阅读说明：本技术 埋入式栅极结构及半导体存储器的形成方法 (Embedded grid structure and method for forming semiconductor memory ) 是由 不公告发明人 于 2019-08-22 设计创作，主要内容包括：本发明提供的埋入式栅极结构及半导体存储器的形成方法包括如下步骤：提供衬底,所述衬底上具有第一掩膜层；形成多个刻蚀结构于所述第一掩膜层表面,所述刻蚀结构包括分隔层和位于所述分隔层表面的第二掩膜层,所述第二掩膜层中具有暴露所述分隔层的第一沟槽,相邻所述刻蚀结构之间具有暴露所述第一掩膜层的第二沟槽；同时沿所述第一沟槽和所述第二沟槽刻蚀所述衬底,形成与所述第一沟槽对应的栅极槽、并同时形成与所述第二沟槽对应的第一隔离槽于所述衬底中,且所述第一隔离槽的深度大于所述栅极槽。本发明极大的简化了埋入式栅极结构的制造工艺,提高了半导体的生产效率,降低了半导体制造成本。(The forming method of the embedded grid structure and the semiconductor memory provided by the invention comprises the following steps: providing a substrate, wherein the substrate is provided with a first mask layer; forming a plurality of etching structures on the surface of the first mask layer, wherein each etching structure comprises a separation layer and a second mask layer positioned on the surface of the separation layer, a first groove exposing the separation layer is formed in the second mask layer, and a second groove exposing the first mask layer is formed between the adjacent etching structures; and simultaneously etching the substrate along the first groove and the second groove to form a gate groove corresponding to the first groove and simultaneously form a first isolation groove corresponding to the second groove in the substrate, wherein the depth of the first isolation groove is greater than that of the gate groove. The invention greatly simplifies the manufacturing process of the embedded grid structure, improves the production efficiency of the semiconductor and reduces the manufacturing cost of the semiconductor.)

1. A method for forming a buried gate structure includes the steps of:

providing a substrate, wherein the substrate is provided with a first mask layer;

forming a plurality of etching structures on the surface of the first mask layer, wherein each etching structure comprises a separation layer and a second mask layer positioned on the surface of the separation layer, a first groove exposing the separation layer is formed in the second mask layer, and a second groove exposing the first mask layer is formed between the adjacent etching structures;

and simultaneously etching the substrate along the first groove and the second groove to form a gate groove corresponding to the first groove and simultaneously form a first isolation groove corresponding to the second groove in the substrate, wherein the depth of the first isolation groove is greater than that of the gate groove.

2. The method of claim 1, wherein the plurality of etched structures are arranged in an array, and a gap exposing the first mask layer is formed between adjacent etched structures along a first direction parallel to the substrate;

the second trench is provided between the adjacent separation layers in a second direction parallel to the substrate, the second mask layer has a plurality of first trenches arranged in the second direction, and the first direction intersects with the second direction.

3. The method of claim 2, wherein the step of etching the substrate along the first trench and the second trench comprises:

and simultaneously etching the first mask layer and the substrate along the first groove, the second groove and the gap, and simultaneously forming the gate groove corresponding to the first groove, the first isolation groove corresponding to the second groove and the second isolation groove corresponding to the gap in the substrate.

4. The method of claim 3, further comprising:

depositing the first mask layer, the separation layer and the second mask layer on the surface of the substrate in sequence;

etching the second mask layer to form a plurality of first openings which are arranged along the first direction and expose the separation layer;

and reducing the width of the first opening along the first direction to form the gap.

5. The method as claimed in claim 4, wherein the spacer layer is deposited to a thickness of 1nm to 100 nm;

the thickness of the deposited second mask layer is 100 nm-500 nm.

6. The method as claimed in claim 4, wherein the step of reducing the width of the first opening along the first direction comprises:

depositing a dielectric layer on the second mask layer and the exposed surface of the partition layer;

depositing a third mask layer on the surface of the medium layer;

and etching the third mask layer, the dielectric layer, the second mask layer and the separation layer to form the gap exposing the first mask layer.

7. The method of claim 6, wherein the width of the void along the first direction is 1/2 times the width of the first opening.

8. The method of claim 6, wherein the thickness of the deposited dielectric layer is 1nm to 50 nm;

the thickness of the deposited third mask layer is 100 nm-500 nm.

9. The method as claimed in claim 6, wherein the spacer layer is made of a different material than the dielectric layer, the dielectric layer is made of a different material than the third mask layer and the second mask layer, and the second mask layer is made of a same material as or a different material than the third mask layer.

10. The method of claim 9, further comprising:

and etching the third mask layer, the dielectric layer, the second mask layer and the separation layer to form a first initial etching structure and a second initial etching structure which are alternately arranged along the first direction, wherein the first initial etching structure comprises the separation layer and the second mask layer positioned on the surface of the separation layer, the second initial etching structure comprises the separation layer and the dielectric layer positioned on the surface of the separation layer, and the gap is formed between the adjacent first initial etching structure and the second initial etching structure.

11. The method of claim 10, further comprising the step of, after forming the void exposing the first mask layer:

depositing a fourth mask layer on the first initial etching structure, the second initial etching structure and the exposed surface of the first mask layer;

depositing a fifth mask layer on the surface of the fourth mask layer;

and etching the fifth mask layer to form a second opening and a third opening which expose the fourth mask layer, wherein the width of the third opening is greater than that of the second opening along the second direction.

12. The method of claim 11, wherein the second openings are alternately arranged with the third openings along the second direction.

13. The method as claimed in claim 11, wherein a width of the third opening is 10nm to 50nm greater than that of the second opening along the second direction.

14. The method of claim 11, wherein the first mask layer, the second mask layer, the third mask layer, the fourth mask layer, and the fifth mask layer are made of one or a combination of more than two of amorphous carbon, silicon oxynitride, silicon nitride, and silicon dioxide.

15. The method of claim 12, wherein after forming the second opening and the third opening exposing the fourth mask layer, the method further comprises:

depositing a dielectric layer on the surface of the side wall of the residual fifth mask layer, wherein the dielectric layer fills the second opening, and a fourth opening which takes the dielectric layer as the side wall and exposes the fourth mask layer is formed in the third opening;

and etching by taking the dielectric layer as a mask pattern, and removing the fifth mask layer, the fourth mask layer, part of the third mask layer and part of the separation layer to form the etching structure.

16. The method of claim 15, wherein the step of depositing a dielectric layer on the sidewall surface of the remaining fifth mask layer comprises:

depositing a dielectric layer on the fifth mask layer and the exposed surface of the fourth mask layer, wherein the dielectric layer fills the second opening and partially fills the third opening;

and etching the dielectric layer to expose the top surface of the fifth mask layer, so that the second opening is filled with the residual dielectric layer, and a fourth opening which takes the dielectric layer as a side wall and exposes the fourth mask layer is formed in the third opening.

17. The method of claim 15, wherein the first trench has a smaller width than the second trench along the second direction.

18. The method of claim 15, further comprising the steps of, after the etching step is performed, forming the etching structure:

and etching the first mask layer and the substrate, and simultaneously forming the gate groove, the first isolation groove and the second isolation groove in the substrate.

19. The method of claim 3, wherein the first isolation trench and the second isolation trench have the same depth.

20. The method of claim 3, further comprising:

filling a conductive material in the gate groove to form an embedded gate structure;

and filling an insulating material in the first isolation groove and the second isolation groove to form a first shallow trench isolation structure and a second shallow trench isolation structure.

21. A method for forming a semiconductor memory device, comprising the steps of:

forming a transistor in a substrate, the transistor comprising a source, a drain, and a buried gate structure formed using the method of forming a buried gate structure according to any of claims 1-20;

and forming a capacitor on the surface of the substrate, wherein the capacitor is electrically connected with the source electrode.

Technical Field

The present invention relates to the field of semiconductor manufacturing technologies, and in particular, to a method for forming a buried gate structure and a semiconductor memory.

Background

Dynamic Random Access Memory (DRAM) is a semiconductor device commonly used in electronic devices such as computers, and is composed of a plurality of Memory cells, each of which typically includes a transistor and a capacitor. The transistor has a gate electrically connected to a word line, a source electrically connected to a bit line, and a drain electrically connected to the capacitor, and a word line voltage on the word line can control the transistor to be turned on and off, so that data information stored in the capacitor can be read or written through the bit line.

With the continuous reduction of the feature size of semiconductor integrated circuit devices, the critical dimension of nonvolatile memories such as DRAM and the like is also smaller and smaller, the process is more and more complex, and the manufacturing cost is also higher and higher. The Buried gate (Buried Word Line) structure can increase the process integration of the semiconductor process, and has a significant advantage in reducing the device size, thereby being widely applied in the field of semiconductor device manufacturing. However, the conventional process for fabricating the buried gate structure is complicated and the manufacturing cost is high.

Therefore, how to simplify the process of the buried gate structure and reduce the manufacturing cost is a technical problem to be solved.

Disclosure of Invention

The invention provides a method for forming an embedded grid structure and a semiconductor memory, which are used for solving the problems of more complex process and higher manufacturing cost of the existing embedded grid structure.

In order to solve the above problems, the present invention provides a method for forming a buried gate structure, comprising:

providing a substrate, wherein the substrate is provided with a first mask layer;

forming a plurality of etching structures on the surface of the first mask layer, wherein each etching structure comprises a separation layer and a second mask layer positioned on the surface of the separation layer, a first groove exposing the separation layer is formed in the second mask layer, and a second groove exposing the first mask layer is formed between the adjacent etching structures;

and simultaneously etching the substrate along the first groove and the second groove to form a gate groove corresponding to the first groove and simultaneously form a first isolation groove corresponding to the second groove in the substrate, wherein the depth of the first isolation groove is greater than that of the gate groove.

Optionally, the plurality of etching structures are arranged in an array, and a gap for exposing the first mask layer is formed between adjacent etching structures along a first direction parallel to the substrate;

the second trench is provided between the adjacent separation layers in a second direction parallel to the substrate, the second mask layer has a plurality of first trenches arranged in the second direction, and the first direction intersects with the second direction.

Optionally, the specific step of etching the substrate along the first trench and the second trench includes:

and simultaneously etching the first mask layer and the substrate along the first groove, the second groove and the gap, and simultaneously forming the gate groove corresponding to the first groove, the first isolation groove corresponding to the second groove and the second isolation groove corresponding to the gap in the substrate.

Optionally, the method further comprises the following steps:

depositing the first mask layer, the separation layer and the second mask layer on the surface of the substrate in sequence;

etching the second mask layer to form a plurality of first openings which are arranged along the first direction and expose the separation layer;

and reducing the width of the first opening along the first direction to form the gap.

Optionally, the thickness of the deposited separation layer is 1nm to 100 nm;

the thickness of the deposited second mask layer is 100 nm-500 nm.

Optionally, the specific step of reducing the width of the first opening along the first direction includes:

depositing a dielectric layer on the second mask layer and the exposed surface of the partition layer;

depositing a third mask layer on the surface of the medium layer;

and etching the third mask layer, the dielectric layer, the second mask layer and the separation layer to form the gap exposing the first mask layer.

Optionally, the width of the gap in the first direction is 1/2 the width of the first opening.

Optionally, the thickness of the deposited dielectric layer is 1 nm-50 nm;

the thickness of the deposited third mask layer is 100 nm-500 nm.

Optionally, the material of the separation layer is different from that of the dielectric layer, the material of the dielectric layer is different from both the third mask layer and the second mask layer, and the material of the second mask layer is the same as or different from that of the third mask layer.

Optionally, the method further comprises the following steps:

and etching the third mask layer, the dielectric layer, the second mask layer and the separation layer to form a first initial etching structure and a second initial etching structure which are alternately arranged along the first direction, wherein the first initial etching structure comprises the separation layer and the second mask layer positioned on the surface of the separation layer, the second initial etching structure comprises the separation layer and the dielectric layer positioned on the surface of the separation layer, and the gap is formed between the adjacent first initial etching structure and the second initial etching structure.

Optionally, after forming the void exposing the first mask layer, the method further includes:

depositing a fourth mask layer on the first initial etching structure, the second initial etching structure and the exposed surface of the first mask layer;

depositing a fifth mask layer on the surface of the fourth mask layer;

and etching the fifth mask layer to form a second opening and a third opening which expose the fourth mask layer, wherein the width of the third opening is greater than that of the second opening along the second direction.

Optionally, the second openings and the third openings are arranged alternately along the second direction.

Optionally, the width of the third opening is 10nm to 50nm greater than that of the second opening along the second direction.

Optionally, the first mask layer, the second mask layer, the third mask layer, the fourth mask layer, and the fifth mask layer are made of one or a combination of more than two of amorphous carbon, silicon oxynitride, silicon nitride, and silicon dioxide.

Optionally, after forming the second opening and the third opening that expose the fourth mask layer, the method further includes the following steps:

depositing a dielectric layer on the surface of the side wall of the residual fifth mask layer, wherein the dielectric layer fills the second opening, and a fourth opening which takes the dielectric layer as the side wall and exposes the fourth mask layer is formed in the third opening;

and etching by taking the dielectric layer as a mask pattern, and removing the fifth mask layer, the fourth mask layer, part of the third mask layer and part of the separation layer to form the etching structure.

Optionally, the specific step of depositing the dielectric layer on the surface of the sidewall of the residual fifth mask layer includes:

depositing a dielectric layer on the fifth mask layer and the exposed surface of the fourth mask layer, wherein the dielectric layer fills the second opening and partially fills the third opening;

and etching the dielectric layer to expose the top surface of the fifth mask layer, so that the second opening is filled with the residual dielectric layer, and a fourth opening which takes the dielectric layer as a side wall and exposes the fourth mask layer is formed in the third opening.

Optionally, the width of the first trench is smaller than that of the second trench along the second direction.

Optionally, after the etching structure is formed, the method further includes the following steps:

and etching the first mask layer and the substrate, and simultaneously forming the gate groove, the first isolation groove and the second isolation groove in the substrate.

Optionally, the first isolation groove and the second isolation groove have the same depth.

Optionally, the method further comprises the following steps:

filling a conductive material in the gate groove to form an embedded gate structure;

and filling an insulating material in the first isolation groove and the second isolation groove to form a first shallow trench isolation structure and a second shallow trench isolation structure.

In order to solve the above problem, the present invention further provides a method for forming a semiconductor memory, comprising the steps of:

forming a transistor in a substrate, wherein the transistor comprises a source electrode, a drain electrode and a buried gate structure formed by adopting the method for forming the buried gate structure;

and forming a capacitor on the surface of the substrate, wherein the capacitor is electrically connected with the source electrode.

According to the embedded grid structure and the forming method of the semiconductor memory, the specific etching structure is formed on the first mask layer on the surface of the substrate, and the substrate is etched by using the etching structure, so that the grid groove and the first isolation groove can be formed in the substrate at the same time through one-step etching, the manufacturing process of the embedded grid structure is greatly simplified, the production efficiency of the semiconductor is improved, and the manufacturing cost of the semiconductor is reduced.

Drawings

Fig. 1 is a flow chart of a method for forming a buried gate structure according to an embodiment of the present invention;

FIG. 2 is a layout diagram of a DRAM with a buried gate structure according to an embodiment of the present invention;

fig. 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B, 9A, 9B, 10A, and 10B are schematic cross-sectional views of main processes in forming a buried gate structure according to an embodiment of the present invention.

Detailed Description

Embodiments of a method for forming a buried gate structure and a semiconductor memory according to the present invention are described in detail below with reference to the accompanying drawings.

In the conventional dram, a gate Trench for forming a buried gate and an Isolation Trench for forming a Shallow Trench Isolation (STI) are formed in a step-by-step manner, which results in an increase in complexity of a manufacturing process and an increase in manufacturing cost, and thus development and application of the buried gate structure are restricted to a certain extent.

In order to simplify the manufacturing process of the buried gate structure and reduce the manufacturing cost, the present embodiment provides a method for forming the buried gate structure, fig. 1 is a flowchart of a method for forming the buried gate structure according to the present embodiment, fig. 2 is a schematic layout diagram of a dram having the buried gate structure according to the present embodiment, and fig. 3A, 3B, 4A, 4B, 5A, 5B, 6A, 6B, 7A, 7B, 8A, 8B, 9A, 9B, 10A, and 10B are schematic process cross-sectional views of the method for forming the buried gate structure according to the present embodiment. The buried gate structure described in this embodiment can be, but is not limited to, a buried gate structure in a dynamic random access memory. The method for forming a buried gate structure according to the present embodiment includes the following steps:

step S11, providing a substrate 30, wherein the substrate 30 has a first mask layer 31 thereon.

In this embodiment, the substrate 30 may be a Si substrate, a Ge substrate, a SiGe substrate, an SOI (Silicon On Insulator) or GOI (Germanium On Insulator) or the like. In this embodiment, the substrate 30 is preferably a silicon substrate. The material of the first mask layer 31 may be a carbon-based material, such as amorphous carbon, a carbon-containing oxide, a carbon-containing oxynitride, a carbon-containing nitride, or the like; the material of the first mask layer 31 may also be any spin-on hard mask material. The thickness of the first mask layer 31 may be selected by a person skilled in the art according to actual needs, for example, the thickness of the first mask layer 31 is 100nm to 500 nm.

Step S12, forming a plurality of etching structures on the surface of the first mask layer 31, where the etching structures include a separation layer 32 and a second mask layer 33 located on the surface of the separation layer 32, the second mask layer 33 has a first trench 21 exposing the separation layer 32, and a second trench 22 exposing the first mask layer 31 is located between adjacent etching structures, as shown in fig. 9B. Fig. 9B is a schematic sectional view along the YY' direction in fig. 2. The term "plurality" as used in the present embodiment means two or more.

Step S13, the substrate 30 is etched along the first trench 21 and the second trench 22 simultaneously, a gate trench 24 corresponding to the first trench 21 is formed, and a first isolation trench 25 corresponding to the second trench 22 is formed in the substrate 30 simultaneously, and the depth of the first isolation trench 25 is greater than that of the gate trench 24, as shown in fig. 10B. Fig. 10B is a schematic sectional view along the YY' direction in fig. 2.

Specifically, the patterned etching structures are formed on the surface of the first mask layer 31, and a plurality of the etching structures correspond to a plurality of Active areas (Active areas) in the substrate 30 one by one. Since the first trench 21 is located above the separation layer 32, the second trench 22 is located above the first mask layer 31, and the separation layer 32 is located on the surface of the first mask layer 31, the depth of the second trench 22 is greater than that of the first trench 21 (the depth difference between the first trench 21 and the second trench 22 is the thickness of the separation layer 32). When the substrate 30 is etched by using the pattern in the etching structure, due to the micro-loading effect, the etching rate along the first trench 21 is lower than the etching rate along the second trench 22, and therefore, the depth of the gate trench 24 etched and formed along the first trench 21 is lower than the depth of the first isolation trench 25 etched and formed along the second trench 22. The first isolation trenches 25 serve to separate the adjacent active regions.

Optionally, the plurality of etching structures are arranged in an array, and a gap 23 exposing the first mask layer 31 is formed between adjacent etching structures along a first direction parallel to the substrate 30, as shown in fig. 9A;

the second trenches 22 are provided between the adjacent spacer layers 32 in a second direction parallel to the substrate 30, and the second mask layer 33 has a plurality of the first trenches 21 therein arranged in the second direction, the first direction intersecting the second direction.

Optionally, the specific step of etching the substrate 30 along the first trench 21 and the second trench 22 includes:

the first mask layer 31 and the substrate 30 are etched along the first trench 21, the second trench 22 and the gap 23 at the same time, and the gate trench 24 corresponding to the first trench 21, the first isolation trench 25 corresponding to the second trench 22 and the second isolation trench 26 corresponding to the gap 23 are formed in the substrate 30 at the same time, as shown in fig. 10A.

The first direction and the second direction may intersect perpendicularly or obliquely, for example, an included angle between the first direction and the second direction is 30 ° to 120 °. In the present embodiment, the XX 'direction in fig. 2 is the first direction, and the YY' direction is the second direction. Fig. 9A is a schematic sectional view taken along the direction XX 'in fig. 2, and fig. 10A is a schematic sectional view taken along the direction XX' in fig. 2.

Specifically, the first isolation trench 25 is used to separate two adjacent active regions arranged in the YY 'direction, and the second isolation trench 26 is used to separate two adjacent active regions arranged in the XX' direction. By simultaneously etching the substrate 30 along the first trench 21, the second trench 22 and the gap 23, the gate trench 24, the first isolation trench 25 and the second isolation trench 26 can be simultaneously formed in the substrate 30, thereby further simplifying the formation step of the buried gate structure and reducing the production cost of the semiconductor.

The depth of each of the first isolation trench 25 and the second isolation trench 26 should be greater than the depth of the gate trench 24, and the depth of the first isolation trench 25 may be greater than, less than or equal to the depth of the second isolation trench 26. In order to further simplify the manufacturing process and reduce the manufacturing cost, optionally, the first isolation groove 25 and the second isolation groove 26 have the same depth.

Optionally, after the gate trench 24, the first isolation trench 25 and the second isolation trench 26 are simultaneously formed in the substrate 30, the method further includes the following steps:

filling a conductive material in the gate trench 24 to form a buried gate structure;

and filling an insulating material in the first isolation groove 25 and the second isolation groove 26 to form a first shallow trench isolation structure and a second shallow trench isolation structure.

Since the first shallow trench isolation structure and the second shallow trench isolation structure are used for separating the adjacent active regions, the same material can be used for simultaneously filling the first isolation groove 25 and the second isolation groove 26, so as to realize the synchronous formation of the first shallow trench isolation structure and the second shallow trench isolation structure, thereby further simplifying the manufacturing process of the dynamic random access memory.

Optionally, the method for forming the buried gate structure further includes the following steps:

depositing the first mask layer 31, the separation layer 32 and the second mask layer 33 on the surface of the substrate 30 in sequence;

etching the second mask layer 33 to form a plurality of first openings 34 arranged along the first direction and exposing the spacer layer 32, as shown in fig. 3A and 3B, where fig. 3A is a schematic cross-sectional view along XX 'in fig. 2, and fig. 3B is a schematic cross-sectional view along YY' in fig. 2;

the width of the first opening 34 in the first direction is reduced to form the gap 23.

The material of the spacer layer 32 may be, but is not limited to, amorphous silicon. The material of the second mask layer 33 may be the same as or different from the first mask layer 31, and those skilled in the art can select the material according to actual needs. Optionally, the thickness of the deposited separation layer 32 is 1nm to 100 nm;

the thickness of the deposited second mask layer 33 is 100nm to 500 nm.

Optionally, the specific step of reducing the width of the first opening 34 along the first direction includes:

depositing a dielectric layer 35 on the second mask layer 33 and the exposed surface of the separation layer 32;

depositing a third mask layer 36 on the surface of the dielectric layer 35, as shown in fig. 4A and 4B, where fig. 4A is a schematic cross-sectional view along the direction XX 'in fig. 2, and fig. 4B is a schematic cross-sectional view along the direction YY' in fig. 2;

the third mask layer 36, the dielectric layer 35, the second mask layer 33, and the spacer layer 32 are etched to form the gap 23 exposing the first mask layer 31, as shown in fig. 5A and 5B, where fig. 5A is a schematic cross-sectional view along XX 'in fig. 2, and fig. 5B is a schematic cross-sectional view along YY' in fig. 2.

Specifically, the dielectric Layer 35 may be deposited by any one of an Atomic Pressure Chemical Vapor Deposition (APCVD), a Low Pressure Chemical Vapor Deposition (LPCVD), a Plasma-Enhanced Chemical Vapor Deposition (PECVD), a High-Density Plasma Chemical Vapor Deposition (HDP-CVD), a Radical-Enhanced Chemical Vapor Deposition (CVD), and an Atomic Layer Deposition (ALD). The dielectric layer 35 covers the top surface and sidewalls of the second masking layer 33 and the exposed surface of the spacer layer 32. The material of the dielectric layer 35 may be, but is not limited to, silicon oxide. The dielectric layer 35 and the third masking layer 36 together fill the first opening 34. After the third mask layer 36 is deposited, a chemical mechanical polishing process may be further used to polish the surface of the third mask layer 36 away from the substrate 30, so as to facilitate the implementation of the subsequent processes.

Optionally, the width W2 of the void 23 in the first direction is 1/2 of the width W1 of the first opening 34.

Optionally, the thickness of the deposited dielectric layer 35 is 1nm to 50 nm;

the thickness of the deposited third mask layer 36 is 100nm to 500 nm.

Optionally, the material of the separation layer 32 is different from that of the dielectric layer 35, the material of the dielectric layer 35 is different from both the third mask layer 36 and the second mask layer 33, and the material of the second mask layer 33 is the same as or different from that of the third mask layer 36.

Optionally, the method for forming the buried gate structure further includes the following steps:

etching the third mask layer 36, the dielectric layer 35, the second mask layer 33, and the separation layer 32 to form a first initial etching structure and a second initial etching structure alternately arranged along the first direction, where the first initial etching structure includes the separation layer 32 and the second mask layer 33 located on the surface of the separation layer 32, the second initial etching structure includes the separation layer 32 and the dielectric layer 35 located on the surface of the separation layer 32, and the gap 23 is formed between the adjacent first initial etching structure and the second initial etching structure, as shown in fig. 5A and 5B.

Specifically, after the deposition process of the third mask layer 36 is completed, the structure shown in fig. 4A is etched from the third mask layer 36, and since the third mask layer 36, the second mask layer 33, the dielectric layer 35, and the spacer layer 32 are alternately stacked, by controlling the etching selection ratio among different film materials, after the etching is completed, mask layer patterns (including the first initial etching structure and the second initial etching structure) with different heights are present in the XX' direction, as shown in fig. 5A. The process is equivalent to the process of shrinking the mask layer pattern originally having the first opening 34, so that the width W2 of the finally formed gap 23 is smaller than the width W1 of the first opening 34, for example, the width W2 of the gap 23 is 1/2 of the width W1 of the first opening 34.

Optionally, after forming the void 23 exposing the first mask layer 31, the method further includes:

depositing a fourth mask layer 37 on the first initial etching structure, the second initial etching structure and the exposed surface of the first mask layer 31;

depositing a fifth mask layer 38 on the surface of the fourth mask layer 37;

the fifth mask layer 38 is etched to form a second opening 41 and a third opening 42 exposing the fourth mask layer 37, and a width W4 of the third opening 42 is greater than a width W3 of the second opening 41 along the second direction, as shown in fig. 6A and 6B, where fig. 6A is a schematic cross-sectional view along the XX 'direction in fig. 2, and fig. 6B is a schematic cross-sectional view along the YY' direction in fig. 2.

Alternatively, the second openings 41 and the third openings 42 are alternately arranged along the second direction.

Optionally, the width W4 of the third opening 42 is 10nm to 50nm greater than the width W3 of the second opening 41 along the second direction, so as to better control the electrical isolation effect between adjacent active regions.

The materials of the fourth mask layer 37 and the fifth mask layer 38 may be the same as or different from the second mask layer 33, and those skilled in the art can select the materials according to actual needs. In order to further reduce the manufacturing cost, optionally, the materials of the first mask layer 31, the second mask layer 33, the third mask layer 36, the fourth mask layer 37, and the fifth mask layer 38 are all one or a combination of two or more of amorphous carbon, silicon oxynitride, silicon nitride, and silicon dioxide.

Optionally, after forming the second opening 41 and the third opening 42 exposing the fourth masking layer 37, the method further includes the following steps:

depositing a dielectric layer 43 on the sidewall surface of the residual fifth masking layer 38, wherein the dielectric layer 43 fills the second opening 41, and a fourth opening 44 which takes the dielectric layer 43 as a sidewall and exposes the fourth masking layer 37 is formed in the third opening 42, as shown in fig. 8A and 8B, fig. 8A is a schematic cross-sectional view along the XX 'direction in fig. 2, and fig. 8B is a schematic cross-sectional view along the YY' direction in fig. 2;

and etching by taking the dielectric layer 43 as a mask pattern, and removing the fifth mask layer 38, the fourth mask layer 37, part of the third mask layer 33 and part of the separation layer 32 to form the etching structure.

In the structure shown in fig. 8B, the fourth opening 44 corresponds to the second trench 22 in the subsequently formed etched structure, and the remaining fifth mask layer 38 corresponds to the first trench 21 in the subsequently formed etched structure.

Optionally, the specific step of depositing the dielectric layer 43 on the sidewall surface of the residual fifth mask layer 38 includes:

depositing a dielectric layer 43 on the surfaces of the fifth masking layer 38 and the exposed surface of the fourth masking layer 37, wherein the dielectric layer 43 fills the second opening 41, and the dielectric layer 43 partially fills the third opening 42;

and etching the dielectric layer 43 to expose the top surface of the fifth masking layer 38, so that the residual dielectric layer 43 fills the second opening 41, and a fourth opening 44 which takes the dielectric layer 43 as a side wall and exposes the fourth masking layer 37 is formed in the third opening 42.

Optionally, the width of the first trench 21 is smaller than the width of the second trench 22 along the second direction.

Specifically, the dielectric layer 43 is deposited on the surface of the structure shown in fig. 6A and 6B, so that the dielectric layer 43 at least fills the second opening 41 and covers the surface of the third opening 42. Since the width of the third opening 42 is greater than the width of the second opening 41, when the dielectric layer 43 fills the second opening 41, the third opening 42 is not filled with the dielectric layer 43, as shown in fig. 7A and 7B, fig. 7A is a schematic cross-sectional view along XX 'in fig. 2, and fig. 7B is a schematic cross-sectional view along YY' in fig. 2. The material of the dielectric layer 43 may be, but is not limited to, silicon nitride, silicon dioxide. The thickness of the dielectric layer 43 may be 1nm to 50 nm. One skilled in the art may use CVD, PVD, PECVD, LPCVD, etc. to form the dielectric layer 43.

After the structure shown in fig. 7A and 7B is formed, the dielectric layer 43 is etched, so that the residual dielectric layer 43 forms a dielectric pattern in the second opening 41 and forms a sidewall of the fourth opening 44 on a sidewall of the third opening 42. At this time, the width W5 of the fourth opening 44 is preferably formed to be greater than the width W6 of the fifth mask layer 38 between the adjacent dielectric layers 43.

Thereafter, an etching process is performed using the dielectric layer 43 as a mask pattern, and a pattern is transferred to the spacer layer 32 and the second mask layer 33 to form the second trench 22 corresponding to the fourth opening 44 and the first trench 21 corresponding to the fifth mask layer 38, as shown in fig. 9A and 9B. Since the fourth opening 44 exposes the fourth mask layer 37 along the YY' direction, the depth of the second trench 22 is made larger than that of the first trench 21 by controlling the etching selection ratio and selecting an appropriate etch stop layer during the downward etching process using the dielectric layer 43 as a mask pattern. The etching of this step enables the definition of the first isolation trenches 25 and the gate trenches 24 in the substrate 30.

Optionally, after the etching structure is formed, the method further includes the following steps:

and etching the first mask layer 31 and the substrate 30, and simultaneously forming the gate trench 24, the first isolation trench 25 and the second isolation trench 26 in the substrate 30.

Specifically, after the structure shown in fig. 9A and 9B is formed, the first mask layer 31 is used as an etching mask, so that the first trench 21 and the second trench 22 extend further into the substrate 30. In the etching process, the reaction product of the etching gas, the first mask layer 31 and the substrate 30 is likely to gather in the first trench 21 with a relatively narrow width (mainly, a polymer is accumulated on the sidewall of the first trench 21), so that the speed of etching the substrate 30 along the first trench 21 is lower than the speed of etching the substrate 30 along the second trench 22, and further the depth of the finally formed gate trench 24 is lower than that of the first isolation trench 25, for example, the depth of the first isolation trench 25 is 1 to 5 times that of the gate trench 24.

Furthermore, the present embodiment also provides a method of forming a semiconductor memory. The semiconductor memory described in this embodiment mode may be, but is not limited to, a DRAM. The forming method of the semiconductor memory comprises the following steps:

forming a transistor in a substrate, wherein the transistor comprises a source electrode, a drain electrode and a buried gate structure formed by adopting the method for forming the buried gate structure;

and forming a capacitor on the surface of the substrate, wherein the capacitor is electrically connected with the source electrode.

In the method for forming the embedded gate structure and the semiconductor memory according to the embodiment, the specific etching structure is formed on the first mask layer on the surface of the substrate, and the substrate is etched by using the etching structure, so that the gate groove and the first isolation groove can be formed in the substrate at the same time by one-step etching, the manufacturing process of the embedded gate structure is greatly simplified, the production efficiency of the semiconductor is improved, and the manufacturing cost of the semiconductor is reduced.

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.