Alignment mark and forming method thereof

Abstract

The invention relates to an alignment mark and a forming method thereof, the alignment mark comprises a first alignment mark and a second alignment mark which are adjacently arranged, the first alignment mark and the second alignment mark are spaced, the first alignment mark comprises a plurality of first rectangular sub-alignment marks which extend along a first direction and are arranged in parallel at intervals, and the second alignment mark comprises a plurality of second rectangular sub-alignment marks; the first alignment mark comprises a plurality of first rectangular sub-alignment marks, the arrangement direction of the first rectangular sub-alignment marks is perpendicular to the first direction, the second alignment mark comprises a plurality of second rectangular sub-alignment marks which extend in the second direction and are arranged in parallel at intervals, and the arrangement direction of the second rectangular sub-alignment marks is perpendicular to the second direction; wherein the extension line of the first rectangular sub-alignment mark in the first direction intersects with the extension line of the second rectangular sub-alignment mark in the second direction. The performance of the alignment mark is improved, and the formation quality of the alignment mark is further improved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of semiconductor manufacturing, and in particular to an alignment mark and a method for forming the same. Background Art

[0002] Photolithography is a crucial technology in semiconductor manufacturing technology. It can transfer patterns from the mask to the surface of the silicon wafer to form semiconductor products that meet the design requirements. In the photolithography process, first, through the exposure step, light passes through the light-transmitting or light-reflecting area in the mask to the silicon wafer coated with photoresist, and a photochemical reaction occurs with the photoresist; then, through the development step, the degree of solubility of the photosensitive and non-photosensitive photoresists in the developer is used to form a photolithography pattern to achieve the transfer of the mask pattern; then, through the etching step, the silicon wafer is etched based on the photolithography pattern formed by the photoresist layer, and the mask pattern is further transferred to the silicon wafer.

[0003] As the size of photolithographic features continues to decrease, the requirements for the overlay accuracy and critical dimension uniformity of the photolithography machine are also increasing. The manufacture of semiconductor devices usually includes dozens of photolithography processes. In order to ensure the correspondence between each layer, the wafer must be aligned before photolithography so that the pattern can be accurately transferred to the photoresist layer of the wafer.

[0004] However, the quality of existing alignment marks still needs to be improved. Summary of the invention

[0005] The problem solved by the embodiments of the present invention is to provide an alignment mark and a method for forming the same, which is beneficial to further improve the performance of the alignment mark.

[0006] To solve the above problems, an embodiment of the present invention provides an alignment mark, including: a first alignment mark and a second alignment mark that are adjacent to each other, the first alignment mark and the second alignment mark are spaced apart, the first alignment mark includes a plurality of first rectangular sub-alignment marks extending along a first direction and arranged in parallel at intervals, the arrangement direction of the first rectangular sub-alignment marks is perpendicular to the first direction, the second alignment mark includes a plurality of second rectangular sub-alignment marks extending along a second direction and arranged in parallel at intervals, the arrangement direction of the second rectangular sub-alignment marks is perpendicular to the second direction; wherein, an extension line of the first rectangular sub-alignment mark in the first direction intersects with an extension line of the second rectangular sub-alignment mark in the second direction.

[0007] Optionally, the area between the first alignment mark and the second alignment mark is a spacing area; the intersection position of the extension line of the first rectangular sub-alignment mark in the first direction and the extension line of the second rectangular sub-alignment mark in the second direction is located in the spacing area.

[0008] Optionally, the first alignment mark and the second alignment mark are symmetrical about the center line axis of the spacing zone, and the center line extends along the extension direction of the spacing zone; the extension line of the first rectangular sub-alignment mark in the first direction and the extension line of the second rectangular sub-alignment mark in the second direction intersect on the center line.

[0009] Optionally, there is a first distance between adjacent first rectangular sub-alignment marks, and there is a second distance between adjacent second rectangular sub-alignment marks, and the first distance is equal to the second distance.

[0010] Optionally, the first alignment mark and the second alignment mark are spaced apart by a distance of 0.5 micrometers to 20 micrometers.

[0011] Accordingly, an embodiment of the present invention provides a method for forming an alignment mark, comprising: providing a substrate, the substrate comprising an alignment mark area, a core layer formed on the top of the substrate in the alignment mark area, the core layer comprising a first core layer and a second core layer arranged adjacent to each other, the first core layer comprising a plurality of first sub-core layers extending in a first direction and arranged in parallel at intervals, the arrangement direction of the first sub-core layers being perpendicular to the first direction, the second core layer comprising a plurality of second sub-core layers extending in a second direction and arranged in parallel at intervals, the arrangement direction of the second sub-core layers being perpendicular to the second direction, and at least a portion of the first sub-core layer and the second sub-core layer The layers are connected at the end positions; part of the material at the end position of the first sub-core layer and part of the material at the end position of the second sub-core layer are removed, so that the remaining first sub-core layer and the remaining second sub-core layer are both rectangular; a first mask side wall is formed on the side wall of the remaining first sub-core layer and the side wall of the remaining second sub-core layer; after the first mask side wall is formed, the remaining first core layer and the second core layer are removed; after the remaining first core layer and the second core layer are removed, the substrate of the alignment mark area is patterned with the help of the first mask side wall to form an alignment groove; an alignment mark is formed in the alignment groove.

[0012] Optionally, a bottom core material layer is also formed on the top of the substrate, and the core layer is formed on the top of the bottom core material layer in the alignment mark area; with the help of the first mask side wall, the substrate in the alignment mark area is patterned, and the step of forming an alignment groove includes: using the first mask side wall as a mask, patterning the bottom core material layer to form a third core layer; forming a second mask side wall on the side wall of the third core layer; after forming the second mask side wall, removing the third core layer; after removing the third core layer, patterning the substrate with the second mask side wall as a mask to form an alignment groove in the substrate; removing the second mask side wall.

[0013] Optionally, the step of forming an alignment mark in the alignment groove includes: forming a hard mask layer at the bottom and sidewalls of the alignment groove; after forming the hard mask layer, forming an alignment mark material layer in the remaining space of the alignment groove, the alignment mark material covering the hard mask layer; and flattening the hard mask layer and the alignment mark material layer above the top of the substrate, retaining the alignment mark material layer and the hard mask layer in the alignment groove to constitute the alignment mark.

[0014] Optionally, the step of removing part of the material at the end position of the first sub-core layer and part of the material at the end position of the second sub-core layer includes: forming a rectangular mask layer on the top of the first sub-core layer and the second sub-core layer, the mask layer exposing the end position of the first sub-core layer and the end position of the second sub-core layer; using the mask layer as a mask, removing part of the material at the end position of the first sub-core layer and part of the material at the end position of the second sub-core layer, so that the remaining first sub-core layer and the remaining second sub-core layer are both rectangular.

[0015] Optionally, after removing part of the material at the end position of the first sub-core layer and part of the material at the end position of the second sub-core layer, the area between the first core layer and the second core layer is a spacing zone; the alignment mark is symmetrical about the center line axis of the spacing zone, and the center line extends along the extension direction of the spacing zone.

[0016] Optionally, the first core layer and the second core layer are spaced apart by a distance of 0.5 micrometers to 20 micrometers.

[0017] Optionally, the step of forming the first mask sidewall includes: forming a first mask sidewall material layer on the top and sidewall of the first core layer, the top and sidewall of the second core layer, and the top of the substrate; removing the first mask sidewall material layer on the top of the first core layer, the top of the second core layer, and the top of the substrate, and the remaining first mask sidewall material layer located on the sidewalls of the first core layer and the second core layer serves as the first mask sidewall.

[0018] Optionally, there is a first distance between adjacent first sub-core layers, and there is a second distance between adjacent second sub-core layers, and the first distance is equal to the second distance.

[0019] Compared with the prior art, the technical solution of the embodiment of the present invention has the following advantages:

[0020] An embodiment of the present invention provides a method for forming an alignment mark, providing a substrate, the substrate comprising an alignment mark area, a core layer formed on the top of the substrate in the alignment mark area, the core layer comprising a first core layer and a second core layer arranged adjacent to each other, the first core layer comprising a plurality of first sub-core layers extending in a first direction and arranged in parallel at intervals, the arrangement direction of the first sub-core layers being perpendicular to the first direction, the second core layer comprising a plurality of second sub-core layers extending in a second direction and arranged in parallel at intervals, the arrangement direction of the second sub-core layers being perpendicular to the second direction, and at least a portion of the first sub-core layer and the second sub-core layer are connected at an end position; removing a portion of material at the end position of the first sub-core layer and the second sub-core layer; Part of the material at the end position of the two sub-core layers makes the remaining first sub-core layer and the remaining second sub-core layer both rectangular, that is, the corners of the first sub-core layer and the second sub-core layer are right angles. Accordingly, in the subsequent process of forming the first mask side wall on the side wall of the remaining first sub-core layer and the side wall of the remaining second sub-core layer, the probability of the first mask side wall tilting and collapsing is reduced. At the same time, the substrate of the alignment mark area is subsequently patterned with the help of the first mask side wall to form an alignment groove. In the process of forming the alignment mark in the alignment groove, the risk of falling off when the material of the alignment mark is deposited at the corner of the alignment groove is reduced, thereby improving the performance of the alignment mark and further improving the formation quality of the alignment mark. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figures 1 to 3 is a schematic diagram of a structure corresponding to an alignment mark;

[0022] Figures 4 to 6 is a schematic diagram of the structure corresponding to an embodiment of an alignment mark of the present invention;

[0023] Figures 7 to 21It is a schematic structural diagram corresponding to each step in an embodiment of a method for forming an alignment mark of the present invention. DETAILED DESCRIPTION

[0024] At present, the formation quality of the alignment mark still needs to be improved. Now, a formation method of the alignment mark is combined to analyze the reasons why its performance needs to be improved.

[0025] Figures 1 to 3 is a schematic diagram of the structure corresponding to the alignment mark, wherein: Figure 1 It is a top view. Figure 2 yes Figure 1 Cross-sectional view along direction aa.

[0026] refer to Figure 1 , providing a substrate 10, the substrate 10 includes an alignment mark area 10A, a core layer 12 is formed on the top of the substrate 10 in the alignment mark area 10A, the core layer 12 includes a first core layer (not shown) and a second core layer (not shown) adjacently arranged, the first core layer includes a plurality of Figure 1 The arrangement direction of the first sub-core layer (as shown in the Y2 direction in FIG. 1 ) is extended and spaced apart and arranged in parallel. Figure 1 The second core layer includes a plurality of layers along the second direction (as shown in the Y1 direction in FIG. Figure 1 The second sub-core layer is arranged in parallel and extends in the direction of X1 in the middle. The arrangement direction of the second sub-core layer is (as shown in the direction of X2 in the middle). Figure 1 The first sub-core layer and the second sub-core layer are perpendicular to each other at least in part at the end.

[0027] refer to Figure 2 , a mask sidewall 13 is formed on the sidewall of the core layer 12 .

[0028] refer to Figure 3 , remove the core layer 12.

[0029] Through research, it is found that the angles at the corners at the end positions of the core layer 12 are acute and obtuse. Accordingly, in the process of forming the mask sidewalls 13 on the sidewalls of the core layer 12, the mask sidewalls 13 at the end positions of the core layer 12 are pointed. After the mask sidewalls 13 are formed on the sidewalls of the core layer 12, in the process of removing the core layer 12, the probability of the mask sidewalls 13 tilting and collapsing is increased. At the same time, in the subsequent process of patterning the substrate 10 of the alignment mark area 10A with the help of the mask sidewalls 13 to form an alignment groove (not shown), in the process of forming the alignment mark in the alignment groove (not shown), the risk of the alignment mark material falling off when being deposited at the corner of the alignment groove is increased, thereby affecting the performance of the alignment mark and further reducing the formation quality of the alignment mark.

[0030] In order to solve the technical problem, an embodiment of the present invention provides a method for forming an alignment mark, comprising: providing a substrate, the substrate comprising an alignment mark area, a core layer is formed on the top of the substrate in the alignment mark area, the core layer comprises a first core layer and a second core layer arranged adjacent to each other, the first core layer comprises a plurality of first sub-core layers extending along a first direction and arranged in parallel at intervals, the arrangement direction of the first sub-core layers is perpendicular to the first direction, the second core layer comprises a plurality of second sub-core layers extending along a second direction and arranged in parallel at intervals, the arrangement direction of the second sub-core layers is perpendicular to the second direction, and at least part of the first sub-core layer and the second The sub-core layers are connected at the end positions; part of the material at the end positions of the first sub-core layer and part of the material at the end positions of the second sub-core layer are removed, so that the remaining first sub-core layer and the remaining second sub-core layer are both rectangular; a first mask side wall is formed on the side wall of the remaining first sub-core layer and the side wall of the remaining second sub-core layer; after forming the first mask side wall, the remaining first core layer and the second core layer are removed; after removing the remaining first core layer and the second core layer, the substrate of the alignment mark area is patterned with the help of the first mask side wall to form an alignment groove; and an alignment mark is formed in the alignment groove.

[0031] An embodiment of the present invention provides a method for forming an alignment mark, which removes part of the material at the end position of the first sub-core layer and part of the material at the end position of the second sub-core layer, so that the remaining first sub-core layer and the remaining second sub-core layer are both rectangular, that is, the corners of the first sub-core layer and the second sub-core layer are both right angles. Accordingly, in the subsequent process of forming the first mask side wall on the side wall of the remaining first sub-core layer and the side wall of the remaining second sub-core layer, the probability of the first mask side wall tilting and collapsing is reduced. At the same time, the substrate of the alignment mark area is subsequently patterned with the help of the first mask side wall to form an alignment groove. In the process of forming the alignment mark in the alignment groove, the risk of the alignment mark material falling off when being deposited at the corner of the alignment groove is reduced, thereby improving the performance of the alignment mark and further improving the formation quality of the alignment mark.

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0033] Figures 4 to 6 : is a schematic diagram of the structure corresponding to an embodiment of an alignment mark of the present invention, wherein: Figure 4 This is a top view of the alignment mark structure. Figure 5 yes Figure 4 Cross-sectional view along the bb direction, Figure 6 yes Figure 4 Cross-sectional view along direction aa.

[0034] The alignment mark 233 includes: a first alignment mark 231 and a second alignment mark 232 that are adjacently arranged, the first alignment mark 231 and the second alignment mark 232 are spaced apart, and the first alignment mark 233 includes a plurality of alignment marks along a first direction (eg, Figure 4 The first rectangular sub-alignment marks 2311 are arranged in parallel and extend in the Y2 direction (as shown in FIG. 1 ). The arrangement direction of the first rectangular sub-alignment marks 2311 (as shown in FIG. 1 ) is Figure 4 The second alignment mark 232 includes a plurality of alignment marks along the second direction (as shown in the Y1 direction in FIG. Figure 4 The second rectangular sub-alignment marks 2321 are arranged in parallel and extend in the X1 direction. The arrangement direction of the second rectangular sub-alignment marks 2321 (as shown in FIG. Figure 4 wherein, the extension line of the first rectangular sub-alignment mark 2311 in the first direction intersects with the extension line of the second rectangular sub-alignment mark 2321 in the second direction.

[0035] It should be noted that in the process of forming the alignment mark 233, it is necessary to perform patterning on the substrate of the alignment mark area with the help of the first mask side wall to form an alignment groove. In the process of forming the alignment mark 233 in the alignment groove, the risk of the alignment mark material falling off when being deposited at the corner of the alignment groove is reduced, thereby improving the performance of the alignment mark 233 and further improving the formation quality of the alignment mark.

[0036] It should also be noted that in the process of forming a semiconductor structure, the wafer must be aligned before the photolithography process, which is beneficial for accurately transferring the pattern to the photoresist layer of the wafer and improving the alignment precision (AP) during the photolithography process. To this end, by setting the alignment mark 233, the overlay error (overlay) during the photolithography process can be reduced.

[0037] Specifically, as an example, the alignment mark 233 is disposed in an alignment mark region of the substrate.

[0038] The substrate also includes a device region for forming a device structure.

[0039] Semiconductor devices such as transistors and capacitors may be arranged in the substrate of the device region, and functional structures such as resistor structures and conductive structures may also be arranged in the substrate of the device region.

[0040] In this embodiment, the region between the first alignment mark 231 and the second alignment mark 232 is a spacing region 200A.

[0041] Specifically, in the process of forming the first alignment mark 231 and the second alignment mark 232 , the first alignment mark 231 and the second alignment mark 232 are removed, and accordingly, there is a spaced area between the first alignment mark 231 and the second alignment mark 232 .

[0042] It should be noted that the distance between the first alignment mark 231 and the second alignment mark 232 should not be too large or too small. If the distance between the first alignment mark 231 and the second alignment mark 232 is too large, it is easy to cause the effective area of ​​the device region used to form the device structure to become smaller; if the distance between the first alignment mark 231 and the second alignment mark 232 is too small, the probability of the adjacent first alignment mark 231 and the second alignment mark 232 overlapping is increased. For this reason, in this embodiment, the distance d between the first alignment mark 231 and the second alignment mark 232 is 0.5 microns to 20 microns.

[0043] In this embodiment, there is a first distance between adjacent first rectangular sub-alignment marks 2311 , and there is a second distance between adjacent second rectangular sub-alignment marks 2321 , and the first distance is equal to the second distance.

[0044] It should be noted that the first distance is equal to the second distance, that is, the distance between adjacent first rectangular sub-alignment marks 2311 and the distance between adjacent second rectangular sub-alignment marks 2321 are equal, so that the uniformity of the alignment marks set in the substrate of the alignment mark area is improved, and the formation quality of the alignment marks is improved, so that in the lithography process of the semiconductor structure, the alignment accuracy in the lithography process can be improved and the overlay error in the lithography process can be reduced.

[0045] In this embodiment, the intersection position of the extension line of the first rectangular sub-alignment mark 2311 in the first direction and the extension line of the second rectangular sub-alignment mark 2321 in the second direction is located in the spacing area 200A.

[0046] In this embodiment, the first alignment mark 231 and the second alignment mark 232 are symmetrical about the center line of the spacing area 200A, and the center line extends along the extension direction of the spacing area 200A.

[0047] In this embodiment, an extension line of the first rectangular sub-alignment mark 2311 in the first direction and an extension line of the second rectangular sub-alignment mark 2321 in the second direction intersect on the center line.

[0048] In this embodiment, the overall outer contours of the first alignment mark 231 and the second alignment mark 232 are both formed into a rectangle.

[0049] Figures 7 to 21 It is a schematic structural diagram corresponding to each step in an embodiment of a method for forming an alignment mark of the present invention.

[0050] refer to Figures 7 to 9 ,in, Figure 7 It is a top view. Figure 8 yes Figure 7 Cross-sectional view along BB direction, Fig. 9 yes Figure 7 A cross-sectional view along the AA direction is provided, wherein a substrate 100 is provided, wherein the substrate 100 includes an alignment mark area 100A, wherein a core layer is formed on the top of the substrate 100 in the alignment mark area 100A, wherein the core layer includes a first core layer 103 and a second core layer 102 disposed adjacent to each other, wherein the first core layer 103 includes a plurality of Figure 7 The first sub-core layers 1031 are arranged in parallel and extend in the Y2 direction. The arrangement direction of the first sub-core layers 1031 is as shown in FIG. Figure 7 The second core layer 102 includes a plurality of layers along the second direction (as shown in the Y1 direction in FIG. Figure 7 The second sub-core layer 1021 is arranged in parallel and extends in the direction of X1 in the middle. The arrangement direction of the second sub-core layer 1021 is as shown in FIG. Figure 7 The first sub-core layer 1031 and the second sub-core layer 1021 are connected at least partially at the end positions.

[0051] The substrate 100 provides a process platform for forming an alignment mark.

[0052] It should be noted that in the process of forming a semiconductor structure, the wafer must be aligned before the photolithography process, which is beneficial for accurately transferring the pattern to the photoresist layer of the wafer and improving the alignment precision (AP) during the photolithography process. To this end, by forming alignment marks, the overlay error (overlay) during the photolithography process can be reduced.

[0053] In this embodiment, the alignment mark area 100A is a region for forming an alignment mark.

[0054] It should be noted that, as an example, the substrate 100 also includes a device region for forming a device structure.

[0055] Specifically, semiconductor devices such as transistors and capacitors may be formed in the substrate 100 in the device area, and functional structures such as resistor structures and conductive structures may also be formed in the substrate 100 in the device area.

[0056] In this embodiment, the core layer is located on the top of the substrate 100 in the alignment mark area 100A.

[0057] Specifically, the core layer provides a process basis for the subsequent formation of the first mask sidewall, so that the pattern is transferred downward through the first mask sidewall. For example, for the alignment mark area 100A, a self-aligned multiple patterning (SAMP) process is used to form the pattern.

[0058] In this embodiment, the material of the core layer includes amorphous silicon, that is, as an example, the material of the first core layer 103 and the second core layer 102 includes amorphous silicon.

[0059] Specifically, the lattice structure of amorphous silicon material has an unstable characteristic, and the etching rate of amorphous silicon is highly uniform, which is conducive to the subsequent removal of the core layer, thereby improving the pattern transfer accuracy of the subsequent patterning process.

[0060] In this embodiment, the first core layer 103 includes multiple first sub-core layers 1031, and the second core layer 102 includes multiple second sub-core layers 1021. Correspondingly, in the subsequent process of forming the first mask side wall, the number of first mask side walls formed in the alignment mark area 100A is also multiple. Subsequently, with the help of the first mask side wall, the substrate 100 of the alignment mark area 100A is patterned to form an alignment groove. After the alignment mark is formed in the alignment groove, the number of alignment marks formed in the substrate 100 of the alignment mark area 100A is multiple. Therefore, in the photolithography process of the semiconductor structure, when the number of alignment marks is multiple, the alignment accuracy during the photolithography process can be improved and the overlay error during the photolithography process can be reduced.

[0061] In this embodiment, there is a first distance between adjacent first sub-core layers 1031 , and there is a second distance between adjacent second sub-core layers 1021 , and the first distance is equal to the second distance.

[0062] It should be noted that the first distance is equal to the second distance, that is, the distance between adjacent first sub-core layers 1031 is equal to the distance between adjacent second sub-core layers 1021. In the subsequent graphic process, the uniformity of the alignment mark formed in the substrate 100 in the alignment mark area 100A is improved, that is, the formation quality of the alignment mark is improved, so that in the lithography process of the semiconductor structure, the alignment accuracy in the lithography process can be improved and the overlay error in the lithography process can be reduced.

[0063] In this embodiment, a bottom core material layer 101 is further formed on the top of the substrate 100 , and the core layer is formed on the top of the bottom core material layer 101 in the alignment mark area 100A.

[0064] The bottom core material layer 101 provides a process basis for the subsequent formation of the third core layer. At the same time, the core layer is located on the top of the bottom core material layer 101 in the alignment mark area 100A, and the bottom core material layer 101 can be patterned using the first mask sidewall formed on the sidewall of the core layer.

[0065] In this embodiment, the material of the bottom core material layer 101 includes amorphous silicon.

[0066] Specifically, the bottom core material layer 101 is used as a material layer for subsequently forming a third core layer. By selecting amorphous silicon as the material for the bottom core material layer 101, the lattice structure of the amorphous silicon material has an unstable characteristic, and the etching rate of amorphous silicon is highly uniform, which is beneficial for the subsequent process of removing the third core layer. The third core layer can be completely removed, thereby improving the graphic transfer accuracy of the subsequent graphic process.

[0067] refer to Figures 10 to 12 ,in, Fig.10 It is a top view. Fig.11 yes Fig.10 Cross-sectional view along BB direction, Fig.12 yes Fig.10 In the cross-sectional view along the AA direction, part of the material at the end of the first sub-core layer 1031 and part of the material at the end of the second sub-core layer 1021 are removed, so that the remaining first sub-core layer 1031 and the remaining second sub-core layer 1021 are both rectangular.

[0068] It should be noted that the remaining first sub-core layer 1031 and the remaining second sub-core layer 1021 are both rectangular in shape, that is, the corners of the first sub-core layer 1031 and the second sub-core layer 1021 are both right angles. Accordingly, in the subsequent process of forming the first mask side wall on the side wall of the remaining first sub-core layer 1031 and the side wall of the remaining second sub-core layer 1021, the probability of the first mask side wall tilting and collapsing is reduced. At the same time, the substrate 100 of the alignment mark area 100A is subsequently patterned with the help of the first mask side wall to form an alignment groove. In the process of forming the alignment mark in the alignment groove, the risk of falling off when the alignment mark material is deposited at the corner of the alignment groove is reduced, thereby improving the performance of the alignment mark and further improving the formation quality of the alignment mark.

[0069] It should also be explained that, as an example, a self-aligned multiple patterning (SAMP) process is used to form a pattern in the substrate 100 of the alignment mark area 100A. Accordingly, after the subsequent formation of the third core layer and the second mask side wall located on the side wall of the third core layer, the probability of collapse of the second mask side wall is also reduced. At the same time, in the process of removing the third core layer, the risk of residual third core layer is also reduced, thereby improving the pattern transfer accuracy, and then greatly improving the formation quality of the alignment mark.

[0070] In this embodiment, the step of removing part of the material at the end position of the first sub-core layer 1031 and part of the material at the end position of the second sub-core layer 1021 includes: forming a rectangular mask layer (not shown) on the top of the first sub-core layer 1031 and the second sub-core layer 1021, the mask layer exposing the end position of the first sub-core layer 1031 and the end position of the second sub-core layer 1021; using the mask layer as a mask, removing part of the material at the end position of the first sub-core layer 1031 and part of the material at the end position of the second sub-core layer 1021, so that the remaining first sub-core layer 1031 and the remaining second sub-core layer 1021 are both rectangular.

[0071] The mask layer is used as an etching mask for removing part of the material at the end of the first sub-core layer 1031 and part of the material at the end of the second sub-core layer 1021 .

[0072] In this embodiment, the material of the mask layer includes photoresist.

[0073] In this embodiment, the process of removing part of the material at the end of the first sub-core layer 1031 and part of the material at the end of the second sub-core layer 1021 includes a dry etching process.

[0074] Specifically, the dry etching process is an anisotropic dry etching process. The anisotropic dry etching process has good cross-sectional controllability, which is conducive to improving the cross-sectional morphology quality of the remaining first sub-core layer 1031 and the remaining second sub-core layer 1021, so that the remaining first sub-core layer 1031 and the remaining second sub-core layer 1021 are both rectangular. In addition, the selected anisotropic dry etching process is conducive to achieving a higher etching selectivity, thereby reducing the probability of causing mis-etching to other film layers.

[0075] It should be noted that, as an example, after removing part of the material at the end of the first sub-core layer 1031 and part of the material at the end of the second sub-core layer 1021, the area between the first core layer 103 and the second core layer 102 is the spacing area 100B.

[0076] It should also be noted that the distance between the first core layer 103 and the second core layer 102 should not be too large or too small. If the distance between the first core layer 103 and the second core layer 102 is too large, and the first core layer 103 and the second core layer 102 are arranged in the alignment mark area, it is easy to cause the effective area of ​​the device area used to form the device structure to become smaller; if the distance between the first core layer 103 and the second core layer 102 is too small, the probability of the adjacent first core layer 103 and the second core layer 102 overlapping is increased. For this reason, in this embodiment, the distance D between the first core layer 103 and the second core layer 102 is 0.5 microns to 20 microns.

[0077] refer to Fig.13 A first mask spacer 110 is formed on the sidewalls of the remaining first sub-core layer 1031 and the sidewalls of the remaining second sub-core layer 1021 .

[0078] It should be noted that, in the subsequent process of patterning the substrate 100 in the alignment mark area 100A with the help of the first mask sidewall 110 , the first mask sidewall 110 is used as an etching mask.

[0079] In this embodiment, the step of forming the first mask sidewall 110 includes: forming a first mask sidewall material layer (not shown) on the top and sidewalls of the first core layer 103, the top and sidewalls of the second core layer 102, and the top of the substrate 100; removing the first mask sidewall material layer on the top of the first core layer 103, the top of the second core layer 102, and the top of the substrate 100, and the remaining first mask sidewall material layer located on the sidewalls of the first core layer 103 and the second core layer 102 serves as the first mask sidewall 110.

[0080] In this embodiment, the process of forming the first mask spacer material layer on the top and sidewalls of the first core layer 103 , the top and sidewalls of the second core layer 102 , and the top of the substrate 100 includes an atomic layer deposition process.

[0081] The atomic layer deposition process includes multiple atomic layer deposition cycles, which is beneficial to improving the thickness uniformity of the first mask side wall material layer, that is, improving the uniformity of the size of the first mask side wall material layer, so that the first mask side wall material layer can cover the top and side walls of the first core layer 103, the top and side walls of the second core layer 102 and the top of the substrate 100.

[0082] In this embodiment, the process of removing the first mask sidewall material layer on the top of the first core layer 103 , the top of the second core layer 102 , and the top of the substrate 100 includes a dry etching process.

[0083] Specifically, the dry etching process includes an anisotropic dry etching process. The anisotropic dry etching process has the characteristics of anisotropic etching, so its longitudinal etching rate is much greater than the lateral etching rate, and a fairly accurate graphic transfer can be obtained. While removing the first mask sidewall material layer at the top of the first core layer 103, the top of the second core layer 102 and the top of the substrate 100, the sidewall morphology quality of the first mask sidewall 110 is improved, so that after the substrate 100 in the alignment mark area 100A is subsequently patterned with the help of the first mask sidewall 110, the size uniformity of the alignment mark is improved, thereby improving the formation quality of the alignment mark.

[0084] In this embodiment, the material of the first mask sidewall spacer 110 includes silicon nitride.

[0085] Specifically, the etching selectivity between the silicon nitride material and the amorphous silicon selected as the material of the core layer is relatively large. In the subsequent process of removing the first core layer 103 and the second core layer 102, the first mask side wall 110 can be retained, and the first mask side wall 110 can be used as a mask to subsequently perform patterning on the substrate 100 of the alignment mark area 100A.

[0086] refer to Fig.14 After forming the first mask sidewall 110 , the remaining first core layer 103 and second core layer 102 are removed.

[0087] Specifically, the remaining first core layer 103 and second core layer 102 are removed, so as to facilitate the subsequent patterning of the substrate 100 in the alignment mark area 100A by using the first mask spacer 110 .

[0088] In this embodiment, the process of removing the remaining first core layer 103 and second core layer 102 includes a plasma dry etching process.

[0089] Specifically, the plasma dry etching process has the characteristics of fast etching rate and high etching controllability. In the process of removing the remaining first core layer 103 and the second core layer 102, the first core layer 103 and the second core layer 102 are completely removed through chemical and physical reactions between plasma and the first core layer 103 and the second core layer 102.

[0090] refer to Figures 15 to 18 After removing the remaining first core layer 103 and second core layer 102 , the substrate 100 in the alignment mark area 100A is patterned with the aid of the first mask sidewall 110 to form an alignment groove 126 .

[0091] It should be noted that the alignment groove 126 provides a spatial position for subsequently forming an alignment mark.

[0092] In this embodiment, the substrate 100 of the alignment mark area 100A is patterned with the help of the first mask side wall 110, and the step of forming the alignment groove 126 includes: using the first mask side wall 110 as a mask, the bottom core material layer 101 is patterned to form a third core layer 112; forming a second mask side wall 116 on the side wall of the third core layer 112; after forming the second mask side wall 116, removing the third core layer 112; after removing the third core layer 112, the substrate is patterned with the second mask side wall 116 as a mask to form an alignment groove 126 in the substrate; and removing the second mask side wall 116.

[0093] Specifically, the third core layer 112 provides a process basis for subsequently forming the second mask spacer 116 , so that the substrate 100 in the alignment mark area 100A is patterned through the second mask spacer 116 .

[0094] In this embodiment, the material of the third core layer 112 includes amorphous silicon.

[0095] Specifically, the lattice structure of amorphous silicon material has an unstable characteristic, and the etching rate of amorphous silicon is highly uniform, which is conducive to the subsequent removal of the third core layer 112, thereby improving the pattern transfer accuracy of the subsequent patterning process.

[0096] It should be noted that the second mask sidewall 116 is used as an etching mask during the process of patterning the substrate 100 in the alignment mark area 100A.

[0097] In this embodiment, the process of forming the second mask spacer 116 includes an atomic layer deposition process.

[0098] In this embodiment, the material of the second mask sidewall spacer 116 includes silicon nitride.

[0099] Specifically, the etching selectivity between the silicon nitride material and the amorphous silicon selected as the material of the third core layer 112 is relatively large. In the subsequent process of removing the third core layer 112, the second mask side wall 116 can be retained, and the second mask side wall 116 can be used as a mask to subsequently perform patterning on the substrate 100 of the alignment mark area 100A to form an alignment groove 126.

[0100] In this embodiment, the process of removing the third core layer 112 includes a plasma dry etching process.

[0101] Specifically, the plasma dry etching process has the characteristics of fast etching rate and high etching controllability. In the process of removing the third core layer 112, the third core layer 112 is completely removed through chemical and physical reactions between plasma and the third core layer 112.

[0102] In this embodiment, the second mask sidewall spacer 116 is removed by a plasma dry etching process.

[0103] refer to Figures 19 to 21 ,in, Fig.19 It is a top view. Fig. 20 yes Fig.19 Cross-sectional view along BB direction, Fig.21 yes Fig.19 In the cross-sectional view along the AA direction, an alignment mark 132 is formed in the alignment groove 126 .

[0104] In the process of forming a semiconductor structure, the wafer must be aligned before the photolithography process, which is beneficial for accurately transferring the pattern to the photoresist layer of the wafer and improving the alignment accuracy during the photolithography process. To this end, by forming an alignment mark 132 in the alignment groove 126, the overlay error during the photolithography process can be reduced.

[0105] In this embodiment, the step of forming an alignment mark 132 in the alignment groove 126 includes: forming a hard mask layer 128 at the bottom and sidewalls of the alignment groove 126; after forming the hard mask layer 128, forming an alignment mark material layer 130 in the remaining space of the alignment groove 126, and the alignment mark 132 material covers the hard mask layer 128; and planarizing the hard mask layer 128 and the alignment mark material layer 130 that are higher than the top of the substrate 100, and retaining the alignment mark material layer 130 and the hard mask layer 128 in the alignment groove 126 to form the alignment mark 132.

[0106] The hard mask layer 128 aligned with the sidewall of the groove plays a role of grinding stop during the process of planarizing the hard mask layer 128 and the alignment mark material layer 130 above the top of the substrate 100 , thereby increasing the flatness of the top of the alignment mark 32 .

[0107] In this embodiment, the process of forming the alignment mark material layer 130 includes a chemical vapor deposition process.

[0108] Specifically, the chemical vapor deposition process has the characteristics of good film filling performance. By forming the alignment mark material layer 130 using the chemical vapor deposition process, the probability of forming a void in the alignment mark 132 is reduced, thereby improving the formation quality of the alignment mark 132.

[0109] In this embodiment, the material of the alignment mark material layer 130 includes one or more of SiN, SiO 2 , SiOC and SiOCN.

[0110] In this embodiment, the alignment mark 132 is symmetrical about the center line of the spacer 100B, and the center line extends along the extension direction of the spacer 100B.

[0111] Specifically, the alignment marks 132 are axially symmetric, which makes the signal strengths of the mutually symmetric alignment marks 132 the same, and can effectively ensure the accuracy of the signal.

[0112] 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. An alignment mark, It is characterized in that include: A first alignment mark and a second alignment mark are arranged adjacent to each other, the first alignment mark and the second alignment mark are spaced apart, the first alignment mark comprises a plurality of first rectangular sub-alignment marks extending along a first direction and arranged in parallel at intervals, the arrangement direction of the first rectangular sub-alignment marks being perpendicular to the first direction, the second alignment mark comprises a plurality of second rectangular sub-alignment marks extending along a second direction and arranged in parallel at intervals, the arrangement direction of the second rectangular sub-alignment marks being perpendicular to the second direction; Wherein, an extension line of the first rectangular sub-alignment mark in the first direction intersects an extension line of the second rectangular sub-alignment mark in the second direction.

2. The alignment mark according to claim 1, It is characterized in that The area between the first alignment mark and the second alignment mark is a spacing area; An intersection position of an extension line of the first rectangular sub-alignment mark in the first direction and an extension line of the second rectangular sub-alignment mark in the second direction is located within the spacing area.

3. The alignment mark according to claim 2, It is characterized in that The first alignment mark and the second alignment mark are symmetrical about a center line of the spacing area, and the center line extends along an extension direction of the spacing area; An extension line of the first rectangular sub-alignment mark in the first direction and an extension line of the second rectangular sub-alignment mark in the second direction intersect on the center line.

4. The alignment mark according to claim 1, It is characterized in that There is a first distance between adjacent first rectangular sub-alignment marks, and there is a second distance between adjacent second rectangular sub-alignment marks, and the first distance is equal to the second distance.

5. The alignment mark according to claim 1, It is characterized in that The first alignment mark and the second alignment mark are spaced apart from each other by a distance of 0.5 micrometers to 20 micrometers.

6. A method for forming an alignment mark, It is characterized in that include: A substrate is provided, the substrate comprising an alignment mark area, a core layer is formed on the top of the substrate in the alignment mark area, the core layer comprises a first core layer and a second core layer arranged adjacent to each other, the first core layer comprises a plurality of first sub-core layers extending along a first direction and arranged in parallel at intervals, the arrangement direction of the first sub-core layers is perpendicular to the first direction, the second core layer comprises a plurality of second sub-core layers extending along a second direction and arranged in parallel at intervals, the arrangement direction of the second sub-core layers is perpendicular to the second direction, and at least a portion of the first sub-core layers and the second sub-core layers are connected at end positions; Removing part of the material at the end of the first sub-core layer and part of the material at the end of the second sub-core layer, so that the remaining first sub-core layer and the remaining second sub-core layer are both rectangular; forming a first mask sidewall on the sidewall of the remaining first sub-core layer and the sidewall of the remaining second sub-core layer; After forming the first mask sidewall, removing the remaining first core layer and second core layer; After removing the remaining first core layer and second core layer, the substrate in the alignment mark area is patterned by means of the first mask sidewall to form an alignment groove; An alignment mark is formed in the alignment groove.

7. The method for forming an alignment mark according to claim 6, It is characterized in that A bottom core material layer is also formed on the top of the substrate, and the core layer is formed on the top of the bottom core material layer in the alignment mark area; With the help of the first mask side wall, the substrate of the alignment mark area is patterned, and the step of forming an alignment groove includes: using the first mask side wall as a mask, patterning the bottom core material layer to form a third core layer; forming a second mask side wall on the side wall of the third core layer; after forming the second mask side wall, removing the third core layer; after removing the third core layer, patterning the substrate with the second mask side wall as a mask to form an alignment groove in the substrate; removing the second mask side wall.

8. The method for forming an alignment mark according to claim 6, It is characterized in that The step of forming an alignment mark in the alignment groove includes: forming a hard mask layer at the bottom and sidewalls of the alignment groove; after forming the hard mask layer, forming an alignment mark material layer in the remaining space of the alignment groove, the alignment mark material covering the hard mask layer; flattening the hard mask layer and the alignment mark material layer above the top of the substrate, and retaining the alignment mark material layer and the hard mask layer in the alignment groove to form an alignment mark.

9. The method for forming an alignment mark according to claim 6, It is characterized in that The step of removing part of the material at the end position of the first sub-core layer and part of the material at the end position of the second sub-core layer comprises: forming a rectangular mask layer on top of the first sub-core layer and the second sub-core layer, wherein the mask layer exposes the end position of the first sub-core layer and the end position of the second sub-core layer; Using the mask layer as a mask, part of the material at the end of the first sub-core layer and part of the material at the end of the second sub-core layer are removed, so that the remaining first sub-core layer and the remaining second sub-core layer are both rectangular.

10. The method for forming an alignment mark according to claim 6, It is characterized in that After removing part of the material at the end of the first sub-core layer and part of the material at the end of the second sub-core layer, the area between the first core layer and the second core layer is a spacing area; The alignment mark is axisymmetric about a center line of the spacer, and the center line extends along an extending direction of the spacer.

11. The method for forming an alignment mark according to claim 10, It is characterized in that The first core layer and the second core layer are spaced apart by a distance of 0.5 micrometers to 20 micrometers.

12. The method for forming an alignment mark according to claim 6, It is characterized in that The step of forming the first mask sidewall includes: forming a first mask sidewall material layer on the top and sidewall of the first core layer, the top and sidewall of the second core layer, and the top of the substrate; removing the first mask sidewall material layer on the top of the first core layer, the top of the second core layer, and the top of the substrate, and the remaining first mask sidewall material layer located on the sidewalls of the first core layer and the second core layer serves as the first mask sidewall.

13. The method for forming an alignment mark according to claim 6, It is characterized in that There is a first distance between adjacent first sub-core layers, and there is a second distance between adjacent second sub-core layers, and the first distance is equal to the second distance.

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