Method for manufacturing a gate dielectric layer and semiconductor structure
By forming a sandwich-structured gate dielectric layer in the integrated circuit, and by heating to diffuse nitrogen in the silicon nitride layer to form a gradient distribution, the problem of excessive nitrogen penetration is solved, thereby improving electrical performance and reliability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NEXCHIP SEMICON CO LTD
- Filing Date
- 2026-05-27
- Publication Date
- 2026-06-23
AI Technical Summary
In integrated circuit technology, existing technologies make it difficult to precisely control the concentration and depth distribution of nitrogen on the surface of the gate oxide layer, leading to excessive penetration of nitrogen into the silicon substrate, which affects the electrical performance and reliability of the device.
A sandwich structure is adopted, in which a first spacer layer, a silicon nitride layer and a second spacer layer are formed on a substrate. By heating, the nitrogen element in the silicon nitride layer diffuses in the thickness direction to form a silicon oxynitride layer with a gradient distribution of nitrogen element concentration. Then, the second spacer layer is removed to form a gate dielectric layer.
This achieves a uniform nitrogen concentration distribution, reduces the probability of nitrogen penetration into the substrate, and improves the electrical performance and reliability of integrated circuit devices.
Smart Images
Figure CN122269774A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of integrated circuit technology, and in particular to a method for preparing a gate dielectric layer and a semiconductor structure. Background Technology
[0002] As integrated circuit technology continues to evolve, the feature size of devices is gradually shrinking to the 0.18μm node, corresponding to a gate oxide layer thickness of less than 3nm. To adapt to the performance requirements of this process node, the industry generally adopts a nitridation process to modify the gate oxide layer: by introducing nitrogen into the gate oxide layer, on the one hand, its equivalent oxide thickness (EOT) can be effectively increased, and on the other hand, its ability to block boron dopants in polysilicon gates can be significantly enhanced, preventing boron from diffusing into the semiconductor substrate and ensuring the stability of the device's switching characteristics.
[0003] However, in related technologies, the precise control of nitrogen concentration and depth distribution (N profile) on the gate oxide surface faces significant challenges: increasing the nitrogen concentration by increasing the nitriding power or extending the nitriding time can easily lead to excessive nitrogen penetration (Drive in) towards the silicon (Si) substrate, which not only disrupts the uniformity of nitrogen concentration distribution in the gate oxide layer, but also damages the interface quality between the silicon substrate and the gate oxide layer in severe cases, causing problems such as increased interface state density and decreased carrier mobility, ultimately affecting the electrical performance and reliability of the device. Summary of the Invention
[0004] Therefore, it is necessary to provide a method for preparing a gate dielectric layer and a semiconductor structure that makes the nitrogen concentration distribution of the gate dielectric layer uniform and greatly reduces the probability of nitrogen penetrating into the substrate.
[0005] In a first aspect, embodiments of this application provide a method for fabricating a gate dielectric layer, comprising:
[0006] Provide substrate;
[0007] A first spacer layer is formed on the substrate;
[0008] A silicon nitride layer is formed, the silicon nitride layer being located on the side of the first spacer layer away from the substrate;
[0009] A second spacer layer is formed, the second spacer layer being located on the side of the silicon nitride layer away from the first spacer layer;
[0010] The silicon nitride layer is heated to oxidize the silicon nitride layer, and the nitrogen element in the silicon nitride layer diffuses in the thickness direction of the silicon nitride layer to form a silicon oxynitride layer, wherein the concentration distribution of the nitrogen element in the silicon oxynitride layer is gradient distribution in the thickness direction of the silicon oxynitride layer.
[0011] At least the second spacer layer is removed, so that the first spacer layer and at least a portion of the silicon oxynitride layer constitute the gate dielectric layer.
[0012] In one embodiment, heating the silicon nitride layer includes:
[0013] The silicon nitride layer is heated to a target temperature on the side of the substrate away from the first spacer layer and / or on the side of the second spacer layer away from the silicon nitride layer.
[0014] In one embodiment, heating to the target temperature includes:
[0015] The target temperature is reached by annealing.
[0016] In one embodiment, heating the silicon nitride layer includes:
[0017] The silicon nitride layer is heated to a target temperature on its side surface.
[0018] In one embodiment, heating to the target temperature includes:
[0019] The target temperature is achieved using a thermal oxidation process.
[0020] In one embodiment, removing at least the second spacer layer, such that the first spacer layer and at least a portion of the silicon oxynitride layer constitute a gate dielectric layer, includes:
[0021] The second spacer layer and a portion of the silicon oxynitride layer are removed, thereby the first spacer layer and the remaining silicon oxynitride layer constitute the gate dielectric layer.
[0022] In one embodiment, removing at least the second spacer layer includes:
[0023] A wet etching process is used to remove at least the second spacer layer.
[0024] In one embodiment, the thickness of the first spacer layer and the thickness of the second spacer layer are the same.
[0025] In one embodiment, both the first spacer layer and the second spacer layer are made of silicon dioxide.
[0026] Based on the same inventive concept, in a second aspect, embodiments of this application provide a semiconductor structure, including:
[0027] Substrate;
[0028] A first spacer layer is located on the substrate;
[0029] A silicon oxynitride layer is located on the side of the first spacer layer away from the substrate, wherein the concentration distribution of nitrogen in the silicon oxynitride layer is gradient distribution in the thickness direction of the silicon oxynitride layer;
[0030] The silicon oxynitride layer is formed by forming a silicon nitride layer on the side of the first spacer layer away from the substrate, then forming a second spacer layer on the side of the silicon nitride layer away from the first spacer layer, then heating the silicon nitride layer to oxidize the silicon nitride layer, and causing nitrogen elements in the silicon nitride layer to diffuse in the thickness direction of the silicon nitride layer, thereby forming the silicon oxynitride layer, and at least removing the second spacer layer, so that the first spacer layer and at least a portion of the silicon oxynitride layer constitute a gate dielectric layer.
[0031] The aforementioned gate dielectric layer fabrication method and semiconductor structure involve sequentially forming a first spacer layer, a silicon nitride layer, and a second spacer layer on a substrate. These three layers form a "sandwich" structure. The silicon nitride layer is then heated to oxidize it, causing nitrogen to diffuse along its thickness, thus forming a silicon oxynitride layer. This silicon oxynitride layer exhibits a uniform gradient distribution of nitrogen concentration, thereby obtaining the desired N-profile gate dielectric layer. Furthermore, the first spacer layer significantly reduces the probability of nitrogen penetration into the substrate, which is beneficial for improving the electrical performance and reliability of integrated circuit devices. Attached Figure Description
[0032] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0033] Figure 1 This is a schematic flowchart of a method for fabricating a gate dielectric layer according to an embodiment;
[0034] Figure 2 This is one of the structural schematic diagrams involved in the fabrication method of the gate dielectric layer according to an embodiment;
[0035] Figure 3 This is a second schematic diagram of the structure involved in the fabrication method of the gate dielectric layer in one embodiment;
[0036] Figure 4 This is the third schematic diagram of the structure involved in the fabrication method of the gate dielectric layer in one embodiment;
[0037] Figure 5 This is a fourth schematic diagram of the structure involved in the fabrication method of the gate dielectric layer in one embodiment;
[0038] Figure 6 This is the fifth schematic diagram of the structure involved in the fabrication method of the gate dielectric layer in one embodiment;
[0039] Figure 7 This is a schematic diagram of the structure involved in the preparation method of the gate dielectric layer in one embodiment;
[0040] Figure 8 This is the seventh schematic diagram of the structure involved in the fabrication method of the gate dielectric layer in one embodiment;
[0041] Figure 9 This is the eighth schematic diagram of the structure involved in the preparation method of the gate dielectric layer in one embodiment;
[0042] Figure 10 This is a schematic diagram of the structure involved in the fabrication method of the gate dielectric layer in one embodiment;
[0043] Figure 11 This is a schematic diagram of the structure involved in the fabrication method of the gate dielectric layer according to an embodiment;
[0044] Figure 12 This is a schematic diagram of the internal nitrogen concentration distribution of a silicon oxynitride layer according to an embodiment;
[0045] Figure 13 This is eleventh of the structural schematic diagrams involved in the fabrication method of the gate dielectric layer in one embodiment.
[0046] Explanation of reference numerals in the attached figures: 110 - substrate, 120 - first spacer layer, 130 - silicon nitride layer, 140 - second spacer layer, 150 - silicon oxynitride layer, 160 - gate dielectric layer. Detailed Implementation
[0047] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.
[0048] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
[0049] It is understood that the terms "first," "second," etc., used herein may be used to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.
[0050] It is understood that the term "connection" in the following embodiments should be understood as "electrical connection," "communication connection," etc., if the connected circuits, modules, units, etc., have electrical signal or data transmission with each other.
[0051] It is understandable that "at least one" refers to one or more, and "multiple" refers to two or more. "At least a part of an element" refers to part or all of an element.
[0052] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising / including” or “having,” etc., specify the presence of the stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. Meanwhile, the term “and / or” as used in this specification includes any and all combinations of the associated listed items.
[0053] In related technologies, the conventional method for preparing gate silicon oxynitride (SiON) thin films involves first growing a silicon dioxide (SiO2) film on the surface of a silicon substrate, which serves as the base oxide layer (BaseOX). Then, the silicon dioxide film is nitrided using a DPN (Decoupled Plasma Nitridation) process to obtain the silicon oxynitride film. However, in these related technologies, the surface nitrogen concentration and longitudinal depth distribution of the gate silicon oxynitride layer are difficult to precisely control. Increasing the nitrogen doping concentration by increasing the nitriding power or extending the nitriding time can easily lead to excessive nitrogen penetration into the silicon substrate. This not only disrupts the uniformity of the nitrogen concentration distribution in the gate silicon oxynitride layer but, in severe cases, can also damage the interface characteristics between the silicon substrate and the gate silicon oxynitride layer, causing problems such as increased interface state density and decreased carrier mobility, ultimately affecting the electrical performance and reliability of the device.
[0054] In view of this, embodiments of this application provide a method for preparing a gate dielectric layer and a semiconductor structure, which makes the nitrogen concentration distribution of the gate dielectric layer uniform and greatly reduces the probability of nitrogen penetrating into the substrate.
[0055] In one exemplary embodiment, reference is made to Figure 1 A method for preparing a gate dielectric layer is provided, which may include the following steps S101 to S106.
[0056] S101 provides a substrate.
[0057] As an example, refer to Figure 2 A substrate 110 may be provided. The substrate 110 is, for example, but not limited to, a silicon substrate. The substrate 110 may be provided as needed according to the actual application; this application does not specifically limit the material of the substrate 110. (See reference...) Figure 2 An STI (Shallow Trench Isolation) structure can be formed on the substrate 110.
[0058] S102, a first spacer layer is formed on the substrate.
[0059] As an example, refer to Figure 3A first spacer layer 120 can be formed on the substrate 110. The first spacer layer 120 can at least isolate the substrate 110 and the silicon nitride layer 130 formed in subsequent steps. In addition, the first spacer layer 120 can also block the diffusion of nitrogen in the silicon nitride layer 130, preventing nitrogen from diffusing into the substrate 110. The first spacer layer 120 can serve as a base oxide layer. The material of the first spacer layer 120 is, for example, but not limited to, silicon dioxide. The material of the first spacer layer 120 can be configured as needed according to the actual application. This embodiment does not specifically limit the material of the first spacer layer 120. In addition, the thickness of the first spacer layer 120 can be configured as needed according to the actual application. This embodiment does not specifically limit the thickness of the first spacer layer 120.
[0060] S103, a silicon nitride layer is formed, which is located on the side of the first spacer layer away from the substrate.
[0061] As an example, refer to Figure 4 A silicon nitride layer 130 may be formed on the side of the first spacer layer 120 away from the substrate 110. The silicon nitride layer 130 is used to form the silicon oxynitride layer 150 in a subsequent step. The thickness of the silicon nitride layer 130 can be configured as needed according to the actual application, and this embodiment does not specifically limit the thickness of the silicon nitride layer 130.
[0062] S104, forming a second spacer layer, the second spacer layer being located on the side of the silicon nitride layer away from the first spacer layer.
[0063] As an example, refer to Figure 5 A second spacer layer 140 may be formed on the side of the silicon nitride layer 130 away from the first spacer layer 120. The material of the second spacer layer 140 may be, for example, but not limited to, silicon dioxide. The material of the second spacer layer 140 may be configured as needed according to the actual application; this embodiment does not specifically limit the material of the second spacer layer 140. Furthermore, the thickness of the second spacer layer 140 may be configured as needed according to the actual application; this embodiment does not specifically limit the thickness of the second spacer layer 140.
[0064] As an example, the thickness of the first spacer layer 120 can be 10 angstroms to 100 angstroms, such as 15 angstroms, 20 angstroms, 25 angstroms, 30 angstroms, etc.; the thickness of the second spacer layer 140 can be 10 angstroms to 100 angstroms, such as 15 angstroms, 20 angstroms, 25 angstroms, 30 angstroms, etc.; the thickness of the silicon nitride layer 130 can be 10 angstroms to 100 angstroms, such as 15 angstroms, 20 angstroms, 25 angstroms, 30 angstroms, etc.; or, for example, the total thickness of the first spacer layer 120, the silicon nitride layer 130 and the second spacer layer 140 is less than 100 angstroms, for example, the thickness of the first spacer layer 120 and the second spacer layer 140 is both 20 angstroms to 25 angstroms, while the thickness of the silicon nitride layer 130 is 15 angstroms to 20 angstroms.
[0065] S105, the silicon nitride layer is heated to oxidize the silicon nitride layer, and the nitrogen element in the silicon nitride layer diffuses in the thickness direction of the silicon nitride layer to form a silicon oxynitride layer, wherein the concentration distribution of the nitrogen element in the silicon oxynitride layer is gradient distribution in the thickness direction of the silicon oxynitride layer.
[0066] The silicon nitride layer 130 can be heated directly or indirectly. In this embodiment, heating the silicon nitride layer 130 aims to oxidize it and simultaneously diffuse nitrogen elements along its thickness, for example, towards the first spacer layer 120 and towards the second spacer layer 140. Based on the oxidation and diffusion of nitrogen elements in the silicon nitride layer 130, as an example, refer to... Figure 6 This forms a silicon oxynitride layer 150. The resulting silicon oxynitride layer 150 has a uniform gradient distribution of nitrogen concentration inside.
[0067] S106, at least the second spacer layer is removed, so that the first spacer layer and at least a portion of the silicon oxynitride layer constitute the gate dielectric layer.
[0068] As an example, refer to Figure 7 This can be achieved by removing the second spacer layer 140, thereby allowing the silicon oxynitride layer 150 and the first spacer layer 120 to form the gate dielectric layer 160, thus completing the fabrication of the gate dielectric layer 160 and obtaining the gate dielectric layer 160 with the target N profile. Additionally, Figure 6 and Figure 7 The diagram shows that the thickness of the silicon oxynitride layer 150 is H, the thickness of a portion of the silicon oxynitride layer 150 is h1, and the thickness of the remaining portion of the silicon oxynitride layer 150 is h2, where H = h1 + h2.
[0069] As an example, refer to Figure 8 Alternatively, a portion of the second spacer layer 140 and the silicon oxynitride layer 150 with a thickness of h1 can be removed, so that the remaining portion of the first spacer layer 120 and the silicon oxynitride layer 150 with a thickness of h2 constitutes the gate dielectric layer 160, thereby obtaining the gate dielectric layer 160 with the target N profile.
[0070] It is understandable that the removal of only the second spacer layer 140, or the removal of the second spacer layer 140 and a portion of the silicon oxynitride layer 150, can be done as needed according to the actual application, as long as the required N-profile gate dielectric layer is obtained.
[0071] In this embodiment, a first spacer layer 120, a silicon nitride layer 130, and a second spacer layer 140 form a "sandwich" structure on a substrate 110. The silicon nitride layer 130 is then heated to oxidize it, causing nitrogen in the silicon nitride layer 130 to diffuse along its thickness, thereby forming a silicon oxynitride layer 150. The silicon oxynitride layer 150 thus formed has a uniform gradient distribution of nitrogen concentration, which allows for the acquisition of the desired N-profile gate dielectric layer. At the same time, the presence of the first spacer layer 120 significantly reduces the probability of nitrogen penetrating into the substrate 110, which is beneficial for improving the electrical performance and reliability of integrated circuit devices.
[0072] In an exemplary embodiment, the removal of at least the second spacer layer in step S106 may include: using a wet etching process to remove at least the second spacer layer.
[0073] Wet etching is an etching technique in semiconductor manufacturing based on chemical etching reactions. It removes materials by selectively reacting liquid etchants with the target material.
[0074] In this embodiment, a wet etching process is used to remove the second spacer layer 140, or a wet etching process is used to remove the second spacer layer 140 and a portion of the silicon oxynitride layer 150. This helps to ensure the flatness of the film interface and has the effects of high selectivity, low damage, low cost, and high uniformity during the removal process.
[0075] In an exemplary embodiment, heating the silicon nitride layer in step S105 may include heating the silicon nitride layer to a target temperature (e.g., a first target temperature) on the side of the substrate away from the first spacer layer.
[0076] refer to Figure 9 Heating is performed on the side of the substrate 110 away from the first spacer layer 120 (the heat source is indicated by an arrow), thus indirectly heating the silicon nitride layer 130 from one side. The first target temperature can be configured as needed according to the actual application and is not specifically limited thereto.
[0077] As an example, when the material of the first spacer layer 120 is silicon dioxide, during the heating process, the oxygen element in the first spacer layer 120 can diffuse into the silicon nitride layer 130, which is beneficial to the oxidation of the silicon nitride layer 130 and to obtain a silicon oxynitride film. In addition, during the heating process, the nitrogen atoms of the silicon nitride layer 130 can diffuse.
[0078] It is understandable that heating is performed on the side of substrate 110 away from the first spacer layer 120, and the material of the first spacer layer 120 is silicon dioxide. Therefore, heat is applied to both the first spacer layer 120 and the silicon nitride layer 130. In other words, not only the silicon nitride layer 130 but also the first spacer layer 120 is heated. By controlling the thicknesses of both the silicon nitride layer 130 and the first spacer layer 120 to be relatively small (e.g., both tens or hundreds of angstroms), or by controlling the heat appropriately, some Si-N bonds in the silicon nitride layer 130 will break, causing some nitrogen atoms in the silicon nitride layer 130 to move and diffuse. Simultaneously, some Si-O bonds in the first spacer layer 120 will break, causing oxygen atoms in the first spacer layer 120 to move and diffuse. The silicon nitride layer 130 can receive heat from the first spacer layer 120. The oxygen atoms in the silicon nitride layer 130 generate new Si-O bonds, thus oxidizing the silicon nitride layer 130 into a silicon oxynitride film. Following the mechanism of natural thermal diffusion, the nitrogen concentration distribution within the film exhibits a gradient distribution. Simultaneously, the first spacer layer 120 also receives trace amounts of nitrogen atoms from the silicon nitride layer 130, generating new Si-N bonds within it. Therefore, the first spacer layer 120 is slightly nitrided, resulting in a certain amount of silicon oxynitride inside. The degree of nitriding depends on the heating intensity and the thickness of the first spacer layer 120 and the silicon nitride layer 130. However, ultimately, following the mechanism of natural thermal diffusion, the nitrogen concentration distribution still exhibits a gradient distribution. Furthermore, it can be understood that heat not only provides the energy to break Si-N and Si-O bonds but also provides kinetic energy for the movement and diffusion of nitrogen and oxygen atoms.
[0079] In some exemplary embodiments, heating can be performed using methods such as lamps, lasers, or microwaves, with corresponding temperatures ranging from 300°C to 2000°C.
[0080] As an example, if the material of the first spacer layer 120 does not contain oxygen, oxygen can be provided additionally during the heating process, for example, by providing an oxygen-containing process environment in the space where the silicon nitride layer 130 is located, thereby achieving the oxidation of the silicon nitride layer 130 and obtaining a silicon oxynitride film. In addition, during the heating process, nitrogen in the silicon nitride layer 130 can diffuse.
[0081] In this embodiment, the method of using the first spacer layer 120 to implant oxygen into the silicon nitride layer 130, or providing oxygen in the space where the silicon nitride layer 130 is located to implant oxygen into the silicon nitride layer 130, is not specifically limited and can be implemented as needed according to actual application.
[0082] In an exemplary embodiment, heating the silicon nitride layer in step S105 may include heating the silicon nitride layer to a target temperature (e.g., a second target temperature) on the side of the second spacer layer away from the silicon nitride layer.
[0083] refer to Figure 10 Heating is performed on the side of the second spacer layer 140 away from the silicon nitride layer 130 (indicated by lines with arrows), thus indirectly heating the silicon nitride layer 130 from one side. The second target temperature can be configured as needed according to the actual application and is not specifically limited thereto.
[0084] As an example, when the material of the second spacer layer 140 is silicon dioxide, during the heating process, the oxygen element in the second spacer layer 140 can diffuse into the silicon nitride layer 130, which is beneficial to the oxidation of the silicon nitride layer 130 and to obtain a silicon oxynitride film. In addition, during the heating process, the nitrogen atoms of the silicon nitride layer 130 can diffuse.
[0085] Similarly to the above embodiments, it can be understood that if the second spacer layer 140 is heated on the side away from the silicon nitride layer 130, and the material of the second spacer layer 140 is silicon dioxide, then heat will be applied to both the second spacer layer 140 and the silicon nitride layer 130. In other words, not only the silicon nitride layer 130 but also the second spacer layer 140 will be heated. By controlling the thickness of both the silicon nitride layer 130 and the second spacer layer 140 to be relatively small (e.g., both tens or hundreds of angstroms), or by controlling the heat appropriately, some Si-N bonds in the silicon nitride layer 130 will break, causing some nitrogen atoms in the silicon nitride layer 130 to move and diffuse. At the same time, some Si-O bonds in the second spacer layer 140 will break, causing oxygen atoms in the second spacer layer 140 to move and diffuse. The silicon nitride layer 130 can receive heat from the second spacer layer 140. Oxygen atoms in spacer layer 140 form new Si-O bonds in silicon nitride layer 130, thereby oxidizing silicon nitride layer 130 into silicon oxynitride film. Following the mechanism of natural thermal diffusion, the nitrogen concentration distribution within it exhibits a gradient distribution. Simultaneously, the second spacer layer 140 also receives trace amounts of nitrogen atoms from silicon nitride layer 130, forming new Si-N bonds within it. Therefore, the second spacer layer 140 is slightly nitrided, resulting in a certain amount of silicon oxynitride inside. The degree of nitriding depends on the heating intensity and the thickness of the second spacer layer 140 and silicon nitride layer 130. However, ultimately, following the mechanism of natural thermal diffusion, the nitrogen concentration distribution still exhibits a gradient distribution. Furthermore, it can be understood that heat not only provides the energy to break Si-N and Si-O bonds but also provides kinetic energy for the movement and diffusion of nitrogen and oxygen atoms.
[0086] In some exemplary embodiments, heating can be performed using methods such as lamps, lasers, or microwaves, with corresponding temperatures ranging from 300°C to 2000°C.
[0087] As an example, if the material of the second spacer layer 140 does not contain oxygen, oxygen can be provided additionally during the heating process, for example, by providing an oxygen-containing process environment in the space where the silicon nitride layer 130 is located, thereby achieving the oxidation of the silicon nitride layer 130 and obtaining a silicon oxynitride film. In addition, during the heating process, nitrogen in the silicon nitride layer 130 can diffuse.
[0088] In this embodiment, the method of using the second spacer layer 140 to implant oxygen into the silicon nitride layer 130, or providing oxygen in the space where the silicon nitride layer 130 is located to implant oxygen into the silicon nitride layer 130, is not specifically limited and can be implemented as needed according to actual application.
[0089] In an exemplary embodiment, heating the silicon nitride layer in step S105 may include heating the silicon nitride layer to a target temperature (e.g., a third target temperature) on the side of the substrate away from the first spacer layer and on the side of the second spacer layer away from the silicon nitride layer.
[0090] refer to Figure 11 Heating is performed on the side of substrate 110 away from the first spacer layer 120 (illustrated by lines with arrows), and simultaneously on the side of second spacer layer 140 away from silicon nitride layer 130 (illustrated by lines with arrows), thus indirectly heating the silicon nitride layer 130 from both sides. The third target temperature can be configured as needed according to the actual application and is not specifically limited thereto. Furthermore, the heating temperature on the side of substrate 110 away from the first spacer layer 120 and the heating temperature on the side of second spacer layer 140 away from silicon nitride layer 130 can be the same or different, depending on the required oxidation degree and N profile of the silicon nitride layer 130 for the actual application. In this embodiment of the application, the heating temperature of the silicon nitride layer 130 in the gate dielectric layer fabrication method is not specifically limited.
[0091] When at least one of the first spacer layer 120 and the second spacer layer 140 is made of silicon dioxide, oxygen in the first spacer layer 120 and / or the second spacer layer 140 can diffuse into the silicon nitride layer 130 during heating, which facilitates the oxidation of the silicon nitride layer 130 to obtain a silicon oxynitride film. Furthermore, nitrogen in the silicon nitride layer 130 diffuses during heating. Moreover, when at least one of the first spacer layer 120 and the second spacer layer 140 is made of silicon dioxide, there is no need to provide additional oxygen, which helps to save costs in oxidizing the silicon nitride layer 130.
[0092] Similarly to the above embodiments, it can be understood that heating is performed on the side of the substrate 110 away from the first spacer layer 120, and simultaneously heating is performed on the side of the second spacer layer 140 away from the silicon nitride layer 130. Since both the first spacer layer 120 and the second spacer layer 140 are made of silicon dioxide, heat will be applied to both the first and second spacer layers 120, and also to the silicon nitride layer 130. In other words, not only will the silicon nitride layer 130 be heated, but the first and second spacer layers 120 will also be heated. If the silicon nitride layer 130, the first spacer layer 120, and the second spacer layer 140 are all relatively small (e.g., tens or hundreds of angstroms each), or if the heat is properly controlled, then some Si-N bonds in the silicon nitride layer 130 will break, causing some nitrogen atoms in the silicon nitride layer 130 to move and diffuse. Simultaneously, some Si-O bonds in the second spacer layer 140 will break, causing oxygen atoms in the second spacer layer 140 to move and diffuse. At the same time, some Si-O bonds in the first spacer layer 120 will also break. The bonds break, causing oxygen atoms in the first spacer layer 120 to move and diffuse. The silicon nitride layer 130 can receive oxygen atoms from the first spacer layer 120 and the second spacer layer 140, forming new Si-O bonds in the silicon nitride layer 130. Thus, the silicon nitride layer 130 is oxidized into a silicon oxynitride film, and, following the mechanism of natural thermal diffusion, the nitrogen concentration distribution exhibits a gradient distribution. Simultaneously, the first spacer layer 120 and the second spacer layer 140 also receive trace amounts of nitrogen atoms from the silicon nitride layer 130. New Si-N bonds are generated in the first spacer layer 120 and the second spacer layer 140. Therefore, the first spacer layer 120 and the second spacer layer 140 will be slightly nitrided. The degree of nitriding depends on the heating intensity and the thickness of the first spacer layer 120, the second spacer layer 140 and the silicon nitride layer 130. However, in the end, referring to the mechanism of natural thermal diffusion, the concentration distribution of nitrogen element is still gradient distribution. In addition, it can be understood that heat not only provides energy to cause the Si-N bond and Si-O bond to break, but also provides kinetic energy for the movement and diffusion of nitrogen atoms and oxygen atoms.
[0093] In some exemplary embodiments, heating can be performed using methods such as lamps, lasers, or microwaves, with corresponding temperatures ranging from 300°C to 2000°C.
[0094] The solution provided in this application embodiment mainly causes bond breakage within the thin film lattice and provides energy for the movement (diffusion) of oxygen and nitrogen atoms. Therefore, heat needs to be transferred to the first spacer layer 120, the second spacer layer 140, and the silicon nitride layer 130. The resulting silicon oxynitride layer has a concentration gradient. In addition, since the thickness of the first spacer layer 120, the second spacer layer 140, and the silicon nitride layer 130 in this application embodiment is thin enough (e.g., tens or tens of angstroms), the provided heat causes bond breakage within the thin film lattice and provides energy for the movement (diffusion) of oxygen and nitrogen atoms, thereby creating new bonds within the thin film lattice. These situations are easy to occur. Therefore, the solution provided in this application embodiment for forming a silicon oxynitride layer (i.e., forming a gate dielectric layer) is easy to implement, reliable, and low in cost.
[0095] When neither the first spacer layer 120 nor the second spacer layer 140 contains oxygen, oxygen can be provided additionally during the heating process. For example, an oxygen-containing process environment can be provided in the space where the silicon nitride layer 130 is located, thereby achieving the oxidation of the silicon nitride layer 130 and obtaining a silicon oxynitride film. In addition, during the heating process, nitrogen in the silicon nitride layer 130 can diffuse.
[0096] Combination Figure 11 and Figure 12 , Figure 12 The vertical axis represents the thickness H of the silicon oxynitride layer 150, and the horizontal axis represents the nitrogen concentration within the silicon oxynitride layer 150. Since the silicon oxynitride layer 130 is heated indirectly from both sides, the nitrogen concentration distribution in the resulting silicon oxynitride layer 150 exhibits a high concentration in the middle and a low concentration on both sides. Based on this N-profile, a portion of the silicon oxynitride layer 150 can be selectively removed to obtain a gate dielectric layer with the target N-profile. This not only results in a uniform and gradient nitrogen concentration distribution but also demonstrates a simple, easy-to-implement, and low-cost solution.
[0097] In one exemplary embodiment, the thickness of the first spacer layer 120 is the same as the thickness of the second spacer layer 140.
[0098] In this embodiment, the thickness of the first spacer layer 120 is the same as the thickness of the second spacer layer 140, so that the "sandwich" structure composed of the first spacer layer 120, the silicon nitride layer 130 and the second spacer layer 140 has symmetry. This is beneficial to the concentration distribution of nitrogen in the silicon oxynitride layer 150 formed during the indirect heating of the silicon nitride layer 130 on both sides, which is characterized by a high concentration in the middle of the film and a low concentration on both sides.
[0099] In an exemplary embodiment, heating to a target temperature (e.g., a first target temperature, a second target temperature, or a third target temperature) in the above embodiments may include heating to the target temperature using an annealing process.
[0100] Among them, the annealing process is, but is not limited to, rapid thermal annealing (RTA), furnace tube annealing, pulsed laser annealing (PLA), or plasma-enhanced thermal annealing (PETA).
[0101] In an exemplary embodiment, heating the silicon nitride layer in step S105 may include heating the silicon nitride layer to a target temperature (e.g., a fourth target temperature) on the side of the silicon nitride layer.
[0102] refer to Figure 13 Heating is performed on each side of the silicon nitride layer 130 (indicated by arrowed lines), thus directly heating the silicon nitride layer 130. The fourth target temperature can be configured as needed according to the actual application and is not specifically limited thereto. As an example, oxygen can be additionally provided during the heating process, for instance, by providing an oxygen-containing process environment in the space surrounding the silicon nitride layer 130, thereby achieving oxidation of the silicon nitride layer 130 to obtain a silicon oxynitride film. Furthermore, nitrogen in the silicon nitride layer 130 diffuses during the heating process.
[0103] It is understandable that when the silicon nitride layer 130 is directly heated on at least one side, the heat will also be transferred to the first spacer layer 120 and the second spacer layer 140 since they are in direct contact with the silicon nitride layer 130. This achieves the effect that all three layers are heated, including the first spacer layer 120, the second spacer layer 140, and the silicon nitride layer 130. Based on the breaking of Si-N and Si-O bonds and the movement (diffusion) of oxygen and nitrogen atoms, a nitrogen-concentration gradient distribution of silicon oxynitride is formed in the first spacer layer 120, the second spacer layer 140, and the silicon nitride layer 130. Finally, the film thickness is removed or thinned according to the required thickness and nitrogen concentration distribution to realize the gate dielectric layer.
[0104] In an exemplary embodiment, heating to a target temperature (e.g., a fourth target temperature) in the above embodiments may include heating to the target temperature using a thermal oxidation process.
[0105] Among them, thermal oxidation processes include, but are not limited to, dry oxidation, wet / oxide steam oxidation, ozone-assisted thermal oxidation, plasma-enhanced thermal oxidation (PETO), or rapid thermal oxidation (RTO).
[0106] Based on the same inventive concept, and referring to Figure 7 or Figure 8 This application also provides a semiconductor structure, which can be prepared by the method for preparing the gate dielectric layer provided in any of the above embodiments.
[0107] The semiconductor structure includes: a substrate 110; a first spacer layer 120 located on the substrate 110; and a silicon oxynitride layer 150 located on the side of the first spacer layer 120 away from the substrate 110, wherein the concentration distribution of nitrogen in the silicon oxynitride layer 150 is gradient in the thickness direction; wherein the silicon oxynitride layer 150 is formed by forming a silicon nitride layer 130 on the side of the first spacer layer 120 away from the substrate 110, then forming a second spacer layer 140 on the side of the silicon nitride layer 130 away from the first spacer layer 120, then heating the silicon nitride layer 130 to oxidize the silicon nitride layer 130, and causing the nitrogen in the silicon nitride layer 130 to diffuse in the thickness direction of the silicon nitride layer 130, thereby forming the silicon oxynitride layer 150, and at least removing the second spacer layer 140, so that the first spacer layer 120 and at least a portion of the silicon oxynitride layer 150 constitute a gate dielectric layer 160.
[0108] The aforementioned semiconductor structure consists of a first spacer layer 120, a silicon nitride layer 130, and a second spacer layer 140 sequentially formed on a substrate 110. These three layers form a "sandwich" structure. The silicon nitride layer 130 is then heated to oxidize it, causing nitrogen to diffuse along its thickness, thus forming a silicon oxynitride layer 150. This silicon oxynitride layer 150 has a uniform gradient distribution of nitrogen concentration, thus achieving the desired N-profile gate dielectric layer. Furthermore, the presence of the first spacer layer 120 significantly reduces the probability of nitrogen penetrating into the substrate, which is beneficial for improving the electrical performance and reliability of integrated circuit devices.
[0109] The semiconductor structure and gate dielectric layer preparation method provided in the embodiments of this application belong to the same inventive concept, can solve the same technical problem, and thus achieve the same technical effect. Repeated content will not be repeated here.
[0110] In the description of this specification, references to terms such as "some embodiments," "other embodiments," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.
[0111] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0112] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.
Claims
1. A method for fabricating a gate dielectric layer, characterized in that, include: Provide substrate; A first spacer layer is formed on the substrate; A silicon nitride layer is formed, the silicon nitride layer being located on the side of the first spacer layer away from the substrate; A second spacer layer is formed, the second spacer layer being located on the side of the silicon nitride layer away from the first spacer layer; The silicon nitride layer is heated to oxidize the silicon nitride layer, and the nitrogen element in the silicon nitride layer diffuses in the thickness direction of the silicon nitride layer to form a silicon oxynitride layer, wherein the concentration distribution of the nitrogen element in the silicon oxynitride layer is gradient distribution in the thickness direction of the silicon oxynitride layer. At least the second spacer layer is removed, so that the first spacer layer and at least a portion of the silicon oxynitride layer constitute the gate dielectric layer.
2. The method for preparing the gate dielectric layer according to claim 1, characterized in that, The heating of the silicon nitride layer includes: The silicon nitride layer is heated to a target temperature on the side of the substrate away from the first spacer layer and / or on the side of the second spacer layer away from the silicon nitride layer.
3. The method for preparing the gate dielectric layer according to claim 2, characterized in that, The heating to the target temperature includes: The target temperature is reached by annealing.
4. The method for preparing the gate dielectric layer according to claim 1, characterized in that, The heating of the silicon nitride layer includes: The silicon nitride layer is heated to a target temperature on its side surface.
5. The method for preparing the gate dielectric layer according to claim 4, characterized in that, The heating to the target temperature includes: The target temperature is achieved using a thermal oxidation process.
6. The method for preparing the gate dielectric layer according to claim 1, characterized in that, The removal of at least the second spacer layer, so that the first spacer layer and at least a portion of the silicon oxynitride layer constitute a gate dielectric layer, includes: The second spacer layer and a portion of the silicon oxynitride layer are removed, thereby the first spacer layer and the remaining silicon oxynitride layer constitute the gate dielectric layer.
7. The method for preparing the gate dielectric layer according to any one of claims 1-6, characterized in that, The removal of at least the second spacer layer includes: A wet etching process is used to remove at least the second spacer layer.
8. The method for preparing the gate dielectric layer according to any one of claims 1-6, characterized in that, The thickness of the first spacer layer is the same as the thickness of the second spacer layer.
9. The method for preparing the gate dielectric layer according to any one of claims 1-6, characterized in that, Both the first spacer layer and the second spacer layer are made of silicon dioxide.
10. A semiconductor structure, characterized in that, include: Substrate; A first spacer layer is located on the substrate; A silicon oxynitride layer is located on the side of the first spacer layer away from the substrate, wherein the concentration distribution of nitrogen in the silicon oxynitride layer is gradient distribution in the thickness direction of the silicon oxynitride layer; The silicon oxynitride layer is formed by forming a silicon nitride layer on the side of the first spacer layer away from the substrate, then forming a second spacer layer on the side of the silicon nitride layer away from the first spacer layer, then heating the silicon nitride layer to oxidize the silicon nitride layer, and causing nitrogen elements in the silicon nitride layer to diffuse in the thickness direction of the silicon nitride layer, thereby forming the silicon oxynitride layer, and at least removing the second spacer layer, so that the first spacer layer and at least a portion of the silicon oxynitride layer constitute a gate dielectric layer.