阅读说明：本技术 半导体结构及其形成方法 (Semiconductor structure and forming method thereof ) 是由 王楠 于 2018-06-04 设计创作，主要内容包括：公开了一种半导体结构及其形成方法,所述方法包括：提供半导体衬底；通过刻蚀半导体衬底上第二介质层露出所述第一介质层,然后在其上形成阻挡层和第三介质层；通过刻蚀源/漏区上方形成多个露出源/漏区的第一凹槽；刻蚀所述第一凹槽相邻区域形成露出所述金属栅极结构的第二凹槽,分别在所述第一凹槽和第二凹槽中形成第一导电结构和第二导电结构。本发明实施例通过增加阻挡层限制形成金属栅极结构上导电结构(M0G)的第二凹槽的深度,可以使得源极/漏极与栅极结构上导电结构之间的侧壁结构的厚度可控,避免了源极/漏极与栅极结构上导电结构形成短路,由此可以改善半导体结构的电学性能和良率。(Disclosed are a semiconductor structure and a method of forming the same, the method comprising: providing a semiconductor substrate; exposing the first dielectric layer by etching the second dielectric layer on the semiconductor substrate, and then forming a barrier layer and a third dielectric layer on the first dielectric layer; forming a plurality of first grooves exposing the source/drain regions by etching the upper side of the source/drain regions; and etching the adjacent area of the first groove to form a second groove exposing the metal gate structure, and respectively forming a first conductive structure and a second conductive structure in the first groove and the second groove. According to the embodiment of the invention, the depth of the second groove of the conductive structure (M0G) on the metal gate structure is limited by the barrier layer, so that the thickness of the side wall structure between the source/drain electrode and the conductive structure on the gate structure can be controlled, the short circuit between the source/drain electrode and the conductive structure on the gate structure is avoided, and the electrical performance and the yield of the semiconductor structure can be improved.)

1. a method of forming a semiconductor structure, comprising:

Providing a semiconductor substrate, wherein a plurality of fin structures, a metal gate structure crossing the fin structures, a first dielectric layer covering the metal gate structure and a second dielectric layer covering the first dielectric layer and the fin structures are formed on the semiconductor substrate;

Etching the second dielectric layer with a preset thickness to expose the first dielectric layer;

Forming a blocking layer to cover the region outside the exposed first dielectric layer;

Forming a third dielectric layer to cover the first dielectric layer and the barrier layer;

Etching the third dielectric layer, the barrier layer and the second dielectric layer above the source/drain region to form a plurality of first grooves exposing the source/drain region;

etching the third dielectric layer of the adjacent area of the first groove until the barrier layer and at least part of the first dielectric layer to form a second groove exposing the metal gate structure, wherein the second groove is isolated from the first groove through a side wall formed by the third dielectric layer;

forming a first conductive structure and a second conductive structure in the first groove and the second groove, respectively.

2. The method of claim 1, wherein the predetermined thickness is set such that a top of the etched second dielectric layer is lower than a top of the metal gate structure.

3. the method of claim 1, wherein the thickness of the barrier layer is set such that the top of the barrier layer is aligned with the top of the first dielectric layer.

4. The method of claim 1, wherein an etch rate of a material of the barrier layer is less than an etch rate of a material of the first, second, and third dielectric layers.

5. The method of claim 4, wherein the material of the second dielectric layer and the third dielectric layer is an oxide for forming a shallow trench isolation structure;

The material of the barrier layer comprises one or more of SiON, SiCO and TiO ₂.

6. The method of claim 1, wherein the source/drain region comprises an epitaxial structure formed on top of a fin structure.

7. the method of claim 1, wherein the metal gate structure is a high-K metal gate stack structure (HKMG).

8. The method of claim 1, wherein the semiconductor structure is a Static Random Access Memory (SRAM), wherein the first conductive structure is used to form a source or a drain of a FinFET, and wherein the second conductive structure is used to form a conductive line connecting to a metal gate structure.

9. A semiconductor structure, comprising:

A fin structure;

a metal gate structure spanning the fin structure;

The first conductive structure covers the source/drain region above the fin structure;

A second conductive structure adjacent to at least one of the first conductive structures and connected to the metal gate structure;

The barrier layer is positioned below the first conductive structure and the side wall structure;

the first dielectric layer covers a part of the metal gate structure;

The second dielectric layer is positioned below the barrier layer and used for isolating different first conductive structures; and

And the third dielectric layer is positioned above the barrier layer and forms the side wall structure for isolating the first conductive structure from the second conductive structure.

10. The semiconductor structure of claim 9, wherein a top of the second dielectric layer is lower than a top of the metal gate structure.

11. The semiconductor structure of claim 9, wherein a top of the barrier layer is aligned with a top of the first dielectric layer.

12. The semiconductor structure of claim 9, wherein an etch rate of a material of the barrier layer is less than an etch rate of a material of the first, second, and third dielectric layers.

13. The semiconductor structure of claim 12, wherein the material of the second dielectric layer and the third dielectric layer is an oxide for forming a shallow trench isolation structure;

the material of the barrier layer comprises one or more of SiON, SiCO and TiO ₂.

14. the semiconductor structure of claim 9, wherein the source/drain region comprises an epitaxial structure formed on an upper portion of a fin structure.

15. The semiconductor structure of claim 9, wherein the metal gate structure is a high-K value metal gate stack structure (HKMG).

16. The semiconductor structure of claim 9, wherein the semiconductor structure is a Static Random Access Memory (SRAM), wherein the first conductive structure is configured to form a source or a drain of a finfet, and wherein the second conductive structure is configured to form a conductive line connected to a metal gate structure.

Technical Field

The present invention relates to the field of semiconductors, and more particularly, to a semiconductor structure and a method for forming the same.

Background

With the development of information technology, the amount of stored information has increased dramatically. The increase in the amount of stored information has promoted the rapid development of memories, and also has made higher demands on the stability of memories.

A Memory cell of a Static Random Access Memory (SRAM) may be formed by four transistors (4T structure) or six transistors (6T structure), and the Memory cell of the 4T structure or the 6T structure includes: a pull-down transistor and a pass transistor. The pull-down transistor is used for storing data, and the transmission transistor is used for reading and writing data.

In order to obtain sufficient anti-interference capability and read stability, a Fin-Field-Effect Transistor (FinFET) is often used as a Transistor for forming a memory. In a FinFET transistor, the gate is a 3D structure covering three surfaces of the fin structure, which can greatly improve circuit control. The application of the FinFET transistor in the memory can improve the data storage stability and the integration level of the memory.

However, in the conventional transistor in the memory, the depth of the groove for forming the metal layer (M0G) is not well controlled during photolithography, and the thickness of the dielectric layer between the drain/source and the conductive structure connected to the gate is easily too small by etching, so that the drain/source and the gate are easily short-circuited, thereby affecting the performance and yield of the semiconductor structure.

Disclosure of Invention

Accordingly, the present invention provides a semiconductor structure and a method for forming the same, which can prevent a short circuit between a source/drain and a conductive structure on a gate, thereby optimizing the electrical performance of the semiconductor structure and increasing the yield.

In a first aspect, a method for forming a semiconductor structure is provided, including:

providing a semiconductor substrate, wherein a plurality of fin structures, a metal gate structure crossing the fin structures, a first dielectric layer covering the metal gate structure and a second dielectric layer covering the first dielectric layer and the fin structures are formed on the semiconductor substrate;

Etching the second dielectric layer with a preset thickness to expose the first dielectric layer;

Forming a blocking layer to cover the region outside the exposed first dielectric layer;

Forming a third dielectric layer to cover the first dielectric layer and the barrier layer;

Etching the third dielectric layer, the barrier layer and the second dielectric layer above the source/drain region to form a plurality of first grooves exposing the source/drain region;

Etching the third dielectric layer of the adjacent area of the first groove until the barrier layer and at least part of the first dielectric layer to form a second groove exposing the metal gate structure, wherein the second groove is isolated from the first groove through a side wall formed by the third dielectric layer;

Forming a first conductive structure and a second conductive structure in the first groove and the second groove, respectively.

Preferably, the predetermined thickness is set such that the top of the etched second dielectric layer is lower than the top of the metal gate structure.

Preferably, the thickness of the barrier layer is set such that the top of the barrier layer is aligned with the top of the first dielectric layer.

Preferably, the etching rate of the material of the barrier layer is smaller than the etching rates of the materials of the first dielectric layer, the second dielectric layer and the third dielectric layer.

Preferably, the second dielectric layer and the third dielectric layer are made of an oxide for forming a shallow trench isolation structure;

The material of the barrier layer comprises one or more of SiON, SiCO and TiO ₂.

Preferably, the source/drain region includes an epitaxial structure formed on an upper portion of the fin structure.

Preferably, the metal gate structure is a high-K value metal gate stack structure (HKMG).

Preferably, the semiconductor structure is a Static Random Access Memory (SRAM), the first conductive structure is used for forming a source electrode or a drain electrode of a fin field effect transistor, and the second conductive structure is used for forming a lead wire connected with a metal gate structure.

In a second aspect, a semiconductor structure is provided, comprising:

A fin structure;

a metal gate structure spanning the fin structure;

the first conductive structure covers the source/drain region above the fin structure;

A second conductive structure adjacent to at least one of the first conductive structures and connected to the metal gate structure;

The barrier layer is positioned below the first conductive structure and the side wall structure;

the first dielectric layer covers a part of the metal gate structure;

the second dielectric layer is positioned below the barrier layer and used for isolating different first conductive structures; and

And the third dielectric layer is positioned above the barrier layer and forms the side wall structure for isolating the first conductive structure from the second conductive structure.

preferably, the top of the second dielectric layer is lower than the top of the metal gate structure.

Preferably, the top of the barrier layer is aligned with the top of the first dielectric layer.

Preferably, the etching rate of the material of the barrier layer is smaller than the etching rates of the materials of the first dielectric layer, the second dielectric layer and the third dielectric layer.

Preferably, the second dielectric layer and the third dielectric layer are made of an oxide for forming a shallow trench isolation structure;

The material of the barrier layer comprises one or more of SiON, SiCO and TiO ₂.

Preferably, the source/drain region includes an epitaxial structure formed on an upper portion of the fin structure.

Preferably, the metal gate structure is a high-K value metal gate stack structure (HKMG).

Preferably, the semiconductor structure is a Static Random Access Memory (SRAM), the first conductive structure is used for forming a source electrode or a drain electrode of a fin field effect transistor, and the second conductive structure is used for forming a lead wire connected with a metal gate structure.

According to the embodiment of the invention, the depth of the second groove of the conductive structure (M0G) on the metal gate structure is limited by the barrier layer, so that the thickness of the side wall structure between the source/drain electrode and the conductive structure on the gate structure can be controlled, the short circuit between the source/drain electrode and the conductive structure on the gate structure is avoided, and the electrical performance and the yield of the semiconductor structure can be improved.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a planar structure of a static random access memory;

FIG. 2 is a schematic circuit diagram of a static random access memory;

FIG. 3 is a schematic cross-sectional view of a semiconductor structure after forming a metal gate structure;

FIGS. 4-6 are schematic structural diagrams corresponding to steps of a forming process of a groove for depositing a metal layer on a gate in the prior art;

FIG. 7 is a flow chart of a method of forming a semiconductor structure of an embodiment of the present invention;

FIGS. 8-12 are schematic structural diagrams corresponding to steps in a process of forming a recess for depositing a metal layer on a gate according to an embodiment of the present invention;

Fig. 13 is a schematic structural diagram of a semiconductor structure according to an embodiment of the invention.

Detailed Description

the present invention will be described below based on examples, but the present invention is not limited to only these examples.

in the following detailed description of the present invention, certain specific details are set forth. It will be apparent to one skilled in the art that the present invention may be practiced without these specific details. Well-known methods, procedures, components and circuits have not been described in detail so as not to obscure the present invention. Further, those of ordinary skill in the art will appreciate that the drawings provided herein are for illustrative purposes and are not necessarily drawn to scale.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, what is meant is "including, but not limited to". In the description of the present invention, "a plurality" means two or more unless otherwise specified.

it will be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it can be directly on, adjacent to, connected or coupled to the other elements or layers or intervening elements or layers may be present. In contrast, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to" or "directly coupled to" other elements or layers, there are no intervening elements or layers present.

Spatial relationship terms such as "below …", "below", "lower", "above …", "above", and the like may be used herein for ease of description to describe the relationship of one element or feature to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below" can encompass both an orientation of above and below. The device may assume other orientations (rotated 90 degrees or at other orientations) and the spatial relationship descriptors used herein interpreted accordingly.

FIG. 1 is a schematic plan view of a SRAM. A static random access memory cell includes a plurality of fin field effect transistors (finfets). The plurality of fin field effect transistors include a Pull-Up (PU) transistor, a Pull-Down (PD) transistor, and a Pass (PG) transistor, wherein the Pull-Up transistor is typically a PMOS transistor, and the Pull-Down transistor and the pass transistor are typically NMOS transistors. The fin field effect transistors respectively comprise a semiconductor substrate 100, a fin structure 101, a metal gate structure 200, a source region 210, a drain region 220 and a second conductive structure 230. Fig. 2 is a schematic circuit diagram corresponding to the sram structure shown in fig. 1. As shown in fig. 2, one sram cell may be formed of 6 finfet transistors. In the channel transistors on both sides of the circuit, the gates of the channel transistors need to be led out to Word Lines (WL) through wires. Correspondingly, in the planar structure, the gate is drawn to the word line by providing a second conductive structure 230 (which may also be referred to as a metal-on-gate layer) electrically connected to the metal gate structure 200.

Fig. 3 is a cross-sectional view of a semiconductor structure after a metal gate structure is formed during the fabrication of the sram shown in fig. 1 according to the prior art. As shown in fig. 3, the semiconductor structure includes a semiconductor substrate 100, a fin structure 101, a metal gate structure 200, a source region 210, a drain region 220, a first dielectric layer 300, and a second dielectric layer 400. A plurality of fin structures 101 are formed on the semiconductor substrate 100. The forming process of the fin structure 101 includes: forming a mask layer on a part of the surface of the semiconductor substrate 100, wherein the mask layer covers a position of a corresponding area where the fin structure 101 is required to be formed; and etching the semiconductor substrate 100 by taking the mask layer as a mask to form the fin structure 101.

The forming of the mask layer includes: forming a mask material film on the surface of the semiconductor substrate 100; forming a patterned layer on the surface of the mask material film; and etching the mask material film by taking the patterning layer as a mask until the surface of the semiconductor substrate 100 is exposed to form a mask layer. The patterning layer is a patterned photoresist layer and can also be titanium nitride or tantalum nitride, and the patterning layer is formed by a coating process and a photoetching process. The process of etching the semiconductor substrate 100 is an anisotropic dry etching process. In this embodiment, the semiconductor substrate 100 may be a silicon substrate, a germanium substrate, a silicon carbide substrate, a silicon-on-insulator substrate, a germanium-on-insulator substrate, a glass substrate, or the like.

the metal gate structure 200 spans the fin structure 101, covering the sidewalls and top of the fin structure 101. The metal gate structure 200 includes a gate dielectric layer 201 and a gate 202 on the gate dielectric layer 201. Preferably, the gate dielectric layer 201 may be a stacked structure of a gate oxide layer and a high-K dielectric layer. The gate oxide layer is used to reduce the interface state density between the high-K dielectric layer and the fin structure 101. The high-K dielectric layer can reduce the leakage current and impurity diffusion of the transistor and improve the integration level of the semiconductor device. A work function layer 203 may be further disposed between the gate 202 and the gate dielectric layer 201. It should be understood that the metal gate structure 200 may be implemented using any conventional fabrication process and structure suitable for finfet devices.

In this embodiment, a source region 210 and a drain region 220 are formed on the sidewalls and the top of the fin structure 101 at two sides of the metal gate structure 200. The schematic cross-sectional structure of the source region 210 and the drain region 220 is shown in fig. 3, in the a-a direction, the source region 210 and the drain region 220 are polygonal structures and are located at the top of the fin structure 101; in the direction B-B, the source region 210 and the drain region 220 are partially located on the sidewall of the same fin structure 101, and partially located on the top of the fin structure 101, and the source region 210 and the drain region 220 are respectively located at two sides of the metal gate structure 200. In this embodiment, the source region 210 and the drain region 220 shown in the a-a direction belong to different transistors (i.e., the source region 210 and the drain region 220 located on different fin structures 101), while the source region 210 and the drain region 220 shown in the B-B direction belong to the same transistor. It is to be understood that the source region 210 and the drain region 220 may be formed by any conventional manufacturing process and structure suitable for fin field effect transistors, for example, by epitaxially growing a silicon germanium layer at the source/drain regions of the fin structure 101 and doping to form the source region 210 and the drain region 220. In the present application, the source/drain region refers to a source region or a drain region.

a first dielectric layer 300 and a second dielectric layer 400 are further disposed on the surfaces of the metal gate structure 200, the source region 210 and the drain region 220, and the first dielectric layer 300 covers the metal gate structure 200, the source region 210 and the drain region 220. A second dielectric layer 400 covers the outside of the first level 300. The second dielectric layer 400 is later used to isolate different first conductive structures. In this embodiment, the material of the second dielectric layer 400 is an oxide, such as silicon oxide, used for forming a Shallow Trench Isolation (STI) structure.

The second dielectric layer 400 is formed by the steps of: forming dielectric films on the surfaces of the first dielectric layer 300 and the semiconductor substrate 100; the dielectric film is planarized to form a second dielectric layer 400. The second dielectric layer 400 may be formed by a Fluid Chemical Vapor Deposition (FCVD), a Plasma Enhanced Chemical Vapor Deposition (PECVD), a high aspect ratio Chemical Vapor Deposition (HARP), or a physical Vapor Deposition (pvd).

Fig. 4-6 are schematic structural diagrams corresponding to steps of a forming process of a groove for depositing a metal layer on a gate in the prior art.

Referring to fig. 4 and 5, after the semiconductor structure shown in fig. 3 is formed, a patterned metal layer 410(M0C) is formed on the surface of the second dielectric layer 400 (see fig. 4). The metal layer 410 blocks an area where the second groove is to be formed later and a sidewall separating the first groove and the second groove. And etching the second dielectric layer 400 above the source/drain region by using the metal layer 410 as a mask, and forming first grooves 211 (see fig. 5) corresponding to the source/drain region on two sides of the metal layer 410. The first recess 211 is used for subsequent filling of a metal layer to form a first conductive structure (M0, not shown). Finally, the metal layer 410 is removed as a mask. The etching process can adopt an isotropic dry etching process or an anisotropic dry etching process.

Then, referring to fig. 6, the second dielectric layer 400 and at least a portion of the first dielectric layer 300 in a region between two adjacent first recesses 211 (i.e., in a region adjacent to the first recesses 211) are etched to form a second recess 213 exposing the metal gate structure 200.

Subsequently, a first conductive structure and a second conductive structure are formed in the first groove 211 and the second groove 213, the first conductive structure may serve as a source/drain (M0), and the second conductive structure may serve as a metal layer on the gate (M0G). As can be seen from the cross-sectional view along the direction a-a in fig. 6, the first conductive structure and the second conductive structure are isolated from each other only by the sidewall between the first recess 211 and the second recess 213.

²during etching, if the distance between the metal layer on the gate (filled in the second groove 213) and the metal layer on the source or drain (filled in the first groove 211) in the layout is too small, the requirement on the accuracy of the etching depth is extremely high, and the thicknesses of the sidewalls of the metal gate structure 200 and the source/drain regions are very easy to be too small, which causes a short circuit and affects the electrical performance and yield of the product.

Fig. 7 is a flow chart of a method of forming a semiconductor structure of an embodiment of the present invention. The method further forms a source/drain conductive structure and a conductive structure on the gate based on the semiconductor structure formed with the metal gate structure shown in fig. 3. As shown in fig. 7, the method includes:

step S100, providing a semiconductor substrate.

Providing a semiconductor substrate 100, as shown in fig. 3, forming a plurality of fin structures 101, a metal gate structure 200 crossing over the fin structures 101, a first dielectric layer 300 covering the metal gate structure 200, and a second dielectric layer 400 covering the first dielectric layer 300 and the fin structures 101 on the semiconductor substrate 100.

The forming process of the fin structure 101 includes: forming a mask layer on a part of the surface of the semiconductor substrate 100, wherein the mask layer covers a position of a corresponding area where the fin structure 101 is required to be formed; and etching the semiconductor substrate 100 by taking the mask layer as a mask to form the fin structure 101.

the metal gate structure 200 spans the fin structure 101, covering the sidewalls and top of the fin structure 101. The metal gate structure 200 is a high-K metal gate stack structure (HKMG). It should be understood that the metal gate structure 200 may be implemented using any conventional fabrication process and structure suitable for finfet devices.

In this embodiment, a source region 210 and a drain region 220 are formed on the sidewalls and the top of the fin structure 101 at two sides of the metal gate structure 200. The cross-sectional structure of the source region 210 and the drain region 220 is schematically illustrated in fig. 3, and the source/drain region includes an epitaxial structure formed on the upper portion of the fin structure 101. In this embodiment, the source region 210 and the drain region 220 shown in the a-a direction belong to different transistors (i.e., the source region 210 and the drain region 220 located on different fin structures 101), while the source region 210 and the drain region 220 shown in the B-B direction belong to the same transistor. It is understood that the source region 210 and the drain region 220 may be formed using any conventional fabrication process and structure suitable for fin field effect transistors.

A first dielectric layer 300 and a second dielectric layer 400 are further disposed on the surfaces of the metal gate structure 200, the source region 210 and the drain region 220, and the first dielectric layer 300 covers the metal gate structure 200, the source region 210 and the drain region 220. A second dielectric layer 400 covers the outside of the first level 300. The second dielectric layer 400 is used to isolate the different sources and drains at a later stage. The second dielectric layer 400 is formed using an oxide for forming a shallow trench isolation structure.

the second dielectric layer 400 is formed by the steps of: forming dielectric films on the surfaces of the first dielectric layer 300 and the semiconductor substrate 100; and flattening the dielectric film to form a second dielectric layer 400. The planarization may employ Chemical Mechanical Polishing (CMP). In this embodiment, the second dielectric layer 400 may be formed by a Fluid Chemical Vapor Deposition (FCVD), a Plasma Enhanced Chemical Vapor Deposition (PECVD), a high aspect ratio Chemical Vapor Deposition (HARP), a physical Vapor Deposition (pvd), or the like.

step S200, etching the second dielectric layer with a preset thickness to expose the first dielectric layer.

Referring to fig. 8, the second dielectric layer 400 is etched to a predetermined thickness so that the top and a portion of the sidewalls of the first dielectric layer 300 are exposed after etching. The predetermined thickness is set such that the top of the etched second dielectric layer 400 is lower than the top of the metal gate structure 200. The etching process can adopt an isotropic dry etching process, an anisotropic dry etching process or a wet etching process.

Step 300, forming a blocking layer to cover the region outside the exposed first dielectric layer.

referring to fig. 9, a barrier layer 500 is formed on top of the second dielectric layer 400 of the structure shown in fig. 8, covering the region except the top of the exposed first dielectric layer 300, wherein the top of the barrier layer 500 is flush with the top of the first dielectric layer 300, the material of the barrier layer 500 may include one or more of SiON, SiCO, and TiO ₂, the barrier layer 500 serves as an etch stop layer when a metal layer on a gate is formed in the second dielectric layer 400, the etch rate of the material of the barrier layer 500 is less than the etch rate of the material of the first dielectric layer 300, the second dielectric layer 400, and the third dielectric layer 600, so that the lower dielectric layer may be protected during the etching process of removing the upper third dielectric layer 600 and a portion of the first dielectric layer 300, thereby controlling the depth of the second recess 213, and the depth of the second recess 213 may be controlled, thereby forming a more stable sidewall structure.

the barrier layer 500 may be formed on the surfaces of the second dielectric layer 400 and the first dielectric layer 300 by a coating process (e.g., a spin-on process or a spray-on process) or a chemical vapor deposition process, and then the barrier layer 500 is planarized until the top of the barrier layer 500 is flush with the top of the first dielectric layer 300. The planarization process may employ a chemical mechanical polishing process (CMP).

Step S400, forming a third dielectric layer to cover the first dielectric layer and the barrier layer.

referring to fig. 10, a third dielectric layer 600 is formed on top of the barrier layer 500 and over the top of the first dielectric layer 300, the third dielectric layer 600 covering the first dielectric layer 300 and the barrier layer 500. The third dielectric layer 600 may be formed by a fluid Chemical Vapor Deposition process (FCVD), a plasma enhanced Chemical Vapor Deposition Process (PECVD), a high aspect ratio Chemical Vapor Deposition process (HARP), or a physical Vapor Deposition process. The material of the third dielectric layer 600 may be an oxide, such as silicon oxide, which forms a shallow trench isolation structure.

Step S500, etching the third dielectric layer, the barrier layer and the second dielectric layer above the source/drain region to form a plurality of first grooves exposing the source/drain region.

Referring to fig. 11, the third dielectric layer 600, the barrier layer 500 and the second dielectric layer 400 over the source/drain regions are etched to form a plurality of first recesses 211 exposing the source/drain regions. The etching process comprises the following steps: forming a metal layer 610 serving as a mask on a part of the surface of the third dielectric layer 600, wherein the metal layer 610 covers the metal gate structure 200, etching the third dielectric layer 600, the barrier layer 500 and the second dielectric layer 400 by using the metal layer 610 as the mask to form a first groove 211, and then removing the hard metal layer 610.

Step S600, etching the third dielectric layer of the adjacent area of the first groove until the barrier layer and at least part of the first dielectric layer to form a second groove exposing the metal gate structure.

referring to fig. 12, the third dielectric layer 600 adjacent to the first recess 211 is etched until the barrier layer 500 and at least a portion of the first dielectric layer 300 form a second recess 213 exposing the metal gate structure 200. The etch depth is set to be flush with the bottom layer of the barrier layer 500.

As shown in fig. 12, after the etching is completed, a second groove 213 is formed in a cross section in the a-a direction in parallel with the first groove 211. On the cross section in the B-B direction, the first dielectric layer 300 in the area of the second recess 213 not covered by the barrier layer 500 is etched to expose the metal gate structure 200 covered thereby. While the second dielectric layer 400 under the barrier layer 500 is not etched. Therefore, during etching, due to the low etching rate of the barrier layer 500, the etching depth can be accurately controlled, and short circuit caused by the fact that the thicknesses of the side walls of the metal gate structure 200 and the source/drain region and the second dielectric layer 400 are reduced after etching is avoided. A second conductive structure is formed in the second groove 213. The second conductive structure is used to form a conductive line connecting the metal gate structure 200.

in this embodiment, the second groove 213 may be formed by anisotropic dry etching, and the etching gas may be HBr, Cl2, He, and O2, and does not contain fluorine-based gas. Before the dry etching is performed, a mask layer needs to be formed, and as an example, the mask layer may be a buffer layer and a stress material layer which are stacked from bottom to top, wherein the buffer layer may be an oxide layer or a silicon oxynitride layer, and the stress material layer may be a silicon nitride layer with tensile stress; next, the second groove 213 is pretreated to ensure that the sidewalls and the bottom of the second groove 213 have clean surfaces. The pretreatment comprises the following steps: firstly, performing wet cleaning to remove etching residues and impurities remained on the side wall and the bottom of the second groove; then, a baking process is performed.

step S700, forming a first conductive structure and a second conductive structure in the first groove and the second groove, respectively.

A first conductive structure and a second conductive structure are formed in the first groove 211 and the second groove 213, respectively. The first conductive structure is used for forming a source electrode or a drain electrode of the fin field effect transistor, and the second conductive structure is used for forming a lead connected with the metal gate structure. The first conductive structure and the second conductive structure may be formed by any conventional manufacturing process and structure suitable for fin field effect transistors.

According to the semiconductor structure provided by the embodiment of the invention, the barrier layer is added to limit the depth of the second groove of the conductive structure (M0G) formed on the metal gate structure, so that the thickness of the side wall structure between the source/drain and the conductive structure on the gate structure can be controlled, the short circuit between the source/drain and the conductive structure on the gate structure is avoided, and the electrical performance and the yield of the semiconductor structure can be improved.

fig. 13 is a schematic structural diagram of a semiconductor structure according to an embodiment of the invention. As shown in fig. 13, the semiconductor structure of the present embodiment includes a fin structure 101, a metal gate structure 200, a first conductive structure 700, a second conductive structure 800, a barrier layer 500, a first dielectric layer 300, a second dielectric layer 400, and a third dielectric layer 600. Wherein fin structures 101 are formed on a semiconductor substrate 100. The metal gate structure 200 spans the fin structure 101, covering the top and sides of the fin structure 101. The first conductive structure 700 covers the source region 210 or the drain region 220 above the fin structure 101 for constituting a source or a drain. The second conductive structure 800 is disposed adjacent to the at least one first conductive structure 700 and is electrically connected to the metal gate structure 200. The barrier layer 500 is located below the first conductive structure 700 and the sidewall structure 900. The first dielectric layer 300 covers a portion of the metal gate structure 200. A second dielectric layer 400 is located below the barrier layer 500 for isolating the different first conductive structures 700. A third dielectric layer 600 is located above the barrier layer 500 to form the sidewall spacer structure for isolating the first conductive structure 700 from the second conductive structure 800. In this embodiment, the top of the second dielectric layer 400 is lower than the top of the metal gate structure 200, so that the barrier layer 500 does not block the etching of the first dielectric layer 300 during the process of forming the recess for accommodating the second conductive structure 800, thereby facilitating the exposure of the metal gate structure 200.

preferably, the top of the barrier layer 500 is aligned with the top of the first dielectric layer.

₂The barrier layer 500 may thus act as an etch stop layer during the etching process to form the recess for accommodating the second conductive structure 800, preventing the etching of the underlying second dielectric layer 400 during the etching process, thereby enhancing the stability of the sidewall structure.

In this embodiment, the source/drain region includes an epitaxial structure formed on an upper portion of the fin structure. The metal gate structure is a high-K value metal gate stack structure (HKMG).

The semiconductor structure of the present embodiment is a Static Random Access Memory (SRAM), the first conductive structure 700 is used to form a source or a drain of a finfet, and the second conductive structure 800 is used to form a conductive line connected to a metal gate structure.

Therefore, in the semiconductor structure of the embodiment, the depth of the second groove for forming the conductive structure (M0G) on the metal gate structure is limited by adding the barrier layer, so that the thickness of the sidewall structure between the source/drain and the conductive structure on the gate structure can be controlled, the short circuit between the source/drain and the conductive structure on the gate structure is avoided, and the electrical performance and the yield can be improved.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.