Method for forming photoresist pattern and projection exposure apparatus

Abstract

The present disclosure provides a photoresist pattern forming method and a projection exposure device. The photoresist pattern forming method comprises: providing a photoresist layer, placing the photoresist layer below a projection objective, and placing a light refracting plate between the photoresist layer and the projection objective; and performing an exposure process on the photoresist layer by the projection objective and the light refracting plate to form an exposure image on the photoresist layer, wherein the light refracting plate is used to reduce the wavelength of light waves incident on the photoresist layer. In the photoresist pattern forming method and the projection exposure device provided by the present disclosure, the light refracting plate arranged between the photoresist layer and the projection objective reduces the wavelength of light waves incident on the photoresist layer, thereby improving the resolution and the accuracy of the photoresist pattern.

Description

Technical Field

[0001] This disclosure relates to the field of semiconductor technology, and more particularly to a method for forming a photoresist pattern and a projection exposure apparatus. Background Technology

[0002] Photolithography is one of the most important processes in the fabrication of integrated circuits (ICs). It is used to form desired patterns on semiconductor substrates. With the development of integrated circuit technology and the continuous shrinking of the critical dimensions of semiconductor devices, the requirements for the precision of photolithography are becoming increasingly stringent. Summary of the Invention

[0003] The following is an overview of the subject matter described in detail in this disclosure. This overview is not intended to limit the scope of the claims.

[0004] This disclosure provides a method for forming a photoresist pattern and a projection exposure apparatus.

[0005] The first aspect of this disclosure provides a method for forming a photoresist pattern, the method being applied to a projection exposure apparatus, the projection exposure apparatus including a projection lens and a light refraction plate, the method comprising:

[0006] A photoresist layer is provided and placed below the projection lens, with the light refraction plate located between the photoresist layer and the projection lens;

[0007] The photoresist layer is exposed through the projection lens and the light refraction plate to form an exposure image on the photoresist layer. The light refraction plate is used to reduce the wavelength of the light wave incident on the photoresist layer.

[0008] According to some embodiments of this disclosure, the step of exposing the photoresist layer through the projection lens and the light refraction plate to form an exposed image on the photoresist layer includes:

[0009] The projection lens emits a first incident light beam with a first wavelength toward the photoresist layer. The first incident light beam is incident on the light refraction plate and is refracted by the light refraction plate into a second incident light beam with a second wavelength, wherein the second wavelength is smaller than the first wavelength.

[0010] The second incident light beam is incident on the photoresist layer, and the second incident light beam forms the exposure image on the photoresist layer.

[0011] According to some embodiments of this disclosure, the exposure process is performed in a first medium, and the first incident light beam emitted by the projection lens toward the photoresist layer passes through the first medium layer before being incident on the photoresist layer.

[0012] According to some embodiments of this disclosure, the first dielectric layer is formed between the photoresist layer and the light refraction plate, or the first dielectric layer is formed between the light refraction plate and the projection lens of the projection exposure apparatus.

[0013] According to some embodiments of this disclosure, the refractive index of the light refractor is greater than that of the first dielectric layer, and the refractive index of the light refractor is less than that of the photoresist layer.

[0014] According to some embodiments of this disclosure, when the first dielectric layer is formed between the photoresist layer and the light refraction plate, the thickness of the first dielectric layer is less than one-tenth of the second wavelength.

[0015] According to some embodiments of this disclosure, the projection exposure apparatus includes a mask stage, and the formation method further includes:

[0016] A photomask is provided, and the photomask is placed on the photomask stage, on which a photomask pattern is formed;

[0017] The photoresist layer is exposed based on the photomask.

[0018] A second aspect of this disclosure provides a projection exposure apparatus, the projection exposure apparatus comprising:

[0019] An illumination system for emitting an initial beam of light;

[0020] A projection lens, which is used to transmit an initial light beam and emit an incident light beam;

[0021] A light refraction plate is disposed on one side of the projection lens, and the light refraction plate is used to reduce the wavelength of the incident light beam emitted by the projection lens.

[0022] According to some embodiments of this disclosure, the thickness of the light refraction plate is greater than one-tenth of the wavelength of the incident light beam emitted by the projection lens.

[0023] According to some embodiments of this disclosure, the projection exposure apparatus further includes:

[0024] A first dielectric layer is disposed between the light refraction plate and the projection lens.

[0025] According to some embodiments of this disclosure, the device further includes an objective lens surround structure surrounding the bottom of the projection objective lens, and the light refraction plate is connected to the objective lens surround structure, the objective lens surround structure being used to provide the first dielectric layer.

[0026] According to some embodiments of this disclosure, the thickness of the first dielectric layer is less than the thickness of the light refraction plate.

[0027] According to some embodiments of this disclosure, the refractive index of the light refraction plate is greater than the refractive index of the first dielectric layer.

[0028] According to some embodiments of this disclosure, the first medium layer includes a first medium, which is water or air.

[0029] According to some embodiments of this disclosure, the light refraction plate is attached to the bottom of the projection lens.

[0030] According to some embodiments of this disclosure, the device further includes an objective lens surround structure surrounding the bottom of the projection objective lens, and the objective lens surround structure is used to provide a first dielectric layer disposed between the light refraction plate and the photoresist layer.

[0031] According to some embodiments of this disclosure, the thickness of the first dielectric layer is less than one-tenth of the wavelength of the incident light beam emitted by the projection lens.

[0032] In the photoresist pattern formation method and projection exposure apparatus provided in this disclosure, the wavelength of light incident on the photoresist layer is reduced by a light refraction plate disposed between the photoresist layer and the projection lens, thereby improving the resolution and the accuracy of the photoresist pattern.

[0033] After reading and understanding the accompanying diagrams and detailed descriptions, the other aspects can be understood. Attached Figure Description

[0034] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of these embodiments. In these drawings, similar reference numerals are used to denote similar elements. The drawings described below are some embodiments of the present disclosure, but not all embodiments. Other drawings will be readily available to those skilled in the art based on these drawings without inventive effort.

[0035] Figure 1 This is a flowchart illustrating a method for forming a photoresist pattern according to an exemplary embodiment.

[0036] Figure 2This is a flowchart illustrating a method for forming a photoresist structure according to an exemplary embodiment.

[0037] Figure 3 This is a flowchart of the exposure process in a method for forming a photoresist pattern according to an exemplary embodiment.

[0038] Figure 4 This is a flowchart of the exposure process in a method for forming a photoresist pattern according to an exemplary embodiment.

[0039] Figure 5 This is a flowchart illustrating a method for forming a photoresist pattern according to an exemplary embodiment.

[0040] Figure 6 This is a schematic diagram illustrating the formation of a photoresist layer on a target layer in a method for forming a photoresist pattern according to an exemplary embodiment.

[0041] Figure 7 This is a schematic diagram illustrating the exposure process of a photoresist layer using a projection exposure apparatus according to an exemplary embodiment.

[0042] Figure 8 This is a schematic diagram illustrating the exposure process of a photoresist layer using a projection exposure apparatus according to an exemplary embodiment.

[0043] Figure 9 This is a schematic diagram illustrating the exposure process of a photoresist layer using a projection exposure apparatus according to an exemplary embodiment.

[0044] Figure 10 This is a schematic diagram illustrating the formation of an exposure image in a photoresist layer in a method for forming a photoresist pattern according to an exemplary embodiment.

[0045] Figure 11 This is a schematic diagram illustrating the development process of a photoresist layer in a method for forming a photoresist pattern according to an exemplary embodiment.

[0046] Figure 12 This is a schematic diagram illustrating the exposure process of a projection exposure apparatus according to an exemplary embodiment.

[0047] Figure 13 This is a schematic diagram illustrating the exposure process of a projection exposure apparatus according to an exemplary embodiment.

[0048] Figure label:

[0049] 10. Photoresist layer; 20. Target layer; 30. Exposure image; 40. Projection exposure apparatus; 41. Illumination system; 42. Projection objective lens; 43. Light refraction plate; 431. Refraction plate body; 432. Connecting part; 44. First dielectric layer; 45. Objective lens surround structure; 451. First dielectric limiting part; 5. First incident beam; 6. Second incident beam; 7. Mask. Detailed Implementation

[0050] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions in the disclosed embodiments will be clearly and completely described below with reference to the 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 creative effort are within the scope of protection of this disclosure. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this disclosure can be arbitrarily combined with each other.

[0051] This disclosure provides an exemplary embodiment of a method for forming a photoresist pattern, such as... Figure 1 As shown, Figure 1 A flowchart illustrating a method for forming a photoresist pattern according to an exemplary embodiment of the present disclosure is shown. Figures 6-11 This is a schematic diagram illustrating the various stages of the photoresist pattern formation process. The following section combines... Figures 6-11 The method for forming photoresist patterns is introduced.

[0052] This disclosure provides an exemplary embodiment of a method for forming a photoresist pattern, which is applied to a projection exposure apparatus. A projection exposure apparatus is an exposure device where the photomask does not directly contact the wafer, but rather transfers the image using a projection method similar to a projector. Figure 7 As shown, the projection exposure apparatus 40 includes a projection lens 42 and a light refraction plate 43. The light beam emitted by the projection lens 42 is refracted by the light refraction plate 43 and then incident on the photoresist layer 10. Figure 1 As shown, the method for forming a photoresist pattern includes the following steps:

[0053] Step S100: Provide a photoresist layer, place the photoresist layer below the projection lens, and position the light refraction plate between the photoresist layer and the projection lens.

[0054] like Figure 7 As shown, the light refraction plate 43 is located between the photoresist layer 10 and the projection lens 42, so that the incident light beam emitted from the projection lens 42 is refracted by the light refraction plate 43 before entering the photoresist layer 10.

[0055] Step S200: Expose the photoresist layer using a projection lens and a light refraction plate to form an exposure image on the photoresist layer. The light refraction plate is used to reduce the wavelength of the light wave incident on the photoresist layer.

[0056] In some embodiments, the light refraction plate 43 can reduce the wavelength of the light wave incident on the photoresist layer 10. When the photoresist layer 10 is exposed, the first incident light beam 5 emitted from the projection lens 42 is refracted by the light refraction plate 43 and converted into a second incident light beam 6 with a smaller wavelength, which is then incident on the photoresist layer 10 to form an exposure image in the photoresist layer 10.

[0057] In photolithography, the resolution affects the quality of the exposed image; higher resolution results in a more precise exposed image. Photolithography resolution follows the Rayleigh equation:

[0058]

[0059] Where R is the lithographic resolution; k1 is the process constant; λ is the exposure wavelength; and NA is the numerical aperture (NA) of the projection lens.

[0060] Photolithography resolution is used to characterize the minimum linewidth achievable in a photolithography process. According to Rayleigh's formula, the smaller the wavelength of the incident light wave, the smaller the process constant, and the smaller the linewidth that can be obtained, that is, the higher the photolithography precision.

[0061] In some embodiments, the method for forming photoresist patterns reduces the exposure wavelength incident on the photoresist layer 10 by using a light refraction plate, thereby improving the photolithography resolution and resulting in higher precision of the exposure image formed on the photoresist layer 10. In some embodiments, the method for forming photoresist patterns can be used to form exposure processes with smaller photolithography feature sizes and more complex and diverse structures.

[0062] According to an exemplary embodiment, some embodiments illustrate the formation process of the photoresist layer 10 in step S100 above, such as... Figure 2 As shown, it includes the following steps:

[0063] Step S110: Coat the target layer with a photoresist solution, the photoresist solution comprising a photoresist composition.

[0064] Photoresist solutions include photoresist compositions and solvents. The photoresist composition includes a photoacid generator (PAG), polymer resin, etc. (See reference...) Figure 6 A photoresist solution is coated on the target layer 20, and the mass percentage of the solvent in the photoresist solution is 10% to 30%.

[0065] Step S120: Soft bake the target layer coated with photoresist solution to evaporate the solvent in the photoresist solution, and the photoresist composition adheres to the target layer to form a photoresist layer.

[0066] Reference Figure 6 The target layer 20 coated with the photoresist solution is soft-baked and heated. Some of the photoresist solution escapes upon heating, reducing the solvent content. The remaining photoresist solution forms a photoresist layer 10 on the surface of the target layer 20. The photoresist layer 10 has a higher concentration of the photoresist composition and thus higher photosensitivity. In some embodiments, the target layer 20 coated with the photoresist solution can be soft-baked at 100°C for 60 seconds.

[0067] According to an exemplary embodiment, some embodiments are descriptions of how step S200 is implemented. During implementation, such as... Figure 3 As shown, it includes the following steps:

[0068] S210: The projection lens emits a first incident light beam with a first wavelength toward the photoresist layer. The first incident light beam is incident on the light refraction plate and is refracted by the light refraction plate into a second incident light beam with a second wavelength, wherein the second wavelength is smaller than the first wavelength.

[0069] Reference Figure 7 As shown, the first incident beam 5, which is the beam emitted from the projection lens 42, has a first wavelength λ1, and the second incident beam 6, which is the beam after passing through the light refraction plate 43, has a second wavelength λ2. The second wavelength is less than the first wavelength, i.e., λ2 < λ1.

[0070] S220, the second incident beam is incident on the photoresist layer, and the second incident beam forms an exposure image on the photoresist layer.

[0071] In some embodiments, the first incident beam 5 is refracted by the light refraction plate 43, converting the first incident beam 5 into a second incident beam 6 with a smaller wavelength. The second incident beam 6 is incident on the photoresist layer 10, thereby forming an exposure image with higher photolithographic resolution.

[0072] In some embodiments, a light refraction plate 43 is provided in the propagation path of the incident light beam into the photoresist layer 10. The refractive index of the light propagation medium changes, converting the first incident light beam 5 into a second incident light beam 6 with a smaller wavelength, thereby reducing the wavelength of the light wave incident into the photoresist layer 10. This overcomes the problem that in the photolithography process, the wavelength of the light wave emitted by the photolithography equipment is difficult to further reduce due to limitations in equipment and process development.

[0073] In some embodiments, the thickness h1 of the light refraction plate 43 is greater than one-tenth of the first wavelength λ1, so that the first incident light beam 5 can be refracted by the light refraction plate 43 when it passes through the light refraction plate 43.

[0074] According to an exemplary embodiment, the exposure process is performed in a first medium, and the first incident light beam 5 emitted by the projection lens 42 towards the photoresist layer 10 passes through the first medium before being incident on the photoresist layer 10, i.e., as shown in the example. Figure 8 As shown, the projection exposure apparatus 40 also includes a first dielectric layer 44, which is disposed between the projection lens 42 and the photoresist layer 10. The first dielectric layer 44 includes a first medium, which, exemplarily, is water or air.

[0075] In some embodiments, a first dielectric layer 44 is formed between the projection lens 42 and the light refraction plate 43, such as Figure 4 As shown, step S210 includes:

[0076] S211, The projection lens emits a first incident beam with a first wavelength;

[0077] S212, The first incident beam is incident on the first dielectric layer, and the first incident beam is refracted by the first dielectric layer into a third incident beam with a third wavelength.

[0078] S213. The third incident beam is incident on the light refraction plate, and the third incident beam is refracted by the light refraction plate into a second incident beam with a second wavelength, wherein the second wavelength is less than the third wavelength.

[0079] like Figure 8 As shown, the third incident beam, i.e. the beam refracted by the first dielectric layer 44, has a third wavelength λ3, and the second incident beam 6, i.e. the beam refracted by the light refracting plate 43, has a second wavelength λ2. The second wavelength is less than the third wavelength, i.e., λ2 < λ3.

[0080] In some embodiments, the refractive index of the first dielectric layer 44 is n1, and the refractive index of the light refractor 43 is n2, where n2 > n1. That is, the refractive index n2 of the light refractor 43 is greater than the refractive index n1 of the first dielectric layer 44. As an example, the material of the light refractor 43 can be high-refractive-index optical glass or high-refractive-index organic optical resin, such as polyimide film.

[0081] When light propagates through two layers of media with different refractive indices, the relationship between the light wave and the refractive index is as follows:

[0082]

[0083] In some embodiments, the refractive index n2 of the light refraction plate 43 is greater than the refractive index n1 of the first dielectric layer 44. The first incident beam 5 enters the first dielectric layer 44 from the projection lens 42, and is refracted by the first dielectric layer 44 into the third incident beam. The third incident beam enters the light refraction plate 43 from the first dielectric layer 44, and is refracted by the light refraction plate 43 into the second incident beam 6. That is, the third incident beam enters the propagation medium with a smaller refractive index from the propagation medium with a larger refractive index, and the third incident beam is formed into the second incident beam 6.

[0084] In some embodiments, the refractive index of the light refracting plate 43 and the refractive index of the first dielectric layer 44 refer to the light refractive index of the light refracting plate 43 and the first dielectric layer 44 for the incident light beam, respectively. For example, when the incident light beam is deep ultraviolet (DUV), the refractive index refers to the refractive index for deep ultraviolet light.

[0085] In some embodiments, a first dielectric layer 44 and a light refraction plate 43 are disposed in the propagation path of the incident light beam into the photoresist layer 10. Due to the change in the refractive index of the light propagation medium, the first dielectric layer 44 converts the first incident light beam into a third incident light beam with a smaller wavelength, and the light refraction plate 43 converts the third incident light beam into a second incident light beam with an even smaller wavelength. As the incident light beam passes through the first dielectric layer 44 and the light refraction plate 43 in sequence and enters the photoresist layer 10, the incident light wave undergoes two conversions, that is, the wavelength of the incident light wave decreases twice. By utilizing the influence of the propagation medium on the wavelength of the light wave, the wavelength of the light wave exposed in the photoresist layer 10 to form the exposed image is reduced, which further improves the resolution and results in a higher precision and better quality photoresist pattern.

[0086] In some embodiments, the refractive index of the light refraction plate 43 is less than the refractive index of the photoresist layer 10. Based on the aforementioned relationship between light waves and refractive index, the refractive index of the light waves entering the photoresist layer 10 can be further reduced.

[0087] According to an exemplary embodiment, such as Figure 8 As shown, the thickness h2 of the first dielectric layer 44 is less than the thickness h1 of the light refraction plate 43 to prevent the first dielectric layer 44 from absorbing too much light wave and to ensure the transmittance of the incident light beam from the light refraction plate 43 to the photoresist layer 10. In some embodiments, the thickness h2 of the first dielectric layer 44 is set as small as possible to reduce the light wave absorbed by the first dielectric layer 44 and increase the transmittance of the incident light beam, thereby resulting in a higher accuracy of the formed exposure image. According to an exemplary embodiment, as Figure 9As shown, the first dielectric layer 44 is formed between the photoresist layer 10 and the light refraction plate 43. Thus, the first incident light beam 5 with a first wavelength emitted by the projection lens 42 is incident on the light refraction plate 43. The first incident light beam 5 is refracted by the light refraction plate 43 into a second incident light beam 6 with a second wavelength. The second incident light beam 6 passes through the first dielectric layer 44 and then enters the photoresist layer 10.

[0088] The refractive index of the light refractor 43 is greater than that of the first dielectric layer 44, and less than that of the photoresist layer 10. For example, when the first dielectric layer 3 is air, the refractive index n2 of the light refractor 43 is greater than 1; when the first dielectric layer 3 is water, the refractive index n2 of the light refractor 43 is greater than 1.44. This design allows for greater flexibility in the selection of materials for the light refractor 43, which is beneficial for cost reduction. Furthermore, the refraction of light waves by the light refractor 43 can reduce the wavelength of the light waves. The thickness of the first dielectric layer 44 is less than one-tenth of the second wavelength. Therefore, the change in wavelength of the second incident beam when it reaches the first dielectric layer 44 is negligible, thus avoiding refraction that increases the wavelength of the light waves when they pass through the first dielectric layer 44, further ensuring that the light waves incident on the photoresist layer 10 have a smaller wavelength.

[0089] In some embodiments, a light refraction plate 43 and a first dielectric layer 44 are disposed in the propagation path of the incident light beam into the photoresist layer 10. Due to the change in the refractive index of the light propagation medium, the light refraction plate 43 converts the first incident light beam 5 into a second incident light beam 6 with a shorter wavelength. Since the thickness of the first dielectric layer 44 is less than one-tenth of the second wavelength, the wavelength change of the second incident light beam 6 after passing through the first dielectric layer 44 can be ignored. For example, the light wavelengths of the lithography equipment include, but are not limited to, G-line (436nm), I-line (365nm), KrF (248nm), ArF (193nm), and extreme ultraviolet (EUV) light (13.5nm). Correspondingly, for example, when using a KrF lithography equipment, the thickness of the first dielectric layer 44 can be set to be less than 24.8nm; when using an ArF lithography equipment, the thickness of the first dielectric layer 44 can be set to be less than 19.3nm; and when using an EUV lithography equipment, the thickness of the first dielectric layer 44 can be set to be less than 1.35nm.

[0090] Because the photoresist layer 10 has a high refractive index, the wavelength will be further reduced when the light beam is incident into the photoresist layer 10. As a result, the incident light wave undergoes two conversions during the process of the incident light beam passing through the light refraction plate 43 and the first dielectric layer 44 and then into the photoresist layer 10. That is, the wavelength of the incident light wave is reduced twice. By utilizing the influence of the propagation medium on the wavelength of the light wave, the wavelength of the light wave that is exposed in the photoresist layer 10 to form the exposed image is reduced, which further improves the resolution and results in a photoresist pattern with higher precision and better quality.

[0091] like Figure 5 As shown, an exemplary embodiment of this disclosure provides a method for forming a photoresist pattern, comprising the following steps:

[0092] Step S10: Provide a photoresist layer, place the photoresist layer below the projection lens, and position the light refraction plate between the photoresist layer and the projection lens.

[0093] Step S10 in some embodiments is implemented in the same way as step S100 in the above embodiments, and will not be described again here.

[0094] Step S20: Provide a mask, place the mask on the mask stage, and form a mask pattern on the mask.

[0095] Continue to refer to Figure 7 A photomask 7 is provided, which includes a photomask pattern. The photomask 7 is positioned between the illumination system 41 and the projection lens 42 of the projection exposure apparatus 40. The photoresist layer 10 is placed below the projection lens 42, and the projection exposure apparatus 40 is adjusted so that the projection lens 42 is aligned with the photoresist layer 10.

[0096] Step S30: Based on the photomask, the photoresist layer is exposed through a projection lens and a light refraction plate to form an exposure image on the photoresist layer.

[0097] In some embodiments, such as Figure 7 and Figure 10 As shown, the illumination system 41 emits an initial beam perpendicularly to the photoresist layer 10. Part of the initial beam passes through the mask 7 and is incident on the projection lens 42. The projection lens 42 focuses the initial beam and refracts it into a first incident beam 5, the wavelength of which is λ1. When the first incident beam 5 passes through the light refraction plate 43, it is refracted into a second incident beam 6, the wavelength of which is λ2, which is less than λ1. Figure 10 As shown, the second incident light beam 6 is incident on the photoresist layer 10. The photoresist layer 10, after being irradiated by the second incident light beam 6, undergoes a photosensitive chemical reaction, forming an exposure image 30. The exposure image 30 is a miniature pattern of the mask pattern. Photoresist in a photoresist layer can generally be divided into positive and negative types. In terms of photosensitive chemical reactions, positive photoresist is characterized by the long-chain molecules of the polymer in the photoresist composition being broken into short-chain molecules by light exposure, while negative photoresist is characterized by the short-chain molecules of the polymer in the photoresist composition being cross-linked into long-chain molecules by light exposure. The short-chain polymer molecules can be dissolved by the developer; therefore, the exposed portion of the positive photoresist is removed, while the exposed portion of the negative photoresist is retained.

[0098] Step S40: Develop the photoresist layer to create a patterned photoresist layer as the photoresist pattern.

[0099] like Figure 12 As shown, a developer is sprayed onto the photoresist layer 10, covering the entire surface of the photoresist layer 10 so that the developer can completely immerse the photoresist layer 10. The developer reacts with the soluble areas in the photoresist layer 10, dissolving the soluble areas of the photoresist layer 10, thereby revealing the exposed image 30 on the photoresist layer and forming a photoresist pattern.

[0100] In some embodiments, the development time is adjusted according to the composition of the photoresist layer 10 and the concentration of the developer, so that the soluble photoresist layer 10 can be fully dissolved in the developer, but without causing over-development and affecting the outline of the formed photoresist pattern.

[0101] After developing the photoresist layer 10, the photoresist layer 10 is cleaned to remove the developer solution containing dissolved photoresist and excess developer solution. Deionized water can be sprayed onto the photoresist layer 10; the flowing deionized water carries away the developer solution containing dissolved photoresist and excess developer solution.

[0102] Step S50: Perform hard baking treatment on the photoresist layer.

[0103] The remaining photoresist layer 10 is hard-baked at a temperature of 130℃~200℃ for 20~40 minutes to allow the solvent in the photoresist layer 10 to completely escape and to further polymerize the photoresist layer 10, thereby enhancing its etching resistance.

[0104] In some embodiments, the formation method improves the photolithographic resolution of the photoresist pattern by using the light refraction plate 43. The photoresist pattern is a miniature image of the mask pattern, and the formed photoresist pattern has clear boundaries and high dimensional accuracy.

[0105] A second aspect of this disclosure provides a projection exposure apparatus, such as... Figure 7 As shown, the projection exposure apparatus 40 includes an illumination system 41, a projection lens 42, and a light refraction plate 43. The illumination system 41 emits an initial light beam, the projection lens 42 transmits the initial light beam, and the light refraction plate 43 is disposed on one side (the light-emitting side) of the projection lens 42. Thus, the initial light beam emitted by the illumination system 41 is transmitted through the projection lens 42 to the light refraction plate 43, and after refraction by the light refraction plate 43, it is incident on the photoresist layer 10. The light refraction plate 43 reduces the wavelength of the light beam emitted by the projection lens 42, resulting in a smaller wavelength of light incident on the photoresist layer 10, thereby improving the lithographic resolution. Therefore, in some embodiments, the projection exposure apparatus 40 can achieve higher precision in the exposure image formed on the photoresist layer 10, thereby enabling an exposure process with smaller lithographic feature sizes and more complex and diverse structures.

[0106] In some embodiments, the thickness h1 of the light refraction plate 43 is greater than one-tenth of the wavelength of the incident light beam emitted by the projection lens 42, so that the light beam can be refracted by the light refraction plate 43 when it passes through it. Accordingly, for example, when using a KrF lithography apparatus, the thickness h1 of the light refraction plate 43 can be set to be greater than 24.8 nm; when using an ArF lithography apparatus, the thickness h1 of the light refraction plate 43 can be set to be greater than 19.3 nm; and when using an EUV lithography apparatus, the thickness h1 of the light refraction plate 43 can be set to be greater than 1.35 nm.

[0107] According to an exemplary embodiment, such as Figure 12 As shown, the projection exposure apparatus 40 also includes a first dielectric layer 44, which is disposed between the light refraction plate 43 and the projection lens 42. The first dielectric layer 44 includes a first medium, which is exemplarily water or air. The refractive index of the first dielectric layer 44 is n1, and the refractive index of the light refraction plate 43 is n2, where n2 > n1. Thus, as the light beam emitted from the projection lens 42 passes through the first dielectric layer 44 and the light refraction plate 43 and is incident on the photoresist layer 10, the incident light wave undergoes two conversions, that is, the wavelength of the incident light wave is reduced twice. By utilizing the influence of the propagation medium on the wavelength of the light wave, the wavelength of the light wave exposed in the photoresist layer 10 to form the exposed image is reduced, further improving the resolution and resulting in a photoresist pattern with higher precision and better quality.

[0108] In some embodiments, the refractive index of the light refraction plate 43 is less than the refractive index of the photoresist layer 10. Based on the aforementioned relationship between light waves and refractive index, the refractive index of the light waves entering the photoresist layer 10 can be further reduced.

[0109] According to an exemplary embodiment, the thickness h2 of the first dielectric layer 44 is less than the thickness h1 of the light refraction plate 43 to prevent the first dielectric layer 44 from absorbing too much light wave and to ensure the transmittance of the incident light beam from the light refraction plate 43 to the photoresist layer 10. In some embodiments, the thickness h2 of the first dielectric layer 44 is set as small as possible to reduce the light wave absorbed by the first dielectric layer 44 and increase the transmittance of the incident light beam, so as to make the formed exposure image more accurate.

[0110] In some embodiments, such as Figure 12As shown, the projection exposure apparatus 40 also includes an objective lens surround structure 45, which surrounds the bottom of the projection objective lens 42. A light refraction plate 43 is connected to the objective lens surround structure 45. For example, the light refraction plate 43 is connected to the objective lens surround structure 45 by means of bonding, thereby fixing the light refraction plate 43 onto the projection exposure apparatus 40. As an example, the light refraction plate 43 includes a refraction plate body 431 and a connecting portion 432 surrounding the refraction plate body 431. The refraction plate body 431 is located directly below the projection objective lens 42. The third incident light beam is refracted by the refraction plate body 431 into a second incident light beam 6. The connecting portion 432, located around the refraction plate body 431, is connected to the objective lens surround structure 45.

[0111] Continue to refer to Figure 12 A first medium limiting portion 451 is provided on the objective lens surrounding structure 45, surrounding the first medium layer 44. The first medium limiting portion 451 is used to limit the area where the first medium 44, such as water, is located, thereby preventing leakage of the first medium 44. As an example, the first medium limiting portion 451 includes a gas outlet, and the gas discharged from the gas outlet forms a barrier to prevent leakage of the first medium. The light refraction plate 43 is connected to the periphery of the first medium limiting portion 451. As an example, such as... Figure 12 As shown, the connecting portion 432 of the light refraction plate 43 is connected to the periphery of the first medium limiting portion 451 to prevent the arrangement of the light refraction plate 43 from affecting the area limitation of the first medium by the first medium limiting portion 451 on the first medium.

[0112] According to an exemplary embodiment, such as Figure 13 As shown, the light refraction plate 43 is attached to the bottom of the projection lens 42, and the light refraction plate 43 can be connected to the projection lens 42 by means of bonding or other methods. As an example, the light refraction plate 43 is in the shape of a cover and is fastened to the bottom of the projection lens 42 to improve the reliability of the connection between the light refraction plate 43 and the projection lens 42. In some embodiments of the projection exposure apparatus, a first dielectric layer 44 can be provided between the projection exposure apparatus 40 and the photoresist layer 10, such as between the light refraction plate 43 and the photoresist layer 10. In some embodiments, the refractive index of the light refraction plate 43 is greater than the refractive index of the first dielectric layer 44, and the refractive index of the light refraction plate 43 is less than the refractive index of the photoresist layer 10. On the one hand, this makes the material of the light refraction plate 43 more flexible and helps to reduce costs; on the other hand, it can reduce the wavelength of the light wave by refracting the light wave using the light refraction plate 43.

[0113] In the use of the projection exposure apparatus 40, the thickness of the first dielectric layer 44 is controlled to be less than one-tenth of the second wavelength. This ensures that the wavelength change of the second incident beam 6 when it strikes the first dielectric layer 44 is negligible, thus preventing refraction and increasing the wavelength of the light wave as it passes through the first dielectric layer 44. This further guarantees that the light wave incident on the photoresist layer 10 has a smaller wavelength. It is understood that the aforementioned thickness of the first dielectric layer 44 refers to the thickness of the first dielectric layer 44 located between the light refraction plate 43 and the photoresist layer 10. By utilizing the influence of the propagation medium on the wavelength of the light wave, the wavelength of the light wave exposed in the photoresist layer 10 to form the exposed image is reduced, further improving the resolution and resulting in a more precise and higher-quality photoresist pattern.

[0114] In some embodiments, such as Figure 13 As shown, the projection exposure apparatus 40 also includes an objective lens surround structure 45, which surrounds the projection objective lens 42. A first medium limiting portion 451 is disposed on the objective lens surround structure 45, surrounding the first medium layer 44. The first medium limiting portion 451 is used to limit the area where the first medium, such as water, is located, thereby preventing leakage of the first medium. As an example, the first medium limiting portion 451 includes a gas outlet, and the gas discharged from the gas outlet forms a barrier to prevent leakage of the first medium.

[0115] In the photoresist pattern formation method and projection exposure apparatus provided in this disclosure, the wavelength of light incident on the photoresist layer is reduced by a light refraction plate disposed between the photoresist layer and the projection lens, thereby improving the resolution and the accuracy of the photoresist pattern.

[0116] The various embodiments or implementation methods described in this specification are presented in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referred to each other.

[0117] In the description of this specification, references to the terms "embodiment," "exemplary embodiment," "some implementation," "illustrated implementation," "example," etc., refer to specific features, structures, materials, or characteristics described in connection with an implementation or example that are included in at least one implementation or example of this disclosure.

[0118] In this specification, the illustrative expressions of the terms used do not necessarily refer to the same implementation or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more implementations or examples.

[0119] In the description of this disclosure, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this disclosure.

[0120] It is understood that the terms "first," "second," etc., as used in this disclosure may be used to describe various structures, but these structures are not limited by these terms. These terms are only used to distinguish one structure from another.

[0121] In one or more accompanying drawings, the same elements are represented by similar reference numerals. For clarity, many parts in the drawings are not drawn to scale. Furthermore, certain well-known parts may not be shown. For simplicity, a structure obtained after several steps may be depicted in a single drawing. Many specific details of this disclosure, such as the structure, materials, dimensions, processing methods, and techniques of the devices, are described below to provide a clearer understanding of the disclosure. However, as those skilled in the art will understand, this disclosure may be implemented without adhering to these specific details.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this disclosure, and are not intended to limit them. Although this disclosure has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this disclosure.

Claims

1. A method for forming a photoresist pattern, characterized in that, The formation method is applied to a projection exposure apparatus, which includes a projection objective lens, a first dielectric layer, an objective lens surround structure, and a light refraction plate. The formation method includes: A photoresist layer is provided and placed below the projection lens, with the light refraction plate located between the photoresist layer and the projection lens; The photoresist layer is exposed using the projection lens and the light refraction plate to form an exposed image on the photoresist layer. The light refraction plate is used to reduce the wavelength of the light incident on the photoresist layer. The objective lens surround structure surrounds the bottom of the projection objective lens, and the light refraction plate is connected to the objective lens surround structure. The objective lens surround structure provides the first dielectric layer, which is confined between the light refraction plate and the projection objective lens. The refractive index of the light refraction plate is greater than the refractive index of the first dielectric layer and less than the refractive index of the photoresist layer. The thickness of the first dielectric layer is less than the thickness of the light refraction plate. The material of the light refraction plate is polyimide.

2. The method for forming a photoresist pattern according to claim 1, characterized in that, The step of exposing the photoresist layer through the projection lens and the light refraction plate to form an exposed image on the photoresist layer includes: The projection lens emits a first incident light beam with a first wavelength toward the photoresist layer. The first incident light beam is incident on the light refraction plate and is refracted by the light refraction plate into a second incident light beam with a second wavelength, wherein the second wavelength is smaller than the first wavelength. The second incident light beam is incident on the photoresist layer, and the second incident light beam forms the exposure image on the photoresist layer.

3. The method for forming a photoresist pattern according to claim 2, characterized in that, The exposure process is performed in the first medium, and the first incident light beam emitted by the projection lens toward the photoresist layer passes through the first medium layer before being incident on the photoresist layer.

4. The method for forming a photoresist pattern according to claim 2, characterized in that, The thickness of the first dielectric layer is less than one-tenth of the second wavelength.

5. The method for forming a photoresist pattern according to claim 1, characterized in that, The projection exposure apparatus includes a mask stage, and the forming method further includes: A photomask is provided, and the photomask is placed on the photomask stage, on which a photomask pattern is formed; Based on the photomask, the photoresist layer is exposed through the projection lens and the light refraction plate to form an exposure image on the photoresist layer.

6. The method for forming a photoresist pattern according to claim 5, characterized in that, The method further includes: The exposed photoresist layer is then developed; the developed photoresist layer is then hard baked at a temperature of 130℃ to 200℃ for 20 to 40 minutes.

7. The method for forming a photoresist pattern according to claim 2, characterized in that, in, The thickness of the light refraction plate is greater than one-tenth of the first wavelength.

8. The method for forming a photoresist pattern according to claim 1, characterized in that, The first medium layer includes a first medium, which is water or air.

9. The method for forming a photoresist pattern according to claim 1, characterized in that, The objective lens surround structure is provided with a first medium limiting part, which surrounds the first medium layer and is used to limit the area where the first medium is located to prevent leakage of the first medium. The connecting part of the light refraction plate is connected to the periphery of the first medium limiting part.

10. The method for forming a photoresist pattern according to claim 9, characterized in that, The first medium limiting part includes an air outlet, and the gas discharged from the air outlet forms a barrier to prevent leakage of the first medium.

11. A projection-type exposure apparatus, characterized in that, The projection exposure device includes: An illumination system for emitting an initial beam of light; A projection lens, which is used to transmit an initial light beam and emit an incident light beam; A light refraction plate is disposed on one side of the projection lens, and the light refraction plate is used to reduce the wavelength of the incident light beam emitted by the projection lens; The projection exposure apparatus further includes a first dielectric layer and an objective lens surround structure. The objective lens surround structure surrounds the bottom of the projection objective lens, and the light refraction plate is connected to the objective lens surround structure. The objective lens surround structure provides the first dielectric layer, which is disposed between the light refraction plate and the projection objective lens. The refractive index of the light refraction plate is greater than the refractive index of the first dielectric layer and less than the refractive index of the photoresist layer. The thickness of the first dielectric layer is less than the thickness of the light refraction plate. The material of the light refraction plate is polyimide.

12. The projection exposure apparatus according to claim 11, characterized in that, The thickness of the light refraction plate is greater than one-tenth of the wavelength of the incident light beam emitted by the projection lens.

13. The projection exposure apparatus according to claim 11, characterized in that, The first medium layer includes a first medium, which is water or air.

14. The projection exposure apparatus according to claim 11, characterized in that, The objective lens surround structure is provided with a first medium limiting part, which surrounds the first medium layer and is used to limit the area where the first medium is located to prevent leakage of the first medium. The connecting part of the light refraction plate is connected to the periphery of the first medium limiting part.

15. The projection exposure apparatus according to claim 14, characterized in that, The first medium limiting part includes an air outlet, and the gas discharged from the air outlet forms a barrier to prevent leakage of the first medium.

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