Method for improving mask pattern cd uniformity in a self-aligned double patterning process
By employing over-etching to form an inverted trapezoidal sacrificial layer and symmetrical sidewalls in a self-aligned dual patterning process, the problem of inconsistent mask pattern CD was solved, and the symmetry and uniformity of the mask pattern were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI HUALI INTEGRATED CIRCUIT CORP
- Filing Date
- 2026-03-25
- Publication Date
- 2026-07-10
AI Technical Summary
In the self-aligned dual patterning process, the CD inconsistency of the mask pattern causes the pattern transferred to the hard mask to be offset.
In the self-aligned double patterning process, an over-etching technique is used to make the pattern of the sacrificial layer into an inverted trapezoid, and symmetrical sidewalls are formed on both sides. Then, the hard mask layer is etched using the sidewalls as a mask to form a symmetrical trapezoidal mask pattern.
It improves the CD uniformity of the mask pattern, avoids pattern offset, and enhances the symmetry and consistency of the mask pattern.
Smart Images
Figure CN122373698A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor technology, and more specifically to a method for improving the uniformity of mask pattern CD in a self-aligned dual patterning process. Background Technology
[0002] The principle of self-aligned double patterning (SADP) is to deposit a mask layer in the groove between the lithographic patterns after a single photolithography step, and then achieve frequency doubling of the spatial pattern through etching. This technology involves only one photolithography step, and therefore is not affected by the overlay error between two photolithography steps.
[0003] The key process flow of SADP is as follows: Figure 1 As shown: First, the film layer to be etched (not shown in the figure), the hard mask layer 101, and the sacrificial layer are sequentially formed on the surface of the substrate 100. The process involves three layers: a 102 layer, an anti-reflective coating 103 layer, and a patterned photoresist layer 105 layer. Etching is then performed to transfer the pattern on the patterned photoresist layer 105 onto the sacrificial layer 102, which is also known as the mandrel. Next, atomic layer deposition (ALD) is used to deposit a relatively uniform film layer 106 (called the sidewall spacer material) on the top and sides of the mandrel. Then, reactive ion etching (RIE) is used to etch back the deposited film layer 106. Due to the geometric effect of the mandrel sidewalls, the film layers 106 on both sides of the mandrel remain, forming the sidewall spacers. Next, a highly selective etchant is used to remove the mandrel, leaving only the sidewalls. The period of the sidewall pattern is half that of the patterned photoresist layer 105, achieving a doubling of the spatial pattern density. Finally, plasma etching is used to transfer the sidewall pattern onto a hard mask 101 to form the mask pattern.
[0004] When etching film 106, due to the geometric effect of the mandrel sidewalls, the resulting sidewall patterns on both sides of the mandrel exhibit asymmetry (CD inconsistency), resulting in conditions such as... Figure 2 The offset phenomenon shown by the middle arrow leads to inconsistencies in the graphic CD transferred onto the hard mask 101. Summary of the Invention
[0005] In view of the shortcomings of the prior art described above, the purpose of this application is to provide a method for improving the uniformity of mask pattern CD in self-aligned dual patterning process, so as to solve the problem of poor uniformity of mask pattern CD in the prior art.
[0006] To achieve the above and other related objectives, this application provides a method for improving the uniformity of mask pattern CD in a self-aligned dual-patterning process, comprising: Step 1: Provide a substrate, and sequentially form the film to be etched, the hard mask layer, the sacrificial layer, the anti-reflection coating, and the patterned photoresist layer on the substrate; Step 2: Using the patterned photoresist layer as a mask, etch the anti-reflective coating and sacrificial layer sequentially until the hard mask layer is exposed; Step 3: Over-etch the lower part of the patterned sacrificial layer to make the pattern of the sacrificial layer into an inverted trapezoidal shape; Step 4: After removing the patterned photoresist layer and anti-reflective coating, sidewalls are formed on both sides of the sacrificial layer; Step 5: After removing the sacrificial layer, etch the hard mask layer using the sidewall as a mask to form the mask pattern.
[0007] Preferably, the over-etching power in step three is greater than the etching power performed in step two, in order to enhance the ion bombardment capability.
[0008] Preferably, the etching pressure in step three is higher than the etching pressure in step two, in order to increase polymer buildup on the surface of the sacrificial layer and ensure that the height of the sacrificial layer does not decrease.
[0009] Preferably, the etching gas used in step three is a mixture of chlorine gas and a gas that can generate sidewall protection.
[0010] Preferably, the gas that provides sidewall protection includes nitrogen.
[0011] Preferably, the steps for forming the sidewalls include: first, forming a sidewall material layer covering the sidewalls and top of the sacrificial layer by a deposition process; and then etching the sidewall material layer by an etching process.
[0012] Preferably, the etching process for removing the sacrificial layer is dry etching or wet etching.
[0013] Preferably, the material of the sacrificial layer includes amorphous silicon.
[0014] Preferably, the etching process for etching the hard mask layer is dry etching.
[0015] Preferably, the hard mask layer is a titanium nitride layer and a TEOS layer stacked from bottom to top.
[0016] As described above, the method for improving the uniformity of mask pattern CD in a self-aligned dual patterning process provided in this application has the following beneficial effects: the formed mask pattern is a symmetrical trapezoid, thereby improving the uniformity of the mask pattern CD. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific 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 from these drawings without creative effort.
[0018] Figure 1 This is a schematic diagram of the key process flow of the existing SADP. Figure 2 The image shows an asymmetry in the sidewall patterns on both sides of the mandrel formed by existing SADP. Figure 3 The flowchart shown is a method for improving the uniformity of mask pattern CD in a self-aligned dual patterning process provided in an embodiment of this application. Figure 4 The diagram shows a cross-sectional structure of the device after step one is completed, based on the method for improving the uniformity of mask pattern CD in a self-aligned dual patterning process provided in the embodiments of this application. Figure 5 The diagram shows a cross-sectional structure of the device after step two is completed, based on the method for improving the uniformity of mask pattern CD in the self-aligned dual patterning process provided in the embodiments of this application. Figure 6 The diagram shows a cross-sectional structure of the device after step three is completed, based on the method for improving the uniformity of mask pattern CD in the self-aligned dual patterning process provided in the embodiments of this application. Figure 7 The diagram shows a cross-sectional structure of the device after step four is completed, based on the method for improving the uniformity of mask pattern CD in a self-aligned dual patterning process provided in the embodiments of this application. Figure 8 The diagram shows a cross-sectional structure of the device after step five, illustrating the method for improving the uniformity of mask pattern CD in a self-aligned dual patterning process based on the embodiments of this application. Detailed Implementation
[0019] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this invention.
[0020] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0021] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," indicating orientation or positional relationships, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0022] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.
[0023] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.
[0024] Please see Figure 3 The diagram illustrates a flowchart of a method for improving the uniformity of a mask pattern CD in a self-aligned dual patterning process, as provided in an embodiment of this application.
[0025] like Figure 3 As shown, the method for improving the uniformity of the mask pattern CD in a self-aligned dual-patterning process includes the following steps: Step 1: Provide a substrate, and sequentially form the film to be etched, the hard mask layer, the sacrificial layer, the anti-reflection coating, and the patterned photoresist layer on the substrate; Step 2: Using the patterned photoresist layer as a mask, etch the anti-reflective coating and sacrificial layer sequentially until the hard mask layer is exposed; Step 3: After removing the patterned photoresist layer and anti-reflective coating, the lower part of the patterned sacrificial layer is over-etched to make the pattern of the sacrificial layer into an inverted trapezoidal shape; Step four: Form sidewalls on both sides of the sacrificial layer; Step 5: After removing the sacrificial layer, etch the hard mask layer using the sidewall as a mask to form the mask pattern.
[0026] In step one, as Figure 4 As shown, optionally, the substrate 300 is a silicon substrate, a germanium substrate, or a silicon-on-insulator substrate, etc.; or the material of the substrate 300 may also include other materials, such as gallium arsenide or other III-V compounds. Those skilled in the art can select the constituent material of the substrate 300 according to the type of device structure formed on the substrate 300, therefore the type of substrate 300 should not limit the scope of protection of this invention.
[0027] For example, the film layer 301 to be etched, the hard mask layer 302 and the sacrificial layer 303 are formed by a deposition process, and the anti-reflective coating 305 is formed by a spin coating process.
[0028] For example, the film layer 301 to be etched can be an interlayer dielectric layer. Optionally, the material of the interlayer dielectric layer is, for example, but not limited to: silicon nitride (Si3N4), silicon oxide (SiO2), fluorinated SiO2 (FSG), hydrogenated carbon silicon oxide (SiCOH), porous SiCOH, borosilicate glass (BPSG), silsesquioxane, carbon (C) doped oxides (i.e., organosilicones) including silicon (Si), carbon (C), oxygen (O) and / or hydrogen (H) atoms, thermosetting polyarylene ether, or other materials with low dielectric constant (<3.9).
[0029] For example, the hard mask layer 302 is a titanium nitride (TiN) layer and a TEOS layer stacked from bottom to top, and the material of the sacrificial layer 303 includes amorphous silicon.
[0030] In step two, as Figure 5 As shown, the anti-reflective coating 305 and the sacrificial layer 303 are etched sequentially using the patterned photoresist layer 306 as a mask until the hard mask layer 302 is exposed.
[0031] For example, the etching is a dry etching process, and the etching gas is a fluorine-based gas.
[0032] In step three, after removing the patterned photoresist layer 306 and the anti-reflective coating 305, as follows: Figure 6 As shown, the lower part of the patterned sacrificial layer 303 is over-etched, so that the pattern of the sacrificial layer 303 is an inverted trapezoid.
[0033] For example, the over-etching power is greater than the etching power performed in step two to enhance the ion bombardment capability. The etching gas is a mixture of chlorine and a gas that can generate sidewall protection capability (such as nitrogen). The over-etching pressure is higher than the etching pressure performed in step two to increase the polymer buildup on the surface of the sacrificial layer 303 and ensure that the height of the sacrificial layer 303 does not decrease.
[0034] In step four, as Figure 7 As shown, sidewalls 307 are formed on both sides of the sacrificial layer 303. The sidewalls 307 are symmetrical trapezoids and will not exhibit [unclear - possibly a specific feature or characteristic]. Figure 2 The offset phenomenon shown.
[0035] For example, the step of forming the sidewall 307 includes: forming a sidewall material layer covering the sidewalls and top of the sacrificial layer 303 by a deposition process; and etching the sidewall material layer by an etching process to form the sidewall 307.
[0036] In step five, after removing the sacrificial layer 303 by etching, as follows Figure 8 As shown, the hard mask layer 302 is etched using the sidewall 307 as a mask to form a mask pattern.
[0037] For example, the etching process for removing the sacrificial layer 303 is either dry etching or wet etching, and the etching process for etching the hard mask layer 302 is dry etching.
[0038] Because side wall 307 is not present Figure 2 The offset phenomenon shown is thus observed, and therefore, the uniformity of the resulting mask pattern CD is significantly improved.
[0039] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of this application. Therefore, the drawings only show the components related to this invention and are not drawn according to the actual number, shape and size of the components. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.
[0040] In summary, the method for improving the uniformity of mask pattern CD in a self-aligned dual-patterning process provided in this application produces a symmetrical trapezoidal mask pattern, thereby improving the uniformity of the mask pattern CD. Therefore, this application effectively overcomes the various shortcomings of the prior art and has high industrial applicability.
[0041] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this invention should still be covered by the claims of this application.
Claims
1. A method for improving the uniformity of mask pattern CD in a self-aligned dual-patterning process, characterized in that, The method includes: Step 1: Provide a substrate, and sequentially form on the substrate a film layer to be etched, a hard mask layer, a sacrificial layer, an anti-reflection coating, and a patterned photoresist layer; Step 2: Using the patterned photoresist layer as a mask, etch the anti-reflective coating and the sacrificial layer sequentially until the hard mask layer is exposed; Step 3: Over-etch the lower part of the patterned sacrificial layer to make the pattern of the sacrificial layer into an inverted trapezoidal shape; Step 4: After removing the patterned photoresist layer and the anti-reflective coating, sidewalls are formed on both sides of the sacrificial layer; Step 5: After removing the sacrificial layer, etch the hard mask layer using the sidewall as a mask to form a mask pattern.
2. The method according to claim 1, characterized in that, The over-etching power in step three is greater than the etching power performed in step two, in order to enhance the ion bombardment capability.
3. The method according to claim 1, characterized in that, In step three, the etching pressure is higher than that in step two, in order to increase the polymer buildup on the surface of the sacrificial layer and ensure that the height of the sacrificial layer does not decrease.
4. The method according to claim 1, characterized in that, In step three, the etching gas used for over-etching is a mixture of chlorine and a gas that can provide sidewall protection.
5. The method according to claim 4, characterized in that, The gas that generates sidewall protection includes nitrogen.
6. The method according to claim 1, characterized in that, The steps for forming the sidewalls include: first, forming a sidewall material layer covering the sidewalls and top of the sacrificial layer by a deposition process; and then etching the sidewall material layer by an etching process.
7. The method according to claim 1, characterized in that, The etching process for removing the sacrificial layer is either dry etching or wet etching.
8. The method according to claim 1 or 7, characterized in that, The material of the sacrificial layer includes amorphous silicon.
9. The method according to claim 1, characterized in that, The etching process for etching the hard mask layer is dry etching.
10. The method according to claim 1 or 9, characterized in that, The hard mask layer consists of a titanium nitride layer and a TEOS layer stacked from bottom to top.