Improved 4 method for improving resolution of photoetching machine

Abstract

According to the improved method for improving the resolution ratio of the photoetching machine, an optical storage unit is arranged between an objective lens and a wafer, during exposure, signal light passes through a lens system and then is temporarily stored in the optical storage unit in an atomic spin wave form, and the energy of the light is converted into the energy of medium atoms of the optical storage unit; subsequently, the stored light information is released according to the original direction and can be regarded as an ideal point light source, the point light source is propagated according to the original direction, the propagation path is not limited by the lens aperture, the effective aperture is increased, the corresponding Airy spot is reduced, and the minimum distinguishable size is reduced; the Airy spot width is narrowed, and the resolution of the photoetching machine is greatly improved, so that the requirement on the aperture of the photoetching machine can be reduced, and in order to realize the same resolution requirement, the lens imaging system can adopt a small aperture, thereby invisibly reducing the manufacturing difficulty and cost.

Description

Technical Field

[0001] The present invention relates to the technical field of photolithography machines, and in particular to an improved method for improving the resolution of a photolithography machine. Background Art

[0002] In the field of chip manufacturing, lithography machine (also known as mask alignment exposure machine, exposure system, lithography system, etc.) is a very critical equipment. It uses optical projection imaging technology to transfer the pattern on the photomask (Photo-mask, also known as photomask) to the wafer, which is the key to achieving mass production of chips.

[0003] With the development of the chip industry, the same chip area needs to accommodate more and more components and wiring, and the resolution of the lithography machine needs to be continuously improved. In optical projection imaging, the diffraction limit of light is an important factor that limits the improvement of resolution. The diffraction limit refers to an ideal object point imaged by an optical system. Due to the limitation of diffraction, an ideal image point cannot be obtained, but a Fraunhofer diffraction image is obtained, which is the so-called Airy disk (diffuse spot). This is an important factor affecting the resolution of the optical projection imaging system. In optical imaging, two object points are imaged and two diffuse spots are obtained. If they are too close, it is difficult to distinguish. The larger the diffuse spot, the lower the resolution. For the same optical system, the smaller the wavelength of light, the smaller the diffuse spot, and the higher the resolution. Therefore, reducing the wavelength of the lithography machine light source can improve the resolution of the lithography machine.

[0004] The evolution of the wavelength of the lithography light source:

[0005]

[0006] When the wavelength is reduced to 193nm, the engineering difficulty of going further is getting greater and greater, because light becomes easily absorbed, and the original lens, photoresist and other supporting materials cannot be used, and all must be redeveloped. Therefore, at 193nm, engineers developed a new technical solution, which is immersion lithography. When light propagates in water, the refractive index of water is greater than that of air, so the wavelength becomes smaller. Using this solution, the wavelength of the light source can be shortened from 193nm to 132nm in one fell swoop. Immersion lithography has a very good effect after application, and it is still a widely used successful solution.

[0007] To manufacture chips below 5 nanometers, the chip industry generally believes that the wavelength of the light source requires EUV. EUV has a wavelength of 13.5nm and is classified as extreme ultraviolet light, but it is no longer strictly optical radiation, but a soft X-ray. Currently, there is no optical material that can refract it, and the air can absorb it, so the EUV lithography machine must be evacuated. The EUV optical path system uses reflectors coated with multi-layer molybdenum silicon interference optical films, and refractive lenses cannot be used. The engineering implementation is very difficult. There is currently only one manufacturer of EUV lithography machines, the Dutch company AXML, and it is currently unavailable in China.

[0008] We have a deep understanding of the underlying physical laws and thinking, and have developed innovative technical routes, which greatly reduce the technical difficulty and can provide excellent performance.

[0009] The inventor has filed the following Chinese patent applications on the same subject:

[0010] Patent 1 (Name: A method for improving the resolution of a photolithography machine Application number: 2023109064718 Application date: 20230724)

[0011] Patent 2 (Name: Improved method for improving the resolution of photolithography machine Application number: 202311159318X Application date: 20230910 Patent number: ZL 2023 1 1159318.X Authorization announcement date: July 2, 2024)

[0012] The present invention application has made some technical improvements on the basis of the above-mentioned Patent 2. Since there are many connections between the two, the present invention application retains part of the content of Patent 2. For ease of reading, the improved parts in the present invention application are specially marked: "The improved part of the present invention application begins" and "The improved part of the present invention application ends". Summary of the invention

[0013] The present invention demonstrates a new technical solution for improving the resolution of a photolithography machine.

[0014] The invention application improvement part 1

[0015] In subsequent research, we found that the patented method solves the interference between different photons, but even for a single photon, when it passes through an optical system with a certain aperture, its inherent Airy disk is still limited by the Rayleigh criterion. An ideal point light source will diffract after passing through an aperture with a diameter of D, which is a small hole or a lens system, and its diffraction pattern is an Airy disk. Because of the Airy disk, the minimum resolvable angle is calculated by the following formula:

[0016]

[0017] In the formula, λ is the frequency of the point light source, and D is the diameter of the aperture.

[0018] The resolution of the lithography machine is limited by the Rayleigh criterion, and the minimum resolvable size of the lithography machine is calculated by the following formula:

[0019]

[0020] In the formula, λ is the wavelength of light, K1 is the process coefficient factor, NA is the numerical aperture of the lithography objective, NA=n.sinθ, n is the refractive index, that is, the refractive index of the medium between the wafer and the lens. If it is air, its refractive index is close to 1.0, if it is a vacuum, its refractive index is 1.0, and the immersion lithography machine uses a transparent liquid with a high refractive index, such as deionized water, whose refractive index is 1.46.

[0021] θ represents the incident angle.

[0022] In order to obtain the smallest possible minimum resolvable size, the current lithography machine has the following method: method 1 is to increase the aperture, so the lens size of the current lithography machine is very large, which invisibly increases the difficulty and cost of manufacturing. Method 2 is immersion, where a high refractive index medium is used between the wafer and the lens, such as deionized water, whose refractive index n is 1.46, which is about 1.46 times the refractive index of air and vacuum.

[0023] This application uses the electromagnetically induced transparency (EIT) effect. The frequency of the probe light (also called signal light) corresponds to the absorption transition frequency of the medium. When it is incident on the medium alone, the probe light cannot pass through the medium due to the strong resonance absorption of the medium at this frequency. Another beam of strong control light (also called coupled light) forms a three-level atomic system with the probe light. When the strong control light exists, the strong control light field causes quantum coherent interference, and the probe light is almost not absorbed and passes through the medium, that is, electromagnetically induced transparency (EIT) occurs, and the refractive index of the medium changes sharply (see the attached figure of the specification). Fig.12 ), which causes the group velocity of the detection light to slow down. The group velocity of the detection light can be adjusted by changing the intensity of the control light. The lower the intensity of the control light, the slower the group velocity of the detection light. When the control light is adiabatically turned off, the group velocity of the detection light becomes 0, that is, the detection light is saved to the medium in the form of atomic spin waves, and the optical information is stored in the medium. This is called the optical writing process, and the control light of this process is called the writing light. The process of reading the stored optical information is called the optical reading process, and the control light of this process is called the reading light. When the reading light is turned on again, if the frequency and direction of the reading light are the same as the writing light, the stored optical information will be released according to the original frequency and direction; if the frequency and direction of the reading light are different from the writing light, the stored optical information will be released according to the new frequency and new direction.

[0024] The detection light, control light writing light and readout light are Figure 1 The timing of the optical storage can be realized.

[0025] Detection light and control light according to Figure 2 The timing of light slow light can be achieved.

[0026] Method 1 of the present application is to place an optical storage unit between an objective lens and a wafer, and control the timing of control light and detection light. During exposure, after the detection light passes through the lens system, it is temporarily stored in the optical storage unit in the form of atomic spin waves, and the energy of the light is converted into the energy of the atoms in the medium of the optical storage unit, and then restored to light according to the original propagation direction. The process of light restoration is to convert the energy of the atoms in the medium of the optical storage unit into the energy of light. If the frequency and direction of the read light are the same as those of the write light, the stored optical information will be released according to the original frequency and direction; if the frequency and direction of the read light are different from those of the write light, the stored optical information will be released according to the new frequency and new direction. After the stored optical information is released, it can be regarded as a newly generated ideal point light source. This point light source propagates in the direction of generation. In this application, it will propagate in the original direction before writing. Since the propagation path is not limited by the lens aperture, the effective aperture becomes larger, the corresponding Airy disk becomes smaller, and the minimum resolvable size will be reduced. When this point light source reaches the wafer, the Airy disk width becomes narrower, and the resolution of the lithography machine is greatly improved. The benefit of this is that the aperture requirements for the lithography machine can be reduced. In order to achieve the same resolution requirements, the lens imaging system can adopt a small aperture, which invisibly reduces the difficulty and cost of manufacturing.

[0027] Method 2 of the present application is to place a light slow light unit between the objective lens and the wafer. During exposure, after the detection light passes through the lens system, in the light slow light unit, because its frequency corresponds to the absorption transition frequency of the medium, when it is incident on the medium alone, due to the medium's strong resonance absorption of this frequency, the detection light cannot pass through the medium. Another beam of strong control light (also called coupled light) forms a three-level atomic system with the detection light. When the strong control light exists, the strong control light field causes quantum coherent interference, and the detection light is almost not absorbed and passes through the medium, that is, electromagnetic induced transparency (EIT) occurs, and the refractive index of the medium changes sharply (see the attached manual). Fig.12 ), which causes the group velocity of the detection light to slow down. Here, our focus is on the refractive index of the medium. When a specific detection light frequency is selected, the group velocity of the detection light when passing through the medium is slowed down, the equivalent wavelength of the detection light becomes shorter, and the refractive index of the medium increases significantly. The medium becomes a super-refractive medium with a large refractive index, just like the working mechanism of an immersion lithography machine. The optical slow light unit narrows the width of the Airy disk, reduces the minimum resolvable size of the lithography machine, and improves the resolution.

[0028] End of the Improvement Part 1 of the Invention Application

[0029] The present invention is further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 : is a working timing diagram of the optical storage unit. Incident detection light refers to detection light before light is stored in the medium (414), outgoing detection light (415) refers to detection light restored after being stored in the medium, outgoing detection light (415) is detection light received by the photoresist (3102), writing light refers to control light (416) for storing detection light in the medium, read light and read light 2 refer to control light (416) for restoring detection light stored in the medium, the difference between these two read lights is that the amplitude of the read light and the writing light is the same, while the amplitude of the read light 2 is greater than the amplitude of the writing light, the read light, the read light 2 and the writing light are all control light (416), and they are subdivided because of different functions, the optical switch signal refers to the switch control signal of the optical switch (417, shown in Patent 2), the opening and closing of the optical switch (417) is controlled by the optical switch signal, the horizontal axis of the curve in the figure represents time, and the vertical axis represents the intensity of light. T1-T8 represent the relevant nodes on the time axis in the figure.

[0031] At time point T1, the write light is turned on. After a certain period of time, at time point T2, the incident detection light is turned on. Due to the existence of the write light as the control light, the electromagnetic induced transparency (EIT) effect is generated, and the incident detection light can propagate in the medium. Due to the slow light effect, its group velocity in the medium is lower than the speed of light propagating in a vacuum. At time point T3, the write light is turned off, and the write light no longer exists as the control light. The propagation of the incident detection light in the medium stops and is stored in the medium. At time point T4, the read light is turned on. Due to the existence of the read light as the control light, the incident detection light stored in the medium is restored to the outgoing detection light and continues to propagate. Due to the slow light effect, its group velocity in the medium is lower than the speed of light propagating in a vacuum. When the read light is replaced by the read light 2, because the amplitude of the read light 2 is greater than the read light, the restored outgoing detection light will be accelerated, thereby achieving the compression of the outgoing detection light pulse on the time axis. If the amplitude of the read light 2 is smaller than the read light, the opposite effect will occur, and the outgoing detection light pulse will be stretched on the time axis. At time T5, the outgoing detection light begins to leave the medium. At time T6, the outgoing detection light completely leaves the medium. The optical switch signal of the optical switch (417) is turned on at time T5 and turned off at time T6, which is precisely aligned with the timing of the outgoing detection light. Only photons in this specific time interval are selected, so a large amount of noise can be filtered out to achieve the purpose of time filtering. At time T7, the readout light (or readout light 2) is turned off. At time T8, a write-read cycle ends, and then the next cycle begins.

[0032] Figure 2This is the working timing diagram of the optical slow light unit. At time T4, the control light is turned on. Due to the existence of the control light, the electromagnetic induced transparency (EIT) effect is generated, and the detection light can propagate in the medium. Due to the slow light effect, its group velocity in the medium is lower than the speed of light propagating in a vacuum. At time T5, the detection light is turned on. Due to the electromagnetic induced transparency (EIT) effect, the detection light can propagate in the medium. At time T6, the detection light completely leaves the medium. At time T7, the control light is turned off. At time T8, a timing cycle ends, and then the next cycle begins.

[0033] The invention application improvement part 2

[0034] Figure 3 Schematic diagram of Airy disks of different widths according to the present invention.

[0035] Figure 3 In the figure, (a) has a larger width and (b) has a smaller width. The smaller the Airy disk width, the smaller the minimum resolvable size, and the higher the resolution of the lithography machine. The purpose of the present invention is to make the width of the Airy disk as small as possible, so that the resolution of the lithography machine can be improved.

[0036] Figure 4 Schematic diagram showing the limitation of Rayleigh criterion of the present invention.

[0037] Figure 4 In the figure, an ideal point light source (1501) emits a light (1502) through an aperture (1503) of diameter D, which is a small hole or a lens system. Due to the diffraction effect, the light spot is an Airy disk (1504). Because of the Airy disk, the minimum resolvable angle θ is calculated by the above formula 1.1.

[0038] Figure 5 It is a schematic diagram showing the principle of the minimum resolvable size of a photolithography machine according to the present invention.

[0039] Figure 5 In the figure, 1601 is the mask, 1602 is the dot pattern on the mask that can transmit light, the light (1603) passes through the dot pattern (1602), and the light (1603) is diffracted. The lens system consists of two lenses (1604 and 1605), 1605 is the photolithography objective lens, the light (1603) propagates in the lens system, 1606 is the medium, n is its refractive index, 310 is the wafer, 3102 is the photoresist on the surface of the wafer (310), θ is the incident angle of the objective lens (1605), and the minimum resolvable size of the photolithography machine is calculated by the above formula 1.2. After the point light source passes through the lens system of the photolithography machine, due to the diffraction effect, its light spot is an Airy disk (1607). The smaller the width of the Airy disk, the higher the resolution of the photolithography machine.

[0040] Figure 6It is a schematic diagram of the structure of the relevant parts of the lithography machine in an embodiment of the present invention.

[0041] Figure 6 In the figure, 301 is a laser, 302 is the output light of the laser (301), 303 is a reflector, 304 is a light processing unit for filtering, homogenizing, beam adjustment, etc., 305 is a reflector, 306 is a core functional unit of the present invention, which is an optical storage unit in Example 1 and an optical compression and light slowing unit in Example 2, 307 is a mask, 308 is a mask positioning table, 309 is a lens group, 310 is a wafer, 311 is a wafer table, 312 is a core functional unit of the present invention, which is an optical storage unit in Example 3 and an optical slowing unit in Example 4. Compared with the existing lithography machine, the main parts improved by the present invention are: laser (301) and the core functional units (306 and 312) of the present invention. The improvement of the laser (301) mainly lies in the frequency, and the selected frequency is the resonance transition frequency of the medium atoms.

[0042] Figure 7 It is a schematic diagram of the principle of a side structure of an enlarged local structure in a photolithography machine in an embodiment of the present invention.

[0043] Figure 7 (a) shows a magnified side structure of a local structure in a photolithography machine, 309 is a lens group, 310 is a wafer, 311 is a wafer stage, 3102 is a photoresist on the surface of the wafer (310), 312 is a core functional unit of the present invention, which is an optical storage unit in Example 3 and an optical slow light unit in Example 4. 415 is a detection light beam, and 416 is a control light beam.

[0044] Figure 7 (b) shows the structure of 312. 413 is a cryogenic cavity. In order to maximize the aperture and make the Airy disk narrower, the cryogenic cavity uses a transparent material (preferably quartz material, including other available transparent materials) and has a diameter as large as possible. The cryogenic cavity also includes a vacuum system and a liquid helium refrigeration system, which are not shown in the figure. The vacuum system provides the required vacuum environment. The liquid helium refrigeration system reduces the temperature of the cryogenic cavity to 3.5K and maintains it, making the temperature of the cryogenic cavity as close to absolute zero as possible, so that the thermal motion of the medium can be reduced and the noise can be reduced. 414 is a medium, which can be selected from praseodymium-doped yttrium silicate crystals (Pr3+:Y2SiO5) or europium chloride hexahydrate (EuCl3.6H2O) single crystals.

[0045] Figure 8 It is a schematic diagram of the side structure principle of another enlarged local structure in the lithography machine in an embodiment of the present invention.

[0046] Figure 8In the figure, 309 is a lens group, 310 is a wafer, 311 is a wafer stage, 3102 is a photoresist on the surface of the wafer (310), 312 is a core functional unit of the present invention, which is an optical storage unit in embodiment 3 and an optical slow light unit in embodiment 4, 414 is a medium, which can be atomic vapor of metal. 415 is a beam of detection light, and 416 is a beam of control light.

[0047] Fig. 9 It is a schematic diagram of the principle of light beam preparation of an optical storage unit in embodiment 3 of the present invention.

[0048] Fig. 9 In the figure, 401 is the incident light, 402 is the half-wave plate, 403 is the beam splitter, which splits one light beam into two light beams, 404 is the detection light focusing lens, which focuses the light (401), 405 is the detection light parallel lens, which collects the focused light (401) into a parallel light beam with a small diameter, 406 is the detection light acousto-optic modulator (AOM), which is responsible for adjusting the frequency of the detection light to the required frequency, and is also responsible for turning the light off and on to achieve timing control. 418 is the focusing lens, which focuses the detection light beam (415), 419 is the parallel lens, which collects the focused detection light beam (415) into a parallel light beam with a large diameter, and 415 is the detection light.

[0049] 420 is a beam splitter, which splits one light beam into two light beams, 408 is a control light focusing lens, which focuses the light (401), 409 is a control light parallel lens, which collects the focused light (401) into a parallel light beam with a small diameter, 410 is a control light acousto-optic modulator (AOM), which is responsible for adjusting the frequency of the control light to the required frequency, and is also responsible for turning the light off and on to achieve timing control, and 4161 is the writing light of the control light.

[0050] 429 is a beam splitter, which splits one light beam into two light beams, 430 is a control light focusing lens, which focuses the light (401), 431 is a control light parallel lens, which collects the focused light (401) into a parallel light beam with a small diameter, 432 is a control light acousto-optic modulator (AOM), which is responsible for adjusting the frequency of the control light to the required frequency, and is also responsible for turning the light off and on to achieve timing control, and 4162 is the readout light of the control light.

[0051] 421 is a reflector, 422 is a pump light focusing lens, which focuses the light (401), 423 is a pump light parallel lens, which collects the focused light (401) into a parallel light beam with a small diameter, 424 is an acousto-optic modulator (AOM) of the pump light, which is responsible for adjusting the frequency of the pump light to the required frequency, and is also responsible for turning the light off and on to achieve timing control, and 427 is the pump light beam. The components described in this paragraph constitute auxiliary pump light beam splitting, referred to as pump light beam splitting, which functions to pump particles at the ground state energy level to a high energy level during the initial state preparation of electromagnetic induced transparency (EIT). Pump light beam splitting is of an auxiliary nature and may not be used in some application scenarios.

[0052] Fig.10 It is a schematic diagram of the principle of light beam preparation of an optical slow light unit in embodiment 4 of the present invention.

[0053] Fig.10 In the figure, 401 is the incident light, 402 is the half-wave plate, 403 is the beam splitter, which splits one light beam into two light beams, 404 is the detection light focusing lens, which focuses the light (401), 405 is the detection light parallel lens, which collects the focused light (401) into a parallel light beam with a small diameter, 406 is the detection light acousto-optic modulator (AOM), which is responsible for adjusting the frequency of the detection light to the required frequency, and is also responsible for turning the light off and on to achieve timing control. 418 is the focusing lens, which focuses the detection light beam (415), 419 is the parallel lens, which collects the focused detection light beam (415) into a parallel light beam with a large diameter, and 415 is the detection light.

[0054] 420 is a beam splitter, which splits one light beam into two light beams, 408 is a control light focusing lens, which focuses the light (401), 409 is a control light parallel lens, which collects the focused light (401) into a parallel light beam with a small diameter, 410 is an acousto-optic modulator (AOM) of the control light, which is responsible for adjusting the frequency of the control light to the required frequency, and is also responsible for turning the light off and on to achieve timing control, and 416 is the control light.

[0055] 421 is a reflector, 422 is a pump light focusing lens, which focuses the light (401), 423 is a pump light parallel lens, which collects the focused light (401) into a parallel light beam with a small diameter, 424 is an acousto-optic modulator (AOM) of the pump light, which is responsible for adjusting the frequency of the pump light to the required frequency, and is also responsible for turning the light off and on to achieve timing control, and 427 is the pump light beam. The components described in this paragraph constitute auxiliary pump light beam splitting, referred to as pump light beam splitting, which functions to pump particles at the ground state energy level to a high energy level during the initial state preparation of electromagnetic induced transparency (EIT). Pump light beam splitting is of an auxiliary nature and may not be used in some application scenarios.

[0056] Fig.11 It is a schematic diagram of the principle of realizing the electromagnetic induced transparency (EIT) effect by multiple reflections with a relatively low controlled light intensity in an embodiment of the present invention.

[0057] Fig.11 In the figure, 312 is the core functional unit of the present invention, and this figure shows its top plan view. In Example 3, it is an optical storage unit, and in Example 4, it is an optical slow light unit. 413 is a cryogenic cavity, and there are quartz light windows on two sides of the cryogenic cavity. The cryogenic cavity also includes a vacuum system and a liquid helium refrigeration system, which are not shown in the figure. The vacuum system provides the required vacuum environment, and the liquid helium refrigeration system reduces the temperature of the cryogenic cavity to 3.5K and maintains it, making the temperature of the cryogenic cavity as close to absolute zero as possible, so that the thermal motion of the medium can be reduced and the noise can be reduced. 414 is a medium, and praseodymium-doped yttrium silicate crystal (Pr3+:Y2SiO5) or europium chloride hexahydrate (EuCl3.6H2O) single crystal can be selected. 4161 is a control light beam serving as writing light, 4162 is a control light beam serving as reading light, 427 is a beam serving as auxiliary light, 1803 and 1804 are half-reflecting mirrors for merging two light beams into one light beam, 1801 is a high-reflectivity mirror located on the left, and 1802 is a high-reflectivity mirror located on the right.

[0058] Fig.12 The figure shows the detection light transmittance curve and the refractive index curve of the medium when the electromagnetic induced transparency (EIT) effect occurs. This figure is quoted from reference [7].

[0059] Fig.12 In the figure, a is the detection light transmittance curve, and b is the refractive index curve.

[0060] End of the Improvement Part 2 of the Invention Application DETAILED DESCRIPTION

[0061] Now, in conjunction with the above-mentioned drawings, the specific implementation process of the present invention is described in detail:

[0062] The invention application improvement part 3 begins

[0063] The medium used in the present invention to realize the slow light effect, optical storage or quantum storage function can be in the form of gas, liquid and solid. The medium in gaseous form includes but is not limited to: atomic vapor of metals, such as rubidium (Rb), cesium (Cs), potassium (K), sodium (Na), strontium (Sr), lead (Pb), praseodymium (Pr), cerium (Ce), etc. When using gas, a transparent gas chamber is often required, as well as a system to maintain a constant temperature for the gas chamber. Because gas and liquid flow, storage distortion will occur, so solid is the preferred storage medium.

[0064] The slow light effect is an important technical feature of the present invention. The existing known methods for realizing slow light can be applied to the present invention, including but not limited to: electromagnetic induced transparency (EIT), coherent population oscillation (CPO), spectral hole burning, Brillouin scattering, Raman scattering, and the like.

[0065] Photon quantum storage is an important technical feature of this embodiment. The solid photon storage or quantum storage function reported in the literature is mostly realized in rare earth doped crystals. There are also reports on the photon storage phenomenon in pure rare earth compound crystal single crystals. For example, there is a literature report on the realization of photon storage in EuCl3.6H2O (europium chloride hexahydrate) single crystals. Due to the lattice distortion caused by impurity rare earth ions, it is usually difficult to directly increase the concentration of rare earth ions to obtain a higher absorption depth. Using pure rare earth compound crystals is a solution, which has a perfect lattice structure, no lattice distortion caused by doping, and has a very high optical density. To perfectly implement the present invention, the key lies in the perfect distribution of medium atoms, and the distribution of atoms in the crystal is perfect, forming an orderly arranged material. At present, it is still difficult to manufacture nanostructures on a large scale in factories, and it is also difficult to ensure that each atom is evenly distributed during doping. Therefore, the optical storage medium of the lithography machine is preferably a monomer or compound crystal, which is a key feature of the present invention to achieve good results. Those skilled in the art can understand that under the direct guidance of the core spirit of the present invention and inspired by the explanation of the present invention, many kinds of suitable dielectric materials will continue to be discovered along this direction, including but not limited to metal single crystals of rare earth elements, pure rare earth compound crystals, single crystals of non-rare earth elements, and non-rare earth element compound crystals. Various replacements, changes and modified versions within the scope of patent protection can be smoothly implemented, and such replacements, changes and modifications should all belong to the scope of patent protection of the present invention. There is another advantage of using pure rare earth compound crystals, which has a perfect lattice structure and no lattice distortion caused by doping, so scattering noise can be effectively reduced. In the application of the lithography machine of the present invention, the noise of the light source will greatly affect the lithography effect. Therefore, in order to minimize the noise, it is preferred to use pure rare earth compound crystals, and the chemical purity should be increased as much as possible, the crystal growth process control should be improved, and the lattice distortion should be reduced. In addition to chemical purity, isotopic purity should also be increased as much as possible. Atoms have different isotopes. It can be found in public literature that after isotope purification of the chlorine (Cl) element, the inhomogeneous broadening of EuCl3.6H2O (europium chloride hexahydrate) can be effectively improved, and a very narrow line width can be obtained. After isotope purification of all elements of the compound, the line width can be even narrower. The narrow line width can improve the efficiency of photon quantum storage. These methods can all be used in the present invention, and many kinds of suitable dielectric materials with very narrow inhomogeneous broadening will continue to be discovered to obtain the best implementation effect.

[0066] It should be noted that for crystalline media, the lattice structure is highly consistent and often has anisotropic characteristics. The incident directions of the detection light and control light need to be precisely adjusted and maintained at a certain angle with the lattice structure to achieve good results.

[0067] There are many solutions for optical storage, including Electromagnetically Induced Transparency (EIT), the similar Spectral Hole Burning (SHB), Off-Resonant Raman-type excitations, Photo Echo, and Faraday Rotation of light. Under the category of Photon Echo, there are many subdivided categories, including Controlled Reversible Inhomogeneous Broadening (CRIB), Atomic Frequency Comb (AFC), Gradient Echo Memory (GEM), Hybrid Photon Echo (HYPER), etc. The principles of Electromagnetically Induced Transparency (EIT) and Off-Resonant Raman (SHB) are similar, and light is stored in the medium in the form of atomic spin waves. The optical storage of the present invention can adopt all known optical storage technical solutions, including but not limited to the above-mentioned optical storage technical solutions, and is not limited to electromagnetic induced transparency (EIT).

[0068] The frequency of the detection light (415) corresponds to the resonant absorption frequency of the medium of the optical slow light unit or the optical storage unit. The frequency is determined by the transition absorption frequency of the energy level selected by the medium (414). If the medium is a praseodymium-doped yttrium silicate crystal (Pr3+:Y2SiO5) and the 3H4→1D2 energy level transition is selected, the wavelength corresponding to the transition frequency is 605.78nm (nanometers). If the medium is a europium chloride hexahydrate (EuCl3.6H2O) single crystal and the 7F0→5D0 energy level transition is selected, the wavelength corresponding to the transition frequency is 579.7033nm.

[0069] Embodiment 3: In this embodiment, the optical storage unit is placed between the objective lens and the wafer. Figure 7 An optical storage unit of this embodiment is shown. Figure 8 Another optical storage unit of this embodiment is shown.

[0070] Figure 1This is a working timing diagram of the optical storage unit. At time point T1, the writing light (4161) of the control light (416) is turned on. After a certain period of time, at time point T2, the incident detection light (415) is turned on. Due to the existence of the writing light as the control light, an electromagnetically induced transparency (EIT) effect is generated, and the incident detection light can propagate in the medium. Due to the slow light effect, its group velocity in the medium is lower than the speed of light propagating in a vacuum. At time point T3, the writing light is turned off, and the writing light no longer exists as the control light. The propagation of the incident detection light in the medium stops and is stored in the medium. At time T4, the readout light (4162) of the control light (416) is turned on. Since the readout light exists as the control light, the incident detection light stored in the medium is restored to the outgoing detection light and continues to propagate. Due to the slow light effect, its group velocity in the medium is lower than the speed of light propagating in a vacuum. When the readout light is replaced by the readout light 2, because the amplitude of the readout light 2 is greater than the readout light, the restored outgoing detection light will be accelerated, thereby achieving compression of the outgoing detection light pulse on the time axis. If the amplitude of the readout light 2 is less than the readout light, the opposite effect will occur, and the outgoing detection light pulse will be stretched on the time axis. At time T5, the outgoing detection light begins to leave the medium. At time T6, the outgoing detection light completely leaves the medium. At time T7, the readout light (or readout light 2) is turned off. At time T8, a write-read cycle ends, and then the next cycle begins.

[0071] The control light (416) includes a write light (4161) and a read light (4162). The frequency, intensity and Airy disk width of the write light and the read light can be the same or different. When they are different, they can have a lot of matching options. Any combination of these can be applied in the present invention. When the intensity of the read light is greater than the intensity of the write light, the light group speed will increase after the stored light information is released. Conversely, when the intensity of the read light is less than the intensity of the write light, the light group speed will slow down after the stored light information is released. The write light and the read light can be modulated by optical systems with different apertures, so they have different Airy disk widths. By using different Airy disk widths, the release process of the stored light information can be finely adjusted and intervened to achieve the best effect. Any combination of the above can be applied in the present invention. By finely adjusting and intervening in the release process of the stored light information, the most suitable parameter combination is found to achieve the best effect. The present invention has no restrictions on the combination of parameters.

[0072] During exposure, after the detection light (415) passes through the lens system, it is temporarily stored in the optical storage unit (312) in the form of atomic spin waves, and the energy of the light is converted into the energy of the atoms in the optical storage unit medium, and then restored to light in the original propagation direction. The process of light restoration is to convert the energy of the atoms in the optical storage unit medium into the energy of light. If the frequency and direction of the read light are the same as those of the write light, the stored optical information will be released in the original frequency and direction; if the frequency and direction of the read light are different from those of the write light, the stored optical information will be released in the new frequency and new direction. After the stored optical information is released, it can be regarded as an ideal point light source. This point light source propagates in the direction of generation. In this application, it will propagate in the original direction before writing. Ideally, since the propagation path has no lens aperture limitation and no other aperture limitation, the aperture is almost infinite. According to the above formula 1.1, the minimum resolvable angle will be infinitesimal. In the actual physical world, infinitesimal does not exist because this leads to infinite energy density, which is a very small unit, much smaller than the resolution target nanometer we need to achieve. We call it the limit small, and the corresponding Airy disk is the limit small. The minimum resolvable size will be reduced to the limit small. When this point light source reaches the wafer, the influence of the Airy disk on the resolution can be ignored, and the resolution of the lithography machine is greatly improved. The above is the most ideal situation. In actual applications, the medium (414) requires support (not shown in the figure) and a low-temperature cavity (413), and the aperture cannot be infinite. The cryogenic cavity is made of transparent material (preferably quartz material, including other available transparent materials), and the diameter is as large as possible. After the light information stored in the medium (414) is released, it can be regarded as an ideal point light source. This point light source propagates in the direction of generation. The propagation path is not limited by the lens aperture. The propagation path is a transparent quartz material with a diameter as large as possible. The aperture limit becomes smaller, the Airy disk becomes narrower, and the resolution of the lithography machine is improved. As long as the aperture is large enough, the Airy disk will be narrow enough, and the resolution of the lithography machine will be high enough to meet the design requirements. It should be noted that the features described in this paragraph are not only applicable to Example 3, but also to Example 4. The optical storage unit can reduce the minimum resolvable size. The benefit of this is that the aperture requirement for the lithography machine can be reduced. In order to achieve the same resolution requirement, a small aperture can be used, which virtually reduces the difficulty and cost of manufacturing.

[0073] In the description of this embodiment, the optical storage unit (312) is placed between the objective lens and the wafer. However, since the light propagates in a straight line in the form of a point light source after leaving the optical storage unit, there is no aperture restriction. Therefore, the optical storage unit can be placed at any position between the mask and the wafer. However, considering that the stored optical information is released in the original direction, there will be a certain deviation in the direction, which is called the beam direction deviation in the present invention. The smaller the distance between the medium (414) in the optical storage unit (312) and the wafer, the better. This can reduce the exposure position deviation caused by the direction deviation. This is also suitable for Example 4. It will be explained later that, at the microscopic level, Example 4 is essentially also Example 3. When light passes through a fine pattern on the mask, there will be diffraction. Therefore, in this embodiment, the optical storage unit should not be placed in front of the mask on the optical path. The optical storage unit can be close to the mask and the wafer. There are examples in practice. For example, the well-known near-field optical microscope technology is to make the distance between the probe and the object to be detected as small as possible, so as to break through the diffraction limit and achieve nanometer-level resolution.

[0074] Embodiment 4: In this embodiment, the light slow light unit is placed between the objective lens and the wafer. Figure 7 A light slow light unit of this embodiment is shown. Figure 8 Another optical slow light unit of this embodiment is shown.

[0075] Figure 2 This is a working timing diagram of the optical slow light unit. At time T4, the control light (416) is turned on. Due to the existence of the control light, an electromagnetically induced transparency (EIT) effect is generated, and the detection light (415) can propagate in the medium (414). Due to the slow light effect, its group velocity in the medium is lower than the speed of light propagating in a vacuum. At time T5, the detection light (415) is turned on. Due to the electromagnetically induced transparency (EIT) effect, the detection light can propagate in the medium. At time T6, the detection light completely leaves the medium. At time T7, the control light is turned off. At time T8, a timing cycle ends, and then the next cycle begins.

[0076] During exposure, after the detection light (415) passes through the lens system, in the light slow light unit, because its frequency corresponds to the absorption transition frequency of the medium, when it is incident on the medium (414) alone, due to the strong resonance absorption of the medium to this frequency, the detection light cannot pass through the medium. Another beam of control light (416) forms a three-level atomic system with the detection light. When the control light exists, the control light field causes quantum coherent interference, and the detection light is almost not absorbed and passes through the medium, that is, electromagnetic induced transparency (EIT) occurs, and the refractive index of the medium changes sharply (see the attached manual). Fig.12), which results in a slow group velocity of the probe light. Here, our focus is on the refractive index of the medium. We select the frequency of the probe light, at which the refractive index is at a maximum. According to formula 1.2, when the refractive index of the medium increases, its minimum resolvable size decreases. When the refractive index increases, the frequency of the light remains unchanged, the group velocity of the light slows down, and the effective wavelength of the light decreases, all of which lead to a narrowing of the Airy disk width.

[0077] In the description of this embodiment, the light slow light unit is placed between the objective lens and the wafer. However, because the light slow light unit allows light to exchange energy with the medium, the width of the Airy disk of light has become narrower, so the light slow light unit can be placed at any position between the mask and the wafer. However, due to the deviation of the light beam direction, the distance between the medium (414) in the optical storage unit (312) and the wafer should be as small as possible.

[0078] When light passes through the fine pattern on the mask, it will be diffracted, so in this embodiment, the light slow light unit should not be placed in front of the mask on the light path. The light slow light unit can be close to the mask and the wafer. There are examples in practice. For example, the well-known near-field optical microscopy technology is to make the distance between the probe and the object to be detected as small as possible, so as to break through the diffraction limit and achieve nanometer-level resolution.

[0079] It should be noted that other descriptions in this specification or in the following patents:

[0080] Patent 1 (Name: A method for improving the resolution of a photolithography machine Application number: 2023109064718 Application date: 20230724)

[0081] Patent 2 (Name: Improved method for improving the resolution of photolithography machine Application number: 202311159318X Application date: 20230910 Patent number: ZL 2023 1 1159318.X Authorization announcement date: July 2, 2024)

[0082] Unless otherwise specified, the features in these descriptions are also applicable to Example 3 and Example 4, and these descriptions will not be repeated below. The following is a summary of some common features of the above-mentioned Example 3 and Example 4:

[0083] In the above embodiment, in order to make the Airy disk width as narrow as possible and thus achieve better resolution, the measures taken include: 1) See Figure 7(b) In order to increase the aperture as much as possible, the low-temperature cavity (413) is made of transparent material (preferably quartz material, including other available transparent materials) and has a diameter as large as possible, and its parallel plate structure is less difficult to manufacture than a lens; 2) The distance between the medium (414) and the wafer (310) is reduced as much as possible; 3) A medium (414) that can be used at room temperature is developed, so that no container is required, including a low-temperature container (413) and a constant temperature heating container (not shown in the figure); 4) The support structure of the medium (414) (not shown in the figure) is made of transparent material (preferably quartz material, including other available transparent materials) and has a diameter as large as possible, and at the same time, the compression structure that fixes the medium (414) is designed to be as small as possible to minimize interference with light propagation.

[0084] In the above embodiment, according to the existing photolithography technology, the exposure area of ​​the wafer is on the order of 33mm x 26mm. The area of ​​the medium (414) is larger than this. In such a large area, to achieve the electromagnetic induced transparency (EIT) effect, the required control light (416) intensity is very large. In order to reduce the requirement for the control light intensity, it is preferred to use Fig.11 The structure in the figure is called a multi-reflected control light to reduce the requirement for the control light intensity. The control light (416) includes a write light (4161) and a read light (4162). The control light (416) is reflected multiple times inside the medium (414) by using high-reflectivity reflectors (1801 and 1802). The reflectors (1801 and 1802) in the figure can be separate or integrated. The mirrors (1801) on the left side of the figure are connected to form a large mirror, and the mirrors (1802) on the right side of the figure are connected to form a large mirror.

[0085] In the above-mentioned embodiments, the core spirit of the present invention is explained by using a transmissive lens system. A reflective projection system is used in an EUV lithography machine, and this type of reflective projection system can also apply the present invention to improve the resolution.

[0086] In the above-mentioned embodiments, the main purpose is to improve the resolution of the lithography machine. The lithography machine is essentially an optical imaging system, so the present invention can be applied to any optical imaging system to narrow the Airy disk width to improve the resolution, including but not limited to optical imaging systems such as microscopes, telescopes, radars, cameras, and cameras.

[0087] In the above embodiments, after the exposure light is processed by the optical slow light or optical storage unit, its Airy disk width becomes narrower in the medium and after leaving the medium. In the above embodiments, the feature of narrowing the Airy disk width after passing through the medium is utilized, but in fact, the feature of narrowing the Airy disk width already exists in the medium and can also be utilized.

[0088] In the above-mentioned embodiments, the light slow-light or light storage unit, the characteristic of narrowing the Airy disk width already exists in the medium and can also be utilized, so the light slow-light or light storage unit can be integrated into the photoresist, so that the photoresist itself is the light slow-light or light storage unit, which itself can narrow the Airy disk width, thereby improving the resolution.

[0089] In the above-mentioned embodiments, the optical slow light or optical storage unit, its medium form includes gas, liquid and solid, the optical slow light or optical storage unit can be in direct contact with the wafer, similar to the immersion lithography technology, the high refractive index liquid is in direct contact with the wafer, in this application environment, it is necessary to add a container for carrying the medium, medium filtering, medium circulation, and medium recovery; when the medium is gas, it is necessary to add auxiliary equipment to make the medium environment reach vacuum, the vacuum environment can be a closed vacuum in a local area of ​​the wafer workbench, or it can be a closed vacuum in the entire lithography machine; in non-vacuum applications, it is necessary to add heating and insulation equipment to keep the medium at a constant temperature. In actual applications, when it is necessary to add a container, follow Figure 7 In the design of (b), the container is made of transparent material (preferably quartz material, including other available transparent materials), and the diameter is made as large as possible. The light propagating in the medium (414) includes: a) the original propagating light; b) or the stored light information is released, which can be regarded as an ideal point light source, and this point light source propagates in the generated direction. The light propagating in the medium (414) propagates along a transparent quartz material with a diameter as large as possible, without a lens aperture, and the aperture limit becomes smaller, the Airy disk width becomes narrower, and the resolution of the lithography machine is improved. As long as the aperture is large enough, the Airy disk width is narrow enough, and the resolution of the lithography machine is high enough to meet the design requirements. It should be noted that these features of this paragraph are applicable to all embodiments.

[0090] In the above-mentioned embodiments, the light slow light or light storage unit controls the direction of the light including the same direction as the detection light, the opposite direction of the detection light, the perpendicular direction of the detection light, and any angle with the detection light. The factors for selecting the direction of the control light need to be added, which is that it cannot interfere with the exposure of the wafer. When the control light is directly incident or indirectly reflected on the exposure area of ​​the wafer, anti-interference measures should be taken. Method 1 is to select the frequency of the control light not to be within the photosensitive frequency range of the photoresist.

[0091] In the above-mentioned embodiment, the measures to reduce the optical noise include: 1) in order to prevent the noise of the control light and the noise of the detection light from interfering with the exposure process of the photoresist, a shutter switch of a physical mechanical or electronic structure such as a liquid crystal can be set at the optical path position on the wafer, and the switching time of the shutter switch is precisely matched with the switching timing of the control light, and the shutter switch is opened and closed when needed; 2) increasing the absorption depth, using pure rare earth compound crystals is a solution, which has a perfect lattice structure, no lattice distortion caused by doping, and has extremely high optical density; 3) increasing the physical thickness of the medium (414). 4) leaving a larger redundancy when controlling the timing; 5) precisely regulating the intensity of the control light and the detection light.

[0092] In the above embodiment, in order to improve efficiency, the optical storage process can be arranged during the unready time of the workbench. At this time, the workbench is not ready for photolithography exposure, but the optical storage step can be performed first. After the workbench is ready, the stored optical information is released for the exposure process.

[0093] In the above-mentioned embodiments, the writing light of the control light, the reading light of the control light and the detection light can come from the same laser light source or from different laser light sources.

[0094] In the above embodiment, the control light writing light (4161), the control light reading light (4162) and the auxiliary light (427) share one optical path, which can be changed to the control light writing light and the control light reading light sharing one optical path, and the auxiliary light separately replicates a similar optical path on the other two sides of the optical slow light or the optical storage unit (312). If the parameters of the control light writing light and the control light reading light are exactly the same, then only one is required.

[0095] In the above embodiment, the directional stability of the controlled light determines the accuracy of the direction in which the stored optical information is released. Assuming that the effective average distance L between the medium of the optical slow light or optical storage unit and the wafer is 3 cm, to achieve a deviation accuracy of 1 nm, the maximum allowable deviation of the directional angle is

[0096]

[0097] It can be deduced that the maximum allowable deviation of the direction angle is 3.33x 10 -8 In order to reduce the deviation, the measures include a) increasing the size of the laser resonant cavity that controls the light and the base size of the laser resonant cavity reflector; b) improving the shockproof capability; c) the optical slow light unit or optical storage unit includes a laser direction feedback correction device. According to the above calculation, the direction deviation of the laser at an optical path of 10 meters cannot be greater than 3.33x 10 -7Meter, that is, 0.333 microns. The function of the feedback correction device is to measure the directional deviation in real time. When a directional deviation occurs, the reflector angle of the laser resonant cavity is fine-tuned in real time to control the directional deviation within the target range. d) Slight changes in temperature can cause deformation of the material. Precise temperature control must be implemented for all relevant components on the laser optical path. e) Light propagates in the medium - after energy exchange between light and the medium, the light energy is converted into the atomic spin wave energy storage of the medium - the atomic spin wave energy storage of the medium is converted into the original direction of light to continue propagating. The shorter the interval of this energy conversion process, the smaller the impact of the controlled light deviation will be. Therefore, a shorter pulse timing and faster frequency switching speed of light closing and opening control are required to achieve this goal. The most ideal effect is that this interval is small enough to be ignored, that is, when the mode of Example 3 is switched to the mode of Example 4, the process of continuous propagation of light in the medium is a continuous process in which the energy conversion continues. Therefore, the directional stability of the controlled light is equally important for Example 3 and Example 4. In essence, Example 4 is a type of Example 3, except that the energy conversion process of the light is very fast. The photons of the controlled light with continuous intensity at the macroscopic level are also discrete. At the microscopic level, the instantaneous light intensity of the photons at the medium atoms is also turned off and on. This is more obvious when the intensity of the controlled light is low.

[0098] In the above-mentioned embodiment 3, if the frequency of the read light is different from that of the write light, the stored optical information will be released at the new frequency. After the stored optical information is released, it can be regarded as an ideal point light source, which propagates in the direction of generation. Since there is no lens system on the propagation path at this time, there is no need to consider chromatic aberration. Light of different frequencies propagates in the same direction, so the frequency of the read light is different from that of the write light, which will not cause chromatic aberration problems.

[0099] The essential differences between the above-mentioned Embodiment 3 and Embodiment 4 and Embodiment 1 and Embodiment 2 are: a) in position. The preferred positions of Embodiment 3 and Embodiment 4 are between the objective lens and the wafer, while the preferred positions of Embodiment 1 and Embodiment 2 are before the photomask; b) in the physical features utilized. Embodiment 3 and Embodiment 4 mainly utilize the feature of the medium of the light-slowing light or the light storage unit to narrow the Airy disk, while Embodiment 1 and Embodiment 2 mainly utilize the feature of the medium of the light-slowing light or the light storage unit to slow down the light.

[0100] End of the Improvement Part 3 of the Invention Application

[0101] The above describes the method and specific embodiments of the invention in conjunction with the accompanying drawings and embodiments. It will be understood by those skilled in the art that the present invention may be implemented in many different ways. Therefore, it should be understood that the present invention is not limited to the preferred embodiments described. As the spirit of the present invention given by the attached claims, the present invention includes various changes, modifications and modifications within the scope of its patent protection.

Claims

1. Improvement 4: A method for improving the resolution of a photolithography machine, comprising a light slow light or light storage unit, characterized in that: After the exposure light is processed by the light slowing unit or the light storage unit, the width of the Airy disk becomes narrower in the medium and after leaving the medium.

2. The method according to claim 1, characterized in that The feature "after the exposure light is processed by the optical slow light or the optical storage unit, its Airy disk width becomes narrower in the medium and after leaving the medium" is replaced by the feature "after the exposure light is processed by the optical storage unit, its Airy disk width becomes narrower in the medium and after leaving the medium".

3. The method according to claim 1, characterized in that The feature "after the exposure light is processed by the optical slow-light unit, the Airy disk width becomes narrower in the medium and after leaving the medium" is replaced by the feature "after the exposure light is processed by the optical slow-light or optical storage unit, the Airy disk width becomes narrower in the medium and after leaving the medium".

4. The method according to claim 1, characterized in that The feature "the exposure frequency corresponds to the absorption frequency of the medium of the optical slow-light or optical storage unit, and the Airy disk width of the exposed light becomes narrower in the medium and after leaving the medium after being processed by the optical slow-light or optical storage unit" is replaced by the feature "the exposure frequency corresponds to the absorption frequency of the medium of the optical slow-light or optical storage unit, and the Airy disk width of the exposed light becomes narrower in the medium and after leaving the medium after being processed by the optical slow-light or optical storage unit".

5. The method according to claim 1, characterized in that The feature "the optical storage medium of the optical slow-light or optical storage unit is a monomer or compound crystal, the material is a rare earth element, and the Airy disk width of the exposed light becomes narrower in the medium and after leaving the medium after being processed by the optical slow-light or optical storage unit" is used to replace the feature "the Airy disk width of the exposed light becomes narrower in the medium and after leaving the medium after being processed by the optical slow-light or optical storage unit".

6. The method according to claims 1 to 5, wherein the optical slow light or optical storage unit is characterized by any one of the following features: (a) The light slow light or light storage unit described above controls the direction of the light including the same direction as the detection light, the opposite direction of the detection light, the perpendicular direction to the detection light, and any angle to the detection light. (b) The optical storage schemes selected include Electromagnetically Induced Transparency (EIT), Off-Resonant Raman-type excitations storage or PhotoEcho storage.

7. The method according to claims 1 to 5, wherein the optical slow light or optical storage unit is characterized by any one of the following features: (a) Light Slowing Schemes for slowing down the speed of light or optical storage units include Electromagnetically Induced Transparency (EIT), Coherent Population Oscillation (CPO), Spectral Hole Burning, Brillouin Scattering or Raman Scattering (b) The exposure frequency corresponds to the resonant absorption frequency of the medium of the optical slow light or optical storage unit. (c) The optical slow light or optical storage unit described above, wherein the medium thereof comprises gas, liquid and solid (c) The optical slow light or optical storage unit can be integrated into the photoresist (d) Multiple reflections of the control light to reduce the requirements for the control light intensity (e) A laser direction feedback correction device is included to monitor and correct the direction deviation of the control light or the detection light in real time. (f) The medium of the optical slow light or optical storage unit is isotopically purified for some or all of its elements to obtain a narrow inhomogeneous broadening.

8. A chip, characterized in that: The chip is prepared by any one of the methods of claims 1 to 7.

9. An optical imaging system, characterized in that: The optical imaging system is prepared by any one of the methods of claims 1 to 7.

10. The optical imaging system according to claim 9, wherein the optical imaging system comprises a microscope, a telescope, a radar, a camera and a video camera.

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