Metasurface polarization mask and photolithography method based on metasurface polarization mask

Abstract

This invention discloses a metasurface polarization mask and a photolithography method based on the metasurface polarization mask. The metasurface polarization mask is formed by arranging multiple unit cells according to a preset metasurface mask modeling pattern. The preset metasurface mask modeling pattern includes an outer image with vertical patterned regions and an inner image with horizontal patterned regions. Unit cells corresponding to the outer image are arranged in a first arrangement, and unit cells corresponding to the horizontal patterns are arranged in a second arrangement at a predetermined angle to the first arrangement. Each unit cell includes a substrate and nanofins placed on the substrate. The metasurface polarization mask enables a photolithography method to obtain the target pattern and ensure accurate exposure patterns on the wafer.

Description

Technical Field

[0001] This invention relates to the field of photolithography, and in particular to a metasurface polarization mask, a photolithography method and apparatus based on the metasurface polarization mask. Background Technology

[0002] Photolithography is one of the core processes in semiconductor manufacturing and a key technology for achieving high-precision pattern transfer. As integrated circuit manufacturing processes continue to advance to smaller nodes, device sizes shrink, and chip integration density increases, semiconductor manufacturing places ever higher demands on the exposure resolution of photolithography. In the photolithography projection system, the photomask, as the core transfer medium in semiconductor manufacturing, directly affects the success or failure of transferring the designed pattern onto the wafer.

[0003] However, current photomask processes are highly complex and suffer from problems such as diffraction caused by intensity distribution, resulting in inaccurate exposure patterns on the wafer.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] The main objective of this invention is to provide a metasurface polarization mask, a photolithography method and apparatus based on the metasurface polarization mask, and to solve the problems of high process complexity of existing masks and diffraction caused by intensity distribution, which lead to inaccurate exposure patterns on wafers.

[0006] To achieve the above objectives, the present invention provides a metasurface polarization mask, wherein the metasurface polarization mask is formed by arranging multiple unit cells according to a preset metasurface mask modeling pattern;

[0007] The preset metasurface mask modeling pattern includes an outer pattern with a vertical pattern area and an inner pattern with a horizontal pattern area. The unit cells corresponding to the outer pattern are arranged in a first manner, and the unit cells corresponding to the horizontal pattern are arranged in a second manner at a predetermined angle to the first manner.

[0008] Each unit cell includes a substrate and nanofins placed on the substrate.

[0009] Optionally, the metasurface mask modeling diagram includes an internal diagram and an external diagram;

[0010] The internal diagram is drawn using a horizontal polarization vector, while the external diagram is drawn using a vertical polarization vector.

[0011] Optionally, the multiple unit cells in the metasurface polarization mask are arranged according to the modeling pattern of the metasurface mask;

[0012] The predetermined angle between the second method and the first method is 45°.

[0013] Optionally, the nanofins on the unit cell are rectangular or elliptical in shape, the nanofins are made of hafnium dioxide, and the substrate is made of silicon dioxide.

[0014] Optionally, when the shape of the nanofin is a cuboid, the process of setting the size of the nanofin includes:

[0015] The length and height of the nanofins are scanned to obtain a first transmission distribution map, and the cuboid height of the nanofins is set according to the first transmission distribution map.

[0016] Based on the height of the cuboid, the length and width of the nanofins are scanned to obtain a second transmission distribution map;

[0017] The unit cell scans the length and width of the nanofin under horizontally polarized light and vertically linearly polarized light to obtain a first phase difference map. Based on the second transmission distribution map and the first phase difference map, the cuboid length and cuboid width of the nanofin are set.

[0018] Optionally, when the shape of the nanofin is an elliptical cylinder, the process of setting the size of the nanofin includes:

[0019] The length of the major axis and the height of the nanofin are scanned to obtain a third transmittance distribution map. The height of the elliptical cylinder of the nanofin is set according to the third transmittance distribution map.

[0020] The unit cell is scanned under horizontally polarized light and vertically linearly polarized light to obtain a second phase difference map by scanning the long axis and short axis of the nanofin.

[0021] The length and width corresponding to the difference of π in the second phase difference graph are selected as the major axis length and minor axis length of the elliptical cylindrical section of the nanofin.

[0022] Furthermore, to achieve the above objectives, the present invention also provides a photolithography method based on a metasurface polarization mask, wherein the photolithography method based on a metasurface polarization mask specifically includes:

[0023] A target beam is generated based on a light source, and the target beam is expanded through a lens group to cover the metasurface polarization mask;

[0024] The target beam is polarized by multiple unit cells at a preset angle on the metasurface polarization mask to obtain a first target beam, which is then incident on the projection lens.

[0025] The first target beam is scaled according to the projection lens to obtain the second target beam, and then incident on the thin film polarizer on the upper surface of the wafer to obtain the third target beam.

[0026] The third target beam reacts with the photoresist on the wafer to complete the exposure, and the exposed wafer is then developed and etched to obtain the target pattern.

[0027] Optionally, the step of polarizing the target beam according to multiple unit cells at a preset angle on the metasurface polarization mask to obtain a first target beam, which is then incident on the projection lens, specifically includes:

[0028] Based on multiple unit cells at a preset angle on the metasurface polarization mask, a specific range in the target beam is converted to obtain a first target beam, wherein the first target beam includes linearly vertically polarized light and linearly horizontally polarized light;

[0029] The first target beam is incident on the projection lens.

[0030] Optionally, the third target beam reacts with the photoresist on the wafer to complete the exposure, and the exposed wafer is then developed and etched to obtain the target pattern, specifically including:

[0031] A third target beam is incident on a thin-film polarizer on the wafer. The linearly horizontally polarized light in the third target beam reacts with the photoresist on the wafer through the thin-film polarizer. The reacted wafer is then developed to dissolve the reacted portion, resulting in a dissolved wafer.

[0032] The dissolved wafer is etched to obtain the target pattern.

[0033] Optionally, the projection lens is a 4:1 or 5:1 magnification projection lens.

[0034] In this invention, a metasurface polarization mask is formed by arranging multiple unit cells according to a preset metasurface mask modeling pattern. The preset metasurface mask modeling pattern includes an outer image with vertical patterned regions and an inner image with horizontal patterned regions. Unit cells corresponding to the outer image are arranged in a first manner, and unit cells corresponding to the horizontal patterned regions are arranged in a second manner at a predetermined angle to the first manner. Each unit cell includes a substrate and nanofins placed on the substrate. This invention uses a metasurface-constructed polarization mask to replace a traditional intensity mask. Each unit cell on the polarization mask can function as a half-wave plate. By rotating unit cells arranged at specific positions by 45°, the polarization mask is fabricated. Using linearly polarized light passing through the metasurface polarization mask, the transferred pattern information is encoded in the polarization dimension rather than the intensity dimension, avoiding light intensity changes due to diffraction and beam transformation during imaging. This also avoids distortion of the transferred pattern, resulting in more accurate exposure patterns on the wafer. Attached Figure Description

[0035] Figure 1 This is a schematic diagram and structural diagram of the metasurface polarization mask of the present invention;

[0036] Figure 2 This is a modeling diagram of the metasurface polarization mask of the present invention;

[0037] Figure 3 This is a structural diagram of the unit cell when the nanofins of the metasurface polarization mask of this invention are cuboids;

[0038] Figure 4 This is a structural diagram of the unit cell when the nanofins of the metasurface polarization mask of this invention are elliptical cylinders;

[0039] Figure 5 This is a transmittance map obtained by scanning the cell length and height according to the present invention;

[0040] Figure 6 This is a transmittance map obtained by scanning the cell length and width according to the present invention;

[0041] Figure 7 This invention obtains a phase difference map by scanning the cell length and width.

[0042] Figure 8 This is a simulation diagram of the electric field intensity at different positions after linearly polarized light passes through a metasurface polarization mask in this invention;

[0043] Figure 9 This is a flowchart of a preferred embodiment of the photolithography method based on a metasurface polarization mask according to the present invention;

[0044] Figure 10This is a schematic diagram of the device structure for implementing the photolithography method based on a metasurface polarization mask according to the present invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer and more explicit, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0046] Photolithography is one of the core processes in semiconductor manufacturing and a key technology for achieving high-precision pattern transfer. As integrated circuit manufacturing processes continue to advance to smaller nodes, device sizes continue to shrink, and chip integration density continues to increase, semiconductor manufacturing places ever higher demands on the exposure resolution of photolithography technology.

[0047] For optical projection lithography systems, the lithography resolution is determined by the Rayleigh formula, which is: ,in, CD This indicates the resolution of the lithography machine. It is the wavelength of the light source. NA It is the numerical aperture of the objective lens. This refers to the process factor. According to the Rayleigh formula, improving resolution can be achieved by reducing the process factor. Reduce the wavelength of the light source Improve numerical aperture NA There are three ways to achieve this. Among these three ways, shortening the wavelength of the light source is one of them. and increasing numerical aperture NA This is currently a key technological challenge for lithography machine manufacturers; however, both of these main approaches face numerous pressing problems that need to be addressed. The first is the issue of the light source: the smaller the wavelength, the higher the resolution, but the greater the manufacturing difficulty; current processing techniques for wavelengths smaller than 7... The high-end lithography machine uses a wavelength of 13.5 nm. The extreme ultraviolet (EUV) light source generates UV radiation by using a high-power laser to strike molten tin twice in a very short time, producing high-temperature, high-density plasma, which then radiates UV radiation at 13.5 ppm. Extreme ultraviolet (EUV) light is expensive to produce and has low energy conversion efficiency; secondly, there is the issue of numerical aperture—the larger the numerical aperture, the higher the resolution, but... It can be seen that in the air, NA It cannot be greater than 1. If an immersion imaging system is used, NA It can reach 1.33, but it is difficult to increase it further, where n is the refractive index of the medium. For the maximum half-reception angle, if an immersion imaging system is used, NAA process factor of 1.33 can be achieved, but it is difficult to improve further. Finally, the process factor also significantly impacts the accuracy and efficiency of photolithography. Common methods for reducing the process factor include phase-shift masking (PSM), off-axis illumination (OAI), optical proximity correction (OPC), and multiple exposure (ME). In addition to these, in the photolithography projection system, the photomask, as the core transfer medium in semiconductor manufacturing, directly affects the success or failure of transferring the designed pattern onto the wafer.

[0048] In photolithography, improving resolution and process precision while reducing mask production cycle and process complexity has always been the goal of continuous improvement and optimization of photolithography imaging systems. Typically, to reduce the difference between actual imaging and theoretical design, on the one hand, the photolithography mask fabrication process requires establishing a reverse photolithography imaging model and optimization algorithm to obtain a mask structure and light intensity distribution that meet the performance requirements of photolithography imaging. Therefore, traditional resolution enhancement techniques need to be incorporated to optimize and control the amplitude, phase, and propagation direction of the imaging light wave, achieving high-resolution imaging that surpasses the Rayleigh diffraction resolution limit; on the other hand, with the development of 28~7... As technology nodes approach advancements, the error tolerance for lithography imaging decreases significantly. Therefore, advanced computational lithography must establish theories of "vector" lithography imaging, non-zero error, multi-target, and full-field imaging, enabling collaborative optimization of multiple parameters across lithography equipment, masks, and processes. However, both traditional resolution enhancement techniques and advanced computational lithography involve optimizing multi-dimensional parameters, resulting in large and complex computational loads, hindering their widespread application in actual production. Furthermore, high precision is required in mask manufacturing, as computational lithography necessitates precise mask structures and light intensity distributions to achieve optimized lithography. Currently, mask manufacturing processes are highly complex and suffer from diffraction issues caused by intensity distribution, leading to inaccurate exposure patterns on the wafer. Therefore, a new technology is needed to address issues such as high mask manufacturing complexity and diffraction caused by intensity distribution, thereby further improving the accuracy and precision of exposure patterns on the wafer.

[0049] To address one or more of the above-mentioned problems, the present invention provides a metasurface polarization mask, wherein the metasurface polarization mask is composed of multiple unit cells arranged according to a metasurface mask modeling pattern; wherein each unit cell is composed of a substrate and nanofins placed on the substrate.

[0050] The preferred embodiment of the metasurface polarization mask of the present invention, such as... Figure 1 As shown, the metasurface polarization mask is formed by arranging multiple unit cells according to a preset metasurface mask modeling pattern;

[0051] The preset metasurface mask modeling pattern includes an outer pattern with a vertical pattern area and an inner pattern with a horizontal pattern area. The unit cells corresponding to the outer pattern are arranged in a first manner, and the unit cells corresponding to the horizontal pattern are arranged in a second manner at a predetermined angle to the first manner.

[0052] Each unit cell includes a substrate and nanofins placed on the substrate.

[0053] Specifically, in Figure 1 In the diagram, 200 represents the substrate of the metasurface polarization mask, composed of substrates for each unit cell, and 201 represents the nanofins. During the construction of the metasurface polarization mask, the corresponding unit cells are arranged according to the metasurface mask modeling diagram. Figure 2 This is the preset metasurface mask modeling diagram, in which Figure 2 In the metasurface mask modeling diagram shown, the corresponding pattern is set as "L". However, it is understood that in this invention, the pattern is designed by the user. The L shown in all the figures of this invention is only for illustrative purposes.

[0054] Furthermore, the metasurface mask modeling diagram includes an internal diagram and an external diagram;

[0055] The internal diagram is drawn using a horizontal polarization vector, while the external diagram is drawn using a vertical polarization vector.

[0056] Specifically, Figure 1 In this diagram, 202 represents the overall schematic diagram of the external image, i.e., the target design pattern, while 206 represents the overall schematic diagram of the internal image, i.e., the internal design shape. From the overall schematic diagrams of the external and internal images, the corresponding theoretical pattern 203 of the photomask can be derived. 204 represents the corresponding external pattern, drawn using a vertical polarization vector, thus obtaining the external image of the vertical pattern region. 205 represents the internal pattern, drawn using a horizontal polarization vector, thus obtaining the internal image of the horizontal pattern region. Figure 1 The diagram shown is a simplified representation of a metasurface mask modeling pattern. In one embodiment of the present invention, a specific metasurface mask modeling pattern is as follows: Figure 2 As shown, the portion composed of horizontal polarization vectors represents the range of the internal diagram, and the portion composed of vertical polarization vectors represents the range of the external diagram. The corresponding unit cells are arranged according to... Figure 2 The corresponding metasurface polarization mask can be obtained by arranging the elements in a specific way.

[0057] Furthermore, the multiple unit cells in the metasurface polarization mask are arranged according to the modeling pattern of the metasurface mask, wherein the predetermined angle between the second mode and the first mode is 45°.

[0058] Depend on Figure 2 It can be concluded that in the metasurface mask modeling diagram, the orientation of the unit cells in the inner diagram is inconsistent with the orientation of the unit cells in the outer diagram. That is, in this invention, multiple unit cells in the metasurface polarization mask are arranged according to the metasurface mask modeling diagram, wherein the unit cells corresponding to the outer diagram are arranged in a first manner, and the unit cells corresponding to the horizontal pattern are arranged in a second manner, which is equivalent to rotating the unit cells corresponding to the inner diagram by 45°.

[0059] In this invention, a polarized vector beam is applied to projection lithography, abandoning the traditional intensity mask scheme. The target pattern is creatively encoded using two orthogonal linear polarization states. Combining the unique propagation and focusing characteristics of the vector beam, and by selecting appropriate length, width, and height, a rotating nanofin can function as a rotating half-wave plate. This nanofin is used to construct a metasurface polarization mask, solving the problem of lithographic accuracy degradation caused by diffraction effects during intensity modulation. The reasoning process for enabling the rotating nanofin to function as a rotating half-wave plate is as follows:

[0060] Given: Jones vector of linearly horizontally polarized light :

[0061] ;

[0062] Jones vector of linearly vertically polarized light :

[0063] ;

[0064] Assume the fast axis phase of the delayer leads the slow axis phase. That is, the phase along the x-axis (fast axis) is The phase along the y-axis (slow axis) is , i This represents the variation along the x-axis. and The first and second output Jones vectors are respectively used to form the output Jones vector; and Let the first input Jones vector and the second input Jones vector be respectively used to form the input Jones vector, then we have:

[0065] ;

[0066] ;

[0067] Therefore, the Jones matrix of the delayer is derived. for:

[0068] ;

[0069] Jones matrix of rotation matrix Represented as:

[0070] ;

[0071] in θ It is the rotation angle.

[0072] Furthermore, rotation θ Jones matrix of angle delay It can be represented as:

[0073] ;

[0074] That is, the Jones matrix It can be further written as:

[0075] ;

[0076] when =180° (λ / 2) θ When the angle is 45°, the Jones matrix of a half-wave plate rotated by 45° can be obtained. and the corresponding output matrix They are respectively:

[0077] ;

[0078] ;

[0079] It can be deduced that linearly horizontally (or vertically) polarized light becomes linearly vertically (or horizontally) polarized light after passing through a 1 / 2 waveplate rotated by 45°.

[0080] Furthermore, the nanofins on the unit cell are in the shape of cuboids or elliptical cylinders, the nanofins are made of hafnium dioxide, and the substrate is made of silicon dioxide.

[0081] Specifically, in this invention, such as Figure 3 and Figure 4 As shown, for a unit cell, its nanofins can be cuboids or elliptical cylinders, and the substrate is made of silicon dioxide, while the raised nanofins on the mask are made of hafnium dioxide, which has a complex refractive index of 365. The wavelength is expressed as (n1=2.1722, k=0.00076), where n1 is the refractive index of the absorbing medium, and k is the imaginary part used to determine the attenuation of light waves propagating in the absorbing medium. In this invention, the period of a single substrate is 350. This effectively avoids higher-order diffraction, improving the resolution and imaging quality of photolithography. Considering current processing precision and other factors, the length and width of the first nanofin 300 are controlled within 100. Up to 300 Inside.

[0082] Furthermore, when the shape of the nanofin is a cuboid, the process of setting the size of the nanofin includes:

[0083] The length and height of the nanofins are scanned to obtain a first transmission distribution map, and the cuboid height of the nanofins is set according to the first transmission distribution map.

[0084] Based on the height of the cuboid, the length and width of the nanofins are scanned to obtain a second transmission distribution map;

[0085] The unit cell scans the length and width of the nanofin under horizontally polarized light and vertically linearly polarized light to obtain a first phase difference map. Based on the second transmission distribution map and the first phase difference map, the cuboid length and cuboid width of the nanofin are set.

[0086] Specifically, such as Figure 3 As shown, 300 represents the first nanofin, i.e., a cuboid nanofin, and 301 represents the corresponding first substrate. When the nanofin is cuboid, its dimensions need to be designed accordingly for different wavelengths. For the cuboid nanofin, in this invention, the length and height of the nanofin need to be scanned to obtain a first transmission distribution map. In the first transmission distribution map, the height corresponding to the highest transmittance is selected as the cuboid height of the nanofin. Then, based on the cuboid height, considering that the nanofin is more likely to generate a large phase difference when the length and width are relatively large to meet the phase requirements, the length and width of the nanofin are scanned to obtain a second transmission distribution map.

[0087] The goal of this invention is to enable a single unit cell to function as a half-wave plate. A half-wave plate is an optical element made of birefringent material that can change the polarization state of incident light. The fast axis and slow axis are two orthogonal directions of the birefringent material, and there is a phase difference of π between them. As shown in the previous derivation, when the half-wave plate is rotated by 45°, the polarization state of linearly polarized light passing through the rotated half-wave plate rotates by 2 × 45° = 90° from its original position. Therefore, this invention needs to scan the length and width under both horizontal and vertical linear polarization states to obtain the corresponding phase distribution maps. The difference between the corresponding positions in the phase maps is then taken to obtain a first phase difference map. From the first phase difference map, the length and width coordinates within a preset range of phase difference near π are selected. Then, the transmittance corresponding to these lengths and widths is obtained from the second transmission distribution map, and the highest transmittance is selected as the corresponding cuboid length and width.

[0088] In one embodiment of the present invention, when the nanofins are cuboids, an ultraviolet lithography machine light source is used, wherein the high-pressure mercury lamp in the lithography machine light source produces a wavelength of 365 nm. The ultraviolet light. The period of a single unit cell is set to 350. This effectively avoids higher-order diffraction, improving the resolution and imaging quality of photolithography. Considering current processing precision and other factors, the length and width of the first nanofin 300 are controlled within 100. Up to 300 Internally; after scanning the corresponding nanofin length and height, the transmittance distribution map is obtained as follows: Figure 5 As shown, nanofins are more likely to generate large phase differences to meet phase requirements when the length and width are relatively large. Figure 5 It can be seen that the height of the nanofins is 400. Up to 500 At this time, the transmittance can be maintained at a high level, therefore a height of 485 is selected accordingly. At this height, the transmittance distribution obtained by scanning the length and width of the nanofins is as follows: Figure 6 As shown, this is the second transmission distribution pattern. Next, the length and width were scanned under both horizontal and vertical linear polarization states to obtain the corresponding phase distribution patterns. The differences between corresponding positions on the phase patterns were then calculated, and the results are shown below. Figure 7 As shown, this is the first phase difference map; find the length and width coordinates corresponding to the point where the phase difference is approximately π, and then according to... Figure 6 While maintaining its high transmittance, the length, width, and height of the nanofins were ultimately selected as follows: 260 and 485 Based on this parameter modeling, a metasurface polarization mask can be derived, with the internal pattern set to "L," and all nanofins within the "L" rotated uniformly by 45°. Under these parameters, the 45° rotated nanofins can function as a half-wave plate. Therefore, if linearly horizontally polarized light passes through this metasurface polarization mask, the light emitted from the "L" region of the pattern will be transformed into linearly vertically polarized light. In the simulation process described in this invention, power field strength monitors are placed at positions of 0.85 μm, 1.58 μm, 2.31 μm, and 4.135 μm behind the polarization mask (PM), respectively, to obtain the following results: Figure 8 The electric field intensity distribution diagram shown can perfectly realize exposure in a specific area based on the intensity difference inside and outside the "L" area, resulting in good simulation results.

[0089] Furthermore, when the shape of the nanofin is an elliptical cylinder, the process of setting the size of the nanofin includes:

[0090] The length of the major axis and the height of the nanofin are scanned to obtain a third transmittance distribution map. The height of the elliptical cylinder of the nanofin is set according to the third transmittance distribution map.

[0091] The unit cell is scanned under horizontally polarized light and vertically linearly polarized light to obtain a second phase difference map by scanning the long axis and short axis of the nanofin.

[0092] The length and width corresponding to the difference of π in the second phase difference graph are selected as the major axis length and minor axis length of the elliptical cylindrical section of the nanofin.

[0093] In one embodiment of the invention, modifications are made to a single unit cell by replacing the cuboid with an elliptical cylinder. By scanning the major and minor axis lengths of the ellipse, the major and minor axis lengths required to achieve the half-wave plate function are also obtained. The single unit cell modeling is as follows: Figure 4 As shown, it includes the second nanofin 700, i.e., the nanofin of the elliptical cylinder, and 701, which is the corresponding second substrate. When setting the size of the elliptical cylinder, firstly, the transmittance distribution map is obtained by scanning the length of the major axis of the ellipse and the height of the elliptical cylinder. The height H corresponding to the highest transmittance is selected. Secondly, the lengths of the major and minor axes are scanned under linear horizontal and vertical polarization states respectively to obtain the corresponding phase distribution maps. After taking the difference between the corresponding positions of the phase maps, the lengths L1 and L2 of the major and minor axes at the phase difference of approximately π are found to complete the construction of a single unit cell. Finally, the entire metasurface PM is constructed according to the pattern requirements of the required exposure.

[0094] It should be noted that, in this invention, Figure 5 , Figure 6 and Figure 7 The results were all obtained using finite-difference time-domain simulation software.

[0095] This invention relates to a metasurface polarization mask, which is composed of multiple unit cells arranged according to a metasurface mask model. Each unit cell consists of a substrate and nanofins placed on the substrate. In this invention, a metasurface-constructed polarization mask is used to replace a traditional intensity mask. Each unit cell on the polarization mask can function as a half-wave plate. By rotating the unit cells arranged at specific positions by 45°, the polarization mask is fabricated. Using linearly polarized light passing through the metasurface polarization mask, the transferred pattern information is encoded in the polarization dimension rather than the intensity dimension. This avoids light intensity variations caused by diffraction and beam transformation during imaging, and also prevents distortion of the transferred pattern, resulting in more accurate exposure patterns on the wafer.

[0096] Furthermore, such as Figure 9 As shown, based on a metasurface polarization mask, the present invention also provides a photolithography method based on a metasurface polarization mask, wherein the photolithography method based on a metasurface polarization mask includes:

[0097] Step S91: Generate a target beam according to the light source, and expand the target beam through a lens group to cover the metasurface polarization mask;

[0098] Step S92: Based on the multiple unit cells at a preset angle on the metasurface polarization mask, the target beam is polarized to obtain a first target beam, which is then incident on the projection lens.

[0099] Step S93: According to the projection lens, the first target beam is scaled to obtain the second target beam, and after being incident on the thin film polarizer on the upper surface of the wafer, the third target beam is obtained.

[0100] Step S94: The third target beam reacts with the photoresist on the wafer to complete the exposure, and the exposed wafer is developed and etched to obtain the target pattern.

[0101] Specifically, the present invention is achieved through, as follows Figure 10 The apparatus shown implements the corresponding photolithography method based on a metasurface polarization mask. A target beam is generated by a laser 100. After passing through a beam expander and lens group 101, the laser beam is expanded to a sufficiently large diameter to cover the entire polarization mask 102 region. The beam above the polarization mask is linearly polarized, and the polarization state of the outgoing region will change. Finally, the beam passes through a projection lens 103 and is incident on the wafer 106 to obtain the target pattern.

[0102] Further, the step of polarizing the target beam according to multiple unit cells at a preset angle on the metasurface polarization mask to obtain a first target beam, which is then incident on the projection lens, specifically includes:

[0103] Based on multiple unit cells at a preset angle on the metasurface polarization mask, a specific range in the target beam is converted to obtain a first target beam, wherein the first target beam includes linearly vertically polarized light and linearly horizontally polarized light;

[0104] The first target beam is incident on the projection lens.

[0105] Specifically, in this invention, the metasurface polarization mask polarizes the target beam by selecting 45° cells corresponding to the internal pattern, converting the light passing through these cells into linearly vertically polarized light, while other light remains linearly horizontally polarized. The first target beam is then incident on the projection lens, and scaled according to the projection lens to obtain a second target beam. This second target beam is then incident on a thin-film polarizer on the upper surface of the wafer to obtain a third target beam.

[0106] Furthermore, the third target beam reacts with the photoresist on the wafer to complete the exposure, and the exposed wafer is then developed and etched to obtain the target pattern, specifically including:

[0107] A third target beam is incident on a thin-film polarizer on the wafer. The linearly horizontally polarized light in the third target beam reacts with the photoresist on the wafer through the thin-film polarizer. The reacted wafer is then developed to dissolve the reacted portion, resulting in a dissolved wafer.

[0108] The dissolved wafer is etched to obtain the target pattern.

[0109] Specifically, the first layer above the wafer is a thin-film polarizer 104, whose main function is to act as an analyzer; the second layer is photoresist 105. After passing through the polarizing mask, some light becomes linearly vertically polarized light. Then, the thin-film polarizer acts as an analyzer, allowing some linearly polarized light parallel to the transmission axis to enter the upper surface of the wafer and react chemically with the photoresist. The linearly polarized light perpendicular to the transmission axis cannot pass through the analyzer and therefore cannot react chemically with the photoresist on the wafer. Thus, the light corresponding to the external pattern passes through the thin-film polarizer and reacts chemically with the photoresist on the wafer, thereby completing the initial transfer of the pattern and realizing the exposure process. After exposure, the wafer is placed in the developer. The areas where the chemical reaction occurred will be dissolved, while the pattern in the areas where the chemical reaction did not occur will be preserved by the photoresist. The pattern of the photoresist layer is then transferred to the wafer through deposition or etching processes.

[0110] Since polarization masks are based on polarization vector control technology, they need to be encoded in the polarization dimension. Therefore, during the imaging process, the polarization needs to be unaffected by the imaging system. The key component of the photolithography imaging system is the projection lens. Therefore, a 4:1 or 5:1 magnification projection lens is selected to achieve the reduction and transfer of the mask pattern.

[0111] Furthermore, in one embodiment of the present invention, when the user determines that the refractive index of the selected medium is not large or the length-to-width ratio of the nanofins is not large, it is not easy to obtain a phase difference of π between the fast axis and the slow axis, but it is easy to achieve a phase difference of π / 2. Therefore, two cascaded quarter-wave plate metasurface masks can be used instead of a half-wave plate metasurface mask. The fast axes of the two quarter-wave plate metasurface masks are set to the same angle, and they are arranged sequentially with a certain distance between them. The first quarter-wave plate metasurface mask converts linearly polarized light into circularly polarized light, and the second quarter-wave plate metasurface mask converts circularly polarized light back into linearly polarized light; finally, by encoding the polarization vector beam, the exposure of a specific area is completed.

[0112] In summary, the lithography method based on metasurface polarization masks proposed in this invention uses metasurface polarization masks instead of traditional intensity masks. By encoding the pattern in the polarization dimension rather than the intensity dimension, it can effectively avoid a series of problems such as pattern distortion and aberration caused by diffraction and beam transformation during the imaging process, as well as light intensity changes. This not only improves the flexibility of light field modulation but also increases the lithography resolution. Thus, it avoids the need for various optical resolution enhancement techniques and advanced computational lithography techniques used in traditional lithography to correct diffraction and other problems caused by intensity changes, reduces the complexity of mask manufacturing processes, and greatly improves pattern transfer accuracy.

[0113] Furthermore, to achieve the above objectives, the present invention also provides a photolithography apparatus based on a metasurface polarization mask, wherein the apparatus comprises three parts: a metasurface polarization mask, a polarization-insensitive imaging system, and a polarization analyzer and developer. The metasurface polarization mask is used to polarize the target beam to obtain a first target beam, which is then incident on a projection lens. The polarization-insensitive imaging system is used to generate the target beam according to the light source, expand the target beam through a lens group to cover the metasurface polarization mask, and scale the first target beam according to the projection lens to obtain a second target beam, which is then incident on a thin-film polarizer on the surface of a wafer to obtain a third target beam. The polarization analyzer and developer are used to react the third target beam with the photoresist on the wafer to complete the exposure, and to develop and etch the exposed wafer to obtain the target pattern. In one embodiment of the present invention, as... Figure 10As shown, the laser 100, the beam expander and lens group 101 and the projection lens 103 constitute a polarization-insensitive imaging system. The polarization mask 102 and the nanofins 107 therein constitute a metasurface polarization mask part. The nanofins 107 are one of the first nanofins and the second nanofins. The thin film polarizer 104, the photoresist 105 and the wafer 106 constitute the polarization analysis and development part.

Claims

1. A metasurface polarization mask, characterized in that, The metasurface polarization mask is formed by arranging multiple unit cells according to a preset metasurface mask modeling pattern; The preset metasurface mask modeling pattern includes an outer pattern with a vertical pattern area and an inner pattern with a horizontal pattern area. The unit cells corresponding to the outer pattern are arranged in a first manner, and the unit cells corresponding to the horizontal pattern are arranged in a second manner at a predetermined angle to the first manner. Each unit cell includes a substrate and nanofins placed on the substrate; The nanofins on the unit cell are in the shape of cuboids or elliptical cylinders, the nanofins are made of hafnium dioxide, and the substrate is made of silicon dioxide. When the shape of the nanofin is cuboid, the process of setting the size of the nanofin includes: The length and height of the nanofin are scanned to obtain a first transmission distribution map. In the first transmission distribution map, the height corresponding to the case with the highest transmittance in the first transmission distribution map is selected as the cuboid height of the nanofin. Based on the height of the cuboid, the length and width of the nanofins are scanned to obtain a second transmission distribution map; The unit cell is scanned under horizontally polarized light and vertically linearly polarized light to obtain the length and width of the nanofins, and the corresponding phase distribution map is obtained. The difference between the corresponding positions of the phase distribution map is then taken to obtain the first phase difference map. Select the length and width coordinates of the phase difference within a preset range near π from the first phase difference map, and obtain the transmittance corresponding to the length and width of the phase difference within a preset range near π from the second transmission distribution map. Select the length and width corresponding to the case with the highest transmittance as the corresponding cuboid length and cuboid width.

2. The metasurface polarization mask according to claim 1, characterized in that, The metasurface mask modeling diagram includes an internal diagram and an external diagram; The internal diagram is drawn using a horizontal polarization vector, while the external diagram is drawn using a vertical polarization vector.

3. The metasurface polarization mask according to claim 2, characterized in that, The multiple unit cells in the metasurface polarization mask are arranged according to the modeling diagram of the metasurface mask; The predetermined angle between the second method and the first method is 45°.

4. The metasurface polarization mask according to claim 1, characterized in that, When the shape of the nanofin is an elliptical cylinder, the process of setting the size of the nanofin includes: The length of the major axis and the height of the nanofin are scanned to obtain a third transmittance distribution map. The height corresponding to the highest transmittance in the third transmittance distribution map is selected as the height of the elliptical cylinder of the nanofin. The unit cell is scanned under horizontally polarized light and vertically linearly polarized light to obtain a second phase difference map by scanning the long axis and short axis of the nanofin. The length and width corresponding to the difference of π in the second phase difference graph are selected as the major axis length and minor axis length of the elliptical cylindrical section of the nanofin.

5. A photolithography method based on the metasurface polarization mask according to any one of claims 1-4, characterized in that, Specifically, it includes: A target beam is generated based on a light source, and the target beam is expanded through a lens group to cover the metasurface polarization mask; The target beam is polarized by multiple unit cells at a preset angle on the metasurface polarization mask to obtain a first target beam, which is then incident on the projection lens. The first target beam is scaled according to the projection lens to obtain the second target beam, and then incident on the thin film polarizer on the upper surface of the wafer to obtain the third target beam. The third target beam reacts with the photoresist on the wafer to complete the exposure, and the exposed wafer is then developed and etched to obtain the target pattern.

6. The photolithography method for a metasurface polarizing mask according to claim 5, characterized in that, The step of polarizing the target beam according to multiple unit cells at a preset angle on the metasurface polarization mask to obtain a first target beam, which is then incident on the projection lens, specifically includes: Based on multiple unit cells at a preset angle on the metasurface polarization mask, a specific range in the target beam is converted to obtain a first target beam, wherein the first target beam includes linearly vertically polarized light and linearly horizontally polarized light; the specific range is the light in the target beam that passes through the multiple unit cells at the preset angle; The first target beam is incident on the projection lens.

7. The photolithography method for a metasurface polarizing mask according to claim 6, characterized in that, The third target beam reacts with the photoresist on the wafer to complete the exposure, and the exposed wafer is then developed and etched to obtain the target pattern, specifically including: A third target beam is incident on a thin-film polarizer on the wafer. The linearly horizontally polarized light in the third target beam reacts with the photoresist on the wafer through the thin-film polarizer. The reacted wafer is then developed to dissolve the reacted portion, resulting in a dissolved wafer. The dissolved wafer is etched to obtain the target pattern.

8. The photolithography method for a metasurface polarizing mask according to claim 5, characterized in that, The projection lens is a 4:1 or 5:1 magnification projection lens.

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