Method for nanopore fabrication using two lithography and two negative development

Abstract

The present disclosure provides a method for realizing nano-pore processing by twice photoetching and twice negative development, and relates to the field of photoetching technology, and comprises the following steps: forming, on a substrate, a to-be-etched film layer, a first photosensitive film layer, a medium layer and a second photosensitive film layer which are sequentially stacked, and the to-be-etched film layer is close to the substrate; performing once exposure on the second photosensitive film layer by using a nano-pore mask, and then performing once negative development to form a nano-pillar photoetching structure on the second photosensitive film layer; transferring the pattern of the nano-pillar photoetching structure to the medium layer to form a pillar pattern structure; performing twice exposure on the first photosensitive film layer by using the pillar pattern structure as a shielding pattern, and then performing twice negative development to form a nano-pore pattern structure on the first photosensitive film layer; and transferring the pattern of the nano-pore pattern structure to the to-be-etched film layer to obtain a nano-pore structure.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of photolithography, and can be applied to the technical fields of storage, sensors, nano-optics, etc., and in particular to a method for realizing nano-hole processing by twice photolithography and twice negative development. BACKGROUND

[0002] As a common nanostructure, nano-holes are widely used in the fields of storage, sensors, nano-optics, etc., and the preparation of small-size high-precision nano-hole arrays has increasingly become a research hotspot in the field of semiconductor devices. With the continuous development of microelectronic industry manufacturing technology, there are currently various process methods for realizing the preparation of nano-hole structures, such as electron beam lithography technology, ion beam lithography technology, nano-imprinting, etc., but these technologies are difficult to realize the low-cost preparation of large-area, ordered, high-quality nano-hole array structures.

[0003] For small-size high-density semiconductor nano-hole structures, the traditional diffraction lithography technology is often used for exposure imaging. This method has the advantages of short time consumption and easy implementation, but the diffraction lithography technology has low contrast for two-dimensional structure imaging, resulting in problems such as insufficient focal depth, profile distortion, poor uniformity, etc. In addition, due to the existence of optical proximity effect, the hole diameter distributed at the edge of the hole array has a large deviation from the designed size, and it is difficult to obtain a nano-hole array structure with good uniformity and high quality. SUMMARY

[0004] Therefore, the present disclosure provides a method for realizing nano-hole processing by twice photolithography and twice negative development, which comprises: forming a to-be-etched film layer, a first photosensitive film layer, a medium layer and a second photosensitive film layer which are sequentially stacked on a substrate, the to-be-etched film layer being close to the substrate; performing once exposure on the second photosensitive film layer by using a nano-hole pattern mask, and then performing once negative development to form a nano-pillar lithography structure on the second photosensitive film layer; transferring the pattern of the nano-pillar lithography structure to the medium layer to form a pillar pattern structure; performing twice exposure on the first photosensitive film layer by using the pillar pattern structure as a shielding pattern, and then performing twice negative development to form a nano-hole pattern structure on the first photosensitive film layer; and transferring the pattern of the nano-hole pattern structure to the to-be-etched film layer to obtain a nano-hole structure.

[0005] According to an embodiment of the present disclosure, the second photosensitive film layer is exposed once by using a nanopore pattern mask, and then is developed negatively once, so as to form a nanopillar lithography structure on the second photosensitive film layer, comprising: exposing the second photosensitive film layer once by using the nanopore pattern mask, so that the region of the second photosensitive film layer corresponding to the light-transmitting region of the nanopore pattern mask is excited to have an optical reaction and is baked to form a hydrophilic polymer which is insoluble in a negative developing solution; developing the second photosensitive film layer negatively once after the first exposure, so as to dissolve the region of the second photosensitive film layer corresponding to the non-light-transmitting region of the nanopore pattern mask; and cleaning the second photosensitive film layer after the second negative development by using an organic solution, so as to form the nanopillar lithography structure.

[0006] According to an embodiment of the present disclosure, the first photosensitive film layer is exposed twice by using a column pattern structure as a shielding pattern, and then is developed negatively twice, so as to form a nanopore pattern structure on the first photosensitive film layer, comprising: exposing the first photosensitive film layer twice by using the column pattern structure, so that the region of the first photosensitive film layer corresponding to the light-transmitting region of the column pattern structure is excited to have an optical reaction and is baked to form a hydrophilic polymer which is insoluble in a negative developing solution; removing the column pattern structure; developing the first photosensitive film layer negatively twice after the second exposure, so as to dissolve the region of the first photosensitive film layer corresponding to the non-light-transmitting region of the column pattern structure; and cleaning the first photosensitive film layer after the second negative development by using an organic solution, so as to form the nanopore pattern structure.

[0007] According to an embodiment of the present disclosure, the exposure mode comprises one of projection lithography, super-resolution lithography, contact lithography and electron beam lithography, and the exposure wavelength comprises i-line, g-line and 193 nm; the negative developing solution comprises at least one of n-butyl acetate, 3-ethoxypropyl acetate and 2-heptanone; and the organic solution comprises at least one of methyl isobutyl ketone, 4-methyl-2-pentanol and isopropyl alcohol.

[0008] According to an embodiment of the present disclosure, the method for forming the second photosensitive film layer on the substrate comprises: forming the second photosensitive film layer on the substrate by using a coating or fumigation method.

[0009] According to embodiments of this disclosure, the material of the film layer to be etched includes at least one of SiO2, Si3N4, Poly-Si, and TiO2; the material of the dielectric layer includes at least one of Si-BARC, SiO2, Si3N4, Poly-Si, TiN, and TiO2; the materials of the first photosensitive film layer and the second photosensitive film layer are the same or different, and the materials of the first photosensitive film layer and the second photosensitive film layer include positive photoresist.

[0010] According to embodiments of this disclosure, the thickness of the film to be etched is 10 nm to 200 nm, the thickness of the dielectric layer is 10 nm to 50 nm, the thickness of the first photosensitive film layer is 10 nm to 200 nm, and the thickness of the second photosensitive film layer is 10 nm to 100 nm.

[0011] According to embodiments of this disclosure, at least one of wet etching, ion beam etching, reactive ion etching, and inductively coupled plasma etching is used to transfer the pattern of the nanopillar lithography structure to the dielectric layer; at least one of ion beam etching, reactive ion etching, and inductively coupled plasma etching is used to transfer the pattern of the nanopore pattern structure to the film layer to be etched.

[0012] According to embodiments of this disclosure, the solution used in wet etching includes at least one of dilute hydrofluoric acid solution, dilute sodium hydroxide solution, and dilute potassium hydroxide solution; the etching gas used in ion beam etching, reactive ion etching, and inductively coupled plasma etching includes at least one of SF6, CF4, CHF3, and Ar.

[0013] According to embodiments of this disclosure, the nanopore structure has a characteristic size of 30 nm to 300 nm and a period of 60 nm to 500 nm.

[0014] The method for fabricating nanopores using two photolithography steps and two negative development steps provided in the embodiments of this disclosure has at least the following technical effects:

[0015] This method employs a double negative development technique to fabricate nanopores, which not only improves the imaging contrast of the nanopore pattern but also avoids the poor image contour quality caused by the optical proximity effect in nanopore array patterns. Furthermore, this method of achieving higher-quality nanopore fabrication through double exposure and double negative development can be applied not only to the manufacture of super-resolution sensors but also to the field of high-tech semiconductor chips. Attached Figure Description

[0016] The above and other objects, features, and advantages of this disclosure will become clearer from the following description of embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0017] Figure 1A flowchart illustrating a method for fabricating nanopores using two photolithography steps and two negative development steps according to an embodiment of the present disclosure is shown.

[0018] Figure 2 The diagram schematically illustrates the structural diagrams corresponding to each stage of the method for fabricating nanopores using two photolithography steps and two negative development steps according to an embodiment of the present disclosure.

[0019] Figure 3A The diagram schematically illustrates a nanopillar lithography structure obtained after a first exposure and negative development process according to an embodiment of the present disclosure.

[0020] Figure 3B The diagram schematically illustrates the nanopore pattern structure after a second exposure and negative development process according to an embodiment of the present disclosure.

[0021] Figure 3C The illustration schematically shows a nanopore pattern obtained by transferring a pattern of a nanopore patterned structure to a film layer to be etched, according to an embodiment of the present disclosure. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure.

[0023] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0024] Similarly, to simplify this disclosure and aid in understanding one or more of the various aspects of the disclosure, in the above description of exemplary embodiments of the present disclosure, various features of the present disclosure are sometimes grouped together in a single embodiment, figure, or description thereof. The use of terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refers to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present disclosure. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0026] The embodiments of this disclosure aim to provide a method for fabricating nanopores using two photolithography steps and two negative development steps, thereby achieving nanopore fabrication through two photolithography steps and two negative development steps.

[0027] Figure 1 A flowchart illustrating a method for fabricating nanopores using two photolithography steps and two negative development steps according to an embodiment of the present disclosure is shown.

[0028] like Figure 1 As shown, the nanopore fabrication method of this embodiment may include operations S110 to S150.

[0029] In operation S110, a film layer to be etched, a first photosensitive film layer, a dielectric layer, and a second photosensitive film layer are formed sequentially on a substrate, with the film layer to be etched close to the substrate.

[0030] In operation S120, the second photosensitive film layer is exposed once using a nanopore pattern mask, followed by negative development, to form a nanopillar lithography structure on the second photosensitive film layer.

[0031] In operation S130, the pattern of the nanopillar lithography structure is transferred to the dielectric layer to form a pillar pattern structure.

[0032] In operation S140, the first photosensitive film layer is exposed a second time using a columnar pattern structure as a masking pattern, followed by a second negative development to form a nanoporous pattern structure on the first photosensitive film layer.

[0033] In operation S150, the pattern of the nanoporous structure is transferred to the film layer to be etched, thus obtaining the nanoporous structure.

[0034] In the embodiments of this disclosure, the nanopore pattern mask is a nanopore pattern mask with the same period and diameter as the required photolithographic pattern. The specific pattern period and diameter can be selected according to actual application requirements, and this disclosure does not impose any limitations. That is, by selecting nanopore pattern masks with different periods and diameters, nanopores with different periods and diameters can be fabricated.

[0035] Although direct exposure and development using a nanopore pattern mask can obtain nanopore structures in a single photolithography step, the two-dimensional aperture array pattern suffers from low imaging contrast, difficulty in exposure, and poor aperture uniformity. Furthermore, stray light and light diffraction phenomena easily distort the nanopore array pattern, making it difficult to meet device performance and yield requirements. The nanopore fabrication method of this disclosure utilizes a nanopore pattern mask for the first exposure of the second photosensitive film layer, followed by a first negative development; then, a pillar pattern structure is used as a masking pattern for the second exposure of the first photosensitive film layer, followed by a second negative development. Compared to obtaining nanopore patterns through a single exposure, this method involves less light scattering and reflection on the nanopillar structure, allowing light to penetrate the photoresist more directly and resulting in more uniform exposure. Simultaneously, the photoresist on the nanopillar structure is easier to remove uniformly during development, improving pattern accuracy. Moreover, the nanopillar structure is less affected by the optical proximity effect, resulting in clearer patterns and reduced pattern distortion. Therefore, the nanopore fabrication method of this disclosure not only improves the imaging contrast of nanopore patterns but also avoids problems such as poor pattern contour quality caused by the optical proximity effect in nanopore array patterns.

[0036] Based on the above embodiments, the operation S120 involves exposing the second photosensitive film layer once using a nanopore patterned mask, followed by negative development, to form a nanopillar lithography structure on the second photosensitive film layer, including:

[0037] The second photosensitive film layer is exposed once using a nanopore pattern mask, which excites an optical reaction in the area of ​​the second photosensitive film layer corresponding to the light-transmitting area of ​​the nanopore pattern mask. After baking, a hydrophilic polymer that is insoluble in the negative developing solution is formed.

[0038] The second photosensitive film layer after one exposure is negatively developed using a negative development solution, which dissolves the area of ​​the second photosensitive film layer corresponding to the non-transparent area of ​​the nanopore pattern mask.

[0039] The second photosensitive film layer after the first negative development is cleaned using an organic solution to form a nanopillar lithography structure.

[0040] Based on the above embodiments, the operation S140, which involves secondary exposure of the first photosensitive film layer using a columnar pattern structure followed by secondary negative development to form a nanopore pattern structure on the first photosensitive film layer, includes:

[0041] The first photosensitive film layer is subjected to secondary exposure using a columnar pattern structure as a masking pattern. This causes the area of ​​the first photosensitive film layer corresponding to the light-transmitting area of ​​the columnar pattern structure to be excited by an optical reaction and then baked to form a hydrophilic polymer that is insoluble in the negative developing solution.

[0042] Remove the columnar graphic structure, i.e., the medium layer.

[0043] A negative development solution is used to perform secondary negative development on the first photosensitive film layer after the second exposure, dissolving the first photosensitive film layer corresponding to the non-transparent areas of the columnar pattern structure.

[0044] The first photosensitive film layer after secondary negative development is cleaned using an organic solution to form a nanoporous pattern structure.

[0045] According to embodiments of this disclosure, the light-transmitting areas on the nanopore pattern mask cause corresponding areas of the second photosensitive film to undergo photochemical reactions, producing acid. After baking, the polarity of the polymer changes, becoming a hydrophilic polymer that is no longer soluble in the negative developing solution. Meanwhile, the material properties of the corresponding areas of the second photosensitive film on the non-light-transmitting areas of the nanopore pattern mask remain unchanged and are still soluble in the negative developing solution. Therefore, the photoresist in the unexposed areas of the second photosensitive film is dissolved, leaving the photosensitive portion. In other words, the hole pattern on the nanopore pattern mask forms a nanopillar photolithographic structure in the corresponding areas of the second photosensitive film.

[0046] Similarly, the light-transmitting areas surrounding the pillar pattern structure trigger photochemical reactions in the corresponding regions of the first photosensitive film, producing acid. After baking, the polarity of the polymer changes, becoming a hydrophilic polymer that is no longer soluble in the negative developing solution. However, in the non-light-transmitting areas below the pillar pattern structure, the material properties of the corresponding regions of the first photosensitive film remain unchanged, and it is still soluble in the negative developing solution. Therefore, the photoresist in the unexposed areas of the first photosensitive film is dissolved, leaving the photosensitive portion. In other words, the pillar pattern structure can form nanoporous patterns in the corresponding regions of the first photosensitive film.

[0047] Since a dielectric layer is formed between the first and second photosensitive film layers, exposing and negatively developing the second photosensitive film layer using a nanopore pattern mask will not affect the first photosensitive film layer. This allows for unrestricted selection of materials, exposure modes, and development methods for the two photoresists, meaning that the two exposure and development processes can be the same or different.

[0048] Based on the above embodiments, the two-exposure method can include one of projection lithography, super-resolution lithography, contact lithography, and electron beam lithography, and the exposure wavelength can include i-line, g-line, and 193 nm. Here, i-line refers to ultraviolet light with a wavelength of 365 nm, and g-line refers to ultraviolet light with a wavelength of 436 nm.

[0049] The negative developing solution for two developments may include at least one of n-butyl acetate, ethyl 3-ethoxypropionate, and 2-heptanone;

[0050] The organic solution may include at least one of methyl isobutyl ketone, 4-methyl-2-pentanol, and isopropanol.

[0051] Based on the above embodiments, the step of forming the etchable film layer, the first photosensitive film layer, the dielectric layer, and the second photosensitive film layer sequentially stacked on the substrate in operation S110 may include:

[0052] The etching film is formed on the substrate by means of thermal oxidation, electron beam evaporation, magnetron sputtering deposition, chemical vapor deposition or coating.

[0053] A first photosensitive film layer is formed on the film layer to be etched by means of coating or fumigation.

[0054] A dielectric layer is formed on the first photosensitive film layer using electron beam evaporation, spin coating, spraying, a combination of spin coating and spraying, printing, or magnetron sputtering.

[0055] A second photosensitive film layer is formed on the dielectric layer by coating or fumigation.

[0056] Furthermore, as some feasible implementations, the material of the film layer to be etched may include at least one of SiO2, Si3N4, Poly-Si, and TiO2. The material of the dielectric layer may include at least one of Si-BARC, SiO2, Si3N4, Poly-Si, TiN, and TiO2. The materials of the first photosensitive film layer and the second photosensitive film layer may be the same or different, and the materials of the first photosensitive film layer and the second photosensitive film layer may include positive photoresist.

[0057] The thickness of the film to be etched can be 10 nm to 200 nm, the thickness of the dielectric layer can be 10 nm to 50 nm, the thickness of the first photosensitive film layer can be 10 nm to 200 nm, and the thickness of the second photosensitive film layer can be 10 nm to 100 nm.

[0058] Based on the above embodiments, at least one of wet etching, ion beam etching (IBE), reactive ion etching (RIE), and inductively coupled plasma etching (ICP) can be used to transfer the pattern of the nanopillar lithography structure to the dielectric layer.

[0059] The pattern of the nanopore pattern structure can be transferred to the film layer to be etched by at least one of ion beam etching, reactive ion etching, and inductively coupled plasma etching.

[0060] Furthermore, as some feasible implementation methods, the solution used in wet etching includes at least one of dilute hydrofluoric acid solution, dilute sodium hydroxide solution, and dilute potassium hydroxide solution.

[0061] The etching gases used in ion beam etching, reactive ion etching, and inductively coupled plasma etching include at least one of SF6, CF4, CHF3, and Ar.

[0062] To more clearly illustrate the effectiveness of the nanopore fabrication method provided in the embodiments of this disclosure, the following is combined with... Figure 2 and Figures 3A-3C The following description is based on some specific embodiments. Figure 2 The diagram schematically illustrates the structural diagrams corresponding to each stage of the nanopore fabrication method according to embodiments of the present disclosure. Figure 3A This schematically illustrates a nanopillar lithographic structure obtained after the first exposure and negative development process according to an embodiment of the present disclosure. Figure 3B This schematically illustrates a nanopore pattern structure after a second exposure and negative development process according to an embodiment of the present disclosure. Figure 3C The illustration schematically shows a nanopore pattern obtained by transferring a pattern of a nanopore patterned structure to a film layer to be etched, according to an embodiment of the present disclosure.

[0063] Example 1:

[0064] The implementation steps of the nanopore fabrication method using two photolithography and two negative development techniques provided in this embodiment are as follows:

[0065] Step 1-1: Deposit an etched layer 2 on substrate 1 using magnetron sputtering. The etched layer 2 is a 70 nm thick Poly-Si.

[0066] Steps 1-2: The first photosensitive film layer 3 is prepared by spin coating. The material of the first photosensitive film layer 3 is I-Line photoresist HTI751. The spin coating speed is 4000 rpm, the spin coating time is 40 s, and it is baked on a hot plate at 100 ℃ for 3 minutes to form a photoresist layer with a thickness of 30 nm.

[0067] Steps 1-3: SiO2 dielectric layer 4 is prepared by vacuum evaporation. The thickness of SiO2 dielectric layer 4 is 20 nm and the deposition rate is 2.5 A / s.

[0068] Steps 1-4: The second photosensitive film layer 5 was prepared by spin coating. The material of the second photosensitive film layer 5 was I-Line photoresist HTI751. The spin coating speed was 4000 rpm, the spin coating time was 40 s, and it was baked on a hot plate at 100 ℃ for 3 minutes to form a photoresist layer with a thickness of 30 nm. The resulting structure is shown below. Figure 2 As shown in Figure a.

[0069] Steps 1-5: Perform a single super-resolution exposure on the second photosensitive film layer 5. The exposure dose is 300 mJ, the aperture size of the aperture mask is 150 nm, and the period is 300 nm. The single exposure structure is as follows: Figure 2 As shown in b.

[0070] Steps 1-6: After the first exposure, the substrate is immersed in n-butyl acetate for 1 minute for negative development. Then, the substrate surface is rinsed clean with isopropanol solution and dried with N2. A columnar pattern structure with a half-period of 150 nm is obtained in the second photosensitive film layer 5. The prepared structure is as follows... Figure 2 c and Figure 3A As shown.

[0071] Steps 1-7: The columnar pattern structure is further transferred to the SiO2 dielectric layer 4 by solution wet etching. The sample is immersed in a 1:100 HF:DI aqueous solution for 10 seconds to remove the SiO2 dielectric layer 4, then rinsed thoroughly and dried with N2. The prepared structure is shown below. Figure 2 As shown in d.

[0072] Steps 1-8: The first photosensitive film layer 3 undergoes a second exposure with an exposure dose of 300 mJ. No mask is required; photolithography transfers the pattern structure of the dielectric layer to the first photosensitive film layer 3. The resulting structure is as follows: Figure 2 As shown in e.

[0073] Steps 1-9: Prepare a 1:100 HF:DI aqueous solution, immerse the above sample for 10 s to remove the SiO2 dielectric layer 4, then rinse it clean and dry it with N2.

[0074] Steps 1-10: After the second exposure, the substrate is immersed in n-butyl acetate for 1 minute for secondary negative development, then rinsed with isopropanol and dried with N2. A nanoporous structure with a half-period of 150 nm is obtained in the first photosensitive film layer 3. The prepared structure is as follows... Figure 2 China f and Figure 3B As shown.

[0075] Steps 1-11: The hole pattern structure is further transferred to the Poly-Si layer using ICP. Etching is performed using a 100 W ICP RF power and a 20 W lower electrode power, with a CHF3 mixture at 20 sccm and an SF6 mixture at 5 sccm. The resulting structure is shown below. Figure 2 As shown in g and Figure 3C As shown, a nanoporous structure with a size of 150 nm and a period of 300 nm was finally prepared.

[0076] Example 2:

[0077] The implementation steps of the nanopore fabrication method using two photolithography and two negative development techniques provided in this embodiment are as follows:

[0078] Step 2-1: Deposit an etched layer 2 on substrate 1 using magnetron sputtering. The etched layer 2 is a SiO2 layer with a thickness of 100 nm.

[0079] Step 2-2: The first photosensitive film layer 3 is prepared by spin coating. The material of the first photosensitive film layer 3 is I-Line photoresist HTI751. The spin speed is 2000 rpm, the spin coating time is 40 s, and it is baked on a hot plate at 100 ℃ for 5 minutes to form a photoresist layer with a thickness of 20 nm.

[0080] Steps 2-3: SiN dielectric layer 4 is prepared by vacuum evaporation. The thickness of SiN dielectric layer 4 is 10 nm and the deposition rate is 2.0 A / s.

[0081] Steps 2-4: The second photosensitive film layer 5 was prepared by spin coating. The material of the second photosensitive film layer 5 was 193nm photoresist ARF-88. The spin coating speed was 3000 rpm, the spin coating time was 40 s, and it was baked on a hot plate at 100 ℃ for 3 minutes to form a photoresist layer with a thickness of 60 nm. The resulting structure is shown below. Figure 2 As shown in Figure a.

[0082] Steps 2-5: Perform a single projection exposure on the second photosensitive film layer 5. The exposure dose is 50 mJ, the aperture size of the aperture mask is 60 nm, and the period is 120 nm. The single exposure structure is as follows: Figure 2 As shown in b.

[0083] Steps 2-6: After the first exposure, the substrate is immersed in n-butyl acetate for 1 min for negative development, then rinsed with isopropanol and dried with N2. A columnar structure with a half-period of 60 nm is obtained in the second photosensitive layer 5. The prepared structure is shown below. Figure 2 c and Figure 3A As shown.

[0084] Steps 2-7: The pillar pattern structure is further transferred to the SiN dielectric layer 4 by RIE etching using 20 W RF power and 20 sccm CHF3 gas. The fabricated structure is shown below. Figure 2 As shown in d.

[0085] Steps 2-8: The first photosensitive film layer 3 is subjected to a second exposure at a dose of 200 mJ. No mask is required; photolithography transfers the pattern structure of the dielectric layer to the first photosensitive film layer 3. The resulting structure is as follows: Figure 2 As shown in e.

[0086] Steps 2-9: Remove the SiN dielectric layer 4 on the surface of the first photosensitive film layer 3 by RIE etching using 20 W radio frequency power and 20 sccm CHF3 gas.

[0087] Steps 2-10: Immerse the substrate after the second exposure in n-butyl acetate for 1 minute for a second negative development, then rinse with isopropanol and dry with N2. This yields a nanoporous structure with a half-period of 60 nm in the first photosensitive film layer 3. The prepared structure is shown below. Figure 2 China f and Figure 3B As shown.

[0088] Step 2-11: The hole pattern structure is further transferred to the SiO2 layer using ICP. Etching is performed using 100 W ICP RF power and 20 W lower electrode power, with 20 sccm of CHF3 gas. The resulting structure is shown below. Figure 2 As shown in g and Figure 3C As shown, a nanoporous structure with a size of 60 nm and a period of 120 nm was finally prepared.

[0089] Based on the processing method provided in the embodiments of this disclosure, the nanopore structure prepared can have a feature size of 30 nm to 300 nm and a period of 60 nm to 500 nm.

[0090] It should be noted that the specific parameters, material types, and processing methods involved in the above examples are all for the purpose of more clearly illustrating the processing methods provided in the embodiments of this disclosure, and are not intended to limit this disclosure.

[0091] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above are merely preferred embodiments and the technical principles applied. Those skilled in the art will understand that this disclosure is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of this disclosure. Therefore, although this disclosure has been described in detail through the above embodiments, this disclosure is not limited to the above embodiments. More other equivalent embodiments may be included without departing from the concept of this disclosure, all of which fall within the scope of protection of this disclosure.

Claims

1. A method for fabricating nanopores using two photolithography steps and two negative development steps, characterized in that, include: An etchable film layer, a first photosensitive film layer, a dielectric layer, and a second photosensitive film layer are formed sequentially on a substrate, with the etchable film layer close to the substrate. The second photosensitive film layer is exposed once using a nanopore pattern mask, followed by negative development, to form a nanopillar lithography structure on the second photosensitive film layer. The pattern of the nanopillar lithography structure is transferred to the dielectric layer to form a pillar pattern structure; The first photosensitive film layer is subjected to secondary exposure using the columnar pattern structure as a masking pattern, followed by secondary negative development to form a nanoporous pattern structure on the first photosensitive film layer. The pattern of the nanopore pattern structure is transferred to the film layer to be etched to obtain the nanopore structure.

2. The method according to claim 1, characterized in that, The process of exposing the second photosensitive film layer once using a nanopore patterned mask, followed by negative development, to form a nanopillar lithography structure on the second photosensitive film layer includes: The second photosensitive film layer is exposed once using the nanopore pattern mask, so that the region of the second photosensitive film layer corresponding to the light-transmitting area of ​​the nanopore pattern mask is excited by an optical reaction and then baked to form a hydrophilic polymer that is insoluble in the negative developing solution. The second photosensitive film layer after one exposure is negatively developed using a negative development solution, thereby dissolving the area of ​​the second photosensitive film layer corresponding to the non-transparent area of ​​the nanopore pattern mask. The second photosensitive film layer after the first negative development is cleaned using an organic solution to form the nanopillar lithography structure.

3. The method according to claim 1, characterized in that, The process of using the columnar pattern structure as a masking pattern to perform secondary exposure on the first photosensitive film layer, followed by secondary negative development, to form a nanopore pattern structure on the first photosensitive film layer includes: The first photosensitive film layer is subjected to secondary exposure using the columnar pattern structure as a masking pattern, so that the first photosensitive film layer area corresponding to the light-transmitting area of ​​the columnar pattern structure is excited by an optical reaction and then baked to form a hydrophilic polymer that is insoluble in the negative developing solution. Remove the column graphic structure; A negative development solution is used to perform secondary negative development on the first photosensitive film layer after secondary exposure, dissolving the first photosensitive film layer area corresponding to the non-transparent area of ​​the columnar pattern structure. The first photosensitive film layer after secondary negative development is cleaned using an organic solution to form the nanoporous pattern structure.

4. The method according to claim 2 or 3, characterized in that, The exposure method includes one of projection lithography, super-resolution lithography, contact lithography, and electron beam lithography, and the exposure wavelength includes i-line, g-line, and 193 nm. The negative developing solution includes at least one of butyl acetate, ethyl 3-ethoxypropionate, and 2-heptanone; The organic solution includes at least one of methyl isobutyl ketone, 4-methyl-2-pentanol, and isopropanol.

5. The method according to claim 1, characterized in that, The process of forming sequentially stacked layers of a film to be etched, a first photosensitive film, a dielectric layer, and a second photosensitive film on a substrate includes: The film layer to be etched is formed on the substrate by methods such as thermal oxidation, electron beam evaporation, magnetron sputtering deposition, chemical vapor deposition, or coating. The first photosensitive film layer is formed on the film layer to be etched by means of coating or fumigation; The dielectric layer is formed on the first photosensitive film layer using electron beam evaporation, spin coating, spraying, a combination of spin coating and spraying, printing, or magnetron sputtering. The second photosensitive film layer is formed on the medium layer by coating or fumigation.

6. The method according to claim 1 or 5, characterized in that, The material of the film to be etched includes at least one of SiO2, Si3N4, Poly-Si, and TiO2; The material of the dielectric layer includes at least one of Si-BARC, SiO2, Si3N4, Poly-Si, TiN, and TiO2; The first photosensitive film layer and the second photosensitive film layer may be made of the same or different materials, and the materials of the first photosensitive film layer and the second photosensitive film layer include positive photoresist.

7. The method according to claim 1 or 5, characterized in that, The thickness of the film to be etched is 10 nm to 200 nm, the thickness of the dielectric layer is 10 nm to 50 nm, the thickness of the first photosensitive film is 10 nm to 200 nm, and the thickness of the second photosensitive film is 10 nm to 100 nm.

8. The method according to claim 1, characterized in that, The pattern of the nanopillar lithography structure is transferred to the dielectric layer by at least one of wet etching, ion beam etching, reactive ion etching, and inductively coupled plasma etching. The pattern of the nanopore pattern structure is transferred to the film layer to be etched by at least one of ion beam etching, reactive ion etching, and inductively coupled plasma etching.

9. The method according to claim 8, characterized in that, The solution used in the wet etching process includes at least one of dilute hydrofluoric acid solution, dilute sodium hydroxide solution, and dilute potassium hydroxide solution. The etching gases used in the ion beam etching, reactive ion etching, and inductively coupled plasma etching include at least one of SF6, CF4, CHF3, and Ar.

10. The method according to claim 1, characterized in that, The nanopore structure has a characteristic size of 30 nm to 300 nm and a period of 60 nm to 500 nm.

Images