A photolithography method

Abstract

The present application provides a photolithography method, which includes: obtaining a structure to be etched, wherein a photoresist coating is provided on the structure to be etched, wherein the photoresist coating includes an alternately stacked first dielectric layer and a photoresist layer having a target thickness, wherein the number of first dielectric layers in the photoresist coating is one more than the photoresist layer, and the refractive index of the first dielectric layer is less than the refractive index of the photoresist layer; exposing the photoresist coating according to light of a preset wavelength and a mask having target size data; removing the first dielectric layer on the photoresist layer, and developing the photoresist layer to obtain a target photoresist layer having a periodic structure, wherein the target photoresist layer is used to etch the structure to be etched. Through the above method, light of the preset wavelength can achieve an ultra-high-resolution regular periodic imaging effect in the photoresist layer, thereby realizing ultra-high-resolution photolithography.

Description

Technical Field

[0001] The present application relates to the field of etching, and in particular to a photolithography method. Background Art

[0002] Photolithography refers to a method of first using exposure and development to obtain a photoresist layer with a geometric structure, and then using an etching process to copy the geometric structure of the photoresist layer onto a target substrate. Photolithography is widely used in the field of semiconductor device preparation.

[0003] With the rapid development of science and technology, the area of semiconductor devices is getting smaller and smaller, and the line width is also getting smaller and smaller, which places higher and higher requirements on the resolution of lithography. In the related art, lithography mainly includes direct lithography and super-diffraction lithography. Specifically, direct lithography refers to a lithography method that uses light of a relatively small wavelength to directly copy the mask pattern onto the photoresist layer, including deep ultraviolet lithography, extreme ultraviolet lithography, electron beam lithography, etc. However, due to the existence of the diffraction limit, direct lithography cannot directly copy smaller mask patterns onto the photoresist layer. For example, when using a 193nm wavelength, the limited resolution of deep ultraviolet lithography can only reach a half-period of 38nm, which is about 20% of the wavelength, and the resolution is relatively low. Super-diffraction lithography is a method of lithography that uses the lateral excitation behavior formed by the lateral transmission of light on the metal surface to perform lithography. It can break the diffraction limit and improve the resolution. Among the related technologies, only the needle-shaped lithography method can achieve the effect of line width compression, with a limited imaging period of 33.3% of the wavelength. This limited imaging period still cannot meet the production requirements of semiconductor devices with smaller areas. In view of this, how to obtain a lithography method with a higher limit imaging cycle is an urgent problem that needs to be solved. Summary of the Invention

[0004] In view of this, the present application provides a lithography method that can obtain a regular periodic imaging effect with higher resolution, thereby achieving ultra-high resolution lithography. The specific scheme is as follows:

[0005] In a first aspect, the present application provides a photolithography method, comprising:

[0006] Obtaining a structure to be etched, wherein a photoresist coating is provided on the structure to be etched, wherein the photoresist coating includes alternately stacked first dielectric layers and a photoresist layer having a target thickness, wherein the number of the first dielectric layers in the photoresist coating is one more than the number of the photoresist layers, and the refractive index of the first dielectric layer is less than the refractive index of the photoresist layer;

[0007] Exposing the photoresist coating layer according to light of a preset wavelength and a mask having target size data, wherein the distance between the mask and the structure to be etched is a target spacing, and the target thickness, the target size data, and the target spacing are used to cause the light of the preset wavelength to periodically form an image in the photoresist layer;

[0008] The first dielectric layer on the photoresist layer is removed, and the photoresist layer is developed to obtain a target photoresist layer with a periodic structure, and the target photoresist layer is used to etch the structure to be etched.

[0009] Optionally, the target thickness, the target size data and the target spacing are determined by:

[0010] Obtaining optical parameters of the mask, the first dielectric layer, the photoresist layer, and the structure to be etched at the preset wavelength, respectively, wherein the optical parameters include a refractive index and an absorption coefficient;

[0011] Constructing a corresponding photolithography simulation model according to the optical parameters and dimensional parameters, wherein the dimensional parameters include the thickness of the photoresist layer, the dimensional data of the mask, and the distance between the mask and the structure to be etched;

[0012] using multiple size parameters as first size data, second size data, and third size data, respectively, setting the first size data to a first preset size, the second size data to a second preset size, and determining, by the photolithography simulation model, the third size data during periodic imaging in the photoresist layer as third target size data;

[0013] When the third size data is the third target size data and the first size data is the first preset size, determining, by the photolithography simulation model, the second size data during periodic imaging in the photoresist layer as the second target size data;

[0014] When the third size data is the third target size data and the second size data is the second target size data, determining, by the photolithography simulation model, the first size data during periodic imaging in the photoresist layer as the first target size data;

[0015] The target thickness, the target size data, and the target distance are determined according to the first target size data, the second target size data, and the third target size data.

[0016] Optionally, the photoresist coating layer includes a plurality of photoresist layers, and the outermost layers of the photoresist coating layer are all the first dielectric layers.

[0017] Optionally, the multiple first dielectric layers in the photoresist coating are made of the same material.

[0018] Optionally, the first dielectric layer includes: a metal material or a metamaterial having a refractive index less than 1 at the preset wavelength.

[0019] Optionally, the structure to be etched includes a substrate, a structure to be led out on the substrate, and a second dielectric layer covering the structure to be led out, and the target photoresist layer is used to etch the second dielectric layer.

[0020] Optionally, a period difference between the mask and the structure to be extracted is smaller than a preset period difference value, and the light-transmitting layer of the mask is arranged opposite to the structure to be extracted.

[0021] Optionally, the number of the photoresist layer is 1, and the method further includes:

[0022] Using the target photoresist layer as a mask, etching the first dielectric layer below the photoresist layer to obtain a target first dielectric layer having a periodic structure;

[0023] The second dielectric layer is etched according to the target first dielectric layer to obtain a target second dielectric layer having a periodic structure, wherein the target second dielectric layer exposes at least a portion of the surface of the structure to be led out.

[0024] Optionally, the structure to be led out includes one or more of a gate structure, a source structure and a drain structure.

[0025] Optionally, a stacked layer and a channel structure penetrating the stacked layer are further included between the substrate and the structure to be led out, or a third dielectric layer or a doped layer is further included between the substrate and the structure to be led out.

[0026] In summary, an embodiment of the present application provides a photolithography method, which includes: obtaining a structure to be etched, wherein a photoresist coating is provided on the structure to be etched, the photoresist coating including alternately stacked first dielectric layers and a photoresist layer with a target thickness, and the number of first dielectric layers in the photoresist coating is one more than the photoresist layer, and the refractive index of the first dielectric layer is less than the refractive index of the photoresist layer; exposing the photoresist coating according to light of a preset wavelength and a mask with target size data, wherein the distance between the mask and the structure to be etched is a target spacing, and the target thickness, target size data, and target spacing are used to make the light of the preset wavelength periodically imaged in the photoresist layer; removing the first dielectric layer above the photoresist layer, and developing the photoresist layer to obtain a target photoresist layer with a periodic structure, and the target photoresist layer is used to etch the structure to be etched. The photoresist coating in the above method can form a Fabry-Perot cavity. Under appropriate parameters such as the target thickness of the photoresist layer, the target size data of the mask, and the target spacing between the mask and the structure to be etched, light of a preset wavelength achieves an ultra-high-resolution regular periodic imaging effect in the photoresist layer, thereby realizing ultra-high-resolution lithography. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 A schematic diagram of a photolithography process provided in an embodiment of the present application;

[0029] Figure 2 This is a top view of a structure to be etched provided in an embodiment of the present application;

[0030] Figure 3 This embodiment of the present application provides Figure 2 AA cross-sectional diagram of ;

[0031] Figure 4 A schematic diagram of a structure to be etched including a photoresist coating provided in an embodiment of the present application;

[0032] Figure 5 A top view of a structure to be etched and a mask provided in an embodiment of the present application;

[0033] Figure 6 A schematic diagram of an exposure of a structure to be etched and a mask provided in an embodiment of the present application;

[0034] Figure 7A schematic diagram of a structure to be etched after development provided in an embodiment of the present application;

[0035] Figure 8 A schematic diagram of etching according to a target photoresist layer provided in an embodiment of the present application;

[0036] Figure 9 A schematic diagram of etching a target first dielectric layer according to an embodiment of the present application;

[0037] Figure 10 A schematic diagram of optimizing the size data of a mask provided in an embodiment of the present application;

[0038] Figure 11 A schematic diagram of optimizing the thickness of a photoresist layer provided in an embodiment of the present application;

[0039] Figure 12 A schematic diagram of optimizing the distance between a mask and a wafer provided in an embodiment of the present application;

[0040] Figure 13 This is a schematic diagram of light intensity simulation in a photoresist layer provided in an embodiment of the present application. DETAILED DESCRIPTION

[0041] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below with reference to the accompanying drawings.

[0042] In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0043] Secondly, this application is described in detail with reference to schematic diagrams. When describing the embodiments of this application, for ease of explanation, cross-sectional views of device structures may be partially enlarged and not to scale. Furthermore, these schematic diagrams are merely illustrative and should not limit the scope of protection of this application. Furthermore, in actual production, three-dimensional dimensions, including length, width, and depth, should be included.

[0044] As described in the background, due to the diffraction limit, traditional photolithography has a low resolution. Its limiting resolution is R = k1*λ / NA, where R is the resolution, λ is the wavelength, NA is the numerical aperture, and k1 is the photolithography process coefficient. Theoretically, k1 can only be as low as 0.25. For example, when using a 193nm wavelength, the limiting resolution of deep ultraviolet lithography is only 38nm per half-period, approximately 20% of the wavelength. Although super-diffraction lithography can break through the diffraction limit, among related technologies, only needle-tip lithography achieves linewidth compression, with a limiting imaging period of 33.3% of the wavelength. This limiting imaging period still cannot meet the requirements for fabricating semiconductor devices with smaller areas.

[0045] Based on the above technical problems, an embodiment of the present application provides a lithography method that can obtain a regular periodic imaging effect with higher resolution, thereby realizing ultra-high resolution lithography.

[0046] For ease of understanding, a photolithography method provided in an embodiment of the present application is described in detail below with reference to the accompanying drawings.

[0047] refer to Figure 1 As shown, Figure 1 A schematic flow chart of a photolithography method provided in an embodiment of the present application, the method may include the following steps.

[0048] S101, obtaining a structure to be etched, wherein a photoresist coating is provided on the structure to be etched, wherein the photoresist coating includes alternately stacked first dielectric layers and a photoresist layer having a target thickness, and the number of the first dielectric layers in the photoresist coating is one more than the photoresist layer, and the refractive index of the first dielectric layer is less than the refractive index of the photoresist layer.

[0049] Specifically, a photoresist coating can be formed on the structure to be etched, so that the photoresist coating can be patterned according to a mask in subsequent steps, and then the structure to be etched can be etched using the patterned photoresist coating.

[0050] The photoresist coating of the embodiment of the present application includes a first dielectric layer and a photoresist layer stacked alternately. Since the number of the first dielectric layer in the photoresist coating is one more than the number of the photoresist layers, the surfaces of both sides of the photoresist coating are always the first dielectric layer. Figure 4 As shown, Figure 4A schematic diagram of a structure to be etched including a photoresist coating is provided in an embodiment of the present application. The structure to be etched in the embodiment of the present application has a photoresist coating 130 thereon, wherein the photoresist coating 130 includes an alternately stacked first dielectric layer 131, a photoresist layer 132, and a first dielectric layer 133. That is, the first dielectric layer 131, the photoresist layer 132, and the first dielectric layer 133 constitute an optical structure similar to a sandwich. Since the refractive index of the first dielectric layer 131 and the first dielectric layer 133 are both smaller than the refractive index of the photoresist layer, the aforementioned sandwich-like structure will constitute a Fabry-Perot resonant cavity, resulting in reflection oscillations being formed in the photoresist coating 130 after light is incident, thereby enhancing the light intensity of the incident light.

[0051] In practical applications, a spin coating process, a deposition process, or an ion sputtering process can be used to sequentially form an alternately stacked first dielectric layer 131, a photoresist layer 132, and a first dielectric layer 133. In order to ensure the flatness and thickness of the first dielectric layer and the photoresist layer, after the first dielectric layer 131, the photoresist layer 132, and the first dielectric layer 133 are formed, a chemical mechanical polishing device can be used to polish the first dielectric layer 131, the photoresist layer 132, and the first dielectric layer 133.

[0052] S102. Expose the photoresist coating according to light of a preset wavelength and a mask having target size data. The distance between the mask and the structure to be etched is the target spacing. The target thickness, target size data, and target spacing are used to enable the light of the preset wavelength to periodically form an image in the photoresist layer.

[0053] Specifically, when the structure to be etched includes the photoresist coating 130, the photoresist coating 130 can be exposed through a mask, such as Figure 5 and Figure 6 As shown, Figure 5 A top view of a structure to be etched and a mask provided in an embodiment of the present application, Figure 6 This is a schematic diagram of an exposure structure to be etched and a mask provided in an embodiment of the present application. Figure 6 The middle mask plate includes a mask base 160 and a mask structure 150 , wherein the mask base 160 is made of a light-transmitting material, such as quartz, and the mask structure 150 is made of an opaque material, such as a metal material.

[0054] Light of a preset wavelength refers to any monochromatic light from extreme ultraviolet to infrared. The wavelength of light is not limited in this application. Light of a preset wavelength can be illuminated in an on-axis, off-axis, or polarized manner.

[0055] It should be noted that light can reflect and oscillate in the Fabry-Perot cavity. In this embodiment, in addition to the first dielectric layer 133, the photoresist layer 132 and the second dielectric layer 131 forming a first Fabry-Perot cavity, the substrate 120, the second dielectric layer 140 and the first dielectric layer 131 can also form a second Fabry-Perot cavity, and the first dielectric layer 133, the air and the mask structure 150 can also form a third Fabry-Perot cavity, thereby further enhancing the light intensity of the preset wavelength of light in the photoresist layer 132.

[0056] In this embodiment, a mask with target size data is selected and placed on the structure to be etched according to the target spacing so that light of a preset wavelength can be periodically imaged in the photoresist layer, such as Figure 6 As shown, when the photoresist coating 130 is exposed to light of a preset wavelength and a mask with a target size, the light will be imaged in the target area 132-1 of the photoresist layer 132, that is, a photochemical reaction will occur in the photoresist layer 132, wherein the target area 132-1 is the area where the photochemical reaction occurs, and this is also the lead-out area where the structure 120 to be led out can be led out after photolithography.

[0057] It should be noted that the thickness of the photoresist layer, the size of the mask, and the distance between the mask and the structure to be etched are crucial to whether light of a predetermined wavelength can form periodic images in the photoresist layer. Therefore, in one possible implementation, the target thickness, target size, and target spacing can be determined by:

[0058] Obtaining optical parameters of the mask, the first dielectric layer, the photoresist layer, and the structure to be etched at a preset wavelength, the optical parameters including refractive index and absorption coefficient;

[0059] Constructing a corresponding photolithography simulation model based on optical parameters and dimensional parameters, where the dimensional parameters include the thickness of the photoresist layer, the size of the mask, and the distance between the mask and the structure to be etched;

[0060] Using multiple size parameters as first size data, second size data, and third size data, respectively, setting the first size data to a first preset size, the second size data to a second preset size, and determining, through a photolithography simulation model, the third size data during periodic imaging in the photoresist layer as third target size data;

[0061] When the third size data is the third target size data and the first size data is the first preset size, determining, by the photolithography simulation model, the second size data during periodic imaging in the photoresist layer as the second target size data;

[0062] When the third size data is the third target size data and the second size data is the second target size data, determining, by a photolithography simulation model, the first size data during periodic imaging in the photoresist layer as the first target size data;

[0063] A target thickness, a target size data, and a target spacing are determined based on the first target size data, the second target size data, and the third target size data.

[0064] Specifically, the optical parameters of the mask, the first dielectric layer, the photoresist layer and the structure to be etched at a preset wavelength are first obtained, wherein the optical parameters mainly include the refractive index and the absorption coefficient.

[0065] A photolithography simulation model is then constructed based on the optical parameters and dimensional parameters. The photolithography simulation model can be used to simulate and optimize the thickness of the photoresist layer, the dimensional data of the mask, and the distance between the mask and the structure to be etched to obtain the target thickness, target dimensional data, and target spacing.

[0066] In order to ensure that light of a preset wavelength can have a better periodic imaging effect in the photoresist layer, it is necessary to determine the target size data of the three size parameters: the thickness of the photoresist layer, the size data of the mask, and the distance between the mask and the structure to be etched. Therefore, multiple size parameters can be used as the first size data, the second size data, and the third size data for optimization calculation. In this embodiment, the optimization calculation method provided in this application is explained by taking the distance between the mask and the structure to be etched as the first size data, the thickness of the photoresist layer as the second size data, and the size data of the mask as the third size data as an example.

[0067] The distance between the mask and the structure to be etched can be set to a preset spacing and the thickness of the photoresist layer can be set to a preset thickness. Then, by changing the size data of the mask in the photolithography simulation model, the relationship between the light intensity at different positions in the photoresist layer and the size data of the mask can be obtained, and then the size data corresponding to periodic imaging in the photoresist layer can be used as the target size data.

[0068] like Figure 10 As shown, Figure 10 This is a schematic diagram of optimizing the size data of a mask provided in an embodiment of the present application. When the period of the mask changes, the light intensity at different positions in the corresponding photoresist layer will also change. Figure 10 The period corresponding to the middle region 200 represents the target period that can be imaged periodically when imaging onto the photoresist layer. In other words, in order to ensure this super-resolution periodic imaging behavior, it is possible to select Figure 10 The period corresponding to the area 200 in FIG. 1 is used as the target size data of the mask.

[0069] After determining that the size data of the mask is the target size data, the distance between the mask and the structure to be etched can still be set as the preset spacing, and then by changing the thickness of the photoresist layer, the relationship between the light intensity at different positions in the photoresist layer and the thickness of the photoresist layer can be obtained, and then the thickness corresponding to periodic imaging in the photoresist layer can be used as the target thickness.

[0070] like Figure 11 As shown, Figure 11 This is a schematic diagram of optimizing the thickness of a photoresist layer provided in an embodiment of the present application. When the thickness of the photoresist layer changes, the light intensity at different positions in the corresponding photoresist layer will also change, wherein: Figure 11 The thickness corresponding to the middle region 300 represents the target thickness that can be imaged periodically when imaging to the photoresist layer. In other words, in order to ensure this super-resolution periodic imaging behavior, it is possible to select Figure 11 The thickness corresponding to the region 300 in FIG. 3 is used as the target thickness of the photoresist layer.

[0071] After determining that the size data of the mask is the target size data and the thickness of the photoresist layer is the target thickness, by changing the distance between the mask and the structure to be etched, the relationship between the light intensity at different positions in the photoresist layer and the distance between the mask and the structure to be etched is obtained, and then the corresponding distance during periodic imaging in the photoresist layer is used as the target spacing.

[0072] like Figure 12 As shown, Figure 12 A schematic diagram of optimizing the distance between a mask and a wafer provided in an embodiment of the present application is provided. Figure 12 The wafer in the invention refers to the structure to be etched in this application. When the distance between the mask and the structure to be etched (wafer) changes, the light intensity at different positions in the corresponding photoresist layer will also change. Figure 12 The distance between the mask and the structure to be etched (wafer) corresponding to the middle area 400 represents the target spacing that can be periodically imaged when imaging to the photoresist layer. In other words, in order to ensure this super-resolution periodic imaging behavior, it is possible to select Figure 11 The distance between the mask and the structure to be etched (wafer) corresponding to the area 400 in FIG. 4 is used as the target spacing between the mask and the structure to be etched.

[0073] In addition, after determining the target size data, target thickness and target spacing, the light intensity in the photoresist layer can be simulated based on the above parameters, such as Figure 13 As shown, Figure 13This is a schematic diagram of light intensity simulation in a photoresist layer provided in an embodiment of the present application. A transverse periodic pattern is implemented inside the photoresist layer, in which the imaging period is 27% of the wavelength and the half period (resolution) is 13.4% of the wavelength, thereby achieving super-resolution imaging and further achieving super-resolution lithography.

[0074] It should be noted that, in actual applications, the target size data of the mask can be one or more. For example, good periodic imaging behavior can occur in the photoresist layer under both the target size data A1 and the target size data A2. The corresponding target thickness A1 and target spacing A1 can be determined according to the target size data A1, and the corresponding target thickness A2 and target spacing A2 can be determined according to the target size data A2. That is to say, multiple sets of optimization results of different size parameters can be obtained. In actual applications, one set can be selected according to the needs of technicians.

[0075] S103 , removing the first dielectric layer on the photoresist layer, and developing the photoresist layer to obtain a target photoresist layer having a periodic structure, wherein the target photoresist layer is used to etch the structure to be etched.

[0076] After the photoresist layer is exposed in S102, the first dielectric layer on the photoresist layer can be removed first, so as to develop the exposed photoresist layer and remove the imaging area in the photoresist layer to obtain a target photoresist layer with a periodic structure, such as Figure 7 As shown, Figure 7 A schematic diagram of a structure to be etched after development is provided in an embodiment of the present application. The first dielectric layer 133 located above the photoresist layer 132 can be removed first, and the photoresist layer 132 is subjected to a development process. After development, the portion of the photoresist layer 132 corresponding to the target area 132-1 is removed to obtain a photoresist layer 132 with a periodic structure.

[0077] The target photoresist layer having the periodic structure can be used as a mask to continue etching the structure to be etched.

[0078] In a possible implementation, when the number of photoresist layers is 1, the structure to be etched may be etched according to the target photoresist layer in the following manner:

[0079] Using the target photoresist layer as a mask, etching the first dielectric layer below the photoresist layer to obtain a target first dielectric layer with a periodic structure;

[0080] The second dielectric layer is etched according to the target first dielectric layer to obtain a target second dielectric layer having a periodic structure, wherein the target second dielectric layer exposes at least a portion of the surface of the structure to be led out.

[0081] like Figure 8 As shown, Figure 8 The schematic diagram of etching according to the target photoresist layer provided in the embodiment of the present application is that the target photoresist layer 132 with a periodic structure is used as a mask to etch the first dielectric layer 131 under the photoresist layer 132 to obtain Figure 8 The target first dielectric layer 131 having a periodic structure is formed in the photoresist layer, and thus the periodic structure is transferred from the photoresist layer to the first dielectric layer.

[0082] like Figure 9 As shown, Figure 9 The schematic diagram of etching according to the target first dielectric layer provided in the embodiment of the present application is that the second dielectric layer 140 can be etched according to the target first dielectric layer 131 having a periodic structure to obtain Figure 9 The target second dielectric layer 140 having a periodic structure is formed in the substrate to expose at least a portion of the surface of the structure to be led out 120 , thereby achieving the lead-out of the structure to be led out 120 .

[0083] In a possible implementation, the photoresist coating in S101 includes multiple photoresist layers, and the outermost layers of the photoresist coating are all first dielectric layers.

[0084] In practical applications, the photoresist coating may include more than one photoresist layer, that is, the photoresist coating may include multiple photoresist layers. Since the photoresist layer and the first dielectric layer in the photoresist coating are alternately stacked and the outermost layer of the photoresist coating is the first dielectric layer, when the photoresist coating has multiple photoresist layers, a multi-layer thin film structure of alternately stacked first dielectric layer-photoresist layer-first dielectric layer-photoresist layer-first dielectric layer is formed. Among them, each set of the first dielectric layer-photoresist layer-first dielectric layer three-layer structure can constitute a Fabry-Perot resonant cavity. In other words, when the photoresist coating includes multiple photoresist layers, the photoresist coating also includes a corresponding number of Fabry-Perot resonant cavities. Since the more Fabry-Perot resonant cavities in the photoresist coating, the better the reflection and oscillation effect of the incident light in the photoresist coating, when the photoresist coating includes multiple photoresist layers, the intensity of the incident light in the photoresist coating can be further enhanced.

[0085] In a possible implementation manner, the multiple first dielectric layers in the photoresist coating in S101 are made of the same material.

[0086] In the actual preparation process of the photoresist coating, the preparation of multiple first dielectric layers is relatively complex in terms of process. Therefore, in order to reduce the process difficulty, the multiple first dielectric layers in the photoresist coating can be made of the same material, thereby increasing the process speed of preparing the multiple first dielectric layers and ensuring the process efficiency of preparing the multiple first dielectric layers.

[0087] In one possible embodiment, the multiple first dielectric layers of the photoresist coating in S101 can be made of different materials. It should be noted that the refractive index of the first dielectric layers of different materials needs to be smaller than the refractive index of the photoresist layer. That is, different materials with a refractive index smaller than that of the photoresist layer need to be selected as the materials of the first dielectric layer.

[0088] In a possible implementation, the first dielectric layer in S101 includes a metal material or a metamaterial having a refractive index less than 1 at a preset wavelength.

[0089] The material in the photoresist layer is photoresist. Since the refractive index of photoresist is greater than 1, the first dielectric layer may include a metal material or a metamaterial with a refractive index less than 1 at a preset wavelength. The metal material may include gold, silver, or copper, etc., whose refractive index is less than 1 under deep ultraviolet light, visible light, or infrared light. The metamaterial may be a combination of certain compound materials and certain materials. The metamaterial is not required to be natural and can be artificially synthesized. By combining various materials, a metamaterial with a refractive index less than 1 at certain wavelengths can be obtained.

[0090] By selecting a metamaterial and a metal material with a refractive index less than 1 as the first dielectric layer, the refractive index of the first dielectric layer can be made smaller than the refractive index of the photoresist layer, thereby causing the first dielectric layer, the photoresist layer and the first dielectric layer to form a Fabry-Perot resonant cavity.

[0091] In a possible implementation, the structure to be etched in S101 includes a substrate, a structure to be extracted on the substrate, and a second dielectric layer covering the structure to be extracted, and the target photoresist layer is used to etch the second dielectric layer.

[0092] like Figure 2 and Figure 3 As shown, Figure 2 This is a top view of a structure to be etched provided in an embodiment of the present application. Figure 3 This embodiment of the present application provides Figure 2 AA cross-sectional schematic diagram, the structure to be etched may include a substrate 110 and a structure to be led out 120, wherein the structure to be led out is located on the substrate.

[0093] The material of the structure to be led out 120 may be a metal material with good electrical conductivity.

[0094] The substrate 110 may be a semiconductor substrate, such as a Si substrate, a Ge substrate, a SiGe substrate, a silicon-on-insulator (SOI) substrate, or a germanium-on-insulator (GOI) substrate. Furthermore, the semiconductor substrate may be a substrate comprising other elemental semiconductors or compound semiconductors, such as quartz, GaAs, InP, or SiC, and may also be a stacked structure, such as Si / SiGe, or another epitaxial structure, such as SGOI (silicon-germanium-on-insulator).

[0095] like Figure 4 As shown, a second dielectric layer 140 is formed on the structure to be led out 120, and the second dielectric layer 140 covers the structure to be led out 120. Since a photoresist coating 130 is provided on the structure to be etched, the second dielectric layer 140 is located between the structure to be led out 120 and the photoresist coating 130, so that the target photoresist layer can be used to etch the second dielectric layer 140 to expose a portion of the surface of the structure to be led out.

[0096] The dielectric material of the second dielectric layer 140 may be a material with good insulation properties, such as silicon oxide.

[0097] In practical applications, a deposition process can be used to deposit a dielectric material to form the second dielectric layer 140. When the dielectric material is deposited on the structure to be led out 120 and the substrate 110 without the structure to be led out 120, the formed second dielectric layer 140 will be conformal to the structure to be led out 120, so that the morphology of the second dielectric layer 140 is similar to the morphology of the structure to be led out 120. At this time, in order to ensure the flatness of the second dielectric layer 140, a chemical mechanical mask device can be used to grind the second dielectric layer 140, and finally a second dielectric layer with higher flatness is obtained, so that a photolithography coating can be subsequently formed on the relatively flat second dielectric layer.

[0098] In a possible implementation, the structure to be extracted includes one or more of a gate structure, a source structure, and a drain structure.

[0099] In a possible implementation, a stacked layer and a channel structure penetrating the stacked layer are further included between the substrate and the structure to be led out, or a third dielectric layer or a doped layer is further included between the substrate and the structure to be led out.

[0100] In practical applications, other film layers may be formed between the substrate and the structure to be led out to form a variety of semiconductor devices for photolithographic imaging. A stacked layer and a channel structure running through the stacked layer may be formed between the substrate and the structure to be led out, and the semiconductor device may serve as a three-dimensional storage device. A doped layer or a third dielectric layer may be formed between the substrate and the structure to be led out, and the semiconductor device may be a logic device, such as a transistor.

[0101] In a possible implementation manner, the period difference between the mask and the structure to be extracted in S102 is smaller than a preset period difference value, and the light-transmitting layer of the mask is arranged opposite to the structure to be extracted.

[0102] If the period difference between the mask and the structure to be led out is less than the preset period difference value, it means that the period of the mask and the structure to be led out is the same, such as Figure 6 As described above, the mask structure 150 and the structure to be extracted 120 have the same period and the same size, and the light-transmitting layer of the mask is arranged opposite to the structure to be extracted.

[0103] Providing a mask with the same period as the structure to be extracted can facilitate periodic imaging behavior of light of a preset wavelength in the photoresist layer.

[0104] In summary, an embodiment of the present application provides a photolithography method, which obtains a structure to be etched, wherein a photoresist coating is provided on the structure to be etched, the photoresist coating comprising alternately stacked first dielectric layers and a photoresist layer having a target thickness, and the number of first dielectric layers in the photoresist coating is one more than the photoresist layer, and the refractive index of the first dielectric layer is less than the refractive index of the photoresist layer; the photoresist coating is exposed according to light of a preset wavelength and a mask having target size data, the distance between the mask and the structure to be etched is the target spacing, and the target thickness, target size data, and target spacing are used to make the light of the preset wavelength periodically imaged in the photoresist layer; the first dielectric layer on the photoresist layer is removed, and the photoresist layer is developed to obtain a target photoresist layer having a periodic structure, and the target photoresist layer is used to etch the structure to be etched. The photoresist coating in the above method can form a Fabry-Perot cavity. Under appropriate parameters such as the target thickness of the photoresist layer, the target size data of the mask, and the target spacing between the mask and the structure to be etched, light of a preset wavelength achieves an ultra-high-resolution regular periodic imaging effect in the photoresist layer, thereby realizing ultra-high-resolution lithography.

[0105] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

[0106] The above is only a preferred embodiment of the present application. Although the present application has been disclosed as a preferred embodiment, it is not intended to limit the present application. Any technician familiar with the art can use the above-disclosed methods and technical contents to make many possible changes and modifications to the technical solution of the present application without departing from the scope of the technical solution of the present application, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present application without departing from the content of the technical solution of the present application are still within the scope of protection of the technical solution of the present application.

Claims

1. A photolithography method, characterized in that: The method comprises: Obtaining a structure to be etched, wherein a photoresist coating is provided on the structure to be etched, wherein the photoresist coating includes alternately stacked first dielectric layers and a photoresist layer having a target thickness, wherein the number of the first dielectric layers in the photoresist coating is one more than the number of the photoresist layers, and the refractive index of the first dielectric layer is less than the refractive index of the photoresist layer; Exposing the photoresist coating layer according to light of a preset wavelength and a mask having target size data, wherein the distance between the mask and the structure to be etched is a target spacing, and the target thickness, the target size data, and the target spacing are used to cause the light of the preset wavelength to periodically form an image in the photoresist layer; The first dielectric layer on the photoresist layer is removed, and the photoresist layer is developed to obtain a target photoresist layer with a periodic structure, and the target photoresist layer is used to etch the structure to be etched.

2. The method according to claim 1, characterized in that The target thickness, the target size data and the target spacing are determined by: Obtaining optical parameters of the mask, the first dielectric layer, the photoresist layer, and the structure to be etched at the preset wavelength, respectively, wherein the optical parameters include a refractive index and an absorption coefficient; Constructing a corresponding photolithography simulation model according to the optical parameters and dimensional parameters, wherein the dimensional parameters include the thickness of the photoresist layer, the dimensional data of the mask, and the distance between the mask and the structure to be etched; using multiple size parameters as first size data, second size data, and third size data, respectively, setting the first size data to a first preset size, the second size data to a second preset size, and determining, by the photolithography simulation model, the third size data during periodic imaging in the photoresist layer as third target size data; When the third size data is the third target size data and the first size data is the first preset size, determining, by the photolithography simulation model, the second size data during periodic imaging in the photoresist layer as the second target size data; When the third size data is the third target size data and the second size data is the second target size data, determining, by the photolithography simulation model, the first size data during periodic imaging in the photoresist layer as the first target size data; The target thickness, the target size data, and the target distance are determined according to the first target size data, the second target size data, and the third target size data.

3. The method according to claim 1 or 2, characterized in that The photoresist coating layer includes a plurality of photoresist layers, and the outermost layers of the photoresist coating layer are all the first dielectric layers.

4. The method according to claim 3, characterized in that The multiple first dielectric layers in the photoresist coating are made of the same material.

5. The method according to claim 1 or 2, characterized in that The first dielectric layer includes: a metal material or a metamaterial with a refractive index less than 1 at the preset wavelength.

6. The method according to claim 1 or 2, characterized in that The structure to be etched includes a substrate, a structure to be led out on the substrate, and a second dielectric layer covering the structure to be led out. The target photoresist layer is used to etch the second dielectric layer.

7. The method according to claim 6, characterized in that A period difference between the mask and the structure to be extracted is smaller than a preset period difference value, and the light-transmitting layer of the mask is arranged opposite to the structure to be extracted.

8. The method according to claim 6, characterized in that The number of the photoresist layer is 1, and the method further comprises: Using the target photoresist layer as a mask, etching the first dielectric layer below the photoresist layer to obtain a target first dielectric layer having a periodic structure; The second dielectric layer is etched according to the target first dielectric layer to obtain a target second dielectric layer having a periodic structure, wherein the target second dielectric layer exposes at least a portion of the surface of the structure to be led out.

9. The method according to claim 6, characterized in that The structure to be led out includes one or more of a gate structure, a source structure and a drain structure.

10. The method according to claim 6, characterized in that A stacked layer and a channel structure penetrating the stacked layer are further included between the substrate and the structure to be led out, or a third dielectric layer or a doped layer is further included between the substrate and the structure to be led out.

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