RU2539730C1 - Method of producing hologram of drawing - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: drawing is converted to raster in digital form and information on the amplitude and phase, characterising each raster point, is recorded. The required parameters of elements of the hologram are calculated, for which elements of the digital raster of the image of the drawing are converted to digital raster of the future hologram. A diffraction pattern is calculated at each point of the future hologram. An interference pattern resulting from interaction of the calculated diffraction pattern with the calculated wave front from a virtual reference radiation source is calculated. The transmission function of the hologram is calculated and regions are selected therein, which, after binarisation, yield transparent elements of an unallowable small size, which physically do not transmit light, after which the transmission function is changed to increase the size of said elements. The result is used to form a diffraction structure of the hologram on a carrier and the hologram is created in the form of a set of transparent discrete elements in an opaque layer deposited on a transparent substrate. Optical correction of the enlarged elements is performed to allow the enlarged elements to transmit an amount of light according to the primary transmission function. Correction is performed by placing on the opaque layer a layer of absorbent substance with a known absorption coefficient for the image reconstructing radiation, and the region over the non-enlarged elements is made transparent.

EFFECT: obtaining a drawing with improved process parameters, high contrast of the obtained drawing and low noise level.

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Description

The invention relates to the field of microlithography and can be industrially implemented, for example, in the manufacture of integrated circuits, binary holograms or structures with a submicron resolution relief formed according to a given program, for the manufacture of hologram masks, and can be used in the optical industry for the manufacture of focusing, scattering and corrective elements of optics, for example kinoforms, in optical control devices of the shape of aspherical surfaces, such as hologram compensators.

Creation of integrated circuits with a characteristic element size of 0.1-0.01 microns is the most important promising direction in the development of modern microelectronics. The technology of high-precision (with submicron and micron tolerances) manufacturing of precision forms with a three-dimensional relief can be industrially used, for example, to create mass technology for manufacturing parts of microrobots, high-resolution elements of diffraction and Fresnel optics, as well as in other areas of technology where it is also necessary to obtain functional a product layer of a three-dimensional drawing of a given depth with a high resolution of its structures, for example, when creating printing forms for the manufacture of cash and other securities.

From the resolution of the microlithography process, which determines the level of development of most branches of modern science and technology, the further development of modern microelectronics decisively depends. Microlithography involves applying to a surface of a solid (usually a substrate of semiconductor material) a layer of material that is sensitive to the effects of the used radiation flux, optical radiation or electron beams, which is most often used as a photoresist layer. Exposing a photoresist through a template, usually called a mask, allows you to create a picture on the photoresist that corresponds to a given topology, for example, the layer topology of the created integrated circuit.

The positioning accuracy of the best projection scanning systems (steppers) produced by the world leader in this field of technological equipment for microelectronics - the Dutch company ASM-Lithography, reaches 10 nm, which is clearly not enough to create VLSI with a characteristic element size of 20-30 nm. The lag of the capabilities of steppers from the needs of industry is natural, because the development of a stepper for submicron technologies requires three to five years, and its cost in serial production, depending on the resolution provided, ranges from 10 to 70 million dollars, not to mention the development cost, which amounts to many hundreds of millions of dollars.

Currently, photomicrorolithography (or photolithography) is the most common in industry. The resolution Dx provided by it is determined by the wavelength λ of the radiation used and the numerical aperture NA of the projection system: Δx = k ₁ λ / NA (W. Moreau "Microlithography": in 2 hours Part 1: Translated from English - M. , World, 1990, p. 478 [1]). Such a dependence naturally stimulated the developers' desire to use increasingly shorter-wavelength radiation sources and increasingly higher-aperture projection systems. As a result, over the past 40 years, industrial projection photolithography has undergone a transition from mercury lamps with a characteristic radiation wavelength of 330-400 nm to excimer lasers with radiation wavelengths of 193 and even 157 nm. Projection lenses of modern steppers reached a diameter of 600-700 mm, which leads to a rapid increase in the cost of steppers.

An increase in resolution leads to a sharp decrease in the focusing depth ΔF, because ΔF = ± λ / 2 (NA) ² [1, p. 478], which leads to a decrease in productivity and a radical complication of the focusing system of giant projection lenses, which means, again, to an increase in the cost of steppers. In addition, edge effects limit the possibility of using the aperture of such a lens when working with the maximum resolution provided by the lens.

In the process of development of projection photolithography, the minimum size of projected parts decreased on average by 30% every 2 years, which made it possible to double the number of transistors on integrated circuits every 18 months (Moore's law). Currently, the industry uses “0.065-micron technology”, which allows printing of parts with a resolution of 65 nm, while the next frontier, according to experts, is the creation of projection systems and radiation sources that provide reliable resolution at 22 nm. This will require a transition to extreme ultraviolet sources (EUV sources) or even a transition to soft X-rays. Currently, experiments are underway with microlithography at λ = 13.4 nm. The first such installation, as reported at the forum of developers of the company INTEL (the leading global manufacturer of VLSI), was created and in 2002 transistors with a characteristic size of 50 nm were obtained on it. However, the cost of such a stepper, even in mass production, will reach, according to experts, $ 70 million, and for debugging the technology of serial production of microprocessors with a characteristic element size of 30 nm, it will take another 3-5 years, according to the most optimistic estimates.

One of the most significant limitations of the use of photolithography is the restriction associated with diffraction from the edges of the mask (diffraction from the edges of the screen) used to obtain the desired projection image on the surface of the photoresist. As the monochromaticity of the radiation used increases, this phenomenon leads to an increasingly noticeable deterioration in the quality of the resulting image due to the appearance of diffraction peaks located at distances of the order of λ from the center of the projected line. If we take into account that currently the leading manufacturers use laser radiation with a wavelength of λ = 193 nm and even less (in experimental steppers!), It becomes obvious how significant the resolution restriction introduced by diffraction at the edge of the mask can be.

Thus, the existing projection devices for creating images on the photosensitive layer have a number of significant disadvantages:

1) the fundamental difficulties of combining in one device a high resolution and a large depth of field;

2) a significant complication of the design and technology of the projection device while reducing the wavelength of radiation used when projecting the image onto the photoresist;

3) a radical complication of the optical system and manufacturing technology of the projected object - the mask as the wavelength used in the projection decreases;

4) a sharp rise in the cost of technology and equipment as the degree of integration of manufactured products increases;

5) the extremely low technological flexibility of the production process and the very high cost of its reconstruction;

6) the fundamental impossibility of creating diversified production, i.e. production of various integrated circuits on one substrate in a single technological process.

A known method for producing a binary hologram in which a plurality of transmission regions are created in a film of material that is opaque to the radiation used in accordance with their predetermined or calculated position so that when illuminating the obtained many transmission regions, a holographic image is formed at a predetermined distance from them (L.M Soroko "Fundamentals of holography and coherent optics." - M., Nauka, 1971, p.420-434 [2]). In this monograph, the possibility of obtaining a “numerical hologram,” also called a synthetic, artificial, or binary hologram, is considered, and a theory is presented that is distinguished by its conciseness and clarity of the mathematical description. However, the known method for producing binary holograms, in which the image of the transmission regions is obtained, for example, graphically, and photographed with a significant reduction, does not allow to obtain a sufficiently high image quality and high resolution, primarily due to insufficient manufacturing accuracy and insufficiently large number of transmission regions used .

A known method of obtaining an image on a material sensitive to the radiation used using a hologram in which light spots are formed on the surface of the material sensitive to the radiation used by obtaining at least one hologram mounted on the surface of the material sensitive to the radiation used (GB 1331076 A, publ. 09/19/1973 [3]). However, the known method of obtaining an image on a material sensitive to the radiation used using a hologram does not allow to obtain high image quality due to the mutual overlap of many diffraction orders, and high resolution due to the impossibility of using short-wave radiation sources. Moreover, the main objective of this method was to provide effective control of visually controlled tags.

A known method of obtaining a binary hologram, known from RU 2262126 [4]. According to the description, in the film of a material opaque to radiation used for image reconstruction, a plurality of transmission areas are obtained in accordance with their predetermined or calculated sizes and positions. When this is preliminarily obtained on the material sensitive to the radiation used, placed on the film of opaque material, the image of the specified set of transmission areas, the image of each of which is performed by forming the total area of overlapping spots of exposure, each of which ensures that the sensitive material receives a radiation dose of less than E _pore , where E _por - the threshold value of the radiation dose corresponding to the sensitivity threshold of the material sensitive to the radiation used, and doses and the radiation that the material sensitive to the radiation used receives in each total area of overlap of the spots of exposure is equal to or greater than E _then . Illumination spots are obtained using a two-dimensional matrix of emitters located in front of the surface of the material sensitive to the radiation used, each of which is configured to control the intensity of the radiation emanating from it and contains at least one element for generating a radiation flux with predetermined dimensions and its cross-sectional shape, interconnected with a radiation source, and upon receipt of each of the total areas of overlapping spots of exposure, at least one before exposure of the spot light from the spots forming the total overlap area of the spot light, the emitter matrix and / or the material sensitive to the radiation used are moved in a plane parallel to the surface of the material sensitive to the radiation used, in one direction or in two mutually perpendicular directions, and then using the appropriate processing the specified set of transmission areas is formed in a film of a material opaque to the radiation used.

The disadvantage of this method is the restriction imposed on the structure of the resulting binary hologram: the formed elementary transmission regions can be located only on a regular grid, the steps of which cannot be less than the steps of the emitters in the matrix, which limits, accordingly, the ability to influence the quality parameters of the holographic image by changing hologram structures. The known method also does not take into account the possibilities of creating a hologram in the form of a set of holes in a medium transparent to radiation that forms a holographic image, or alternating depressions in a medium reflecting this radiation, or combinations of parts of these options, which does not allow the maximum use of the opportunities provided by the holographic method for obtaining high quality images. In addition, the known method does not consider the possibilities of making adjustments to its structure prior to the manufacture of the hologram, taking into account the physical conditions for obtaining a holographic image and performed in order to obtain the highest possible quality of the latter.

Closest to the claimed in its technical essence and the achieved result is a method of manufacturing holographic images of the pattern, known from RU 2396584 [5]. The method is implemented as follows. The original drawing, for example, the image of the topology of the integrated circuit layer, is converted to a raster in digital form. The conversion is carried out as follows: the original picture in the form of a black-and-white image is placed in some coordinate system. In the particular case, the picture can be two-tone, when the image consists, for example, of white elements on a black background, and in the general case, grayscale, when the image consists of parts having one of a predetermined number of levels, the brightness level, for example, from 0 to 255 A fine grid with a predetermined step is placed in the same coordinate system. In the area occupied by the figure, the coordinates of this node and the brightness of the figure at this point are recorded for each grid node. If you want to reproduce a picture with a given distribution of the radiation phase according to this picture, then this phase distribution is also presented in black and white, in the general case - grayscale, image and is also placed in the same coordinate system. The list of four values: two coordinates, brightness and phase for all grid nodes located in the area occupied by the original figure, presented, for example, in the form of a list, vector or matrix, and is a raster in digital form. Thus, information on the amplitude and phase characterizing each point of the raster as a point emitter is recorded. If you want to represent each point of the raster as an extended emitter, for example a circle or a square, then the coordinates of this point are considered the coordinates of the center of the extended emitter, the brightness of the point is considered the brightness in the center of the extended emitter, the phase of the point is considered the phase in the center of the extended emitter, and the shape of the extended emitter is additionally set, amplitude and phase distribution over its surface. Then, the diffraction pattern at each point of the future hologram is calculated, created from the entire set of emitters - elements of the digital image raster of the image. To do this, use a computer equipped with appropriate software. Then, the interference pattern is calculated, which will be obtained from the interaction of the calculated diffraction pattern with the calculated wavefront from the virtual reference radiation source, the wavefront of which is identical to the inverse wavefront of the real radiation source, which will then be used to reconstruct the image recorded on the hologram. The obtained data is used to modulate the radiation beam, which is used to record the hologram on the carrier. As a radiation source, lasers or accelerated particle sources can be used, under the influence of which a change in the properties of individual sections of the irradiated carrier can occur. As the latter, a photoresist of some type sensitive to the radiation used can be used.

The disadvantage of this method is the complexity and complexity of calculating the corrections that must be made in the hologram to obtain from it the restored high quality images. In addition, the known method does not allow to obtain holograms with high contrast and resolution due to the impossibility of obtaining a wide range of sizes of transmission elements in the produced hologram.

The inventive method for manufacturing a hologram of a pattern is aimed at obtaining a pattern with high technological parameters, increasing the contrast of the resulting pattern and reducing noise.

This result is achieved by the fact that the image is converted into a raster in digital form, information on the amplitude and phase is recorded that characterizes each dot of the raster as an extended or point emitter, the necessary parameters of the hologram elements are calculated, for which the elements of the digital raster of the image of the picture are converted into a digital raster of the future hologram at the same time, at each point of the future hologram, a diffraction pattern is calculated, created from the entire set of emitters - elements of the digital raster of the image of the picture, p calculate the interference pattern obtained from the interaction of the calculated diffraction pattern with the calculated wavefront from a virtual reference point or extended radiation source identical to the inverse real wavefront of the source, which will be used when reconstructing the holographic image of the pattern, determine the transmission function of the hologram and select areas in it after binarization, they will give transparent elements of an unacceptably small size that physically do not transmit light, after They change the transmission function, providing an increase in the size of these elements, use the obtained result to form the diffraction structure of the hologram on the carrier, create a hologram in the form of a set of transparent discrete elements in an opaque layer deposited on a transparent substrate, and conduct optical correction of the enlarged elements to ensure transmission of these increased elements of the amount of light in accordance with the primary transmission function, while the correction is carried out by placing on rachnom layer a layer of absorbing material with a known absorption coefficient for reducing the radiation image, and the region above the transparent Nonincrease elements operate therein.

The indicated result is also achieved by the fact that optical correction is carried out repeatedly, for which a subsequent layer of absorbing substance with a known absorption coefficient for the recovering radiation image is applied onto the surface of the previous absorbing substance layer with a known absorption coefficient, and the region above the regions of the previous layer is not providing the transmission of an amount of light in accordance with the primary transmission function, perform transparent .

The indicated result is also achieved by the fact that after the optical correction is completed, a layer of a transparent substance is applied to the layer of the absorbing substance with a known absorption coefficient for the recovery image of radiation, which provides a phase shift of the recovery image of radiation by a predetermined amount, for which a set of discrete elements is performed within it, within the area which there is no phase shift, the shape, size and location of which are determined by calculation, for which the digital raster is first calculated the hologram transmission functions, and then digital rasters of the opaque and phase-shifting layers of the proposed two-layer mask are calculated, for which the average transmission coefficient of all elements of the digital raster of the hologram transmission function is determined, the obtained average value is subtracted from the initial values, in areas where the difference is positive value, attribute to the elements of the digital raster of the opaque layer positive values equal to the difference values, attribute to the element m of a digital raster providing a phase shift of the layer with a value of "zero", in areas where the difference is a negative value, assign elements of a digital raster of an opaque layer positive values equal to negative values of the difference in absolute value, attribute the elements of a digital raster of a phase shifting layer with a value of "one" , and based on the analysis of the obtained digital raster of the opaque layer, the necessary optical correction is calculated, which must be performed before applying the layer I, providing a phase shift of the recovery image of radiation by a given value.

The indicated result is also achieved by the fact that the hologram is provided with a layer providing the required change in the polarization vector of the reconstructing image of radiation in the calculated regions of this layer.

The specified result is also achieved by the fact that transparent discrete elements perform different sizes and shapes.

This result is also achieved by the fact that transparent discrete elements perform different sizes, but the same shape.

The specified result is also achieved by the fact that transparent discrete elements are placed on a uniform or uneven grid.

The indicated result is also achieved by the fact that transparent discrete elements are made in the form of holes in an opaque layer.

The indicated result is also achieved by the fact that as a means of forming transparent discrete elements in an opaque medium, an electrically controlled transparency is used.

The indicated result is also achieved by the fact that an electrically controlled transparency is used as a layer with a known absorption coefficient for the recovery image of the radiation, in which transparent discrete elements are formed.

The specified result is also achieved by the fact that the layer that provides the change in the polarization vector of the reconstructing image of radiation in the calculated areas is made in the form of an electrically controlled transparency.

The indicated result is also achieved by the fact that a set of discrete elements within the area of which there should be no phase shift is made in the form of holes in the layer providing a phase shift of the recovery image of radiation by a predetermined amount.

This result is also achieved by the fact that a set of discrete elements, within the area of which the phase shift should be absent, is performed in the form of transparent sections in an electrically controlled transparency.

Converting the original pattern into a raster in digital form and recording information about the amplitude and phase characterizing each dot of the raster as an extended or point emitter provides the ability to calculate the diffraction pattern created by the pattern as the sum of the diffraction patterns created by all its elements using a previously known solution diffraction (propagation of electromagnetic waves) problems for the aforementioned extended or point radiator.

The translation of the elements of the digital raster of the image of the picture into the digital raster of the future hologram and the calculation of the diffraction pattern at each point of the future hologram created from the entire set of emitters - the elements of the digital raster of the image of the picture provides a wavefront (called the "object") from the given picture. This wavefront depends only on the given pattern and on the method of illumination adopted in calculating the diffraction pattern, and does not depend on the amplitude or distribution of amplitudes, phase or phase distribution, and the location of the reference radiation source. Therefore, the same object wavefront obtained can be used to calculate several holograms with different recovery beams and different optical schemes.

Calculation of the interference pattern obtained from the interaction of the calculated diffraction pattern with the calculated wavefront from a virtual reference point or extended radiation source identical to the reversed real wavefront of the source, which will be used to form the holographic image of the pattern, is necessary in order to obtain the distribution function of the optical hologram properties, such as transmittance or reflectance.

The determination of the transmission function of the hologram and the selection of points in it that, after binarization, will produce elements of an unacceptably small size that do not allow light to pass through, makes it possible to identify areas of the hologram mask within which technical implementation in the form of a single layer of transparent discrete elements does not allow for a given transmission accuracy of the transmission function, and a change in the transmission function, providing an increase in the size of these elements, allows to increase the accuracy of transmission of the initial transmission function in these selected areas.

The lack of accuracy in the implementation of the required transmission function of the hologram mask is due to the fact that for transmitting this transmission function using a set of discrete transparency regions in the opaque layer, the method of spatial pulsed modulation is used, passing through the hologram mask of the recovery wave, in which, to transmit bright places, the function maxima transmittance - transparency areas or groups of transparency zones of the largest size are used, and to transmit dark places - minima of the skip function Ania - using transparency region or group of regions transparency smallest. If the transmission function of the hologram mask has minima close to zero, for their transmission it is necessary to apply transparency zones with dimensions that start from zero. Meanwhile, when the size of the transparent zones is less than half the wavelength of the restoration image of the radiation, the proportionality between the area of the transparent zone and the amount of light passing through this zone is violated. Moreover, if the technical implementation of an opaque layer does not allow this layer to be made with a thickness much shorter than the wavelength, transparent regions in a relatively thick layer - with a thickness of more than 1/10 of the wavelength, begin to exhibit noticeable waveguide properties, which are expressed in the fact that the transparency zones - short waveguides - do not transmit light (do not emit) when the size of the cross section of the end face is less than ½ of the wavelength and at sizes close to one wavelength. With sizes from 0.6 to 0.9 and from 1 to 1.7 wavelengths, the amplitude and phase of the radiation of such a short waveguide strongly depend on the manufacturing errors of each transparency zone, which leads to phase noise that mixes with the reconstructed image. Therefore, in the manufacture of a hologram mask, the use of transparency regions with transverse dimensions of less than 1.7 wavelengths should be avoided.

Creating a hologram in the form of a set of transparent discrete elements in an opaque layer deposited on a transparent substrate allows the calculated continuous transmission function of the hologram mask to be transmitted with the required accuracy using the actual discrete transmission function, i.e. implement the spatial pulse modulation method.

Optical correction of the enlarged elements, ensuring the transmission of the amount of light by these enlarged elements in accordance with the primary transmission function, allows to increase the accuracy of reproducing the minima (dark spots) of the original transmission function.

Correction by placing on an opaque layer a layer of an absorbing substance with a known absorption coefficient for the recovery image of the radiation, when the regions above the unexpanded elements are made transparent in it, instead of transmitting regions of an unacceptably small size, it allows using the transmission function of the transmission zone of an acceptable size to transmit minima (dark places) by reducing the amplitude of the radiation passing through them using a layer of absorbing substance.

Creating a hologram in the form of a set of discrete elements that differ in their optical properties allows, as in the prototype, to provide the possibility of obtaining binary holograms that create a high quality image. In this case, the resolution of the synthesized binary holograms is fully consistent with the classical theory of diffraction: the angular diameter is of the order of the ratio of the wavelength of the illuminating light or monokinetic corpuscular beam to the total size of the hologram, and therefore it can be higher than that of traditional optical elements.

Thus, it is possible to use the resulting binary holograms to create images on a material sensitive to the radiation used, which ensures the absence of any focusing or other traditional optical elements for converting wave fronts between a hologram containing image information in the form of a set of elements made on a substrate the required size, and a plate coated with a layer of material sensitive to the type of radiation used, and The holographic image located on the plate is determined by the location and shape of the hologram elements, the relative position of the hologram and the plate, and also the parameters of the reading radiation beam, in particular the spectral composition (wavelength) and the wavefront shape, which are determined by the radiation source and, if necessary, a special beam forming system.

At the same time, the amount of information contained in the hologram and in the image created during the restoration of the hologram coincides, which allows you to pre-calculate the necessary dimensions of the hologram, its structure and the time of its manufacture.

In some cases, one optical correction to achieve the required high quality may not be enough. Then, optical correction is carried out repeatedly, for which purpose a subsequent layer of absorbing substance with a known absorption coefficient for the recovering radiation image is applied to the surface of the previous absorbing substance layer with a known absorption coefficient for the radiation image, and the regions above the regions of the previous layer that do not allow light transmission in accordance with the primary transmission function, perform transparent in it. Repeated correction allows you to further increase the accuracy of the transmission of the minima (dark places) of the original hologram transmission function. If, after applying the first correction, it turns out that the transparent elements of the minimum allowable size still transmit too much light, despite the first darkening layer already applied, then one more additional darkening layer or several such layers can be applied to such elements. This will increase the dynamic range of the amplitude of radiation transmitted by each transparency zone, due to which it is possible to improve the quality of the reconstructed image at the previous hologram size or reduce the size of the hologram while maintaining the quality of the reconstructed image.

In particular cases of implementation, it is advisable, after completing the optical correction, to apply a layer of a transparent substance on the layer of the absorbing substance with a known absorption coefficient for the recovery image of radiation, which provides a phase shift of the recovery image of radiation by a predetermined amount. This will significantly reduce the power of the zero-order radiation generated by the hologram, which will lead to the possibility to reduce the size and increase the efficiency of the hologram mask, as well as reduce the level of coherent noise created by the zero order in the region of the reconstructed image.

To do this, in a transparent layer, a set of discrete elements is performed, within the area of which there is no phase shift, the shape, size and location of which are determined by calculation. First, a digital raster of the hologram transmission function is calculated, and then digital rasters of an opaque and phase-shifting layer of the proposed two-layer mask are calculated, for which the average transmittance value for all elements of the digital raster of the hologram transmission function is calculated, the obtained average value is subtracted from the initial values, in the areas where the difference is a positive value. Assign the positive values equal to the difference values to the elements of the digital raster of the opaque layer, assign the value “zero” to the elements of the digital raster of the layer providing the phase shift, in the regions where the difference is a negative value, assign the positive values equal to the negative values of the absolute difference to the elements of the digital raster of the opaque layer the value is attributed to the elements of the digital raster providing the phase shift of the layer with the value “one”. Based on the analysis of the obtained digital raster of the opaque layer, the necessary optical correction is calculated, which must be done before applying the layer, which provides a phase shift of the recovery image of the radiation by a predetermined amount.

In some cases, the implementation of the hologram provide a layer that provides the desired change in the polarization vector of the recovery image of the radiation in the calculated areas of this layer. This will improve the conditions for the interference of rays converging in the region of the reconstructed image by eliminating the crossing of the electric vectors of the rays formed by the opposite, symmetrically located relative to the center regions of the hologram. When using linearly polarized regenerating radiation, an additional polarization rotation on the hologram mask will eliminate the polarization resolution anisotropy in the reconstructed image.

In particular cases of implementation, the elements perform the same size and shape. If transparent discrete elements are made in the form of holes in an opaque layer, this provides the possibility of the fastest and most accurate manufacturing of the entire set of holes, since it is the most technologically advanced when using modern equipment (in particular, electron-lithographic plants). In addition, the calculation is simplified and accelerated, since the solution of the problem of radiation diffraction at the hole of the selected shape is sufficient to be done only once.

In special cases, the implementation of the transparent elements can be made of different sizes, but the same shape. This allows us to simplify and speed up the calculation, since the solution of the problem of radiation diffraction by elements of the selected shape is sufficient to be done only once.

It is advisable to place the transparent elements on a uniform or uneven grid. This is necessary in order to ensure the best approximation (transmission) of the produced hologram, enclosed in the calculated digital raster of the future hologram.

In this case, the transparent elements can be made not only in the form of holes in an opaque layer deposited on a transparent substrate, but also in the form of transparent discrete elements in an opaque medium, which is used as an electrically controlled transparency. Using banners provides a number of benefits. For example, the creation of electrically controlled holograms. Indeed, having once created a layered structure, it can be used repeatedly by applying to the electrically controlled transparency a signal obtained from the results of calculations of a digital raster and optical corrections for different patterns. At the same time, such an option is possible when all the layers included in the hologram structure will be made of electrically controlled transparencies, including those that provide the required optical correction.

The essence of the proposed method is illustrated by examples of its implementation.

Example 1. In the most general case, the method is implemented as follows. The original drawing, such as an integrated circuit or topology image, is digitally converted to a raster. The conversion is carried out as follows: the original picture in the form of a black-and-white image is placed in some coordinate system. In the particular case, the picture can be two-tone, when the image consists, for example, of white elements on a black background, and in the general case, grayscale, when the image consists of parts having one of a predetermined number of levels, the brightness level, for example, from 0 to 255 A fine grid with a predetermined step is placed in the same coordinate system. In the area occupied by the figure, the coordinates of this node and the brightness of the figure at this point are recorded for each grid node. If you want to reproduce a picture with a given distribution of the radiation phase according to this picture, then this phase distribution is also presented in black and white, in the general case - grayscale, image and is also placed in the same coordinate system. The list of four values: two coordinates, brightness and phase for all grid nodes located in the area occupied by the original figure, presented, for example, in the form of a list, vector or matrix, and is a raster in digital form. Thus, information on the amplitude and phase characterizing each point of the raster as a point emitter of an electromagnetic field is recorded. If you want to represent each point of the raster as an extended emitter, for example a circle or a square, then the coordinates of this point are considered the coordinates of the center of the extended emitter, the brightness of the point is considered the brightness in the center of the extended emitter, the phase of the point is considered the phase in the center of the extended emitter, and the shape of the extended emitter is additionally set, amplitude and phase distribution over its surface.

Then the diffraction pattern at each point of the future hologram is calculated, created from the entire set of virtual emitters - elements of the digital raster of the electromagnetic field. To do this, use a computer equipped with appropriate software. Then, the interference pattern is calculated, which will be obtained from the interaction of the calculated diffraction pattern with the calculated wavefront from the virtual reference radiation source, the wavefront of which is identical to the inverse wavefront of the real radiation source, which will then be used to reconstruct the image recorded on the hologram.

The obtained data is used to determine the location of transparent elements in the layers of the hologram mask, for which the characteristics of the transparent phase-shifting layer are first calculated based on the calculated transmission function, and the transmission function is then changed (recounted). Then, the recalculated transmission function is analyzed and the binarization (hole arrangement) method for the main amplitude layer is selected according to the analysis results, the number and required characteristics of additional darkening layers are calculated, the arrangement of transparent elements (holes) for the opaque layer is calculated, binarization for additional darkened layers is calculated, and binarization is calculated for a transparent layer.

The obtained data is used for the manufacture of a multilayer hologram mask consisting of a layer of opaque substance, several layers of a darkening (partially transparent) substance and a transparent phase-shifting layer.

Example 2. As the initial drawing, an image of sets of various geometric shapes (squares, triangles, circles connected by straight lines) was used. The geometric figures had different sizes (2.5-6 mm), and the lines connecting them had different thicknesses (2.5-6 mm). The original image was converted to a digital raster using the following steps. The original picture in the form of a black and white grayscale image is placed in some coordinate system. A fine grid with a predetermined step is placed in the same coordinate system. In the area occupied by the figure, the coordinates of this node and the brightness of the figure at this point are recorded for each grid node. If you want to reproduce a picture with a given distribution of the radiation phase according to this picture, then this phase distribution is also presented in black and white, in the general case - grayscale, image and is also placed in the same coordinate system. The list of four values: two coordinates, brightness and phase for all grid nodes located in the area occupied by the original figure, presented, for example, in the form of a list, vector or matrix, and is a raster in digital form.

Thus, information on the amplitude and phase characterizing each point of the raster as a point emitter was recorded.

Then, the digitally defined pattern was used to calculate the digital raster of the optimized electromagnetic field on the surface of the photoresist. For this, we applied a method for simulating photoresist exposure by electromagnetic radiation that passed through a projection system consisting of a coherent radiation source, a condenser, a projection mask, and a projection lens. The mask parameters were automatically adjusted so that in the end, the simulated image on the photoresist did not match the original digital raster of the picture by no more than a predetermined value. To implement this method, a computer equipped with appropriate software was used.

Then we calculated the diffraction pattern at each point of the future hologram, created from the entire set of virtual emitters - elements of a digital raster of an optimized electromagnetic field on the surface of the photoresist. To do this, we used the method of calculating sums of convolution type using the Fourier transform and using the fast Fourier transform algorithm. For its implementation, a personal computer equipped with appropriate software was used. Then we calculated the interference pattern, which will be obtained from the interaction of the calculated diffraction pattern with the calculated wavefront from the virtual reference radiation source, the wavefront of which is identical to the inverse wavefront of the real radiation source, which will be used to reconstruct the image recorded on the hologram. The calculation was carried out by calculating the complex amplitude of the radiation generated by the reference source at each point of the hologram and then adding this amplitude to the complex amplitude of the calculated diffraction pattern.

The data obtained were used to modulate the radiation beam, which was used to record the hologram on the carrier. As a hologram carrier, a 0.1-μm-thick layer of chromium deposited on a transparent substrate was used, coated with an 0.4-µm-thick ERP-40 brand of electroresist, which was exposed in a ZBA-21 electron-beam installation. After recording the hologram in the form of a set of discrete elements, the electron resist and chromium were successively processed to remove irradiated areas.

The image recorded on the obtained hologram was reconstructed using a radiation source, which was used as a PLASMA He-Cd laser with a power of 90 mW and a radiation wavelength of 0.442 μm. As a result, a reconstructed image of the original pattern was obtained, reduced by 10,000 times, while the characteristic size of the geometric figures was 0.25-0.6 microns.

Example 3. As the initial drawing, the image of sets of various geometric shapes (squares, triangles, circles connected by straight lines) was used. The geometric figures had different sizes (2.5-6 mm), and the lines connecting them had different thicknesses (2.5-6 mm). The original image was converted to a digital raster using the following steps. The original picture in the form of a black and white grayscale image is placed in some coordinate system. A fine grid with a predetermined step is placed in the same coordinate system. In the area occupied by the figure, the coordinates of this node and the brightness of the figure at this point are recorded for each grid node. If you want to reproduce a picture with a given distribution of the radiation phase according to this picture, then this phase distribution is also presented in black and white, in the general case - grayscale, image and is also placed in the same coordinate system. The list of four values: two coordinates, brightness and phase for all grid nodes located in the area occupied by the original figure, presented, for example, in the form of a list, vector or matrix, and is a raster in digital form.

Thus, information on the amplitude and phase characterizing each point of the raster as a point emitter was recorded.

Then we calculated the diffraction pattern at each point of the future hologram, created from the entire set of virtual emitters - elements of the digital raster of the original pattern. To do this, we used the method of calculating sums of convolution type using the Fourier transform and using the fast Fourier transform algorithm. For its implementation, a personal computer equipped with appropriate software was used. Then we calculated the interference pattern, which will be obtained from the interaction of the calculated diffraction pattern with the calculated wavefront from the virtual reference radiation source, the wavefront of which is identical to the inverse wavefront of the real radiation source, which will be used to reconstruct the image recorded on the hologram. The calculation was carried out by calculating the complex amplitude of the radiation generated by the reference source at each point of the hologram and then adding this amplitude to the complex amplitude of the calculated diffraction pattern.

The data obtained were used to calculate the transmission function of the hologram and to determine the coordinates and properties of elements in two electrically controlled transparencies, for which, first, based on the calculated transmission function, the phase change was calculated for each cell of the transparent phase-shifting transparency, and the transmission function itself was then changed. Then, based on the results of the analysis of the changed transmission function, the required degree of transmission was calculated for each transparency cell with variable transparency.

Then, a two-layer hologram mask was set up as follows: on a transparent substrate, a transparency consisting of cells with adjustable transparency, and on it a transparency consisting of cells with adjustable phase shift (phase shifter).

The image recorded on the obtained hologram was reconstructed using a radiation source, which was used as a PLASMA He-Cd laser with a power of 90 mW and a radiation wavelength of 0.442 μm. As a result, a reconstructed image of the original pattern was obtained, reduced by 10,000 times, while the characteristic size of the geometric figures was 0.25-0.6 microns.

Example 4. As the initial drawing, we used the image of sets of various geometric shapes (squares, triangles, circles connected by straight lines). The geometric figures had different sizes (2.5-6 mm), and the lines connecting them had different thicknesses (2.5-6 mm). The original image was converted to a digital raster using the following steps. The original picture in the form of a black and white grayscale image is placed in some coordinate system. A fine grid with a predetermined step is placed in the same coordinate system. In the area occupied by the figure, the coordinates of this node and the brightness of the figure at this point are recorded for each grid node. If you want to reproduce a picture with a given distribution of the radiation phase according to this picture, then this phase distribution is also presented in black and white, in the general case - grayscale, image and is also placed in the same coordinate system. The list of four values: two coordinates, brightness and phase for all grid nodes located in the area occupied by the original figure, presented, for example, in the form of a list, vector or matrix, and is a raster in digital form.

Thus, information on the amplitude and phase characterizing each point of the raster as a point emitter was recorded.

Then we calculated the diffraction pattern at each point of the future hologram, created from the entire set of virtual emitters - elements of the digital raster of the original pattern. To do this, we used the method of calculating sums of convolution type using the Fourier transform and using the fast Fourier transform algorithm. For its implementation, a personal computer equipped with appropriate software was used. Then we calculated the interference pattern, which will be obtained from the interaction of the calculated diffraction pattern with the calculated wavefront from the virtual reference radiation source, the wavefront of which is identical to the inverse wavefront of the real radiation source, which will be used to reconstruct the image recorded on the hologram. The calculation was carried out by calculating the complex amplitude of the radiation generated by the reference source at each point of the hologram and then adding this amplitude to the complex amplitude of the calculated diffraction pattern.

The data obtained were used to calculate the transmission function of the hologram and determine the location of transparent elements in the layers of the hologram mask, for which, first, based on the found transmission function, the location of the holes in the transparent layer was calculated, which provides a phase shift of the transmitted radiation by 180 degrees, and the transmission function itself was then recounted . Then, based on the analysis of the recalculated transmission function, the characteristics of the additional darkening layer were calculated, the location of the holes for the opaque layer was calculated, and the location of the holes in the additional darkening layer was calculated.

Then, the calculated configurations of the holes in the layers were used to make a three-layer hologram mask consisting of a layer of opaque substance, a layer of a darkening (partially transparent) substance, and a transparent phase-shifting layer.

The image recorded on the obtained hologram mask was reconstructed using a radiation source, which was used as a PLASMA brand He-Cd laser with a power of 90 mW and a radiation wavelength of 0.442 μm. As a result, a reconstructed image of the original pattern was obtained, reduced by 10,000 times, while the characteristic size of the geometric figures was 0.25-0.6 microns.

Example 5. As the initial drawing, the image of sets of various geometric shapes (squares, triangles, circles connected by straight lines) was used. The geometric figures had different sizes (2.5-6 mm), and the lines connecting them had different thicknesses (2.5-6 mm). The original image was converted to a digital raster using the following steps. The original picture in the form of a black and white grayscale image is placed in some coordinate system. A fine grid with a predetermined step is placed in the same coordinate system. In the area occupied by the figure, the coordinates of this node and the brightness of the figure at this point are recorded for each grid node. If you want to reproduce a picture with a given distribution of the radiation phase according to this picture, then this phase distribution is also presented in black and white, in the general case - grayscale, image and is also placed in the same coordinate system. The list of four values: two coordinates, brightness and phase for all grid nodes located in the area occupied by the original figure, presented, for example, in the form of a list, vector or matrix, and is a raster in digital form.

Thus, information on the amplitude and phase characterizing each point of the raster as a point emitter was recorded.

Then we calculated the diffraction pattern at each point of the future hologram, created from the entire set of virtual emitters - elements of the digital raster of the original pattern. To do this, we used the method of calculating sums of convolution type using the Fourier transform and using the fast Fourier transform algorithm. For its implementation, a personal computer equipped with appropriate software was used. Then we calculated the interference pattern, which will be obtained from the interaction of the calculated diffraction pattern with the calculated wavefront from the virtual reference radiation source, the wavefront of which is identical to the inverse wavefront of the real radiation source, which will be used to reconstruct the image recorded on the hologram. The calculation was carried out by calculating the complex amplitude of the radiation generated by the reference source at each point of the hologram and then adding this amplitude to the complex amplitude of the calculated diffraction pattern.

The obtained data was used to calculate the transmission function of the hologram and to determine the coordinates and properties of elements in three electrically controlled transparencies, for which, first, on the basis of the calculated transmission function, the phase change was calculated for each cell of the transparent phase-shifting transparency, and the transmission function itself was then changed. Then, based on the results of the analysis of the changed transmission function, the required degree of transmission was calculated for each transparency cell with variable transparency. Separately, the distribution of the rotation of the plane of the polarization vector over the area of the hologram was calculated.

Then they set up a three-layer hologram mask made up of electrically controlled banners as follows: directly on a transparent substrate - a banner consisting of cells with adjustable transparency, in the middle - a banner consisting of cells with adjustable phase shift (phase shifter) and on top - a banner that rotates plane of polarization.

The image recorded on the obtained hologram mask was reconstructed using a radiation source, which was used as a PLASMA brand He-Cd laser with a power of 90 mW and a radiation wavelength of 0.442 μm. As a result, a reconstructed image of the original pattern was obtained, reduced by 10,000 times, while the characteristic size of the geometric figures was 0.25-0.6 microns.

Example 6. As the initial drawing, an image of sets of various geometric shapes (squares, triangles, circles connected by straight lines) was used. The geometric figures had different sizes (2.5-6 mm), and the lines connecting them had different thicknesses (2.5-6 mm). The original image was converted to a digital raster using the following steps. The original picture in the form of a black and white grayscale image is placed in some coordinate system. A fine grid with a predetermined step is placed in the same coordinate system. In the area occupied by the figure, the coordinates of this node and the brightness of the figure at this point are recorded for each grid node. If you want to reproduce a picture with a given distribution of the radiation phase according to this picture, then this phase distribution is also presented in black and white, in the general case - grayscale, image and is also placed in the same coordinate system. The list of four values: two coordinates, brightness and phase for all grid nodes located in the area occupied by the original figure, presented, for example, in the form of a list, vector or matrix, and is a raster in digital form.

Thus, information on the amplitude and phase characterizing each point of the raster as a point emitter was recorded.

Then we calculated the diffraction pattern at each point of the future hologram, created from the entire set of virtual emitters - elements of the digital raster of the original pattern. To do this, we used the method of calculating sums of convolution type using the Fourier transform and using the fast Fourier transform algorithm. For its implementation, a personal computer equipped with appropriate software was used. Then we calculated the interference pattern, which will be obtained from the interaction of the calculated diffraction pattern with the calculated wavefront from the virtual reference radiation source, the wavefront of which is identical to the inverse wavefront of the real radiation source, which will be used to reconstruct the image recorded on the hologram. The calculation was carried out by calculating the complex amplitude of the radiation generated by the reference source at each point of the hologram and then adding this amplitude to the complex amplitude of the calculated diffraction pattern.

The obtained data was used to calculate the transmission function of the hologram and determine the location of transparent elements in the layers of the hologram mask, for which, first, based on the calculated transmission function, the location of the holes in the transparent layer was determined, which provides a phase shift of the transmitted radiation by 180 degrees, and the transmission function was then recounted . Then, based on the analysis of the recalculated transmission function, the transmission coefficient of the first additional dimming layer was calculated, after which the transmission function was recounted again. Based on the second recalculated transmission function, the location of the holes for the opaque layer was calculated, then the location of the holes in both additional darkening layers was calculated. Separately, the distribution of the rotation of the polarization vector over the area of the hologram was calculated.

Then, the data on the rotation of the plane of polarization and the calculated configuration of the holes in the layers were used to fabricate and adjust a five-layer hologram mask consisting of an electrically controlled transparency that rotates the plane of the polarization vector, a layer of an opaque substance, a layer of a darkening (partially transparent) substance, and a transparent phase-shifting layer.

The image recorded on the obtained hologram mask was reconstructed using a radiation source, which was used as a PLASMA brand He-Cd laser with a power of 90 mW and a radiation wavelength of 0.442 μm. As a result, a reconstructed image of the original pattern was obtained, reduced by 10,000 times, while the characteristic size of the geometric figures was 0.25-0.6 microns.

Claims (13)

1. A method of manufacturing a hologram of a picture, characterized in that the picture is converted into a raster in digital form, record information about the amplitude and phase characterizing each point of the raster as an extended or point emitter, calculate the necessary parameters of the hologram elements, for which the elements of the digital raster of the picture image are translated into a digital raster of the future hologram, while calculating the diffraction pattern at each point of the future hologram, created from the entire set of emitters - elements of the digital race In the image image, the interference pattern calculated from the interaction of the calculated diffraction pattern with the calculated wavefront from a virtual reference point or extended radiation source identical to the reversed real wavefront of the source, which will be used when reconstructing the holographic image of the pattern, is determined by the transmission function of the hologram and highlighted in areas that, after binarization, will give transparent elements of an unacceptably small size, physically that transmit light, and then change the transmission function, providing an increase in the size of these elements, use the result to form a diffraction structure of the hologram on the carrier, create a hologram in the form of a set of transparent discrete elements in an opaque layer deposited on a transparent substrate, and conduct optical correction of the enlarged elements, providing the transmission of these increased elements of the amount of light in accordance with the primary transmission function, while the correction is carried out by placing on an opaque layer a layer of an absorbing substance with a known absorption coefficient for the recovery image of the radiation, and the regions above the unexpanded elements are made transparent in it. 2. The method according to claim 1, characterized in that the optical correction is carried out repeatedly, for which a subsequent layer of absorbing substance with a known absorption coefficient for the recovery image of radiation and the area above areas of the previous layer, not transmitting the amount of light in accordance with the primary transmission function, perform transparent in it. 3. The method according to claim 1 or 2, characterized in that after the optical correction is completed, a layer of a transparent substance is applied to the absorbing substance layer with a known absorption coefficient for the radiation recovery image, which provides a phase shift of the radiation recovery image by a predetermined amount, for which they perform a set of discrete elements within whose area there is no phase shift, the shape, size and location of which are determined by calculation, for which the digital raster function is first calculated and transmission of the hologram, and then digital rasters of the opaque and phase-shifting layers of the proposed two-layer mask are calculated, for which the average transmission coefficient of all elements of the digital raster of the hologram transmission function is determined, the obtained average value is subtracted from the initial values, in areas where the difference is positive value, attribute to the elements of the digital raster of the opaque layer positive values equal to the values of the difference, attribute to the elements of the digital In the regions where the difference is a negative value, assign the positive values equal to negative absolute difference values to the elements of the digital raster of the opaque layer, attribute the value “one” to the elements of the digital raster of the layer providing the phase shift, and based on the analysis of the obtained digital raster of the opaque layer, the necessary optical correction is calculated, which must be carried out before applying the layer, both ensures, reducing the phase shift of the radiation image by a predetermined amount. 4. The method according to claim 1, characterized in that the hologram is provided with a layer that provides the required change in the polarization vector of the restoration image of the radiation in the calculated areas of this layer. 5. The method according to claim 1, characterized in that the transparent discrete elements perform different sizes and shapes. 6. The method according to claim 1, characterized in that the transparent discrete elements perform different sizes, but the same shape. 7. The method according to claim 1, or 5, or 6, characterized in that the transparent discrete elements are placed on a uniform or uneven grid. 8. The method according to claim 1, or 4, or 5, or 6, characterized in that the transparent discrete elements are made in the form of holes in the opaque layer. 9. The method according to claim 1 or 2, characterized in that as a means of forming transparent discrete elements in an opaque medium, an electrically controlled transparency is used. 10. The method according to claim 1 or 2, characterized in that an electrically controlled transparency is used as a layer with a known absorption coefficient for the recovery image of the radiation, in which transparent discrete elements are formed. 11. The method according to claim 4, characterized in that the layer that provides the change in the polarization vector of the restoration image of the radiation in the calculated areas is made in the form of an electrically controlled banner. 12. The method according to claim 3, characterized in that the set of discrete elements within the area of which the phase shift should be absent, is performed in the form of holes in the layer, providing a phase shift of the recovery image of the radiation by a predetermined amount. 13. The method according to claim 3, characterized in that the set of discrete elements, within the area of which the phase shift should be absent, is performed in the form of transparent sections in an electrically controlled transparency.