Semiconductor structure and method for forming the same

Abstract

A semiconductor structure and a method for forming the same, wherein the method comprises: providing a substrate, the substrate having a layer to be etched; forming a first sacrificial layer and a second sacrificial layer on the layer to be etched, wherein the first sacrificial layer is doped with ions, and the second sacrificial layer is not doped with ions; forming a third sacrificial layer on part of the first sacrificial layer and the second sacrificial layer; patterning the first sacrificial layer, the second sacrificial layer and the third sacrificial layer; and transferring a pattern to the layer to be etched. The method is advantageous in that in the process of removing the second sacrificial layer on the first area, the over-etching degree of the first sacrificial layer is small, and is advantageous in the accuracy of the pattern transfer.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular to a semiconductor structure and a forming method thereof. Background Art

[0002] In the process of manufacturing semiconductor devices, the pattern on the mask is usually transferred to the substrate by using a photolithography process. The photolithography process includes: providing a substrate; forming a photoresist on the substrate; exposing and developing the photoresist to form a patterned photoresist so that the pattern on the mask is transferred to the photoresist; etching the substrate using the patterned photoresist as a mask so that the pattern on the photoresist is transferred to the substrate; and removing the photoresist.

[0003] The basic idea of ​​the self-aligned double patterning technology is to form the final target pattern through two patterns to overcome the lithography limit that cannot be broken through by a single patterning. Among them, the self-aligned double patterning (SADP) process is widely used because of its simple process. Through the self-aligned double patterning process, a device smaller than the minimum size formed by the lithography process can be formed.

[0004] In order to meet specific process requirements, a larger mask is formed through a photolithography process, and a smaller mask is formed through a self-aligned double patterning process. At the same time, the larger mask and the smaller mask are used to etch the etched layer to achieve pattern transfer.

[0005] However, the accuracy of graphics transfer achieved by existing methods needs to be improved. Summary of the invention

[0006] The technical problem solved by the present invention is to provide a semiconductor structure and a method for forming the same, so as to improve the accuracy of pattern transfer.

[0007] In order to solve the above technical problems, the technical solution of the present invention provides a method for forming a semiconductor structure, including: providing a substrate, wherein the substrate has a layer to be etched; forming a first sacrificial layer and a second sacrificial layer on the layer to be etched, and the first sacrificial layer is doped with ions, and the second sacrificial layer is not doped with ions; forming a third sacrificial layer on part of the first sacrificial layer and the second sacrificial layer; patterning the first sacrificial layer, the second sacrificial layer and the third sacrificial layer; and transferring the pattern to the layer to be etched.

[0008] Optionally, the thickness of the first sacrificial layer ranges from 300 angstroms to 600 angstroms.

[0009] Optionally, the layer to be etched includes adjacent first and second regions; a plurality of second sacrificial layers are formed on the first and second regions, respectively, and the first sacrificial layer is provided between adjacent second sacrificial layers; the method for forming the semiconductor structure further includes: after patterning the first sacrificial layer, the second sacrificial layer and the third sacrificial layer, before transferring the pattern to the layer to be etched, removing the first sacrificial layer on the second region, and forming an opening between adjacent second sacrificial layers on the second region; forming a mask layer on the side wall surface of the opening, and the thickness of the mask layer is greater than the thickness of the first sacrificial layer; after forming the mask layer, removing the second sacrificial layer on the first and second regions; etching the layer to be etched using the mask layer and the first sacrificial layer on the first region as masks, and transferring the pattern on the layer to be etched.

[0010] Optionally, the method for forming the first sacrificial layer and the second sacrificial layer includes: forming a first sacrificial material film on the first area and the second area; doping ions in part of the first sacrificial material film to form adjacent first sacrificial layers and second sacrificial layers, and the first sacrificial layer is doped with ions, and the second sacrificial layer is not doped with ions.

[0011] Optionally, the method of doping ions into part of the first sacrificial material film includes: forming a first patterned layer on the surface of the first sacrificial material film, the first patterned layer exposing part of the surface of the first sacrificial material film; using the first patterned layer as a mask, performing ion implantation into the first sacrificial material film to form the first sacrificial layer and the second sacrificial layer; after forming the first sacrificial layer and the second sacrificial layer, removing the first patterned layer.

[0012] Optionally, the method for forming the third sacrificial layer includes: after forming the first sacrificial layer and the second sacrificial layer, and before removing the first sacrificial layer on the second area, forming a second sacrificial material film on the surfaces of the first sacrificial layer and the second sacrificial layer; in the process of removing the first sacrificial layer on the second area, etching the second sacrificial material film to form the third sacrificial layer on the surfaces of the first sacrificial layer and the second sacrificial layer on the first area and the second sacrificial layer on the second area, and the mask layer is also located on the side wall surface of the third sacrificial layer; after forming the mask layer, removing the third sacrificial layer.

[0013] Optionally, the first sacrificial material film and the second sacrificial material film are made of the same material; the materials of the first sacrificial material film and the second sacrificial material film include: amorphous silicon, amorphous carbon, polysilicon, silicon oxide, silicon oxycarbide or silicon oxyhydrogencarbide.

[0014] Optionally, a thickness ratio of the first sacrificial material film to the second sacrificial material film is in a range of 3:7 to 6:4.

[0015] Optionally, the total thickness of the first sacrificial material film and the second sacrificial material film ranges from 400 angstroms to 1000 angstroms.

[0016] Optionally, the method for removing the first sacrificial layer on the second area includes: forming a second patterned layer on the surface of the second sacrificial material film, the second patterned layer covering the first sacrificial layer and the second sacrificial layer on the first area, and the surface of the second sacrificial material film on the second sacrificial layer on the second area; using the second patterned layer as a mask, etching the second sacrificial material film and the first sacrificial layer located at the bottom of the second sacrificial material film until the substrate surface is exposed, so that the second sacrificial material film forms a third sacrificial layer, and removing the first sacrificial layer on the second area, and forming the opening between adjacent second sacrificial layers on the second area.

[0017] Optionally, the second sacrificial material film and the first sacrificial layer are etched using a first etching process, the first etching process is a dry etching process, and the parameters of the dry etching process include: the gas used includes CF 4 , HBr, O 2 , Cl 2 , where CF 4 The flow rate of is 30 standard ml / min to 80 standard ml / min, the flow rate of HBr is 10 standard ml / min to 300 standard ml / min, and the flow rate of O 2 The flow rate is 30 standard ml / min to 80 standard ml / min, Cl 2 The flow rate is 50 standard ml / min to 3000 standard ml / min, and the time is 5 seconds to 40 seconds.

[0018] Optionally, a second etching process is used to remove the second sacrificial layer and the third sacrificial layer on the first area and the second area, and the etching rate of the second etching process on the second sacrificial layer and the third sacrificial layer is greater than the etching rate on the first sacrificial layer.

[0019] Optionally, the second etching process is a wet etching process, and parameters of the wet etching process include: the etching solution is dilute ammonia water, the dilution ratio is 3:10 to 7:10, and the time is 100 seconds to 500 seconds.

[0020] Optionally, the method for forming the mask layer includes: forming a mask material film on the surface of the layer to be etched, the exposed surface of the third sacrificial layer, and the exposed surface of the second sacrificial layer; and back-etching the mask material film until the top surface of the third sacrificial layer and the surface of the layer to be etched are exposed to form the mask layer.

[0021] Optionally, the method further includes: before forming the first sacrificial material film, the method further includes: forming a transition layer on the surface of the layer to be etched.

[0022] Correspondingly, the technical solution of the present invention also provides a semiconductor structure, including: a substrate, having a layer to be etched on the substrate, the layer to be etched including adjacent first and second regions; a first sacrificial layer located on the first region; a mask layer located on the second region, and the thickness of the mask layer is greater than the thickness of the first sacrificial layer.

[0023] Optionally, the thickness of the first sacrificial layer ranges from 300 angstroms to 600 angstroms.

[0024] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0025] In the method for forming a semiconductor structure provided by the technical solution of the present invention, by making the thickness of the formed first sacrificial layer smaller than the thickness of the mask layer, that is, the thickness of the first sacrificial layer is smaller, which is beneficial to the subsequent process of removing the second sacrificial layer on the first area, and the degree of over-etching caused to the first sacrificial layer between adjacent second sacrificial layers on the first area is smaller, thereby reducing the degree of reduction in the size of the bottom of the first sacrificial layer, so that the size difference between the top and bottom of the first sacrificial layer is reduced, and the morphology of the first sacrificial layer is effectively improved, so that when the first sacrificial layer and the mask layer are used as masks to etch the layer to be etched, it is beneficial to the accuracy of the graphic transfer.

[0026] Furthermore, the method for forming the semiconductor structure also includes: forming a second sacrificial material film on the surface of the first sacrificial layer and the second sacrificial layer on the first area and the second area, so that the total thickness of the first sacrificial material film and the second sacrificial material film is thicker, and the thickness of the first sacrificial material film is reduced, which is beneficial to improve the accuracy of the pattern transfer, while making the thickness of the mask layer formed on the side wall surface of the second sacrificial layer and the third sacrificial layer thicker, so that the thickness of the mask layer is thick enough to ensure that it plays a better masking role during the pattern transfer process. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figures 1 to 5 It is a structural schematic diagram of each step of a method for forming a conventional semiconductor structure;

[0028] Figures 6 to 15 It is a structural schematic diagram of each step of a method for forming a semiconductor structure in one embodiment of the present invention. DETAILED DESCRIPTION

[0029] It should be noted that the terms “surface” and “on” in this specification are used to describe relative positional relationships in space and are not limited to direct contact.

[0030] First, the reasons why the performance of the existing semiconductor structure is poor are described in detail with reference to the accompanying drawings. Figures 1 to 5 The present invention is a structural schematic diagram of each step of a method for forming a conventional semiconductor structure.

[0031] Please refer to Figure 1 , providing a substrate 100 and a layer to be etched 110 located on the surface of the substrate 100, wherein the layer to be etched 100 includes adjacent first regions I and second regions II; and forming a sacrificial material film 120 on the surface of the layer to be etched 100.

[0032] Please refer to Figure 2 , forming a patterned layer 130 on the surface of the sacrificial material film 120, wherein the patterned layer 130 exposes a portion of the surface of the sacrificial material film 120; using the patterned layer 130 as a mask, ion implantation is performed on the sacrificial material film 120 to form a plurality of second sacrificial layers 140 on the first region I and the second region II, wherein a first sacrificial layer 150 is provided between adjacent second sacrificial layers 140, and the first sacrificial layer 150 is doped with ions, while the second sacrificial layer 140 is not doped with ions.

[0033] Please refer to Figure 3 , remove the first sacrificial layer 150 on the second region II; after removing the first sacrificial layer 150 on the second region II, form a mask layer 160 on the side wall surfaces of the first sacrificial layer 150 and the second sacrificial layer 140 on the first region I, and the side wall surfaces of the second sacrificial layer 140 on the second region II.

[0034] Please refer to Figure 4 After forming the mask layer 160 , the second sacrificial layer 140 on the first region I and the second region II is removed.

[0035] Please refer to Figure 5 , using the mask layer 160 and the first sacrificial layer 150 as masks, etching the layer to be etched 110 .

[0036] It should be noted that the thickness refers to the dimension along a direction perpendicular to the surface of the substrate 100 .

[0037] In the above method, the mask layer 160 and the first sacrificial layer 150 are used together as a mask for etching the layer to be etched 110. The method for forming the mask layer 160 includes: forming a mask material film on the surface of the layer to be etched 110 and the top surface and side wall surface of the first sacrificial layer 150 and the second sacrificial layer 140 on the first region I, and the top surface and side wall surface of the second sacrificial layer 140 on the second region II; etching back the mask material film until the surface of the layer to be etched 100 and the top surface of the first sacrificial layer 150 and the second sacrificial layer 140 are exposed to form the mask layer 160. The above multiple patterning method is conducive to forming a mask layer 160 with a smaller size. At the same time, the size of the first sacrificial layer 150 can be larger, which can be achieved by a photolithography process, so that the size of the formed first sacrificial layer 150 meets the process requirements. Since the thickness of the second sacrificial layer 140 determines the thickness of the mask layer 160 , in order to make the mask layer 160 play a better masking role when etching the to-be-etched layer 110 , the thickness of the sacrificial material film 120 needs to be thicker.

[0038] However, the morphology of the first sacrificial layer 150 is poor, resulting in poor accuracy of the pattern formed in the layer to be etched 110 using the first sacrificial layer 150 as a mask. The specific reason is that, first, the first sacrificial layer 150 and the second sacrificial layer 140 are formed by ion implantation of the sacrificial material film 120 using the patterned layer 130 as a mask. Since the morphology of the patterned layer 130 is poor, specifically, the side wall of the patterned layer 130 is inclined. Using the poorly morphological patterned layer 130 as a mask, the uniformity of the doped ion concentration distribution in the first sacrificial layer 150 formed is poor, specifically, as the distance from the top surface of the first sacrificial layer 150 increases, the ion concentration in the first sacrificial layer 150 decreases. Furthermore, after the mask layer 160 is formed, when a wet etching process is used to remove the second sacrificial layer 140 on the first region I, due to the uneven concentration distribution of the first sacrificial layer 150 and the thick thicknesses of the first sacrificial layer 150 and the second sacrificial layer 140, it is easy to cause a lot of over-etching to the bottom of the first sacrificial layer 150, resulting in the size of the bottom of the first sacrificial layer 150 being smaller than the size of the top of the first sacrificial layer 150, that is, the morphology of the formed first sacrificial layer 150 is poor.

[0039] In order to solve the technical problem, an embodiment of the present invention provides a method for forming a semiconductor structure, including: providing a substrate, wherein the substrate has a layer to be etched; forming a first sacrificial layer and a second sacrificial layer on the layer to be etched, and the first sacrificial layer is doped with ions, and the second sacrificial layer is not doped with ions; forming a third sacrificial layer on part of the first sacrificial layer and the second sacrificial layer; patterning the first sacrificial layer, the second sacrificial layer and the third sacrificial layer; transferring a pattern to the layer to be etched, because the thickness of the first sacrificial layer is relatively small, it is beneficial to reduce the degree of over-etching of the first sacrificial layer in the subsequent process of removing the second sacrificial layer on the first area, which is beneficial to the accuracy of the graphic transfer.

[0040] In order to make the above-mentioned objects, features and beneficial effects 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.

[0041] Figures 6 to 15 It is a structural schematic diagram of each step of a method for forming a semiconductor structure in one embodiment of the present invention.

[0042] Please refer to Figure 6 , providing a substrate 200, wherein the substrate 200 has a layer 210 to be etched, and the layer 210 to be etched includes a first region I and a second region II adjacent to each other.

[0043] In this embodiment, the substrate 200 is single crystal silicon. In other embodiments, the substrate may be made of semiconductor materials such as single crystal germanium, silicon germanium, gallium arsenide, etc., or may be a semiconductor-on-insulator structure.

[0044] Please continue to refer to 6. In this embodiment, it also includes: forming a transition layer 211 on the surface of the layer to be etched 210.

[0045] The transition layer 211 has good adhesion to the layer to be etched 210 and the first sacrificial material film formed subsequently, thereby playing a role of buffering transition.

[0046] The transition layer 211 and the layer to be etched 210 are made of different materials.

[0047] The material of the transition layer 211 includes: tetraethoxysilane or an organic material containing carbon and oxygen. In this embodiment, the material of the transition layer 211 is tetraethoxysilane.

[0048] Next, a plurality of second sacrificial layers are formed on the first region I, and a plurality of second sacrificial layers are formed on the second region, with a first sacrificial layer between adjacent second sacrificial layers. For the specific process of forming the first sacrificial layer and the second sacrificial layer, please refer to Figure 6 to Figure 7 .

[0049] Please refer to Figure 7, a first sacrificial material film 220 is formed on the first region I and the second region II.

[0050] The first sacrificial material film 220 is used to provide material for subsequently forming the first sacrificial layer and the second sacrificial layer, so the thickness of the first sacrificial material film 220 determines the thickness of the first sacrificial layer and the second sacrificial layer.

[0051] Specifically, the first sacrificial material film 220 is formed on the surface of the transition layer 211 .

[0052] The material of the first sacrificial material film 220 includes: amorphous silicon, amorphous carbon, polysilicon, silicon oxide, silicon oxycarbide or silicon oxyhydrogencarbide.

[0053] In this embodiment, the material of the first sacrificial material film 220 is amorphous silicon.

[0054] Please refer to Figure 8 , ions are doped into a portion of the first sacrificial material film 220 to form adjacent first sacrificial layers 230 and second sacrificial layers 240 , and the first sacrificial layer 230 is doped with ions, while the second sacrificial layer 240 is not doped with ions.

[0055] Since the first sacrificial layer 230 is doped with ions and the second sacrificial layer 240 is not doped with ions, the materials of the first sacrificial layer 230 and the second sacrificial layer 240 are different. Subsequently, by selecting a suitable etching process, the first sacrificial layer 230 and the second sacrificial layer 240 have a better etching selectivity.

[0056] Please continue to refer to Figure 8 The method for doping ions in part of the first sacrificial material film 220 includes: forming a first patterned layer 221 on the surface of the first sacrificial material film 220, wherein the first patterned layer 221 exposes part of the surface of the first sacrificial material film 220; using the first patterned layer 221 as a mask, ion implanting the first sacrificial material film 220 to form the first sacrificial layer 230 and the second sacrificial layer 240.

[0057] In this embodiment, the first patterned layer 221 is a multi-layer structure, including: a first mask layer (not shown in the figure) located on the surface of the first sacrificial material film 220, a second mask layer (not shown in the figure) located on the surface of the first mask layer, and a third mask layer (not shown in the figure) located on the surface of the second mask layer.

[0058] In this embodiment, the material of the first mask layer is spin-coated oxide, which serves as a buffer transition and increases the adhesion between the first patterned layer 221 and the first sacrificial material film 200; the material of the second mask layer is an anti-reflective material, which can reduce the reflection of light and thus improve the accuracy of the photolithography process; the material of the third mask layer is photoresist.

[0059] The thickness of the first sacrificial layer 230 is in a range of 300 angstroms to 600 angstroms.

[0060] In this embodiment, the second sacrificial layer 240 and the first sacrificial layer 230 have the same thickness.

[0061] It should be noted that the thickness refers to the dimension along a direction perpendicular to the surface of the substrate 200 .

[0062] Please refer to Fig. 9 After forming the first sacrificial layer 230 and the second sacrificial layer 210, the first patterned layer 221 is removed.

[0063] In this embodiment, the process of removing the first patterned layer 221 is an ashing process.

[0064] In other embodiments, the first patterned layer may be removed by an etching process or a chemical mechanical polishing process.

[0065] Please refer to Fig.10 , a second sacrificial material film 250 is formed on the surfaces of the first sacrificial layer 230 and the second sacrificial layer 240 .

[0066] The second sacrificial material film 250 is used to provide material for the subsequent formation of a third sacrificial layer.

[0067] The first sacrificial material film 220 and the second sacrificial material film 250 are made of the same material.

[0068] Since the first sacrificial material film 220 and the second sacrificial material film 250 are made of the same material, and the second sacrificial layer 240 and the subsequently formed third sacrificial layer are made of the same material, it is advantageous to use the same etching process to remove the second sacrificial layer 240 and the third sacrificial layer, thereby simplifying the process.

[0069] The material of the second sacrificial material film 250 includes: amorphous silicon, amorphous carbon, polysilicon, silicon oxide, silicon oxycarbide or silicon oxyhydrogencarbide.

[0070] In this embodiment, the material of the second sacrificial material film 250 is amorphous silicon.

[0071] The thickness ratio of the first sacrificial material film 220 to the second sacrificial material film 250 is in a range of 3:7 to 6:4.

[0072] The sum of the thicknesses of the first sacrificial material film 220 and the second sacrificial material film 250 ranges from 400 angstroms to 1000 angstroms.

[0073] By forming a second sacrificial material film 250 on the surface of the first sacrificial layer 230 and the second sacrificial layer 240 on the first area I and the second area II, the thickness of the first sacrificial material film 220 is reduced when the total thickness of the first sacrificial material film 220 and the second sacrificial material film 250 is thicker, which is beneficial to improve the accuracy of the pattern transfer. At the same time, the thickness of the mask layer subsequently formed on the side wall surface of the second sacrificial layer 240 and the third sacrificial layer is thicker, so that the thickness of the mask layer is thick enough to ensure that it plays a better masking role in the pattern transfer process.

[0074] Next, the first sacrificial layer 230 on the second region II is removed, and an opening is formed between adjacent second sacrificial layers 240 on the second region II.

[0075] In this embodiment, while removing the first sacrificial layer 230 on the second region II, the second sacrificial material film 250 is also etched to form a third sacrificial layer on the surface of the first sacrificial layer 230 and the second sacrificial layer 240 on the first region I and the second sacrificial layer 240 on the second region II. For the specific process of removing the first sacrificial layer 230 on the second region II, please refer to Figure 11 to Figure 12 .

[0076] Please refer to Fig.11 A second patterned layer 260 is formed on the surface of the second sacrificial material film 250, and the second patterned layer 260 covers the surface of the second sacrificial material film 250 on the first sacrificial layer 230 and the second sacrificial layer 240 on the first area I, and the surface of the second sacrificial material film 250 on the second sacrificial layer 240 on the second area II.

[0077] Specifically, the second patterned layer 260 exposes the surface of the second sacrificial material film 250 on the first sacrificial layer 230 on the second region II.

[0078] In this embodiment, the second patterned layer 260 is a multi-layer structure. The structure of the second patterned layer 260 is the same as that of the first patterned layer 221 , which will not be described in detail herein.

[0079] Please refer to Fig.12 , using the second patterned layer 260 as a mask, the second sacrificial material film 250 and the first sacrificial layer 230 located at the bottom of the second sacrificial material film 250 are etched until the surface of the substrate 200 is exposed, so that the second sacrificial material film 250 forms a third sacrificial layer 270, and the first sacrificial layer 230 on the second area II is removed, and the opening 280 is formed between adjacent second sacrificial layers 240 on the second area II.

[0080] In this embodiment, the opening 280 is located between the second sacrificial layer 240 and the third sacrificial layer 270 on the adjacent second region II.

[0081] It should be noted that the opening 280 is also located between the second sacrificial layer 240 and the third sacrificial layer 270 on the adjacent second region II and the second sacrificial layer 240 and the third sacrificial layer 270 on the first region I.

[0082] The second sacrificial material film 250 and the first sacrificial layer 230 are etched using a first etching process.

[0083] The first etching process is a dry etching process, and the parameters of the dry etching process include: the parameters of the dry etching process include: the gas used includes CF 4 , HBr, O 2 , Cl 2 , where CF 4 The flow rate of is 30 standard ml / min to 80 standard ml / min, the flow rate of HBr is 10 standard ml / min to 300 standard ml / min, and the flow rate of O 2 The flow rate is 30 standard ml / min to 80 standard ml / min, Cl 2 The flow rate is 50 standard ml / min to 3000 standard ml / min, and the time is 5 seconds to 40 seconds.

[0084] After removing the first sacrificial layer 230 on the second region II, the method further includes: removing the second patterned layer 260 .

[0085] The process of removing the second patterned layer 260 is the same as the process of removing the first patterned layer 221 , and will not be described again.

[0086] Please refer to Fig.13 A mask layer 290 is formed on the sidewall surface of the opening 280 , and the thickness of the mask layer 290 is greater than the thickness of the first sacrificial layer 230 .

[0087] The mask layer 290 is used to provide a mask for subsequent etching of the to-be-etched layer 210 .

[0088] Specifically, the mask layer 290 is located on the sidewall surfaces of the second sacrificial layer 240 and the third sacrificial layer 270 on the second region II and the sidewall surfaces of the second sacrificial layer 240 and the third sacrificial layer 270 on the first region I.

[0089] The method for forming the mask layer 290 includes: forming a mask material film (not shown in the figure) on the surface of the layer to be etched 210, the exposed surface of the third sacrificial layer 270, and the exposed surface of the second sacrificial layer 240; and back-etching the mask material film until the top surface of the third sacrificial layer 270 and the surface of the layer to be etched 210 are exposed to form the mask layer 290.

[0090] Specifically, in this embodiment, the mask material film is etched back until the top surface of the third sacrificial layer 270 and the surface of the transition layer 211 located on the surface of the layer to be etched 210 are exposed.

[0091] The material of the mask layer 290 is different from the materials of the first sacrificial material film 220 , the second sacrificial material film 250 , and the to-be-etched layer 210 .

[0092] The material of the mask layer 290 includes silicon oxide, silicon nitride, silicon oxynitride or titanium dioxide.

[0093] In this embodiment, the material of the mask layer 290 is silicon nitride.

[0094] Please refer to Fig.14 After forming the mask layer 290 , the second sacrificial layer 240 on the first region I and the second region II is removed.

[0095] By removing the second sacrificial layer 240 , the first sacrificial layer 230 on the first region I is exposed, and the first sacrificial layer 230 on the first region I is used to provide a mask for subsequent etching of the to-be-etched layer 210 .

[0096] The first sacrificial layer 230 has a larger size, and the size of the pattern transferred to the layer to be etched 210 is larger. The mask layer 290 has a larger size, and the size of the pattern transferred to the layer to be etched 210 is smaller, thereby meeting the process requirements of forming patterns with different sizes.

[0097] In this embodiment, the surfaces of the first sacrificial layer 230 and the second sacrificial layer 240 in the first region I and the surface of the second sacrificial layer 240 in the second region II also have a third sacrificial layer 270, and therefore, it also includes: removing the third sacrificial layer 270 to expose the surfaces of the first sacrificial layer 230 and the second sacrificial layer 240 in the first region I and the surface of the second sacrificial layer 240 in the second region II; removing the second sacrificial layer 240.

[0098] Since the thickness of the first sacrificial layer 230 and the third sacrificial layer 270 jointly determine the thickness of the formed mask layer 290, the thickness of the formed first sacrificial layer 230 is less than the thickness of the formed mask layer 290, that is, the thickness of the first sacrificial layer 230 is relatively small, which is beneficial to reducing the degree of over-etching of the first sacrificial layer 230 between adjacent second sacrificial layers 240 on the first area I during the process of removing the second sacrificial layer 240 on the first area I, thereby reducing the degree of reduction in the bottom size of the first sacrificial layer 230, reducing the size difference between the top and bottom of the first sacrificial layer 230, and effectively improving the morphology of the first sacrificial layer 230, so that when the first sacrificial layer 230 and the mask layer are used as masks to etch the layer 210 to be etched, it is beneficial to improve the accuracy of the pattern transfer.

[0099] In this embodiment, the removal of the second sacrificial layer 240 and the third sacrificial layer 270 is completed in the same process.

[0100] The second sacrificial layer 240 and the third sacrificial layer 270 on the first region I and the second region II are removed by a second etching process, and the etching rate of the second etching process on the second sacrificial layer 240 and the third sacrificial layer 270 is greater than the etching rate on the first sacrificial layer 230 .

[0101] The second etching process is a wet etching process, and the parameters of the wet etching process include: the etching solution is dilute ammonia water, the dilution ratio is 3:10 to 7:10, and the time is 100 seconds to 500 seconds.

[0102] The second etching process causes less etching damage to the first sacrificial layer 230 during the process of simultaneously removing the second sacrificial layer 240 and the third sacrificial layer 270 .

[0103] Please refer to Fig.15 , using the mask layer 290 and the first sacrificial layer 230 on the first region I as masks, the layer to be etched 210 is etched.

[0104] Specifically, the transition layer 211 and the to-be-etched layer 210 at the bottom of the transition layer 211 are etched using the mask layer 290 and the first sacrificial layer 230 on the first region I as masks, and the pattern is transferred into the to-be-etched layer 210 .

[0105] Correspondingly, the embodiment of the present invention further provides a semiconductor structure formed by the above method, please refer to Fig.13 , comprising: a substrate 200, wherein the substrate 200 has a layer 210 to be etched, wherein the layer 210 to be etched includes adjacent first and second regions I and II; a first sacrificial layer 230 located on the first region I; and a mask layer 290 located on the second region II, wherein the thickness of the mask layer 290 is greater than the thickness of the first sacrificial layer 230.

[0106] In this embodiment, the thickness of the first sacrificial layer 230 ranges from 300 angstroms to 600 angstroms.

[0107] 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 a substrate, wherein the substrate has a layer to be etched; forming a first sacrificial layer and a second sacrificial layer on the layer to be etched, wherein the first sacrificial layer is doped with ions, and the second sacrificial layer is not doped with ions; forming a third sacrificial layer on portions of the first sacrificial layer and the second sacrificial layer; patterning the first sacrificial layer, the second sacrificial layer and the third sacrificial layer; Transferring a pattern to the layer to be etched; The thickness of the first sacrificial layer ranges from 300 angstroms to 600 angstroms; The layer to be etched includes adjacent first and second regions; a plurality of second sacrificial layers are formed on the first and second regions respectively, and the first sacrificial layer is provided between adjacent second sacrificial layers; the method for forming the semiconductor structure further includes: after patterning the first sacrificial layer, the second sacrificial layer and the third sacrificial layer, before transferring the pattern to the layer to be etched, removing the first sacrificial layer on the second region, and forming an opening between adjacent second sacrificial layers on the second region; forming a mask layer on the side wall surface of the opening, and the thickness of the mask layer is greater than the thickness of the first sacrificial layer; after forming the mask layer, removing the second sacrificial layer on the first and second regions; etching the layer to be etched using the mask layer and the first sacrificial layer on the first region as masks, and transferring the pattern on the layer to be etched.

2. The method for forming a semiconductor structure according to claim 1, wherein: The method for forming the first sacrificial layer and the second sacrificial layer includes: forming a first sacrificial material film on the first area and the second area; doping ions in part of the first sacrificial material film to form adjacent first and second sacrificial layers, and the first sacrificial layer is doped with ions, and the second sacrificial layer is not doped with ions.

3. The method for forming a semiconductor structure according to claim 2, wherein: The method for doping ions in part of the first sacrificial material film includes: forming a first patterned layer on the surface of the first sacrificial material film, the first patterned layer exposing part of the surface of the first sacrificial material film; using the first patterned layer as a mask, ion implanting the first sacrificial material film to form the first sacrificial layer and the second sacrificial layer; after forming the first sacrificial layer and the second sacrificial layer, removing the first patterned layer.

4. The method for forming a semiconductor structure according to claim 2, wherein: The method for forming the third sacrificial layer includes: after forming the first sacrificial layer and the second sacrificial layer, before removing the first sacrificial layer on the second area, forming a second sacrificial material film on the surfaces of the first sacrificial layer and the second sacrificial layer; in the process of removing the first sacrificial layer on the second area, etching the second sacrificial material film to form the third sacrificial layer on the surfaces of the first sacrificial layer and the second sacrificial layer on the first area and the second sacrificial layer on the second area, and the mask layer is also located on the side wall surface of the third sacrificial layer; after forming the mask layer, removing the third sacrificial layer.

5. The method for forming a semiconductor structure according to claim 4, wherein: The first sacrificial material film and the second sacrificial material film are made of the same material; the materials of the first sacrificial material film and the second sacrificial material film include: amorphous silicon, amorphous carbon, polysilicon, silicon oxide, silicon oxycarbide or silicon oxyhydrogencarbide.

6. The method for forming a semiconductor structure according to claim 4, wherein: The thickness ratio of the first sacrificial material film to the second sacrificial material film is in a range of 3:7 to 6:

4.

7. The method for forming a semiconductor structure according to claim 4, wherein: The sum of the thicknesses of the first sacrificial material film and the second sacrificial material film ranges from 400 angstroms to 1000 angstroms.

8. The method for forming a semiconductor structure according to claim 4, wherein: The method for removing the first sacrificial layer on the second area includes: forming a second patterned layer on the surface of the second sacrificial material film, the second patterned layer covering the first sacrificial layer and the second sacrificial layer on the first area, and the surface of the second sacrificial material film on the second sacrificial layer on the second area; using the second patterned layer as a mask, etching the second sacrificial material film and the first sacrificial layer located at the bottom of the second sacrificial material film until the substrate surface is exposed, so that the second sacrificial material film forms a third sacrificial layer, and removing the first sacrificial layer on the second area, and forming the opening between adjacent second sacrificial layers on the second area.

9. The method for forming a semiconductor structure according to claim 8, wherein: The second sacrificial material film and the first sacrificial layer are etched using a first etching process, wherein the first etching process is a dry etching process, and the parameters of the dry etching process include: the gases used include CF4, HBr, O2, and Cl2, wherein the flow rate of CF4 is 30 standard ml / min to 80 standard ml / min, the flow rate of HBr is 10 standard ml / min to 300 standard ml / min, the flow rate of O2 is 30 standard ml / min to 80 standard ml / min, the flow rate of Cl2 is 50 standard ml / min to 3000 standard ml / min, and the time is 5 seconds to 40 seconds.

10. The method for forming a semiconductor structure according to claim 2, wherein: The second sacrificial layer and the third sacrificial layer on the first area and the second area are removed by a second etching process, and the etching rate of the second etching process on the second sacrificial layer and the third sacrificial layer is greater than the etching rate on the first sacrificial layer.

11. The method for forming a semiconductor structure according to claim 10, wherein: The second etching process is a wet etching process, and the parameters of the wet etching process include: the etching solution is dilute ammonia water, the dilution ratio is 3:10 to 7:10, and the time is 100 seconds to 500 seconds.

12. The method for forming a semiconductor structure according to claim 1, wherein: The method for forming the mask layer includes: forming a mask material film on the surface of the layer to be etched, the exposed surface of the third sacrificial layer, and the exposed surface of the second sacrificial layer; etching back the mask material film until the top surface of the third sacrificial layer and the surface of the layer to be etched are exposed to form the mask layer.

13. The method for forming a semiconductor structure according to claim 2, wherein: Also includes: Before forming the first sacrificial material film, the method further includes: forming a transition layer on the surface of the layer to be etched.

14. A semiconductor structure, characterized in that: The semiconductor structure is formed by the method for forming a semiconductor structure according to any one of claims 1 to 13, wherein the semiconductor structure comprises: A substrate having a layer to be etched thereon, wherein the layer to be etched includes a first region and a second region adjacent to each other; a first sacrificial layer located on the first region; a mask layer located on the second region, wherein the thickness of the mask layer is greater than the thickness of the first sacrificial layer; The thickness of the first sacrificial layer ranges from 300 angstroms to 600 angstroms.

Images