Semiconductor structure and method of manufacture thereof

Abstract

The present invention relates to a semiconductor structure and a method for manufacturing the same. The semiconductor structure manufacturing method includes providing a substrate, forming a plurality of gate structures arranged at intervals on the substrate, forming sacrificial sidewalls of a predetermined thickness on the sidewalls of the gate structures, forming a first dielectric layer between adjacent sacrificial sidewalls so that the top of the first dielectric layer is flush with the top of the gate structures and the top of the sacrificial sidewalls, removing the sacrificial sidewalls to form an air gap structure on the sidewalls of the gate structures, and forming a second dielectric layer covering the top of the gate structures, the top opening of the air gap structure, and the top of the first dielectric layer. The semiconductor structure and the manufacturing method thereof provided by the present invention are favorable for reducing parasitic capacitance, and realize a balanced control of the size of the parasitic capacitance corresponding to different devices, and effectively improve the device performance of the semiconductor structure. This reduces the RC-Delay of the semiconductor structure and improves the life of the semiconductor structure.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS The present invention claims priority to a Chinese patent application filed with the China Patent Office on June 7, 2022, bearing application number 202210634400.2 and entitled "Semiconductor structure and manufacturing method thereof", the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to the field of semiconductor integrated circuit manufacturing, and more particularly to semiconductor structures and methods for their manufacture. [Background technology]

[0003] As semiconductor technology advances, the feature sizes of devices within integrated circuits decrease. After semiconductor processing advances to the deep submicron stage, the size of Dynamic Random Access Memory (DRAM), a semiconductor structure commonly used in computers and other electronic devices, decreases. Correspondingly, the size of each component device of a DRAM and the pitch between adjacent devices also decrease.

[0004] Currently, in the manufacturing process of DRAM, the back end of line (BEOL) is used to build several layers of wiring, and the wirings of different layers are connected by conductive vias. However, the wirings and conductive vias are mostly made of metal, and there is a tendency for parasitic capacitance to exist between adjacent wirings. Furthermore, with the reduction of device feature size, the aforementioned parasitic capacitance between wirings increases, while the RC-Delay effect in DRAM is obvious, and the device life of DRAM also tends to decrease. Summary of the Invention

[0005] According to various embodiments of the present invention, an embodiment of the present invention provides a semiconductor structure and a method for fabricating the same.

[0006] According to some embodiments, the present invention provides a method for manufacturing a semiconductor structure, the method including: providing a substrate; forming a plurality of spaced apart gate structures on the substrate; forming sacrificial sidewalls of a predetermined thickness on sidewalls of the gate structures; forming a first dielectric layer between adjacent sacrificial sidewalls, where a top of the first dielectric layer is flush with a top of the gate structure and a top of the sacrificial sidewall; removing the sacrificial sidewalls to form an air gap structure on a sidewall of the gate structure; and forming a second dielectric layer covering the top of the gate structure, an opening at the top of the air gap structure, and a top of the first dielectric layer.

[0007] According to some embodiments, forming a sacrificial sidewall of a predetermined thickness on a sidewall of the gate structure includes forming an initial sacrificial layer of uniform thickness on a surface of the gate structure and the substrate, and removing the initial sacrificial layer located on a top of the gate structure and on a surface of the substrate to retain the initial sacrificial layer located on the sidewall of the gate structure to form the sacrificial sidewall.

[0008] According to some embodiments, prior to forming a sacrificial sidewall of a predetermined thickness on a sidewall of the gate structure, the manufacturing method further comprises forming a protective layer covering a portion of the sidewall of the gate structure, the sacrificial sidewall covering an outer surface of the protective layer.

[0009] According to some embodiments, the gate structure comprises a metal layer. Forming a plurality of spaced apart gate structures on the substrate includes forming a plurality of spaced apart initial gate structures on the substrate, the initial gate structures comprising an initial metal layer, oxidizing a portion of a sidewall of the initial metal layer to form the protective layer, and forming a portion of the non-oxidized initial metal layer on the metal layer.

[0010] According to some embodiments, oxidizing a portion of the sidewalls of the initial metal layer includes treating with a liquid ozone solution.

[0011] According to some embodiments, the gate structure further comprises a first barrier layer, the first barrier layer covering a top of the metal layer and the protection layer.

[0012] According to some embodiments, after forming sacrificial sidewalls of a predetermined thickness on the sidewalls of the gate structure, the manufacturing method further includes forming an initial first dielectric layer between adjacent sacrificial sidewalls and above the gate structure, and employing a planarization process to remove portions of the initial first dielectric layer to form the first dielectric layer, wherein a top of the first dielectric layer is flush with a top of the first barrier layer.

[0013] According to some embodiments, the gate structure further comprises a second barrier layer, the second barrier layer being located between the substrate, the metal layer and the protection layer.

[0014] According to some embodiments, the plurality of gate structures include a plurality of first gate structures and a plurality of second gate structures, wherein adjacent first gate structures have a first pitch between adjacent second gate structures, and wherein adjacent second gate structures have a second pitch between adjacent first gate structures, the first pitch being smaller than the second pitch. Forming sacrificial sidewalls of a predetermined thickness on sidewalls of the gate structures and forming air gap structures on sidewalls of the gate structures includes forming first sacrificial sidewalls on sidewalls of the first gate structures and removing the first sacrificial sidewalls to form a first air gap structure, and forming second sacrificial sidewalls on sidewalls of the second gate structures and removing the second sacrificial sidewalls to form a second air gap structure.

[0015] According to some embodiments, a thickness of the first sacrificial sidewall is the same as a thickness of the second sacrificial sidewall, and a width of the first air gap structure in a direction parallel to the substrate is the same as a width of the second air gap structure in a direction parallel to the substrate.

[0016] According to some embodiments, a thickness of the first sacrificial sidewall is smaller than a thickness of the second sacrificial sidewall, and a width of the first air gap structure in a direction parallel to the substrate is smaller than a width of the second air gap structure in a direction parallel to the substrate.

[0017] According to some embodiments, removing the sacrificial sidewalls includes removing the sacrificial sidewalls by treating with a low temperature phosphoric acid solution, where the temperature of the low temperature phosphoric acid solution is less than or equal to 120° C.

[0018] According to some embodiments, another aspect of the present invention provides a semiconductor structure formed by the method for manufacturing a semiconductor structure according to some embodiments above, the semiconductor structure including a substrate, a plurality of gate structures arranged on the substrate with a space between them, air gap structures located on sidewalls of the gate structures, a first dielectric layer located between the air gap structures on sidewalls of adjacent gate structures, and a second dielectric layer covering tops of the gate structures, openings in the tops of the air gap structures, and a top of the first dielectric layer.

[0019] According to some embodiments, the semiconductor structure further includes a protective layer covering a portion of a sidewall of the gate structure, the air gap structure being located between the protective layer and the first dielectric layer.

[0020] According to some embodiments, the gate structure includes a metal layer and a first barrier layer located on a side of the metal layer away from the substrate, where the protective layer covers a sidewall of the metal layer and the first barrier layer covers a top of the metal layer and the protective layer.

[0021] According to some embodiments, a top of the first dielectric layer is flush with a top of the first barrier layer.

[0022] According to some embodiments, the gate structure further comprises a second barrier layer, the second barrier layer being located between the substrate, the metal layer and the protection layer.

[0023] According to some embodiments, the plurality of gate structures include a plurality of first gate structures and a plurality of second gate structures, wherein adjacent first gate structures have a first pitch and adjacent second gate structures have a second pitch, the first pitch being smaller than the second pitch, wherein the air gap structure located on a sidewall of the first gate structure is a first air gap structure and the air gap structure located on a sidewall of the second gate structure is a second air gap structure, and a width of the first air gap structure in a direction parallel to the substrate is the same as a width of the second air gap structure in a direction parallel to the substrate, or a width of the first air gap structure in a direction parallel to the substrate is smaller than a width of the second air gap structure in a direction parallel to the substrate.

[0024] Embodiments of the invention may have / at least have the following advantages:

[0025] In the embodiment of the present invention, a sacrificial sidewall of a predetermined thickness is formed on the sidewall of a gate structure without using a photomask, and then an air gap structure of a predetermined size is formed after removing the sacrificial sidewall, so that the gate structure can be effectively isolated using the air gap structure, and the parasitic capacitance of the device in which the gate structure is located can be effectively reduced. The above-mentioned method process provided by the embodiment of the present invention is simple, and is also advantageous in reducing implementation and production costs. Furthermore, the embodiment of the present invention can realize a balanced control of the size of the parasitic capacitance corresponding to different devices by controlling the size of the air gap structure (e.g., the height and width of the air gap structure) in different devices, thereby effectively improving the device performance of the semiconductor structure. Thus, the RC-Delay of the semiconductor structure can be reduced.

[0026] Furthermore, the static current (i.e., IDD current, which refers to the leakage current when the device is in a static state) of a transistor device in a semiconductor structure is proportional to the corresponding parasitic capacitance. In an embodiment of the present invention, an air gap structure is provided on the sidewall of the gate structure, which can reduce the corresponding parasitic capacitance and reduce the leakage current of the device, thereby reducing the power consumption when the transistor device is in an off state, thereby effectively improving the life of the transistor device and the semiconductor structure.

[0027] The details of one or more embodiments of the invention are set forth in the drawings and description that follow. Other features, objects, and advantages of the invention will become more apparent from the description, the accompanying drawings, and the claims. [Brief description of the drawings]

[0028] [Figure 1] 1 is a flow chart of a method for manufacturing a semiconductor structure provided by one embodiment. [Diagram 2] 4 is a flowchart of another method for manufacturing a semiconductor structure provided by an embodiment. [Diagram 3] 5A-5C are cross-sectional views of intermediate and resultant structures corresponding to step S100 in one embodiment. [Figure 4] 5A-5C are cross-sectional views of intermediate and resultant structures corresponding to step S100 in one embodiment. [Diagram 5] 5A-5C are cross-sectional views of intermediate and resultant structures corresponding to step S100 in one embodiment. [Figure 6] FIG. 11 is a cross-sectional view of a resulting structure corresponding to step S150 in one embodiment. [Figure 7] 5A-5C are cross-sectional views of intermediate and resultant structures corresponding to step S200 in one embodiment. [Figure 8] 5A-5C are cross-sectional views of intermediate and resultant structures corresponding to step S200 in one embodiment. [Figure 9] 5A-5C are cross-sectional views of intermediate and resultant structures corresponding to step S300 in one embodiment. [Figure 10] 5A-5C are cross-sectional views of intermediate and resultant structures corresponding to step S300 in one embodiment. [Figure 11] FIG. 4 is a cross-sectional view of a resulting structure corresponding to step S400 in one embodiment. [Figure 12] 5 is a cross-sectional view of a resulting structure corresponding to step S500 in one embodiment, and also a structural diagram of a semiconductor structure in one embodiment. [Figure 13] FIG. 2 is a structural diagram of another semiconductor structure in one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] In order to more clearly describe the embodiments of the present disclosure or the technical solutions in the prior art, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and those skilled in the art can also obtain other drawings from these drawings without creative efforts.

[0030] In order to facilitate an understanding of the present invention, the present invention will now be described more fully with reference to the accompanying drawings, in which: FIG. 1 is a block diagram of a semiconductor memory device according to an embodiment of the present invention; FIG. 2 is a block diagram of a semiconductor memory device according to an embodiment of the present invention;

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. The terms used in the description of the present invention in this specification are intended to describe specific examples and are not intended to limit the present invention.

[0032] When an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" another element or layer, it is understood that it may be directly on, adjacent to, connected to, or coupled to the other element or layer, or that intervening elements or layers may be present. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers present.

[0033] Spatial relationship terms, such as "under," "below," "below," "below," "above," and the like, may be used herein to describe the relationship of one element or feature to another element or feature as depicted in the figures. In addition to the orientation depicted, it should be understood that the spatial relationship terms include different orientations of the device during use and operation. For example, if the device in the accompanying figures is inverted, an element or feature described as "under" or "below" another element or feature would be oriented "above" the other element or feature. Thus, by way of example, the terms "under" and "below" may include both an above and below orientation. Additionally, the device may include other orientations (e.g., rotated 90 degrees or other orientations) and the spatial descriptors used herein should be interpreted accordingly.

[0034] As used herein, the singular forms "a", "an", and "the" can include the plural unless the context clearly dictates otherwise. It is to be further understood that terms such as "comprising", "having", and the like specify the presence of described features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the presence or additional possibility of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, in this description, the term "and / or" includes any and all combinations of the associated listed items.

[0035] As used herein, a "deposition" process includes, but is not limited to, physical vapor deposition (PVD), chemical vapor deposition (CVD), or atomic layer deposition (ALD).

[0036] Additionally, embodiments of the invention are described herein with reference to schematic illustrations that are idealized embodiments (and intermediate structures) of the invention, and as such, variations in the shapes of the illustrated shapes due, for example, to manufacturing techniques and / or tolerances, are to be expected. Thus, embodiments of the invention should not be limited to the specific shapes of regions illustrated herein, which may include, for example, geometric distortions due to manufacturing techniques. The regions illustrated in the figures are schematic in nature, and these shapes are not intended to represent the actual shapes of regions on a device and do not limit the scope of the invention.

[0037] As semiconductor technology advances, the feature size of devices in integrated circuits decreases. After semiconductor processing advances to the deep submicron stage, the size of DRAM decreases. Correspondingly, the size of each component in the DRAM and the pitch between adjacent components also decrease.

[0038] Currently, in the manufacturing process of DRAM, the back end of line (BEOL) is used to build several layers of wiring, and the wirings of different layers are connected by conductive vias. However, the wirings and conductive vias are mostly made of metal, and there is a tendency for parasitic capacitance to exist between adjacent wirings. Furthermore, with the reduction of device feature size, the aforementioned parasitic capacitance between wirings increases, while the RC-Delay effect in DRAM is obvious, and the device life of DRAM also tends to decrease.

[0039] On this basis, an embodiment of the present invention provides a semiconductor structure and a manufacturing method thereof, which are advantageous for reducing parasitic capacitance and realizing balanced control of the sizes of parasitic capacitances corresponding to different devices, thereby effectively improving the device performance of the semiconductor structure, thereby reducing the RC-Delay of the semiconductor structure, and improving the life of the semiconductor structure.

[0040] 1, some embodiments of the present invention provide a method for fabricating a semiconductor structure, the method including the following steps:

[0041] S100, providing a substrate and forming a plurality of spaced apart gate structures on the substrate;

[0042] S200, a sacrificial sidewall of a predetermined thickness is formed on a sidewall of the gate structure.

[0043] S300 forms a first dielectric layer between adjacent sacrificial sidewalls, where a top of the first dielectric layer is flush with a top of the gate structure and a top of the sacrificial sidewalls.

[0044] S400, removing the sacrificial sidewall to form an air gap structure on the sidewall of the gate structure.

[0045] S500, forming a second dielectric layer covering the top of the gate structure, the opening at the top of the air gap structure, and the top of the first dielectric layer.

[0046] In the embodiment of the present invention, a sacrificial sidewall of a predetermined thickness is formed on the sidewall of a gate structure without using a photomask, and then an air gap structure of a predetermined size is formed after removing the sacrificial sidewall, so that the gate structure can be effectively isolated using the air gap structure, and the parasitic capacitance of the device in which the gate structure is located can be effectively reduced. The above-mentioned method process provided by the embodiment of the present invention is simple, and is also advantageous in reducing implementation and production costs. Furthermore, the embodiment of the present invention can realize a balanced control of the size of the parasitic capacitance corresponding to different devices by controlling the size of the air gap structure (e.g., the height and width of the air gap structure) in different devices, thereby effectively improving the device performance of the semiconductor structure. Thus, the RC-Delay of the semiconductor structure can be reduced.

[0047] Furthermore, the static current (i.e., IDD current, which refers to the leakage current when the device is in a static state) of a transistor device in a semiconductor structure is proportional to the corresponding parasitic capacitance. In an embodiment of the present invention, an air gap structure is provided on the sidewall of the gate structure, which can reduce the corresponding parasitic capacitance and reduce the leakage current of the device, thereby reducing the power consumption when the transistor device is in an off state, thereby effectively improving the life of the transistor device and the semiconductor structure.

[0048] Referring to FIG. 2, in some embodiments of the present invention, before step S200 of forming a sacrificial sidewall of a predetermined thickness on a sidewall of the gate structure, the manufacturing method further includes step S150, in which a protective layer is formed to cover a portion of the sidewall of the gate structure, and the sacrificial sidewall covers an outer surface of the protective layer.

[0049] It should be noted that the gate structure, which is the control element of the device, has a conductive function. In some embodiments of the present invention, the gate structure includes a metal layer. The step S100 of forming a plurality of spaced apart gate structures on the substrate includes forming a plurality of spaced apart initial gate structures on the substrate, the initial gate structures including an initial metal layer, oxidizing a portion of a sidewall of the initial metal layer to form a protective layer, and the non-oxidized initial metal layer forms a metal layer. In this way, the protective layer can be directly formed based on the initial metal layer, which is advantageous to simplify the process and ensure that the subsequent process will not adversely affect the metal layer of the gate structure, thereby ensuring the electrical performance of the gate structure.

[0050] In some embodiments of the present invention, bonding the material of the initial metal layer and oxidizing a portion of the sidewall of the initial metal layer includes treating with a liquid ozone solution, thus forming a dense metal oxide on the surface of the initial metal layer, which can be used as a protective layer.

[0051] In addition, in some embodiments of the present invention, the gate structure further includes a first barrier layer, the first barrier layer covers the top of the metal layer and the protective layer. In some embodiments of the present invention, the gate structure further includes a second barrier layer, the second barrier layer is located between the substrate and the metal layer and the protective layer. From the above, the gate structure can have various embodiments, for example adopting a single layer structure or a stacked structure, and can be specifically selected and set according to actual needs.

[0052] It is to be noted that in some embodiments of the present invention, in step S200, forming a sacrificial sidewall of a predetermined thickness on a sidewall of the gate structure includes: forming an initial sacrificial layer of a uniform thickness on a surface of the gate structure and the substrate; and removing the initial sacrificial layer located on a top of the gate structure and on the surface of the substrate, thereby retaining the initial sacrificial layer located on the sidewall of the gate structure to form the sacrificial sidewall.

[0053] Here, the initial sacrificial layer is formed by adopting a deposition process, and its thickness can be selected and set according to needs. The thickness of the initial sacrificial layer is uniform, and the sacrificial sidewalls formed on the sidewalls of different gate structures subsequently have the same thickness, and further, the air gap structures having the same width in a direction parallel to the substrate can be precisely controlled to keep the size of the parasitic capacitance corresponding to different devices in balance.

[0054] In some embodiments of the present invention, after forming the sacrificial sidewalls of a predetermined thickness on the sidewalls of the gate structure in step S200, the manufacturing method further includes forming an initial first dielectric layer between adjacent sacrificial sidewalls and above the gate structure, and employing a planarization process to remove a portion of the initial first dielectric layer to form the first dielectric layer, so that the top of the first dielectric layer is flush with the top of the first barrier layer. In this way, the first barrier layer can be directly used as a polishing barrier layer for planarizing the initial first dielectric layer, that is, in the process of employing a planarization process to remove a portion of the initial first dielectric layer, the first dielectric layer located between adjacent sacrificial sidewalls can be directly formed without using a photomask, and the top of the first dielectric layer can be guaranteed to be flush with the top of the first barrier layer, which is advantageous to simplify the manufacturing process.

[0055] In order to more clearly explain the manufacturing method of the semiconductor structure in the above embodiments, please refer to Figures 3 to 12. In the following embodiments, the manufacturing method will be described in detail by taking as an example that the gate structure includes a first barrier layer, a metal layer and a second barrier layer that are stacked.

[0056] In step S100, referring to FIGS. 3 to 5, a substrate 1 is provided, and a plurality of gate structures 2 arranged in a spaced apart relationship are formed on the substrate 1.

[0057] In some embodiments, the substrate 1 may be constructed using a semiconductor material, an insulating material, a conductive material, or any combination thereof. The substrate 1 may be a single layer structure or a multi-layer structure. For example, the substrate 1 may be a Si substrate, a SiGe substrate, a SiGeC substrate, a SiC substrate, a GaAs substrate, an InAs substrate, an InP substrate, or other III / V semiconductor substrates or II / VI semiconductor substrates. Or, for example, the substrate 1 may be a layered substrate including, for example, a Si / SiGe substrate, a Si / SiC substrate, a silicon-on-insulator (SOI) substrate, or a silicon-germanium-on-insulator layer.

[0058] For example, a trench isolation structure (not shown in FIGS. 3 to 5) may be provided in the substrate 1, and the trench isolation structure may be used to divide a plurality of active regions in the substrate 1 so that each transistor is formed in a corresponding active region. That is, as a component of the transistor, the above-described gate structure 2 may be provided in the corresponding active region. Furthermore, other components of the transistor may be implemented with reference to the embodiments in the related art, and the embodiments of the present invention are not limited thereto.

[0059] In some embodiments, the gate structure 2 includes a first barrier layer 22, a metal layer 21, and a second barrier layer 23 disposed in a stacked manner. Correspondingly, forming a plurality of spaced apart gate structures 2 on the substrate 1 includes the following steps:

[0060] As shown in FIG. 3, according to the gate structure 2 to be formed, a second barrier material layer 230, a metal material layer 210 and a first barrier material layer 220 are sequentially stacked on the substrate 1. Here, the materials of the second barrier material layer 230 and the first barrier material layer 220 may be the same or different. Exemplarily, the materials of the second barrier material layer 230 and the first barrier material layer 220 are one of Ta, TaN, Cu or TiN, respectively. The material of the metal material layer 210 is, for example, Al. The second barrier material layer 230 is located between the metal material layer 210 and the substrate 1, and can prevent the metal material layer 210 from contacting with the oxide in the substrate 1 and being oxidized. The first barrier material layer 220 is located on the top of the metal material layer 210, and can protect the metal material layer 210 from being damaged by etching, thereby ensuring good electrical performance of the metal material layer 210.

[0061] 4, a photoresist PR is applied on top of the first barrier material layer 220, and a mask pattern is formed in the photoresist PR. The mask pattern is for defining the position where the gate structure 2 is to be formed.

[0062] As shown in FIG. 5, based on the mask pattern in the photoresist PR, the first barrier material layer 220, the metal material layer 210 and the second barrier material layer 230 can be etched to form the first barrier layer 22, the initial metal layer 21A and the second barrier layer 23, respectively, so that the first barrier layer 22, the initial metal layer 21A and the second barrier layer 23 together constitute an initial gate structure.

[0063] It can be understood that the metal material layer 210 can be directly formed into the metal layer 21 after being etched. In this way, the first barrier layer 22, the metal layer 21A and the second barrier layer 23 together can constitute the gate structure 2, i.e., directly complete the fabrication of the gate structure 2.

[0064] In the embodiment, the metal material layer 210 is etched to form the initial metal layer 21A, so that the protective layer 3 can be directly formed on the surface of the initial metal layer 21A in the subsequent process.

[0065] In step S150, referring to FIG. 6, a protective layer 3 covering a part of the sidewall of the gate structure 2 is formed.

[0066] Here, the protective layer 3 can be formed on the sidewall of the gate structure 2 by adopting a deposition process, or by adopting other methods.

[0067] Exemplarily, after forming a plurality of spaced apart initial gate structures on the substrate 1, a portion of the sidewall of the initial metal layer 2A is oxidized to form a protective layer 3. In this manner, the unoxidized initial metal layer 2A forms a metal layer 21. In this manner, the protective layer 3 can be directly formed based on the initial metal layer 2A, which is advantageous for simplifying the process and ensuring that the subsequent process steps will not adversely affect the metal layer 21 of the gate structure 2, thereby ensuring the electrical performance of the gate structure 2.

[0068] For example, oxidizing a portion of the sidewall of the initial metal layer 2A includes using a liquid ozone solution to treat the sidewall, so that a dense metal oxide can be formed on the surface of the initial metal layer 2A as the protective layer 3.

[0069] Here, the treatment using the liquid ozone solution can be expressed as using the liquid ozone solution to clean the wafer after the formation of the initial gate structure, in which case fine particles on the surface of the wafer can be removed, and the sidewalls of the initial metal layer 21A exposed to air can be oxidized to form dense oxides, for example, an aluminum oxide film can be formed on the surface of the aluminum metal layer as the protective layer 3.

[0070] Furthermore, liquid ozone solution can be used with room temperature acidic solution or frozen deionized water to effectively clean the wafer after the initial gate structure formation without involving corrosive chemicals. In this way, production costs can be reduced due to the reduced use of chemicals. Furthermore, less work space is required to employ and process liquid ozone solution, and the work efficiency is faster than the bench work required to employ chemicals to perform wet etching, thereby improving production efficiency.

[0071] Exemplarily, the thickness of the protective layer 3 does not exceed 1 nm, but is not limited thereto.

[0072] 7 and 8, in step S200, a sacrificial sidewall 4 having a predetermined thickness is formed on the sidewall of the gate structure 2.

[0073] In the example where the semiconductor structure includes a protective layer 3 , the sacrificial sidewall 4 covers the outer surface of the protective layer 3 .

[0074] Here, the sacrificial sidewall 4 may be formed of a nitride material such as silicon nitride, and the thickness of the sacrificial sidewall 4 may be designed and determined by the pitch between adjacent gate structures 2 and the associated size of the air gap structure G to be formed.

[0075] Exemplarily, step S200 includes the following steps.

[0076] As shown in FIG. 7, an initial sacrificial layer 4A of uniform thickness is formed on the surfaces of the gate structure 2 and the substrate 1.

[0077] Here, the initial sacrificial layer 4A is formed by adopting a deposition process, and its thickness can be selected and set according to needs. In an example where the semiconductor structure further includes a protective layer 3, the initial sacrificial layer 4A covers the outer surfaces of the first barrier layer 22, the protective layer 3 and the second barrier layer 23, for example.

[0078] As shown in FIG. 8, the initial sacrificial layer 4A located on the top of the gate structure 2 and on the surface of the substrate 1 is removed, thereby retaining the initial sacrificial layer 4A located on the sidewalls of the gate structure 2 to form sacrificial sidewalls 4.

[0079] Here, the initial sacrificial layer 4A located on the top of the gate structure 2 and the surface of the substrate 1 can be removed by adopting dry etching. In this way, it can be ensured that the thickness of the initial sacrificial layer 4A is uniform, and the sacrificial sidewalls 4 formed on the sidewalls of different gate structures 2 have the same thickness, and further, by forming the air gap structures G having the same width in the direction parallel to the substrate 1, the size of the parasitic capacitances corresponding to different devices can be precisely controlled to keep the balance.

[0080] Furthermore, it can be seen that after dry etching the initial sacrificial layer 4A, based on the material loss due to etching, the top of the sacrificial sidewall 4 tends to be sloped, i.e., there is an included angle between the top of the sacrificial sidewall 4 and the sidewall of the first barrier layer 22, and the included angle is an acute angle.

[0081] In step S300, referring to Figures 9 and 10, a first dielectric layer 5 is formed between adjacent sacrificial sidewalls 4, and the top of the first dielectric layer 5 is flush with the top of the gate structure 2 and the top of the sacrificial sidewalls 4.

[0082] Exemplarily, step S300 may specifically include the following steps:

[0083] 9, an initial first dielectric layer 5A is formed between adjacent sacrificial sidewalls 4 and above the gate structure 2. The material of the initial first dielectric layer 5A is different from the material of the sacrificial sidewalls 4, and the initial first dielectric layer 5A can be formed by depositing an oxide such as silicon oxide. The initial first dielectric layer 5A fills the gap between adjacent sacrificial sidewalls 4 and covers the top of the sacrificial sidewalls 4 and the gate structure 2.

[0084] As shown in FIG. 10, a planarization process is adopted to remove a portion of the initial first dielectric layer 5A to form the first dielectric layer 5.

[0085] Here, the planarization process is, for example, chemical mechanical polishing (CMP). The first barrier layer 23 can be directly used as a polishing barrier layer for planarizing the initial first dielectric layer 5A, that is, in the process of adopting the planarization process to remove a part of the initial first dielectric layer 5A, the first dielectric layer 5 located between the adjacent sacrificial sidewalls 4 can be directly formed without setting a photomask, and the top of the first dielectric layer 5 can be guaranteed to be flush with the top of the first barrier layer 23, which is advantageous to simplify the manufacturing process.

[0086] In step S400, referring to FIG. 11, the sacrificial sidewall 4 is removed to form an air gap structure G on the sidewall of the gate structure 2.

[0087] In some embodiments of the present invention, the sacrificial sidewall 4 is formed of a material of silicon nitride. The sacrificial sidewall 4 can be removed by employing a low-temperature phosphoric acid solution, where the temperature of the low-temperature phosphoric acid solution is below 120° C. Compared with a high-temperature phosphoric acid solution (e.g., the temperature is higher than 150° C.), the etching selectivity of the low-temperature phosphoric acid solution to nitride and oxide is higher.

[0088] Pure phosphoric anhydride is a colorless crystal, hygroscopic, easily soluble in water, and soluble in water at any ratio. The low-temperature phosphoric acid solution in the embodiment of the present invention is a colorless viscous liquid, where the concentration ratio of phosphoric acid is, for example, 85% to 98%. The reaction mechanism of removing the sacrificial sidewall 4 by using the low-temperature phosphoric acid solution can be expressed as Si3N4+4H3PO4+12H2O→3Si(OH)4+4NH4H4PO4.

[0089] Combining several embodiments described above, it can be seen that there is an included angle between the top of the sacrificial sidewall 4 and the sidewall of the first barrier layer 22, and the included angle is an acute angle. Thus, after forming the air gap structure G by removing the sacrificial sidewall 4, the top of the air gap structure G is easily closed and has a smaller top opening.

[0090] In step S500, referring to FIG. 12, a second dielectric layer 6 is formed, where the second dielectric layer 6 covers the top of the gate structure 2, the top opening of the air gap structure G, and the top of the first dielectric layer 5.

[0091] Here, the second dielectric layer 6 can be formed by deposition of an oxide such as silicon oxide, and the top of the air gap structure G is narrowed and has a smaller top opening, so that in the process of depositing the second dielectric layer 6, the second dielectric layer 6 is easy to close the top opening of the air gap structure G and synchronously cover the top of the gate structure 2 and the first dielectric layer 5.

[0092] It should be mentioned that, referring to FIG. 13, in some embodiments of the present invention, the multiple gate structures 2 include multiple first gate structures 2A and multiple second gate structures 2B, in which a first pitch L1 is defined between adjacent first gate structures 2A and a second pitch L2 is defined between adjacent second gate structures 2B, and the first pitch L1 is smaller than the second pitch L2.

[0093] Here, it can be generally understood that a semiconductor structure has a cell array region R1 and a peripheral circuit region R2 located on at least one side of the cell array region R1. Here, the cell array region R1 is a region for forming a cell array in the semiconductor structure, for example, a region for forming a memory cell array. In a DRAM, any memory cell in the memory cell array has a transistor and a storage capacitor. The peripheral circuit region R2 is located on at least one side of the cell array region R1, for example, on the side or periphery side. The peripheral circuit region R2 is a region for forming a peripheral circuit in the semiconductor structure. In a DRAM, the peripheral circuit can realize a specific function by connecting multiple transistors and other electronic elements (capacitors, resistors, etc.) according to design requirements.

[0094] For convenience of explanation, a transistor located in the cell array region R1 can be defined as a cell transistor, and a transistor located in the peripheral circuit region R2 can be defined as a peripheral transistor, where the cell transistor may have a faster turn-on speed than the peripheral transistor. Correspondingly, the above-mentioned first gate structure 2A can be the gate structure of the cell transistor, and the second gate structure 2B can be the gate structure of the peripheral transistor. Thus, if the pitch between adjacent first gate structures 2A in the cell array region R1 is narrower and only the first dielectric layer (such as oxide) is used for filling, a larger parasitic capacitance tends to be generated, which greatly reduces the turn-on speed of the cell transistor. Furthermore, if the pitch between adjacent second gate structures 2B in the peripheral circuit region R2 is wider and only the first dielectric layer (such as oxide) is used for filling, a smaller parasitic capacitance tends to be generated, which keeps the turn-on speed of the peripheral transistor unchanged or reduces it less. As a result, the read speed of the cell transistor and the peripheral transistor is unpredictable due to the delay caused by the corresponding parasitic capacitance.

[0095] Based on this, forming a sacrificial sidewall 4 of a predetermined thickness on the sidewall of the gate structure 2 and forming an air gap structure G on the sidewall of the gate structure 2 includes forming a first sacrificial sidewall on the sidewall of the first gate structure 2A and removing the first sacrificial sidewall to form a first air gap structure G1, and forming a second sacrificial sidewall on the sidewall of the second gate structure 2B and removing the second sacrificial sidewall to form a second air gap structure G2.

[0096] It can be appreciated that the first sacrificial sidewall on the sidewall of the first gate structure 2A and the second sacrificial sidewall on the sidewall of the second gate structure 2B can be formed synchronously or stepwise.

[0097] 13, it should be understood that in some embodiments of the present invention, the thicknesses of the first and second sacrificial sidewalls are the same, and the widths of the first and second air gap structures G1 and G2 in a direction parallel to the substrate 1 are the same, i.e., W1=W2, where W1 is the width of the first air gap structure G1 in a direction parallel to the substrate 1, and W2 is the width of the second air gap structure G2 in a direction parallel to the substrate 1. In this way, in order to simplify the manufacturing process and at the same time keep the size values ​​of the parasitic capacitances corresponding to the transistor devices in different regions consistent, the first and second sacrificial sidewalls can be formed synchronously, and the first and second air gap structures G1 and G2 can be formed synchronously.

[0098] 13, it should be understood that in some embodiments of the present invention, the thickness of the first sacrificial sidewall is smaller than the thickness of the second sacrificial sidewall. The width W1 of the first air gap structure G1 in a direction parallel to the substrate 1 is smaller than the width W2 of the second air gap structure G2 in a direction parallel to the substrate 1. In this manner, the first sacrificial sidewall and the second sacrificial sidewall can be formed in a stepwise manner. The first sacrificial sidewall and the second sacrificial sidewall can be formed synchronously or stepwise, thereby controlling the first air gap structure G1 and the second air gap structure G2 to adopt different sizes for transistor devices in different regions, and further controlling the size of the corresponding parasitic capacitance.

[0099] It should be noted that the first sacrificial sidewall and the second sacrificial sidewall are formed by a deposition process. Since the first pitch L1 between the adjacent first gate structures 2A is smaller than the second pitch L2 between the adjacent second gate structures 2B, in the same deposition process, the thickness of the first sacrificial sidewall deposited on the sidewall of the first gate structure 2A tends to be thicker, and the thickness of the second sacrificial sidewall deposited on the sidewall of the second gate structure 2B tends to be thinner. Based on this, the deposition rates of the first sacrificial sidewall and the second sacrificial sidewall can be respectively controlled to form the first sacrificial sidewall and the second sacrificial sidewall of the same thickness or a predetermined thickness correspondingly, and further, the first air gap structure G1 and the second air gap structure G2 are used to balance the parasitic capacitances corresponding to the transistor devices in different regions by controlling the molding sizes of the first air gap structure G1 and the second air gap structure G2 with high precision.

[0100] For example, the calculation formula for the capacitance value C of the parasitic capacitance is C=εS / d, where ε is the dielectric constant, S is the relative area between the equivalent electrode plate, and d is the distance between the equivalent electrode plate. In this way, when the installation position of the gate structure 2 is combined and the gate structure 2 is equivalent to the electrode plate, the distance between the equivalent electrode plate is the distance between them in the direction parallel to the substrate 1. In the embodiment of the present invention, by controlling the width of the first air gap structure G1 and the second air gap structure G2 in the direction parallel to the substrate 1, the dielectric constant ε can be correspondingly controlled, and further, the control of the capacitance value of the parasitic capacitance can be realized. In this way, the parasitic capacitances of the transistor devices in the cell array region R1 and the peripheral circuit region R2 can be balanced and matched. Thereby, the transistor devices in the cell array region R1 and the peripheral circuit region R2 can be controlled to turn on according to a predetermined turn-on speed ratio, and the appearance of the impact on the performance of the semiconductor structure device caused by the mismatch in the size of the parasitic capacitance can be suppressed.

[0101] 12 and 13, some embodiments of the present invention provide a semiconductor structure formed through the manufacturing method of the semiconductor structure described in some embodiments above. The semiconductor structure includes a substrate 1, a gate structure 2, an air gap structure G, a first dielectric layer 5, and a second dielectric layer 6. The number of gate structures 2 is plural, and the gate structures 2 are arranged on the substrate 1 with a space therebetween. The air gap structure G is located on the sidewall of the gate structure 2. The first dielectric layer 5 is located between the air gap structures G on the sidewalls of adjacent gate structures 2. The second dielectric layer 6 covers the top of the gate structure 2, the top opening of the air gap structure G, and the top of the first dielectric layer 5.

[0102] In the embodiment of the present invention, the air gap structure G can be formed by forming a sacrificial sidewall of a predetermined thickness on the sidewall of the gate structure 2 and removing the sacrificial sidewall without using a photomask. In this way, not only can the gate structure 2 be effectively isolated by using the air gap structure G, but also the parasitic capacitance corresponding to the device in which the gate structure 2 is located can be effectively reduced. The manufacturing process of the semiconductor structure provided by the embodiment of the present invention is simple, which is advantageous in reducing implementation and production costs. Furthermore, the embodiment of the present invention can control the size of the air gap structure G in different devices to be a predetermined size by controlling the thickness at which the sacrificial sidewall is formed. In this way, the device performance of the semiconductor structure can be effectively improved by realizing a balanced control of the size of the parasitic capacitance corresponding to different devices. As a result, the RC-Delay of the semiconductor structure can be reduced.

[0103] In addition, the static current (i.e., IDD current, which refers to the leakage current when the device is in a static state) of a transistor device in a semiconductor structure is proportional to the corresponding parasitic capacitance. In the embodiment of the present invention, an air gap structure G is provided on the sidewall of the gate structure 2, which can reduce the corresponding parasitic capacitance, and further reduce the leakage current of the device, thereby reducing the power consumption when the transistor device is in an off state, and thus effectively improving the life of the transistor device and the semiconductor structure.

[0104] In some embodiments, the substrate 1 may be composed of a semiconductor material, an insulating material, a conductive material, or any combination thereof. The substrate 1 may be a single layer structure or a multi-layer structure. For example, the substrate 1 may be a Si substrate, a SiGe substrate, a SiGeC substrate, a SiC substrate, a GaAs substrate, an InAs substrate, an InP substrate, or other III / V semiconductor substrates or II / VI semiconductor substrates. Or, for example, the substrate 1 may be a layered substrate including, for example, a Si / SiGe, a Si / SiC, a silicon-on-insulator (SOI), or a silicon-germanium-on-insulator layer.

[0105] For example, a trench isolation structure (not shown in FIGS. 12-13) may be provided in the substrate 1, and the trench isolation structure may be used to divide a plurality of active regions in the substrate 1 so that each transistor is formed in a corresponding active region. That is, as a component of the transistor, the above-mentioned gate structure 2 may be provided in the corresponding active region. Furthermore, other components of the transistor may be implemented with reference to the embodiments in the related art, and the embodiments of the present invention are not limited thereto.

[0106] In addition, the above-mentioned air gap structure G can not only be formed on the sidewall of the gate structure 2, but can also be extended or applied to the sidewall of the wiring connected to the gate structure 2, thereby further reducing the parasitic capacitance and realizing balanced control of the size of the parasitic capacitance corresponding to different transistor devices, thereby effectively improving the performance of the semiconductor structure device.

[0107] 12, in some embodiments of the present invention, the semiconductor structure further includes a protective layer 3 covering a portion of a sidewall of the gate structure 2. An air gap structure G is located between the protective layer 3 and the first dielectric layer 5.

[0108] Continuing with reference to FIG. 12, in some embodiments of the present invention, the gate structure 2 includes a metal layer 21 and a first barrier layer 22 located on the side of the metal layer 21 facing away from the substrate 1, where a protective layer 3 covers the sidewalls of the metal layer 21 and the first barrier layer 22 covers the top of the metal layer 21 and the protective layer 3.

[0109] Exemplarily, the protective layer 3 is a metal oxide layer, and is formed by oxidizing, for example, the same metal material as the metal layer 21 .

[0110] Exemplarily, the first barrier layer 22 is one of a Ta layer, a TaN layer, a Cu layer, or a TiN layer, and is located on top of the metal layer 21 and the protective layer 3, which can protect the metal layer 21 from etching damage during the manufacturing process of the semiconductor structure, thereby ensuring good electrical performance of the metal layer 21.

[0111] 12, in some embodiments of the present invention, the top of the first dielectric layer 5 is flush with the top of the first barrier layer 22. That is, the first barrier layer 23 can be directly used as a polishing barrier layer in the process of forming the first dielectric layer 5, so that the first dielectric layer 5 located between adjacent sacrificial sidewalls 4 can be directly formed without the need to set up a photomask, simplifying the manufacturing process.

[0112] 12, in some embodiments of the present invention, the gate structure 2 further comprises a second barrier layer 23. The second barrier layer 23 is located between the substrate 1 and the metal layer 21 and the protective layer 3.

[0113] Exemplarily, the second barrier layer 23 is one of a Ta layer, a TaN layer, a Cu layer, and a TiN layer. The second barrier layer 23 is located between the metal layer 21 and the substrate 1, and can suppress oxidation due to contact between the metal layer 21 and an oxide in the substrate 1.

[0114] Referring to FIG. 13, in some embodiments of the present invention, the multiple gate structures 2 include multiple first gate structures 2A and multiple second gate structures 2B, wherein a first pitch L1 is provided between adjacent first gate structures 2A and a second pitch L2 is provided between adjacent second gate structures 2B, the first pitch L1 being smaller than the second pitch L2, and wherein the air gap structure G located on the sidewall of the first gate structure 2A is a first air gap structure G1, and the air gap structure G located on the sidewall of the second gate structure 2B is a second air gap structure G2.

[0115] Generally, it can be understood that a semiconductor structure has a cell array region R1 and a peripheral circuit region R2 located on at least one side of the cell array region R1. Here, the cell array region R1 is a region for forming a cell array in the semiconductor structure, for example, a region for forming a memory cell array. In a DRAM, any memory cell in the memory cell array has a transistor and a storage capacitor. The peripheral circuit region R2 is located on at least one side of the cell array region R1, for example, on the side or periphery side. The peripheral circuit region R2 is a region for forming a peripheral circuit in the semiconductor structure. In a DRAM, the peripheral circuit can realize a specific function by connecting multiple transistors and other electronic elements (capacitors, resistors, etc.) according to design requirements.

[0116] For convenience of explanation, a transistor located in the cell array region R1 can be defined as a cell transistor, and a transistor located in the peripheral circuit region R2 can be defined as a peripheral transistor. Correspondingly, the first gate structure 2A described above can be a gate structure of a cell transistor, and the second gate structure 2B can be a gate structure of a peripheral transistor.

[0117] 13, in some embodiments, the widths of the first air gap structure G1 and the second air gap structure G2 in a direction parallel to the substrate 1 are the same, i.e., W1=W2, where W1 is the width of the first air gap structure G1 in a direction parallel to the substrate 1, and W2 is the width of the second air gap structure G2 in a direction parallel to the substrate 1. In this way, the first air gap structure G1 and the second air gap structure G2 can be formed synchronously to simplify the manufacturing process and at the same time keep the sizes of the parasitic capacitances corresponding to the transistor devices in different regions consistent.

[0118] 13, in some other examples, the width W1 of the first air gap structure G1 in a direction parallel to the substrate 1 is smaller than the width W2 of the second air gap structure G2 in a direction parallel to the substrate 1. In this manner, the first air gap structure G1 and the second air gap structure G2 can be formed synchronously or stepwise, thereby controlling the first air gap structure G1 and the second air gap structure G2 to adopt different sizes respectively for transistor devices in different regions, and further controlling the size of the corresponding parasitic capacitance.

[0119] For example, the calculation formula for the capacitance value C of the parasitic capacitance is C=εS / d, where ε is the dielectric constant, S is the relative area between the equivalent electrode plate, and d is the distance between the equivalent electrode plate. In this way, when the installation position of the gate structure 2 is combined and the gate structure 2 is equivalent to the electrode plate, the distance between the equivalent electrode plate is the distance between them in the direction parallel to the substrate 1. In the embodiment of the present invention, by controlling the width of the first air gap structure G1 and the second air gap structure G2 in the direction parallel to the substrate 1, the dielectric constant ε can be correspondingly controlled, and further, the control of the capacitance value of the parasitic capacitance can be realized. In this way, the parasitic capacitances of the transistor devices in the cell array region R1 and the peripheral circuit region R2 can be balanced and matched. Thereby, the transistor devices in the cell array region R1 and the peripheral circuit region R2 can be controlled to turn on at a predetermined turn-on speed ratio, and the appearance of the impact on the performance of the semiconductor structure device caused by the mismatch in the size of the parasitic capacitance can be suppressed.

[0120] The technical features of the embodiments described above can be combined in any combination, and for the sake of brevity, not all possible combinations of the technical features of the embodiments described above are described, but as long as there is no contradiction in the combinations of these technical features, they should all be considered to be within the scope of this specification.

[0121] The above-described examples only represent some embodiments of the present invention, and although the descriptions are more specific and detailed, they should not be construed as limiting the protection scope of the present invention. It should be noted that those skilled in the art can make some improvements or modifications without departing from the principle of the present invention, and these improvements and modifications should also be considered as the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the attached claims.

Claims

1. 1. A method for manufacturing a semiconductor structure, comprising the steps of: providing a substrate and forming a plurality of spaced apart gate structures on the substrate; forming a sacrificial sidewall of a predetermined thickness on a sidewall of the gate structure; forming a first dielectric layer between adjacent sacrificial sidewalls, a top of the first dielectric layer being flush with a top of the gate structure and a top of the sacrificial sidewalls; removing the sacrificial sidewall to form an air gap structure on a sidewall of the gate structure; forming a second dielectric layer covering a top of the gate structure, a top opening of the air gap structure, and a top of the first dielectric layer; forming a sacrificial sidewall of a predetermined thickness on a sidewall of the gate structure; forming an initial sacrificial layer of uniform thickness on the surface of the gate structure and the substrate; removing an initial sacrificial layer located on a top of the gate structure and on a surface of the substrate, thereby retaining the initial sacrificial layer located on a sidewall of the gate structure to form the sacrificial sidewall, wherein a top of the sacrificial sidewall is a slope.

2. Prior to forming a sacrificial sidewall of a predetermined thickness on a sidewall of the gate structure, the method further includes forming a protective layer covering a portion of the sidewall of the gate structure; the sacrificial sidewall covers an outer surface of the protective layer; A method for manufacturing a semiconductor structure according to claim 1.

3. The gate structure includes a metal layer, and forming a plurality of spaced apart gate structures on the substrate includes: forming a plurality of spaced apart initial gate structures on the substrate, the initial gate structures including an initial metal layer; oxidizing a portion of a sidewall of the initial metal layer to form the protective layer; forming an initial metal layer that is not oxidized, the metal layer comprising: A method for manufacturing a semiconductor structure according to claim 2.

4. oxidizing a portion of the sidewall of the initial metal layer includes treating with a liquid ozone solution; A method for manufacturing a semiconductor structure according to claim 3.

5. The gate structure further includes a first barrier layer, the first barrier layer covering a top of the metal layer and the protection layer. A method for manufacturing a semiconductor structure according to claim 3.

6. After forming a sacrificial sidewall of a predetermined thickness on a sidewall of the gate structure, the method includes: forming an initial first dielectric layer between adjacent sacrificial sidewalls and over the gate structure, and employing a planarization process to remove portions of the initial first dielectric layer to form the first dielectric layer, wherein a top of the first dielectric layer is flush with a top of the first barrier layer. A method for manufacturing a semiconductor structure according to claim 5.

7. the gate structure further includes a second barrier layer, the second barrier layer being between the substrate and the metal layer and the protection layer. A method for manufacturing a semiconductor structure according to claim 3.

8. the plurality of gate structures include a plurality of first gate structures and a plurality of second gate structures, having a first pitch between adjacent first gate structures and a second pitch between adjacent second gate structures, the first pitch being smaller than the second pitch; forming a sacrificial sidewall of a predetermined thickness on a sidewall of the gate structure and forming an air gap structure on the sidewall of the gate structure includes forming a first sacrificial sidewall on a sidewall of the first gate structure and removing the first sacrificial sidewall to form a first air gap structure; and forming a second sacrificial sidewall on a sidewall of the second gate structure and removing the second sacrificial sidewall to form a second air gap structure. A method for manufacturing a semiconductor structure according to claim 1.

9. a thickness of the first sacrificial sidewall is the same as a thickness of the second sacrificial sidewall and a width of the first air gap structure in a direction parallel to the substrate is the same as a width of the second air gap structure in a direction parallel to the substrate; or a thickness of the first sacrificial sidewall is less than a thickness of the second sacrificial sidewall, and a width of the first air gap structure in a direction parallel to the substrate is less than a width of the second air gap structure in a direction parallel to the substrate; The method of claim 8 .

10. removing the sacrificial sidewalls includes treating with a low temperature phosphoric acid solution to remove the sacrificial sidewalls; The temperature of the low-temperature phosphoric acid solution is 120° C. or less; A method for manufacturing a semiconductor structure according to any one of claims 1 to 9.

11. 1. A semiconductor structure comprising: A substrate; a plurality of gate structures arranged in spaced relation on the substrate; an air gap structure located on a sidewall of the gate structure, the top of the air gap structure being a slope; a first dielectric layer filling between air gap structures on sidewalls of adjacent gate structures; a second dielectric layer covering a top of the gate structure, a top opening of the air gap structure, and a top of the first dielectric layer.

12. the semiconductor structure further includes a protective layer covering a portion of a sidewall of the gate structure, the air gap structure being located between the protective layer and the first dielectric layer; the gate structure includes a metal layer and a first barrier layer located on a side of the metal layer away from the substrate; the protective layer covers a sidewall of the metal layer, and the first barrier layer covers a top of the metal layer and the protective layer.

12. The semiconductor structure of claim 11.

13. a top of the first dielectric layer is flush with a top of the first barrier layer; the gate structure further includes a second barrier layer, the second barrier layer being between the substrate and the metal layer and the protection layer.

13. The semiconductor structure of claim 12.

14. the plurality of gate structures include a plurality of first gate structures and a plurality of second gate structures; a first pitch between adjacent first gate structures and a second pitch between adjacent second gate structures, the first pitch being smaller than the second pitch; the air gap structure located on a sidewall of the first gate structure is a first air gap structure, the air gap structure located on a sidewall of the second gate structure is a second air gap structure, and a width of the first air gap structure in a direction parallel to the substrate is the same as a width of the second air gap structure in a direction parallel to the substrate, or a width of the first air gap structure in a direction parallel to the substrate is smaller than a width of the second air gap structure in a direction parallel to the substrate; 13. The semiconductor structure of claim 12.

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