Semiconductor device and preparation method therefor

Abstract

A semiconductor device and a preparation method therefor. The semiconductor device comprises a substrate; active strips and first trenches, which are located on the surface of the substrate and extend in a first direction and which are alternately arranged in a second direction; a plurality of active columns, which are located on the surfaces of active strips and are arranged at intervals in the first direction; a first isolation layer, which extends in the first direction and is located at the bottom of the first trenches; bit line structures, which are located on the top surface of the first isolation layer and cover side walls of a portion of the active strips; a first isolation structure, which is located between adjacent bit line structures in first trenches; and an air gap, which is located in a first isolation structure.

Description

Semiconductor device and method for manufacturing the same

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on June 12, 2023, with application number 202310699691.8 and application name “Semiconductor device and its preparation method”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of semiconductor technology, and relates to, but is not limited to, a semiconductor device and a method for manufacturing the same. Background Art

[0003] Currently, a dynamic random access memory (DRAM) having a buried bit line structure is formed to improve the integration of the DRAM and achieve miniaturization.

[0004] However, the buried bit line structures in related art exhibit severe coupling and large parasitic capacitance, which affects the sensing margin of the sense amplifier (SA). Furthermore, the buried bit line structures in related art exhibit severe leakage, which affects DRAM performance.

[0005] Summary of the Invention

[0006] In view of this, embodiments of the present application provide a semiconductor device and a method for manufacturing the same.

[0007] In a first aspect, an embodiment of the present application provides a semiconductor device, comprising:

[0008] substrate;

[0009] Active strips and first trenches are located on the surface of the substrate and extend along a first direction and are alternately arranged along a second direction, and a plurality of active pillars are located on the surface of the active strips and are spaced apart along the first direction;

[0010] a first isolation layer extending along the first direction and located at the bottom of the first trench;

[0011] A bit line structure is located on the top surface of the first isolation layer and covers a portion of the sidewall of the active strip;

[0012] a first isolation structure located between adjacent bit line structures in the first trench;

[0013] an air gap located in the first isolation structure;

[0014] The first direction intersects with the second direction and is located in the plane where the substrate is located.

[0015] In some embodiments, further comprising:

[0016] The second isolation layer is located between the bit line structure and the first isolation structure.

[0017] In some embodiments, the active strip includes a first semiconductor layer, a first insulating layer, and an ohmic contact layer located on the surface of the substrate;

[0018] The first isolation layer is located in the first trench between the first semiconductor layers, and a bottom surface of the first insulating layer along a third direction exceeds a top surface of the first isolation layer along the third direction; the third direction intersects with a plane where the substrate is located;

[0019] The bit line structure covers the first insulating layer, the ohmic contact layer, and a portion of the sidewall of the first semiconductor layer not covered by the first isolation layer.

[0020] In some embodiments, the method further includes: a second trench located between the active pillars and extending along the second direction;

[0021] a second isolation structure, located at the bottom of the second trench;

[0022] A gate structure is located on the top surface of the second isolation structure and covers a portion of the sidewall of the active pillar; wherein the top surface of the active pillar exceeds the top surface of the gate structure.

[0023] In some embodiments, the gate structure is a single-gate structure, a double-gate structure, or a full-all-around gate structure.

[0024] In some embodiments, the semiconductor device further includes: a third isolation structure, wherein the third isolation structure is located between the gate structures and fills the second trench.

[0025] In some embodiments, the third isolation structure is flush with a top surface of the active pillar.

[0026] In some embodiments, the material of the third isolation structure includes silicon dioxide.

[0027] In some embodiments,

[0028] The material of the first isolation layer includes silicon nitride;

[0029] The material of the second isolation layer includes a low dielectric constant material;

[0030] The material of the first isolation structure includes silicon dioxide.

[0031] In a second aspect, an embodiment of the present application provides a method for manufacturing a semiconductor device, comprising:

[0032] Providing a substrate, the substrate comprising initial active strips and first trenches extending along a first direction and alternately arranged along a second direction;

[0033] forming a first isolation layer extending along the first direction at the bottom of the first trench;

[0034] forming a bit line structure on a top surface of the first isolation layer and a portion of an inner wall of the first trench; wherein a gap exists between two adjacent bit line structures located in the same first trench;

[0035] forming a first isolation structure in the gap and an air gap in the first isolation structure;

[0036] The first direction intersects with the second direction and is located in the plane where the base is located.

[0037] In some embodiments, before forming the first isolation structure and the air gap, the method further includes:

[0038] A second isolation layer is formed on the surface of the bit line structure.

[0039] In some embodiments, providing a substrate comprises:

[0040] Providing a substrate and a semiconductor layer; the semiconductor layer includes a first semiconductor layer, a first insulating layer, and a second semiconductor layer stacked in sequence along a third direction; the third direction intersects with the plane where the substrate is located;

[0041] The semiconductor layer is patterned until the substrate is exposed to form the initial active strip and the first trench; wherein the initial active strip includes the first semiconductor layer, the first insulating layer, and the second semiconductor layer stacked in sequence along the third direction.

[0042] In some embodiments, providing the semiconductor layer includes:

[0043] providing an initial semiconductor structure;

[0044] implanting oxygen ions into the initial semiconductor structure to form a buried layer within the initial semiconductor structure;

[0045] The initial semiconductor structure and the buried layer are annealed to form the first insulating layer; wherein the first insulating layer material includes silicon dioxide, the initial semiconductor structure located below the first insulating layer constitutes the first semiconductor layer; and the initial semiconductor structure located above the first insulating layer constitutes the second semiconductor layer.

[0046] In some embodiments, forming a first isolation layer extending along the first direction at the bottom of the first trench includes:

[0047] forming a first initial isolation layer in the first trench;

[0048] The first initial isolation layer is etched back, and the portion of the first initial isolation layer that is retained and located below the first insulating layer and between the first semiconductor layers constitutes the first isolation layer; wherein the bottom surface of the first insulating layer along the third direction exceeds the top surface of the first isolation layer along the third direction.

[0049] In some embodiments, before forming the bit line structure, the method further includes:

[0050] forming a metal layer on a surface of the first isolation layer in the first trench; a top surface of the metal layer is located between the second semiconductor layers;

[0051] performing heat treatment on the metal layer and the second semiconductor layer to form an ohmic contact layer located at the bottom of the second semiconductor layer;

[0052] The first semiconductor layer, the first insulating layer and the ohmic contact layer constitute an active strip, and the bit line structure covers a portion of a sidewall of the active strip.

[0053] In some embodiments, forming a bit line structure on a top surface of the first isolation layer and a portion of an inner wall of the first trench includes:

[0054] forming an initial bit line structure on an inner wall of the first trench and a surface of the first isolation layer;

[0055] The initial bit line structure on the sidewall of the second semiconductor layer is removed, and the initial bit line structure remaining on the first insulating layer, the ohmic contact layer and the sidewall of the first semiconductor layer constitutes the bit line structure.

[0056] In some embodiments, the first isolation structure further fills the first trench; and the method further includes:

[0057] Etching the first isolation structure and the second semiconductor layer to form a plurality of active pillars arranged in an array along the first direction and the second direction, and a second trench extending along the second direction between the active pillars; the second trench exposing the ohmic contact layer and the first isolation structure;

[0058] forming a second isolation structure at the bottom of the second trench;

[0059] A gate structure is formed on a sidewall of the second trench portion having the second isolation structure; wherein a top surface of the active pillar exceeds a top surface of the gate structure.

[0060] In some embodiments, the material of the first isolation layer includes silicon nitride;

[0061] The material of the second isolation layer includes a low dielectric constant material;

[0062] The material of the first isolation structure includes silicon dioxide.

[0063] In some embodiments, the method further comprises:

[0064] A semiconductor isolation layer or a second insulating layer is formed between the substrate and the semiconductor layer.

[0065] In some embodiments, the semiconductor isolation layer is an N-type doped layer or a P-type doped layer, and the semiconductor isolation layer forms an inverse PN junction between the semiconductor layers.

[0066] Embodiments of the present application provide a semiconductor device and a method for manufacturing the same, wherein the semiconductor device includes: a substrate comprising active strips and first trenches extending in a first direction and alternately arranged in a second direction, and a plurality of active pillars located on the surface of the active strips and spaced apart along the first direction; a first isolation layer extending in the first direction and located at the bottom of the first trench; a bitline structure located on the top surface of the first isolation layer and covering the sidewalls of the active strips; a first isolation structure located between adjacent bitline structures in the first trench; and an air gap located in the first isolation structure. Because the air gap is formed in the first isolation structure between the bitline structures, coupling between adjacent bitline structures can be reduced, parasitic capacitance can be lowered, and thus the sensing margin of the sense amplifier can be improved. Furthermore, because the first isolation layer is formed at the bottom of the bitline structure, leakage between the bitline structure and the substrate can be prevented, thereby improving the electrical performance of the semiconductor device. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] In the accompanying drawings (which are not necessarily drawn to scale), like reference numerals may describe similar components in different views. Like reference numerals with different letter suffixes may represent different examples of similar components. The accompanying drawings generally illustrate various embodiments discussed herein by way of example and not limitation.

[0068] FIG1 is a schematic flow chart of a method for manufacturing a semiconductor device according to an embodiment of the present application;

[0069] 2 to 21 are schematic structural diagrams of the semiconductor device during the formation process provided by the embodiments of the present application. DETAILED DESCRIPTION

[0070] The exemplary embodiments disclosed herein will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the specific embodiments described herein. Rather, these embodiments are provided to enable a more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0071] In the following description, numerous details are provided to provide a more thorough understanding of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced without one or more of these details. In other instances, certain technical features known in the art are not described to avoid confusion with the present application; that is, all features of actual embodiments are not described herein, nor are well-known functions and structures described in detail.

[0072] In the drawings, the sizes of layers, regions, elements and their relative sizes may be exaggerated for clarity. Like reference numerals denote like elements throughout.

[0073] It should be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it may be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there may be no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Therefore, without departing from the teachings of the present application, the first element, component, region, layer, or part discussed below may be represented as a second element, component, region, layer, or part. And when the second element, component, region, layer, or part is discussed, it does not necessarily mean that the first element, component, region, layer, or part exists in the present application.

[0074] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present application. When used herein, the singular forms "a", "an", and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "comprising", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0075] Currently, buried bitline structures suffer from severe coupling and large parasitic capacitance, which impacts the sensing margin of sense amplifiers. Furthermore, leakage between the buried bitline structures and the substrate is severe, impacting the performance of semiconductor devices.

[0076] Based on this, embodiments of the present application provide a semiconductor device and a method for manufacturing the same. The semiconductor device includes: a substrate comprising active strips and first trenches extending in a first direction and alternately arranged in a second direction, and a plurality of active pillars located on the surface of the active strips and spaced apart along the first direction; a first isolation layer extending in the first direction and located at the bottom of the first trench; a bitline structure located on the top surface of the first isolation layer and covering the sidewalls of the active strips; a first isolation structure located between adjacent bitline structures in the first trench; and an air gap located in the first isolation structure. The air gap formed in the first isolation structure between the bitline structures can reduce coupling between adjacent bitline structures, lower parasitic capacitance, and thus improve the sensing margin of the sense amplifier. Furthermore, the first isolation layer formed at the bottom of the bitline structure can prevent leakage between the bitline structure and the substrate, thereby improving the electrical performance of the semiconductor device.

[0077] Below, the semiconductor device and the manufacturing method thereof in the embodiments of the present application are described in detail with reference to the accompanying drawings.

[0078] Before introducing the embodiments of the present application, the three directions of describing the three-dimensional structure that may be used in the following embodiments are defined. Taking the Cartesian coordinate system as an example, the three directions may include the X-axis, the Y-axis, and the Z-axis directions. The thickness direction of the substrate is defined as the third direction. In the plane direction where the substrate is located, two directions that intersect with each other (for example, perpendicular to each other) are defined as the second direction and the third direction. For example, the arrangement direction of the active strip and the first groove can be defined as the second direction. Here, the first direction can be, for example, the X-axis direction, the second direction can be, for example, the Y-axis direction, and the third direction can be, for example, the Z-axis direction.

[0079] Figure 1 is a flow chart of the semiconductor device preparation method provided in an embodiment of the present application, and Figures 1 to 21 are schematic diagrams of various structures in the semiconductor device preparation process provided in an embodiment of the present application. Below, the formation process of the semiconductor device is described in detail in combination with Figures 1 to 21.

[0080] As shown in FIG. 1 , the method for manufacturing a semiconductor device includes the following steps S101 to S104 .

[0081] First, referring to FIG. 1 to FIG. 7 , step S101 is performed to provide a substrate, wherein the substrate includes initial active strips 20 b and first trenches 12 extending along a first direction and alternately arranged along a second direction.

[0082] It should be noted that the initial active strips 20 b are used to form source regions, drain regions and channel regions of transistors in the semiconductor device, and the bit line structure and word line structure of the semiconductor device will be formed in the first trenches 12 .

[0083] In some embodiments, providing a substrate comprises the steps of:

[0084] Step 1: providing a substrate 10 and a semiconductor layer 20 as shown in FIG4 ; the semiconductor layer 20 comprises a first semiconductor layer 201 , a first insulating layer 202 and a second semiconductor layer 203 stacked in sequence along a third direction.

[0085] Here, the substrate 10 may be a silicon substrate, and the substrate 10 may also include other semiconductor elements, such as germanium (Ge), or include semiconductor compounds, such as silicon carbide (SiC), gallium arsenide (GaAs), gallium phosphide (GaP), indium phosphide (InP), indium arsenide (InAs) or indium antimonide (InSb), or include other semiconductor alloys, such as silicon germanium (SiGe), gallium arsenic phosphide (GaAsP), aluminum indium arsenide (AlInAs), aluminum gallium arsenide (AlGaAs), gallium indium arsenide (GaInAs), gallium indium phosphide (GaInP), and / or gallium indium arsenide phosphide (GaInAsP) or a combination thereof.

[0086] The main material layer of the semiconductor layer 20 may be the same material as the substrate 10 , or may be a surface-treated silicon wafer (ie, a single-crystal silicon material layer), or may be a material layer containing other semiconductor elements such as polycrystalline silicon.

[0087] In some embodiments, the semiconductor layer 20 may be formed using SIMOX technology. Specifically, providing the semiconductor layer 20 may include the following steps:

[0088] Step 1: providing an initial semiconductor structure 20a as shown in FIG2;

[0089] Step 2: implanting oxygen ions into the initial semiconductor structure 20 a to form a buried layer 202 a located inside the initial semiconductor structure 20 a as shown in FIG. 3 ;

[0090] It should be noted that the buried layer 202 a is a layer doped with a high dose of oxygen ions inside the initial semiconductor structure 20 a , and the high dose of oxygen ions can be implanted under high temperature conditions.

[0091] Step 3: Anneal the initial semiconductor structure 20a and the buried layer 202a to form a first insulating layer 202; wherein the material of the first insulating layer 202 includes silicon dioxide, and the initial semiconductor structure 20a located below the first insulating layer 202 constitutes the first semiconductor layer 201; the initial semiconductor structure 20a located above the first insulating layer 202 constitutes the second semiconductor layer 203.

[0092] It should be noted that the semiconductor layer 20 composed of the second semiconductor layer 203, the first insulating layer 202, and the first semiconductor layer 201 can be understood as a silicon-on-insulator (SOI) wafer. The first semiconductor layer 201 is equivalent to the bulk silicon in the SOI wafer, the first insulating layer 202 is equivalent to the buried silicon dioxide layer in the SOI wafer, and the second semiconductor layer 203 is equivalent to the top silicon in the SOI wafer.

[0093] It should also be noted that the first semiconductor layer 201 and the substrate 10 can be made of the same material, thereby forming a continuous layer.

[0094] In other embodiments, the semiconductor layer 20 may also be formed by the following steps:

[0095] Depositing a semiconductor material on the surface of the substrate 10 to form a first initial semiconductor layer; wherein the semiconductor material includes a polycrystalline semiconductor material;

[0096] Depositing an insulating material on the surface of the first semiconductor layer 201 to form a first insulating layer 202; wherein the insulating material may be silicon dioxide;

[0097] Depositing semiconductor material again on the surface of the first insulating layer 202 to form a second initial semiconductor layer;

[0098] The first preliminary semiconductor layer and the second preliminary semiconductor layer are subjected to a high-temperature heat treatment to form a first semiconductor layer 201 and a second semiconductor layer 203 .

[0099] It should be noted that the first initial semiconductor layer and the second initial semiconductor layer formed by deposition are polycrystalline semiconductor materials. High-temperature heat treatment can be used to convert polycrystalline semiconductor materials into single-crystalline semiconductor materials, which can increase the mobility of carriers in the channel structure, thereby increasing the driving current of the formed transistor, and further increasing the response speed of the semiconductor device.

[0100] It should also be noted that the polycrystalline semiconductor material may include polycrystalline silicon, polycrystalline germanium, or polycrystalline silicon germanium.

[0101] The semiconductor layer 20 is patterned until the substrate 10 is exposed, forming an initial active strip 20 b and a first trench 12 ; wherein the initial active strip 20 b includes a first semiconductor layer 201 , a first insulating layer 202 and a second semiconductor layer 203 stacked in sequence along the third direction.

[0102] During implementation, for example, a first photoresist layer 11 having a predetermined pattern as shown in Figures 5 to 7 can be formed on the surface of the semiconductor layer 20. The predetermined pattern includes a plurality of sub-patterns spaced apart along the Y-axis, each sub-pattern extending along the X-axis and exposing a portion of the semiconductor layer 20. Next, the semiconductor layer 20 is etched through the first photoresist layer 11 to remove the portion of the semiconductor layer 20 exposed by each sub-pattern, thereby forming initial active strips 20b and first trenches 12 located between the initial active strips 20b as shown in Figures 5 and 7. The bottom of the first trenches 12 exposes the substrate 10.

[0103] It should be noted that Figure 5 is a three-dimensional view of the semiconductor device, Figure 6 is a top view of Figure 5, and Figures 7 to 19 are all cross-sectional views along a-a', bb', and cc' in Figure 6, which will not be specifically explained later.

[0104] It should also be noted that since the initial active strip 20b is formed by patterning the semiconductor layer 20, when the main material of the semiconductor layer 20 is single crystal silicon, since single crystal silicon has high electron mobility, using single crystal silicon as the channel structure can increase the mobility of carriers in the channel structure, thereby increasing the driving current of the formed transistor, and further increasing the response speed of the semiconductor device.

[0105] Next, with continued reference to FIG. 1 and FIG. 8 to FIG. 10 , step S102 is performed to form a first isolation layer 15 extending along a first direction at the bottom of the first trench 12 .

[0106] It should be noted that the first isolation layer 15 is located at the bottom of the first trench 12, and a bit line structure will be formed on the surface of the first isolation layer 15 in the first trench 12 subsequently. The first isolation layer 15 is located between the bit line structure and the substrate 10. In this way, the bit line structure can be prevented from leaking electricity to the substrate 10, thereby improving the electrical performance of the semiconductor device.

[0107] It should also be noted that in the embodiment of the present application, the material of the first isolation layer 15 may be silicon nitride. In other embodiments, the material of the first isolation layer 15 may also include silicon dioxide, silicon oxynitride, or a combination thereof, or a combination thereof with silicon nitride.

[0108] In some embodiments, step S102 may include the following steps:

[0109] A first preliminary isolation layer 13 is formed in the first trench 12 .

[0110] During implementation, an isolation material may be deposited in the first trench 12 to form the first initial isolation layer 13 as shown in FIG8 . For example, the isolation material may be deposited by a chemical vapor deposition (CVD) process, a physical vapor deposition (PVD) process, an atomic layer deposition (ALD) process, a spin coating process, a coating process, or a thin film process to form the first initial isolation layer 13. Here, the isolation material may be silicon nitride.

[0111] The first initial isolation layer 13 is etched back, and the portion of the first initial isolation layer 13 retained below the first insulating layer 202 and between the first semiconductor layers 201 constitutes a first isolation layer 15; wherein the bottom surface of the first insulating layer 202 along the third direction exceeds the top surface of the first isolation layer 15 along the third direction.

[0112] During implementation, first, a second photoresist layer 14 is formed on the surface of the first initial isolation layer 13, as shown in FIG9 . The second photoresist layer 14 has the same pattern as the first photoresist layer 11, that is, the second photoresist layer 14 exposes the first initial isolation layer 13 in the first trench 12. Next, the first initial isolation layer 13 is etched to remove the portion of the first initial isolation layer 13 exposed by the second photoresist layer 14. The remaining first initial isolation layer 13 at the bottom of the first trench 12 forms the first isolation layer 15, as shown in FIG10 . The bottom surface of the first insulating layer 202 in the Z-axis direction extends beyond the top surface of the first isolation layer 15 in the Z-axis direction.

[0113] It should be noted that, referring to FIG. 10 , during the etching back of the first initial isolation layer 13 , the first initial isolation layer 13 located on the top surface of the initial active strip 20 b is not removed.

[0114] In some embodiments, the method for forming a semiconductor device may further include: forming a semiconductor isolation layer and / or a second insulating layer between the substrate 10 and the semiconductor layer 20 .

[0115] It should be noted that the material of the second insulating layer may be silicon dioxide. The second insulating layer can reduce leakage between the bit line structure and the substrate.

[0116] The semiconductor isolation layer can be an N-type doped layer or a P-type doped layer, and a reverse PN junction is formed between the semiconductor isolation layer and the semiconductor layer 20 (i.e., the first semiconductor layer 201), so that the current of the bit line structure cannot flow to the substrate 10. In this way, the leakage between the bit line structure and the substrate 10 can be further reduced.

[0117] In some embodiments, referring to FIG. 11 , the method for preparing a semiconductor device further includes:

[0118] A metal layer 17 is formed on the surface of the first isolation layer 15 in the first trench 12 ; a top surface of the metal layer 17 is located between the second semiconductor layers 203 .

[0119] During implementation, a metal material is first deposited on the surface of the first isolation layer 15 and the retained first initial isolation layer 13 to form an initial metal layer 16 as shown in FIG11 . Then, the initial metal layer 16 is etched back to remove the initial metal layer 16 on the surface of the first initial isolation layer 13 and a portion of the initial metal layer 16 in the first trench 12 to form a metal layer 17 as shown in FIG12 . The metal material may be at least one of nickel, cobalt, or platinum.

[0120] The metal layer 17 and the second semiconductor layer 203 are heat-treated to form an ohmic contact layer 18 located at the bottom of the second semiconductor layer 203 as shown in FIG. 13 .

[0121] It should be noted that the heat treatment process for the metal layer 17 and the second semiconductor layer 203 can be a rapid thermal processing (RTP) process. During the rapid thermal processing, metal ions in the metal layer 17 diffuse into the surrounding second semiconductor layer 203, undergoing a silicide reaction with the second semiconductor layer 203 to form a metal silicide serving as the ohmic contact layer 18. Since a bit line structure will subsequently be formed on the sidewalls of the ohmic contact layer 18 and in the first trench 12, the metal silicide has a low resistance and can therefore reduce the contact resistance between the bit line structure and the second semiconductor layer 203, thereby reducing the power consumption of the resulting semiconductor device.

[0122] It should also be noted that the process of heat treating the metal layer 17 and the second semiconductor layer 203 to form metal silicide is generally prone to inducing leakage between the bitline structures, that is, it is easy to form a leakage path between the bitline structures. In the embodiment of the present application, since the first insulating layer 202 is formed at the bottom of the second semiconductor layer 203, the first insulating layer 202 can serve as a stop layer for metal ion doping, which can limit the location where the metal ions are doped into the second semiconductor layer 203, thereby preventing the formation of a conductive path (i.e., a leakage path) between the bitline structures.

[0123] In addition, the position of the first insulating layer 202 can also control the thickness of the ohmic contact layer 18 in contact with the bit line structure. Due to the presence of the first insulating layer 202, the concentration and energy of the ohmic contact layer 18 (i.e., metal silicide) are relatively unrestricted, which can better reduce the contact resistance between the ohmic contact layer 18 and the bit line structure, thereby reducing the power consumption of the semiconductor device.

[0124] In some embodiments, the first semiconductor layer 201 , the first insulating layer 202 , and the ohmic contact layer 18 constitute an active strip 20 c as shown in FIG. 13 .

[0125] In some embodiments, after forming the ohmic contact layer 18, the method for forming a semiconductor device further includes: removing the metal layer 17. For example, the metal layer 17 may be removed by etching using a dry etching process.

[0126] Next, referring to FIG1 , FIG15 and FIG16 , step S103 is performed to form a bit line structure 19 on the top surface of the first isolation layer 15 and a portion of the inner wall of the first trench 12 ; wherein a gap exists between two adjacent bit line structures 19 in the same first trench 12 .

[0127] It should be noted that forming the bit line structure 19 on part of the inner wall of the first trench 12 means that the top surface of the bit line structure 19 is lower than the top surface of the initial active strip 20 b , that is, the bit line structure 19 is formed relatively close to the bottom of the first trench 12 .

[0128] In some embodiments, step S103 may include the following steps:

[0129] An initial bit line structure 19a is formed on the inner wall of the first trench 12 and the surface of the first isolation layer 15;

[0130] During implementation, a bitline material can be deposited on the first initial isolation layer 13, the inner wall of the first trench 12, and the top surface of the first isolation layer 15 as shown in FIG14 , to form an initial bitline structure 19a as shown in FIG15 . The bitline material can be a single metal, a metal compound, or an alloy. The single metal can be copper, aluminum, tungsten, gold, or silver, for example; the metal compound can be tantalum nitride or titanium nitride; and the alloy can be an alloy material composed of at least two of copper, aluminum, tungsten, gold, or silver.

[0131] The initial bit line structure 19 a on the sidewall of the second semiconductor layer 203 is removed, and the remaining initial bit line structure 19 a located on the sidewall of the first insulating layer 202 , the ohmic contact layer 18 and the first semiconductor layer 201 constitutes a bit line structure 19 .

[0132] During implementation, part of the initial bit line structure 19a on the top surface of the first initial isolation layer 13 can be first removed by etching or chemical mechanical polishing, and then part of the initial bit line structure 19a on the inner wall of the first trench 12 can be removed by dry etching technology. The retained initial bit line structure 19a located on the side wall of the first insulating layer 202, the ohmic contact layer 18 and the first semiconductor layer 201 not covered by the first isolation layer 15 constitutes the bit line structure 19 shown in Figure 16, that is, the bit line structure 19 covers the side wall of the active strip 20c.

[0133] Finally, with continued reference to FIG. 1 , FIG. 17 and FIG. 18 , step S104 is performed to form a first isolation structure in the gap and an air gap in the first isolation structure.

[0134] During implementation, a first isolation material is deposited between adjacent bit line structures 19 in the first trench 12. A deposition process is controlled to form first isolation structures 23 located between adjacent bit line structures 19 in the first trench 12, and air gaps 22 located within the first isolation structures 23. Here, the first isolation material of the first isolation structures 23 may be silicon dioxide.

[0135] It should be noted that, referring to FIG. 17 , the first isolation structure 23 still fills the first trench 12 .

[0136] In the embodiment of the present application, the air gap 22 can isolate the bit line structure 19, reduce the coupling effect between adjacent bit line structures 19, reduce the parasitic capacitance, and thus improve the sensing margin of the sense amplifier.

[0137] In some embodiments, referring to FIG. 18 , before forming the first isolation structure 23 and the air gap 22 , the method for preparing the semiconductor device further includes: forming a second isolation layer 24 on the surface of the bit line structure 19 .

[0138] It should be noted that the material of the second isolation layer 24 includes a low dielectric constant material, ie, a Low-K material. The second isolation layer 24 can be formed by any suitable deposition process, such as ALD or CVD.

[0139] In the embodiment of the present application, the second isolation layer 24 formed of a low dielectric constant material can further reduce the parasitic capacitance between the bit line structures 19, thereby improving the sensing margin of the sense amplifier and the performance of the semiconductor device.

[0140] In some embodiments, referring to FIG. 19 to FIG. 21 , the method for preparing a semiconductor device further includes:

[0141] The first isolation structure 23 and the second semiconductor layer 203 are etched to form a plurality of active pillars 30 arrayed along the first and second directions, and second trenches 31 extending along the second direction between the active pillars 30 ; the second trenches 31 expose the ohmic contact layer 18 and the first isolation structure 23 .

[0142] During implementation, a third photoresist layer (not shown) having a specific pattern can be formed on the surface of the first isolation structure 23 and the second semiconductor layer 203. The specific pattern includes a plurality of sub-patterns arranged at intervals along the X-axis direction, and each sub-pattern extends along the Y-axis direction. The exposed first isolation structure 23 and the second semiconductor layer 203 are etched away through the third photoresist layer to form active pillars 30 and second trenches 31 extending along the Y-axis direction and arranged at intervals along the X-axis direction as shown in Figures 19 and 20.

[0143] It should be noted that FIG20 is a top view of FIG19 , and FIG21 is a cross-sectional view along lines aa′, bb′, cc′, and dd′ in FIG19 .

[0144] A second isolation structure 33 is formed at the bottom of the second trench 31 .

[0145] During implementation, a second isolation material is deposited at the bottom of the second trench 31 to form a second isolation structure 33 as shown in FIG. 21 . The second isolation material may be silicon dioxide, silicon nitride, silicon oxynitride, or a combination thereof.

[0146] It should be noted that the second isolation structure 33 in the embodiment of the present application is used to isolate adjacent bit line structures 19 and gate structures 32 .

[0147] A gate structure 32 is formed on a portion of the sidewall of the second trench 31 having the second isolation structure 33 ; wherein the top surface of the active pillar 30 exceeds the top surface of the gate structure 32 .

[0148] It should be noted that the gate structure 32 includes a gate dielectric layer and a gate conductive layer located on the surface of the gate dielectric layer. The gate dielectric layer may be made of silicon oxide or other suitable materials; the gate conductive layer may be made of any material with good electrical conductivity, such as titanium (Ti), titanium nitride (TiN), tungsten nitride (WN), tungsten (W), cobalt (Co), platinum (Pt), palladium (Pd), ruthenium (Ru), or copper (Cu). The gate dielectric layer and the gate conductive layer may be formed by any suitable deposition process, such as chemical vapor deposition, physical vapor deposition, or atomic layer deposition.

[0149] It should also be noted that the gate structure in the embodiment of the present application is a double-gate structure. In other embodiments, the gate structure may also be a full-ring gate structure or a single-gate structure.

[0150] It can be understood that the bottom and top portions of the active pillars 30 not covered by the gate structure 32 constitute the first source and drain 34 and second source and drain 35 of the semiconductor device, respectively, and the portion of the active pillars 30 covered by the gate structure 32 constitutes the channel region of the semiconductor device. The first source and drain 34 are connected to the bit line structure 19 via the ohmic contact layer 18.

[0151] In some embodiments, after forming the gate structure 32 , the method for forming a semiconductor device further includes:

[0152] A second isolation material is deposited in the second trench 31 to form a third isolation structure 36. The third isolation structure 36 fills the second trench 31 and is flush with the top surface of the active pillar 30. The second isolation material may be silicon dioxide.

[0153] It should be noted that the third isolation structure 36 in the embodiment of the present application is used to isolate adjacent gate structures 32 to prevent leakage or short circuit. In addition, the third isolation structure 36 fills the second trench 31 to make the semiconductor structure have a flat surface, which is convenient for the subsequent formation of other functional structures.

[0154] In some embodiments, the method for forming a semiconductor device further includes: forming a capacitor structure connected to the second source and drain electrodes 35. It can be understood that the semiconductor device formed in the embodiment of the present application can be a DRAM.

[0155] In other embodiments, the formed semiconductor device may also be other memory devices or logic devices.

[0156] The semiconductor device in the embodiment of the present application has a vertical channel, which can reduce the size of the semiconductor device and achieve miniaturization; in addition, it can also improve the control capability of the semiconductor device, thereby improving the electrical performance of the semiconductor device.

[0157] The semiconductor device formation method provided by the embodiments of the present application forms a first isolation layer at the bottom of the bitline structure, thereby preventing leakage between the bitline structure and the substrate and improving the electrical performance of the semiconductor device. Furthermore, the air gap formed between adjacent bitline structures reduces coupling between adjacent bitline structures, lowering parasitic capacitance and thereby improving the sensing margin of the sense amplifier, thereby enhancing the performance of the resulting semiconductor device.

[0158] Another embodiment of the present application provides a semiconductor structure as shown in FIG21 . As shown in FIG21 , the semiconductor device includes:

[0159] substrate 10;

[0160] Active strips 20 c and first trenches extending along the X-axis and alternately arranged along the Y-axis on the surface of the substrate 10 , and a plurality of active pillars 30 spaced apart along the first direction on the surface of the active strips 20 c ;

[0161] a first isolation layer 15 extending along the X-axis direction and located at the bottom of the first trench;

[0162] A bit line structure 19 is located on the top surface of the first isolation layer 15 and covers a portion of the sidewall of the active strip 20c;

[0163] a first isolation structure 23 located between adjacent bit line structures 19 in the first trench;

[0164] The air gap 22 is located in the first isolation structure 23 .

[0165] In some embodiments, the material of the first isolation layer 15 includes silicon nitride; and the material of the first isolation structure 23 includes silicon dioxide.

[0166] In the embodiment of the present application, first isolation layer 15 can prevent electrical leakage from bitline structures 19 to substrate 10, thereby improving the electrical performance of the semiconductor device. Furthermore, the air gaps within first isolation structures 23 between bitline structures 19 can reduce coupling between adjacent bitline structures 19, lowering parasitic capacitance and thereby improving the sensing margin of the sense amplifier, thereby enhancing the performance of the semiconductor device.

[0167] In some embodiments, referring to FIG. 21 , the semiconductor device further includes a second isolation layer 24 located between the bit line structure 19 and the first isolation structure 23 .

[0168] It should be noted that the second isolation layer 24 can further reduce the parasitic capacitance between the bit line structures 19 , thereby improving the sensing margin of the sense amplifier and the performance of the semiconductor device.

[0169] It should be noted that the material of the second isolation layer 24 includes a low dielectric constant material, ie, a Low-K material.

[0170] In some embodiments, please continue to refer to Figure 21, the active strip 20c includes a first semiconductor layer 201, a first insulating layer 202 and an ohmic contact layer 18 located on the surface of the substrate 10; the first isolation layer 15 is located in the first groove between the first semiconductor layers 201, and the bottom surface of the first insulating layer 202 along the third direction exceeds the top surface of the first isolation layer 15 along the third direction.

[0171] In some embodiments, the bit line structure 19 covering a portion of the sidewalls of the active strip 20 c means that the bit line structure 19 covers the first insulating layer 202 , the ohmic contact layer 18 , and the sidewalls of the first semiconductor layer 201 not covered by the first isolation layer 15 .

[0172] In some embodiments, please continue to refer to Figure 21, the semiconductor device also includes: a second trench located between the active pillars 30 and extending along the second direction; a second isolation structure 33, located at the bottom of the second trench; a gate structure 32, located on the top surface of the second isolation structure 33 and covering a portion of the side wall of the active pillar 30; wherein the top surface of the active pillar 30 exceeds the top surface of the gate structure 32.

[0173] In some embodiments, the gate structure 32 includes a gate dielectric layer and a gate conductive layer located on the surface of the gate dielectric layer. It should also be noted that the gate structure 32 in the embodiment of the present application is a dual-gate structure. In other embodiments, the gate structure 32 may also be a full-ring gate structure or a single-gate structure.

[0174] The material of the second isolation structure 33 includes silicon dioxide.

[0175] In some embodiments, the bottom and top portions of the active pillars 30 not covered by the gate structure 32 constitute the first source and drain 34 and second source and drain 35 of the semiconductor device, respectively. The portion of the active pillars 30 covered by the gate structure 32 constitutes the channel region of the semiconductor device. The first source and drain 34 is connected to the bit line structure 19 via the ohmic contact layer 18.

[0176] In some embodiments, referring to FIG. 21 , the semiconductor device further includes a third isolation structure 36 . The third isolation structure 36 is located between the gate structures 32 and fills the second trench. The third isolation structure 36 is flush with the top surface of the active pillar 30 .

[0177] The material of the third isolation structure 36 includes silicon dioxide.

[0178] In some embodiments, the semiconductor device further includes a capacitor structure (not shown); the capacitor structure is connected to the second source and drain 35 .

[0179] It can be understood that the semiconductor device in the embodiment of the present application can be a DRAM. In other embodiments, the semiconductor device can also be other types of memory, such as NAND flash memory or phase change memory.

[0180] It should be noted that the semiconductor device formed in the embodiment of the present application is similar to the semiconductor device in the above embodiment. For the technical features not fully disclosed in the embodiment of the present application, please refer to the above embodiment for understanding, and no further details will be given here.

[0181] The semiconductor device provided by the embodiment of the present application includes a first isolation layer, and the first isolation layer is at the bottom of the bit line structure. Therefore, leakage between the bit line structure and the substrate can be prevented, thereby improving the electrical performance of the semiconductor device.

[0182] In addition, since the semiconductor device includes an air gap and the air gap is located in the first isolation structure between the bit line structures, the coupling effect between adjacent bit line structures can be reduced, the parasitic capacitance can be reduced, and the sensing margin of the sense amplifier can be improved.

[0183] In the several embodiments provided in this application, it should be understood that the disclosed structures and methods can be implemented in non-targeted ways. The structural embodiments described above are merely illustrative. For example, the division of units is merely a logical functional division. In actual implementation, other division methods may be used, such as: multiple units or components can be combined, or can be integrated into another system, or some features can be ignored or not executed. In addition, the components shown or discussed are coupled or directly coupled to each other.

[0184] The features disclosed in the several method or structural embodiments provided in this application can be arbitrarily combined without conflict to obtain new method embodiments or structural embodiments.

[0185] The above are only some embodiments of the present application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by any person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of this application. Therefore, the scope of protection of this application should be based on the scope of protection of the claims.

Claims

1. A semiconductor device, include: A substrate (10); Active strips (20c) and first grooves (12) located on the surface of the substrate (10) and extending along a first direction (X) and arranged alternately along a second direction (Y), and a plurality of active pillars (30) located on the surface of the active strips (20c) and arranged at intervals along the first direction (X); A first isolation layer (15), extending along the first direction (X) and located at the bottom of the first groove (12); A bit line structure (19) located on the top surface of the first isolation layer (15) and covering a portion of the side wall of the active strip (20c); A first isolation structure (23) located between adjacent bit line structures (19) in the first trench (12); An air gap (22) located in the first isolation structure (23); The first direction (X) intersects with the second direction (Y) and is located in the plane where the substrate (10) is located.

2. The semiconductor device according to claim 1, in, Also includes: A second isolation layer (24) is located between the bit line structure (19) and the first isolation structure (23).

3. The semiconductor device according to claim 1 or 2, in, The active strip (20c) comprises a first semiconductor layer (201), a first insulating layer (202) and an ohmic contact layer (18) located on the surface of the substrate (10); The first isolation layer (15) is located in the first groove (12) between the first semiconductor layers (201); the bottom surface of the first insulating layer (202) along a third direction (Z) exceeds the top surface of the first isolation layer (15) along the third direction (Z); the third direction (Z) intersects with the plane where the substrate (10) is located; The bit line structure (19) covers the first insulating layer (202) and the ohmic contact layer (18). and a portion of the side wall of the first semiconductor layer (201) not covered by the first isolation layer (15).

4. The semiconductor device according to claim 3, in, It also includes: a second groove (31) located between the active pillars (30) and extending along the second direction (Y); A second isolation structure (33), located at the bottom of the second trench (31); The gate structure (32) is located on the top surface of the second isolation structure (33) and covers a portion of the side wall of the active column (30); wherein the top surface of the active column (30) exceeds the top surface of the gate structure (32).

5. The semiconductor device according to claim 4, in, The gate structure (32) is a single-gate structure, a double-gate structure or a full-ring gate structure.

6. The semiconductor device according to claim 4 or 5, in, The semiconductor device further comprises: a third isolation structure (36), wherein the third isolation structure (36) is located between the gate structures (32) and fills the second trench (31).

7. The semiconductor device according to claim 6, in, The third isolation structure (36) is flush with the top surface of the active pillar (30).

8. The semiconductor device according to claim 6, in, The material of the third isolation structure (36) includes silicon dioxide.

9. The semiconductor device according to claim 2, in, The material of the first isolation layer (15) includes silicon nitride; The material of the second isolation layer (24) includes a low dielectric constant material; The material of the first isolation structure (23) includes silicon dioxide.

10. A method for preparing a semiconductor device, the method comprising: include: Providing a substrate, the substrate comprising initial active strips (20b) and first grooves (12) extending along a first direction (X) and alternately arranged along a second direction (Y); forming a first isolation layer (15) extending along the first direction (X) at the bottom of the first trench (12); A bit line structure (19) is formed on the top surface of the first isolation layer (15) and a portion of the inner wall of the first trench (12); wherein two adjacent bit line structures located in the same first trench (12) are connected to each other. There is a gap between the structures (19); forming a first isolation structure (23) in the gap, and an air gap (22) located in the first isolation structure (23); The first direction (X) intersects with the second direction (Y) and is located in the plane where the base is located.

11. The method according to claim 10, in, Before forming the first isolation structure (23) and the air gap (22), the method further comprises: A second isolation layer (24) is formed on the surface of the bit line structure (19).

12. The method according to claim 10 or 11, in, The providing of a substrate comprises: A substrate (10) and a semiconductor layer are provided; the semiconductor layer comprises a first semiconductor layer (201), a first insulating layer (202) and a second semiconductor layer (203) stacked in sequence along a third direction (Z); the third direction (Z) intersects with the plane where the substrate is located; The semiconductor layer is patterned until the substrate (10) is exposed, thereby forming the initial active strip (20b) and the first groove (12); wherein the initial active strip (20b) comprises the first semiconductor layer (201), the first insulating layer (202) and the second semiconductor layer (203) sequentially stacked along the third direction (Z).

13. The method according to claim 12, in, Providing the semiconductor layer, comprising: providing an initial semiconductor structure; Performing oxygen ion implantation on the initial semiconductor structure to form a buried layer inside the initial semiconductor structure; The initial semiconductor structure and the buried layer are annealed to form the first insulating layer (202); wherein the material of the first insulating layer (202) includes silicon dioxide, the initial semiconductor structure located below the first insulating layer (202) constitutes the first semiconductor layer (201); and the initial semiconductor structure located above the first insulating layer (202) constitutes the second semiconductor layer (203).

14. The method according to claim 12, in, A first isolation layer (15) extending along the first direction (X) is formed at the bottom of the first trench (12), comprising: forming a first initial isolation layer in the first trench (12); The first initial isolation layer is etched back, and the portion of the first initial isolation layer that is retained and located below the first insulating layer (202) and between the first semiconductor layers (201) constitutes the first isolation layer (15); wherein the bottom surface of the first insulating layer (202) along the third direction (Z) exceeds the top surface of the first isolation layer (15) along the third direction (Z).

15. The method according to claim 12, in, Before forming the bit line structure (19), the method further comprises: forming a metal layer on the surface of the first isolation layer (15) in the first groove (12); the top surface of the metal layer is located between the second semiconductor layers (203); Performing heat treatment on the metal layer and the second semiconductor layer (203) to form an ohmic contact layer (18) located at the bottom of the second semiconductor layer (203); The first semiconductor layer (201), the first insulating layer (202) and the ohmic contact layer (18) form an active strip (20c), and the bit line structure (19) covers a portion of the side wall of the active strip (20c).

16. The method according to claim 15, in, A bit line structure (19) is formed on the top surface of the first isolation layer (15) and a portion of the inner wall of the first trench (12), comprising: forming an initial bit line structure (19a) on the inner wall of the first trench (12) and the surface of the first isolation layer (15); The initial bit line structure (19a) on the side wall of the second semiconductor layer (203) is removed, and the initial bit line structure (19a) remaining on the first insulating layer (202), the ohmic contact layer (18) and the side wall of the first semiconductor layer (201) constitutes the bit line structure (19).

17. The method according to claim 15, in, The first isolation structure (23) also fills the first trench (12); the method further comprises: The first isolation structure (23) and the second semiconductor layer (203) are etched to form a plurality of active pillars (30) arranged in an array along the first direction (X) and the second direction (Y), and a second trench (31) located between the active pillars (30) and extending along the second direction (Y); the second trench (31) exposes the ohmic contact layer (18) and the first isolation structure (23); forming a second isolation structure (33) at the bottom of the second trench (31); A gate structure (32) is formed on a partial sidewall of the second trench (31) having the second isolation structure (33); wherein the top surface of the active column (30) exceeds the top surface of the gate structure (32).

18. The method according to claim 11, in, The material of the first isolation layer (15) includes silicon nitride; The material of the second isolation layer (24) includes a low dielectric constant material; The material of the first isolation structure (23) includes silicon dioxide.

19. The method according to claim 12, in, The method further comprises: A semiconductor isolation layer or a second insulating layer is formed between the substrate (10) and the semiconductor layer.

20. The method according to claim 19, in, The semiconductor isolation layer is an N-type doped layer or a P-type doped layer, and the semiconductor isolation layer forms a reverse PN junction between the semiconductor layers.

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