Photolithography method based on a two-layer photoresist

Abstract

The present invention relates to a photolithography method based on two-layer photoresist, which includes the steps of (1) coating and drying a layer of positive photoresist on a substrate, and then coating and drying a layer of negative photoresist on the positive photoresist, (2) exposing the two layers of photoresist under an exposure source with a photomask having a stencil pattern or by focus direct writing, and then drying, (3) developing the negative photoresist with a negative developer, (4) controllably developing the positive photoresist with a positive developer, (5) forming a pattern on the substrate material by material deposition technology or etching technology, and (6) removing the photoresist. The method of the present invention is simpler than the traditional one-time exposure photolithography technology, and can achieve smaller line width than the traditional technology by contouring the pattern, and the method is widely applicable to semiconductor processes and is worthy of being widely studied and applied.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor microfabrication technology, and more particularly to a photolithography method based on a two-layer photoresist.

Background Art

[0002] The rapid development of integrated circuits depends on the development of photolithography technology, which is a related manufacturing process. Photolithography technology is the highest-precision processing technology that has been achieved so far. Photolithography technology is a precise microfabrication technology. Conventional photolithography technology uses ultraviolet light with a wavelength of 135 - 4500 Å as an image information carrier, a photoresist as an intermediate or image recording medium, realizes pattern conversion, transfer, and processing, and finally transfers the image information to a wafer, mainly a silicon wafer, or a media layer.

[0003] In principle, photolithography technology is a technology for transferring a pattern on a mask onto a substrate through a photoresist (also known as Photoresist) under light irradiation. Its main process is as follows: First, irradiate ultraviolet light on the surface of the substrate with a photoresist thin film attached through a mask to cause a chemical reaction of the photoresist in the exposed area; next, use a developing technique to dissolve and remove the photoresist in the exposed area or unexposed area to replicate the pattern on the mask onto the photoresist thin film; finally, use an etching technique to transfer the pattern onto the substrate. Among them, photoresists can be mainly divided into positive photoresists and negative photoresists. Positive photoresists have the property that the exposed part undergoes a photochemical reaction and dissolves in the developer, while the unexposed part does not dissolve in the developer. Negative photoresists have the property that the exposed part becomes insoluble in the developer due to crosslinking hardening or photochemical reaction, while the unexposed part is soluble in the developer.

[0004] Photolithography is the most important processing technology for integrated circuits, and its role is similar to that of a lathe in a metalworking factory. In the entire chip manufacturing process, the technology of photolithography is indispensable for the implementation of almost all processes. Photolithography is also the most important technology in chip manufacturing, accounting for more than 35% of the chip manufacturing cost.

[0005] Photolithography technology is mainly divided into optical lithography including ultraviolet light source (UV), deep ultraviolet light source (DUV), extreme ultraviolet light source (EUV) as common light sources by the exposure light source, and particle beam lithography generally including X-ray, electron beam and ion beam lithography, etc.

[0006] Usually, in optical lithography, UV can only achieve a pattern resolution of about 1 micron. On the other hand, although DUV and EUV can achieve higher resolutions, expensive equipment that can only be obtained by large companies in the industry is required. Also, in particle beam lithography, electron beam lithography and focused ion beam lithography can also improve the resolution to a certain extent, but it takes time and requires a drawing process that cycles many times, greatly reducing the working efficiency.

Summary of the Invention

Means for Solving the Problems

[0007] The object of the present invention is to provide a photolithography method based on a two-layer photoresist that is simple in method, has a smaller line width than the prior art, is widely applicable to semiconductor processes, and has broad research and application value in order to overcome the above-mentioned disadvantages of the prior art.

[0008] The object of the present invention can be achieved by the following technical solutions: By utilizing the differences in the responses of positive and negative photoresists, i.e., positive photoresist and negative photoresist, to the light source and the differences in the exposure energies obtained during exposure, and by using the difference in the pattern sizes after actually developing the mutually compatible positive and negative photoresists, a contour line pattern based on the characteristics of the original pattern is obtained, achieving a contour line width smaller than the characteristic line width of the original pattern and a doubling of the line density. Subsequently, by combining an etching process for the substrate material or the deposited material, the pattern can be further transferred to the target material. The specific solution is as follows: A photolithography method based on a two-layer photoresist, comprising: (1) cleaning the substrate material, coating a layer of positive photoresist on the substrate and drying it, and further coating a layer of negative photoresist on the positive photoresist and drying it; (2) exposing the two-layer photoresist under an exposure light source using a photomask having a stencil pattern or by direct focus writing, forming exposure patterns of different sizes on the negative photoresist and the positive photoresist respectively after exposure, and drying; (3) developing the negative photoresist with a negative developer; (4) controllably developing the positive photoresist with a positive developer, washing away only the edge portion of the exposure pattern on the positive photoresist to expose the substrate material; (5) forming a pattern on the substrate material by a material deposition technique or an etching technique; (6) removing the photoresist. A photolithography method based on a two-layer photoresist.

[0009] Furthermore, by performing the above step (4), the stencil pattern is converted into a contour line pattern, and by performing the above step (5), the contour line pattern is transferred to the substrate material.

[0010] Furthermore, the substrate material includes semiconductors, metals, insulators, polymers, or composite materials. For example, it is a silicon wafer or a silicon wafer with a silicon oxide film deposited on its surface.

[0011] Furthermore, a method for transferring a contour linear pattern after two-layer lithography onto a deposition material on a silicon wafer substrate, specifically including the following steps: (1) Spin-coating a positive photoresist: Place the cleaned silicon wafer in a spin-coating apparatus, fix it under vacuum, spray or drop-apply the positive photoresist, perform spin-coating of the photoresist, and then dry it. (2) Spin-coating a negative photoresist: Place the cooled silicon wafer in a spin-coating apparatus, fix it under vacuum, spray or drop-apply the negative photoresist, perform spin-coating of the negative photoresist, and then dry it. (3) Exposure: Closely fix the silicon wafer substrate that has undergone the above steps on an exposure stage, place it under an exposure light source, turn on the light source, perform an exposure operation through a mask or an exposure light source focusing device, adjust the exposure time or exposure amount based on the type of photoresist pair set and the thickness of the photoresist layer, and after the exposure is completed, move the exposed silicon wafer to a heating table to dry it. (4) Development: After the post-bake is completed and the silicon wafer is cooled to room temperature, develop it separately. The process is as follows: Immerse the silicon wafer after photolithography in a negative photoresist developer to wash the unexposed negative photoresist on the silicon wafer, then take out the silicon wafer, wash it with deionized water, and dry it with nitrogen gas (note: if the developers for positive and negative photoresists are the same, the deionized water washing step can be omitted). Furthermore, place the silicon wafer in a positive photoresist developer, without completely removing the unexposed positive photoresist under the exposed negative photoresist, then take out the silicon wafer, wash it with deionized water, and dry it with nitrogen gas to create a contour linear pattern based on the stencil pattern. (6) Material Deposition (for metallic materials): Place the developed silicon wafer inside the vapor deposition apparatus, and thermally deposit a 5-nanometer titanium thin film and a 50-nanometer gold thin film respectively. Use the 5-nanometer titanium thin film as the adhesion layer for the gold thin film. (7) Photoresist Removal: After cooling the cavity, release the vacuum and take out the silicon wafer after plating. Immerse the silicon wafer in acetone and perform ultrasonic cleaning until all the photoresist is removed, leaving the metal contour line pattern.

[0012] Furthermore, regarding fabricating a contour line pattern of silicon oxide on the surface of a silicon wafer with a thick silicon oxide film grown on its surface, specifically, it includes the following steps: (1) Spin-coat positive photoresist: For the silicon oxide wafer, perform spin-coating of positive photoresist and then dry it. (2) Spin-coat negative photoresist: Place the cooled silicon wafer in the spin-coating apparatus, fix it under vacuum, perform spin-coating of negative photoresist, and then dry it. (3) Exposure: Closely fix the silicon wafer substrate that has gone through the above steps on the exposure table, place it directly under the exposure light source, turn on the light source, and perform the exposure operation through a mask or an exposure light source focusing device. Adjust the exposure time or exposure amount based on the type of photoresist pair set and the thickness of the photoresist layer. After the exposure is completed, move the exposed silicon wafer to the heating table to dry it. (4) Development: After the post-bake is completed and the silicon wafer is cooled to room temperature, perform development separately. The process is as follows: Put the silicon wafer after photolithography into the negative photoresist developer to wash the unexposed negative photoresist on the silicon wafer. Then, take out the silicon wafer, wash it with deionized water, and dry it with nitrogen gas (note: when the developers for positive and negative photoresists are the same, the deionized water washing step can be omitted). Furthermore, the silicon wafer is placed in a positive photoresist developer, and the unexposed positive photoresist under the exposed negative photoresist is not completely removed. Then, the silicon wafer is taken out, washed with deionized water, and dried with nitrogen gas to form a contour linear pattern based on the stencil pattern. (5) Dry etching: Place the silicon wafer in an ion etching machine and etch the silica mask layer with plasma gas, then a square contour linear pattern can be used to remove the previously deposited silica layer and expose the underlying silicon base. (6) Photoresist removal: Immerse the silicon wafer in acetone and perform ultrasonic cleaning until all the photoresist is removed to form a square contour line of silica.

[0013] Furthermore, the spin coating process includes spin coating at a rotational speed of 500 - 8000 rpm, and the drying temperature after spin coating is 30°C - 300°C.

[0014] Furthermore, the spin coating process includes spin coating at a rotational speed of 2000 - 8000 rpm for 30 - 40 s, and the drying temperature after spin coating is 90 - 100°C, and the time is 30 - 90 seconds.

[0015] Furthermore, the exposure uses a single exposure method.

[0016] Furthermore, multiple exposure methods may be used for the exposure. That is, it may be realized by dividing it into multiple exposures with shorter time or lower dose and overlapping them. Furthermore, the exposure light source may be an ultraviolet light source, a deep ultraviolet light source, an extreme ultraviolet light source, an ion beam, an electron beam, or an X-ray.

[0017] Furthermore, the wavelength of the exposure light source is 1 - 500 nm, and the drying temperature after exposure is 30 - 300°C.

[0018] Furthermore, the wavelength of the exposure light source is 350 - 400 nm, and the drying temperature after exposure is 95 - 105°C.

[0019] Furthermore, the positive photoresist includes positive ultraviolet photoresist, positive deep ultraviolet photoresist, positive extreme ultraviolet photoresist, positive electron beam photoresist, positive ion beam photoresist, or positive X-ray photoresist, and includes MICROPOSIT S1800 series photoresist, BCI-3511 photoresist, AZ series photoresist (e.g., AZ111, AZ1500, AZ3300, AZ4999, AZ6600, AZ8112, AZ3000, AZ1075, AZ700, AZ900), HNR 500 series photoresist, OiR series photoresist, TDMR-AR80 HP 6CP, PR1 series photoresist, ma-P 1200 series photoresist, SPR series photoresist (e.g., SPR 220, SPR 660, SPR3000, etc.), PMMA series photoresist, and the like.

[0020] The negative photoresist includes negative ultraviolet photoresist, negative deep ultraviolet photoresist, negative developing deep ultraviolet photoresist, negative extreme ultraviolet photoresist, negative electron beam photoresist, negative ion beam photoresist, or negative X-ray photoresist, and includes NANO SU-8 Series, HSQ, AZ series photoresist (e.g., AZ N4000, AZ N6000), HNR series photoresist, SC series photoresist, ma-N series photoresist (e.g., ma-N 400, ma-N 1400), AZ nLOF 2000 Series (registered trademark), AZ nLOF 5500 Photoresis (registered trademark), NR7-PY Series, NR9-PY Series, JSR WPR Series, NR71 Series, NR9 Series, etc., and is not limited thereto.

[0021] Furthermore, the photoresist developer is generally a developer corresponding to the photoresist to be used. For example, the positive photoresist developer may be 2.38% TMAH, MF-26A, and the negative photoresist developer may be 2.38% TMAH, SU-8 developer, etc.

[0022] Furthermore, the characteristic line width or characteristic size of the stencil pattern is 2 nm - 1000 μm.

[0023] Furthermore, the characteristic line width or characteristic size of the stencil pattern is 2 nm - 1 μm.

[0024] Furthermore, the material deposition technology includes, but is not limited to, electrochemical deposition, plating, CVD deposition, laser sputtering, magnetron sputtering, thermal evaporation, electron beam evaporation, or atomic deposition.

[0025] The etching technology includes wet etching or dry etching. The wet etching includes electrochemical etching or selective etching liquid etching, and the dry etching includes ion etching or chemical reaction ion etching.

[0026] Furthermore, in the exposure step, by projection exposure, under the exposure light source, through the photomask having the stencil pattern, the two-layer photoresist is exposed.

[0027] Furthermore, in the exposure step, by shadow exposure, under the exposure light source, through the photomask having the stencil pattern, the two-layer photoresist is exposed.

[0028] Furthermore, in the exposure step, by reflection exposure, under the exposure light source, by reflecting on the photomask having the stencil pattern, the two-layer photoresist is exposed.

[0029] Furthermore, the focus direct writing includes, but is not limited to, ultraviolet light direct writing, deep ultraviolet light direct writing, extreme ultraviolet light direct writing, ion beam direct writing, electron beam direct writing, or X-ray direct writing.

[0030] Furthermore, the substrate material includes semiconductors, metals, insulators, polymers, or composite materials.

[0031] The present invention further provides a photolithography system, comprising a spin coating unit, a drying unit, an exposure unit, a development unit, a deposition etching unit, and a photoresist removing unit. The photolithography system (1) A step of spin coating a layer of positive photoresist on a substrate by the spin coating unit, drying it by the drying unit, and further spin coating a layer of negative photoresist compatible with the positive photoresist on the positive photoresist by the spin coating unit and drying it by the drying unit; (2) A step of exposing the two-layer photoresist by the exposure unit under an exposure light source using a photomask having a stencil pattern or by focus direct writing, forming exposure patterns of different sizes on the negative photoresist and the positive photoresist respectively, and drying it by the drying unit; (3) A step of developing the negative photoresist with a negative developer by the development unit; (4) A step of controllably developing the positive photoresist with a positive developer by the development unit, washing away only the edge portion of the exposure pattern on the positive photoresist, and exposing the substrate material; (5) A step of forming a pattern on the substrate material by a material deposition technique or an etching technique by the deposition etching unit; (6) A step of removing the photoresist by the photoresist removing unit; is executed.

[0032] The present invention further provides a photolithography system control method for controlling the above photolithography system to execute each step.

[0033] The present invention further provides a computer device comprising a memory, a processor, and a computer program stored in the memory and executable by the processor, wherein the processor realizes the above photolithography system control method when executing the computer program.

[0034] The present invention further provides a computer-readable medium storing a computer program that realizes the above photolithography system control method when executed by a processor.

[0035] Compared with the prior art, the present invention has the following advantages: (1) The present invention continues the characteristics of conventional photolithography, such as high efficiency, low cost, and simple operation, and makes up for the limitations of conventional photolithography in pattern fabrication with sub-micron resolution. (2) The present invention realizes the miniaturization of dimensions with respect to the original mask pattern.

Brief Description of the Drawings

[0036]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0037] Hereinafter, the present invention will be described in detail in conjunction with the accompanying drawings and specific examples. This example is implemented on the premise of the technical solution of the present invention, and detailed embodiments and specific operation procedures are shown, but the protection scope of the present invention is not limited to the following examples.

[0038] <Photolithography Method Based on Two-Layer Photoresist> The present invention provides a photolithography method based on a two-layer photoresist, and the method includes the following steps: (1) Applying a positive photoresist on a substrate and drying it, further applying a negative photoresist on the positive photoresist and drying it, The positive photoresist includes a positive ultraviolet photoresist, a positive deep ultraviolet photoresist, a positive extreme ultraviolet photoresist, a positive electron beam photoresist, a positive ion beam photoresist, or a positive X-ray photoresist. The negative photoresist includes a negative ultraviolet photoresist, a negative deep ultraviolet photoresist, a negative extreme ultraviolet photoresist, a negative electron beam photoresist, a negative ion beam photoresist, or a negative X-ray photoresist.

[0039] In fact, it is necessary to confirm the compatibility of different model numbers of positive and negative photoresists in advance, and the following two pairs of positive and negative photoresist sets are provided: As the first group, the positive photoresist model number is SPR 660, and the negative photoresist model number is SU-82. As the second group, the positive photoresist model number is AZ 1500, and the negative photoresist model number is AZ nlof 2020. In the process of spin-coating the positive photoresist (such as SPR 660, AZ 1500), first spin-coat at a rotation speed of 800-1000 rpm for 5-10 seconds (this step can be omitted), then spin-coat at a rotation speed of 2000-5000 rpm for 30-40 seconds, and bake at 90-100 °C for 30-50 seconds.

[0040] As a process of spin-coating a negative photoresist (e.g., SU-82, AZ nlof2020), first spin-coat at a rotational speed of 800 - 1000 rpm for 5 - 10 seconds (this step can be omitted), then spin-coat at a rotational speed of 4000 - 8000 rpm for 30 - 40 seconds, and bake at 95 - 100 °C for 60 - 90 seconds. Different rotational speeds determine the degree of the photoresist film thickness. According to different film thicknesses, adjust the pre-bake temperature, time, and subsequent exposure amount, exposure time, development time, etc.

[0041] Here, the substrate material includes semiconductors, metals, insulators, polymers, or composite materials.

[0042] (2) Under the exposure light source, use a photomask with a stencil pattern or by direct focus writing, expose the two-layer photoresist once. After exposure, form exposure patterns of different sizes on the negative photoresist and the positive photoresist respectively, and then dry. Here, the exposure light source includes ultraviolet light sources, deep ultraviolet light sources, extreme ultraviolet light sources, ion beams, electron beams, or X-rays. Direct focus writing includes ultraviolet light direct writing, deep ultraviolet light direct writing, extreme ultraviolet light direct writing, ion beam direct writing, electron beam direct writing, or X-ray direct writing. The characteristic line width or characteristic size of the stencil pattern is 2 nm - 1000 μm.

[0043] After fixing the pre-baked silicon wafer under the mask, place it under the ultraviolet light source, turn on the ultraviolet light source to perform photolithography, and adjust the exposure time according to the positive-negative photoresist pair set used. In the example of the aforementioned pair, for the photoresist pair sets of SPR 660 and SU-82, AZ 1500 and AZ nlof2020, at a wavelength of 350 - 400 nm, 100 - 200 mJ / cm 2The exposure flux is applied. The use of the UV wavelength and the exposure flux must take into account the ultraviolet absorption effects of negative photoresists (such as SU-82, AZ nlof2020, etc.) with different thicknesses to ensure that the underlying positive photoresists (such as SPR 660, AZ 1500, etc.) can obtain sufficient exposure flux. Since the photoresist pairs of SPR660 and SU-82, AZ1500 and AZ nlof 2020 respond differently to the exposure flux at a specific wavelength, different-sized patterns based on the mask pattern can be obtained.

[0044] (3) Developing the negative photoresist with a negative developer, (4) Controllably developing the positive photoresist with a positive developer, washing away only the edge part of the exposure pattern on the positive photoresist, and exposing the substrate material to convert the stencil pattern into a contour line pattern. In the example of the above pair, after the exposure is completed, the mask is removed, and the exposed silicon wafer is transferred to a heating stage and baked at 95 - 105 °C for 40 - 90 seconds. After the post-baking is completed, each development is carried out. The process is as follows: The silicon wafer after photolithography is placed in the corresponding negative photoresist developer (for example, SU-8 developer, TMAH-2.38%) to wash away the unexposed negative photoresist on the silicon wafer. Then the silicon wafer is taken out, washed with water, dried with a nitrogen gas stream, and then the silicon wafer is placed in the corresponding positive photoresist developer (for example, MF-26A, TMAH-2.38%) to wash away the exposed and unexposed positive photoresist on the silicon wafer. The unexposed negative photoresist under the exposed negative photoresist is not completely removed. Then, the silicon wafer is taken out, washed with water, and dried with a nitrogen gas stream. A punched line pattern based on the stencil pattern is fabricated.

[0045] When selecting a developer, if the main components of the selected developer are different, the developer for the negative photoresist will not act on the positive photoresist, ensuring a step-by-step development process and enabling the obtaining of the highest quality patterns. Also, as a result of research, when developing a positive photoresist simultaneously with the negative developer used, by overlapping the development times of two steps, after removing the unexposed negative photoresist, partial development of the positive photoresist is achieved. As a result of confirmation with a scanning electron microscope, it has no significant impact on the contour patterning. From the above, it is necessary to conduct cross-experiments on the positive photoresist, negative photoresist, and corresponding developers before the experiment to formulate an optimal development process.

[0046] (5) Transferring a contour line pattern to a substrate material by a material deposition technique or an etching technique. Here, examples of the material deposition technique include electrochemical deposition, plating, CVD deposition, laser sputtering, magnetron sputtering, thermal evaporation, electron beam evaporation, and atomic deposition. The etching technique includes wet etching or dry etching. The wet etching includes electrochemical etching or selective etching liquid etching, and the dry etching includes ion etching or chemical reaction ion etching.

[0047] (6) Removing the photoresist.

[0048] <Photolithography system> The present invention further provides a photolithography system, which includes a spin coating unit, a drying unit, an exposure unit, a development unit, a deposition etching unit, and a photoresist removal unit, and the photolithography system implements the photolithography method based on the two-layer photoresist. Specifically, (1) Spin-coat a single layer of positive photoresist on the substrate by a spin-coating unit, dry it by a drying unit, and further spin-coat a single layer of negative photoresist compatible with the positive photoresist on the positive photoresist by the spin-coating unit and dry it by the drying unit; (2) Expose the two-layer photoresist under an exposure light source by an exposure unit using a photomask having a stencil pattern or by direct focus writing to form exposure patterns of different sizes on the negative photoresist and the positive photoresist respectively, and dry it by the drying unit; (3) Develop the negative photoresist with a negative developer by a developing unit; (4) Develop the positive photoresist controllably with a positive developer by the developing unit to wash away only the edge portion of the exposure pattern on the positive photoresist and expose the substrate material; (5) Form a pattern on the substrate material by a deposition etching unit using a material deposition technique or an etching technique; (6) Remove the photoresist by a photoresist removing unit. Execute the above steps.

[0049] The present invention further provides a photolithography system control method for controlling the above photolithography system to execute each step.

[0050] The present invention further provides a computer device comprising a memory, a processor, and a computer program stored in the memory and executable by the processor, wherein the processor realizes the above photolithography system control method when executing the computer program.

[0051] The present invention further provides a computer-readable medium storing a computer program which realizes the above photolithography system control method when executed by a processor.

[0052] <Example> The following describes in detail specific embodiments of a photolithography method based on a two-layer photoresist of the present invention.

[0053] Example 1 In this Example 1, the fabrication process of a gold nanowire array based on the photolithography technology of a positive-negative two-layer photoresist is as shown in FIG. 1, and specifically includes the following steps: (1) Cleaning of the silicon wafer: Ultrasonic cleaning with concentrated sulfuric acid for 20 - 30 minutes, Ultrasonic cleaning with deionized water for 20 - 30 minutes, Ultrasonic cleaning with ethanol for 20 - 30 minutes, Dry the silicon wafer substrate with nitrogen gas, place it in a dry etching apparatus, and clean it by oxygen plasma etching for 1 - 2 minutes.

[0054] (2) Spin-coating of positive photoresist Place the cleaned silicon wafer in a spin-coating apparatus and fix it under vacuum. Drop 2 - 4 drops of positive photoresist SPR660 or AZ1500 with a burette, perform spin-coating of the photoresist under the conditions of 800 rpm × 5 s + 2500 rpm × 30 s, and bake at 95 - 100 °C for 40 seconds.

[0055] (3) Spin-coating of negative photoresist Place the cooled silicon wafer in a spin-coating apparatus and fix it under vacuum. Drop 2 - 4 drops of negative photoresist SU-82 or AZnlof2020 with a burette, perform spin-coating of the photoresist under the conditions of 1000 rpm × 5 s + 4000 rpm × 40 s, and bake at 100 - 110 °C for 60 seconds.

[0056] (4) Ultraviolet exposure The silicon wafer substrate that has gone through the above steps is closely fixed under a mask of a 5-μm line array, evacuated, placed directly under an ultraviolet light source, and the light source is turned on to perform photolithography. Adjust the exposure time according to the type of photoresist pair set and the thickness of the photoresist layer. After the exposure is completed, remove the mask, move the exposed silicon wafer to a heating stage, and bake it at 100 °C for 45 seconds. Here, the exposure flux is, for example, 100 mJ / cm 2 and can be changed as needed.

[0057] (5) Development After the post-baking is completed and the silicon wafer has cooled to room temperature, development is performed separately. The process is as follows: Place the silicon wafer after photolithography in the corresponding negative photoresist developer SU-8 developer or TMAH-2.38% to wash away the unexposed negative photoresist on the silicon wafer. Then, take out the silicon wafer, wash it with deionized water, and dry it with a nitrogen gas flow (note: when the developers for positive and negative photoresists are the same, the steps of washing with deionized water and drying with nitrogen gas can be omitted), further place the silicon wafer in the corresponding positive photoresist developer MF-26A or TMAH-2.38% to completely remove the unexposed positive photoresist under the exposed negative photoresist. Then, take out the silicon wafer, wash it with water, and dry it with a nitrogen gas flow. A contour line pattern based on the stencil pattern is fabricated.

[0058] (6) Deposition of materials Place the developed silicon wafer in a deposition apparatus, evacuate it to a vacuum of 10 -6 Pa, and thermally deposit a 5-nanometer titanium thin film at a rate of 1 Å / s and a 50-nanometer gold thin film at a rate of 0.5 Å / s. A 5-nm titanium thin film is used as the adhesion layer for the gold thin film.

[0059] (7) Removal of photoresist After cooling the cavity, release the vacuum and take out the silicon wafer after plating. Immerse the silicon wafer in acetone and ultrasonically clean it until all the photoresist is removed, leaving a gold nanowire pattern with a line width of ~200 nm. The scanning electron micrograph of the metal nanowires obtained by this method shows that the characteristic line width is less than 200 nm, as shown in Figure 3.

[0060] Example 2 In this Example 2, based on the photolithography technology of a positive-negative two-layer photoresist, the process of creating a contour pattern of silicon oxide on the surface of a silicon wafer with a 100-nm-thick silicon oxide film grown on the surface is shown in Figure 2. Specifically, it includes the following steps: (1) Spin-coat a positive photoresist For the silicon oxide silicon wafer, spin-coat a positive photoresist SPR660 or AZ1500 for 30 - 40 seconds at 2500 rpm, and then bake it at 95 - 100 °C for 40 seconds.

[0061] (2) Spin-coat a negative photoresist Place the cooled silicon wafer in a spin-coater and fix it under vacuum. Spin-coat a negative photoresist SU-82 or AZnlof2020 for 30 - 40 seconds under the condition of 4000 rpm, and bake it at 100 - 110 °C for 60 seconds.

[0062] (3) Ultraviolet exposure Fix the silicon wafer substrate that has gone through the above steps in close contact under a mask with a 5-μm square pattern, evacuate it, place it directly under an ultraviolet light source, turn on the light source, and perform photolithography work. Adjust the exposure time according to the type of photoresist pair set and the thickness of the photoresist layer. After the exposure is completed, remove the mask, move the exposed silicon wafer to a heating stage, and bake it at 100 °C for 45 seconds. Here, the exposure flux is, for example, 100 mJ / cm 2 and can be changed as needed.

[0063] (4) Development After post-baking is completed and the silicon wafer is cooled to room temperature, development is performed separately. The process is as follows: The silicon wafer after photolithography is placed in a negative photoresist developer SU-8 developer or TMAH-2.38% to wash away the unexposed negative photoresist on the silicon wafer. Then, the silicon wafer is taken out and washed with deionized water and dried with a nitrogen gas flow (Note: When the developers for positive and negative photoresists are the same, the steps of washing with deionized water and drying with nitrogen gas can be omitted). Furthermore, the silicon wafer is placed in a positive photoresist developer MF-26A or TMAH-2.38% without completely removing the unexposed positive photoresist under the exposed negative photoresist. Then, the silicon wafer is taken out, washed with water, and dried with a nitrogen gas flow. A square contour line pattern based on the stencil pattern is fabricated.

[0064] (5) Dry etching The silicon wafer is placed in an ion etching machine, and the silica mask layer is etched with a plasma gas, so that in the square contour line pattern, the previously deposited silica layer can be removed to expose the underlying silicon substrate.

[0065] (6) Removal of photoresist The silicon wafer is immersed in acetone and ultrasonic cleaning is performed until all the photoresist is removed to create a square contour line of silica.

[0066] Example 3 Regarding exposure, in Examples 1 and 2, an exposure method was used in which the silicon wafer substrate was closely fixed under the mask and evacuated and placed under an ultraviolet light source, but the present invention is not limited thereto. For example, the photolithography technology of the positive-negative two-layer photoresist of the present invention can also use a projection exposure method. Hereinafter, in this Example 3, the main steps of the photolithography technology of the positive-negative two-layer photoresist of the present invention will be described by taking a projection-type ultraviolet photolithography system having an ultraviolet light wavelength of less than 400 nm as an example.

[0067] (1) Spin coat a positive photoresist Place the cleaned silicon wafer on a spin coater and fix it under vacuum. Drop and apply the positive photoresist with a burette, perform spin coating of the photoresist under the conditions of 500 rpm × 5 s + 4000 rpm × 40 s, and bake at 130 °C for 10 seconds.

[0068] (2) Spin coat a negative photoresist Place the cooled silicon wafer on a spin coater and fix it under vacuum. Drop and apply the negative photoresist with a burette, perform spin coating of the photoresist under the conditions of 500 rpm × 5 s + 4000 rpm × 40 s, and bake at 90 °C for 60 seconds.

[0069] (3) Projection ultraviolet exposure Adhere and fix the silicon wafer substrate that has undergone the above steps tightly on the sample stage of a projection lithography apparatus, and perform projection ultraviolet exposure through a photomask. Adjust the exposure time according to the type of photoresist pair set and the thickness of the photoresist layer. After the exposure is completed, move the exposed silicon wafer to a heating stage and bake at 110 °C for 90 seconds. Here, the exposure flux is, for example, 100 mJ / cm 2 and can be changed as required.

[0070] (4) Development After the post-bake is completed and the silicon wafer is cooled to room temperature, perform development separately. The process is as follows: Place the silicon wafer after photolithography in a negative photoresist developer (TMAH - 2.38%) to wash the unexposed negative photoresist on the silicon wafer. Using a positive photoresist developer (TMAH - 2.38%), partially develop and remove the unexposed positive photoresist under the exposed negative photoresist. Then, take out the silicon wafer, wash it with water, and dry it with a nitrogen gas flow. Produce a contour line pattern based on the stencil pattern.

[0071] (5) Subsequently, a convex or concave structure can be realized in combination with steps such as further material deposition or dry / wet etching. However, since it is similar to steps (6) and (7) of Example 1 and steps (5) and (6) of Example 2, it will not be repeatedly described here.

[0072] Example 4 Regarding exposure, in Examples 1 and 2, an exposure method was used in which the silicon wafer substrate was closely fixed under a mask, evacuated, and placed directly under an ultraviolet light source. In Example 3, a projection exposure method was used. However, the present invention is not limited to this. For example, the photolithography technology of the positive-negative two-layer photoresist of the present invention can also use an electron beam direct writing exposure method. Hereinafter, in this Example 4, the main steps of the photolithography technology of the positive-negative two-layer photoresist of the present invention using electron beam direct writing exposure will be described.

[0073] (1) Spin-coat a positive photoresist Place the washed silicon wafer on a spin-coater and fix it under vacuum. Dropwise apply the positive electron beam photoresist PMMA, perform spin-coating of the photoresist, and perform pre-baking.

[0074] (2) Spin-coat a negative photoresist Place the cooled silicon wafer on a spin-coater and fix it under vacuum. Dropwise apply the negative electron beam photoresist HSQ, perform spin-coating of the photoresist, and perform pre-baking.

[0075] (3) Electron beam direct writing exposure Place the silicon wafer substrate that has undergone the above steps into an electron beam direct writing system and perform an electron beam direct writing operation. Adjust the electron beam exposure amount according to the type of photoresist pair set and the thickness of the photoresist layer. After the electron beam direct writing exposure is completed, move the exposed silicon wafer onto a heating stage and perform post-baking. Here, the exposure flux is, for example, 500 μC / cm 2 and can be changed as needed.

[0076] (4) Development After the post-bake is completed and the silicon wafer is cooled to room temperature, development is carried out separately. The process is as follows: The silicon wafer after photolithography is placed in an electron beam negative photoresist developer (TMAH developer) to wash the unexposed negative photoresist on the silicon wafer. Then, the silicon wafer is taken out, washed with water, and dried with a nitrogen gas stream. Next, the silicon wafer is placed in a positive electron beam photoresist developer (MIBK:IPA developer) to partially remove the unexposed positive photoresist PMMA under the exposed negative photoresist. Then, the silicon wafer is taken out, washed with water, and dried with a nitrogen gas stream. A contour line pattern based on the stencil pattern is fabricated.

[0077] (5) Subsequently, a convex or concave structure can be realized in combination with steps such as further material deposition or dry / wet etching. Since it is similar to steps (6)(7) of Example 1 and steps (5)(6) of Example 2, it will not be repeatedly described here.

[0078] Example 5 Regarding exposure, in Examples 1 and 2, an exposure method was used in which the silicon wafer substrate was closely fixed under a mask and evacuated, and placed directly under an ultraviolet light source. In Example 3, a projection exposure method was used. In Example 4, an electron beam direct writing exposure method was used. However, the present invention is not limited thereto. For example, the photolithography technology of the positive-negative two-layer photoresist of the present invention can also use an ultraviolet direct writing exposure method. Hereinafter, in this Example 5, the main steps of the photolithography technology of the positive-negative two-layer photoresist of the present invention using ultraviolet direct writing exposure will be described.

[0079] (1) Spin-coat a positive photoresist Place the washed silicon wafer on the spin coater and fix it under vacuum. Drop and apply a positive photoresist (e.g., AZ 1500) with a burette, perform spin coating of the photoresist under the conditions of 500 rpm × 5 s + 4000 rpm × 40 s, and bake at 100 °C for 10 seconds.

[0080] (2) Spin coat negative photoresist Place the cooled silicon wafer on the spin coater and fix it under vacuum. Drop and apply a negative photoresist (e.g., AZ nlof2020) with a burette, perform spin coating of the photoresist under the conditions of 500 rpm × 5 s + 4000 rpm × 40 s, and bake at 110 °C for 60 seconds.

[0081] (3) UV direct writing exposure Fix the silicon wafer substrate that has undergone the above process in close contact under the exposure light source, turn on the UV direct writing system, and perform the direct writing exposure operation. Adjust the exposure time according to the type of photoresist pair set and the thickness of the photoresist layer. After the exposure is completed, remove the mask, move the exposed silicon wafer to the heating stage, and bake at 110 °C for 60 seconds. Here, the exposure flux is, for example, 100 mJ / cm 2 and can be changed as required.

[0082] (4) Development After the post-bake is completed and the silicon wafer is cooled to room temperature, perform development separately. The process is as follows: Place the silicon wafer after photolithography in a negative photoresist developer (TMAH - 2.38%) to wash the unexposed negative photoresist on the silicon wafer. Using a positive photoresist developer (TMAH - 2.38%), partially develop and remove the unexposed positive photoresist under the exposed negative photoresist. Then, take out the silicon wafer, wash it with water, and dry it with a nitrogen gas stream. Produce a contour line pattern based on the stencil pattern.

[0083] (5) Subsequently, a convex or concave structure can be realized in combination with steps such as further material deposition or dry / wet etching. Since it is similar to steps (6) and (7) in Example 1 and steps (5) and (6) in Example 2, it will not be repeatedly described here.

[0084] The above are only better embodiments of the present invention and do not limit the present invention to other forms. Those skilled in the art can make changes or modifications to equivalent embodiments with equivalent changes by using the technical content disclosed above. However, as long as it does not deviate from the content of the technical solution of the present invention, any simple modification, equivalent change, and deformation made to the above embodiments based on the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Industrial Applicability

[0085] The photolithography method based on the two-layer photoresist of the present invention can be widely applied in fields such as semiconductor processes and chip manufacturing, and has broad research and application value.

Claims

1. A photolithography method based on a two-layer photoresist, comprising: (1) spin-coating and drying a layer of positive photoresist on a substrate, and further spin-coating and drying a layer of negative photoresist compatible with the positive photoresist on the positive photoresist; (2) exposing the two-layer photoresist using a photomask having a stencil pattern or by direct focusing exposure under an exposure light source, and forming different-sized exposure patterns on the negative photoresist and the positive photoresist respectively such that the exposure pattern of the positive photoresist is larger than that of the negative photoresist because the two-layer photoresists have different responses to the exposure flux at a specific wavelength, and then drying; (3) developing the negative photoresist with a negative developer; (4) controllably developing the positive photoresist with a positive developer to wash away only the edge portion of the exposure pattern on the positive photoresist, thereby exposing the substrate material; (5) forming a pattern on the substrate material using a material deposition technique or an etching technique; (6) removing the photoresist. A photolithography method based on a two-layer photoresist, characterized by comprising the above steps.

2. By performing step (4), the stencil pattern is converted into a contour line pattern. By performing step (5), the contour line pattern is transferred onto the substrate material. A photolithography method based on a two-layer photoresist according to claim 1, characterized by the above.

3. The spin-coating process includes spin-coating at a rotational speed of 500 - 8000 rpm, and the drying temperature after spin-coating is 30 - 300°C. The photolithography method based on a two-layer photoresist according to claim 1, characterized in that...

4. The exposure uses a single-exposure method. The photolithography method based on a two-layer photoresist according to claim 1, characterized in that...

5. The exposure uses a multi-exposure method. The photolithography method based on a two-layer photoresist according to claim 1, characterized in that...

6. The exposure light source includes an ultraviolet light source, a deep ultraviolet light source, an extreme ultraviolet light source, an ion beam, an electron beam, or an X-ray. The photolithography method based on a two-layer photoresist according to claim 1, characterized in that...

7. The wavelength of the exposure light source is 1 to 500 nm, and the drying temperature after exposure is 30 to 300 °C. The photolithography method based on a two-layer photoresist according to claim 1 or 6, characterized in that...

8. The positive photoresist includes a positive ultraviolet photoresist, a positive deep ultraviolet photoresist, a positive extreme ultraviolet photoresist, a positive electron beam photoresist, a positive ion beam photoresist, or a positive X-ray photoresist. The negative photoresist includes a negative ultraviolet photoresist, a negative deep ultraviolet photoresist, a negative-developed deep ultraviolet photoresist, a negative extreme ultraviolet photoresist, a negative electron beam photoresist, a negative ion beam photoresist, or a positive X-ray photoresist. The photolithography method based on a two-layer photoresist according to claim 1, characterized in that...

9. The developer is a developer corresponding to the photoresist used. The photolithography method based on a two-layer photoresist according to claim 1, characterized in that...

10. The characteristic line width or characteristic size of the stencil pattern is 2 nm to 1000 μm. The photolithography method based on a two-layer photoresist according to claim 1, characterized in that.

11. The material deposition technology includes, but is not limited to, electrochemical deposition, plating, CVD deposition, laser sputtering, magnetron sputtering, thermal evaporation, electron beam evaporation, or atomic deposition. The etching technology includes wet etching or dry etching. The wet etching includes electrochemical etching or selective etching liquid etching. The dry etching includes ion etching or chemical reaction ion etching. The photolithography method based on a two-layer photoresist according to claim 1, characterized in that.

12. In step (2), by projection exposure, under the exposure light source, through a photomask having a stencil pattern, a two-layer photoresist is exposed. The photolithography method based on a two-layer photoresist according to claim 1, characterized in that.

13. In step (2), by shadow exposure, under the exposure light source, through a photomask having a stencil pattern, a two-layer photoresist is exposed. The photolithography method based on a two-layer photoresist according to claim 1, characterized in that.

14. In step (2), by reflection exposure, under the exposure light source, by reflecting on a photomask having a stencil pattern, a two-layer photoresist is exposed. The photolithography method based on a two-layer photoresist according to claim 1, characterized in that.

15. The focus direct writing includes, but is not limited to, ultraviolet light direct writing, deep ultraviolet light direct writing, extreme ultraviolet light direct writing, ion beam direct writing, electron beam direct writing, or X-ray direct writing. A photolithography method based on a two-layer photoresist according to claim 1, characterized in that...

16. The substrate material includes a semiconductor, a metal, an insulator, a polymer, or a composite material. A photolithography method based on a two-layer photoresist according to claim 1, characterized in that...

17. A photolithography system comprising a spin coating unit, a drying unit, an exposure unit, a development unit, a deposition etching unit, and a photoresist removal unit, (1) Spin-coating a layer of positive photoresist on a substrate by the spin coating unit, drying it by the drying unit, and further spin-coating a layer of negative photoresist compatible with the positive photoresist on the positive photoresist by the spin coating unit, and drying it by the drying unit; (2) Exposing the two-layer photoresist by the exposure unit under an exposure light source using a photomask having a stencil pattern or by direct writing with focus, so that the exposure patterns of the positive photoresist and the negative photoresist are different in size such that the exposure pattern of the positive photoresist is larger than that of the negative photoresist due to the different responses of the two-layer photoresist to the exposure flux at a specific wavelength, and drying it by the drying unit; (3) Developing the negative photoresist with a negative developer by the development unit; (4) Controllably developing the positive photoresist with a positive developer by the development unit, washing away only the edge portion of the exposure pattern on the positive photoresist to expose the substrate material; (5) Forming a pattern on the substrate material by a material deposition technique or an etching technique by the deposition etching unit; (6) Removing the photoresist by the photoresist removal unit. A photolithography system that executes the above steps.

18. A photolithography system control method for controlling the photolithography system according to claim 17 to execute each step.

19. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable by the processor, wherein the processor realizes the photolithography system control method according to claim 18 when executing the computer program.

20. A computer-readable medium storing a computer program that realizes the photolithography system control method according to claim 18 when executed by a processor.

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