Exposure structure and exposure equipment

Abstract

The invention relates to the technical field of holographic lithography, in particular to an exposure structure and exposure equipment. When exposure light beams pass through a transparent mask substrate and are completely imaged in immersion liquid in an exposure structure, the theoretical distance of imaging is larger than the thickness of the transparent mask substrate and smaller than the sum of the maximum thickness of immersion liquid drops and the thickness of the transparent mask substrate; the exposure light beam is ensured to be capable of completely imaging the interior of the immersion liquid drop after passing through the immersion liquid drop, so that the exposure light beam is ensured to be completely imaged on the wafer substrate after passing through the immersion liquid drop, and the photoetching quality can be greatly improved. Meanwhile, a smaller imaging distance is set through calculation, immersion liquid drops are formed by using surface tension, and the transparent mask substrate or the wafer substrate does not need to be completely immersed in immersion liquid, so that a smaller imaging structure size and less immersion liquid consumption are realized, and the wafer substrate and the transparent mask substrate are convenient to clean after photoetching is completed.

Description

Technical Field

[0001] The present invention relates to the technical field of holographic lithography, and in particular to an exposure structure and an exposure device. Background Art

[0002] Laser holographic lithography is a very promising lithography technology. Its basic principle is diffraction imaging. The light beam illuminates the holographic mask and diffracts on the microstructures arranged according to a certain pattern. These diffractions are finally superimposed on the silicon wafer to obtain the desired pattern.

[0003] In traditional photolithography, in addition to reducing the wavelength of the laser, immersion lithography is often used to improve resolution in order to address the increasing demand for smaller feature sizes. Immersion lithography replaces the air medium between the projection lens and the silicon wafer in traditional photolithography with water, which has a higher refractive index. This increases the numerical aperture and further improves the resolution of the photolithography machine. In holographic lithography, when photolithography resolution reaches its limit, immersion can be used to improve resolution.

[0004] To achieve smaller lithographic feature sizes, existing holographic lithography devices typically immerse the optical path that generates the holographic image at a set distance from the optical diffraction element in water. Simultaneously, the amplitude diffraction element, phase diffraction element, and substrate to be etched with photoresist in the device are all immersed in water, allowing holographic lithography to be performed in water. However, due to the small gaps between the micro-nanostructures on the mask, a small gap exists between the water and the micro-nanostructures due to air pressure and surface tension when the mask is immersed in water. This results in poor projection quality of the laser after passing through the mask, thereby affecting the quality of the lithography. Furthermore, due to the large distance of the optical path, immersing the entire optical path in water results in high water consumption, resulting in a larger imaging structure for the entire system and making it difficult to handle the water between the mask and substrate when the substrate is removed after lithography is completed. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defect in the prior art holographic lithography system that the lithographic structure on the mask cannot be completely immersed in water, which affects the lithographic quality, thereby providing an exposure structure and exposure equipment.

[0006] In order to solve the above technical problems, the present invention provides an exposure structure, comprising:

[0007] a wafer substrate having a photoresist layer disposed on one side thereof;

[0008] A transparent mask substrate having a holographic pattern disposed thereon, wherein the holographic pattern is disposed on a side of the transparent mask substrate facing away from the wafer substrate, and a side of the wafer substrate having a photoresist layer disposed toward the transparent mask substrate;

[0009] An immersion liquid droplet is disposed between the transparent mask substrate and the wafer substrate. The immersion liquid droplet is adsorbed between the transparent mask substrate and the wafer substrate by surface tension, and both the transparent mask substrate and the wafer substrate are in contact with the immersion liquid droplet.

[0010] When the exposure beam passes through the transparent mask substrate and forms a complete image in the immersion liquid, the theoretical imaging distance is greater than the thickness of the transparent mask substrate and less than the sum of the maximum thickness of the droplet and the thickness of the transparent mask substrate.

[0011] Optionally, when the exposure light beam passes through the transparent mask substrate and forms a complete image in the immersion liquid, the theoretical imaging distance z is calculated according to the following formula:

[0012] z=(z0-z1 / n1)n2

[0013] Wherein, z0 is the perfect air imaging distance set by the transparent mask substrate, n1 is the refractive index of the transparent mask substrate, and n2 is the refractive index of the immersion droplet.

[0014] Optionally, a hydrophilic layer is provided on the surface of the photoresist layer.

[0015] Optionally, a hydrophobic structure layer is provided on the transparent mask substrate, and the hydrophobic structure layer and the holographic pattern are respectively provided on two opposite sides of the transparent mask substrate.

[0016] Optionally, a limiting groove is provided on a side of the transparent mask substrate facing away from the holographic pattern, and the limiting groove is provided corresponding to the holographic pattern.

[0017] Optionally, a drainage channel is further provided on the transparent mask substrate, one end of the drainage channel is connected to the limiting groove, and the other end extends to the edge of the transparent mask substrate and is connected to the outside world. The drainage channel is connected to a fluid drive pump.

[0018] Optionally, the volume of the immersion droplet is the product of the bottom area of ​​the limiting groove and the theoretical distance.

[0019] Optionally, a photonic crystal layer is provided on the bottom surface of the limiting groove.

[0020] The present invention also provides another exposure structure, comprising:

[0021] a wafer substrate having a photoresist layer disposed on one side thereof;

[0022] a transparent mask substrate having a holographic pattern disposed thereon, wherein the holographic pattern is disposed on a side of the transparent mask substrate facing away from the wafer substrate, and a side of the wafer substrate having the photoresist layer disposed thereon is disposed toward the transparent mask substrate;

[0023] An immersion liquid droplet is suitable for being arranged between the transparent mask substrate and the wafer substrate. The immersion liquid droplet is suitable for being adsorbed on the surface of the wafer substrate by surface tension. The immersion liquid droplet is separated from the transparent mask substrate.

[0024] The present invention also provides an exposure device having the exposure structure described in the present invention, and also including an exposure light source, an illumination light path, a reflector and a mask loading platform. The transparent mask substrate is installed on the mask loading platform. The exposure light source emits a light beam which passes through the illumination light path in sequence for light path adjustment, is reflected by the reflector and then irradiated onto the transparent mask substrate.

[0025] The technical solution of the present invention has the following advantages:

[0026] 1. The exposure structure provided by the present invention, when the exposure structure is patterned on a wafer substrate, the exposure beam optical path first passes through the holographic pattern on the transparent mask substrate to form optical information with the pattern, and then passes through the transparent mask substrate into the immersion droplet. After the immersion droplet shrinks, it irradiates the photoresist layer of the wafer substrate to complete the photolithography of the wafer substrate. By arranging the immersion droplet between the transparent mask substrate and the wafer substrate, and arranging the holographic pattern on the side of the transparent mask substrate facing away from the wafer substrate, the exposure beam first passes through the holographic pattern and then shrinks through the immersion droplet to form an image. The immersion droplet can completely immerse the surface of the transparent mask substrate or the wafer substrate. However, due to the different imaging parameters of different transparent mask substrates, the imaging position of the exposure beam after passing through the transparent mask substrate may be inside the transparent mask substrate or on the back of the wafer body, resulting in the photoresist layer of the wafer substrate being unable to be etched, and immersion photolithography of the wafer substrate cannot be performed. By limiting the theoretical imaging distance of light passing through the transparent mask substrate to be greater than the thickness of the transparent mask substrate and less than the sum of the maximum thickness of the immersion droplet and the thickness of the transparent mask substrate, the exposure beam is ensured to be able to fully image the interior of the immersion droplet after passing through the immersion droplet. By adjusting the position of the wafer substrate, it can be ensured that the exposure beam can be fully imaged on the wafer substrate after passing through the immersion droplet, which can greatly improve the quality of photolithography. At the same time, by setting a smaller imaging distance through calculation and using surface tension to form immersion droplets, without completely immersing the transparent mask substrate or wafer substrate in the immersion liquid, a smaller imaging structure size and less immersion liquid consumption are achieved, facilitating the cleaning of the wafer substrate and transparent mask substrate after photolithography is completed.

[0027] 2. In the exposure structure provided by the present invention, a hydrophilic layer is provided on the surface of the photoresist layer to increase the surface tension between the photoresist layer and the immersion droplets, thereby increasing the maximum thickness of the immersion liquid on the surface of the photoresist layer, thereby increasing the imaging distance, increasing the distance within the immersion droplets at which the holographic pattern image can be received, and reducing the assembly accuracy required for the normal operation of the device.

[0028] 3. The exposure structure provided by the present invention comprises a hydrophobic structural layer disposed on a transparent mask substrate, with the hydrophobic structural layer and the holographic pattern disposed on opposite sides of the transparent mask substrate. The hydrophobic structural layer enhances the adhesion between the transparent mask body and the immersion droplet, and by varying the surface micro-nanostructure, both hydrophobic high-adhesion and hydrophobic low-adhesion surfaces can be achieved. This allows for both high adhesion before immersion to increase liquid thickness and hydrophobicity after immersion, thereby protecting the transparent mask substrate.

[0029] 4. In the exposure structure provided by the present invention, a limiting groove is provided on the side of the transparent mask substrate facing away from the holographic pattern, and the limiting groove is arranged corresponding to the holographic pattern. By providing the limiting groove corresponding to the holographic pattern, the position of the immersion droplet is restricted, allowing the immersion droplet to flow accurately to the area corresponding to the holographic pattern, improving the accuracy of the immersion droplet positioning and the lithographic quality of the exposure structure.

[0030] 5. The exposure structure provided by the present invention also includes a drainage channel on the transparent mask substrate. One end of the drainage channel communicates with the retaining groove, and the other end extends to the edge of the transparent mask substrate and communicates with the outside world. The drainage channel is connected to a fluid-driven pump. Etching the drainage channel achieves drainage, and then the fluid-driven pump extracts residual liquid, thereby cleaning the transparent mask body after photolithography is completed.

[0031] 6. The exposure structure provided by the present invention has a photonic crystal layer disposed on the bottom surface of the limiting groove. By etching the photonic crystal layer within the limiting groove corresponding to the holographic pattern area, a light field of a specific wavelength is confined within the photonic crystal structure, thereby improving the utilization rate of the exposure beam energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 This is a schematic structural diagram of an exposure device provided in the first embodiment of the present invention, wherein the direction of the arrow is the propagation direction of the exposure light beam.

[0034] Figure 2 This is a schematic diagram of a liquid droplet staying on a solid surface under the action of surface tension provided in an embodiment of the present invention.

[0035] Figure 3Schematic diagram of the gradual increase in droplet volume when the droplet resides on a solid surface under the action of surface tension, provided in an embodiment of the present invention.

[0036] Figure 4 This is a force analysis diagram of a liquid droplet provided in an embodiment of the present invention when it rests on a solid surface under the action of surface tension.

[0037] Figure 5 Schematic diagram of the change of the hydrophobic structure layer from hydrophobic to being immersed in liquid droplets provided in an embodiment of the present invention.

[0038] Figure 6 This is a schematic structural diagram of the limiting groove provided in an embodiment of the present invention.

[0039] Figure 7 Schematic diagram of the structure of the photonic crystal layer provided in an embodiment of the present invention.

[0040] Figure 8 This is a schematic structural diagram of an exposure device provided in another embodiment of the present invention, wherein the direction of the arrow is the propagation direction of the exposure light beam.

[0041] Explanation of the accompanying drawings: 1. Exposure light source; 2. Illumination light path; 3. Reflector; 4. Mask loading platform; 5. Transparent mask base; 6. Immersion droplet; 7. Exposure platform; 8. Limiting groove; 9. Drainage channel; 10. Fluid drive pump; 11. Hydrophobic structure layer; 12. Photonic crystal layer. DETAILED DESCRIPTION

[0042] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0043] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0044] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0045] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0046] Figure 1 The exposure apparatus provided in this embodiment is shown, comprising an exposure structure consisting of a wafer substrate, a transparent mask substrate 5, and immersion droplets, and further comprising a laser as an exposure light source 1, an illumination optical path 2, a reflector 3, and a mask loading platform 4. The wafer substrate is fixedly mounted on an exposure platform 7. In some other embodiments, the exposure light source 1 may also be a laser light source, an extreme ultraviolet light source, an x-ray light source, or other light source capable of exposing the wafer.

[0047] The transparent mask substrate 5 is fixedly mounted on the mask loading platform 4. The laser light beam emitted by the laser passes through the illumination optical path 2 for optical path adjustment, is reflected by the reflector 3, and then irradiates the transparent mask substrate 5. After carrying the holographic pattern information, it passes through the immersion droplet 6 and irradiates the wafer substrate to perform photolithography on the wafer substrate.

[0048] A photoresist layer is provided on the side of the wafer substrate exposed to the laser. A holographic pattern is provided on a transparent mask substrate 5, the holographic pattern being provided on the side of the transparent mask substrate 5 facing away from the wafer substrate, while the side of the wafer substrate provided with the photoresist layer is provided facing the transparent mask substrate 5. An immersion liquid droplet 6 is provided between the transparent mask substrate 5 and the wafer substrate, adsorbed to the surfaces of the transparent mask substrate 5 and the wafer substrate through surface tension. In this embodiment, the exposure structure adopts a positive structure, with the transparent mask substrate 5 provided below the wafer substrate, and both the transparent mask substrate 5 and the wafer substrate in contact with the immersion liquid droplet 6. It should be noted that in this embodiment, the transparent mask substrate 5 is made of a quartz glass substrate. Except for the transparent holographic pattern area, the rest of the transparent mask substrate 5 is shielded by a metal film. The metal film is provided on the side of the transparent mask substrate 5 provided with the holographic pattern to block stray light, allowing only the holographic pattern area to transmit light. The side of the transparent mask substrate 5 not provided with the holographic pattern is entirely a smooth quartz substrate surface.

[0049] In order to ensure that the laser light path can project the image of the holographic pattern onto the wafer substrate, when preparing the transparent mask substrate 5, it is limited that when the laser passes through the transparent mask substrate 5 and is completely imaged in the immersion liquid, the theoretical distance that the laser propagates in the immersion liquid is not greater than the maximum thickness of the droplet on the surface of the transparent mask substrate 5.

[0050] The light beam is emitted by a laser, passes through the illumination optical path 2 to adjust the wavefront and beam radius, and is reflected by the reflector 3 to illuminate the transparent mask substrate 5 on the mask loading platform. By dripping immersion droplets 6 on the transparent mask substrate 5, the pattern in the light beam is reduced when passing through the immersion droplets 6, and finally the designed integrated circuit pattern is obtained on the wafer substrate on the exposure platform 7.

[0051] In the exposure structure, after the laser beam is shaped and collimated into a plane wave through the illumination optical path 2, it is reflected by the reflector 3 onto the vertical mask loading platform. The transparent mask substrate 5 is flipped downward to separate the immersion droplet 6 and the holographic pattern serving as the mask micro-nano structure. Then, water is dripped on the back of the transparent mask substrate 5. The surface tension of water on the quartz substrate achieves immersion. Finally, the integrated circuit pattern formed by the transparent mask substrate 5 forms a holographic image in the set immersion area. The wafer substrate coated with photoresist on the exposure platform 7 is exposed to obtain the designed integrated circuit pattern.

[0052] In this embodiment, the transparent mask substrate 5 is flipped and immersed, with the holographic pattern facing downward. This allows for complete immersion without damaging the micro-nanostructure of the holographic pattern. Back-side immersion also facilitates the removal of liquid from the surface of the transparent mask substrate 5. By calculating and setting a smaller imaging distance and utilizing the tension of the liquid on the surface of the transparent mask substrate 5, a smaller imaging structure size and reduced water consumption are achieved.

[0053] The advantages of the technical solution provided by this embodiment are explained below with reference to theoretical derivation and accompanying drawings:

[0054] Imagine a situation where water is slowly poured onto an absolutely smooth substrate. Assuming that as the volume increases, the water can still remain a whole, forming a large droplet on the surface. The relationship between the thickness and volume of the droplet is analyzed as follows:

[0055] When the volume of liquid is very small, the droplet falls on the solid surface as follows Figure 2 As shown, the height e of the droplet at this time is:

[0056]

[0057] In formula (1), r is the radius of the droplet, and θ is the contact angle between the liquid and the solid surface.

[0058] The volume V of the droplet at this time is:

[0059]

[0060] As the volume of liquid increases, the droplet on the solid surface changes as follows Figure 3 As shown. When the droplet volume is very small, the effect of surface tension is dominant and the effect of gravity can be ignored, so the droplet can maintain a spherical cap shape. However, when the droplet size is larger than the capillary length (about 2.71mm), gravity begins to play a dominant role. The droplet becomes flat under the action of gravity. The following mechanical analysis shows that the thickness e of this flat droplet and the contact angle θ of the solid surface E The force analysis of a part of the droplet is carried out to establish its force balance equation in the horizontal direction. The force diagram is shown in Figure 4 Shown: From Figure 4 It can be seen that the two forces acting on this part of the droplet are the surface tension f1 and the static pressure P of the liquid, where the surface tension f1 is:

[0061] f1=γ SO -(γ+γ SL ) (3)

[0062] In formula (3), γ SO is the pulling force of the droplet edge to spread outward, γ is the pulling force of the top of the droplet to gather toward the middle, and γ SL It is the pulling force that pulls the bottom of the droplet toward the middle.

[0063] The static pressure P of the liquid acts on the entire height of the liquid film. By integrating the entire liquid film thickness, we can get:

[0064]

[0065] In formula (4), ρ is the droplet density, g is the gravitational constant, and z is the angle between any position on the droplet surface and the horizontal direction.

[0066] The force balance equation for the droplet per unit length is:

[0067]

[0068] According to Young's equation, the surface tension above can be converted into the formula expressing the contact angle:

[0069] γ SO -(γcosθ E +γ SL )=0 (6)

[0070] Combining the above formulas, we can get:

[0071]

[0072] The volume of the droplet at this time is:

[0073]

[0074] In formula (8), S is the bottom area of ​​the droplet.

[0075] Through the above mechanical analysis, it can be concluded that the thickness of the large droplet has nothing to do with its volume, but is only related to the wettability of the solid surface. According to formula (7), under the condition of constant surface tension and contact angle, the maximum thickness that the droplet can reach on the substrate surface is

[0076] The following theoretical calculation is used to calculate the imaging position of the laser beam after it irradiates the holographic pattern and then passes through the transparent mask substrate 5 and the immersion droplet 6:

[0077] Parallel light is vertically incident on the transparent mask body. The holographic pattern micro-nano structure on the transparent mask body is a small hole structure. Considering the complex amplitude field of single hole diffraction:

[0078]

[0079] In formula (9), U represents the diffraction complex amplitude of a single square hole, with the center located at the origin of the coordinate system, L represents the size of the square hole, and λ represents the wavelength of light.

[0080] Behind the holographic pattern is a transparent mask body medium with a refractive index of n, then the medium located at z g The complex amplitude U at g for

[0081]

[0082] Then spread z in the immersion droplet 6 a Complex amplitude of distance U a for:

[0083]

[0084] It can be seen that if z a Defined as Then U a with U g Only the phase factor is different (In the sense that r is expanded to the second order, and y / r and x / r are expanded to the first order).

[0085] Therefore, assuming that the original light beam propagates a distance z in the air after being diffracted by the holographic pattern to form an image, and the current light beam first propagates a distance z1 in the transparent mask substrate 5, the final imaging distance is approximately z1+z-z1 / n.

[0086] Assuming that the complete air imaging distance set by the transparent mask substrate 5 is z0 and the thickness of the transparent mask substrate 5 is z1, the laser beam finally passes through the holographic pattern on the transparent mask substrate 5 and then passes through the transparent mask substrate 5 to be imaged in the immersion droplet 6. The theoretical distance of the laser beam imaging is z = (z0-z1 / n1)n2, where n1 is the refractive index of the transparent mask substrate 5 and n2 is the refractive index of the immersion droplet 6.

[0087] When preparing the transparent mask substrate 5, it is important to ensure that the laser beam, after being diffracted by the holographic pattern and passing through the transparent mask substrate 5, forms an image in the immersion liquid droplet 6. The theoretical distance for the laser beam to be completely imaged in the immersion liquid after passing through the transparent mask substrate 5 is the distance between the surface of the transparent mask substrate 5 where the holographic pattern is located and the imaging surface in the immersion liquid. To ensure that the laser beam is imaged within the immersion liquid droplet 6 and not within the transparent mask substrate 5 or behind the wafer substrate, the theoretical imaging distance z of the laser beam should be greater than the thickness of the transparent mask substrate 5 and less than the sum of the maximum thickness e of the immersion liquid droplet 6 on the surface of the transparent mask substrate 5 and the thickness of the transparent mask substrate 5, thereby ensuring that the laser beam can form an image on the photoresist layer of the wafer substrate.

[0088] In order to fully utilize the surface tension of the immersion droplet 6, a hydrophobic structure layer 11 is provided on the transparent mask substrate 5. The hydrophobic structure layer 11 and the holographic pattern are respectively provided on the two opposite sides of the transparent mask substrate 5. By etching some micro-nano structures in the hydrophobic structure layer 11 on the back side of the transparent mask substrate 5, the adhesion between the transparent mask substrate 5 and the immersion droplet 6 is increased. By changing the position of the micro-nano structures in the hydrophobic structure layer 11 on the surface of the transparent mask substrate 5, a hydrophobic high-adhesion surface and a hydrophobic low-adhesion surface can be achieved, such as Figure 5 Specifically, a spherical micro-nano array structure can be etched on the back of the transparent mask substrate 5 as a hydrophobic structure layer 11, which can achieve high adhesion to increase the thickness of the immersion droplet 6 and achieve hydrophobicity, thereby protecting the transparent mask substrate 5.

[0089] like Figure 6As shown, a limiting groove 8 is provided on the side of the transparent mask substrate 5 facing away from the holographic pattern, and the limiting groove 8 is arranged corresponding to the holographic pattern. A drainage channel 9 is also provided on the transparent mask substrate 5. One end of the drainage channel 9 is connected to the limiting groove 8, and the other end extends to the edge of the transparent mask substrate 5 and communicates with the outside world. The drainage channel 9 is connected to a fluid-driven pump 10. In the exposure light path of the upright structure, the drainage channel 9 is etched to achieve the purpose of drainage, allowing the immersion droplets 6 to accurately flow to the corresponding area of ​​the holographic pattern. In this case, the required amount of water can be accurately obtained based on the area of ​​the holographic pattern area and the depth of the etching of the limiting groove 8. The immersion droplets 6 are drained from the drainage channel 9 on one side of the transparent mask substrate 5 into the limiting groove 8, which is of a fixed size. After the algorithm calculates the theoretical imaging distance of the transparent mask substrate 5 and the area of ​​the limiting groove 8 is determined as S, the volume of the immersion droplet 6 is the product of the bottom area of ​​the limiting groove 8 and the theoretical distance. The volume of the droplet dripped into the limiting groove 8 is precisely controlled to completely cover the limiting groove 8, achieving complete immersion. After photolithography is completed, the waste liquid is drained out through the right drainage channel 9, and the remaining liquid is extracted by a fluid-driven pump 10 to clean the transparent mask substrate 5.

[0090] In the upright exposure light path, on the basis of the drainage structure, some micro-nano structures of the photonic crystal layer 12 can be further etched on the bottom surface of the limiting groove 8 to improve the energy utilization rate of the transparent mask substrate 5 at the limiting groove 8. Specifically, Figure 7 As shown, the micro-nano structure of the photonic crystal layer 12 is a series of periodically arranged photonic crystal structures, which realizes light field confinement of a specific wavelength on the photonic crystal structure to improve energy utilization.

[0091] The exposure structure provided in this embodiment achieves separation of the immersion droplet 6 and the holographic pattern mask structure on the transparent mask substrate 5 by flipping the transparent mask substrate 5. This can achieve complete immersion of the immersion droplet 6 with the surface of the transparent mask substrate 5, thereby protecting the transparent mask substrate 5 and making it easier to clean the droplets on the back of the transparent mask substrate 5 after the photolithography is completed. By calculating and setting a smaller imaging distance and using the tension of the droplets on the surface of the transparent mask substrate 5, a smaller imaging structure size and less water consumption are achieved. By providing a hydrophobic structure layer 11 on the surface of the transparent mask substrate 5, the maximum thickness of the immersion droplet 6 on the surface of the transparent mask substrate 5 is increased, thereby increasing the imaging distance. By using the limiting groove 8 and drainage channel 9 on the surface of the transparent mask substrate 5, the immersion droplet 6 is accurately drained to the limiting groove 8, thereby accurately achieving immersion of the limiting groove 8. By combining the drainage structure with the micro-nano structure of the photonic crystal layer 12, the energy utilization rate of the limiting groove 8 area is improved. After the size of the limiting groove 8 and the imaging distance are determined, the volume of the liquid dripping into the limiting groove 8 can be quantitatively controlled, so that complete immersion can be achieved while saving liquid consumption.

[0092] When testing the imaging quality of the exposure equipment, first fix the transparent mask body, adjust the angle of the transparent mask body to be perpendicular to the direction of the laser beam, and then inject water with the same volume as the limiting groove into the limiting groove on the surface of the transparent mask body as immersion droplets. Move the wafer substrate to the imaging area to find a suitable focal plane, and then start the laser for immersion exposure. In this embodiment, the laser wavelength is 354.776nm, the size of the projected pattern on the transparent mask body is 1.5mm×1.5mm, the aperture size on the projected pattern is 300nm, and the minimum line width of the exposure pattern finally obtained on the wafer substrate is 350nm. If immersion droplets are not set, imaging is performed directly in the air, and the minimum line width of the exposure pattern finally obtained on the wafer substrate is 450nm. It can be seen that the minimum line width of the laser imaging is reduced after passing through the immersion droplets. As an alternative embodiment, the exposure structure in this embodiment adopts an inverted structure, and the overall structure of the exposure equipment is as follows. Figure 8 As shown, a transparent mask substrate 5 is disposed above the wafer substrate. By utilizing the surface tension of the immersion droplets 6 on the surface of the photoresist layer, the positions of the exposure stage 7 and the mask loading stage can be adjusted at will. The surface tension of a liquid is essentially an intermolecular force. Intermolecular forces are van der Waals forces, which include inductive forces, dispersion forces, and orientation forces, and these forces are of course related to the polarity of the molecules. In this embodiment, a hydrophilic layer is provided on the surface of the photoresist layer. The adhesion of the droplets to the solid surface is related to the surface energy of the solid. On a flat solid surface, the greater the surface energy of the solid, the more hydrophilic it appears, that is, the greater its adhesion to water. The smaller the surface energy of the solid, the more hydrophobic it appears, and the smaller its adhesion to water. Hydrophilic surfaces generally contain groups such as hydroxyl groups, carboxyl groups, and amino groups, while hydrophobic surfaces contain groups such as fluorine, chlorine, and carbon side chains. In the inverted structure exposure light path, in order to better utilize the surface tension of the liquid on the surface of the photoresist layer in the inverted light path, the surface tension between the droplets and the photoresist layer is increased by performing some treatment on the surface of the photoresist layer. Since the photolithography precision requirements on the surface of the photoresist layer make it impossible to etch some micro-nano structures, the surface of the photoresist layer can be subjected to some hydrophilic treatment before exposure without affecting the photolithography process, so that its surface has hydroxyl, carboxyl, amino and other groups.

[0093] As an alternative embodiment, the exposure structure in this embodiment employs an inverted structure, with a transparent mask substrate 5 positioned above the wafer substrate. An immersion droplet 6 is positioned between the transparent mask substrate 5 and the wafer substrate. The immersion droplet 6 is adapted to be adsorbed to the surface of the wafer substrate through surface tension. The immersion droplet is separated from the transparent mask substrate 5, creating a gap between the immersion droplet and the transparent mask substrate. In this case, there is no need to define the imaging parameters of the transparent mask substrate 5. During operation, the position of the wafer substrate is simply fixed by adjusting the position of the wafer substrate until the exposure beam can produce a clear image on the photoresist layer of the wafer substrate. Because the immersion droplet is in direct contact with the wafer substrate, the exposure beam, carrying the holographic pattern information through the transparent mask substrate, will inevitably form an image on the wafer substrate.

[0094] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. An exposure structure, characterized in that: include: a wafer substrate having a photoresist layer disposed on one side thereof; A transparent mask substrate (5) having a holographic pattern provided thereon, the holographic pattern being provided on a side of the transparent mask substrate (5) facing away from the wafer substrate, and a side of the wafer substrate provided with the photoresist layer being provided facing the transparent mask substrate (5); An immersion droplet (6) is suitable for being arranged between the transparent mask substrate (5) and the wafer substrate, and the immersion droplet (6) is suitable for being adsorbed between the transparent mask substrate (5) and the wafer substrate by surface tension, and both the transparent mask substrate (5) and the wafer substrate are in contact with the immersion droplet (6); When the exposure light beam passes through the transparent mask substrate (5) and forms a complete image in the immersion liquid, the theoretical imaging distance is greater than the thickness of the transparent mask substrate (5) and less than the sum of the maximum thickness of the immersion liquid droplet (6) and the thickness of the transparent mask substrate (5).

2. The exposure structure according to claim 1, wherein: When the exposure light beam passes through the transparent mask substrate (5) and forms a complete image in the immersion liquid, the theoretical imaging distance z is calculated according to the following formula: z=(z0-z1 / n1)n2 Wherein, z0 is the complete air imaging distance set by the transparent mask substrate (5), n1 is the refractive index of the transparent mask substrate (5), and n2 is the refractive index of the immersion droplet (6).

3. The exposure structure according to claim 1 or 2, characterized in that: A hydrophilic layer is provided on the surface of the photoresist layer.

4. The exposure structure according to claim 1 or 2, characterized in that: A hydrophobic structural layer (11) is provided on the transparent mask substrate (5), and the hydrophobic structural layer (11) and the holographic pattern are respectively provided on two opposite sides of the transparent mask substrate (5).

5. The exposure structure according to claim 1 or 2, characterized in that: A limiting groove (8) is provided on a surface of the transparent mask substrate (5) facing away from the holographic pattern, and the limiting groove (8) is arranged corresponding to the holographic pattern.

6. The exposure structure according to claim 5, characterized in that: The transparent mask substrate (5) is further provided with a drainage channel (9), one end of which is in communication with the limiting groove (8), and the other end of which extends to the edge of the transparent mask substrate (5) and is in communication with the outside world. The drainage channel (9) is in communication with a fluid drive pump (10).

7. The exposure structure according to claim 5, wherein: The volume of the immersion droplet (6) is the product of the bottom area of ​​the limiting groove (8) and the theoretical distance.

8. The exposure structure according to claim 5, wherein: A photonic crystal layer (12) is provided on the bottom surface of the limiting groove (8).

9. An exposure structure, characterized in that: include: a wafer substrate having a photoresist layer disposed on one side thereof; A transparent mask substrate (5) having a holographic pattern provided thereon, the holographic pattern being provided on a side of the transparent mask substrate (5) facing away from the wafer substrate, and a side of the wafer substrate provided with the photoresist layer being provided facing the transparent mask substrate (5); An immersion droplet (6) is suitable for being arranged between the transparent mask substrate (5) and the wafer substrate. The immersion droplet (6) is suitable for being adsorbed on the surface of the wafer substrate through surface tension. The immersion droplet is separated from the transparent mask substrate (5).

10. An exposure device, characterized in that: The exposure structure according to any one of claims 1 to 8 or the exposure structure according to claim 9 further comprises an exposure light source (1), an illumination light path (2), a reflector (3) and a mask loading platform (4), wherein the transparent mask substrate (5) is mounted on the mask loading platform (4), and the exposure light source (1) emits an exposure light beam which sequentially passes through the illumination light path (2) for light path adjustment, is reflected by the reflector (3) and then irradiates the transparent mask substrate (5).

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