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 纪世良 张海洋 于 2019-01-09 设计创作，主要内容包括：一种半导体结构及其形成方法,其中方法包括：提供基底,所述基底包括相邻的第一区和第二区,所述第一区和第二区沿第一方向排列,所述第一区基底表面具有若干鳍部,相邻鳍部之间具有第一开口,且在第一方向上所述第二区的尺寸大于所述第一开口的尺寸,所述若干鳍部中包括待去除鳍部；在所述鳍部侧壁形成第一介质层,且所述第一介质层填充满所述第一开口；以所述第一介质层为掩膜,刻蚀第二区的基底,在第二区基底内形成第一沟槽；形成所述第一沟槽后,去除所述待去除鳍部和位于所述待去除鳍部底部的部分基底,在第一区基底内形成第二沟槽。所述方法形成的半导体性能较好。(A semiconductor structure and a method of forming the same, wherein the method comprises: providing a substrate, wherein the substrate comprises a first area and a second area which are adjacent, the first area and the second area are arranged along a first direction, the surface of the substrate in the first area is provided with a plurality of fin parts, a first opening is arranged between the adjacent fin parts, the size of the second area in the first direction is larger than that of the first opening, and the fin parts to be removed comprise fin parts to be removed; forming a first dielectric layer on the side wall of the fin part, wherein the first dielectric layer fills the first opening; etching the substrate of the second area by taking the first dielectric layer as a mask, and forming a first groove in the substrate of the second area; and after the first groove is formed, removing the fin part to be removed and part of the substrate positioned at the bottom of the fin part to be removed, and forming a second groove in the first region substrate. The semiconductor formed by the method has better performance.)

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

providing a substrate, wherein the substrate comprises a first area and a second area which are adjacent, the first area and the second area are arranged along a first direction, the surface of the substrate in the first area is provided with a plurality of fin parts, a first opening is arranged between the adjacent fin parts, the size of the second area in the first direction is larger than that of the first opening, and the fin parts to be removed comprise fin parts to be removed;

forming a first dielectric layer on the side wall of the fin part, wherein the first dielectric layer fills the first opening;

etching the substrate of the second area by taking the first dielectric layer as a mask, and forming a first groove in the substrate of the second area;

and after the first groove is formed, removing the fin part to be removed and part of the substrate positioned at the bottom of the fin part to be removed, and forming a second groove in the first region substrate.

2. The method of forming a semiconductor structure of claim 1, wherein the method of forming the first dielectric layer comprises: forming a first dielectric film on the surface of the substrate, the top of the fin part and the side wall, wherein the first opening is filled with the first dielectric film; and etching back the first dielectric film until the surface of the second area substrate is exposed to form the first dielectric layer.

3. The method of forming a semiconductor structure of claim 2, wherein the step of back-etching the first dielectric film comprises: etching the first dielectric film by adopting a first dry etching process until the surface of the substrate in the second area is exposed; the parameters of the first dry etching process comprise: the gas used comprises CF₄、CF₆、O₂And N₂Said CF₄And CF₆The flow rate of (A) is 10 standard ml/min to 300 standard ml/min, and the O is₂The flow rate of (A) is 10 to 500 standard ml/min, N₂The flow rate of the pressure sensor is 50-1000 standard ml/min, the pressure is 3-400 mTorr, and the temperature is 30-120 ℃.

4. The method of forming a semiconductor structure of claim 3, wherein the method of etching back the first dielectric film further comprises: after the surface of the substrate in the second area is exposed, thinning the first dielectric film on the surface of the side wall of the fin part by adopting a second etching process; the second etching process is a SICONI process, and parameters of the SICONI process comprise: the gas used comprises NF₃And NH₃Said NF₃And NH₃The flow rate of the water is 100 standard milliliters/minute to 5000 standard milliliters/minute, and the temperature is 0 ℃ to 100 ℃.

5. The method of claim 2, wherein the forming of the first dielectric film comprises: and (5) an atomic layer deposition process.

6. The method of forming a semiconductor structure of claim 1, wherein a material of the first dielectric layer comprises: silicon oxide, silicon nitride, silicon carbonitride, silicon carbide, aluminum oxide, hafnium oxide, silicon oxynitride, or silicon oxycarbide.

7. The method for forming a semiconductor structure according to claim 1, wherein the step of etching the substrate of the second region using the first dielectric layer as a mask comprises: one or two of the wet etching process and the dry etching process are combined.

8. The method of forming a semiconductor structure of claim 1, wherein the method of forming the second trench comprises: forming a second dielectric layer on the surface and the side wall of the first dielectric layer and in the first groove, wherein the top surface of the second dielectric layer is higher than the top surface of the fin part; forming a first mask layer on the surface of the second dielectric layer, wherein the first mask layer exposes the surface of the second dielectric layer on the fin portion to be removed; and etching the second dielectric layer, the first dielectric layer, the fin part to be removed and the first area substrate positioned at the bottom of the fin part to be removed by taking the first mask layer as a mask, and forming a second groove in the first area substrate.

9. The method of forming a semiconductor structure of claim 8, wherein a material of the second dielectric layer comprises: an organic material.

10. The method for forming the semiconductor structure according to claim 8, wherein the step of etching the second dielectric layer, the first dielectric layer, the to-be-removed fin portion, and the first region substrate at the bottom of the to-be-removed fin portion by using the first mask layer as a mask comprises the steps of: one or two of the wet etching process and the dry etching process are combined.

11. The method of claim 1, wherein the number of fins to be removed is one or more.

12. The method of forming a semiconductor structure of claim 1, wherein the fin top further comprises: the protective layer structure comprises a first protective layer and a second protective layer, wherein the first protective layer is located on the top surface of the fin portion, and the second protective layer is located on the surface of the first protective layer.

13. The method of forming a semiconductor structure of claim 12, wherein the material of the first protective layer comprises: silicon oxide, silicon nitride, silicon carbonitride, silicon carbide, aluminum oxide, hafnium oxide, silicon oxynitride, or silicon oxycarbide; the material of the second protective layer is different from the material of the first protective layer, and the material of the second protective layer comprises: silicon oxide, silicon nitride, silicon carbonitride, silicon carbide, aluminum oxide, hafnium oxide, silicon oxynitride, or silicon oxycarbide.

14. A semiconductor structure formed by the method of any of claims 1 to 13.

Technical Field

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

Background

With the increase of integration level of semiconductor devices and the shrinking of critical dimensions of transistors, the design of three-dimensional structures such as Fin field effect transistors (Fin FETs) becomes a focus of attention in the art. A Fin field effect transistor (Fin FET) is an emerging multi-gate device, and generally has a plurality of thin fins extending vertically upward from a substrate, channels of the Fin FET are formed in the fins, a gate structure is formed on the fins, active regions and drain regions are formed in the fins on both sides of the gate structure, and adjacent fins are isolated from each other by an isolation structure.

With the continuous miniaturization of devices, in order to manufacture smaller and respectively denser fins, new technologies have appeared for manufacturing isolation structures, such as a single diffusion isolation Structure (SDB) manufacturing technology, which is generally distributed along the length direction of a fin, and by removing some regions of the fin, one or more isolation trenches are formed in the fin, and after the trenches are filled with insulating materials such as silicon dioxide, the fin can be separated into a plurality of small fins.

The manufacturing process of the single diffusion partition isolation structure and the quality of the formed structure affect the isolation performance of the single diffusion partition isolation structure, and even cause defects to surrounding fin portions and gate structures, thereby affecting the performance of the fin field effect transistor device.

Disclosure of Invention

The invention provides a semiconductor structure and a forming method thereof, which can ensure that a groove formed in a substrate with uneven fin parts has better appearance, thereby forming the semiconductor structure with better performance.

To solve the above technical problem, an embodiment of the present invention provides a method for forming a semiconductor structure, including: providing a substrate, wherein the substrate comprises a first area and a second area which are adjacent, the first area and the second area are arranged along a first direction, the surface of the substrate in the first area is provided with a plurality of fin parts, a first opening is arranged between the adjacent fin parts, the size of the second area in the first direction is larger than that of the first opening, and the fin parts to be removed comprise fin parts to be removed; forming a first dielectric layer on the side wall of the fin part, wherein the first dielectric layer fills the first opening; etching the substrate of the second area by taking the first dielectric layer as a mask, and forming a first groove in the substrate of the second area; and after the first groove is formed, removing the fin part to be removed and part of the substrate positioned at the bottom of the fin part to be removed, and forming a second groove in the first region substrate.

Optionally, the method for forming the first dielectric layer includes: forming a first dielectric film on the surface of the substrate, the top of the fin part and the side wall, wherein the first opening is filled with the first dielectric film; and etching back the first dielectric film until the surface of the second area substrate is exposed to form the first dielectric layer.

Optionally, the method for etching back the first dielectric film includes: etching the first dielectric film by adopting a first dry etching process until the surface of the substrate in the second area is exposed; the parameters of the first dry etching process comprise: the gas used comprises CF₄、CF₆、O₂And N₂Said CF₄And CF₆The flow rate of (A) is 10 standard ml/min to 300 standard ml/min, and the O is₂The flow rate of (A) is 10 to 500 standard ml/min, N₂The flow rate of the pressure sensor is 50-1000 standard ml/min, the pressure is 3-400 mTorr, and the temperature is 30-120 ℃.

Optionally, the method for etching back the first dielectric film further includes: after the surface of the substrate in the second area is exposed, thinning the first dielectric film on the surface of the side wall of the fin part by adopting a second etching process; the second etcherThe process is a SICONI process, and the parameters of the SICONI process comprise: the gas used comprises NF₃And NH₃Said NF₃And NH₃The flow rate of the water is 100 standard milliliters/minute to 5000 standard milliliters/minute, and the temperature is 0 ℃ to 100 ℃.

Optionally, the forming process of the first dielectric film includes: and (5) an atomic layer deposition process.

Optionally, the material of the first dielectric layer includes: silicon oxide, silicon nitride, silicon carbonitride, silicon carbide, aluminum oxide, hafnium oxide, silicon oxynitride, or silicon oxycarbide.

Optionally, the process for etching the substrate in the second region by using the first dielectric layer as a mask includes: one or two of the wet etching process and the dry etching process are combined.

Optionally, the forming method of the second trench includes: forming a second dielectric layer on the surface and the side wall of the first dielectric layer and in the first groove, wherein the top surface of the second dielectric layer is higher than the top surface of the fin part; forming a first mask layer on the surface of the second dielectric layer, wherein the first mask layer exposes the surface of the second dielectric layer on the fin portion to be removed; and etching the second dielectric layer, the first dielectric layer, the fin part to be removed and the first area substrate positioned at the bottom of the fin part to be removed by taking the first mask layer as a mask, and forming a second groove in the first area substrate.

Optionally, the material of the second dielectric layer includes: an organic material.

Optionally, the process for etching the second dielectric layer, the first dielectric layer, the fin portion to be removed, and the first region substrate located at the bottom of the fin portion to be removed by using the first mask layer as a mask includes: one or two of the wet etching process and the dry etching process are combined.

Optionally, the number of the fins to be removed is one or more.

Optionally, the fin top further has: the protective layer structure comprises a first protective layer and a second protective layer, wherein the first protective layer is located on the top surface of the fin portion, and the second protective layer is located on the surface of the first protective layer.

Optionally, the material of the first protective layer includes: silicon oxide, silicon nitride, silicon carbonitride, silicon carbide, aluminum oxide, hafnium oxide, silicon oxynitride, or silicon oxycarbide; the material of the second protective layer is different from the material of the first protective layer, and the material of the second protective layer comprises: silicon oxide, silicon nitride, silicon carbonitride, silicon carbide, aluminum oxide, hafnium oxide, silicon oxynitride, or silicon oxycarbide.

Correspondingly, the embodiment of the invention also provides a semiconductor structure formed by any one of the methods.

Compared with the prior art, the technical scheme of the embodiment of the invention has the following beneficial effects:

according to the forming method of the semiconductor structure, provided by the technical scheme of the invention, the first dielectric layer is used as a mask, the substrate of the second area is etched, and a first groove is formed in the substrate of the second area; and removing the fin part to be removed and part of the substrate positioned at the bottom of the fin part to be removed, and forming a second groove in the substrate in the first area. The first grooves are formed by etching the first dielectric layer positioned in the second area as a mask, and the first dielectric layer positioned in the second area is good in appearance, so that the first grooves with good appearance can be formed in the substrate of the second area by etching the substrate by using the first dielectric layer as the mask, and the performance of the semiconductor structure is improved. Meanwhile, the second groove is formed through a one-time etching process, so that the strengthening of the shape defect of the second groove caused by multiple etching processes is avoided, the shape of the second groove is better, and the performance of the semiconductor structure is improved. Through the steps, the first groove is formed in the second area substrate, and then the second groove is formed in the first area substrate, so that the first groove and the second groove are different in size along the first direction, the first groove and the second groove are good in appearance, and the formed semiconductor structure is good in performance.

Further, the process for forming the first dielectric film comprises the following steps: and (5) an atomic layer deposition process. Because the step coverage of the formed film by the atomic layer deposition process is good, the atomic layer deposition process is favorable for subsequent back etching of the first dielectric film to form a first dielectric layer with good appearance and thick thickness while ensuring that the formed first dielectric film is thick enough to fill the first opening between the fin parts of the first area, so that when the first dielectric layer is used as a mask for etching, a first groove with good appearance is favorable for being formed in the substrate of the first area, and the formed semiconductor and structure have good performance.

Drawings

FIGS. 1-4 are schematic structural diagrams illustrating steps of a method of forming a semiconductor structure;

fig. 5 to 11 are schematic structural diagrams of steps of a method for forming a semiconductor structure according to an embodiment of the invention.

Detailed Description

As described in the background, the prior art techniques have poor trench profiles formed in substrates having non-uniform fins.

Fig. 1 to 4 are schematic structural diagrams of steps of a method for forming a semiconductor structure.

Referring to fig. 1, a substrate 100 is provided, where the substrate 100 includes a first region a and a second region B adjacent to each other, the first region a and the second region B are arranged along a first direction, the surface of the substrate 100 in the first region a has a plurality of fins 110, a plurality of first openings 120 are formed between adjacent fins 110, the size of the second region B in the first direction is larger than that of the first openings 120, first dielectric layers 130 are located on the surface of the substrate 100 and on the top and sidewall surfaces of the fins 110, the first openings 120 are filled with the first dielectric layers 130, and the top surface of the first dielectric layers 130 is higher than that of the top surfaces of the fins 110;

referring to fig. 2, a first mask layer 140 is formed on the surface of the first dielectric layer 130, and the first mask layer 140 exposes a portion of the surface of the first dielectric layer 130 in the first region a; and etching the first dielectric layer 130 and the fin portion 110 by using the first mask layer 140 as a mask until the surface of the substrate 100 is exposed, and forming a second opening 150 in the first dielectric layer 130.

Referring to fig. 3, the first dielectric layer 130 and the first mask layer 140 on the surface of the first dielectric layer 130 are removed, a second dielectric film 160 is formed on the bottom surface of the second opening 150, the top and the sidewall of the fin 100, and the surface of the substrate 100, and the first opening 120 is filled with the second dielectric film 160.

Referring to fig. 4, the second dielectric film 160 is etched back until the surface of the substrate 100 is exposed, so as to form a second dielectric layer 161; and etching the substrate 100 by using the second dielectric layer 161 as a mask, forming a first groove 170 in the first region a substrate 100, and forming a second groove 180 in the second region B substrate 100.

In the above method, the first mask layer 140 is used as a mask to remove at least one fin 110 on the surface of the first region a, so as to form the second opening 150 between adjacent fins 100 in the first region a. After the second opening 150 is formed, the substrate 100 located at the bottom of the second opening 150 in the first region a and the substrate 100 in the second region B are removed by using the second dielectric layer 161 as a mask, so that a first trench 170 is formed in the substrate 100 in the first region a, the first trench 170 is located at the bottom of the second opening 150, and a second trench 180 is formed in the substrate 100 in the second region B.

However, when the first dielectric layer 130 and the fin portion 110 are etched by using the first mask layer 140 as a mask to form the second opening 150, a certain amount of material of the fin portion 110 remains on the surface of the first region a, so that the bottom of the formed second opening 150 has a poor topography. The second dielectric film 160 formed subsequently covers the bottom surface of the second opening 150, the top and the sidewalls of the fin portion 100, and the surface of the substrate 100, and when the second dielectric film 160 is etched back to form the second dielectric layer 161, the material of the second dielectric film is easily left on the bottom surface of the second opening 150 due to the influence of the material of the fin portion 110. Therefore, when the substrate 100 is etched by using the second dielectric layer 161 as a mask to form the second trench 180 in the substrate 100 in the second region B, the defects existing on the bottom surface of the second opening 150 are easily further strengthened by the second trench formed by etching, and the first trench 170 formed in the substrate 100 in the first region a has a poor morphology, which is not favorable for forming a semiconductor structure with good performance.

In order to solve the technical problem, the invention provides a method for forming a semiconductor device, which comprises the following steps: etching the substrate of the second area by taking the first dielectric layer as a mask, and forming a first groove in the substrate of the second area; and removing the fin part to be removed and part of the substrate positioned at the bottom of the fin part to be removed, and forming a second groove in the substrate in the first area. Through the steps, the first groove is formed in the second area substrate, and then the second groove is formed in the first area substrate, so that the first groove and the second groove are different in size along the first direction, the first groove and the second groove are good in appearance, and the formed semiconductor structure is good in performance.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.

Fig. 5 to 11 are schematic structural diagrams of steps of a method for forming a semiconductor structure according to an embodiment of the invention.

Referring to fig. 5, a substrate 200 is provided, where the substrate 200 includes a first region a and a second region B adjacent to each other, the first region a and the second region B are arranged along a first direction, the surface of the substrate 200 in the first region a has a plurality of fin portions 210, a first opening 220 is formed between adjacent fin portions 210, a size of the second region B in the first direction is larger than a size of the first opening 220, and the plurality of fin portions 210 include a fin portion 211 to be removed.

In this embodiment, the material of the substrate 200 is monocrystalline silicon. The substrate may also be polysilicon or amorphous silicon. The substrate can also be made of semiconductor materials such as germanium, silicon germanium or gallium arsenide. The substrate can also be a semiconductor-on-insulator structure comprising an insulator and a semiconductor material layer on the insulator, wherein the semiconductor material layer comprises a semiconductor material such as silicon, germanium, silicon germanium, gallium arsenide or indium gallium arsenide.

In the present embodiment, the material of the fin portion 210 is the same as the material of the substrate 200, that is, the material of the fin portion 210 is monocrystalline silicon.

The number of the fins 211 to be removed is one or more.

In this embodiment, the number of the fins 211 to be removed is one.

In this embodiment, the top surface of the fin 210 further has: a first passivation layer (not shown) on the top surface of fin 210 and a second passivation layer (not shown) on the surface of the first passivation layer.

The first protective layer is located on the top surface of the fin portion 210 and is used as a stop layer for a subsequent etching process.

The second protective layer is located on the surface of the first protective layer and used for protecting the first protective layer and preventing the first protective layer from being damaged in a subsequent process, so that the surface of the first protective layer is relatively flat, and the first protective layer is favorable for being used as a stop layer of an etching process.

The material of the first protective layer comprises: silicon oxide, silicon nitride, silicon carbonitride, silicon carbide, aluminum oxide, hafnium oxide, silicon oxynitride, or silicon oxycarbide.

In this embodiment, the first protection layer is made of silicon nitride.

The material of the second protective layer comprises: silicon oxide, silicon nitride, silicon carbonitride, silicon carbide, aluminum oxide, hafnium oxide, silicon oxynitride, or silicon oxycarbide; the material of the second protective layer is different from the material layer of the first protective layer.

In this embodiment, the material of the second protection layer is silicon oxide.

In this embodiment, a first dielectric layer is formed on the sidewall of the fin portion 210, and the first opening 220 is filled with the first dielectric layer, please refer to fig. 7 to 8, which describe a forming process of the first dielectric layer.

Referring to fig. 6, a first dielectric film 240 is formed on the surface of the substrate 200, the top of the fin 210 and the sidewall, and the first opening 220 is filled with the first dielectric film 240.

The first dielectric film 240 is used for forming a first dielectric layer in the following.

The material of the first dielectric film 240 includes: silicon oxide, silicon nitride, silicon carbonitride, silicon carbide, aluminum oxide, hafnium oxide, silicon oxynitride, or silicon oxycarbide.

In this embodiment, the first dielectric film 240 is made of silicon oxide, and correspondingly, the first dielectric layer formed subsequently is made of silicon oxide.

The forming process of the first dielectric film 240 comprises the following steps: a chemical vapor deposition process, a physical vapor deposition process, or an atomic layer deposition process.

The dimension of the first dielectric film 240 along the first direction is: 1 to 10 nanometers.

The dimensions of the first openings 220 between the fins 210 along the first direction are: 1 to 10 nanometers.

In this embodiment, the forming process of the first dielectric film 240 is as follows: and (5) an atomic layer deposition process. Due to the good step coverage of the film formed by the atomic layer deposition process, the atomic layer deposition process is beneficial to subsequently etching back the first dielectric film 240 to form a first dielectric layer with good appearance and thick thickness while ensuring that the formed first dielectric film 240 is thick enough to fill the first openings 220 between the fin parts 210 of the first area a, so that when the first dielectric layer is used as a mask to perform an etching process, a first groove with good appearance is beneficial to be formed in the substrate 200 of the second area B, and the formed semiconductor and the structure have good performance.

Referring to fig. 7, after the first dielectric film 240 is formed, the first dielectric film 240 is etched back until the surface of the second region B substrate 200 is exposed, so as to form the first dielectric layer 241.

The process for etching back the first dielectric film 240 comprises: wet etching process and dry etching process or SICONI process.

In this embodiment, the method for etching back the first dielectric film 240 includes: etching the first dielectric film 240 by adopting a first dry etching process until the surface of the substrate 200 in the second region B is exposed; after the surface of the substrate 200 in the second region B is exposed, the first dielectric film 240 on the sidewall surface of the fin portion 210 is thinned by using a second etching process to form the first dielectric layer 241.

The parameters of the first dry etching process comprise: the gas used comprises CF₄、CF₆、O₂And N₂Said CF₄And CF₆The flow rate of (A) is 10 standard ml/min to 300 standard ml/min, and the O is₂The flow rate of (A) is 10 to 500 standard ml/min, N₂The flow rate of the pressure sensor is 50-1000 standard ml/min, the pressure is 3-400 mTorr, and the temperature is 30-120 ℃.

In this embodiment, the second etching process is a SICONI process; the parameters of the SICONI process comprise: the gas used comprises NF₃And NH₃Said NF₃And NH₃The flow rate of the water is 100 standard milliliters/minute to 5000 standard milliliters/minute, and the temperature is 0 ℃ to 100 ℃.

The SICONI process can thin the first dielectric film 240 on the sidewall surface of the fin portion 210, so that the first dielectric layer 241 is used as a mask to facilitate forming a first trench in the substrate 200 in the second region B during the etching process.

In other embodiments, the method of etching back the first dielectric film to form the first dielectric layer only includes: and carrying out a first dry etching process until the surface of the second region substrate is exposed.

The first dielectric film 240 is located on the surface of the second area B substrate, the surface of the second area B substrate 200 is flat, and the first dielectric film 240 formed on the surface of the second area B substrate 200 through the atomic layer deposition process is good in appearance, so that the first dielectric layer 241 formed by back-etching the first dielectric film 240 is good in appearance and thick in thickness.

The first dielectric layer 241 is used as a mask for forming a first trench in the second region B substrate 200.

Referring to fig. 8, the second region B substrate 200 is etched using the first dielectric layer 241 as a mask, and a first trench 250 is formed in the second region B substrate 200.

The process for etching the second region B substrate 200 by using the first dielectric layer 241 as a mask includes: one or two of the wet etching process and the dry etching process are combined.

In this embodiment, the process of etching the second region B substrate 200 includes: one or a combination of the wet etching process and the dry etching process.

The first grooves 250 are formed by etching with the first dielectric layer 241 in the second area B as a mask, and the first dielectric layer 241 in the second area B has a good appearance, so that the first grooves 250 with a good appearance can be formed in the substrate 200 in the second area B by etching with the first dielectric layer 241 as a mask, and the performance of the semiconductor structure is improved.

After the first trench is formed, the fin portion to be removed and a portion of the substrate located at the bottom of the fin portion to be removed are removed, and a second trench is formed in the first region of the substrate, and a forming process of the second trench is described in detail with reference to fig. 9 to 11.

Referring to fig. 9, after the first trench 250 (shown in fig. 8) is formed, a second dielectric layer 260 is formed on the surface and the sidewall of the first dielectric layer 241 and in the first trench 250, and the top surface of the second dielectric layer 260 is higher than the top surface of the fin 210.

The material of the second dielectric layer 260 includes: an organic material.

In this embodiment, the second dielectric layer 260 is a bottom anti-reflective coating.

The forming process of the second dielectric layer 260 comprises the following steps: and (4) spin coating.

The surface of the second dielectric layer 260 is flat, which is beneficial to forming a first mask layer on the surface of the second dielectric layer 260 in a subsequent step.

Referring to fig. 10, a first mask layer 270 is formed on the surface of the second dielectric layer 260, and the first mask layer 270 exposes the surface of the second dielectric layer 260 on the fin portion 211 to be removed.

The first mask layer 270 material includes: silicon oxide, silicon nitride, silicon carbonitride, silicon carbide, aluminum oxide, hafnium oxide, silicon oxynitride, or silicon oxycarbide.

In this embodiment, the material of the first mask layer 270 is silicon nitride.

The forming process of the first mask layer 270 includes: a chemical vapor deposition process or a physical vapor deposition process.

The first mask layer 270 is used as a mask for forming a second trench later.

Referring to fig. 11, the second dielectric layer 260, the first dielectric layer 241, the to-be-removed fin portion 211, and the first region a substrate 200 located at the bottom of the to-be-removed fin portion 211 are etched by using the first mask layer 270 as a mask, and a second trench 280 is formed in the first region a substrate 200.

In the present embodiment, one to-be-removed fin 211 in the first region a and the substrate 200 located at the bottom of the to-be-removed fin 211 are removed, and the second trench 280 is formed in the substrate 200 in the first region a.

The process for etching the second dielectric layer 260, the first dielectric layer 241, the fin portion 211 to be removed, and the first region a substrate 200 located at the bottom of the fin portion 211 to be removed by using the first mask layer 270 as a mask includes: one or two of the dry etching process and the wet etching process are combined.

In this embodiment, the etching process is a dry etching process. The parameters of the dry etching process comprise: the gas used comprises CF₄、CF₆、O₂、N₂HBr and Cl₂Said CF₄And CF₆The flow rate of (A) is 10 standard ml/min to 300 standard ml/min, and the O is₂The flow rate of (A) is 10 to 500 standard ml/min, N₂The flow rate of (A) is 50 standard milliliters/minute to 1000 standard milliliters/minute, the flow rate of HBr is 10 standard milliliters/minute to 500 standard milliliters/minute, and the Cl₂The flow rate of the gas is 10-500 standard ml/min, the pressure is 3-400 millitorr, and the temperature is 30-120 ℃.

In this embodiment, the second trench 280 is formed by a single etching process, and the single etching process is performed by using the same first mask layer 270 as a mask, so that the enhancement of the shape defect of the second trench 280 caused by multiple etching processes is avoided, and thus the shape of the second trench 280 is better, which is favorable for improving the performance of the semiconductor structure.

In summary, according to the method, by using a step-by-step etching process, the first trench 250 is formed in the second region B substrate 200, and then the second trench 280 is formed in the first region a substrate 200, so that the first trench 250 and the second trench 280 have different sizes along the first direction, and the first trench 250 and the second trench 280 have better shapes, so that the formed semiconductor structure has better performance.

Correspondingly, the embodiment of the invention also provides a semiconductor structure formed by adopting the method.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.