Blocking structure, blocking structure preparation method and interconnection structure

Abstract

The invention provides a barrier structure, a barrier structure preparation method and an interconnection structure, the barrier structure is used for diffusion barrier of a metal interconnection structure, the barrier structure comprises a first barrier layer, the first barrier layer is a nitrogen-rich barrier layer to block metal diffusion in the metal interconnection structure; the second barrier layer is located on one side of the first barrier layer, and the second barrier layer is a carbon-rich barrier layer so as to reduce the dielectric constant value of the barrier structure; the third barrier layer is located on the side, away from the first barrier layer, of the second barrier layer, and the third barrier layer is a nitride barrier layer so as to prevent oxygen atoms from diffusing in the barrier structure. According to the invention, RC delay can be reduced, and the barrier effect on diffusion of metal and oxygen atoms can be improved.

Description

Technical Field

[0001] This application relates to the field of semiconductor technology, specifically to a barrier structure, a method for fabricating the barrier structure, and an interconnect structure. Background Technology

[0002] In the semiconductor field, as process nodes continue to shrink, the requirements for signal transmission efficiency and stability of high-performance integrated circuit chips are becoming increasingly stringent. Reducing the resistance-capacitance (RC) signal delay and signal crosstalk of interconnects has become one of the core requirements for improving device performance.

[0003] To achieve this goal, the industry commonly uses low-resistivity copper (Cu) as the metal interconnect material to effectively reduce line resistance. However, Cu atoms readily diffuse into the surrounding dielectric layer, requiring diffusion barrier layers to block Cu diffusion. Silicon nitride (SiN) and silicon carbon nitride hydrogen (SiCNH) layers have high density and are widely used in back-end Cu interconnect processes as Cu diffusion barrier layers and via etching stop layers. However, with the increasing requirements of process nodes (e.g., <32 nm), the density of back-end metal interconnects gradually increases. The intrinsic high dielectric constant (K value) of SiN and SiCNH is gradually becoming one of the key factors affecting the RC (resistance-capacitance) delay of devices; for example, the dielectric constant of SiN is 7, and that of SiCNH is 5.3. Reducing the K value of the barrier layer is a necessary means to reduce RC delay. Furthermore, in advanced processes, the high interface defect density between SiNCH and Cu is difficult to adapt to the reliability requirements of narrow-pitch interconnect structures. Therefore, improving the interface defect state between SiNCH and Cu to enhance electromigration performance has become an urgent problem to be solved in this field. Summary of the Invention

[0004] In view of the problems in the prior art, the purpose of this application is to provide a barrier structure, a method for preparing the barrier structure, and an interconnect structure, which are beneficial to reducing RC delay and improving the barrier effect on the diffusion of metal and oxygen atoms.

[0005] A first aspect of this application provides a barrier structure for diffusion blocking in a metal interconnect structure, the barrier structure comprising: A first barrier layer, which is a nitrogen-rich barrier layer, is used to block metal diffusion in the metal interconnect structure. A second barrier layer is located on one side of the first barrier layer. The second barrier layer is a carbon-rich barrier layer to reduce the dielectric constant of the barrier structure. A third barrier layer is located on the side of the second barrier layer opposite to the first barrier layer. The third barrier layer is a nitride barrier layer to prevent oxygen atoms from diffusing in the barrier structure.

[0006] In some embodiments, the first barrier layer is a nitrogen-rich silicon nitride layer, the second barrier layer is a carbon-rich silicon-carbon-nitrogen-hydrogen layer, and the third barrier layer is a silicon nitride layer conforming to stoichiometry.

[0007] In some embodiments, the thickness of the first barrier layer is 3-10 nm, the thickness of the second barrier layer is 15-50 nm, and the thickness of the third barrier layer is 3-10 nm.

[0008] In some embodiments, the dielectric constant of the first barrier layer is 6 to 6.6, the dielectric constant of the second barrier layer is 3 to 3.5, and the dielectric constant of the third barrier layer is 6.8 to 7.2.

[0009] In some embodiments, the blocking structure satisfies the following condition: the sum of the product of the dielectric constant and thickness of the first blocking layer, the product of the dielectric constant and thickness of the second blocking layer, and the product of the dielectric constant and thickness of the third blocking layer is less than the product of a preset dielectric constant threshold and the thickness of the blocking structure.

[0010] A second aspect of this application provides a method for preparing a barrier structure, used to prepare the barrier structure described in the first aspect, the method comprising the following steps: A first barrier layer is formed on the surface of the metal interconnect structure. The first barrier layer is a nitrogen-rich barrier layer to block metal diffusion in the metal interconnect structure. A second barrier layer is formed on the side of the first barrier layer away from the metal interconnect structure. The second barrier layer is a carbon-rich barrier layer to reduce the dielectric constant of the barrier structure. A third barrier layer is formed on the side of the second barrier layer opposite to the first barrier layer. The third barrier layer is a nitride barrier layer to prevent oxygen atoms from diffusing in the barrier structure.

[0011] In some embodiments, a first barrier layer is formed on the surface of the metal interconnect structure. The first barrier layer is a nitrogen-rich barrier layer, comprising: depositing a nitrogen-rich silicon nitride layer using a plasma-enhanced chemical vapor deposition method with in-situ ammonia / hydrogen plasma treatment to obtain the first barrier layer; wherein the high-frequency radio frequency power during the deposition process is 50~100W and the low-frequency radio frequency power is 50~100W.

[0012] In some embodiments, a second barrier layer is formed on the side of the first barrier layer opposite to the metal interconnect structure. The second barrier layer is a carbon-rich barrier layer, comprising: depositing a carbon-rich silicon-carbon-nitrogen-hydrogen layer using tetramethylsilane and ammonia as precursors by plasma-enhanced chemical vapor deposition to obtain the second barrier layer; wherein the high-frequency radio frequency power during the deposition process is 50~150W.

[0013] In some embodiments, a third barrier layer is formed on the side of the second barrier layer opposite to the first barrier layer. The third barrier layer is a nitride barrier layer, comprising: depositing a stoichiometric silicon nitride layer using silane and ammonia as precursors by plasma-enhanced chemical vapor deposition to obtain the third barrier layer; wherein the high-frequency radio frequency power during the deposition process is 300~600W.

[0014] A third aspect of this application also provides an interconnect structure, comprising: a metal interconnect structure; and a barrier structure as described in the first aspect, wherein the first barrier layer, the second barrier layer, and the third barrier layer are sequentially stacked on the surface of the metal interconnect structure.

[0015] The barrier structure, barrier structure fabrication method, and interconnection structure provided in this application have the following advantages: This application provides a barrier structure formed by at least three sequentially stacked barrier layers for blocking diffusion in a metal interconnect structure. The first barrier layer has a high nitrogen content, which significantly enhances the ability to block metal diffusion in the metal interconnect structure. It also effectively optimizes the interface bonding between the metal and the barrier layer, reduces interface defect density, and thus extends the electromigration lifetime of the metal interconnect structure, improving the operational reliability of semiconductor devices with this barrier structure. The second barrier layer has carbon-rich properties, which facilitates a low dielectric constant, significantly reduces RC signal delay, improves signal transmission efficiency, and meets the high-speed performance requirements of advanced processes. The third barrier layer possesses excellent barrier properties, effectively blocking the diffusion of external impurities such as oxygen atoms into the barrier structure and the interior of the metal interconnect structure, preventing metal oxidation failure, and resisting environmental corrosion in subsequent processes, ensuring the stability of the barrier structure. The three barrier layers synergistically constitute a composite barrier structure, balancing high metal barrier performance, low dielectric constant, and high environmental barrier performance. While reducing RC delay and improving electromigration lifetime, it optimizes the stress balance and interface adhesion of the barrier structure, comprehensively improving the overall performance and process compatibility of the metal interconnect structure. Attached Figure Description

[0016] Other features, objects, and advantages of this application will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0017] Figure 1 This is a schematic diagram of an interconnect structure that uses a single silicon-carbon-nitrogen-hydrogen layer as a barrier layer; Figure 2 This is a schematic diagram of a blocking structure according to an embodiment of this application; Figure 3 This is a schematic diagram of an interconnection structure according to an embodiment of this application; Figure 4 This is a flowchart of a method for preparing a blocking structure according to an embodiment of this application. Detailed Implementation

[0018] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this application will be comprehensive and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and therefore repeated descriptions of them will be omitted. Although the terms “upper,” “lower,” “between,” etc., may be used in this specification to describe different exemplary features and elements of this application, these terms are used herein only for convenience, such as the orientation of the examples described in the accompanying drawings. Nothing in this specification should be construed as requiring a specific three-dimensional orientation of the structure to fall within the scope of this application. Although “first” or “second,” etc., are used in this specification to denote certain features, they are merely indicative of function and not as a limitation on the number or importance of specific features.

[0019] The stacked structure, thickness, and interface morphology of the various membrane layers shown in the accompanying drawings are merely illustrative examples intended to clearly explain the technical concept and core principles of this application, and not to limit the scope of protection of this application.

[0020] Figure 1 A schematic diagram of an interconnect structure using a single silicon-carbon-nitrogen-hydrogen layer as a barrier layer is shown. The interconnect structure includes a substrate 100', a metal layer 200', a first dielectric layer 300', a second dielectric layer 500', and a barrier layer 400'. This barrier layer 400' is a single silicon-carbon-nitrogen-hydrogen layer, which suffers from technical problems such as high dielectric constant, poor adhesion to the dielectric layer interface, and high interface defects. To address these technical problems, embodiments of this application provide a barrier structure to replace the single-material barrier layer in the prior art, reducing RC delay and improving the barrier effect against the diffusion of metal and oxygen atoms.

[0021] like Figure 2 As shown, this application provides a barrier structure for diffusion blocking in metal interconnect structures, the barrier structure comprising: A first barrier layer 410, which is a nitrogen-rich barrier layer, is used to block metal diffusion in the metal interconnect structure. The first barrier layer 410 has a high nitrogen content, which can significantly enhance the ability to block metal diffusion in the metal interconnect structure. At the same time, it can effectively optimize the interface bonding state between the metal and the barrier layer, reduce the interface defect density, and thus extend the electromigration lifetime of the metal interconnect structure and improve the operational reliability of the semiconductor device with the barrier structure. The metal interconnect structure is, for example, a copper interconnect structure. The second barrier layer 420 is located on one side of the first barrier layer. The second barrier layer is a carbon-rich barrier layer to reduce the dielectric constant (K value) of the barrier structure. The carbon-rich characteristics of the second barrier layer 420 are beneficial to achieving a low dielectric constant, significantly reducing the RC signal delay of the device, improving the signal transmission efficiency of the device, and adapting to the high-speed performance requirements of advanced processes. The third barrier layer 430 is located on the side of the second barrier layer away from the first barrier layer. The third barrier layer is a nitride barrier layer to prevent oxygen atoms from diffusing in the barrier structure. The third barrier layer 430 has excellent barrier properties, which can effectively prevent external impurities such as oxygen atoms from diffusing into the barrier structure and the metal interconnect structure, avoid metal oxidation failure, and resist environmental corrosion in subsequent processes, thus ensuring the stability of the barrier structure.

[0022] This application provides a barrier structure formed by sequentially stacking at least three barrier layers for blocking the diffusion of metal interconnect structures. The three barrier layers work together to form a composite barrier structure, which balances high metal barrier performance, low dielectric constant, and high environmental barrier performance. While reducing RC delay and improving electromigration lifetime, it optimizes the stress balance and interface adhesion of the barrier structure, comprehensively improving the overall performance and process compatibility of the metal interconnect structure.

[0023] In this embodiment, the first barrier layer, the second barrier layer, and the third barrier layer form a sandwich composite structure stacked sequentially. Optionally, the first barrier layer is a nitrogen-rich silicon nitride layer (N-rich SiN). High-nitrogen-content silicon nitride layers have the characteristics of strong metal barrier effect and low SiN / Cu interface defects. Using a high-nitrogen-content silicon nitride layer as the bottom layer further enhances the diffusion barrier effect of nitrogen atoms on metals (such as Cu), preventing the metal from being oxidized. Using a suitable silicon nitride layer is beneficial for enhancing the adhesion between the barrier structure and the underlying dielectric and metal layers, reducing interface defects, and thus increasing electromigration lifetime. This first barrier layer is a nitrogen-rich silicon nitride layer (N-rich SiN), whose nitrogen to silicon atomic ratio (N / Si) is higher than that of stoichiometric silicon nitride (Si3N4) (1.33), thereby strengthening the diffusion barrier capability against metals. For example, in this nitrogen-rich silicon nitride layer, the nitrogen to silicon atomic ratio (N / Si) is 1.4~1.6.

[0024] In this embodiment, the second barrier layer is a carbon-rich silicon-carbon-nitrogen-hydrogen (C-CNH) layer. The dielectric constant of the high-carbon-content C-CNH layer is 3-3.5. As an intermediate layer, the high-carbon-content C-CNH layer helps to reduce the overall dielectric constant of the barrier structure, thereby effectively reducing the RC delay of the device. The dielectric constant of a conventional C-CNH layer is 5.3. The carbon content of the second barrier layer is higher than that of a conventional C-CNH layer. By increasing the carbon content, the dielectric constant of the carbon-rich C-CNH layer is satisfied to be 3-4 (more specifically, 3-3.5). Therefore, the carbon-rich C-CNH layer in this embodiment is a C-CNH layer that satisfies a dielectric constant of 3-4 after increasing the carbon content.

[0025] In this embodiment, the third barrier layer is a stoichiometric silicon nitride layer (Si3N4). A stoichiometric silicon nitride layer exhibits strong oxygen ion blocking, strong water vapor blocking, and strong resistance to ultraviolet radiation. As the top layer, a stoichiometric silicon nitride layer helps prevent oxygen ions from diffusing deeper into the barrier structure, increases the interfacial adhesion between the barrier structure and the upper dielectric layer, controls the overall barrier structure to be under compressive stress, and prevents the thin film of the barrier structure from splitting.

[0026] Therefore, this embodiment provides a novel sandwich-structured composite barrier layer [(N-rich SiN)-(C-rich SiCNH)-Si3N4] for back-end Cu process interconnection. In the intermediate layer, increasing the carbon content effectively reduces the dielectric constant of the barrier structure. However, simply increasing the carbon content increases defects in the SiCNH layer, decreases its density, and consequently reduces its metal-blocking ability. Furthermore, the carbon-rich SiCNH layer further reduces film density during UV photosensitization after dielectric layer deposition. The film stress gradually changes from compressive stress to tensile stress, leading to decreased film adhesion, increased risk of film peeling, and reduced process reliability. By combining a bottom nitrogen-rich SiN layer and a top Si3N4 layer, and combining the high metal blocking ability and low SiN / Cu interface defect characteristics of the nitrogen-rich SiN layer with the high oxygen ion blocking ability, high water vapor blocking ability and high UV radiation resistance of Si3N4 which conforms to the stoichiometry, it is possible to reduce the overall RC delay of the back-end metal interconnect structure, improve the interface defects of the barrier structure, extend the electromigration lifetime, and improve the diffusion blocking effect.

[0027] like Figure 3As shown, this application embodiment also provides an interconnect structure, including a metal interconnect structure and the aforementioned barrier structure. The metal interconnect structure includes a metal layer 200 and a first dielectric layer 300, with the first barrier layer 410, the second barrier layer 420, and the third barrier layer 430 sequentially stacked on the surface of the metal interconnect structure. The interconnect structure also includes a substrate 100 at the bottom and a second dielectric layer 500 above the third barrier layer 430. The first dielectric layer 300 and the second dielectric layer 500 are, for example, silicon-carbon-oxygen-hydrogen (SiCOH) layers. The first barrier layer 410 can enhance the adhesion between the barrier structure and the interface between the first dielectric layer 300 and the metal layer 200, reducing interface defects and thus increasing electromigration lifetime. The third barrier layer 430 can increase the interface adhesion between the barrier structure and the second dielectric layer 500, controlling the overall barrier structure to be in a compressive stress state and preventing the thin film of the barrier structure from splitting. The second barrier layer 420 helps to reduce the dielectric constant of the overall barrier structure, thereby effectively reducing the RC delay of the device. The three barrier layers work together to form a composite barrier structure, which takes into account high metal barrier performance, low dielectric constant and high environmental barrier performance. While reducing RC delay and improving electromigration lifetime, it optimizes the stress balance and interface adhesion of the barrier structure, and comprehensively improves the overall performance and process compatibility of the metal interconnect structure.

[0028] Table 1 below shows the performance comparison between the composite barrier structure of this application and the existing single silicon-carbon-nitrogen-hydrogen layer.

[0029] Table 1

[0030] In this embodiment, the thickness T1 of the first barrier layer is 3~10 nm, the thickness T2 of the second barrier layer is 15~50 nm, and the thickness T3 of the third barrier layer is 3~10 nm. Since the thickness of the second barrier layer is greater than the thicknesses of the first and third barrier layers, a more significant decrease in the dielectric constant of the barrier structure can be achieved. The dielectric constant K1 of the first barrier layer is 6~6.6, the dielectric constant K2 of the second barrier layer is 3~4 (further, it can be 3~3.5), and the dielectric constant K3 of the third barrier layer is 6.8~7.2. The barrier structure satisfies the following condition: the sum of the products of the dielectric constant and thickness of the first barrier layer, the second barrier layer, and the third barrier layer is less than the product of a preset dielectric constant threshold and the thickness of the barrier structure, i.e., K1... T1+ K2 T2+ K3 T3 < preset dielectric constant threshold T total thickness Among them, T total thicknessLet K be the thickness of the overall barrier structure. The dielectric constant of this barrier structure is K1. (T1 / T total thickness )+ K2 (T2 / T total thickness )+ K3 (T3 / T total thickness The dielectric constant of the barrier structure is less than a preset dielectric constant threshold. By adjusting the thickness relationship between the various barrier layers, the barrier structure can meet the requirement of being less than the preset dielectric constant threshold. This preset dielectric constant threshold can be set to a small value, for example, a value less than the dielectric constant (5.3) of a single SiCNH barrier layer.

[0031] The thickness of each barrier layer can be selected as needed. For example, when K1, K2, and K3 are 6.5, 3.3, and 7 respectively, and T1, T2, and T3 are 5 nm, 20 nm, and 5 nm respectively, the thickness of the barrier structure is 30 nm, and the dielectric constant of the sandwich-structured composite barrier structure prepared with these parameters is 6.5. (5 / 30) + 3.3 (20 / 30)+7 (5 / 30) = 4.45 < 5.3, which meets the requirement of low dielectric constant of the film.

[0032] Therefore, this application constructs a novel sandwich-structured composite barrier structure based on the traditional use of a single material such as SiN / SiCNH for the diffusion barrier layer. In this embodiment, C-rich SiCNH is used as the intermediate layer to reduce the dielectric constant of the barrier structure, thereby reducing RC delay; N-rich SiN with high nitrogen content and high step coverage is used as the bottom layer to enhance the barrier properties of the film against metals (such as Cu) and reduce SiN / Cu interface defects, thereby improving electromigration properties and extending electromigration lifetime; Si3N4 with excellent stoichiometry is used as the top layer to increase the interfacial adhesion of SiN / SiCOH, improve the overall stress properties of the barrier layer, and prevent film peeling.

[0033] like Figure 4 As shown, this application provides a method for preparing a barrier structure, used to prepare the barrier structure described in the first aspect, the method comprising the following steps: S100: A first barrier layer is formed on the surface of the metal interconnect structure. The first barrier layer is a nitrogen-rich barrier layer to block metal diffusion in the metal interconnect structure. S200: A second barrier layer is formed on the side of the first barrier layer away from the metal interconnect structure. The second barrier layer is a carbon-rich barrier layer to reduce the dielectric constant of the barrier structure. S300: A third barrier layer is formed on the side of the second barrier layer away from the first barrier layer. The third barrier layer is a nitride barrier layer to prevent oxygen atoms from diffusing in the barrier structure.

[0034] In this embodiment, step S100, forming a first barrier layer on the surface of the metal interconnect structure, includes: depositing a nitrogen-rich silicon nitride layer using a plasma-enhanced chemical vapor deposition method with in-situ ammonia / hydrogen plasma treatment to obtain the first barrier layer; wherein, the high-frequency radio frequency power during the deposition process is 50~100W, and the low-frequency radio frequency power is 50~100W.

[0035] In this embodiment, in step S100, N-rich SiN is first deposited using plasma-enhanced chemical vapor deposition (PECVD) with in-situ ammonia (NH3) / hydrogen (H2) plasma treatment to obtain a first barrier layer. The thickness of the first barrier layer is 3~10 nm. Silane (SiH4) and ammonia (NH3) are used as the reaction gas sources, and nitrogen (N2) or N2 / helium (He) is used as the ambient gas to control the chamber pressure. The flow rates of SiH4, NH3, N2, and He are 20~50 sccm, 100~300 sccm, 10000~30000 sccm, and 5000~30000 sccm, respectively. The deposition temperature is 350~450 ℃, the deposition pressure is 0.5~5 Torr, the high-frequency RF power is 50~100 W, and the low-frequency RF power is 50~100 W.

[0036] In this embodiment, in step S200, a second barrier layer is formed on the side of the first barrier layer away from the metal interconnect structure. The second barrier layer is a carbon-rich barrier layer, which includes: using tetramethylsilane and ammonia as precursors, a carbon-rich silicon-carbon-nitrogen-hydrogen layer is deposited by plasma-enhanced chemical vapor deposition to obtain the second barrier layer; wherein, the high-frequency radio frequency power during the deposition process is 50~150W.

[0037] In this embodiment, in step S200, C-rich SiCNH is deposited using tetramethylsilane (4MS[Si(CH3)4]) and NH3 as precursors via PECVD to obtain a second barrier layer. A relatively low high-frequency radio frequency power (50-150 W) is used to prevent over-dissociation of 4MS, thus maintaining a high methyl content in the SiCNH film and reducing its dielectric constant. Optionally, the dielectric constant of the SiCNH layer is reduced to 3-4. The thickness of the second barrier layer is 15-50 nm. The flow rates of the reactant gases 4MS[Si(CH3)4], NH3, and N2 are 50-200 sccm, 50-300 sccm, and 4000-20000 sccm, respectively. The deposition temperature is 330-380°C, and the deposition pressure is 1-5 Torr. By employing this process, a carbon-rich SiCNH layer with a dielectric constant between 3 and 4 is obtained.

[0038] In this embodiment, in step S300, a third barrier layer is formed on the side of the second barrier layer away from the first barrier layer. The third barrier layer is a nitride barrier layer to block the diffusion of oxygen atoms in the barrier structure. This includes: using silane and ammonia as precursors, a stoichiometric silicon nitride layer is deposited by plasma-enhanced chemical vapor deposition to obtain the third barrier layer; wherein the high-frequency radio frequency power during the deposition process is 300~600W.

[0039] In this embodiment, in step S300, using SiH4 and NH3 as precursors, a Si3N4 top layer conforming to the stoichiometric ratio is deposited using PECVD to obtain the third barrier layer. The excellent stoichiometric ratio of SiN results in a lower defect density, effectively preventing material deformation after ultraviolet irradiation and thus reducing the film reliability of the third barrier layer. The thickness of the third barrier layer is 3–10 nm. The fluxes of SiH4, NH3, and N2 are 20–100 sccm, 150–400 sccm, and 10000–3000 sccm, respectively. The deposition temperature is 400 °C, the deposition pressure is 3–8 Torr, and single-frequency high-frequency radio frequency deposition with a power of 300–600 W is used to improve the material's crystallinity.

[0040] By employing this method for fabricating the barrier structure, a novel sandwich-structured barrier structure can be obtained to block the diffusion of metal interconnect structures. Using a high-carbon-content SiCNH layer as the intermediate layer reduces the dielectric constant of the barrier layer, thereby decreasing RC delay. Using a high-nitrogen-content SiN layer with high step coverage as the bottom layer enhances the barrier structure's ability to block metals (such as Cu) and reduces SiNCH / Cu interface defects, extending electromigration lifetime. Using Si3N4 with excellent stoichiometry as the top layer increases the SiN / SiCOH interfacial adhesion, improves the overall stress properties of the barrier layer, and prevents film peeling.

[0041] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of this application and should not be construed as limiting the specific implementation of this application to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of this application, and all such modifications or substitutions should be considered within the scope of protection of this application.

Claims

1. A blocking structure, characterized in that, A diffusion barrier for a metal interconnect structure, the barrier structure comprising: A first barrier layer, which is a nitrogen-rich barrier layer, is used to block metal diffusion in the metal interconnect structure. A second barrier layer is located on one side of the first barrier layer. The second barrier layer is a carbon-rich barrier layer to reduce the dielectric constant of the barrier structure. A third barrier layer is located on the side of the second barrier layer opposite to the first barrier layer. The third barrier layer is a nitride barrier layer to prevent oxygen atoms from diffusing in the barrier structure.

2. The blocking structure according to claim 1, characterized in that, The first barrier layer is a nitrogen-rich silicon nitride layer, the second barrier layer is a carbon-rich silicon-carbon-nitrogen-hydrogen layer, and the third barrier layer is a silicon nitride layer conforming to stoichiometry.

3. The blocking structure according to claim 1, characterized in that, The thickness of the first barrier layer is 3~10nm, the thickness of the second barrier layer is 15~50nm, and the thickness of the third barrier layer is 3~10nm.

4. The blocking structure according to claim 1, characterized in that, The dielectric constant of the first barrier layer is 6 to 6.6, the dielectric constant of the second barrier layer is 3 to 3.5, and the dielectric constant of the third barrier layer is 6.8 to 7.

2.

5. The blocking structure according to claim 1, characterized in that, The blocking structure satisfies the following condition: the sum of the product of the dielectric constant and thickness of the first blocking layer, the product of the dielectric constant and thickness of the second blocking layer, and the product of the dielectric constant and thickness of the third blocking layer is less than the product of a preset dielectric constant threshold and the thickness of the blocking structure.

6. A method for preparing a barrier structure, characterized in that, The method for preparing the barrier structure according to any one of claims 1 to 5 comprises the following steps: A first barrier layer is formed on the surface of the metal interconnect structure. The first barrier layer is a nitrogen-rich barrier layer to block metal diffusion in the metal interconnect structure. A second barrier layer is formed on the side of the first barrier layer away from the metal interconnect structure. The second barrier layer is a carbon-rich barrier layer to reduce the dielectric constant of the barrier structure. A third barrier layer is formed on the side of the second barrier layer opposite to the first barrier layer. The third barrier layer is a nitride barrier layer to prevent oxygen atoms from diffusing in the barrier structure.

7. The method for preparing the barrier structure according to claim 6, characterized in that, A first barrier layer is formed on the surface of the metal interconnect structure. The first barrier layer is a nitrogen-rich barrier layer, which includes: depositing a nitrogen-rich silicon nitride layer using a plasma-enhanced chemical vapor deposition method with in-situ ammonia / hydrogen plasma treatment to obtain the first barrier layer; wherein the high-frequency radio frequency power during the deposition process is 50~100W and the low-frequency radio frequency power is 50~100W.

8. The method for preparing the barrier structure according to claim 6, characterized in that, A second barrier layer is formed on the side of the first barrier layer opposite to the metal interconnect structure. The second barrier layer is a carbon-rich barrier layer, comprising: depositing a carbon-rich silicon-carbon-nitrogen-hydrogen layer using tetramethylsilane and ammonia as precursors by plasma-enhanced chemical vapor deposition to obtain the second barrier layer; wherein the high-frequency radio frequency power during the deposition process is 50~150W.

9. The method for preparing the barrier structure according to claim 6, characterized in that, A third barrier layer is formed on the side of the second barrier layer away from the first barrier layer. The third barrier layer is a nitride barrier layer, comprising: depositing a stoichiometric silicon nitride layer using silane and ammonia as precursors and employing plasma-enhanced chemical vapor deposition to obtain the third barrier layer; wherein the high-frequency radio frequency power during the deposition process is 300~600W.

10. An interconnection structure, characterized in that, include: Metal interconnect structure; The barrier structure as described in any one of claims 1 to 5, wherein the first barrier layer, the second barrier layer, and the third barrier layer are sequentially stacked on the surface of the metal interconnect structure.

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