Method for producing lithographically positioned markings

Abstract

This application provides a method for fabricating photolithographic positioning marks, relating to the field of semiconductor technology. The method includes forming a mask layer on a target layer; patterning the mask layer using a first photolithographic etching process to form a first positioning mark within the mask layer; and patterning the mask layer using a second photolithographic etching process to form a second positioning mark within the mask layer; wherein the orthographic projections of the first positioning mark and the second positioning mark on the target layer are staggered. This application can prevent the mask layer from being etched through, thereby preventing over-etching of the target layer located below the positioning marks and thus avoiding damage to the target layer.

Description

Technical Field

[0001] This application relates to the field of semiconductor process technology, and in particular to a method for preparing photolithographic positioning marks. Background Technology

[0002] In semiconductor manufacturing, photolithography is a crucial process for transferring circuit patterns. Photolithography involves transferring a pattern from a photomask onto a wafer through exposure and development. Currently, target patterns have high densities. To ensure the accuracy of the critical dimensions of the formed target pattern, Double Patterning Technology (DPT) or Multiple Patterning Technology (MPT) is typically used. This involves splitting a high-density mask pattern into two or more lower-density mask patterns, and then sequentially performing the corresponding exposure and etching processes to ultimately form the desired high-density mask pattern.

[0003] In forming high-density mask patterns, related technologies typically require the formation of photolithographic positioning marks on the mask layer to facilitate the measurement of critical dimensions of the mask pattern. However, during the patterning process of the mask layer, the target layer located below the photolithographic positioning marks may be over-etched, causing damage to the target layer and consequently reducing the performance of the semiconductor device fabricated using this photolithographic positioning mark method. Summary of the Invention

[0004] This application provides a method for preparing photolithographic positioning marks, including:

[0005] A mask layer is formed on the target layer;

[0006] The mask layer is patterned using a first photolithography etching process to form a first positioning mark in the mask layer;

[0007] The mask layer is patterned using a second photolithography etching process to form a second positioning mark in the mask layer; the orthographic projections of the first positioning mark on the target layer and the second positioning mark on the target layer are staggered.

[0008] In one possible implementation, patterning the mask layer using a first photolithography etching process to form a first positioning mark in the mask layer further includes:

[0009] A first photoresist layer is formed on top of the mask layer, and the first patterned structure is obtained after the first photoresist layer is exposed and developed.

[0010] The mask layer is etched using the first patterned structure as a mask to form a first positioning mark in the mask layer.

[0011] In one possible implementation, the second positioning mark surrounds the first positioning mark.

[0012] In one possible implementation, the first positioning mark and the second positioning mark have the same center of symmetry.

[0013] In one possible implementation, the first positioning mark and the second positioning mark can be circular or polygonal in shape on a plane parallel to the target layer.

[0014] In one possible implementation, the first positioning mark and the second positioning mark have the same shape.

[0015] In one possible implementation,

[0016] The step of patterning the mask layer using a second photolithography etching process to form a second positioning mark in the mask layer further includes:

[0017] A second photoresist layer is formed on top of the mask layer, and the second photoresist layer is exposed and developed to obtain a second patterned structure.

[0018] The mask layer is etched using the second pattern structure as a mask to form a second positioning mark in the mask layer. In one possible implementation, the mask layer includes an etch stop layer and a first hard mask layer, the etch stop layer being formed on the target layer and the first hard mask layer being formed on the etch stop layer;

[0019] The patterning of the mask layer stops at the etch stop layer.

[0020] In one possible implementation, the mask layer includes a second hard mask layer formed on the side of the first hard mask layer opposite to the etch stop layer; the material of the second hard mask layer is different from the material of the first hard mask layer.

[0021] In one possible implementation, the preparation method further includes:

[0022] The mask layer is patterned using a third photolithography etching process to form a third positioning mark in the mask layer. The third positioning mark is located inside the first positioning mark, and the orthographic projection of the third positioning mark on the target layer is offset from the orthographic projection of the first positioning mark on the target layer. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A schematic diagram illustrating a method for fabricating photolithographic positioning marks in related technologies;

[0025] Figure 2 A process flow diagram of the method for preparing photolithographic positioning marks provided in the embodiments of this application;

[0026] Figure 3 A schematic diagram of the positioning markers provided in the embodiments of this application. Figure 1 ;

[0027] Figure 4 A schematic diagram of the positioning markers provided in the embodiments of this application. Figure 2 ;

[0028] Figure 5 A schematic diagram of the positioning markers provided in the embodiments of this application. Figure 3 ;

[0029] Figure 6 This is a schematic diagram illustrating the formation of the first positioning mark in the method for preparing the photolithographic positioning mark provided in the embodiments of this application;

[0030] Figure 7 A schematic diagram illustrating the formation of a sacrificial layer in the method for preparing photolithographic positioning marks provided in this application embodiment;

[0031] Figure 8 This is a schematic diagram illustrating the formation of the second photoresist layer in the method for preparing photolithographic positioning marks provided in the embodiments of this application;

[0032] Figure 9 This is a schematic diagram illustrating the formation of a second positioning mark in the method for preparing a photolithographic positioning mark according to an embodiment of this application;

[0033] Figure 10 This is a schematic diagram showing the process after removing the second photoresist layer in the method for preparing photolithographic positioning marks provided in the embodiments of this application.

[0034] Figure label:

[0035] 100: Target layer;

[0036] 200: Mask layer; 210: First positioning mark; 220: Second positioning mark; 230: Etching stop layer; 240: First hard mask layer; 250: Second hard mask layer; 260: Third positioning mark;

[0037] 300: First anti-reflective layer;

[0038] 400: First photoresist layer;

[0039] 500: Sacrifice Layer;

[0040] 600: Second anti-reflective layer;

[0041] 700: Second photoresist layer;

[0042] 10: Target layer; 20: Mask layer. Detailed Implementation

[0043] The patterning process of the mask layer often results in over-etching of the target layer located below the photolithography positioning marks, causing damage to the target layer. Please refer to the appendix. Figure 1 When different positioning marks are formed by etching, the different positioning marks have overlapping areas, which causes the positions of the overlapping areas of the positioning marks on the mask layer 20 to be etched multiple times, resulting in an increased etching depth in the area. This leads to over-etching of the mask layer 20, which in turn causes the target layer 10 located below the mask layer 20 to be etched, resulting in damage to the target layer 10. On the other hand, after etching the mask layer 20, it is necessary to use wet cleaning to clean the etching byproducts. If the mask layer 20 is etched through at this time, the wet cleaning may come into contact with the target layer 10 below the mask layer 20, causing more serious damage.

[0044] To make the above-mentioned objectives, features, and advantages of the embodiments of this application more apparent and understandable, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0045] This application provides a method for preparing photolithographic positioning marks, which are used to form positioning marks on a mask layer.

[0046] Please refer to the attached document. Figure 2 , Figure 2 This is a flowchart illustrating the method for fabricating photolithographic positioning marks in an embodiment of this application. The method for fabricating photolithographic positioning marks includes the following steps:

[0047] Step S100: Form a mask layer on the target layer.

[0048] In some embodiments of this application, please refer to the appendix. Figure 6 To be continued Figure 10The target layer 100 can be a substrate. For example, a mask layer 200 can be used as a mask to form multiple arrayed active regions in the target layer 100. The substrate material can be semiconductor materials such as silicon, germanium, silicon germanide, arsenic germanide, silicon on insulator (SOI), or germanium on insulator (GOI), or other materials. This application embodiment is not limited to these materials.

[0049] In some embodiments of this application, the target layer 100 may also be a metal layer (e.g., M0, M1 to Mn), in which case the mask layer 200 can be used as a mask to form metal wiring in the target layer 100.

[0050] In some embodiments of this application, the target layer 100 may also be a via layer, which includes conductive plugs for interconnecting adjacent metal layers. In this example, a mask layer 200 can be used as a mask to form multiple vias in the target layer 100, and then a conductive material is formed in the multiple vias using a deposition process to form the via layer.

[0051] In order to measure the mask pattern in the mask layer 200, in this embodiment, positioning marks need to be formed in the mask layer 200 to provide a clear positioning reference point for the measurement device.

[0052] Step S200: Pattern the mask layer using a first photolithography etching process to form a first positioning mark in the mask layer.

[0053] Please refer to the attached document. Figure 6 In some examples, a first photoresist layer 400 is formed over the mask layer 200 to expose and develop the first photoresist layer 400 to obtain a first patterned structure.

[0054] In some embodiments of this application, a first photoresist layer 400 of a certain thickness can be formed on top of the mask layer 200 using a spin coating method. It should be noted that the first pattern structure can be freely configured according to specific device design and process requirements. For example, patterns of different shapes, sizes, and arrangements can be designed to meet different functional needs.

[0055] It should be understood that in this embodiment, the first photoresist layer 400 is formed above the mask layer 200. This can be understood as the first photoresist layer 400 being formed directly on the mask layer 200 or indirectly on the mask layer 200.

[0056] In some embodiments of this application, please refer to the appendix. Figure 6A first anti-reflective layer 300 is formed on the side of the mask layer 200 opposite to the target layer 100, and a first photoresist layer 400 is formed on the first anti-reflective layer 300. For example, the first photoresist layer 400 can be formed on the surface of the first anti-reflective layer 300 opposite to the mask layer 200 by coating.

[0057] In some embodiments of this application, the material of the first antireflective layer 300 may include nitrides. For example, the material of the first antireflective layer 300 may include silicon nitride or silicon oxynitride, but is not limited thereto. The first antireflective layer 300 can alleviate or eliminate the standing wave effect of the first photoresist layer 400, thereby increasing the accuracy of transferring the desired pattern from the mask onto the first photoresist layer 400, and thus improving the accuracy of the pattern transfer process.

[0058] In some embodiments of this application, after obtaining the first patterned structure, the mask layer 200 is etched using the first patterned structure as a mask to form a first positioning mark 210 in the mask layer 200.

[0059] In some embodiments of this application, after the first positioning mark 210 is formed, the first photoresist layer 400 and the first anti-reflection layer 300 are removed by an ashing process and a stripping process.

[0060] Step S300: The mask layer is patterned using a second photolithography etching process to form a second positioning mark in the mask layer; the orthographic projection of the first positioning mark on the target layer and the orthographic projection of the second positioning mark on the target layer are staggered.

[0061] Please refer to the attached document. Figure 8 To be continued Figure 10 The process of patterning the mask layer 200 using a second photolithography etching process to form a second positioning mark in the mask layer further includes:

[0062] A second photoresist layer 700 is formed above the mask layer 200, and the second photoresist layer 700 is exposed and developed to obtain the second pattern structure.

[0063] It should be noted that, since the first positioning mark 210 has been formed in the mask layer 200, in order to protect the first positioning mark, a sacrificial layer 500 needs to be formed in the first positioning mark 210 before the second photoresist layer 700 is formed.

[0064] In some embodiments of this application, a sacrificial layer 500 is formed by a deposition process, which fills the first positioning mark 210. The top surface of the sacrificial layer 500 is flush with the top surface of the mask layer 200 to ensure the flatness of the mask layer 200 and to facilitate the formation of the second photoresist layer 700 on the top surfaces of the mask layer 200 and the sacrificial layer 500.

[0065] In some embodiments of this application, after the sacrificial layer 500 is formed, in order to improve the surface flatness of the sacrificial layer 500, it is usually necessary to planarize the top surface of the sacrificial layer 500 using a chemical mechanical polishing (CMP) process. When the shape of the second positioning mark 220 is polygonal, the line width of the second positioning mark 220 can be reduced. In this way, the risk of the top surface of the sacrificial layer 500 forming a depression is reduced, which helps to maintain the flatness of the sacrificial layer, thereby further improving the reliability and accuracy of subsequent processes.

[0066] In some embodiments of this application, the material of the sacrificial layer 500 can be spin-coated carbon (SOC). Utilizing the good fluidity of spin-coated carbon (SOC), the sacrificial layer 500 can better fill the first positioning mark and make the sacrificial layer 500 have a relatively flat surface morphology.

[0067] In some embodiments of this application, please refer to the appendix. Figure 8 A second anti-reflective layer 600 is formed between the mask layer 200 and the second photoresist layer 700. The second patterned structure is formed by exposing, developing and etching the second photoresist layer 700.

[0068] In some embodiments of this application, please refer to the appendix. Figure 9 and attached Figure 10 After forming the second pattern structure, the mask layer 200 is etched using the second pattern structure as a mask to form the second positioning mark 220 in the mask layer.

[0069] It should be understood that the number of second positioning marks 220 can be one or more. When there are multiple second positioning marks 220, the above step S300 can be repeated to form (n-1) second positioning marks 220 in the mask layer 200; where n is a positive integer greater than or equal to 2.

[0070] In some embodiments of this application, after the second positioning mark 220 is formed, an ashing process and a stripping process are required to remove the second photoresist layer 700 and the second anti-reflection layer 600.

[0071] Using the photolithographic positioning mark fabrication method provided in this application, the first positioning mark 210 and the second positioning mark 220 are offset. In other words, the orthographic projections of the first positioning mark and the second positioning mark on the target layer are staggered. This arrangement avoids the first and second photolithographic etching processes from etching at the same location on the mask layer 200, preventing over-etching of the mask layer 200, and thus preventing the target layer 100 located below the mask layer 200 from being etched. This ensures that the structure of the target layer 100 remains intact during the etching process, which helps to improve the quality and reliability of the product.

[0072] Furthermore, while avoiding over-etching of the mask layer 200, this preparation method allows etching to be performed within a wider range of process parameters, thereby expanding the process window and increasing the flexibility and adaptability of the etching process.

[0073] Please refer to the attached document. Figure 4 and attached Figure 5 In one possible implementation, the second positioning mark 220 surrounds the first positioning mark 210. That is, the first positioning mark 210 is located within the area enclosed by the second positioning mark 220.

[0074] Thus, through nested layout, the first positioning mark 210 and the second positioning mark 220 can be arranged more compactly, avoiding unnecessary space waste, thereby significantly reducing the area occupied by the positioning mark group in the overall design or product, which helps to optimize the overall layout structure and improve the compactness and aesthetics of the design or product.

[0075] In some embodiments of this application, the first positioning mark 210 and the second positioning mark 220 have the same center of symmetry, that is, the first positioning mark 210 and the second positioning mark 220 can be set concentrically. In this way, since all positioning marks are arranged around the same center point, their relative positional relationship is clearer, positioning and calibration can be performed more easily, which helps to reduce positioning errors and improve the overall positioning accuracy.

[0076] It should be noted that the first positioning mark 210 and the second positioning mark 220 are not simply nested. Please refer to the appendix for some possible examples. Figure 3 The first positioning mark 210 and at least one second positioning mark 220 are arranged in an array in the mask layer 200 so that the multiple positioning marks are arranged in a certain pattern.

[0077] In some embodiments of this application, the first positioning mark 210 and at least one second positioning mark 220 may be arranged in multiple rows and columns, or the first positioning mark 210 and at least one second positioning mark 220 may be arranged at intervals along the row direction, or the first positioning mark 210 and at least one second positioning mark 220 may be arranged at intervals along the column direction, or the first positioning mark 210 and at least one second positioning mark 220 may also be arranged in a circular array.

[0078] In this way, the space on the mask layer 200 can be used efficiently, ensuring that a sufficient number of positioning marks can be placed within a limited area. This not only improves positioning accuracy but also makes the design of the mask layer 200 more compact and efficient.

[0079] In some embodiments of this application, the first positioning mark 210 and the second positioning mark 220 can be circular or polygonal in shape on a plane parallel to the target layer 100. Thus, both the first positioning mark 210 and the second positioning mark 220 are annular structures, so that the second positioning mark 220 can be positioned around the first positioning mark 210.

[0080] In some embodiments of this application, the shape of the first positioning mark 210 and the shape of the second positioning mark 220 may be the same or different. For example, the shape of the first positioning mark 210 and the shape of the second positioning mark are the same.

[0081] In some embodiments of this application, the first positioning mark 210 and the second positioning mark 220 are both polygons. The polygonal design gives the second positioning mark 220 multiple distinct corners, resulting in higher recognizability and stability, making it easier for measurement equipment to capture and identify, thereby improving the efficiency and accuracy of measurement.

[0082] Meanwhile, the polygonal structure is more mechanically stable and can resist certain external force interference, ensuring that the shape and position of the positioning mark remain unchanged during the measurement process, thereby improving the accuracy of the measurement.

[0083] In some embodiments of this application, the polygon can be selected from a variety of options. For example, the polygon can be a triangle, a quadrilateral (e.g., a rectangle), or even other structures.

[0084] In some embodiments of this application, please continue to refer to the appendix. Figure 4 The first positioning mark 210 and the second positioning mark 220 are both cross-shaped. The cross-shaped second positioning mark 220 has a clearer directionality, clearly indicating the horizontal and vertical directions, making the measurement process simpler and more direct.

[0085] In some embodiments of this application, the first positioning mark 210 is located on the innermost side, and the shape of the first positioning mark 210 is polygonal or cross-shaped. The shape of the first positioning mark 210 may be the same as or different from that of the second positioning mark 220.

[0086] In some embodiments of this application, when the second positioning mark 220 is a polygon, the innermost first positioning mark 210 can also be a polygon or a cross shape. This allows for more flexible design of the positioning marks, enabling them to adapt to different manufacturing needs and process conditions. Furthermore, by selecting appropriate positioning mark shapes and combinations, manufacturing costs can be reduced while ensuring positioning accuracy.

[0087] In some embodiments of this application, please continue to refer to the appendix. Figure 5 The first positioning mark 210 and the second positioning mark 220 are rectangular in shape. The rectangular first positioning mark 210 and the second positioning mark 220 have clear boundaries and corners, which makes it easier for the measuring device to capture and identify these corners, thereby improving the accuracy of the measurement.

[0088] In some embodiments of this application, please continue to refer to the appendix. Figure 6 To be continued Figure 10 The mask layer 200 may include an etch stop layer 230 and a first hard mask layer 240. The etch stop layer 230 is formed on the target layer 100, and the first hard mask layer 240 is formed on the etch stop layer 230.

[0089] The etch stop layer 230 has a large etch selectivity ratio with the first hard mask layer 240, which can ensure that the patterning of the mask layer 200 stops at the etch stop layer 230.

[0090] In some embodiments of this application, the etch stop layer 230 may be made of oxides or nitrides, such as silicon nitride. The first hard mask layer 240 may be made of silicon oxide, silicon nitride, titanium nitride, amorphous carbon, or other materials.

[0091] It should be noted that both the etch stop layer 230 and the first hard mask layer 240 can be formed by deposition processes. These deposition processes can include chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD).

[0092] In some embodiments of this application, the mask layer 200 may further include other film layers. For example, the mask layer 200 may also include a second hard mask layer 250, which is formed on the side of the first hard mask layer 240 opposite to the etch stop layer 230. The material of the second hard mask layer 250 is different from that of the first hard mask layer 240.

[0093] In some embodiments of this application, the second hard mask layer 250 is made of spin-on carbon (SOC) or spin-on glass (SOG). Spin-on carbon (SOC) exhibits excellent photolithography performance, enabling the formation of clear and precise patterns during the photolithography process. This improves the accuracy of the positioning marks and mask patterns formed on the mask layer 200, which is crucial for manufacturing semiconductor devices with high precision requirements.

[0094] In one possible implementation, the method for preparing the positioning marker further includes:

[0095] The mask layer 200 is patterned using a third photolithography etching process to form a third positioning mark 260 in the mask layer 200. The third positioning mark 260 is located inside the first positioning mark 210, and the orthographic projection of the third positioning mark 260 on the target layer 100 is offset from the orthographic projection of the first positioning mark 210 on the target layer 100.

[0096] This setting increases the number of positioning markers, thereby increasing the area of ​​the mask layer that is exposed, ensuring that a certain position of the mask layer 200 is not repeatedly opened.

[0097] It should be noted that the preparation process of the third positioning mark 260 can refer to the preparation process of the first positioning mark 210, and will not be described in detail in this embodiment.

[0098] The various embodiments or implementation methods described in this specification are presented in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other.

[0099] In the description of this specification, references to terms such as “one embodiment,” “some embodiments,” “illustrative embodiment,” “example,” “specific example,” or “some examples” refer to specific features, structures, materials, or characteristics described in connection with an embodiment or example that are included in at least one embodiment or example of this application.

[0100] In this specification, the illustrative expressions of the terms used do not necessarily refer to the same implementation or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more implementations or examples.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing photolithographic positioning marks, characterized in that, include: A mask layer is formed on the target layer; The mask layer is patterned using a first photolithography etching process to form a first positioning mark in the mask layer; The mask layer is patterned using a second photolithography etching process to form a second positioning mark in the mask layer; The orthographic projections of the first positioning mark and the second positioning mark on the target layer are offset.

2. The method for preparing photolithographic positioning marks according to claim 1, characterized in that, The step of patterning the mask layer using a first photolithography etching process to form a first positioning mark in the mask layer further includes: A first photoresist layer is formed on the mask layer, and the first patterned structure is obtained after the first photoresist layer is exposed and developed. The mask layer is etched using the first patterned structure as a mask to form a first positioning mark in the mask layer.

3. The method for preparing photolithographic positioning marks according to claim 1, characterized in that, The second positioning mark surrounds the first positioning mark.

4. The method for preparing photolithographic positioning marks according to claim 3, characterized in that, The first positioning mark and the second positioning mark have the same center of symmetry.

5. The method for preparing photolithographic positioning marks according to claim 4, characterized in that, On a plane parallel to the target layer, the first positioning mark and the second positioning mark can be circular or polygonal in shape.

6. The method for preparing photolithographic positioning marks according to claim 5, characterized in that, The first positioning mark and the second positioning mark have the same shape.

7. The method for preparing photolithographic positioning marks according to any one of claims 1-6, characterized in that, The step of patterning the mask layer using a second photolithography etching process to form a second positioning mark in the mask layer further includes: A second photoresist layer is formed on top of the mask layer, and the second patterned structure is obtained after the second photoresist layer is exposed and developed. The mask layer is etched using the second pattern structure as a mask to form a second positioning mark in the mask layer.

8. The method for preparing the positioning marker according to any one of claims 1-6, characterized in that, The mask layer includes an etch stop layer and a first hard mask layer, wherein the etch stop layer is formed on the target layer and the first hard mask layer is formed on the etch stop layer; The patterning of the mask layer stops at the etch stop layer.

9. The method for preparing the positioning marker according to claim 8, characterized in that, The mask layer includes a second hard mask layer, which is formed on the side of the first hard mask layer away from the etch stop layer; the material of the second hard mask layer is different from the material of the first hard mask layer.

10. The method for preparing the positioning marker according to claim 9, characterized in that, The preparation method further includes: The mask layer is patterned using a third photolithography etching process to form a third positioning mark in the mask layer. The third positioning mark is located inside the first positioning mark, and the orthographic projection of the third positioning mark on the target layer is offset from the orthographic projection of the first positioning mark on the target layer.

Images