Method for improving water immersion type defect of immersed photoetching pattern

Abstract

The invention discloses a method for improving a water immersion type defect of an immersed photoetching pattern. The method comprises the following steps: sequentially forming a target photoresist layer and a sacrificial photoresist layer on a substrate; performing immersion type exposure treatment on the target photoresist layer and the sacrificial photoresist layer; the sacrificial photoresist layer is removed; and developing the residual target photoresist layer. According to the method for improving the water immersion type defect of the immersed photoetching pattern provided by the embodiment of the invention, the sacrificial photoresist layer is formed on the surface of the target photoresist layer, and the immersion type defect is formed in the sacrificial photoresist layer, so that the immersion type defect is prevented from being formed in the target photoresist layer, the process yield is improved, and meanwhile, the water immersion type defect of the immersed photoetching pattern is improved. The reduction of the immersion water defect is beneficial to improving the stability of the photoetching and etching line width.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, and in particular to a method for improving water immersion defects in immersion photolithography patterns. Background Technology

[0002] With the development and evolution of photoresist materials, photolithography technology, and process generations, immersion lithography has been widely used in advanced processes of 40nm and below. It primarily improves the resolution and depth focal length of the lithography process by introducing a high-refractive-index liquid (usually water) between the lens and the wafer.

[0003] While immersion lithography effectively improves process capabilities, it inevitably leads to immersion defects in the lithographic patterns. Currently, the main methods for addressing these defects in immersion water-based photoresist are reducing scan speed and spin-coating a topcoat. However, scan speed has limitations and reduces throughput. Topcoats are also gradually being phased out, primarily because material incompatibility can cause delamination; secondly, differences in transmittance / refractive index inevitably lead to losses in optical resolution and uniformity; and finally, the topcoat is a potential source of contamination, easily generating precipitates. Summary of the Invention

[0004] In view of the above problems, the purpose of this application is to provide a method for improving water immersion defects in immersion lithography patterns.

[0005] According to one aspect of the present invention, a method for improving water immersion defects in immersion photolithography patterns is provided, comprising: sequentially forming a target photoresist layer and a sacrificial photoresist layer on a substrate; performing immersion exposure processing on the target photoresist layer and the sacrificial photoresist layer; removing the sacrificial photoresist layer; and performing development processing on the remaining target photoresist layer.

[0006] Optionally, the method for sequentially forming a target photoresist layer and a sacrificial photoresist layer on a substrate includes: forming a target photoresist layer on the substrate; baking the target photoresist layer before a first exposure; forming a sacrificial photoresist layer on the target photoresist layer; and baking the target photoresist layer and the sacrificial photoresist layer before a second exposure; wherein, compared to the target photoresist layer, the sacrificial photoresist layer has better hydrophobicity.

[0007] Optionally, the thickness of the target photoresist layer is h1, and the thickness of the sacrificial photoresist layer is h2, where 5%h1≤h2≤20%h1.

[0008] Optionally, the baking temperature before the first exposure is T1, the baking time before the second exposure is T2, and T1+5℃≤T2≤T1+30℃.

[0009] Optionally, after exposure, the process further includes a step of drying the surface of the sacrificial photoresist layer. The drying step includes: a cycle of spin drying and rinsing; and a step of drying the surface of the sacrificial photoresist layer with a drying gas.

[0010] Optionally, after exposure, the process also includes a post-exposure baking step for both the target photoresist layer and the sacrificial photoresist layer.

[0011] Optionally, after exposure and baking, the sacrificial photoresist layer and the target photoresist layer form photoacid diffusion regions of different sizes, wherein the photoacid diffusion region of the sacrificial photoresist layer has a first opening size D1, and the photoacid diffusion region of the target photoresist layer has a second opening size D2, and D1 > D2, so as to form a "T" to form a photoacid diffusion region.

[0012] Optionally, after removing the sacrificial photoresist layer, the process further includes a supplementary exposure and baking step, followed by a development step.

[0013] Optionally, the time for baking to end after exposure is Ta, and the time for development to begin is Tb, with a preset time interval between Ta and Tb.

[0014] Optionally, the preset time interval is QT, the baking time after exposure is t3, the baking time after supplementary exposure is time, and time = (10%t3~50%t3) * QT / 6h.

[0015] The unexpected technical effect of this application is:

[0016] The method for improving water immersion defects in immersion lithography patterns provided in this application forms a sacrificial photoresist layer on the surface of the target photoresist layer. Immersion defects are formed in the sacrificial photoresist layer, thus avoiding the formation of immersion defects in the target photoresist layer and improving the process yield. At the same time, the reduction of immersion water defects is beneficial to improving the stability of lithography and etching linewidth.

[0017] Furthermore, the sacrificial photoresist layer is removed after exposure, along with immersion defects formed on the surface of the sacrificial photoresist layer, to prevent the sacrificial photoresist layer and its immersion defects from affecting the accuracy of the pattern after development.

[0018] In a preferred embodiment, the sacrificial photoresist layer has better hydrophobicity than the target photoresist layer to reduce immersion defects formed on the surface of the sacrificial photoresist layer.

[0019] In a preferred embodiment, the thickness of the target photoresist layer is h1, and the thickness of the sacrificial photoresist layer is h2, where 5%h1≤h2≤20%h1. By setting an upper limit on the thickness of the sacrificial photoresist layer, the sacrificial photoresist layer is prevented from becoming too thick, making it easier to remove in subsequent steps. By setting a lower limit on the thickness of the sacrificial photoresist layer, the sacrificial photoresist layer is prevented from becoming too thin, ensuring that immersion defects only form in the sacrificial photoresist layer during subsequent immersion exposure processing and do not extend into the target photoresist layer.

[0020] In a preferred embodiment, a first pre-exposure baking and a second pre-exposure baking are performed separately. The first pre-exposure baking causes a portion of the solvent in the target photoresist layer to evaporate, while the second pre-exposure baking causes the solvent in the target photoresist layer to evaporate, and simultaneously causes the remaining solvent in the sacrificial photoresist layer to evaporate.

[0021] In a preferred embodiment, the baking temperature before the first exposure is T1, and the baking time before the second exposure is T2, where T1+5℃≤T2≤T1+30℃. The first exposure baking uses an under-temperature baking method to prevent over-baking of the target photoresist layer during the subsequent second exposure baking process, which could lead to photoresist layer failure.

[0022] In a preferred embodiment, over-time post-exposure baking is used to eliminate the post-exposure baking delay (PEB delay). Attached Figure Description

[0023] The above and other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0024] Figure 1 A flowchart is shown below illustrating a method for improving water immersion defects in immersion lithography patterns according to an embodiment of this application.

[0025] Figures 2a to 2j The diagram shows cross-sectional schematics of each stage of the immersion lithography pattern water immersion defect improvement method according to embodiments of this application, wherein:

[0026] Figure 2a This diagram illustrates a schematic of the formation of a target photoresist layer on a substrate according to an embodiment of this application.

[0027] Figure 2b This illustration shows a schematic diagram of baking the target photoresist layer before the first exposure, according to an embodiment of this application.

[0028] Figure 2c This illustration shows a schematic diagram of a sacrificial photoresist layer formed on the target photoresist layer according to an embodiment of this application;

[0029] Figure 2d This illustration shows a schematic diagram of the pre-exposure baking of the target photoresist layer and the sacrificial photoresist layer according to an embodiment of this application;

[0030] Figure 2e This illustration shows a schematic diagram of an immersion exposure process performed on the target photoresist layer and the sacrificial photoresist according to an embodiment of this application;

[0031] Figure 2f This diagram illustrates the drying process of the surface of the sacrificial photoresist layer according to an embodiment of this application.

[0032] Figure 2g This illustration shows a schematic diagram of the exposure and baking process of the target photoresist layer and the sacrificial photoresist layer according to an embodiment of this application;

[0033] Figure 2h A schematic diagram of removing the sacrificial photoresist layer according to an embodiment of this application is shown;

[0034] Figure 2i This illustration shows a schematic diagram of the baking process following supplementary exposure in an embodiment of this application.

[0035] Figure 2j This diagram illustrates the development process of the remaining target photoresist layer according to an embodiment of this application. Detailed Implementation

[0036] The present application will now be described in more detail with reference to the accompanying drawings. In the various drawings, the same elements are indicated by similar reference numerals. For clarity, the various parts in the drawings are not drawn to scale. Furthermore, some well-known parts may not be shown.

[0037] When describing the structure of a device, when referring to a layer or region as being "above" or "on top of" another layer or region, it can mean that it is directly above another layer or region, or that it contains other layers or regions between it and another layer or region. Furthermore, if the device is flipped, the layer or region will be located "below" or "under" another layer or region.

[0038] To describe a situation where it is located directly on another layer or another area, this article will use the expressions "directly on top of" or "on and adjacent to".

[0039] This application may be presented in various forms, some of which will be described below.

[0040] Figure 1 A flowchart of a method for improving water immersion defects in immersion lithography patterns according to an embodiment of this application is shown, such as... Figure 1 As shown, the method includes:

[0041] Step S110: A target photoresist layer and a sacrificial photoresist layer are sequentially formed on the substrate;

[0042] Step S120: Immersion exposure processing is performed on the target photoresist layer and the sacrificial photoresist layer;

[0043] Step S130: Remove the sacrificial photoresist layer;

[0044] Step S140: Develop the remaining target photoresist layer.

[0045] Figures 2a to 2j The following are cross-sectional schematic diagrams illustrating various stages of the immersion lithography pattern water immersion defect improvement method provided according to embodiments of this application. Figures 2a to 2j The method for improving water immersion defects in immersion lithography patterns provided in the embodiments of this application will be described.

[0046] In step S110, a target photoresist layer 102 and a sacrificial photoresist layer 103 are sequentially formed on the substrate 101, such as... Figures 2a to 2d As shown.

[0047] Specifically, such as Figure 2a As shown, a target photoresist layer 102 is formed on a substrate 101.

[0048] In this step, for example, a spin coating method is used to form a target photoresist layer 102 on the substrate 101.

[0049] like Figure 2b As shown, the target photoresist layer 102 is subjected to the first pre-exposure baking (PRB).

[0050] In this step, the target photoresist layer 102 is subjected to under-temperature baking, which causes a portion of the solvent in the target photoresist layer 102 to evaporate.

[0051] It is worth noting that after the sacrificial photoresist layer 103 is formed, it needs to be baked before exposure. If the target photoresist layer 102 is baked at a sufficient temperature in this step, it will fail due to over-baking during the subsequent pre-exposure baking of the sacrificial photoresist layer 103. Therefore, under-temperature baking is used in this step to harden the target photoresist layer 102, thereby giving it sufficient hardness to support the subsequently formed sacrificial photoresist layer 103.

[0052] like Figure 2c As shown, a sacrificial photoresist layer 103 is formed on the target photoresist layer 102.

[0053] In this step, a sacrificial photoresist layer 103 is formed on the target photoresist layer 102, for example, using a spin-coating method. The sacrificial photoresist layer 103 has better hydrophobicity than the target photoresist layer 102, and also has a smaller thickness than the target photoresist layer 102.

[0054] In this step, a sacrificial photoresist layer 103 is formed on the target photoresist layer 102. Subsequent immersion defects are formed in the sacrificial photoresist layer 103 covering the target photoresist layer 102. The sacrificial photoresist layer 103 protects the target photoresist layer 102 to avoid the formation of immersion defects in the target photoresist layer 102.

[0055] Furthermore, the good hydrophobicity of the sacrificial photoresist layer 103 can reduce the formation of defects on the surface of the immersion solution to a certain extent.

[0056] Furthermore, both the sacrificial photoresist layer 103 and the target photoresist layer 102 are photoresist mask layers, which can form the same pattern during the photolithography process, so they will not affect the photolithography process of the target photoresist layer 102.

[0057] Furthermore, the thickness of the sacrificial photoresist layer 103 is less than the thickness of the target photoresist layer 102. In one embodiment, the target photoresist layer 102 has a first thickness h1, and the sacrificial photoresist layer 103 has a second thickness h2, where 5%h1≤h2≤20%h1. In this embodiment, by setting an upper limit on the thickness of the sacrificial photoresist layer 103, the sacrificial photoresist layer 103 is not too thick, making it easier to remove in subsequent steps. By setting a lower limit on the thickness of the sacrificial photoresist layer 103, the sacrificial photoresist layer 103 is not too thin, ensuring that immersion defects only form in the sacrificial photoresist layer 103 during subsequent immersion exposure processing and do not extend into the target photoresist layer 102.

[0058] like Figure 2d As shown, the target photoresist layer 102 and the sacrificial photoresist layer 103 are baked a second time before exposure.

[0059] In this step, the target photoresist layer 102 and the sacrificial photoresist layer 103 are subjected to a short-term overheat baking process to evaporate the solvent in the target photoresist layer 102 and the remaining solvent in the sacrificial photoresist layer 103. Furthermore, the baking temperature before the second exposure is higher than the temperature before the first exposure. In one embodiment, a first temperature T1 is used for the first pre-exposure baking of the target photoresist layer 102, and a second temperature T2 is used for the second pre-exposure baking of both the target photoresist layer 102 and the sacrificial photoresist layer 103, where T1+5℃≤T2≤T1+30℃. The baking time for the second pre-exposure is, for example, 10 seconds to 30 seconds.

[0060] In step S120, the target photoresist layer 102 and the sacrificial photoresist layer 103 are subjected to immersion exposure processing, such as... Figure 2e As shown.

[0061] In this step, the target photoresist layer 102 and the sacrificial photoresist layer 103 are immersed in a circulating immersion liquid 30 (e.g., circulating immersion water), and then a photomask 20 is placed above the circulating immersion liquid 30. The photomask 20 is illuminated by a light source in order to transfer the pattern on the photomask 20 to the target photoresist layer 102 and the sacrificial photoresist layer 103.

[0062] It is worth noting that after step S120, there is also a step of drying the surface of the sacrificial photoresist layer 103.

[0063] Specifically, such as Figure 2f As shown, after exposure, the substrate 101 with the target photoresist layer 102 and the sacrificial photoresist layer 103 formed undergoes a cycle of spin-drying and rinsing to remove the immersion liquid on the surface of the sacrificial photoresist layer 103. Specifically, for example, a spin-drying step is performed first, followed by rinsing the surface of the sacrificial photoresist layer 103, and then spin-drying is performed again, and this cycle is repeated. Although the sacrificial photoresist layer 103 uses a hydrophobic material, the surface of the sacrificial photoresist layer 103 may still have immersion liquid 30. In this embodiment, after the spin-drying and rinsing cycle, a drying gas (e.g., nitrogen) is used to dry the surface of the sacrificial photoresist layer 103 to remove as much immersion liquid 30 as possible from the surface of the sacrificial photoresist layer 103, thereby reducing immersion defects on the surface of the sacrificial photoresist layer 103.

[0064] Furthermore, it also includes a post-exposure baking (PEB) step on the target photoresist layer 102 and the sacrificial photoresist layer 103, such as... Figure 2g As shown.

[0065] In this step, the target photoresist layer 102 and the sacrificial photoresist layer 103 are exposed and then baked. During the baking process, photoacids in the target photoresist layer 102 and the sacrificial photoresist layer 103 diffuse, forming photoacid diffusion regions. These photoacid diffusion regions are removed in the subsequent development step, while the remaining regions are retained. Due to the difference in photoacid content between the target photoresist layer 102 and the sacrificial photoresist layer 103, after baking, the sacrificial photoresist layer 103 and the target photoresist layer 102 form photoacid diffusion regions of different sizes. Specifically, the first photoacid diffusion region 103a of the sacrificial photoresist layer 103 has a first opening size D1, and the second photoacid diffusion region 102a of the target photoresist layer 102 has a second opening size D2, where D1 > D2. The first photoacid diffusion region 103a and the second photoacid diffusion region 102a together form a "T" shape to create the photoacid diffusion region.

[0066] It is worth noting that although the drying process has been completed, some of the immersion solution will still seep into the surface of the sacrificial photoresist layer 103, forming defect D on the surface of the sacrificial photoresist layer 103. However, this application provides a sacrificial photoresist layer 103, which isolates the immersion solution from the target photoresist layer 102, so that defect D is formed only on the surface of the sacrificial photoresist layer 103, while the target photoresist layer 102 is not affected by the immersion solution.

[0067] Furthermore, the target photoresist layer 102 and the sacrificial photoresist layer 103 are subjected to over-time post-exposure baking to eliminate the post-exposure baking delay effect (PEB delay).

[0068] In step S130, the sacrificial photoresist layer is removed, such as... Figure 2h As shown.

[0069] In this step, for example, an etching process is used to remove the sacrificial photoresist layer 103. In one embodiment, for example, a low-temperature plasma gas is used to etch the sacrificial photoresist layer 103 to remove the sacrificial photoresist layer 103 and simultaneously remove the defects D formed in the sacrificial photoresist layer 103, so that the target photoresist layer 102 is free of defects D.

[0070] It is worth noting that in this step, the thickness of the photoresist layer (including the target photoresist layer 102 and the sacrificial photoresist layer 103) removed is h3, and h2≤h3≤h2+5%h1. By setting the thickness of the photoresist layer to be etched away, the sacrificial photoresist layer 103 is completely removed without sacrificing too much of the target photoresist layer 102.

[0071] Furthermore, it also includes a post-exposure baking step, such as... Figure 2i As shown.

[0072] Further, in step S140, the remaining target photoresist layer 102 is developed to obtain a patterned target photoresist layer 102, such as... Figure 2j As shown.

[0073] It is worth noting that, Figure 2g The time shown to end the post-exposure baking (PEB) is Ta. Figure 2j The development start time shown is Tb, and there is a preset time interval QT between Ta and Tb. Within this preset time interval QT, [the following can be performed / performed]... Figure 2h The steps for removing the sacrificial photoresist layer shown are as follows: Figure 2i The step shown is baking after supplementary exposure. Further, Figure 2i The baking time shown after the supplementary exposure is time. Figure 2gThe baking time for post-exposure baking (PEB) shown is t3, and time = (10%t3 ~ 50%t3) * QT / 6h. In one embodiment, the preset time interval QT is 6 hours.

[0074] The unexpected technical effect of this application is:

[0075] The method for improving water immersion defects in immersion lithography patterns provided in this application forms a sacrificial photoresist layer on the surface of the target photoresist layer. Immersion defects are formed in the sacrificial photoresist layer, thus avoiding the formation of immersion defects in the target photoresist layer and improving the process yield. At the same time, the reduction of immersion water defects is beneficial to improving the stability of lithography and etching linewidth.

[0076] Furthermore, the sacrificial photoresist layer is removed after exposure, along with immersion defects formed on the surface of the sacrificial photoresist layer, to prevent the sacrificial photoresist layer and its immersion defects from affecting the accuracy of the pattern after development.

[0077] In a preferred embodiment, the sacrificial photoresist layer has better hydrophobicity than the target photoresist layer to reduce immersion defects formed on the surface of the sacrificial photoresist layer.

[0078] In a preferred embodiment, the thickness of the target photoresist layer is h1, and the thickness of the sacrificial photoresist layer is h2, where 5%h1≤h2≤20%h1. By setting an upper limit on the thickness of the sacrificial photoresist layer, the sacrificial photoresist layer is prevented from becoming too thick, making it easier to remove in subsequent steps. By setting a lower limit on the thickness of the sacrificial photoresist layer, the sacrificial photoresist layer is prevented from becoming too thin, ensuring that immersion defects only form in the sacrificial photoresist layer during subsequent immersion exposure processing and do not extend into the target photoresist layer.

[0079] In a preferred embodiment, a first pre-exposure baking and a second pre-exposure baking are performed separately. The first pre-exposure baking causes a portion of the solvent in the target photoresist layer to evaporate, while the second pre-exposure baking causes the solvent in the target photoresist layer to evaporate, and simultaneously causes the remaining solvent in the sacrificial photoresist layer to evaporate.

[0080] In a preferred embodiment, the baking temperature before the first exposure is T1, and the baking time before the second exposure is T2, where T1+5℃≤T2≤T1+30℃. The first exposure baking uses an under-temperature baking method to prevent over-baking of the target photoresist layer during the subsequent second exposure baking process, which could lead to photoresist layer failure.

[0081] In a preferred embodiment, over-time post-exposure baking is used to eliminate the post-exposure baking delay (PEB delay).

[0082] As described above, these embodiments of this application do not exhaustively cover all details, nor do they limit the application to merely the specific embodiments described. Clearly, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of this application, thereby enabling those skilled in the art to effectively utilize this application and its modifications. This application is limited only by the claims and their full scope and equivalents.

Claims

1. A method for improving water immersion defects in immersion photolithography patterns, comprising: A target photoresist layer and a sacrificial photoresist layer are sequentially formed on a substrate; The target photoresist layer and the sacrificial photoresist layer are subjected to immersion exposure processing; Remove the sacrificial photoresist layer; The remaining target photoresist layer is then developed.

2. The method for improving water immersion defects in immersion photolithography patterns according to claim 1, wherein, Methods for sequentially forming a target photoresist layer and a sacrificial photoresist layer on a substrate include: A target photoresist layer is formed on the substrate; The target photoresist layer is baked before the first exposure; A sacrificial photoresist layer is formed on the target photoresist layer; The target photoresist layer and the sacrificial photoresist layer are baked a second time before exposure. Among them, the sacrificial photoresist layer has better hydrophobicity than the target photoresist layer.

3. The method for improving water immersion defects in immersion photolithography patterns according to claim 2, wherein, The thickness of the target photoresist layer is h1, and the thickness of the sacrificial photoresist layer is h2, where 5%h1≤h2≤20%h1.

4. The method for improving water immersion defects in immersion photolithography patterns according to claim 2, wherein, The baking temperature before the first exposure is T1, and the baking time before the second exposure is T2, where T1+5℃≤T2≤T1+30℃.

5. The method for improving water immersion defects in immersion photolithography patterns according to claim 1, wherein, Following exposure, the process also includes drying the surface of the sacrificial photoresist layer. The drying process includes: Perform a cycle of spin-drying and rinsing; and The step of drying the surface of the sacrificial photoresist layer with a drying gas.

6. The method for improving water immersion defects in immersion photolithography patterns according to claim 1, wherein, Following the exposure, the process also includes a deprecated post-exposure baking step for both the target photoresist layer and the sacrificial photoresist layer.

7. The method for improving water immersion defects in immersion photolithography patterns according to claim 6, wherein, After exposure and baking, the sacrificial photoresist layer and the target photoresist layer form photoacid diffusion regions of different sizes. The photoacid diffusion region of the sacrificial photoresist layer has a first opening size D1, and the photoacid diffusion region of the target photoresist layer has a second opening size D2, with D1 > D2, to form a "T" to form the photoacid diffusion region.

8. The method for improving water immersion defects in immersion photolithography patterns according to claim 6, wherein, After removing the sacrificial photoresist layer, the process includes a supplementary exposure and baking step, followed by a development step.

9. The method for improving water immersion defects in immersion photolithography patterns according to claim 8, wherein, The time after exposure and baking ends is Ta, and the time after development begins is Tb. There is a preset time interval between Ta and Tb.

10. The method for improving water immersion defects in immersion photolithography patterns according to claim 9, wherein, The preset time interval is QT, the baking time after exposure is t3, the baking time after supplementary exposure is time, and time = (10%t3~50%t3) * QT / 6h.

Images