench.

[0011] Optionally, the depth of the deep trench is 3.6 μm to 4.4 μm.

[0012] Optionally, the width of the deep trench is 0.36 μm to 0.44 μm.

[0013] Optionally, the width of the first air gap is 0.1 μm to 0.15 μm.

[0014] Based on the same inventive concept, the present invention also provides a method for preparing a radio frequency switch, comprising:

[0015] providing a substrate, and forming a plurality of deep trenches in the substrate;

[0016] forming an epitaxial layer on the substrate, wherein the epitaxial layer covers the inner wall of the deep trench and extends to cover the substrate;

[0017] forming a trench isolation structure in the deep trench, wherein the shallow trench isolation structure at least covers an opening of the deep trench, so that a first air gap is formed in the deep trench;

[0018] A gate structure is formed on the epitaxial layer, and the gate structure is located between adjacent deep trenches.

[0019] Optionally, the step of forming the epitaxial layer includes:

[0020] forming an epitaxial material layer on the substrate, wherein the epitaxial material layer covers the inner wall of the deep trench and extends to cover the substrate, and covers the opening of the deep trench, so as to form a second air gap in the deep trench;

[0021] The epitaxial material layer is etched to expose the second air gap, and the remaining epitaxial material layer constitutes the epitaxial layer.

[0022] Optionally, the depth of the second air gap is 0.36 μm to 0.44 μm.

[0023] Optionally, the step of forming the trench isolation structure includes:

[0024] forming an isolation material layer on the epitaxial layer, wherein the isolation material layer also covers at least an opening of the second air gap to form the first air gap;

[0025] A planarization process is performed on the isolation material layer until the epitaxial layer is exposed, and the remaining isolation material layer forms the trench isolation structure.

[0026] Optionally, when etching the epitaxial material layer, a plurality of shallow trenches are also formed in the epitaxial layer simultaneously; when forming the isolation material layer on the epitaxial layer, the isolation material layer also fills the shallow trenches to form a plurality of shallow trench isolation structures.

[0027] The present invention provides a radio frequency switch and a method for manufacturing the same, comprising: a substrate having a plurality of deep trenches therein; an epitaxial layer covering the inner walls of the deep trenches and extending over the substrate; a trench isolation structure located within the deep trenches and at least covering the openings of the deep trenches, thereby forming a first air gap within the deep trenches; and a gate structure located on the epitaxial layer and between adjacent deep trenches. Because the first air gaps have a very low dielectric constant, the first air gaps and the trench isolation structure provide excellent isolation, preventing signals from being transmitted on the substrate when the radio frequency switch is in the off state. This provides the radio frequency switch with improved isolation and enhances its performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A flow chart of a method for preparing a radio frequency switch provided by the present invention;

[0029] Figures 2 to 9 A schematic structural diagram corresponding to the corresponding steps of a method for preparing a radio frequency switch provided by the present invention;

[0030] The accompanying drawings are as follows:

[0031] 100 - substrate; 101 - deep trench; 102 - epitaxial material layer; 103 - first air gap; 104 - epitaxial layer; 106 - isolation material layer; 107 - second air gap; 108 - trench isolation structure; 110 - gate structure. DETAILED DESCRIPTION

[0032] The following is a more detailed description of the specific embodiments of the present invention with reference to schematic diagrams. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the drawings are greatly simplified and not to exact scale, and are only used for the purpose of conveniently and clearly illustrating the embodiments of the present invention.

[0033] Hereinafter, the terms "first," "second," and the like are used to distinguish between similar elements and are not necessarily used to describe a particular order or chronological sequence. It is to be understood that these terms, when used in this manner, are interchangeable where appropriate. Similarly, if a method described herein comprises a series of steps, the steps presented herein are not necessarily the only order in which the steps may be performed, and some of the steps described may be omitted and / or other steps not described herein may be added to the method.

[0034] Figure 9 A schematic diagram of the structure of a radio frequency switch provided in this embodiment is shown in FIG. Figure 9As shown, this embodiment provides a radio frequency switch, including: a substrate 100, wherein the substrate 100 has a plurality of deep trenches 101; an epitaxial layer 104, covering the inner walls of the deep trenches 101 and extending to cover the substrate 100; a trench isolation structure 108, located in the deep trenches 101 and covering at least the openings of the deep trenches 101, so that a first air gap 107 is formed in the deep trenches 101; and a gate structure 110, located on the epitaxial layer 104 and located between adjacent deep trenches 101.

[0035] The trench isolation structure 108 may also fill a portion of the deep trench 101. The trench isolation structure 108 isolates the substrate 100 from the epitaxial layer 104. Since the dielectric constant of the first air gap 107 is very low, when the RF switch is in the off state, the trench isolation structure 108 and the first air gap 107 can effectively block the transmission of signals between adjacent gate structures 110 on the substrate 100, thereby reducing signal loss while enhancing the isolation of the RF switch and increasing the sensitivity of the RF switch to achieve better performance.

[0036] Among them, the depth of the deep trench 101 is 3.6μm~4.4μm, and the width of the deep trench 101 is 0.36μm~0.44μm, ensuring the ratio between the depth and width of the deep trench 101, ensuring that the epitaxial layer 104 only covers the inner wall of the deep trench 101, rather than filling the deep trench 101, thereby ensuring the width of the first air gap 107 and achieving better isolation effect.

[0037] The width of the first air gap 105 is 0.1 μm to 0.15 μm.

[0038] The RF switch further includes a gate structure, a source region, and a drain region. The gate structure is located on the epitaxial layer and between the deep trenches. The source region and the drain region are located in the epitaxial layer on both sides of the gate structure. The gate structure, the source region, and the drain region constitute a transistor structure.

[0039] Figure 1 This is a flow chart of a method for preparing a radio frequency switch provided in this embodiment, as shown in FIG. Figure 1 As shown, the present invention provides a method for preparing a radio frequency switch, comprising:

[0040] Step S1: providing a substrate, and forming a plurality of deep trenches in the substrate;

[0041] Step S2: forming an epitaxial layer on the substrate, wherein the epitaxial layer covers the inner wall of the deep trench and extends to cover the substrate;

[0042] Step S3: forming a trench isolation structure in the deep trench, wherein the shallow trench isolation structure at least covers the opening of the deep trench, so that a first air gap is formed in the deep trench;

[0043] Step S4: forming a gate structure on the epitaxial layer, wherein the gate structure is located between adjacent deep trenches.

[0044] Figures 2 to 9 The following is a schematic diagram of the structure corresponding to the corresponding steps of the method for preparing a radio frequency switch provided in this embodiment, Figures 2 to 9 A method for preparing a radio frequency switch provided in this embodiment is described in more detail, wherein an optional embodiment of the present invention is illustrated.

[0045] like Figure 2 As shown, a substrate 100 is provided, and the substrate 100 is etched to form a plurality of deep trenches 101 in the substrate 100. The depth of the deep trenches 101 is 3.6 μm to 4.4 μm, and the width of the deep trenches 101 is 0.36 μm to 0.44 μm.

[0046] like Figure 4 As shown, an epitaxial material layer 102 is formed on the substrate 100. The epitaxial material layer 102 covers the inner wall of the deep trench 101 and extends to cover the substrate 100. Since the ratio between the depth and width of the deep trench 101 is large and the filling ability of the epitaxial material layer 102 is weak, during the formation of the epitaxial material layer 102, the epitaxial material layer 102 covers the opening of the deep trench 101 and forms a second air gap 103 in the deep trench 101.

[0047] In this embodiment, the second air gap 103 has a depth of 1.6 μm to 2.4 μm and a width of 0.1 μm to 0.15 μm.

[0048] Figure 3 and Figure 5 They are Figure 2 and Figure 4 The corresponding electron microscope scanning diagram of the RF switch structure diagram is as follows: Figure 3 and Figure 5 As shown, after the epitaxial material layer 102 is formed on the substrate 100 , the epitaxial material layer 102 only covers the inner wall of the deep trench 101 and covers the opening of the deep trench 101 to form the second air gap 103 , but does not completely fill the deep trench 101 .

[0049] like Figures 6 to 7 As shown, the epitaxial material layer is etched to expose the second air gap 103 , and the remaining epitaxial material layer constitutes the epitaxial layer 104 .

[0050] Furthermore, an isolation material layer 106 is formed on the epitaxial layer 104. The isolation material layer 106 at least covers the opening of the second air gap 103. In this embodiment, the isolation material layer 106 also fills a portion of the depth of the second air gap 103. The isolation material layer 106 can be made of silicon oxide.

[0051] Since the epitaxial material layer is deposited on the sidewall of the deep trench 101 during the formation process, the ratio between the depth and width of the second air gap 103 is further increased compared to the ratio between the depth and width of the deep trench 101, and the filling ability of the isolation material layer 106 is also relatively weak. When the isolation material layer 106 is formed on the epitaxial layer 104, the isolation material layer 106 cannot fill the second air gap 103, but only covers the opening of the second air gap 103. It can also fill part of the depth of the second air gap 103, thereby forming a first air gap 107 in the deep trench 101.

[0052] The isolation material layer 106 slightly covers the sidewalls of the second air gap 103. In this embodiment, the width of the first air gap 107 is 0.1 μm to 0.15 μm. It should be understood that the width of the first air gap 107 is only one example of this embodiment. In other embodiments, the width of the first air gap 107 can be adjusted according to actual conditions. The presence of the first air gap 107 can effectively isolate the substrate 100 from the epitaxial layer 104. The present invention does not impose any restrictions on the width and depth of the first air gap 107.

[0053] like Figure 8 As shown, the isolation material layer 106 is planarized to thin the isolation material layer 106 . The planarization process may be chemical mechanical polishing. The isolation material layer 106 is polished until the epitaxial layer 104 is exposed. The remaining isolation material layer 106 forms a trench isolation structure 108. The trench isolation structure 108 is located within the epitaxial layer 104.

[0054] like Figure 9 As shown, a first ion implantation process is performed on the epitaxial layer 104 between the deep trenches 101 to form an active region (not shown) in the epitaxial layer 104, and then a gate structure 110 is formed on the active region. A second ion implantation process is performed on the epitaxial layer 104 on both sides of the gate structure 110 to form a source region and a drain region, respectively. The gate structure 110, the source region and the drain region constitute a transistor structure.

[0055] Since the trench isolation structure 108 is insulating and the dielectric constant of the first air gap 107 is very low, the trench isolation structure 108 and the first air gap 107 can effectively isolate the substrate 100 from the epitaxial layer 104. When the RF switch is in the on state, the signal is transmitted between the epitaxial layer 104 and the transistor structure; when the RF switch is in the off state, no signal is transmitted in the substrate 100, thereby enhancing the isolation of the RF switch, reducing the signal loss when the RF switch is turned off, and enhancing the sensitivity of the device.

[0056] In addition, when etching the epitaxial material layer, the epitaxial material layer on the substrate 100 can also be etched simultaneously to form a number of shallow trenches in the epitaxial layer 104; when forming the isolation material layer on the epitaxial layer 104, the isolation material layer also fills the shallow trenches to form a number of shallow trench isolation structures in the epitaxial layer 104, further enhancing the isolation of the RF switch, reducing the latch-up effect, and reducing the process steps.

[0057] In summary, the present invention provides a radio frequency switch and a method for manufacturing the same, comprising: a substrate 100 having a plurality of deep trenches 101 therein; an epitaxial layer 104 covering the inner walls of the deep trenches 101 and extending over the substrate 100; a trench isolation structure 108 located within the deep trenches 101 and covering at least the openings of the deep trenches 101, thereby forming a first air gap 107 within the deep trenches 101; and a gate structure 110 located on the epitaxial layer 104 and between adjacent deep trenches 101. Because the first air gaps 107 have a very low dielectric constant, the first air gaps 107 and the trench isolation structures 108 better isolate the substrate 100 from the epitaxial layer 104, preventing signals from being transmitted on the substrate 100 when the radio frequency switch is in the off state, thereby providing the radio frequency switch with improved isolation and enhancing its performance.

[0058] The above description is merely a preferred embodiment of the present invention and does not limit the present invention in any way. Any person skilled in the art who, without departing from the scope of the present invention, makes any equivalent substitution, modification, or other changes to the technical solution and technical content disclosed in the present invention shall be deemed to be within the scope of the present invention and still fall within the scope of protection of the present invention.

Claims

1. A radio frequency switch, characterized in that: include: a substrate having a plurality of deep trenches therein; an epitaxial layer covering an inner wall of the deep trench and extending to cover the substrate; a trench isolation structure located in the deep trench and covering at least an opening of the deep trench, so as to form a first air gap in the deep trench; The gate structure is located on the epitaxial layer, and each of the gate structures is located between two adjacent deep trenches.

2. The radio frequency switch according to claim 1, wherein: The trench isolation structure also fills a portion of the depth of the deep trench.

3. The radio frequency switch according to claim 1, wherein: The depth of the deep trench is 3.6 μm to 4.4 μm.

4. The radio frequency switch according to claim 1, wherein: The width of the deep trench is 0.36 μm to 0.44 μm.

5. The radio frequency switch according to claim 1, wherein: The width of the first air gap is 0.1 μm to 0.15 μm.

6. A method for preparing a radio frequency switch, characterized in that: include: providing a substrate, and forming a plurality of deep trenches in the substrate; forming an epitaxial layer on the substrate, wherein the epitaxial layer covers the inner wall of the deep trench and extends to cover the substrate; forming a trench isolation structure in the deep trench, wherein the shallow trench isolation structure at least covers an opening of the deep trench, so that a first air gap is formed in the deep trench; A gate structure is formed on the epitaxial layer, and each of the gate structures is located between two adjacent deep trenches.

7. The method for preparing a radio frequency switch according to claim 6, wherein: The steps of forming the epitaxial layer include: forming an epitaxial material layer on the substrate, wherein the epitaxial material layer covers the inner wall of the deep trench and extends to cover the substrate, and covers the opening of the deep trench, so as to form a second air gap in the deep trench; The epitaxial material layer is etched to expose the second air gap, and the remaining epitaxial material layer constitutes the epitaxial layer.

8. The method for preparing a radio frequency switch according to claim 7, wherein: The depth of the second air gap is 0.36 μm to 0.44 μm.

9. The method for preparing a radio frequency switch according to claim 7, wherein: The steps of forming the trench isolation structure include: forming an isolation material layer on the epitaxial layer, wherein the isolation material layer at least covers the opening of the second air gap to form the first air gap; A planarization process is performed on the isolation material layer until the epitaxial layer is exposed, and the remaining isolation material layer forms the trench isolation structure.

10. The method for preparing a radio frequency switch according to claim 9, wherein: When etching the epitaxial material layer, a plurality of shallow trenches are simultaneously formed in the epitaxial layer. When forming the isolation material layer on the epitaxial layer, the isolation material layer also fills the shallow trenches to form a plurality of shallow trench isolation structures.

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