Patterning method

Abstract

This invention provides a patterning method, comprising: providing a substrate; forming a first mandrel pattern; forming a first sidewall, wherein first isolation layers on both sides of the first sidewall have a height difference; forming a third isolation layer filling the gaps between the first sidewalls and forming a third mandrel isolation pattern; forming a second mandrel pattern; forming a second sidewall, wherein second isolation layers on both sides of the second sidewall have a height difference; and forming a fourth isolation layer filling the gaps between the second sidewalls, and removing the second sidewalls to form the fourth mandrel isolation pattern, using the fourth mandrel isolation pattern as a mask pattern. In this invention, the third isolation layer fills both sides of the first sidewall to eliminate the height difference of the first isolation layer, and the fourth isolation layer fills both sides of the second sidewall to eliminate the height difference of the second isolation layer, thereby facilitating the formation of a mask pattern with a better morphology and reducing the difficulty of process debugging during patterning.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of integrated circuit technology, and particularly to a patterning method. BACKGROUND

[0002] With the continuous miniaturization of chip size and the reduction of pattern period, the requirement for patterning technology is getting higher and higher.

[0003] Taking the existing patterning technology as an example, when forming a side wall by dry etching, the profile (side wall) of the side wall formed after etching is required to be vertical, and the loss of the isolation layer at the bottom of the side wall is required to be as small as possible, so as to avoid the height difference of the isolation layer on both sides of the side wall, because the height difference will cause the deformation (unevenness, asymmetry) of the pattern structure when the pattern is further etched to transfer to the next layer. However, based on the existing anisotropic etching process, the above two requirements are contradictory, that is, the higher the verticality of the side wall with respect to the substrate after dry etching, the stronger the etching of the isolation layer at the bottom of the side wall, and the greater the etching difference of the isolation layer on both sides of the side wall, resulting in a greater height difference of the isolation layer on both sides of the side wall, and thus bringing great difficulty to the process debugging of the patterning technology. SUMMARY

[0004] The purpose of the present application is to provide a patterning method to form a mask pattern with better profile and reduce the difficulty of process debugging during patterning.

[0005] To address the aforementioned technical problems, the present invention provides a patterning method, comprising: providing a substrate, wherein a second isolation layer, a second core layer, a first isolation layer, and a first core layer are sequentially formed from bottom to top on the substrate; forming a patterned mask layer; using the patterned mask layer as a mask, etching the first core layer to form a first core pattern; forming a first sidewall material layer covering the first core pattern and the first isolation layer; etching away the top wall of the first core pattern and the first sidewall material layer on the first isolation layer, retaining the first sidewall material layer on the sidewall of the first core pattern to form a first sidewall, wherein the first isolation layers on both sides of the first sidewall have a height difference; and forming a third isolation layer to fill the gaps of the first sidewall. The substrate is patterned by: forming a third mandrel isolation pattern by removing the first sidewall; etching the second mandrel layer using the third mandrel isolation pattern as a mask to form a second mandrel pattern; forming a second sidewall material layer covering the second mandrel pattern and the second isolation layer, and etching away the top wall of the second mandrel pattern and the second sidewall material layer on the second isolation layer, retaining the second sidewall material layer on the sidewall of the second mandrel pattern to form a second sidewall, wherein the second isolation layers on both sides of the second sidewall have a height difference; and forming a fourth isolation layer filling the gap between the second sidewalls, and removing the second sidewalls to form a fourth mandrel isolation pattern, and using the fourth mandrel isolation pattern as a mask pattern to pattern the substrate.

[0006] Optionally, the process of forming the third mandrel isolation pattern includes: forming a third isolation layer that fills between and covers the first sidewalls; flattening the third isolation layer and the first sidewalls, exposing the first sidewalls and removing the top rounded corners of the first sidewalls; and removing the first sidewalls to form the third mandrel isolation pattern, which has a flat top surface.

[0007] Optionally, the step of forming the second mandrel pattern includes: using the third mandrel isolation pattern as a mask, etching the first isolation layer and the second mandrel layer to expose the second isolation layer; forming a sacrificial layer that fills the spaces between the third mandrel isolation patterns and covers the top surface of the third mandrel isolation patterns; etching back a portion of the sacrificial layer to expose the side surfaces of the first isolation layer; and removing the third mandrel isolation pattern, the first isolation layer, and the remaining sacrificial layer to form the second mandrel pattern.

[0008] Optionally, the material of the sacrificial layer includes a carbon-containing organic spin coating.

[0009] Optionally, the forming of the fourth core shaft isolation pattern comprises: forming a fourth isolation layer, the fourth isolation layer filling between the second side walls and covering the top surface of the second side walls; performing a planarization treatment on the fourth isolation layer and the second side walls, exposing the second side walls and removing the top corners of the second side walls; and removing the second side walls to form the fourth core shaft isolation pattern, the fourth core shaft isolation pattern having a flat top surface.

[0010] Optionally, the first isolation layer, the second isolation layer, the third isolation layer and the fourth isolation layer are made of the same material, the first core shaft layer and the second core shaft layer are made of the same material, and the first side wall and the second side wall are made of the same material.

[0011] Optionally, the first isolation layer, the second isolation layer, the third isolation layer and the fourth isolation layer are made of silicon oxide.

[0012] Optionally, the third isolation layer and / or the fourth isolation layer are formed by using an FCVD process.

[0013] Optionally, the first core shaft layer and the second core shaft layer are made of amorphous silicon.

[0014] Optionally, the first side wall and the second side wall are made of silicon nitride.

[0015] In summary, the third isolation layer is used to compensate for the height difference of the first isolation layer on both sides of the first side wall, and the third core shaft isolation pattern is formed to further eliminate the height difference of the first isolation layer on both sides of the third core shaft isolation pattern, thereby avoiding the non-uniformity and asymmetry of the second core shaft pattern caused by using the third core shaft isolation pattern as a mask for etching downward. Moreover, the fourth isolation layer is used to compensate for the height difference of the second isolation layer on both sides of the second side wall, and the fourth core shaft isolation pattern is formed to further eliminate the height difference of the second isolation layer on both sides of the fourth core shaft isolation pattern, thereby avoiding the non-uniformity and asymmetry of the structure caused by using the fourth core shaft isolation pattern as a mask pattern for etching the substrate downward, so as to form a mask pattern with better topography and reduce the process debugging difficulty during patterning. BRIEF DESCRIPTION OF DRAWINGS

[0016] Those skilled in the art will understand that the provided drawings are for the purpose of better illustrating the present application and do not constitute any limitation on the scope of the present application.

[0017] Figure 1 is a flowchart of the patterning method provided by the embodiments of the present application;

[0018] Figures 2 to 18 is a structural schematic diagram corresponding to the respective steps of the patterning method provided by the embodiments of the present application.

[0019] In the drawings:

[0020] 10 - substrate; 20 - mask layer; 21 - photoresist layer; 211 - photoresist pattern; 22 - antireflection layer; 23 - carbon-containing organic spin-on layer; L1 - first pitch;

[0021] 31 - first mandrel layer; 311 - first mandrel pattern;

[0022] 32 - first spacer layer; 33 - first sidewall material layer; 33' - recess; 331 - first sidewall; 331a - rounded corner;

[0023] 32a - first recess; L2 - second pitch;

[0024] 34 - third spacer layer; 341 - third mandrel spacer pattern;

[0025] 41 - second mandrel layer; 42 - second spacer layer; 43 - sacrificial layer; 411 - second mandrel pattern;

[0026] 44 - second sidewall material layer; 441 - second sidewall; 441a - rounded corner; 45 - second recess; L3 - third pitch;

[0027] 46 - fourth spacer layer; 461 - fourth mandrel spacer pattern. DETAILED DESCRIPTION

[0028] In order to make the objects, advantages and features of the present application clearer, the following further describes the present application in conjunction with the accompanying drawings and specific embodiments. It should be noted that the drawings are all very simplified and not drawn to scale, and are only used to facilitate and clarify the purpose of assisting the description of the embodiments of the present application. In addition, the structures shown in the drawings are often part of the actual structures. In particular, the emphasis shown in each drawing is different, and sometimes different scales are used.

[0029] As used in the present application, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. The term "or" is generally employed in its sense including "and / or" unless the content clearly dictates otherwise. The term "plurality" is generally employed in its sense including "at least one" unless the content clearly dictates otherwise. The term "at least two" is generally employed in its sense including "two or more" unless the content clearly dictates otherwise. In addition, the terms "first," "second," "third," are only used for the purpose of description and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined as "first," "second," "third" can explicitly or implicitly include one or at least two of the features, unless the content clearly indicates otherwise.

[0030] Figure 1is a flowchart of the patterning method provided in the embodiments of the present application.

[0031] As shown in Figure 1 , the patterning method provided in the embodiments of the present application includes the following steps:

[0032] S01: providing a substrate, the substrate is sequentially formed with a second isolation layer, a second mandrel layer, a first isolation layer and a first mandrel layer from bottom to top;

[0033] S02: forming a patterned mask layer, etching the first mandrel layer to form a first mandrel pattern with the patterned mask layer as a mask;

[0034] S03: forming a first sidewall material layer covering the first mandrel pattern and the first isolation layer, etching to remove the first sidewall material layer on the top wall of the first mandrel pattern and the first isolation layer, and retaining the first sidewall material layer of the first mandrel pattern sidewall to form a first sidewall, the first isolation layer on both sides of the first sidewall has a height difference;

[0035] S04: forming a third isolation layer filling the gap of the first sidewall, and removing the first sidewall to form a third mandrel isolation pattern;

[0036] S05: etching the second mandrel layer to form a second mandrel pattern with the third mandrel isolation pattern as a mask;

[0037] S06: forming a second sidewall material layer covering the second mandrel pattern and the second isolation layer, and etching to remove the second sidewall material layer on the top wall of the second mandrel pattern and the second isolation layer, and retaining the second sidewall material layer of the second mandrel pattern sidewall to form a second sidewall, the second isolation layer on both sides of the second sidewall has a height difference; and,

[0038] S07: forming a fourth isolation layer filling the gap between the second sidewall, and removing the second sidewall to form a fourth mandrel isolation pattern, and performing patterning on the substrate with the fourth mandrel isolation pattern as a mask pattern.

[0039] Figures 2 to 18 is a structural schematic diagram corresponding to the corresponding steps of the patterning method provided in the embodiments of the present application. Next, the patterning method will be described in detail in combination with Figures 2 to 18 .

[0040] First, please refer to Figure 2 , execute step S01 to provide a substrate 10, sequentially form a second isolation layer 42, a second mandrel layer 41, a first isolation layer 32, a first mandrel layer 31 and a mask layer 20 on the substrate 10.

[0041] The substrate 10 can be any suitable substrate material known to those skilled in the art, for example, at least one of the following: silicon, silicon-on-insulator (SOI), silicon-on-silicon (SSOI), silicon-germanium-on-insulator (S-SiGeOI), silicon-germanium-on-insulator (SiGeOI), germanium-on-insulator (GeOI), etc. In the present embodiment, the substrate 10 is taken as an example of silicon. The substrate 10 can also have a film layer (not shown in the figure) to be patterned thereon to form a patterned structure of a corresponding device. In some embodiments, the film layer to be patterned on the substrate 10 can be a single-crystal silicon layer to form a fin of a fin field effect transistor device. In other embodiments, the film layer to be patterned on the substrate 10 can be a polysilicon layer to form a core of a semiconductor device. In yet other embodiments, the film layer to be patterned on the substrate 10 can also be a metal layer to form a back-end-of-line metal interconnection structure.

[0042] The material of the second core layer 41 and the first core layer 31 can be, but is not limited to, amorphous silicon. The thickness of the second core layer 41 and the first core layer 31 can be different according to actual requirements, for example, the thickness of the second core layer 41 can be 500 angstroms to 900 angstroms, and the thickness of the first core layer 31 can be 700 angstroms to 1100 angstroms.

[0043] The material of the second isolation layer 42 and the first isolation layer 32 can be, but is not limited to, silicon oxide, to achieve isolation of the second core layer 41 and the first core layer 31 and to serve as an etching stop layer during etching of the second core layer 41 and the first core layer 31. Further, the second isolation layer 42 and the first isolation layer 32 can also serve as a mask to achieve pattern transfer during the patterning process.

[0044] The mask layer 20 can be any material layer suitable for serving as a photolithography mask layer. Specifically, in the present embodiment, the mask layer 20 includes, in sequence (from bottom to top), a carbon-containing organic spin-on coating layer 23 (SOC), an anti-reflective layer 22 (SiARC), and a photoresist layer 21. The thickness of the carbon-containing organic spin-on coating layer 23 is, for example, 1600 angstroms to 2400 angstroms, the thickness of the anti-reflective layer 22 is, for example, 300 angstroms to 500 angstroms, and the thickness of the photoresist layer 21 is, for example, 600 angstroms to 1000 angstroms.

[0045] Next, step S02 is performed to pattern the mask layer 20 to form a patterned mask layer having a first pitch L1. Specifically, please refer to Figure 3 The photoresist pattern 211 can be formed first, and then the anti-reflective layer 22 and the carbon-containing organic spin-on coating layer 23 are patterned in sequence using the photoresist pattern 211 to expose the first core layer 31, thereby obtaining the patterned mask layer.

[0046] Please refer to Figure 4The first core shaft layer 31 is etched to expose the first isolation layer 32 to obtain a first core shaft pattern 311. Specifically, the first core shaft layer 31 can be etched by an ICP (inductively coupled plasma) process to form the first core shaft pattern 311. The first core shaft pattern 311 has a first pitch L1.

[0047] Next, referring to Figure 5 , a first side wall material layer 33 is formed to cover the outer wall of the first core shaft pattern 311 and the surface of the first isolation layer 32. The first side wall material layer 33 between adjacent first core shaft patterns 311 has a recess 33'. The material of the first side wall material layer 33 can be any material suitable for a hard side wall. In this embodiment, the material of the first side wall material layer 33 is silicon nitride, which is preferably formed by an ALD (Atomic Layer Deposition) process to obtain a film layer with good uniformity. It should be understood that, due to the limitations of the deposition process, the first side wall material layer 33 is thinner at the top corner 331a where the top wall and the side wall of the first core shaft layer 31 meet, so that the shape of the top corner 331a is a circular arc.

[0048] Referring to Figure 6 , the first side wall material layer 33 is etched to remove the first side wall material layer 33 on the top wall of the first core shaft pattern 311 and the first side wall material layer 33 below the recess 33'. Then, the first core shaft pattern 311 is removed to obtain a first side wall 331. The first isolation layer 32 on both sides of the first side wall 331 has a height difference. The first side wall 331 has a second pitch L2, which is about 0.5 times the first pitch L1.

[0049] Specifically, during the process of removing the first side wall material layer 33 on the top wall of the first core shaft pattern 311 and the first side wall material layer 33 below the recess 33' by dry etching perpendicular to the substrate 10, the first side wall material layer 33 on the side wall of the first core shaft pattern 311 is retained to form the first side wall 331. The first side wall 331 has a top corner 331a.

[0050] It can be seen that, during the process of etching the first side wall material layer 33 vertically by anisotropic dry etching to remove part of the first side wall material layer 33 and the first core shaft layer 31 to form the first side wall 331 perpendicular to the side wall, due to the different film layers and thicknesses on the first isolation layer 32 on both sides of the first side wall 331, the first isolation layer 32 as an etching stop layer has different degrees of loss (etched degrees) on both sides of the first side wall 331, thereby forming a plurality of first grooves 32a on the surface of the first isolation layer 32, i.e., the thicknesses of the first isolation layer 32 in different regions are different.

[0051] Referring toFigure 7 The step S04 is performed to form a third spacer layer 34, which covers the first spacer layer 32 and fills the gap between the first side walls 331 and extends to cover the top of the first side walls 331. Specifically, the third spacer layer 34 can have the same material as the first spacer layer 32, for example, silicon oxide, which can be formed by the FCVD process to obtain a better filling effect. Moreover, as shown in the figure, the third spacer layer 34 fills the gap between the first side walls 331 and naturally fills the first groove 32a on the first spacer layer 32 generated by the etching, thereby compensating for the height difference on the first spacer layer 32 on both sides of the first side walls. Figure 7

[0052] Next, referring to Figure 8 , the third spacer layer 34 and the first side walls 331 are subjected to a planarization process, which is performed by the chemical mechanical polishing (CMP) process to expose the first side walls 331 and continue to polish to remove the top rounded corners 331a of the first side walls 331, so that the remaining third spacer layer 34 and the first side walls 331 have a flat top surface to improve the size accuracy (line width, pitch) in the subsequent pattern transfer process. In actual operation, the first side walls 331 with a thickness of 100-300 angstroms can be removed by chemical mechanical polishing to eliminate the top rounded corners 331a of the first side walls 331, so that the top surface of the first side walls 331 is flat.

[0053] Next, referring to Figure 9 , the first side walls 331 are removed to form a third core spacer pattern 341 from the remaining third spacer layer 34. The third core spacer pattern 341 has a second pitch L2, which is about 0.5 times the first pitch LI. The first side walls 331 can be removed by a wet etching process. In this embodiment, the material of the first side walls 331 is silicon nitride, and the material of the third spacer layer 341 is silicon oxide. Preferably, an etching liquid with a high selectivity to silicon nitride and silicon oxide (for example, greater than 100:1) is used to form the third core spacer pattern 341 with a vertical side wall and uniform structure (better topography). Moreover, the surfaces of the first spacer layer 32 on both sides of the third core spacer pattern 341 are flush or substantially flush, without obvious height difference, and the top corners of the third core spacer pattern 341 are right-angled, without arc-shaped rounded corners.

[0054] Referring to Figure 10 ​, the step S05 is performed to etch the first isolation layer 32 and the second core shaft layer 41 in sequence with the third core shaft isolation pattern 341 as a mask, so as to expose the second isolation layer 42. In the etching process, since the structure of the third core shaft isolation pattern 341 as a mask is uniform and has right-angled top corners, and the first isolation layer 32 on both sides of the third core shaft isolation pattern 341 has a uniform thickness, the structure formed by etching is better, more uniform and symmetrical as a whole, and has better dimensional accuracy. It should be understood that in the above etching process, the third core shaft isolation pattern 341 as a mask is reduced in height due to etching loss.

[0055] Next, please refer to Figure 11 , the sacrificial layer 43 is formed to fill the gap between the third core shaft isolation patterns 341 and extend to cover the top of the third core shaft isolation patterns 341, and the sacrificial layer 43 has a flat surface. Preferably, the sacrificial layer 43 can be a carbon-containing organic spin-on coating (SOC) which can be formed by a spin-on process to facilitate improving the flatness of its surface.

[0056] Next, please refer to Figure 12 , the sacrificial layer 43 is etched back to expose the first isolation layer 32 and the sidewall of the third core shaft isolation pattern 341.

[0057] Next, please refer to Figure 13 , the first isolation layer 32 and the third core shaft isolation pattern 341 are removed, and the remaining sacrificial layer 43 is also removed to expose the second isolation layer 42, thereby obtaining the second core shaft pattern 411. The second core shaft pattern 411 has a second pitch L2. In this embodiment, the carbon-containing organic spin-on coating is used as the sacrificial layer, and the remaining sacrificial layer 43 can be removed by an ashing process.

[0058] Please refer to Figure 14 and Figure 15 , the step S06 is performed to form a second side wall 441 exposing the second isolation layer 42 with the second core shaft pattern 411, and the second side wall 441 has a third pitch L3 which is about 0.25 times of the first pitch L1.

[0059] Specifically, a second side wall material layer 44 covering the second core shaft pattern 411 and the second isolation layer 42 is formed, and the second core shaft pattern 411 and the second side wall material layer 44 above it are etched and removed, and the second side wall material layer 44 of the sidewall of the second core shaft pattern 411 is retained to form the second side wall 441. Similar to the formation of the first side wall, the formed second side wall 441 has a top rounded corner, and the second isolation layer 42 on both sides of the second side wall 441 has a height difference, i.e., a second groove 45.

[0060] Please refer to Figure 16After step S07, a fourth spacer layer 46 is formed, which covers the second spacer layer 42, fills the gap between the second side walls 441, and extends over the top surface of the second side walls 441.

[0061] The material of the fourth spacer layer 46 can be the same as that of the third spacer layer 34, for example, silicon oxide, which is formed by FCVD to achieve better filling effect. Moreover, the fourth spacer layer 46 also fills the second recess 45 formed on the surface of the second spacer layer 42, eliminating the height difference of the second spacer layer 42, i.e., filling the second recess 45.

[0062] Next, referring to FIG. 4C, Figure 17 A planarization process is performed on the fourth spacer layer 46 and the second side walls 441, for example, a chemical mechanical polishing process, to expose the second side walls 441 and continue to polish to eliminate the top rounded corners of the second side walls 441.

[0063] Next, referring to FIG. 4D, Figure 18 The second side walls 441 are removed, leaving the fourth spacer layer 46 as a fourth core spacer pattern 461, and the substrate 10 is patterned using the fourth core spacer pattern 461 as a mask pattern. The fourth core spacer pattern 461 has a third pitch L3, which is about 0.25 times the first pitch L1.

[0064] Specifically, the second side walls 441 can be removed by a method similar to that used to remove the first side walls 331, for example, wet etching. The formed fourth core spacer pattern 461 has a flat top surface (the top corners are right-angled), and the second spacer layer 42 on both sides of the fourth core spacer pattern 461 is flush or substantially flush, i.e., there is substantially no height difference, and a mask pattern with better topography (uniform and symmetrical structure) is formed using the fourth core spacer pattern 461.

[0065] The mask pattern formed by the above method has a more uniform and symmetrical structure, and the shape of the top rounded corners is right-angled, which can accurately transfer the pattern to the film layer to be patterned in the substrate 10.

[0066] In summary, the present application compensates the height difference of the first isolation layer on both sides of the first side wall by using the third isolation layer, and forms a third core shaft isolation pattern to further eliminate the height difference of the first isolation layer on both sides of the third core shaft isolation pattern, thereby avoiding the non-uniformity and asymmetry of the second core shaft pattern caused by using the third core shaft isolation pattern as a mask to etch downward. Moreover, the fourth isolation layer is used to compensate the height difference of the second isolation layer on both sides of the second side wall, and a fourth core shaft isolation pattern is formed to further eliminate the height difference of the second isolation layer on both sides of the fourth core shaft isolation pattern, thereby avoiding the non-uniformity and asymmetry of the structure caused by using the fourth core shaft isolation pattern as a mask pattern to etch the substrate downward, so as to form a mask pattern with better topography, and reduce the process debugging difficulty during patterning.

[0067] The above description is only a description of the preferred embodiments of the present application, and is not any limitation on the scope of the present application. Any modification or change made by a person skilled in the art according to the above disclosure is within the protection scope of the claims.

Claims

1. A graphical method, characterized in that, include: A substrate is provided, wherein a second isolation layer, a second core layer, a first isolation layer and a first core layer are formed thereon from bottom to top; A patterned mask layer is formed, and the first mandrel layer is etched using the patterned mask layer as a mask to form a first mandrel pattern; A first sidewall material layer is formed covering the first mandrel pattern and the first isolation layer. The top wall of the first mandrel pattern and the first sidewall material layer on the first isolation layer are etched away. The first sidewall material layer of the sidewall of the first mandrel pattern is retained to form a first sidewall. The first isolation layers on both sides of the first sidewall have a height difference. A third isolation layer is formed to fill the gap of the first sidewall, and the first sidewall is removed to form a third mandrel isolation pattern; Using the third mandrel isolation pattern as a mask, the second mandrel layer is etched to form the second mandrel pattern; A second sidewall material layer is formed covering the second mandrel pattern and the second isolation layer, and the top wall of the second mandrel pattern and the second sidewall material layer on the second isolation layer are etched away, leaving the second sidewall material layer on the sidewall of the second mandrel pattern to form the second sidewall, wherein the second isolation layers on both sides of the second sidewall have a height difference; and, A fourth isolation layer is formed to fill the gap between the second sidewalls, and the second sidewalls are removed to form a fourth mandrel isolation pattern, which is then used as a mask pattern to pattern the substrate.

2. The graphical method according to claim 1, characterized in that, The process of forming the third mandrel isolation pattern includes: A third isolation layer is formed, which fills the space between the first sidewalls and covers the first sidewalls; The third isolation layer and the first sidewall are flattened to expose the first sidewall and remove the top rounded corners of the first sidewall; The first sidewall is removed to form the third mandrel isolation pattern, which has a flat top surface.

3. The graphical method according to claim 1, characterized in that, The steps for forming the second mandrel pattern include: Using the third mandrel isolation pattern as a mask, the first isolation layer and the second mandrel layer are etched to expose the second isolation layer; A sacrificial layer is formed, which fills the spaces between the third mandrel isolation patterns and covers the top surface of the third mandrel isolation patterns; The sacrificial layer is etched back to expose the sides of the first isolation layer; The third mandrel isolation pattern, the first isolation layer, and the remaining sacrificial layer are removed to form the second mandrel pattern.

4. The graphical method according to claim 3, characterized in that, The sacrificial layer is made of a carbon-containing organic spin coating material.

5. The graphical method according to claim 1, characterized in that, The process of forming the fourth mandrel isolation pattern includes: A fourth isolation layer is formed, which fills the space between the second sidewalls and covers the top surface of the second sidewalls; The fourth isolation layer and the second sidewall are flattened to expose the second sidewall and remove the top rounded corners of the second sidewall; The second sidewall is removed to form the fourth mandrel isolation pattern, which has a flat top surface.

6. The graphical method according to any one of claims 1-5, characterized in that, The first isolation layer, the second isolation layer, the third isolation layer, and the fourth isolation layer are made of the same material; the first mandrel layer and the second mandrel layer are made of the same material; and the first sidewall and the second sidewall are made of the same material.

7. The graphical method according to claim 6, characterized in that, The first isolation layer, the second isolation layer, the third isolation layer, and the fourth isolation layer are made of silicon oxide.

8. The graphical method according to claim 6, characterized in that, The third isolation layer and / or the fourth isolation layer are formed using the FCVD process.

9. The graphical method according to claim 6, characterized in that, Both the first mandrel layer and the second mandrel layer are made of amorphous silicon.

10. The graphical method according to claim 6, characterized in that, Both the first sidewall and the second sidewall are made of silicon nitride.

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