Preparation method of mask structure
By forming a second hard mask layer on top of the hard mask layer and positioning its pattern, the problem of abnormal hard mask morphology caused by photoresist tilting was solved, thus improving the fabrication quality and product yield of the hard mask structure.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-13
- Publication Date
- 2026-04-10
AI Technical Summary
During the fabrication of hard mask structures, high aspect ratio photoresist is prone to tipping over, leading to abnormal hard mask morphology and affecting product yield.
By forming a first hard mask layer on a substrate and a second hard mask layer on one side thereon, the pattern position of the second hard mask layer is located using the first opening pattern. The second hard mask layer adjacent to the bottom wall of the first opening pattern is removed, and the second hard mask layer adjacent to its side wall is retained as the side wall of the second opening pattern, thus avoiding the photoresist from covering and blocking the side wall of the second opening pattern with a high aspect ratio.
This avoids the morphological defects caused by high aspect ratio photoresist tilting, and improves the fabrication quality and product yield of hard mask structures.
Smart Images
Figure CN121843500A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor fabrication technology, and more particularly to a method for fabricating a mask structure. Background Technology
[0002] In power devices, to improve device performance, it is necessary to reduce the device cell size. Therefore, the linewidth parameter in the fabrication of power devices also requires narrower lines. These small lithographic lines usually require the use of a hard mask structure as a barrier layer. However, during the fabrication of the hard mask structure, abnormal etching morphology of the hard mask is prone to occur, thus affecting the product yield. Summary of the Invention
[0003] This invention provides a method for fabricating a mask structure that avoids the problem of poor hard mask structure morphology caused by the tilting of high aspect ratio photoresist.
[0004] This invention provides a method for fabricating a mask structure, comprising: Provide substrate; A first hard mask layer is formed on the surface of the substrate; A first opening pattern is formed in the first hard mask layer; the first opening pattern protrudes from the surface of the substrate. A second hard mask layer is formed on the side of the first hard mask layer away from the substrate; the second hard mask layer at least covers the sidewall and bottom wall of the first opening pattern; A second opening pattern is formed in the second hard mask layer, the second opening pattern is located inside the first opening pattern, and the second opening pattern protrudes from the substrate surface; the opening size of the second opening pattern is equal to the spacing between the second hard mask layers adjacent to the opposite sidewalls of the first opening pattern; Remove the first hard mask layer.
[0005] Optionally, forming a first opening pattern in the first hard mask layer includes: A photoresist layer is formed on the side of the first hard mask layer away from the substrate; A mask pattern is formed on the photoresist layer; The first opening pattern is formed by etching the first hard mask layer according to the mask pattern.
[0006] Optionally, forming a second opening pattern in the second hard mask layer includes: Remove the second hard mask layer on the surface of the first hard mask layer, as well as the second hard mask layer adjacent to the bottom wall of the first opening pattern; The second hard mask layer adjacent to the opposite sidewall of the first opening pattern is retained, and the spacing between the retained second hard mask layers forms the second opening pattern; wherein the retained second hard mask layers constitute the sidewall of the second opening pattern.
[0007] Optionally, in the first direction, the spacing between the sidewalls of the first opening pattern is the sum of the widths of the sidewalls of the two second opening patterns and the spacing between the sidewalls of the second opening patterns; the first direction is perpendicular to the thickness direction of the substrate.
[0008] Optionally, the sidewall width of the second opening pattern is 0.3μm-0.8μm.
[0009] Optionally, the spacing between the sidewalls of the second opening pattern is 1μm-4um.
[0010] Optionally, in the first direction, the sidewall width of the first opening pattern is greater than the sidewall width of the second opening pattern.
[0011] Optionally, the thickness of the second hard mask layer is less than that of the first hard mask layer.
[0012] Optionally, the thickness of the second hard mask layer is 3,000 to 8,000 angstroms.
[0013] Optionally, the first hard mask layer is a single film layer or a composite film layer; The single film layer is a silicon dioxide layer or a silicon nitride layer; The composite film is a stacked structure of a silicon dioxide layer, a silicon nitride layer, and a silicon dioxide layer.
[0014] The mask structure fabrication method provided in this embodiment of the invention involves forming a first hard mask layer on a substrate, forming a first opening pattern on the first hard mask layer, and forming a second hard mask layer on the side of the first hard mask layer away from the substrate. The first opening pattern is used to position the pattern on the second hard mask layer. The second hard mask layer adjacent to the bottom wall of the first opening pattern is removed, while the second hard mask layer adjacent to the sidewall of the first opening pattern is retained. The retained second hard mask layer serves as the sidewall of the second opening pattern. Compared to traditional hard mask fabrication processes, when transferring the second opening pattern on the second hard mask layer, it avoids using photoresist or other photolithographic materials to cover and block the sidewall of the high aspect ratio second opening pattern, thereby avoiding the problem of poor morphology in the second opening pattern fabrication caused by the high aspect ratio photoresist tipping. Attached Figure Description
[0015] Figure 1 This is a schematic flowchart illustrating a method for fabricating a mask structure according to an embodiment of the present invention; Figures 2-6 This invention provides a schematic diagram of the intermediate structure of a mask structure according to an embodiment of the present invention; Figure 7 This invention provides a schematic diagram of the intermediate structure of a mask structure according to an embodiment of the present invention; Figure 8 This invention provides a schematic diagram of the intermediate structure of a mask structure according to an embodiment of the present invention; Figure 9 A schematic diagram of yet another mask structure is provided for embodiments of the present invention; Figures 10-12 for Figure 9 The diagram shows the intermediate structure of the mask structure. Detailed Implementation
[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0017] A hard mask is a film layer produced using a chemical vapor deposition (CVD) process. In the hard mask fabrication process, a photoresist pattern is typically transferred onto the hard mask first, and then the final pattern is etched onto the substrate through the hard mask.
[0018] With the miniaturization of semiconductor devices, in order to improve device performance, it is necessary to reduce the cell size of the device. This also means that smaller scribe lines need to be formed in semiconductor devices. As the width of the scribe lines becomes narrower, the sidewalls of the pattern on the hard mask also need to be narrower. This leads to problems such as poor morphology or tilting of the high-depth-ratio photoresist portion when transferring the pattern to the hard mask using photoresist, resulting in abnormal morphology of the prepared hard mask.
[0019] In view of this, Figure 1 This is a schematic flowchart illustrating a method for fabricating a mask structure according to an embodiment of the present invention. Figures 2-6 This invention provides an intermediate structure diagram of a mask structure, applicable to hard mask fabrication in semiconductor device manufacturing processes. The method specifically includes the following steps: S110, Provides a substrate; The substrate can be the semiconductor body of a semiconductor device. The semiconductor body may include a substrate 110 and an epitaxial layer 120. The semiconductor body may also include conductive regions deposited on or implanted within the epitaxial layer 120, thereby forming the functional structure of the semiconductor device. The substrate 110 and the epitaxial layer 120 may be made of silicon carbide, with the epitaxial layer 120 formed on one side of the substrate 110. For example, the epitaxial layer 120 can be formed on the surface of the substrate 110 by epitaxial growth. Its structure is as follows... Figure 2 As shown.
[0020] S120, A first hard mask layer 130 is formed on the surface of the substrate; Specifically, the main components of the first hard mask layer 130 typically include one or more combinations of titanium nitride, silicon nitride, and silicon dioxide. The first hard mask layer 130 can be deposited on the surface of the substrate using a CVD process. The material of the first hard mask layer 130 can be selected according to the substrate. For example, in this embodiment of the invention, the substrate is a silicon carbide substrate, and the first hard mask layer 130 can be a silicon dioxide layer or a silicon nitride layer. In some embodiments, the first hard mask layer 130 can also be a multilayer composite layer. For example, the first hard mask layer 130 formed by stacking silicon dioxide, silicon nitride, and silicon dioxide layers utilizes the differences in properties between the materials of each layer to reduce the risk of over-etching in the subsequent etching process of the first hard mask layer 130 and avoid damage to the silicon carbide surface.
[0021] S130, a first opening pattern 140 is formed in the first hard mask layer 130; the first opening pattern 140 protrudes from the substrate surface. Specifically, using photoresist or electron beam lithography to define micron or nanometer-scale patterns, the first opening pattern 140 is transferred to the first hard mask layer 130 through an etching process. The first opening pattern 140 is a defined pattern and can be designed as a continuous or discontinuous shape according to application needs. In this embodiment of the invention, the first opening pattern 140 is illustrated as a groove. The spacing between the sidewalls of the first opening pattern 140, i.e., the opening of the first opening pattern 140, can be subsequently used to locate the pattern position on the second hard mask layer. Its structure is as follows: Figure 3 As shown.
[0022] S140, a second hard mask layer 150 is formed on the side of the first hard mask layer 130 away from the substrate; the second hard mask layer 150 at least covers the sidewall and bottom wall of the first opening pattern 140. Specifically, the second hard mask layer 150 can be deposited on the surface of the first hard mask layer 130 using a CVD process. The second hard mask layer 150 at least covers the first opening pattern 140, wherein the second hard mask layer 150 is deposited at least on the sidewalls and bottom wall of the first opening pattern 140. The second hard mask layer 150 can be one or more combinations of silicon dioxide, silicon nitride, and polysilicon layers. Exemplarily, the second hard mask layer 150 can be a polysilicon layer, which can withstand mechanical stress during high aspect ratio etching, thereby reducing pattern deformation. Its structure is as follows... Figure 4 As shown.
[0023] S150, a second opening pattern 160 is formed in the second hard mask layer 150. The second opening pattern 160 is located inside the first opening pattern 140 and protrudes from the substrate surface. The opening size of the second opening pattern 160 is equal to the spacing between the second hard mask layers 150 adjacent to the opposite sidewalls of the first opening pattern 140. Specifically, the second hard mask layer 150 adjacent to the sidewall of the first opening pattern 140 is used as the sidewall of the second opening pattern 160. Therefore, when forming the second opening pattern 160, only the second hard mask layer 150 adjacent to the bottom wall of the first opening pattern 140 needs to be removed. For example, the second opening pattern 160 can be formed by dry etching. Utilizing the anisotropic etching of the dry etching process, the second hard mask layer 150 adjacent to the bottom wall of the first opening pattern 140 can be directionally removed, while retaining the second hard mask layer 150 adjacent to the sidewall of the first opening pattern 140. The retained second hard mask layers 150 serve as the sidewall of the second opening pattern 160, and the spacing between the retained second hard mask layers 150 is the opening size of the second opening pattern 160, as shown in the diagram. Figure 5 As shown. In some embodiments, if protection of the non-etched area is considered, a photoresist barrier can be provided in the non-etched area. In this case, the sidewall of the first opening pattern 140 and the second hard mask layer 150 of the sidewall of the first opening pattern 140 are equivalent to increasing the contact area with the photoresist, thereby reducing the aspect ratio of the photoresist portion and avoiding problems such as photoresist tipping.
[0024] S160. Remove the first hard mask layer 130 and form a hard mask structure using the second hard mask layer 150. The second opening pattern 160 is the hard mask pattern, and its structure is as follows: Figure 6 As shown, hard mask patterns are transferred onto a substrate through etching or implantation processes.
[0025] The mask structure fabrication method provided in this embodiment of the invention involves forming a first hard mask layer 130 on a substrate, forming a first opening pattern 140 on the first hard mask layer 130, and forming a second hard mask layer 150 on the side of the first hard mask layer 130 away from the substrate. The first opening pattern 140 is used to position the pattern on the second hard mask layer 150. The second hard mask layer 150 adjacent to the bottom wall of the first opening pattern 140 is removed, while the second hard mask layer 150 adjacent to the sidewall of the first opening pattern 140 is retained. The retained second hard mask layer 150 serves as the sidewall of the second opening pattern 160. Compared to traditional hard mask fabrication processes, when transferring the second opening pattern 160 onto the second hard mask layer 150, the use of photoresist or other photolithographic materials to cover and block the sidewall of the high aspect ratio second opening pattern 160 can be avoided, thus preventing the problem of poor morphology in the fabrication of the second opening pattern 160 caused by the pouring of high aspect ratio photoresist.
[0026] Based on the above embodiments, optionally, forming a first opening pattern 140 in the first hard mask layer 130 includes: A photoresist layer 210 is formed on the side of the first hard mask layer 130 away from the substrate; A mask pattern is formed in the photoresist layer 210; The first opening pattern 140 is formed by etching the first hard mask layer 130 according to the mask pattern.
[0027] Specifically, Figure 7 This is a schematic diagram of an intermediate structure of a mask structure provided in an embodiment of the present invention. Photoresist is uniformly spin-coated onto the surface of a first hard mask layer 130 to form a photoresist layer 210 with controllable thickness. The photoresist layer 210 is exposed through a mask with a mask pattern. For example, the photoresist layer 210 here uses a positive photoresist. The mask pattern here can be the same shape as the first opening pattern 140. A developer is used to dissolve and expose the mask, forming a pattern consistent with the mask pattern on the mask. Then, using the pattern of the photoresist layer 210 as a mask, the first hard mask layer 130 is subjected to dry etching or wet etching to obtain the first opening pattern 140. In subsequent processes, residual photoresist is removed by oxygen plasma ashing or chemical solvents, thereby completing the processing of the first opening pattern 140.
[0028] Based on the above embodiments, optionally, forming the second opening pattern 160 in the second hard mask layer 150 includes: Remove the second hard mask layer 150 from the surface of the first hard mask layer 130, as well as the second hard mask layer 150 adjacent to the bottom wall of the first opening pattern 140; A second hard mask layer 150 is retained adjacent to the opposite sidewall of the first opening pattern 140, and the spacing between the retained second hard mask layers 150 forms a second opening pattern 160; wherein the retained second hard mask layers 150 constitute the sidewall of the second opening pattern 160.
[0029] Specifically, the second hard mask layer 150 can be deposited on the surface of the first hard mask layer 130 using a CVD process, combined with... Figure 4 and Figure 5 A second hard mask layer 150 is deposited on the surface of the first hard mask layer 130 on one side of the first opening pattern 140, on the sidewall of the first opening pattern 140, and on the bottom wall of the first opening pattern 140. When forming the second opening pattern 160, the second hard mask layer 150 on the surface of the first hard mask layer 130 on one side of the first opening pattern 140 can be removed by a dry etching process, making the surface of the first hard mask layer 130 flush with the second hard mask layer 150 on the sidewall of the first opening pattern 140. The second hard mask layer 150 on the bottom wall of the first opening pattern 140 can be removed by a dry etching process, thus allowing the second opening pattern 160 to be formed between the remaining second hard mask layers 150.
[0030] Figure 8 This is a schematic diagram of the intermediate structure of a mask structure provided in an embodiment of the present invention. See also: Figure 8 During the deposition process, the second hard mask layer 150 exhibits a relatively large deposition thickness at the bottom corner of the first opening pattern 140, while the deposition thickness is relatively thin at the top corner of the first opening pattern 140. This is in contrast to the previous process. Figure 5By removing the second hard mask layer 150 from the surface of the first hard mask layer 130 on one side of the first opening pattern 140, the problem of thin deposition thickness at the top corner of the first opening pattern 140 can be mitigated. Furthermore, when removing the second hard mask layer 150 from the bottom wall of the first opening pattern 140 using a dry etching process, the anisotropic etching characteristic of the dry etching process can be utilized to make the etching rate much higher in the vertical direction than in the horizontal direction, thereby forming a vertical sidewall structure. This mitigates the problem of large deposition thickness at the bottom corner of the first opening pattern 140, resulting in a more uniform sidewall morphology and a more vertical sidewall appearance for the second opening pattern 160. It should be noted that the height of the sidewall of the second opening pattern 160 in the thickness direction can be set according to the thickness of the first hard mask layer 130. For example, if it is necessary to increase the height of the sidewall of the second opening pattern 160 in the thickness direction, the thickness of the first hard mask layer 130 can be increased, so that the second hard mask layer 150 retained after etching follows the sidewall of the first opening pattern 140, ensuring that the sidewall of the second opening pattern 160 can have a larger height. When it is necessary to decrease the height of the sidewall of the second opening pattern 160 in the thickness direction, the thickness of the first hard mask layer 130 can be decreased, so that the second hard mask layer 150 retained after etching follows the sidewall of the first opening pattern 140, ensuring that the sidewall of the second opening pattern 160 can have a smaller height.
[0031] Furthermore, in combination Figure 4 The thickness of the deposited second hard mask layer 150 is less than the thickness of the first hard mask layer 130. Therefore, after the second hard mask layer 150 is deposited, the first opening pattern 140 will not be completely filled by the second hard mask layer 150. The surface of the second hard mask layer 150 may also have a groove shape 220. Therefore, when removing the second hard mask layer 150 from the bottom wall of the first opening pattern 140, etching can be performed along the edge of the groove shape 220 on the surface of the second hard mask layer 150, thereby preserving the second hard mask layer 150 adjacent to the sidewall of the first opening pattern 140. The groove shape 220 on the surface of the second hard mask layer 150 is used to locate the etching position of the second hard mask layer 150, avoiding etching displacement that would affect the morphology of the second opening pattern 160. Figure 5The width of the second hard mask layer 150 adjacent to the sidewall of the retained first opening pattern 140, i.e., the sidewall of the second opening pattern 160, in a first direction can be adjusted by the deposition thickness of the second hard mask layer 150, wherein the first direction is perpendicular to the substrate thickness direction. For example, when it is necessary to widen the sidewall of the second opening pattern 160, the thickness of the second hard mask layer 150 can be increased, thereby increasing the thickness of the retained second hard mask layer 150. When it is necessary to narrow the sidewall of the second opening pattern 160, the thickness of the second hard mask layer 150 can be reduced, thereby reducing the thickness of the retained second hard mask layer 150. For example, the deposition thickness of the second hard mask layer 150 ranges from 3000 angstroms to 8000 angstroms, and the corresponding sidewall width of the second opening pattern 160 can range from 0.3 μm to 0.8 μm.
[0032] Combination Figure 5 In the first direction, the spacing between the sidewalls of the first opening pattern 140, i.e., the opening size of the first opening pattern 140, can be used to define the sidewall width of the second opening pattern 160 and the spacing between the sidewalls of the second opening pattern 160. The opening size of the first opening pattern 140 is the sum of the sidewall widths of the two second opening patterns 160 and the opening size of the second opening pattern 160. That is, by removing the second hard mask layer 150 from the bottom wall of the first opening pattern 140 through an etching process, the opening of the second opening pattern 160 can be obtained. For example, the sidewall width of the second opening pattern 160 is 0.3μm-0.8μm, such as 0.3μm, 0.4μm, 0.5μm, 0.6μm, 0.7μm, or 0.8μm. The spacing between the sidewalls of the second opening patterns 160 is 1μm-4μm. For example, the spacing between the sidewalls of the second opening pattern 160 can be 1 μm, 2 μm, 3 μm or 4 μm.
[0033] Combination Figure 5 and Figure 7 In the first direction, the sidewall width of the first opening pattern 140 is greater than the sidewall width of the second opening pattern 160, thereby ensuring that the sidewall of the first opening pattern 140 has sufficient width. When the pattern is transferred to the first hard mask layer 130 using the photoresist layer 210, the aspect ratio of the photoresist portion on the sidewall of the first opening pattern 140 is reduced, thereby avoiding problems such as photoresist tipping and improving the morphological quality of the first opening pattern 140.
[0034] Figure 9 This invention provides a schematic diagram of yet another mask structure. Figures 10-12 for Figure 9 The schematic diagram of the intermediate structure of the mask structure shown is available in [reference]. Figures 9-12 In this embodiment of the invention, compared to Figure 3 , Figure 4 and Figure 5 The difference in this embodiment of the invention is that a plurality of first opening patterns 140 are formed on the first hard mask layer 130. Therefore, after the second hard mask layer 150 is deposited, the second hard mask layer 150 at least covers the sidewall and bottom wall of each first opening pattern 140. When forming the second opening pattern 160, the second hard mask layer 150 on the surface of the first hard mask layer 130 on one side of the first opening pattern 140 can be removed by a dry etching process, so that the surface of the first hard mask layer 130 is flush with the second hard mask layer 150 on the sidewall of the first opening pattern 140. The second hard mask layer 150 on the bottom wall of the first opening pattern 140 is removed by a dry etching process, so that the second opening pattern 160 can be formed between the second hard mask layers 150 on the sidewall of the first opening pattern 140. See also Figure 9 After removing the first hard mask layer 130, a second opening pattern 160 can be formed between each adjacent portion of the second hard mask layer 150. The opening size of each second opening pattern 160 can be the same or different according to the design requirements. The width of the sidewall of the first opening pattern 140, i.e., the width of the corresponding first hard mask layer 140, defines the opening size of the corresponding second opening pattern 160. Furthermore, since the sidewall width of the first opening pattern 140 is greater than that of the second opening pattern 160 in the first direction, the photoresist layer 210 between multiple first opening patterns 140 can have a smaller aspect ratio compared to traditional hard mask fabrication processes. This avoids problems such as photoresist tipping and improves the morphology quality of the first opening pattern 140.
[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention 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 of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims
1. A method for fabricating a mask structure, characterized in that, include: Provide substrate; A first hard mask layer is formed on the surface of the substrate; A first opening pattern is formed in the first hard mask layer; The first opening pattern protrudes from the surface of the substrate; A second hard mask layer is formed on the side of the first hard mask layer away from the substrate; The second hard mask layer at least covers the sidewalls and bottom wall of the first opening pattern; A second opening pattern is formed in the second hard mask layer, the second opening pattern is located inside the first opening pattern, and the second opening pattern protrudes from the surface of the substrate. The opening size of the second opening pattern is equal to the spacing between the second hard mask layers adjacent to the opposite sidewalls of the first opening pattern; Remove the first hard mask layer.
2. The method for fabricating the mask structure according to claim 1, characterized in that, Forming a first opening pattern in the first hard mask layer includes: A photoresist layer is formed on the side of the first hard mask layer away from the substrate; A mask pattern is formed on the photoresist layer; The first opening pattern is formed by etching the first hard mask layer according to the mask pattern.
3. The method for fabricating the mask structure according to claim 1, characterized in that, Forming the second opening pattern in the second hard mask layer includes: Remove the second hard mask layer on the surface of the first hard mask layer, as well as the second hard mask layer adjacent to the bottom wall of the first opening pattern; The second hard mask layer adjacent to the opposite sidewall of the first opening pattern is retained, and the spacing between the retained second hard mask layers forms the second opening pattern; wherein the retained second hard mask layers constitute the sidewall of the second opening pattern.
4. The method for preparing the mask structure according to claim 3, characterized in that, In the first direction, the spacing between the sidewalls of the first opening pattern is the sum of the widths of the sidewalls of the two second opening patterns and the spacing between the sidewalls of the second opening patterns; The first direction is perpendicular to the thickness direction of the substrate.
5. The method for preparing the mask structure according to claim 4, characterized in that, The sidewall width of the second opening pattern is 0.3μm-0.8μm.
6. The method for preparing the mask structure according to claim 4, characterized in that, The spacing between the sidewalls of the second opening pattern is 1μm-4um.
7. The method for fabricating the mask structure according to claim 1, characterized in that, In a first direction, the sidewall width of the first opening pattern is greater than the sidewall width of the second opening pattern.
8. The method for preparing the mask structure according to claim 1, characterized in that, The thickness of the second hard mask layer is less than that of the first hard mask layer.
9. The method for preparing the mask structure according to claim 8, characterized in that, The thickness of the second hard mask layer is 3,000 to 8,000 angstroms.
10. The method for fabricating the mask structure according to claim 1, characterized in that, The first hard mask layer is a single film layer or a composite film layer; The single film layer is a silicon dioxide layer or a silicon nitride layer; The composite film is a stacked structure of a silicon dioxide layer, a silicon nitride layer, and a silicon dioxide layer.