Method for forming a semiconductor structure

Abstract

Method for forming a semiconductor structure, comprising: providing an initial substrate; sequentially forming a hard mask material layer and a bottom mandrel material layer on the initial substrate; forming a plurality of discrete first mandrel layers and a first composite mandrel layer on the bottom mandrel material layer; a protective layer covers the top of the first composite mandrel layer, and the top of the first mandrel layer is not covered with a protective layer; forming a first sidewall mask layer covering the sidewalls of the first mandrel layer and the first composite mandrel layer; removing the first mandrel layer, and etching the bottom mandrel material layer with the first sidewall mask layer and the first composite mandrel layer as masks to form a plurality of discrete second mandrel layers; forming a second sidewall mask layer covering the sidewalls of the second mandrel layers; removing the second mandrel layer, and etching the hard mask material layer with the second sidewall mask layer as a mask to form a patterned hard mask layer; patterning the initial substrate with the patterned hard mask layer as a mask to form a target pattern. The above solution can meet the different pitch requirements of the target pattern.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor integrated circuits, and particularly to a method for forming a semiconductor structure. Background Art

[0002] With the rapid development of semiconductor manufacturing technology, semiconductor devices are evolving towards higher element density and higher integration. Transistors, as the most basic semiconductor devices, are currently widely used. Therefore, as the density and integration of semiconductor devices increase, the feature size of planar transistors is getting smaller and smaller.

[0003] Lithography is a commonly used patterning method and is the most critical production technology in semiconductor manufacturing processes. As the semiconductor process nodes continue to decrease, the self-aligned double patterning (SADP) method has become a favored patterning method in recent years. This method can increase the density of patterns formed on the substrate, further reduce the pitch between two adjacent patterns, so that the lithography process can overcome the limit of lithography resolution.

[0004] As the critical dimension (CD) of patterns continues to shrink, the self-aligned quadruple patterning (SAQP) method has emerged. The density of patterns formed on the substrate by the self-aligned double patterning method is twice the density of patterns formed on the substrate by the lithography process, that is, a 1 / 2 minimum pitch can be obtained. Without changing the current lithography technology (i.e., the size of the lithography window remains unchanged), the density of patterns formed on the substrate by the self-aligned quadruple patterning method is four times the density of patterns formed on the substrate by the lithography process, that is, a 1 / 4 minimum pitch can be obtained. Thus, the density of semiconductor integrated circuits can be greatly increased, the feature size of patterns can be reduced, and further, it is beneficial to improve the device performance. Summary of the Invention

[0005] The problem solved by the present invention is to provide a method for forming a semiconductor structure to meet the different pitch requirements of target patterns.

[0006] To solve the above problems, the present invention provides a method for forming a semiconductor structure, including:

[0007] Providing an initial substrate for forming a target pattern;

[0008] Forming a hard mask material layer on the initial substrate and a bottom mandrel material layer on the hard mask material layer;

[0009] Form a plurality of discrete first mandrel layers and first composite mandrel layers on the bottom mandrel material layer; a protective layer is covered on the top of the first composite mandrel layer, and the protective layer is not covered on the top of the first mandrel layer;

[0010] Form a first sidewall mask layer covering the sidewalls of the first mandrel layer and the first composite mandrel layer;

[0011] Remove the first mandrel layer, and etch the bottom mandrel material layer with the first sidewall mask layer and the first composite mandrel layer as masks to form a plurality of discrete second mandrel layers, such that the sizes of each of the second mandrel layers in the target pattern width direction are at least partially different;

[0012] Form a second sidewall mask layer covering the sidewalls of the second mandrel layer;

[0013] Remove the second mandrel layer, and etch the hard mask material layer with the second sidewall mask layer as a mask to form a patterned hard mask layer;

[0014] Pattern the initial substrate with the patterned hard mask layer as a mask to form the target pattern.

[0015] Optionally, the step of forming a plurality of discrete first mandrel layers and first composite mandrel layers on the bottom mandrel material layer includes:

[0016] Form a top mandrel material layer on the bottom mandrel material layer;

[0017] Form a plurality of discrete protective material layers on the top mandrel material layer;

[0018] Form a planar layer covering the top mandrel material layer and the protective material layer, an anti-reflection layer on the planar layer, and a patterned photoresist layer on the anti-reflection layer;

[0019] Using the patterned photoresist layer as a mask, sequentially etch the anti-reflection layer, the planar layer, the protective material layer, and the top mandrel material layer to form a plurality of discrete first mandrel layers and first composite mandrel layers.

[0020] Optionally, the step of forming the first sidewall mask layer includes:

[0021] Form a first sidewall film conformally covering the bottom mandrel material layer, the first mandrel layer, and the first composite mandrel layer;

[0022] Remove the first sidewall film on the top of the first mandrel layer, the top of the first composite mandrel layer, and the bottom mandrel material layer, and retain the first sidewall film on the sidewalls of the first mandrel layer and the first composite mandrel layer as the first sidewall mask layer.

[0023] Optionally, the step of forming the second sidewall mask layer includes:

[0024] Form a conformal second sidewall film covering the hard mask material layer and the second mandrel layer;

[0025] Remove the second sidewall film on the top of the second mandrel layer and the hard mask material layer, and retain the second sidewall film on the sidewall of the second mandrel layer as the second sidewall mask layer.

[0026] Optionally, the material of the protection layer is silicon oxide.

[0027] Optionally, the thickness of the protection layer is 30 to 150 angstroms.

[0028] Optionally, the dimensions of multiple discrete protection layers in the width direction of the target pattern are the same or different.

[0029] Optionally, before forming the hard mask material layer on the initial substrate, it further includes:

[0030] Form a buffer material layer on the initial substrate.

[0031] Optionally, the material of the buffer material layer is silicon oxide.

[0032] Optionally, before forming the bottom mandrel material layer on the hard mask material layer, it further includes:

[0033] Form a first etch hard mask on the hard mask material layer.

[0034] Optionally, the material of the first etch hard mask is silicon oxide.

[0035] Optionally, before forming discrete first mandrel layer and first composite mandrel layer on the bottom mandrel material layer, the method further includes:

[0036] Form a second etch hard mask on the bottom mandrel material layer.

[0037] Optionally, the material of the second etch hard mask includes silicon oxide.

[0038] Optionally, after patterning the initial substrate with the patterned hard mask layer, the remaining substrate serves as a substrate, and the target pattern is fins.

[0039] Optionally, after forming the target pattern, the method further includes: removing part of the target pattern.

[0040] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0041] The above solution provides an initial substrate for forming a target pattern; a hard mask material layer is formed on the initial substrate and a bottom mandrel material layer is located on the hard mask material layer; a plurality of discrete first mandrel layers and first composite mandrel layers are formed on the bottom mandrel material layer; a protective layer covers the top of the first composite mandrel layer, and the top of the first mandrel layer is not covered by the protective layer; a first sidewall mask layer is formed to cover the sidewalls of the first mandrel layer and the first composite mandrel layer; the first mandrel layer is removed, and the bottom mandrel material layer is etched with the first sidewall mask layer and the first composite mandrel layer as masks to form a plurality of discrete second mandrel layers, such that the sizes of each of the second mandrel layers in the width direction of the target pattern are at least partially different; a second sidewall mask layer is formed to cover the sidewalls of the second mandrel layers; the second mandrel layers are removed, and the hard mask material layer is etched with the second sidewall mask layer as a mask to form a patterned hard mask layer; the initial substrate is patterned with the patterned hard mask layer as a mask to form the target pattern. During the process of removing the first mandrel layer, the protective layer on the top of the first composite mandrel layer plays a blocking role, so that the first composite mandrel layer is retained. When transferring the pattern to the bottom mandrel material layer through the first composite mandrel layer and the first sidewall mask layer, second mandrel layers with different sizes in the width of the target pattern can be formed, so that second sidewall mask layers with different spacings in the width of the target pattern can be formed, and further the spacings between the finally formed target patterns can be different, meeting the different spacing requirements of the target patterns. Description of the Drawings

[0042] Figure 1 It is a schematic flow chart of a method for forming a semiconductor structure in an embodiment of the present invention.

[0043] Figures 2 to 13 It is a schematic diagram of an intermediate structure formed by each step of a method for forming a semiconductor structure in an embodiment of the present invention. Detailed Embodiments

[0044] As can be seen from the background art, as the graphic feature size continues to shrink, the self-aligned quadruple patterning method is usually selected to form the target pattern, so that the target pattern can obtain a 1 / 4 pitch without changing the current lithography technology. Although the self-aligned quadruple patterning method can reduce the pitch of the target pattern, the pitches of the target patterns are equal and cannot meet the requirements of different pitches of the target patterns.

[0045] To solve the above technical problem, in an embodiment of the present invention, a plurality of discrete first mandrel layers and first composite mandrel layers are formed on the bottom mandrel material layer; a protective layer covers the top of the first composite mandrel layer, and the protective layer does not cover the top of the first mandrel layer. Due to the blocking effect of the protective layer, during the process of removing the first mandrel layer, the protective layer on the top of the first composite mandrel layer plays a blocking role, enabling the first composite mandrel layer to be retained. When transferring a pattern to the bottom mandrel material layer through the first composite mandrel layer and the first sidewall mask layer, a second mandrel layer with different dimensions in the width direction of the target pattern can be formed, thereby forming a second sidewall mask layer with different spacings in the width direction of the target pattern. Furthermore, the spacings between the finally formed target patterns can be made different to meet the different spacing requirements of the target patterns.

[0046] Figure 1 FIG. shows a schematic flow chart of a method for forming a semiconductor structure in an embodiment of the present invention. Refer to Figure 1 A method for forming a semiconductor structure in an embodiment of the present invention may specifically include:

[0047] Step S101: Provide an initial substrate for forming a target pattern;

[0048] Step S102: Form a hard mask material layer on the initial substrate and a bottom mandrel material layer on the hard mask material layer;

[0049] Step S103: Form a plurality of discrete first mandrel layers and first composite mandrel layers on the bottom mandrel material layer; a protective layer covers the top of the first composite mandrel layer, and the protective layer does not cover the top of the first mandrel layer;

[0050] Step S104: Form a first sidewall mask layer covering the sidewalls of the first mandrel layer and the first composite mandrel layer;

[0051] Step S105: Remove the first mandrel layer, and etch the bottom mandrel material layer using the first sidewall mask layer and the first composite mandrel layer as masks to form a plurality of discrete second mandrel layers, such that the dimensions of each of the second mandrel layers in the width direction of the target pattern are at least partially different;

[0052] Step S106: Form a second sidewall mask layer covering the sidewalls of the second mandrel layer;

[0053] Step S107: Remove the second mandrel layer, and etch the hard mask material layer using the second sidewall mask layer as a mask to form a patterned hard mask layer;

[0054] Step S108: Pattern the initial substrate using the patterned hard mask layer as a mask to form the target pattern.

[0055] To make the above objects, features, and advantages of the embodiments of the present invention more obvious and understandable, the following specifically describes the embodiments of the present invention with reference to the accompanying drawings.

[0056] The following will combine Figures 2 to 13 to further describe in detail a method for forming a semiconductor structure in an embodiment of the present invention.

[0057] Refer to Figure 2 , and provide an initial substrate 100.

[0058] The initial substrate 100 is used to form a target pattern. In this embodiment, the target pattern formed by the initial substrate 100 is a fin, and the remaining initial substrate serves as a substrate.

[0059] In this embodiment, the material of the initial substrate 100 is silicon. In other embodiments, the material of the initial substrate can also be other materials such as germanium, silicon germanide, silicon carbide, gallium arsenide, or indium gallium, and the initial substrate can also be other types of substrates such as a silicon-on-insulator substrate or a germanium-on-insulator substrate. In addition, the initial substrate may further include a first semiconductor layer and a second semiconductor layer epitaxially grown on the first semiconductor layer. The first semiconductor layer is used to provide a process basis for forming the subsequent substrate, and the second semiconductor layer is used to provide a process basis for forming the subsequent fin. In other embodiments, the initial substrate may further include other etched functional layers, such as a gate material layer.

[0060] Refer to Figure 3 , form a hard mask material layer 110 on the initial substrate 100 and a bottom mandrel material layer 120 located on the hard mask material layer 110.

[0061] The hard mask material layer 110 is used to form an etching mask for etching the initial substrate 100 subsequently to form a target pattern.

[0062] In this embodiment, the material of the hard mask material layer 110 is silicon nitride (SiN). In other embodiments, the material of the hard mask material layer 110 can also be silicon oxide (SiO2), silicon oxynitride (SiON), silicon oxycarbide (SiOC), amorphous carbon (a-C), silicon oxycarbonitride (SiOCN), or a stack thereof.

[0063] The process for forming the hard mask material layer 110 includes physical vapor deposition process, chemical vapor deposition process, or atomic layer deposition process, etc.

[0064] In this embodiment, before forming the hard mask material layer 110 on the initial substrate 100, a step of forming a buffer material layer 105 on the initial substrate 100 is further included. The buffer material layer 105 is used to provide a buffering effect when forming the hard mask material layer 110, and can avoid the problem of misalignment when directly forming the hard mask material layer 110 on the initial substrate 100.

[0065] In this embodiment, the material of the buffer material layer 105 is silicon oxide.

[0066] The bottom mandrel material layer 120 is used to provide a process basis for subsequently forming a plurality of discrete second mandrel layers.

[0067] The bottom mandrel material layer 120 provides a process basis for subsequently forming a patterned second mandrel layer. Among them, the second sidewall mask layer formed on the sidewall of the second mandrel layer is used as a mask for patterning the hard mask material layer 110.

[0068] After forming the second sidewall mask layer on the sidewall of the second mandrel layer, the second mandrel layer needs to be removed. Therefore, the bottom mandrel material layer 120 is made of a material that is easy to be removed, and the process of removing the second mandrel layer causes less damage to other film layers. In this embodiment, the material of the bottom mandrel material layer 120 is amorphous silicon. In some other embodiments, the material of the bottom mandrel material layer 120 is silicon nitride. In other embodiments, the material of the bottom mandrel material layer can also be amorphous carbon, amorphous germanium, silicon oxide, silicon oxynitride, carbon nitride, polysilicon, silicon carbide, silicon carbonitride, silicon carbon oxynitride or an organic dielectric layer (Organic Dielectric Layer, ODL) material.

[0069] The process of forming the bottom mandrel material layer 120 is an atomic layer deposition process, a chemical vapor deposition process or a physical vapor deposition process, etc.

[0070] In this embodiment, before forming the bottom mandrel material layer 120 on the hard mask material layer 110, a step of forming a bottom etch hard mask 111 on the hard mask material layer 110 is further included. The bottom etch hard mask 111 is used as an etch mask for the hard mask material layer 110, and can also be used to provide a buffering effect when forming the hard mask material layer 110, and can avoid the problem of misalignment when directly forming the bottom mandrel material layer 120 on the hard mask material layer 110.

[0071] In this embodiment, after forming the bottom mandrel material layer 120, it further includes: forming a first etch hard mask 121 on the bottom mandrel material layer 120.

[0072] The first etching hard mask 121 serves as an etching mask for subsequent etching of the bottom mandrel material layer 120, and can provide a buffering effect for the bottom mandrel material layer 120 formed subsequently on the first etching hard mask 121.

[0073] In this embodiment, the material of the first etching hard mask 121 is silicon dioxide.

[0074] The process for forming the first etching hard mask 121 is an atomic layer deposition process, a chemical vapor deposition process, or an atomic layer deposition process, etc.

[0075] See Figure 4 , and a top mandrel material layer 130 is formed on the bottom mandrel material layer 120.

[0076] The top mandrel material layer 130 provides a process basis for subsequent formation of the first mandrel layer.

[0077] After forming the second sidewall mask layer on the sidewall of the second mandrel layer, the second mandrel layer needs to be removed. Therefore, the top mandrel material layer 130 is made of a material that is easy to remove, and the process of removing the second mandrel layer causes less damage to other film layers. In this embodiment, the material of the bottom mandrel material layer 120 is amorphous silicon. In some other embodiments, the material of the bottom mandrel material layer 120 is silicon nitride. In other embodiments, the material of the bottom mandrel material layer can also be amorphous carbon, amorphous germanium, silicon oxide, silicon oxynitride, carbon nitride, polysilicon, silicon carbide, carbon silicon nitride, carbon silicon oxynitride, or an organic dielectric layer (Organic Dielectric Layer, ODL) material.

[0078] The process for forming the top mandrel material layer 130 is an atomic layer deposition process, a chemical vapor deposition process, or a physical vapor deposition process, etc.

[0079] See Figure 5 , and a plurality of discrete protective material layers 140 are formed on the top mandrel material layer 130.

[0080] The protective material layer 140 provides a process basis for subsequent formation of the protective layer. Among them, the protective layer and the first mandrel layer formed below it constitute the first composite mandrel layer.

[0081] The protective layer is used to protect the first mandrel layer formed below it during the subsequent process of removing the first mandrel layer that is not covered by it. Therefore, compared with the top mandrel material layer 130, the protective material layer 140 has a lower etching selectivity rate. In this embodiment, the material of the protective material layer 140 is silicon oxide. In other embodiments, the protective material layer 140 can also be silicon nitride, silicon carbide, and aluminum oxide, etc.

[0082] The steps of forming multiple discrete protective material layers 140 include: forming a protective layer material layer (not shown in the figure) on the top mandrel material layer 130; forming a first flat layer on the protective layer material layer; forming a first anti-reflection layer (not shown in the figure) on the first flat layer; forming a patterned first photoresist layer (not shown in the figure) on the first anti-reflection layer; sequentially etching the first anti-reflection layer, the first flat layer, and the protective layer material layer with the first photoresist layer as a mask, and the remaining protective layer material layer serves as the protective material layer 140.

[0083] In an embodiment of the present invention, the thickness of the protective layer is 30 to 150 angstroms.

[0084] See Figure 6 , pattern the protective material layer 140 and the top mandrel material layer 130 to form multiple discrete first mandrel layers 150 and first composite mandrel layers 155 on the bottom mandrel material layer 120.

[0085] The steps of forming multiple discrete first mandrel layers 150 and first composite mandrel layers 155 include: forming a second flat layer (not shown in the figure) covering the top mandrel material layer 130 and the protective material layer 140; forming a second anti-reflection layer (not shown in the figure) on the second flat layer; forming a patterned second photoresist layer on the second anti-reflection layer; sequentially etching the second anti-reflection layer, the second flat layer, the protective material layer, and the top mandrel material layer with the first photoresist layer as a mask, the top mandrel material layer 130 not covered by the remaining protective material layer 140 serves as the first mandrel layer 150, and the remaining protective material layer and the remaining top mandrel material layer 130 below it serve as the first composite mandrel layer 155.

[0086] The second anti-reflection coating is used to reduce the reflection effect during exposure, thereby improving the pattern transfer accuracy, and further improving the topography quality and dimensional accuracy of the second photoresist layer. In this embodiment, the second anti-reflection coating is a Si-ARC layer.

[0087] The top surface of the second flat layer is a flat surface, which is used to improve the surface flatness of the second anti-reflection coating, thereby improving the topography quality and dimensional accuracy of the second photoresist layer. In this embodiment, the second flat layer is a spin-on carbon (SOC) layer. The spin-on carbon layer is formed by a spin coating process, with a low process cost and can ensure the surface flatness of the second flat layer. In other embodiments, the material of the second flat layer can also be silicon oxide.

[0088] It should be noted that during the pattern transfer process, the second photoresist layer and the second anti-reflection coating will also be lost. In this embodiment, after the first core layer 300 is formed, the first photoresist layer 400 and the anti-reflection coating 320 have been removed, and only the flat layer 310 remains in the first mandrel layer 150 and the first composite mandrel layer 155.

[0089] Therefore, after the first mandrel layer 150 and the first composite mandrel layer 155 are formed, the second flat layer can be directly removed in the same etching machine tool using an ashing process, which is simple in process and does not require changing the machine tool.

[0090] See Figure 7 , a first sidewall mask layer 165 covering the sidewalls of the first mandrel layer 150 and the first composite mandrel layer 155 is formed.

[0091] The first sidewall mask layer 165 and the first composite mandrel layer 155 are used together as a mask for subsequent patterning of the bottom mandrel material layer 120, thereby forming a second mandrel layer with different sizes in the target pattern width direction.

[0092] The step of forming the first sidewall mask layer 165 includes: forming a first sidewall film (not shown in the figure) that conformally covers the bottom mandrel material layer 120, the first mandrel layer 150, and the first composite mandrel layer 155; removing the first sidewall film covering the bottom mandrel material layer 120, the first sidewall film on the top of the first mandrel layer 150, and the first sidewall film covering the top of the first composite mandrel layer 155, and only retaining the first sidewall film covering the sidewalls of the first mandrel layer 150 and the first composite mandrel layer 155 as the first sidewall mask layer 165.

[0093] In this embodiment, in order to improve the uniformity of the thickness of the first sidewall mask material layer and reduce the difficulty of controlling its thickness, an atomic layer deposition process is used to form the first sidewall mask material layer. In other embodiments, the first sidewall mask material layer can also be formed by a chemical vapor deposition process.

[0094] In this embodiment, the material of the first sidewall mask layer 165 is silicon nitride. Silicon nitride is a commonly used sidewall mask material in the SAQP process. Silicon nitride has a high hardness and density, and the etching selectivity between silicon nitride and amorphous silicon is relatively large, which can reduce the probability of damage to the first sidewall mask layer 165 during the subsequent removal of the first mandrel layer 150.

[0095] In this embodiment, when a second etching hard mask 131 is further formed on the bottom mandrel material layer 120, the first sidewall mask material layer also conformally covers the second etching hard mask 131 and the first mandrel layer 150.

[0096] In this embodiment, an anisotropic blanket dry etch process is used to selectively etch the first sidewall mask material layer along the normal direction of the surface of the initial substrate 100, so as to form a first sidewall mask layer 165 on the sidewalls of the first mandrel layer 150.

[0097] See Figure 8 , after forming the first sidewall mask layer 165, the first mandrel layer 150 is removed.

[0098] Removing the first mandrel layer 150 provides a process basis for subsequent patterning of the bottom mandrel material layer 120.

[0099] In this embodiment, a wet etch process is used to etch and remove the first mandrel layer 150. Specifically, the material of the first mandrel layer 150 is amorphous silicon, and the etchant solution used in the wet etch process is a mixed solution of Cl2 and HBr or a TMAH solution. In other embodiments, a dry etch process or a combination of dry etch and wet etch processes can also be used to remove the first mandrel layer 150.

[0100] It should be noted that since the top of the first composite mandrel layer 155 has a protective layer, during the process of removing the first mandrel layer 150, the protective layer on the top of the first composite mandrel layer 155 plays a blocking role, enabling the first composite mandrel layer 155 to be retained, thus providing a process basis for subsequent formation of a second mandrel layer with different dimensions in the target pattern width direction.

[0101] See Figure 9 , using the first sidewall mask layer 165 and the first composite mandrel layer 155 as masks to etch the bottom mandrel material layer 120, multiple discrete second mandrel layers 125.

[0102] The second mandrel layer 125 provides a basis for subsequent formation of a second sidewall mask layer. Among them, in subsequent processes, the second sidewall mask layer is formed on the sidewalls of the second mandrel layer 125, and the second sidewall mask layer is used to pattern the bottom mandrel material layer 120 to form a patterned planarization layer.

[0103] In this embodiment, the material of the second mandrel layer 125 is correspondingly amorphous silicon.

[0104] It can be understood that among the multiple discrete second mandrel layers 125, there are second mandrel layers 125 etched with only the first sidewall mask layer 165 as the mask, and second mandrel layers 125 etched with the first composite mandrel layer 155 and the first sidewall mask layer 165 formed on its sidewalls as the mask. Among them, the size of the second mandrel layer 125 etched with only the first sidewall mask layer 165 as the mask in the target pattern width direction is the same as the size of the first sidewall mask layer 165 in the target pattern width direction, while the size of the second mandrel layer 125 etched with the first composite mandrel layer 155 and the first sidewall mask layer 165 formed on its sidewalls as the mask in the target pattern width direction is the sum of the size of the first composite mandrel layer 155 in the target pattern width direction and twice the size of the first sidewall mask layer 165 in the target pattern width direction. Therefore, the sizes of the formed second mandrel layers 125 in the target pattern width direction are at least partially different, so that in the subsequent pattern transfer process, target patterns with different pitches can be formed.

[0105] In this embodiment, in the direction from the initial substrate 100 to the bottom mandrel material layer 120, a second etch hard mask 121 is formed on the bottom mandrel material layer 120. Therefore, using the first sidewall mask layer 165 and the first composite mandrel layer 155 as masks, the bottom etch hard mask 132 and the bottom mandrel material layer 120 are sequentially etched by a dry etching process to form a patterned second etch hard mask layer 131' and a second mandrel layer 125.

[0106] After forming the multiple discrete second mandrel layers 125, it further includes the step of removing the first sidewall mask layer 165 and the first composite mandrel layer 155.

[0107] When a second etch hard mask 122 is formed on the bottom mandrel material layer 120, after removing the first sidewall mask layer 165, it further includes the step of removing the patterned second etch hard mask layer 121'.

[0108] See Figure 10 , a second sidewall mask layer 175 is formed on the sidewalls of the second mandrel layer 125.

[0109] The second sidewall mask layer 175 is used as a mask for patterning the bottom mandrel material layer 120.

[0110] In this embodiment, the material of the second sidewall mask layer 175 is silicon nitride. The description of the material of the second sidewall mask layer 175 can refer to the description of the first sidewall mask layer 165 above, and will not be elaborated here.

[0111] Specifically, the steps of forming the second sidewall mask layer 175 include: forming a conformal second sidewall film covering the second mandrel layer 125 and the hard mask material layer 110; removing the second sidewall film on the top of the second mandrel layer 125 and the hard mask material layer 110 by a maskless etching process, and retaining the remaining second sidewall film on the sidewalls of the second mandrel layer 125 as the second sidewall mask layer 175.

[0112] For a specific description of the steps of forming the second sidewall mask layer 175, reference may be made to the relevant description of forming the first mask sidewall 135 above, which will not be elaborated here.

[0113] It can be understood that when the dimensions of the second mandrel layer 125 in the target pattern width direction are different, the second sidewall mask layer 175 formed on the sidewalls of the second mandrel layer 125 will also have different spacings. Thus, when the pattern is transferred to the target pattern through the second sidewall mask layer 175 subsequently, target patterns with different spacings can be formed.

[0114] See Figure 11 , after forming the second sidewall mask layer 175, remove the second mandrel layer 125.

[0115] Removing the second mandrel layer 125 provides a process basis for subsequent patterning of the mask material layer 110.

[0116] In this embodiment, the second mandrel layer 125 is etched and removed by a wet etching process. For a specific description of the process of removing the second mandrel layer 125, reference may be made to the corresponding description when removing the first mandrel layer 150 above, which will not be elaborated here.

[0117] See Figure 12 , using the second sidewall mask layer 175 as a mask to etch the hard mask material layer 110 to form a patterned hard mask layer 110'.

[0118] The process of forming the patterned hard mask layer 115 is a dry etching process. Specifically, using the second sidewall mask layer 175 as a mask, the bottom etch hard mask layer of 111 and the hard mask material layer 110 are sequentially etched by a dry etching process to form a patterned bottom etch hard mask layer 111' and the hard mask layer 110'.

[0119] After forming the patterned bottom etch hard mask layer 111' and the hard mask layer 110', the step of removing the second sidewall mask layer 175 is further included.

[0120] In this embodiment, the second sidewall mask layer 175 is removed by a wet etching process. In other embodiments, the second sidewall mask layer 175 can also be removed by a dry etching process or a process combining dry etching and wet etching.

[0121] It should be noted that due to the different spacings between the second sidewall mask layers 175, after transferring the pattern to the hard mask layer material layer 110 through the second sidewall mask layers 175, there are also different spacings between the formed hard mask layers 110'.

[0122] See Figure 13 , using the patterned hard mask layer 110' as a mask to etch the initial substrate 100 to form the target pattern 101.

[0123] In this embodiment, after patterning the initial substrate 100, the remaining initial substrate 100 is used as the substrate 102, and the target pattern 101 is a fin, and the fin 101 and the substrate 102 are an integral structure.

[0124] It should be noted that when there are different spacings between adjacent hard mask layers 110', after transferring the pattern to the initial substrate 110 through the hard mask layer 110' to form the target pattern 101, there will be different spacings between the formed target patterns 101.

[0125] In other embodiments, when the initial substrate includes a first semiconductor layer and a second semiconductor layer epitaxially grown on the first semiconductor layer, in the step of etching the substrate, only the first semiconductor layer is etched, and the first semiconductor layer is used as the substrate, and the remaining second semiconductor layer protruding from the first semiconductor layer is used as the fin. Correspondingly, the material of the fin can also be different from the material of the substrate.

[0126] After forming the target pattern 101, it further includes the step of removing part of the target pattern 101.

[0127] In this embodiment, the target pattern 101 is a fin, and the step of removing part of the fin includes: forming a third planar material layer (not shown in the figure) covering the substrate 102 and the fin 101; forming a third anti-reflection material layer (not shown in the figure) covering the third planar material layer; forming a patterned third photoresist layer (not shown in the figure) on the third anti-reflection material layer, and the third photoresist layer has corresponding openings (not shown in the figure); etching the third anti-reflection material layer, the third planar material layer, and the fin at the bottom of the opening in sequence with the patterned third photoresist layer. It should be noted that when there is still a bottom etch hard mask layer 111', the hard mask layer 110', and a buffer layer 105' remaining on the top of the fin 101, the third planar material layer also covers the bottom etch hard mask layer 111', the hard mask layer 110', and the buffer layer 105'.

[0128] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A method for forming a semiconductor structure, characterized in that: include: providing an initial substrate for forming a target pattern; forming a hard mask material layer and a bottom mandrel material layer on the hard mask material layer on the initial substrate; forming a plurality of separate first mandrel layers and first composite mandrel layers on the bottom mandrel material layer; the top of the first composite mandrel layer is covered with a protective layer, and the top of the first mandrel layer is not covered with the protective layer; forming a first spacer mask layer covering the sidewalls of the first mandrel layer and the sidewalls of the first composite mandrel layer; removing the first mandrel layer, and etching the bottom mandrel material layer using the first spacer mask layer and the first composite mandrel layer as masks to form a plurality of discrete second mandrel layers, such that the sizes of the second mandrel layers in the width direction of the target pattern are at least partially different; forming a second spacer mask layer covering the sidewalls of the second mandrel layer; removing the second mandrel layer, and etching the hard mask material layer using the second spacer mask layer as a mask to form a patterned hard mask layer; patterning the initial substrate using the patterned hard mask layer as a mask to form the target pattern; The step of forming a plurality of separate first mandrel layers and a first composite mandrel layer on the bottom mandrel material layer comprises: forming a top layer of mandrel material on the bottom layer of mandrel material; forming a plurality of discrete layers of protective material over the top mandrel material layer; forming a planar layer covering the top mandrel material layer and the protective material layer, an anti-reflective layer on the planar layer, and a patterned photoresist layer on the anti-reflective layer; Using the patterned photoresist layer as a mask, the anti-reflection layer, the flat layer, the protective material layer and the top mandrel material layer are etched in sequence to form a plurality of discrete first mandrel layers and a first composite mandrel layer.

2. The method for forming a semiconductor structure according to claim 1, wherein: The step of forming the first spacer mask layer includes: forming a first sidewall film conformally covering the bottom mandrel material layer, the first mandrel layer and the first composite mandrel layer; The first spacer film on the top of the first mandrel layer, the top of the first composite mandrel layer and the bottom mandrel material layer is removed, and the first spacer film on the sidewall of the first mandrel layer and the sidewall of the first composite mandrel layer is retained as the first spacer mask layer.

3. The method for forming a semiconductor structure according to claim 1, wherein: The step of forming the second spacer mask layer includes: forming a second spacer film conformally covering the hard mask material layer and the second mandrel layer; The second spacer film on the top of the second mandrel layer and the hard mask material layer is removed, and the second spacer film on the sidewall of the second mandrel layer is retained as the second spacer mask layer.

4. The method for forming a semiconductor structure according to claim 1, wherein: The material of the protective layer is silicon oxide.

5. The method for forming a semiconductor structure according to claim 1, wherein: The thickness of the protective layer is 30 to 150 angstroms.

6. The method for forming a semiconductor structure according to claim 1, wherein: The sizes of the plurality of separate protection layers in the width direction of the target pattern are the same or different.

7. The method for forming a semiconductor structure according to claim 1, wherein: Before forming a hard mask material layer on the initial substrate, the method further includes: A buffer material layer is formed on the initial substrate.

8. The method for forming a semiconductor structure according to claim 7, wherein: The buffer material layer is made of silicon oxide.

9. The method for forming a semiconductor structure according to claim 1, wherein: Before forming a bottom mandrel material layer on the hard mask material layer, the method further includes: A first etching hard mask is formed on the hard mask material layer.

10. The method for forming a semiconductor structure according to claim 9, wherein: The material of the first etching hard mask is silicon oxide.

11. The method for forming a semiconductor structure according to claim 1, wherein: Before forming the separate first mandrel layer and the first composite mandrel layer on the bottom mandrel material layer, the method further comprises: A second etch hard mask is formed on the bottom mandrel material layer.

12. The method for forming a semiconductor structure according to claim 11, wherein: The material of the second etching hard mask includes silicon oxide.

13. The method for forming a semiconductor structure according to claim 1, wherein: After the initial substrate is patterned using the patterned hard mask layer as a mask, the remaining substrate serves as a backing, and the target pattern is a fin.

14. The method for forming a semiconductor structure according to claim 1, wherein: After forming the target pattern, the method further includes: removing part of the target pattern.

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